【作者】 陈冬琴；

【导师】 唐仲华；

【作者基本信息】 中国地质大学 ， 水文学与水资源， 2016， 博士

【摘要】 随着经济的发展及大规模城市建设的推进,地质灾害问题日益频发,严重阻碍了城市化建设的进程。武汉市城区岩溶塌陷开始于20世纪30年代,这阶段主要是由于降雨及局部抽水引起的岩溶塌陷；90年代以后,由于工程建设及地下水开采加剧,岩溶塌陷频繁发生；2013年以来因为地下水开采减少,加之地面变形等得到有效监测,岩溶塌陷处于控制阶段。尽管如此,由于工程建设施工排水,引发的岩溶塌陷还是时有发生,严重影响人民生命财产安全。为此,本文选择武汉市岩溶塌陷典型区-青菱乡,在对其自然地理、工程地质及水文地质条件进行研究分析的基础上,结合该区域的岩溶塌陷历史,总结分析了可溶岩分布及岩溶发育规律,研究了岩溶塌陷分布特征及成因机制,研究建立了岩溶塌陷数学模拟方法,构建了研究区水流-应力应变耦合模型,对不同影响因素作用下的岩溶塌陷可能性进行了定量模拟预测研究。主要结论认识如下：1、研究分析了可溶性岩的发育特征：平面上基岩面溶蚀程度最强的是阮家巷、司法学校、烽火村及毛坦港四个区域;受地质构造的控制,青菱寺压扭性断裂带区域钻孔遇洞率高达73%,线岩溶率22.6%；垂向上强发育带在高程-5--10m处,钻孔遇洞率15.7%。2、统计分析了溶洞的充填特征：平面上阮家巷—陆家街—涂家沟司法学校、烽火村乔木湾—余家湾以及毛坦港一带,洞内部分充填砂、粘土和碎石岩；垂向上埋深约20-40m段,充填率最高达67.39%。3、研究分析了岩溶发育与可溶性岩的矿物化学成分及形成的地质年代的关系：石灰岩的二叠系地层中Ca(O含量最高,比溶蚀度最大0.93-1.17。研究区内二叠系地层分布不广,但下伏基岩出现的溶蚀现象较普遍,岩溶塌陷密度最高3个/km2。4、总结分析了岩溶塌陷的空间及时间分布特征：①塌陷区全部分布在南部石灰岩条带上,石灰岩中溶洞或裂隙发育强；②在地形地貌上,所有的塌陷点均局限在两岸滨江的长江一级阶地上,因为该处地下水与长江水随着季节变化有密切的水利交替联系；③有些塌陷分布在铁路沿线以及有重大工程建设的地点。④在地质构造上,许多塌陷点发生在青菱寺压扭性断裂带及五通-汤逊湖性断裂带500m范围以内。塌陷的发生时间主要在6-8月份和12-2月份期间。5、研究了岩溶塌陷的影响因素及作用机理：①地貌影响及作用机理,阶地堆积物中有二元结构存在,上部为粘土,下部为粉细砂及卵砾石层直接覆盖在石灰岩之上,在地下水的内动力作用下极易被潜蚀。②盖层岩性结构对地面塌陷的影响及作用机理,粘聚力愈高,土的抗剪强度愈强,抗塌能力愈高。青菱乡烽火村砂层厚度最大,平均厚度36m,塌陷密度最大。砂性土在水的渗透压作用下较易发生塌陷,所以主要作用机理是潜蚀及渗压致塌。③地质构造的影响及作用机理,沿着青菱寺压扭性断裂带分布的塌陷点全部在500m范围,作用机理是断裂带处是地下水的通道,潜蚀作用增强。④地下岩溶及土洞发育程度、土层扰动对地面塌陷的影响及作用机理,青菱乡烽火村扰动带以多剖面的方式相互贯通,砂层的多个扰动带相互影响,在一处塌陷点处形成密集的多个地面塌陷坑；扰动带以多剖面的方式相互贯通使土层中的土颗粒随着水流加速迁移,松散的扰动带提供了迁移的物质,所以主因是潜蚀致塌。另外降雨及抽水都增加垂直渗透压力,还使土层的自重应力增大,抽水还会产生真空吸蚀作用,所以塌陷成因还有渗透致塌、重力致塌、真空吸蚀致塌。6、在对研究区可溶岩分布规律、岩溶发育规律、岩溶塌陷分布特征、影响因素及作用机理研究的基础上,建立了重点塌陷区的水流-应力应变三维耦合模型,并引入格里菲斯判据及摩尔-库伦破坏准则。7、基于GMSMODFLOW程序及编制的程序对以青菱乡烽火村为地质背景建立的理想模型进行了模拟计算与预测,计算结果与定性分析及实际的塌陷情况相符,验证了程序的正确性。8、利用以上验证的程序计算了青菱乡2009年1月至2013年7月的地下水流场及土体应力应变值,并进行了模型识别,拟合效果较好。利用以上拟合的模型对青菱乡烽火村塌陷区的长江水位动态、工程建设排水、大气降水等几种工况进行了预测,为预防岩溶塌陷提供了科学依据。主要创新点：(1)结合青菱乡岩溶塌陷背景条件和机理,提出了地下水流-应力应变耦合模型。(2)编制程序实现了地下水流-应力应变耦合过程数值模拟,并设计了长江水位变化、周边工程建设排水施工、大气降雨三种工况对武汉市青菱乡烽火村岩溶塌陷区进行了预测。更多还原

【Abstract】 With the economic development and large-scale urban construction, geological disaster is becoming increasingly frequent; this seriously influences the process of urbanization. Karst collapse in Wuhan City began in the 1930s, and was mainly due to the rain and local groundwater pumping. After 1990, karst collapse occurred frequently, due to the increase of constructions and groundwater pumping. Karst collapse was controlled in the years 2011 due to the decrease of groundwater pumping, and with an effective monitoring of ground deformation. Despite this, due to the engineering drainage, karst collapse still occurred sometimes, the people’s lives and property were seriously affected by karst collapses. Therefore, we selected a typical karst collapse area-Qingling Town in this study, Based on the study and analysis of the Research area’s geography, engineering geology and hydrogeological conditions, combined with the karst cave history of this area, the characteristics and mechanism of karst collapse were studied. The mathematical model for describing karst collapse is discussed, a water-soil-rock model has been established. The model is used to predict the quantitative evaluation of karst collapse under different affecting factors. The main conclusions are as follows:1. The distribution of dissoluble rock was investigated and analyzed based on the dissolution experimental data. Ruanjia alley, Sifa School, and Fenghuo village were under the most extensive bedrock surface corrosion degree. The results showed under the control of geological structure, dissolution rate in boreholes was 73% in pressure shear fault zone of Qingling village. The limestone cave encounter rate was 22.6%. the extensive development of dissoluble rock in vertical zone located in-5-10 m with a dissolution rate of 15.7%.2. A statistical analysis of the filling characteristics of karst cave was employed. The fillings in karst cave around Ruanjia alley-Lujia street-Sifa school-Qiaomu village-Yujia village and Maotangang village were filled with sand, clay and gravel in the plan. The vertical zone between 20m and 40m reached a filling rate of 67.39%.3. The relationship between development of karst and chemical composition of minerals in soluble rock with the formation time was analyzed. CaO content and the specific dissolution ratio in the Triassic were lower than that in Permian with a specific dissolution ratio ranging from 0.93 to 1.17. Permian strata was Not widely distributed while the underlying bedrock of corrosion phenomenon was relatively common with highest density 3 per km2.3. The relationship between development of karst and chemical composition of minerals in soluble rock with the formation time was analyzed. CaO content and the specific dissolution ratio in the Triassic were lower than that in Permian with a specific dissolution ratio ranging from 0.93 to 1.17. Permian strata was Not widely distributed while the underlying bedrock of corrosion phenomenon was relatively common with highest density 3 per km2.4.We analyzed and summarized the spatial and temporal distribution of karst collapse:① collapse area all located in the southern strip of limestone, limestone caves or fissures;② in the topography, the collapse of all points are confined to the first terrace on both sides of the Yangtze Riverside on the ground, where the groundwater and the Yangtze River with the seasonal changes in water conservancy closely alternate contact;③ distributed along the railway as well as the location of major construction projects.④ on the geological structure, many collapse point occurred in Qingling Temple pressure-shear fault and Wutong-Tangxun Lake fault zone within 500m range.⑤ collapse point generally occurs in the Quaternary limestone Looking at the results from the current statistics. Collapse occurred mainly in the 6-8 month period and 12-2 during the month.5. We studied influencing factors of karst collapse:① The topography influence, terrace deposits in the presence of the dual structure, the upper for cohesive, fine sand and the lower part of the gravel layer directly overlying limestone, within dynamic role of groundwater in the area can easily be hidden eclipse. ② The influence of the upper soil structure on the ground collapse lithology, cohesion higher, stronger shear strength, resistance to collapse the higher capacity. The maximum thickness of the sand layer in the Fenghuo village is 36m, with maximum density collapse. It is easy to collapse under the effect of the osmotic pressure of the groundwater. ③The influence of the geological structure, the collapse pressure points along the Qingling Temple twist of fault distribution are all in 500m range. The mechanism can be explained that the faults accelerate the groundwater flow causing a much more extensive latent erosion of groundwater.④ Underground the karst cave development and degree of soil, soil disturbance on ground subsidence, Village disturbance flames with a multi-profile way interconnected, multiple sand disturbance with mutual influence, forming dense ground subsidence pits more than one place at the point of collapse. Disturbed belts consisting of one or more profiles with inter-permeation make soil accelerate to migrate with the groundwater flow. The inter-permeation disturbed belts provides a better environment for migration. In addition, rainfall increase vertical seepage pressure as well as pumping. Furthermore, the rainfall also increases the weight of stress in the soil. Therefore this type of collapse can be explained as penetration collapse, gravitational collapse.7. Based on the research on spatial distribution of Karst geological conditions, the characteristics of Karst collapse development and genetic mechanism analysis, a coupled model integrated with groundwater flow and stress-strain was constructed in subsidence area of study area. In addition, the Coulomb-Mohr principle and Griffith principle were applied in the present study.8. The groundwater table and the value of stress-strain of soil were calculated using GMS software and a Fottran program form the January of 2009 to July of 2013. The verification procedure indicated a good precision for the model.9. The water level of Yangtze River, construction drainage and rainfall were predicated using the above model in Fenghuo village of Qinglin town. It could provide scientific basis for prevention of Karst collapse.The main innovations in the present study:(1)Proposed coupled model of groundwater flow and stress-strain model for modeling of karst collapse and mechanism in Qingling Town.(2)A coupling model is proposed which contains dynamics of groundwater flow and mechanics model. In this model, karst breakdown problem in Qingling Town which under change of water level of Yangtze river and construction drainage around is simulated and the problem under rainfall condition is also analyzed.更多还原