平谷地裂缝基本特征与成因分析

Characteristics and Genesis Analysis of Pinggu Ground Fissures

平谷地裂缝是平谷盆地内一类重要的地质灾害,近年来,裂隙有所加剧,已经影响了人们的生产生活。为此,对平谷地裂缝及隐伏夏垫断裂北段进行勘探研究,总结了平谷地裂缝的基本特征,讨论了地裂缝发育的成因机制及其与隐伏夏垫断裂关系。结果表明:平谷地裂缝主要分布于古白河冲洪积扇地下水溢出带,沿今错河河道分布,主要发育为北东或北西向两组,性质为张裂隙;地裂缝发育长度、深度规模有限,一般埋深7~8 m,无“断裂根”构造;地裂缝浅表层充填震动砂脉,揭示了震动液化的根本成因,而现今呈现裂缝塌陷是早期震动液化裂隙在降水或灌溉淋滤作用下砂土流失表现;隐伏夏垫活动断裂构造可能制约了平谷地裂缝发育位置和地裂缝分布特征,断裂带附近应力集中和节理破裂可能是地裂缝发育的构造基础。

As an important geological disaster in the Pinggu Basin,the Pinggu ground fissures have exacerbated and affected people’s normal production and living in recent years.Therefore,through the exploration of the Pinggu ground fissures and the northern section of the buried Xiadian fault,the fundamental characteristics of the Pinggu ground fissures were summarized,and the genetic mechanism of ground fissures evolution and its relationship with the Xiadian buried fault were discussed.The results show that the Pinggu ground fissures are mainly distributed in the underground water overflow zone of the ancient Bai River alluvial fan,along the modern Cuo River channel,and they are classified as tensil fractures that developed well in NE and NW direction.The ground fissures with alimited range of length and depth,are generally buried in 7~8 m without“fault root”structure.The fundamental cause of vibrating liquefaction is revealed by the sand veins,which filled in the shallow surface layer of ground fissures,and the current fracture collapses are caused by the precipitation or irrigation leaching of sand soil loss in early vibrating liquefaction fissure.The development location and distribution characteristics of the Pinggu ground fissures may be restricted by the Xiadian buried active fault structure.Stress concentration and joint fractures near the fault zone may be the structural basis of ground fissures.