Analysis On Characteristics Of The Stress And Deformation Of Double Model-building Concrete Lining

In recent years,the state increased traffic construction in the western region,The northwest loess plateau region which is famous for “thousands of ditch mountains and valleys”,is also in a steady high speed of railway and highway construction.And the tunnel advantage of transportation line choice makes a lot of construction in the northwest loess tunnel.Double Model-building Concrete Lining is superior to the traditional spray + 2 lining structure in the control of surrounding rock deformation and waterproof.But studies of this aspect almost had no at present,therefore,it is necessary to carry out the research on characteristics of the stress and deformation of double model-building concrete lining.In this paper,on the basis of the Dingyuan 2# loess tunnel engineering of Lanzhou south ring of the Lin-huo highway,by means of numerical simulation,analyze characteristics of the tunnel surrounding rock deformation and rules of the stress of double model-building concrete lining,Comparatively analyze the influence of different deformation control measures such as different excavation methods,different excavation step length,different step length and step height to the tunnel surrounding rock deformation and the stress of double model-building concrete lining,select the optimization of deformation control measures.The main work and results in this paper are as follows:Combined with the field monitoring data of dingyuan 2# tunnel,analyze the interaction relations and characteristics between the surrounding rock deformation and the supporting force.The results show that,the dingyuan 2# loess tunnel in weak rock has characteristics as follows: high rate of early deformation? large amount of early deformation and long duration of deformation.Through the numerical simulation analysis of the construction of double model-building concrete lining tunnel which is under highway,found that the simulation results is less than the measured results,analysis of the reason is that the finite element model did not consider the reinforce of cross section such as big arch springing,and it is unable to accurately know the load sharing ratio of the surrounding rock pressure between steel arch and initial model-building concrete lining.The regularity of deformation and stress from the finite element results can provide valuable reference for actual construction.The change of step length and excavation step length largely influnced the tunnel surrounding rock deformation and the stress of the supporting sturcture,Considering as the actual situation in which Dingyuan 2# tunnel is located in the loess,we should try to reduce the disturbance of surrounding rock,so the suggestion is that,in the process of excavation,on the premise of closing in time?avoiding overbreak?guaranteeing strength and stiffness of the supporting structure,we should try to reduce the excavation steps length and the disturbance frequency of surrounding rock,and build inverted arch in a timely manner to make the tunnel lining form a closed structure,effectively impact on the supporting role to the surrounding rock.Through three-dimensional finite element numerical simulation,analyzed the surrounding rock deformation?supporting force and construction schedule under the condition of different excavation of surrounding rock,and do the optimization analysis in the light of different deformation control measures,finally the optimum construction scheme is concluded.First of all,do the finite element contrast and analysis for four types of excavation method which are three steps of seven excavation method?three steps method?CD method and two step method,two step ring reserved core soil excavation method is suggested to adopt.Secondly,on the premise of using two step excavation method,do the finite element contrast and analysis for different excavation step length?different step length and different step height.Finally concluded the optimal deformation control measures:two step ring reserved core soil excavation method?1.5m excavation step length?3m step length and 7.3m step height.