Abstract
The supporting pressure value of excavation face directly determines the stable state of excavation face, and its value will directly lead to instability of excavation face if the value is too small. When the shield is underneath the existing tunnel, special attention should be paid to the support pressure setting of the shield working face. When setting support pressure, the rigidity constraint of existing tunnel on surrounding soil should be fully considered. In this paper, we used ABAQUS software to analyse the failure mode of the soil around the existing tunnel due to the instability of the excavation surface caused by the small pressure setting of the excavation face, which is caused by the small pressure setting of the excavation face. By using the method of theoretical analysis, we optimized the prism in the traditional wedge model to chamfer platform with different opening angles to make it closer to the actual situation, and calculated the critical support pressure of shield tunnel face when it passes through the built tunnel. The research results can provide a reference for the effective value of support force of shield excavation face when the shield tunnel passes under the existing tunnel at a short distance.
Highlights
In recent years, with the development of underground engineering, the construction of new tunnels crossing existing tunnels is increasing day by day, which is one of the unavoidable projects in the process of tunnel development
The predecessors have done a lot of research on the construction of tunnel crossing and the stability of excavation face under various working conditions [8,9,10], there are still no research results on the stability of excavation face of new tunnel crossing existing tunnel working conditions
As the stiffness of the tunnel is far greater than the stiffness of the surrounding soil, the damage area is restrained by the existing tunnel, so the opening angle of the sliding surface along the excavation direction is not equal, and the sliding angle of the sliding surface near the existing tunnel is relative to the sliding distance from the existing tunnel
Summary
With the development of underground engineering, the construction of new tunnels crossing existing tunnels is increasing day by day, which is one of the unavoidable projects in the process of tunnel development. Unstable failure of excavation face, surface subsidence, cracking and leakage of existing tunnel caused by insufficient support pressure of excavation face are very concerned problems. Xu (2012) used a three-dimensional wedge model based on limit equilibrium theory to study the stability of excavation surface of super-large diameter slurry shield [15]. Jancsecz (1994) and others used the principle of limit equilibrium to build a wedge model, and analyzed the ultimate support force of the excavation surface in the shield construction process and studied it. What’s more, the ultimate support force of the excavation face in the shield construction is analysed and studied [16]. In view of the situation of shield tunnel crossing under existing tunnels, we used ABAQUS software to simulate the instability failure caused by too small support force on excavation face, and analyzed the failure shape.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
