COMPRESSIVE INDICES OF COHESIVE SOIL AND RELATION TO DEGREE OF SATURATION

The compression coefficient and compression modulus are two important parameters of soil to evaluate the compressibility of soil. They are of great significance to the calculation of soil settlement. However, there are still some problems in the method of determining the compressibility index of soil in practice. Based on the definition of the compression coefficient and the compression modulus, this paper theoretically analyzed the relationship of the compression coefficient, compression modulus and the void ratio of soil. Two kinds of the calculation formula about these three parameters were also derived. Then these corresponding relations among the compression coefficient, compression modulus and the void ratio of soil were studied. This paper takes the weak swelling cohesive soil in Hefei area as the research object. The fast-consolidation tests of six sets of cohesive soil samples from Hefei with different saturation were carried out through multi-cycle loading and unloading. The problem of amending formula of deformation commonly used in the fast-consolidation test was pointed out and then the improved method was proposed. The correlation of the compression index, the number of loading and unloading and the degree of saturation were discussed. Then the exponential function was used to fit the relationship between the compression modulus and the degree of saturation. Using the probabilistic method, the fitting coefficients were obtained. The results show that the soil samples transmit from plastic state to elastic state with the increase in the time of loading and unloading cycle. With the increase of the degree of saturation, the compression modulus decrease gradually until come to stable.