温度对饱和黏性土剪切特性影响的试验研究
Experimental study on effect of temperature on shear behavior of saturated clays
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摘要: 采用温控三轴仪,考虑不同的温度–应力路径,对两种正常固结的饱和黏性土进行了固结不排水和固结排水剪切试验,研究了温度变化对土体强度、应力应变关系、孔压响应和流动法则等的影响。结果表明,温度效应的强弱与土的类别有关,温度变化对粉质黏土的剪切特性基本没有影响,但对黏土的影响不容忽视。随着温度的增加,黏土的不排水和排水峰值强度有明显的提高,临界摩擦角基本保持不变。不同温度下黏土不排水剪切过程中均产生正的超孔压,排水剪切中土体体积均持续减小,表明高温下偏应力偏应变曲线出现软化的原因与强超固结土的剪胀机理有区别。黏土剪切特性的变化程度与温度–应力路径相关,先升温后固结试样的不排水强度比固结后升温试样的低。温度循环一周后,黏土的不排水强度较室温下有明显提高。Abstract: The effect of temperature on shear behavior of saturated clays is investigated by means of the temperature-controlled triaxial tests. Two kinds of normally consolidated saturated clays are tested. The test program involves different heating and consolidation sequences and drained conditions. The influences of the temperature change on the shear strength, the stress-strain relationship, the excess pore water pressure response and the flow rule are analyzed. The experimental results show that the temperature change significantly affects the shear behavior of the clay, while the temperature effect on the shear behavior of the silty clay is negligible. An increase in temperature increases the undrained and drained peak strength, but the critical friction angle does not change. The excess pore water pressures built up during undrained shear of clay specimens at different temperatures are all found to be positive, and the volume changes under drained shear are always contractive. It implies the reason that the stress-strain softening behavior at high temperature is not shear dilatancy, which is usually used to explain the softening behavior of heavily over-consolidated clays. The temperature effect on the shear behavior is also relevant with the temperature-stress path. The undrained shear strength of the specimen subjected to heat after consolidation is smaller than that of the specimen first heated. After a temperature cycle, the undrained shear strength increases markedly.