长屿采矿遗址1997年采石塌陷及地震记录

QUARRYING-INDUCED COLLAPSE IN 1997 AND SEISMIC RECORDS AT CHANGYU CAVERN RELICS SITE

采矿塌陷在开采施工中被给予了特别关注,也是施工地质灾害重要表现形式之一。已有地震记录中不乏对其形态辨识,然而少见对塌陷机理和发生过程中能量转换等较全面的研究。温岭市长屿硐天采矿遗址区碧玉潭洞室群1997年8月11日早晨发生持续时间约20 s大塌方。现场残留了面积约31 380 m^2、体积约1.35×10~6m^3的塌陷岩体。通过现场工程地质调查、塌陷过程追溯、邻近地震台站频谱记录分析,笔者认为这次发生在凝灰岩中的大规模塌陷系因地下采石过程中保安矿柱被过量开挖掉而引发局部顶板破裂和应力分布的大改变,进而发展至整个矿区岩体塌落破坏,使矿坑积水飞溅和压缩空气冲击波带来了沿途150 m范围内人员伤亡、树木折断和财产损失。塌陷区南93 km的温州台地震波谱记录了这次采矿塌陷地震活动,其波形数据与现场塌陷破坏能量转化情况基本吻合。在采矿活动中保安矿柱的合理配置、为人员安全设置变形破坏过程监测等,是需考虑的预防塌陷措施。

Quarrying-induced collapse,an issue of particular concern in mining industry,is a typical form of manmade disaster. Identification of the morphological characteristics of such collapses is commonly based on seismic records. But comprehensive studies regarding the mechanism and energy conversion mode utilizing the seismic record are seldom undertaken. A huge collapse event occurred at the Biyutan mining cavern at Changyu Dongtian in Wenling city,China. It lasted for about 20 seconds and was observed and recorded on August 11,1997. After the collapse,nearly 1. 35×10~6 m^3 of rock blocks were left on the floor and occupied an area of about 31 380 m^2. the authors conducted a field survey on engineering geology,retrospectively analyzed the collapsing process through interviewing local residents and referring related documents,and identified the seismic records from surrounding seismic stations. The roof collapse is established at the Biyutan cavern that was excavated in massive tuff. The over excavation of several pillars substantially affected the stress field in cavern roof,which gave a rise to a local failureof the roof and then gradually developed into a widespread failure. During the collapse,outbursts of water and air shock waves resulted in loss of life and property within a distance of 150 m from the mine opening. The seismic records of Wenzhou Station 93 km south from the site revealed the collapse event,which is agreement with the energy transformation in site retrospective analysis on building failures and subject movement. This event reminds us that reasonable allocation of sufficiently strong safety pillars and installation of monitoring system are absolutely essential in underground quarrying operations to avoid overall failure and ensure the safety of the people nearby.