Large Direct Shear Tests Research Articles

Characterization of embankment material using sand tire mix as additive and validating the results obtained from large scale direct shear test in Abaqus software

Laboratory direct shear tests often overlook larger particles due to limitations in shear box design, resulting in an inadequate portrayal of real-world soil conditions. To address this gap, the use of large-scale direct shear apparatus capable of accommodating larger particles is essential. However, conducting such tests with varied sizes of tire shreds, mixing ratios, and loads is intricate and resource-intensive. Therefore, the utilization of numerical modeling is suggested to simulate sand-tire mixtures under diverse conditions. This study presents conclusions derived from comparing numerical results with experimental observations, demonstrating a close correspondence between the two. It offers a comprehensive examination of the impact of sand and shredded tires mixtures on shear strength, indicating a consistent pattern: increased quantities of tire shreds correspond to heightened friction angles. Furthermore, specimens containing larger shredded tire particles display elevated friction angles, implying a possible connection between particle size and frictional behavior. This investigation underscores the importance of numerical modeling as a cost-efficient and effective approach to complement experimental inquiries, enriching our comprehension of soil-tire mixture dynamics and guiding practical applications in transportation and geotechnical engineering.

Study on large scale direct shear test on soil-rock mixture with multiple grain grades in high fill slope engineering

Soil-rock mixtures are multiphase natural geological materials composed of mineral particles of multiple grain sizes, and have significant natural characteristics of multiscale material groups. In order to investigate the shear strength characteristics and deformation failure characteristics of soil-rock mixtures with multiple grain sizes under in-situ conditions in fill engineering, samples of soil-rock mixtures with multiple grain sizes under in-situ conditions were prepared, and large-scale in-situ direct shear tests were conducted under natural and water-soaked conditions. The test results showed that the shear strength of soil-rock mixtures is relatively high, and after saturated by water immersion, its shear strength decreases significantly, mainly manifested in the decrease of internal friction angle while the cohesion remains basically unchanged. The cohesion of soil-rock mixtures with multiple grain sizes is mainly provided by the shear-breaking cohesion of coarse particles such as gravel in the soil-rock mixture, and its degree of exertion is controlled by the grading characteristics and particle morphology of the soil-rock mixture and affected by constraints. The reason for the significant decrease in shear strength of soil-rock mixtures with multiple grain sizes after water-soaked saturation can be explained as follows: the clay film covering the surface of coarse particles becomes soft after water immersion, resulting in a significant decrease in the sliding friction resistance between coarse particles and the clay film, as well as the occlusion friction resistance generated by the rotation transfer between coarse particles through the clay film interface.

Thin layer interface: An alternative modeling consideration in soil-structure interaction system

The numerical modeling of a soil-structure interaction (SSI) system subjected to lateral loads depends mainly upon the interface behavior. The soil stiffness in relation to the structure is quite low, and the structure generally has a rough surface in contact with the soil. As a result of the slipping and rolling of soil grains caused by friction, a thin layer of shear zone forms in soil with the application of lateral loads. A thin layer interface is represented by the shear zone. As a result, the decision on the thickness requirement is critical for appropriate modeling of the thin layer interface, which is rarely documented by researchers. Furthermore, it has been reviewed in the literature that modeling the SSI system with a thin layer interface more accurately replicates the physical system than modeling it with a zero-thickness interface. The methodology for effective usage (in terms of proper interface thickness) of the thin-layer interface in SSI system using finite element (FE) modeling is proposed in this work. The thickness of the interface has also been determined via numerical modeling of a large direct shear test (DST).

Utilization of recycled construction and demolition waste to improve the bearing capacity of loose sand: an integrated experimental and numerical study

ABSTRACT The present study examines the efficacy of the thickness of recycled construction and demolition waste (RCDW) layer (0.4D, 0.6D, 0.8D, 1D and 1.2D; D: diameter of footing) prepared at different relative densities (30%, 50% and 70%) overlaying on loose sand. Two sizes of RCDW, 5 mm named RCDW-I and 10.6 mm named RCDW-II, were used in this investigation. The plate load test and finite element analysis using ABAQUS were carried out on different combinations. Moreover, a large box direct shear test was conducted to determine the angle of internal friction (α) of RCDW-I and RCDW-II at relative densities (ID) of 30%, 50% and 70%. With the usage of RCDW layer over sand, the ultimate bearing capacity increases by 640% for RCDW-I and 597% for RCDW-II, and the corresponding decrement in the settlement was 36.86% and 33.54% (at ID = 70% and u = 1.2B), respectively. The conjoined analysis shows that RCDW-II performs better than RCDW-I at lower ID. Whereas the opposite trend is witnessed at higher ID. The experimental results were compared to the numerical model created in ABAQUS 3D. In addition, regression analysis was performed using SPSS software to build empirical expressions of the given results.

The Shear Strength of Root–Soil Composites in Different Growth Periods and Their Effects on Slope Stability

Vegetation slope protection plays an important role in improving the slope stability and protecting the environment. In this study, the mechanical properties of root–soil composites in different growth periods and their effects on slope stability were investigated. First, the shear strength of undisturbed root–soil composites associated with Cynodon dactylon (C.d), Magnolia multiflora (M.m) and grass and shrub mixture (G.s) were measured by large direct shear tests. Then, the effects of plant reinforcement in different growth periods on slope stability were analyzed using ABAQUS. The results show that the shear strength of the root–soil composites were significantly higher than that of the unreinforced soil. The root–soil composites met the Mohr–Coulomb criterion. The shear strength of the three root–soil composites increased first and then decreased during the vegetation growth period. The calculation results show that the factor of safety (FS) of the bare slope was 1.482. The FS values of the C.d, M.m, and G.s slopes were 1.601, 1.658 and 1.715, which increased by 8%, 11.9% and 15.7% compared to the bare soil slopes. Therefore, vegetation could significantly improve slope stability, especially the grass–shrub mixture model. This could provide a rational basis for designing and constructing plant slope protection.

Case History of Random Material Shear Strength Evaluation using In-situ Large Scale Direct Shear Test in the Construction of the Longest Dam in the Southeast Asian

A modern dam offers many benefits to society, including water conservation, farming sustainability, energy source, and recreational activities. In Indonesia, more than 50 dams are constructed as strategic national projects within the last decade. A zoned earth-fill dam, built using soil and rock materials, is one of the most common dam types in Indonesia. This dam allows a specific material type to be placed in a particular zone, including random material fill zone. A random material is usually obtained from dam excavation work as well as borrow area. It normally contains wide range of grain sizes and a variety of weathering degree. On one hand, this material is very economic. On the other hand, it introduces a challenge in shear strength assessment. Random material frequently contains large size grain that inhibits regular laboratory test use. A catastrophic Indonesian dam construction failure in 2021 was partly attributed to inadequacy in assessing shear strength of random material. This case history highlighted the importance of a proper random material shear strength evaluation. The other dams coincidentally under construction at that time then experienced rigorous shear strength evaluations, including Semantok Dam in Nganjuk, East Java. This dam, designed to be approximately 33-m max high and 3.1-km long, is the current longest dam in the Southeast Asian. An in-situ large scale direct shear device as large as 80 cm × 80 cm × 30 cm was developed to test random material in Semantok Dam. Eight locations in random fill zones were selected. Three series of direct shear test were conducted in each location. Testing results based on 24-large size sample showed a great variability in Mohr-Coulomb parameters. The angle of internal friction ranged from 11.4° to 36.7° with average value of 27.8°, whereas the cohesion varied from 25.3 kPa to 138.6 kPa with average value of 85.2 kPa. High variation in shear strength parameters showed that such test should be performed to verify the design parameter. This in-situ large scale direct shear test provides an appealing method to assess shear strength of random material. This large-scale test is strongly recommended for a common practice in dam construction.

Analysis of direct shear test of incineration slag reinforced with waste tire strips by discrete element method

The mechanical properties of incineration slag and waste tire reinforced incineration slag (RIS) were investigated by a series of large direct shear tests. The results show that the addition of waste tire strips can improve the shear mechanical properties of incineration slag. The mechanical behavior and evolution law of RIS were mainly studied by macroscopic laboratory tests, discrete element method (DEM) simulation and microscopic theory analysis. At the same time, the microscopic mechanical properties are analyzed from the microscopic perspectives of contact force chain, porosity, velocity field, stress deflection, fabric analysis and coordination number. At the microscopic level, the contact force chain, the principal stress field and the contact fabric all show similar evolution laws. It reflects the consistency of the microscopic response of particles under the effect of macroscopic external force. The porosity and coordination number reflect the macroscopic dilatancy of the sample from the microscopic change, and explain the reinforcement mechanism from the microscopic point of view.

Evaluating the Shear Strength of Subbase-subgrade Interface Using Large Scale Direct Shear Test

The inclusion of geogrid in road pavements can improve pavement performance through increasing the lateral confinement, bearing capacity, and overall rigidity of the pavement, as well as reducing the vertical and lateral pavement deformations. The materials used in the present study are: subbase granular materials Type B, two types of subgrade soil; clay and sandy soil, and two nonwoven biaxial geogrids (G1 and G2) used as reinforcing materials. Direct shear testing was adopted by manufacturing a large-scale direct shear apparatus consisted of an upper, square box of size 20 cm × 20 cm × 10 cm, and a lower, rectangular box of size 200 mm × 250 mm × 100 mm is used in the present study. The results show that, for the four normal stresses equal to 25, 50, 75 and 100 kPa, the interface shear stress curves increased and followed similar trend. For clay-subbase interface, installation of geogrid decreases the apparent cohesion of the material from 16.5 kPa (without reinforcement) to be 8 kPa and 13.5 kPa for G1 and G2, respectively. At sand-subbase interface, using geogrid leads to increase the cohesion of the material from 3.5 kPa to be 15.5 and 16 kPa for G1 and G2, respectively. The friction angle increases slightly from 30o (without reinforcement) to be 35o for G1 and G2 when the interface is subbase over clay. While, it decreased from 35.8o to be 32.1o for G1 and G2 at sand-subbase interface. The interaction coefficient for G1 and G2 increased when the normal strength increased at the clay-subbase interface. Otherwise, the behavior of interaction coefficient of the sand-subbase interface appears deferent trend, where increasing normal stress leads to decrease the interaction.

Sustainable utilisation of steel slag as granular column for ground improvement in geotechnical projects

Granular column is an attractive mitigation method which is widely used in geotechnical engineering to enhance the bearing capacity, reduce settlement and accelerate consolidation. Utilisation of industrial wastes such as steel slag in soil stabilization can be an environment-friendly and cost-effective extraction technique to the disposal of solid waste materials. Previous studies investigated the bearing capacity and settlement of ground improved with granular columns with or without the geosynthetic encasement. However, very limited number of studies have investigated the response of ordinary stone columns without encasement and geosynthetic encased steel slag columns under lateral loading. In this paper, the lateral load capacity of steel slag granular column-soil composites has been investigated. For this purpose, a series of large direct shear tests were performed on the column-soil composites with the steel slag column and the ordinary stone column with or without the geosynthetic encasement. The effect of type of column materials (steel slag and sand), column diameter, number of columns, columns arrangement, and geosynthetic encasement on the shear strength parameters of column-soil composites have been studied. The experimental results show the effectiveness of using the steel slag columns to improve the lateral load-bearing performance of soil.

Effect of one cycle of heating-cooling on the clay-concrete pile interface shear strength parameters

This study investigated the effect of applying a one heating-cooling cycle on the interface strength parameters of saturated clay soil in contact with concrete, and the potential use of heating to improve/increase the pile capacity. A large direct shear test device with inner dimensions of 300 mm, 300 mm, and 200 mm for width, length, and height, respectively, was modified to perform the soil-concrete interface tests. A concrete block was built and placed in the bottom section of the shear device. Heating rods system were used to heat the circulating water that heated the specimens. The experimental tests were conducted on low plasticity soil with PI = 12, medium plasticity soil with PI = 29, and high plasticity soil with PI = 60. The specimens were first consolidated to a target normal stress prior to shearing. Two tests were performed for each normal stress and clay type with one test performed without heating-cooling cycle at ∼20 °C and the other test performed at ∼20 °C after a heating-cooling cycle up to 70 °C. The specimens were tested under different normal stresses ranging from 30 to 150 kPa. The specimens' temperature was increased gradually during the heating process from room temperature (∼20 °C) to ∼70 °C. The specimens were then gradually cooled back to room temperature. The test results showed significant increase in both the peak and residual interface friction angles by a percent ranges from 13.6% to 35.5%. The specimens subjected to a one heating-cooling cycle during shear experienced significant volumetric reduction by a percent ranges from 11.3% to 96%. The thermally induced “contraction” volumetric strain (TIVS) was found to increase with increasing temperature loading and the plasticity index, PI, but independent of the applied normal stress.

A Shear Device with Controlled Boundary Conditions for Very Large Nonplanar Rock Discontinuities

Abstract The shear strength of rock discontinuities is an important design parameter that is noted to be scale dependent. Historically, discontinuity shear strength and scale dependency studies have used small to medium size laboratory shear devices that accommodate specimens with a relatively small area (0.01 to 1 m2) compared to real discontinuities. In the literature, there is a limited amount of shear strength studies available on discontinuity surfaces with areas of several square meters. This is inherently linked to the challenging nature of performing large shear tests. As shear strength scale dependency is still a timely topic, there is still a need for conducting large scale direct shear tests to support research. To facilitate investigations into the shear response of large discontinuities, a very large shear device was designed and built at the University of Newcastle, Australia. The device is designed to accommodate 2 m by 2 m specimens and restrict rotation and translations of the top surface during shearing. This article presents the design and characteristics of the shear device, the process undertaken to create 2 m by 2 m mortar discontinuity replicas and the experimental results of the first series of direct shear tests conducted. The experimental results confirm the systems design for restricting undesired translations and rotations of the tested specimen surfaces and test repeatability.

Shear Mechanical Properties of the Interphase between Soil–Rock Mixtures and Benched Bedrock Slope Surfaces

A series of benched excavations are typically carried out on bedrock slope surfaces to improve the stability of soil–rock mixtures (SRMs) on the fill slopes. In this paper, the shear characteristics and micromechanisms of SRMs–bedrock interphases were studied by means of large direct shear tests and discrete-element numerical simulation. In the process, this study also investigated the influences of rock block content and interface roughness by combining the direct shear test and discrete-element method (DEM) numerical simulation results. This showed that the samples exhibit obvious bulk shrinkage during shearing. As the rock block content increases, fluctuations in the postpeak shear stress–displacement curves become more obvious. Cohesion is more sensitive to roughness, while internal friction angle is insensitive to roughness. Also, the internal friction angle is very sensitive to rock block content. Moreover, the shear strength and cohesion of the interphase increase along with the superficial roughness, demonstrating a quadratic correlation with rock block content. However, this increase in roughness also increases the fracturing of rock blocks in the interphase. Within a certain interval, the shear strength of SRMs–bedrock interphases can be estimated according to a fitted empirical formula.

Geotechnical assessment and large scale direct shear testing on recycled brick aggregates

The current scenario of handling and recycling of construction and demolition (C&D) waste in India is not very promising. The proper management of C&D waste material is necessary to achieve sustainability goals in the field of Civil Engineering. In this research, the utility of recycled brick aggregates (RBA) in geotechnical applications is assessed by performing an extensive experimental program which includes tests like: particle size distribution, specific gravity, water absorption, modified proctor compaction, relative density, aggregate crushing, slake durability index, aggregate impact and Los Angeles abrasion. Shear strength parameters of RBA are evaluated by performing large scale direct shear test (DST). Source of origin of recycled brick aggregates (RBA) for the present study is MNIT campus, Jaipur. The RBA are found to have good compaction and shear strength characteristics as the values of maximum dry density (MDD), optimum moisture content (OMC), cohesion (c’) and angle of shearing resistance (Ф’), evaluated as 2.03 gm/cm3, 11.52 %, 55.82 kPa and 68° respectively. The large scale DST results are also compared with the available literature. The RBA are found to have susceptibility towards crushing failure, thus this study concludes that the RBA may provide good performance as a base/sub-base or backfill material only under the light loading conditions like: - footpath sub-base, light traffic loading road base and sub-base etc. It is recommended that the incorporation of geosynthetic reinforcements or some durable C&D waste aggregates in RBA may enhance its applicability as a sub-base material under heavy traffic pavements.

A study on soil interface interaction

Interfaces between soil-concrete, soil-steel, soil-root, soil-wood, soil-polymer frequently stumble upon various geotechnical engineering applications. Several studies agree that the material properties interfacing with the soil, the properties and the performance of the soil at the interface makes it even more multifaceted and interesting. Highly plastic, over consolidated clays, crushable calcareous sands, soft marine clays, clays with organic content etc., show unusual complications related to cast in situ and driven pile shaft capacity calculations, functioning of various infrastructural projects that comes in contact with soil. Several testing methodologies have been developed to examine the interface behaviour under different conditions, it substantiates determination of the interface shear strength parameters for design. Such studies involve real time understanding of the frictional anisotropy which is possible through large scale direct shear tests, tilting frames, simple shear tests and radial shear experiments for finding the interface between soil and material. In addition, microstructural investigations are also to be piloted to realize the shearing mechanism of the soil material interfaces. Yet standard testing conditions for evaluating the interface angle simulating the real time environment is not yet available. A systematic review of the study on appropriate mechanisms available for investigating the Soil Material Interface is done, which will aim to suggest improvements by critically identifying their shortcomings.

Influencing Factors of Interfacial Behavior between Geogrid and Coal Gangue

Coal gangue is a type of solid waste that is generated in the process of coal mining and washing. This concept can be effectively used in reinforced engineering fillings. The influences of shear rates and geogrid transverse ribs were studied using a large indoor direct shear test. The test results showed that the relationship between shear stress and shear displacement of geogrid‐coal gangue is nonlinear, and the shear process is accompanied by the crushing of coal gangue particles. The addition of geogrid significantly improved the shear stress and interfacial quasi‐cohesion of geogrid‐coal gangue, whereas the interfacial quasi‐friction angle remained almost unaffected. When normal stress was greater than 25 kPa, the shear stress gradually increased as the shear rate was increased from 1 to 5 mm/s. With an increasing shear rate, the interfacial quasi‐friction angle increased, whereas the interfacial quasi‐cohesion decreased. The interfacial shear stress, interfacial adhesion, and interfacial friction angle decreased with the number of geogrid ribs; the contribution of the middle transverse rib to the interfacial shear strength was smaller than that of the transverse rib at the far end in the shearing direction.

Analysis of Progressive Failure between Soil and Structure Interface in the Direct Shear Test Using a New Method

Abstract In recent years, the trend of landslide disasters increases year by year with the rapid development of economic construction. The landslide caused massive casualties and economic losses. In this paper, a new kind of stress-displacement sensor, which can monitor the stress and displacement of local points on the contact surface, is developed. A large indoor direct shear test of the contact surface between red clay in Chongqing and structure is carried out by using this sensor. Furthermore, stress and deformation response evolution characteristics of the contact surface under shear loads and different soil compactness and normal stress are discussed. The shear failure of the contact surface between soil and structure is characterized by progressive failure; the normal stress of the contact surface and the compaction degree of the soil has a significant influence on the progressive failure. The test results indicate that the peak stress along the shear direction of the contact surfaces shows obvious inhomogeneity features. Considering the progressive failure characteristics of soil, the shear strength parameters obtained by the traditional large direct shear test underestimated the soil shear strength before the peak shear stress of shear curves. Then, in the post-peak shear stress stage (post-failure zone), the residual strength obtained by large direct shear tests represents the real residual strength of the soil.

Analysis of shear characteristics of prestressed anchor cable and shear resistance of anchor joint plane

Reinforcing a high and steep rock slope is important in a water conservancy project. Accordingly, a prestressed anchor cable is the most commonly used slope reinforcement technology. In relevant standards, the prestressed anchor cable is considered as a tensile structure. In practical engineering, prestressed anchor cable is subjected not only to tensile load, but also to shear load. In this study, a large indoor direct shear test was designed to examine the shear characteristics of a jointed rock mass and the shear rupture rule of the prestressed anchor cable. The shear tests of different anchorage modes (i.e., full-length bond and full-length non-bond), different vertical normal stresses, and different prestress were designed. The results show a significant difference in the shear displacement curves between the full-length bonded anchor cable and the full-length unbonded anchor cable during shearing. The vertical normal stress and the prestress can effectively improve the shear strength of the joint in the front period; however, the higher the prestress, the smaller the shear displacement when the anchor cable is destroyed. The damage of the two types of prestressed anchor cables is basically the same and occurs first at the plastic hinge position.

Generalized Interface Shear Strength Equation for Recycled Materials Reinforced with Geogrids

In this research, large direct shear tests were conducted to evaluate the interface shear strength between reclaimed asphalt pavement (RAP) and kenaf geogrid (RAP–geogrid) and to also assess their viability as an environmentally friendly base course material. The influence of factors such as the gradation of RAP particles and aperture sizes of geogrid (D) on interface shear strength of the RAP–geogrid interface was evaluated under different normal stresses. A critical analysis was conducted on the present and previous test data on geogrids reinforced recycled materials. The D/FD, in which FD is the recycled materials’ particle content finer than the aperture of geogrid, was proposed as a prime parameter governing the interface shear strength. A generalized equation was proposed for predicting the interface shear strength of the form: α = a(D/FD) + b, where α is the interface shear strength coefficient, which is the ratio of the interface shear strength to the shear strength of recycled material, and a and b are constants. The constant values of a and b were found to be dependent upon types of recycled material, irrespective of types of geogrids. A stepwise procedure to determine variable a, which is required for analysis and design of geogrids reinforced recycled materials in roads with various gradations was also suggested.

Comparative Study of Hybrid Artificial Intelligence Approaches for Predicting Peak Shear Strength Along Soil-Geocomposite Drainage Layer Interfaces

Peak shear strength of soil-Geocomposite Drain Layer (GDL) interfaces is an important parameter in the designing and operating related engineering structures. In this paper, a database compiled from 316 large direct shear tests on soil-GDL interfaces has been established. Based on this database, five different machine learning models: Back Propagation Artificial Neural Network (BPANN) and Support Vector Machine (SVM), with hyperparameters optimised by Particle Swarm Optimisation Algorithm (PSO) and Genetic Algorithm (GA), respectively, and Extreme Learning Machine (ELM) optimised by Exhaustive Method, were adopt to assess the peak shear strength of soil-GDL interfaces. Then, a comprehensive investigation and comparison of the predictive performance for the models was conducted. Also, based on the selected optimal machine learning model, sensitivity analysis was conducted, and an empirical equation developed based on it. The research indicated that GA and PSO could significantly increase forecasting precision in a small number of iterations. The BPANN model optimised by PSO has the highest forecasting precision based on the statistics criteria: Root-Mean-Square Error, Correlation Coefficient, Coefficient of Determination, Wilmot’s Index of Agreement, and Mean Absolute Percentage Error. The normal stress has the biggest impact on the peak shear strength, followed by drainage core type, moisture saturation of the soil layer, shearing surface, soil type, consolidation condition, geotextile specification, soil density and drainage core thickness, and the ranking is affected partly by the data distribution of input parameters in the database based on mechanism analysis. An empirical equation developed from the optimal model was proposed to estimate the peak shear strength, which provides convenience for geotechnical engineering personnel with limited knowledge of machine learning technique.

Utilisation of steel slag as a granular column to enhance the lateral load capacity of soil

ABSTRACT Granular columns are widely used to enhance the bearing capacity of weak soil. The filling material of columns is generally stone, gravel or sand. The use of industrial wastes such as steel slag in civil engineering applications not only reduces environmental pollution, but also leads to cost benefits. So far, many studies have been done on the behaviour of granular columns with and without geosynthetic encasement under vertical loads; however, very limited studies were conducted on the behaviour of waste granular columns with and without geosynthetic encasement under lateral loads. Therefore, this study aims to evaluate the lateral load capacity of steel slag granular columns reinforced with geosynthetic using a large direct shear test apparatus. Results demonstrated that the use of steel slag column improved the lateral load capacity of soil. The use of geosynthetic encasement in floating steel slag column could significantly enhance both the peak and critical state shear strength. The results indicated the viability of using steel slag column as a soil reinforcement providing sustainable and technical benefits mainly when using geosynthetic reinforcement.