Problematic Soils and Geoenvironmental Concerns

Municipal solid waste (MSW) incineration has recently started in India with many new MSW waste-to-energy (WtE) plants underway. The process residue of MSW Incineration (MSWI) is primarily bottom ash (BA), which is being dumped to MSW landfills. The present study is an attempt to investigate the geotechnical properties of MSWI BA from two such plants in Delhi with an objective to evaluate its potential for reuse in bulk geotechnical applications. The results have been compared with coal BA (CBA) from a nearby thermal power plant and local sand. It was found that MSWI BA is comparatively coarser but strength properties are in the similar range to that of CBA and local sand. Compaction densities and specific gravity were lower than local soil but much higher than CBA. With new plants emerging all across the country, this study is a starting point for operators to plan the disposal of these residues effectively as well as save the limited land resources.

Old municipal solid waste (MSW) unengineered dumps, which have reached considerable height, have sloping sides with inadequate stability. The traditional technique of flattening the slope has to overcome the twin challenges of high cost of moving an enormous volume of waste and availability of area for placing the excavated material. In this study, an attempt has been made to strengthen the slopes of old MSW landfills for heights of 40 m, resting on firm base, by stabilizing them with reinforced soil, placed along the length of the slope and its width restricted to 10 m. Slope stability computations, using limit equilibrium methods, have been made for the original waste slope and that strengthened by the reinforced soil by varying soil strength and geometric properties. The study reveals that the waste slope, stabilized by the use of reinforced soil, can provide a feasible alternative to the removal of large quantity of excess waste.

Shear strength of soil is a very important property in geotechnical engineering, in order to study the strength of soils. According to classical soil mechanics, the soil is generally assumed to be either fully saturated or completely dry conditions. However, 40% of the natural soil on the earth’s surface encountered as an unsaturated/partially saturated condition. The problems faced at the time of designing the retaining structures, considering the soil mass in dry condition, affects in reducing the factor of safety of the slope due to wetting/drying conditions. The present study aims to investigate the loss/gain in the strength of the soils during the wetting and drying process, and it was observed that the strength is higher in drying path than that of wetting path.

The major problem of embankment on soft soil foundations is to overcome excessive settlement, initiating undrained failure of the infrastructure, provided proper ground improvement is not planned. One of the most widely used solution to this problem is to stabilize the soft soil foundations under embankment, by the installation of prefabricated vertical drains (PVD), which is carried out throughout the world. It is observed that the installation of vertical drains highly increases the settlement rate, improves pore water pressure dissipation, and decreases the lateral deformation of the soft clay foundation. The paper presents a numerical model to analyze the response of PVD-reinforced soft soil under embankment loading to the rate of embankment construction by finite element modeling. Apart from predicting the dissipation of excess pore water pressure, lateral displacement and the resulting consolidation settlement with time, the stability factors for different rates of embankment construction have been studied. It is observed that higher stability is manifested by the embankment having a slower rate of construction.

The dispersive soil is a highly erodible soil containing a high percentage of exchangeable sodium ions. In the present work, an attempt has been made to enhance the strength of dispersive soil by adding various proportions of ground granulated blast furnace slag (GGBS) (5, 10, and 15%) and cement clinker (5, 10, 15, 20, 25, and 30%), respectively. The combined effect of GGBS and cement clinker on stabilizing dispersive soil is also studied. The soil used in this study is a virgin and identified as a highly dispersive soil by conducting a double hydrometer test. For these purposes, mechanical properties of the various mixes are investigated by the standard Proctor tests, unconfined compressive strength (UCS), and California bearing ratio (CBR). The strength of dispersive soil under UCS is found to increase significantly by adding various proportions of GGBS and cement clinker.

The hydraulic conductivity of waste is an important parameter that influences the design of leachate recirculation system in a bioreactor landfill. The hydraulic conductivity of waste varies with respect to depth and time in a landfill. These variations can be attributed to the settlement of waste, and the corresponding changes in the void ratio can be related to permeability. In this study, experiments were conducted to find the values of permeability index (Ck, the ratio of the slope of the void ratio—coefficient of permeability relationship) at four different placement densities of waste. The relation between the compression index (Cc) and Ck for waste is discussed. Estimation of permeability using Ck is presented and compared with the reported values in the literature. The effect of initial placement density of waste on the design of injection wells in a typical bioreactor landfill is presented to demonstrate the applicability of Ck and Cc values with the help of HYDRUS-2D simulations.

Sand–bentonite mixtures are used to construct clay liner in engineered landfills. Clay-lined landfills when exposed to organic wastes produce leachate which affects the properties of the clay liner extensively, and it may become unreliable in being a permanent barrier to the wastes. This work is to investigate the behaviour of different bentonite–sand mixtures through one-dimensional consolidation using ethanol–water solution mixed in the ratio of 20:80 by volume, as the permeating fluid. The same series of experiments were performed with pure water also as the permeating liquid to get a good comparison of the change in properties. The percentage swell, swelling pressures and permeability were high in the mix with pure water solution. Compressibility was found to be high in the mix with ethanol–water solution. Good correlation exists between per cent swell and swelling pressure in the mix using ethanol–water solution and in the mix using water.

Coal gangue, a residue obtained during the coal mining process, accounts for 10–15% of raw coal produced. Usually, this coal gangue is transported and stacked loosely in the nearby areas. Long term piling up of this mine waste can volatilize large amounts of potentially toxic heavy metals which have the ability to infiltrate surrounding ecosystems. In the present study, coal gangue from an open cast mining area in Bhupalpally in Telangana state, India, has been analyzed for its physical and chemical characteristics. Further, column leaching test was performed to evaluate the leachability of selected heavy metal ions simulating field conditions using deionized double distilled water. The column tests proved that the selected heavy metal ions from coal gangue can be easily mobilized.

In the present state, the utilization of various waste materials in a different geotechnical application is increase manifold. All the waste materials possess different characteristics depending upon its raw materials and processing techniques. Utilization of these waste materials needs greater concern of its properties and compatibility with parent material. Out of many waste materials available, blast furnace slag is one of them. Blast furnace slags are by-products of metallurgical processes. It is glassy material, vesicular textures, typically with sand-to-gravel-size particles can be converted into powder form as well as particular desire size particles. In this paper, critical review has been made for the utilization of this blast furnace slag in various geotechnical applications depending upon the situation in weak and problematic soil condition. The review of this nature will lead the path in which various experimental program can be perform to find out the solution of different on-site geotechnical problems. The blast furnace slag has versatile characteristics by which it can compatible with all types of soil and provide appropriate solution for any soil stabilization process. Based on the review findings, some suggestion can be made for various geotechnical problems by utilizing this underutilized material, especially in Indian context. This paper ultimately become source for one of the interesting areas of research in which utilization of blast furnace slag in geotechnical application will have technical advantage as well as beneficial in protection and perseverance of natural resources.

Clayey soils rich in montmorillonite content are increasingly used as liner material for various landfill facilities because of their very low saturated hydraulic conductivity, high sorption potential and better self-sealing capacity. However, the performance assessment of such a facility requires long-term hydraulic conductivity and diffusion studies of the clayey soil under the influence of different pore fluids. In this paper, an extensive study was carried out to understand the effect of various inorganic salt solutions such as lithium chloride, sodium chloride and potassium chloride on the montmorillonite rich bentonite clay by performing long-term hydraulic conductivity tests and transient through-diffusion tests. A software package named CONTRADIS was utilized in the present study which was able to perform inverse analysis for estimating the diffusion parameters from the experimental data. The experimental study suggests that the electrolyte concentration changes the hydraulic conductivity and diffusion coefficient significantly. The hydrated cationic radius also has considerable effect on the equilibrium hydraulic conductivity of the soil.

Kota city is having major problem of disposing of Kota stone slurry powder. It is a by-product which is obtained during cutting, grinding and polishing operations of locally available Kota stone in stone industries. One of the innovative ground improvement techniques can be practiced by using Kota stone slurry powder (KSSP) as stabilizing agent or admixture. This technique may simultaneously offer the other advantages such as space saving, environmental sustainability and material availability. In the present study, Kota stone slurry powder is used as a stabilizing material for black cotton soil. The cone penetration, shrinkage limit, differential free swell, standard proctor test, UCS test and swell pressure test are conducted on soil and mix specimens to predict and ascertain the behaviour of mix. Results of these experiments conclude that engineering properties of the black cotton soil like shrinkage limit, maximum dry density (MDD), optimum moisture content (OMC) and UCS are improved by mixing Kota stone slurry powder depending on its proportion. With the percentage increase of Kota stone slurry powder, swelling characteristics of expansive soil are also improved such as decrement in the swelling percentage and swelling pressure. UCS decreases beyond 20% of mix.

Solid waste management is a serious setback over the world. Therefore, reduction, reuse and recycling of waste have become major issue in recent days. The use of recycled bassanite in ground improvement projects is initiated recently in Japan to eliminate the huge quantities of gypsum wastes. The use of recycled bassanite has a positive effect on the environment and economy. It has challenges like release of fluorine more than the standard limits results in contaminate soil. This paper represents the effect of bassanite on clay stabilized soil by taking in consideration of the compressive strength and release of fluorine. Test results showed that the addition of bassanite had a significant effect on the improvement of compressive strength by increasing the amount of bassanite. The release of fluorine increases with the amount of bassanite in soil mixture, and it had a negative effect on the improvement of strength and consuming the amount of admixture. Recycled bassanite produced from gypsum wastes had a potential to be used as a stabilizer material for expansive clay soil and meets the standards of environment.

The present study investigated the influence of biochar on various geotechnical properties of clayey soil. Biochar, a carbon-rich product, was amended with the soil at different percentages such as 5, 10 and 15%. Laboratory tests were conducted to evaluate the feasibility of utilization of biochar in enhancing the integrity of soil slopes with an emphasis on landfill covers and bioengineered slopes. Scanning electron microscopy (SEM) tests were conducted to analyse micro-porous structure of biochar and soil-biochar mix. The SEM micrographs indicated the porous structure of the biochar and a good interaction with the clay particles. It was concluded from the present study that the biochar amended soil can have steeper and stable slopes compared to soil without biochar amendments. The compressibility of the soil was also decreased with biochar amendment.

Amidst the numerous techniques of remediation researched, the immobilization technique achieved through solidification/stabilization appears to be most effective due to its ability to entrap the waste within a solid cementitious matrix and its cost effectiveness. Due to growing environmental concerns, there is a need to replace conventional stabilization binders with more efficient, environment-friendly stabilizer. In this study, artificially lead contaminated Kaolinite is treated using different concentrations of Olivine, a natural mineral. The effectiveness of the treatment is assessed through unconfined compressive strength test and column leachate test. The optimum concentration of Olivine for remediation is determined. The experimental results show that olivine can be effectively used for the treatment of lead contaminated soil.

The present study focuses on the release of dark colored leachate from soil-like material (SLM) reclaimed from aged municipal solid waste (MSW) at three dumps of India (located at Delhi, Hyderabad and Kadapa). If the material is to be used in filling low-lying areas or in embankments or subgrade, the leaching of colored liquid can cause coloration of the surrounding water bodies and ground water. Local soil was used as a base material for comparison of release of color. Mined soil-like material from MSW releases dark and objectionable color of leachate. The intensity of color of leachate from mined SLM is found to range between 380 and 400 Hazen, 460 and 480 Hazen and 900 and 1000 Hazen in the samples from Delhi, Kadapa and Hyderabad landfill, respectively. In contrast, the intensity of color in water released from local soil varies between 25 and 30 Hazen. The study concludes that small amount of mined SLM requires large quantity of water (70–100 times) for washing the material before the intensity of color reduces to acceptable level, thereby demonstrating the potential to significantly impact nearby ground water wells. Thermal treatment is observed to be reducing the color to acceptable level before reuse.

Recent years, the rate of coastal erosion is considerably increased in India due to human interference and natural drivers. The coastline of the Western part of West Bengal is severely eroded. Months from June to October, as the monsoon wind affects the direction and magnitude of the waves affecting the coastline with intense erosion hotspots making zone vulnerable for the coastal community. Transportation gets open during monsoon induces erosion. Frontal beaches seaward of seawalls dissolves bringing wave breakers closer to seawalls. Abrasion at the base of seawalls accelerates slumping. In the monsoon season, overtopping of the landward of the seawall also causes high waves breaking very near to the seawalls. Many places in alongshore have been observed seawalls abruptly ended which is indicate the ‘end erosion hotspot’. The paper tries to access the drivers and processes conducting to erosion hotspots.

One of the major causes of groundwater contamination in urban areas is the flow of leachate from non-engineered landfills. Use of conventional test wells to predict the contamination is a cumbersome process. In this pilot study, a small-scale landfill having dimensions 4 m × 2.4 m × 0.6 m height was prepared to determine the efficiency of electrical resistivity tomography (ERT) in predicting groundwater contamination due to uncontrolled landfill. ERT survey was performed for five months, and the variations in groundwater contamination were observed. Water samples from the site were analysed for contaminant concentrations. The resistivity of the soil was found to be decreased considerably from around 200 to 20 Ω-m. This low resistivity zone ensured the presence of leachate flow followed by contamination of groundwater. The increased depth of low resistive zone below landfill evidenced the extended depth of groundwater contamination. Charts were prepared by correlating the contaminant concentrations in groundwater with the resistivity values. This chart may help in predicting the groundwater contamination and contaminant concentration using ERT, without making any borehole at a site. The study has evidenced the potential of ERT in predicting groundwater contamination.

Early plant establishment period for bioengineered structure is important to assess its soil erosion protection and green restoration capability. The use of lignocellulose-based fibers has been recently explored for enhancing vegetation growth. Moreover, the soil–lignocellulose fiber composite has been reported to enhance the water retention and reduce erosion potential. However, the effects of fiber type, i.e., filament type and biochemical composition has not been explored. The objective of the study aims to explore these effects on early plant establishment period by incorporating two contrasting lignocellulose fibers–coir and water hyacinth. Soil column of bare soil and soil–fiber composite compacted at 0.9MDD were prepared and instrumented for measurement of suction and moisture content. An indigenous grass species Axonopus Compressus was transplanted and the growth parameter was monitored for a period of 60 days under greenhouse condition. The results indicated that monofilament fiber such as WH is better suited as a lignocellulose fiber for grass growth in compacted soil based on its water retention, easy root propagation and resistance to desiccation cracking.

Landfill liner is the most important component in the landfill disposal site to prevent the seepage of leachate to the ground below. This study mainly focused to study the effect of the industrial waste material from Kerala Metals and Minerals Limited (KMML) which is very fine powder with locally available clay as a landfill liner material. The effect of both index and engineering properties of mixtures was analyzed with the addition of iron oxide-rich industrial waste material. A mix containing 75% clay soil, 25% industrial waste and 5% bentonite was found to satisfy all the requirements of a clay liner material. Batch adsorption tests were performed on these mixes to study the lead (Pb) adsorption capacity of mixtures and it is observed that as the iron oxide-rich waste content increased in the natural soil, lead removal efficiency of soil is also increased.

The environment is getting contaminated due to un-engineered disposal of waste produced by rapid industrialization and urbanization to fulfill the needs of increasing population. Environmental pollutants can harm people’s health through a series of complex transport by various exposure pathways. Heavy metals are continuously being dump into the environment which create serious problems to human health. In this study, the soil and dust samples were collected to know their distribution and concentration of various heavy metals like As, Cd, Cr, Cu, Ni, Pb, Zn, etc., and their health risk assessment had been determined. The health risk was assessed using hazard quotient (HQ) and hazard index (HI). The samples were collected from ten different locations including industrial, residential, highways and mixed use in Allahabad, UP (India). The equipment used for heavy metals detection was hand held portable X-ray fluorescence (PXRF) analyzer. The dry and finely powdered soil samples were placed in a plastic container and packed by polypropylene thin film from both sides. Three measurements were performed, and detail descriptions were recorded for each soil samples. The assessment of health risk was analyzed for three exposure pathways: ingestion, dermal contact and inhalation. The main exposure pathway of heavy metals to both children and adults is ingestion. The result shows that the heavy metal concentration is found below hazardous level for adults and at higher level for child below six years. The study will be beneficial for the municipality in terms of non-point source pollution control and management to give the healthy environment to local people.

Bulk utilization of marble dust needs to be done to enhance the sustainable construction activities and to embrace safe environment. In the present study, the geotechnical properties of untreated and treated black cotton soil with marble dust are studied in detail to check its potential to improve the properties of soil. The experimental works include particle size analysis, free swell index, specific gravity, compaction characteristics, California bearing ratio (CBR), and pH. The results show that the physical properties of black cotton soil are improved significantly by addition of marble dust. An addition of marble dust leads to an increase in the pH and reduction in the swell index of soil. Further, the CBR values of mixes compacted at their respective optimum water content and maximum dry density increases with addition of marble dust up to 25%. The improvement in the gradation of soil and the formation of cementitious compounds are the key factors to improve the properties of soil with addition of marble dust.

The oil, gas and petroleum industries are considered as a potential source of pollution. Oil contamination has a negative impact on environment. The engineering properties of soil will get adversely affected due to oil contamination making it unsuitable for construction purposes. A good knowledge of change in geotechnical properties of soil due to contamination is required for providing proper recommendations regarding its use in the construction activities. The behaviour of different soils after oil contamination will be different based on the constituents present in it. This paper discusses effect of oil contamination on lateritic soil. Used engine oil was added to soil in the amount of 0%, 2%, 4% and 6% by weight to artificially contaminate the soil, and the variation in properties was identified. The effect of contamination was studied based on the change in consistency limits, compaction characteristics, CBR value and shear strength parameters.

Bauxite residue or red mud is the iron-oxide rich waste produced when bauxite ore is processed by the Bayer’s process to extract aluminum. Red mud characteristics and production depend on origin, quality and composition of bauxite. Storage and disposal of red mud is the biggest problem faced by the aluminum industries. Red mud residue is associated with being chemically basic, high in heavy metals and low level of naturally occurring radioactive materials. The objective of this study was to characterize red mud which is collected from Hindalco, Belgaum, on the basis of traditional geotechnical methods that may contribute to the behavior of the material and to analyze the chemical constituents of its leachate which helps to understand the leachate characteristics. The characterization of the material included index properties like moisture content, specific gravity, grain size distribution, liquid limit, plastic limit and their indices, engineering properties like shear strength by cohesion intercept and angle of internal friction, compaction characteristics by OMC and MDD and chemical properties by SEM, XRD and TCLP. The findings, in terms of leachate characteristics, showed that red mud has undergone reactions during the leaching process giving leachate with sodium, silica and calcium in highest concentration. Red mud shows acceptable characteristics for potential reuse as a civil engineering material.

Controlled low-strength material (CLSM) also known by names such as flowable fill or controlled density fill is self-compacted in nature and used in civil engineering works such as backfills, void fills, conduit bedding and many more. These materials have strength lesser than 8.3 MPa. Generally, it consists of Portland cement, fine aggregate, fly ash and water but several other materials such as foundry dust and quarry dust can also be used. In this study, the different engineering properties of CLSM with different mix proportion were evaluated. Mix proportion mainly consists of red mud having 70%, 60% and 50% by weight of total composition along with fly ash of 20%, 30% and 40%, respectively, and phosphogypsum of 10% was studied. Portland cement was used as the binder material in all the composition in the proportion of 10% and 7% of the above composition. For different mix proportions considering flow value as an important parameter firstly percentage of water required for desired flow value (0.15–0.3 m) was evaluated by the trial method and then at those water content along with above mixture, other important engineering properties of CLSM such as compressive strength, bleeding and durability were evaluated. Except for the property of reexcavatibility (strength lesser than 2.1 MPa) for some composition all the other properties of all the composition were within the permissible limit. Overall it can be stated that red mud can be effectively used as one of the materials in CLSM.

In landfill disposal sites, bentonite is used as liner material because of its high contaminant adsorption limit, high swelling capacity and low hydraulic conductivity. However, the effectiveness of liner may reduce due to the chemicals present in the leachate. Swelling and sorption capacity of bentonite may effect in the presence of various chemicals present in the leachate, which in turn reduces the thickness of the diffuse double layer (DDL). Consolidation is an important parameter of liner material, which is essential for settlement calculation. Therefore, it is necessary to study the change in the behaviour of bentonite in the presence of heavy metal. In this investigation, the effects of zinc (Zn2+) of varying concentrations were studied on the behaviour of bentonite. Solutions of zinc 0 (i.e. de-ionized (DI) water), 100 and 1000 ppm concentration were prepared by dissolving salts of zinc nitrate. The results revealed that rate of consolidation and hydraulic conductivity increases with the increase in concentration because of the presence of Zn2+ in pore water. However, liquid limit, swelling pressure and swelling potential were decreased. Results also illustrate that at higher concentration, the impact of Zn2+ on the behaviour of the bentonite is more significant.

Expansive clays exhibit some attractive features such as high swelling capacity and very low hydraulic conductivity, for which it is deemed as the most suitable naturally available material for the design of barrier/buffer material in many geo-environmental engineering practices. Equilibrium sediment volume (ESV) is an important surrogate compatibility test used for assessing the expansiveness of soil. It is also utilized for qualitative understanding of the swelling characteristics of clays, mineral identification, and correlating with different geotechnical properties of clays. A detailed understanding on effect of the influencing parameters on ESV provides useful insights into the fundamental behavior of expansive clays. The main objective of this work was to develop a theoretical model for equilibrium sediment volume of clays in the presence of salt solutions using the concept of diffuse double-layer theory. The ESV showed a linear relationship with the specific surface area of soils.

Reinforcement of soil with fibres in different forms has been a regular practice since early days. Utilizing the waste tire fibres instead of other types of fibres will serve the dual purpose of utilization of waste as well as improving the behaviour of expansive soils. This paper presents the effect of tire fibres on swelling behaviour of expansive soils with a change in size as well as the percentage of fibres. The consolidation tests were performed and swelling potential was identified and compared for different fibre types A (L/B = 8.95), B(L/B = 6.387) and C (L/B = 4.457) with varying fibre content as 0.25%, 0.5%, 0.75% and 1.00%. The swelling potential for 12 combinations was computed and compared with that of the virgin soil to calculate the swelling potential ratio (SPR) to find out the optimum percentage and aspect ratio at which the fibres are most effective in reducing the swelling behaviour of the problematic soils.

Microbial-induced calcite precipitation (MICP) is a sustainable biological ground improvement technique, which is capable of altering and improving physical properties of black cotton soil. In order to evaluate MICP as a soil ground improvement technique for black cotton soil, four types of microbes were used in this study. These were Bacillus pasteurii, Bacillus subtilis, Bacillus megaterium, and Pseudomonas. These microbes in liquid medium were mixed with the soil sample for different percentages (4%, 8%, 12%, 16%, and 20%) by weight of sample. The soil samples were kept for different reaction periods (3 days, 7 days, and 14 days). The physical properties of MICP-treated soil such as liquid limit, plastic limit, shrinkage limit, and swelling pressure were examined. The results show that the plasticity index decreases when upto 20% of microbes were mixed and when microbes were more than 20%, plasticity index increases. The reaction period shows the influence on plasticity index. The shrinkage limit test was performed for soil with 20% bacteria for 3, 7, and 14 days reaction period. The MICP-treated soil shows reduction in shrinkage limit values. Swelling pressure tests were performed for soil with 20% microbes for 7 days reaction period, and swelling pressure was also reduced to 80%. Thus, the use of microbes helps in controlling the swelling and shrinkage characteristics of black cotton soil.

Many past research works proved the successful usage of synthetic geotextiles and geogrids as road subgrade reinforcement. However, reinforcing subgrades with natural geotextiles is found to be more economic and eco-friendly. The usage of this is limited by its short degradation time period in soil, and to overcome this, researchers started using treated geotextiles. In this study, a systematic lab investigation has been made to understand the behavior of subgrade strength of roads reinforced with alkali activated binder (AAB) treated jute geotextile. Unreinforced soils, untreated and treated jute reinforced soils are tested for CBR, bearing capacity, and the results showed a considerable increase of CBR, bearing values in treated jute geotextiles. Durability tests such as soil burial tests and tensile strengths of degraded JGT are also carried to study the increase in life expectancy of AAB treated jute geotextile. Alkali activated binder improves life expectancy and mechanical properties of jute, and therefore, treated jute geotextile may be used as alternative material for subgrade soil reinforcement applications.

Expansive soils undergo considerable amounts of volume changes due to moisture content fluctuations, and it causes problems to infrastructures on them. Also, due to industrialization, the production and the accumulation of various wastes have created serious problems of handling and disposal. One of the possible solutions of it is to utilize the waste materials for the improvement of soil. Jarofix is one of such waste material from zinc industries. So, in this study, the utilization of Jarofix to control the expansive nature of clay mixing along with lime has studied. For that, the variation of free swell index, swell potential and swell pressure of bentonite clay was studied by adding different percentages of Jarofix. The variation of the same has studied by adding different percentages of lime also. The results reveal that the Jarofix and lime can be used as an effective agent for reducing the expansive nature of soil.

This paper mainly deals with the fly ash modified with 20–50% of bentonite and 5–10% of quicklime (CaO = 84.94%) by dry weight basis. The specific gravity of fly ash, bentonite, fly ash–bentonite mix and fly ash–lime mix is 2.21, 2.80, 2.30–2.51 and 2.23–2.21, respectively, and liquid limit, plastic limit and plasticity index found for fly ash–bentonite mixin between 85.02–98.02, 17.55–25.23 and 67. 47–72.79%. OMC and MDD of fly ash and bentonite are 26.20% and13.00 kN/m3 and 33.60% and 13.72 kN/m3, respectively; fly ash–bentonite mix and fly ash–lime mix are in between 23.40–21.20% and 13.76–14.68 kN/m3 and 22.30–23.40% and 13.33–13.09 kN/m3, respectively, which shows increasing trend in MDD in case of fly ash–bentonite mix and decreasing trend for fly ash–lime mix. To confirm the mineralogical and microstructural changes of particles together with the spectrum of all elements and to validate the results, energy dispersive spectroscopy (EDS) is carried out where different peaks of different components observed with different shapes and sizes of structures are also identified from X-ray diffraction and scanning electron microscope (SEM). The results are reliable for field applications like landfilling purposes.

A developing country like India has to show its development by leaps and bounds in the fields of infrastructure development, transportation, and communication system. The peninsular India is having a lengthy coastal belt of around 7700 km; except north all three sides of India is surrounded by Bay of Bengal in the east, Indian Ocean in the south, and Arabian Sea on the west. The areas surrounded by the coast are being utilized since ages. So, inevitably several national and international authorities are doing research and development on coastal structures. The various potential problems associated with this marine clay are land slippage slope stability, poor foundation support, and poor drainage. Owing to such soils of poor engineering properties, a great diversity of ground improvement techniques such as soil stabilization and chemical treatment is employed to improve their mechanical behavior, thereby enhancing the reliability of construction. Metakaolin is applied in soil stabilization for foundations or road subgrade. However, metakaolin along with calcium chloride treatment for these poor soils, as an alternative to the traditional “remove and replace” strategies commonly utilized was found to be satisfactory in the laboratory evaluation. Hence, the authors arrived at an optimum content of metakaolin mixed to soft marine clay, and then further, it is chemically treated with calcium chloride. The optimum dosage of calcium chloride in combination with the optimum content of metakaolin was evaluated from the tests conducted in the laboratory. Further, the authors studied the performance of soft marine clay beds prepared with different alternative treatments by conducting load tests in the laboratory. The test results indicated that the load-carrying capacity of the metakaolin-treated marine clay bed was improved and further it was increased by chemical treatment with calcium chloride.

The performance of the pavement is dependent on the type and properties of the sub-grade soil. Various techniques are used for the stabilization of sub-grade soils having inadequate properties. Combination of Enzyme and lime found to be effective in improvement of strength of the soft soils. In the present work, the behaviour of enzymatic lime stabilized soil under varying environmental conditions is analysed. An extensive study was carried out on a soil sample having pH 3, 7 and 10 using optimum dosages of lime, enzyme, and enzymatic lime. The variation in the unconfined compressive strength was investigated after 3, 7, 14 and 28 days of curing. By using enzymatic lime accelerated enhancement of properties were obtained in comparison to lime and enzyme. Enzymatic stabilization found to be suitable for all conditions of soil while lime and enzymatic lime stabilization enhance properties much better in a neutral environment than the acidic and alkaline environment.

This paper reports the experimental results of using two chemical additives to enhance the properties of marine clay collected from Vypin, Cochin area. Modifications in properties of marine clay by lime are investigated to compare the nano-silica particles’ effect in mechanical properties of clay. The engineering properties studied included Atterberg limits, maximum dry unit weight, optimum moisture content and unconfined compressive strength. Lime to soil ratios of 3, 4 and 5% were used. Nano-silica used for the study varied from 0.5, 0.8 and 1%. Atterberg limits variation and unconfined compressive strength variation were evaluated for the curing period of 3, 7, 14 and 28 days. Strength is enhanced three times for amended clay with nano-silica. Optimum lime content for lime stabilized clay was obtained as 4% and nano-silica as 0.8%. Plasticity characteristics are remarkably modified in the lime-amended clay compared to nano-silica additive. Unconfined compressive strength improvement shows similar variations for both nano-silica and lime.

Dredged soil is a waste of sediments including organic matter, soils etc., excavated from a river and has low shear strength, low bearing capacity and high compressibility. Post-September 2014 floods in Srinagar–Kashmir, several lakhs of tones of dredged material was targeted for dredging out by 2017–18. However, dredged material posed serious disposal and environmental problem in and around the flood channels and Jhelum River in the capital city Srinagar. Therefore, in this study, boulder dust, a waste product of boulder crushing units which is left in huge quantities and poses enormous environmental, health as well as disposal problems was chosen as an additive for stabilization of dredged soils. Basic tests were performed on soil samples from three different sites on the flood channel running through HMT area in the outskirts of Srinagar–Kashmir. A comparison of the test results was run, and the weakest soil sample was selected for further research work of stabilization. The mechanical properties of the dredged soil were enhanced by using boulder dust in increments of 4%. Atterberg limits, compaction characteristics, CBR values and UC strength were studied. The experimental results revealed that the boulder dust is a promising additive for stabilization of the dredged soil keeping in view the environmental concerns and the economy of the material.

Electro-osmosis is a powerful technique, as a means of dewatering soils of high compressibility and moisture content. Electro-osmosis is an established technique and has been investigated by many researchers as long as a century ago. The treatment factors that contribute to the effectiveness of electro-osmotic consolidation are type of electrode, voltage gradient, polarity reversal, current intermittence and duration of treatment. Copper, mild steel and stainless steel in different shapes and forms have been used as electrodes. Electrokinetic geosynthetics (EKG) used in electro-osmotic consolidation applications provide electrokinetic function in addition to the filtration and drainage functions. The EKG electrodes are less susceptible to corrosion due to the polymeric cover or treatment against corrosion. Even though most studies claim the effectiveness of this technique, the procedure is not widely accepted in the industry due to the risks and costs involved. This paper aims to review the suitability of this technique on soils around the world. Also, this paper looks closely into the properties of the soil that make it ideal for the success of this technique. With reference to Indian soils, the results of electro-osmosis studies on Kuttanad clay are presented.

Properties of soft soils largely influence their behavior and the design scheme of the ground improvement that would be required. The time for 90% consolidation could be estimated theoretically with time factor, coefficient of consolidation, compressibility and permeability. As the reproducibility of these tests is very less, estimating the properties accurately is highly challenging. Repeating the test also would usually result in obtaining a wide range of values. Since the ground improvement scheme is largely dependent on these properties, probabilistic tools and reliability-based design must be used. In soft soils, prefabricated vertical drains (PVDs) along with preloading is a popular method of increasing the bearing capacity of soils wherein the improvement is achieved by accelerating the consolidation process. The spatial and temporal variability of the soil properties affects the performance of the PVDs installed in the ground, and the same is investigated using probability distribution of the various properties used in the design of the ground improvement scheme. Monte Carlo simulations using the probability distribution and statistics of the design properties are used to capture the effect of variability of the design properties on the time for consolidation.

This paper presents the outcomes of a 3-D finite element analysis performed to study the time-dependent behavior of embankment resting on the geosynthetic-encased stone column (GESC). The numerical analysis is carried out on both fixed and floating GESC. The results of the study show the effect of encasement stiffness, encasement length and length of the geosynthetic encased stone column on time-dependent behavior of the system. The use of GESC has provided significant improvement in reducing the generation and dissipation of excess pore water pressure, settlement and lateral displacement of the column along its length. The study indicates that the higher stress concentration in the case of GESC results in better time-dependent behavior. Additionally, the results also confirm that there is an optimum value of encasement stiffness, encasement length and length of geosynthetic-encased column beyond which no substantial improvement is attained.

The storage of hazardous bauxite residue mud obtained from the Bayer’s process in alumina industry leads to serious environmental impact on land, air and water. The detailed laboratory works and micro-analyses have been performed in the present paper to characterize the red mud and to investigate the effect of class F fly ash on the geotechnical properties of red mud for possible use as a construction material. The characterization of materials shows the higher value of specific gravity, liquid limit, optimum water content (OWC), maximum dry unit weight (γmax), pH value and electrical conductivity of red mud as compared to fly ash. The micro-analyses show the presence of sodalite, hematite, goethite, calcite in red mud; and mullite and quartz in fly ash as predominant minerals. Further, treatment with various fly ash contents (0–80%) has observed a significant effect on the plasticity, compaction characteristics, alkalinity and electrical conductivity of red mud.

Soil–lime interactions involve concomitant short-term and long-term alterations of the fine-grained soil resulting in the formation of a workable material bonded by various pozzolanic compounds. These pozzolanic compounds being cementitious in nature are expected to hold the soil particles together and bring long-term strength and stability to the soil–lime composites. However, the durability of cementitious phases formed due to pozzolanic reactions is highly subjective owing to the variations in the moisture and physiochemical factors like pH under diverse environmental conditions. The relative humidity and presence of atmospheric gases like carbon dioxide have a significant impact on the performance of the stabilized system. Carbonation of reaction products, as well as the effects of seasonal moisture fluctuations, can cause the decalcification of the cementitious phases and further degradation in the stabilized system. However, the type of reaction products and their chemical composition, which is a function of the mineralogy of the soil, will determine their durability in adverse conditions. The present study attempts to review the chemistry of reaction products formed in view of its inherent mineralogy. In addition, the degradation nature of the soil–lime composites under adverse conditions like moisture ingress and carbonation is evaluated for their long-term performance.

Global warming is a very common problem worldwide. One of the reason is due to use of unsustainable natural resources for construction activities. This situation has forced engineers to think of alternative construction materials and methods of construction to minimize adverse impacts and protect environment from natural disasters. In this context, rammed earth is one of the sustainable and eco-friendly alternative construction techniques. In this study, two local soils were selected for rammed earth application which possesses varied colour. The soils were mixed in 1:1 proportion for aesthetic appearance. Initially, the basic properties of both the soils were determined, and then the properties of the mix were determined. To further improve the strength property of the soil, cow dung was selected as admixture. The cow dung dosage was varied from 2 to 8% with an increment of 2%. A series of compressive strength tests were carried out on unstabilized and cow dung stabilized soil blocks with varied percentages of cow dung and varied curing period. Based on the test results, 2% cow dung is found to be optimum. The compressive strength of the rammed earth is increased by 1.5–2 times that of the unstabilized soil block with a curing period of 28 days. Thus, cow dung can be an eco-friendly and economic alternative for rammed earth application.

Black cotton soil (BCS) is highly expansive in nature when it is exposed to moisture. This property renders BCS unsuitable for use in geotechnical applications. Cement stabilization is one of the most popular methods for reducing the swelling properties of BCS. However, the production of cement leads to the emission of greenhouse gases, which is a threat to modern society. Hence, the present study aims to make use of two waste materials, fly ash and ground granulated blast furnace slag (GGBS) for stabilizing BCS. The study proposes a method of geopolymerizing BCS with alkali-activated binders (AAB). AAB is produced by the reaction of an aluminosilicate precursor (fly ash and/or GGBS) with an alkaline activator solution containing sodium silicate and sodium hydroxides. The water-to-solid (w/s) ratio is varied from 0.3 to 0.5 in this study. To identify the variations in chemical characteristics and surface morphology for both untreated BCS and BCS treated with AAB, mineralogical and chemical characterizations are performed through X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The index and shear strength properties before and after the treatment of BCS with AAB are compared. It is observed that the effect of geopolymerization in BCS significantly increases the UCS and CBR value and reduces the free swell and plasticity index. Recommendations on the practical implementation of this technique for stabilization of expansive soils are proposed based on the findings of this study.

A number of studies have been carried out to investigate the effect of addition of waste materials on modifying the properties of soil. The present study shows the modification of soil properties by adding locally available materials such as rice husk ash and fly ash. The cost of stabilization may be reduced by replacing by a good proportion of stabilizing agent using rice husk ash. The soil used in the present study is clay with high compressibility, which needs to be strengthened to minimize volume changes in the soil. The soil is stabilized by varying different percentages of rice husk ash and also fly ash. Observations are made for changes in compaction characteristics of the soil, unconfined compressive strength and California bearing ratio values of the soil. From the results, it is observed that the maximum dry density is increased with increase in percentages of rice husk ash, and the corresponding optimum moisture content is decreased and vice versa with the addition of fly ash to the soil. The optimum amount of rice husk ash and fly ash for improving the properties of the soil are discussed in detail.

Augmentation as well as stabilization of soils is extensively used as a substitute due to the lacking of appropriate material on site. In this manuscript, universally available bioenzymes (TerraZyme) and their effect on engineering properties of soil are discussed. Differential Free Swell, Consistency Limit, Modified Compaction and Consolidation tests were conceded out in the laboratory for dissimilar mix proportions of TerraZyme with black cotton soil and from the results addition of the TerraZyme to the soil reduces the clay content and increases in the % of coarser particles, reduces Liquid limit values are decreasing and plastic limit increasing irrespective of the percentage of addition of TerraZyme. Maximum dry density increases and OMC goes decreasing with increase in % of TerraZyme. The consolidation parameters compressive index and coefficient of compressibility are decreased. From the above results, TerraZyme can be utilized for intensification of the expansive soil with a substantial save in cost of construction.

The soils that exhibit volume changes with change in moisture content are called expansive or swelling soils. These soils are characterized generally by their blackish colour, high plasticity and the enriched presence of the clay mineral montmorillonite as the principal constituent. As the expansive soils have a tendency to change its volume with change in the moisture content, they can cause severe damage and distress to lightweight structures constructed over them due to the increased swell pressure evolved as a result of the swelling. Hence while designing the foundations on expansive soils, it is highly imperative to get an idea of the anticipated swell and the associated swell pressure that may damage the structural element. The various soil properties which clearly indicate the swelling characteristics of the expansive soils are free swell index, swelling index, shrinkage limit, swelling potential, swelling pressure, etc. The activity of clay derived from plasticity index and percentage of clay sizes present in the soil is also used as an indicator for identifying the expansive soil. If these swelling parameters can be derived from easily determinable index properties of soil, that would be really informative regarding the usefulness of the soil or the quantum of modification or improvement required for reclamation of such type of soil. A great deal of research has been done in correlating the swelling characteristics with the index properties and physical state of soil. The present work is an attempt to develop predictive models for the swelling characteristics based on their interrelationship with the index properties like liquid limit, plasticity index, shrinkage index, etc. and the physical properties like dry unit weight, grain size, especially the clay percentage, etc. The expansive soils investigated at Central Soil and Materials Research Station, New Delhi, are used to develop the predictive models. The applicability of the developed equations is finally checked by conducting validation study using three different data sets.

Due to rapid industrialization and development in urban areas, every year, huge quantity of plastic wastes are being generated throughout the world. Disposal of these wastes in landfills creates serious environmental problems. The study on the utilization of plastic waste with clayey soil and with clay–fly ash mixture is limited. This paper presents the effect of plastic waste on the strength of clayey soil and clay–fly ash mixture, and the results are presented in terms of compressive strength, shear strength, and California bearing ratio (CBR). The different percentage of plastic waste (0.5%, 1.0%, 1.5%, and 2.0% by dry weight) and 10% fly ash by dry weight were mixed into the clayey soil. From the experimental results, incorporation of the plastic waste into the clayey soil and clay fly ash mixture gives a decreasing trend of maximum dry density and increasing trend of optimum moisture content. The addition of 1% plastic waste in clayey soil and clay–fly ash mixture increases the unconfined compressive strength (UCS), internal friction angle and in the CBR value under soaked and unsoaked condition. The present study will help in consuming the considerable quantity of waste plastic, thereby reducing the environmental threat.

Black cotton (BC) soils are inorganic clays of medium to high compressibility and form a major soil group in India. They are characterized by high shrinkage and swelling properties. Due to its peculiar characteristics, it forms a very poor foundation material for road construction. R&D efforts have been made to improve the strength characteristics of BC soil by many researchers. Soil replacement with buffer layer remains is a very common technique but still there is no reliable formula or technique is available to estimate the required replacement depth. Therefore, this paper intends to optimize the replacement thickness of buffer layer required to maintain the heave within the acceptable range and to evaluate efficacy and impact of placing a very thin layer of stabilized BC soil (BC soil + 3% lime) or cohesive non-swelling material (Murram/Murram + 3%Lime) or impermeable geomembrane between the buffer layer and BC soil using laboratory studies.

Weak soil is very problematic soil, and it has shrinking and swelling properties which can damage the structure constructed over it. Waste material on the daily basis is likely to become a problem for disposal. It creates environmental contamination and health risks. Hence, the utilization of waste material in the stabilization of weak soil effectively minimizes the negative effect on the environment. In this paper, the aim is to stabilize the weak soil using combinations of waste material. The waste materials used for the study are stone dust and solid waste from silica sand beneficiation plant. Stone dust is coming from polishing, cutting of stones, and cruising process during rock quarrying activities. Solid waste from silica sand beneficiation plant is a granular material, and it contains quartz and very less amount of clay, coal, and other minerals. Stone dust and solid waste from silica sand beneficiation plant are combined in different proportion with weak soil. Geotechnical properties of weak soil individually and in combination with varying proportion were investigated. The standard Proctor test and the California bearing ratio test have been performed. The results of these tests resemble that the combination of stone dust and solid waste from silica sand beneficiation plant is very effective for stabilizing the weak soil.

Stabilization is an established remediation for contaminated soils and for hazardous wastes. The main objective of this work is to study the behaviour of geotechnical characteristics of the tailing materials (TMs) which are stabilized using cement, lime and fly ash in different proportions and to propose an optimum percentage of blending agents. The geotechnical parameters like specific gravity, optimum moisture content, maximum dry density, California bearing ratio, unconfined compressive strength of mine tailing alone and mine tailing treated with pozzolanic reagents like cement, lime and fly ash in different proportions was studied. All the tests were performed as per the IS specifications and codal reference. The stabilized tailing material achieved considerable strength upto 1801.17 kN/m2 at 28 days of curing period, thus making the stabilized TMs suitable for bulk fill construction. Fly ash can potentially stabilize the TMs treated along with cement and lime to reduce the construction cost.

Ground granulated blast furnace slag (GGBS)-based geopolymer is an effective binder that attains high strength by curing at different temperatures. This paper presents the experimental results obtained from tests conducted on alkali-activated GGBS lateritic soil blends. Unconfined compressive strengths were determined for alkali-activated blends to which GGBS was added in varying quantities (5, 10, 15, 20, and 25% by dry weight of soil). UCS samples were tested at different curing temperatures. The processing temperature is found to influence the development of compressive strength. Further, samples were conducted for SEM analysis to know the structural development. Test results indicated that unconfined compressive strength increased with increasing GGBS content and curing period. This study illustrated that GGBS-based geopolymer can be an effective soil stabilizer for lateritic soils.

This paper presents a case study of the stabilization of expansive soil using lime sand piles. The technique was used in the construction of flexible pavement on expansive soil of Dr. MGR Bus terminus of the Salem Municipal Corporation in Tamil Nadu, India. The soil profile at the site was a layered system with the first layer filled with earth from Salem quarry. The second layer is silty clay followed by silty sand in only certain locations. The fourth layer was gravelly sand followed by weathered rock. The filled up earth in this site is non-plastic silty sand. The silty clay layer possesses high plasticity which will undergo volume change due to moisture content. This clay was black in color and indicated the presence of organic content between 20 and 30%. This kind of soil is always referred to as a problematic soil and is locally known as black cotton soil. Generally, any new structure is to be laid on the surface of original ground level but as in this site the original ground is a problematic soil and would always cause the failure of lightly loaded structure it required stabilization. The stabilization of second silty layer which required improvement in strength and improvement of reduction in volume change characteristics was achieved using lime stabilization. Out of many different lime stabilization techniques, lime sand pile was preferred for the site because of its proven performance, durability, constructability, and low cost. The stabilization using lime sand piles was achieved methodically. After curing the site for maximum of 30 days, flexible pavement was laid on the prepared ground. The design field CBR value of 15% was ensured after ground improvement before laying the pavement. The selection of material and construction of pavement were as per MORTH revision 5 “Specification for road and bridge works,” 2013, and design of pavement was as per IRC 37-2012.

Urease enzyme derived from the agricultural source precipitates calcium carbonate (CaCO3) from an aqueous solution of urea and calcium chloride via urea hydrolysis, which strengthens the soil by cementing and bridging soil particles. Different combinations of urea, calcium chloride and urease enzyme will have varying influence on the mechanical properties of the treated soil. This work aims to analyse the efficiency of enzyme-induced carbonate precipitation (EICP) on three different soil types (silty sands, clayey sand and silt). The optimum combination of urea, calcium chloride and urease enzyme is studied by mixing different concentrations, and the combination of these reagents in beakers and optimum precipitation is evaluated by gravimetrically measuring the amount of CaCO3 precipitated. The observed optimum combination is applied to three different soil types, and the improvement in the compressive strength of the soils specimens due to carbonate precipitation is observed by conducting unconfined compressive strength (UCS) tests. The precipitation experiments in the beakers reveal that the increase of the urea-CaCl2 concentration may inhibit the activity of urease, thereby precipitating lower amount of CaCO3. The results of the UCS tests show that the technique of enzymatic calcium carbonate precipitation improves the shear strength of the all the three types of soils, however, more strength gain was obtained in the case of clayey sand. The microstructural observations with the help of scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) tests verify the existence of calcite in the pores of compacted soil specimens.

India, being a peninsular country, has a long coastline and also been the habitat for a good amount of the population. On the other hand, the accumulation of various waste materials is now becoming a major concern to the environmentalists. New methods and new materials of construction have been continuously explored, and hence, in order to achieve both the needs of improving the soft marine clays and also to make use of the industrial wastes in the best possible way. The present study was done by partially replacing the marine clay with palm oil fuel ash (POFA), a relative new agro-waste and further adding it with lime and discrete reinforcing waste plastic inclusions (DRWPI). The results obtained revealed that the penetration and the strength characteristics of POFA improved for modified soft marine clay and are further improved with an optimum percentage of lime and optimum dosage of discrete waste fiber.

The xanthan gum biopolymer is mixed with expansive soil in different proportions such as 0, 0.2, 0.5, 0.8 and 1.0% by weight of the dry soil mass. The plasticity, compaction and strength characteristics are studied by performing the liquid limit, plastic limit, shrinkage limit, linear shrinkage and unconfined compressive strength tests. The optimum moisture content (OMC) and maximum dry density (MDD) of different mixes are determined by performing light and heavy compaction tests. The UCS value of specimens compacted to MDD at OMC corresponding to heavy compaction effort is evaluated at curing periods of 0, 3, 7 and 28 days. With an addition of xanthan gum, the liquid limit and plastic limit values increase substantially, however, the plasticity index is found to decrease. An improvement in strength of the magnitude of 93% is observed at 1% xanthan gum. Finally, scanning electron microscope images depict the reason behind the UCS strength increment.

In India, nearly 23% of land surface is covered with expansive soil. The problems associated with such soils caused the tremendous cost to the project if proper geo-technical investigation and stabilization are not done. To prevent the failures of structures like foundations, retaining structures, slopes, lightweight structures, pavements, the improvement of swelling soil should be done which is economical and environmentally friendly. The use of lignin-based organic polymer which is a by-product of pulp industry is a sustainable and viable technique. An assessment of lignosulfonate as a stabilizer is necessary, and thus in the current study, the compaction, plasticity, swelling, and strength characteristics of expansive soil are checked with addition of sodium lignosulfonate in percentages varying from 0 to 12. The plasticity characteristics of expansive soil are seen to be improved significantly. However, a marginal increase in strength occurs with the addition of lignosulfonate which further increases with curing period.

The stability of lightweight structure such as pavement is majorly influenced by subgrade soil. Expansive soil has high strength but it becomes problematic in the presence of water; it expands and shrinks during wet and dry conditions, respectively, because of its mineralogical composition. To minimize the cost of stabilization and to improve the load bearing capacity of such soil, these are the major concerns for problematic high plastic expansive subgrades. In this study, the experiment has been carried out to examine the feasibility of waste materials bagasse ash and ground granulated blast furnace slag as a soil stabilizer to improve subgrade. Consistency limits, California bearing ratio, unconfined compressive strength, and swelling pressure were studied to check the effect on high plastic clay when treated with waste material. The experimental results showed the improvement in soaked California bearing ratio and reduction in the swell–shrink behavior of soil when combined with bagasse ash and ground granulated blast furnace slag. Hence, these wastes can be used as a pozzolanic material to stabilize the high plastic expansive clay of the pavement subgrade.

Being a challenge to deal with structural foundations in soft clays, several techniques were promulgated across the world. This paper presents the load–settlement behaviour of soft clay provided with soil-cement columns in test tanks. Based on the experimental work performed on 10% cement mixed single clay column resting on hard stratum simulating end bearing condition, it is revealed that load-carrying capacity of clay bed increased by 3–4 times that of virgin clay. Also, the load-carrying capacity of clay bed increased 5–7 times that of virgin clay with the group of three columns arranged in triangular pattern with centre to centre spacing of two times the diameter of column. Group capacity of soil-cement column is 1.5–2 times of single column which is not multiplicative of single column. UCC tests were carried to find out the optimum fibre content by varying the fibre content from 0 to 3%. From UCC test, it is observed that 2% fibre content is suitable for the present study considering the strength improvement and ease of mixing. It is observed from the tests that with the addition of 2% fibre in soil-cement column, load-carrying capacity of clay bed increased by 5.5–7.5 times when tested with group of columns. There is 10–20% increase in ultimate load-carrying capacity of soil-cement column after addition of fibre and the mode of failure of columns changed from brittle to bulging failure.

Being a challenge to deal with structural foundations in soft clays, several techniques were promulgated across the world. This paper presents the load–settlement behavior of soft clay provided with soil–cement columns in test tanks. This study revealed that the load-carrying capacity of clay bed with soil–cement columns increases with increasing initial clay consistency and it is increased by about 3.5 times when the consistency is increased from 0.1 to 0.5. The threshold cement content is found to be 15% for the floating soil–cement columns and a 25% replacement of cement with fly ash has shown a slight increase of about 1.15 times that of the capacity attained with cement alone. SEM and EDAX results support that there is an improvement of surrounding clay bed due to diffusion of calcium ions from the soil–cement columns.

This study focuses on the productive utilization of discarded and used polymeric fabric bags in the construction of rural roads. The paper describes the analysis of soil–plastic fiber waste composite. The materials used are locally available silty sand from NIT Jamshedpur campus and waste discarded cement bags. Experimental tests have been conducted to determine engineering properties of soil as envisaged by Indian standard codes. Apart from this, a series of California bearing ratio tests have been done on reinforced soil and un-reinforced soil under soaked and unsoaked conditions. Reinforcement of soil has been done in two different ways: small pieces mixed with soil sample and inserting layers of fabric in the specimen. Comparative study has been done to determine the optimum value of CBR for ascertaining the most effective soil–fiber mix. To evaluate the behavior of un-reinforced and reinforced soil subgrade, PLAXIS-2D software is used.

Expansive soil which is found in several parts of India possesses high swelling and shrinkage properties. The volume change and uplift pressure generated in these soil deposits cause severe damage to the lightweight structures and pavements. In order to mitigate the problems associated with expansive soils, it is necessary to stabilize this soil. Among all the stabilization techniques, lime treatment is one of the best suitable methods for expansive soils. In the present study, lime stabilization technique is used to improve the engineering properties of black cotton soil including the resilient modulus value, which is important for mechanistic flexible pavement design. Optimum amount of lime required for stabilization was determined using Atterberg’s limits. Considerable increment was observed in unconfined compressive strength values and California bearing ratio values of black cotton soil stabilized with 6% lime. Repeated load triaxial tests under different confining pressures and deviatoric stress levels were conducted on the treated samples in order to determine the resilient modulus. The effect of curing period and moisture content on the resilient modulus was investigated. In order to study the durability of lime stabilized clayey subgrade soil, the effect of wetting and drying cycles on the engineering properties of the treated material was examined. The results show that the strength and stiffness characteristics of lime treated clay have considerably reduced after five wetting and drying cycles.

The characteristics of subgrade soil play a vital role in designing the pavement structure so that the pavement has required support from the bottom layer. During adverse weather conditions and higher traffic loads moving on any pavement, it should be able to withstand the impact and perform well for longer duration. Load is transmitted from pavement to the subgrade layer and distributed evenly through the soil particles. All types of soil are not capable of handling such impacts by their own and needs additional stabilization processes. Several stabilization processes are available in which the best one has to be taken into consideration. Fibers such as coconut coir are important in giving extra stability to the soil particles. Cement is well-known material in construction sector along with aggregates. Lateritic soil is available abundantly in coastal areas of southern parts of India which has porous structure and demands stabilization when the intended purpose is specific and requires higher strength and durability. In this study, coconut coir along with cement and aggregate are taken as stabilization materials to stabilize lateritic soil. Initially, basic properties of soil like plastic limit, liquid limit and plasticity index are determined. Grain size analysis is done and modified Proctor test is conducted to determine the optimum moisture content (OMC) and maximum dry density (MDD) of the soil. Unconfined compression test (UCS), California bearing ratio test (CBR), flexural fatigue analysis, durability properties with respect to wet-dry cycles and freeze–thaw cycles are evaluated for untreated and treated soil specimen. As per UCS values, cement can be taken at an optimum dosage of 6%. The coir fibers from natural husk of coconut and aggregates of 10 mm below size were added to the soil–cement mixes and an optimum dosage of coir and aggregate is determined. The study showed positive results in terms of CBR values of cement-aggregate treated soil.

Estimation of swell pressure prior to any construction activity in expansive soil is an indispensable step. The purpose of this paper is to check the efficacy of mechanical and chemical means in restraining the swelling of expansive soil through a series of swell consolidation tests by installing geostrip reinforced fly ash-lime columns in compacted soil specimen. To begin with, several swell consolidation tests were performed in conventional oedometer cell to examine the influence of dry unit weight, initial water content, and sand drains on swell parameters of compacted soil specimen. Later, tests were conducted on custom made large-scale swell consolidation apparatus to check the efficacy of the proposed treatment method. The study reveals reinforcing the soil specimen with seven geostrip reinforced fly ash-lime columns at three times the diameter spacing results in minimal swelling. The proposed method can turn out to be an in situ method in order to restrain swelling of expansive subgrade.

Conventional methods for strengthening the subgrade soil are time-consuming and are not economically feasible. In this paper, studies were performed to understand the effect of bio-enzyme, bio-enzyme–fly ash mixture and bio-enzyme–lime mixture on kaolinite clay collected from Thonnakkal, Thiruvananthapuram District, Kerala, India. In this study, a popular bio-enzyme known as terrazyme is used as stabilizer. Unconfined compressive strength tests and California bearing ratio tests were conducted on pure soil and soil mixed with terrazyme and its combinations with lime and fly ash. From the study, it was observed that there is a considerable increase in UCC and CBR value for the treated soil compared to untreated one. The optimum dosage of terrazyme obtained was 0.1 ml/kg and that of lime was 8%. With the increase in fly ash content on soil stabilized with terrazyme, an improvement in UCC value was observed, whereas there was not much improvement in CBR value up to 30% addition of fly ash compared to soil stabilized with terrazyme alone. Hence, the combination of terrazyme and lime is an effective method for stabilizing kaolinitic subgrade soil.

India is an agricultural country producing plenty of rice husks which is mostly used as fuel in the boilers for processing paddy, producing energy through direct combustion or by gasification. In India, about 122 million tonnes of paddy is produced annually and about 20–22% rice husk is generated from paddy and 20–25% of the total husk becomes as rice husk ash. After burning, each ton of paddy produces about 40 kg of rice husk ash. The rice husk creates great environment threat causing severe damage to the land and the atmosphere. Therefore, in this study, rice husk ash was used to stabilize the laterite soil which covers large area in India and elsewhere. Laterite soil was collected from Kodakani, Shimoga district, and was stabilized with varying percentages of rice husk ash, geopolymer, and rice husk-based geopolymer. A series of unconfined compressive strength tests was carried out on the above-specified sample conditions with varied dosages of the stabilizer and curing period. Based on the test results, it was found that the strength of the soil is increased by 2, 3, and 5 times, respectively, with geopolymer, RHA and RHA-based geopolymer as stabilizer with a curing period of 7 days. RHA-based geopolymer can be effectively used as a stabilizer for subgrade stabilization and this technique leads to an eco-friendly sustainable pavement.

A detailed numerical analysis has been performed on a unit cell stone column by varying parameters such as shear strength of clay, angle of internal friction of the column material, slenderness ratio (L/d) of the column, area replacement ratio, and the modular ratio, Poisson's ratio of clay and column material. A parametric study is conducted for floating stone column by using the finite element package PLAXIS. A drained analysis was performed using Mohr–Coulomb criterion for both the materials. Validation was done by taking experimental data for a single unit cell stone column. From the analysis, it is observed that the bearing stress increases with increase in the aspect ratio (L/d) up to a particular range beyond which there is negligible change in the bearing capacity. Bulging is the main cause of failure of a single stone column when loaded alone. An increase in the area ratio caused an increase in the bearing value of the stone column-reinforced soil due to higher relative stiffness. The most influential parameters for the design of stone column-reinforced soil are the angle of internal friction of the column material and area replacement ratio whereas the cohesion of surrounding material, slenderness ratio and Poisson's ratio contribute to a lesser magnitude.

The type and quantity of effluents and wastewater disposed of into highly polluted Bellandur and Kengeri lakes are different because of the nature and type of zone under the purview of two lakes. Study on the concentration of heavy metals in the lakebed sediments around both the lakes helps to identify the source of contamination and such a comparative study is almost non-existent. The present study comparatively assesses heavy metal contamination of surface soil around these lakes through grab sampling along with physical properties of soil to identify the presence of organic contents. Three locations of Kengeri Lake and four locations of Bellandur Lake were selected depending on the waste discharge locations. Samples of both the lakebed sediments indicate the presence of organic content. Both the lake sediments indicated heavy dosage of iron and chromium, in addition to nickel and zinc beyond the prescribed limits of FAO and WHO standards. The presence of mercury is also confirmed in both the contaminated lakebed sediments of both the lakes. However, the concentration of Fe is more compared to all heavy metals and the concentration of other heavy metals was found to be lower than permissible limits set by FAO as there was no defined source of heavy metal origin.

Contamination of soils due to caustic alkali has significant effect on the volume change behavior of soils, which in turn can have direct bearing on their geotechnical properties and can affect the stability of structures built on them. The existing literature strongly highlights the fact that failure of structures along with alterations in mineralogy and morphology occurs due to NaOH contamination. Efforts were made to simulate long-term effects of NaOH on mineralogical and morphological alteration by varying the experimental conditions in laboratory, so that preventive measures can be taken at a much faster rate. On the other hand, KOH is another strong alkali which is extensively used for commercial purposes. However, no studies were reported in literature to highlight the adverse effects of KOH. Thus, to understand the long-term effect of KOH on mineralogical and morphological alterations, a preliminary investigation is carried out in the present study by considering different experimental conditions (field contamination, long-term interactions, and temperature effects at 4 N KOH). Two types of kaolinitic clays, namely red earth and kaolin with varying mineral content were selected for the study. Micro-level investigations (XRD and SEM) have been carried out to noticeably understand impact of varying experimental conditions at particle-level interaction. Test results indicated that neogenic formations varied with type of experimental conditions along with variation in the morphology of soils. Further, it is observed that, long-term effects of KOH can be simulated within short period of time by conducting the experiments at elevated temperature.

This study investigates the characteristics of natural zeolite amended kaolin clay, to be used as an impervious liner in the landfill. A landfill liner or composite liner is a low permeable barrier, which is laid down under engineered landfill sites. The ingredient zeolite was chosen due to its high absorption capacity for heavy metals as well as pozzolanic properties. A B/Z ratio of 0.5 was found to be an ideal landfill liner material considering its low hydraulic conductivity. Hydraulic conductivity tests on zeolite-embedded clay liner systems show that the hydraulic conductivity of all the mixtures prepared with varying proportions of zeolite, meet the common regulatory requirements. The micro-porous structure of natural zeolite results in a very high absorption rate, which in turn reduces the hydraulic conductivity. In order to estimate the optimum dosage of zeolite to the clay mixture, an extensive study on the strength and compaction characteristics was done.