Study On Construction Mechanical Behavior Of Jointed Rock Tunnel In Complex Downtown Environment

The overall length of Yuzhong Connecting Tunnel is715meters in design whichconnects the Dongshuimen Bridge and the Qiansimen Bridge in Chongqing. Accordingto the change of local topography, the tunnel is constructed by open cut method andundercutting method respectively. The joint development in the wall rock is welldeveloped. The space has a complicated environment because there are many buildingsaround the tunnel and the metro line six through the tunnel from the lower space.Depending on the study of Yuzhong Connecting Tunnel, this paper use the DiscreteElement Method and the Finite Element Method to give a deeply study about theconstruction mechanics of the small spacing tunnel, the bored tunnel which crosses themetro line six from the higher space and the open cut tunnel which crosses the metroline six from the higher space. The study can effectively direct the construction of thetunnel and can also provide a reference for the tunnel’s design, construction andscientific research about jointed rock mass urban engineering in complex environment.The main study findings are as follows:Firstly, based on the analysis of the engineering geology and the experiment ofrock mechanics, the parameters of jointed rock mass in accord with the practicalengineering should be selected in order to establish the mechanical model of jointedrock.Secondly, according to the small spacing tunnel, a three-dimensional finite elementmodel and a two-dimensional discrete element model are established respectively. Sothe construction mechanics of the small spacing tunnel can be studied. Then a detailedanalysis about the displacement and stress variation characteristics of the wall rock andthe influence on buildings according to the excavation of the tunnel are given. Moreover,in considering the presence of the joint the supporting and construction method of thetunnel is optimized.Thirdly, on the basis of the bored tunnel which crosses the metro line six from thehigher space, a three-dimensional finite element model and a two-dimensional discreteelement model are established respectively. A detailed analysis about the displacementand stress variation path of the wall rock, the influence on buildings and on the metroline six according to the excavation of the tunnel are given. Finally by comparing the numerical simulation results with the field measured data, the numerical simulationresults are proved correct.Fourth, depend on the open cut tunnel which crosses the metro line six from thehigher space, a three-dimensional finite element model and a two-dimensional discreteelement model are established respectively. A detailed analysis about the displacementand stress variation path of the wall rock, the influence on buildings and on the metroline six according to the excavation of the tunnel are given. Moreover, in consideringthe presence of the joint the influence of underpinning pile on wall rock and metro linesix are obtained.