Discussion on the stability evaluation standard of a rock slope in a noncoal open-pit mine
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摘要: 根據露天礦山的生產工藝特征,將巖質邊坡劃分為總體邊坡、路間邊坡和臺階邊坡三種尺度,并對其控制因素、破壞模式進行了分析;結合土木工程邊坡規范和非煤露天礦山邊坡規范的邊坡設計安全系數取值,討論了國內外非煤露天礦山邊坡設計安全系數的要求,提出了六條建議;綜合考慮服務年限、邊坡尺度規模的設計安全系數改進方案,并引入失穩概率,拓展了不同尺度邊坡穩定性評價的設計標準,可有效提升非煤露天礦巖質邊坡穩定性評價的合理性和科學性,進一步完善了礦山邊坡設計理論和方法。Abstract: As an important way to obtain mineral resources, open-pit mining has accounted for about 77% of the total production of the mined iron ore, and about 52% of the total production of non-ferrous ore, indicating huge development potential. With the continuous development of open-pit mines to deep and large-scale directions, the height of mine slopes is constantly increasing and the maximum height has exceeded kilometers. Slope instability disaster is a major problem faced by open-pit mines, and the evaluation and analysis of the stability of mine slopes are of great importance. However, in the stability evaluation and analysis of rock slopes in many open-pit mines, the engineering scale is ignored, the value of design safety factor is too conservative, and the evaluation index is single, rendering it difficult to consider the economy and safety of mine slope evaluation and resulting in the waste of resources and frequent accidents. In this paper, rock slopes were divided into three scales according to the production process characteristics of open-pit mines: (1) overall slope, (2) inter-ramp slope, and (3) bench slope. Moreover, the control elements and failure modes of the slopes were analyzed. Combined with the design safety factor value of the civil-engineering slope standards and specifications of a non-coal open-pit mine slope, the design safety factor requirements of non-coal open-pit mine slopes at home and abroad were discussed, then six suggestions were put forward. Comprehensively taking service years and the improved scheme of design safety factor in slope scale into consideration, the instability probability were introduced to extend the design standard of slope stability evaluation in different scales, which can effectively improve the rationality and scientificity of the rock slope stability evaluation in non-coal open-pit mines, further improving the mining slope design theory and method.
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Key words:
- open-pit mine /
- rock slope /
- design safety factor /
- instability probability /
- slope stability /
- evaluation standard
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表 1 露天礦山邊坡設計方案
Table 1. Slope design scheme of the open-pit mine
Slope design scheme Overall angle/ (°) Safety factor Scheme 1 38 1.462 Scheme 2 40 1.364 Material type Conditions Design safety factor Soil earthworks Normal loads and service conditions 1.5 Maximum loads and worst environmental conditions 1.3 Earth retaining Normal loads and service conditions 2.0 Slopes Temporary 1.25 Permanent 1.5 表 3 邊坡危害等級
Table 3. Slope hazard grade
Slope hazard grade Possible casualties Potential economic risk/(106 ¥) Comprehensive assessment Direct Indirect Ⅰ Casualties ≥1.0 ≥10 Very serious Ⅱ Injured 0.5?1.0 5?10 Serious Ⅲ Unharmed ≤0.5 ≤5 Ordinary 表 4 邊坡工程安全等級劃分
Table 4. Safety classification of slope engineering
Slope engineering safety grade Slope height, H/m Slope hazard grade Ⅰ H>500 Ⅰ, Ⅱ, Ⅲ 300<H≤500 Ⅰ, Ⅱ 100<H≤300 Ⅰ Ⅱ 300<H≤500 Ⅲ 100<H≤300 Ⅱ, Ⅲ H≤100 Ⅰ Ⅲ 100<H≤300 Ⅲ H≤100 Ⅱ, Ⅲ 表 5 不同荷載組合下總體邊坡的設計安全系數
Table 5. Design safety factor of the overall slope under different load combinations
Slope engineering
safety gradeSlope engineering design safety factor Load combination Ⅰ Load combination Ⅱ Load combination Ⅲ Ⅰ 1.25?1.20 1.23?1.18 1.20?1.15 Ⅱ 1.20?1.15 1.18?1.13 1.15?1.10 Ⅲ 1.15?1.10 1.13?1.08 1.10?1.05 表 6 邊坡危害等級建議
Table 6. Recommendation on the grade of the slope hazard
Slope hazard grade Possible casualties Potential economic risk/
(106 ¥)Comprehensive assessment Direct Indirect 1 Casualties ≥10 ≥50 Very serious 2 Injured 2?10 10?50 Serious 3 Unharmed ≤2 ≤10 Ordinary 表 7 邊坡工程安全等級劃分建議
Table 7. Suggestions on the safety classification of slope engineering
Slope engineering safety grade Slope height, H/m Slope hazard grade Note Ⅰ H>500 1, 2, 3 The engineering security levels should be increased a level for open-pit mine slope whose security level belong to II or III, or service years greater than 25 300<H≤500 1, 2 100<H≤300 1 Ⅱ 300<H≤500 3 100<H≤300 2, 3 H≤100 1 Ⅲ 100<H≤300 3 H≤100 2, 3 表 8 采礦巖石邊坡可接受的失穩概率
Table 8. Acceptable instability probability of mining rock slopes
Category Description Acceptable instability probability 1 Critical slopes where failure may affect the continuous operation and pit safety <5% 2 Slopes where failure have a significant impact on costs and safety <15% 3 Slopes where failure has a notable impact on costs and where minimal safety hazards exist <30% 表 9 露天礦巖質邊坡設計安全系數與失穩概率建議值
Table 9. Suggested value of the design safety factor and instability probability of the rock slope in the open-pit mine
Slope scale Slope engineering safety grade Acceptable criteria Minimum design safety factor (static) Minimum design safety factor (dynamic) Maximum instability probability/% Bench Ⅰ, Ⅱ, Ⅲ 1.1 — 25 Inter-ramp Ⅲ 1.15 1.0 20 Ⅱ 1.2 1.0 15 Ⅰ 1.2 1.1 Overall Ⅲ 1.2 1.0 15 Ⅱ 1.25 1.05 10 Ⅰ 1.3 1.1 5 Important production Ⅰ, Ⅱ, Ⅲ 1.3 1.1 5 www.77susu.com -
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