Shear Strength Of Sand Research Articles

Experimental Study of Cationic-Modified Biopolymer for Increasing the Shear Strength of Sand

The application of biopolymers as a more environmentally friendly alternative to cement has emerged as an interesting research subject.The purpose is to enhance the shear strength of sandy soils. In this article, the selected biopolymer is cationic-modified starch. It is expected that cationic starch will have less water absorption properties since modified starch has cationic groups in place of the OH- groups found in the normal starch. This cationic-modified starch namely Amylofax. Five types of samples are created for this testing, including Sample A is prepared with the composition of (silica sand + 2% Amylofax T1100 (w/w) + 20% water (w/w))., Sample B consists of (silica sand + 2% Amylofax T2200 (w/w) + 20% water (w/w))., Sample C is comprised of (silica sand + 2% Amylofax T1100 (w/w) + 2% Glucomannan (w/w) + 20% water (w/w)), Sample D consists of (silica sand + 2% Amylofax T2200 (w/w) + 2% Glucomannan (w/w) + 20% water (w/w)), and Sample E includes (Ottawa sand + 2% cement (w/w) + 20% water (w/w)). The samples were tested using a direct shear test apparatus to determine the soil shear strength parameters (c) cohesion and (Ø) internal friction angle. After conducting the tests on the sand samples with the addition of modified starch biopolymer (cationic starch), it was found that the cohesion value was 961kPa, and the internal friction angle was 63°. These results indicate higher shear strength values compared to sand mixed with natural starch.

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.

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.

Not a Rolling Stone: On Dragging a Stone Weight-Anchor on the Seabed

The force required to drag a stone anchor over several types of surfaces was measured, recorded, and analyzed. It was found that the force involved in the movement of the anchor over the various surfaces cannot be described just by the sliding solids theory, but it involves several additional physical processes, such as increasing the sand shear strength by the pressure the anchor applies on the sand under it; the sinking of the anchor into the saturated sand; shearing the sand in front of the moving anchor and accelerating it to the velocity of the anchor; accumulating sand in front of the anchor, thus adding to the pulled mass; and moving some of the accumulated sand sideways. In many instances, the beginning of the anchor movement involves the liquefaction of the sand under it, thus enabling the relatively easier sliding of the anchor. In addition, movement over rocky surfaces, encountering the irregularities that abound on such surfaces, also differs from classic sliding friction theory. In several situations, the use of an effective coefficient of friction, combining all the processes, can serve to obtain approximate values of the required forces.

Normalized Behavior and Residual Shear Strength of Sand

Normalized Behavior and Residual Shear Strength of Sand

Influence of geosynthetics reinforcement on liquefaction and post-liquefaction behaviors of calcareous sand

To provide new insights into the liquefaction and post-liquefaction behaviors of calcareous sand with and without geosynthetics reinforcement, a series of multi-stage cyclic triaxial tests were conducted. The geosynthetics employed in this study include geogrid, geotextile, and geotextile-geogrid composite. The multi-stage tests consist of an initial cyclic loading applied to cause liquefaction, followed by undrained monotonic loading without excess pore pressure dissipation. The effect of different arrangements of reinforcement layer on the behaviors of calcareous sand is examined and discussed in this study. The test results indicate that a unique relationship can be observed between the double amplitude axial strain and the pore pressure ratio of calcareous sand, irrespective of the influence of reinforcement layer arrangement, providing an effective means of predicting the strain at a given pore pressure level. The liquefaction resistance of calcareous sand increases with the increase in the number of reinforcement layer and decreases with the increase in the distance from the first layer of reinforcement to the sample’s top surface. Compared to geogrid and geotextile, the proposed geotextile-geogrid composite exhibits better efficiency in enhancing the liquefaction resistance of calcareous sand. The reinforcement also accelerates the recovery of strength for liquefied calcareous sand and increases the maximum shear strength of sand at large axial strain during the post-liquefaction stage.

Physical and mechanical properties and microstructures of submarine soils in the Yellow Sea

AbstractIn recent years, the exploration of seabed has been intensified, but the submarine soils of silt and sand in the Yellow Sea area have not been well investigated so far. In this study, the physical and mechanical properties of silt and sand from the Yellow Sea were measured using a direct shear apparatus and their microstructures were observed using a scanning electron microscope. The test results suggest that the shear strength of silt and sand increases linearly with the increase of normal stress. Based on the direct shear test, the scanning electron microscope was used to observe the section surface of sand. It is observed that the section surface becomes rough, with many “V”‐shaped cracks. Many particles appear on the surface of the silt structure and tend to be disintegrated. The X‐ray diffraction experiment reveals that the sand and silt have different compositions. The shear strength of sand is slightly greater than that of silt under high stress, which is related to the shape of soil particles and the mineral composition. These results can be a reference for further study of other soils in the Yellow Sea; meanwhile, they can serve as soil parameters for the stability and durability analyses of offshore infrastructure construction.

A Simplified Model for Shear Behavior of Mortar Using Biomimetic Carbonate Precipitation.

As a common molecule in biomineralization, L-aspartic acid (L-Asp) has been proven to be able to induce in vitro CaCO3 precipitation, but its application in sand reinforcement has never been studied. In this study, L-Asp was employed in sand reinforcement for the first time through the newly developed biomimetic carbonate precipitation (BCP) technique. Specimens with different number of BCP spray cycles were prepared, and a series of direct shear tests were conducted to investigate the impact of spray number on shear strength, critical displacement, and residual strength. Then a simplified power model for shear stress-displacement behavior was established and calibrated with the measured data. The results show that BCP can significantly improve the shear strength of sand. As the number of spray cycles increases, both the shear strength and residual strength increase, while the critical displacement decreases. Such variations can be described with two sigmoid models and a linear model, respectively. The simplified power model performs well in most cases, especially at higher spray numbers. This study is expected to provide a practical model for the shear behavior of BCP-treated mortar.

Evaluating the Influence of Sand Particle Morphology on Shear Strength: A Comparison of Experimental and Machine Learning Approaches

Particulate materials, such as sandy soil, are everywhere in nature and form the basis for many engineering applications. The aim of this research is to investigate the particle shape, size, and gradation of sandy soil and how they relate to shear strength, which is an essential characteristic that impacts soil stability and mechanical behaviour. This will be achieved by employing a combination of experimental methodology, which includes the use of a microscope direct shear apparatus, and machine learning techniques, namely multiple linear regression and random forest regression. The experimental findings reveal that angular-shaped sand particles enhance the shear strength characteristics compared to spherical, rounded ones. Similarly, coarser sand particles improve these characteristics compared to finer sand particles, as do well-graded particles when compared to poorly graded ones. The machine learning findings show the validity of both models in predicting shear strength when compared to the experimental results, showing high accuracy. The models are designed to predict shear strength of sand considering six input features: mean particle size, uniformity coefficient, curvature coefficient, dry density, normal stress, and particle regularity. The most important features from both models were identified. In addition, an empirical equation for calculating shear strength was developed through multiple linear regression analysis using the six features.

Study on macro and micro shear strength of continuously graded and gap-graded sand

The particle gradation of sand has a significant influence on its shear strength, yet the similarities and differences between the effects of continuous and gap grading have yet to be fully explored. In this study, the discrete element method (DEM) was used to simulate biaxial tests on granular samples that were both continuously graded and gap-graded. The macroscopic analysis revealed that the shear strength of continuously graded sands increases initially and then decreases as the uniformity of particle size distribution decreases. On the other hand, the lack of medium particles in gap-graded sands amplifies the difference in particle size between coarse and fine particles, leading to a decrease in shear strength. Microscopically, both continuous and gap gradings affect the internal packing structure of the particle assembly, which consequently affects particle stress distributions, contact forces, coordination numbers, stress-induced anisotropies, and contact force networks, thus having an impact on the macroscopic shear strength. The global uniformity of particle size distribution was unidirectionally affected by continuous grading, while gap grading had a locally bidirectional influence. These findings provide a better understanding of the effects of particle grading on the macroscopic shear strength of sands.

Investigation of shear strength of sand–bentonite mixtures with boron additives at high temperature for energy geo-structures

The soils surrounding energy geo-structures are exposed to high temperatures and temperature cycles. Changes in the engineering properties of soils should be investigated under thermal effects and soils that are highly durable against temperature changes are needed for thermo-active geo-structures. Generally, bentonite or sand–bentonite mixtures (SBMs) are preferred as natural barrier soil materials. Hence, the engineering properties of these natural soil materials against high temperatures should be improved. Boron, which has high thermal resistivity, reduces the heat expansion of materials, when added to soils may increase the durability of buffer materials at high temperatures. In the present study, the effects of tincal and ulexite additives were observed on the shear strength behavior of SBMs at 80 °C and room temperature. The general results showed that with the contribution of boron, the shear strength of the SBMs increased with increasing temperature. The effect was more pronounced for 20% SBMs at high temperature. Tincal and ulexite can be used to increase the shear strength of SBMs at high temperatures.

Experimental study on the effects of triangular groove inclination angles on the mechanical behavior of sand–concrete interfaces

The mechanical properties of pile–soil interfaces directly affect the bearing capacity of pile foundations. In this study, the effects of triangular groove inclination angles on the mechanical properties of sand–concrete interfaces were investigated. Random rough concrete surfaces were obtained through slurry intrusion testing, and the roughness of concrete surfaces was evaluated based on the sand cone method. According to the roughness of random concrete surfaces, five regular concrete surfaces with different triangular groove inclination angles were constructed. A series of direct shear tests between (i) sand and random concrete surface, (ii) sand and regular concrete surface, as well as (iii) sand and smooth concrete surface were performed. Moreover, a direct shear test of natural sand was conducted. Lastly, a shear strength model considering the triangular groove inclination angle of sand–concrete interfaces was established, and the shear failure mechanism of interfaces was discussed. The results firstly indicated that the shear stress-displacement curves of random rough concrete surfaces were ideal elastic-plastic curves; and the regular rough concrete surfaces were found to incur strain softening under a normal stress of 300 kPa. Secondly, the shear strength of sand–concrete interfaces increased with the increase in groove inclination angle of concrete interfaces. Thirdly, sand was found to achieve the highest shear strength, while sand–smooth concrete interfaces proved to attain the lowest. Lastly, the internal friction angle value of random concrete interfaces was shown to range between the values of concrete surfaces with triangular groove inclination angles of 70° and 90°.

Study on the Safety Analysis of Dredger Fill Sea Sand Reused in Embankment Slope near the Yangtze River

In view of the shortage of sand and gravel aggregates, the sea sand in coastal areas is used as roadbed filler in road restoration of tunnel project by the Yangtze river. The basic mechanical performance tests were carried out to demonstrate the particle gradation and consistency limit of dredger fill sea sand. Triaxial test and direct shear test were performed to analyze the stress-strain relationship of sea sand shear strength in riverside environment and the law of shear displacement under vertical pressure. The road performance was analyzed by testing the compaction characteristics and deformation resistance of dredger fill sea sand. The riverside slope is always damaged by water flow, therefore, the stability of the dredger fill sea sand road slope under the measures of wrapping soil was analyzed. Based on the analysis of existing measures to improve the safety of sea sand used in road, the technology of sea sand solidified by alkaline coupling agent is proposed.

Effect of particle size and shape on shear strength of sand–rubber granule mixtures

Effect of particle size and shape on shear strength of sand–rubber granule mixtures

Dilatant Nature of Sand Shear Strength

Many shear strength criteria have been proposed for soils. The Mohr–Coulomb, Matsuoka–Nakai, and Lade–Duncan criteria are more frequently used for sands. For sands sheared in drained conditions, the general stress–dilatancy relationship is obtained from the frictional state concept. It is shown that, in failure states, the dilatancy for triaxial compression, the plane strain condition (biaxial compression), triaxial extension, and general states can be expressed by the ratio of the volumetric and axial strain increments for triaxial compression. By using the frictional state concept, the shear strength of sand for general states can be expressed by the critical state angle and the dilatancy for drained triaxial compression. It is shown that the calculated shear strength of the sand is similar to that obtained by using the Mohr–Coulomb, Matsuoka–Nakai, and Lade–Duncan criteria for the non-dilative, moderate-dilative, and high-dilative behaviors of sand, respectively. Therefore, the shear strength of sand has a purely dilative nature for deformations without breakage effects.

Neural network model to predict strength parameters of dune sand at Jodhpur City

The shear strength of the soil is a significant factor in determining bearing value and determining stability. This study investigates a neural network model for determining the strength parameters (cohesion & friction angle) of locally accessible dune sand in Jodhpur city in India. Model has been developed considering grain sizes ,dry density ,relative density , void ratio, liquid limit, plastic limit etc as independent variables and strength of dune sand as dependent variable. The findings show that the model is capable of forecasting dune sand shear strength parameters . R programming is used to generate an ANN model, which is then compared to MS-Excel. A response analysis was used to establish the best algorithm and neuronal numbers for improving the model design. The use of a neural network to forecast dune sand strength variables was shown to be very accurate. For the experimental results and model outputs, the relative mean squared error, coefficient of decision (R2), and mean absolute relative error are determined. For performance analysis, Levenberg Marquardt algorithm is used. In the ANN model, the quantity and least value of R2 for training data sets are 98.2 percent and 96.2 percent, respectively. The suggested ANN models for dune sand strength are accurate and highly close to the experimental values, according to statistical results. As a result, the ANN model appears to be a useful tool for predicting dune sand strength parameters.

Shear behaviour of sandy soil from Chlef river reinforced with different types of fibres

Direct shear box tests were carried out in order to evaluate the effect of different types of randomly distributed fibres; two synthetic fibres (Polypropylene and Glass fibre) and one natural fibre (Sisal fibre) on the improvement of Chlef sandy soil shear strength. All of the inclusions were randomly distributed in the soil mass with a length of 12 mm and fibre contents of (0, 0.25, 0.5, 0.75 and 1% by dry soil mass). Samples were prepared at a relative density of 50% representing medium dense state and performed at normal stresses of 50, 100 and 200 kPa. The present work is conducted in order to study the effect of material properties and fibre content on the shear strength of sand. The experimental results show that all types of fibre greatly improved the shear strength, cohesive intercept and friction angle of Chlef sand. However, samples reinforced with sisal fibres have shown a more pronounced increase in strength parameters than those reinforced with glass or polypropylene fibres. The effect of the soil initial state was also discussed.

Ultimate pullout capacity of single vertical plate anchors in sand

This paper presents a limit equilibrium solution for calculating the ultimate pullout resistance of shallow vertical plate anchors in sand, considering the combined effects of anchor embedment ratio, sand shear strength, sand-anchor interface strength and anchor aspect ratio. The geometry of the failure mechanism in the solution reflects observations from model tests. The ultimate failure load of a strip plate anchor was then determined by global equilibrium analysis of the passive and active failure soil wedge. The two-dimensional limit equilibrium solution is extended for rectangular plate anchors by introducing the shape factors of Ovesen and Strømann. The solution is compared with a database of 102 pullout model tests of vertical plate anchors in sand assembled from the literature and some limit analysis results. The comparison results suggest that the proposed solution can provide a reliable analytical tool for the ultimate pullout capacity prediction of shallow vertical plate anchors buried in sand.

Study of silty sand slope protection from seepage flows using short fiber-sand mixtures

Silty sand slopes are prone to damage due to seepage or rainfall. A partial reinforcement method using short polypropylene fiber and sand mixtures was proposed to protect silty sand slopes from seepage flow failure. The effects and the reinforcement mechanism were explored. First, triaxial tests were performed on sand samples reinforced with fiber lengths (6 and 12 mm) and contents (0.25 and 0.50%) to verify the reinforcement effect. Then, model tests were conducted on sand slopes under lateral seepage flow and the failure mode with different fiber contents and reinforcement method were examined. The results showed that the cohesion and shear strength of sand were significantly improved with the increase of fiber content and length. The suction of unsaturated sand was also enhanced by the fibers. The change in stress-strain behavior from strain softening to strain hardening indicated that static liquefaction could be effectively prevented. The failure mode and extent of slope damage depended on the fiber content. However, it was noted that the slope surface with small reinforcement range performed similarly to that with large reinforcement range. In conclusion, the partial reinforcement method with short discrete synthetic fibers can be used as an effective alternative for slope reinforcement.

Investigating the effect of Lignocellulose Mulch on Sand Shear Strength

Investigating the effect of Lignocellulose Mulch on Sand Shear Strength