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GIS and ANN coupling model: an innovative approach to evaluate vulnerability of karst water inrush in coalmines of north China 总被引：5，自引：0，他引：5
Evaporites, including rock salt (halite) and gypsum (or anhydrite), are the most soluble among common rocks; they dissolve
readily to form the same types of karst features that commonly are found in limestones and dolomites. Evaporites are present
in 32 of the 48 contiguous states in USA, and they underlie about 40% of the land area. Typical evaporite-karst features observed
in outcrops include sinkholes, caves, disappearing streams, and springs, whereas other evidence of active evaporite karst
includes surface-collapse structures and saline springs or saline plumes that result from salt dissolution. Many evaporites
also contain evidence of paleokarst, such as dissolution breccias, breccia pipes, slumped beds, and collapse structures. All
these natural karst phenomena can be sources of engineering or environmental problems. Dangerous sinkholes and caves can form
rapidly in evaporite rocks, or pre-existing karst features can be reactivated and open up (collapse) under certain hydrologic
conditions or when the land is put to new uses. Many karst features also propagate upward through overlying surficial deposits.
Human activities also have caused development of evaporite karst, primarily in salt deposits. Boreholes (petroleum tests or
solution-mining operations) or underground mines may enable unsaturated water to flow through or against salt deposits, either
intentionally or accidentally, thus allowing development of small to large dissolution cavities. If the dissolution cavity
is large enough and shallow enough, successive roof failures can cause land subsidence and/or catastrophic collapse. Evaporite
karst, natural and human-induced, is far more prevalent than is commonly believed. 相似文献
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Kenneth S. Johnson 《Environmental Geology》2005,48(3):395-409
Evaporites, including gypsum (or anhydrite) and salt, are the most soluble of common rocks; they are dissolved readily to form the same type of karst features that typically are found in limestones and dolomites, and their dissolution can locally result in major subsidence structures. The four basic requirements for evaporite dissolution to occur are: (1) a deposit of gypsum or salt; (2) water, unsaturated with CaSO4 or NaCl; (3) an outlet for escape of dissolving water; and (4) energy to cause water to flow through the system. Evaporites are present in 32 of the 48 contiguous states of the United States, and they underlie about 35–40% of the land area. Karst is known at least locally (and sometimes quite extensively) in almost all areas underlain by evaporites, and some of these karst features involve significant subsidence. The most widespread and pronounced examples of both gypsum and salt karst and subsidence are in the Permian basin of the southwestern United States, but many other areas also are significant. Human activities have caused some evaporite–subsidence development, primarily in salt deposits. Boreholes may enable (either intentionally or inadvertently) unsaturated water to flow through or against salt deposits, thus allowing development of small to large dissolution cavities. If the dissolution cavity is large enough and shallow enough, successive roof failures above the cavity can cause land subsidence or catastrophic collapse. 相似文献
4.
Kenneth S. Johnson 《Environmental Geology》2008,53(5):945-950
Gypsum is a highly soluble rock and is dissolved readily to form caves, sinkholes, disappearing streams, and other karst features
that typically are also present in limestones and dolomites. Gypsum karst is widespread in the USA and has caused problems
at several sites where dams were built, or where dam construction was considered. Gypsum karst is present (at least locally)
in most areas where gypsum crops out, or is less than 30–60 m below the land surface. These karst features can compromise
on the ability of a dam to hold water in a reservoir, and can even cause collapse of a dam. Gypsum karst in the abutments
or foundation of a dam can allow water to pass through, around, or under a dam, and solution channels can enlarge quickly,
once water starts flowing through such a karst system. The common procedure for controlling gypsum karst beneath the dam is
a deep cut-off trench, backfilled with impermeable material, or a close-spaced grout curtain that hopefully will fill all
cavities. In Oklahoma, the proposed Upper Mangum Dam was abandoned before construction, because of extensive gypsum karst
in the abutments and impoundment area. Catastrophic failure of the Quail Creek Dike in southwest Utah in 1989 was due to flow
of water through an undetected karstified gypsum unit beneath the earth-fill embankment. The dike was rebuilt, at a cost of
US $12 million, with construction of a cut-off trench 600 m long and 25 m deep. Other dams in the USA with severe gypsum-karst
leakage problems in recent years are Horsetooth and Carter Lake Dams, in Colorado, and Anchor Dam, in Wyoming. 相似文献
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鄂尔多斯盆地下古生界马家沟组顶部遭受长期风化剥蚀,形成了以膏云岩为主的风化壳岩溶储层。通过偏光显微和超微扫描电镜深入观察了（含）膏云岩的孔隙类型及充填规律,分析了其岩溶作用特点,研究了以膏云岩为主的岩溶作用特征与传统碳酸盐岩岩溶作用特征的区别,探讨了膏云岩发育区的岩溶作用模式。结果表明:硬石膏结核和石膏晶体以其强亲水性和远高于白云石、方解石的溶解度,极易率先吸水发生溶解形成组构选择性溶蚀孔隙,导致膏云岩层蜂窝状溶孔的形成。硬石膏的高溶解度和力学不稳定性使得研究区以膏云岩、白云岩和灰云岩互层的风化壳储层以膏模孔、扩溶膏模孔及与之伴生的胀缩微裂缝为主要储集空间,孔隙大小具有明显的自限性。岩性—（含）膏云岩和沉积微相—海平面低位期潮上带（含）膏云坪沉积是储层形成的先天物质基础和环境条件,并因此直接导致（含）膏云岩储层的成层分布特征。表层膏云岩首先遭受淡水淋滤形成蜂窝状溶孔,多层成层分布膏云岩这种独特的物理化学性质使风化壳内的岩溶水以弥散性渗透为主,这是膏云岩发育区岩溶作用特征和模式与碳酸盐岩产生重要差异的根本原因。 相似文献
6.
The foundations of dams containing soluble material, typically gypsum and limestone, undergo a dissolving process as a consequence of reservoir seepage. In due course, such dissolution of soluble material increases the volume of holes through which water may flow, in turn involving an increase in flow rate through the dam foundation. To adapt dam design to the particular conditions of these foundations, especially in foundations containing gypsum, with the main aims of delaying the dissolution process and avoiding damage or loss of functionality during dam lifespan, a procedure that models the dissolution process coupled with seepage phenomena is necessary. The objective of this paper is to provide this procedure and test it under experimental conditions. This entails coupling a conventional code for calculation of seepage networks, by means of the finite-element method, with a code developed by the authors to calculate the solution front advance (the zone where the dissolution is taking place). The procedure is verified by performing permeameter testing using sand and soluble material mixtures, with the tests being numerically modelled. 相似文献
7.
The Jandagh–Moalleman road, which crosses the Great Kavir of Iran, was completed in 1999. Less than 1 year after completion,
road subsidence problems began. In order to determine the causes of failure, field observations were taken along with surface
and subsurface samples from road segments exhibiting typical problems. Laboratory experiments were conducted to determine
their physical, chemical, and engineering properties. The results indicate that there are two typical layers in this playa:
an upper, hard, salty crust layer composed of up to 46% soluble materials; and a lower, thick, muddy layer which is mostly
composed of silt, clay minerals, gypsum, and halite. It was concluded that mineral dissolution of the upper salt crust layer
and the sinking of road fill materials into the lower muddy layer, are the main causes of road settlement. An appropriate
method to protect the road against the dissolution of its soluble materials is recommended. 相似文献
8.
Ehsan Behnamtalab 《Journal of the Geological Society of India》2012,80(2):262-266
Karstic rocks exist in different areas of the world having by case useful/harmful structural and environmental impacts. These rocks like gypsum and salt are dissolved against water. 相似文献
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Regional groundwater flow and geochemical evolution in the Amacuzac River Basin,Mexico 总被引：1，自引：0，他引：1
Eric Morales-Casique Jacobo Guinzberg-Belmont Adrián Ortega-Guerrero 《Hydrogeology Journal》2016,24(7):1873-1890
An approach is presented to investigate the regional evolution of groundwater in the basin of the Amacuzac River in Central Mexico. The approach is based on groundwater flow cross-sectional modeling in combination with major ion chemistry and geochemical modeling, complemented with principal component and cluster analyses. The hydrogeologic units composing the basin, which combine aquifers and aquitards both in granular, fractured and karstic rocks, were represented in sections parallel to the regional groundwater flow. Steady-state cross-section numerical simulations aided in the conceptualization of the groundwater flow system through the basin and permitted estimation of bulk hydraulic conductivity values, recharge rates and residence times. Forty-five water locations (springs, groundwater wells and rivers) were sampled throughout the basin for chemical analysis of major ions. The modeled gravity-driven groundwater flow system satisfactorily reproduced field observations, whereas the main geochemical processes of groundwater in the basin are associated to the order and reactions in which the igneous and sedimentary rocks are encountered along the groundwater flow. Recharge water in the volcanic and volcano-sedimentary aquifers increases the concentration of HCO3 –, Mg2+ and Ca2+ from dissolution of plagioclase and olivine. Deeper groundwater flow encounters carbonate rocks, under closed CO2 conditions, and dissolves calcite and dolomite. When groundwater encounters gypsum lenses in the shallow Balsas Group or the deeper Huitzuco anhydrite, gypsum dissolution produces proportional increased concentration of Ca2+ and SO4 2–; two samples reflected the influence of hydrothermal fluids and probably halite dissolution. These geochemical trends are consistent with the principal component and cluster analyses. 相似文献
11.
This paper reveals the geochemical processes of dissolution, precipitation and cation exchange that took place during water–rock interaction between water seepages through the Tannur Dam. The Schoeller diagram indicates that there are three major water types originating during water–rock interaction. The first water type is characterized by low salinity that ranges from 1,300 to 2,800 µs/cm, which represents the reservoir water and the water in the right side of the central gallery. The second water type is in the left side of the central gallery, which exhibits medium salinity that reaches about 4,400 µs/cm. The third water type is characterized by very high salinity that reaches a value of around 8,500 µs/cm and represents the water in the right existing adit. The increase of salinity can be explained due to the dissolution of carbonate and sulfate minerals that form the matrix of the foundation and the abutment rocks, and the dissolution of the grout curtain, which is composed of cement and bentonite. Hydrogeochemical modeling, using a computer code PHREEQC, was used to obtain the saturation indices of specific mineral phases, which might be related to interaction with water seepages, and to identify the chemical species of the dissolved ions. The thermodynamic calculations indicate that most of the water samples were undersaturated with respect to gypsum, anhydrite and halite, and were saturated and/or supersaturated with respect to calcite and dolomite. Ca(HCO3)2 is the primary water type, as a result of dissolution of carbonate minerals such as calcite and dolomite prevailing at the dam site. However, cation-exchange processes are responsible for the formation of the Na2SO4 water type from the CaSO4 type that formed due to the dissolution of gypsum. 相似文献
12.
Karst is a complex geological phenomenon that relates to terranes composed of limestone, dolomites, gypsum, halite, or other soluble rocks. Protection of groundwater in karst against pollution is needed because of the high velocity of its flow (several hundreds of thousands of meters per day) and where polluted materials are carried without being filtered. Protection of karstic aquifers against pathogens and rapidly degradable chemicals is carried out for the catchment areas with an estimated delay time of 60 days and for a distance of more than 30 m. Tracer methods have recently become quite useful in karst regions; a tracer may respond as a multiimpulse because of different flow lines, flow velocities, and water aquifers. Therefore, if a total water balance has to be established, nearly all answer-back impulses should be considered. 相似文献
13.
M. A. Díaz-Puga A. Vallejos F. Sola L. Daniele L. Molina A. Pulido-Bosch 《International Journal of Environmental Science and Technology》2016,13(11):2579-2596
In order to identify the origin of the main processes that affect the composition of groundwater in a karstic aquifer, a hydrogeochemical and isotopic study was carried out of water from numerous observation wells located in Sierra de Gador, a semiarid region in SE Spain. Several natural and anthropogenic tracers were used to calculate groundwater residence time within this complex aquifer system. Analysis of major ions enabled the principal geochemical processes occurring in the aquifer to be established, and the samples were classified into four distinctive solute groups according to this criterion. Dissolution of carbonate rocks determines the chemical composition of less mineralized water. In another group, the concurrent dissolution of dolomite and precipitation of calcite in gypsum-bearing carbonate aquifer, where the dissolution of relatively soluble gypsum controls the reaction, are the dominant processes. Marine intrusion results in highly mineralized waters and leads to base exchange reactions. The groundwater enrichment of minor and trace elements allowed classification of the samples into two classes that are linked to different flow patterns. One of these classes is influenced by a slow and/or deep regional flow, where the temperature is generally elevated. The influence of sulphate reduces by up to 40 % the barium concentration due to the barite precipitation. Isotope data (T, 14C) confirm the existence of recent local flows, and regional flow system, and ages of ground water may reach 8000 years. The importance of gypsum dissolution in this aquifer is proved by the δ34S content. 相似文献
14.
The aging of gypsum in underground mines 总被引：1，自引：0，他引：1
The aging properties of gypsum extracted from two underground mines in France (Livry–Gargan and Grozon) have been highlighted by means of observation performed using scanning electron microscopy on samples taken along horizontal boreholes drilled through to the middle of several pillars. The aging process is exhibited by the presence of traces of dissolution (edges of the dissolved crystals, corroded crystalline surfaces, important intra- and intercrystalline space). These dissolution figures decrease in number and in intensity from the wall heading towards the middle of the pillar. The “older” pillars display a greater number of dissolution traces than the “more recent” pillars. Then, the role of the aging has been assessed by determining various physical and mechanical parameters on cylindrical samples of 38 mm in diameter and 76 mm in height, machined from the set of drilled boreholes. The following parameters have been quantified: density, grains density, total porosity, porosity accessible to water, intrinsic permeability to nitrogen, velocity of ultrasonic compression and shear waves, dynamic Young's modulus, dynamic Poisson's ratio, uniaxial compressive strength and static Young's modulus. Significant variations in parameter values between the wall and the middle of the pillar were recorded and recognized as being strongly correlated with the intensity of dissolution traces, and hence with gypsum aging. 相似文献
15.
The GIS approach to evaporite-karst geohazards in Great Britain 总被引：2，自引：0，他引：2
A. H. Cooper 《Environmental Geology》2008,53(5):981-992
Evaporite karst in Great Britain has formed in Permian and Triassic gypsum, and in Triassic salt. Active dissolution of these
deposits can occur on a human rather than a geological timescale causing subsidence and building damage. The British Geological
Survey has taken two approaches towards understanding and advising on hazards caused by dissolution of these soluble rocks.
At a detailed level, a national database and GIS of karstic features is being populated. Information gathered includes dolines,
springs, stream sinks, caves and building damage. At a national level, the soluble rocks in Great Britain have been identified
and digital-map polygon information relating to them was extracted from the British 1:50,000-scale digital geological map.
These areas have been assessed, and in places their margins extended to include some overlying rocks where subsidence features
are known to penetrate upwards through the overlying sequence. The national areas have then been assessed using detailed local
information to assign a susceptibility rating from A (extremely low) to E (high), depending on the nature and regularity of
the subsidence events that occur. This national zonation of the soluble rocks can be used for planning, construction and in
the insurance businesses. This has proved useful for assessing the potential stability of linear routes, such as roads and
pipelines or for other important structures such as bridges and buildings. The information can also be used to delineate zones
of karstic groundwater flow. 相似文献
16.
针对成都地区红层软岩溶蚀空洞现象,以成都半岛城邦项目场地的红层软岩为例,选取不同深度的岩样进行室内浸水试验、淋滤试验和溶蚀试验,观察岩样在不同类型环境水下的作用性状和溶蚀特征,分析经历不同作用的含膏红层软岩 可溶成分的流失程度及其对环境水的影响。结果表明,红层软岩中的石膏含量随着深度的增加而增加,含膏红层及其环境水的腐蚀性显著增强;遇水后,红层软岩中的可溶成分逐渐溶解、流失,随着时间的积累;红层软岩孔隙增大,渗透性增强,红层的完整性丧失,强度衰减;在酸性环境水的作用下红层软岩中的钙质胶结物流失加剧,结构连接破坏严重,对红层的结构强度影响较大。对浸泡、淋滤和溶蚀作用后的试样,重点测试了抗压强度、波速等参数。试验结果表明,红层软岩经硫 酸溶液腐蚀后岩样的结构被破坏,单轴抗压强度从8.5 MPa降低到2 MPa,降低了76%;波速明显减小,从2 204 m/s减小至1 355 m/s,减小了40%;红层试样的pH与电导率变化也比较显著,pH值从8.77减小至7.29;电导率从55 ?s/cm增加到1 100 ?s/cm。 相似文献
17.
激光探针稳定同位素分析技术的现状及发展前景 总被引：8，自引：0，他引：8
以揭示碳酸盐岩和硫酸盐岩相伴沉积时发生的复合岩溶形成机制为目的 ,采用室内模拟实验方法 ,利用反应路径模型研究了水流路径上碳酸盐岩→硫酸盐岩 (简称层序 1)和硫酸盐岩→碳酸盐岩 (简称层序 2 )两种层序时发生的地球化学作用 ,根据质量平衡原理 ,计算了水岩间发生的地球化学作用强度 ;探讨了硫酸盐岩成因、岩溶发育的环境温度对复合岩溶的影响。结果表明 ,复合岩溶形成机理与可溶岩层序关系密切 ,层序 1中 ,发生两种可溶岩的溶解作用 ;层序 2中 ,除硫酸盐岩 (石膏和半水石膏 )溶解外 ,碳酸盐岩 (白云岩 )发生的是去白云化作用。这些作用间通过不同的机制相互促进 ,导致复合岩溶较单一可溶岩的岩溶更发育。复合岩溶的发育程度还受溶液 pH值和环境温度影响 ,溶液pH值降低、环境温度升高都利于复合岩溶发育。 相似文献
18.
高放废物处置库甘肃北山野马泉预选区地下水化学特征及水-岩作用模拟 总被引：6，自引：0，他引：6
在高放废物处置库场地选择和性能评价中,地下水化学特征是最重要的因素之一。文中以野外水文地球化学调查资料为基础,应用水文地球综合分析方法和地下水地球化学模拟技术,探讨中国高放废物处置库甘肃北山野马泉预选区地下水化学特征、时空分布规律及水岩作用机理。主要结论是:野马泉地区地下水以咸水为主, 具有高矿化的特征,水化学类型以Cl·SO4 Na和SO4·Cl Na型为主,pH值大多在7~8 之间;地下水化学成分显示出明显的分带特征;地下水对石盐和石膏欠饱和,对黄铁矿以及铝硅酸盐过饱和;方解石、钠长石在补给区地下水中呈不饱和状态,在排泄区地下水中呈饱和状态。由水岩作用模拟可知,沿水流路径地下水溶解岩石中的钠长石、黑云母、石盐等矿物,溶解二氧化碳,沉淀析出方解石、伊利石和萤石等矿物;发生明显地下水蒸发作用、二氧化碳溶解作用和Ca2+/ Na+离子交换作用, 说明溶滤、沉淀、离子交换和蒸发浓缩作用是区内地下水化学行为的控制因素。 相似文献
19.
The aim is to define the mechanism of chemical reactions that are responsible for the salinization of the Azraq basin along groundwater flow path, using inverse modeling technique by PHREEQC Interactive 2.8 for Windows. The chemical analysis of representative groundwater samples was used to predict the causes of salinization of groundwater. In addition, the saturation indices analysis was used to characterize the geochemical processes that led to the dissolution of mineral constituents within the groundwater aquifer system. According to the modeling results, it was noted that the groundwater at the recharge area was undersaturated with respect to calcite, dolomite, gypsum, anhydrite, and halite. Thus, the water dissolved these minerals during water rock interaction, and therefore, the concentration of Ca, Mg, Na, and SO4 increased along the groundwater flow path. Furthermore, the groundwater at the discharge area was oversaturated with respect to calcite and dolomite. This meant that the water would precipitate these minerals along the flow path, while the water was undersaturated with respect to gypsum and halite throughout the simulated path; this showed the dissolution processes that take place during water-rock interaction. Therefore, the salinity of the groundwater increased significantly along the groundwater flow paths. 相似文献
20.
Evaporite Dissolution Subsidence in the Historical City of Calatayud,Spain: Damage Appraisal and Prevention 总被引：6，自引：0，他引：6
Calatayud in NE Spain is an historically important city built on recent alluvial deposits underlain by gypsum and other soluble rocks. Since its foundation by the Muslims in 716 A.D., the city development has been strongly influenced by geohazards including flooding, subsidence and slope movements. Most of the flooding problems have been mitigated by diversion of the local drainage. However, dissolution of the evaporite bedrock in the urban areas continually causes subsidence and triggers rock-falls from the gypsum cliffs overlooking the city. Subsidence is also caused by the hydrocollapse of gypsiferous silt in the alluvial fan deposits. Building damage in the city was surveyed using a classification scheme developed originally to record damage in British coal mining areas. The Calatayud damage survey shows that the worst building subsidence is concentrated along the line of a buried channel that runs underneath the gypsiferous silt alluvial fan. Natural subsurface drainage causes the dissolution and subsidence, which is aggravated by leakage from water and sewage pipes. Some building damage has been exacerbated during reconstruction by incomplete piling leaving buildings partially unsupported. Mitigation measures include the control of water leakage by the installation of flexible service pipes. Careful construction techniques are needed for both conservation and new developments, especially when piled and minipiled foundations are used. Geomorphological mapping is cost-effective in helping to locate and avoid the zones of subsidence for future development. 相似文献