Strength Characteristics Of Sand Research Articles

Swelling and Strength Characteristics of Sand Treated with Paper Sludge Ash-Based Stabilizer

Swelling and Strength Characteristics of Sand Treated with Paper Sludge Ash-Based Stabilizer

Post-liquefaction deformation and strength characteristics of sand in torsional shear tests

The estimation of strength deterioration with the increase in the undrained cyclic shear-induced strain in liquefiable soils is an important topic in geotechnical earthquake engineering that is still poorly understood and needs to be properly addressed. In this paper, in an attempt to provide new insights into this topic, the post-liquefaction undrained strength and deformation of Toyoura sand were investigated through a series of laboratory tests performed by using a large-strain torsional shear apparatus. In the tests, simple shear conditions were reproduced on a medium-size hollow cylindrical specimen to apply stress conditions that soil experiences in the field during earthquakes. Specimens prepared by the air-pluviation method were first liquefied by applying a constant amplitude undrained cyclic shearing to induce a target cyclic shear-induced damage strain (γΔ). The tests were terminated at different amplitudes of γΔ and subsequently loaded monotonically in undrained conditions to obtain stress-strain and excess pore water generation responses. The test results indicate that the post-liquefaction monotonic loading (ML) stress-strain behavior of sand can be divided into three regions, namely Region 1, 2 and 3. The sand behavior changes to strain-hardening from essentially zero strength and stiffness from Region 1 to 2. While Region 3 marks the beginning of strain-softening state in the sand. It is found that the strain localization is associated with the transition of sand behavior from strain-hardening to strain-softening state. It is proposed that the sand undrained strength in monotonic shearing is the true representation of specimen response until the state of uniform deformation is maintained, based on the sudden drop of the differential stress (σd = σ v′ - σh′). The test results also revealed that there is a progressive degradation in the shear strength with the increase in the amplitude of γΔ. A correlation depicting the degradation ratio (τd) with the increase in the γΔ is proposed. This correlation can be used to estimate the degree of degradation with the increase in the applied γΔ, and it is valid for different density states, confining stresses and cyclic stress ratios.

Comparative study of shear strength characteristics of dry cohesionless sands from triaxial, plane-strain and direct shear tests

ABSTRACT Knowledge of strength properties and deformational behaviour of soils under different loading conditions is necessary in the analysis of most of the geotechnical engineering problems. This paper presents a comparative study of shear strength characteristics of sands as obtained from triaxial, plane-strain and direct shear test results. The experimental results on shear strength characteristics of dry sands obtained from triaxial, plane-strain and direct shear tests, were analyzed in order to investigate the effect of soil relative density or soil porosity on the angle of shearing resistance, dilatancy factor, particles interlocking, and volumetric strain and axial strain at failure. Furthermore, the results were used to develop correlations connecting between the angle of shearing resistance of triaxial condition test and the direct shear test, and between the angle of shearing resistance of plane-strain and triaxial compression conditions. The correlations developed take into account the interaction between soil relative density, dilatancy factor and particles interlocking. Good agreement has been obtained between the predicted results values using the proposed methods and the results of the present experimental investigation and those available in the literature

Improving microdisintegration processes of sands of an integrated deposit of precious metals with high strength characteristics

The results of an investigation into the sands of the highly clayey placer complex integrated deposit of the Fadeevskoe ore-placer site with high strength characteristics of sands and an increased content of fine fractions of valuable components are considered. Energy-dispersive microanalysis of rock samples is performed. Samples contain microelements of a broad range of precious (including gold, silver, and platinum), rare earth, and other elements. It is established that the sands of the gold-bearing placer under study are a rather complex object for disintegration. Acoustic characteristics of the sands under study in the initial state and under water saturation, which evidence that the fraction of maximal values of the shear modulus is considerably exceeded, are determined by the experimental–analytical method. To solve the question of microdisintegration, in order to recover spark and fine gold using more environmentally and technologically efficient means, it is proposed to use systems based on processes of the cavitation-acoustic effect on a mineral mixture component.

Effects of Cementation on Stress-Strain and Strength Characteristics of Sands

This paper presents a series of tests performed on uncemented and cemented sands along conventional and unconventional stress paths using a true (or cubical) triaxial testing device. The tests were planned such that the influence of cementation on constitutive behavior of sands could be comprehended. The true triaxial device used for this study was a flexible boundary type that could allow testing of a 4 in. (10.2 cm) cubical soil specimen under any stress path in the first octant of stress space. The stress paths considered in this investigation included hydrostatic compression, conventional triaxial compression, and tests along different directions on different octahedral planes. All the tests were stress controlled, and performed under drained condition. The specimens were prepared by the method of undercompaction using Monterey No. 0 sand and Portland cement type I. The test results show that the effect of cementation on failure, shear strength, stress-strain, and volume change behavior of sands is significant and depends strongly on the stress path.

Failure and Deformation of Sand in Torsional Shear

The deformation and strength characteristics of sand was studied by means of the torsional shear tests on hollow cylindrical samples with a height of 20 cm, an outer radius of 5 cm and an inner radius of 3 cm. It was found that in order to obtain accurate results it is essential both to very precisely measure the axial load, the torque and the effective confining pressure σc′ and to correct measured stress values for the membrane forces. The methods for this purpose are described in detail. Each test was performed at a constant confining stress σc′ between 0.3 ~ 2.0 kgf/cm2 (29.4 ~ 196.2 kN/m2) and σ3′ at failure ranged between 0.08 ~ 0.75 kgf/cm2 (7.9 ~ 73.7 kN/m2). It was found by measuring local strain distributions throughout the sample height that the deformation is rather uniform when shear distortion γat is less than approximately 5%. Correspondingly the pre-peak stress ratio-strain relationship is rather independent of σc′ or σ3′. It was also found that with increasing σc′ a shear band or shear bands start to appear at a smaller γat and the degree of post-peak strain softening becomes more pronounced. The dependency of φ on σ3′ in the torsional shear tests for the range of σ3′ in this study was found small as well as in the triaxial and plane strain compression tests. A tendency was obtained that the value of is slightly influenced by the deformation pattern at failure. The pre-peak stress and strain relationship by the torsional shear test was found similar to that by the plane strain compression test under similar values of b =(σ2′− σ3′)/(σ1′− σ3′) and the angle of bedding plane δ to the σ1′-direction. The value of φ by the torsional shear test was found slightly larger than or similar to the value of φ by the plane strain compression test under similar values of b and δ depending on the stress level at which the value of φ is compared.

Cubical Triaxial Tests on Cohesionless Soil

A new type of cubical triaxial apparatus was used for an investigation of the influence of the intermediate principle stress on the drained stress-strain and strength characteristics of sand. For the same value of the minor principle stress and increasing value of the intermediate principle stress, both dense and loose specimens showed increasing slope of the stress-strain curve, decreasing strain-to-failure, and increasing rate of dilation. The strength of the sand as represented by the friction angle increased from triaxial compression to a maximum before a slight decrease at triaxial extension. Observations regarding the applicability of the normality condition of classical plasticity theory to sand were made. Expressions were derived for the variations of the friction angle in the immediate vicinity of the conditions of triaxial compression and extension, and the test results were shown to fit these expressions.

Closure to “Drained Strength Characteristics of Sands”

Closure to “Drained Strength Characteristics of Sands”

Discussion of “Drained Strength Characteristics of Sands”

Discussion of “Drained Strength Characteristics of Sands”