The Stability Analysis Of The Arch-cover Tunnel Cavern And Dynamic Risk Assessment Of The Construction

Subway transportation mode has many advantages,such as fast,convenient,not affected by the ground conditions。Although the subway has been built in many cities,is still far from the needs of people,so in the future for a long time,the subway is still a hot project。With the continuous development of science and technology as well as construction technology,the underground space workers have made a research on the construction methods of the roads with special geological conditions。Arch construction method is a combination of geological intelligence staff in China,it has the advantages of fast construction,safe construction and so on in upper-soft lower-hard ground special stratum construction。In this paper,we taking Liaoyang East Station of Qingdao Metro Line 11 as the research background,by means of numerical simulation,the excavation simulation is carried out by using the 4 common excavation methods。Through the analysis results of numerical simulation,arch construction method is better than the double side drift method and much better than the other two methods in the situation of crown settlement and surface settlement。In the part of plastic zone volume,both side drift method has smaller effect for the entire tunnel,CD method and CRD method have a certain plastic zone to the around parts of tunnel and the surface of ground,due to twice damage on balance with arch construction method and larger stress of the lower surrounding rocks,the plastic zone is larger in volume andit distributed below the tunnel with the X type,for the arch feet and arched shoulders,there is a large compression area.By learning through BP neural network,we can get inversion of excavation parameters with arch construction method.Also,we can use it to simulate for step excavation.Through the simulation,it is found that the surrounding rock disturbance caused by the excavation of the middle part is the largest,the second is the excavation of the left hole,and the excavation of the right tunnel is relatively small,removal of support did not have a significant impact on it.It can be discovered from horizontal displacement field that the distribution of the horizontal displacement is symmetrical and mainly happen in both sides of the road.Then obtain the field monitoring measurement data and make a comparison of calculation results.Crown settlement and the monitoring point of surface settlement are similar with the curve of calculation results,also it is divided into three stages,decrease points belong to the left tunnel excavation and middle tunnel excavation.Finally,based on the extension comprehensive evaluation method,the core data and the monitoring data are obtained respectively from cave sections which to be evaluated.The risk score is calculated in the judgment system after bring in the data,the corresponding countermeasures are formulated at the same time.