Fragmentation fractal characteristics of sandy mudstone under impact load
To study the fragmentation fractal characteristics of sandy mudstone under impact load,the split Hopkinson pres-sure bar(SHPB)test device was used to conduct the impact compression tests on the sandy mudstone samples,and the stress-strain curve characteristics and failure modes under five-stage impact pressure and two length-to-diameter ratios were explored.Furthermore,the fractal dimension was introduced to quantify the fragmentation degree and the distribution of frag-mentation size,and the relationship between the fractal dimension and the loading value,strength value,and energy value was analyzed.The results show that the failure evolution of sandy mudstone under impact load can be divided into the crack com-paction section,elastic-plastic stable section dominated by elastic deformation,plastic-elastic unstable section dominated by plastic deformation,and macroscopic failure section.For the sandy mudstone sample with a length of 20 mm before impact,the sample is compressed to 19.86 mm in the crack compaction section,with a compression amount of 0.7％.Under the impact load,the sandy mudstone sample exhibits the splitting failure,and the fragmentation size distribution has a good fractal pat-tern.The fractal dimension of LD 0.4(length-to-diameter ratio of 0.4)and LD 0.8(length-to-diameter ratio of 0.8)is pos-itively correlated with the strain rate,dynamic compressive strength,and fragmentation energy dissipation density.Under the same impact pressure,LD 0.4 has a stronger sensitivity to strain rate and dynamic compressive strength.Under the same frag-mentation energy dissipation density,the fractal dimension of LD 0.4 is larger.The research results can provide certain theo-retical support for the anti-erosion treatment of roadways with sandy mudstone roof and floor.
rock dynamicssplit Hopkinson pressure bar(SHPB)fractal dimensionstrain ratefragmentation morpholo-gy
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