Abstract
This study investigates the influence of subsequent tunnel boring machine (TBM)-driven processes on the responses of the first tunnel in twin-tunnel construction using the ultra-rapid underground pass (URUP) method. A comprehensive finite element analysis (FEA) is performed to simulate the URUP TBM tunneling, considering the non-uniform convergence caused by the TBM geometry, the tunnel face supporting pressure, and the tail-grouting pressure. The FEA model is validated by the monitoring results of the bending element of the first tunnel lining. The FEA results reveal that the grouting pressure of the second tunnel has significant influence on lining deformation of the first tunnel, while the face supporting pressure shows little effect. The relationship between the grouting pressure and the maximum bending moment of adjacent first tunnel can be fitted by linear function. A grouting pressure equals to the lateral earth pressure is able the reduce the variation of the bending element of the first tunnel during the TBM-driven process of the second tunnel. The bending element of the first tunnel shows a typical lognormal relationship with the face supporting pressure during the TBM advance of the second tunnel. A critical cover-to-depth ratio, under which the horizontal and vertical soil arching effect vanishes, can be deduced to be within the range of 0.55–0.60.
Highlights
Mechanized tunneling method has been widely employed in tunnel construction in recent decades.The tunnel boring machine, a.k.a
The field monitoring and nonlinear finite element analyses (FEA) on this underground pass (URUP) demonstration work revealed that [33,34]: (1) the grouting pressure should be considered as a non-uniform distribution during negative- and shallow-overburden tunneling phases; (2) a cover–diameter ratio of 0.55 can be considered as a critical magnitude under which the tunnel face cannot maintain stability; and (3) the Gaussian curve can be employed for the settlement prediction at the ground surface during shallow URUP
Existing studies have been focused on the ground responses without detailed investigation on segment internal forces during URUP tunneling, especially for tunnel boring machine (TBM) launching of the second tunnel which is adjacent to the first URUP tunnel
Summary
Mechanized tunneling method has been widely employed in tunnel construction in recent decades. The field monitoring and nonlinear finite element analyses (FEA) on this URUP demonstration work revealed that [33,34]: (1) the grouting pressure should be considered as a non-uniform distribution during negative- and shallow-overburden tunneling phases; (2) a cover–diameter ratio of 0.55 can be considered as a critical magnitude under which the tunnel face cannot maintain stability; and (3) the Gaussian curve can be employed for the settlement prediction at the ground surface during shallow URUP tunneling under a C/D < 0.55 (C/D is cover-to-diameter ratio). Existing studies have been focused on the ground responses without detailed investigation on segment internal forces during URUP tunneling, especially for TBM launching of the second tunnel which is adjacent to the first URUP tunnel. The paper presents a comprehensive FEA investigation of the TBM-driven influence on adjacent first tunnel during twin-tunneling using the URUP method. The influence of TBM launching on the segment internal forces of adjacent first tunnel is explored by FEA parametric study
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