红层岩溶发育特征与地面塌陷形成机理-以咸宁地区为例

通过收集整理前人研究资料、实地踏勘以及现场灰质砾岩取样、磨片及显微镜观测等方法手段,分析了红层岩溶发育特征与灰质砾岩溶蚀机理,同时,结合咸宁地区实际地质条件,建立了岩溶地面塌陷室内物理模型,通过监测抽(排)水与降雨两种情况下土压力、孔隙水压力以及土体位移变化情况,分析了抽(排)水和降雨对岩溶地面塌陷的影响机制。模型试验结果表明研究区岩溶地面塌陷形成机制主要为潜蚀作用,真空吸蚀作用次之。降雨对地表土体产生冲刷,地下水渗流作用造成土体潜蚀、运移;抽(排)水时水位发生骤变,水力梯度变大,加速了泥沙带出,导致含砂砾黏土层逐渐被潜蚀、掏空,加之真空负压的吸蚀叠加作用,促进土体破坏导致失稳,最终发生地面塌陷。由此可知,咸宁地区红层岩溶地面塌陷的形成机制主要是潜蚀作用与真空吸蚀作用交互反应,抽水是其诱发岩溶地面塌陷的主要外因。

Research on Development Characteristics of Redbed Karst and Formation Mechanism of Ground Collapse- Taking Xianning for Example

This paper analyzes the development characteristics of red bed karst and the corrosion mechanism of calcirudyte by collecting and sorting previous research data, conducting field reconnaissance, taking samples of calcirudyte on site, carrying out ground section and microscope observation etc., and meanwhile, establishes the laboratory physical model for karst ground collapse in combination with the practical geological conditions in the research area, and analyzes the influence mechanism of pumping (drainage) and rainfall on karst ground collapse through monitoring the change in soil pressure, pore water pressure and soil displacement under two circumstances above, i.e. pumping (drainage) and rainfall. According to the result of model test, karst ground collapses are primarily formed by underground erosion, followed by vacuum suction erosion. Under the effect of rainfall, surface soil will be scoured and groundwater seepage will give rise to underground erosion and migration of soil masses. In case of pumping (drainage), water level will suffer sudden change, hydraulic gradient will be greater and outward movement of sediments will be speeded up, so that the clay layers containing sand gravel will be gradually eroded and emptied. Together with the effects from suction erosion under vacuum negative pressure, it will promote the soil damage, give rise to instability and finally cause ground collapse. Therefore, red bed karst ground collapses in Xianning are mainly formed under the interactive reaction of underground erosion and vacuum suction erosion and water pumping is the main external cause giving rise to karst ground collapse.