3D numerical investigation on the interaction between mechanized twin tunnels in soft ground

Abstract

During the construction of twin tunnels excavated in close proximity to each other, the prediction of the influence of a new tunnel construction on an already existing one plays an important role in the design and construction of the tunnels. The researches in the literature indicate that this influence depends to a great extent on the distance between the tunnels. However, most of the reported cases in the literature on the mechanized excavation of twin tunnels have focused on the effects of the relative position between the two tunnels on surface settlements. Some of them have dealt with the behaviour of the tunnel structure through the use of simplified numerical models. The numerical investigation performed in this study, using the FLAC 3D finite difference code, has made it possible to predict the impact between tunnels using full three-dimensional simulations, in which most of the elements of a mechanized tunnel process have been modelled. The effects of tunnel distance on the structural forces induced in both tunnels, and the displacements in the surrounding ground have been highlighted. A modification has been made to the superposition method to predict the settlement surface trough over twin tunnels.

Three-Dimensional Numerical Investigation of the Interaction Between Twin Tunnels

“…Ng et al (2004) investigate via 3D-FE analyses the in uence of the lagging distance between the faces of shallow, non-circular, twin tunnels, constructed with the NATM, and discuss the load transferring mechanism between the tunnels focusing on the settlements, the radial displacements and the internal forces developing in the tunnel lining. Similar research with 3D-FE analyses targeted to twin mechanized tunneling interaction in soft ground is presented by Do et al (2014), Do et al (2015) and Do et al (2016) 2012) carry out 3D-FE analyses for analogous parameters and conditions focusing on the effect of the ground, the tunnel size and depth and the relative position of the tunnels on the ground surface settlement, highlighting that the in uence of the new tunnel on the existing decisively depends on the relative position and the spacing of the tunnels. Chang et al (1996), based on a case study of twin tunnels in Taiwan, propose a simpli ed method to estimate the safety factor for the pillar and qualitatively analyze measures capable of mitigating the interaction and preventing potential failures.…”

Three-dimensional numerical simulation of mechanized twin stacked tunnels in soft ground

“…Stiffness is adopted as a function of the effective confinement, which leads to a higher value for unloading-reloading stiffness. Parameters of the soil are presented in Table 1. The numerical model, the 3D simulation procedure for a mechanized tunnel, and the parameter calibration of the CYsoil model are described by Do et al (2014a;2014b;2014d). Therefore, only a short overview is given here.…”

“…As far as the excavation of mechanized twin tunnels in close proximity is concerned, most cases reported in previous studies have focused on the interactions between two horizontally driven tunnels, using physical tests (Kim, 1996;Chapman et al, 2007;Choi and Lee, 2010;He et al, 2012;Ng et al, 2013;Ng, 2014;Ng and Lu, 2014), field measurements (Yamaguchi et al, 1998;Suwansawat and Einstein, 2007;Chen et al, 2011;Zhou et al, 2012;Ocak, 2013), empirical/analytical methods (Wang et al, 2003;Hunt, 2005;Suwansawat and Einstein, 2007;Yang and Wang, 2011), and numerical analyses (Yamaguchi et al, 1998;Hefny et al, 2004;Zheng and Qiu, 2005;Karakus et al, 2007;Hage Chehade and Shahrour, 2008;Afifipour et al, 2011;Chakeri et al, 2011;Ercelebi et al, 2011;Mahmutoğlu, 2011;Channabasavaraj and Vishwanath, 2012;Hasanpour et al, 2012;Li et al, 2012;Do et al, 2014b;2014d). However, less work has been devoted to the interactions between tunnels stacked over each other (Yamaguchi et al, 1998;Hefny et al, 2004;Suwansawat and Einstein, 2007;Hage Chehade and Shahrour, 2008;Liu et al, 2008;Channabasavaraj and Vishwanath, 2012;…”

Impact Analysis for Safety Prevention and Control of Special-Shaped Shield Construction Closely Crossing Multiple Operational Metro Tunnels in Shallow Overburden

“…At present, many researchers have conducted indepth studies on multiple existing subway tunnels adjacent to the new line and used different methods to evaluate the impact of the new tunnel on the existing tunnel. Do et al (2015) and Ratan Das et al (2017) used the finite element method to study the interaction between excavations of two tunnels and the law of ground settlement. Based on the Peck formula and the equivalent layering method, some scholars have studied the influence of the stiffness of the existing tunnel on the settlement of the new tunnel (Jiancheng Wang 2014; Zhou et al 2020).…”