Study On The Development Of Transparent Similar Materials For Rock Mass And Its Experimental Applications

As everyone knows, surrounding rock of deep roadway is often in extremely complexstress states. The spatio-temporal evolution law of rock deformation and fracture directlyaffect the stability and supporting.The internal deformation and fracture mode cannot be seendirectly in today’s study so that the basic problems such as rock deformation and fracture, thespatio-temporal evolution of the internal fissures are not entirely clear. Therefore, exploring akind of transparent rock material to solve the assignable problem of the internal deformationand fracture of rock is imperative, which has important meaning of theory for revealing thespatio-temporal evolution mechanism of rock fracture in deep roadway and establishing amore reasonable constitutive model and the strength criterion. Meanwhile, it has great valueof application for solving problems of stability control and spatio-temporal forecasting ofengineering disasters caused by rock fracture in deep engineering such as reinforcement timeand area of broken rock.This article is a part of the experimental study based on transparentrock of spatio-temporal evolution mechanism of cracking in deep rock mass, supported by theNational Natural Science Foundation, No.51174197and the National Key Basic ResearchDevelopment Plan973Project "deep compound formation of surrounding rock and theinteraction mechanism of TBM and security control"(No.2014CB046905). To summarize theexperiences of predecessors in the manufacture method of transparent similar material ofsoil-rock mass, the similar material of transparent rock mass can be configured by selectionand proportion experiment. Then the basic mechanical properties of rock mass are tested onconfigured specimen by mono-axis test, direct shear test, triaxial test and model experiment ofsmall-scale roadway. The spatio-temporal evolution law of internal deformation and fracturein transparent rock mass specimen is preliminarily analyzed by virtue of self-developeddigital photogrammetric technique of the supervisor. The main conclusions are as follows:(1) By summing up predecessors experience and my own experiment exploring, it can befound that only when the aggregate particle size in200to300mesh and mineral oil in whichthe mass ratio of silica gel powder and cementing material is1to0.835are mixed, thetransparency of sample is best.(2) Through experiment study, the key factors of transparency and strength similarity intransparent similar rock material are found and analyzed. The transparency depends on fouraspects such as refractive index matching degree of silica gel powder and mineral oil, gascontent of mixed silica gel solution in vacuum,the purity and transparency of silicon powderand mineral oil, and loading and unloading rate. Moreover, except for the human factors in the experiments, the strength is mainly related to consolidation stress and consolidation strength.The specific relationship is that in the same consolidation time, the strength of transparentrock similar material grows with consolidation stress, and it also grows with the consolidationtime in the same consolidation stress. But when the consolidation time is more than ten days,the mechanical properties of transparent rock similar material basically no longer change.(3) The cylindrical specimens are adopted to make the basic mechanics experiments oftransparent rock similar material, including uniaxial compression, direct shear test and triaxialtest. The results show that the maximum value of strength, elastic modulus, density, internalfriction angle,cohesion of the material developed in this paper are0.36MPa,23.7MPa,1.11g/cm3,7.56°,22.03kpa respectively.(4) By developed transparent rock similar material, the digital photogrammetricexperiment of small specimens under uniaxial compression is conducted. The deformationand fracture rules of the transparent cube (100mm×100mm×100mm) under uniaxialcompression are analyzed. The spatio-temporal evolution rules of cracking in roadway(100mm×100mm×100mm) under excavation, voltage regulator, loading pressure, pressurerelief are also analyzed..The results show that the postpeak of stress-strain curves of cubespecimens appear apparent strain softening stage. The deformation differ in the center, topside, two flanks, and bottom,The rock stress and deformation are affected largely under theexcavation, voltage regulator, loading and unloading.(5) By the particle flow software PFC3D, the deformation characteristics and regularityof transparent rock mass in micro are analyzed based on the physical test results. the plasticdeformation of transparent rock similar material is obvious, and the cracks are mainly tensilecracks and shear crack; The deformation evolution process has obvious symmetry in a sectionof surrounding rock in roadway, and the final fracture mode has obvious regionalcharacteristics.(6) By comparative analysis on basic physical and mechanical properties of developeddeveloped transparent rock specimen with common similar material simulation of the softrock, it can be found that the rock similar material developed in this article can simulate softrock of deep roadway through similar ratios.