基于能量原理的上覆饱水砂层隧道突水灾变

A disaster with water inrush based on energy theorem in tunnels under saturated sandy stratum

基于能量原理对某地铁隧道突水突泥灾变机理进行了分析,深入揭示了大规模(11 679 m^(3))突水突泥灾害的本质是掌子面围岩失稳,既而导致上覆软弱富水地层的势能转化为动能,并得到瞬间释放。灾害现场调查发现:该地区地质构造特殊,在空间上呈"漏斗型",且底部应力集中明显;地铁左线隧道恰好穿过"漏斗"底部;隧道上覆软弱强风化凝灰岩层过薄且构造裂隙丰富;"漏斗型"地层为天然"蓄水库",灾前大量降雨导致上覆7.1 m厚中粗砂层饱和,水头升高且水量增大,势能增加,渗透力增高,围岩软化加剧。根据灾害发生位置隧道围岩条件,服从三度空间理论中的支护困难空间。基于数值模拟分析表明,当采用超前小导管加固时,考虑渗透力时掌子面不能稳定;当采用管棚注浆加固或掌子面前方围岩加固时,即使考虑渗透力,掌子面也可以稳定。综合分析,此次灾害是由于急剧增加的水压力、高围岩压力、渗透力共同作用于裂隙发育及劣化的强风化凝灰岩,导致围岩因强度不足而失稳,平衡被打破,从而饱水砂层的高势能转化为动能形成了大规模的突水突泥。

The paper aimed to investigate the natural mechanism for this water inrush and mud outburst disaster in certain subway tunnels by energy theorem. The fundamental reason why this disaster was so large( approximately 11 679 m^(3)) was that the equilibrium of the surrounding rock around the tunnel face was broken,and thus the volume of potential energy was transformed into kinetic energy and released instantaneously. Based on the field survey,some reasons were concluded as follows: the geological tectonic profile seemed like a "funnel",where stress concentration was obvious;the tunnels crossed the bottom of the"funnel";the weak and thin strongly-weathered tuff with many cracks located on the crown;the"funnel"stratum could collect a large amount of rainwater,and before this disaster,the rainfall resulted in the mediumcoarse sand being saturated,so the water-head rose,seepage force increased,and the surrounding rock was weakened.These conditions could be classified into DI space. It could be seen from the numerical simulation that,the tunnel face applied by seepage force was unstable when strengthened by leading injected conduit whereas by taking account of the influences of seepage function,the tunnel face strengthened by steel piles could keep stable. By comprehensively analysis,it could conclude that the natural reasons for this disaster were that the combined effects consisting of increasing water pressure,concentrated stresses,seepage forces,applied to the degrading rocks,and then the potential energy transforming into kinetic energy formed this disaster on a large scale.