School of Energy and Mining Engineering, China University of Mining and Technology-Beijing
Beijing Key Laboratory for Precise Mining of Intergrown Energy and Resources, China University of Mining and Technology-Beijing

切顶留巷工程实践中切顶高度和角度是直接影响因素，而顶板厚度变化范围较大的坚硬顶板所允许的合理切顶参数又有其特殊性。以同忻矿2号煤层北翼三盘区切顶留巷实践为工程背景，基于现场切顶留巷厚基本顶难以垮落形成大面积悬顶造成留巷效果差的事实，通过现场调查、理论建模研究、数值模拟分析及工业性试验相结合的方法研究了随坚硬顶板厚度变化的合理切顶参数。调查研究发现固定的切顶高度是无法适应顶板厚度的变化，在较小的基本顶厚度情况下，留巷效果较好，在较大的基本顶厚度情况下，留巷围岩变形较大。建立了切顶留巷力学模型，推导了未切顶部分拉应力与切顶高度、角度和顶板厚度的关系，得出在相对较小的切顶角度范围之内，随着切顶角度的减小，未切顶面处所受到的拉应力增大，且随着切顶高度的增加拉应力增加的越显著；未切顶处拉应力大于基本顶极限抗拉强度所允许的合理切顶角度范围随着基本顶厚度的增加而减小，从工程实践来看可以达到减小悬顶长度的目的；在一定基本顶厚度条件下，未切顶处拉应力大于基本顶极限抗拉强度所允许的切顶角度范围随着切顶高度的增加而增大，即切顶高度越高，对切顶角度的限制越小；基本顶厚度越大，未切顶面拉应力达到相同值所需的切顶高度越大，基本顶厚度较小时，切顶角度变化对未切顶面拉应力影响较小，随着基本顶厚度的增大，切顶角度影响程度增大。从顶板断裂面凹凸程度、巷道顶板裂隙发育特征、巷道顶板下沉情况、完成时间步数4个指标进行数值模拟分析，得到科学实施部分切顶方案，使未切顶部分在矿山压力作用下完成垮落，就可以达到工程实践目的。基于上述研究在现场进行工业性试验，以顶板变形量和切顶侧支架工作阻力为指标对留巷进行现场监测分析，结果表明留巷效果良好。

In the engineering practice of gob side entry retaining by roof cutting, the height and angle of roof cutting are the direct influencing factors, and the reasonable roof cutting parameters allowed by the hard roof with a wide range of roof thickness change have their particularity. Taking the practice of gob side entry retaining by roof cutting in the third panel of the north wing of coal seam No.2 in Tongxin Coal Mine as the engineering background. Based on the fact that difficulty of the thick main roof to collapse and form a large area of suspended roof, resulting in poor roadway retention effect, the reasonable roof cutting parameters varying with the thickness of the hard roof are studied through the combination of field investigation, theoretical modeling research, numerical simulation analysis and industrial test. Detailed field investigation and research found that the fixed cutting height could not adapt to the change of roof thickness. Under the condition of small main roof thickness, the effect of gob side entry retaining was better, and under the condition of large main roof thickness, the deformation of roadway surrounding rock was larger. The mechanical model of gob side entry retaining by roof cutting is established, and the relationship between the tensile stress of uncut part with the cutting height, angle and roof thickness is derived. It is concluded that within the relatively small range of cutting angle, the tensile stress on the uncut roof surface increases with the decrease of cutting angle, and the tensile stress increases more significantly with the increase of cutting height; with the increase of main roof height, the reasonable range of cutting angle allowed by the tensile stress at the uncut roof greater than the ultimate tensile strength of the main roof decrease. From the perspective of engineering practice, the purpose of reducing the length of suspended roof can be achieved; under certain main roof thickness, with the increase of cutting height, the range of cutting angle allowed by the tensile stress at the uncut roof greater than the ultimate tensile strength of the main roof increases, that is, the higher cutting height is, the smaller limit on the cutting angle is; the greater the thickness of main roof, the greater cutting height required for the tensile stress of uncut roof face to reach the same value. When the thickness of main roof is smaller, the change of cutting angle has little effect on the tensile stress of uncut roof face. With the increase of main roof thickness, the influence of cutting angle increases. The numerical simulation analysis is carried out from the four indicators of concave convex degree of roof fracture surface, the development characteristics of roadway roof fissures, the roadway roof subsidence and the completion time steps. It is concluded that the purpose of engineering practice can be achieved by scientifically implementing the partial cutting roof scheme and making the rock stratum of non cutting roof collapse under the action of mine pressure. Based on the above research, the industrial test is carried out in the field, and the on-site monitoring analysis was carried out on the reserved roadway with the roof deformation and the working resistance of support on the roof cutting side as indicators, and the results show that the effect of gob side entry retaining is good.

国家自然科学基金资助项目(51974317)；中央高校基本科研业务费专项资金资助项目(2022YJSNY09)

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XU Xuhui，HE Fulian，LÜ Kai，et al. Research on reasonable cutting roof parameters of gob side entry retaining by roof cutting in thick and hard roof[J]. Journal of China Coal Society，2023，48(8)：3048−3059.