Study On The Design And Construction Of Shallow Bias Soft Surrounding Rock Tunnel

With the rapid development of expressways,more and more tunnels have been built.Some tunnels with complex engineering geology and poor conditions have become the keys for opening to traffic.The construction of tunnels has evolved from a safe and convenient environment to a harsh and complex environment.The design and construction of tunnels under complex geological conditions is still based on a combination of engineering analogy and information feedback.It is more difficult to build tunnels under complex geological conditions such as shallow-buried and biased soft rock.In the tunnel design specification,the classification of surrounding rocks is larger.It is difficult to apply a variety of complex geological conditions.This article first set in Baxiang tunnel.The ground angle and the normal distance between the ground and the tunnel excavation contour are two variables.Adopting the characteristics of tunnel surrounding rock and supporting force as a classification index.Grade V surrounding rocks further subdivided into three types.Then,based on the classification,the supporting parameters recommended by the tunnel design specifications are optimized.The results show: For Type I surrounding rocks,the safety of supporting parameters is sufficient.But,it have excessive use of materials and poor economy.Type II surrounding rock is safe and economical.It can be selected according to the specification and support parameters.Grade III surrounding rock is less safe.It must optimize the support parameters in the specification.Under different construction method conditions,the effects of stress and deformation on the lining are different.Affected by the bias,The settlement of the vault occurs on the more soiled side.It is easier to move toward the ground with less soiling.In addition,the stresses on the arches at one side of the overlying soil layer are greater and the deformation needs to be observed.Comparing the simulation analysis of three different construction methods in different types of surrounding rock conditions,reach conclusion: In case of type I surrounding rocks,the core soil method is easier and more economical than the CD method and CRD method.In the case of type II surrounding rocks,the CD method can effectively control the vault settlement and horizontal displacement during tunnel construction.CRD method can adapt to various working conditions and another methods need reinforcement.Monitoring measurement is the main method of tunnel information construction and it is an important part of information feedback design method.Based on numerical simulation of three construction methods,get the tunnel displacement data.And then compar the actual settlement and convergence data.It Highlight the necessity of classification of surrounding rocks,and proposed a tunnel monitoring and measurement plan.This article innovatively proposes classification methods under different shallow-buried bias conditions.It can provide reliable technical support for tunnel design and construction under different shallow-buried bias conditions.It also has implications for tunnel engineering under similar complex geological conditions.