采空区缓冲垫层最小安全厚度分析

Study on the minimum safety thickness of goaf cushion

为了分析采空区顶部垮落过程对下部结构体的影响,文中以2号矿体采空区为背景展开分析。首先通过建立数值模型计算,确定2号矿体的平衡拱极限垮落跨度为51.38 m,冒落拱的高度为12.8 m,结果表明,上盘围岩冒落不会通达地表;然后,通过PFC2D模拟软件,建立缓冲垫层分别为14 m、16 m、18 m、20 m、22 m五种方案进行分析,通过对采空区下部结构体内部裂纹数和结构体受到的冲击力进行监测,对比理论计算结果进行分析,结果表明,当垫层厚度为20 m和22 m时,下部结构内裂纹数为0,且结构体受到的冲击力小于其所能承受的最大应力(0.525 MPa),由此可知2号矿体采空区最小安全垫层厚度为20 m,案例对比分析验证了20 m缓冲垫层厚度的合理性。

In order to analyze the influence of caving process on the substructure of goaf,the goaf of No.2 orebody is taken as the background to carry out the analysis.Firstly,the numerical model was established to determine that the ultimate caving span of the equilibrium arch of No.2 orebody was 51.38 m and the height of the riser arch was 12.8 m.The results show that the riser of the surrounding rock of the upper wall would not reach the surface.Then,by PFC2D simulation software,five schemes of cushion are established,which are 14 m,16 m,18 m,20 m and 22 m respectively.Based on the analysis of the internal crack in the lower part of the goaf and the impact force of the structure,the results show that when the thickness of cushion layer is 20 m and 22 m,the lower part structure crack number is 0,and the impact force of the structure is less than the maximum stress of it can withstand(0.525 MPa),thus the minimum safety cushion thickness of No.2 orebody is 20 m,which is verifyied by case comparison analysis.