天然和饱水状态下泥岩力学性质及损伤变形能量特征分析

An analysis of the mechanical properties and energy characteristics of damage deformation of mudstone under natural and saturated states

为研究三溪村滑坡滑带泥岩的力学性质和滑带的形成机制,进行天然和饱水状态下单轴和常规三轴压缩试验。结果表明:饱水状态对泥岩的变形强度、破坏形式和围压效应具有显著影响,饱水使泥岩的应力应变曲线由应变软化型转化为"弹-塑-蠕变"型,破坏形式由剪断破坏变成塑性破坏,围压敏感性减弱,而似软化系数随围压的增加而减小。从能量角度分析表明:两种状态下能量的变化规律相似,但天然状态能量以弹性应变能储存,饱水以耗散能释放,且饱水使总应变能U、峰前弹性应变能Ue及二者的变化速率均小于自然状态,而耗散能Ud则相反;试样峰值点和残余点处各应变能具有围压效应,呈线性递增关系。饱水导致各应变能的累积、转化、耗散和释放的差异,使得弹性应变能急剧降低,耗散能增加,力学强度也伴随着滑带的损伤变形而产生衰减效应。

In order to study the mechanical properties of the mudstone in the sliding zone and the formation mechanism of the sliding zone of the Sanxi landslide,uniaxial and triaxial compression tests are carried out under natural and saturated states. Experimental results show that deformation,intensity,failure mode and the confining pressure effect of the mudstone are influenced seriously when saturated. The saturated condition makes the stress strain curves of the mudstone convert from strain softening to ＂elastic- plastic- creep＂,the damage modes convert from shear damage to plastic collapse,and the confining pressure sensitivity abate,and the softening coefficient decrease with the increasing confining pressure. From the perspective of energy,it is found that the change in the energy rule of two kinds of states of energy is similar. Under the natural state,the energy stores in the form of the elastic strain energy,but it releases in the form of dissipation. The total absorbed energy U and the releasable strain energy U^e before the peak stress and their increasing rates in axial strain under the saturated conditions are less than the corresponding values of the natural specimen,but the dissipation U^d process is opposite. The peak point strain energy and the residual point strain energy are both in linear relation with the confining pressure. The differences in the strain energy accumulation,transformationprocess,dissipation and release of the mudstone are caused when saturated. The Ueof the saturated mudstone decreases greatly,but its Udincreases. As a result,its mechanical strength will be damped with the sliding zone out of shape and damaged.