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Complex hydraulic interactions between compartmentalized carbonate aquifers and heterogeneous siliciclastic successions: a case study in southern Italy 
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下载免费PDF全文 The sedimentary sequences containing lithologic units with low permeability represent hydrogeologic systems, which, as of now, have been little studied despite their diffusion worldwide. A hydrogeologic study, aimed to assess the main factors controlling the groundwater flow dynamics in such systems and their hydraulic interactions with nearby carbonate aquifers, has been carried out in Longano (Isernia, Southern Italy). The analysis of the hydraulic heads, combined with the regimes of the springs and the electric conductivity of the groundwater, mainly reflect vertical and lateral heterogeneities of the media in terms of hydraulic properties. In particular, the flow system is controlled by lateral heterogeneities, which characterize a surficial horizon made up of clayey colluviums and talus deposits, separated from the deeper saturated, fissured bedrock. One‐to‐ten relationships in hydraulic heads, monitored in piezometers crossing the fissured media, further uphold the crucial role played by the lateral contrasts of permeability in controlling the flow dynamics. On the whole, significant interactions with the nearby carbonate hydrostructure take place. Nevertheless, the heterogeneities of the siliciclastic succession and surficial horizon, coupled with the compartmentalization of the carbonate system, lead to a complex hydrogeological scenario. In a wider perspective, this study gives information of utmost importance in order to improve the implementation of mathematical models and configuration of tapping works within these heterogeneous and complex settings. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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The aim of this study was to analyse the hydrogeologic role of siliciclastic deposits and marly‐clayey‐calcareous successions within the carbonate Apennine chain (southern Italy). The study was carried out along the northern part of the Matese carbonate massif through (1) the hydraulic characterization of siliciclastic rocks in a test site, by means of Lugeon tests, and (2) the identification of the groundwater flow system discharging at an important spring located within a marly‐clayey‐calcareous succession in a second test site, by means of isotopic investigations. The results showed that the investigated siliciclastic deposits and marly‐clayey‐calcareous successions may allow significant groundwater discharge from carbonate aquifers. Thus, they do not everywhere behave as aquitard, contrary to the previous model. Instead, groundwater flows through the upper part of these successions, where stress release fracturing enhanced rock permeability in the near‐surface bedrock. Thus, these successions may locally be a new groundwater source within the southern Apennine chain. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Analytical solutions expressed using the hydraulic head for the one-dimensional consolidation of layered structured aquitard soils in a leakage system are deduced by transforming the n-layered structured soils into n + i (i = 1,2,…, n)-layered soils with gradually changing thicknesses, therein considering the behaviors of structured aquitard soils. The solutions are given in the case of instantaneous and linear decreasing confined aquifer water levels. By comparing three different examples, the effects of the structured behaviors on the consolidation characteristics are analyzed for the instantaneous decline of the confined aquifer water level. 相似文献
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Abstract A borehole is developed in a shallow multi-layered aquifer and used to derive the porosity, specific storage and hydraulic conductivity of the aquitard. Local values of hydrodynamical parameters are estimated from petrophysical analysis of core samples, and the empirical relationship between porosity and permeability. Vertical diffusivity is determined from the response of the aquitard to a loading cyclic signal using pressure records at different depths. Hydraulic conductivities deduced from the petrophysical analysis ranged from 10?8 to 10?10 m s?1 and are comparable with those of facies of marine/lacustrine clay observed in samples. The permeability values calculated based on diffusivity are within the range 10?9 to 10?11 m s?1 with a quasi-systematic bias of one order of magnitude. These values are average for a larger part of the aquitard and correspond to an integrated value. The methodology retained for the aquitard characterization is discussed with emphasis on the implications for the management of a complex aquifer system. Citation Larroque, F., Cabaret, O., Atteia, O., Dupuy, A., and Franceschi, M., 2013. Vertical heterogeneities of hydraulic aquitard parameters: preliminary results from laboratory and in situ monitoring. Hydrological Sciences Journal, 58 (4), 912–929. 相似文献
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R. I. Acworth W. A. Timms B. F. J. Kelly D. E. Mcgeeney T. J. Ralph Z. T. Larkin 《Australian Journal of Earth Sciences》2013,60(6):657-680
The Liverpool Plains in northern New South Wales contain some of the best agricultural land in Australia and are underlain by extensive smectite clay-dominated soils sourced from weathering the alkali basalts of the Liverpool Ranges. It had been thought that a relatively simple geological model explained the underlying Cenozoic sequence with salt-rich clays of the Narrabri Formation overlying sands and gravel aquifers comprising the Gunnedah Formation. Extensive groundwater modelling based upon this simple conceptualisation has been used in management plans proposed by the mining and agricultural industries. A 31.5 m core has been recovered using minimally disturbed triple-tube coring methods at Cattle Lane (Latitude –31.52° S, Longitude 150.47° E) to resolve uncertainty concerning the aquitard status of the upper layer. Recovered core has been examined and tested to determine grainsize, cation-exchange capacity, X-ray diffraction, X-ray fluorescence and microscopic examination of granular components. These measurements complement surface and borehole geophysical techniques, hydrogeological data and hydrochemical analysis of water samples recovered from a series of specially constructed piezometers adjacent to the cored hole. The sequence overlies a Late Cretaceous channel cut into Permian bedrock at 91 m depth with sands and clays below 31.5 m considered to represent various alluvial fill events mostly occurring since the Early Pliocene. Erosion of Late Eocene alkali basalts on the Liverpool Ranges, with the formation of smectite clays, pedogenic carbonates and with the addition of quartz from both eolian sources and locally derived from adjacent Triassic sandstone hills, provides the great majority of the sediment recovered from the cores. Late Pleistocene (114 ka) to Holocene ages were determined for the core from three optically stimulated luminescence (OSL) measurements on fine sands (13, 23 and 29 m BG). Detailed examination has failed to detect any evidence of a boundary between Narrabri and Gunnedah formations revealing rather a gradual change in dominance of clays and silts over sands and gravels embedded in a clay-rich matrix. This result challenges the conceptualisation used to conduct groundwater modelling on the Liverpool Plains. 相似文献
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考虑非达西流的弱透水层固结计算 总被引：13，自引：1，他引：12
由于成岩作用的影响,深部弱透水层中的黏性土较为坚硬、致密,在这种黏土层中的孔隙渗流规律有偏离达西定律的现象,而在现有的地面沉降研究中,对深部弱透水层的固结变形计算始终沿用以达西定律为基础的固结方程进行,这显然是与实际情况不相符的。鉴于此,以孔隙渗流为非达西流为基础,对太沙基一维固结方程进行了重新推导,并采用半解析法对非达西流-太沙基一维固结方程进行了求解。分别采用达西流-太沙基固结方程和非达西流-太沙基固结方程对同一固结问题进行了计算,结果表明,考虑非达西流后土层达到某一固结度所需的固结时间较之不考虑非达西流时明显增加了,而且固结时间增长的趋势与实测的增长趋势较为一致。 相似文献
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A coupled one‐dimensional viscoelastic–plastic model for aquitard consolidation caused by hydraulic head variations in aquifers 下载免费PDF全文
下载免费PDF全文 T.‐L. Tsai 《水文研究》2015,29(22):4779-4793
Accurate and practical calculation of aquitard consolidation is required for a reliable analysis of land subsidence caused by groundwater overexploitation in a multilayered aquifer system because aquitards are generally more compressible than aquifers are. This study proposes a coupled one‐dimensional viscoelastic–plastic consolidation model that considers the combined effect of changes in soil parameters and body force to simulate aquitard consolidation caused by hydraulic head variations in neighbouring aquifers. The proposed model uses variable total stress and simultaneously solves hydraulic head and vertical soil displacement. The constitutive relation based on the Voigt model with different elastic moduli of the spring in normally consolidated and overconsolidated soils is used to describe the viscoelastic–plastic deformation mechanism of aquitards. In addition, the proposed model considers the combined effect of variations in hydraulic conductivity, elastic moduli, and body force on the calculation of aquitard consolidation. Three hypothetical scenarios with various hydraulic head variations in aquifers are used to examine the coupled one‐dimensional viscoelastic–plastic consolidation model. The results show that neglecting plasticity and viscosity of soil causes aquitard consolidation to be respectively underestimated and overestimated. In addition, ignoring body force variation underestimates aquitard consolidation, whereas neglecting soil parameters variation overestimates aquitard consolidation. Two real case scenarios are also studied to further demonstrate the applicability of the coupled one‐dimensional viscoelastic–plastic consolidation model. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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弱透水层与含水层相互作用是国际水文地质学界关注的热点问题,特别是黏性土弱透水层与孔隙含水层的相互作用。近年来,在自然沉积、过量开采地下水、现代化农业机械与建筑业重型机械应用等自然与人为活动影响下,黏土弱透水层会发生有效应力增加、孔隙结构变形和孔隙度减少、渗透性降低、溶解氧和贮水能力减少以及侧向和垂向排水等的压实作用,导致地下水污染、地面沉降等环境问题的发生。本文重点介绍了黏性土弱透水层压实作用的原理,分析了地下水系统中4种不同状态下沉积物压实与孔隙流体压力的关系,基于压实物理模拟和数值模拟两个方面对压实作用的研究方法与技术进行了系统总结,随后探讨了压实作用下黏性土弱透水层对地下水水量与水质的影响,并对此研究的发展趋势及其在地球科学、环境科学等研究领域的潜在应用提出了展望。 相似文献