北京宋庄地裂缝灾害特征及影响因素分析

摘要

近年来由于北京市平原区地裂缝灾害凸显,不仅加速地表水土流失,而且对灾害区基础设施建设造成严重影响.为分析地裂缝形成原因,缓解及减轻地裂缝灾害造成的经济、财产损失,本文以新发现的宋庄地裂缝作为靶区,通过地质调查、In SAR监测、槽探、钻探等方法,揭示了宋庄地裂缝空间发育特征,从地质构造、地层岩性、地面沉降等方面,深入分析成因.结果显示:(1)宋庄地裂缝影响长度达8.7 km,NEE向延伸,受灾体主要展现出拉张形变;(2)区域拉张应力场为宋庄地裂缝形成提供内动力条件,构造影响下的第四系沉积厚度差异及地层岩性不均一,为宋庄地裂缝形成提供重要地质背景;(3)南苑—通县断裂为宋庄地裂缝形成提供了应力积累和传递媒介;(4)地下水超采引发的土体水平、垂向变形是地裂缝形成的诱发条件.受基底伸展变形、隐伏断裂及地下水开采影响,土体发生水平及垂向变形,使得在非饱和带断层区附近形成拉应力集中区,当达到土体抗拉强度时,形成盲裂缝,在雨水侵蚀或潜水位回升作用下,扩展至地表形成裂缝及串珠状土洞.%In recent years, the occurrence of geological fracture disaster has increased at the Beijing Plain. The geological crack disaster accelerates soil erosion and impacts negatively on infrastructure construction in the area.This paper aims to analyze the generation of geological cracks and reduce the potential losses of economy and property. With geological survey, InSAR monitoring, trenching and drilling methods, the spatial characteristics ofground fissures at Shongzhuang Village are investigated. The factors responsible for the ground fissures and the occurrence mechanism are analyzed based on geological structure, lithology and land subsidence. The conclusions are as follows. (1) The ground fissures at Songzhuang Viallge are sourced at Xiaozhong River, extend along the way through the Shuangbutou Village quay, Gouqu Village, Dapang Village, and end at the Pingjiatuan Village. Its influencing length is up to 8.7 kilometers and extends to the NEE direction. The houses, walls and pavements along the fissures have been damaged to varying degree. The affected objects exhibit tensile deformation. (2) Under the influence of tectonics, the thickness of the Quaternary sedimentary strata is different in two sides of the fissures. The difference in regional sedimentary environment leads to the heterogeneity of stratum lithology. Both of them are the important geological background for the formation of the fissures. (3) Nanyuan-Tongxian fault zone, conceals in the lower part of the ground fissure turn out to be a tensional fracture. Although moving under the ground, it provides the geological conditions for the accumulation and transmission of stress for the formation of the fissures. (4) The long-term and excessive exploitation of groundwater resources has changed the stable environment of the soil, and caused the horizontal and vertical deformation of the soil. The two kinds of deformations altogether caused the ground fissure. The superimposed effects of extensional deformation basement, buried fracture and groundwater overexploitation are the causes of horizontally or vertically compression of soils. The tensile stress concentrated zone is formed near the fault zone in the unsaturated zone. When the stress reaches the tensile strength of the soil, a blind crack is formed. The blind crack is extended to the surface due to rain erosion or of phreatic water table going up and developed to geological cracks and beads-like collapses.