西安市地下水与地面沉降地裂缝耦合关系及风险防控技术

Coupling Relationship between Groundwater and Ground Fissures of Land Subsidence in Xi’an City and Risk Prevention and Control Technology

西安市地面沉降地裂缝发育,世界罕见,一直是该领域研究的热点地区。近年来又出现新的发展趋势,严重制约城市发展和威胁地铁等重大工程安全运营。笔者依据254个地下水动态监测资料,总结了西安地下水资源开发历史与地下水头动态变化规律,耦合分析了地面沉降地裂缝与地下水位下降之间的关系,提出了基于地下水头管理的地面沉降地裂缝风险防控技术。结果显示:西安市地面沉降地裂缝是多种因素综合作用的结果,其发生和发展过程及其严重程度均与地下水头下降密不可分,并受黏性土层厚度的影响;空间上地下水头降落漏斗中心与地面沉降中心基本吻合,时间上地面沉降发育时间滞后地下水头降落2-3年,沉降速率是地下水头每下降1m的累计最大地面沉降量50mm;地下水头回升会引起短时和少量地面回弹量,并能够缓解或遏制地面沉降。挖掘历史地下水头与地面沉降地裂缝监测数据,建立了基于地下水头的地面沉降地裂缝预警阈值和风险防控技术。

The ground fissures of land subsidence are developed in Xi’an,which are rare in the world and have been a hot research area in this field.In recent years,new trends have emerged,seriously restricting the development of cities and threatening the safe operation of major projects such as metro.After collecting and analyzing 254 groundwater dynamic monitoring data,this paper summarizes the development history of groundwater resources in Xi’an and the dynamic change law of groundwater head,analyses the relationship between ground fissures in land subsidence and the decline of groundwater level,and puts forward the risk prevention and control technology of ground fissures in land subsidence based on groundwater head management.The results show that the ground fissures of land subsidence in Xi’an are result in the comprehensive action of many factors.The occurrence and development process of these fissures and their severity are closely related to the decline of groundwater head,which have been affected by the thickness of clay layer.The center of groundwater head depression funnel basically coincides with the center of land subsidence in space,and the development time of land subsidence lags falls behind that of groundwater head depression for 2-3 years,and then the subsidence occurs.The related rate is the accumulated maximum land subsidence of 50 mm for every 1 mdrop of groundwater head.And the rebound of groundwater head will cause short-term and small amount of land rebound,which can alleviate or restrain land subsidence.After excavated the monitoring data of historical groundwater head and ground subsidence ground fissures,the warning threshold and risk prevention and control technology of ground subsidence ground fissures has been established on the basis of groundwater head.