苏锡常地区地裂缝灾害危险性评价与预测

GIS-aid evaluation and prediction on earth fissure hazard in Suzhou-Wuxi-Changzhou area

苏锡常地区是我国近年来地裂缝灾害最为活跃的地区之一。作者在深入研究其灾害成因机理和形成过程的基础上 ,提取了基岩面起伏、浅部含水砂层差异、隐伏灰岩、浅部土层结构条件、累计地面沉降量、地面沉降速率和主采层水位共 7个主要影响因素 ,选用层次分析法确定权值 ,建立了苏锡常地裂缝危险性评价模型。以GIS软件Arcinfo为主要工具 ,利用其强大的空间分析功能 ,将各影响因素专题图层按照权重进行多重叠加操作 ,进行了不同时期地裂缝灾害危险性分区评价和发展趋势的预测。目前研究区地裂缝灾害危险性仍在增加 ,常州马杭镇与湖塘镇中间、武进横林镇铁路以北和无锡堰桥镇西北地区危险指数最大 ,是今后几年苏锡常地区防治地裂缝灾害的重点区域。

Suzhou-Wuxi-Changzhou area lies in the south of the Yangtzs River delta. It is one of the most developed areas in China. Twenty-two earth fissures have been discovered within this area and they have caused a direct economic loss of 0.5 billion Yuan RMB. So, it's very important to evaluate the harmfulness of earth fissures and predict their developing trend and to delimit the hazard-susceptible areas.The earth fissures occurred in Suzhou-Wuxi-Changzhou area are resulted principally from ground differential subsidence. Biggish undulation of the bedrock table,differential shallow aquifer and the existence of buried limestone constitute the inner factors for earth fissures. Nevertheless, excessive withdrawal of groundwater is the direct cause inducing earth fissures, and the soil texture in the sub-surface affects the growth extent of earth fissures. Seven primary factors are selected, including undulation of the bedrock table,differential shallow aquifer, existence of buried limestone, soil texture condition,accumulative land subsidence volume,land subsidence rate and the ground water level, and calculates the weight of each factor by AHP(Analytical Hierarchy Process) to generate the evaluation model of earth fissure hazard. With the help of the strong function of Arcinfo in the field of spatial analysis, the researcher overlies each of the coverage of seven factors according to their weights, evaluates the hazard divisions in different time periods and predicts the developing trend reasonably.Presently, the hazard of earth fissures in the study area is still increasing. The hazard indices of the part between Mahang and Hutang of Changzhou city,the north of railway in Henlin of Wujin city and the west-north of Yanqiao in Wuxi city are the biggest among the Suzhou-Wuxi-Changzhou area. The result of this study suggests that they are the major work areas of hazard prevention and mitigation in the next few years.