Experimental Research On Creep Of Liupan Mountain Diversion Tunnel

As one of the important mechanical properties of rock,creep is closely related to the long-term stability and safety of the project.Engineering practice shows that the destruction and instability of the underground tunnel is not due to the excavation occurred immediately in many cases,the deformation of the tunnel is a complex nonlinear time-dependent accumulative process from beginning to the final failure.One of the important reasons of the tunnel's large deformation and instability is the creep characteristic of the rock.Therefore,it has important theoretical significances of describing and revealing the time-dependent mechanical behavior of the rock and then cognizing the time-dependent law of deformation and failure characteristics has important theoretical and practical value.It always encounters the problem of soft rock during the process of underground engineering,The compressive strength of soft rock is relatively low and easily subject to the changing environment,the relatively significant creep properties and larger creep deformation bring many adverse effects to the safety of the project and often lead to the failure and destruction of the supporting system.Cretaceous mudstone is main outcropped soft rock strata in the area of Baijia village tunnel of Liupan Mountain diversion project and mudstone creep mechanical properties directly affects the tunnel's long-term stability and security.Therefore,the creep characteristics research on cretaceous mudstone for explaining aging mechanical behavior of the proposed tunnel project reasonably and grasping the stress and deformation characteristics has very important significance on evaluating long-term stability and the safe operation of the project.Then,we conduct the triaxial compression creep experiment of the cretaceous mudstone on the automatic rheology servo apparatus and analyze the creep properties of rock based on the test results.The factors of external conditions and internal structure affect the mechanical characteristics of rock material very complicated.The element model is one of the important methods which are used to describe the creep properties of rocks.It is made up of ?spring? element which represents the elasticity of materials,?glue? component represents viscosity character and ?friction plate? component which represents plastic characteristics.The combination of different models can be used to describe the deformation characteristics of different types of rocks.Burgers model has been used by many scholars to describe the rock rheological characteristics.This paper uses Burgers constitutive model to make a curve fitting for creep under the action of axial strain and radial strain based on the analysis of test data.Identify the characteristic parameter of rheological mechanics and analyze the creep mechanical parameters of the rocks under different axial strain can provide some theoretical bases for the stability analysis of engineering surrounding rocks.In the end,we analyze and research on the stability of tunnel during construction period and operation period by using the FLAC3 D numerical software on the basis of experimental data and then analyze the supporting time of the engineering and time effect of the stability of surrounding rocks.It has some reference meanings on the construction of the diversion project based on above studies.