Experimental Study On Crack Predominance Of Rock-like Material Containing Two Parallel Flaws Under Uniaxial Compression

Fractured rock mass is a relatively complex and universal engineering medium in water conservancy engineering,underground construction engineering and mining engineering.A lot of engineering practice shows that the initiation,expansion and transfixion process of fractures in rock mass under engineering disturbance leads to instability and failure of many rock masses,and the main failure mode of fractured rock mass is that adjacent joints and fractures expand and transfixate each other.Therefore,it is of great significance to study the crack growth and failure rules of fractured rock mass under stress.In this paper,prefabricated parallel double-fissure rock materials are taken as research objects to study two key influencing factors(crack length difference and crack spacing)on the failure rule of specimens under uniaxial compression condition,and the test results are analyzed by relevant fracture mechanics theories.Finally,according to the physical test parameters,PFC2 D particle flow software was used to conduct numerical simulation of the test process for comparative analysis.The main conclusions are as follows:1)According to different crack length and crack spacing of combination way,according to the prefabricated parallel double slit type rock under uniaxial compression material physical test,on the basis of classification statistics the same crack length difference circumstances,different crack spacing and the same specimen fracture spacing,different crack length difference crack damage propagation form of specimen,summarizes the physical test of specimen damage rule.2)Relevant theories of fracture mechanics are applied to analyze the failure rules of the specimens obtained from physical tests.The test results obtained are in line with theoretical calculations,verifying the correctness of the physical test plan,and providing theoretical support for the test rules,which can be used for practical reference.3)Combining the physical test and numerical simulation results to analyze the crack propagation and specimen failure mode,it can be concluded that:(1)The impact of crack length difference on specimen failure is as follows: when the specimen reaches failure,the crack length difference is 0,and new cracks are generated in both prefabricated cracks,resulting in expansion.With the increase of the crack length difference,the growth of the lower short crack is less obvious or even does not occur.In particular,when the crack length difference increases to 40 mm,the lower short crack does not expand at all,and the crack predominance of the upper long crack grows.(2)The influence of crack spacing on the failure of specimens is as follows: when the specimen reaches the failure,the smaller the crack spacing is,the less obvious the lower short crack propagation is.When the crack spacing is less than 10 mm,the lower short crack does not even expand,and the crack predominance of the upper long crack expands.(3)In the influence of crack length difference and crack spacing on specimen failure,crack length difference is the dominant factor.When the crack length difference is large enough(40mm and above),the influence of the change of crack spacing on whether the lower short crack expands or not cannot be seen through the test.At this time,the lower short crack does not expand,and the crack predominance of the upper long crack expands.When the crack length difference is small enough(10mm or less),new cracks will appear in the two prefabricated cracks and expand.It is impossible to see whether the change of crack spacing has an effect on the growth of the lower short crack.