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11.
The complex functioning of karst systems depends on several factors (e.g., geology, karstification status, climate) which
influence flow conditions. Understanding a system requires monitoring that includes a sampling interval well adapted to the
system's size, and the use of hydrodynamic and geochemical approaches. From our own observations, the general physical and
geochemical characteristics of the aquifers are perennial and representative of karst evolution at a given moment. The Notre-Dame-des-Anges
karst system, which is situated in France on the rim of the Vaucluse karst region, was studied during 2 water years. This
study demonstrates that several parameters are not definitive, and that they do not provide information about the actual status
of the karst evolution of the system. We were able to observe that hydrological parameters in particular are dependent on
the configuration of the outlets, which can dramatically change. For example, a heavy storm (300 mm of rain in 4 h), which
occurred in the intake area on 22 September 1992, produced a piston effect in the aquifer, which was expressed by extensive unclogging of the whole aquifer. The appearance of a new gryphon at the
outlet induced a change in the flow rate and added to the unclogging.
The other major result of this study is the demonstration of intensive, even preponderant, participation of water originating
in the infiltration zone in the behavior of the system. This contribution, often minimized in previous studies, is closely
dependent upon flow conditions and especially upon the recharge status of the infiltration zone. Physical and chemical parameters
allowed us to trace this water, and to demonstrate the existence of an actual hanging reserve which plays not a negligible part in flow, during both high and low water levels.
This paper demonstrates the necessity of coupling a hydrodynamic study with a hydrochemical approach, and of questioning the
representativeness of parameters during a given period, for a better understanding of the functioning of the karst system.
This is especially true if the infiltration zone of the karst system is heavily developed, and if external factors (e.g.,
river, landslip, clogging) influence the outlet
Received: 10 June 1996 / Accepted: 11 November 1996 相似文献
12.
Laboratory study of the clogging process and factors affecting clogging in a tailings dam 总被引：2，自引：0，他引：2
Laboratory simulation of clogging in the Lixi tailings dam (Shaanxi Province, China) is urgently required because clogging
is an important factor affecting the dam stability. This work firstly presents the results of ferrous iron oxidation experiments
using buffer solution. The results indicate that the ferrous iron oxidation follows first order kinetics, and the oxidation
process is strongly dependent on pH, a higher pH resulting in a higher oxidation rate. Furthermore, when the pH exceeds 7.0,
the oxidation rate constant increases significantly. Secondly, a column experiment was carried out under the conditions of
the pH ranging from 6.8 to 7.5 and the natural oxygen supply. Ferrous iron oxidation and precipitation were found to reach
equilibrium under these conditions. After 23 days, the column experiment was stopped when the clogging materials blocked the
column outlet. The clogging materials were found to be a mixture of ferric hydroxide and its converted products, and these
existed in amorphous form with a loose cluster microstructure according to the results of XRD and SEM. 相似文献
13.
Column test-based features analysis of clogging in artificial recharge of groundwater in Beijing 
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下载免费PDF全文 With the completion of South-North Water Transfer Project in China, plenty of high quality water will be transported to Beijing. To restore the groundwater level in Beijing, part of transferred water is planned to be used for artificial recharge. Clogging is an unavoidable challenge in the artificial recharge process. Therefore, a test is designed to analyse clogging duration and scope of influence and to test the reinjection properties of different recharge media. The test employs the self-designed sand column system with variable spacing and section monitoring, composed of four parts: Sand column, water-supply system, pressure-test system and flow-test system, to simulate the clogging of artificial recharge of sand and gravel pits. The hydraulic conductivity levels of all sand column sections are obtained to analyse the clogging of the injection of different concentrations in media of different particle sizes. In this experiment, two kinds of media are used–round gravel from sand and gravel pit in Xihuang village and the sand from sand and gravel pit by the Yongding River. The concentrations of recharge fluid are respectively 0.5 g/L and 1 g/L. The results show that clogging usually lasts for 20 hrs., and the hydraulic conductivity drops to the original 10%. Clogging usually occurs at 0–12 cm section of the sand column. The scope of influence is 0–60 cm. In column 3 and 4, whose average particle sizes are larger, section 20–50 cm also suffers from clogging, apart from section 0–12 cm. The effective recharge times are respectively 33 hrs. in column 1, 14 hrs. in column 2, 12 hrs. in column 3 and 12 hrs. in column 4. The larger the average particle size is, the quicker the clogging occurs. In media of larger particles, the change in suspension concentration does not have significant influence on the development of clogging. In conclusion, it is suggested that during artificial recharge, the conditions of reinjection medium should be fully considered and effective method of recharge be employed in order to improve effective recharge time. 相似文献
14.
Groundwater which occurs in fractured rock or porous aquifers or other geological weak zones such as faults and fractures is usually extracted via boreholes, hand wells or other sources such as springs.Water scarcity has become a severe problem due to many factors, such as an alarming increase in population and per capita water consumption, over exploitation of groundwater resources and abrupt global climatic change along with its related eco-environmental geological problems. In such situation, application of artificial recharge systems(e.g. surface recharge basin and deep injection well systems) can help to effectively manage and augment the unitization of groundwater resources. However, the clogging problem,which may be caused by a complex interdependent mechanisms of physical, chemical and biological has been a challenge for the efficacy and the implementation of recharge facilities. Clogging can reduce the permeability, recharge rate and longevity of recharge facilities and increase the operational and maintenance costs. Major influencing factors associated with the occurrence of clogging include the chemical composition of groundwater(both the recharge water and native groundwater), aquifer medium and microbial diversity, together with other environmental factors such as temperature, pressure, total dissolved solids, total soluble salts, pH, Eh, nutrients, gases, carbonates and others; these factors ultimately increase the piezometric head but reduce the permeability and infiltration rates of porous/seepage media.Pretreatment of recharge water can minimize the potential clogging. In the case of clogged wells,rehabilitation methods need to be deployed. In the meantime, there is an urgent needs to understand the basic causes and developmental processes/mechanisms of clogging in order to mitigate this problem. This paper reviews the major clogging mechanisms and their possible preventive measures and redevelopments in artificial recharge systems. 相似文献
15.
Field investigations and laboratory simulation of clogging in Lixi tailings dam of Jinduicheng,China
Clogging is one of the most important factors affecting the stability of the tailings dams. Firstly, this work investigates
the clogging materials of Lixi tailings dam using ICP-AES, X-ray powder diffraction (XRD) and SEM analysis methods. The ICP-AES
results indicate that Fe is the dominant element in the clogging materials. The iron contents of clogging samples collected
from 2# radial-well pipe and the access hole of the starter dam are 54.35 and 40.24%, respectively. XRD spectra show that
ferric hydroxide is the main initial component of the clogging materials. Other compounds such as akaganeite, hematite and
goethite are products from ferric hydroxide transformation. Therefore, the clogging materials are a mixture of ferric hydroxide
and its converted products. The clogging materials commonly exist in an amorphous form with a cluster microstructure when
viewed under SEM. Secondly, this work uses a continuous flow column to simulate clogging in the laboratory, and the clogging
materials are analyzed with XRD and SEM. The chemical analysis indicates that the iron content of the clogging materials from
the experiment is 45.43%. XRD spectra show that hematite is the only compound detected. The clogging materials generated experimentally
are also in amorphous cluster microstructure when viewed under SEM. 相似文献
16.
Clogging mechanism in the process of reinjection of used geothermal water: A simulation research on Xianyang No.2 reinjection well in a super-deep and porous geothermal reservoir 下载免费PDF全文
下载免费PDF全文 In the process of geothermal exploitation and utilization, the reinjection amount of used geothermal water in super-deep and porous reservoir is small and significantly decreases over time. This has been a worldwide problem, which greatly restricts the exploitation and utilization of geothermal resources. Based on a large amount of experiments and researches, the reinjection research on the tail water of Xianyang No. 2 well, which is carried out by combining the application of hydrogeochemical simulation, clogging mechanism research and the reinjection experiment, has achieved breakthrough results. The clogging mechanism and indoor simulation experiment results show: Factors affecting the tail water reinjection of Xianyang No. 2 well mainly include chemical clogging, suspended solids clogging, gas clogging, microbial clogging and composite clogging, yet the effect of particle migration on clogging has not been found; in the process of reinjection, chemical clogging was mainly caused by carbonates (mainly calcite), silicates (mainly chalcedony), and a small amount of iron minerals, and the clogging aggravated when the temperature rose; suspended solids clogging also aggravated when the temperature rose, which showed that particles formed by chemical reaction had a certain proportion in suspended solids. 相似文献