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Hydraulic Behavior of Karst Aquifers
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Hydraulic Behavior of Karst Aquifers

A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Hydraulics and Hydrodynamics".

Deadline for manuscript submissions: closed (28 February 2019) | Viewed by 50581

Special Issue Editors

Dr. Francesco Fiorillo

E-Mail Website
Guest Editor
Department of Science and Technology, University of Sannio, 82100 Benevento, Italy
Interests: hydrogeology; karst springs; hydrology; landslides; floods
Special Issues, Collections and Topics in MDPI journals
Dr. Peter Malik

E-Mail Website
Guest Editor
Dpt. of Hydrogeology and Geothermal Energy, Štátny geologický ústav Dionýza Štúra - Geological Survey of Slovak Republic, Mlynská dolina 1, 81704 Bratislava 11, Slovakia
Interests: hydrogeology; groundwater resources; hydrogeological maps; groundwater in karst; isotope hydrology

Special Issue Information

Dear Colleagues,

In many regions of the world, karst aquifers constitute a fundamental resource for water supply. Their hydraulic characteristics are very different from other aquifer types as being formed by a complex conduit network, which is “immersed” in a low permeability fractured limestone volume. Besides, karstification processes leads to development of hierarchical conduit network within the aquifer, which causes the drainage to be converged to very specific points: The karst springs.

Contributes from different karst areas of the world, dealing with the hydraulic behaviour of karst aquifers are welcome. The topic involves both classical hydraulic modelling adopted for karstic aquifers and recharge-discharge models, time series analyses, tracer tests, water geochemistry, isotope studies, etc. The aim is to provide local and general schemes of the water flow in karst aquifers, water table fluctuations and changes of hydraulic heads in the conduits during recharge and discharge periods resulting in different flow component types (either laminar or turbulent). Any hydraulic anomalies of karst aquifers connected to earthquakes, droughts, and man-made modifications are also included.

Prof. Francesco Fiorillo
Dr. Peter Malik
Guest Editor

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Water is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Karst aquifer
  • hydraulic
  • recharge
  • discharge
  • karst hydrology
  • monitoring
  • in situ tests
  • geochemistry
  • isotopes

Published Papers (14 papers)

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Editorial

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6 pages, 184 KiB  
Editorial
Hydraulic Behavior of Karst Aquifers
by Francesco Fiorillo and Peter Malik
Water 2019, 11(8), 1563; https://doi.org/10.3390/w11081563 - 29 Jul 2019
Cited by 10 | Viewed by 2952
Abstract
The objective of this Special Issue, “Hydraulic Behavior of Karst Aquifers”, is to focus on recent advances in karst hydrogeology in different areas of the world, focusing on topics dealing with the peculiar characteristics of karst aquifers. In particular, thirteen peer-reviewed articles were [...] Read more.
The objective of this Special Issue, “Hydraulic Behavior of Karst Aquifers”, is to focus on recent advances in karst hydrogeology in different areas of the world, focusing on topics dealing with the peculiar characteristics of karst aquifers. In particular, thirteen peer-reviewed articles were collected, focusing on hydraulic aspects and their relationship with geological features, geochemical and bacteriological aspects, tunneling and engineering mining inrush, and forecasting water resources and drought occurrences. Overall, these contributions describe several aspects of karst aquifers and are of great value for water resource management and protection. Full article
(This article belongs to the Special Issue Hydraulic Behavior of Karst Aquifers)

Research

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14 pages, 2534 KiB  
Article
Seasonal and Spatial Variation of Mo Isotope Compositions in Headwater Stream of Xijiang River Draining the Carbonate Terrain, Southwest China
by Jie Zeng, Guilin Han and Jian-Ming Zhu
Water 2019, 11(5), 1076; https://doi.org/10.3390/w11051076 - 23 May 2019
Cited by 15 | Viewed by 3672
Abstract
The dissolved molybdenum (Mo) contents and Mo isotope in water samples from the upper Xijiang River (XJR), draining the carbonate terrain, southwest China, are reported to investigate the seasonal and spatial variations, sources, ion budget, and isotopic fractionation of dissolved Mo. The results [...] Read more.
The dissolved molybdenum (Mo) contents and Mo isotope in water samples from the upper Xijiang River (XJR), draining the carbonate terrain, southwest China, are reported to investigate the seasonal and spatial variations, sources, ion budget, and isotopic fractionation of dissolved Mo. The results show that the Mo concentrations (5.3–18.9 nmol/L) exhibit an extensive variation along the mainstream without significant spatial pattern, but the Mo concentrations are slightly higher in the dry season than in the wet season caused by the dilution effect. There is a slight spatial tendency for δ98/95Mo to become higher along the mainstream (0.51–1.78%), while the seasonal variations in δ98/95Mo values of NPR (Nanpanjiang River) reach and BPR (Beipanjiang River) reach can be identified higher in the dry season but lower in the wet season. Based on the hydro-geochemical analysis, the sources of dissolved Mo are identified as the carbonates and sulfide/sulfate minerals weathering with a seasonal contribution. Moreover, our results suggest there is no significant Mo isotopic fractionation during weathering and riverine transportation. The calculation of Mo budget demonstrates that the dissolved δ98/95Mo of river draining the carbonate terrain is underestimated, which could significantly influence the redox history of oceans by Mo isotope model. Full article
(This article belongs to the Special Issue Hydraulic Behavior of Karst Aquifers)
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18 pages, 14049 KiB  
Article
Three-Dimensional Geophysical Characterization of Deeply Buried Paleokarst System in the Tahe Oilfield, Tarim Basin, China
by Fei Tian, Zhongxing Wang, Fuqi Cheng, Wei Xin, Olalekan Fayemi, Wang Zhang and Xiaocai Shan
Water 2019, 11(5), 1045; https://doi.org/10.3390/w11051045 - 20 May 2019
Cited by 16 | Viewed by 4265
Abstract
Paleokarst reservoirs are the major type of the Ordovician carbonate reservoirs in the Tahe Oilfield. Due to the strong heterogeneity in distribution, it is a real challenge to detect the spatial distribution of paleokarst reservoirs, especially those deeply buried more than 5500 m [...] Read more.
Paleokarst reservoirs are the major type of the Ordovician carbonate reservoirs in the Tahe Oilfield. Due to the strong heterogeneity in distribution, it is a real challenge to detect the spatial distribution of paleokarst reservoirs, especially those deeply buried more than 5500 m in the Tahe area. Based on the abundant core samples, this paper first described the structure of paleocaves drilled by well. Second, after time–depth conversions, the results from drilled wells were tied to three-dimensional (3D) seismic datasets, and then the threshold of host rocks and caves in wave impedance were identified. Third, the seismic-scale mapping and visualization of the paleokarst reservoirs were achieved by tracing the distribution of paleocaves. This approach was applied in the well T403 area, and the structure of the paleokarst, especially the runoff zone, was interpreted. 3D structure and spatial distribution of the paleokarst system was demonstrated by plane, vertical, and 3D models. Additionally, according to the hydrology genetic relationships, the paleocaves in the runoff zone were divided into sinkholes, main channel, and branch channel. The approach of a 3D geophysical characterization of a deeply buried paleokarst system can be applicable to Tahe and other similar paleokarst oilfields, which will guide hydrocarbon exploration in paleokarst reservoirs. Full article
(This article belongs to the Special Issue Hydraulic Behavior of Karst Aquifers)
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18 pages, 5879 KiB  
Article
Study on the Control of Underground Rivers by Reverse Faults in Tunnel Site and Selection of Tunnel Elevation
by Peixing Zhang, Zhen Huang, Shuai Liu and Tiesheng Xu
Water 2019, 11(5), 889; https://doi.org/10.3390/w11050889 - 28 Apr 2019
Cited by 9 | Viewed by 3974
Abstract
Along with the need for western economic development, the number of long tunnel projects which go through mountains is constantly on the rise. In the process of construction, various disaster-causing structures are frequently exposed, which leads to many geological disasters. The traditional idea [...] Read more.
Along with the need for western economic development, the number of long tunnel projects which go through mountains is constantly on the rise. In the process of construction, various disaster-causing structures are frequently exposed, which leads to many geological disasters. The traditional idea is that the reverse fault is not easily developed for an underground river, which means that the tunnel elevation design is not considered adequately. When some tunnels cross the bottom of the river, the fractures near the fault between the underground river and the excavation space may be activated and then evolve into channels, causing serious water inrush accidents during construction and operation processes. Taking the Qiyueshan Tunnel site as an example, on the premise of the anatomy of the control mechanism of the reverse fault on the development of the underground river, based on the multiperiod typical structural traces of the tunnel and surface outcrop, it was found that stratifications, dip joints, transverse joints, and tension joints of good aperture grade are important control factors. The cut block easily loses its stability and provides space for karst development, while intermittent uplifting of regional structures provides hydrodynamic conditions for the development of the underground river, causing the hydraulic gradient to be inconsistent in the overall underground river. Finally, the rainwater dynamic monitoring and tracer connectivity are data that can be fully utilized to demonstrate that a reverse fracture can control the development of the underground river. The authors further considered the effect of the vertical zoning of the fault structure and the excavation disturbance, and, drawing on the experience of the relative location of the same site in the same field, put forward the suggestion that the construction of the follow-up tunnel in the study area should be slightly higher than the elevation of the underground river. The research results can provide useful reference for similar engineering problems in the future. Full article
(This article belongs to the Special Issue Hydraulic Behavior of Karst Aquifers)
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19 pages, 14114 KiB  
Article
The Upwelling Groundwater Flow in the Karst Area of Grassano-Telese Springs (Southern Italy)
by Francesco Fiorillo, Guido Leone, Mauro Pagnozzi, Vittorio Catani, Giovanni Testa and Libera Esposito
Water 2019, 11(5), 872; https://doi.org/10.3390/w11050872 - 26 Apr 2019
Cited by 14 | Viewed by 4849
Abstract
The hydraulic phenomenon of upwelling groundwater flow affecting the karst area of the Grassano-Telese springs (southern Italy) has been investigated through piezometric measurements, discharge, and chemical–physical monitoring of springs, radon activity included. Locally, both large karst springs and sulfurous thermal springs are closely [...] Read more.
The hydraulic phenomenon of upwelling groundwater flow affecting the karst area of the Grassano-Telese springs (southern Italy) has been investigated through piezometric measurements, discharge, and chemical–physical monitoring of springs, radon activity included. Locally, both large karst springs and sulfurous thermal springs are closely located, and raise several questions on their origin. In this study, the phenomenon of the upwelling flow is supported by different types of evidences: Amazing density of sinkholes connected to hypogenic speleogenesis processes, constancy of temperature, and hydraulic conductivity of spring water, change of radon activity during the hydrological year, increasing of the hydraulic head with depth. Numerical code provides an estimation of the upwelling phenomenon in an unconfined aquifer feeding the karst springs, using MODFLOW tools. Based on the results reached, the phenomenon of the upwelling flow is able to explain the hydrological processes observed in the Telese karst area. Full article
(This article belongs to the Special Issue Hydraulic Behavior of Karst Aquifers)
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21 pages, 5870 KiB  
Article
Methodology for Determining the Die-Off Coefficient of Enterococci in the Conditions of Transport through the Karst Aquifer—Case Study: Bokanjac–Poličnik Catchment
by Željko Šreng, Goran Lončar and Marin Grubišić
Water 2019, 11(4), 820; https://doi.org/10.3390/w11040820 - 19 Apr 2019
Cited by 1 | Viewed by 2973
Abstract
This paper presents the methodology for determining the die-off coefficient of faecal indicator bacteria (enterococci) when transported in a karst environment. The main problem in exploring karst environments, which this methodology strives to cope with, is lack of field measurements, poor data on [...] Read more.
This paper presents the methodology for determining the die-off coefficient of faecal indicator bacteria (enterococci) when transported in a karst environment. The main problem in exploring karst environments, which this methodology strives to cope with, is lack of field measurements, poor data on karst rock formation, fractures and channels within it, and groundwater level dynamics. The analysed karst catchment (Bokanjac–Poličnik) is situated in the hinterland of the city of Zadar (Republic of Croatia) and covers an area of 235.07 km2. In the water supply wells within the analysed catchment, a frequent occurrence of enterococci was observed. The proposed methodology consists of two basic steps. Preliminary analyses as the initial step were used in the accumulation of certain assumptions related to the detection of increased concentrations of enterococci as well as in determination of the potential source of pollution. In the second step, the analytical model was constructed with the aim of resolving processes of sorption and die-off and determining the dominant factor in the process of natural removal of enterococci when transported in karst environment. Within the model, two parts of the pollutant transport are integrated: vertical percolation and horizontal seepage flow and transport. The mean value of the total die-off coefficient by transport through the unsaturated zone in the analysed case is k t o t = 8.25. Within the saturated zone the total die-off coefficient k t o t is within the limits of 0.1 and 0.5. Full article
(This article belongs to the Special Issue Hydraulic Behavior of Karst Aquifers)
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13 pages, 5143 KiB  
Article
Evaluation of Minimum Karst Spring Discharge Using a Simple Rainfall-Input Model: The Case Study of Capodacqua di Spigno Spring (Central Italy)
by Giuseppe Sappa, Francesco Maria De Filippi, Silvia Iacurto and Gerardo Grelle
Water 2019, 11(4), 807; https://doi.org/10.3390/w11040807 - 18 Apr 2019
Cited by 18 | Viewed by 3712
Abstract
The increasing occurrence of widespread drought phenomena is a global environmental emergency, especially for the effects of ongoing climate change on groundwater availability. Dry years and extreme temperatures are common drivers of current climate impacts all over the world, including, for example, the [...] Read more.
The increasing occurrence of widespread drought phenomena is a global environmental emergency, especially for the effects of ongoing climate change on groundwater availability. Dry years and extreme temperatures are common drivers of current climate impacts all over the world, including, for example, the freshwater supply for drinking and agriculture purposes, ecosystems, forestry, health, etc. In this frame, to ensure temporal water availability in water-stressed areas, sustainable groundwater management is an increasing challenge. Most groundwater in the South-East Latium Region, Central Italy, as in the whole Apennine Mountains chain, is stored in karst aquifers. In this area important water resources are present, but even here in the last decades they are affected by groundwater depletion as a consequence of occurring drought events, the upward trend in the global average temperature and the increase in groundwater extraction. Due to the lack of flow rate data of springs in many areas of Italy, spring response modeling could be a useful tool for supporting proper water resource management. Several research studies proposed methods based on relationships between spring discharges and rainfall data. The goal of this paper is to propose a simple linear model, based on rainfall-discharge cross correlations, in order to be able to simulate the effects of variation in rainfall on water resource connected Capodacqua di Spigno Spring minimum discharge. The results obtained using the developed model has been compared to an existing method that uses the Standard Precipitation Index (SPI) for the estimation of the minimum annual spring discharge. Full article
(This article belongs to the Special Issue Hydraulic Behavior of Karst Aquifers)
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19 pages, 7218 KiB  
Article
Recharge Impulse Spreading in Western Carpathian’s Mountainous Fissure–Karst Aquifer
by Peter Malík, Marián Coplák, Marián Kuvik and Jaromír Švasta
Water 2019, 11(4), 763; https://doi.org/10.3390/w11040763 - 12 Apr 2019
Cited by 4 | Viewed by 2157
Abstract
Foreseen construction of a highway tunnel in the northern part of the Veľká Fatra Mts. (Slovakia) triggered the need for extensive hydrogeological investigations. The projected tunnel axis would cut through a large body buildup of Middle Triassic carbonate rocks. Dolomites and limestones with [...] Read more.
Foreseen construction of a highway tunnel in the northern part of the Veľká Fatra Mts. (Slovakia) triggered the need for extensive hydrogeological investigations. The projected tunnel axis would cut through a large body buildup of Middle Triassic carbonate rocks. Dolomites and limestones with fissure–karstic permeability are surrounded by less-permeable marls, so that all springs dewatering this uplifted plate of carbonates are found above the erosion base on its edges. Detailed, hourly-based discharge monitoring of all four major springs was performed during the spring and summer period of 2014. In the meantime, groundwater table observations in two boreholes, located in the center of the fissure–karst aquifer, were run in the same time interval. Based on air temperature and precipitation records, the 2013–2014 winter period was practically without snow cover. In the middle of March 2014, an intense rainfall event caused a sudden rise of the groundwater table in the TK-04 borehole located in the southern part of the carbonate plate. Spreading of this singular hydraulic impulse throughout the structure was differently registered at individual springs within the time shift span of 1.38 to 65.25 days. Groundwater level rise of 0.40 m in the TK-04 borehole was postponed in 5.33 days. The response time of spring discharge to sudden groundwater table rise within the structure occurred later at springs with a higher water temperature. Water temperature differences between individual springs were still within the 2.46 °C narrow interval (5.57–8.03 °C). The vertical component of groundwater flux should play an important role even in a relatively simple, plate-shaped mountainous karstic aquifer fully uplifted above the erosional base, as was the case of the investigated Kopa Mt. hydrogeological structure. Full article
(This article belongs to the Special Issue Hydraulic Behavior of Karst Aquifers)
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11 pages, 4904 KiB  
Article
Flux of Inorganic Carbon as Dissolved, Suspended, and Bed Loads through a Karstic Basin
by Randall Paylor and Carol Wicks
Water 2019, 11(4), 644; https://doi.org/10.3390/w11040644 - 28 Mar 2019
Cited by 2 | Viewed by 2317
Abstract
Most studies of carbonate bedrock weathering have focused on the dissolved inorganic carbon (DIC) flux while dismissing particulate inorganic carbon (PIC) as insignificant. However, under certain flow conditions PIC flux may be an important term in carbonate weathering. In this study, the total [...] Read more.
Most studies of carbonate bedrock weathering have focused on the dissolved inorganic carbon (DIC) flux while dismissing particulate inorganic carbon (PIC) as insignificant. However, under certain flow conditions PIC flux may be an important term in carbonate weathering. In this study, the total inorganic carbon (TIC) flux was calculated in a fluviokarst basin. Water samples and in situ data loggers were used to determine suspended sediment concentration and water chemistry. The mass of PIC within suspended sediments was quantified by cation/anion analysis of dual filtered/unfiltered samples. The flux of bed load material was calculated via stream power calculations. The analysis of recorded storm events indicated that PIC flux is moderate but can be significant during peak storm discharges. A small storm with a 0.87-month return period produced a PIC flux of 14 g s−1 and a DIC flux of 150 g s−1 at 1.4 m3 s−1 discharge. The largest storm had a return period of 7.7 months, a peak discharge of 4.6 m3 s−1, and peak PIC flux of 620 g s−1 compared to a peak DIC flux of 350 g s−1. During storm events, bed load was the most significant component of the total PIC flux, exceeding the suspended load flux by an order of magnitude. When calculated on an annual basis, the data show that PIC contributes about 10 percent to total inorganic carbon removal. Full article
(This article belongs to the Special Issue Hydraulic Behavior of Karst Aquifers)
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10 pages, 3477 KiB  
Article
The Importance of Detailed Groundwater Monitoring for Underground Structure in Karst (Case Study: HPP Pirot, Southeastern Serbia)
by Marina Čokorilo Ilić, Ana Mladenović, Marina Ćuk and Igor Jemcov
Water 2019, 11(3), 603; https://doi.org/10.3390/w11030603 - 22 Mar 2019
Cited by 6 | Viewed by 2978
Abstract
The establishment of detailed monitoring of quantitative and qualitative parameters of groundwater in the zone of possible interactions between a water-conveyance tunnel and the geologic/hydrogeologic environment is of the utmost importance for assessing the risk of adverse effects and of tunnel performance. The [...] Read more.
The establishment of detailed monitoring of quantitative and qualitative parameters of groundwater in the zone of possible interactions between a water-conveyance tunnel and the geologic/hydrogeologic environment is of the utmost importance for assessing the risk of adverse effects and of tunnel performance. The water-conveyance tunnel of the Pirot Hydropower Plant (HPP Pirot) is a good example of applying detailed monitoring in complex geologic/hydrogeologic conditions resulting from the presence of an underground structure. The research scheduling was conditional upon the operating regime of the tunnel (whether it is in or of operation—online or offline). While the tunnel was operating (online), monitoring was conducted at observation wells along the tunnel (approx 15 m distant), a control gate (water losses), springs, and a stream in the vicinity of the tunnel. Areas of the potential hydraulic instability were indicated by synchronous measurements of water level and temperature changes in the observation wells and at the control gate. While the tunnel was offline (empty tunnel) it was possible to access the tunnel, and in situ monitoring proved to be of great importance. Observations of quantitative parameters pointed out hydraulically critical tunnel zones, whilst the qualitative characteristics of groundwater revealed their potential aggressiveness to the concrete lining of the tunnel. The applied methodology shows that a detailed observation program should be an important task of sustainable tunnel management. Full article
(This article belongs to the Special Issue Hydraulic Behavior of Karst Aquifers)
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15 pages, 2371 KiB  
Article
Dynamics of the Flow Exchanges between Matrix and Conduits in Karstified Watersheds at Multiple Temporal Scales
by Vianney Sivelle, David Labat, Naomi Mazzilli, Nicolas Massei and Hervé Jourde
Water 2019, 11(3), 569; https://doi.org/10.3390/w11030569 - 19 Mar 2019
Cited by 26 | Viewed by 4439
Abstract
The focus of this paper is to investigate the ability to assess the flow exchanges between the matrix and the conduits in two karstified watersheds (Aliou and Baget, Ariège, France) using the KarstMod modeling platform. The modeling is applied using hourly and daily [...] Read more.
The focus of this paper is to investigate the ability to assess the flow exchanges between the matrix and the conduits in two karstified watersheds (Aliou and Baget, Ariège, France) using the KarstMod modeling platform. The modeling is applied using hourly and daily time series. First, the flow dynamics between the conduit and the surrounding matrix are described on a rainfall event scale (i.e., a few days). The model allows us to describe a physical reality concerning the flow reversal between matrix and conduit when there is a significant rainfall event. Then, the long-term trends (i.e., inter-annual) in the matrix water level are evidenced using the moving average over shifting horizon method (MASH). The mean water level in the matrix dropped about 10% to 15% since the late 1960s. Also, the matrix recharge has been delayed from February in the late 1960s to April since the 1990s. Moreover, the contribution of the matrix in the total spring flow is estimated though mass balance. It is estimated that the annual matrix contribution in the total spring flow is about 3% and it can increase to up to 25% during periods with low rainfall. Full article
(This article belongs to the Special Issue Hydraulic Behavior of Karst Aquifers)
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21 pages, 2957 KiB  
Article
A New Perspective to Explore the Hydraulic Connectivity of Karst Aquifer System in Jinan Spring Catchment, China
by Zhengxian Zhang, Weiping Wang, Shisong Qu, Qiang Huang, Shuai Liu, Qiaoyi Xu and Ludong Ni
Water 2018, 10(10), 1368; https://doi.org/10.3390/w10101368 - 30 Sep 2018
Cited by 26 | Viewed by 2909
Abstract
Investigating the hydraulic connectivity of a complex karst aquifer system is an important research topic for sustainable operation and optimization layout of karst groundwater exploitation and recharge. However, the identification of preferential sites of recharge and exploitation is usually subject to regional hydrogeology [...] Read more.
Investigating the hydraulic connectivity of a complex karst aquifer system is an important research topic for sustainable operation and optimization layout of karst groundwater exploitation and recharge. However, the identification of preferential sites of recharge and exploitation is usually subject to regional hydrogeology conditions and the mechanisms of recharge and exploitation. The conventional research methods of hydraulic connectivity often have some limitations. In this study, we developed an improved grey amplitude relation model to explore the hydraulic connectivity in Jinan spring catchment and presented a quantized evaluation index water table fluctuation relation degree (WTFRD) using karst groundwater table data in Western Jinan and Jinan spring groups from 2014 to 2017. Results showed that the total WTFRD was 0.854 between Western Jinan and Jinan spring groups when the external distraction for karst groundwater table was the smallest, which was in high relation degree grade. Meanwhile, the change rules of karst groundwater table in the two sites were basically the same. Accordingly, a high connectivity occurred between the two karst aquifers from a statistical perspective, and further illustrated that Western Jinan could be selected as preferential experiment sites. A comprehensive case in Jinan spring catchment indicated that the WTFRD provided a preliminary idea to investigate hydraulic connectivity quantitatively. This method could be considered as a pre-study of the conventional experiments to form a high-efficiency and low-cost combined method, which has great potential and merits further study. Full article
(This article belongs to the Special Issue Hydraulic Behavior of Karst Aquifers)
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24 pages, 14810 KiB  
Article
Experimental Study of Influence of Karst Aquifer on the Law of Water Inrush in Tunnels
by Weimin Yang, Zhongdong Fang, Xin Yang, Shaoshuai Shi, Jing Wang, Hao Wang, Lin Bu, Liping Li, Zongqing Zhou and Xueqing Li
Water 2018, 10(9), 1211; https://doi.org/10.3390/w10091211 - 07 Sep 2018
Cited by 22 | Viewed by 3439
Abstract
Water inrush is a geological hazard often encountered in tunnel construction. In order to overcome problems encountered when using the existing water-inrush simulation model test, such as single function, low repetition utilization rate, and poor visibility, we developed a multi-type water-inrush model test [...] Read more.
Water inrush is a geological hazard often encountered in tunnel construction. In order to overcome problems encountered when using the existing water-inrush simulation model test, such as single function, low repetition utilization rate, and poor visibility, we developed a multi-type water-inrush model test system. Our test system can be a precursor to large-scale studies, handle multiple types, and perform serialization and visualization. We conducted cavity water-inrush simulation testing using this device, and studied the failure model of aquifuge rock. We reveal the evolution laws of water inrush from the cavity, including the initiation of fracture in the aquifuge rock, the formation of water-inrush channels, and the rupture of the aquifuge rock. By analyzing the seepage pressure changes at the monitoring points of the aquifuge rock, we divided the water-inrush process of the cave into a rack generation stage, a holing-through of fracture and forming of water-inrush channel stage, and a water-inrush stage. Test results show that the system is stable and reliable, only requiring a short test period, and can be used to guide large water-inrush testing and related projects. Full article
(This article belongs to the Special Issue Hydraulic Behavior of Karst Aquifers)
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17 pages, 5581 KiB  
Article
In-Situ and Numerical Investigation of Groundwater Inrush Hazard from Grouted Karst Collapse Pillar in Longwall Mining
by Dan Ma, Xin Cai, Qiang Li and Hongyu Duan
Water 2018, 10(9), 1187; https://doi.org/10.3390/w10091187 - 04 Sep 2018
Cited by 67 | Viewed by 4692
Abstract
Groundwater inrush is a typical hydrologic natural hazard in mining engineering. Since 2000 to 2012, there have been 1110 types of mine groundwater inrush hazards with 4444 miners died or missing. As a general geological structure in the northern China coalfields, the karst [...] Read more.
Groundwater inrush is a typical hydrologic natural hazard in mining engineering. Since 2000 to 2012, there have been 1110 types of mine groundwater inrush hazards with 4444 miners died or missing. As a general geological structure in the northern China coalfields, the karst collapse pillar (KCP) contains a significant amount of granular rocks, which can be easily migrated under high hydraulic pressure. Therefore, the KCP zone acts as an important groundwater inrush pathway in underground mining. Grouting the KCP zone can mitigate the risk of groundwater inrush hazard. However, the fracture or instability of the coal pillar near KCP can cause the instability of surrounding rock and even groundwater inrush hazard. To evaluate the risk of groundwater inrush from the aquifer that is caused by coal pillars instability within grouted KCP in a gob, an in-situ investigation on the deformation of the surrounding strata was conducted. Besides, a mechanical model for the continuous effect on the coal pillar with the floor-pillar-roof system was established; then, a numerical model was built to evaluate the continuous instability and groundwater inrush risk. The collective energy and stiffness in the floor-pillar-roof system are the two criterions for judging the stability of the system. As a basic factor to keep the stability of floor-pillar-roof system, the collective energy in coal pillar is larger than that in floor-roof system. Moreover, if the stiffness of floor-roof or coal pillar meets a negative value, the system will lose stability; thus, the groundwater inrush pathway will be produced. However, if there is a negative value occurring in floor-pillar-roof system meets, it indicates that the system structure is situated in a damage state; a narrower coal pillar will enlarge the risk of continuous instability in the system, leading to a groundwater inrush pathway easily. Continuous coal pillars show a lower probability of instability. Conversely, the fractured coal pillars have a greater probability of failure. The plastic zone and deformation of the roadway roof in the fractured coal pillar are larger than that of continuous coal pillar, indicating that the continuous coal pillars mitigate the risk of groundwater inrush hazard effectively. Full article
(This article belongs to the Special Issue Hydraulic Behavior of Karst Aquifers)
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