基于热-水-力数值模拟的饱和正常固结黏土热压缩现象

Thermal Contraction of Saturated Normally Consolidated Clay Based on Thermo-Hydro-Mechanical Numerical Simulation

摘要:

既有饱和正常固结土体加热试验研究表明，温度升高时，土体的体积变化表现为体积收缩，这与热胀冷缩基本通识相违背。针对这一问题，通过热?水?力（THM）完全耦合有限元程序对饱和正常固结黏土的加热试验进行了数值模拟。结果表明，由于黏土的热传导系数及渗透系数都比较低，在升温过程中，试样内部会形成温度差，进而产生超孔隙水压，随着超孔隙水压的消散，最终使土体表现为热压缩现象。当增大土体的渗透系数时，土体内部不产生超孔隙水压，这时土体表现为热膨胀。因此，饱和正常固结土体升温引起的热压缩现象并非土体基本力学特性，而是一个边界值问题。

Abstract:

Many experimental studies on the thermal consolidation of saturated normal-consolidated soil show that the volume change of the soil has a thermal compression behavior when the temperature increases， which is contrary to the principle of thermal expansion and contraction. To solve this problem， a numerical simulation of the thermal consolidation test of saturated normally consolidated soil was conducted by the thermal-hydro-mechanical （THM） fully coupled finite element program in this paper. Because the thermal conductivity and permeability of clay are relatively small， in the heating process， a temperature difference will occur inside the sample， which will cause excess pore water pressure， and finally the soil will show thermal contraction with the dissipation of the excess pore water pressure. When the permeability coefficient of the soil is increased， the excess pore water pressure is not generated inside the soil， and the soil exhibits thermal expansion. Therefore， the thermal contraction phenomenon of saturated normally consolidated soil caused by the increase of temperature is not the basic mechanical property of the soil， but a boundary value problem.