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Publisher: Springer-Verlag (Total: 2351 journals)

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 International Journal of Geosynthetics and Ground EngineeringNumber of Followers: 4      Subscription journal ISSN (Print) 2199-9260 - ISSN (Online) 2199-9279 Published by Springer-Verlag  [2351 journals]
• Direct Shear Behavior of a Mixture of Sand and Tire Chips Using X-ray
Computed Tomography and Discrete Element Method
• Abstract: Granular materials such as soils, powders, and other particulate materials have been widely used in geotechnical engineering. In particular, sandy soils are one of the representative ones. Recently, there has been attention on environment-friendly materials such as tire chips or other waste materials. Besides, one of the key behaviors for these materials is shear behavior, including the effect of dilatancy. In this paper, direct shear behavior of sands as rigid particles and tire chips as elastic particles is discussed. Here, micro-focus-type X-ray-computed tomography (CT) scanner is used with direct shear tests to investigate the close behavior in granular materials. To discuss the results of CT scanning quantitatively, a digital image correlation method is used and then, the distribution of the displacements in the shear box, shear strain, and volumetric strain are measured using CT data. In addition, a series of numerical analysis using discrete element method (DEM), which is often used for granular materials, is carried out for the same cases as direct shear test to validate the CT results. Finally, based on the comparative discussion between test results with CT scanning and DEM results, the direct shear behavior of different granular materials is precisely investigated for the first time using X-ray CT. The use of tire chips mixed with sand decreases the dilatant behavior under shear stress, and the peaks in shear stress are no longer observed. In addition, tire chips seem to prevent shear bands to propagate in the material.
PubDate: 2019-03-22

• Effects of Fly Ash on Liquefaction Characteristics of Ottawa Sand
• Abstract: This paper presents the results of effects of non-plastic fines (Class F fly ash) on liquefaction behavior of Ottawa sand. Stress-controlled cyclic triaxial tests were performed on clean Ottawa sand, fly ash, and sand–fly ash mixtures containing 10, 20, 25, 30, 50, and 70% of fly ash. For the evaluation of the effects of confining pressure on liquefaction resistance, three series of tests were conducted at 34.48, 68.96, and 103.42 kPa initial effective confining pressures, except for pure fly ash. In the case of pure fly ash, tests were conducted only at an effective confining pressure of 34.48 kPa. The reversible shear stress was applied systematically by varying Cyclic Stress Ratio from 0.1 to 0.5. Addition of fly ash to sand resulted in decrease in liquefaction resistance initially and then increase in liquefaction resistance for fly ash contents up to about 20–25%. Increase in fly ash content beyond 25% was seen to decrease the liquefaction resistance.
PubDate: 2019-03-12

• Effect of Clay Content on Soil Stabilization with Alkaline Activation
• Abstract: This paper presents the role of clay portion in soil used to stabilize soils during alkaline activation with potassium-based alkaline activator. A 10 M potassium hydroxide solution was utilized to activate the soils with and without palm oil fuel ash (POFA) at a solution. Soils with and without POFA mixtures were tested using unconfined compression tests and microstructural analysis (using scanning electron microscopy and X-ray diffraction). Comparing the strength of the mixtures with and without POFA, the results presented that short-term compressive strength was higher for mixtures with POFA. However, after longer curing the admixtures of higher kaolinite content with POFA reached significantly higher strength levels than the admixtures without POFA. This work brings new insights to the soil stabilization by alkaline activation providing a relatively new avenue for effective utilization of aluminosilicate source materials with parent-treated soils. The clay minerals of hosted soil play an important role in soil stabilization with alkaline activation that affects the behavior of binder with hosted soil.
PubDate: 2019-02-22

• Analytical Investigation of Load Over Pipe Covered with
Geosynthetic-Reinforced Sandy Soil
• Abstract: A geosynthetic reinforcement layer can be placed above the pipe in a ditch within the sandy soil cover to reduce the load on the crown of the pipe. The vertical load (V) on the crown of the rigid pipe without the geosynthetic layer is given as $$V={C_{\text{d}}}\gamma {B^2}$$ , where $$\gamma$$ is the total unit weight of sandy soil, B is the ditch width and $${C_{\text{d}}}$$ is the load coefficient. The analytical formulation for load on the crown of the pipe covered with a single layer of geosynthetic-reinforced sandy soil has been developed earlier. In this paper, an attempt is made to derive an analytical formulation to investigate the load coefficient for pipe covered with sandy soil reinforced with two layers of geosynthetic reinforcement. It is observed that the two layers of geosynthetic reinforcement provide more benefits than a single-layer reinforcement in terms of the load reduction on the pipe. It is also noted that the stiffness of geosynthetic, buried depth, layer spacing and rut depth affect the load on the crown of the pipe. An illustrative example is presented in order to explain how the engineers can determine the load on the pipe using the analytical expression presented in this paper.
PubDate: 2019-02-22

• Bearing Capacity of Square Footing Resting on Fibre-Reinforced Pond Ash
Overlying Soft Clay
• Abstract: This paper presents the results of an experimental and numerical investigation carried out on a two layered soil system which contains unreinforced/randomly distributed fibre-reinforced pond ash (RDFP) layer overlying a soft clay layer. Model tests have been performed on square footing resting on unreinforced/RDFP layer overlying soft clay. The effect of pond ash layer (unreinforced/reinforced) has been studied by varying its thickness as 0.5B, 1.0B and 1.5B where B is the width of the footing. The effect of polypropylene fibres of lengths 6 mm, 12 mm and 18 mm have also been studied with varying in their percentage as 0.5%, 0.75% and 1%. Results have shown that there is significant amount of improvement in ultimate bearing capacity as well as in the settlement of the soil system due to the provision of pond ash layer over soft clay. Finite element analysis of the model footing has also been done with PLAXIS 3D software. The experimental results have been validated by the results obtained numerically.
PubDate: 2019-02-14

• Laboratory Study on Single Stone Columns Reinforced with Steel Bars and
Discs
• Abstract: Stone columns are widely used as an effective and environmental friendly improvement method for increasing the load-carrying capacity of soft clay soils. In very soft clay soils, reinforced stone columns are used because of the lack of the lateral confinement created by the surrounding soil. To provide lateral additional confinement, geosynthetics are usually used. This study intends to evaluate the use of vertical steel bars and horizontal steel discs as an alternative way to geosynthetics to investigate the effect of reinforcement on the footing load-carrying characteristics. Therefore, some large-scale laboratory tests were conducted on stone columns with diameters of 80 and 100 mm and a length to diameter of 5. The results show that changing the arrangement of the bars to a higher stiffness leads to increase in load-carrying capacity. Reinforcing the full-length of the stone columns with the bars in comparison to half-length reinforced has significant influence in capacity. However, in the case of horizontal discs, this increase is negligible. Also by decreasing the space of the discs, load-carrying capacity increases. Moreover, the performance of the vertical reinforced stone column seemed to be better than the horizontal reinforced stone column. The increase of load-carrying capacity in reinforced stone columns with vertical bars or horizontal discs is higher than geotextile reinforcement in the same conditions.
PubDate: 2019-01-29

• Experimental and Numerical Modeling of Nano-clay Effect on Seepage Rate in
Earth Dams
• Abstract: Earth dams control and store river water. Type of the earth dam is selected on the basis of available borrow sources. Where it is not possible to have access to suitable fine-grained sources for constructing an earth dam, then using homogeneous materials and an impermeable blanket is recommended. In this research, a mixture of sandy soil with 0.25, 0.5, 0.75, and 1 wt% of montmorillonite nano-clay was used to make the impermeable blanket. After initial tests of gradation, permeability, and optimum moisture content on the soils, experimental models of homogeneous earth dam with an impermeable blanket were constructed. The time needed to reach the steady-state phreatic line and seepage discharge in the models was compared in transient and unsaturated cases. Results showed that increasing the amount of nano-clay from 0.25 to 1.0%, decreased seepage discharge by 19, 67, 89, and 97%, respectively, compared to the control model. Then, a numerical model of the earth dam was prepared using SEEP/W software and was validated with the experimental results. Results of measured and modeled phreatic lines indicated that the numerical model is accurate enough. Results of sensitivity analysis for blanket thickness showed that seepage rate in 0.5% nano-clay model was 9.46 × 10−6, 8.93 × 10−6, and 8.01 × 10−6 m3/s and in 1.0% nano-clay model was 2.1 × 10−6, 1.44 × 10−6, and 7.80 × 10−7 m3/s for 3, 5, and 10 cm blankets, respectively. In general, using a blanket with small amount of nano-clay on the reservoir side of the earth dam could alleviate seepage problems.
PubDate: 2018-12-19

• Behavior of an Embankment on Column–Slab Improved Clay Deposit
• Abstract: The performance of an embankment constructed on a cement deep mixing-formed column–slab system improved soft clay deposit was analyzed using field measurements and finite element simulation results. By back-fitting the measured surface settlement curve, it was interpreted that parts of the columns might have failed in compression, and the field mobilized compressive strength was lower than the designed value. Further, the numerical results indicate that some of the columns under the toe of the embankment failed by bending, but the current design method used in Japan does not check for this failure mechanism. In addition, for a soil–cement slab constructed on the ground surface, under a relatively high embankment load, tensile cracks will most likely form in the slab. Therefore, it is suggested that in design, the main function of the slab can be considered for reducing the differential settlement between columns and the surrounding soils; the strength of the slab may be ignored in stability analysis.
PubDate: 2018-10-29

• Performance of Compacted Lime Column and Lime-Fly Ash Column Techniques
for Cochin Marine Clays
• Abstract: Large deposits of marine clays are encountered all along the Indian coastal belt. The marine clays are soft clays characterized by low shear strength and high compressibility. In Cochin, most of the areas consist of soft marine clay deposits. The presence of weak marine clays demands the use of expensive deep foundations in these areas. Also the settlement of foundations is a major problem associated with the structures constructed over these areas. This paper presents the results of laboratory studies to determine the improvement of engineering properties of Cochin marine clay by introduction of compacted lime column and lime fly ash column techniques with and without preloading. The test results indicate that the compacted lime column and lime fly ash column improve the physical, chemical and engineering characteristics of soft clay very effectively. From the studies, it is noted that the columnar intrusion with preloading can substantially improve the soil properties and can lead to economy in design of foundations and retaining systems during deep excavations.
PubDate: 2018-10-28

• Load and Deformation Mechanisms in Geosynthetic-Reinforced Piled
Embankments
• Abstract: Geosynthetic-reinforced piled embankments have been increasingly used to stabilise embankments over soft soils. The presence of the reinforcement reduces the stresses transferred to the soft foundation and improves the efficiency of the transference of loads to the piles. Therefore, significant reductions in fill settlements and in lateral displacements of the soft soil can be obtained. However, the design of this type of work is still complex and simple theoretical approaches are commonly employed in practice. This paper investigates the load transference and deformation mechanisms in reinforced piled embankments by means of large-scale laboratory tests. Four types of geosynthetics, including a geogrid and three geotextiles, were tested with varying values of tensile stiffness. Surcharges on the fill surface of up to 40 kPa (200 kPa under prototype conditions) were applied. Test measurements were compared with predictions from some currently employed analytical methods. The results obtained showed the benefits of using geosynthetic reinforcement in this type of work and that significant variations among predictions by analytical methods and measurements may occur. It is recommended that sound engineering judgement be exercised when using analytical solutions in the design of geosynthetic-reinforced piled embankments on soft subgrades.
PubDate: 2018-10-26

• Efficacy of Engineered Backfilling in Limiting Settlements During Future
Deep Excavations
• Abstract: Nuclear power plants and their associated facilities are supported by rock formations and require deep excavation to reach an appropriate level, which is often between 15 and 20 m in the context of India. Currently, these facilities are planned with provisions for future expansion and to facilitate future excavation, retaining walls are designed and constructed along with the main plant. Engineering backfilling is carried out with field compaction around the counterfort retaining wall, where few critical structures will be located. The efficacy of this engineering backilling in limiting the settlements during future excavation was studied using finite element software PLAXIS employing constitutive models, namely, the Mohr–Coulomb and Hardening Soil models. Stiffness properties of improved soil were determined using pressuremeter tests and compared with that obtained from back analysis using field instrumentation data. Since the settlements of engineered backfill soil mass were found to be beyond the permissible limits during future excavation, additional measures such as strutting and stiffness improvement of already placed backfill are essential to limit the settlements within the permissible limit. This is required to ensure the safety of critical structures which will be located in this zone of influence. However, a proper instrumentation scheme to monitor settlement of soil mass must be employed during the future excavation for identifying corrective actions required to ensure the safety of adjacent structures.
PubDate: 2018-10-20

• Predicting the Settlement of Raft Resting on Sand Reinforced with Planar
and Geocell Using Generalized Regression Neural Networks (GRNN) and Back
Propagated Neural Networks (BPNN)
• Abstract: In this study, geogrid and geocell as soil improvement methodologies had been used to improve the tensile characteristics of soil. The variation in settlement by using geogrid as reinforcing material at different relative density, different combination of reinforcement depths with different layers of reinforcement of soil with geogrid had been studied by conducting lab experiments. The results of the various experiments have been modeled using back propagated neural networks (BPNN) and generalized regression neural networks (GRNN) for predicting settlements at different combinations of placing of geogrid in soil. Both the models had been compared and it was found that in case of geogrid as a reinforcing material BPNN model with Levenberg–Marquardt algorithm gave better results compared to GRNN models. The results of experiments with geocell as a reinforcing material were also used separately with variable parameters such as relative density, depth of reinforcement, number of layers, and height of geocell for making BPNN and GRNN models.
PubDate: 2018-10-15

• Shear Resistance Characteristics of Soil–Geomembrane Interfaces
• Abstract: The shear resistance at soil–geomembrane interfaces is critically important for the proper design of geomembrane-lined side slopes of landfills, reservoirs, and canals. The dependable design and construction of such applications is enhanced by the experimental documentation of the interaction behavior between different soils and various geomembrane types. Toward this end, direct shear tests were conducted on 29 soil–geomembrane interfaces using a conventional (100 mm) shear box. Two dry and dense uniform sands, one with rounded and one with sub-angular grains of the same size, and one compacted cohesive soil of low plasticity were tested in contact with seven geomembranes of different types with smooth or rough surfaces. The direct shear tests yielded linear failure envelopes with no adhesion for the sand–geomembrane interfaces and polynomial failure envelopes for the cohesive soil–geomembrane interfaces, possibly indicating a transition from drained to undrained conditions at the interface with increasing normal stress. Sub-angular sand grains, soft geomembranes, and rough geomembrane surfaces were found to mobilize interface shear resistance more effectively. The shear resistance parameters are functions of the shearing displacement at the cohesive soil–geomembrane interfaces and their values at failure reveal a transition from “friction-like” behavior to “adhesion-like” behavior as normal stress increases. The ratio between the friction coefficient values for the sand–geomembrane interfaces tested ranges from approximately 1 to 2. For the geomembrane types tested, differences in failure shear stress at the cohesive soil–geomembrane interfaces are generally limited to ± 20%.
PubDate: 2018-10-08

• Passive Force–Displacement Behaviour of GRS Bridge Abutments
• Abstract: Many bridge abutments suffered severe damages due to pounding of superstructure elements of the bridge during seismic excitation. Collision of the girder is resisted by passive pressures mobilised in the backfill soils. Seismic load on the bridge structure causes the bridge abutments to undergo lateral translation (Δ) and rotation. The present study focuses on the evaluation of passive force (Pp) developed in the reinforced backfills of the geosynthetic-reinforced soil (GRS) bridge abutments. The GRS abutments of nine configurations with three different geogrid spacing and three different geogrid lengths are modelled using finite element (FE) approach under lateral push. Hypoplastic soil constitutive model with inter-granular strain concept is used to model the soil behaviour. User material subroutine, VUMAT is developed to simulate the soil behaviour in Abaqus. The maximum passive resistance (Pp,ult) increases by 12% in the GRS abutments with closer geogrid spacing.
PubDate: 2018-09-21

• Effect of Anisotropy on Cyclic Properties of Chennai Marine Clay
• Abstract: Variations of normalized shear modulus (G/Gmax) and damping ratio (D) with strain are important for site response studies, analysis of machine foundation, etc. In this study, an attempt was made to investigate the effect of anisotropic consolidation on cyclic behaviour of the Chennai marine clay. The anisotropic consolidation on the specimens was represented through a parameter called stress ratio (Kc), which is defined as the ratio of radial stress to the axial stress on the specimen. A series of cyclic triaxial and resonant column tests were conducted on reconstituted marine clay specimens at three stress ratio (Kc) of 1.00, 0.67 and 0.55. In this study, all the tests were conducted on normally consolidated specimen, where stress ratio (Kc) is less than or equal to one. The test results show that the normalized shear modulus and damping ratio are affected by the stress ratio (Kc). Moreover, the effect of cyclic loading parameters such as loading cycles and loading frequency on normalized shear modulus (G/Gmax) and damping ratio curves with stress ratio (Kc) is also presented. Based on the cyclic test results, a hyperbolic model was proposed to predict the variation of normalized shear modulus curve (G/Gmax) with stress ratio (Kc).
PubDate: 2018-08-30

• Experimental Study on the Load-Carrying Capacity of Single Stone Columns
• Abstract: Stone columns are considered as one of the influential soil-stabilising methods that can increase the strength and workability of soft soil foundations considerably. In order to enhance stone columns workability, in this experimental study, some laboratory tests were carried out on different columns. They consist of various gravel shapes and particles distributions and columns reinforced by steel fibre reinforcements as well. Some additional tests were also conducted on columns covered by an ordinary gravel mattress reinforced by geotextile. In addition, stone columns with diameters of 63 and 92 mm were tested with a length-to-diameter ratio of 5. The test results were compared with different shapes of geotextiles, such as routine (full-length sleeve) and ring shapes, as the encasing material. It has been observed that using the mattress, geotextile and steel-fibre reinforcements enhances the load-carrying capacity of them that provide a basis for reasonable predictions on their settlement behaviour.
PubDate: 2018-08-28

• Long-term Performance Studies on Strength Characteristics of Black Cotton
Soil Reinforced with Untreated and Treated Coir Fibre
• Abstract: Strength retention on the long run can be improved by making coir fibres less water absorbent. In the present study, coir fibres have been alkali treated and admixed in black cotton soil. Use of untreated and treated coir fibres (UCF and TCF) to black cotton soil is comparatively investigated in terms of UCS using remoulded specimens compacted with wide range of dry densities and water contents on the basis of compaction test. Long-term performance is evaluated by curing the remoulded specimens for periods ranging from 0 to 360 days. The test results indicated that the strength of black cotton soil reinforced with UCF and TCF is significantly affected by fibre content, dry density and water content and changes the failure behaviour from brittle to ductile. Long-term performance can be significantly improved by using treated coir fibres, in which the reduction in strength of black cotton soil admixed with treated coir fibres indicated marginal loss of strength, at around 21.16%.
PubDate: 2018-08-16

• Determination of Required Reinforcement Force in Geosynthetic Reinforced
• Abstract: This paper presents a simplified analytical approach for computing the required reinforcement tensile force of the geosynthetic reinforced soil walls subjected to earthquake loads using the method of horizontal slices. In the analysis, the earthquake load is taken into account by following the pseudo-static approach. The proposed formulation considers the equilibrium of potential failure mass bounded by a nonlinear slip surface similar to that observed in the earlier experimental investigation. The effects of pseudo-static seismic acceleration in horizontal and vertical directions, as well as the friction angle along the soil–wall interface, have been considered in the analysis. It has been found that the computed values of total tensile force required by the geosynthetic reinforcements from the present study compare favorably well with the methods reported in the literature. Furthermore, the present approach is straightforward and can be easily implemented through a simple spreadsheet application.
PubDate: 2018-08-03

• Numerical Modelling of Stone Column Installation Effects on Performance of
Circular Footing
PubDate: 2018-08-03

• Spectral Analysis of the Response of Coarse Granular Material to Dynamic
Penetration Test Modelled with DEM
• Abstract: Dynamic penetration tests are often used to determine the strength properties of surface soils. The paper presents a study on the use of spectral analysis on dynamic cone penetration tests results, modelled with discrete element method. This method is applied to assess the effect of the variation of the grain size distribution of the soil on test results. A two-dimensional discrete model is used to reproduce cone penetration tests in dynamic conditions: the tip of the penetrometer is driven in the material by successive impacts of a hammer on the penetrometer. For each impact of the hammer, a curve of the load applied by the tip on the soil is obtained versus the penetration distance of the tip. The curves of the load versus penetration traditionally used to calculate the tip resistance of the soil are analyzed with discrete Fourier transform in order to investigate curve’s shape. The effect of the variation of the grain size distribution of the soil on these curves is investigated, i.e. average particle diameter and span of particle size distribution. It was found out that the grain size distribution influences tip resistance but also the shape and oscillation modes of the curve of the stress–penetration curve. Based on these indicators, the exploitation of the load–displacement curve obtained with dynamic penetration tests could be enlarged to determine other properties of the soils.
PubDate: 2018-07-25

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