A Qualitative Study of the Critical Conditions for the Initiation of Mine Waste Debris Flows

Yanbo Cao,Bangxiao Liu,Yalin Nan,Xinghua Zhu

doi:10.3390/w12061536

Abstract

Mine waste debris flows are a type of man-made debris flow that commonly lead to major disasters. In this study, the Xiaotong Gully, which is located in the Xiaoqinling gold mining area in China and contains a typical mine waste debris flow gully, was selected as the study area. Since a debris flow can be classified as either a geotechnical debris flow or hydraulic debris flow based on its initiation mode, we conducted 46 experimental model tests to explore the initiation conditions of these two different types of debris flows. According to our tests, the initiation conditions of hydraulic debris flows were mainly affected by the flume gradient, the water content of the mine waste, the inflow discharge, the water supply modes, and the clay particle content. A larger flume gradient and higher mine waste water content were more conducive to initiating a hydraulic debris flow. However, the influence of the water supply mode on the initiation of a hydraulic debris flow was complex (influenced by factors such as water content of mine waste, runoff discharge rate and rainfall intensity). The critical runoff of a hydraulic debris flow, which starts with a parabolic relationship to the clay particle content of the mine waste, decreased with increasing clay particle content and then increased. There was a minimum critical runoff when the clay content of the mine waste was 30%. The initiation conditions of a geotechnical debris flow were mainly affected by the flume gradient, the water content, and the clay particle content. The critical gradient of a geotechnical debris flow decreased with increasing water content and had a parabolic relationship to the clay particle content. In tests 31–46 of this study, the second and third critical slopes both decreased and then increased with increasing clay particle content. These preliminary research results provide a scientific reference for subsequent research on the prevention and mitigation of mine waste debris flows.

Highlights

Debris flows occur when masses of poorly sorted agitated sediment that are saturated with water surge downslope in response to gravity [1,2,3]
The initiation process of hydraulic debris flows with different flume gradients, initial water contents, water supply modes, inflow discharges, and clay particle contents were all considered separately
The mine waste debris flows in the Xiaoqinling gold mining area generally have two initiation modes: geotechnical debris flow and hydraulic debris flow

Summary

Introduction

Debris flows occur when masses of poorly sorted agitated sediment that are saturated with water surge downslope in response to gravity [1,2,3]. Debris flows, which consist of a mixture of water, sediment, rocks, and soils, cause more damage than other kinds of geo-hazards due to their enormous impact force, rapid velocity, and long spread distance [4]. Prior research conducted on the formation mechanism of debris flows has focused on geological disasters. Scholars in China and abroad have done a great deal of research on the formation mechanism of debris flows [1,5,6,7]. The initiation modes of debris flows can be divided into two types: Water 2020, 12, 1536; doi:10.3390/w12061536 www.mdpi.com/journal/water

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Results

Conclusion