TBM Tunnelling Under Adverse Geological Conditions: Case Study of a Long-Distance and Deep-Buried Water Conveyance Tunnel
Authors: Xie Wei-Qiang , Zhang Xiao-Ping , Liu Xiao-Li , Qian Rui-Peng , Liu Quan-Sheng 
Published: August 2024

ABSTRACT:
The adverse geological conditions have significant influences on the safety and efficiency of tunnel boring machine (TBM) tunnelling. Feasible solutions for TBM tunnelling under adverse geological conditions are summarized based on a long-distance and deep-buried water conveyance tunnel. The engineering background of the tunnel is briefly presented. Then the challenges of TBM tunnelling encountered in adverse geological conditions are highlighted, including fractured and faulted rock mass, squeezing rock mass and deep-buried rock mass. Series of solutions carried out successfully in the field to overcome these challenges are elaborated. It is necessary to install a geological drilling rig on TBM. The hazards frequently occur in the L1 zone in TBM tunnel. The noxious gases present within 6-12 meters away from the tunnel face. The large squeezing deformation commonly occurs at the TBM shield. Most rockburst events occur within 1 hour after the surrounding rock is revealed. A commonly used construction technology system for assisting TBM tunnelling under adverse geological conditions is proposed.

1. INTRODUCTION
With the development of civil engineering, hydraulic engineering and mining engineering, more and more tunnels are being and will be constructed in the world (Gong et al., 2021b; Keshtegar et al., 2021; Koopialipoor et al., 2018; Tajik et al., 2012). Most of these tunnels are long-distance and deep-buried. Tunnel boring machines (TBMs) are widely used in these tunnel constructions due to their advantages in safety, environmental friendliness and high efficiency (Tang et al., 2021a; Tang et al., 2021b; Xie et al., 2021; Zhang et al., 2021a; Zhang et al., 2021b). The geological conditions encountered during the long-distance tunnelling become more and more complicated. Previous cases have shown that the geological conditions have significant influence on the TBM performance, causing a very low TBM utilization and high additional cost, even leading to TBM jamming or burying (Gong et al., 2016a; Gong et al., 2016b).
To control and prevent the unacceptable geological hazards during the TBM tunnelling process, a great number of studies have been carried out. These studies can be roughly categorized into three classes: field investigations (Chen et al., 2013; Huang et al., 2018; Liu et al., 2020; Zhang et al., 2012), laboratory experiments (Faivre et al., 2019; Gong et al., 2021a; Liu et al., 2021; Yong et al., 2016), numerical simulations (Yong et al., 2016; Zhang et al., 2011; Zhou et al., 2011). Usually, field monitoring and in-situ testing are used during the field investigations (Li et al., 2020; Qiu et al., 2020; Rajib et al., 2018; Trifu and Shumila, 2010; Wu et al., 2019; Xutao et al., 2018; Zhang et al., 2021b). These two solutions are found useful to acquire the conditions of the surrounding rock. Various laboratory experiments have been proposed to obtain the properties of rock specimen, such as uniaxial compression test, point load test, indentation test, etc. Although these experiments are relatively convenient in preparation and operation, their results cannot represent the actual conditions of the surrounding rock (Xie et al., 2021; Zhang et al., 2021b). The TBM tunnelling process in different rock masses is actually a rock mass breakage process (Gong and Zhao, 2009). It depends on the interaction between the surrounding rock and the boring machine. Numerical simulations can present this process well. Thus, numerical simulations are widely used to study the occurrence mechanism of geological hazards (Deng et al., 2022; Yang et al., 2017). However, the conditions of the surrounding rock used in numerical models usually differ from the field conditions.