Shear Box Research Articles

Laboratory Study of Interface Friction between Sand and Steel Surfaces

Abstract In this study, results have been reported from a series of laboratory tests to determine the interface friction angle of steel surfaces with sand through modified direct shear testing. For completion, steel surfaces with different surface geometry to replicate the roughness have been slid against various sands compacted at different relative densities under both dry and wet conditions. The standard square shape direct shear box has been modified into circular and rectangular boxes to sufficiently enhance the contact area and to subsequently quantify its effect on interface friction angle. A mild steel interface of smooth and rough texture with a groove depth of 0.2 mm and tipping at an angle of 90° has been used in this study. The analysis of results revealed that the interface friction angles obtained from the standard direct shear box agree closely with those obtained from both modified rectangular and circular shear boxes. However, the ratio of the interface friction angle from the modified apparatus and soil’s angle of internal friction significantly depends upon the roughness of the surface in contact with the sand, its median particle size, and is independent of the effects of box size, soil’s relative density, and dry or wet condition. A comparison between existing well-accepted guidelines and current observations has been presented for use by the practicing engineers dealing with soil-structure interaction.

Multiscale evaluation of sand-geomaterial interface shear response in terms of material geometry effects

This study evaluates the effects of particle and surface geometric features on the interface shear behavior of sand-geomaterial. Particle shape and size were adjusted for the sand, and surface roughness form and height were set for the geomaterial part. 3D printing technology was used to produce geomaterials in the desired form. A custom-made transparent interface shear box was developed to perform digital image processing. For macroscale response, peak and residual strengths and dilation angle were measured. Sliding percentage and shear band thickness were determined from digital image correlation analyses for the mesoscale response. The experimental results showed that the macroscale response parameters increased as the overall regularity of the sand particles decreased. The increase in mean particle size and roughness height led to an increase in macroscale parameters. Digital image correlation analyses showed that the sliding percentage had an inverse correlation with the shear band thickness in terms of the particle shape and the roughness height effects. The roughness form controlled the trend of mean particle size effects on the sliding percentage. Overall, the mesoscale parameters revealed the traces of interlocking response, particle kinematics, and the failure mechanism in the interface region. Thus, a bridge was established between meso- and macro-scale responses.

Global and Local Shear Behavior of the Frozen Soil–Concrete Interface: Effects of Temperature, Water Content, Normal Stress, and Shear Rate

The interface between soil and concrete in cold climates has a significant effect on the structural integrity of embedded structures, including piles, liners, and others. In this study, a novel temperature control system was employed to conduct direct shear tests on this interface. The test conditions included normal stress (25 to 100 kPa), temperature (ranging from 20 to −6 °C), water content (from 10 to 19%), and shear rates (0.1 to 1.2 mm/min). Simultaneously, the deformation process of the interface was continuously photographed using a modified visual shear box, and the non-uniform deformation mechanism of the interface was analyzed by combining digital image correlation (DIC) technology with the photographic data. The findings revealed that the shear stress–shear displacement curves did not exhibit a discernible peak strength at elevated temperatures, indicating deformation behavior characterized by strain hardening. In the frozen state, however, the deformation softened, and the interfacial ice bonding strength exhibited a positive correlation with decreasing temperature. When the initial water content was 16% and the normal stress was 100 kPa, the peak shear strength increased significantly from 99.9 kPa to 182.9 kPa as the test temperature dropped from 20 °C to −6 °C. Both shear rate and temperature were found to have a marked effect on the peak shear strength, with interface cohesion being the principal factor contributing to this phenomenon. At a shear rate of 0.1 mm/min, the curve showed hardening characteristics, but at other shear rates, the curves exhibited strain-softening behavior, with the softening becoming more pronounced as shear rates increased and temperatures decreased. Due to the refreezing of interfacial ice, the residual shear strength increased in proportion to the reduction in shear rate. On a mesoscopic level, it was evident that the displacement of soil particles near the interface exhibited more pronounced changes. At lower shear rates, the phenomenon of interfacial refreezing became apparent, as evidenced by the periodic changes in interfacial granular displacement at the interface.

The Comparison of Performance of Root Vetiver Grass Between Coconut Fiber and Eggshell Toward Slope Stabilization

Slope stability using vegetation has emerged as a more environmentally friendly and sustainable solution for slope stabilization, replacing traditional structural engineering methods and shotcrete cover. However, despite the application of Vetiver grass, failures in the form of deformation, cracks, and slope collapse still occur. The main objectives of this study are to identify the root properties and analyze the mechanical properties of Vetiver grass with coconut fiber and eggshell fertilizers. Laboratory testing was conducted to determine the mechanical properties of Vetiver grass roots using shear box and universal testing machine. As a result, the root diameter and root length with egg shell exhibit larger values than coconut fiber for 21 days (0.40 – 1.27 cm) and 35 days (11.5 – 61.4 cm). The direct shear test results for Vetiver root with eggshell showed highest shear strength which is 43.67 kN/m2 (21 days) and 168.17 kN/m2 (35 days) compared to Vetiver root with coconut fiber which is 42.94 kN/m2 (21 days) and 61.13 kN/m2 (35 days). For tensile strength, the Vetiver root with egg shell consist higher value which is 0.066 N/mm² (group 1) and 0.068 N/mm² (group 2) compared to Vetiver root with coconut fiber which is 0.059 N/mm² (group 1) and 0.060 N/mm² (group 2). Additionally, in group 1 and 2 of 35 days, eggshell fertilizer showed higher maximum tensile strength, measuring 0.071 N/mm² and 0.094 N/mm², respectively. While, coconut fiber fertilizer 1 and 2 recorded lower tensile strengths of 0.063 N/mm² and 0.062 N/mm², respectively. The significance of this study indicates that the eggshell fertilizers have greater impact towards Vetiver root than coconut fiber fertilizers and without fertilizer.

Grading scalping and sample size effects on critical shear strength of mine waste rock through laboratory and in-situ testing

Geotechnical stability analyses of mine waste rock (WR) piles require the critical friction angle (ϕcr) of the coarse blasted rock. However, due to the presence of oversized rock clasts, shear strength can only be characterized on small samples prepared using grading scaling techniques, such as scalping. Thus, considering a testing device able to handle samples of characteristic size D, the material should be scaled down to a maximum particle size dmax given by the minimum sample aspect ratio α = D/dmax. However, a practical concern about how far the size scale can be reduced while keeping representative results remains a matter of debate in the geotechnical community. International standards do not agree on the minimum recommended α, and its effects on the mechanical behavior remain poorly understood. This paper aims to investigate the grading effects and sample size effects on ϕcr of WR materials using the scalping technique, to provide insights on the minimum recommended α. Triaxial tests were conducted on loose and dense samples of diameters D = 150 and 300 mm. Samples were scalped from field material having dmax = 75 mm, to allow a range of α from 4 to 30. Additionally, one of the world largest in-situ direct shear boxes (120 × 120 × 38 cm3) was developed to test the same WR material. The results show that scalping is an appropriate technique to assess the critical shear strength of WR. The minimum α for ϕcr assessment in triaxial testing is not sensitive to grading nor sample size, but it is affected by sample density. The aspect ratio was found to be α ≥ 12 and α ≥ 16 for loose and dense samples, respectively. This finding advocates that α values recommended by worldwide standards, such as ASTM D7181-20, might be too low and should be revisited after comprehensive testing.

A Novel Model for Evaluation of Dynamic Properties of Highly Plastic Clay through Cyclic Large Box Shear Test

A Novel Model for Evaluation of Dynamic Properties of Highly Plastic Clay through Cyclic Large Box Shear Test

Development of the triaxial equipment: a state of art

Triaxial shear testing is one of the most crucial investigations in geotechnical laboratories. It is essential for designing specific projects and understanding soil behavior in geotechnical engineering. Since Casagrande developed the modern shear apparatus at Harvard University, it has been refined to provide a more accurate characterization of shear strength behavior. This research paper aims to offer a concise overview of triaxial equipment development, focusing on apparatus that is easy to set up, prepare, and operate reliably, while remaining cost-effective. The primary objective is to contribute to the accurate determination of suitable techniques and devices that meet specific testing objectives. We review the theoretical background of both the triaxial apparatus and the direct shear box and illustrate the basic working principles of various volume change measurement techniques using triaxial devices. We also present different operational principles employed in designing volume change devices for soil testing. Our analysis reveals that some of these devices require complex operational techniques and equipment, making them challenging to use for repetitive testing. Consequently, we conclude that the ideal volume change device for soil mechanics testing should prioritize robustness and ease of operation.

Study on the seismic wave input method for earth-rock dam on overburden foundation with dynamic nonlinearity based on nonlinear artificial boundary

Accurately obtaining the seismic response of earth-rock dams on overburden foundations is crucial for seismic safety assessment and design, and a reasonable seismic input method is necessary. The seismic wave input method based on artificial boundaries is widely used in elastic foundations. However, the overburden with obvious dynamic nonlinearity is an insurmountable obstacle for the traditional method. In this research, relying on a specific earth-rock dam project, the essence of the seismic wave input method for nonlinear foundations is analyzed in detail from equivalent loads and viscous boundaries, respectively. The mechanism of inapplicability of the traditional seismic wave input method is illustrated, and an effective modified method is validated and presented. The research indicated that equivalent loads for the nonlinear dynamic response of the overburden foundation can be accurately acquired with the shear box model. The dynamic parameters of soil can be captured dynamically by the nonlinear viscous coupling boundary. The states of the lateral boundary of the overburden foundation are consistent with the free field precisely with the modified seismic wave input method by combining the shear box model and the nonlinear viscous coupling boundary. A large error will be caused by neglecting the dynamic nonlinear behavior of the overburden foundation, where the maximum deviation of peak acceleration may be over 55 % or more. A numerical model with a relatively small lateral range of overburden foundation will be obtained when the modified seismic wave input method is engaged. Moreover, the computational accuracy is enhanced remarkably, with a maximum deviation of no more than 5 %. This study provides effective theoretical support for seismic analysis and safety assessment of earth-rock dams on deep overburden foundations.

Laboratory investigation of the influence of fines content on the mechanical behavior of sand

The present article seeks to examine and discuss the experimental results that were obtained from a series of straight box shear tests. For this, different soils were prepared with clean sand, which was brought from the Wilaya (Province) of Chlef that is located in northern Algeria, mixed with silt from the same site, clay from the town of M'zilla or clayey loam that is composed half of this same clay and half of silt. The percentages of sand replacement by the selected additions were 0, 10, 20, 30, and 40% in mass ratio. The samples thus prepared were then tested with respect to dry shear, under the normal stresses equal to 100, 200, and 400 kPa. The results obtained showed that the shear strength of the sand from Chlef decreases when the silt content increases from 0 to 40%. With regard to the sand-clay and sand-silt-clay mixtures, it was found that the shear strength decreases until reaching a threshold value that coincides with the addition content of 20%. Then, beyond that value, it begins to increase as the addition fraction increases. Likewise, it turned out that cohesion increases with increasing silt content, while for sand-clay and sand-silt-clay mixtures, this cohesion increases until reaching a maximum value which coincides with the addition of 20% silt content. The same trend was observed for the variation of the direct shear strength, while the friction angle exhibited an inverse behavior.

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.

Mechanical and rheological behaviors of sands containing fines

The present work was carried out with the aim of investigating the rheological behavior, in terms of contractance and dilatancy, and the mechanical behavior, in terms of shear resistance and mechanical characteristics, of sands containing different types of fines. This study is based on direct box shear tests that were carried out on three types of soils which were reconstructed by mixing clean sand with fines, namely silt, clay and clay loam. It is important to indicate that the mass percentages for sand replacement were 0, 10, 20, 30 and 40%. To do this, dry samples were prepared and subjected to shearing, under vertical stresses of the order of 100, 200 and 400 kPa. The results obtained showed that the maximum shear strength and friction angle of sand containing silt decreased while its cohesion increased, as the fines content increased. In addition, the maximum shear strength and friction angle of sand containing clay and silty clay decreased until reaching their minimum values ​​for contents equal to 20% clay and 30% clay and clay loam, respectively. The opposite phenomenon occurred for their cohesion which increased then decreased. It has also been observed that the more plastic the fines are, the higher their content in sand, the more this sand becomes contracting rather than dilatant.

Contribution to the experimental and theoretical study of the behavior of soil-structure interfaces

Designing civil engineering works often requires taking into consideration the contact and interface conditions between the soil and structure. These may refer to the discontinuity surfaces between the soil and a structure such as foundations, geotechnical works, and others. Current research aims to improve the calculation methods for structures through a better understanding of the behavior of materials and interfaces. The present work falls into this context. It involves two parts. The main purpose of the first part is to present the results of the monotonic and cyclic soil-structure interface tests which were carried out using a modified direct shear box apparatus. The tests were conducted using a local material, namely the sand from the town of Messâad in the Wilaya of Djelfa (Algeria), in accordance with a constant normal stress path. In addition, a parametric study, dealing with the effect of density, interface roughness, and type of adhesive used on the behavior of the interfaces, was carried out as well. As for the second part, it primarily aims to validate the Modjoin interface model, which was developed at the Lille Mechanical Laboratory, based on the tests that were carried out in the first part. It is important to know that this model includes the main concepts used in soil modeling, such as isotropic hardening, characteristic state, critical state, softening, and others. Moreover, several validation tests are also presented in this work in order to describe the behavior of the soil-structure interface under monotonic loading to assess the performance of the model.

Effect of Slope Gradient on The Application of Vetiver Grass for Slope Stabilization

Slope failure has been a common disaster that occurred all over the world and causes infrastructure damage or/and causalities. The application of vegetation as part of slope stability and to control erosion has proven to be cost-effective for stabilizing the surface of the slope. This research describes the unique characteristics of Vetiver Grass as a bioengineering technique to use for stabilizing slopes. The objectives of this research are to measure the mechanical properties and tensile shear strength of roots in soil with different slope gradients (45°, 50°, and 60°). The methodologies of this study were carried out through physical modeling and lab work to analyze the objective. Shear boxes were applied to measure the mechanical properties and tensile strength of roots in soil with different slope gradients. For 21 days, the greatest soil and root shear stress for 45°, 50°, and 60° slope gradients is 13.73 kN/m2,13.70 kN/m2, and 13.25 kN/m2, respectively. Meanwhile, for 30 days, the greatest shear stress of soil with roots at 45°, 50°, and 60° slope gradients is 32.93 kN/m2, 27.71 kN/m2, and 27.22 kN/m2 respectively. Therefore, the 45° slope gradient has the largest shear stress for a period of 21 days and 30 days. According to this research, among slope gradients of 50° and 45°, the Vetiver root for the 60° slope gradient has the greatest value for tensile strength, which is 0.025 kN for 30 days, while for a period of 21 days it is 0.024 kN. However, to have better approach its appropriate if the Vetiver grass planted with slope gradient 450 since obtained great Vetiver root strength compared to others slope gradient. This study can be used as a reference to produce a slope stabilization method by using Vetiver Grass as its medium of bioengineering technique in the future.

Shaking table test on the seismic performance of prefabricated utility tunnel passing through hard-soft strata under longitudinal excitation

The earthquakes have adverse effects on utility tunnels passing through hard-soft strata. This paper is the first to conduct shaking table test on the seismic performance of prefabricated utility tunnel passing through hard-soft strata under longitudinal excitation. The standard segments of utility tunnel were made by microconcrete. The prefabricated utility tunnel was assembled by standard segments of utility tunnel through bolts. The silty clay and fine sand were selected to simulate the prototype soft and hard soils. The tests were conducted using the laminar shear box. The test cases were numerically simulated, and numerical results matched experimental results well. By analyzing the seismic responses of the acceleration distribution of the soil, the utility tunnel strain, and the opening of joint, the law and mechanism of seismic response of prefabricated utility tunnel passing through hard-soft strata were revealed. The research results indicated that the relative compressive deformation between soft and hard soils fundamentally caused the axial compressive strains at the utility tunnel segments near hard-soft soils interface. The closer the segment was to hard-soft soils interface, the larger the axial compressive strain of segment. The relative tensile deformation between soft and hard soils fundamentally caused the openings of joints near hard-soft soils interface. The closer the joint was to hard-soft soils interface, the larger the opening of joint. The different mechanical characteristics of prefabricated utility tunnel joints under tension and compression were the reason for the significant difference in seismic responses between prefabricated and integral cast-in-place utility tunnels.

EFFECT OF MOISTURE CONTENT ON SOME SELECTED MECHANICAL PROPERTIES OF FARO 44 AND 57 VARIETY OF RICE (PADDY AND DEHUSKED)

The mechanical properties of rice are among the most important parameters for designing and development of a rice milling machine, destoning machine as well as materials handling. The objective of the study was to determine the mechanical (angle of sliding and internal frictions) properties of (FARO 44 and FARO 57) paddy and dehusked at three different moisture content (5, 10 and 15%) moisture content dry basis. These properties were determined using Funnel and Baker technique and shear box apparatus respectively. The results showed that, angles of internal friction were at least 15.2°, on the average within the moisture ranges tested however, 35° angles were also obtained. Angles of sliding friction ranged between 40° - 50°. This study concludes that moisture content and variety affect the engineering property; angle of internal friction is useful in the determination of lateral and horizontal stress in the silo for grain storage.

GEOTECHNICAL AND MINERALOGICAL CHARACTERISTICS OF LATERITIC SOIL AND LOCUST BEAN (PARKIA BIGLOBOSA) PODS ASH AS CONSTRUCTION SOIL

African locust bean (Parkia Biglobosa) has been in great demand and consequently yielding large amounts of the pods which could be a potential hazard to the environment. Converting the pods to ash that would be utilized as construction material is another way of handling them properly. The effects of the mineralogy of the soil on its geotechnical characteristics when the soil is treated with locust bean pod ash have been given very little attention. Therefore, this study considered the effects of locust bean pod ash (LBPA) and the mineralogy of lateritic soil on some geotechnical properties necessary for it to be used as subgrade or foundation soil. The determination of the chemical constituents of the LBPA was carried out using Atomic Absorption Spectrometer. The lateritic soil was characterized by identifying the clay minerals as well as non-clay minerals present in the soil using the x-ray diffraction technique and preliminary tests were also carried out to properly rate the soil. The soil was treated by applying dosages of LBPA 0 – 25% at intervals of 5% and the percentages were measured by weight of the dry soil. The tests conducted on the prepared soil samples with LBPA were specific gravity, consistency indices, compaction (British Standard Light), California bearing ratio and direct shear box test. The LBPA was found to be an acceptable pozzolanic material for the treatment of the lateritic soil. The lateritic soil was observed to belong to soil groups A-2-6(0) in the AASHTO and poorly graded sand (SP) in USCS ratings. It was also observed that the non-clay minerals present in the soil were quartz, feldspar and mica whereas the clay minerals present were kaolinite, iolite, vermiculite and chlorite which had a significant influence on the geotechnical characteristics of the soil. The specific gravity of the LBPA was relatively low and the additions of LBPA reduced the specific gravity of the soil. The consistency indices also dropped and subsequently increased with the further addition of LBPA. The increase in LBPA contents caused increments in the optimum moisture content while the maximum dry density and shear strength parameters reduced. The strength characteristics like the California Bearing Ratio of the lateritic soil improved by 173.91% at the addition of 5% LBSA content which was determined to be the optimum dosage.

Grain size effect on the anisotropic shear behavior of sand–textured geomembrane interface

A set of direct shear tests was conducted to investigate the effects of sand mean grain size and geomembrane surface roughness on the shear behaviour of the sand–geomembrane interface. Four types of sands with different mean grain sizes were used and the interfaces included a smooth geomembrane (SGM) and four textured ones with different asperity characteristics. The samples were prepared in a direct shear box at five sedimentation angles. The experimental results showed that the peak friction angle of the soil–textured geomembrane interface was dependent on the mean grain size, inherent anisotropy and surface roughness of the geomembrane. The shear strength of sand–textured geomembranes was two to three times larger than that of the sand–SGM interface. The peak and residual friction angles of sand-SGM interface occurred at sedimentation angle of 72° while it was 108° for sand-TGM interfaces. An increase in mean grain size increased the shear strength of the sand–textured geomembrane interface; while a reverse condition occurred for the sand–SGM interface. The shear strength occurred at larger horizontal displacement as mean particle size increased and the effect of relative roughness on peak friction angle increased with increase in mean grain size.

Characteristics of Sand-Waste Tyre Rubber Composite as Backfill Material

Waste tyre rubber offers an alternative to natural sand as a backfill material, potentially reducing the dependency on natural sand usage in construction. The purpose of this study is to investigate the properties of waste rubber as a potential backfill material for retaining walls and to assess the shear strength characteristics of the sand-rubber composite when used as a backfill for retaining walls, ultimately identifying the optimal sand-rubber composite ratio for effective backfill application. This study employed sieve analysis and specific gravity testing to identify the physical attributes of waste tyre rubber. Subsequently, direct shear box tests were conducted utilizing ratios of 100%, 50%, 75%, and 25%. Two types of rubber were utilized in this study Granulated Rubber (GR) with particle sizes ranging from 1 to 5 mm, and Mulch (MR) with particle sizes exceeding 25 mm. The findings reveal that the Cu value for waste rubber is less than 2.50 and the Gs value is less than 1.5, indicating favourable characteristics. Moreover, the 25% GR and MR compositions exhibit the highest shear stress values at 0.0347 N/m² and 0.0296 N/m², respectively. In conclusion, it has been determined that the optimal proportion of waste rubber for the application of the sand-waste tyre rubber composite as a backfill material is 25%.

Investigation of Cement and Fly Ash on the Improvement of Fine Sand Soil

Soil stabilization problems like liquefaction, bearing capacity, permeability, excessive settlement and swelling can be solved by improving soil’s engineering properties by using various methods. The use of fly ash as a stabilizer has become popular in recent years since it is eco-friendly and effective on soil stabilization, especially for fine-grained soils. This study investigated the reuse of fly ash as a stabilizer (5–25% by weight) and cement (constant 3% by weight) as an activator to enhance the geotechnical properties of poorly graded sand (SP). Standard proctor tests were conducted to determine optimum water content and maximum dry unit weight, followed by direct shear box, falling head permeability and CBR tests at the determined optimum water content. Direct shear box experiments were carried out at two relative densities (30% and 80%) and CBR experiments were performed after 7 and 28 days of curing time. The results demonstrated that the addition of fly ash and cement improved the geotechnical properties, including shear strength, permeability and bearing capacity of the fine sand soil.

Shear strength recovery of sand with self-healing polymeric capsules

Self-healing approaches are increasingly being explored in various fields as a potential method to recover damaged material properties. By self-recovering without external intervention, self-healing techniques emerge as a potential solution to arrest or prevent the development of large strains problems in soils (e.g., landslides) and other ground effects that influence the serviceability of structures (e.g., differential settlement). In this study, a microcapsule-based self-healing sand was developed, and its performance during mixing and compaction, shearing, and recovery of shear strength was demonstrated. The cargo used for sand improvement, a hardening oil, tung oil, was encapsulated in calcium alginate capsules by the ionic gelation method. The surface properties, internal structure, thermal stability and molecular structure of the capsules were evaluated by advanced material characterization techniques. The survivability of capsules during mixing and compaction was assessed by measuring the content of tung oil released into the sand, while their influence on sand shear strength and its recovery was assessed with shear box tests. The results showed that the capsules could rupture due to movement of the sand particles, releasing the tung oil cargo, leading to its hardening and minimizing its strain-softening response and enhancing up to 76% of the sand shear strength (at a normal stress of 10 kPa and capsules content of 4%). This study demonstrates the potential of a capsules-based self-healing system to provide ‘smart’ autonomous soil strength recovery and thus with potential to actively control the large strain behavior of soils.