Drainage and flooding in karst terranes

Flooding in karst terranes is a commonly occurring geo-hazard. It causes damage to property, businesses, and roadways. It can lead to the formation of cover-collapse sinkholes and groundwater contamination. Generally, three types of flooding or their combinations are related to karst: recharge-related sinkhole flooding, flow-related flooding, and discharge-related flooding. Understanding of the type of flooding is essential for solving the flooding problem. Areas prone to karst flooding should be recognized, and restrictions and laws on land use should be implemented. Runoff and erosion control plans should address the unique characteristics of karst features. Digging out clogged sinkholes, creating retention basins, or installing Class V Injection Wells are possible solutions to improve drainage of storm water. Solutions to flooding problems in karst areas should also be coordinated with the water quality control to prevent groundwater contamination.     

The applicability of the Florida mandatory endorsement for sinkhole collapse coverage. Part I. Legal aspects

Florida statute §627 706 was enacted to provide sinkhole collapse coverage The legislative intent of the Statute was to protect the property owner from the unexpected damage to structures and personal property arising from the occurrence of sinkholes However, since the Statute was enacted, litigation involving considerable expense to the insurance companies and property owners has occurred because of various interpretations of the Statute The technical and legal interpretations do not appear always to be the same. This article discusses some of the interpretations accepted by the court, and it addresses the role of the engineer, geologist, and hydrologist in the technical interpretations of the Statute. In an attempt to reduce litigation and associated court costs, recommendations are made to resolve some of the vagueness and ambiguities in the Statute and still maintain the Statute's flexibility and intent to protect public welfare     

Roadway construction in karst areas: management of stormwater runoff and sinkhole risk assessment

In karst-rich regions, it is inevitable that roadways cross karst landscapes. Road building across such terranes faces environmental and engineering challenges because of impacts on water quality from stormwater runoff and concerns of sinkhole collapse under or near roadways. When highway runoff drains rapidly into subsurface conduit networks through open sinkholes and/or sinking streams, the impact of the runoff on the karst aquifer can be qualitatively evaluated by mixing cell models. Formulation of a comprehensive stormwater runoff management plan prior to roadway construction can minimize the associated adverse impacts. The commonly used best management practices help manage the stormwater runoff effectively in some sites. Site-specific management plans are preferable for other sites because of concerns of flooding and land stability. Proactive measures should be taken to identify areas of the greatest sinkhole collapse risk along the proposed route and the associated groundwater drainage patterns.     

Identification, prediction, and mitigation of sinkhole hazards in evaporite karst areas

Sinkholes usually have a higher probability of occurrence and a greater genetic diversity in evaporite terrains than in carbonate karst areas. This is because evaporites have a higher solubility and, commonly, a lower mechanical strength. Subsidence damage resulting from evaporite dissolution generates substantial losses throughout the world, but the causes are only well understood in a few areas. To deal with these hazards, a phased approach is needed for sinkhole identification, investigation, prediction, and mitigation. Identification techniques include field surveys and geomorphological mapping combined with accounts from local people and historical sources. Detailed sinkhole maps can be constructed from sequential historical maps, recent topographical maps, and digital elevation models (DEMs) complemented with building-damage surveying, remote sensing, and high-resolution geodetic surveys. On a more detailed level, information from exposed paleosubsidence features (paleokarst), speleological explorations, geophysical investigations, trenching, dating techniques, and boreholes may help in investigating dissolution and subsidence features. Information on the hydrogeological pathways including caves, springs, and swallow holes are particularly important especially when corroborated by tracer tests. These diverse data sources make a valuable database—the karst inventory. From this dataset, sinkhole susceptibility zonations (relative probability) may be produced based on the spatial distribution of the features and good knowledge of the local geology. Sinkhole distribution can be investigated by spatial distribution analysis techniques including studies of preferential elongation, alignment, and nearest neighbor analysis. More objective susceptibility models may be obtained by analyzing the statistical relationships between the known sinkholes and the conditioning factors. Chronological information on sinkhole formation is required to estimate the probability of occurrence of sinkholes (number of sinkholes/km² year). Such spatial and temporal predictions, frequently derived from limited records and based on the assumption that past sinkhole activity may be extrapolated to the future, are non-corroborated hypotheses. Validation methods allow us to assess the predictive capability of the susceptibility maps and to transform them into probability maps. Avoiding the most hazardous areas by preventive planning is the safest strategy for development in sinkhole-prone areas. Corrective measures could be applied to reduce the dissolution activity and subsidence processes. A more practical solution for safe development is to reduce the vulnerability of the structures by using subsidence-proof designs.     

Application of water quality control charts to spring monitoring in karst terranes

Presence of springs in karst terranes provides a unique opportunity to study the rather complex, multi-porosity, and multi-permeability system. When springs are used to evaluate the integrity of storage facilities for hazardous materials or waste disposal facilities constructed in karst areas, the spatial heterogeneity of karst aquifers makes intra-spring comparisons preferred statistical tests. One of the commonly used statistical tests is water quality control procedure such as Shewhart-CUSUM control charts. Appropriate application of the water quality control procedure to intra-spring monitoring depends on whether the assumptions can be justified about the aquifer that drains to the spring and the dataset collected at the spring. Violation of the assumptions would render the statistical tests invalid, which may result in a failure of the groundwater monitoring program. In intra-spring monitoring, it is the temporal variations of water quality at a karst spring need to be addressed, whereas the water quality at the spring is closely associated with the characteristics of the aquifer. The example datasets presented in the paper indicate that both false negative and false positive detections can occur if the temporal variation is not well characterized.     

我国红层岩溶与红层岩溶塌陷刍议

中国岩溶地区面积广阔,岩溶地貌和现象类型多样。其中我国南方地区红层中出现的岩溶现象较为特殊:可溶岩类型复杂,成岩作用差,溶蚀机理多样,还易风化崩解。近年来红层岩溶塌陷多有发生,成为一个不可回避的问题。文章对我国红层岩溶与红层岩溶塌陷研究现状进行了系统梳理。红层岩溶主要存在于以可溶物质胶结的或含碳酸盐岩砾石的红色沉积岩为主的地区。红层岩溶的特点可以概括为:(1)可溶岩类型复杂,溶蚀机理多样;(2)成岩作用差,力学强度低,易风化崩解;(3)与地质构造密切相关。红层岩溶地区不但会出现覆盖型岩溶区的土层塌陷,而且由于其特殊的岩溶作用还可能出现基岩塌陷。根据红层岩溶地区地质结构,其塌陷模式可概化为红层上覆松散层塌陷、红层溶洞顶板垮塌以及红层整体垮塌三类。今后有必要从红层溶蚀特点和红层岩溶塌陷模式出发,开展红层溶蚀对岩溶塌陷作用机理的专项研究,为红层地区岩溶塌陷地质灾害的风险评估和防治处理提供科学依据和技术支撑。     

Development and validation of sinkhole susceptibility models in mantled karst settings. A case study from the Ebro valley evaporite karst (NE Spain)

A preliminary sinkhole susceptibility analysis has been carried out in a stretch 50 km² in area of the Ebro valley alluvial evaporite karst (NE Spain). A spatial database consisting of a sinkhole layer and 27 thematic layers related to causal factors was constructed and implemented in a GIS. Three types of sinkholes were differentiated on the basis of their markedly different morphometry and geomorphic distribution: large subsidence depressions (24), large collapse sinkholes (23), and small cover-collapse sinkholes (447). The susceptibility models were produced analysing the statistical relationships between the mapped sinkholes and a set of conditioning factors using the Favourability Functions approach. The statistical analyses indicate that the best models are obtained with 6 conditioning factors out of the 27 available ones and that different factors and processes are involved in the generation of each type of sinkhole. The validation of two models by means of a random-split strategy shows that reasonably good predictions on the spatial distribution of future dolines may be produced with this approach; around 75% of the sinkholes of the validation sample occur on the 10% of the pixels with the highest susceptibility and about 45% of the area can be considered as safe.     

Use of sinkhole and specific capacity distributions to assess vertical gradients in a karst aquifer

The carbonate-rock aquifer in the Great Valley, West Virginia, USA, was evaluated using a database of 687 sinkholes and 350 specific capacity tests to assess structural, lithologic, and topographic influences on the groundwater flow system. The enhanced permeability of the aquifer is characterized in part by the many sinkholes, springs, and solutionally enlarged fractures throughout the valley. Yet, vertical components of subsurface flow in this highly heterogeneous aquifer are currently not well understood. To address this problem, this study examines the apparent relation between geologic features of the aquifer and two spatial indices of enhanced permeability attributed to aquifer karstification: (1) the distribution of sinkholes and (2) the occurrence of wells with relatively high specific capacity. Statistical results indicate that sinkholes (funnel and collapse) occur primarily along cleavage and bedding planes parallel to subparallel to strike where lateral or downward vertical gradients are highest. Conversely, high specific capacity values are common along prominent joints perpendicular or oblique to strike. The similarity of the latter distribution to that of springs suggests these fractures are areas of upward-convergent flow. These differences between sinkhole and high specific capacity distributions suggest vertical flow components are primarily controlled by the orientation of geologic structure and associated subsurface fracturing.     

Legal aspects of development on dolomite land in South Africa

 Dolomite rock formations underlie large areas of the Gauteng, North, North-West and Mpumalanga Provinces in South Africa. Sinkholes, subsidences and dolines that may form at any place and at any time on these formations pose a threat to the properties and lives of thousands of people who live and work there. Since much urban, industrial and mining development has taken place in these areas, and the demand for housing development is on the increase, the risk of surface damage must be minimized by means of proper site investigations, hazard and risk evaluation and selection of appropriate development. The legal aspects pertaining to development on dolomite land in South Africa and the requirements for geotechnical investigations as outlined in the various ordinances and acts are reviewed here. Received: 15 September 1996 · Accepted: 12 May 1998     

Geometric analysis of fold development in overthrust terranes

Fault-bend folding, fault-propagation folding, and detachment (or décollement) folding are three distinct scenarios for fold-thrust interaction in overthrust terranes. Simple kink-hinge models are used to determine the geometric associations implicit in each scenario. Bedding maintains constant thickness in the models except in the forelimb of the fold. The forelimb is allowed to thicken or thin without limit. The models address individual folds, and the calculated fold geometries are balanced structures.Each mode of fold-thrust interaction has a distinct set of geometric relationships. Final fold geometry is adequate in itself to discern many fault-bend folds. This is not the case for fault-propagation and detachment folds. These two fold forms have very similar geometric relationships. Some knowledge of the nature of the underlying thrust or décollement zone is usually needed to distinguish between them. The geometry of a fold is altered, in a predictable fashion, by transport through an upper ramp hinge and by fault-parallel shearing of the structure. The shearing results in a tighter fold, whereas transport through the ramp hinge produces a broader fold.The viability of the geometric analysis technique is demonstrated through its application to a pair of detachment folds from the Canadian Cordillera. The geometric analysis is also used to evaluate cross-sections through subsurface structures. In an example from the Turner Valley oil field, the analysis indicates how the interpretation should be altered so as to balance the cross-section. The analysis reveals hidden assumptions and specific inconsistencies in structural interpretations.     

防治公路岩溶塌陷的土工合成材料设计理论研究

高速公路路基岩溶塌陷通常可以采用水平加筋体防治,系统地研究其受力特性及设计理论具有重要的工程意义和实际价值。首先,针对公路路基荷载及岩溶塌陷的特点,分析了塌陷坑上方水平加筋体的受力和传力特性,采用太沙基土拱理论,计算溶洞上方荷载。深入探讨了水平加筋体设计方法,认为锚固段端部加筋体应变及锚固段传力长度是设计中的关键值,且其与锚固段端部加筋体拔出量密切相关。然后,引入水平加筋体与土体界面的线弹性-全塑性模型,由基本方程导出锚固段水平加筋体弹塑性解答,并结合边界条件建立了锚固段端点拔出量及传力长度的解算流程。在此基础上,引入某实际工程计算参数进行分析,将该方法结果与基于全塑性模型的分析结果进行对比,探讨了不同临空段宽度、加筋体刚度、上覆土体高度、界面摩擦角等因素对临空段端部拔出量计算误差的影响,并分析了上覆土体高度与锚固段传力长度之间的关系。由分析可知,基于线弹性-全塑性模型计算的拔出量和传力长度均较全塑性模型计算结果大,某些情况下,传力长度的计算误差高于40%,若采用全塑性模型计算有可能引起较大的误差,导致设计偏于不安全     

Kinematics of compressional fold development in convergent wrench terranes

Kinematic models are presented for compressional fold development in wrench and convergent wrench terranes that relate fold shortening, axial rotation, and axial extension. Fold shortening may be derived from final fold geometry. Existing fold geometry and axial orientation, two readily measurable quantities, provide the data needed to determine the relative components of shearing and convergence within the fold system. Analyses utilizing these kinematic models indicate that folds developed in sedimentary rocks in the wrench borderlands of both the Rineonada and San Andreas wrench faults in central California are the product of strongly convergent wrenching. The axes of these folds have been rotated no more than a few degrees during the course of their development. In contrast, folds developed in the Alpine Schists along the Alpine fault in New Zealand and in Pleistocene sediments along the southern limit of the San Andreas fault suggest an almost pure wrench setting and large (>25 °) axial rotations.

Significant axial extension is inherent in wrench-related compressional folds. This axial extension is commonly manifest in the form of normal and strike-slip faults that are internal to the folds and trend at high angles to the fold axes. The relative amount of axial extension diminishes as the degree of convergence increases. This axial extension, and the associated extensional features, can be a diagnostic indication of the influence of wrenching.     

Hydrogeologic role in sinkhole development in the desert of Kuwait

Sinkhole development is unlikely in desert areas with very low precipitation. However, a few cases of land subsidence and sinkhole development took place within the suburbs of Kuwait City. A few sinkholes developed in a sudden and rapid way, leading to great economic losses. In this paper the mechanism and causes of such a land subsidence are described. Decline in groundwater level and downward infiltration of excess irrigation are suggested to be the main factors in the development of the land subsidence in Kuwait. Urbanization and excessive garden irrigation are most probably the triggers of the sudden and rapid land subsidence.     

The influence of urbanization of sinkhole development in central Pennsylvania

The karsted limestone valleys of central Pennsylvania contain two populations of sinkholes. Solution sinkholes occur in the Champlainian limestone units along the margins of the valleys. Solution sinkholes are permanent parts of the landscape and, although a nuisance to construction, do not present other problems. The second population is the suffosional or soil-piping sinkholes These occur on all carbonate rock units including the Beekmantown and Gatesburg dolomites that comprise the two principal carbonate aquifers in the valley. Suffosional sinkholes are the principal land-use hazard. Suffosional sinkholes are transient phonomena. They occur naturally but are exacerbated by runoff modifications that accompany urbanization Suffosional sinkholes are typically 1.5–2.5 m in diameter depending on soil thickness and soil type. The vertical transport of soil to form the void space and soil arch that are the precursors to sinkhole collapse is through solutionally widened fractures and cross-joints and less often through large vertical openings in the bedrock. The limited solution development on the dolomite bedrock combined with soil thickness, seldom greater than 2 m, limits the size of the sinkholes. All aspects of suffosional sinkhole development are shallow processes: transport, piping, void and arch formation, and subsequent collapse take place usually less than 10 m below the land surface Factors exacerbating sinkhole development include pavement, street, and roof runoff which accelerates soil transport Such seemingly minor activities as replacing high grass and brush with mowed grass is observed to accelerate sinkhole development. Dewatering of the aquifer is not a major factor in this region     

Environmental and legal aspects of karst areas

 Environmental impacts on karst settings are common as they are more sensitive than those of other rock terrains. Regulatory procedures that are effective in other rock terrains are not necessarily applicable to karst settings. Development and exploitation by man that affect the karst hydrology regime can trigger catastrophic events and result in numerous legal actions where the effects of changes go beyond property boundaries. A great variety of regulations and examples of litigation exist for karst areas. Received: 25 October 1994 · Accepted: 17 October 1995     

Reliability of dipole-dipole electrical resistivity tomography for defining depth to bedrock in covered karst terranes

 Sinkhole collapse is one of the main limitations on the development of karst areas, especially where bedrock is covered by unconsolidated material. Studies of sinkhole formation have shown that sinkholes are likely to develop in cutter (enlarged joint) zones as a result of subterranean erosion by flowing groundwater. Because of the irregular distribution of pinnacles and cutters on the bedrock surface, uncertainties arise when "hit-or-miss" borehole drilling is used to locate potential collapse sites. A high-resolution geophysical technique capable of depicting the details of the bedrock surface is essential for guiding the drilling program. Dipole-dipole electrical resistivity tomography (ERT) was used to map the bedrock surface at a site in southern Indiana where limestone is covered by about 9 m of clayey soils. Forty-nine transects were conducted over an area of approximately 42,037 m². The electrode spacing was 3 m. The length of the transects varied from 81 to 249 m. The tomographs were interpreted with the aid of soil borings. The repeatability of ERT was evaluated by comparing the rock surface elevations interpreted from pairs of transects where they crossed each other. The average difference was 2.4 m, with a maximum of 10 m. The discrepancy between interpreted bedrock-surface elevations for a transect intersection may be caused by variations in the subsurface geology normal to the transect. Averaging the elevation data interpreted from different transects improved the ERT results. A bedrock surface map was generated using only the averaged elevation data at the transect junctions. The accuracy of the map was further evaluated using data from four exploratory boreholes. The average difference between interpreted and actual bedrock surface-elevations was less than 0.4 m. The map shows two large troughs in the limestone surface: one coinciding with an existing sinkhole basin, while the other is in alignment with a small topographic valley. Because sinkholes were observed at the same elevation interval in similar valleys in the vicinity, the delineated trough may have implications for future land use at the site. Received: 4 January 1999 · Accepted: 8 March 1999     

岩溶动力学理论与现代岩溶学发展

岩溶动力学理论的核心是碳水钙循环,强调系统思维和全球视野观,提出了岩溶动力系统概念模型、结构与功能。岩溶动力学研究产生的新的学科生长点,对现代岩溶学形成与发展具有里程碑式的意义。“岩溶形态组合”概念的提出为岩溶不均一性研究、岩溶类型与形成环境划分奠定了完整的方法体系;将岩溶学研究成功引入全球变化领域,由此开辟了岩溶碳循环与碳汇效应研究,为重新认识岩溶作用在全球碳循环中的地位打开了窗口;将岩溶地球化学研究延伸至无机与有机过程的融合研究,为脆弱岩溶环境修复与保护提供了更加清晰的思路与方法。岩溶IGCP项目的执行,体现了岩溶动力学理论为建立联合国教科文组织国际岩溶研究中心的指导意义,同时,岩溶动力学理论为我们自觉融入国家“一带一路”倡议、生态文明发展战略和“双碳”目标等奠定了坚实的理论与方法基础。     

武汉地区浅层岩溶发育特征与岩溶塌陷灾害防治

运用综合分析和数学统计的方法,较为深入地研究了武汉地区浅层岩溶的发育特征。武汉地区存在6个走向 NWW-SEE、各自相对独立的碳酸盐岩条带。根据上覆盖层工程地质性能的差异,划分出5种岩溶地质结构类型。武汉地区浅层岩溶主要类型有溶隙、落水洞及小型溶洞等,钻孔遇洞率46.0%~50.1%,线岩溶率5.93%~6.00%。浅层岩溶带中,1/3的溶洞洞高小于0.6 m,50%小于1.0 m,90%小于3.0 m。1/3的溶洞顶板在基岩面以下2.5 m 以内,50%在4.5 m 以内,90%在12.5 m 以内。溶洞充填物主要是黏土,含有灰岩碎块石。全充填溶洞占70.8%,未充填溶洞约占1/5,半充填溶洞不到8%。全充填溶洞顶板在基岩面以下平均埋深5.13 m,半充填5.71 m,无充填7.69 m,且具有全充填和半充填溶洞埋深较小、无充填溶洞埋深较大的特点,反映出溶洞充填方式是自上而下充填,充填物主要来源于上部覆盖层。武汉地区浅层岩溶为上部“垂直渗流岩溶带”地下水垂直渗流作用下的产物。根据岩溶发育程度的差异,基岩面以下浅部碳酸盐岩在垂直方向上可分为上部强岩溶和下部弱岩溶两个带;岩溶塌陷灾害平面上可划分出高、中、低3个危险性区,各区防治原则不同。高危险区是岩溶塌陷灾害防治的重点,防治的基本原则是阻止上覆粉细砂的流失;中等危险区的防治原则是保护中部老黏土层或红层的完整性;低危险区应注意远城区土洞存在的可能性。各危险区治理应以岩溶地质结构为基础,在防治原则指导下制定相应的防治措施。此外,工程建设中应合理选择和利用弱岩溶带。     

Mechanism of sinkhole formation during groundwater-level recovery in karst mining area,Dachengqiao, Hunan province,China

The Meitanba Coal Mine area in Hunan province, China, had been impacted by severe cover collapse sinkholes since 1982 due to mine dewatering. After the coal mine was closed in February 2015, the groundwater level has increased significantly. A series of sinkholes were recorded in the study area during groundwater-level recovery. Analysis of monitoring results and in-situ investigation indicated that 13 sinkhole collapses were more likely induced by abrupt change of groundwater–air pressure in response to heavy rainfall from March 2015 to July 2016 when the groundwater level increased by as much as 76 m. When the karst conduit was flooded, a relatively sealed environment was formed between saturated sediments and flooded karst conduit. Implosion of entrapped air might have caused the cave roof to collapse followed by surface collapses in a short time. On the other hand, four sinkholes occurred in November 2016 when the groundwater levels were near the soil–bedrock interface at elevations between 52.5 and 58.9 m amsl and the groundwater-level increase was at slower paces. Field measurements indicate that the groundwater-level fluctuation at the soil–bedrock interface could enlarge the soil cavity and accelerate the subsoil erosion process.     

Review: Carbonate aquifers and future perspectives of karst hydrogeology in India

About 3 % of India’s total land surface is occupied by carbonate rocks which are mostly karstified and constitute a significant source of groundwater. The groundwater drawn from these aquifers matches the water demand of ~35 million people living in 106 districts of the country and also the water needs of livestock, irrigation and industry. The studies on karst in India carried out so far have mostly addressed geology, hydrology and groundwater contamination. A literature survey suggests that there is a need for detailed research, applying new approaches and techniques for proper carbonate aquifer identification, characterization and management. Such specific approaches will improve modeling, exploitation and protection of karst groundwater. An overview of the research carried out on groundwater resources of karst formations in India is presented, which also throws light on the protection of karst aquifers from existing anthropogenic activities such as mining and groundwater over-exploitation.