Analysis Of The Excavation Effect Of The Tunnel Anchorage Chamber Of Chongqing Fuma Yangtze River Bridge

Tunnel anchorage is one of the main forms of anchorage of suspension bridge, it through in the rock mass excavation chamber, pouring concrete in the chamber, with the surrounding rock anchorage to withstand the tension of the bridge cable.The influence of tunnel anchorage chamber excavation on the stability of surrounding rock and overlying rock mass is a subject that needs attention in the engineering construction, and is also an important link of engineering construction safety. Chongqing Fuma Yangtze River Bridge is the key control engineering of a highway across the Yangtze River. The tunnel anchorage on the South Bank of the suspension bridge, of which overlying rock is weak, the chamber excavation of large cross-section, belongs to the shallow buried soft rock tunnel with large section, and in former anchor chamber surface excavation construction of access roads have further weakened the burial depth of tunnel anchorage chambers, and is not conducive to overlying rock mass stability of the tunnel type anchorage.Therefore, the safety of tunnel excavation, the bearing capacity of surrounding rock, the long-term stability of the surrounding rock and the settlement of the ground surface of the overlying rock are the main problems of the engineering construction.This article describes the engineering geology and environmental conditions of the study,and discusses the monitoring and measurement program of chamber and overlying rock and soil stability, and analysizes deformation characteristics and influencing factors of in the process of tunnel excavation, based on monitoring results obtained by field measurement. Then establish the geomechanical model, using FLAC software on tunnel anchorage chamber excavation process numerical simulation analysis is carried out, and with the measured results of comparative analysis, to evaluate the stability of surrounding rock of chamber. The conclusion and understanding of the research are mainly as follows:(1)Stable arch is not easy to forme in the shallow buried tunnel strata, settlement deformation of overlying rock and soil of tunnel anchorage greatly influenced by shallow buried tunnel chamber excavation, and the timely support measures such as the advance support of the chamber are the key to ensure the stability of the mountain deformation.(2)Excavation of the pioneer road on ground surface of overlying rock mass of tunnel anchorage producing disturbance to stratum, further weakening the buried depth of tunnel type anchorage chamber, is not conducive to the stability of the overlying strata.(3)Sandstone / mudstone interbedded soft rock tunnel on ground water seepage has strong sensitivity and sand gushing water flow is an important cause of deformation of tunnel surrounding rock and the overlying rock and soil.(4)Tunnel face slope support and nursing measures can effectively inhibit tunnel overlying strata to the airport side deformation, closed chamber of a supporting structure can better restrain the deformation of surrounding rock of development, disadvantage is formation in large deformation, surrounding rock will be applied to support structure of large stress, may lead to a supporting structure of the crack.(5)The influence depth of rock loosening less than 1m, rock mass quality of the former anchor is relatively poor, and anchor plug body range is relatively good.(6)The distribution of stress, displacement field and plastic zone are obtained by numerical simulation, and the results of numerical simulation are consistent with the results of monitoring and analysis.