Proceedings of the 8th International Congress on Environmental Geotechnics Volume 3

This paper presents the first study on CO2-EOR potential of the LH11-1 oilfield offshore Guangdong Province, China. LH11-1 field is a reef heavy oilfield (16–23° API), and overall development efficiency is not ideal. In this study, the CO2 flooding potential in LH11-1 field was evaluated through a compositional simulation using the Petrel and CMG-GEM tools. A detailed fluid characterization was performed to accurately represent the reservoir fluid. 1D slim tube and core flood simulations were interpreted to understand the physical mechanisms of oil recovery. A reservoir geological (structure, facies and fluids) model was constructed in Petrel system and the model was calibrated using manual and assisted history matching methods. The natural depletion and continuous CO2 injection scenarios were simulated by GEM. Results indicate that the minimum miscibility pressure (MMP) of crude oil in Liuhua field is approximately 20 MPa. Therefore, the mechanism of oil recovery by CO2 EOR in Liuhua field should be suitable for immiscible CO2 flooding. The continuous CO2 injection would recover an incremental 7% of OOIP in Liuhua field, and the CO2 storage efficiency is relatively high with more than 95.5% of injection CO2 has been stored in the reservoir which indicate an important significance for CO2-EOR and storage potential in offshore carbonate oilfield.

In this paper, two intact cylindrical sandstones were bonded with the fiber Bragg grating sensors for laboratory experimental studying the injection and migration process of carbon dioxide (CO2) under varying temperature and sequestration pressures. A series of core flooding experiments were conducted under undrained conditions with different confining and pore pressures without changing the effective confining pressure. As a result, the strain responses of CO2 in three different states after injecting into specimen rose with the increase in the pore pressure. And the dynamic strain responses of supercritical CO2 (scCO2) was slightly higher than that of liquid CO2 due to the character of sCO2 and the effect of temperature. The initial time differences of axial strain measurement along the three gratings on a single fiber can precisely indicate the migration fronts of scCO2 plume. The difference in strain response time of the three gratings is in a descending order of liquid CO2, scCO2, and gaseous CO2.

Gas hydrate is encountered in reservoir rock at low temperature and high pressure circumstances. Exploitation gas hydrate commonly invokes to heating or reducing pressure, leading the solid phase transited into liquid phase. With phase transition, the heat is transferred not only in the form of specific heat but also in the form of latent heat. Moreover, the melting point is not constant but depends on the pore size for the phase transition in porous solid. Considering these characteristics, a governing equation of heat transfer with phase transition is established using the equivalent heat capacity method. The equivalent heat capacity is assessed by the pore size distribution curve. Heating tests are conducted and simulated using the model established. The process of heat transfer and its dependences on temperature are discussed.

Clay rock is being investigated in many countries as a potential host rock for nuclear waste repositories. Due to the state of over-consolidation and water saturation, characterisation of undisturbed rock with regard to its hydraulic and mechanical properties is a big challenge. Increased complexity is caused by temperature change in the repository of high-level waste. In situ measurement of single component, e.g. rock permeability, was conducted in the Mont Terri Rock Laboratory (CH) and the French Underground Research Laboratory Bure. Several so-called heater experiments are being carried out at different scale. The measured data including temperature, humidity, pore pressure, and deformation in various boreholes shows strong coupling effects. For interpretation of the experimental data, a numerical 3D code OpenGeoSys (OGS) was developed taking into account the strongly coupled thermal, hydraulic and mechanical processes. Because of the significant dependency of the thermal conductivity on the water saturation, the determination of the saturation state, which is again controlled by hydraulic permeability, is therefore important. The evaluated permeability from packer tests can be validated using numerical modelling. The state-dependency on the pressure, saturation and temperature is discussed.

Power-to-Gas (PtG) is a chemical energy storage technology that converts electrical energy into a high-energy density combustible gas. This technology alleviates the contradiction between power supply and demand due to the intermittent electricity production from environment-friendly renewable energy. Hydrogen (H2), produced by electrolysis, can be used to produce synthetic methane (CH4) by reacting with carbon dioxide (CO2) that is captured from carbon emission sources. Subsurface gas storage is one of the most important processes in a PtG system. However, nearly a half of the total stored gas is used as cushion gas to maintain a suitable reservoir pressure, indicating large amounts of CH4 might be wasted and trapped in geological formations. Based on a PtG system, CO2 can be a promising choice as a cushion gas due to its high effective compressibility near its critical conditions. In this paper, a numerical model is established based on the theory of the fluid flow and molecular diffusion to study the role of CO2 as a cushion gas in increasing the gas storage capacity. The accuracy of this model is verified by comparing with that of Curtis M. Oldenburg. However, because of the declining purity of recovered gas induced by the convection and diffusion of two kinds of gases in the same reservoir. The influences of reservoir thickness on the distribution of mixed region are discussed. The results show that thicker reservoir would be a better choice for the geological storage of CH4 with CO2 as a cushion gas.

This paper examines the potential for soil carbon sequestration in the oil palm plantations of Malaysia. Due to the rising awareness of climate change and its negative influence on the environment, the contributions of both human and natural processes towards climate change are being widely studied. In Malaysia, peatlands are used as oil palm plantations and store large amounts of soil organic carbon, which if not maintained could have a serious and negative influence on the environment if allowed to escape to the atmosphere as carbon dioxide. The escape of major nutrients including carbon (as carbon dioxide) and nitrogen (as nitrous oxide) as a result of land use change has seriously degraded the peatlands and resulted in a net release of greenhouse gases. Measures to promote carbon sequestration in soil address the soil degradation by preserving and increasing the soil organic carbon pool. This paper addresses the important topics of peatland degradation and the associated carbon sequestration potential by considering: (i) the impact of peatland conversion on soil properties, (ii) relevant factors influencing the soil organic carbon, (iii) the application of biofertiliser and waste biomass to restore depleted soil organic carbon (SOC) pools, (iv) the economic valuation of soil carbon sequestration, and (v) the contribution policy and management practices.

Gaomiaozi (GMZ) bentonite has been confirmed as the buffer material in the Chinese disposal program of high-level waste. To investigate the thermal volumetric behaviour of compacted GMZ bentonite, several stress paths were performed on the specimens presaturated with NaCl solutions to obtain the scheduled OCR and verticle stress. Then multi-step heating-cooling tests were conducted. Test results show that thermal volume change strongly depends on the vertical pressure, OCR and concentration of the presaturation solution. For the specimens presaturation with deionized water, heating induces contraction below the transition temperature and followed by dilation at normal consolidation state, while only induces dilation at overconsolidation state. A larger vertical pressure leads to a larger transition temperature. For the specimens presaturated with NaCl solutions, heating basically induces dilation. The specimens with large vertical pressure accumulate a total contraction after a thermal cycle. For a given concentration and verticle pressure, the specimens cumulate a larger irreversible dilation at higher OCR. The influence of salt solution is non-monotonic. The dilute solution and high saline solution significantly promote the thermal expansion of saturated GMZ bentonite during heating.

Accurate assessment on the subsurface geothermal resources remains challengeable from the scientific point of view. The parameter uncertainties and incomplete knowledge of initial conditions for the subsurface environment make the prediction of subsurface temperature based on the thermal models present a strong uncertainty. Forward modeling of the temperature at depth may be highly dependent on the radiogenic heat production of the geological layers which are affected by the concentration of uranium, thorium and potassium, and density. It shows that the average concentration of uranium, thorium and potassium is 1.78 ppm, 6.01 ppm and 2.64%, with the standard deviation error of 3.57, 7.27 and 1.85 respectively for the selected region in southwestern Quebec. The sequential gaussian simulation (SGS) method was used to obtain the spatial distribution of the radiogenic elements in a selected region with the size of 35 km × 80 km. Using the density values for specific rocks, the distribution of the radiogenic heat production over the study area is also simulated. Results show that the difference between the minimum and the maximum radiogenic heat production value is 30% when considering the difference in density.

Nowadays, the cement industry is under pressure to reduce the carbon footprint and energy demands of cement-based construction materials. Carbonation technology is a process that the Ca-/Mg- alkaline materials can react with CO2 to form stable carbonates, thus it is regarded as a potentially attractive technology of CO2 sequestration, including mineral carbonation, cement/concrete carbonation, and carbonation of reactive MgO-stabilized material. This paper investigates the CO2 uptake of reactive MgO-stabilized soils after accelerated carbonation under the high CO2 concentration (99.9%). The CO2 uptake is examined through the HNO3 acidification test and thermal analysis technology. Key results revealed that the carbonation of reactive MgO-stabilized soils could consume large amounts of water and CO2 to produce expansive carbonation products. The CO2 uptake is observably affected by several factors such as MgO content, water content, carbonation time and CO2 pressure. After the several hour’s carbonation (about 3–6 h), the CO2 uptake can basically achieves about 0.8–1.0 times matter quantity of reactive MgO.

Controlled disposal sites generally rely on impermeable barrier layers to prevent groundwater contamination. Because bentonite has low hydraulic conductivity and high swelling pressures in the presence of water, soil-bentonite mixtures are commonly used with geomembrane to construct hydraulic barriers. If inexpensive materials could be used instead, the potential cost reduction is dramatic. Sedimentary rock is widely distributed in Japan, and it is common for such rock to be excavated from the disposal site itself. This study evaluated the water-shielding performance of bentonite mixtures made with friable Neocene mudstone and commercially available graded sand. The hydraulic conductivity of the friable Neocene mudstone mixture compared favourably with that of the purchased sand mixture, even at half of the standard bentonite mixing ratio (5%). The results also confirmed our hypothesis that the friability of the mudstone could be used practically to improve mixture performance. This study demonstrated the fundamental properties of an efficient construction method that utilised roller compaction to ensure an effective seal. Construction of hydraulic barrier layers using a method that takes advantage of the friability of in situ excavated sedimentary rock, without adjusting its grain size, has the potential to greatly lower construction costs.

Geologic carbon storage is usually viewed as injecting, or rather as storing, CO2 in supercritical phase. This view is very demanding on the caprock, which must display: (1) high entry pressure to prevent an upward escape of CO2 due to density effects; (2) low permeability to minimize the upwards displacement of the brine induced by the injected CO2; and (3) high strength to ensure that the fluid pressure buildup does not lead to caprock failure. We analyze the possibility of injecting dissolved CO2 and, possibly, other soluble gases for cases when the above requirements are not met. The approach consists of extracting saline water from one portion of the aquifer, reinjecting it in another portion of the aquifer and dissolving CO2 downhole. Mixing at depth reduces the pressure required for brine and CO2 injection at the surface. We find that dissolved CO2 injection is feasible and eliminates the risk of CO2 leakage because brine with dissolved CO2 is denser than brine without dissolved CO2 and thus, it sinks towards the bottom of the saline aquifer.

In geological disposal of high level radioactive waste, it is essential to start considering consolidation accompanying cementation, taking into consideration high earth pressure and solution of groundwater. For engineering application of natural analogue, the authors thought consolidated buffer material will have similar physical properties to bentonite ore. In this study, we aimed to quantitatively evaluate the influence of cementation on swelling properties. In order to achieve this aim, we focused on swelling pressure and swelling strain of bentonite, using two kinds of bentonite ore whose generation dates are different respectively. As a result, swelling pressure was decreased by approximately one order of magnitude due to the influence of cementation. In addition, the swelling strain of younger bentonite ore did not decline, but those of older bentonite ore declined about half of original whether consolidation was retained or not. Therefore, there is a possibility that the swelling deformation of buffer will decline as cementation gets stronger over the course of time.

The 2011 off the Pacific coast of Tohoku earthquake affected Japan, wreaking severe damage to the Nuclear Power Station in Fukushima. Heavy Bentonite-Based Slurry has been examined the use as filling-type water sealing materials in damaged nuclear reactors. This research was conducted to investigate and define the water stopping capabilities of Heavy Bentonite-Based Slurry for controlling the nuclear accidents. In this study, the falling head permeability tests were conducted to quantify it. The results show that the hydraulic conductivity decreased from k = 10−8 m/s to k = 10−10 m/s with sedimentation of specimens.

This paper presents a numerical investigation of non-isothermal effects during high pressure carbon dioxide injection in deep coalbeds. Whilst coalbeds provide storage security owing to the large carbon dioxide adsorption capacity of coal, high pressure gas injection may disturb the temperature of the coalbed and influence flow behaviour. A numerical model of coupled heat transfer and gas flow incorporating the Joule-Thomson cooling effect is presented in this paper to study the temperature change induced by carbon dioxide injection. The numerical model is firstly compared with existing results in the literature for verification, and then applied to simulate changes in temperature and pressure of a coalbed during gas flow. Results of predicted temperature and pressure under different injection temperatures show that a zone of cooling occurs when gas injection under the same and low temperature than that of coalbeds, leading to a further drop of pressure in this zone. Although injection under higher temperature can suppress cooling effect, the time for pressure to reach steady state increases.

Geologic carbon storage (GCS) is the process to store large amount of carbon dioxide (CO2) captured from stationary CO2 emission sources in deep subsurface for permanent storage. GCS is widely recognized as a promising strategy to reduce emissions of greenhouse gas (GHG). However, the potential for mobilization of radioactive uranium (U) from U-bearing minerals in deep subsurface due to CO2 injection remains a concern. In this study, A TOUGHREACT model was developed to investigate the potential of U-bearing mineral (UO2) dissolution in a hypothetical deep CO2 storage reservoir. An average reservoir temperature of 67.5 °C, an average reservoir pressure of 18.7 MPa and a CO2 injection rate of 0.1 MMT/year (3.17 kg/s) were used in this study. Numerical simulation results show that HCO3– concentration increased as a result of CO2 dissolution after injection of CO2, which led to release of [UO2(CO3)3]4–. However, released [UO2(CO3)3]4– did not migrate toward the shallow aquifer through leakage pathways specified in the model, while CO2 could migrate upward through the leakage pathways. In summary, the area of uranium contamination is restrained in deep subsurface and notable migration of uranium to shallow aquifer caused by CO2 injection does not occur.

This work emphasizes on the alteration in pile-soil interaction in case of geothermal energy piles during thermal cycle. The geothermal energy piles are investigated numerically using finite element software Abaqus. To simulate the soil mechanical and thermal response, two user defined material subroutines are used for the soil surrounding the piles. The behaviour of soil is reproduced using CASM; a soil constitutive model which is based on the concepts of critical state soil mechanics. To investigate the additional strains induced in the piles due to the thermal load, parametric analyses are carried out considering the effect of (i) different pile end restraints, (ii) relative densities of the soil, (iii) pile dimensions and (iv) lateral earth pressure coefficient. The analysis results indicate that the axial and radial strains are induced in the pile due to pile expansion during thermal loading. The increase in lateral earth pressure coefficient at interface of pile and soil can be correlated to the thermally induced radial strains. Moreover, the pile response to the thermal cycle can be considered to the governed by soil stiffness and the magnitude of thermal load applied on the pile. Analyses are also performed to investigate the influence of thermal parameters of soil and thermal load on the soil earth pressure coefficient at interface of pile and soil. The lateral earth pressure coefficient increases following the increase in magnitude of thermal load, however the effect of thermal conductivity of soil is not significant.

Geological CO2 storage is viewed as a potentially viable strategy for reducing greenhouse gas emissions from point sources such as power plants, fertilizer production facilities and bio-ethanol fermenters, etc. However, for this strategy to be successful at its aim of reducing greenhouse gas emissions, a monitoring strategy is required to ensure that the CO2 remains in the intended storage reservoir and does not leak. Furthermore, monitoring is required in most jurisdictions around the water as a permitting condition. It is also necessary to provide assurance to the community and other stakeholders that the CO2 being stored is not affecting the environment. There are many subsurface monitoring techniques including pressure monitoring, 4D seismic, etc.; however, these must be complemented by surface monitoring approaches. Based on our experience monitoring fugitive methane emissions for the gas industry, we have found that mobile surveys using vehicles containing real-time spectroscopic analysis equipment that sample gases from the atmosphere can be used to identify potential leaks. Similarly, this approach could be used for monitoring of the nearby region surrounding a CCS storage site. However, this strategy suffers from several disadvantages such as limited land access, poor wind conditions, variation in leak rate over time and interference from other sources (e.g. agriculture, vehicles and industry) that might preclude the detection of an actual CO2 leak. Furthermore, this strategy only provides a snapshot of the leak characteristics at a particular time which may or may not be indicative of long term behavior. To complement this approach, fixed site monitoring can be utilized; however, current fixed-site monitoring approaches can be quite expensive. This can lead to a situation where a very limited number of fixed monitoring sites are implemented. Furthermore, the site selected for the fixed monitoring station may be biased or not indicative of the actual overall emissions in the field. To rectify this, a high density of low-cost and reliable sensors is required. This approach would meet regulatory requirements, provide assurance to the community and provide actionable information in the event of a substantial leak. In this paper, we will show that the combined approach of fixed-site and mobile monitoring can each address many of the disadvantages of the other.

In this study, laboratory-scale Permeable reactive barrier (PRB) reactors were designed with the mixture of non-valent iron, active carbon, hydrated lime and quartz sands as reaction media. The feasibility and effectiveness of treating uranium mine pit water by PRB were tested under 3 different proportions of media through dynamic simulation tests, which came out the optimal proportion of contaminants. The result indicated that the remediation effect of reactor B was the best, whose average removal rate to U was up to 99%, as well as the average value of total α, total β, and 226Ra in effluent were 0.78 Bq/L, 3.52 Bq/L and 0.47 Bq/L respectively. The quality of effluent met the requirement of relevant standards, which indicated that the PRB technology is a feasible method for the treatment of uranium mine pit water.

The reflection coefficient, also known as the chemico-osmotic efficiency coefficient, is commonly measured in order to quantify the ability of clays to act as semipermeable porous media. However, it should be pointed out that this parameter is not a soil property, but it rather represents the soil response to hydraulic and chemical stresses, so that it depends on which test is used and may vary significantly when the clay void ratio, the specimen preparation method and/or the chemical composition of the pore solution are changed. A physically sound model is used to assess the flow mechanisms that govern the experimental determination of this parameter, considering also the effects of clay fabric.

A numerical model coupling of water flow and electrical transport in a deformable porous medium is developed to simulate the electroosmosis drainage in the unsaturated soil. This model is in accounting for unsaturated-induced nonlinear changes in the physical and geoelectrical properties that take place on the soil, with the additions of two-dimensional consolidation, and an external hydraulic gradient. The exponential relation is used to represent nonlinear changes in the hydraulic and electro-osmotic conductivities, and soil-water retention curve. The algorithm of this model is conducted using finite-element method. The pore water pressure, settlement, moisture content, drainage, and electric potential and current density as a function of time and position within the soil can be obtained. Finally, the proposed numerical solution is verified to be accurate compared with the experimental measurement.

In this study, waste tires-biaxial geogrids combining reinforced retaining walls were thoroughly investigated using the independently-developed apparatus for simulating cyclic loading. A comparative analysis was conducted between biaxial geogrids, waste tires, geocells, and different layout schemes of tire-geogrids. The dynamic earth pressures and accelerations of different reinforced retaining walls subjected to cyclic loading were investigated to determine the optimal combining scheme of tire-geogrids. The tests demonstrate that the tire-geogrid reinforcement materials are propitious to enhancing anti-seismic performance and the stability of reinforced retaining walls. Additionally, in the scheme of tire-geogrid reinforcement, the effectiveness is better when the space between tires equals to the radius of the tire, which could save 30% of material cost. Under the cyclic load, the dynamic earth pressure and acceleration of the tire-geogrid reinforced retaining wall increase with increasing relative wall height (y/H). The acceleration peaks at the top of the wall. Moreover, the dynamic earth pressure changes with the variations of cyclic loading amplitude, and after reaching its peak value, the growth rate slows down and the value becomes stable.

Mine backfilling is an environment friendly solution. It has become a common practice in many underground mines around the world. Despite numerous advantages associated with this practice, efforts are needed to adequately design a retaining structure, called barricade to hold the backfill slurry in the stopes. This requires a good knowledge of the backfill pressures on the barricades. When a slurried backfill is poured in the stope, self-weight consolidation takes place with a quick generation and a slow dissipation of excess pore water pressure (PWP). When the dissipation of excess PWP advances sufficiently, effective stresses can develop in the backfill and shear stresses generate along fill-wall contacts. The shear stresses along the fill-wall contacts tend to reduce the stresses in the backfill and known as arching effect. Until now, the pressure estimation in backfilled stopes has been done mostly by considering only one of the two processes. In this paper, a solution is presented to evaluate the stresses in backfilled stopes by taking into account the self-weight consolidation and arching effect. The proposed solution is validated against numerical modeling performed with PLAXIS2D.

Waste slurry is an inevitable product of construction and is characterized by high water content, high content of fine particles, high void ratio, and extremely low strength. Its treatment requires consideration of the economic and environmental implications. In this paper, vacuum filtration test was conducted indoor to investigate the effect of volume reduction and consolidation behaviors of waste slurry. The monitored parameters included the filtration rate, height of slurry surface, solid content of filtrate, and moisture content of slurry column after testing. The effect of vacuum filtration is remarkable: the volume of slurry (desanding) and slurry (with sand) decreased by 80% and 63.3% respectively after 10 days’ test, the filtrate was comparatively clear and the solid content were only 0.17% and 0.14%, and the moisture content of the bottom of the slurry column was reduced to 53.31% and 45.97% respectively, which is equivalent to the moisture content of the soft soil.

The exploitation of mineral resources produces large amount of mine tailings. Usually these tailings are pumped into a sedimentation pond in a slurry state to be stored. However, the process of tailings slurry transformation from the muddy fluid state to the natural sedimentary soil has not been understood adequately. This paper studies the mechanism of tailings sedimentation and consolidation process by model test. The sedimentation and consolidation of muddy soil was carried out in a one-dimensional experimental setup to obtain the tempo-spacial variations of displacement and pore water pressure during the process, and the physical mechanism was further investigated. The deposition process of tailings can be divided into two stages and three zones, which can be distinguished by the change of slurry surface and pore water pressure. The results of this paper can provide new understanding about the mechanism of transformation process of slurry.

Lime treated lateritic soils are among the commonly applied construction materials in tropical and subtropical regions where they are widely distributed, due to the humid climate. However, the long-term performance of this material has been greatly influenced by the changes in the geoenvironment, for instance, under the action of contaminants lime-treated laterite may not perform as well as it would have in their absence. To characterize the changes in the geoenvironment, determining the degree of its acidity or alkalinity i.e. pH has been adopted by most scholars, and it has been shown that pH has a profound effect on the solubility of contaminants. In order to observe these issues experimental setups where established to monitor the effect of aggregate size, and addition of Meta-Kaolin (MK) on pH, Electrical conductivity (EC) and calcium ion (Ca2+) concentration of lime treated laterite. The results show that MK lowers the pH slightly in the short term and tends to maintain a very narrow range in the long term. Moreover, this property significantly influences the erosional and permeability properties. It was also observed that for the same percentage of lime a sample with 5 mm maximum aggregate had a pH slightly higher than the one with 0.5 mm maximum aggregate size sample. Further, a decrease in the amount of Ca2+ concentration, inevitably translates into a decrease in pH values and EC for a lime-laterite mixture.

The miniature penetrometer tests are often used to investigate the distribution and strength of aggregates in soils. In this work, seven different diameters of probe and three different penetration speeds were used in the miniature penetrometer tests. The results show that: Smaller probe diameter is not suitable for stiffer clay; therefore, determining suitable diametric probes is necessary before conducting miniature penetrometer tests on different types of clay. However, the influence of the probe diameter on penetration can be ignored, if the probe is non-deformed. Faster penetration speed results in larger penetration stress when the penetration speeds are in the range of 8.9 mm/min to 50.5 mm/min. When the probe diameters are in a range of 2.35 to 2.95 mm, the penetration speed will have a significant influence on penetration stress.

Water repellent soils, or hydrophobic soils, are described as having delayed wetting of the soil surface and reduced amount of water infiltration, which has been proposed as alternative slope cover materials. The degree of soil water repellency is usually judged by the droplet interaction with the soil surface in the experimental studies. Hence, in this study, the potential capability of the Lattice Boltzmann (LB) method in studying the droplet dynamics on a granular surface with varying wettability is demonstrated, of which the implications to characterizing the soil water repellency are discussed. Simulations are performed on the droplet standing, infiltrating and sliding. On a horizontal surface, LB method can be used to interpret the intrinsic contact angle (CA) at the particle level by simulating the droplet standing with an apparent CA or the time for a droplet to infiltrate. On an inclined surface, LB method helps seek the critical combination of CA and slope angle to trigger the droplet movement, which prevents the accumulation of water on a slope. Therefore, performing the LB simulations within those scenarios will reveal the performance of the water repellent soils in resisting the water infiltration.

Paste fill is popularly used in underground mines. A large amount of water is added into fills to facilitate their pipe transportation. Upon placement, the self-weight consolidation in paste fill can lead to the generation of excess pore-water pressures. To avoid excess pressures applied on the retaining structure, filling is usually staged with an undesirable curing interval. Recent numerical analyses conducted by the authors indicated that pre-installing wick drains in backfilled stopes can accelerate the consolidation, and thus enable continuous filling. In previous analyses, however, a zero pressure head was imposed along the wick drains and the effect of third dimension was ignored. These tend to overestimate the fill’s consolidation. In this paper, more representative numerical models are performed with GeoStudio, with the three-dimensional drainage around a wick drain converted to an equivalent plane-strain condition. Moreover, the fill permeability in the drift is reduced, compared to that in the stope, to mimic the restricted flow via the drawpoint. The results show that the consolidation of paste fill depends largely on the wick drain layout (spacing). The effect of wick drain size is also evaluated.

Knowledge of consistency limits is considered important in predicting the engineering properties (viz., swelling, shrinkage, strength, etc.) as well as for identifying and classifying the geomaterials. Determination of these consistency indices becomes even more imperative when selecting geomaterials (soil or waste) as a resource material for constructing earthen structures. This paper focuses on evaluating the consistency limits (or Atterberg’s limits such as liquid limit, plastic limit, and plasticity index) of red mud waste admixed with oxalic acid, gypsum, sodium silicate, and the combination of fly ash and gypsum additives in different proportions, in a comprehensive way. The results show significant variations in the value of Atterberg’s limits of ameliorated red mud waste vis-à-vis with that of raw waste. It has been inferred that the results reported in the study are of great help in asserting the suitability of the red mud waste in geotechnical engineering applications.

Usually, the values of the resistance parameters of the material disposed in the mine waste rock piles differ from those that were used in the design phase, so it becomes necessary to know how the resistance parameters are affected by the change in granulometry. The present work aims to evaluate the variations of the geotechnical properties and the effect that causes the scale of the granulometry in the behavior of the sterile rock. An extensive experimental program, including laboratory testing techniques and the use of sophisticated equipment, starting with the knowledge of its characteristics, in a vision to improve the implementation of the experimental program, always under international standards, samples obtained from tests were used of physical characterization. The methodology accompanying the behavior of a sample of mine waste rock deposited in sterile waste pile to which was artificially modifying their granulometry unchanged the original design of the granulometric curve was subjecting each specimen tests direct shear to ob tain resistance parameters based on these modifications. The friction angle obtained for these new granulometric correlations was made by processing data with an empirically known relative compactness which highlighted the influence of these parameters of the sterile rock. Impressions and proposals were witnessed and certified quality by their consistency and reproducibility for different granulometries comprised proposals artificially, by its granular material characteristic studied strength parameters obtained from the test run shear it turned proper technique. It is concluded that there is a very close relationship between the reduction of the granulometry and decrease in the value of the angle of friction being these proportional, there being a dependence on the resistance to shear and its diameter of the grain. It is worth highlighting that by carrying out a good analysis and design of a sterile waste pile knowing the correct values ​​of the resistance parameters for its real granulometry, the project will be oriented towards safety and contributing to the reduction of deposit areas, so that the environmental impact will then be minimized.

The use of mining tailings to stabilize the materials normally used in civil works is already a fairly common practice. Tailings are commonly used in landfill layers, in the construction of houses where they replace conventional materials, as well as their use as a filler in the cement industry, among other applications. Thus reducing the exploitation of the deposits and preserving the environment. However, while studies show improvement in mechanical behavior in soils with the addition of tailings, they can also act to contaminate soil and water resulting from excess heavy metals. In this context, the present research aims to evaluate the mobility and availability of the metals present in the tailings. The iron reject studied comes from the Iron Quadrangle and the gold is from northwestern Minas Gerais, Brazil. The studies covered the physical and geochemical-environmental characterization of the material. With the results, it was possible to know the characteristics of these materials when they are in contact with water as a means of dissolution, allowing the evaluation of the influence of such aspects on the behavior of the mixtures and to evaluate the potential use of these materials in civil works.

Based on the principles of electron currents conservation and mass conservation, this paper considers the two kinds biochemical reactions of organic aerobic oxidation and simultaneous nitrification-denitrification under the condition of aerobic degradation of municipal solid waste (MSW). Select rapid degradation cellulose (RDC), slow degradation cellulose (SDC), total sugar, fat, protein, and microorganisms as the limiting substrates, and write an aerobic biochemical reaction stoichiometric equation that can reflect the mass linkages among various substances. First-order kinetic equations were used to describe the kinetic behavior of biodegradable organics in the process of aerobic degradation, meanwhile the effects of temperature, water content, and oxygen concentration on the aerobic degradation rate of organic matter were also considered. The microorganism decay was described using a first-order kinetic equation. A model with a clear physical meaning and capable of simulating the time-varying process of aerobic degradation of MSW has been established. The robustness of the model still requires instance validation.

Microbially induced calcite precipitation (MICP) offers potential for the development of innovative and environmental friendly techniques for soil improvement. The main purpose of this study is deepening the understanding of bio-geochemical processes involved in MICP by means of numerical modelling. In this paper a coupled bio-geochemo-hydraulic model considering multispecies bio-reactive transport is presented. Generally, this model is based on the theory of porous media, continuum mechanics and solved by finite element method (FEM). Utilizing this model a numerical case study is performed. It is estimated that this model is able to predict a rational bio-geochemical behavior of MICP. Besides, sensitivity analysis regarding the relevant model parameters has been performed to identify key factors in the MICP processes.

We have designed a new phytoremediation technique called phytosuction separation (PS-S). To date, it has indicated that the PS-S can remove antimony 69–533 times higher than that removed by phytoextraction (PE). However, it should be deeply investigated that PS-S can effectively remove the metalloid other than antimony. Arsenic-contaminated soil was used in this study. Ferryhydrite synthesized in the laboratory was used as an immobilization material. Four treatments for PS-S were prepared changing the amount of contaminated soil put in the pot: 1.6, 1.0, 0.5, 0.2 cm soil depth, respectively. The removal ratios of PS-S system were higher than that of PE despite the soil depth of PS-S system. The removal ratios of PS-S system increased with the decrease in the soil depth, indicating that the PS-S system could remove arsenic from less than 0.5 cm soil layer. This study indicates that the PS-S system can remove arsenic from the contaminated soil compared with PE, and it can be more effective with more shallow soil layer.

Bentonite-sand mixture is often used as the artificial engineering barriers for the high-level radioactive waste repository and the anti-seepage barriers in civil geotechnical engineering, and it is very important to study its deformation and permeability characteristics in evaluating the service performance and durability. The compression test was used to obtain the compression deformation characteristics and saturated hydraulic conductivity of the mixtures with different sand content saturated on salt solution of different concentrations. The concepts of the actual effective stress pe and the montmorillonite void ratio em are introduced, and the change rules of em-pe relationships and the em-k relationships of the mixtures with different sand content saturated on salt solution of different concentrations are summarized.

Deep geological sequestration of anthropogenic carbon dioxide is a plausible way to reduce global greenhouse gas impacts. Long-term containment of sequestered CO2 can be achieved by preventing leakage and by ensuring further entrapments such as solubility-trapping and mineral-trapping. These processes can be enhanced by involving subsurface microbial community that restrict flows by forming biofilms and/favours biomineralization. For example, ureolytic bacteria, Sporosarcina pasteurii, catalyzes urea hydrolysis and accelerate calcite precipitations in presence of dissolved calcium ions. However, subsurface flows and reactions are complex and often involve multiple phases, chemicals and minerals as well as pressure and thermal gradients. These complex coupled behaviours are challenging and limitedly attempted.Within the scope of an ongoing study, a coupled numerical model has been developed under a THCM framework including subsurface microbial processes and associated bio-geochemical reactions. The model deals with liquid flow, multicomponent gas flows, dissolved chemicals and suspended microbes flows in liquid phase, heat flow, biofilms and minerals growths, mechanical deformations and geochemical/bio-geochemical reactions. In this paper, the coupled microbial model has been used to investigate the effects of thermal gradient on microbial growth and mineral precipitation as well as their overall impacts on the flow properties of the medium.

Similar to calcium carbonate, magnesium carbonate also has a cementing character, and the strength of magnetite ore is much higher than calcium ore. In this paper, firstly, the effects of different ions, such as the concentration of Ca2+ and Mg2+, on the urease activity of Sporosarcina pasteurii were researched. Then the productive rates for calcium carbonate and magnesium carbonate were comparatively analyzed. Finally, with adding various amounts of urea to medium, the productive rates for magnesium carbonate were compared. The results show that the increase in the magnesium ion enhances urease activity, while calcium with high concentration significantly impairs it. Under the same conditions, productive rate for magnesium carbonate is smaller than its calcium counterpart. However, the method adding urea to the medium significantly promotes to form precipitation, and with higher urea concentration, more magnesium precipitation is got. Therefore, the presented method can solve the problem that insufficient magnesium precipitation cannot solidify sands, which acts as a guide for the magnesium carbonate sand solidification technology.

With the increase in population and infrastructure, the search for areas for occupation has increased significantly. Therefore, there is also an increase in the environmental impacts associated with the bad use of the soil, thus making these soils need an improvement for their use. Soil improvement techniques used involve the addition of mechanical energy and/or synthetic materials. However, the bionanocementation technique has the purpose of improving the mechanical properties in a sustainable way. Biocementation is the formation of calcium carbonate that binds the soil particles by microorganisms metabolism. It only occurs when the microorganisms have a source of calcium and urea and the potential for biocementation. The objective of this work was evaluate the increase in mechanical strength, through the technique of bionanocementation, in sandy soil with different concentrations of calcium (20, 30 and 40 g/L). Calcium substrate was supplied at nano and micro scale. Four different treatments were performed in the experiment: SN−B; SN+B; CN−B and CN+B. Biochemical test of urease production, CO2 evolution test, compression strength test and MEV and EDS were performed. During the study, we observed that the product at nano scale was already in CaCO3, making the treatments with nutrient medium CN did not obtain good results. The CPs with nutrient medium SN stood out in the trials, as well as the treatments that had no bioaumentation. In addition, the results with higher concentration (40 g/L) stood out.

In order to study the feasibility and microbial mechanism of sludge barrier for acid mine drainage (AMD), the microbial functional diversity in the compacted sludge with different seepage conditions (the distilled water (DW), the pH2.1 sulfuric acid and the simulate AMD) was studied using Biolog and Most Probable Number (MPN) testing system. The results showed that the average well color development (AWCD), the Shannon index (H), the Evenness index (E), the number of positive Ecoplate wells (S), the total bacteria (TB), and the sulfate reducing bacteria (SRB) quantity differed between different seepage conditions. Compared with the DW seepage condition, the acidity and AMD condition had the lower AWCD, S, H, E values which showed the latter inhibition effect be stronger. The seepage conditions changed the microbial quantity of carbon utilization and ability to utilize the single carbon source. So the property of the microbial functional diversity in the compacted sludge might indicate the microbial differences under the different seepage conditions in this study.

Size and distribution of precipitated particles significantly influence the efficiency of ground improvement by introducing fine particles in the original soil matrix mechanically, chemically, or biologically. However, direct measurement of these fine particles poses challenges to the existing non-destructive methods. Recent advancement in low-frequency (0.01–100 Hz) complex conductivity showed promising results in obtaining the size and accumulation pattern of fine particles distributed in coarse-grained soils. In this study, low-frequency complex conductivity measurements were conducted to monitor the spectral induced polarization (SIP) responses of Ottawa 50–70 sand mixed with eggshell powder at sieve size between No. 80 and 140. Vertical stresses of 5, 25, 50 and 100 kPa were progressively added to the sample. Shear wave velocity (Vs) was also monitored by bender element technique. Relaxation frequency of imaginary conductivity increased with the increment of vertical stress, which was attributed to crack generation of eggshell as vertical stress increased. The calculated particle size at 5 kPa from complex conductivity measurement was close to the size of eggshell powder used, suggesting the accuracy of the prediction of SIP method. Shear wave velocity detected increment of stiffness of the mixture as stress increased.

Compacted sewage sludge (CSS), also known as reducing barrier, can be used as barrier for tailings of mines. CSS is an effective means to isolate and eliminate acid mine drainage (AMD) produced by tailings. We studied the dynamics of bacterial community structure diversity over 75 days in the CSS. Samples were taken from two seepage conditions: pH 2.1 sulfuric acid water (SA) and the synthetic AMD. Deionized water (DW) was used as control. We used PCR-DGGE technique, which is denaturing gradient gel electrophoresis. The results indicated that Clostridiales, Bacillaceae, and Carnobacteriaceae dominated in the CSS samples with different relative abundance ranged from 46.26% to 10.25% at the start point (SP) of seepage, the 41st day (T1) of seepage or at the 75th day (T2) of seepage, under different seepage conditions (DW, SA and AMD). By redundancy analysis on the influences between environmental factors and microbial-community, microbial- mechanisms differed.

In this study, a series of enrichment tests were conducted to investigate the effectiveness of two enriching media on the indigenous ureolytic bacteria in Hawaiian coastal beach sand. Sand collected from the intertidal zone of the Kailua Beach was used in the study, which was subjected to the erosion action of wave and tide periodically. Two media applied were YE (yeast extract only) and YEU medium (yeast extract with urea). Shaking incubation test was conducted up to 72 h to stimulate the indigenous ureolytic bacteria. The pH, ammonium concentration, ureolytic activity, and viable bacterial colony number of the enriched bacterial solution were measured at 6 h, 12 h, 24 h, 48 h and 72 h respectively. Results show that the primary stimulation occurred within the first 48 h. The concentration of ammonium ions and ureolytic activity were significantly increased and the viable bacterial colony number was slightly decreased at the end of the enrichment. These observations indicate that the ureolytic bacteria resided in the intertidal zone can be enriched effectively.

Different soil improvement techniques have been used to intensify the engineering properties of soil. Three different lignocellulose fiber-reinforced (jute, coir and water hyacinth (WH)) have been explored on the desiccation potential of compacted clayey silt coil. The experimental methodology involved the mixing of fibers with soil at requisite amount and subjecting them to natural environment with controlled irrigating. The controlled irrigation comprised of 15 wetting/drying cycles for 105 days. Parameters like matric suction and water content were focused upon and recorded along with the surface crack formation. The data obtained from the field experiments were analyzed using the Artificial Neural Network (ANN) approach, which is developed in house using C++ language. From the analysis, it can be comprehended that coir is more effective as a reinforcement due to its multifilament nature and higher lignin content which is suitable in resisting crack formation. Further, optimization analysis and sensitivity analysis suggested mechanism of cracking for each fiber.

A large amount of methane gas released during the service of a landfill will not only cause the greenhouse effect, but it may also cause an explosion when the methane reaches a certain concentration in the air or soil. In the background of promoting energy conservation and environmental protection, it is of great significance to effectively reduce the methane release content in landfills, ensure the normal service of landfill and the safety of people’s life and property. The mechanism of methane oxidation by methane oxidizing bacteria is reviewed and the factors affecting the efficiency of methane oxidizing bacteria to oxidize methane are analyzed in order to reduce the emission reduction of hazardous gases in the landfill and provide a reference for the design of other new landfills.

To investigate the applicability of microbial induced calcite precipitation (MICP) to the solidification of municipal solid waste incineration (MSWI) fly ash, the following work are carried out. Firstly, three ureolytic strains, UR1, UR2 and UR3, were isolated and identified as Sphingobacterium cladoniae, Bacillus aryabhattai and Raoultella ornithinolytica, respectively. Secondly, the fly ash samples were solidified by the above three strains, and the case with strain UR2 displayed largest unconfined compressive strength of 0.740 MPa. Lastly, heavy metal leaching test was carried out for the solidified samples. The immobilization ratios for Cu, Pb, and Cd were in the range of 41–77%. The case with UR1 displayed higher immobilization ratios for Cu, Cr, and Cd, and UR2 exhibited higher immobilization ratio for Pb. Overall, strains UR1 and UR2 provide promising use for the solidification of MSWI fly ash.

Numerical modelling of changes in the flow regimes in soil due to bioclogging of the pore space are considered. Biomass growth dynamics are described by the Monod equation and changes in hydraulic conductivity due to the accumulation of biomass within the pore space are represented by a theoretical model of pore space clogging. The model is validated by comparison with results from experiments performed using the bacterium Beijerinckia indica within sand columns with model parameters determined from independent experimental work. The model is then applied to investigate flow diversion within heterogeneous systems composed of a number of regions made up different sand fractions. Finally, the potential of using controlled biomass growth to engineer flow within heterogeneous porous media is considered.

Development of green infrastructure is widely adopted as a key strategy for enhancing socio-ecological benefits in urban areas. Generally, four categories of vegetation exist in urban green infrastructure. Those are (i) vegetated soil under tree shade during entire daylight period, (ii) vegetated soil under tree shade during 3–4 h of daylight period, (iii) vegetated soil under light during entire daylight period and (iv) soil surface covered by mix grass and shredded leaves. Previous studies have shown that presence of vegetation may influence hydraulic conductivity. The main factors those govern such influence are found to be growth of vegetation, which is directly related to photosynthesis and stomatal conductance. Stomatal conductance is the measure of passage of carbon dioxide or water vapor through stomata of leaf. The objective of this study is to investigate role of plant health parameters in understanding spatial heterogeneity of hydraulic conductivity in urban green infrastructure. Field monitoring of mix vegetated soil was conducted for about three months. Plant health is investigated in terms of vegetation growth and stomatal conductance. Stomatal conductance and hydraulic conductivity were measured in 150 locations in selected site once every month. Stomatal conductance was measured using an electronic sensor (leaf porometer). Mini disk infiltrometer was used to measure hydraulic conductivity. Stomatal conductance of mix grass under light for longer duration (around 8 h) was found to be higher than that under light for shorter duration (3–4 h) and shade. Hydraulic conductivity of mix grass cover under shade was found to be relatively low. As compared to stomatal conductance, preferential flow is found to be more dominant in governing the hydraulic conductivity.

Vegetation improves the soil stability by virtue of its mechanical and hydrological characteristics that are governed by its root morphology. Root network supports the friction between the roots and soil thereby increasing the pull-out resistance and also imparts additional cohesion by induced suction characteristics. Therefore, in order to mitigate landslides and to achieve soil stability, it is needful to have adequate knowledge about root traits. Several researchers evaluated root tensile strength for different species by adopting different mechanisms but it appears from literature that no common clamping arrangement has been developed and it has been modified as per the testing requirement to meet the problems due to root crushing, breaking and slipping at clamps. In the present study, architectural and mechanical characteristics of two Himalayan tree species namely Deodar, Amla and Pine roots were determined. A novel and robust technique for gripping of roots has been developed for testing tensile strength of roots. The effect of diameter on the tensile strength of roots has been shown along with the variation of root network characteristics of plants that were grown under same environmental conditions.

Spatial variation of hydraulic conductivity governs the performance of green infrastructure. Previous studies show that, hydraulic conductivity of vegetated soil may vary by 400% due to presence of vegetation. However, spatial variation of hydraulic of wilted grass in the vicinity of a tree was rarely studied previously. The objective of this study is to investigate spatial variation of hydraulic conductivity of wilted mix grass in the vicinity of a tree. Field monitoring was conducted for two months in the site consisting live grass and wilted grass. The selected site consists of (i) mix grass cover under tree shade during entire daylight period, (ii) mix grass cover under tree shade during 3–4 h of daylight period, (iii) mix grass cover under light during entire daylight period and (iv) soil surface covered by mix grass and shredded leaves. Hydraulic conductivity was measured at 150 locations in the selected site using mini disk infiltrometer. Hydraulic conductivity of wilted and live grass near the tree stem (i.e., under tree shade during entire daylight period) was found to be lower than that away from tree stem. In addition, hydraulic conductivity of wilted and live grass under light during entire daylight period was found to be higher than that under shade for 3–4 h of daylight period. Furthermore, hydraulic conductivity of wilted grass was found to be lower than that of live grass in case of all the selected categories. The obtained results help to analyze the performance of green infrastructure accurately.

The study considered the use of Bacillus pumilus to trigger microbial-induced calcite precipitation (MICP) process for the improvement of the unconfined compressive strength (UCS) of lateritic soil to be used as a hydraulic barrier in waste containment application. The lateritic soil was treated with stepped Bacillus pumilus suspension densities of 0, 1.5 × 108, 6.0 × 108, 12 × 108, 18 × 108 and 24 × 108 cells/ml, respectively. Specimens were prepared at moulding water contents –2, 0, 2 and 4% relative to the optimum moisture content (OMC) that simulate field variation in moisture and compacted with British Standard light (or standard Proctor) energy. The UCS values increased with higher Bacillus pumilus suspension densities and moulding water content. Peak UCS values of 1159.08, 1169.52, 1298.27 and 1884.58 kN/m2 were obtained at 6.0 × 108/ml, 24.0 × 108/ml, 6.0 × 108/ml and 18 × 108/ml Bacillus pumilus suspension densities for specimens prepared at –2%, 0%, +2% and +4% relative to OMC, respectively. A compaction plane of acceptable zones for UCS based on regulatory value (i.e., > 200 kN/m2) gave 6.0 × 108/ml Bacillus pumilus suspension density as optimum treatment for lateritic soil to be used in waste containment application.

This work evaluates the strength of a tropical residual lateritic soil treated with Sporosarcina pasteurii (a microorganism cultured from the soil) in stepped densities of suspension of 0/ml, 1.50 × 108/ml, 6.0 × 108/ml, 1.20 × 109/ml, 1.80 × 109/ml and 2.40 × 109/ml, respectively and cured for 12 h in polythene bags at 24 ± 2 °C. Specimens were prepared at moulding water contents between –2% and +4% relative to optimum moisture content (OMC) and compacted with British Standard light (BSL) energy (or standard Proctor). The compacted soil specimens were then permeated under gravity with a cementation reagent consisting of 20 g of Urea, 10 g of NH4Cl, 3 g of Nutrient broth, 2.8 g of CaCl2 and 2.12 g of NaHCO3 per litre of de ionized water to initiate microbial-induced calcite precipitation (MICP). Permeation was carried out in three cycles with 2/3 pore volume each, specimens were extruded 24 h after the last permeation and cured for another 48 h before subjection to unconfined compressive strength (UCS) test. Results obtained showed a general decrease in UCS values with higher moulding water content regardless of the density of S.pasteurii suspension. Peak UCS values were recorded for specimens prepared at –2% relative to OMC for all densities of S.pasteurii suspension. S.pasteurii suspension density of 1.20 × 109/ml, can be considered the optimal treatment of the lateritic soil, which recorded a peak UCS value of 2232 kN/m2 that underscores its efficacy in strength improvement.

In this study a laboratory column test has been conducted on a compacted soil modified by a rice-stalk derived biochar to model its methane mitigation capability as a municipal solid waste (MSW) landfill cover material. Preliminary test results showed that gas adsorption was the principal mechanism that reduced the methane emission in the early stage of soil column test. As time passed, microbial methane oxidation became the dominant mechanism over gas adsorption to reduce methane emission. Besides, it was found that the most active zone for methane oxidation was the top 250 mm where the availability of oxygen was adequate for the aerobic activity of methane-oxidising bacteria.

Hangzhou is one of the eight pilot cities for the sorting, collection and disposal of municipal solid waste (MSW) in China. An overview of current status and future plan of MSW disposal in Hangzhou is carried out. The sorting ratio of MSW was estimated to be less than 25% in 2016. It imposes heavy burden on government’s plan of increasing the incineration ratio from 40% to 80% and composting 200 tons of food waste daily in 2020. Through comparison of the landfills, incineration plants and composting plants in Hangzhou, the current standards for the pollution control of MSW disposal facilities are discussed. The risk evaluation during the design period and the monitoring data disclosure during the operation period are suggested to be the mandatory provisions in the future revision of these standards. The work conducted in this paper would provide reference for other cities facing the problem of MSW disposal during the fast urbanization process.

This study aimed to define a method applied to remediation of contaminated sites that best represents sustainability. We identified the methods developed and applied in the world scenario and analyzed them as to the satisfaction of nine decision criteria established by the authors to verify the sustainability in the approach of methods. Eight methods of sustainability assessment in remediation of contaminated sites were identified, and a tendency in the graphical representation for decision-making was observed regarding the structures of identified methods. Regarding the criteria, the participation of the different stakeholders in the remediation project obtained the best performance, being approached in all the analyzed methods. In this context, ITRC method obtained the best performance among the analyzed methods. It is concluded that this type of analysis, through the satisfaction of criteria in approach of the methods, provides a more detailed understanding of contributions of different methods to sustainable results.

Landfilling remains one of the main municipal solid waste (MSW) disposal methods worldwide. And the refuse dam is one of the most important facilities to ensure the safety of landfill. Therefore, it is of great significance to evaluate the safety of the refuse dam. This study aims to analyze the stability of the refuse dam using the finite element method based on PLAXIS3D. The landfill is replaced by the equivalent load applied, which is calculated by three methods including static earth pressure at rest, PLAXIS2D simulation and retaining wall with gentle back surface methods. And the calculation results of above-mentioned methods are compared and the reasons for the different results are explained. The results showed that the calculation of factor of safety by static earth pressure at rest method is the most reliable. And the alarm water level corresponding to the safety coefficient 1.35 is –4.85 m.

Mountain hazards behave a relatively high incidence under regional climate change condition. This compound hazard is often initiated by environment and climate change. A combination of glacial melting and rainfall-induced compound disaster event happened in Tianmo Ravine, Bomi County, Tibet, China on 25 July and 4 September 2010, separately. The debris flow with 450,000 m3 volume transported along gully and then flushed into Parlung Tsangpo River in the deposition zone, resulting in a destruction of 400 m length section of the G318 highway from Bomi County to Lhasa. A detailed interpretation of this disaster was conducted using unique and high-resolution images obtained through remote sensing. The source material, terrain condition, and climate condition were analyzed to have a comprehensive understanding of environmental background for hazard initiation. It is concluded that the occurring of this disaster event is the comprehensive result of multiple factors led by the climate change. Abundant antecedent precipitation, melting of the glacier, and the instability of soil caused by wetting-drying cycles, led to the occurrence of the Tianmo Ravine disaster. Based on taking various factors into account synthetically, the comprehensive hazards pattern is named using “Mountain hazards pattern in glacial alpine region under climate change (MH-GA-CC)”. The climate is the special factor feature that should be taken into account emphatically. The study here provides a scientific base pattern for the future risk assessment of glacial alpine areas under regional climate change background.

An innovative dynamic test simulation system was used for impact drilling, a series of experiments were carried out on intact sandstone, limestone, gabbro and marble rocks. The reflected stress wave in the experimental bar was measured and the corresponding strain energy was calculated. The results have shown that the response degree of reflected stress wave depends on impact energy and lower threshold value of response. It is hard to detect under current technical conditions if the impact energy is below the threshold value. The peak reflected stress wave and the specific strain energy relate to rock type, strength and wave impedance. For the same type of rock, it grows with increasing impact energy, the ratio is related to the wave impedance instead of impact energy when it is over or equal to the threshold value. It shows significant differences in experimented rocks.

In the present study, a hazardous waste (HW) landfill on a sloping ground is considered. The base profile of the landfill exhibited significant elevation difference from one end to the other. Due to the inclined base and fixed waste footprint area, the waste retaining capacity of the landfill decreases significantly in comparison to a same plain base area. As a consequence, an engineered berm is provided at the lower end to act as a stabilizing berm and also to increase the waste filling space.This paper describes the study done to check the stability of the HW landfill on the sloping ground for (a) without berm; (b) with earthen toe berm; and (c) engineered berm or mechanically stabilised earth (MSE) wall for the following critical influencing parameters: (a) leachate head due to temporary clogging; (b) pore water pressures in wet waste; (c) seismic forces. Limit equilibrium methods of analysis is adopted to check the stability for all the cases. Along with the stability, waste filling capacity for each configurations are evaluated. Eventually it is observed that on a sloping ground, the waste filling capacity is highest in case of landfill with MSE walls with optimal solution for stability with significant difference in waste filling capacity from the landfill without berm and earthen berm.

The unplanned process of urbanization during the years has resulted in the emergence of risk areas occupied by the population in social and economic vulnerability. These areas, in it definition, are suject to risks of natural or induced disasters, such slides of earth and flood. In some cities in Brazil, the level of occupation is practically irreversible. The risks originating by this situation are since material losses to damages for the physical integrity, being this sometimes unrecoverable. The mapping of risk areas turn up indispensable to the mitigation plans of the risks found. The methodology adopted by the Brazil’s Ministry of Cities was used as base for the mapping. The community Filipeia located in the neighbor of Tambiá at João Pessoa, Paraíba, Brazil, is a potential area of risk. Based on the collected data, the map of risk of Filipeia was developed. The mapping produced revealed that natural and anthropic factors are directly related with the risks for the human life and material assets, such the slope gradient, the kind of vegetation present there, the launch of wastewater on the face of the slope and the self-construction in improper areas.

The rainfall and earthquake are two main causes of instability and failure of slope. To analyze the excess pore water pressure, the safety coefficient of slope and slope feature point displacement change with the time under the different earthquake intensity. The numerical modeling results of slope under the action of earthquake is inputted to the finite element analysis software, to the analysis dynamic change rule of volume moisture content and the formation of pore water pressure of slope soil mass under the condition of rainfall. Using the limit equilibrium method calculates and comparative analysis the slope stability after Coupling of earthquake and rainfall infiltration,and under the action of alone that earthquake or rainfall alone. The result shows that the earthquake makes slope geotechnical body to produce permanent deformation and increase the permeability coefficient of slope. Moreover, the rainfall infiltration will further decrease shear strength of slope, lead to the emergence of landslide. The earthquake combines with rainfall is more easily to induce landslide than single factor.

Stability forecast models for earthworks are based on the transfer function modeling of two-time series (Xt and Yt) of field variables obtained by monitoring. The time series obtained in the geotechnical instrumentation monitoring of civil works can be considered as an atypical time series, since it usually contains missing and lagged observations, requiring regularization as continuous series for modelling. This paper presents concepts related to inferential prediction models and the results of predictive models of geotechnical behaviour obtained for a tunnel of the São Paulo Rodoanel Highway from data of surface settlement, depth settlement and water levels. Based on these results, considerations are raised for the utilization of forecast models in geotechnical instrumentation monitoring of mining tailings dams.

Issues associated with the production of waste and their disposal continue to be a major preoccupation for governments, public and private organizations and the general community around the world. This paper includes the current trends on the possible reuse of various waste streams for geotechnical and geo-environmental applications. After a general overview, specific examples will be described and new results on amended recycled sediments and amended soils will be presented. Examples of this sustainable concept to be further promisingly developed include: (1) the possible use of waste heat for the production of new amended raw materials, (2) the reuse of dredged sediments for various geotechnical and geo-environmental applications, (3) the use of various recycled soil amendments for mechanical and hydraulic enhancement techniques.

Permeability tests of the compacted bentonite-sand mixture using salt solutions were carried out. Exposure of the Ca type-bentonite to NaCl or KCl solutions after fully saturation with deionized water caused ion exchange of the montmorillonite. After Ca ion exchanged to Na ion, the swelling pressure of the sample increased and the permeability decreased when the low ionic strength condition, comparing with the initial value before Na ion exchange. While, after Ca ion exchanged to K ion, increase in the swelling pressure and reduction of the permeability were insignificant. K and Na ions showed the different effect of ion exchange on the engineering properties of the bentonite.

When choosing a site for the construction of high-risk objects, it is necessary to take into account all the processes that may adversely affect the safety of the station. In connection with planning the construction of nuclear power plant in the region, where karst is the most dangerous process, several methods of assessing karst risk have been developed. Formulas, that allow to find physical damage from the destruction of territories and engineering objects by geological processes, are written in the article. It is shown that physical risk values are used as the basis for constructing a scale that allows to objectively evaluate the degree of failure hazard by two generally accepted indicators - the average diameter of karst-suffosion sinkholes and the intensity of their formation. The physical risk of land loss is the simple integral characteristic of the both probability and strength of karst impact on the technosphere objects. The evaluation of karst danger of territory of construction of object of the raised danger is given.

The use of nanoparticles in soil remediation is an emerging and innovative technology. With the advancement of sustainable remediation, concern about the remediation technologies sustainability should be considered as criteria in decision-making. Countless tools can be employed in order to assess sustainability in soil remediation, e.g. life cycle analysis (LCA) for environmental impacts assessment. However, to be considered sustainable the LCA must also understand the economic and social aspects. This study aims to carry out a systematic and bibli- ometric analysis of scientific production in the field of LCA, sustainability and nanoparticles applied in the remediation of contaminated sites. Represented by the scientific articles indexed in the database Scopus and Web of Science. It is concluded that the evaluation of sustainability by means of the Sustainable-LCA in soil remediation is an innovative tool. The application of sustainability in its principles, environmental, economic and social, has not yet been carried out in nanoremediation.

The paper presents the results of reliability assessment of the suitability of two tropical soils (laterite and clay sand) for use as liner materials in waste containment application. The evaluation was based on the use of compositional variables (moulding water content relative to optimum, hydraulic conductivity, initial saturation, plasticity index, clay content and compactive effort) using the First Order Reliability Method (FORM) version 5. The results of the study revealed the variation of reliability indices as the coefficient of variation (COV) for the independent variables increases using the normal and lognormal distributions. Three compactive efforts of standard Proctor (SP), West African standard (WAS) and modified Proctor (MP) were considered. The predictive model was developed with a view to assessing the safety of the hydraulic barrier for waste containment facilities.

Municipal solid waste (MSW) have increased in the accumulation rate in China and landfill is the most common method of MSW disposal management. A landfill failure occurs when the great majority of rocks, soil materials or debris flows move down from a slope due to gravity. The physical vulnerability of the catastrophic landfill failure occurred in Shenzhen 2015 is analyzed in this paper. It deduced that the vulnerability would increase with the impact pressure and maximum bending moment of each building. Typical deformation characteristics of affected buildings, such as bending moment and shear force are simulated using ETABS to determine whether the building will collapse after the impact of the landfill failure. A vulnerability curve indicates the relationship between impact pressure of the landfill failure, the building type, building use and the damage degree of the building.

Seventy-three people dead and 4 people missing in a landfill failure occurred at Shenzhen, China at 11:40 a.m. 20 December 2015. The Shenzhen landfill failure was caused by the accumulation of waste in a former quarry in the Shenzhen. To evaluate the loss of life caused by the Shenzhen landfill failure, a quantitative risk assessment was conducted. The risk could be defined as the product of the probability of occurrence, the consequence and the element at risk in a quantitative measurement. A slope model is used to analyze the slope stability and reliability. The runout behavior, temporal-spatial probability, and the element at risk are analyzed. The vulnerability factor is referred to established table based on different degree of damaged buildings. The potential annual loss of life from a single hazard is then obtained by combining the probability of occurrence and the consequence as a societal risk. The societal risk is visualized and evaluated by the presentation of F-N curves resulting in an unacceptable region which proved that the real case of landfill failure was under an unacceptable risk. This study provides a quantitative way for the risk assessment of Shenzhen landfill failure and develops a risk assessment model for landfill.