Study On Mechanical Behaviors Of Buried Pipelines Induced By Shield Tunneling Construction

Assessing the impact on the pipelines around tunnel induced by shield tunneling is an arduous problem, which is also one of the most important research subjects in civil and environmental engineering research area. Giving a study on this research subject has important theoretical consequences and utility value. This paper gave comprehensive study on the measured displacement patterns of buried pipelines, the soil pressure around the pipe and pipe soil interaction, the deformation mechanism and displacement of flexible jointed pipes, the theory analysis and numerical simulation of the buried pipelines, the parameter study that influence the pipes' mechanics and the soil displacement field around the tunnel caused by the pipelines, by using the methods of on-site test, numerical simulation and theory study. The main research contents are as follows:(1)Through analysis of large numbers of on-site measured data, the single tunnel and double tunnel was studied, according to two cases, one is pipe transverse to tunnel and the other is pipe parallel to the tunnel. The displacement curve with time of the pipelines during the five stages about before shield arriving, shield arriving, after shield passing, shield tail passing and continued consolidation settlement was given.(2)According to the shortcoming of calculating the soil pressure around the pipe at present, the pipe soil interaction was studied to give a soil pressure distribution model around pipe, based on the on-site test. At the same time, the vertical deformation mechanism of flexible jointed pipes was studied, and the vertical displacement model of flexible jointed pipes was given.(3)Based on the elastic foundation beam theory and previous research foundation, the vertical displacement analysis model of the rigid and flexible jointed pipes were given. Compared with the results of other formula, this paper's formula gave more reasonable results and could be applied in engineering calculation and for verifying the numerical results. By using this formula, the parameter sensitivity analysis was done.(4)The numerical results were compared with the on-site test data, which show great reasonability and probability for using the FLAC^3D to simulate the complex pipe-soil-tunnel interaction. According to the different cases (pipe transverse to tunnel and pipe parallel to the tunnel), the corresponding finite difference analysis models were build up to analyze the displacement and force mechanics of the rigid and flexible jointed pipes around the tunnel. We simulated the displacement and force mechanics of flexible jointed pipes successfully, and obtained some phenomenon, which are different from the rigid jointed pipes.(5)Using the finite difference software FLAC^3D, the pipe transverse to tunnel case and the pipe parallel to the tunnel case were simulated individually. The parameters such as soil type, pipe diameter, pipe thickness, pipe section shape, pipe material, distance between the pipe and tunnel, tunnel diameter, excavation surface location, extra excavation amount, supporting pressure, driving velocity, ground stress release rate and distance of the double tunnel, which would affect the mechanics of buried pipelines, were studied. In addition, the influences of the shield tunneling under special situations such as the internal pressure of the pipe, the pipe supporting losting, were also studied. The research results offer credible theoretical foundation for pipelines protection during the shield tunneling construction.(6)According to the engineering example and numerical results, the influence of the soil vertical displacement distribution around the tunnel due to the existence of pipelines was studied, under the pipe transverse to tunnel case and pipe parallel to the tunnel case.