## 1 Introduction  
The increasing demand for coal due to global economic growth and the depletion of coal resources from favorable geological sites force engineers to re-evaluate the safety of underground mining and to create more effective tunneling methods and better supporting procedures. Ground control in weak rock is always an interesting challenge for researchers. Designing good supports for tunnels created in weak rocks is a complex problem [1] due to the low quality of the rock mass and the possibility of large deformations. Therefore, the pipe-jacking method with thick concrete pipe supports is proposed in this paper. Rocks with an estimated uniaxial compressive strength [2] of less than 25 MPa can be classified as weak, very weak, and extremely weak. Weak rocks that have low strength and high expansibility easily result in large deformations and severe fractures in the surrounding rock, which lead to instability.  
The rock bolt system has been widely used in UK and Australian underground coal mining practices. However, the deformation and fracture behavior of roadways in weak rocks cannot be controlled by a rock bolting system in cases where the development rate is slow and when the roadway/entry has to be maintained for a long time; consequently, additional support needs to be installed [3]. Due to the difficulty of achieving an adequate anchorage of the rock bolts and cables, steel-set or concrete/shotcrete-lining support systems are more appropriate [1]. Moreover, to prevent large deformations in the surrounding rocks due to the dynamic disturbances caused by mining, a support consisting of constant resistance, large deformation bolts, steel strips, and grouting bolt pipes was suggested by [4]. In addition, in the Xingdong mine, a support system based on the bearing strength theory combined a super-imposed arch using an \"anchor spray net+anchor cable\" to support the deep, weak surrounding rock [5] and the \"elliptical concrete-filled steel tube supports + deep + shallow cross grouting reinforcement\" composite scheme to reduce the number of deformations in the surrounding rock, which has worked effectively [6].  
Moreover, the application of rigid steel-arc support as a primary support system in a weak surrounding rock roadway was suggested, and a comparison of actual field measurements and numerical results has been made [7]. Additionally, \"a high-strength concrete-filled steel tube\" support structure has shown significant improvement when used to control the deformation around the roadways in the Chaganmuer mine and, thus, to effectively control the deformation and to ensure its safety [8]. Recently, many Chinese researchers have suggested using a concrete-filled steel tube support combined with auxiliary supports for deep, soft rock tunnels that are under high in situ stress.  
The main gate of a mine is excavated horizontally (or gently) for purposes such as coal haulage, material transportation, worker access, and ventilation from the ground to the coal deposits; thus, its stability is imperative. In this paper, we study the stability of the main gate based on numerical analysis with a three-dimensional finite element method (3D-\(\sigma\) software).  
To determine the level of crown deformation in the rocks from the roof of the tunnel and the failure proximity of a concrete pipe, the mechanical properties of the rocks in a coal mine in Indonesia were used in this analysis. An increasing number of new mines are being planned and a number of existing mines are being extended, with life spans of over 40 years. For such projects, it may be prudent to consider adopting design standards that are commensurate with civil engineering tunnels [9].