冻结粉土三轴压缩变形破坏与能量特征分析

对不同温度和不同围压下的青藏冻结粉土进行了三轴压缩与加卸载试验,得到冻结粉土应力-应变关系曲线、抗压强度等力学参数随温度与围压变化的关系。结果表明,冻结粉土典型应力-应变曲线在低围压下大致可以分为线弹性、峰前塑性变形与峰后软化3个阶段。当σ33.0MPa时,应力-应变曲线具有明显的峰后软化现象,随围压的增大,软化现象逐渐减弱,当σ3达到14MPa,应变软化现象重新变得明显;冻结粉土的强度与变形模量均随围压的增加先升后降;低围压作用下冻结粉土体积随轴向应变的增加先缩后胀,而高围压下体积变形只有体缩;低围压下冻结粉土体积塑性变形耗散能先是随着体积塑性变形增大而增大,之后由于剪胀而减少,高围压下体积塑性变形耗散能始终增加;剪切塑性变形耗散能与塑性剪应变之间近似成抛物线的关系。

Experimental study of deformation failure and energy properties of frozen silt under triaxial compression

To study the mechanical characteristics of frozen silt of Qinghai-Tibet, the triaxial compression and the loading and unloading tests were performed at temperatures of -2 °C, -4 °C, and -6 °C under the confining pressures of 1.0-14.0 MPa. The stress-strain curve, strength and other mechanical characteristics of frozen silt were obtained. Results indicate that the stress–strain curves could be divided into three stages: the linear elastic stage, the plastic stage, and the strain-softening stage. When ? 3 <3.0 MPa, the strain-softening stage appeared and mitigated as the increase of confining pressure; when ? 3 increased to 14.0 MPa, the strain-softening stage would appear again. The strength and elastic modulus of frozen silt increased with increase of confining pressure; then decreased with further increase of confining pressures. The volume of frozen silt reduced with the increase of axial strain at first; then expanded with further increase of axial strain under low confining pressures; however, the volume only reduced under high confining pressures. The plastic volumetric strain dissipated energies increased to a peak value with increase of volume under low confining pressures, then decreased with decreasing in plastic volumetric strain for dilatation; but the plastic volumetric strain dissipated energies increased with increasing plastic volumetric strain all the time under high confining pressures. The plastic shear strain dissipated energies increased with increase of plastic shear strain; and the plastic shear strain has a good parabolic relationship with the dissipated energy.