Numerical and Laboratory Investigation of Optimal FIROZBAHRAM-soil Improvement with Lime and Cement and Its Impact on Reduction of Soil Settlement in West Tehran Wastewater Treatment Plant

In this research, lime and cement additives were used to stabilize clay and therefore to reduce the settlement in raft foundations. Lime and cement were mixed with clay and the effect of the use of these two additives on the stabilization of fine clay soil in the laboratory was investigated. Soil samples in normal state and in combination with different percentages of lime and cement equal to 3, 6 and 8 percent dry weight of soil for laboratory tests including Atterberg limits Test, Grading Test, Standard Compaction Test, Uniaxial Compressive Strength Test and California Bearing Ratio Test, and Also, Consolidated Undrained Triaxial Compression Strength Test (CU) and direct shear tests were used. The results show a decrease in the plasticity and maximum dry unit weight of soil and an increase in optimum moisture content, compressive strength, and also the California Bearing ratio of clay by adding these two materials. The cohesion and internal friction angle that obtained from Consolidated Undrained Triaxial Compression Strength tests (CU) and direct shear tests increase with increasing cement and lime percentages. After laboratory tests the effects of the use of soil improvement with depths of 1m, 2m, 4m, 6m, 8m and 10m using Plaxis software suggests that as the depth of improvement Increases, the amount of settlement decreases, which is a lot different from that of the plate loading test prior to improvement while the difference between the results obtained from Plaxis and plate loading test after improvement are negligible.