Research On Key Technical Problems In Tunnels Construction Adjacent To Existing Buildings By Methods Of Drilling And Blasting

The JWSG-V section of Jinwen railway tunnel has many characteristics,such as complex construction environment,various surrounding structures,many construction interference factors,complex geological and hydrological conditions,high engineering technology,and tunnel interchange construction.In order to ensure the smooth completion of the tunnel project,the key technical issues of construction of tunnel groups are studied.The main work carried out and the research results obtained is as follows:(1)The drilling and blasting construction scheme of Xi’ao tunnels No.1 and No.2 over the Yongtaiwen three-line tunnel is optimized;the blasting design scheme for the tunnel construction of the upper span section is determined;the stability during the tunnel construction and impacts of blasting vibration are studied.Based on the numerical simulation analysis of the upper span section,the author concludes that the impacts of the blasting construction of new tunnels on the lining structures of existing tunnels are basically controllable,thus the blasting design scheme is feasible.The numerical simulation provides a theoretical basis for the smooth implementation of the construction methods and safety measures of Xi’ao tunnel No.2 over the existing Yongtaiwen third-line high speed rail tunnel.(2)The stabilities of the construction of the large-section and small-interval tunnel of the Xia’ao No.1 main line and the upstream contact line parallel sections are studied.The changes and mechanical characteristics of the large section tunnel system during the construction by using the step method and the expansion excavation method are compared and analyzed.Based on the numerical simulation analysis,the author puts forward the suggestion that the four-step method should be adopted preferentially in large-section tunnels to guide the construction.Aiming at the construction of the tunnel with small clear distance,based on the numerical analysis,the construction scheme is proposed that the upstream rail contact tunnel(the smaller hole)is excavated after the No.1 tunnel(the larger hole),which guides the construction of the tunnel and brings good results.(3)Numerical simulation analysis of the construction stability of the Xia’ao No.1 Tunnel and the downstream bus relief line Xia’ao No.2 across the Wenzhou westbound drainage tunnel is done,and the stress and deformation characteristics of No.1 and No.2 tunnels during construction are studied.Based on the stress and deformation characteristics of the tunnel,recommendations on support measures and monitoring during the construction are proposed to help guide the construction of the tunnels.