Shear behavior of unsaturated soils at constant suction | |
| Author | Tamrakar, Surendra Bahadur |
| Call Number | AIT Thesis no.GE-96-16 |
| Subject(s) | Shear strength of soils--Testing Strains and stresses |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Civil Engineering |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. GE-96-16 |
| Abstract | In order to investigate the unsaturated shear behavior of Khon Kaen loessial soil, triaxial tests were carried out in a specially modified triaxial apparatus. Specimens were statically compacted so that they had 1.2 kN/m3 initial density and 8 % initial water content which were similar to the field conditions. Consolidated drained triaxial tests were performed at three different confining pressures (50, I 00 and 200 kPa) with constant suction condition of 0, 10, 50,100 and 200 kPa. Axis translation technique was used for the making the initial suction condition before starting the tests. The apparatus being specially designed, we could measure the overall volume change of the sample more accurately than in conventional triaxial apparatus. Hence the shear behavior could be observed more precisely. Also, pore-air and pore-water pressures could be controlled separately in this test. The tests were performed in accordance with the programming. The test results showed that the amount of suction greatly influence the shear behavior of the soils. Stress-strain relationship of test results showed that initial slope (stiffness) of the curves are lower at the lower suction values, but the slope increases with the increase in suction. It is also seen that suction effect; an increase in suction increases the yield stress is dependent on the confining pressure. At lower confining pressure the effect of suction is higher than at the higher confining pressure where it decreases. From results of the volumetric strain and axial strain relationship, it is seen that with the increase in suction there is a decrease in volume change of the specimens. This is due to the increase in inhibition of plastic deformation of the sample with the increase in suction. Also, from e - logp' lines during shearing, we can see the decrease in slopes of these lines as the suction increases. At higher suction values, the amount of drainage increases with the mcrease m suction whereas at lower suction values, water goes into the sample. All of the changes in shear behavior of the unsaturated soils are due to the effect of suction which are explained by the Kohgo's elastoplastic model with two suction effects; (i) an increase in suction increases the effective stress and (ii) an increase in suction increases both the yield stress and stiffness against plastic deformation. |
| Year | 1997 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. GE-96-16 |
| Type | Thesis |
| School | School of Civil Engineering |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Geotechnical Engineering (GE) |
| Chairperson(s) | Kohgo, Yuji; |
| Examination Committee(s) | Balasubramaniam, A. S. ;Shibuya, Satoru; |
| Scholarship Donor(s) | Government of Japan; |
| Degree | Thesis (M. Eng.) - Asian Institute of Technology |