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

通过变温垂直恒压固结试验和恒定应变速率固结试验，研究了粘性土在一维压缩条件下的温度和时间特性，并在20~80℃的变温试验结果中考虑了土颗粒热膨胀的影响。热膨胀由密度-温度关系确定。通过测量长度变化和利用密度-温度关系两种试验测定金属的热膨胀系数，评价了该方法的有效性。温度升高会导致空洞率下降，二次压缩也会导致空洞率下降。推导出了温度变化与二次压缩持续时间之间的理论关系，两者都会导致空隙比相同的下降。在考虑…的情况下，给出了粘性土的关系式。更多的是热膨胀。考虑热膨胀会导致较高的热促进固结程度，由于基本理论和确定本构关系的方法中包含的假设，无法通过CRS固结试验确定土的本构性质。因此，为了考察压缩速率对本构性能的影响，我们必须以某种方式估计真实的性能。首先，在CRS固结试验的基础上建立时间本构模型，并用该模型对CRS固结行为进行数值模拟；其次，将数值模拟的结果与实际固结试验的结果进行比较，如果差异超过一定范围，则对模型进行修正。采用有限变形有限元方法进行数值模拟。这一过程可以评估压缩速率对本构模型参数的影响。较少

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