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This volume contains contributions on advances in geosynthetics engineering. Soil reinforcement is a very useful technique to construct several cost-effective soil structures in an environmentally friendly and sustainable manner. The most commonly used reinforcement materials are galvanised steel strips, geosynthetics in the form of woven geotextiles, geogrids and geocomposites, and fibres from natural and waste products. In recent years, there have been advances in the area of soil reinforcement, especially in the utilization of the technique in field projects. The researchers have also been working to understand the behaviour of reinforced soil considering the field challenges of reinforced soil structures. The volume is based on the best contributions to the 2nd GeoMEast International Congress and Exhibition on Sustainable Civil Infrastructures, Egypt 2018 – The official international congress of the Soil-Structure Interaction Group in Egypt (SSIGE).



Experimental and Numerical Modelling of a Reinforced Structure

The paper presents a complex of research of the soil retaining structure. The results of a numerical analysis, as well as laboratory modelling in the 1/40 scale, are presented in this paper. The paper includes constructive solution analysis for the retaining structure construction. Solution implies the usage of piles as retaining element and geogrid as an element of soil reinforcement. A methodology for optimizing a constructive solution by using modern finite element method is also proposed. A quantitative estimate of the geogrid application efficiency for different task design within the single constructive solution of retaining structure (RS hereinafter) is given. The model tests include model testing of an RS without geosynthetic reinforcement elements (geogrid); and series of model tests of an RS with a geogrid for various piles spans as well. The test results are summarized in a graphical and tabular form. In general, the results of the research showed the effective use of geosynthetic reinforced material, as an element of soil strengthening.
R. E. Lukpanov, Talal Awwad

Employment of Sisal Natural Fibers as Soil Reinforcement

The use of natural fibers as a reinforcement for soils is a technique known for a long time by humanity. This practice has a great performance as a reinforcement material for has a high tensile strength, promoting improvement in the mechanical properties of the soils, conferring gain of mechanical resistance and reduction of his compressibility. The performance of the mechanical behavior of clay-silt soil at the Brasília Landfill, Brazil is analyzed by reinforcing the soil with natural sisal fibers with lengths of 75, 50, and 25 mm for a 0.5% fiber content of the total volume of dry soil. The aim to finding the optimal fiber length for the analyzed percentage. The mechanical strength conferred to the soil when applying such reinforcement is analyzed using the California Bearing Ratio and simple compression tests, and the results are compared with those obtained in natural soil. The plastic deformation and the reduction of the voids index are analyzed through the consolidation tests for each sample. The 75 mm sisal fiber was expected to be more viable for the reinforced soil, but it presents great difficulty of homogenization with the soil and high agglomeration of the fibers, making it difficult to evaluate. However, the 50 mm fiber presented higher mechanical strength and greater readiness for homogenization with the soil for the 0.5% content analyzed.
Hellen Fonseca, Rideci Farias, Ivonne Gongora, Dra. Leidiane Garcia, Matheus Viana

Bearing Capacity of Surface Treated Coir Geotextile Reinforced Sand

Natural fiber used as Reinforcement in composites has in modern times paying attention due to low cost, easy availability, low density, acceptable specific properties, ease of separation, enhanced energy recovery, CO2 neutrality, biodegradability and recyclable in nature. Although glass and other synthetic fiber-reinforced plastics have high specific strength, their fields of application are very restricted because of their inherent higher cost of production. In this connection, an investigation has been carried out to make use of coir; a natural fiber abundantly available in India. Whenever the water absorption capacity of fiber reduces the longevity will be increased. Coir can be efficiently used as reinforcing material if a proper treatment is adopted. Whenever the water absorption capacity of fiber reduces the longevity will be increased. Natural-fibre-reinforcement when treated with chemicals could be successfully produced with good mechanical properties and the tensile and flexural properties can be further enhanced by alkali treatment. In the present investigation, the coir geotextile is proposed to be used as reinforcement in sand has been made less water absorbent by surface. Chemical treatment of reinforcement material is one of the main ways of improving mechanical properties of natural fiber reinforced polymer composites treatment using Sodium Hydroxide. The effect of surface treated coir mat was used as reinforcement in the form of layer below the model footing, to assess and compare its performance with untreated coir mat reinforced sand. Peak load intensity was evaluated to determine the optimum position of layer for the geotextile reinforcement was determined experimentally.
R. Sridhar, M. T. Prathapkumar

Load Carrying Capacity of Expansive Clay Beds Reinforced with Geogrid-Encased Granular Pile-Anchors

Plate load tests were conducted on unreinforced expansive clay beds and clay beds reinforced with Granular Pile Anchor (GPA) and geogrid-encased GPA to compare their compressive load response. It was found from the tests that the expansive clay beds reinforced with geogrid-encased GPA showed higher load-carrying capacity and improved compressive load response compared with GPA and unreinforced beds. The applied pressure to cause a settlement of 25 mm in the unreinforced clay bed and clay bed reinforced with GPA of length 97 mm and diameter 30 mm (\( \frac{{l_{gp} }}{{d_{gp} }} = 3.23 \)) was respectively 152.78 kPa and 789.4 kPa, showing an improvement of 416.7%. However, the clay bed reinforced with geogrid-encased GPA required a pressure of 858.16 kPa for the same amount of settlement. This shows an improvement of 461.7% with respect to the unreinforced clay bed. Among three types of anchors used in this study, the one with a length of 97 mm and a diameter of 30 mm showed the best load response when tested without geogrid, resulting in an improvement of 659.3% whereas, the same GPA showed a better improvement of 955.57% when encased with geogrid.
A. S. S. Raghuram, B. R. Phanikumar, A. S. Rao

Ultimate Bearing Capacity Prediction of Eccentrically Loaded Rectangular Foundation on Reinforced Sand by ANN

Laboratory model tests were conducted on a rectangular surface foundation resting over multilayered geogrid-reinforced dry sand bed subjected to eccentric load. Based on the model test results, a neural network model was developed to predict the reduction factor that can be used in computing the ultimate bearing capacity of an eccentrically loaded rectangular foundation. This reduction factor (Rk) is the ratio of the ultimate bearing capacity of the foundation subjected to an eccentric load to the ultimate bearing capacity of the foundation subjected to a centric load. A thorough sensitivity analysis was carried out to evaluate the parameters affecting the reduction factor. Based on the weights of the developed neural network model, a neural interpretation diagram is developed to find out whether the input parameters have direct or inverse effect to the output. An ANN equation is developed based on trained weights of the neural network model. The results from artificial neural network (ANN) were compared with the laboratory model test results and these results are in good agreement.
R. Sahu, C. R. Patra, K. Sobhan, B. M. Das

Rehabilitation of Canals with Watertight Geomembranes, in the Dry and Underwater

Geomembranes are watertight synthetic materials, factory-manufactured under computer-controlled procedures that guarantee constant properties and quality, and supplied as flexible sheets a few millimetres thick. Geomembranes have been used to waterproof all types of hydraulic structures since more than half a century. In canals, their use started after World War II. They have been adopted to restore watertightness of deteriorated concrete or bituminous concrete linings, and to repair failing joints. Besides this waterproofing function, exposed geomembrane systems provide the additional function of increasing the water flow. All types of canals have been lined, be it hydropower canals with high water velocity, or large irrigation canals with varying sections, or small flumes and aqueducts. The paper discusses, through some significant case histories, the design options for the various projects, addressing the anchorage and drainage systems, taking into account the dynamic action of water flowing inside the canal, of water acting behind the geomembrane because present in the slopes, and the generally worst-case scenario of water infiltrated via accidental damage under the geomembrane; the influence of the drainage system and of the type of geomembrane on the anchorage will also be addressed. The paper finally introduces a totally innovative technology, SIBELONMAT®, which allows repairing canals underwater, without impacting on the operation, if needed with un-manned procedures, using ROVs. This new technology, which uses panels of a double geomembrane mattress filled with mortar, and joined with a watertight device, has already been successfully installed underwater in two pilot projects in two water supply canals, with no reduction of water speed. The technology can be considered also for new construction of canals and of embankment dams.
Alberto Scuero, Gabriella Vaschetti

Rehabilitation of Dams with Watertight Geomembranes, in the Dry and Underwater

Geomembranes are watertight synthetic materials, factory-manufactured under computer-controlled procedures that guarantee constant properties and quality, and supplied as flexible sheets a few millimetres thick. Geomembranes are used to waterproof all types of hydraulic structures, for rehabilitation and for new construction, in the dry and underwater. In dams, geomembranes were first used at the end of the 1950ies. This paper focuses on rehabilitation, discussing the available options for concrete and embankment dams, and for RCC dams. The state-of-the-art systems place the geomembrane liner at the upstream face of the dam, generally in exposed position, and with a drainage system behind, to allow discharging possible backpressure, and monitoring the performance of the system. This flexible technology can be adopted to line the entire upstream face of the dam, or only the area/s causing most seepage, or only cracks/failing joints. Projects include all types of dams and subgrades (concrete, bituminous concrete, granular subgrades or RCC). Geomembrane systems do not require heavy equipment and site organization. Large use other types of geosynthetics is made to perform functions that with traditional materials would require complicated and time-consuming operations: thick unwoven geotextiles to provide anti-puncture protection avoiding surface preparation, geogrids or high-performance technical woven geotextiles to provide support over cavities in the subgrade, geonets to enhance drainage capacity. The face anchorage and peripheral anchorage are calculated to resist acting loads such as uplift by wind and waves. Face anchorage on solid subgrades is generally linear, with a tensioning system, while on granular subgrade it is made at points, with deep anchors. Ballast anchorage is rarely used. The paper presents case histories of repairs in the dry and underwater.
Alberto Scuero, Gabriella Vaschetti

Long Term Behavior of EPS Geofoam for Road Embankments

In recent years expanded polystyrene (EPS) geofoam has successfully been used to reduce the acting vertical and horizontal stresses in several geotechnical applications due to its light weight, compressibility, and durability. In this study the efficiency of utilizing EPS blocks as a replacement for typical soil embankments under roadways was investigated. Accordingly, a detailed laboratory program was completed to measure the short- and long-term behaviors of EPS, which included unconfined compression (UC) and creep strain (CS) tests based on the time–temperature–stress superposition (TTSS) technique. Loading type applied during testing was cyclic loading to mimic the actual conditions under roadways, while the EPS density used was 35 kg/m3 to minimize deformations. The main outcome of this study was providing measured properties for local EPS considering creep stain after 100 years of cyclic loading, and these properties are ought to provide reliable design for EPS embankments under roadways.
Sherif S. AbdelSalam, Mona B. Anwar, Sylvia S. Eskander

Flexural and Shear Characterization of Geosynthetic Reinforced Asphalt Overlays

In the current study, the flexural and shear characteristics of geosynthetic-reinforced asphalt overlays placed on a pre-cracked old pavement layer are evaluated in two different stages. The unreinforced and geosynthetic reinforced two-layered asphalt beam specimens with 40 mm deep notch (crack) in the bottom layer are tested under repeated four-point bending test and interface shear strength test equipments to understand the flexural and shear characteristics, respectively. The two-layered asphalt specimen consists of a 45 mm thick old pavement layer extruded from an existing highway as a bottom layer, a binder tack coat, an interlayer and finally a hot mix asphalt (HMA) overlay. Two different types of geosynthetic-interlayers, namely, biaxial polyester grid coated with polymer modified binder having a square aperture of 18 mm (PET) and a glass-grid composite (GGC) are used in the study.
The flexural fatigue and interface shear strength test results indicate that the reinforced specimens improved the fatigue life of overlays and among them, the performance of GGC specimens are superior. However, the inclusion of geosynthetic-interlayers at the interface of old and new layers reduce the interface shear strength, resulting in a possible delamination of the pavement layers. A reduction of 17% and 36% in interface shear strength was witnessed in PE, and GGC reinforced specimens, respectively. Overall, the geosynthetic-interlayers improved the performance life of asphalt overlays invariably, before failure.
V. Vinay Kumar, Sireesh Saride

Evaluation of Strength and Resilient Modulus Characteristics of Fly Ash Geopolymer Stabilized Reclaimed Asphalt Pavement Material

Utilization of sustainable road construction materials has been the focus of research worldwide in recent times. Virgin aggregate is a primary material in the pavement industry; hence, finding an alternative is of extreme importance, concerned with the more prudent use of natural resources and the protection of the environment. The present research explored the usage of a significant portion of reclaimed asphalt pavement (RAP), activated with low calcium fly ash (FA) as a binding material. A liquid alkaline activator comprising sodium silicate solution (Na2SiO3) and sodium hydroxide (NaOH) was used for the alkali activation of the mix. The fundamental design parameters including Unconfined Compressive Strength (UCS) and resilient modulus (Mr) characteristics of the stabilized RAP:VA+FA geopolymer specimens were studied at room temperature. The resilient modulus (Mr) value in mechanistic-empirical analyses has been widely accepted in design/analysis of the pavement structures. Therefore, the present study aims to examine the resilient behaviour of the pavement base material stabilized with alkali activated low calcium Indian fly ashes, obtained from the southern region of India. The effect of additives on the microstructure of RAP:VA+FA blends were verified for one day and 28 days cured samples using X-ray diffraction (XRD) studies. Since the UCS and Mr values met the specified strength requirements, the stabilized mix can be used as a pavement base material.
Maheshbabu Jallu, Sireesh Saride

How Stiffness of Reinforcement Affects the Type of Major Reinforcement Force Developed at Various Orientations in Reinforced Sand?

Reinforced soil is any soil system in which some reinforcing elements called inclusions are placed to improve its mechanical properties. The reinforcement acts by restraining the deformation of the soil mass achieved by soil-reinforcement interface bonding. It results in increased stiffness and consequently the strength by increasing confinement and reducing dilation tendency of the soil mass. Large scale experimental study on soil-reinforcement interaction in the literature supported the conclusion that the improvement in soil strength attained from the bending stiffness of the reinforcement is always small as compared to the improvement obtained from the axial capacity of reinforcement. The objective of the current investigation is to evaluate the effect of relative stiffness of the reinforcement on the type of major reinforcement force developed in the reinforcement at various orientations of reinforcement with respect to shear plane using small-scale direct shear tests. In this study, a series of small size direct shear tests were conducted on clean, poorly graded medium grained sand under undrained condition. Two types of reinforcements of annealed rigid reinforcement binding wire and flexible Geogrid (SGi-100) strips were used of relatively varying stiffnesses. The reinforcements were only embedded in the sand and were not anchored to the shear box at any point. The sand was tested in loose and medium dense states with reinforcement oriented at various angles with the vertical plane. Based on the test results, it was concluded that the attainment of maximum increase in shear strength was observed for specific (optimum) orientations with the vertical for both inward and outward orientations and that the stiffness of reinforcement influenced the optimum orientation of reinforcement corresponding to the attainment of maximum shear strength in terms of both, the composite friction angle as well as the apparent cohesion developed due to reinforcement in the reinforced soil mass.
B. A. Mir, R. Shah

A Review on Improvement of Subgrade Soil Using Coir Geotextiles

India has one of the largest road networks in the world, aggregating to about 33 lakh km at present. However many of the existing roads are becoming structurally inadequate because of the rapid growth in traffic volume and axle loading. At locations with adequate subgrade bearing capacity/CBR value, a layer of suitable granular material can improve the bearing capacity to carry the expected traffic load. But at sites with CBR less than 2%, problems of shear failure and excessive rutting are frequently encountered. The ground improvement alternatives such as excavation and replacement of unsuitable material, deep compaction, chemical stabilization, pre loading and polymeric geosynthetics etc., are often used at such sites. The cost of these processes as well as virgin material involved is usually high and as such they are yet to be commonly used in developing nations like India. In this situation natural fiber products hold promise for rural road construction over soft clay. The Review has been made on the performance coir geotextile as a reinforcement in various soil conditions.
Sridhar Rajagopalaiah

Cantilever Segmental Retaining Walls

A unique entry into the technology of segmental retaining walls is becoming popular in the U.S. and several other countries, including Egypt where it has been approved and used extensively for highway retaining walls. Using a well-proven concept of cantilever-enhanced stability, the Cantilever Segmental Retaining Wall (CSRW) system creates an extremely stable facing system, combined with mechanically-stabilized earth (MSE) technology to offer new options for engineers to consider. Of particular interest is the ability of the CSRW system, comprised of a two-part concrete facing system combined with geogrid-reinforced soil, to be wet-cast produced on the jobsite in lightweight reusable molds. This creates a new reduced-cost paradigm while maintaining acceptable engineering factors of safety in accordance with international standards. This paper proposes to present the core science behind this innovation, as well as pertinent construction and benefit details for a full 360° view of how the CSRW system could become a displacement retaining wall technology in many geographic areas.
Chip Fuller

Pre-stressed Segmental Retaining Walls (PSRWs)

This paper introduces an innovative system of retaining walls named “pre-stressed segmental retaining walls (PSRWs)”. In this system, interlocking blocks are assembled together with dry joints (mortarless) and the integrity of the wall is maintained by pre-stressing forces. The pro-posed system has a collection of advantages over the conventional systems for construction of cantilever retaining walls or mechanically stabilized earth walls. In particular precast concrete/masonry segments can be incorporated which reduces the construction time and cost for cantilever type structures and if combined with mechanically stabilized earth wall system, it can reduce the number of layers of reinforcement and add flexibility to the design. These walls will be suitable for both water front and soil retention purposes.
Reza Hassanli, Md Rajibul Karim, Md Mizanur Rahman, Arman Kamalzadeh, Julie Mills, Mehdi Javadi

Waterproofing a Heterogeneous Soil (Sand-Bentonite) with Water and Leachate

The existence of stocks of industrial waste, and household garbage on the surface poses major environmental problems. In Algeria, this problem begins to be felt, and becomes a concern of the environmental and geotechnical specialists, who care for the achievement of the sustainable developments. The primary interest for environment protection increases the requirement of high quality and reliable sealing systems, which the qui main characteristics Sought are a maximum dry density of the compacted sand mixtures/bentonite and a low hydraulic conductivity (K ≤ E-9 m/s) with water first and then with heavy metals (cadmium) to minimize leakage using a small percentage of bentonite.
Debieche Messaouda, Mokadem Hassiba

Geotechnical Evaluation and Sizing of the Reinforcement Layer on Moles in the North Triangle Clover Project, in Brasília/DF, Brazil

The increase of the fleet of vehicles makes the Engineering is dynamic in solutions for the traffic flow. In Brasília, Distrito Federal, Brazil, it is no different. The city was designed for 500 thousand inhabitants, and currently, in the metropolitan region, circulate near 3 million. The growth of the city to a northern region, led to the development of a road complex called “Trevo de Triagem Norte” (TTN), composed of vehicles, road access, creation of new tracks and duplication of the Bridge of Bragueto on the lake Paranoá, giving access to the BR-020, as a solution to constant congestion. In the geopedological context, in the region, there are stretches with hydromorphic soils and water level at some times of the year. In geotechnical terms, soils are usually soft. Thus, this work presents a geotechnical evaluation of a region, but also the dimensioning of the reinforcement layer on the soils constitutes an end of future pathologies.
Rideci Farias, Haroldo Paranhos, Elson Oliveira de Almeida, Joyce Maria Lucas Silva, Hellen Evenyn Fonseca da Silva, Lucas Inácio da Silva

Evaluation of the Drainage Capacity of a Geocomposite Applied to the Green Roof of the Office of the Attorney General’s Office in Brasilia, After 14 Years of Its Application

The purpose of this research was to verify such actions of the time in a geocomposite and to verify the general functioning of the system, thus allowing an in depth knowledge about the effectiveness of the use of this technological solution applied in drainage works. The research was carried out using a geocomposite from the suspended garden of 22,000 m2 (green roof) of the building of the attorney general’s office, located in Brasilia, after 14 years of its application. After the analysis, good stability of the drainage system was verified, through the evaluation of physical and biological clogging.
Haroldo Paranhos, Rideci Farias, Joyce Maria Lucas Silva, Leonardo Ramalho Sales, Ranieri Araújo Farias Dias, Roberto Pimentel de Sousa Júnior

Abstract: The Long Term Performance of Geocomposite Drainage Materials Used as Capillary Break Layers

In arid regions, groundwater is often saline and the water table can be relatively close to the surface. Capillary rise above the water table brings dissolved salts near to the surface of the ground which can result in severe problems for both vegetation and the foundations of building structures.
For vegetation to survive, it is essential that there is a barrier between the saline ground and the clean ground and that this barrier also provides good drainage. A capillary break layer is installed above the highest level of the water table so that the void is never totally saturated by ground water and that the capillary break has high in-plane flow capacity to remove excess precipitation and irrigation water that enters through the clean ground above.
Chloride ions within saline moisture can be drawn into stone and concrete where the resultant chemical reaction causes expansion and weakening of foundations and the degradation of architectural finishes such as marble flooring. An effective barrier is to provide a capillary break layer between saline ground and clean ground. The capillary break layer creates a void across which capillary rise of saline moisture is prevented.
In both instances it has become common to use geosynthetic drainage layers to provide this capillary break. This paper introduces the application of capillary break layers and discusses in detail the need for ample understanding of the in situ and long term performance characteristics of the different types of drainage composite.
Alain Hérault, Dave Woods

Carbon Footprint of Geomembrane Alvatech HDPE vs Traditional Waterproofing Barrier

Lowering the Carbon Footprint is one of the strongest advantage by using HDPE geomembrane instead of traditional way for waterproofing as compacted clays.
A HDPE liner 1.5 mm could give similar watertight as 0.60 m compacted of high quality and homogeneous clay with lower permeability than 1 × 10–11 m/s (ASTM D 5887). Based on several scientist survey, considering all resources and energy to become either products as a waterproofing barrier, the geosynthetics (geomembrane HDPE 1.5 mm) takes up lower carbon dioxide equivalent, therefore it is more environmentally friendly solution.
Jose Miguel Muñoz Gomez

Uniaxial GEOGRID Pullout Mechanism Characterization from Calcareous Sand Backfill

There are two primary failure mechanisms associated with Reinforced Soil Systems (RSS) walls using geogrids including rupture and pullout. The failure mechanism with relevance to this research is the pullout failure. This type of failure mechanism depends on the interaction between the backfill soil and reinforcement. In order to select a type of backfill soil or reinforcement that will provide sufficient interaction strength, the soil reinforcement interaction should be tested and characterized using pullout tests. Siliceous sands have been widely used as a backfill soil in MSE walls. Also, most published researches addresses the geogrid pullout resistance embedded in siliceous sands. geogrid pullout design empirical equations and parameters in design codes such as AASHTO are based on using siliceous sand as a backfill material. In this paper, the aim is to evaluate the interaction between calcareous sand as a backfill soil and two types of geogrids including High Density Poly Ethylene (HDPE) and polyester, performing and analyzing laboratory pullout test results. Pullout tests were performed at vertical stresses of 100, 150 and 200 kPa corresponding to approximate wall heights of 5 to 11 m. The results of pullout test are used to define geogrid pullout resistance parameters from calcareous sand. The results of this study show that: (1) Pullout resistance force for HDPE geogrid embedded in siliceous sand are higher than those embedded in calcareous sand by 17%, (2) Pullout resistance force for polyester geogrid embedded in calcareous sand are higher than those embedded in siliceous sand by 6%, (3) The pullout resistance factor for polyester geogrids embedded in calcareous sand is greater by 4% than the same factor for geogrids embedded siliceous sand. However the pullout resistance factor for HDPE geogrid embedded in calcareous sand is smaller by 16% than the same factor for geogrids embedded in siliceous sand.
Ahmad M. Abdelmawla, Yasser A. Hegazy, Ashraf A. Al-ashaal, Sherif A. Akl, Hesham K. Ameen


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