| With the rapid development of underground railways and the continuous improvement of the railway network,there are many kinds of complicated construction conditions among the large number of railways,for example the crossing through,the parallel,laminated and conditions like that.During the construction of the new tunnel crossing the running tunnels,it will cause the redistribution of deformation and stress of the ground.So that it will form additional stress and strain in the running tunnels.At the same time,because the construction of the running tunnels have already caused the change of the initial stress field in the soil and the construction of the new tunnel will cause that change again,the influence on the running tunnels when building the new can’t be calculated in the initial mechanical environment when building the new one.It will make that become complicated and unpredictable.Therefore,during the crossing construction of the new tunnels,the prediction and the control of the influence on the running tunnels is becoming a crucial problem in the civil engineering area.This paper is on the shield tunneling crossing above or under the running tunnels.Establishing a three dimension shield tunneling model by the finite element software,it has analyzed the influence on the running tunnels which is caused by the crossing construction of the new tunnel.Furthermore,it has discussed the influence on the tunnel subsidence in the under crossing construction when changing the reinforcement scope of the ground.The main contents and results are as follow:(1)Based on the theory of finite element and nonlinear analysis,the three dimension tunnel excavation model which contains ground,running tunnels and new tunnels are established.This model which consideres the initial balance of ground stress,the supporting force of the excavation,grouting and hardening behind the shield and so on can accurately reflect the excavation process of shield tunneling.Based on that,it can analyze the subsidence of running tunnel caused by the crossing construction and that is consistent with the law in the related literature,which has been proved the feasibility of the model.(2)Based on the three dimension shield excavation model mentioned above,the comparisons are made the under crossing and the above crossing,the influence on the running tunnel is different for those two kinds of construction sequences.When building in two different kinds of sequence,under crossing first and then above crossing or above crossing first and then under crossing,and according to the change of the deformation and the internal force of the running tunnels,here draw a conclusion that the latter sequence is better.(3)The grouting reinforcement process is simulated by replacing the soil material properties of the reinforcement area.Considering the reinforcement scope is composed of three directions,the influence of reinforcement scope on the running tunnels in three directions are studied.By comparing and analyzing the subsidence law in different scope,the influence on the subsidence of running tunnels is totally different because of the different scope direction of reinforcement.According to that law,the appropriate reinforcement scope can be received.(4)Based on the finite elemental shield tunnel model of double under crossing the running tunnel in which horizontal space of new tunnels is 3 to 5 meter,the disturbance on the running tunnels caused by the different horizontal space has been discussed.It has summarized the changing law of tunnel subsidence,axial force and the plastic area of the excavation ground.And according to the changing law,the horizontal space of the under crossing has a serious influence on the running tunnels.With the increase of the horizontal space,the disturbance of the running tunnel will decrease. |
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