醴陵市区岩溶发育规律与岩溶地基工程分类

本文从研究基础地质入手，探讨醴陵市区的岩溶发育规律。结合钻探、地球物理勘查等手段，对岩溶地基工程分类进行探讨，以反映建筑场地的复杂程度和岩溶发育等级，进而指导勘查工作，为设计和基础施工处理提供更加符合实际的工程地质评价。     

Evidence of NAO control on subsurface ice accumulation in a 1200 yr old cave-ice sequence, St. Livres ice cave, Switzerland

Mid-latitude ice caves are assumed to be highly sensitive to climatic changes and thus represent a potentially interesting environmental archive. Establishing a precise chronology is, however, a prerequisite for the understanding of processes driving the cave-ice mass balance and thus allows a paleoenvironmental interpretation. At St. Livres ice cave (Jura Mountains, Switzerland), subfossil trees and organic material are abundant in the cave-ice deposit, therefore allowing the dating of individual ice layers. The dendrochronological analysis of 45 subfossil samples of Norway spruce (Picea abies (L.) Karst.) from the overhanging front of the ice outcrop as well as the dating of seven wood samples with ¹⁴C dating allowed for a reconstruction of the St. Livres cave-ice sequence and for the determination of periods of ice accumulation and ablation. Results suggest a maximal age of 1200 ± 50 ¹⁴C yr BP for the observed ice sequence and indicate the presence of four major deposition gaps dated to the 14th, 15th, mid-19th and late 19th century, which can be related with periods of positive North Atlantic Oscillation anomalies (NAO+) over the winter half-year and/or anthropogenic cave-ice abstraction. Similarly, there is evidence that periods of cave-ice accumulation as observed between AD 1877-1900 and AD 1393-1415 would correspond with phases of negative NAO indices. Cave ice represents therefore an original climate archive for the winter half-year and is complementary to other continental proxies recording preferentially summer conditions (e.g., tree rings, varves).     

Effects of restricted recharge in an urban karst system

Urban karst systems are typically considered more vulnerable to contamination and excess storm discharge because of potential source areas, increased sediment loading, and focusing of water from impervious surfaces. However, urban hydrology can lead to unexpected patterns, such as pirating of recharge into man-made storm systems. Valley Creek Basin in southeastern Pennsylvania, presents such an urban karst system. Four springs were monitored for suspended sediment, water chemistry, and storm response for an 18-month period. The baseflow suspended sediment concentrations were low, less than 4.0 mg/l. Furthermore, trace metal analysis of baseflow water samples and spring mouth sediment showed only low concentrations. The response to storms within the system was rapid, on the order of 1–3 h. The maximum water stage increases at the urban springs were typically less than 15 cm, with springs from more commercialized areas showing <2 cm increase. A nearby retention basin, in contrast, had water level rises of 100 cm, suggesting that pirating of recharge into stormwater systems occurs. Thus, the concept of an urban karst system as a contaminant conduit is not the only one that applies. In Valley Creek Basin, reduced infiltration due to paving led to smaller storm response and less contaminant input, and the smaller capture area due to diversion of stormwater led to short flow paths and rapid storm response. Although contaminant levels have not increased due to urbanization, the springs may be at risk for future contamination. Short flow paths may reduce flushing, which means that the system will not cleanse itself if contamination occurs.     

Water losses from a reservoir built in karst: the example of the Boljunčica reservoir (Istria,Croatia)

The paper presents the case of the Boljunčica reservoir, which began operation in 1973. It is situated on the Istria peninsula (Croatia). This is a multipurpose reservoir which was built in order to protect the downstream area from flood, to store water for irrigation, and to control sediment transport. The reservoir is situated on the contact zone between water impermeable Eocene flysch and deep Eocene and Cretaceous limestone. The bottom of the reservoir is covered partly by both flysch and quaternary deposits. Water losses from the reservoir bottom are so large that the main service intended for the reservoir, the storage of water for irrigation, is impossible. After every intensive precipitation, which occurs often in this region, the reservoir fills very quickly. The problem is that its retention of water is very short, and lasts only a few days. The water volume of the reservoir at the spillway altitude of 93.00 m a. s. l. is about 6.5 × 10⁶ m³. Because of water losses from the reservoir bottom, the mean annual volume of water stored in it, during the period of 1977–2005 was only 0.5 × 10⁶ m³, which is less than 8% of the full reservoir volume. On the reservoir bottom, many new swallow holes opened through the sediment cover after each time it filled and emptied with water. Special attention is paid to the groundwater level analyses. Interdisciplinary analyses and investigations of hydrological and hydrogeological factors causing the formation of swallow holes and water losses from the Boljunčica reservoir are discussed. The example given in this paper explains one unsuccessful case of building a reservoir in Dinaric karst, caused mainly due to insufficient geological, hydrogeological and hydrological investigations. In order to prevent water losses from the Boljunčica reservoir, very complex and expensive work needs to be done, but its success regarding the reasonable reduction of water losses from the reservoir is in question.     

Geophysical investigation of a sinkhole in the northern Harz foreland (North Germany)

The creek Jerstedter Bach is part of the Ringelheimer Mulde along the northern rim of the Harz Mountains in Northern Germany, a trough structure comprising steeply dipping limestones. The limestones are well karstified and drain parts of the region efficiently via sub-surface flow. As the entire region is intensively used by agriculture, contamination of the fast-flowing karst aquifer is a potential problem. During 2006, a small sinkhole (Windmühlenweg) developed alongside the Jerstedter Bach close to the city of Goslar. The sinkhole enlarged rapidly, with a small cave within the gravel cover diverting part of the creek to the subsurface karst catchment. Geophysical methods (gravimetry, geoelectrics) were used around the sinkhole to determine its extent and possible evolution. A negative Bouguer anomaly was found over the sinkhole, indicating more voids further downstream. The geoelectric survey helped to identify the old meandering course of the small river, which was straightened during the cultural land reform in the twentieth century.     

Hydrogeology of karst aquifer systems in SW Turkey and an assessment of water quality and contamination problems

The aim of this research is to determine the relationship between groundwater flow and water quality of different ground and surface water basins in the southwest Turkey. In addition, groundwater vulnerability is assessed taking into consideration groundwater flow and quality. The autochthonous Beydaglari limestone is the major karstic aquifer in the region. According to the groundwater level map of alluvium aquifers in the basins, groundwater discharge toward the carbonate aquifer is direct and indirect. The hydrogeological connection between ground and surface water basins occurs via the karstic aquifer located at the bottom of the alluvium bottom. In Egirdir lake, water also discharges in the karstic aquifer via karstic sinkholes at the western border of the lake. In the research area, general groundwater discharge is toward the Mediterranean Sea by means of autochthonous carbonate system, according to hydrogeological investigations, research of lineament and hydraulic conductivities. This result is supported by the locations of lineaments and shore springs discharging from the limestone. In addition, spreading of contaminants via karstic aquifer to great distance has been clearly identified.     

福建马坑矿区地下水化学成分的变化特征研究

地下水在含水层中运移,不断与其含水介质发生水岩作用,溶解介质中化学元素。在地下水运移过程中,地下水的化学成分与含量不断发生变化。影响矿区地下水化学成分的主要因素有含水层的岩石组合、矿物的溶解度、地下水的径流特点、混合作用及人为作用等。     

利川压气站岩溶场区消防水井选址及其供水需求评估

在前期野外地质调查及工程水文物探勘察的基础上,研究压气站场区地层发育特征及水文地质条件,确定经济合理的消防水井宜井区。并根据非稳定流抽水试验数据,求取该场区地下水含水层的水文地质参数,同时利用泰斯井流公式对该区消防井的地下水供水需求作出预测评估,结果满足消防井的设计水量要求,且按Q=240m^3／d此等强度抽水,不会引起地下水位持续下降造成的各种生态环境地质问题。     

Study on the Formation and Development of Xiaoyanwan Tiankeng in Xingwen World Geopark,Sichuan

Chinese scholars Zhu xuewen put forward Tiankeng and defined it as a collapse feature which was diffe rent from the ordinary doline and developed in large-scale underground river channel.This paper analyzed the sasic conditions of Xiaoyanwan Tiankeng formation,such as sedimentary environment,climatic and hydrological conditions and so on;and deeply discussed the development course of Xiaoyanwan Tiankeng on this basis.The research result showed that Xiaoyanwan Tiankeng was completely accord with Tiankeng’ definition,and was a well-developed and especially big Tiankeng in the maturation stages.     

云南特困乡的类型划分--以红河州为例

云南的贫困和全国的贫困状况基本一致,首先是区域性贫困,其次是结构性和阶层性贫困。红河州位于滇东南岩溶地区,干旱缺水,交通闭塞,经济和社会发展十分落后。文章应用较为先进的因子生态分析法对红河州49个特困乡进行分类并解释了几个类型的贫困特征。