Research On Surrounding Rock Stability Based On The Shield Driving Under Overpass Structure

This paper has been studied on the overall stability of the shield beneath the overpass structure of the surrounding rock on the background of K1+110～K1+700mileage shield to wear a city Metro Line2civil1.Firstly, summarize the study area tunnel surrounding rock deformation and failure mechanisms and geological factors affecting the stability of surrounding rock as a whole, combined with the surrounding rock classification results of the qualitative evaluation of the overall stability of the tunnel surrounding the study area. The results showed that:in the study area surrounding rock lower grade (I class), the overall stability of surrounding rock easily contained by the distance from the tunnel face bridge base load.Secondly, establish two-dimensional model to analyze the overall stability of the study area to represent the meaning of the four face tunnel excavation surrounding rock. The results showed that:the far right the line K268.628section of without bridge groups and bridge-based distance the tunnel face in the right line K278.228face tunnel excavation, rock deformation, stress concentration and plastic zone distribution area than small, the surrounding rock higher overall stability; closer to the bridge base from the tunnel excavation face left the line K588.168section and right line K715.129section. tunnel excavation, surrounding rock deformation, stress concentration and plastic zone. The distribution of the larger, surrounding rock low overall stability in the construction process, it is recommended to improve the overall stability of the tunnel surrounding steel reinforcement.Establishing of three-dimensional model to represent the meaning of the right line K248.228-K308.228section interval shield dynamic tunneling process simulation in the study area. The results showed that:Shield surrounding rock deformation in the region in the tunneling process, small, no significant stress concentration, the smaller the plastic zone, the overall stability of the tunnel surrounding higher.Finally, taking into account the non-homogeneous characteristics of the soil material, right the line K268.628section, right line K278.228of section, left line K588.168section and the right line K715.129section tunnel surrounding rock, progressive failure process and AE Laws conduct research and to calculate the safety factor. The results showed that:the right line K268.628section and right line K278.228of cross-section of tunnel surrounding rock high safety factor, respectively,2.08and2.0, while the left line K588.168section and right line K715.129section tunnel surrounding security lower coefficient of only1.19and1.14, after taking reinforcement measures, the safety factor of1.85and1.61, respectively. From the law of acoustic emission in the process of surrounding rock mass, the main failure modes for the shear failure and tensile failure. At present, the overall stability of the evaluation of tunnel surrounding rock and there is no uniform model, this paper adopts the engineering geological method, finite element method and taking into account the heterogeneity of the soil material, combined with the monitoring measurement data, a variety of ways, respectively, from the qualitative and quantitative point of view a comprehensive evaluation of the study area shield beneath the overall stability of the overpass structure surrounding rock. The evaluation showed that:in the process of the entire study area, tunnel, except in the left line K588.168section and right line K715.129of section recommendations to the reinforcement measures, the overall stability of surrounding rock basically meet the safety requirements of construction. Methods and results in this study can give some guidance and help in the design and construction of similar projects.