冲击损伤砂岩动静组合加载力学特性研究

An investigation of the mechanical properties of sandstone under coupled static and dynamic loading

利用霍布金森压杆试验装置对灰砂岩试样进行预加静载的循环冲击,使试样产生初始损伤,并分析此过程中试样的损伤演化规律。使用能够施加轴压的霍布金森压杆进行预损伤试样动静组合加载试验,获得试样破坏模式、动态应力-应变关系等指标。基于应变等价原理分析预损伤试样动静组合加载条件下的总损伤变量,建立相应的损伤演化方程及损伤本构关系,并与完整试样进行对比。研究结果表明:循环冲击过程中试样损伤变量分为快速上升、低速发展、高速发展3个阶段,预加轴压越大低速发展阶段损伤变量平均值越小;相同动静组合加载条件下预损伤试样动态强度较小,完整试样应变率增强效应更加显著;循环冲击预损伤变量D01、预加静载损伤变量D02对于应力-应变关系的影响是较为复杂的,D01、D02值之和可能为负值;建立的本构关系与试验曲线具有较好的一致性,得到的总损伤变量曲线不仅能够解释试样宏观破坏与细观损伤过程的一致性,并且能够反映循环冲击和预加静载两种因素对岩石总损伤发展的非线性影响。

Through the application of SHPB(split Hopkinson pressure bar)test,this research firstly analyzed the law of damage under the cyclical impact on grey sandstone samples with the condition of static load.After that,to obtain the sample failure mode and speculate the relationship between dynamic stress and strain,the static-dynamic loading experiments on pre-damaged rock samples were also performed.Finally,based on the principle of strain equivalence,the total damage variable under the condition of static-dynamic loading was analyzed to derive the damage evolution equation to explain the relation of damage constitutive.Based on above tests,the research suggests:(1)the damage variable of rock sample can be divided into three stages during the process of cyclical impact,which are rapid increase,low-speed development and high-speed development,meanwhile,a higher axial pressure will lead to a lower damage variable in the stage of low-speed development;(2)compared with pre-damaged sample,the effect of strain rate enhancement on intact samples is more significant under the same condition;(3)the joint impact of pre-damaged variable(D01)and static-load damage variable(D02)might be negative,which therefore explained the fact that the dynamic strength increases with the static pressure under the condition of static-dynamic loading;(4)the constructed constitutive relation is also in perfect agreement with the curve of test value,which can in turn show a consistency between the macro-and micro-damage of the rock and then reflect the nonlinear influence of cyclical impact and static loading on total damage development.