动静组合加载下裂隙试样力学特性和破坏模式

Mechanical Properties and Failure Modes of Fissured Samples underCombined Static-dynamic Loading

目的为了深入了解裂隙岩石在同时受到地应力和动力扰动时的工程灾变机制。方法采用改进的分离式霍普金森压杆系统,对预制裂隙类岩石试样进行了动静组合加载试验。研究了应变率、裂隙倾角和预应力对试样动态力学特性和能耗特征的影响,并对试样的破坏模式进行了分析。结果当应变率从61.82s^(-1)增加到195.57s^(-1),裂隙试样的动态增长因子不断增大,具有显著的应变率效应;动态弹性模量变化规律不明显,应变率效应不显著。随着入射能的增加,裂隙试样的单位耗散能密度不断增加。当裂隙倾角由0°变化到90°,试样的动态增长因子增不断增加,动态弹性模量和单位耗散能密度不断降低。当施加预应力后,30°、45°和60°裂隙试样的动态增长因子增长均有所增加;45°裂隙试样动态弹性模量有所增加,30°和60°裂隙试样的变化规律不明显;45°和60°裂隙试样单位耗散能密度有所降低,30°裂隙试样的变化规律不明显。裂隙试样的破坏模式主要包括张拉破坏、剪切破坏和张拉-剪切复合破坏3种,施加预应力对试样破坏模式的影响不明显。结论0°裂隙对工程岩体的承载能力削弱程度最小,90°裂隙有利于提高破岩效率。预应力在一定程度上会提高工程岩体的承载能力。研究结果可以为预测和评估岩石工程中的风险,制定合理的加固措施提供参考。

Objective In order to understand the engineering disaster mechanism of fissured rock subjected to in-situ stress and dynamic disturbance at the same time.Methods The improved split Hopkinson pressure bar system was used to carry out static-dynamic loading tests on prefabricated fissured rock samples.The effects of strain rate,fissure angle and prestress on dynamic mechanical properties and energy consumption of the sample were studied,and the failure mode of the sample was analyzed.Results The results showed that the dynamic increase factor of the fissure sample,when the strain rate increased from 61.82s^(-1) to 195.57s^(-1),increased continuously,and the strain rate effect was significant.The dynamic elastic modulus change law was not obvious and the strain rate effect was not significant.With the increase of incident energy,the unit dissipative energy density of the fissure sample increased continuously.When the fissure angle changed from 0°to 90°,the dynamic increase factor of the sample increased continuously,and the dynamic elastic modulus and unit dissipative energy density decreased continuously.The dynamic increase factors of 30°,45°and 60°fissure samples all increased after prestressing.The dynamic elastic modulus of 45°fissure samples increased obviously except for the 30°and 60°fissure samples while the unit dissipative energy density of 45°and 60°fissure samples decreased obviously except for 30°fissure samples.The failure modes of fissure samples mainly included tensile failure,shear failure and tension-shear composite failure,and the influence of prestress on the failure modes of fissure samples was not obvious.Conclusion The 0°fissure have the least effect on the bearing capacity of engineering rock mass,and the 90°fissure is beneficial to improve the rock breaking efficiency,while the prestressing improves the bearing capacity of engineering rock mass to some extent,which provides reference for predicting and evaluating the risks in rock engineering and formulating reasonable reinforcement measures.