Comparison And Selection Of Construction Schemes For Tunnel With Large Section In Weak Surrounding Rock

With the continuous improvement of social requirements for transportation,highways,railways and rail transits have been vigorously developed.Tunnels,as the key nodes in transportation,play an important role in the field of transportation.Therefore,it is of great significance to study the theory,technology and experience of tunnel construction.Based on the XinMenShua 2# Tunnel of Jingneng Shiyan Thermal Power Railway Special Line and Shiyan Jiangsu Road Extension Line 1# Tunnel,this paper introduces the geological predication in tunnel,tunnel monitoring measurement and data processing of the tunnel,summarizing the commonly used excavation methods of the tunnel at present stage,and on this basis,introduces the improved excavation method-bench method with core soil and temporary invert.By means of on-site monitoring measurement and theoretical analysis,the advantages and disadvantages of cantilever tunneling machine construction method and traditional drilling and blasting method in the construction of adjacent existing railway tunnels are compared.By means of theoretical analysis,on-site monitoring measurement and numerical simulation,the 3-bench 7-step excavation method and bench method with core soil and temporary invert adopted in the 1 # tunnel of Jiangsu Road Extension Line are coMPared and analyzed.The main contents and conclusions of this paper are as follows.1)Common construction methods of tunnel with large section in weak surrounding rock have been investigated at home and abroad.On the basis of comprehensive consideration of safety,construction efficiency and economy,four construction methods are preliminarily selected for further comparison.2)Based on the 1 # tunnel of Jiangsu Road Extension Line in Shiyan City,by means of numerical simulation,the plastic zone of surrounding rock,displacement of tunnel body,circumferential stress and radial stress of ring excavation reserved core soil,3-bench 7-step excavation method,center diaphragm method and bench method with core soil and temporary invert are compared and analyzed.Combined with the monitoring data,the bench method with core soil and temporary invert and 3-bench 7-step excavation method are compared from three aspects of surface subsidence,vault subsidence and clearance change,in order to obtain the most suitable construction method.The results show that the bench method with core soil and temporary invert has a smaller plastic zone distribution and it is superior to the 3-bench 7-step excavation method in controlling surface subsidence and clearance change.According to the analysis results,the bench method with core soil and temporary invert is recommended.3)ABAQUS is used to establish the finite element model and analyze the supporting effect of the systematic bolt.The numerical simulation results show that the application of systematic bolt can reduce the distribution range of plastic zone in surrounding rock,but it has little effect on reducing the combined displacement of tunnel body.4)Based on the XinMenShua 2# Tunnel of Jingneng Shiyan Thermal Power Railway Special Line.this paper introduces the application of CTR260 cantilever roadheader in the construction of adjacent existing line tunnels,giving the tunneling progress of cantilever roadheader and the consumables of cutting teeth(the main consumables of roadheader in construction)based on the different compressive strength of rock.Compared with the traditional drilling and blasting method in construction efficiency,manpower,mechanical configuration,economy and over-and-under-excavation,the cantilever excavator has faster construction progress,less demand for personnel and machinery,better economy and less over-and-under-excavation.At the same time,the surrounding rock deformation and the influence on adjacent existing tunnels caused by the excavation of cantilever excavator is decreased compared with the traditional drilling and blasting method.