栖霞中桥地区岩溶塌陷时空分布规律及成因分析

岩溶塌陷是岩溶地区一种特有的地质灾害,在时间上具有突发性,空间上具有隐蔽性.栖霞中桥地区位于山东省胶东半岛中北部,区内分布岩溶地层,岩溶发育较为强烈,近年来随着周边人类工程活动强度增大,加之一些自然因素影响,先后发生多次岩溶塌陷,给区内人民群众生产和生活带来了较大影响.以栖霞中桥地区作为研究区,通过收集资料、实地勘查、地球物理勘探、钻探、抽水试验、水位监测等工作方法取得本区岩溶塌陷、地层、降水、水位等翔实资料,研究分析了本区岩溶塌陷的时空分布规律:时间上主要发生于枯水期与丰枯交替时期,空间上多发生于覆盖型岩溶区岩溶水径流通道的两翼且地下水水力坡度急剧变化地段,均为断裂构造上盘区,第四系厚度多小于25 m,为黏性土与砂土互层的多层结构,与基岩面接触的岩性为粉质黏土及碎石土.在此基础上,分析了该区地下水位、降水变化对岩溶塌陷的影响机理:塌陷发生期间,区内地下水水位呈持续下降、骤然上升或上下起伏变化,已形成的土洞负压与高压相互交替,对土洞顶板产生吸力与压力,剪应力快速降低,岩溶地层上覆土体无法承受自身重力条件下引发岩溶塌陷,是潜蚀、真空、气爆及重力作用相互作用的结果,以潜蚀、真空效应为主.为栖霞市各级政府及相关主管部门开展岩溶塌陷地质灾害防治、地区规划建设等提供地质科学依据,为胶东半岛岩溶塌陷后续相关分析研究工作提供翔实的理论基础.

Temporal and spatial distribution and genesis analysis of karst collapse in Qixia Zhongqiao area

Karst collapse is a special geological disaster in karst area, which is sudden in time and hidden in space.Qixia Zhongqiao area is located in the middle and north of Jiaodong Peninsula, Shandong Province. Karst strata are distributed in the area, and karst development is relatively strong. In recent years, with the increase of the intensity of human engineering activities around, coupled with the influence of some natural factors, multiple karst collapses have occurred successively,which has brought great impact on the production and life of the people in the area. In this paper, Qixia Zhongqiao area is taken as the research area. Through collecting data, on-the-spot investigation, geophysical exploration, drilling, pumping test, water level monitoring and other working methods, detailed data of karst collapse, karst stratum, quaternary overburden, precipitation, water level change, etc. in this area are obtained, and it is studied and analyzed that the karst collapse in this area has a certain spatial-temporal distribution law: it mainly occurs in time In the period of alternation between dry season and dry season, it occurs in the two wings of karst water runoff channel in covered karst area and the section where the hydraulic gradient of groundwater changes sharply. It is the upper plate area of fracture structure. The lithology is limestone. The thickness of quaternary system is more than 25m. The soil layer is the multi-layer structure of clay and sand soil. The lithology contacting with the bedrock surface is silty clay and gravelly soil. On this basis, the influence mechanism of the change of groundwater level and precipitation on the karst collapse is analyzed: during the collapse, the groundwater level in the area shows a continuous decline, a sudden rise or a fluctuation change, the negative pressure and high pressure of the soil cave alternates with each other, the suction and pressure of the soil cave roof are produced, the shear stress is rapidly reduced, and the overlying soil body of the karst stratum cannot bear its own gravity the karst collapse is caused by the interaction of potential erosion, vacuum, gas explosion and gravity. It provides geological scientific basis for Qixia governments and relevant competent departments to carry out the prevention and control of karst collapse geological disasters, regional planning and construction, and provides detailed theoretical basis for the follow-up related analysis and research work of karst collapse in Jiaodong Peninsula.