北京平原区地裂缝受灾体形态特征及影响因素

Characteristics of disaster-affected bodies and influence factors for earth fissure in Beijing Plain

在调查和监测中发现北京平原区地裂缝受灾体灾害表现形式不同,具有显著的区域特点。为揭示其形成过程,指导地裂缝防治工作,本文以宋庄地裂缝、高丽营地裂缝两处典型地裂缝作为靶区,从受灾体、剖面、深度、活动四方面揭示两处地裂缝形态特征,分析不同因素对二者差异化形态特征塑造的影响。结果显示:(1)宋庄地裂缝受灾体表现出明显的拉张变形,剖面上地裂缝上宽下窄铅直纵向延伸,深部未与隐伏断裂重接复合;高丽营地裂缝受灾体表现为显著的垂向错动及剪切破坏,剖面上地裂缝曲折纵向延伸,错开上下两盘地层,深部与隐伏断裂重接复合。(2)地震及区域应力场对两处地裂缝的水平形态特征进行塑造;地下水超采引发的土体差异性水平运动形成的拉应力作用于宋庄地裂缝,并对宋庄地裂缝形态进行再次塑造;高丽营地裂缝继承了黄庄—高丽营断裂形态特征;小区域差异沉降对垂向形态特征进行再次塑造。(3)宋庄地裂缝发育主要受地下水开采影响,对此类地裂缝防治应实施地下水减采、压采限采等方式,高丽营地裂缝发育受地下水开采及隐伏断裂双重影响。对此类地裂缝的防治除控制水位下降外,还需实时监测隐伏断裂活动情况,建立有效的预警预报体系。

In the investigation and monitoring,it is found that the forms of the ground fissure disaster body in the Beijing plain area are different and are of remarkable regional characteristics.This paper aims to reveal the formation process and guide the prevention work of the earth fissures.Two typical ground fissures,namely the Songzhuang fissures and Gaoliying fissures,are selected in this study.The morphological characteristics of the Songzhuang and Gaoliying fissures are investigated,including the affected bodies,profiles,depths and activity aspects.The different morphological characteristics of the occurrence for the Songzhuang and Gaoliying fissures are analyzed based on varieties factors.The results indicate that(1)the affected body of the Songzhuang fissure exhibits obvious tensile deformation,the fissures extend vertically in trench.It is not in contact with the buried faults.The fracture affected body of the Gaoliying fissure shows obvious vertical dislocation and shear,and it extends with zigzag feature in trench,and offsets the strata.It is compounded with the buried faults.(2)The level morphological characteristics of the ground fissures are influenced by the earthquake and the regional stress field,and the morphology of the ground fissures in Songzhuang is reshaped by concentration of tensile stress,which were developed by the horizontal movement of soil mass caused by groundwater overdraft.The Gaoliying ground fissures inherits the morphological characteristics of the Huangzhuang-Gaoliying fault,and differential settlement in the small area accelerates the development of the Gaoliying fracture.(3)Groundwater exploitation is the main factor affecting the Songzhuang fissures.Groundwater exploration should be reduced for prevention and control of the ground fissure.Both the buried faults and groundwater exploitation are the main factors for the developmennt of the Gaoliying crack.For prevention and control of the ground fissure,decline in groundwater levels should be limited,real-time monitoring of the fault activities is needed,and an effective warning and forecasting system is established.