Shallow Buried High-speed Railway Tunnel Surrounding Rock Deformation And Control Technology

During the construction of high-speed railway tunnels,the design and construction of tunnels are constrained by factors such as line orientation,topography and geomorphology,and geological environment,and shallow buried-biased tunnel design schemes are often used.Shallow buried tunnels are generally weak and broken in surrounding rocks,with poor stability and complex geological conditions.After tunnel excavation,it is difficult for rock bodies to form natural bearing arches,and the surrounding rock pressure is asymmetrical.The supporting structures are subjected to a bias load.During the construction process,large rock deformation or collapse accidents are likely to occur.In this paper,based on the construction of the Xin Dali Temple Tunnel,the relevant researches on the deformation law and control measures of the surrounding rock in the shallow-disturbed and unsymmetrical tunnel construction have obtained the following conclusions:(1)Through the analysis of typical cross-section monitoring data,the deformation of surrounding rock in shallow-disturbed and unsymmetrical tunnels has strong spatial-temporal distribution characteristics.In terms of time effect,the initial deformation of surrounding rocks is larger and the deformation develops faster.The deformation curve is in the open.During the excavation process,there are leaps and bounds;in terms of spatial effects,as the excavation advances,the deformation of the surrounding rock is gradually smaller,and after the initial support is closed into a ring,it is generally 2 to 3 times the diameter of the surrounding rock.In stability;In addition,the deformation of surrounding rock under the influence of bias is significantly asymmetrical,and the deep side deformation is greater than the shallow side.(2)Using FLAC~3D simulation software,the excavation process of the core soil method with the middle septal method,the three-step method,and the three steps was simulated.The results show that the excavation of the upper step has a greater influence on the deformation of the dome and occupies the total deformation.About 50% to 60% of the volume,the maximum horizontal displacement occurs at the location of the arch,the distribution of the maximumprincipal stress is approximately the same,mainly the compressive stress,the tensile stress occurs in the surrounding rock of the tunnel arch and the arch bottom;Bias pressure affects the deformation of the surrounding rock mainly occurs on the deep buried side,and the construction with the middle partition wall method has little effect on the deformation of the surrounding rock.(3)According to the control principles and concepts of the deformation of surrounding rock in shallow-disturbed tunnel,the method of controlling the deformation of surrounding rock is proposed.By adopting advanced pre-support and optimization of step length,double-layer small-tube pre-support and short-step are adopted to make the surrounding rock.The deformation control is within the reference value and it is better to control the partial collapse of the excavation process.