冻土机械切削破碎机理的研究进展

Research progress on mechanical cutting fracture mechanism of frozen soil

冻土开挖困难、破碎效率低是高寒地区工程建设、地基施工等面临的技术难题。冻土机械切削破碎是冻土开挖的主要方法,其机理研究是提高冻土破碎效率的前提和基础。首先总结了温度、含水率、围压等对冻土复杂力学特性的影响,进而调研分析了冻土机械切削破碎的典型切削力学模型,发现冻土切削机械破碎模式不仅与冻土力学特性密切相关,也与切削参数和刀具结构直接相关,冻土切削过程中存在着最优的切削前角(30°~60°),且深切削和浅切削时冻土内部受力方式存在差异也会导致破坏形式的不同;温度、含水率、围压所造成的冻土力学性能变化会直接导致冻土破坏过程和切削破碎机理的改变,冻土强度随着温度降低表现出先升高然后保持稳定的特性,随着含水率升高呈现出先升高后降低的趋势,冻土破碎存在脆性、塑脆过渡及塑性等不同破坏形式。通过系统总结冻土切削破碎机理研究进展,进一步明确了冻土力学性质主要影响因素、变化特点及其切削破坏损伤特征,为冻土机械切削破碎的切削参数和切削具结构优化提供了设计依据。

The difficulty of permafrost excavation and low crushing efficiency are the technical problems faced by engineering construction and foundation construction in alpine region. Mechanical breakage of frozen soil is the main method of frozen soil excavation,and the research on the mechanism of frozen soil mechanical cutting and crushing is the prerequisite and basis for improving the efficiency of frozen soil crushing. In this paper,the influences of temperature,water content and confining pressure on the complex mechanical properties of permafrost are summarized. The typical cutting mechanical models of permafrost mechanical breakage are investigated and analyzed. It is found that the breaking mode of frozen soil cutting machine is not only closely related to the mechanical properties of frozen soil,is also directly related to the cutting parameters and tool structure. There is an optimal cutting rake angle(30°~60°)during the cutting process of frozen soil,and the difference in the internal force mode of the frozen soil during deep cutting and shallow cutting will also cause different types of damage. Moreover,the mechanical properties of permafrost caused by temperature,moisture content and confining pressure will directly lead to the change of permafrost failure process and breaking mechanism,the strength of frozen soil will increase firstly and then remain stable as the temperature decreases. As the moisture content increases,it shows a trend of increasing firstly and then decreasing. Moreover,there are different failure forms such as brittleness,plastic brittle transition and plasticity. The research progress of permafrost fracture mechanism further clarifies the main influencing factors,variation characteristics and cutting damage characteristics of permafrost mechanical properties,which provides design basis for optimizing cutting parameters and cutting tool structure of permafrost mechanical fracture.