Climate change in Central Europe and the sensitivity of the hard rock aquifer in the Bohemian Massif to decline of recharge: case study from the Bohemian Massif

Climate change in Central Europe is manifested by periods of drought during the summer months of years when there is a reduction in atmospheric precipitation and temporary accumulation of water in the form of snow during winter period. The shallow sub-surface aquifer in crystalline rocks is very vulnerable to this decline in rainfall. Monitoring and subsequent model simulations revealed that the groundwater level in recharge areas had been lowered by almost 10 m, but the study also showed that levels in discharge areas are significantly more stable. The transmissivity of hard rock aquifers evidently shows changes in both space and time. The temperature rise results in increasing values of evapotranspiration that is manifested by a gentle but long-lasting groundwater-level decline.     

Groundwater exploration using integrated geophysics method in hard rock terrains in Mount Betung Western Bandar Lampung,Indonesia

The presence of hard rock in Mount Betung has caused the misalignment of the groundwater aquifers,and resulted in many drilling failures for groundwater.An integrated geophysics method using gravity survey and Geoelectric Vertical Electrical Soundings(VES)were conducted to study the effect of basement and hard rock on groundwater prospects.From the gravity method,38 mapping points were carried out randomly,with a distance of 1-2 km in-between.Meanwhile,from the geoelectric method,51 VES points were acquired at the foot of Mount Betung.The acquisition was conducted with a Schlumberger configuration with AB/2=1 m to 250 m.The results show the Bouguer Anomaly in the west is 50-68 mgal due to the presence of hard rock in Mount Betung.This anomaly responds to relatively shallow hard rocks near surface.Hard rocks composed of andesite and breccia normally present at the depth of 5-180 m during well construction.Resistivity isopach mapping from VES data(at AB/2=50 m,100 m,and 150 m)shows the dominant constituents of hard rock.Fractures in hard rock contribute to secondary porosity,which could be a prospect zone that transmit groundwater.This finding shows that the fractures are randomly scattered,causing several well failures that have been worked.Furthermore,the fractures in the hard rock at the foot of Mount Betung acts as conduits between recharge at Mount Betung and the aquifer in the Bandar Lampung Basin.     

Delayed failure in rock loaded in uniaxial compression

Summary The long-term response to sustained compressive loading of two crystalline hard rocks of the Canadian Shield has been investigated. Static fatigue tests conducted on granite and anorthosite have shown that in a humid environment the long-term strengths of these crystalline igneous rocks could be less than 60 percent of their dry instantaneous strengths. Such reduction in strength has implications for the design and construction of deep tunnels, mines and other underground installations. The particular case of a nuclear fuel waste vault located at a depth of one kilometer is considered.Considering a service life of 1,000 years, a vault one kilometer deep in granite could suffer time-dependent spalling in highly stressed regions of the rock where the maximum principal stress exceeds about 130 MPa. Anorthosite has a lower instantaneous strength than granite and it is sensitive to static fatigue as well. A vault in anorthosite would be subject to time-dependent spalling of the perimeter rock in places where the maximum principal stress is above 80 MPa.     

Hydrogeochemical genesis of groundwaters with abnormal fluoride concentrations from Zhongxiang City,Hubei Province,central China

The groundwaters from Zhongxiang City, Hubei Province of central China, have high fluoride concentration up to 3.67 mg/L, and cases of dental fluorosis have been found in this region. To delineate the nature and extent of high fluoride groundwaters and to assess the major geochemical factors controlling the fluoride enrichment in groundwater, 14 groundwater samples and 5 Quaternary sediment samples were collected and their chemistry were determined in this study. Some water samples from fissured hard rock aquifers and Quaternary aquifers have high fluoride concentrations, whereas all karst water samples contain fluoride less than 1.5 mg/L due to their high Ca/Na ratios. For the high fluoride groundwaters in the fissured hard rocks, high HCO₃ ⁻ concentration and alkaline condition favor dissolution of fluorite and anion exchange between OH⁻ in groundwater and exchangeable F⁻ in some fluoride-bearing minerals. For fluoride enrichment in groundwaters of Quaternary aquifers, high contents of fluoride in the aquifer sediments and evapotranspiration are important controls.     

The gravity method in groundwater exploration in crystalline rocks: a study in the peninsular granitic region of Hyderabad, India

The application of variations in the earth's gravity in groundwater exploration on a regional scale, especially in sedimentary basins, metamorphic terrains, valley fills, and for buried alluvial channels, is well established. However, its use in hard crystalline rocks is little known. In granite, for example, the upper weathered layer is a potential primary aquifer, and the underlying fractured rock can form a secondary aquifer. Fracturing and weathering increases the porosity of a rock, thereby reducing the bulk density. Changes in gravity anomalies of 0.1–0.7 mGal for granites, due to weathering or variations in lithology, can be detected. To test the use of gravity as a groundwater exploration tool for crystalline rocks, a gravity survey of the peninsular shield granites underlying Osmania University Campus, Hyderabad, India, was undertaken. At the site, gravity anomalies reflect variations in the lithology and in the thickness of weathered zones. These anomalies also define the position of intrusives and lineaments. Areas of more deeply weathered granite that contain wells of higher groundwater yield are represented by negative gravity values. In the weathered zone, well yield has an inverse relation to the magnitudes of residual gravity. The study confirms the feasibility of gravity as a tool for groundwater exploration in crystalline rocks. Electronic Publication     

综合物探技术在煤系上覆薄硬岩矿区的应用初探——以山西潞安集团司马矿区为例

山西潞安集团司马矿区东高西低,西部延至长治盆地,矿区水系发育。主采3#煤层埋藏较浅,层位稳定。新生界不整合于下伏基岩之上,厚度变化较大,属典型的薄硬岩煤矿区。为准确提供矿区煤炭开采上限的地质依据,采用了综合勘探技术,其中利用三维地震勘探技术追踪新生界底面反射波及第四系"天窗"位置,利用直流电法与瞬变电磁法提供电性分层,并对其解释结果进行相互印证。勘探实例表明,三维地震勘探、电法勘探与钻探的综合运用不仅可解决薄硬岩煤矿区新生界厚度、含水层富水性及第四系缺失等问题,还可提供新生界含水层与基岩含水层之间的水力联系、制约因素等资料。     

Long-term stability of flow-path structure in crystalline rocks distributed in an orogenic belt, Japan

Most evaluations of the contaminant retardation processes likely to be important in geological disposal (e.g. for high level radioactive waste (HLW)) consider only the present characteristics of fractures and associated mineral infills. Relatively little attention has been given to possible long-term changes in these features, and their influence on groundwater flow. The work reported here seeks to provide analogous evidence that such changes are not likely to be important and hence to improve confidence in the presently adopted evaluation methodology and its long-term applicability.

In the orogenic belt that is formed by the Japanese islands, there are wide areas of crystalline rock. The rocks in each area have a distinctive age sequence which is partly reflected in the characteristics of the fracture systems and associated mineral fillings that occur. These characteristics generally imply that groundwater and solutes can be conducted through fracture networks, except in the cases of fault zones or crushed zones. The structural and mineralogical features of these networks readily illustrate how certain contaminants might react and be retarded by the fracture fillings and open pore geometry, due to chemical sorption and/or physical retardation.

Here, we describe the fracture systems developed in crystalline rocks with different ages that are intruded into the Japanese orogenic belt. The aim is to build a model for the long-term fracturing process and hence to evaluate fracture ‘stability’. In particular, the comparisons are made between the fracture geometries and the frequencies observed in the 1.9–0.8 Ma Takidani Granodiorite (the youngest exposed pluton in the world), the ca. 67 Ma Toki Granite and the ca. 117 Ma Kurihashi Granodiorite located in central to northwest Japan. The observations show that all these crystalline rocks have similar fracture frequencies, with 1 to 2 fractures per meter in the massive part of rock bodies. Mineralogical studies and dating analyses of fracture fillings also suggest that fractures are relatively physically stable. Major new fractures tend not to be created in the massive part of rock bodies even when a pluton has been subjected to the regional stresses of plate movements with a duration of about 100 Ma. The results show the unique characteristics of the fracture forming process and the relatively stable geometries of fracture network systems in crystalline rocks distributed within the orogenic belt. This analogue also enables us to provide a model to build confidence in a technical approach applicable for modeling of hydrogeology and geology over long time scales under the orogenic stress field present in Japan. The model may also be useful for other stable tectonic settings as well as for a characterizing sites in crystalline rocks for the possible geological disposal of HLW and other toxic wastes.     

Which water formed Australian sediment-hosted precious and potch opal?

The means and timing of the formation of Australian sediment-hosted precious opal remain a subject of continuing debate. In this study, the question of which water formed the opal is addressed by examination of rare earth element data for opals and host rocks. The available data, mainly for Lightning Ridge, NSW, suggest a positive Eu anomaly, relative to the neighbouring Sm and Dy, occurs in opals whereas no such anomaly was found for the weathered Cretaceous sediments hosting the opal. Such anomalies may be inherited from the source rock with a similar positive Eu anomaly or generated in situ by severe reduction. There is no indication of major reduction processes during the opal formation that could have led to such a Eu anomaly so this is likely inherited from a source rock. As the opal host rocks did not show this anomaly, the source rocks must be external to the opal fields. Calcite cements within rocks hosting the aquifers of the Eromanga and Surat basins of the Great Artesian Basin have been reported to have a positive Eu anomaly, which strongly suggests that opal was formed by upwelling Great Artesian Basin artesian waters. This work has also highlighted variations in trace-element concentrations in opals, which indicate significant variation in the source water composition during opal formation or different water sources were involved. Either of these is indicative of the source for the opal with its trace elements derived from external sources. These conclusions have significant implications to considerations of how opal formed, and hence, for the exploration for other deposits and to the chemistry and timing that led to the formation of opal.     

Environmental impact on groundwater of Maheshwaram Watershed,Ranga Reddy district,Andhra Pradesh

Maheshwaram watershed is situated in Ranga Reddy district of at a distance of about 30 km south of Hyderabad. The watershed has an area of 53 km² and has hard rock aquifers with semi-arid climate. The study area has been expanding at a fast pace and now has the distinction of being one of the fastest growing urban centers, facing the problem of groundwater depletion and quality deterioration due to the absence of perennial source of surface water and also due to over exploitation. Human activities involving industrial and agricultural development and the inadequate management of land and water resources have, directly or indirectly resulted in the degradation of environment viz. water and soil.     

Evaluation of regional fracture properties for groundwater development using hydrolithostructural domain approach in variably fractured hard rocks of Purulia district,West Bengal,India

Estimation of geohydrologic properties of fractured aquifers in hard crystalline and/or metamorphosed country rocks is a challenge due to the complex nature of secondary porosity that is caused by differential fracturing. Hydrologic potentiality of such aquifers may be assessed if the geological controls governing the spatial distribution of these fracture systems are computed using a software-based model. As an exemplar, the Precambrian metamorphics exposed in and around the Balarampur town of Purulia district, West Bengal (India) were studied to find out the spatial pattern and consistency of such fracture systems. Surfer and Statistica softwares were used to characterize these rock masses in terms of hydrological, structural and lithological domains. The technique is based on the use of hydraulically significant fracture properties to generate representative modal and coefficient of variance (Cν) of fracture datasets of each domain. The Cν is interpreted to obtain the spatial variability of hydraulically significant fracture properties that, in turn, define and identify the corresponding hydrolithostructural domains. The groundwater flow estimated from such a technique is verified with the routine hydrological studies to validate the procedure. It is suggested that the hydrolithostructural domain approach is a useful alternative for evaluation of fracture properties and aquifer potentiality, and development of a regional groundwater model thereof.     

Hydrogeochemical evolution of groundwaters with excess fluoride concentrations from Dashtestan, South of Iran

Hydrogeochemical investigations were carried out in the Dashtestan, the eastern part of Borazjan, with a focus on fluoride content. The study area is underlain by a complex geology that is dominated by three lithological units, namely marl, alluvial sediments, and carbonate rocks. To assess the major geochemical factors controlling the fluoride enrichment in water, 37 groundwater and 12 surface water samples were collected from the three lithological units. Fluoride concentrations ranged up to 3?mg/L, and average concentrations varied from 1.12 (in carbonate aquifers) to 1.73 (in alluvial aquifers) to 1.82?mg/L (in marl aquifers). To study the influence of rocks and soils on groundwater quality, an additional 41 soil and rock samples were also taken and analyzed for fluoride. The order of average fluoride content in both rocks and soils is: marl?>?alluvial sediments?>?limestone, which confirms that marl is a likely source of fluoride.     

Effects on ground water caused by excavation of rock store caverns

Unlined rock caverns for oil storage are very common in Sweden. Most of them are excavated in hard rocks (compact, non-carbonate, non-volcanic rocks). The fundamental idea of underground oil storage is that the rock caverns are located below the natural ground water level. Hereby the ground water keeps the oil inside the caverns and prevents products migration.

During the excavating period the water seeping through the fractures of a cavern is pumped up to avoid flooding. This discharge causes a local drop in the ground-water level around the cavern and a cone of depression develops.

A local study of the development of such a cone of depression has been made by means of a network of observation holes around the cavern. On enlargement of an oil storage (by constructing new caverns close to the old ones), the cone of depression moves according to the progress of the new excavations. This process has been studied and described in two cases.

Underground storages in Sweden are very often closely spaced in order to use common facilities such as entrance tunnel, pumping station, housing etc. Therefore an artificial ground-water divide sometimes must be arranged between different caverns in order to prevent products migration. This paper describes how such an artificial recharge of water between some caverns is made. The control of its effectiveness is shown as well as the method for sealing off undesirable leakage.     

The use of low-grade and unsound crushed rock aggregates in Ghana for construction

Summary Ghana and many developing countries have relied heavily, in the past, on hard granites and granitic gneisses for the production of rock aggregates and rock products for civil engineering works including the construction of roads and buildings. Experience in Ghana has shown however, that the quantity of crushed rock aggregates produced from hard rocks have proved insufficient for the needs of the country. This situation has called for engineering geological studies into the use of rock types and rock formations previously designated as low grade and unsound for the production of aggregates. The major objective of this study was to review the occurrences of non-conventional hard rocks and gravels such as quartzites, silicified sandstones, metagreywackes, dolomitic limestones and quartz gravels. This was followed by the application of appropriate standard specification tests to establish criteria for the selection and recommendation for the use of low grade and unsound rocks and gravels for various civil engineering projects in Ghana and other developing countries, especially those of the subregion with similar geological formations.     

Rare earth elements in groundwater from different Alpine aquifers

Rare earth elements (REE) were determined in 39 groundwater samples collected at 14 sites under low- and high-flow conditions. Water samples derived from aquifers hosted in crystalline, molasse, flysch, carbonate and evaporite rocks located in Western Switzerland. The concentration of REE in groundwater circulating in different rocks showed large variations: lowest concentrations (ΣREE≤10 ng/L) occurred in groundwater from evaporite aquifers; highest concentrations (ΣREE up to 516 ng/L) were observed in carbonate aquifers, although REE in these waters do vary under different hydrological conditions; groundwater from other aquifers had ΣREE from 10 to 100 ng/L. Distinct REE signatures were observed in waters draining specific rocks. The REE patterns in groundwater from crystalline, molasse and flysch aquifers showed heavy-REE enrichment at different degrees. Groundwaters circulating in crystalline rocks were distinguished by negative anomalies in Ce and Eu, whereas those from carbonate aquifers were nearly flat with ΣREE and the magnitude of negative anomaly in Ce is likely to be controlled by iron concentrations. The REE-Post-Archean Australian Shales (PAAS) normalized patterns appear useful to recognize the aquifer type and suggest the possibility to use the REE as geochemical tracers.     

Origin of salinity of deep groundwater in crystalline rocks

Deep groundwater in fractured crystalline basement has been reported from deep mines and from scientific deep wells. Highly saline brines have been described from several km depth in the continental basement of the Canadian, Fennoscandian and Ukrainian shields and elsewhere in the world. The origin of salinity is unknown and many different possibilities have been presented. We compare the compositional evolution of deep waters in the Black Forest basement, SW Germany, with those of other deep crystalline waters, and use halogen systematics (e.g. Cl/Br ratios) and other parameters of the waters to deduce the origin of their salinity. In the Black Forest the composition of deep thermal waters results from chemical interaction of surface water with the rock matrix (mainly weathering of plagioclase and mica) and from mixing of the reacted water with stagnant saline deep water. Here we show by Na/TDS-and Cl/TDS-investigations, by molality-ratios of the Na and Cl concentrations, and by Cl/Br systematics that these deep saline waters have a marine origin. The Cl/Br ratios in deep crystalline waters are very close to normal marine ratios (Cl/Br = 288 ppm basis). In contrast, Cl/Br ratios of other possible sources of salinity show distinctly different Cl/Br ratios: water derived from dissolved Tertiary halite deposits of the rift valley is in the order of Cl/Br = 2400 and water from dissolved Muschelkalk halite deposits has values of about Cl/Br = 9900. Leaching experiments on crystalline rocks, on the other hand, show that the average Cl/Br ratio of crystalline rocks is far below Cl/Br = 100.     

论岩土工程中水-岩相互作用研究的焦点问题--特殊软岩的力学变异性

水－岩相互作用研究是力学和地球科学领域中的前沿课题之一。在力学领域中称之为“固流耦合作用”，在地球科学领域中称之为“水－岩相互作用”。前者研究的焦点在于固体和流体间力学耦事的基本规律；后者主要研究在高温高压条件下，岩石和水发生的化学反应规律及其地球化学特征。岩土工程作为土木工程与地质学的交叉学科，水－岩相互作用研究的侧重点以往主要集中于岩体力学方面，即从渗流场和形变场的相互作用角度研究其基本规律，目前，已开始注意到水和岩石的化学作用问题。从工程实践中迫切需要解决的共性课题－－特殊软弱岩体与水作用后力学性能大幅度变异的问题出发，探讨了某些特殊岩体与水作用的化学规律、矿物学规律及其化学与矿物学损伤所导致的力学损伤规律，并建立软岩－水相互作用的时间效应模型；确定软岩性质软化的标志性监界阈值，为建立水－岩相互作用理论体系奠定软岩研究基础，为重大工程的设计、施工等提供有效的参考的指导。     

地下含水层水资源赋存条件及其水化学特征—以贵州省安龙县幅为例

以贵州省安龙县1∶50 000水文地质图幅为例,采用含水层探采井的水质、水量监测数据,分析不同含水层水资源赋存特征及其与水化学的相关性。研究结果表明:（1）研究区含水层可分为纯碳酸盐岩管道含水层、非纯碳酸盐岩裂隙含水层、碎屑岩裂隙含水层、松散岩类孔隙含水层4种类型,各含水层中地下水水化学类型均以HCO-Ca?Mg型为主;（2）除非纯碳酸盐岩含水层探采井的降深与水体中Mg2+、HCO-3浓度呈现出显著的负相关性（R2=-0.77/-0.74）外,其余离子浓度与钻井单位涌水量、降深的相关性均不显著,相关系数(R2)均小于0.3;（3）非纯碳酸盐岩含水层和松散岩类含水层的总矿化度（TDS）、总硬度（TH）含量均比纯碳酸盐岩含水层低5 mg?L-1以上,TDS、TH的高值区均集中于纯碳酸盐岩含水层中,而低值区则分布于松散岩类含水层。      

强渗漏与坚硬岩层组合条件下旋挖钻机施工工法研究

通过对强渗漏与坚硬岩层组合条件下桩基工程旋挖钻机施工技术的探索,总结出高压旋喷防渗漏与旋挖钻机牙轮筒钻和截齿取心筒钻交叉钻进入岩联合成孔施工工法,并在工程中成功应用。在处理大直径入坚硬岩层钻孔灌注桩方面效果明显,技术先进,有明显的社会效益和经济效益。     

Improvement in the interpretation of stress measurements by use of the overcoring method: development of a new approach

Determination of the state of the initial stresses in a rock formation is still one of the most important and complex problems in geotechnics. The over-coring method of measuring the stresses is one of the measurement methods most frequently used in geotechnics. It has been shown to be highly suitable for measuring the stresses in “hard and sound” rocks. However, applied to rocks which have a partialy elastic behaviour the method comes up against many problems the biggest of which are: (1) the non-elastic behaviour of the rock; and (2) the presence of natural fractures or those caused by the overcoring operation. These problems make it impossible to obtain correct deformation measurements which can be interpreted in terms of stresses. To overcome these problems, a new method has been developed based on the use of the deformations recorded at the start of the overcoring tests this method is the subject of the present article.     

Assessment of naturally occurring arsenic contamination in the groundwater of Sarkisla Plain (Sivas/Turkey)

High arsenic levels in groundwater of the aquifers, belonging to the Pliocene terrestrial layers and Quaternary alluvial sediments, have become a significant problem for the inhabitants living in Sarkisla (Turkey). The main objective of this study was to determine the origin and arsenic contamination mechanisms of the Sarkisla drinking water aquifer systems. The highest arsenic concentrations were found in Pliocene layers and alluvial sediments with concentrations ranging from 2.1 to 155 mg/kg. These rocks are the main aquifers in the study area, and most of the drinking groundwater demand is met by these aquifers. Groundwater from the Pliocene aquifer is mainly Ca-HCO₃ and Ca-SO₄ water type with high EC values reaching up to 3,270 μS/cm, which is due to the sulfate dissolution in some parts of the alluvial aquifer. Stable isotope values showed that the groundwater was of meteoric origin. Tritium values for the groundwater were between 8.31 and 14.06 TU, representing a fast circulation in the aquifer. Arsenic concentrations in the aquifers were between 0.5 and 345 μg/L. The highest arsenic concentrations detected in the Pliocene aquifer system reached up to 345 μg/L with an average value of 60.38 μg/L. The arsenic concentrations of the wells were high, while the springs had lower arsenic concentrations. These springs are located in the upper parts of the study area where the rocks are less weathered. The hydrogeochemical properties demonstrated that the water–rock interaction processes in sulfide-bearing rocks were responsible for the remarkably high groundwater arsenic contamination in the study area. In the study area, the arsenic levels determined in groundwater exceeded the levels recommended by the WHO. Therefore, it is suggested that this water should not be used for drinking purposes and new water sources should be investigated.