Apparent Cohesion and Small-Strain Soil Modulus of Unsaturated Compacted Lateritic Soil

• Main Authors: Jia-Hao Li, 李家豪
• Other Authors: Horn-Da Lin
• Format: Others
• Language: en_US
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/m8cbzv

碩士 === 國立臺灣科技大學 === 營建工程系 === 105 === The water content and matric suction of the unsaturated compacted lateritic soils are affected by the wetting and drying process. The strain induced by the external loading may influence the soil modulus. In addition, the confining pressure effect on the soil modulus is also an important issue. Therefore, the soil modulus varying with the matric suction, strain and confining pressure is an interesting issue worthy of further study. In addtion, the matric suction effect on the unsaturated shear strength parameters of compacted unsaturated lateritic soil is also investigated in this study. Soil specimens were compacted at three different initial water contents including the dry side, OMC and the wet side. They are then subjected to designated drying and wetting paths using the environmental simulation apparatus. Subsequently, a series of laboratory tests were conducted including the pressure plate test, the unconfined compression test, the unsaturated triaxial test and the bender element test (confined and unconfined condition) to assess the relationship among soil structure, matric suction, apparent cohesion and strain-dependent soil modulus. Moreover, a new unsaturated triaxial testing system was developed in this study to satisfy the testing purpose. Test results demonstrated that the soil modulus of dry side decreased substantially after wetting and increased less significantly as suction increase upon drying. Matric suction characteristics of the wet side and the OMC are similar However, soil modulus of OMC increased less rapidly than wet side upon drying due to the weakening of fabric upon saturation. Moreover, the test results indicate that the soil modulus is significantly affected by increasing the confining pressure. The test results also exhibit that the apparent cohesion increase with matric suction with a nonlinear relationship. In addition, the apparent cohesion increase become milder when the soil suction reaches high matric suction.