Research And Experimental Research On Modular Portable Rock Mechanics Tester

There is a wide demand for rock mechanical parameters in the engineering investigation site,and the indoor large-scale test instruments can no longer meet the needs of rapid acquisition of various rock mechanical parameters in the engineering site.In view of the current situation,the concept of modular portable rock mechanics tester is put forward,which makes the indoor test equipment with large volume and weight portable by using the principle of rock strength size effect.This paper focuses on the research and development of modular portable rock mechanics tester,related technical verification and size effect.Systematic planning and design are carried out from the whole process of test sampling,sample preparation,test process,data acquisition and data analysis,so that it can be easily and quickly applied to the project site,and test data can be obtained quickly and efficiently.Provide data support for engineering design.Through the study of the size effect of small size(diameter 20 mm?50mm)rock specimens under uniaxial compression test and triaxial compression test,it is found that:(1)When the diameter increases,the size effect curve of siltstone sample obeys exponential distribution,while the size effect curve of basalt sample obeys logarithmic distribution.Combined with the research of other scholars on larger size samples,it is found that the rock strength size effect curve should be fitted in stages,and it can be concluded that the law of rock strength size effect curve is as follows: the small size stage curve rises and then tends to smooth.The large size stage curve gradually decreases and then tends to be flat,and the full-size rock strength size effect curve shows a sharp "?" shape.(2)With the increase of diameter,the overall failure mode of the specimen changes from tensile failure to monoclinic shear failure and then to Xshaped conjugate inclined plane shear failure.(3)Under the same confining pressure,the size effect curve of triaxial compressive strength of siltstone specimens increases gradually with the increase of diameter.With the increase of confining pressure,the difference of triaxial compressive strength of siltstone samples with diameter 20 mm increases gradually,and the triaxial compressive strength tends to be equal to the triaxial compressive strength of diameter 30 mm siltstone samples.The modular portable rock mechanics tester mainly solves the following technical problems:(1)The modular assembly of multiple functions is realized under the controllable weight,and the parts of the functional modules can be used for each other and combined efficiently.The modular portable rock mechanics tester can complete rock triaxial compression test,rock uniaxial compression test,rock point load test and rock external friction angle measurement.(2)Through ingenious design,the triaxial pressure chamber solves the problem of isolation between oil and rock samples,and can be used permanently after the oil is injected into the silo at one time.The problem that the heat shrinkable tube must be used in the triaxial compression test of the indoor triaxial test instrument is solved.The loading and sampling time of the triaxial pressure chamber can be controlled at about 20 s,which solves the problem of time consuming in the triaxial compression test of the indoor triaxial test instrument.(3)Compared with the test results obtained by MTS triaxial pressure tester,it is found that the stress-strain curves and elastic modulus of triaxial compression tests obtained by the two kinds of confining pressure loading methods are basically the same,and the test results of the newly developed triaxial pressure chamber confining pressure loading system are credible.