高密度电法在湘西北岩溶石山区找水中的应用

湘西北岩溶石山区地质构造复杂，岩溶发育且具分布不均匀性，找水难度大，为提高含水构造的异常分辨力，各种物探方法的优化组合中，以高密度电法在确定最佳井位方面发挥了重要作用，它采集的数据量大，对异常特征反映灵敏度高，在湘西北不同的岩溶水文系统中找水，取得了成功的范例。     

高密度电阻率法探测岩溶的应用研究

应用高密度电阻率法查清三家子地段输油管道地下岩溶的分布状态，解决了岩溶对输油管道影响的问题。     

缓倾岩层洞穴系统发育模式的模拟试验

为模拟洞穴系统的发生、演化及分布规律。对缓倾岩层(倾角<15°)裂隙疏散或密集及多层或单层含水层结构的模型所做的溶蚀试验表明:均匀介质含水层在平面上洞穴发育呈不均匀状况,剖面上以浅饱水带及承压含水层顶板附近洞穴较发育;在裂隙不发育或不贯通时洞穴发育受层面裂隙控制;在缓倾岩层中,洞穴发育循反倾向的方向逐渐减弱。     

Occurrence of hypogenic caves in a karst region: Examples from central Italy

The caves of the Umbria and Marche regions in central Italy are made up of three-dimensional maze systems that display different general morphologies due to the various geological and structural contexts. At the same time, the internal morphologies of the passages, galleries, and shafts present some similarity, with solutional galleries characterized by cupolas and blind pits, anastamotic passages, roof pendants, and phreatic passages situated at different levels. Some of these caves are still active, as is the case for Frassassi Gorge, Parrano Gorge, and Acquasanta Terme, with galleries that reach the phreatic zone, where there is a rising of highly mineralized water, rich in hydrosulfydric acid, and with erosion of limestone walls and the formation of gypsum. Elsewhere there are fossil caves, such as Monte Cucco and Pozzi della Piana, where large speleothems of gypsum are present 500 m or more above the regional water table. In all of these important karst systems it is possible to recognize basal input points through fracture and intergranular porosity networks at the base of the oxidizing zone in the core of the anticline, where mineralized water rises up from the Triassic evaporitic layers in small hydrogeological circuits. Different underground morphologies can derive from the presence of a water table related to an external stream or from the confined setting of the carbonate rocks, underlying low permeable sedimentary cover, where artesian conditions can occur.     

试论岩溶在沉积—改造铅锌矿床形成中的作用

在碳酸盐岩地区广泛分布着一些沉积—改造铅锌矿床.其主要改造作用目前一般概括为地下(热)水作用.本文通过比较地下水改造成矿作用与岩溶作用之间的关系,论证岩溶在矿床形成中起着重要作用,即地下水改造富积成矿作用主要为岩溶作用.     

Application of matrix analysis in delineating sinkhole risk areas along highway (I-70 near Frederick,Maryland)

Sinkhole collapse in the area of Maryland Interstate 70 (I-70) and nearby roadways south of Frederick, Maryland, has been posing a threat to the safety of the highway operation as well as other structures. The occurrence of sinkholes is associated with intensive land development. However, the geological conditions that have been developing over the past 200 million years in the Frederick Valley control the locations of the sinkholes. Within an area of approximately 8 km², 138 sinkholes are recorded and their spatial distribution is irregular, but clustered. The clustering indicates the existence of an interaction between the sinkholes. The point pattern of sinkholes is considered to be a sample of a Gibbsian point process from which the hard-core Strauss Model is developed. The radius of influence is calculated for the recorded sinkholes which are most likely to occur within 30 m of an existing sinkhole. The stochastic analysis of the existing sinkholes is biased toward the areas with intensive land use. This bias is adjusted by considering (1) topography, (2) proximity to topographic depressions, (3) interpreted rock formation, (4) soil type, (5) geophysical anomalies, (6) proximity to geologic structures, and (7) thickness of overburden. Based on the properties of each factor, a scoring system is developed and the average relative risk score for individual 30-m segments of the study area is calculated. The areas designated by higher risk levels would have greater risk of a sinkhole collapse than the areas designated by lower risk levels. This risk assessment approach can be updated as more information becomes available.     

Main concepts of the "European approach" to karst-groundwater-vulnerability assessment and mapping

In order to achieve some consistency in the establishment of groundwater intrinsic vulnerability maps in Europe, a new approach is proposed by Working Group 1 of the European COST Action 620 on "Vulnerability mapping for the protection of carbonate (karst) aquifers". A general procedure is offered which provides consistency while allowing the required flexibility for application to a continent and under conditions of varying geology, scale, information availability, time, and resources. The proposed methodology is designed to be clearly more physically based than the existing vulnerability-mapping techniques. It takes the specificity of the karstic environments into account without necessarily excluding the applicability to other geological conditions. Combined "core factors" for overlying layers and for concentration of flow account for the relative protection of groundwater from contamination while taking into account any bypass of the overlying layers. A precipitation factor is distinguished for describing characteristics of the input of water to the system. Differentiation is made between groundwater resource intrinsic vulnerability mapping and source intrinsic vulnerability mapping. For the latter, a factor describing the karst network development is relevant. This short technical note describes a first step in the work program of Working Group 1 of the COST Action 620. Future steps are now in progress to quantify the approach and to apply it in various European pilot areas. Electronic Publication     

Reliability of dipole-dipole electrical resistivity tomography for defining depth to bedrock in covered karst terranes

 Sinkhole collapse is one of the main limitations on the development of karst areas, especially where bedrock is covered by unconsolidated material. Studies of sinkhole formation have shown that sinkholes are likely to develop in cutter (enlarged joint) zones as a result of subterranean erosion by flowing groundwater. Because of the irregular distribution of pinnacles and cutters on the bedrock surface, uncertainties arise when "hit-or-miss" borehole drilling is used to locate potential collapse sites. A high-resolution geophysical technique capable of depicting the details of the bedrock surface is essential for guiding the drilling program. Dipole-dipole electrical resistivity tomography (ERT) was used to map the bedrock surface at a site in southern Indiana where limestone is covered by about 9 m of clayey soils. Forty-nine transects were conducted over an area of approximately 42,037 m². The electrode spacing was 3 m. The length of the transects varied from 81 to 249 m. The tomographs were interpreted with the aid of soil borings. The repeatability of ERT was evaluated by comparing the rock surface elevations interpreted from pairs of transects where they crossed each other. The average difference was 2.4 m, with a maximum of 10 m. The discrepancy between interpreted bedrock-surface elevations for a transect intersection may be caused by variations in the subsurface geology normal to the transect. Averaging the elevation data interpreted from different transects improved the ERT results. A bedrock surface map was generated using only the averaged elevation data at the transect junctions. The accuracy of the map was further evaluated using data from four exploratory boreholes. The average difference between interpreted and actual bedrock surface-elevations was less than 0.4 m. The map shows two large troughs in the limestone surface: one coinciding with an existing sinkhole basin, while the other is in alignment with a small topographic valley. Because sinkholes were observed at the same elevation interval in similar valleys in the vicinity, the delineated trough may have implications for future land use at the site. Received: 4 January 1999 · Accepted: 8 March 1999     

An example of identifying karst groundwater flow

 Hydrogeological investigations for the purpose of regulating the karst aquifer were carried out in the mountain massif of Kucaj in the Carpatho-Balkan range of eastern Serbia. Different geophysical methods were applied in order to identify the position of karstified zones with active circulation of karst underground streams. Especially good results were obtained by using the spontaneous potential method for the exploration and construction of boreholes and wells. In the valleys of Crni Timok and Radovanska reka the measurements have been carried out upstream along the whole width of the alluvium to the limestone periphery. A number of positive and negative anomalies have been recorded. In the centres of positive anomalies several boreholes were located: HG-19 (centre of anomaly +30 mV, total length of the biggest cavern is 9 m); HG-1 (+20 mV, cavern of 2 m); HG-15 (max. +114 mV, effective cavernousness is 17%). Received: 20 February 1995 · Accepted: 12 September 1997     

直流电法在水文地质勘查中的应用研究

直流电法主要有电阻率法（联合剖面法和电测深法）和充电法,广泛应用于工程地质和水文地质勘察中,如地基勘察,水库涌水处理,矿山岩溶水测量等。直流电法能有效地圈定含水体的位置,确定其产状,特别是选择的方法组合应用效果更佳,为工程水文地质提供准确的资料。