灰岩三轴循环力学特性及能量演化特征试验研究

Study on Triaxial Mechanical Properties and Energy Evolution Characteristics of Limestone Under Cyclic Load

岩石的三轴力学特性及变形破坏特征对于指导地下工程稳定具有重要的意义。针对徐州地铁地层中灰岩开展了常规三轴和三轴循环加卸载试验,基于围压变化,分析其应力应变曲线、强度特征、破坏模式和能量演化特征,确定了灰岩力学特性及能量演化特征。具体结论如下,围压的升高会造成灰岩的弹性模量、变形模量、峰值强度和损伤阈值均逐渐增大,破坏模式由拉伸破坏转变为剪切破坏;三轴循环加卸载下灰岩的材料属性劣化程度要低于常规三轴,裂纹的贯通网络要比常规三轴的更为复杂;循环加卸载过程中能量演化呈现不同趋势,可依据单个循环内弹性能快速降低和耗散能快速升高作为岩石破坏的前兆信息。研究结果可为徐州地铁隧道和硐室的开挖及支护提供一定的指导。

Triaxial mechanical properties and deformation failure characteristics of rock are of great significance to guide the stability of underground engineering.Conventional triaxial and triaxial cyclic loading and unloading experiments were carried out on the limestone in Xuzhou Metro stratum.Based on the confining pressure change,the stress-strain curve,strength characteristics,failure mode and energy evolution characteristics were analyzed,and the mechanical properties and energy evolution characteristics of the limestone were determined.The concrete conclusions are as follows:The increase of confining pressure will gradually increase the elastic modulus,deformation modulus,peak strength,and damage threshold of limestone,also cause the failure mode of specimen to change from tensile failure to shear failure.The deterioration degree of material properties of limestone under triaxial cyclic loading and unloading is lower than that under conventional triaxial loading and unloading,and the crack penetration network is more complex than that under conventional triaxial loading and unloading.The energy evolution shows different trends in the process of cyclic loading and unloading,which can be regarded as the precursory information of rock failure according to the rapid decrease of elastic properties and the rapid increase of dissipated energy in a single cycle.The research results can provide some guidance for the excavation and support of Xuzhou Metro tunnels and chambers.