Semi-diagenetic Station Tunnel Study On Deformation Law Of Excavation

Based on the construction of complex tunnel group in Qingxiu Mountain Station of Nanning Rail Transit Line 3,the whole model of the station was established by using the large-scale finite element software MIDAS/GTS.The construction of the inclined escalator tunnel between the station hall and the lower tunnel was simulated.Based on the results of numerical model,it was concluded that the main influence range of inclined escalator tunnel construction on surrounding rock was the area between the tunnel and the station hall,and the influence increases with the construction of the tunnel,because of the tunnel direction.The disturbance of surrounding rock was persistent.For the tunnel structure,the displacement and force of the tunnel lining structure in the three directions caused by three excavation methods increase with the increase of the buried depth of the tunnel.In the area where the line of inclined escalator tunnel was changed from inclined down to horizontal,the stress situation of lining structure was complex,the displacement distribution was not uniform,and the stress concentration was easy to occur.Three The influence of CD method and CRD method on the construction of inclined escalator tunnel under the condition of this project was basically the same.However,because of the large excavation area,the large disturbance of surrounding rock easily makes the lining structure deform.Considering the construction difficulty,time and economic cost,it was more appropriate to excavate inclined escalator tunnel by CD method.By comparing the displacement and stress changes of inclined escalator tunnel with different excavations,it was concluded that the large excavation advance would have adverse effects on the stability of tunnel lining structure,especially in the position of tunnel alignment change.Used as small as possible if duration conditions permit The excavation advance of the tunnel was beneficial to the safety of the tunnel.The excavation of inclined escalator tunnel would have a great influence on the transverse passage,and would produce a large tensile stress concentration after the hole break,so it was necessary to strengthen the monitoring of the horizontal passage and the installation of tensile reinforcement in the broken hole during the construction process.The excavation sequence of shaft and inclined escalator tunnel was compared.It was beneficial to the overall stability of the structure to excavate the inclined escalator tunnel first and then to do the second lining and then the shaft.The influence of shaft construction on the existing structure was mainly due to the large tensile force at the junction,which needs to be strengthened.