Research And Analysis On Point Load Test Of Rock

Point load test is an effective method to predict rock strength rapidly.It is very important to carry out the experimental research and Analysis on the strength and failure characteristics of rock point load for the improvement of rock point load testing technology and the evaluation of the safety and stability of geotechnical engineering.In this paper,the influencing factors of point load strength index of rock are summarized,The point load strength tests of rocks with different shapes and sizes are carried out,and the influence of two main calculation modes and different correction index m on the calculation of point load strength is analyzed,The influence of anisotropy on the strength characteristics and failure mode of rock is analyzed.Based on the test results,the conversion relationship between point load strength and uniaxial compressive strength is obtained?The failure mechanism of rock under point load is analyzed by using EPCA.The main contents are as follows:?1?The point load tests of three different shape specimens?cylinder,block,irregular block?and three different diameter specimens?38mm,50mm,75mm?were carried out.Through the correlation and error analysis of the failure area A_f and the square of the equivalent diameter D_e and the failure load P,respectively,the two most classic point load calculation modes are compared,and the effects of shape effects and size effects on the point load strength index are analyzed at the same time.Finally,combining with the point load strength I_s?50?calculated by the correction index m in the main domestic and foreign codes,the influence of different correction index m on the point load strength index is discussed.?2?Point load test and uniaxial compression test of gneiss are carried out to analyze the influence of anisotropy on the correction index m,strength characteristics and failure mode of point load strength.Finally,the anisotropic index of rock strength is obtained.?3?Based on the analysis and statistics,the transformation relationship between I_s?50?and UCS is established.?4?The numerical test of point load is carried out by using the elastic-plastic cellular automata analysis system?EPCA?in the process of rock fracture.The fracture form and strength characteristics of rock under different homogeneity are analyzed,and the failure mechanism of point load test is revealed.