Catastrophe theory-based risk evaluation model for water and mud inrush and its application in karst tunnels

This paper presents a risk evaluation model of water and mud inrush for tunnel excavation in karst areas.The factors affecting the probabilities of water and mud inrush in karst tunnels are investigated to define the dangerousness of this geological disaster.The losses that are caused by water and mud inrush are taken into consideration to account for its harmfulness.Then a risk evaluation model based on the dangerousness-harmfulness evaluation indicator system is constructed,which is more convincing in comparison with the traditional methods.The catastrophe theory is used to evaluate the risk level of water and mud inrush and it has great advantage in handling problems involving discontinuous catastrophe processes.To validate the proposed approach,the Qiyueshan tunnel of Yichang-Wanzhou Railway is taken as an example in which four target segments are evaluated using the risk evaluation model.Finally,the evaluation results are compared with the excavation data,which shows that the risk levels predicted by the proposed approach are in good agreements with that observed in engineering.In conclusion,the catastrophe theory-based risk evaluation model is an efficient and effective approach for water and mud inrush in karst tunnels.

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 420×10^8 m^3 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 km^2 to over 4,000 km^2, of which the average discharge appears to be from about 1 m^3/s to 13 m^3/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.

Characteristics of Underground Water Flow at Different Water Levels in Tianshengan Karst Area, Yunnan, China

Three tracing tests from the same injection point executed at low, medium, and high water levels in the karst aquifer near Tianshengan village, Lunan Stone Forest, Yunnan Province, China, have revealed the basic properties of underground water flow. They showed the general directions of water flows; tracer concentrations were observed at six successive points allowing for the calculation of apparent dominant flow velocities at these sections towards the Dalongtan karst spring. For the high water level, the discharge between single sections was between two and 10 times greater than that at low water level. For the medium water level, the flow velocity at different sections was between 1.4 and 3.7 times faster than that at low water level; and for high water level, it was between 1.3 and 2.7 times faster than that at medium water level. The fastest water flow appeared at the first section （23 cm/s at medium water level）; and the slowest （0.6 cm/s at low water level） appeared where water flow must cross the Tianshengan fault （north-south direction）, and later, a layer of 20-30 m thickness of quartz sandstone and shale clay-stones. It was also possible to calculate the recovery of the tracer for point 4, Dakenyan, where discharge was measured. At the medium water level, 50% of the injected tracer was detected a half-day after its first appearance and at low water level after more than 3 days. The previously published research illustrates the transport velocities of possible contaminants and their solubilities in water at different hydrological conditions.

Detection and treatment of water inflow in karst tunnel：A case study in Daba tunnel

In a karst tunnel, fissures or cracks that are filled with weathered materials are a type of potential water outlet as they are easily triggered and converted into groundwater outlets under the influence of high groundwater pressure. A terrible water inrush caused by potential water outlets can seriously hinder the project construction. Potential water outlets and water sources that surrounding the tunnel must be detected before water inflow can be treated. This paper provides a successful case of the detection and treatment of water inflow in a karst tunnel and proposes a potential water outlet detection(PWOD) method in which heavy rainfall(>50 mm/d) is considered a trigger for a potential water outlet. The Daba tunnel located in Hunan province, China, has been constructed in a karst stratum where the rock mass has been weathered intensely by the influence of two faults. Heavy rain triggered some potential water outlets, causing a serious water inrush. The PWOD method was applied in this project for the treatment of water inflow, and six potential water outlets in total were identified through three heavy rains. Meanwhile, a geophysical prospecting technique was also used to detect water sources. The connections between water outlets and water sources were identified with a 3-D graphic that included all of them. According to the distribution of water outlets and water sources, the detection area was divided into three sections and separately treated by curtain grouting.

Groundwater resources in karst area in Southern China and sustainable utilization pattern

Occurrence conditions of groundwater in southern karst area are complicated. The water-bearing media in the karst have multiplicity, and the groundwater is hosted in holes, gaps, seams, pipes and caves. The karst water shows heterogeneity where fast and slow flow coexist, and the Darcy and non-Darcy flow coexist, and the liquid flow, the gas flow and solid flow coexist. The evaluation and investigation indicates that the mineable resource of karst groundwater is about 53.44 billion m^3/y, and the current exploitation quantity is merely 6.565 billion m^3/year. The exploitation and utilization potential is gigantic. In the region there are altogether 2 763 karst subterranean rivers with a total length of 12 687 km. The dry season runoff volume equals to 47 billion m^3/year. At present the exploitation is only 10%. Four effective utilization models of karst groundwater resources have been put forward.(1) The karst hills-depression zone formed the surface-underground united reservoir. By digging tunnels, water diversion irrigation and generating electricity, the ecological economy is developed.(2) In the deep-cut peak cluster depression area, by using the high-part Epikarst spring and constructing the regulation and storage water tank, the stereo ecological agriculture is developed.(3) In the karst peak forest plain and hilly-gully area, the pump-type underground regulating reservoir is constructed and the water-saving ecological agriculture is strengthened.(4) In the fault basin region with the surrounding groundwater runoff belting beam backwater, the water resources are jointly controlled to develop a fruit crop base within the basin.

Super-absorbent swellable polymer as grouting material for treatment of karst water inrush

Grouting is the most commonly used method to control water inrush in underground engineering.Traditional cement-based materials are easy to dilute and hard to coagulate under the influence of large flow and high-velocity water inrush.To address these deficiencies,a new type of polymer grouting material with an excellent expansion ratio was synthesised.The material quickly absorbs water and has an expansion ratio of 1:300.The material is composed of a superabsorbent polymer(SAP),glycerol,and ethanol.The effects of water quality on the expansion ratio and expansion rate of the material were examined,and the best solid–liquid ratio for the slurry was determined by fluidity measurements.A karst specially designed pipeline water inrush test device showed that 800 g of SAP can achieve 0.6 m/s water flow blockage in the smooth pipeline,demonstrating that the ability of the SAP slurry to block water inrush is superior to those of other materials.This study provides a reference for water inrush plugging,and has important implications for the reduction and control of karst pipeline-type water inrush disasters,ensuring the safety of construction sites and preventing loss of life and damage to property.

The influence of land use change on karst water quality of Shuicheng Basin in Guizhou Province

The influence of land use and land cover on ecological environment is a focus of global change research. The paper chooses an industrial city-Shuicheng in Guizhou Province-as a study area because the karst water quality around the city is deteriorating with land use and land cover change. The natural susceptibility of karst water system is an important factor leading to karst water pollution. But land use and land cover change is also a main factor according to the chemical analysis of karst water quality and land use change. So it is a good way to protect karst water through rational planning and managing of land use and land cover.

Movement characteristics of Karst water in a deep mining area

In order to study the movement characteristics of groundwater in a deep mining area and solve the dispute of the distri- bution rule of hydro-chemical zoning which is contradicted by lixiviation water zoning in a horizontal direction, we directed our attention to the source of deep groundwater, its seepage and hydro-chemical characteristics in a typical mining area. We used a neotectonic water-control theory, chemical and isotope methods, as well as a method for analyzing dynamic groundwater conditions. The results indicate that 1) Karst water in the deep and medium parts of this mining area is recharged by vertical leakage through neotectonic fractures rather than seepage along strata from subcrop parts or surrounding flows; 2) from surface to deep leakage paths, the variation in the types of chemical groundwater agrees with the normal lixiviation water distribution rule and the age of mixed groundwater increases; 3) the water-rich zones along neotectonic fractures correspond with water-diluted zones in a hori-zontal direction; 4) the leakage coefficient and water capacity of aquifers increases during the flow process of Karst water along the antidip direction (from west to east) and 5) Karst water in shallow mining areas forms a strong runoff belt along strikes and quickly dilutes the water from deep and medium mining areas. Overall, chemical and dynamic water characteristics actually agree with in terms of the entire consideration for differences in vertical leakage and abnormalities in the zone of water chemical distribution, along a horizontal runoff direction.

Study on the characteristics and causes of carbon tetrachloride pollution of karst water in eastern suburbs of Jinan

By comparing the testing data of the hydrochemistry components and organic pollution of karst water sample in Jinan with large amount of historical data, the author finds the long-existing problem of carbon tetrachloride pollution and the great change of hydrochemical characteristics of karst water in eastern suburbs of Jinan. Since karst water is the main water-supply source in eastern suburbs of Jinan, these problems have greatly affected the safety of water supply. Based on the analysis of hydrogeological condition in eastern suburbs of Jinan, this thesis discusses the causes of carbon tetrachloride pollution and hydrochemical variation with hydrogeochemical theories so as to protect the precious karst groundwater and Jinan spring water. It is found that through research and analysis that there are mainly two causes of carbon tetrachloride pollution and hydrochemical variation: the vulnerability of karst water in this area; the other being the serious pollution in this area caused by remaining pollution sources of the last century.

Geophysical Prospecting of Karst Water in Yunnan Province,China

由于岩溶发育的不均匀性，决定了岩溶水的埋藏分布也具有不均匀的特征，含水层富水性的空间差异极大。岩溶水的不均匀性给岩溶水勘查和开发工作带来了很大的困难，以至于裸露型岩溶石山区的供水勘探孔成井率仍然很低。要有效地发挥岩溶水资源的优势，合理有效地开发岩溶水资源，解决岩溶地区严重干旱缺水问题，关键是解决找水难的问题。要解决岩溶地区普遍存在的找水难题，

Geoecological Monitoring of Karst Water in Georgia, Caucasus (Case Study of Racha Limestone Massif)

Karst groundwater is the major natural resource of drinking water for many countries in the world. Especially in karstic regions, karst water requirements for settlements are provided from karst aquifers. Also, we should consider, that karst groundwater is becoming more and more valuable for drinking water supply. Thus, karst groundwater quality and permanent ecological monitoring are very important for populations. Moreover, if we consider that the karst landscape is the extremely sensitive system towards anthropogenic activities, since exaclty the anthropogenic activities largely identify the karst water pollution-turbidity causing factors. This paper presents a new study regarding the quality of the karst groundwater of the study area, which contains important resource of drinking water. In the mentioned study, 12 water samples were collected from different locations of the 4 main karst springs (Krikhula, Dolabistavi, Kidobana and Sakishore) during the spring and summer of 2014 and 2015 years. The main aim was to identify chemical compositions (Ni, Ag, Co, Cd, Zn, Pb, Al, Mg, Fe, F, Cu), and also, it was important to detect Escherichia coli (E. coli). Our research regarding all these chemical compositions shows that all the values are low and under the environmental limit according to the Georgian standards. We measured chemical parameters of all these samples by Atomic Absorption Spectroscopy (AAS) in the chemical laboratory of Ivane Javakhishvili Tbilisi State University, country of Georgia.

Role of hydro-geochemical functions on karst critical zone hydrology for sustainability of water resources and ecology in Southwest China

Focusing on sustainability of water resources and ecology in the complex karst critical zone, we illustrated functions of the hydro-geochemical analysis on hydrology from the aspects of connection and interaction among hydrology–vegetation–soils/rock fractures along the karst subsurface profile. We reviewed isotopic and geochemical interpretations on tracing water sources for plant uptake, quantifying watershed outlet flow composition and residence times, and evaluating long-term evolution among climate–landscape–hydrology in the karst critical zone. In this paper, the application of the hydro-geochemical analysis on the above aspects in the karst areas of southwest China was summarized.

Combinatorial analysis on spatial information statistics for the karst water environment in Guiyang,China

The karst groundwater system is extremely vulnerable and easily contaminated by human activities.To understand the spatial distribution of contaminants in the groundwater of karst urban areas and contributors to the contamination,this paper employs the spatial information statistics analysis theory and method to analyze the karst groundwater environment in Guiyang City.Based on the karst ground water quality data detected in 61 detection points of the research area in the last three years,we made Kriging evaluation isoline map with some ions in the karst groundwater,such as SO4 2-,Fe 3+,Mn 2+and F -,analyzed and evaluated the spatial distribution,extension and variation of four types of ions on the basis of this isoline map.The results of the analysis show that the anomaly areas of SO4 2-,Fe 3+,Mn 2+,Fand other ions are mainly located in Baba’ao,Mawangmiao and Sanqiao in northwestern Gui- yang City as well as in its downtown area by reasons of the original non-point source pollution and the contamination caused by human activities(industrial and domestic pollution).

Characteristics of Oil Contamination and Numerical Modelling of Its Transport in Fracture-Karst Water in Zibo City,China

In this paper, the hydraulic characteristics of the fracture-karst aquifer and the distribution patterns of petrochemical contaminants are studied. Then, a numerical model using the mixed Eulerian-Lagrangian approach is constructed to predict the distribution and transport of petrochemical compounds in groundwater. The results of numerical modelling and sensitivity analysis show that it may be a workable way for aquifer remediation to combine contamination sources control and capture zone establishment.

Isotope Hydrogeological Study of Karst Water in the Lu' an Mining District and the Xin'ancun Spring Basin, Shanxi

Isotope hydrogeological study has shown that the water supply exploration area in the Lu' an coal mine may be divided into four zones of hydrodynamic conditions and the Xin'ancun Spring Basin where the mine is located may be divided into three Middle Ordovician karst water systems. This paper discusses the features of recharge, runoff and discharge of karst water in various zones, and hydrogeological parameters such as the age, flow rate and natural recharge of karst water have been estimated.

Exploration of Water Resource and Multiple Model for Water Resource Development in Karst Areas with the Preferred Plane Theory

According to the theory of preferred plane, preferred planes (faults) alwayscontrol the distribution of bedrock fissure water and hold abundant groundwater. Thus, theexploration of fissure or karst water can be converted into searching for the watery preferred plane(WPP). In the paper, the characteristic of watery preferred planes is analyzed and a series ofsuperior indices has been set up. It is introduced that WPPs are determined by the methods ofgeological analysis, superior index and complex geophysical analysis. Meanwhile, new multiple modelfor water resource development in the water-scarce areas of karst mountainous regions are advanced.

Problems for water resources development in typical small karst drainage basins and countermeasures

In karst area water deficit is one of the main factors constraining sustainable economic development. In 1979 the comprehensive karstic observational field station was set up in Houzhai drainage basin located,\ in Puding county of Guizhou Province, which can represent most of the small karst drainage basins on the dividing line of the Guizhou Plateau. Geomorphology, water resources and water chemistry were investigated and observed. Based on comparisons of water supply with water demand and analysis of the main problems in water exploitation and utilization. it is found out that the water deficiency was not directly caused by the scarcity of natural water resources. The true reason is the insufficient capacity of water supply caused by the dismatch of the water and soil water resources which can be dealt with by building more irrigation works. Some solutions such as to build scientific basis for water exploitation and utilization and sustainable economic development in karst drainage basins on dividing line of the Guizhou Plateau.

Analysis of Chemical Composition Characteristics and Cause of Formation of Karst Water of Taiyuan Formation in the Lower Part of the Coal Seam in Panxie Mining Area

Huainan mining area is located in the southern margin of the North China Plate, which is an important coal-producing base in the eastern part of China, its deep coal seam mining is threatened by karst water inrush disasters in the bottom plate, analyzing hydrogeochemical characteristics and exploring its causes are an important prerequisite for preventing karst water hazards in the coal floor. This paper takes the karst water of the Taiyuan Formation in the lower part of the A-group coal seam of the Xieqiao-Zhangji-Gubei three mines in the Panxie mining area as the research object, and multivariate statistics, hydrochemical analysis were combined with hydrogeochemical simulation. The hydrogeochemical Component characteristics and cause of formation of the karst water-bearing system covered by huge thick unconsolidated layer are discussed. The results show that the cations are dominated by Na+ + K+, and the anions are mainly Cl−and HCO3−in the karst water in Taiyuan Formation in the study area, mainly affected by the dissolution of salt rock and the oxidation of pyrite, there are cations exchange and adsorption and desulfurization.

Study of soil and water conservation Function on Slope with Different Planting Patterns for a Typical Small Watershed in Karst Region of Guizhou Province

Ten runoff plots with different planting patterns were established for experimental observation in Yangjichong small watershed of Longli County in Karst region of Guizhou Province. Results show that under the same rainfall condition, shrub land, natural grassland and abandoned land presented the best function of soil and water conservation. The function of soil and water conservation was poor for arbor planting pattern, because the shrub layer, herb layer and forest floor were not formed. Because of no-tillage, surface crust and other effects, the function of soil and water conservation in slope farmland was better than that in runoffplots with arbor planting pattern.

Hydrogeochemistry of karst underground waters at shallow depth in Guiyang City, Guizhou Province

The aim of this study is to shed light on the hydrogeochemical characteristics of karst underground waters at shallow depth in Guiyang City, Guizhou Province with an emphasis on the geochemistry of major elements. Guiyang City bears abundant underground waters and it is also an important representative of the karst areas throughout the world. Ca+{2+} and Mg+{2+} are the dominant cations, accounting for 81%-{99.7%} of the total, and HCO+--3 and SO+{2-}-4 are the dominant anions. Weathering of limestones and dolostones is the most important factor controlling the hydrogeochemistry of underground waters, and weathering of sulfate and evaporite rocks is less important. Moreover, the precipitation and human activities also have a definite influence on the hydrogeochemistry of underground waters in the region studied.