Lithological control of land subsidence induced by groundwater withdrawal in new urban AREAS (Granada Basin,SE Spain). Multiband DInSAR monitoring          下载免费PDF全文

Davide Notti  Rosa María Mateos  Oriol Monserrat  Nùria Devanthéry  Tomás Peinado  Francisco Javier Roldán  Francisca Fernández‐Chacón  Jorge Pedro Galve  Francisco Lamas  Jose Miguel Azañón 《水文研究》2016,30(13):2317-2331

Ground subsidence in the southeastern border of the Granada Basin (SE Spain) has been studied using remote sensing techniques. Over the last decades, the region has experienced a huge urban expansion, which has caused a substantial increase in water supply requirements. Water needs are exclusively met by groundwater by means of numerous pumping wells, which exploit a confined detrital aquifer of alluvial fan deposits with a heterogeneous facies distribution. A general piezometric level decline (up to 50 m) has been recorded in the aquifer during the past 30 years that has induced the generation of a subsiding area with oval shape oriented WNW‐ESE just where the new urban areas and pumping wells are located. Subsidence has been monitored by exploiting synthetic aperture radar (SAR) images from ENVISAT (2003–2009) and Cosmo‐SkyMed (2011–2014). A new approach, which combines A‐DInSAR and small‐area persistent scatterer interferometry (PSI) analysis, has been applied obtaining a good accuracy regarding temporal and spatial dimension of the subsidence. ENVISAT data (2003–2009) reveal subsidence rates up to 10–15 mm/year, and Cosmo‐SkyMed (2011–2014) values slightly lower; up to 10 mm/year. Temporal variations in the subsidence velocity are in accordance with the rainfall pattern and piezometric fluctuations in the aquifer. The sector with highest rates of subsidence does not correspond to the area with more intense groundwater exploitation but to the area with greater presence of clays in the confining layer of the aquifer. There is a clear lithological control in the spatial distribution of the ground subsidence. This work integrates detailed geological and hydrogeological data with differential SAR interferometry monitoring with the aim to better understand subsidence processes in detrital aquifers with small‐scale heterogeneity. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Reducing vertical acceleration in ballast layers of railways to mitigate geometrical disorders in high‐speed lines          下载免费PDF全文

A. Martin  O. Chupin  J.‐M. Piau  P.‐Y. Hicher 《国际地质力学数值与分析法杂志》2017,41(12):1349-1361

According to field feedbacks from high‐speed lines (HSL), the increase of train operating speeds is responsible for unusual fast evolving geometrical disorders in ballasted tracks. This paper deals with the search of solutions applicable at the design stage to mitigate these disorders. The starting point of the present work relies on the assumption, comforted by the literature, of a strong correlation between disorders and vertical accelerations in the ballast layer induced by the train passages. This led us focus herein on the calculation and the analysis of accelerations in the railway structure. The vertical accelerations (γ_z) are computed using the in‐house developed numerical program ViscoRail and on the basis of a reference HSL. These are shown to increase strongly with the train speed attesting to the link between the train speed and the geometrical disorders in ballast. Then, other simulations are run varying some structural parameters to evaluate their impact on the acceleration field γ_z. In that way, we show that decreasing the stiffness of the mechanical connection between the rails and the ballast, increasing the moment of inertia of the rails or the Young modulus of the sub‐ballast layer, leads to a decrease of γ_z and could provide solutions for the design of future HSL. The solution consisting in the incorporation of an asphalt sub‐ballast layer, as already experimented on sites, is finally examined in more details. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Geomechanical modeling of hydrate‐bearing sediments during dissociation under shear          下载免费PDF全文

Jeen‐Shang Lin  Yongkoo Seol  Jeong Hoon Choi 《国际地质力学数值与分析法杂志》2017,41(14):1523-1538

Methane hydrate‐bearing sediments exist throughout the world in continental margins and in Arctic permafrost. Hydrates are ice‐like compounds when dissociate due to temperature rise or reduction in fluid pressure, release gas. Because of the mechanical property changes caused by dissociation in which the loads supported by the hydrates are transferred to soil grains, these sediments may become unstable. To quantify the risk of ground instability triggered by dissociation, which may happen during operation to extract methane gas or from climate changes, a reliable predictive model is indispensable. Even though many models have been proposed, a detailed validation of the ability to model dissociation impact is still needed. This study investigated the adequacy of an spatially mobilized plane constitutive model and a modeling framework using laboratory‐induced dissociation tests under shear from literature. Using laboratory‐imposed temperature and pressure changes and the resulting hydrate saturation changes as input, this study was able to capture the geomechanical responses and determine the stability state of methane hydrate‐bearing sediments as observed. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Long‐term Holocene groundwater fluctuations in a chalk catchment: evidence from Rock‐Eval pyrolysis of riparian peats          下载免费PDF全文

Andrew J. Newell  Christopher H. Vane  James P.R. Sorensen  Vicky Moss‐Hayes  Daren C. Gooddy 《水文研究》2016,30(24):4556-4567

The depositional history of peat‐dominated wetlands can be used to understand palaeoclimate and palaeohydrology and also constrain the impacts of future climate change. However, in chalkland valleys, seasonal water table fluctuations and a high alkalinity have diminished key environment indicators such as pollen, and there is a need for alternative investigative techniques. The method of Rock‐Eval pyrolysis can track changes in organic matter source and degradation, potentially relating to historic changes in vegetation cover. This is the first Rock‐Eval on cores from a groundwater‐dependent riparian chalk valley wetland combined with radiocarbon dating. The dating showed that the cores represented approximately 4000 years of depositional history. Changes in hydrocarbon chemistry including normal alkane composition of the peat indicated shifts of around 500 to 1000 years between terrestrial and more aquatic species, relating to periods of climate wetness. These climatic shifts are broadly consistent with other evidence from ombrotrophic peatland and lacustrine sediments across northwest Europe. However, the connection between climate wetness and groundwater dependent chalkland wetlands is complicated by external anthropogenically driven factors relating to land use and vegetation cover changes in the catchment. Nonetheless, this study suggests that Rock‐Eval pyrolysis is a useful and cost‐effective tool that can provide evidence for long‐term Holocene groundwater fluctuations. Copyright © 2016 British Geological Survey.  相似文献   

Probabilistic analyses of soil consolidation by prefabricated vertical drains for single‐drain and multi‐drain systems          下载免费PDF全文

Mohammad Wasiul Bari  Mohamed A. Shahin  Abdul‐Hamid Soubra 《国际地质力学数值与分析法杂志》2016,40(17):2398-2420

Natural soils are one of the most inherently variables in the ground. Although the significance of inherent soil variability in relation to reliable predictions of consolidation rates of soil deposits has long been realized, there have been few studies that addressed the issue of soil variability for the problem of ground improvement by prefabricated vertical drains. Despite showing valuable insights into the impact of soil spatial variability on soil consolidation by prefabricated vertical drains, available stochastic works on this subject are based on a single‐drain (or unit cell) analyses. However, how the idealized unit cell solution can be a supplement to the complex multi‐drain systems for spatially variable soils has never been addressed in the literature. In this study, a rigorous stochastic finite elements modeling approach that allows the true nature of soil spatial variability to be considered in a reliable and quantifiable manner, both for the single‐drain and multi‐drain systems, is presented. The feasibility of performing an analysis based on the unit cell concept as compared with the multi‐drain analysis is assessed in a probabilistic context. It is shown that with proper input statistics representative of a particular domain of interest, both the single‐drain and multi‐drain analyses yield almost identical results. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Explanatory analysis of the relationship between atmospheric circulation and occurrence of flood‐generating events in a coastal city          下载免费PDF全文

Helena L. A. Åström  Maria Sunyer  Henrik Madsen  Dan Rosbjerg  K. Arnbjerg‐Nielsen 《水文研究》2016,30(16):2773-2788

The aim of this study is to enhance the understanding of the occurrence of flood‐generating events in urban areas by analysing the relationship between large‐scale atmospheric circulation and extreme precipitation events, extreme sea water level events and their simultaneous occurrence, respectively. To describe the atmospheric circulation, we used the Lamb circulation type (LCT) classification and re‐grouped it into Lamb circulation classes (LCC). The daily LCCs/LCTs were connected with rare precipitation and water‐level events in Aarhus, a Danish coastal city. Westerly and cyclonic LCCs (W, C, SW and NW) showed a significantly high occurrence of extreme precipitation. Similarly, for extreme water‐level events westerly LCCs (W and SW) showed a significantly high occurrence. Significantly low occurrence of extreme precipitation and water‐level events was obtained in easterly LCCs (NE, E and SE). For concurrent events, significantly high occurrence was obtained in LCC W. We assessed the change in LCC occurrence frequency in the future based on two regional climate models (RCMs). The projections indicate that the westerly directions in LCCs are expected to increase in the future. Consequently, simultaneous occurrence of extreme water level and precipitation events is expected to increase in the future as a result of change in LCC frequencies. The RCM projections for LCC frequencies are uncertain because the representation of current LCCs is poor; a large number of days cannot be classified and the frequencies of the days that can be classified differ from the observed time series. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Spatial and temporal variability of surface water repellency in sandy loam soils of NW Spain under Pinus pinaster and Eucalyptus globulus plantations     

M. Rodríguez‐Alleres  E. Benito 《水文研究》2011,25(23):3649-3658

This work was undertaken for two main purposes. One was to examine spatial and temporal variability in surface water repellency under field conditions in sandy loam forest soils of NW Spain, and its relationship to weather and soil moisture conditions. The other purpose was to get further inside in the dynamics of soil water repellency by studying a wetting–drying cycle under controlled laboratory conditions. Both for the field and laboratory study, water repellency was determined using the Water Drop Penetration Time test. Soil water repellency under field conditions was found to exhibit a seasonal pattern, i.e. it peaked during the summer and was absent between November and May. The time required for repellency to become re‐established during the spring was shorter under eucalyptus than under pine. Spatial variability peaked at an early stage of soil drying and was minimal during the wet period when soils were hydrophilic as well as at the end of the summer, when repellency was strongest. Spatial and temporal variability in water repellency was found to be negatively correlated with soil moisture and, to a lesser extent, with antecedent rainfall. The moisture range of the so‐called transition zone (below which the soil is hydrophobic and also above which it is hydrophobic) differed for the pine (21–50%) and eucalyptus plantations (17–36%). The lower and upper bounds of the transition zone agreed well with the soil moisture contents at the permanent wilting point and at field capacity, respectively. The laboratory results with samples in the wetting phase confirmed those of the field tests. Water repellency increased slightly during the drying phase, but not so much as in the field. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Numerical modeling of the elastoplastic damage behavior of dry and saturated concrete targets subjected to rigid projectile penetration          下载免费PDF全文

Hanbing Bian  Yun Jia  Christophe Pontiroli  Jian‐Fu Shao 《国际地质力学数值与分析法杂志》2018,42(2):312-338

The objective of the present paper is to present a numerical study on the penetration performance of concrete targets with 2 different water contents. Numerical analysis has been performed by using the finite element code Abaqus/Explicit, in which a coupled elastoplastic damage model has been developed for saturated/unsaturated concrete under a wide range of confining pressures. The performance of proposed model has been firstly verified by simulating the triaxial compression tests and penetration tests realized with saturated/dry concretes. Comparisons of available experimental results and numerical simulations show that the proposed model is able to reproduce satisfactorily the mechanical behavior of saturated and dry concretes. A higher failure stress and a more important pores closing are generally obtained in dry concrete samples with respect to saturated ones. Furthermore, the main observed patterns of penetration test realized with saturated concrete targets are also satisfactorily simulated by the numerical results. Therefore, the proposed model is used to numerically predict the penetration performance of dry concrete target, and the penetration performance of dry/saturated concrete target is discussed. We observe that in dry concrete target, the penetration of projectile is strongly declined, and a smaller damage zone is created. The numerical predictions and discussions can help engineers to enhance their understandings on the influence of hydraulic conditions on structural vulnerability of concrete structures subjected to near‐field detonations or impacts.  相似文献   

Multivariate statistical analysis and environmental isotopes of Amman/Wadi Sir (B2/A7) groundwater,Yarmouk River Basin,Jordan     

Mutewekil Mamdouh Obeidat  Muheeb Awawdeh  Fahmi Abu Al‐Rub 《水文研究》2013,27(17):2449-2461

Multivariate statistical techniques, cluster and factor analyses were applied on the Amman/Wadi Sir groundwater chemistry, Yarmouk River basin, north Jordan. The main objective was to investigate the main processes affecting the groundwater chemical quality and its evolution. The k‐means cluster analysis yields three groups with distinct ionic concentrations. Cluster 1 comprises the vast majority of the sampled wells, and the water that belongs to this cluster can be classified as freshwater. Cluster 2 comprises only 2% of the sampled wells; it has the highest ionic concentration. The water of this cluster can be classified as brackish water. Cluster 3 involves 23% of the sampled wells, and it has total ionic concentration intermediate to that of clusters 1 and 2. Factor analysis yields a three‐factor model, which explains 76.77% of the groundwater quality variation. Factor 1 ‘salinity factor’ involves EC, Na⁺, Cl^‐, SO₄^‐2, K⁺ and Mg⁺² and reflects groundwater salinization because of overpumping. Factor 2 ‘hardness factor’ includes Ca⁺², HCO₃^‐ and the pH value and signifies soil–water/rock interaction. Factor 3 ‘nitrate factor’ involves only NO₃^‐ and points to groundwater contamination because of human activities, mainly untreated wastewater, and crops and animal cultivation in the unconfined portion of the aquifer. Factors 1 and 3 can be described as human‐induced factors, whereas factor 2 can be described as geogenic factor. Factors' scores were mapped to deduce the controlling processes on the groundwater chemistry. Stable isotope composition of ¹⁸O and ²H has revealed that the groundwater is a mixture of two water types. The radioactive isotopes tritium and ¹⁴ C were used to evaluate present day recharge to the aquifer and to estimate the groundwater age, respectively. Present day recharge to the groundwater is taking place in the unconfined portion of the aquifer as it is indicated by the measurable tritium content and low groundwater age. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Applications of the cyclic spectral analysis to the surface temperature fluctuations in a stochastic climate model and a GCM simulation     

Jian‐Ping Huang  Han‐Ru Cho  >Gerald R. North 《大气与海洋》2013,51(4):627-646

Abstract

In this paper, we introduce the cyclostationary processes into climate analysis and undertake a systematic study of the cyclic spectra of surface temperature fluctuations. The technique is adapted from cyclostationarity theory in signal processing. To demonstrate the usefulness of this technique, a very simple cyclostationary stochastic climate model is constructed. Our results show that the seasonal cycle strongly modulates the amplitudes of the covariance and the spectrum. The technique was also applied to the surface temperature fluctuations in a fifteen‐year seasonal run of the National Center for Atmospheric Research (NCAR) Community Climate Model (CCM2, R15) using a zonally symmetric all‐land surface as the lower boundary. The results indicate that intraseasonal oscillations localized according to time of year are still present even after the surface temperature fields have been normalized using the commonly used procedure. Both examples suggest that the “annual cycle” cannot be “removed” by simply using a normalization procedure. The climate is not as completely represented when modelled as stationary processes.  相似文献