Geological conditions of strata, properties of rocks, and results of classification of rock masses at Chuankou Wolfram mine are introduced briefly. Bases on the in-situ investigation and survey in underground, the comparison sketch of boundary of underground excavating opening and the collapse border of surface is presented; and caving characteristics is analyzed and a typical collapse of straight part of covering strata is proved. According to the different ratings of joint-fissure between country rockmass of opening and covering strata, Terzaghi＇s theory is used to explain the mechanism and fracturing characteristics of country rockmass surrounding the opening and covering strata. Then Terzaghi＇s theory is improved according to the properties of rockmasses, and pressure formula is derived ; for the more, limited equilibrium method is employed for analyzing the stability of covering strata with different mining spans. On condition that the collapse does not occur, the quantitative relationships between safe mining spans and coefficients with different heights of covering strata.%介绍了川口钨矿塌陷区岩层的地质条件、岩石的力学性质和工程地质调查与评价的结果;通过井下和地表现场调查和勘察测定,给出了井下采空区的边界范围和地表塌陷范围的对照图,分析了上覆岩层的塌陷特点,确定了采空区上覆岩层呈现典型的筒状直壁塌陷。根据采空区围岩和上覆岩层的节理裂隙发育程度不同,采用太沙基地压理论解释了采空区周边围岩和上覆岩层的力学作用机理和破坏特点,对太沙基理论进行了改进,并给出了力学分析图、推导了地压计算公式;进而采用极限破坏理论对不同开采跨度时上覆岩层的稳定性进行了分析和计算,并给出了在保证不产生筒形塌陷条件下、不同覆盖层厚度时的安全开采跨度和安全系数之间的量化关系。
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