寒区黏土与结构接触面冻结强度特性试验研究
Experimental Study on the Freezing Strength Characteristics of Clay-Structure Interface in Cold Regions

寒区土与结构接触面冻结强度可以视为是与土性、温度、含水量、界面粗糙度、法向压力等诸多因素直接相关的复杂函数形式，并直接影响到上部结构的承载能力及稳定性。以青藏高原黏土与不同粗糙度的钢板结构接触面为研究对象，通过不同含水率，不同温度及不同法向压力下冻结黏土与钢板结构接触面的直剪正交试验，研究土与结构接触面冻结强度的影响因素及影响程度大小，并对冻结强度的变化规律进行初步分析和探讨。研究结果表明含水量对抗剪强度的影响最大，在不同影响因素共同作用下，界面抗剪强度最小值为0.13 MPa，最大值为0.45 MPa。界面抗剪强度随含水量的增加，温度的升高而明显降低，随界面法向压力和粗糙度的增大呈明显增大趋势。界面强度基本可通过摩尔-库仑准则，利用界面的黏聚力和内摩擦角进行表示，并在文中给出了界面强度的参考值。
Frozen soil is a composite material composed of soil particles, ice, unfrozen water, and gas, and with unstable mechanical properties. The amount of ice determines its temperature sensitivity, and previous research has shown that its negative temperature is the most critical factor that determines its strength; therefore, temperature is a key factor in regulating the bearing capacity of a frozen soil foundation. As the main foundation of major constructions in unstable and ice-rich permafrost regions, a pile foundation is widely used because of its relative stability during permafrost degradation. The freezing strength of a soil-structure interface in the cold regions can be viewed as a complicated functional form of the soil property, temperature, water content, interface roughness, and normal pressure, which directly influence the bearing capacity and stability of the upper structure. Series of laboratory direct shear tests of the interface between the Qingzang Clay and a steel plate of different roughness were performed. Based on the direct shear tests and an orthogonal design method, the influence factors, influence degree, and mechanical behavior of the shear strength of soil-structure interface were studied. The results show that the amount of water content in the interface has the greatest influence on its shear strength. From laboratory tests, the maximum and minimum interfacial shear strength is 0.45 MPa and 0.13 MPa, respectively, under the different test conditions. Moreover, the shear strength of interface decrease with increasing water content and temperature, and the shear strength increase with increase in the interface roughness and normal pressure. Based on the experimental results, the shear strength of interface can be determined based on Mohr-Coulomb strength criterion; the cohesive strength and internal friction angle are presented in this paper. The results of this study can help prevent and control the disasters of pile foundations at permafrost regions; thus it is of great scientific importance.