寒区地下工程建设中,围岩长期处于低温环境,其内部自由水会发生冻结,显著影响围岩结构的力学性能。同时,地下工程常遭受地震、爆破等动荷载作用而发生失稳破坏。然而,当前针对冻结岩石的动态压缩力学特性的研究尚显不足。为探究冲击荷载作用下低温含冰岩石的动态压缩特性,利用分离式霍普金森杆测试系统开展了红砂岩试样的动态压缩冲击试验,分析了温度及含水率对于红砂岩动态压缩力学特性的影响,揭示了其破碎程度与能量耗散的关系。结果表明:(1)低温含冰红砂岩的动态压缩强度、应变和弹性模量表现出显著的温度和应变率效应,随含水率的增加,低温含冰红砂岩的动态压缩强度和动态压缩弹性模量增加,动态峰值应变减小;(2)低温含冰红砂岩的耗散能随温度的降低或应变率的增加而增加,随含水率的增加而减小;(3)低温含冰红砂岩破碎程度和分形维数与温度、含水率和应变率密切相关,随着温度的降低或应变率的增加,低温含冰红砂岩的破碎程度和分形维数增加,含水率的增加使得低温含冰红砂岩的破碎程度和分形维数减小;(4)岩石的分形维数随耗散能密度的增大而增大。研究结果可为寒区工程的建设与防护提供借鉴。

In the development of underground projects in cold areas, the surrounding rock mass is in an environment with low temperature for a long time, and its internal free water freezes, which significantly affects the mechanical properties of the surrounding rock mass. At the same time, the underground projects will be subjected to earthquake, blasting and other dynamic loads, resulting in instability failure. However, current study on the dynamic compressive properties of frozen rock is insufficient. In order to explore the compression characteristics of frozen rock under dynamic load, the dynamic compression tests of red sandstone were carried out by using split Hopkinson pressure bar. The effect of temperature and water content on dynamic compression properties of red sandstone was analyzed, and the relationship between the degree of fragmentation and energy dissipation was revealed. The results show that: (1) The dynamic compressive strength, strain and elastic modulus of frozen red sandstone present a significant effect of temperature and strain rate. With the water content increases, the dynamic compressive strength and dynamic elastic modulus increase, while the dynamic peak strain decreases. (2) The dissipated energy of frozen red sandstone increases with the decrease of temperature and the increase of strain rate, and decreases with the increase of water content. (3) The degree of fragmentation and fractal dimension of frozen red sandstone are closely related to temperature, water content and strain rate. With the decrease of temperature or the increase of strain rate, the degree of fragmentation and fractal dimension of frozen red sandstone increase. With the water content increases, the degree of fragmentation and fractal dimension of low temperature frozen red sandstone decrease. (4) In addition, the fractal dimension of rock increases with the increase of dissipated energy density. The findings of this study provide guidance for the construction and protection of civil, hydraulic, tunnel, and other engineering projects in cold regions, which have significant engineering value.