Abstract:Based on onedimensional compression tests,compressionreboundcompression curve and the compression index and rebound index of Shanghai soft soil were obtained.At the same time,the influences of suction on the strength of the unsaturated soil were analyzed.Then the test results were simulated with Alonso elasticplastic model,and the preconsolidation pressure versus suction (loadingcollapse curve) curve was fitted.Results show that the compressibility of the soil decreases while the matric suction increases.For certain suctions,elg p curve clearly step phases in elastic,elasticplastic and rebound recompressed phases.With compression of unsaturated soil,the preconsolidation pressure decreases with suction decreases.There is a surface among pore ration,suction and vertical stress.