Firas A. Salman

Numerical Simulation of Triaxial Test in Clayey Soil Using Different Constitutive Relations

The stress paths to which specimens are subjected in triaxial tests together with the yield surfaces, which may be exercised in different models of such a test are simulated. A laboratory testing on undisturbed clay soil samples was performed in order to characterize the stress-strain behaviour of the residual soils in Sao Paulo sedimentary deposit. The sample is tested under isotropically consolidated drained triaxial compression. Strain controlled procedure was used to simulate stress-strain relationships of the soil. Seven models are used; namely: linear elastic, Duncan-Chang hyperbolic, Mohr-Coulomb, Cam clay, modified Cam clay, new Mohr-Coulomb and Cap model. It was concluded that the results of Cam clay and Duncan Chang models are the closest to the experimental data under low confining pressures; 49 and 98 kPa. Both models exhibit parabolic stress-strain relationships while the linear elastic model results are far away from experimental ones especially at large stress levels. At high confining pressure; 196 kPa, the modified Cam clay best correlates the stress and strain.

Frictional behaviour of segmental retaining wall units infilled with recycled concrete aggregate

The use of segmental retaining wall units as the facing column for mechanically stabilized earth (MSE) retaining walls has increased noticeably all over the world. Hollow and solid, both types of modular block units are used in dry-stacked facing columns. Nowadays, Hollow concrete units are being implicated frequently because of its cost-effectiveness and other technical advantages. The cavities of hollow concrete units are filled with natural (fresh) aggregates for better shear resistance. The use of fresh aggregates as in-fillers in retaining wall constructions is expensive and unsustainable (annihilation of natural resources). This study mainly focuses on frictional behavior of newly designed and manufactured precast “I” blocks infilled with fresh and recycled aggregates. A series of tests were performed using a specially designed & fabricated direct shear apparatus to assess the frictional behavior of infilled blocks under different normal loading conditions. The tests were executed based on the exiting ASTM and National Concrete Masonry Association (NCMA) test protocols. Test results were outlined in the form of shear stress-displacement relationship to compare the effect of recycled aggregate against the fresh aggregate. Shear capacity envelopes were also plotted using Mohr-Coulomb failure criteria to find out the angle of friction for each case. Test results revealed that the angle of friction of the blocks infilled with the recycled aggregate is almost equal to those with the fresh aggregate.