Abstract
The gob-side entry retaining plays an important role in improving working face ventilation, alleviating working face connection, and increasing mining revenue. According to the characteristics of the crossheading roof at the 2103 working face of a mine in Shanxi, a structural mechanics model of the roof was established to derive the theoretical formulae for the ultimate hanging arch length of the layered roof with anchors and the initial support resistance of the entry-side support. The influence factors of the ultimate hanging arch length were evaluated using local sensitivity analysis. Based on the theoretical study, the work proposed the collaborative support technology of the crossheading, collaborative support at the 2103 working face. The results showed that the ultimate hanging arch length was most influenced by the width of the plastic zone, followed by the width of the roadway, supporting strength, anchoring strength, layered thickness, and mining depth, while the ultimate tensile strength had little influence. The initial support resistance of the entry-side supports was closely related to the ultimate hanging arch length and the process of gob-side entry retaining. The improved entry-retaining supporting process could control the sharp surface convergence of the surrounding rocks of the entry retaining, the sinkage of the roof of the entry-retaining section was controlled below 100 mm, and that of the advanced section was controlled below 50 mm. The stability of the supports next to the entry is improved, and the needs of the site project are met.
Highlights
Gob-side entry retaining retains the haulage roadway of the upper-section working face for ventilation of the lowersection working face by strengthening the supports or using other effective methods after the upper section of the working face has been mined [1,2,3,4]
When the parameters fluctuate within the same range, increased Δl caused by mining depth, stratification thickness, and ultimate tensile strength are all below ±0.02 m, which means that the hanging arch length is less affected by these three factors
We studied the ultimate hanging arch length of the layered roof with anchors and the gob-side entry retaining by theoretical analysis, numerical simulation, and field test. e following results were obtained: (1) A simplified mechanical model of the cantilever beam in the stable period of the layered roof with anchors was established, and the theoretical formula of its ultimate hanging arch length was derived . e local sensitivity analysis method was used to study the priority of the influencing factors of the ultimate hanging arch length. e width of the plastic zone had the greatest influence on the hanging arch length, followed by the width of the roadway, support strength, anchorage strength, layered thickness, mining depth, and the ultimate tensile strength orderly
Summary
Gob-side entry retaining retains the haulage roadway of the upper-section working face for ventilation of the lowersection working face by strengthening the supports or using other effective methods after the upper section of the working face has been mined [1,2,3,4]. E design principles of controlling the support resistance of the filling body along the gob-side entry retaining at each stage are determined to establish the corresponding mathematical model of support. Wu et al [16], aiming at the control problem that the roof of the deep shaft along the gob-side entry retaining was difficult to form the bearing structure or even the topping disaster, integrated field research, theoretical analysis, and actual measurement methods and classified the deformation and damage forms in depth. E research results are of great practical guidance for the control of the top slab of the gob-side entry retaining and the understanding of the interaction mechanism of the surrounding rock and support.
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