This paper deals with the stress-controlled cyclic triaxial response of saturated sand rubber chips (RC) mixtures at different gravimetric contents. Three types of sand were utilised, namely, uniform medium and coarse sands, as well as a combination of the two at two relative densities. A series of consolidated undrained and drained single-stage cyclic triaxial tests was performed using standard equipment to evaluate the development of the accumulated excess pore-water pressures, permanent axial and volumetric strains. Samples were anisotropically consolidated prior to cyclic loading. The results showed that for all sands adding 10% RC increases the liquefaction potential. Compared to pure sand, increasing the chips content beyond 20–30% generally yields an improvement as long as the sand is not too coarse. Expressions have been derived for the evolution of accumulated pore-water pressure and the relation between excess pore-water pressure from the undrained test and cumulative volumetric strain from drained tests. Although the findings were derived for a single set of loads, they reveal the basic characteristics of the cyclic composite material behaviour.
The highway pavement quality and lifetime depend on its different layers such as subgrade, sub-base and base courses. It is of great importance for subgrade soil layer to have the excellent properties as it is the one to lower or increase the project cost. This paper discusses the utilization of lime and fines from concrete waste to enhance the strength of silty sand soil. California Bearing Ratio (CBR) and shear strength were evaluated. The content such as 0%, 2%, 4%, 6%, 8% and 10% were used. The CBR and shear strength of soil increased with the increase of lime or concrete content. The optimum lime and concrete content which maximized CBR were 6% and 8% respectively. The shear strength improvement was also noticed. No optimum content from both stabilizers which gave maximum shear strength.
The dynamic behaviour of unsaturated sand rubber chips mixtures at various gravimetric contents is evaluated through an experimental study comprising resonant column tests in a fixed-free device. Chips were irregularly shaped with dimensions ranging from 5 to 14 mm. Three types of sand with different gradation have been considered. Relative density amounted to 0.5 for all specimens. Due to the large size of the chips, the diameter of the specimens had to be equal to 100 mm, which in turn required a re-calibration of the device assuming a frequency-dependent drive head inertia. The effects of confining stress, rubber chips content, and sand gradation on shear modulus and damping ratio are determined over wide ranges of the shear strain. At small strains, as known for sands, increasing the confining stress stiffens the mixtures. Increasing the rubber chips content reduces significantly the shear modulus and increases the damping ratio. At higher strains, increasing the confining stress or the rubber content flattens the reduction of the shear modulus with strain. Damping at high strains does not show any appreciable dependence on rubber content. Unloading–reloading sequences are used to assess shear modulus degradation and threshold strains. Finally, design equations are derived from the test results to predict the dynamic response of the composite material.
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