Research On Indirect Measurement Of Rock Tensile And Compressive Strength Based On Leeb Hardness And Point Load Tes

With the implementation of the 14 th Five-Year Plan,infrastructure construction has always been a focus of development,involving many geotechnical engineering issues.Rock strength parameters,as basic mechanical parameters,play a very important role in engineering construction.Rapid and accurate acquisition of strength parameters can benefit the implementation of engineering construction.Directly measuring rock strength parameters is complex,time-consuming,and laborious,so indirect testing methods are widely used in engineering.Currently,the main indirect measurement methods include the Schmidt hammer test,indentation test,needle penetration test,as well as point load and Equotip hardness test methods.To improve the accuracy of indirect measurement of rock strength parameters and fully utilize the convenience of indirect measurement,this paper mainly discusses two indirect methods,namely the point load test and the Equotip hardness test.Firstly,this experiment found that the method of calculating point load strength through the real failure area is more accurate.In addition,considering that the real failure area is difficult to test on-site,this paper innovatively proposes a method of calculating point load strength through the measurement of section cracks,which has a smaller calculation error.Through in-depth research and analysis of the phenomenon of the cone penetrating rock specimens in the point load test,it was found that the penetration depth is positively correlated with the density of the rock,while the penetration degree is negatively correlated with the failure load of the specimen.Secondly,taking six types of rocks as examples and considering factors such as the number of tests,testing methods,dry and wet states,and size effects,through multiple test comparisons and combined with the standard specifications in the field of metallic materials,this paper proposes a suggestion for the standardization of the Equotip hardness tester in the geotechnical engineering field,as well as an innovative idea for classifying rocks based on Equotip hardness.Furthermore,by fitting the rock point load strength and Equotip hardness with the tensile and compressive strength parameters,linear,power,exponential,and logarithmic indirect measurement models were obtained.Comparing the results,the linear model was more accurate for indirect testing of uniaxial compressive and tensile strength with point load strength,while the power function model was more accurate for calculating uniaxial compressive strength with Equotip hardness value,and the linear model was more accurate for calculating tensile strength.From a microscopic perspective,indirect measurement of rock tensile and compressive strength through Equotip hardness is feasible.In addition,this paper proposes a rock classification fitting method and a dual-parameter fitting method to improve the accuracy of indirect measurement.In summary,taking six types of rocks as examples,this paper studied the indirect measurement of rock tensile and compressive strength through the point load test and the Equotip hardness test,and improved the accuracy of measurement through two methods.It also innovatively proposed a suggestion for standardizing the Equotip hardness tester in geotechnical engineering,which can be used in tunnel excavation,railways,highways,water conservancy,and slope projects,and is beneficial to infrastructure construction and development.