不同应变速率下非贯通裂隙介质的单轴抗压强度分析

UNIAXIAL COMPRESSIVE STRENGTH ANALYSIS OF FRACTURED MEDIA CONTAINING INTERMITTENT FRACTURES AT DIFFERENT STRAIN RATES

采用滑移型裂纹模型模拟分支裂纹扩展,并采用裂纹密度的方法考虑多裂隙的相互作用,对不同应变速率下含不同裂隙空间位置、不同裂隙数目的非贯通裂隙模型试样强度变化规律进行了分析。研究结果表明:采用滑移型裂纹模型可以较好地模拟裂隙试样产生拉伸及拉剪复合型贯通破坏的强度,但不能反映裂隙试样出现剪切型贯通的强度;不同应变速率荷载作用下含多条裂隙试样的强度特性并不与试样内预存的裂隙总数有关,而与引起试样破坏的贯通裂隙数目(即控制性裂纹数目)有关;在中低加载速率条件下(应变速率为1.7×10-5～1.7×10-1 s-1),通过提高试样断裂韧度即可很好模拟裂隙试样的强度随加载速率的变化。

The strength properties of jointed rock mass have attracted many researchers′ attention in rock mechanics.In the paper,the fractured samples made by gypsum mixture containing two or three intermittent fractures with different allocations in the samples are loaded at different strain rates.In virtue of the sliding crack model（SCM） to simulate the branch crack propagation and using crack density method to consider interaction of multi-fractures,the uniaxial compressive strength of the fractured samples is analyzed at different strain rates.The studies show that the SCM can simulate the coalescence of cracks in tension and tension-shear mixed mode,but it isn′t applicable to the shear coalescence mode;the strength properties of the fractured samples are not related to the pre-existed cracks in the fractured samples,but the coalesced cracks,i.e.controlled cracks.The variation of the strength of fractured samples vs.loading rates can be simulated through increasing the fracture toughness of the experimental material under low loading rate to medium loading rate condition,i.e.strain rates from 1.7×10-5 to 1.7×10-1 s-1.So,the SCM can be used to analyze the strength variation of the fractured media under low loading rate to medium rate condition and the variable of crack density can reflect the interaction of multi-fractures well.