The cavernous features are considered one of the geological hazards that are dominant in the carbonate rocks as a results of dissolution effect of groundwater. The dissolution process extends for many years at the subsurface layers and causes catastrophic collapse if migrated to the surface layers. The problem become crucial in the urbanization areas where there are wide varieties of construction activities. Beside the natural weathering process, the human interventions, representing in the wastewater, can accelerate the weathering process of the prevailing cracks. Al Kharj governorate is one of the promising areas close to Riyadh, the capital of Saudi Arabia, that attracts wide aspects of urbanization, agriculture and industrial activities. The study area is located inside an urban neighborhood at the western part of Al Kharj city. The site is surrounded by buildings extensions from three sides and the fourth side was excluded from urbanization activities due to existence of surface cracks along the area especially at the northern direction. Excavations and boring tests reveal that the exposed cracks are extended downward and may be connected to subsurface karstic features in the limestone rocks. Two surface geophysical measurements have been planned to provide clear information about the locations, horizontal and vertical extensions of the cavernous features along the study site. The Time Domain Electromagnetic (TEM) and Electrical Resistivity Tomography (ERT) methods were applied for investigating the subsurface characteristics up to 40m depth with different resolutions. The data have been acquired along profiles path across most of the surface fractured features. In spite of the inverted TEM data representing the subsurface resistivity variations in 1D mode, the dense TEM stations and the direct comparing the results with the available borehole lithology, enabled to trace the subsurface cavernous features laterally and vertically with reasonable resolution. Moreover, the 2D ERT processed data have been compared with the TEM results along some localities for guiding the data interpretation to locate the subsurface cavernous features. The two methods are analyzing the subsurface in two different resolutions, the TEM can explore the deeper parts and the layer successions, whereas the ERT methods can provide the lateral extension tracing of cavernous features. Based on the results 3D fence diagrams, most of the cavernous features that are located along the northern part of the study area related to fractured limestone zones extend vertically to more than 20m in some localities. Data interpretation has been flowed by excavation process for confirming the interpreted anomalies and resulted in discovery of huge cavity system extended laterally and vertically at deeper massive limestone layer.

海绵状特征被认为是碳酸盐岩中主要的地质灾害之一，是地下水溶解作用的结果。溶解过程在地下层持续多年，如果迁移到表层，会导致灾难性的塌陷。在建筑活动种类繁多的城市化地区，这个问题变得至关重要。除了自然风化过程之外，废水中的人为干预也可以加速现有裂缝的风化过程。哈吉省是沙特阿拉伯首都利雅得附近最有前景的地区之一，吸引了广泛的城市化、农业和工业活动。研究区域位于 Al Kharj 市西部的一个城市社区内。该场地被三侧的建筑物延伸所包围，第四侧由于该地区尤其是北向存在表面裂缝而被排除在城市化活动之外。挖掘和钻孔测试表明，暴露的裂缝向下延伸，可能与石灰岩的地下岩溶特征有关。计划进行两次表面地球物理测量，以提供有关研究地点沿线海绵状特征的位置、水平和垂直延伸的清晰信息。应用时域电磁 (TEM) 和电阻率断层扫描 (ERT) 方法以不同的分辨率研究 40m 深度的地下特征。数据是沿着大部分表面断裂特征的剖面路径获取的。尽管反演的 TEM 数据代表一维模式下的地下电阻率变化，但密集的 TEM 站以及将结果与可用的钻孔岩性进行直接比较，能够以合理的分辨率横向和纵向追踪地下海绵体特征。此外，还将二维 ERT 处理的数据与一些地点的 TEM 结果进行了比较，以指导数据解释以定位地下海绵状特征。这两种方法以两种不同的分辨率分析地下，TEM可以探索更深的部分和层序，而ERT方法可以提供海绵体特征的横向延伸追踪。根据 3D 栅栏图结果，位于研究区北部的与裂隙灰岩带相关的大多数海绵状特征在某些地方垂直延伸超过 20m。数据解释通过挖掘过程进行，以确认所解释的异常，并导致在更深的块状石灰岩层中发现横向和垂直延伸的巨大空洞系统。