###### Abstract  
In recent years, tunnel-boring machines (TBMs) have been widely applied in deep coal mining. Turning is an inevitable challenge in TBM tunneling, and a TBM turning roadway exhibits greater instability than a straight roadway, as engineering experience has indicated. This study aimed to explore the failure mechanism and evaluate the support performance of a deep-turning roadway. Several numerical models were established to investigate the deformation of the roadway, the stress distribution, and the failure zone of the surrounding rocks under different tunneling conditions. The results show that the tunneling depth influences the failure pattern of the turning roadway: deep tunneling with high in situ stress can cause asymmetric failure of the turning roadway, while shallow tunneling with low in situ stress does not. Moreover, the change in turning radius, namely the change in roadway geometry, does not influence the stability of the turning roadway. In addition, the support actions for both the straight and turning roadways do not differ significantly, and the amount of controlled deformation of the surrounding rocks is proportional to their natural deformation. TBM; turning roadway; failure characteristics; support Article  
Numerical Investigation with Failure Characteristic Analysis and Support Effect Evaluation of Deep-Turning Roadways  
1  
[PERSON]  
1 State Key Laboratory of Coking Coal Resources Green Exploitation, Pingdingshan 467000, China 12 State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering, China University of Mining and Technology, Xuzhou 221116, China 2  
drilling and blasting method [7]. In 2016, a gripper TBM was employed in the Zhangji coal mine to construct a 1308 m roadway, and two inclined drifts were built using a 7.6 m dual-mode TBM in the Xinjie coalfield [8]. The successful implementation of TBM tunneling provides valuable experience for its future application. Therefore, TBM tunneling will likely become the preferred and inevitable development trend for constructing deep rock roadways in coal mines. TBM tunneling is significantly influenced by in situ stress, rock strength, geological structure, and other factors during tunnel excavation [9; 10; 11]. Numerous researchers have explored the disturbance behavior of TBM tunneling and the control of roadway deformation. [PERSON] et al. demonstrated that the relative position of a tunnel and the sliding surface are the principal factors determining the deformation characteristics of the tunnel. They established four geomechanical models to analyze the influence of the sliding surface on tunnel deformation [12]. [PERSON] et al., [PERSON] et al., and [PERSON] et al. employed the finite difference code FLAC3D to study the disturbance mechanism of TBM tunneling and the deformation characteristics of the surrounding rocks [13; 14; 15]. [PERSON] et al. analyzed the failure mechanism of a coal roadway roof in the fault area, established an axial elastic beam mechanical model of the roof in the normal and reverse fault areas, and deduced its stress component and maximum effective shear stress, respectively. Based on the Mohr-Coulomb failure criterion, they discussed the fracture mechanism of the roof under different pressures, support strengths, and span height ratios [16]. [PERSON] et al. and [PERSON] et al. applied the limit analysis method in elastic-plastic mechanics to investigate the failure mechanism of roof caving in shallow underground chambers [17; 18]. [PERSON] et al. analyzed the deformation and failure mechanism of a deep coal roadway with a composite roof, indicating that the geomechanical environment of the roadway and the mechanical properties of the surrounding rocks were objective factors affecting the deformation and failure of the roadway, while the excavation and support of the roadway were subjective factors [19].