中文摘要：

通过控制基质吸力的直剪和三轴试验，研究非饱和膨胀土强度参数随基质吸力的变化规律．试验结果表明：直剪和三轴试验得出的强度参数随基质吸力的变化规律基本相同，黏聚力随基质吸力的增加而增加，内摩擦角随基质吸力的增加而有所减小．非饱和土的内摩擦角并非常数，也受基质吸力大小的影响，当基质吸力小于或等于土样的进气值时，与基质吸力有关的内摩擦角保持不变，而土样内摩擦角随基质吸力的增大而减小．直剪试验得出强度参数相对三轴试验得出的强度参数偏大．

英文摘要：

In this paper, a series of suction-controlled direct tests and tri-axial tests are carried out to study the shear strength parameters of unsaturated expansive soils. Tests are performed on remolded expansive soil under different matrix suctions condition. The resuits show that the strength parameters derived from direct shear and tri-axial tests have the same variation with suction. Cohesion increases with increasing matrix suction. Internal friction angle decreases with increasing the suction. The internal friction angle of unsaturated soil is not a constant; however, it is also controlled by suction. When matrix suction is less or equal to the air entry value of soil sample, the suction friction angle is a constant, but the internal friction angle decreases with increasing the suction. The strength pa- rameters obtained from the direct shear tests are larger than those from tri-axiat tests. Results in this paper are important for the theory study of unsaturated soil.