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To investigate the deformation and strength characteristics of reinforced soil, a series of large scale direct shear tests (LDST) were performed on reinforced and unreinforced specimens of Toyoura sand using eight different types of reinforcements and rubber sheet. Two layers of reinforcement, 600mm × 500mm in cross section were installed perpendicular to shear direction in a shear box of size L x W x H 800mm × 500mm × 600mm. The tests results confirmed the accuracy of data obtained from LDST. Also, it was found that the tensile strain developed in the reinforcement was only about 2 ∼3% at peak state and much less than the rupture strain. The reinforced specimens exhibited high peak stress ratio and more dilative behavior provided mobilization of tensile stress was large enough to compensate the reduction of strength of sand, resulting in the spreading of the shear strain development area along with reinforcement. The pressure dependency of reinforced specimen was found to be higher than that of unreinforced specimen. Also the role of the mobilized tensile stress to cater the reduction of soil strength caused by strain softening became higher with lower constant pressures. I hope to provide a simple guideline about the paper. [ABSTRACT FROM AUTHOR]

Permeation grouting has been developed as one of countermeasures against soil liquefaction during earthquakes. This study aims at examining the small strain properties and cyclic resistance of jellied sand improved by silicate-based permeation grouting. In the first part of the present study, the small strain properties and cyclic resistance of jellied sand were examined based on the measurements of propagation velocities of longitudinal and shear waves travelling through triaxial specimens and the results from subsequently conducted undrained cyclic triaxial tests. In the second part, straincontrolled small-amplitude cyclic triaxial tests are conducted using non-contact gap displacement transducers to examine the initial elastic moduli of silicate gel itself and intact sand as well as jellied sand. The roles of the stiffness at small and large strains of silicate gel in increasing the undrained cyclic resistance of jellied sand are discussed in detail. [ABSTRACT FROM AUTHOR]

A series of consolidated drained triaxial compression (TC) tests were performed on a crushed concrete aggregate (CCA) compacted using three different levels of energy. A wide range of moulding water content, w, and two different confining pressures were employed. The compressive strength and stiffness of the tested CCA when highly compacted at water content close or slightly higher than the optimum value, wopt, were very high, higher than those of a typical natural well-graded gravelly soil having similar grading characteristics used as the backfill material of highest quality. The compressive strength and stiffness of the tested CCA was not highly sensitive to changes in w, in particular when w ≥ wopt, but it decreased sharply when w became lower than wopt. The strength and stiffness was very sensitive to compaction energy, therefore the degree of compaction. All the test results show that highly compacted CCA can be used as the backfill material for important civil engineering soil structures, such as retaining walls and bridge abutments, that need a high stability while allowing limited deformation. [ABSTRACT FROM AUTHOR]

The viscous property of kaolin and the ageing effect on its stress-strain behaviour as well as their interactions were evaluated by performing a series of drained triaxial compression (TC) tests on air-dried and saturated specimen with and without cement-mixing. The axial strain rate was changed stepwise many times as well as drained creep and relaxation tests were performed during otherwise monotonic loading (ML). Different types of viscous properties (called Isotach type as well as weak and strong TESRA types) were observed depending on test conditions. The ageing effects by hydration of cement, interacted with the viscous property, were observed with saturated cement-mixed kaolin. It is shown that the effects of viscosity property and ageing, which interact with each other, can be simulated by a non-linear three-component rheology model modified from the original one to account for ageing effects. [ABSTRACT FROM AUTHOR]

The viscous properties of a wide variety of reconstituted loose and dense unbound granular materials, including natural sands and gravels, were evaluated by a series of drained triaxial compression (TC) tests at fixed confining pressure. In total sixteen granular materials having different mean particle diameters, D50, coefficients of uniformities, Uc, fines contents, FC, degrees of crushability and particle shapes were newly tested. The viscous properties were quantified basically by many times changing stepwise the axial strain rate and partially by performing drained sustained loading during otherwise drained monotonic loading (ML) at a constant strain rate. It is shown that the viscous properties can be represented by the rate-sensitivity of the stress upon a step change in the strain rate, the decay rate of a viscous stress increment during the subsequent ML at a constant strain rate and the dependency of the residual stress during ML at a constant strain rate. The effects of the particle characteristics on the viscous properties were evaluated by summarising the results from the present and previous studies. As a new and surprising fact, with poorly graded unbound round granular materials, the stress for the same strain during ML at a constant strain rate decreases with an increase in the strain rate. [ABSTRACT FROM AUTHOR]

Unusual failures of river banks and river training structures have been reported during construction and shortly after commissioning of several structures along Jamuna river in Bangladesh that raised widespread questions regarding the design principles and parameters used. The natural sand deposit along the Jamuna river contain relatively larger amount of mica than most other natural soils. Jamuna sand needs to be studied under wide range of loading conditions (such as triaxial, plane strain, simple shear etc.), drainage and density conditions (i.e. drained / undrained, dry / saturated, dense/loose state etc.) to reveal the extent of variation of its strength and deformation characteristics in order to facilitate understanding of the mechanism of past failures of structures and suggest rational design parameters. A series of plane strain compression tests were performed on Jamuna sand. It is observed that Jamuna sand is highly contractive under shear and more anisotropic than other non-mica sands. [ABSTRACT FROM AUTHOR]