Abstract

Water–sand inrush is one of the most serious disasters for mining in China. The evaluation of the occurrence and development of a high-concentration water and sand mixed fluid is an important issue for mining in China. In this study, contraposing to the 3 phases of water–sand inrush, three kinds of experiments are designed for the investigation of initiation, development, and occurrence of the disaster. A new sand–water transport testing system is setup to perform the tests. The results show that there are two key points in the disaster: (1) sand particle incipient motion and (2) porous skeleton structural instability. The incipient motion of sand grains is accompanied with the phenomena of volumetric dilatation and granular fluidization. The critical velocity of the incipient motion of the water–sand mixed fluid is significantly affected by the particle size and external stress. The interaction between water and sand grains is the key factor affecting the motion characteristics of water–sand mixture. When the hydraulic conditions exceed the threshold, the water and sand grains are mutually promoted, and the aquifer skeleton becomes unstable. Furthermore, during the water–sand inrush, the curves of volumetric flow rates of sand and water, respectively, for different samples manifest as two distinct waveforms.

Highlights

  • Water–sand inrush is a most serious mine disaster in western China, in the Shaanxi province, the major energy resource centre of China [1, 2]

  • According to the statistics data on the scenario of the water–sand inrush occurring in western China, accidents during coal mining extremely affect over 47.5% of the estimated reserves, equivalent to an excess of 100 billion tons [3]

  • Electronic scale A reads the difference in the masses of the sand and the water it replaces, and electronic scale B reads the mass of the water with the same volume as the mixed fluid, i.e., where Vs,j is the volume of SFO and Vw,j is the volume of water flowing through the sample (WFT); the volumetric flow rate can be determined as follows: vs,j

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Summary

Introduction

Water–sand inrush is a most serious mine disaster in western China, in the Shaanxi province, the major energy resource centre of China [1, 2]. The entire longwall mining face and a large part of the roadways were buried, and two large cone-shaped subsidence areas were formed with a height of 12 m and diameter of 47 m and a height of 9 m and diameter of 23 m, respectively Another typical example is that of a highly serious water–sand inrush accident occurrence at the Ciyaowan coal mine of the Shenfu ore district in 1990 [6]. Over the past few years, simulation and laboratory investigations of the effects of a water–sand inrush on the hydrogeological characteristics, mechanism properties, and mining environment have been performed extensively [1, 9,10,11,12] The results of these investigations show that during the process of a water and sand inrush, the sand– water mixed fluid can migrate through the cracks and broken rock mass and swarm into the working areas. The dominant relationship between water and sand and rheological feature of a water and sand mixture fluid were revealed

Experimental Equipment
Materials and Methods
Effect of Particle Diameter and Axial Stress on Sand Grain Incipient Motion
Characteristics of Water–Sand Mixture Migration in Quartz Gravel Skeleton
Character of High-Concentration Water–Sand Mixed Fluid Migration
Sample C10
Conclusions
Full Text
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