Basic Research on Temperature- and Time-Depending Constitutive Equations for Cohesive Soils

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Temperature- and time-depending behavior of cohesive soils in one-dimensional compression conditions was studied vertical-pressure-constant consolidation tests under varying temperature and constant-rate-of-strain (CRS) consolidation tests.The effects of thermal expansion of soil particles were considered in results from tests conducted with varying temperature from 20 to 80℃. The thermal expansion was determined from density-temperature relationships. The validity of the method was evaluated by determining thermal expansion coefficients of a metal from two kinds of tests : to measure the change in length and to use the density-temperature relationships.Raising temperature causes the decrease in void ratio and secondary compression also causes it. A theoretical relationship between the change in temperature and the secondary compression duration both of which will cause an identical decrease in void ratio was derived. The relationship for a cohesive soil was presented with the consider … More ation of the thermal expansion. The account of thermal expansion resulted in a higher degree of thermally promoted consolidation.Constitutive properties of a soil can not be determined from the CRS consolidation test because of assumptions included in the basic theory and the method for determining constitutive relationships. Therefore, in order to examine the effects of compression rate upon the constitutive properties, we have to estimate true properties in certain ways. The following procedures were employed : at first, to make a temporal constitutive model based on the CRS consolidation test and to numerically simulate the behavior in the CRS consolidation with the model ; second, to compare the behavior of numerical simulation with that of the real consolidation test and to modify the model if the difference is observed beyond a certain limit. The numerical simulation was done by the finite-deformation finite-element method. This process could assess the effects of compression rate on the parameters in the constitutive model. Less