湖南郴州地区岩溶塌陷分布规律及其影响因素浅析

Distribution and influence factors of sinkholes in the Chenzhou area,Hunan Province

通过地质环境调查,分析湖南郴州地区岩溶塌陷分布规律及其影响因素,结果表明:(1)1980-1983年为岩溶塌陷盛发期,平均8.5个·年^(-1);2012-2020年塌陷发生频率增加,平均5.88个/年;岩溶塌陷主要发生在3-7月份雨季;(2)低丘冲沟中发生塌陷54个,占塌陷总数的55.67%;岩溶平原中发生塌陷40个,占41.24%。97个岩溶塌陷主要发生在石炭系壶天群及泥盆系中统棋梓桥组下段地层;塌陷区域多为断裂构造带及褶皱轴部;(3)冲洪积成因土层共发生岩溶塌陷58个,占塌陷总数的59.79%,而残坡积成因土层发生塌陷39个,占40.21%。粉质黏土层发生塌陷数量多于黏土层,而粉质黏土与卵石土,粉质黏土、淤泥质黏土和砂土等组合土层分布面积较小,发生数量偏少。单层结构土体发生岩溶塌陷63个,占总数的64.94%;双层结构与多层结构土体发生塌陷数量占比35.06%。土层厚度小于10 m的区域发生岩溶塌陷48个,占总数的49.48%;土层厚度为10~15 m的区域发生塌陷49个,占总数的50.52%;(4)本地区浅部岩溶强发育,覆盖层薄且力学性能较弱,满足发生岩溶塌陷的基本条件;城市供水和采矿开采地下水是岩溶塌陷的主要触发因素。

The Chenzhou area is characterized by widely distributed carbonate rocks and thin overburden soil.The sinkholes occur frequently due to long-term dewatering of mines.Based on geological investigations,this paper analyz⁃es the distribution and influencing factors of sinkholes in this area.Results show that,(1)most sinkholes took place from 1980 to 1983,with 8.5 sinkholes per year on average.But severe sinkholes occurred since 2012,with 5.88 sink⁃holes per year.Sinkholes tended to occur during rainy seasons between March and July.(2)Fifty-four sinkholes(55.67%of the total)are distributed in low hilly gullies,and 40 sinkholes(41.24%of the total)are distributed in karst plain.Ninety-seven sinkholes took place in Carboniferous Hutian Group strata and Lower Qiziqiao Formation of Mid⁃dle Devonian strata.Many sinkholes appeared in fault zones and fold zones.(3)40.21%of sinkholes are distributed in alluvium layer,and 59.79%of sinkholes are distributed in diluvial beds.Collapse sinkholes were more likely to occur in silty clay because of its large distribution and more prone to subsoil erosion than other types of overburden materi⁃als.There are 63 sinkholes distributed in single-layer soil structure areas,and 34 sinkholes occurred in double-layer and multilayer soil structure.Double-layer soil consists of silty clay and pebble soil,whereas multilayer soil is form of silty clay,mud clay and sandy soil.49.48%of sinkholes occurred in the overburden soil with thickness less than 10 m,and 50.52%of sinkholes took place in the overburden soil with thickness 10 m to 15 m.(4)The basic conditions of sinkholes include well developed karst in the shallow subsurface,and thin and weak overburden soil.The primary trig⁃gering factor is pumping karst groundwater for urban water supply and mining.