Study On The Mechanical Properties Of Railway Tunnel Invert Under The Influence Of Different Factors

Invert is a very essential part of tunnel lining structure,which can integrate support and lining,restrain the deformation of surrounding rock and improve the stability of surrounding rock.However,under the combined action of the surrounding rock and the vibration load of the train,a large number of diseases have appeared in invert structure,which affects the stability of the tunnel structure and the safety of the train operation.Therefore,this paper analyzes the main causes of invert diseases by investigating the tunnels with invert deformation and damage.Therefore,combined with theoretical analysis and numerical simulation,this paper takes the tunnel arch structure as the research object and takes an existing railway tunnel as the basis to study the mechanical response characteristics of the arch structure under the static load of the surrounding rock and the train load and the factors affecting the mechanical performance of the tunnel inverted arch.The influence of factors on the mechanical properties of the tunnel arch.The main research contents and achievements are as follows:(1)The main factors leading to the uplift of the invert arch at the bottom of the tunnel are analyzed statistically.Through the investigation of 16 domestic railway tunnels,the analysis of the failure of the upward arches is carried out.(2)The influence of different factors on mechanical properties of invert structure under static load of surrounding rock is studied.Through numerical simulation and field verification,the structural deformation and stress distribution characteristics of inverted arch under the static load of surrounding rock are analyzed.The upper surface of the fill layer of the invert is pulled and the upper arch deformation occurs,and the deformation in the middle position is the largest;The influence of the mechanical properties of invert structure on the variation of the ultimate expansion force of surrounding rock,the ratio of invert to span,the strength of concrete and the thickness of invert is analyzed.With the increase of the swelling force of surrounding rock,the ratio of invert to span decreases,the maximum tensile stress on the top of the filled layer increases,and the upper arch displacement increases.With the increase of invert strength and thickness,the maximum tensile stress on the top of the filled layer decreases and the uplift displacement decreases.(3)The excitation force function is used to simulate the force between the wheel and rail,and the influence of different factors on the mechanical properties of the invert arch structure is studied.The results show that under the load of the train,the overall structure of the invert arch moves downwards.The vertical displacement,acceleration,and dynamic stress time-history curves of the structure peak at the beginning of the train load,and then tend to stabilize,fluctuating around a certain value.The vertical displacement,vibration acceleration and dynamic stress response of the invert arch structure are positively correlated with the train running speed,the vertical displacement and acceleration are positively correlated with the inverse span vector ratio,the dynamic stress response is inversely correlated with the invert arch vector span ratio,and the vertical displacement is related to The thickness of the arch is positively correlated,and the dynamic stress response is negatively correlated with the thickness of the upward arch.The change of two variables,driving speed and vertical arch ratio,has a greater impact than the change of vertical arch thickness.(4)The effects of softening of bedrock and basement void on the mechanical properties of invert structures under train load were studied.The results show that the displacement,vibration acceleration and principal stress of each part of the invert arch structure increase with the increase of the thickness of the bedrock softening layer at the bottom of the tunnel and the increase of the base void width.The appearance of the softening layer and cavity in the tunnel basement will not change the overall distribution and time history of the mechanical properties of the inverted arch,but will lead to the increase of the vibration response of the structure and the deterioration of the stress conditions,which will affect the long-term use of the lining.In the project,we should avoid the appearance of bad basement surrounding rock and repair it in time.