A numerical model in predicting the initial karst development in porous limestone

The numerical model proposed in this paper represents a new method in predicting initial karst spatial distribution of carbonate aquifers. Karstification Index, \( \varPhi_{\text{K}} \), is a measure of the possible largest amount of calcite that can be dissolved from a unit area of rock and transported by groundwater flow during a unit length of time. Mathematically, it is defined as \( \varPhi_{\text{K}} = q \cdot s \), where q is the flux of groundwater and s is the rock solubility; and Karstification Index, \( \varPhi_{\text{K}} \), is the function of flow, heat, and calcium concentration. The numerical model simulates the time- and space-dependent susceptibility to, and process of, karstification by iterative calculations between \( \varPhi_{\text{K}} \) and hydraulic conductivity. A sample calculation is presented on a hypothetical limestone plateau with steep escarpment, a spring, and a river on one side, a vertical no flow boundary on the other side, and a horizontal impermeable base. The rock has an equivalent porous-medium hydraulic conductivity of K?=?5E?8 ms^?1, which is characteristic to non-karstified limestone. Initially, the spring is located at the intersection of the water table and the escarpment’s face some distance above the river. The simulation result showed that the water table is lowered in 2325 years across the plateau, but the spring’s drop is stopped after 65 years. Karstification is most intensive along the water table due to the higher value of Karstification Index which resulted from the intensive flux of the water. The continual decline of the water table results in a laterally elongated and progressively expanding body of karstified rock and finally as a horizontal conduit at river level. The concentration of Ca²⁺ and conduit diameter decrease from the spring toward the impermeable vertical wall on the opposite side and downward to the base of the plateau. The results are consistent with general theories and empirical observations of karst and cave evolution.     

喀斯特洼地石灰岩水平溶蚀凹槽研究

以云南石林喀斯特洼地灰岩水平凹槽为模拟对象,用氧化钙粉柱（CaO)和岩盐柱（NaCl为主）进行水平凹槽发育实验。实验结果表明,在流动湖水、水渠、静水湖泊和湿地中形成了半环形颈状水平凹槽、环形颈状水平凹槽、倾斜凹槽、双层水平凹槽,湖岸高坡土层中不发育凹槽。岩盐柱溶蚀水平凹槽深度发育速度（1.2~4.56 cm/h）大于钙粉柱水平溶蚀凹槽发育速度（0.000 4~ 0.008 9 cm/h）。相同成分岩石的水平凹槽发育速度在流水和静水中的差值为3~22倍,水中发育速度是土层中的2倍。石林地区喀斯特洼地石灰岩凹槽类型多样。实验和调查结果对比,发现能指示湖泊湿地水位变动凹槽类型主要有半环形颈状水平凹槽、环形颈状水平凹槽、环形半曲面凹槽,分别对应湖泊岸坡、湖泊、湿地中心。实测水平凹槽平均深度63.95±33.40 cm。用碳酸盐岩综合侵蚀率（化学溶蚀率的1.5倍,135 mm·ka-1）与气岩界面溶蚀率（5.2 mm·ka-1）的差值（129.8 mm·ka-1）为水平溶蚀凹槽发育速率,算得到石林喀斯特洼地石灰岩水平凹槽持续发育时间为4.92±2.573 ka。据此推断,约5 000年前,石林喀斯特洼地石灰岩底部开始发育水平凹槽,湖泊湿地密度16%(0.15km2/km2),属高原喀斯特湖泊湿地区,现今湖泊湿地密度不到0.5%。这有可能表明研究区从5 000年前的湿润降雨丰沛期转向了现代干湿季气候与人类强烈活动干扰,湖泊湿地面积发生深刻变化。      

Ordovician limestone karst development law in Feicheng coal field

Being the basement of coal measure strata in North China coal mine, the Ordovician karst aquifer is the baleful source of water for exploiting the Carboniferous coal bed. The coal mines that the exploitation transfers into the deep stratum will be threatened by deep high or super-high pressure confined water from Ordovician. Mastering the vertical development law is one of the basal and prerequisite works for emancipating deep coal resources and ensuring safety for exploiting the deep coal bed. Based on the statistics of exploratory boring data, a slide test and an X-ray diffraction experiment, the results of Ordovician vertical development were obtained. The results are as follows: limestone karsts 0–30 m below the top are undeveloped; those 30–50 m away from the top are the most developed, and those over 50 m are also undeveloped similar to the first ones. The property of the aquifer of the Ordovician limestone karsts from the working face floor (numbered as 101002) in the Caozhuang coal mine is explored using a 3D high-density electrical technique for the well and drill hole data. This confirms the vertical development law and provides evidence for floor prevention and control of water disasters.     

土壤-灰岩岩溶系统中水文地球化学动力学过程模拟及其意义

在实验室模拟了土壤－灰夺岩溶系统,对降水 滤下元素地球化学动态进行了系统监测。结果表明,岩溶作用使土壤中易移动性组分淋溶,Ｃａ＾２＋、ＨＣＯ３＾－的淋出动态表现为开始的快速下降和随之的平衡两个淋出阶段,淋出量与土壤中水溶性Ｃａ、可氧化有机质的含量有关。土壤对ＨＣＯ３＾－的淋出与排释有促进作用。这种动力学特征对解释岩溶沉积古记录和岩溶作用的大气ＣＯ２汇效应具有重要意义。     

A dye-tracing test as an aid to studying karst development at an artesian limestone sub-aquifer: Zagros Zone,Iran

A dye-tracing test is employed to study the karst development and flow regime at an artesian limestone sub-aquifer, the Khersan3 Dam site, Zagros Zone, Iran. Tracer breakthrough curves showed an early dominant peak followed by a pronounced tailing effect. The peak concentration was a response to induced pressure during dye injection. The results suggest that the dye was pushed into the small pores and fissures around the injection point during dye injection. Hence, the dye moved out as a result of matrix and fissure diffusive processes and created a long pronounced tailing. The maximum flow velocity in the upper artesian sub-aquifer ranged from 0.97 to 2.9 m/h. However, the mean tracer velocity ranged from 0.19 to 0.51 m/h based on the mean residence tracer time; consequently, the flow regime in the artesian sub-aquifer was determined to be mainly diffusive. The results reveal (1) a low hydraulic gradient from upstream of the dam axis to downstream; consequently, there is no considerable flow; (2) poor karst development and diffuse flow at the tracing test area; (3) a discharge zone at a location downstream of the dam axis which is the main terminal of general flow direction at the dam site.     

地震属性技术在奥灰裂隙发育带预测中的应用初探

简单介绍了地震属性技术和模式识别方法及其在许厂煤矿奥陶系灰岩裂隙发育带预测中的具体应用。预测结果表明,地震属性技术及模式识别方法的综合应用为预测奥灰裂隙发育带提供了一种有效的方法。     

Characterization of shallow karst using electrical resistivity imaging in a limestone mining area

The Guangxi area is famous for its high degree of karstification due to a long period of groundwater erosion and the development of fracture networks. Karst collapse appeared during the mining process and caused many environmental problems. Applying electrical resistivity imaging (ERI) is the most cost-effective method to study the characteristic of the subsurface karst environment. In this area, more than 24 km of ERI profiles around a mining area is carried out to present the development of karst which will be used to evaluate the effects on the ground water and the surrounding environment. The area represents a classical limestone rock which is of high quality and is used for cement production. In this study, the ERI is used to determine the geometry of the karst range at depth. The results are in good agreement with drilling experiments. The ERI survey provided near-surface resistivity information, which is very useful for establishing the geometry and the position of potential karst.     

喀斯特坡地石灰土硫形态分布及其同位素组成特征

土壤中S形态及各形态硫化物的稳定S同位素组成的分布特征对于土壤S循环研究具有重要意义。利用S形态连续提取方法测定了喀斯特坡地石灰土总S、SO4^2- -S、S^0-S、FeS—S、FeS2-S和有机S含量及其δ^34S值。有机S是石灰土主要的S形态,占总S的76．5％～93．6％。总S和有机S含量随土壤深度加深而降低,这与有机S矿化有关,对应有机S的δ^34S值逐渐增大。总体来看,FeS2是石灰土主要的无机S形态,其次为SO4^2-、FeS和S^0。石灰土表层以下深度FeS2-S增加与SO4^2-异化还原反应速率增大有关,对应SO4^2-和FeS2的δ^34S值平行增大。深层土壤FeS2-S降低则主要与SO4^2-异化还原反应速率减小及无机S厌氧氧化有关。土壤各形态S含量及其δ^34S值的分布特征,可以记录与深度相关的S形态转化过程。值得注意的是,受石灰土类型、植被状况及地形特征等因素的影响,喀斯特坡地石灰土中SO4^2-、FeS2和有机S组分容易迁移,这也是石灰土中各形态S分布变异的主要原因。     

Impacts of karst phenomena on engineering properties of limestone foundation bed,Ar Riyadh,Saudi Arabia

Evaluation of mechanical and petrophysical properties of the karst limestone became essential to avoid future risks in the construction of new urban cities built on limestones. Therefore, this study aims to evaluate the impact of karsts phenomena on engineering properties of limestone foundation bed at Ar Riyadh in Saudi Arabia. Three hundred core plugs were obtained by rotary drilling at depths ranging from the ground surface to 20 m collected from 24 boreholes in two sites: (1) karst limestone (KL) at Al Aziziyah district and (2) massive hard limestone (HL) at Hittin district in Ar Riyadh city, Saudi Arabia. Petrographic, SEM, EDX, and XRD analyses are used to identify the mineralogical composition and microstructures of limestone samples. The petrophysical properties included the ovendry density, P-wave, and porosity where the mechanical properties covered the uniaxial compressive strength (UCS), point load strength index (PLI), and rock quality designation (RQD) for the karst and hard limestone samples. KL is characterized by 17.11% total porosity, 14.71% water absorption, 32.1 MPa UCS, 1.70 g/cm³ ovendry density (γ dry), 51% weathered RQD, 5.49 MPa medium shear strength, and low modulus of deformation of the plate loading test. HL showed 11.63% total porosity, 9.45% water absorption 43.1 MPa UCS, 2.50 g/cm³ ovendry density (γ dry), 78% hard to fresh rock affinity RQD, and 9.93 MPa high strength and high modulus of deformation of the plate loading test. For the water absorption (%), KL at Al Aziziyah district showed a range of 12.85–17.80% averaged 14.71%. HL at Hittin district varied between 7.04 and 11.29% with an average of 9.45%. KL proved to be dense with ovendry density (γ dry) averaged at 1.70 g/cm³ while HL showed very dense affinity of 2.50 g/cm³. KL clarified a UCS range from 22.5 to 40.1 MPa and an average of 32.1 MPa while HL showed a range from 35.4 t o 48.1 MPa with an average of 43.1 MPa. KL is moderately weathered with RQD average of 51% while HL showed a hard to fresh rock affinity of 78%. Point load test clarified a medium shear strength with 5.49 MPa for KL and high strength of 9.93 MPa for HL. Plate loading tests indicated low and high modulus of deformation for KL and HL, respectively. Results of petrographical analyses and XED of limestone samples showed that the strength parameters of samples mostly composed of micrite (mudstone/wackestone) and dolomite in hard limestone of Hittin district. In Al Aziziyah district (KL), the samples mostly consist of foraminifera and high amount of calcite as in karst limestone (wackestone/packstone). Rock mechanical tests with combination of fabric analyses have shown that strength parameters depend not only on the amount of karst but also on the amount of allochem. Major geomechanical differences between the two types of limestone provide the proper base for prioritizing areas to alleviate future risks and sustainable urban planning for decision makers. The karstic limestone, therefore, is considered as an acceptable foundation bed for light engineering structures. However, for heavy structures and buildings, improving the foundation bed strength by grouting, cement injection, and mat foundations is necessary to avoid future failure risks.     

三峡库区泥灰质岩石斜坡带构造对岩溶地质灾害的控制机理

三峡库区三叠系巴东组(T26)泥灰质岩石岩溶是移民迁建中发现的重大工程地质问题。泥灰质岩石中的构造非常复杂，包括老构造、新构造和表生构造，它们共同控制了岩溶作用。老构造中，褶皱和断裂带等局部构造控制着岩溶的重要部位和重要层位，节理和层理等小构造使岩溶普遍存在。新构造时期地表隆升和河流切割使岩体卸荷松动，岩溶通道扩宽。表生岩溶构造加密了岩溶通道，使岩溶作用增强。三峡库区泥灰质岩石斜坡带地质灾害形成的机理遵循着构造控制下岩溶发育的规律性，致使岩溶地质灾害具有范围广、规模大和结构复杂的特点。岩溶地质灾害的形式包括地面不均匀沉降、地裂缝、滑坡、崩塌、泥石流和地面塌陷。     

炭质灰岩地区抽水致塌控制因素和影响因素

为研究炭质灰岩地区抽水致塌控制因素和影响因素,通过电法物探、地质钻探及抽水致塌试验相结合的综合手段,对兴安县石炭系下统岩关组（C₁y）炭质灰岩地区的岩溶塌陷进行关联分析,建立降深水位与时间、恢复水位与时间的关系对比曲线。研究结果表明:在炭质灰岩地区进行抽水活动时,其主要补给源为小溶洞内储存水,运输通道为岩溶裂隙;该炭质灰岩地区岩溶裂隙具有不规则性,因此,在同类地层中测得的渗透系数k及影响半径R有较大差异;研究区域内抽水致塌的位置受地质构造的影响较为明显;钻井人为抽水致塌受多种因素共同作用影响,而地下水位升降为主要影响因素。     

钙、铁、铝形态对岩溶石灰土磷有效性的影响

为揭示钙、铁、铝形态与岩溶地区土壤磷有效性关系,通过改进的BCR元素形态连续提取法获取石灰土不同发育阶段土壤矿质元素赋存形态,并分析与总磷及速效磷含量之间的相关关系。初步研究表明:石灰土壤中全磷和速效磷在石灰土发育过程呈降低趋势,从黑色石灰土到黄色石灰土,总磷降低了76.7%,速效磷减少了84.7%。石灰土总磷与速效磷同酸溶态、可还原态及残渣态钙,可氧化态铁、铝和可还原态铝显著正相关,而同总铁、总铝以及残渣态铝显著负相关,相关系数绝对值均达到0.9以上。随着石灰土发育进行,钙总量及其形态均降低,而铝、铁总量和形态呈增加趋势,可能导致岩溶地区石灰土磷及其有效性缺乏越发突出。      

Tufa: a freshwater limestone

Tufa, or travertine, is a deposit of calcium carbonate precipitated with the loss of carbon dioxide from springs or streams saturated with calcium bicarbonate. Algae or bacteria may assist in this process, which is favoured by raised temperatures. British and overseas examples of tufa deposits show various features including their role in damming up lakes.     

A framework for karst ecohydrology

Ecohydrology can be defined as the science of integrating hydrological and biological processes over varied spatial and temporal scales. There exists in karst a strong and direct interaction between the circulation and storage of groundwater and surface water. These fluxes in turn affect the spatial distribution of organisms in these habitats. Because of the fact that the appearance, storage and circulation of water in karstified areas is significantly different from other more homogenous and isotropic terrains, karst ecohydrology should develop original methods and approaches. At the same time, traditional approaches are also very useful. Large karst underground geomorphological patterns occur in many sizes and varieties, ranging from a few meters long or deep to very large, the deepest being deeper than 1 km and longer than hundreds of kilometres. In this article, special attention is paid to ecohydrological functions of karst underground features (caves, pits, conduits, etc.), which play a crucial dual role in (1) hydrology and hydrogeology of water circulation and storage and (2) ecology of many rare and endangered species. Differences in morphology, hydrology, hydrogeology and climate have resulted in a range of different environments, which provide the opportunity for the coexistence of different species. The role of the epikarst and vadose zones, as well as caves in ecohydrological processes, is discussed. The importance of the flood factor in karst ecology is analysed. The aim of this article is to move forward the discussion among different disciplines to promote and develop a conceptual framework for karst ecohydrology.     

Multiple-pumped-well aquifer test to determine the anisotropic properties of a karst limestone aquifer in Pasco County, Florida, USA

Groundwater-level data from an aquifer test utilizing four pumped wells conducted in the South Pasco wellfield in Pasco County, Florida, USA, were analyzed to determine the anisotropic transmissivity tensor, storativity, and leakance in the vicinity of the wellfield. A weighted least-squares procedure was used to analyze drawdowns measured at eight observation wells, and it was determined that the major axis of transmissivity extends approximately from north to south and the minor axis extends approximately from west to east with an angle of anisotropy equal to N4.54°W. The transmissivity along the major axis ${\left( {T_{{\xi \xi }} } \right)}$ is 14,019 m² day^–1, and the transmissivity along the minor axis ${\left( {T_{{\eta \eta }} } \right)}$ is 4,303 m² day^–1. The equivalent transmissivity $T_{e} = {\left( {T_{{\xi \xi }} T_{{\eta \eta }} } \right)}^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-0em} 2}} = 7,767{{\text{m}}^{2} } \mathord{\left/ {\vphantom {{{\text{m}}^{2} } {{\text{day}}^{{ - {\text{1}}}} }}} \right. \kern-0em} {{\text{day}}^{{ - {\text{1}}}} }$ , and the ratio of anisotropy is 3.26. The storativity of the aquifer is 7.52?×?10^?4, and the leakance of the overlying confining unit is 1.37?×?10^?4 day^?1. The anisotropic properties determined for the South Pasco wellfield in this investigation confirm the results of previous aquifer tests conducted in the wellfield and help to quantify the NW–SE to NE–SW trends for regional fracture patterns and inferred solution-enhanced flow zones in west-central Florida.     

岩溶塌陷机理研究进展

岩溶塌陷机理是开展岩溶塌陷监测、预警、防控及治理工作的基础。长期以来,岩溶塌陷机理研究都是以事后调查的定性推测为主,缺乏必要的科学观测数据支持,导致目前的岩溶塌陷机理仍然处于假设阶段,并成为岩溶塌陷灾害监测预警与防治方面的理论瓶颈问题。文章总结了近年来国内外岩溶塌陷机理的最新研究进展,提出目前的岩溶塌陷机理都可以归结为土岩体的渗透变形,但其临界或破坏指标还需进一步探讨,此外指出随着高频采样的水压力、 加速度计及声波等传感器的实用化,塌陷机理研究将面临着从静水压力到动水压力方面的挑战,并且压力脉动造成的气蚀破坏、共振破坏也将是下步探究的重点。     

岩溶峰丛洼地区降水入渗系数——以寨底岩溶地下河流域为例

大气降水入渗系数α、地下水径流模数M是最基础的水文地质参数,文章以封闭型寨底岩溶地下河流域结合2013年3月至2014年2月一个完整水文年的水位、流量、雨量高频率监测数据,采用水量均衡法得到了岩溶区枯平丰水期大气降水入渗系数,分别为0.352、0.528、0.726,平均入渗系数为0.635。地下水径流模数分别为8.32、19.80、61.15 L·s-1·km-2,年平均径流模数为33.36 L·s·-1·km-2。其计算方法和计算结果对同类型岩溶区水资源评价等有一定的借鉴意义。      

The Upper Oligocene of Antigua: the volcanic to limestone transition in a limestone Caribbee

Antigua is a small island at the northern end of the Lesser Antilles chain. Its geology is largely limited to the Upper Oligocene and it records with unusual fidelity the transition from island arc volcanism to quiescence and limestone deposition. Despite the apparent limitation of a rock record confined to a short stratigraphical interval, Antigua has a geodiversity that ranges from thick andesites through silicified logs and freshwater snails in cherts to limestones that include both shallow and deeper water facies, and fine karstic features.     

西南岩溶区农田生态系统岩溶作用及碳汇效应：以重庆南川市三泉镇为例

岩溶地区的碳循环是地质作用和生物作用最好的结合点,系统研究农田生态系统中石灰岩溶蚀作用强度对精确估算岩溶作用的碳汇效应具有重要意义。通过在重庆南川市三泉镇选择菜地、旱地、冬水田、两季田、草地、未利用地等样地类型进行以一个水文年为周期的标准溶蚀试片溶蚀试验、土壤剖面与植被样方观测以及土壤、标准溶蚀试片样品分析,探讨了农田...     

Summary editorial for karst hydrogeology: advances in karst collapse studies

Karst collapses occur in various sizes and by various mechanisms. No karst collapses are the same, and each needs to be treated individually. Decades of investigation of and experience with these collapses make it clear that addressing karst collapse hazards requires a multi-disciplinary approach that integrates geomorphology, engineering geology, hydrology, hydrogeology, biology, geophysics, geochemistry, and risk assessment. This thematic issue contains 12 papers that illustrate the recent advancement in karst collapse studies, covering a spectrum of topics from karst collapse mechanism study, geophysical application to karst collapse investigation, karst collapse investigation standards, karst collapse monitoring and early warning, and karst collapse remediation.