中文摘要：

围压和温度是影响冻土强度的两个重要指标，并最终决定冻土的微观结构。文中利用MTS应变式冻土三轴仪进行了3个围压水平（300，400，500kPa）、3个负温水平（-5，-10，-15℃）共9个试样的强度试验，并根据莫尔一库仑破坏准则确定了不同条件下的抗剪强度参数。基于土微结构研究方法，对从不同围压和不同负温破坏试样上获得的样品进行了电镜扫描观察，利用LeicaQWin图像分析软件提取到了11个孔隙体微结构参数和11个颗粒体微结构参数。在此基础上，基于统计学原理，对孔隙体微结构参数和颗粒体微结构参数进行了主成分分析。对微结构参数的研究表明，第1主成分代表了微观参数水平截距、垂直截距、周长、颗粒密度，可以反映孔隙71％和颗粒50％以上的信息，第2主成分主要代表微观参数的面积分数和面积填充，可以反映孔隙17％信息和颗粒36％左右的信息。另外，围压梯度（100kPa）在恒负温下对冻土强度的影响要比负温梯度（5℃）在恒围压下对冻土强度影响大，其强度变化的比值约为4，并在此基础上得出围压与负温对冻土强度的影响关系。冻土微结构孔隙和颗粒参数同时受到围压和负温的影响，其主成分E变化基本一致，而主成分R变化趋势则相反。

英文摘要：

Confining pressure and temperature are the two important indexes of the shear strength and microstructure of frozen soil. Therefore, a frozen triaxial test of 9 samples under the confining pressures at 300 kPa, 400 kPa, 500 kPa and the negative temperatures at -5 ℃, -10℃, -15 ℃ was conducted to study the effect of confining pressure and negative temperature on the shear strength and microstructure of frozen soil by using the strain control triaxial shear apparatus of MTS. The shear strength was measured and the parameters of shear strength were obtained with the envelope line determined in accordance with the limit stress circle given by Mohr-Coulomb criterion. The samples that were destroyed at different contining pressures and different negative temperatures were scanned by the electron microscopic autoradiography, and 11 microstructure parameters of particle and pore of the soil samples were obtained by using the image analysis software of Leica QWin. Based on the statistical theory, 11 microstructure parameters of particle and pore were analyzed by the principal component analysis. The studies on parameters of the microstructure show that the pa- rameters of pore and particle of soil samples can be expressed about 71% and 50% with the first component including Intercept H, Intercept V, Perimeter, Count/Area and about 17% and 36% with the second component including Area Fill, Area Fract, respectively. In addition, the effect of confining pressure on the strength of frozen soil is about 4 times as much as that of temperature on the strength, and the influence of confining pressure and temperature on the strength of frozen soil is obtained. The microstructure parameters of pore and particle of frozen soil are affected simultaneously by confining pressure and temperature. The parameter variation of pore is basically the same as that of particle in principal component of F~, while the principal component of F2 is opposite.