陕西韩城桑树坪煤矿3315工作面回采巷道采用留设沿空巷道窄煤柱，但由于受残余动压、煤体水力冲孔等影响沿空巷道变形剧烈，施工困难，顶板破碎，后期返修频繁，变形量极难控制。为提出最优支护方案，有效的控制围岩变形，需对窄煤柱加固机理及沿空留巷围岩稳定性进行研究。基于此，综合运用了理论分析、相似模拟、数值模拟及现场实测等技术方法，探讨了对拉锚索在窄煤柱双向加固技术的实际应用效果，分析了对拉锚索的作用机理和变化规律，为双向加固技术应用于沿空巷道窄煤柱加固工程提供了坚实的理论依据，主要结论如下：

（1）现场调研分析得出3315回风巷围岩控制关键难题为：①当3317回顺开挖，煤柱体处于塑性状态，受力状态更加复杂，进一步导致煤体强度降至残余强度，承载能力进一步下降。②由于自旋锚杆支护力的滞后性，以及在3317回顺掘巷期间施工的不协调性，导致支护结构未能及时形成有效的力学联系，限制了对煤柱承载力的提升。尽管锚杆表面未见明显断裂，实际上锚杆作为一个整体发生外移，其锚固点分布在煤柱的中央和侧壁，由于煤柱已进入塑性状态，内部裂隙增多，缺乏有效的中央残余应力恢复区，使锚固效果受限。

（2）基于3315工作面关键硬岩层破断的特性，构建了关键三角板块结构力学模型，评估了掘进阶段和回采阶段煤体对上覆关键岩块的支撑力以及弧形三角岩块的受力情况，确保窄煤柱顶部弧形三角岩块稳定；建立了实体煤弹塑性力学模型，分析了其上部承受的覆岩压力分布规律，结合侧向支承压力峰值表达式和窄煤柱留设合理宽度，代入参数，考虑到煤层为三软煤层，需在原支护基础上进行加强支护。

（3）以3315工作面沿空巷道窄煤柱为研究对象，基于相似原理，设计试验方案，对对拉锚索加固煤柱承压性能进行研究。分别开展了原支护及优化支护等多种方案下的相似模拟试验，对拉锚索加固下的模型较未加固模型承载力有了显著提高，且随着间排距减小，承载强度在提高。当加载到最大外部荷载时，双排对拉锚索和四排对拉锚索的小间距模型均未发生破坏，变形量不大，可以起到加固煤柱的目的。

（4）根据实际工况建立数值分析模型，并基于理论分析和相似模拟试验的结果，模拟原支护和加强支护方案下沿空巷道围岩变形特征，研究得出原支护方案下工作面的回采对沿空巷道造成应力叠加，应力集中系数增大，随着矿山压力增加，煤柱帮一侧顶板将会形成贯通性裂隙至煤柱帮底部。但双向对拉锚索加固使围岩整体强度提高，使集中应力系数变小，能够有效抵抗顶板来压，同时限制了围岩进一步滑移破坏，并且控制围岩变形量。

（5）针对桑树坪煤矿3315回顺巷道变形量极难控制的问题，设计了新型对拉锚索，提出双排对拉锚索加固煤柱为最优加强支护方案，应用于现场并进行数据监测，分析监测数据得出采用最优加强支护方案的巷道帮部收敛量平均仅为37.3mm，顶板的平均下沉量为21.6mm，围岩的平均变形量仅为原支护方案的18.6%。此外，巷道顶板的离层量也较小，围岩稳定后平均深部位移仅为原支护方案的17.8%，提出的最优加强支护方案对控制沿空巷道围岩变形有效性显著，同时验证了研究方法的科学性。

Shaanxi Hancheng Sangshuping coal mine 3315 working face back to mining roadway using leave along the empty roadway narrow coal pillar, but due to the residual dynamic pressure, coal hydrodynamic punching and other impacts along the empty roadway deformation is intense, construction difficulties, the roof plate is broken, the later return to repair frequently, the amount of deformation is extremely difficult to control. In order to propose the optimal support scheme and effectively control the deformation of the surrounding rock, it is necessary to study the reinforcement mechanism of the narrow coal pillar and the stability of the surrounding rock along the hollow stay roadway. Based on this, the theoretical analysis, similar simulation, numerical simulation and field measurement and other technical methods are comprehensively used to explore the practical application effect of the two-way reinforcement technology of the pulling anchor cable in the narrow coal column, and analyse the mechanism of the role of the pulling anchor cable and the change rule, which provides a solid theoretical basis for the application of the two-way reinforcement technology in the reinforcement of the narrow coal column along the empty roadway, and the main conclusions are as follows:

(1) The key difficulties in controlling the surrounding rock of 3315 back to the wind tunnel were analysed from the on-site research: ①When 3317 back to the excavation, the coal pillar body was in the plastic state, and the stress state was more complicated, which further led to the strength of the coal body dropping to the residual strength, and the bearing capacity was further reduced. Due to the lagging of the support force of the spinning anchors and the uncoordinated construction during the excavation of 3317, the support structure failed to form an effective mechanical connection in time, which limited the enhancement of the bearing capacity of the coal pillar. Although the surface of the anchor rods did not see any obvious fracture, in fact, the anchor rods as a whole shifted outward, and their anchorage points were distributed in the centre and sidewalls of the coal column, which limited the anchorage effect due to the fact that the coal column had entered the plastic state, the internal fissures increased, and the lack of an effective central residual stress recovery zone.

(2) Based on the characteristics of breaking the key hard rock layer in the 3315 working face, a structural mechanics model of the key triangular slab was constructed to evaluate the support force of the coal body on the overlying key rock block and the force of the arc-shaped triangular rock block at the stage of digging and mining back to ensure the stability of the arc-shaped triangular rock block on the top of the narrow coal pillar; an elasticity-plasticity mechanics model of the solid coal was established to analyse the distribution law of the overlying pressure on the overlying rock borne by the upper part of the coal body, and combined with the expression of the peak value of the support pressure and the reasonable width left for the narrow pillar to substitute the parameters. The expression of peak bearing pressure and the reasonable width of the narrow coal pillar are substituted into the parameter, considering that the coal seam is three soft coal seams, the support needs to be strengthened on the basis of the original support.

(3) Taking the narrow coal pillar along the open roadway of 3315 working face as the research object, based on the principle of similarity, the test scheme was designed to study the pressure-bearing performance of the coal pillar reinforced by pulling anchor cable. Similar simulation tests were carried out under the original support and optimised support schemes, and the load carrying capacity of the model reinforced with tie-anchor cables was significantly improved compared with that of the unreinforced model, and the load carrying strength was improved with the reduction of the spacing between the rows. When loaded to the maximum external load, the small spacing models with two rows of tie-anchors and four rows of tie-anchors were not damaged, and the deformation was not large, which could serve the purpose of reinforcing the coal pillar.

(4) Numerical analysis model is established according to the actual working conditions, and based on the results of theoretical analysis and similar simulation tests, the deformation characteristics of the surrounding rock along the open roadway under the original and reinforced support scheme are simulated, and the study concludes that the return of the working face under the original support scheme causes the superposition of stresses on the roadway along the open roadway, and the concentration coefficient of the stresses increases, and with the increase of the pressure in the mine, the roof plate of the side of the coal pillar gang will form a penetrating fracture to the bottom of the coal pillar gang. However, the two-way tensile anchor cable reinforcement improves the overall strength of the surrounding rock, so that the concentrated stress coefficient becomes smaller, and can effectively resist the roof to pressure, and at the same time limit the further slippage damage of the surrounding rock, and control the amount of deformation of the surrounding rock.

(5) Aiming at the problem that it is extremely difficult to control the deformation of 3315 return roadway of Sangshuping Coal Mine, a new type of tie-back anchor cable was designed, and the optimal strengthening support scheme was proposed to strengthen the coal pillar with double rows of tie-back anchor cables, which was applied in the field and data monitoring was carried out, and the analysis of the monitoring data showed that the average amount of convergence of the gang part of the roadway using the optimal strengthening support scheme was only 37.3mm, and the average amount of roof plate sinking was 21.6mm.The average deformation of the surrounding rock is only 18.6% of the original support scheme. In addition, the amount of the roadway top plate is also smaller, and the average deep displacement of the surrounding rock after stabilisation is only 17.8% of the original support scheme. The proposed optimal strengthening support scheme is effective in controlling the deformation of the surrounding rock along the open roadway, and it also verifies the scientific validity of the research method.

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