Precise control of blasting-induced excavation boundaries in deep phosphate stopes presents significant challenges under complex backfill constraints, with current overbreak/underbreak evaluation methods frequently lacking quantitative rigor. Using the 875-level stope of Shaft No. 2 at Guizhou's Xinqiao Phosphate Mine as a case study, this research develops an advanced methodology for blasting boundary characterization and control that leverages three-dimensional (3D) laser point cloud data analysis. High-precision post-blast point cloud data were collected using a mobile laser scanning system, followed by the development of a comprehensive analytical framework incorporating point cloud denoising, preprocessing, registration correction, surface reconstruction, and geometric discrepancy analysis. This system allows quantitative evaluation of the spatial distribution of overbreak and underbreak, volumetric deviation, and the degree of contour matching between the excavation boundary and the design profile. Utilizing point cloud diagnostic results from representative stopes, the effects of blasting energy distribution and initiation sequence on boundary formation were analyzed, subsequently developing a control strategy integrating zoned millisecond-delay initiation with optimized blasthole layouts. Field trials at the 875-13# stope confirmed the method's capability to precisely characterize post-blast boundary morphology and deviation characteristics, achieving over 90% contour matching accuracy for both A₁ and A₂ rows. Volumetric difference analysis of point cloud data provided a reliable quantitative basis for assessing overbreak and underbreak and for guiding blasting parameter optimization. The developed boundary control technique demonstrates consistent stability and robustness even under challenging conditions, including drilling deviations in the A₃ and A₄ rows. This methodology offers a quantitative, traceable technical solution for precision blasting design and boundary control in deep mining stopes, delivering practical value by minimizing ore dilution and enhancing stope extraction efficiency.

To address the issues of backfill damage and stope boundary irregularities caused by fan-shaped borehole blasting in sublevel open stoping with subsequent backfilling, this study focuses on the underground stope of Xinqiao Phosphate Mine as a case study. Numerical models were developed using LS-DYNA finite element software to comprehensively analyze the blasting performance of fan-shaped medium-deep holes under various operational conditions. Field-measured blasting contours of the stope were compared with numerical simulation results to evaluate the influence of different loading application methods on the blasting damage prediction accuracy. The simulations employed both experimentally recorded borehole wall pressure time-histories and a constitutive explosive material model coupled with the JWL equation, revealing that the measured load time-histories yielded more precise blasting effect representations. Building upon this foundation, the study systematically simulated fan-shaped blasting under one-step mining, two-step mining, and special stope conditions by examining two key variables: inter-sidewall distance and initiation delay time. Subsequent analysis focused on surrounding rock mass damage distribution patterns and blastinginduced vibration characteristics. Results indicate that in one-step mining scenarios, inter-sidewall distance exhibits limited impact on surrounding rock mass stability, while initiation delay time emerges as the predominant factor governing blast fragmentation efficiency. At a 0.3 m inter-sidewall distance, blasting damage primarily concentrated within the ore caving zone, achieving effective bulk fragmentation while substantially mitigating surrounding rock damage risks. In two-step mining scenarios, backfill stability demonstrates high sensitivity to toe burden distance, with damage risks markedly damage decreasing when exceeding 0.6 m. While sequential hole initiation enhanced fragmentation, it exacerbated backfill damage. Special stope conditions required asymmetric sidewall parameter design and optimized borehole arrangement to minimize backfill impacts. These findings culminate in an optimized fanshaped blasting parameter system tailored for Xinqiao Phosphate Mine's A-orebody, delivering both theoretical frameworks and practical methodologies for backfill mining blasting operations.