在支承压力分析中通常认为,从煤壁到支承压力峰煤层处于屈服软化状态,支承压力峰前方煤层处于弹性状态,忽略了软化与弹性状态之间还存在硬化状态。针对此问题,将煤层分为煤壁附近的软化区、支承压力峰前的硬化区和再前方的弹性区,提出煤层硬化和软化区支承压力表达式,给出各区段煤层支承压力连续的确定法,在已有研究基础上,推导得基于煤层弹性、硬化和软化区支承的周期来压前坚硬顶板的挠度方程。据所得表达式用Matlab给出弹性、硬化、软化区参数变动时煤层对顶板的支承压力和相应坚硬顶板弯矩分布算例。结果表明:煤层任一区段的参数变动会引起其他区段支承压力变化;在假定煤壁处煤层残强为0的条件下,顶板弯矩峰超前距为6.04 m,越过软化区而处于煤层硬化区段。将所得结果与仅有弹性和软化区支承(假定)的顶板弯矩进行比较,发现前者的顶板挠度、弯矩峰值及弯矩峰超前距,均显著大于后者的对应量值。在对前者的煤层支承压力和顶板弯矩数据作深入分析后,得到一个重要认识:煤层软化区支承压力(反力)形成的反弯矩小,相应顶板的弯矩峰值和弯矩峰超前距就大。究其原因是,顶板与煤层是承受上覆荷载的共同体,煤层软化区支承压力形成的反弯矩小,顶板便要通过加大弯曲范围和弯曲变形程度抵抗其上覆荷载,这使得顶板的弯矩峰超前距和弯矩峰值必须增大。
It was usually considered that the yield soften state of coal seam was derived from coal wall to abutment pressure peak in coal seam and coal seam was in elastic state in front of the abutment pressure peak. The hardening state between the soft and elastic state was neglected. Given this above,the coal seam was divided into the softened zone near the coal wall,the hardened zone in front of peak abutment pressure and the elastic zone ahead again. Then expressions of abutment pressure in hardened and softened zone of coal seam were proposed and determination methods of abutment pressure in each section of coal seam were continuous. On the basis of reference [13],expressions of deflection of hard roof supported by elastic zone,hardened zone and softened zone of coal seam were derived before periodic weighting. According to the expressions,cases of abutment pressure of coal seam to roof and corresponding bending moment distribution curve of hard roof were given by Matlab when the elastic,hardening and softening zone parameters were changed. From the above,the changeable parameters of any section of the coal seam could cause the change of abutment pressure in other sections. Pre-distance of bending moment peak of the roof was 6.04 m which had crossed the softening zone and was in coal seam hardening section under the assumption that the coal seam residual strength was 0. Compared the cases with abutment pressure and corresponding roof bending moment under the assumption that only supported by elastic and softening zones,the roof deflection,peak bending moment and pre-distance of bending moment peak of the former were significantly greater than the corresponding value of the latter. After the analysis of abutment pressure of coal seam and the corresponding roof bending moment data of the former,an important understanding was obtained that anti bending moment formed by abutment pressure of softening zone in coal seam was small,thecorresponding peak value of bending moment and pre-distance of bending moment peak of the r