Experimental Study On Unloading Creep Of Deep Fractured Rock Mass And Its Engineering Application

A large number of engineering practices and researches show that in many cases,the failure and instability of rock mass engineering does not occur immediately after the completion of the excavation or after the completion of the project.After a long period of time,the rock mass Stress and deformation continue to change and develop,eventually leading to the destruction and instability of rock mass engineering.The large deformation and deformation control of fractured rock mass under deep burial conditions is a worldwide problem.The timeliness of rock mass is very demanding for the safe construction and stability of tunnel construction during the construction period of the fractured rock mass.Requirements.Based on this,based on the previous studies,this paper uses a combination of laboratory experiments,theoretical research and software simulation calculations.The creep evolution model of fractured rock mass under constant stress is established systematically to establish a creep model reflecting the long-term deformation of deep fractured rock mass.Based on the established creep model,a deep tunnel excavation in southwest China is carried out.Numerical simulation analysis of the surrounding rock deformation during the process and operation period.The main research contents of the thesis are as follows:1 A conventional triaxial compression test is carried out on the intact rock mass and the fractured rock mass under different fracture angles to study the strength and deformation characteristics of the intact rock mass and the fractured rock mass.The TDF-2000L microcomputer servo-controlled rock triaxial rheological test machine was used to carry out the unloading creep test under the confining pressure and unloading confining stress path under different crack angle conditions,and the fracture angle of the fractured rock mass in different cracks was studied.Under the creep law,the influence of the graded unloading on the triaxial creep characteristics of the fractured rock mass and the deformation characteristics are analyzed.2 According to the above test results,based on the aging mechanism of unloading creep damage of deep fractured rock mass,the damage factor is introduced,combined with the existing creep component model,it can be established to describe the attenuation creep and stability of the unloading creep process of deep fractured rock mass.Creep model of nonlinear deformation characteristics of various stages of creep and accelerated creep.The three-dimensional form is derived and the proposed model is parameterized.3 Using FISH language,the above creep constitutive model is written based on FLAC~3DD software for secondary development,and the calculation application program of creep of rock mass is obtained,and its correctness is verified.4 Based on the calculation application obtained by the secondary development of FLAC~3DD software,combined with the actual engineering of a deep buried tunnel in Southwest China,the creep deformation characteristics of surrounding rock during tunnel excavation and during operation period are analyzed,which is reasonable design and safe construction of tunnel lining.Provide a theoretical basis.