Influence Assessments For Tunnel Construction On Adjacent Different Types Of Foundation Bridges And Its Application

Because of the lack of land resource and high utilization, many newly-built urban tunnels only constructs along to the overpass. It's very complicated for tunnel underneath pass exsiting bridges, so at present it urgently needs a comprehensive and systematic research for the phenomenon. Based on theoretical analysis, numerical analysis and field test, the paper emphatically studied the distribution of displacement and stress of surrounding rock, the influence arising from foundation of bridge and its additional deformation. The main research work of the dissertation can be summarized as follows:1. Through the reference of massive literatures, the difference between bridge structure and building frame are realized, and the stress and deformation of bridge structure and its effects for distribution of displacement and stress of surrounding rock are discussed, including the additional distortion and internal force rule of spread foundation and pile foundation.2. With the aid of the complex function method of problem of holes, the analytic solution is obtended through computer process by transforming the spread foundation deadweight into the surface uniform load, which is applied in Xi'an metro line 2 parallel underpasses Chang'an Overpass and Jinshazhou Tunnel vertical underpass Shabei Overpass.3. Firstly boundary conditions of end-bearing pile and floating pile are appointed, then negative friction and pile displacement of end-bearing pile and floating pile are programming calculation by MATLAB according to two-stage method. In addition, through the parametrization research of influencing factors negative frictiona, the paper obtains the relations between influencing factors and negative friction of single pile.4. According to the single pile's shielding effect, the interaction of friction pile groups caused by tunnel excavation are obtained, then the evaluation factor K, which is defined as sum of negative friction devided by floating pile bearing capacity, is proposed to assess the decreased degree of floating pile bearing capacity, which are applied in group action of piles for Shenzhen metro running tunnel underpass Meilong Bridge.5. Through the field observation for Jinshazhou Tunnel underpass Shabei Overpass, surrounding rock deformation, inner force of support structure, surface settlement, spread foundations pier settlement, pile foundations settlement and bridge top beam settlement are observed, which are applied for evaluation of influence between tunnel excavation and bridge.6. The paper systematically studied the dynamic deformation rule of surrounding rock, stratum displacement distribution, additional distortion of supporting structure and bridge foundations by virtue of three dimensional finite-element computation considering interaction between the pile and soil, then construction difference, stratum stress and strain distribution of different section(Greenfield, underpass spread foundation section and underpass pile foundation section) are discussed based on these and field observation results, finally the interaction for tunnel underpass different foundation type bridge are systematically studied.7.Based on Jinshazhou Tunnel underpass Shabei Overpass, Xi'an metro line 2 underpass Chang'an Overpass and Shenzhen metro running tunnel underpass Meilong Bridge, the paper systematically studied the impact assessments of tunnel underpass different types foundation bridges by theoretical analysis, field test and numerical analysis, and the satisfied effect is achieved.