Research On Stress Model And Deformation Mechanism Of Tunnel-landslide System

Tunnel,as an important structure in land traffic engineering,has great social and economic benefits.It can overcome the limitation of route selection caused by terrain and elevation in mountainous areas,and plays an irreplaceable role in the huge traffic system.At the same time,the frequent occurrence of landslides and geological disasters in China has posed a serious threat to the safety of tunnel engineering in the construction process and smooth operation after completion of construction.At the same time,landslide geological hazards occur frequently in China.It poses a serious threat to the safety of the tunnel project under construction and the smooth operation of the tunnel after completion.However,at present,due to the lack of systematic model generalization and calculation theory related to stress and deformation modes,it is impossible to determine the minimum safety distance between tunnel engineering and landslide and the external loads acting on tunnel structure in the area avoiding potential slope diseases.Therefore,based on the typical tunnel-landslide engineering example,this paper constructs the tunnel deformation model and geomechanical model in the landslide area,and studies the theoretical solution of the external load and deformation of the tunnel structure and the evolution process of the tunnel-landslide parallel system under different supports.The following conclusions are drawn:(1)Selecting typical tunnel-landslide engineering examples with obvious destruction phenomena,the paper analyses the disease characteristics of tunnel lining in landslide section of practical engineering,synthesizes the geological conditions of slope creep and tunnel deformation,the relative position relationship,the action mechanism of slope and tunnel,and constructs three typical models of tunnel crossing sliding body,tunnel crossing sliding surface and tunnel crossing landslide.Geomechanics model of tunnel-landslide system.(2)Based on the classical theory of soil mechanics and structural mechanics,the calculation model of tunnel structure under residual landslide thrust is established.Through the law of load transfer,the additional loads acting on the tunnel structure are calculated,which are superimposed on the surrounding rock pressure of the tunnel.The theoretical solutions of the load and deformation of tunnel structure under the mode of "tunnel passing through sliding zone and tunnel passing through sliding body" are put forward.(3)According to the model of "sliding body under tunnel",the Businesk method and Rossetti method are used to analyze the load distribution at the sliding zone above the tunnel,and the additional load on the arch and side wall of the tunnel is considered.Combining with the theory of compressive strength and loosening circle of tunnel,the formula for calculating the minimum safe distance of sliding body under tunnel is put forward.By setting different downward landslide distances,the calculation method of additional load and minimum safe distance of downward landslide of tunnel is verified by model test.(4)The stress mode of tunnel structure is the same in the two stages of stress adjustment and creep deformation of slope.At first,it is only affected by the pressure of surrounding rock,then it is transformed into the combined action of landslide thrust and surrounding rock pressure.It can be simplified to calculate beam structure on elastic foundation.The evolution process of its stress and deformation mode can be realized by increasing the landslide thrust in the theoretical calculation of elastic foundation beam.For the whole sliding stage,there is a process from elastic foundation beam to large disturbance beam,which can be solved by coupling structural mechanics and elastic foundation beam theory.The change of stress and deformation mode can be realized by reducing the resistance coefficient of rock and soil.(5)According to the three evolution processes of semi-infinite beam model,semi-infinite beam-cantilever beam model and semi-infinite beam-simply supported beam model.Based on the deformation characteristics of the rock and soil mass of the sliding landslide and the different supporting modes of the tunnel entrance,It is revealed that the essence of progressive failure of tunnel is the change of landslide thrust and rock resistance.It is verified and analyzed by geomechanical model test,which shows that the theory can evaluate the stress and deformation of tunnel in different stages of landslide evolution.It also predicts the development of stress and deformation of tunnels in landslides and provides guidance for the design and reinforcement of tunnels in landslides.