菏泽矿区深部黏土层冻结土的力学性状试验研究

 对万福矿井400～700 m深度3个巨厚黏性土层取样进行冻土力学性状试验研究，获得如下结果：(1) 深部黏性土冻土的应力–应变曲线关系主要表现为应变硬化特点，达到峰值应力之前显现较大幅度的屈服形变；(2) 从－15 ℃，－20 ℃和－25 ℃三种对比温度的冻土力学性状看，温度对于冻土蠕变性的影响较对强度的影响更明显，－20 ℃是有效控制深部黏土冻结壁蠕变性的冻结状态界限值。经分析认为，深层黏土冻土力学性状及其与冻结温度的关系特点主要与层深部黏性土的含水性和结构性有关。试验土样处于半坚硬状态，所含水分以结合水为主。因结合水冻结温度要比重力水低得多，温度降低至－20 ℃以下，土中胶结冰含量会因结合水的冻结而明显增加，胶结冰和粒间摩擦力对于冻土强度的发挥程度趋于稳定，由此导致冻结土流变性的急速降低。

TESTING STUDY OF MECHANICAL BEHAVIORS OF FROZEN CLAY IN HEZE DEEP MINING AREA

According to mechanical behavior tests using frozen soil samples from three huge thickness clay strata situated between 400 and 700 m deep in Wanfu mine，the following results are obtained：(1) the stress-strain curves of frozen clay mostly show strain hardening and large yield deformation before the peak stress；(2) contrasting mechanical behaviors of frozen clay under frozen temperatures of －15 ℃，－20 ℃ and －25 ℃，the impact of temperature on creep properties of the deep frozen clay is greater than strength，and －20 ℃ is the limit value for freeze state of the deep-seated clay which can effectively control the creep characteristics of deep frozen wall. The relationship between the deep frozen clay mechanical behaviors and frozen temperature reflected in the results of the test is analyzed to be chiefly relative to the water content and structure of deep frozen clay. The soil samples used in the test are under half-solid state in which the bound water is principal part of pore water. Because the frozn temperature of bound water is much lower than that of gravitational water，when the temperature is lower than －20 ℃，the cementation ice content in the frozen soil increases obviously because of the freeze of bound water，and the impact degrees of cementation ice and inter-particle frictional force on strength of frozen soil become stable，and that leads to the rheological property of frozen soil to decrease sharply.