分级循环加卸载试验下砂岩的力学特性研究

Study on Mechanical Properties of Sandstone under Grading Cyclic Loading and Unloading Test

采矿工程中岩体受开挖过程影响易发生不可逆破坏,为保证矿山开采的安全运行,须研究扰动荷载下岩石的力学特性。为此,探讨了不同围压条件下,致密砂岩在常规三轴加载和分级循环加卸载作用下的力学特性,并将二者进行对比分析。得出结论:破坏形式均属脆性破坏,循环加卸载下的砂岩试样破碎程度更大;循环加卸载试验中,试样峰值强度较常规三轴试验有所减小,轴向峰值应变有所增大;增大围压能够提高砂岩抵抗变形的能力;随着分级循环上限应力值的增加,滞回环曲线的面积逐渐增大,产生的耗散能也逐渐累积;循环加卸载过程对砂岩弹性模量起到强化效应;同时,循环荷载加剧了裂纹损伤。此研究结果对砂岩在复杂应力下的矿山安全工程实践具有重要的理论指导意义。

In mining engineering,the rock mass is subjected to irreversible damage due to the influence of the excavation process.In order to ensure the safe operation of mining,it is necessary to study the mechanical properties of the rock under disturbance load.For this reason,mechanistic properties of tight sandstone under different confining pressure conditions under conventional triaxial loading and staged cyclic loading and unloading are discussed,and the two are carried out comparative analysis.It is concluded that the failure mode is brittle failure,and the sandstone sample under cyclic loading and unloading is more broken;in the cyclic loading and unloading test,the peak strength of the sample is reduced compared with the conventional triaxial test,and the axial peak strain is somewhat increase;increasing confining pressure can improve the ability of sandstone to resist deformation;with the increase of the upper limit stress value of the grading cycle,the area of the hysteresis loop gradually increases,and the generated dissipation energy gradually accumulates;the cyclic loading and unloading process affects elastic modulus of sandstone plays a strengthening role;at the same time,cyclic loading aggravates the crack damage.This research result has important theoretical guiding significance for mine safety engineering practice of sandstone under complex stress.