Strengthen safety risk control of open-pit mine slope to prevent collapse accidents

First, strict mine access, reduce the inherent safety risk of slope

(1) Reasonable demarcation of mine boundaries. The newly built and expanded mining scope of the expansion of open pit mines shall strictly implement the "Zhejiang Provincial Department of Land and Resources Zhejiang Province Work Safety Supervision Administration on the Management of sand and gravel mineral development and safety production supervision" (Zhejiang Soil Capital Development [2014] No. 32) the relevant requirements for the establishment of fixed point demarcation of mines, the mountain can be developed as a whole, shall not be divided and demarcation. As far as possible to achieve the whole mountain displacement mining or contour demarcation; Ridgeline should not be used as the mining boundary, and the mining boundary should not be demarcated by "peeling skin" to reduce the final slope height as much as possible, so as to create conditions for the implementation of stepped mining.

(2) Strengthening early geological exploration. The geological exploration data based on joint exploration, safety pre-assessment and safety facility design of open-pit mine construction projects must reach the level of detailed investigation and above, and meet the requirements of relevant design norms, and may not be used as the basis for the establishment of mines. For open-pit mine construction projects with medium or above engineering geology and hydrogeology complexity within the proposed mining scope, the geological exploration data must reach the exploration level. For open-pit mine construction projects with final slope height of 100 meters and above, the Final Slope Stability Study Report shall be prepared; After the slope stability study, and after taking feasible safety technical measures, the final slope is still unable to achieve stability or basically stable, no mine shall be established.

(3) Standardize the general layout. Offices, dormitories for workers, houses and other structures or living facilities with personnel activities shall not be set up within the scope of the hazard of mine slope collapse. No fixed production sites such as crushing and beneficiation shall be set up within 50 meters from the bottom line of the working step slope or the bottom line of the final side slope of a new mine; Where the final slope height is above 50 meters or stratified mining is used, fixed production sites such as crushing and mineral processing shall not be set up within the scope of slope collapse hazards, and the hazards caused by slope collapse shall be strictly controlled.

(4) Strict design review. The "Safety Facilities Design" of mine construction projects should be compiled in strict accordance with the "Safety Regulations for Metal and non-metal mines" and related design manuals, and reasonably determine the height of the step, the working slope Angle and the slope Angle of the final slope, the width of the safety platform and the cleaning platform. The final slope with hard rock and no dangerous structural plane shall not exceed 55 degrees; The final slope with hard rock (medium hard rock) and no dangerous structural plane shall not exceed 42 degrees; The final slope of soft rock without dangerous structural plane shall not exceed 30 degrees. The slope Angle of a slope with a dangerous structural plane shall not be greater than the dip Angle of the dangerous structural plane. For the final slope with a height of more than 90 meters, the slope Angle should be appropriately reduced, and the slope Angle should be reduced by 1 degree every 30 meters.

Second, strengthen technical support to improve slope risk identification ability

(1) Strengthen daily research and judgment of slope safety risks. Open-pit mining enterprises should be equipped with geological engineering technicians in accordance with the requirements of the "Guide for Mine Safety Technical Work in Zhejiang Province", and carry out geological work in a standardized manner. After each operation cycle of mining construction, geological data should be collected in time to investigate and judge the stability of the exposed site slope and put forward countermeasures. It is necessary to strengthen the daily investigation of the dangerous structural plane of the slope. Where it is found that there are adverse geological phenomena in the slope, such as rock strata inclination in the stope, multi-group joint fracture space combination structural plane inclination in the stope, large weak structural plane and weak rock strata cutting slope, the person in charge of the mining enterprise should immediately organize professional and technical personnel to conduct research and judgment. Rectification and control measures must be implemented in accordance with major accident hazards.

(2) Conduct regular research and judgment on slope safety risks. The person in charge of the mining enterprise or the technical person in charge shall hold a technical analysis meeting at least once a month to analyze the dynamic changes of geological conditions and the effectiveness of slope safety risk control measures. The main person in charge of the mining enterprise shall organize a systematic study and judgment of slope safety risks every year, and conduct a systematic analysis and judgment of slope stability and the effectiveness of control measures based on the slope safety production situation, risk events, disclosed geological conditions and safety monitoring data in recent years.