ABSTRACT:

There is a large number of unbound water in rich-water packing material hardening body. The stability conditions of filling body will be changed during the mining disturbance and variable load. This paper analyzed the microstructure characteristic of the hardening body by SEM. Studied the stress-strain characteristics during loading by stress-strain test. By creep experiment analyzed the characteristics of the deformation and the strain of filling body changing over the time during the creep process. As a result, ettringite is the main hydration product of rich-water filling material. The rich-water filling material of water-solid ratio is 2: I can maintain elastic deformation in a long period of time when it is subjected to external force. It no brittle destruction immediately when the load is maximum. Creep process includes two stages when once load reach 80% of filling body uniaxial compressive strength. Decay stage, stable stage and no acceleration stage. It can make sure the long-term stable of filling body.

1 INTRODUCTION

The production of mine reduced greatly, it is due to the factors of coal under building in China. So protective mining is needed urgently. Filling mining is one of the effective protective mining methods (Qian et al. 2003). Packing material is the key of filling mining. In order to reduce the cost of filling further and expand the application scope of filling mining technology. High water packing material and super high water packing material are developed (Sun & Song 1994, Feng 2009, Feng et al. 2010, Ding et al. 2011). The rich-water packing material is provided with good fluidity and low cost. However, its widely application in engineering practice is affected by its poor stability because of its high water-solid ratio.

Research has shown that the mainly hydration product of rich-water packing material is ettringite. Its strength depends on the ettringite crystals quantity, formation rate and the final stability (Feng et al. 2010). Peng Meixun (2011) found that high-water filling material is composed of columnar ettringite formed network connection. The ettringite crystals will smaller if the water content higher. Chen Hongling (2009) used aluminum sulfate to modify the high-water filling material based on sulphoaluminate cement. It could promote the formation of ettringite, improve the micro pore structure of hydrate, and increase the compactness and strength of the high-water material.

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