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181.
A low-dimensional model that describes both saturated and unsaturated flow processes in a single equation is presented. Subsurface flow processes in the groundwater, the vadose zone, and the capillary fringe are accounted for through the computation of aggregated hydrodynamic parameters that result from the integration of the governing flow equations from the bedrock to the land surface. The three-dimensional subsurface flow dynamics are thus described by a two-dimensional equation, allowing for a drastic reduction of model unknowns and simplification of the model parameterizations. This approach is compared with a full resolution of the Richards equation in different synthetic test cases. Because the model reduction stems from the vertical integration of the flow equations, the test cases all use different configurations of heterogeneity for vertical cross-sections of a soil-aquifer system. The low-dimensional flow model shows strong consistency with results from a complete resolution of the Richards equation for both the water table and fluxes. The proposed approach is therefore well suited to the accurate reproduction of complex subsurface flow processes. 相似文献
182.
Salt crystallisation is a major problem of deterioration in historic stone buildings, monuments and sculptures. The capillary rise of soil water is one of the primary sources of salts in stone structures, which evaporates leaving the salts behind. It has been noted that the spatial distribution profile of different species of salts crystallised in historic stone buildings is not homogeneous, i.e. different salts crystallise at different locations. The capillary transport and inhomogeneous spatial distribution of different salts in the porous building materials has been considered to be a result of solubility-dependent crystallisation; however, the factors responsible for this phenomenon are not clearly known. This paper aims to investigate the factors influencing the differential distribution of salts during capillary rise of soil water. In this study, the capillary transport of salts was simulated on two different sandstones—Locharbriggs, a Permo–Triassic, red sandstone and Stoke Hall, a Carboniferous, buff sandstone. The experiments were carried out under controlled environmental conditions to eliminate the possibility of evaporation-driven crystallisation of salts depending on their solubilities. The results indicate that fractionation or differential distribution of salts takes place even in the absence of evaporation and crystallisation. The sandstones exhibit properties like an ion exchange column, and ionic species present in the salt solution show differential distribution within the porous network of sandstone. 相似文献
183.
渤海湾北岸晚新生代沉积环境和沉积体系不仅是区域水文地质、工程地质的基础,也为古近纪沉积模式提供“将今论古”的依据。本文依据沉积物色度和粒度,以及沉积物岩性、结构和构造等,将渤海湾北岸TZ02孔划分了6个沉积组合、4个沉积阶段:1)2.10~3.22Ma,沉积组合Ⅰ和Ⅱ,湖盆填充期,发育湖相-泛滥平原相或湖相-曲流河相,该时期处于构造稳定期,干冷气候时期发育河流相、泛滥平原相,湿润气候时期发育湖泊相。2)1.33~2.10Ma,沉积组合Ⅲ,湖盆开始发育期,主要为浅湖相,仅有少量砂体,下部多有机质,上部多钙质淀积结核,指示了盆山之间的构造分异后,湖泊初始发育的特征。3)0.62~1.33Ma,沉积组合Ⅳ,湖盆扩张期,以湖相为主,多砂体,且有短期湖泊水位变浅和成陆过程;指示了盆山构造分异后,盆地加速沉降,湖盆扩张;山体隆起、河流下切,盆地中湖相砂体增多;此时TZ02孔附近为湖相中心,BG10孔为湖泊边缘。4)0~0.62Ma,沉积组合Ⅴ和Ⅵ,湖泊填充期,BG10孔为湖相的沉积中心,而TZ02孔为湖泊的边缘,接受滦河迁移摆动后的沉积物;中更新世后,构造沉降形成湖相,而间冰期发育海相,埋深0~22.5m的海相-河流相更直接地反映了末次冰消期海平面变化过程。
相似文献184.
Weidong Li 《Mathematical Geosciences》2007,39(3):321-335
Multi-dimensional Markov chain conditional simulation (or interpolation) models have potential for predicting and simulating categorical variables more accurately from sample data because they can incorporate interclass relationships. This paper introduces a Markov chain random field (MCRF) theory for building one to multi-dimensional Markov chain models for conditional simulation (or interpolation). A MCRF is defined as a single spatial Markov chain that moves (or jumps) in a space, with its conditional probability distribution at each location entirely depending on its nearest known neighbors in different directions. A general solution for conditional probability distribution of a random variable in a MCRF is derived explicitly based on the Bayes’ theorem and conditional independence assumption. One to multi-dimensional Markov chain models for prediction and conditional simulation of categorical variables can be drawn from the general solution and MCRF-based multi-dimensional Markov chain models are nonlinear. 相似文献
185.
186.
Yan Li Peng Li Hong-jun Qu Gui-wen Wang Xiao-han Sun Chang Ma Tian-xing Yao 《China Geology》2024,41(1):12-25
The well-developed coal electricity generation and coal chemical industries have led to huge carbon dioxide (CO2) emissions in the northeastern Ordos Basin. The geological storage of CO2 in saline aquifers is an effective backup way to achieve carbon neutrality. In this case, the potential of saline aquifers for CO2 storage serves as a critical basis for subsequent geological storage project. This study calculated the technical control capacities of CO2 of the saline aquifers in the fifth member of the Shiqianfeng Formation (the Qian-5 member) based on the statistical analysis of the logging and the drilling and core data from more than 200 wells in the northeastern Ordos Basin, as well as the sedimentary facies, formation lithology, and saline aquifer development patterns of the Qian-5 member. The results show that (1) the reservoirs of saline aquifers in the Qian-5 member, which comprise distributary channel sand bodies of deltaic plains, feature low porosities and permeabilities; (2) The study area hosts three NNE-directed saline aquifer zones, where saline aquifers generally have a single-layer thickness of 3‒8 m and a cumulative thickness of 8‒24 m; (3) The saline aquifers of the Qian-5 member have a total technical control capacity of CO2 of 119.25 × 106 t. With the largest scale and the highest technical control capacity (accounting for 61% of the total technical control capacity), the Jinjie-Yulin saline aquifer zone is an important prospect area for the geological storage of CO2 in the saline aquifers of the Qian-5 member in the study area. 相似文献
187.
一种改进的基于非高斯性最大化的预测反褶积算法 总被引:2,自引:1,他引:2
The predictive deconvolution algorithm (PD), which is based on second-order statistics, assumes that the primaries and the multiples are implicitly orthogonal. However, the seismic data usually do not satisfy this assumption in practice. Since the seismic data (primaries and multiples) have a non-Gaussian distribution, in this paper we present an improved predictive deconvolution algorithm (IPD) by maximizing the non-Gaussianity of the recovered primaries. Applications of the IPD method on synthetic and real seismic datasets show that the proposed method obtains promising results. 相似文献
188.
The present experimental investigation focuses on the characteristics of near bed turbulence in a fully rough, uniform open-channel
flow over a gravel-type bed. Due to bed topography small scale heterogeneity, the flow is not uniform locally in the near
bed region and a double averaging methodology is applied over a length scale much larger than the gravel size. The double-averaged
Turbulent Kinetic Energy (TKE) budget derived in the context of the present flow over a gravel bed differs from the TKE budget
written for flow over a vegetation canopy. The non-constant shape of the roughness function measured in our gravel bed leads
to an additional bed-induced production term which is null for vertical roughness elements, such as simplified vegetation
elements.
The experimental estimation of the terms of the TKE budget reveals that the maximum turbulent activity takes place away from
the reference plane, near the roughness crests. However, within the interface sublayer the work of the bed induced velocity
fluctuations against the Reynolds stress is of the same magnitude as the main turbulence production term. Consequently, the
characteristics of the TKE budget have similarities with uniform flows over canopies and strongly differ from uniform flows
over smooth and transitionally rough flows over sedimentlike beds. 相似文献
189.
Bouchet in 1963 hypothesized that for large homogeneous land surface with minimum advection of heat and moisture, there exists
a 1:1 complementary relationship of potential and actual evaporation coupled through land-atmosphere feedbacks. The complementary
relationship has been widely used to estimate regional actual evaporation and explain the pan evaporation paradox. We examine
the standardized potential evaporation (potential evaporation divided by wet environment evaporation) at 102 observatories
at different elevations across China. Generally, the relationship is appropriate at the low elevations (<1000 m). With the
increase of elevation, vapor transfer power becomes much less than radiation energy budget because of lower vapor pressure
deficit and stronger global solar radiation. As a result, at the high elevations (over 1000 m), the excess energy resulted
by limited moisture availability is not enough to be converted into drying power of the air. This result suggests that the
complementary relationship is asymmetric at the high elevations.
Supported by the Presidential Special Award Foundation, the Chinese Academy of Sciences (Grant No. O7R70020SD) and the National
Key Technology R & D Program (Grant No. 2006BAC08B0408) 相似文献
190.