Study On Interaction Between Tunnel Support And Surrounding Rock In Soft Rheology Rock

At present,there are more and more tunnels constructed in the deep high-stress soft rocks.However,most of the tunnels may produce the large deformation of surrounding rock in construction,and the tunnel lining is also likely to be deformed and cracked during operation.Soft rocks generally have strong rheological properties.The time-dependent deformations and failures of tunnels in the soft rock are mainly related to the strong rheological properties of surrounding rock.When tunnel constructing in this soft rock,it is not only need to consider the instantaneous behaviors between surrounding rock and support,but also need to apply the rheology theory to settle the time-dependent behavior in the long-time.However,how to reasonably consider the time-dependent behavior of surrounding rock,and more accurately to predict the long-term dynamic relationship between the surrounding rock and supports has become an urgent problem to be solved.In this paper,based on the theoretical analysis and similarity simulation method,the time-dependent behavior between surrounding rock and support of tunnel in the viscoelastic and visco-plastic rock and the physical simulation method considering the rheological properties of soft rock are studied.The following contents have been completed,(1)In view of the circular tunnel in the viscoelastic rock mass under hydrostatic stress field,the time-dependent solution between surrounding rock and support is derived,which takes account to the coupling of rock rheology and the stress release effect caused by tunnel face advancing.At the same time,assuming that the surrounding rocks are generalized Kelvin(H-K)and Burgers models,the surrounding rock deformation,stress and support force under the two kinds of constitutive are solved by means of Laplace transform and integral transformation,and the solution can be degraded in the past.(2)On the basis of the viscoelastic solution of lined tunnel in continuous excavation of tunnel face,the stress release parameters(m,a),supporting time t0,support stiffness Ks and parameters of constitutive model are all studied on the general Kelvin model(H-K)and Burgers model.The relationship between the stress,deformation of surrounding rock and support force under the influence of various parameters is obtained.(3)Based on the viscoelastic solution without the influence of the tunnel face,the convergence-confinement method is studied in viscoelastic rock.The result demonstrates that the ground reaction curve(GRC)in the viscoelastic rock are a series of time-dependent curves,and the "equilibrium points" in the traditional sense are also a series of dynamic points,which are intersected by the ground reaction curve and support reaction curve(SCC).what's more,the support-rock characteristic curve(S-GRC)has to be defined since the traditional GRC and SCC curves are independent,which can't consider the coupling effect of ground and support.The final analysis shows that,the "equilibrium derived by the traditional GRC and SCC curves obviously underestimate the stress on support,and the safety of the support can't be guaranteed effectively.(4)On the basis of the solution of tunnel continuous excavation,the aging solution between the surrounding rock and the support is deduced after the tunnel face stopped.The changes of the converge displacement and support stress with time and space are obtained as the surrounding rock subjected to the generalized Kelvin and Burgers models.As a result,the coupling mechanism of the stress release and the creep effect along the tunnel longitudinal section is revealed.(5)Analytical viscoelastic solutions are derived by the correspondence principle and complex variable method for the lined circular tunnels with the full contact and smooth contact conditions between liner and ground in non-uniform stresses field.The solutions can apply to tunnels subjected to all kinds of linear viscoelastic models.When the surrounding rock is the generalized Kelvin model(H-K)with the lateral pressure coefficient of ?=0.5,the results indicate that the distribution of the ground displacements,liner stresses,displacements and internal forces under the two contact conditions are quite different along the circumferential direction,and as the time increase,the greater difference will be.(6)The spatiotemporal evolution characteristics between surrounding rock and support are divided into the elastoplastic stage and the creep stage for the viscoelastic-plastic rock mass.The whole process evolution law of surrounding rock and support is obtained by solving the coupling between support and surrounding rock in two stages.Finally,the solution is applied to the advanced auxiliary tunnel of Mont Terri tunnel in Switzerland.The theoretical results are basically consistent with the actual monitoring data.(7)A new rheological similar material of soft rock(IBSRO)was developed,which is mixed with the iron ore powder,barites powder and sand as aggregate,the solution of rosin and alcohol as glue,and the hydraulic oil as viscous agent.The creep characteristics of the similar material are fitted and analyzed by Burgers viscoelastic model and Nishihara viscoplastic model.When the Burgers model is used,a method for determining the proportioning of the similar material is proposed based on multiple linear regression analysis.The range of elastic-plastic and rheological parameters of the similar material generally corresponds to that of soft rock,which can be used to simulate the instantaneous and rheological properties of soft rock.This new soft rock rheological similarity material(IBSRO)provides a good guarantee for underground engineering model test in soft rock.(8)Based on the new r-heological similarity material of soft rock(IBSRO),the model test is carried out on the shield inclined shaft in the weak sandy mudstone in Shenhua Xinjie coal mine.The results of the model test show that the interaction between rock and support has instantaneous and long-term effect.Under the loading at all levels,the support force,deformation and internal force of liner are all increasing with time until stability,and the greater the load,the stronger the time-dependent interaction between support and surrounding rock.The range of creep pressure on support for each load stage is 12.1%?33.8%,31.8%?51.1%and 28.9%?56.3%,respectively.