The calculation of characteristic values of Niantoucha slag debris flow in the Xiaoqinling gold mining area

The debris motion parameters constitute an important foundation for the main contents of debris flow and control design. With the slag debris flow as the study object and through topographic survey and geological mapping, the authors found that the Niantoucha area is characterized by steep land form and straight gullies, which provides favorable topographic conditions for the formation of debris flow. Drilling and trenching detected that the sources probably include slag, slope loose layers and small gully slump. Engineering geomechanics analysis shows that the stability coefficient of the mining slag is 1.022-1.063 under the condition of dead weight, lying between not very stable and basically stable; under the condition of dead weight plus heavy rain, the stability coefficient is 0.889-0.947, belonging to the instable condition. So slag is a major debris flow material source. Calculation based on the rainfall shows that the maximum peak discharge should be over 30m3/s. Under such a hydrodynamic condition, It is predicted that the weight of the debris flow is 22.80kN/m3, and the velocity of the debris flow is 5.11m/s. The debris flow discharge rates during the flood at intervals of 20 years, 50 years and 100 years are estimated to be 4.31m3/s, 44.6m3/s and 95.5m3/s respectively. The overall impact of mudslides should be 58.34kPa, 2.13m in excess of the height. The maximum hazard range of the debris flow accumulation is 0.21km2. These data provide basic parameters for the design of the engineering scheme for prevention and control of slag debris flow in the Xiaoqinling gold mining area.