Optimized layout and excavation sequence of deep chambers

The stability of deep chamber groups is crucial for safe mining operations and is closely related to the spatial layout and excavation sequence. Proper spatial arrangement and optimized construction sequencing not only help control the deformation and failure of the surrounding rock but also improve the overall stability and safety of mining operations. This study focused on the chamber group of the wet-mix shotcrete batching station at the 941 level of Jinchuan No. 2 Mine. A combination of theoretical analysis, numerical simulations, and field monitoring was employed to systematically investigate the effects of cross-sectional shape and size, spatial layout, and construction sequence on the stability of the chamber group. First, the study analyzed the effects of cross-sectional shape and size on the chamber stability and investigated the constraints imposed by the in situ stress orientation on the chamber layout. The results showed that the optimal cross-sectional shape for large-section chambers was a straight-walled circular arch section, which effectively reduced the stress concentration in the surrounding rock and enhanced the overall stability. Further analysis revealed that the lateral pressure coefficient was a critical factor influencing the deformation of the surrounding rock. Under the condition of equal cross-sectional areas, a larger width-to-height ratio significantly increased the deformation of the roof and floor of the chamber, resulting in a deteriorated stress state in the surrounding rock. Additionally, increasing the chamber size with a constant lateral pressure coefficient exacerbated the failure of the roof rock mass and increased the roof subsidence, which negatively affected the long-term stability of the chamber. Under the same height conditions, an increase in the chamber size intensified the failure of the roof and floor surrounding the rock. Therefore, in the chamber layout design, critical parameters, such as the lateral pressure coefficient and width-to-height ratio, must be comprehensively considered to optimize the chamber shape and spatial distribution. In terms of spatial arrangement, this study proposed fundamental principles for the arrangement of primary and auxiliary chambers and, based on numerical simulation results, prioritized the arrangement of the primary chambers. The axis of the chamber should be oriented at an angle between 45° and 60° to the maximum principal stress direction to optimize stability. The study also examined the influence of different chamber layout methods on stability and provided layout guidelines for primary chamber prioritization, parallel arrangements, and intersecting layouts. The results indicated that when chambers were arranged in an intersecting layout, it was crucial to select an appropriate spacing and ensure that the intersection angle is as close to 90° as possible to reduce the risk of surrounding rock failure and improve the overall stability. Furthermore, the study revealed that as the angle between the maximum horizontal stress and the chamber axis increased, the chamber stability first improved and then declined, highlighting the importance of an optimal axial layout to maintain the surrounding rock stability. Regarding the excavation sequencing, this study optimized the excavation order based on an incremental stability characterization model for the chamber group. The results indicated that the optimal construction scheme was Scheme I, with the excavation sequence as follows: first, the batching machine chamber; second, the mixing machine chamber; finally, the cement silo chamber. The numerical simulation and field monitoring results demonstrated that in this construction scheme, the chamber support structure exhibited high stability, with the surrounding rock convergence rate significantly reduced to below 0.06 mm·d⁻¹, effectively controlling the deformation of the chamber group and ensuring the success of the excavation process. In conclusion, this study systematically analyzed the impact mechanisms of the cross-sectional shape, spatial layout, and construction sequence on the stability of chamber groups and proposed targeted optimization schemes. These findings provide essential scientific and engineering guidance for the design and construction of surrounding rock stability controls in deep mining operations. These results have significant theoretical and practical value for the safe and efficient extraction of deep rock masses in mining engineering.