The Research Of Large Deformation Control Technologies For Soft Rock Tunnel With High Ground Stress Based On ADECO-RS

With the continuous improving of China’s railway construction capability,the standards of railway construction have been advanced too and more and the tunnel which has the features of high construction risks,high costs and long construction period would be increasingly constructed.The New Austrian Tunnelling Method has gradually been proved that it was unsuitable for using in condition where high ground stress and extremely complex geological environment exists.So,it’s necessary to search a more advanced systemized tunnel design and construction method.Based on the theory of ADECO-RS,combined with numerical simulation and monitoring,the following aspects were specifically carried out:(1)Exploring the cause and failure mechanism of large deformation of soft rock tunnel with high ground stress;Comparing and analyzing the two different surrounding rock classification method of soft rock tunnel which based on the NATM and ADECO-RS;Through theoretical analysis combined with numerical simulation,Studying the effects of different advanced support measures on the stability of the face were studied,and classify the stability of the tunnel face.(2)According to the geological conditions of the Muzhailing tunnel,analyze the causes of the large deformation and classify the surrounding rock.The finite element softvware Midas/GTS is used to establish a three-dimensional numerical model based on the actual situation of the tunnel’s large deformation.Without considering the seepage,numerical simulation calculations for the four construction methods of three-step method,the bench reservation core soil method,the piolt heading method and ADECO-RS,get the change law of crown settlement,lateral displacement of side wall,the stress of surrounding rock and primary support.From the results of numerical simulation,it is concluded that the ADECO-RS is the preferred construction method for controlling large deformation.(3)The control technology of large deformation of soft rock tunnel with high ground stress is discussed,emphasis on the effect of reserved deformation and GFRP.The influencing factors of the reserved deformation amount are analyzed,and the two different methods of calculating the reserved deformation amount are compared and analyzed,along with the conditions of use are proposed.The numerical Simulation of the effect of non-reinforcement measures,pre-reinforcement with advanced small conduits,and different lengths of GFRP in soft rock tunnels with high ground stress,It is concluded that the deformation of the tunnel can be significantly controlled by the pre-reinforcement of the GFRP when the length of the bolt is 18m,and the control effect of it towards large deformation is the best.The two rows of GFRP on the lower edge of the face are prone to stress concentration.