Karst Ground Research Articles

Оценка уязвимости карстовых подземных вод к загрязнению на основных массивах Горного Крыма с использованием региональной методики

Introduction. Assessment of groundwater vulnerability to contamination is an effective tool for scientific substantiation of the sanitary protection zones for drinking water sources. Karst ground waters of the Mountain Crimea form the main resources for water supply in the Crimean Peninsula. This study has a purpose to perform the assessme nt and mapping of karst ground waters resource vulnerability to contamination on such representative massifs of the Crimean Mountains as Chatyrdag, Dolgorukovsky, Karabi and Ay-Petri . Materials and methods. Assessment of karst ground waters vulnerability is conducted by use of Mountain -Crimean method. It has been developed on the base of some wide-tested European methods (COP-method and Slovene approach) with methodological modification and adaptation to regional conditions of the Mountain Crimea. The input data for assessment is spatial information about ground waters vulnerability factors: protective layers in vadose zone, flow concentration by streams, sinkholes and caves, precipitation regime etc. The collected spatial information was converted into attributed geo data layers, which were subsequently subjected to overlay operations in Arc GIS 10 software according to assessment scheme. Results. According to the assessment results, approximately 34 and 14% of the Chatyrdag massif area gained the category of high and very high vulnerability, on the Karabi massif – 14 and 17%, on the Dolgorukovsky massif – 14 and 2%, on the Ay-Petri massif – 19 and 7% of total area respectively. The result ing vulnerability maps demonstrate significant mosaics and contrast, which is associated with discrete distribution of protective covers and high differentiation of ground water recharge conditions within the catchments of karst massifs. Discussion. Analysis of the resulting vulnerability maps have revealed that the leading factors determining areas of high and very high vulner ability of karst waters are runoff concentration factors, while the factors of protective cover mainly determine the areas with low vulnerability. The zones of high vulnerability on the Chatyrdag and Karabi massifs are mainly coincide with areas of high density of karst forms (sinkholes and caves), while high vulnerability zones of the Ay-Petri and Dolgorukovsky massifs are predominantly associated with areas near permanent and temporary watercourses. In general, the obtained maps of groundwater vulnerability are quite consistent with the known data on the hydro-geological conditions of the assessed massifs. Conclusions. The identified differences in the area ratio and spatial distribution of ground waters vulnerability categories between the assessed massifs are a consequence of local geological, geo-morphological and hydrological features. The obtained results confirm high applicability of the Mountain-Crimean regional method for groundwater vulnerability assessment, at least for the karst massifs of the Mountain Crimea. Suggestions for practical application and direction for future research. The produced groundwater vulnerability maps create a scientific basis for delineation of water protection zones, assessing the risks of groundwater pollution and developing the territorial planning schemes within studied areas. The next stage of study is an assessment of groundwater source vulnerability for individual karst springs used in water supply.

The Analyses of Land Use and Prevention in High-Density Main Urban Areas under the Constraint of Karst Ground Subsidence: Study of Wuhan City, China

The development and utilization of land in the main urban area have significantly impacted the stability of the regional geological environment through various means, such as increased load and subway construction, primarily manifested as rock and soil mass deformation leading to geological hazards. Therefore, it is worth exploring how to reduce the occurrence of karst ground subsidence (KGS) through reasonable land development and control measures in the main urban areas with large-scale developments of buried karst formations. This study focuses on the main urban area of Wuhan City. An evaluation model for KGS was constructed using the analytic hierarchy process (AHP) and comprehensive index evaluation method by analyzing the geological conditions that affect KGS. The susceptibility zoning of KGS was obtained with GIS spatial analysis technology. The results show that the susceptible areas can be divided into extreme, high, medium, and weak susceptibility, accounting for 4.93%, 15.30%, 33.21%, and 46.56%, respectively, which are consistent with the distribution density of past KSGs. Furthermore, by selecting the subway construction as a human activity type, it indirectly discusses the influence of land development intensity on KGS. The results show that past KSGs are mainly concentrated in areas with high engineering construction density and significant land development intensity. Based on the above, strategies for regional land development and prevention and control of KGSs are proposed.

A random forest model of karst ground collapse susceptibility based on factor and parameter coupling optimization

The purpose of this study is to develop a coupling model to improve the ability of random forest model to accurately predict karst collapse. Therefore, an inventory map consisting of 327 collapse points and 1962 non-collapse points was created. The database also contains 18 influencing factors, ranked with GeoDetector. 16 optimized factors were obtained. Bayesian algorithm was used to optimize the parameters of RF model. The optimized factors and RF model were used to create a collapse map, compared with the original map. After coupling and optimizing the factors and parameters, the accuracy of the RF model was 0.935; precision, 0.964, and AUC value, 0.977. Compared with the unoptimized model, the accuracy, precision and AUC value of the optimized RF model improved by 0.197, 0.146 and 0.134, respectively. The results show that the method of optimizing and coupling the factors and parameters contributes to improve the karst collapse susceptibility model.

Measurement and prediction of tunnelling-induced ground settlement in karst region by using expanding deep learning method

This paper presents the measurement and prediction of the tunnelling-induced surface response in karst ground, Guangzhou, China. A predictive method of ground settlement is proposed named as the expanding deep learning method. This method kinetically uses the expanding tunnelling data to predict ground settlement in real time. Four types of deep learning methods are compared, including artificial neural network (ANN), long short-term memory neural networks (LSTM), gated recurrent unit neural networks (GRU), and 1d convolutional neural networks (Conv1d). Based on static Pearson correlation coefficient, a kinetic correlation analysis method is proposed to evaluate the variable significance of input data on the ground settlement. The effect of cemented karst caves and variable geological conditions are then analysed. The results indicate that the expanding Conv1d model precisely predict the tunnelling-induced ground settlement. The kinetic correlation analysis can reflect the variable influence of geological condition and tunnelling operation parameters on the ground settlement.

PREDICTION OF KARST GROUND COLLAPSE BASED ON FACTOR ANALYSIS-GA-ELM MODEL

Karst ground collapse is the result of many factors, and has the characteristics of concealment and abruptness. In order to predict karst ground collapse quickly and accurately, this paper presents a karst ground collapse prediction model which is based on factor analysis, genetic algorithm(GA) and extreme learning machine(ELM). Firstly, we identify eight typical influencing factors in the karst area. Then, we extract five common factors by factor analysis. Finally, we input the common factors into GA-ELM model and predict karst ground collapse. The sample data contains 20 groups of actual case data, of which 12 groups as training sets and the other 8 groups as test sets. The conclusions are as follows: Factor analysis can not only simplify the ELM model network structure, but also improve the prediction accuracy under the same number of hidden layer of neuron nodes. In the case of a small number of samples, the prediction accuracy of the ELM model can be improved by increasing the number of hidden layer neuron nodes. Compared with the ELM model, the prediction accuracy of GA-ELM model is improved significantly, with stronger learning and prediction ability. The prediction method of karst ground collapse based on Factor Analysis-GA-ELM model is simple, accurate and efficient.

Analysis of water flow during the drought and flood seasons case study: The Mosul dam, Iraq

Mosul Dam is a structure facilitated to create a reservoir or a human-made lake named Lake Dahuk. Tigris river is the upstream water supply of the Mosul dam. The dam located at the western of Mosul city, the center of the governorate of Nineveh in the north of Iraq. The only drawback of the dam is the position; it is built on unstable karst ground. This worry situation led to take serious efforts and treatment decisions since the occupation of Iraq in 2003. Unfortunately, no concrete news till now whether the dam is safe or not and what is the prudential supervision needed. The data of this research are obtained from the Iraqi ministry of water resources/Mosul dam department. Schedule reports and 442 monthly data values have been monitored using advanced electronic instruments and technical programming, under experience engineers and special supervisors within the period 2000-2016. The objectives of this study are; Analysis the water flow during the drought and flood seasons, also to study the impact of the Ilisu dam on the Mosul dam efficiency. In addition, this analysis gives the answers to the puzzling questions and probably hundreds of researches concerns. It was noticed that within the period 2009 to 2015 the monthly inlet water discharge values are the same values of the outlet discharge. And the highest value observed of the water level achieved by the dam in the year 2002 is 329.55 m above means sea level, while the less value is 287.89 m in 2011. In addition to the continuous operation of foundation concrete grouting, it is highly recommended to increase the depth of the grouting. Finally, the Ilisu dam has no direct impact on Mosul dam efficiency.

Mechanism of Shallow Soil Cave–Type Karst Collapse Induced by Water Inrush in Underground Engineering Construction

Water inrush disasters are the main cause of karst collapse. In this study, a physical model test was conducted to investigate the mechanism of karst collapse. The formation, expansion, and variation of a soil cave induced by water inrush were studied, including the expansion pattern of soil cavities, the voids between the bottom of the hole, cavity disengagement, wall collapse, and soil cavity expansion. The variation of shear stress in soil under the dynamic change in groundwater level was simulated and analyzed using a finite-difference method. When the groundwater level falls, the expansion and collapse of a soil cave are caused by the concentrated action of shear stress on the arch foot of the soil cave. Results of this study deepen the understanding of karst collapse induced by water inrush in underground engineering and provide guidance for the prevention and control of karst ground collapse.

Interactive geotechnical design in karst and ex-mining ground in Malaysia

The Kinta Formation is one of the prominent and complex karst formations in Malaysia. Karst ground has an abundance of cavities, solution channels, pinnacles, overhangs and floaters. Design and construction of foundations in such ground conditions are complicated. If a given site has karst geology and is an also ex-mining ground, the challenges are compounded. Often, generalised and one-size-fits-all designs are used in geotechnical engineering. However, in such unpredictable and challenging soil conditions, this approach can be either conservative or unsafe. An interactive geotechnical design approach is vital to achieving an economical and practical solution. In this paper, the role of interactive design in foundation design and construction of a lime-processing plant in Malaysia is discussed. The site, located in the eastern part of Peninsular Malaysia, sits within the bounds of the Kinta Formation and was a former tin-mining ground. Over the 34 ha of the project site, earthworks and foundations were required to be executed. Some examples of solutions derived by interactive design in geotechnical engineering as applied to this project are discussed.

Formulation and performance of grouting materials for underwater shield tunnel construction in karst ground

Grouting is one of most important techniques for underwater tunnelling in karst ground which is actually difficult to be resolved due to the presence of underground water flow. This paper proposed a new grouting material to fill karst caverns when there is flowing underground water prior to shield tunnel construction. The grout uses bentonite and cement as the base material, and a curing agent were added to form excellent fluidity, stability and scour resistance. The effects of the composition and formulation on the performance of the grouting material, and the optimal formulations were determined through a series of laboratory experiments. The recommended parameters for the grout are a specific gravity for the bentonite slurry from 1.30 to 1.35, a cement content of 30%, a meta-aluminate content of 1.25% and a lignin content of 0.20%. The effectiveness of the hardened cement-bentonite grouting material (HCBGM) was checked by a field grouting application for a underwater shield tunneling in karst area, and the results illustrated that the proposed grouting material not only can fulfill the engineering requirements but also turns out cost effective and eco-friendly.

Susceptibility mapping of instability related to shallow mining cavities in a built-up environment

Anthropogenic activities and urbanization frequently spread over areas underlain by unstable karst ground or man-made cavities, leading to potential risk situations for buildings, infrastructure and population. The roof of the cavities may rapidly propagate upwards, eventually resulting in progressive ground settlement and/or sudden collapse. These processes are frequently accelerated or triggered by various human activities (e.g., overloading, water recharge, water table decline). In this paper, the susceptibility to instability of artificial cavity networks under an urban area in Apulia Region, Southern Italy, was assessed and evaluated. Here, there is dense network of underground quarries excavated for the extraction of massive calcarenite for building and ornamental stone that are currently affected by severe instability problems. Identifying the zones of the cavities most prone to instability is of great practical importance. Susceptibility models have been developed analyzing the statistical relationships between the cavity sections with evidence of instability and a number of predisposing factors mainly related to the 3D geometry of the voids, roof thickness and the presence of overloads. The models produced by the discriminant analysis and the logistic regression approaches were independently and quantitatively evaluated through the construction of ROC curves. Although the two models are characterized by different input data treatment, as the logistic regression allows using continuous and discrete variables or any combination of both types even if they do not have a normal distribution, the ROC curves highlighted, for both methods, a satisfactory congruence between the model results and the observed data. Consequently, from the model performance analysis, the two models were evaluated comparable in terms of result reliability. The methodology should be considered as a general first-level analysis for near surface underground cavities aimed at identifying critical cave sectors that can be the focus of more detailed analyses, especially those associated with sensitive zone related to the presence of buildings, roads and frequent presence of human activity.

Vegetation Recovery in Karst Areas in Central Guizhou, China

Due to the unique environment of karst landscapes, there are many uncertainties regarding the recovery of vegetation following human disturbance. Through standard wood parsing and growth ring investigation in Puding county in Guizhou province, China, we studied the process of vegetation restoration in karst areas. According to our results, during the recovery of karst vegetation height increases and ground diameter enlargement of tree layers occurred. Increases in the height and ground diameter followed logarithmic and growth curves, respectively. The development time of trees showed continuity, and growth points were randomly distributed. However, with large propagule quantities, vegetation can be directly restored and developed into a secondary high forest without a grass filling stage, and the recovery time is shortened.

Research on the natural features of karst water, on the example of some water intakes

The existence of safe and abundant raw water sources is a priceless treasure for any country. Water resources are of particular importance for Montenegro, especially for the development of tourism and agriculture which represent the backbone of its economic development. With respect to water potential, Montenegro is at the top of Europe. However, it is not a sufficient factor, but the very way it is used and protected, as well as the improvement of its valorization. Economic development which is not based on the conservation and good governance of natural resources may have negative consequences for the overall development. The aim of the paper is the study of natural properties of karst ground waters and their changes through interrelation of some ions, as indicators, on the example of five intakes in use. The paper presents the results of the research on the said waters and the values of indicators which point to their exceptional benefits for the water supply. However, the effects of the anthropogenic factor are evident, which are reflected in the range of the mole ratio of Ca /Mg ions ranging from 5.4 to 9.6, and the values (eqv.SO4/Cl) ranging from 0.3 to 2.0. Protection of the environment, especially preservation of the quality of water resources of Montenegro, imposes the urgency of implementation of the objectives of the Water Framework Directive.

Effects of Anthropogenic on Karst Groundwater Geohydrochemistry in an Urbanized Area

Laolongdong Underground River used to be important drinking water source, but the water quality has been deteriorated since 1990s and the underground river becomes a sewer nowadays because of anthropogenic and urbanization influence. In order to find out the impacts of water-bedrock interaction, domestic sewage and agricultural activities on groundwater, the chemical characteristics of the groundwater were monitored each month to research the contamination sources and the contributed factors. The result shows that the groundwater is characterized as the HCO3-SO4-Ca type, which implys that groundwater geochemistry is controlled by middle and lower Triassic carbonate rocks. Moreover, the concentrations of K+, Na+, Cl-, and PO43-reveale an increasing trend and NO3-deceasing from 2008 to 2012. According to general contamination sources, the data implys that urbanization process and land use changing caused karst ground water pollution process and contaminations convert from agriculture effort to sewage and animal feces effort.

Geological engineering problems associated with tunnel construction in karst rock masses: The case of Gavarres tunnel (Spain)

A representative example of the problems associated with the excavation and support of tunnels in karst ground is presented. It is a peculiar case in terms of heterogeneity and spatial distribution of zones of poor geotechnical quality, requiring the need to define, preferably in the study phases, adequate site investigation, suitable design procedures, efficient construction techniques and appropriate ground treatment. The difficulties associated with the instability of the karstified ground, and the presence of cavities, wholly or partially filled with soils of low cohesion, are discussed via retrospective analysis. The solutions adopted to solve the problems encountered during the tunnel construction enabled a systematic approach, useful for new construction projects in limestone terrains of medium to high karstification.

Estimating potential for exploitation of karst aquifer: case example on two Serbian karst aquifer

Rational use of karst water resources depends considerably on the existence of a successful approach to estimating karst groundwater potential for exploitation. The term groundwater potential for exploitation involves the application of regulatory measures affecting natural outflow regime. Generally, the concept of controlling the artificial discharge regime is based on two principles. The first one, the “borrowing” of water from deeper (storage) part of storage, is based mainly on the construction of groundwater wells. The second one, considers increasing dynamic reserves by providing additional artificial water storage thereby controlling the groundwater discharge regime, is based on the construction of underground dams. This paper examines how these two concepts can be used to increase potential groundwater usage from two karst springs in Serbia—St. Petka and Perucac. The ability to potentially increase the amount of karst ground water available for future exploitation may facilitate and give important directions to the future research.

GIS-Based Risk Assessment to Karst Susceptibility of Shenzhen Universiade Center (China)

Abstract Shenzhen Universiade Center is located in Longgang District, Shenzhen city, Guangdong province. There are various size karst cave and soil cave on site and their buried depth are from 2m to 50m. With the application of GIS technology and statistical techniques, three assessment models were established to karst spatial distribution of Shenzhen Universiade Center. Model I was the Logistic model based on geophysical information with dependent variables as anomalous areas revealed by geophysical prospecting. Model II was the Logistic model based on drilling information with dependent variables as karst caves and soil caves revealed by drilling. The independent variables of both models were the geological factors affecting karst susceptibility, including lithology, groundwater depth and the distance away from tectonic lines. Model III was the Bayesian model with integrated information of Model I and Model II. The correct probability of the model I is 58.17% when karst occurs; when does not occur karst, the correct probability is 86.75%. The fitness rate is 90.75%. The correct probability of the model II is 60.34% when karst occurs; when does not occur karst, the correct probability is 79.13%. The fitness rate is 88.38%. The result shows that Bayesian model can establish integrated assessment model including multi- source data to a certain extent, which can be employed in karst susceptibility assessment. The results of Logistic model and Bayesian model can be used as evidence for karst ground collapse vulnerability in the site.

Groundwater Systems and Eco-hydrological Features in the Main Karst Regions of China

: Different karst water features and related water resources are present both in southern and northern China. There are over 3,358 well-developed karst ground river systems with total discharges in the dry season of about 420times108 m3 in the main karst regions in the southern part of China. Exploitation rates are only 8–15%. Over 100 larger karst spring systems in the main karst regions of northern China cover a catchment area from 500 km2 to over 4,000 km2, of which the average discharge appears to be from about 1 m3/s to 13 m3/s and the exploitation rates are 70–80%. Six aspects of the eco-hydrological features of some typical karst regions in China comprising water environment, ecological features, materials and structures between parent rock and soil, bio-geological processes and palynological studies (spore-pollen) are discussed. Qualitative evaluation of eco-geology and rocky desertification in the karst regions should be based on the main karst ecological conditions as well as artificial, i.e., man-made impacts.

Observations of stage and temperature dynamics in the epiphreatic caves within the catchment area of the Ljubljanica river (Slovenia)

Karst ground water dynamics between the Planinsko polje and the springs of Ljubljanica (Slovenia) was studied based on the monitoring of stage and temperature of ground water in four caves. The Unica River, which flows over the Planinsko Polje, and sinks at its E and N rim, is considered as the main input to the observed system. At small flood events its role is none or questionable. At medium and large events, when the discharge of Unica exceeds 25 m 3/s, it becomes an important and/or the dominant input to the system. When the capacity of the primary (eastern) ponors in the polje is exceeded, the stage in a cave, which is fed solely through these ponors, reaches the plateau followed by a very slow recession. The surplus flow goes towards northern ponors causing a fast rise of the stage in adjacent to them. In two of the northernmost caves, the stage response is almost identical, but the temperature variations are different. The uniform water level suggests a highly permeable region bounded by a low permeability barrier in the down-flow direction, while different temperature behavior indicates a different origin of the waters for each cave.

Hydrogeology of Carbonate Aquifers: A Short History

Introduction Research on carbonate aquifers has followed two tracks that have been largely separate and have had limited cross communication. One approach has focused on data from wells, used Darcy’s law, and often assumed that aquifers behave as porous media. The second approach has largely focused on data from springs and caves, and often used the Darcy-Weisbach equation to interpret flow through the major conduits in the aquifer. The history of the former approach has been well described (e.g., Fetter 2004), and so this account will largely focus on the second approach, which is commonly termed ‘‘karst hydrogeology,’’ although the term ‘‘karst’’ does extend beyond carbonates to evaporites and some silicate rocks. In many, but by no means all, karst regions, there is a clear link between landforms (both on the surface and underground) and ground water. Thus, there is greater interaction between geomorphologists and ground water scientists for carbonate rocks than for other lithologies. For example, the work of Cvijic (1893) laid the foundation of modern ideas in karst geomorphology, while his 1918 paper was the first to develop the idea of a dynamically evolving karst ground water system with three hydrographic zones (Ford and Williams 2007, 7).

Sinkhole hazard case histories in karst terrains

With few exceptions, the ground collapses that constitute the karst geohazard in engineering activity in limestone terrains are induced by human activity. Subsidence sinkholes, formed entirely within the soil profile, constitute the most widespread karst geohazard, but are largely induced by engineered works, either directly or accidentally. Water table decline (as a result of pumped abstraction or quarry de-watering) and uncontrolled surface drainage input are the two key factors that induce subsidence sinkholes, especially where both are involved. Collapse sinkholes, formed by failure of bedrock over a cavity, are rare in natural karst landscapes, but may be induced by excessive loading imposed on limestone that lies above an open cave; the risks associated with this geohazard should be eliminated by implementation of an appropriate site investigation that includes proof drilling. Case studies to demonstrate the karst geohazard concern: (1) homes damaged by new sinkholes around a de-watered limestone quarry in Pennsylvania; (2) problems with sinkholes for a railway across dolomite karst in South Africa; (3) collapse of ground in pseudokarst in Guatemala; (4) failure of a viaduct pier into an unseen cave in Florida; (5) estimation of potential sizes of collapse sinkholes along a pipeline route over gypsum karst in Turkey. As hazardous new sinkholes in karst are almost entirely induced by either uncontrolled drainage or excessive loading, they should be largely eliminated by appropriate engineering design and works. These need to be based on a proper understanding of karst ground conditions.