北京西山侏罗纪煤系变质特征与地质灾害的关系

The Relationship Between Geological Disaster and Metamorphic Characteristics of Jurassic Coal-bearing Formation in Xishan(Western Hills), Beijing

北京西山侏罗纪煤系与京东煤田和相邻省 (自治区 )的同期煤系存在诸多差异 ,尤其是在采空区地质灾害类型方面具有明显的特殊性。它既有别于周边地区同期煤系 ,也有别于同一地区下伏石炭 二叠纪煤系采空区地质灾害链。对于形成这种差异的因素研究 ,既是基础地质课题 ,也是工程地质课题。北京西山侏罗纪煤系岩石中新生矿物组合及煤层的高变质特征表明 ,煤系曾经历了绿片岩相区域变质作用的改造过程。这一改造过程可能起始于晚侏罗世早期 ,是燕山构造运动中期发生在地下 5～ 1 0km的区域变质作用。同期 (或同地区 )煤系灾害类型的差异起因于变质程度的不同。绿片岩相区域变质作用对岩石的“加工硬化” ,是北京西山侏罗纪煤系岩石及煤层强度提高的主要原因 。

There are many differences between the Jurassic coal\|bearing formations in Xishan (Western Hills) of Beijing and them in the eastern part of Beijing Municipality as well as the neighbouring provinces (or autonomous region); especially, the geological disaster type in worked\|out area of Xishan has its own specialty The geological disasters of Jurassic coal\|beating series in Xishan is different with the disasters occurred in same strata exposed areas of adjacent regions, and also different with the disasters occurred in Carboniferous\| Permian strata exposed areas of same localities The research on factors controlling this disaster specialty is a topic of fundamental as well as engineering geology The assemblage of new\|formed minerals in rocks and the high\|grade metamorphic feature of coal in Jurassic coal\|beating formation of Xishan mean that, the strata had suffered regional metamorphism of greenschist facies The metamorphism maybe began in the early stage of Late Jurassic Epoch, and occurred at 5 to 10 km depth beneath surface during Middle Yanshanian The differences of disaster's type among coal\|bearing formation exposed regions are due to the variation of metamorphism grade The work hardening effect of greenschist facies metamorphism is the main factor to increase the strength of rocks and coal beds in Jurassic coal series of Xishan, and the internal factor causing the specialty of geological disasters in worked\|out areas of Xishan's coalfields.