Study On 200MPa High Artificial Rock Mass Production Technology

With the application of mechanical rock breaking in geotechnical engineering,the study of rock crushing mechanism has come into the focus across the world.Due to the difficult of the sampling of large rock mass on site,it is a burning issue to develop indoor artificial rock mass.For this purpose,the manufacture technology of high strength artificial rock mass was studied in this dissertation.Through comparative analysis of sample tests,the optimum mixture ratio and the optimum curing condition of reactive powder concrete(RPC)were determined.Then the distribution law of thermal stress field in large rock mass was studied by numerical simulation method,and effective measures to reduce tensile stress in large volume rock mass were proposed.The main research contents and achievements are as follows.(1)In the atmospheric curing sample test,through the single factor analysis of affecting factors,such as fineness modulus,water reducer,ratio of silica fume to fly ash,sand-binder ratio,water-binder ratio,compound mineral admixture content and concrete expansion agent,the influences of all factors on the fluidity and compressive strength of RPC were studied.Based on those two indicators,the optimum mixture ratio of RPC under normal pressure curing condition was obtained.(2)In the sample tests under different curing conditions,the variation law of compressive strength and porosity of RPC under 4 different curing conditions was studied.The result shows that under the curing condition of high temperature and high pressure the compressive strength of RPC increases obviously and the porosity decreases seriously,and the lower the water cement ratio is,the more obvious the effect is.It shows that high temperature and high pressure curing could improve the microstructure and the compactness of RPC,and then it improves the compressive strength of concrete.According to results,the maintenance system of high temperature and high pressure was put forward to obtain RPC with the strength up to 200 MPa.(3)Numerical simulation results show that,1)no matter what outer boundary is given,the temperature field of the medium volume rock mass is close to the uniform temperature field.However,there is a large temperature gradient in the large volume rock mass.2)By comparison of the distribution of temperature stress field in large volume rock mass during temperature rising,temperature maintaining and cooling stage,it is concluded that large volume rock mass has greater tensile stress at the outer surface during cooling stage.3)Through comparative analyses of three different cooling and depressurization methods,the results show that the method of depressurization after cooling down could be effectively reduce the maximum tensile stress in the large rock mass.4)It is concluded that lowering the speed of cooling and depressurization could effectively reduce the thermal stress in the large rock mass by controlling the cooling and depressurization rate.Overall,in this thesis,the optimum proportioning of RPC was obtained by sample experiments,and the optimum curing condition was also proposed;in numerical simulation,the optimal cooling and reducing path was obtained,which has guiding significance for making large volume of high strength artificial rock without macro defect,and it provides the pre-condition for the research on mechanical rock breaking in laboratory.