Abstract
In grouting support projects, due to the small concealment of micro-fractures, the support effect often fails to meet design requirements. The percolation effect is a common factor that causes grouting failure, and the influence of grouting pressure on the percolation effect is very obvious. In this article, a design of a micro-fracture grouting experimental system is presented that can realize high-pressure grouting and then uses a variety of ultrafine cements to carry out high- and low-pressure grouting tests under different fracture opening conditions, thereby obtaining the grouting pressure and accumulated grouting weight during the grouting process. The results show that a combination of the grouting pressure curve and the cumulative grouting weight curve can determine whether the ultrafine cement will have a percolation effect. Increasing the grouting pressure can reduce the critical fracture opening value and also reduce the occurrence of the percolation effect. The research results provide a theoretical basis for the high-pressure grouting of micro-fracture rock masses and offer certain guiding significance for the design of high-pressure grouting support schemes.
Highlights
With the continuous reduction of shallow coal resources, coal mines in many areas have entered the mining stage featuring wells thousands of meters deep [1]
High- and low-pressure grouting experiments of various ultrafine cement grouting under different fracture opening conditions were carried out, and the grouting permeability characteristics under different conditions were obtained
The results show that a combination of the grout pressure curve and the cumulative grout weight curve can determine whether the ultrafine cement has a percolation effect
Summary
With the continuous reduction of shallow coal resources, coal mines in many areas have entered the mining stage featuring wells thousands of meters deep [1]. Deep coal mining is exposed to high in situ stress and poor surrounding rock lithology, which makes it difficult to support mine roadways. Under the action of high in situ stress, the fractures in the surrounding rocks of the roadway are commonly squeezed closed or squeezed into micro-fractures with small openings [4,5,6]. Due to the concealment of these micro-fractures, the supporting effect is poor. Under the action of long-term seepage factors, the surrounding rock mass of the roadway becomes seriously weakened, causing the roadway to significantly deform, affecting the construction progress and even causing casualties [7,8]
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