徐州岩溶塌陷时空分布规律及成因分析

文章通过对以往岩溶地面塌陷勘查工作成果进行系统梳理,揭示了徐州地区裸露型岩溶和覆盖型岩溶的分布规律及历史上岩溶塌陷的时空分布特征,发现塌陷的分布具有明显的规律性:(1)塌陷受废黄河断裂带控制,离废黄河断裂带越近岩溶发育越强烈,离废黄河断裂带较远的部位岩溶发育明显减弱;(2)塌陷主要分布于浅部岩溶强烈发育地段的奥陶系灰岩中,少数分布于寒武系灰岩之中;(3)塌陷集中分布在古河道形成的,砂性土单层结构地段,少数分布在砂性土-黏性土双层结构地段;(4)塌陷全部位于岩溶水开采降落漏斗内。结合岩溶塌陷的时间与地下水的动态活动过程之间的关系,全面分析地面塌陷形成的原因,提出了古河道与废黄河断裂带的重叠部位为岩溶地面塌陷发生的有利部位,但最终发生地面塌陷则是人类工程活动过程引起岩溶水位剧烈波动——大幅、快速下降的结果。该研究成果可为徐州市今后进一步防治岩溶塌陷地质灾害提供地质科学依据,有重要的实用价值。

Spatial-temporal distribution and causes of karst collapse in the Xuzhou area

Xuzhou is the only city in the Jiangsu Province to use the karst underground water as the municipal water. Due to the long-term absurd use of the Karst underground water, karst collapse often happens in the Xuzhou region. This paper looks into the distribution of bare karst and covered karst in the Xuzhou region in northern Jiangsu Province and the special and temporal distribution of karst collapse in the history, and summarizes rules of the karst collapse. Firstly, as controlled by the fault zone of the ancient Yellow River, the Karst developed more intensive when closer to the ancient Yellow River and vice versa. Secondly, the collapse occurs in sections with shallow well developed karst, mostly in Ordovician limestone and a few in the Cambrian limestone. Thirdly, the collapse is concentrated within the ancient channel. Most collapse happens in the sand soil monolayer, some in the clay sand-clay layer. Lastly, all collapse is in the cone of depression due to the extraction of karst water. In combination with the correlation between the timing of karst collapse and the dynamics of ground water, this paper comprehensively analyzes the causes of ground collapse. Though the overlap section of the ancient watercourse and the fault zone of the ancient Yellow River provides favorable condition for the karst underground collapse, its final occurrence is resulted from human engineering activities, which change the karst water level significantly and causes rapid decline in volatility. The results of this study would provide scientific basis for prevention of karst collapse hazards in the Xuzhou city in the future.