CT技术探测岩溶发育及分布的可行性研究

Study on CT Scan Technology for Detecting Karst Rock Cavities and Distribution

电磁波CT是工程勘察探测溶洞的重要手段和方法,地下岩溶的发育类型和程度以及其分布特征对工程设计具有重要的参考价值。以武汉某地铁站为研究对象,对场地可溶性碳酸盐进行化学和矿物成分分析,探讨其岩溶类型和发育程度,利用CT技术从岩溶异常点铅直高度、高程分布、与基岩面的空间关系等角度对岩溶空间分布特征进行研究,同时采用钻孔技术验证探测结果。研究结果表明:可溶盐岩结构构造主要为泥灰岩、生屑灰岩、泥晶灰岩,矿物成分主要由方解石和白云石组成,场区内岩溶中等发育;物探CT推测岩溶异常点与钻孔揭露溶洞位置一致,岩溶异常点铅直高度主要分布在0~4 m,铅直高度大于4 m的异常点较少;岩溶异常点高程主要分布在-27 m~-13 m,约占总数70%,而受钻孔密度等因素影响钻孔揭露溶洞所占比例为60%;岩溶异常点和溶洞集中分布在基岩面以下6 m内,约占总数的63%,溶洞、岩溶异常点的分布数量随着深度的增加而减小,以上研究结果表明CT探测岩溶发育及分布是完全可行的。

The electronic-magnetic computed tomography(CT)is an important means and method for the engineering exploration of karst cavities.The development type and degree of the underground karst cavities and their distribution characteristics have important reference value for the engineering design.This paper presents a case history of a subway station in Wuhan.The chemical and mineral composition analysis of the soluble carbonate at the site were analyzed to investigate the karst type and development degrees.The CT scan method was used to study the spatial distribution characteristics of the karst from the vertical height of karst anomalies,elevation distribution,and spatial relationship with bedrock.Meanwhile,borehole technology is used to verify the detection results.The results show that,the structures of the soluble rock are mainly marl,bioclastic limestone and micrite,and the mineral composition is mainly composed of calcite and dolomite,and karst is moderately developed in the field.The locations of the karst anomalies inferred by the geophysical CT are consistent with those revealed by borehole methods.The vertical height of karst anomalies is mainly distributed in 0~4m,and there are few anomalies with the vertical height greater than 4m.The elevation of the karst anomaly points mainly distributed in 27m~13m,accounting for 70% of the total,while the proportion of karst cavities exposed by the drilling is 60% affected by factors such as the drilling density.Karst anomalies and karst cavities are concentrated within 6m below the bedrock surface,accounting for about 63% of the total,and the number of the karst anomalies and karst anomalies decreases with the increase of the depth.The above research indicates that CT detection of karst cavity development and distribution is completely feasible.