# Key Technology of TBM Excavation in Soft and Broken Surrounding Rock
## 1 Introduction  
Nowadays, we are witnessing an ever-increasing need for tunnels in China because of their unique characteristics and potential applications. Tunnels are artificial underground spaces with a capacity for particular goals, such as water transfer, road tunnels, and mining. Therefore, tunneling techniques play a significant role in varying infrastructure projects. Among them, the Tunnel Boring Machine (TBM) is one of the most common methods for tunneling due to its high excavation rate [1]. Compared with the traditional drilling and blasting method of tunnel construction, TBM has many advantages of safety, high speed, high quality, etc., and is conducive to environmental protection, saving labor, and improving work efficiency [2, 3]. However, TBM designs must be changed with different stratum types because of the interaction mechanism, which should be studied between the rock and machine in varying strata [4, 5, 6], otherwise, a lot of unnecessary losses and trouble in the construction process could arise [7, 8, 9, 10]. For example, the TBM construction in soft and broken strata could greatly reduce the construction efficiency and even lead to the consequences of the TBM being buried [11]. To improve the geological adaptability of TBMs in extremely complex geological environments and improve the operating efficiency of the equipment in tunnel construction, many scholars have carried out a lot of research on equipment design, geological adaptability, construction technology, and other aspects. [PERSON] analyzed construction technical problems faced by complex geological engineering and summarized the corresponding technical measures and countermeasures for TBM construction under a complex geological environment [12]. [PERSON] et al. studied the key technologies of TBM equipment and construction, and they believed that the key to solving TBM equipment constructionunder extremely complex geological conditions is to speed up the construction progress and avoid long-term downtime [13]. [PERSON] et al. studied the key technology of TBM design for complex geological environments and proposed the TBM adaptive design method [14]. [PERSON] et al. studied the key technologies of TBM construction in the complex geological environment, and they proposed the construction methods of advanced geological prediction, shotcrete coordinated installation of reinforcement bars, and steel arch support [15]. [PERSON] studied different equipment utilization prediction models under complex geological environments and proposed a process simulation prediction method that can improve equipment utilization prediction [16]. [PERSON] studied the application of TBM in unfavorable geological engineering cases and believed that appropriate equipment selection design and advanced geological geophysical exploration are closely related to the speed of equipment construction [17]. [PERSON] et al. studied the key technology of TBM construction under unfavorable geological conditions, classified and defined the unfavorable geological conditions, and pointed out that the three major factors affecting efficient TBM tunneling are the geological and hydrological conditions, cutter head and tool system, and support system [18]. [PERSON] et al. studied the mechanism of TBM shield-jamming disaster tunneling through deep squeezing ground [19]. [PERSON] et al. studied the 3D numerical simulation of the interaction between rock mass and shield TBM passing through the fault fracture zone [20]. [PERSON] et al. studied the construction technologies for open TBM used in karst areas and soft-weak and broken grounds via a case study of the Songhua river water diversion project [21]. [PERSON] et al. studied the development of TBM in extremely complex geology and the key technology of efficient construction [22]. [PERSON] studied the causes and treatment measures of the large-scale collapse of open-type TBM in a weak stratum [23].