高温冻结粉土力学特性试验研究

为了探讨高温冻结粉土的力学特性，进行了一系列常规三轴压缩和三轴压缩加卸载试验。结果表明：（1）随着围压的增大，应力应变曲线先表现为应变软化，后应变硬化，最后又应变软化。（2）体积应变曲线均表现为先体缩后体胀，且围压越大，体胀越弱。（3）通过引入改进的双曲线模型，能较好地模拟应变软化和硬化特性。在q-p平面内建立了一个新的强度准则，并利用修正Mohr-Coulomb屈服准则，探讨了黏聚力c和内摩擦角φ的变化规律。根据试验结果，确定了不同围压及不同加卸载循环次数下高温冻结粉土的回弹模量及其损伤变化规律。最后，建立了塑性体积变形和塑性剪切变形之间的关系式和表达式，进一步探讨了高温冻结粉土的剪胀特性。

Experimental study on the mechanical properties of warm frozen silt soils

In order to investigate the mechanical properties of warm frozen silt soils, a series of triaxial compression tests and repeated shear loading-unloading tests were conducted. Experimental results indicated that:(1) with the increasing of the confining pressures, the stress-strain changing from strain softening to strain hardening, then strain softening occurred again; (2) the volumetric curves presented a compressive tendency at first, followed by a dilation; the higher the confining pressures were, the smaller the dilation phenomenon would become; (3) the stress-strain curves, which presented strain softening and hardening phenomenon, were well simulated by an improved hyperbolic model. A new strength criterion was proposed in q-p plane, which could well describe the evolution of increasing first and then decreasing with increasing of mean effective stress. The regularities of cohesion c and internal frictional angle φ for warm frozen silt soils were investigated on the basis of the modified Mohr-Coulomb yield criterion. According to the repeated triaxial shear loading-unloading tests, the resilient modulus of warm frozen silt soils were determined with different loading-unloading cycles under different confining pressures. At the same time, the damage evolution was explored. Finally, the relationship between plastic volumetric strain and plastic shear strain was established and expressed by an empirical mathematical formulation. Later, the characteristics of dilatancy were investigated under different confining pressures as well.