Study On Mechanical Model Of The Key Stratum Under The Support From Grouting Into The Isolated Areas Within Overburden

In recent years, technology of grouting into the isolated areas within overburden has successfully controlled the surface subsidence of single mined-out panel in Huaibei mining area. Extraction of adjacent panel, however, inevitably leads to the increase of the overlying strata subsidence of the first panel. And its mechanical mechanism of interior rock movement is not clear. Therefore aiming at such a practical problem, this article abstracts a mechanical model regarding the primary key stratum and analyzes it.On the basis of key strata theory and theory of the elastic foundation beam, theoretical derivation of the mechanical model under the support of the injected grouting is carried out. And then the paper gives the main research results:(1)Deflection equation of the primary key stratum in single or double face mining after overburden grouting is solved.(2)With the theoretical derivation of the mechanical model under the support of grouting,two factors that influence the subsidence of the primary key stratum under the grouting into overburden separation are analyzed. Results showed that the deflection of any point on the key stratum almost linearly increase with the decreasing of injection-production ratio; From the relationship of the key strata subsidence and the grouting elevation, the higher grouting elevation is, the smaller the key strata subsidence is.(3)With the theoretical derivation of the mechanical model under the support of grouting, the paper studies the influence of the isolated coal pillars on the subsidence of the primary key stratum when mining the neighboring panel as well. With calculation, this paper hold the opinion that the required pillar width differs from different geological conditions, but there exists a minimum pillar width with which the adjacent mining face would be isolated from the influence of the next working face. This also shows that the increase of the overlying strata subsidence of the first panel after the extraction of the second panel results from the compression of the pillar between the two panels.(4)The numerical simulation verifies the theoretical results. They show that the mechanical model of elastic foundation beam of the primary key stratum is correct.There are 23 figures, 4 tables and 108 references in this thesis.