一侧采空(煤柱)弹性基础边界基本顶薄板初次破断

建立长壁工作面,一侧采空(煤柱)、三边弹性基础边界基本顶薄板结构力学模型,运用有限差分法计算并研究了基本顶主弯矩分布特征及破断规律。得到:基本顶的起始破断位置为长边偏煤柱侧深入煤壁上表面(基本顶的弹性模量E、厚度h较小,弹性基础系数k较大时)或中部偏煤柱侧下表面(E,h较大,k较小时);煤柱的宽度Lm及支撑系数k_m变化时基本顶长边区,实体煤侧短边区以及中部区的主弯矩极值几乎不改变,但是煤柱区基本顶主弯矩极值变化显著、即显著影响煤柱侧基本顶的破断形式及基本顶整体的破断形态;由于考虑煤柱支撑的作用,当h,E较小,L_m,k_m较大时,基本顶深入煤柱区的上表面会发生破断,此种条件下基本顶的破断顺序为:长边深入煤壁上表面→中部下表面或实体煤侧短边深入煤壁上表面→煤柱区上表面,最终破断形态为非对称"O-X"型;h,E较大,L_m,k_m较小时煤柱区基本顶的上表面不破断,此种条件下基本顶的破断顺序为:中部下表面→长边深入煤壁上表面→实体煤侧短边深入煤壁上表面,最终破断形态为"U-X"型。

First fracture of the thin plate of main roof with three sides elastic foundation boundary and one side coal pillar

In long wall face,by establishing the mechanical model of the thin plate of main roof at a long wall face,one side coal pillar and three sides elastic foundation boundary,and using finite difference method,the paper calculated and studied the distribution characteristics of primary moments and fracture law of main roof.It concludes that the width of the coal pillar Lm and the pillar support coefficient km almost have no influence on the extreme values of primary moments of the long side,short side of the solid coal side and central section,but obviously affect the primary moment of coal pillar side and fracture form of the main roof.Because of the existence of pillar support area,when the thickness h and elastic modulus E of main roof are small and the values of Lm and km are large,the upper surface of main roof in the coal pillar area will not fracture.Under this condition,the fracture sequence of the main roof is that the upper surface of long side advanced coal wall→lower surface of central region or short side advanced coal wall in solid coal side→upper surface in coal pillar area,and the final fracture form is the type of asymmetric “O X”.When the values of E and h are large,and the values of Lm and km are small,the upper surface of main roof in coal pillar area will not fracture.Under this condition,the fracture sequence of main roof is that the lower surface of central region→upper surface of long side advanced coal wall→upper surface of short side advanced coal wall in solid coal side,and the final fracture form is the type of “U X”.