基于归一化植被指数反演地表比辐射率方法的对比研究

针对只有一个热红外通道的遥感数据,利用归一化植被指数与地表比辐射率具有较高的线性相关性进行地表比辐射率的遥感反演,介绍了基于归一化植被指数定量反演地表比辐射率的4种方法,以湖北省荆门市地区的Landsat5 TM数据为研究对象,精度0.01的MODIS LSE产品为标准数据,对比分析了4种基于NDVI的地表比辐射率反演方法,分别从像元尺度和分类尺度总结了4种地表比辐射率反演方法的普适性和精度。     

遥感数据的温度反演方法及其试验算例

我国是一个冻土分布较多的国家,以前利用遥感图像对冻土的研究与应用主要体现在冻土亚类划分等方面.红外遥感图像能够反演地表温度,而冻土区在不同亚类别地区,其地表温度也具有一定的差异性,因此本文在介绍了几种温度反演方法的基础上,利用Aster数据对冻土区地表温度进行了反演和分析.通过分析和研究,发现Aster数据能够反演冻土...     

超大直径泥水平衡顶管时的横向地表沉降流固耦合研究

以上海一超大直径泥水平衡顶管工程为依托,基于流固耦合分析原理,利用数值模拟方法对顶管横向地表沉降进行研究。建立由顶管管片、泥浆套、施工扰动层和周围土层组成的流固耦合模型以及非耦合模型,分析注浆压力以及泥膜形成与否对地下水位和顶管横向地表沉降的影响,同时也分析了注浆与停止注浆时的地表沉降变化。实践证明,现场横向沉降实测数据与耦合结果一致,说明耦合数值模型具有可行性,可以为顶管工程的后续施工提供指导。     

采样方案对反演岩体渗透参数的影响

利用地下水位的观测资料对岩体渗透参数进行反演是较为可靠的方法。目前常用随机布点的方法获得地下水位的观测资料。这种方法没有考虑地下水位的空间变异性。通过对地下水位空间变异性的分析，将总体估计误差作为评价样本好坏的标准，并用它研究了3种不同采样方案下等效连续介质的主渗透参数反演结果。分析结果表明：在满足反演精度的前提下，采用优化的方案可降低采样费用；采用随机布点，在相同布点数时，反演结果的误差较优化方案的误差大；增加随机布点数对反演结果改善不明显。     

基于地表移动矢量的概率积分法参数反演方法

为解决概率积分法参数反演时计算不稳定、初值依赖、优化指标难以选取、非矩形工作面,多工作面影响下难以反演的问题,提出采用地表空间移动矢量反演概率积分法参数的遗传算法模型。该模型采用地表移动矢量的误差平方和最小作为计算指标,以遗传算法作为参数优化的核心算法进行概率积分法参数反演。用空间移动矢量指标可以解决分别采用下沉、水平移动监测值反演结果不相同、精度难以估算的难题。矢量反演模型对观测站设置没有特别严格的要求,降低了设站不当引起的计算误差。为解决遗传算法多次计算结果不同的问题,建立了组合预测计算方法,依据中误差加权均值得到唯一的计算结果。基于矢量移动值的反演模型,避免了传统计算方法的多个缺陷,计算效率高、易于与已有开采沉陷预计程序结合,为解决非矩形、多工作面地表移动观测站参数反演的工程应用问题提供了新的解决思路和计算方法。     

基于动态代理模型的顶管掘进时邻近构筑物变形预测

在顶管法施工穿越既有隧道时,控制顶管掘进导致的既有隧道变形以及地表沉降对设计、施工至关重要,有必要对顶管掘进引起的既有隧道变形以及地表沉降进行预测。采用动态代理模型优化方法对顶管掘进引起的隧道水平收敛和地表沉降进行了反演预测,同时对比了动态代理模型方法和静态代理模型方法的计算准确度和效率。结果表明,使用优化后的参数得到的隧道水平收敛和地表沉降计算值与监测值较为接近,相比静态代理模型方法,动态代理模型方法所使用的样本数更少,计算效率更高。     

二维粘弹性问题反分析计算的统一模型

本文就地下工程中二维平面应变问题提出了反演确定洞室围岩初始地应力及其粘弹性参数的统一方法,用五种常见的描述岩土体变形性态的粘弹性模型的参数作反演计算.文中在描述岩土体材料的粘弹性性态的本构方程用统一公式表示,通过论证提出了依据现场量测信息对初始地应力和围岩粘弹性参数进行反演计算的原理、方法和公式,包括可据以进行线弹性反演计算的数值法方程,以及可用于确定围岩粘弹性参数的反演计算方程等.此外,文末还通过算例验证对所提方法的适用性进行了论证.     

基于PCA特征提取的SVR地下水位动态预测方法

本文提出了一种基于PCA特征提取的SVR地下水位动态预测方法.PCA用来对地下水位样本值进行相关性分析和特征提取,将得到的最佳特征向量子集输入SVR模型,并通过网格搜索的方法进行SVR参数寻优,进行地下水位预测.通过地下水位的实例分析和UCI标准数据集对模型的有效性进行验证,结果表明该方法不仅降低了预测所需的计算工作量...     

水位上升对地裂缝场地地铁隧道影响的数值模拟

基于FLAC3D有限差分软件建立了包括地裂缝和地铁隧道的数值模拟模型,分析了从下向上、从左向右和从右向左三种渗流方式使地下水位上升不同的高度对地裂缝场地地铁隧道的影响。发现随着地下水位的上升,地表回弹量不断增大,在地裂缝和地铁隧道对应的地表附近存在回弹位移减小区,相比于其他两种渗流方式,从下向上渗流引起的地表位移值最大;隧道衬砌内力受渗流方式及水位上升区间的影响而变化,10 m处为转折点;隧道衬砌水平位移增量呈线性不断增长,竖向位移增量呈先增大后减小的趋势,从左向右渗流方式对隧道衬砌水平位移的影响最大。     

基于生态竞争模型的岩土本构模型辨识新算法

为了进行模型类间辨识及参数反演 ,基于分子生物学原理 ,模拟自然界多物种竞争的现象 ,以更能反应生物进化本质的进化规划为框架 ,提出了一种模拟生态竞争模型。在此基础上进行了岩土本构模型类间辨识及参数反演的研究 ,提出了一种模型辨识新算法 ,初步解决了从一组模型类中抉择最佳模型并同时反演参数的问题。最后 ,用一个简单算例证明了该算法是可行和有效的。     

Brauchen wir ein faunistisch begründetes Grundwassermonitoring, und was kann es leisten?

Groundwater is populated by a diversified and highly specialized fauna. It obviously prevents clogging of interstitial spaces and enhances the ability of self purification of the aquifers. Lowering of groundwater tables and intrusions of pollutants endanger this subterranean biotope. The effects of pollutants are not clear, but the consequences of infiltration of surface water or of a decreasing groundwater table typically cause replacement of the groundwater animals by epigean species and thus hcanged communities' characteristics. As a result, it seems to be possible to use faunstic surveys to interprete the influence of surface water and changes in the groundwater table. However, standards for faunistic biomonitoring have not been developped, but are urgently required.     

Hydrochemical characteristics and water quality assessment of surface water and groundwater in Songnen plain, Northeast China

Water quality is the critical factor that influence on human health and quantity and quality of grain production in semi-humid and semi-arid area. Songnen plain is one of the grain bases in China, as well as one of the three major distribution regions of soda saline-alkali soil in the world. To assess the water quality, surface water and groundwater were sampled and analyzed by fuzzy membership analysis and multivariate statistics. The surface water were gather into class I, IV and V, while groundwater were grouped as class I, II, III and V by fuzzy membership analysis. The water samples were grouped into four categories according to irrigation water quality assessment diagrams of USDA. Most water samples distributed in category C1-S1, C2-S2 and C3-S3. Three groups were generated from hierarchical cluster analysis. Four principal components were extracted from principal component analysis. The indicators to water quality assessment were Na, HCO₃, NO₃, Fe, Mn and EC from principal component analysis. We conclude that surface water and shallow groundwater are suitable for irrigation, the reservoir and deep groundwater in upstream are the resources for drinking. The water for drinking should remove of the naturally occurring ions of Fe and Mn. The control of sodium and salinity hazard is required for irrigation. The integrated management of surface water and groundwater for drinking and irrigation is to solve the water issues.     

海潮影响区抽水试验静止水位取值的探讨

滨海地区地下水受潮汐影响而波动,在该地区进行抽水试验,其静止水位取值是一个难点.本文以宁波市蛇蟠涂围垦区S1号孔抽水试验为例,通过建立孔内地下水与潮水的峰谷值水位联动关系,利用易获取的潮水位峰、谷值数据来推算地下水位的峰、谷值,从而计算地下水的静止水位.研究表明,S1号孔内水位大致呈正弦曲线形态波动,与临近闸口的潮水位...     

大降深矿井排水预测地下水位迭代精度的影响因素

本文讨论了大降深矿井排水预测中 ,利用迭代法求解数值模型时 ,地下水位计算误差的影响因素。利用理想模型讨论了地下水位计算误差与开采量、迭代收敛误差限、计算时间和含水量参数之间的关系。经讨论得知地下水位计算误差与迭代收敛误差限、计算时间和含水层参数有关 ,与开采量和水位变幅无关。     

新疆阿瓦提绿洲灌区约束供水条件下地下水开采模式

针对干旱内陆河绿洲灌区地下水位上升及塔里木河源流区限额供水的现实条件,本文以新疆阿瓦提绿洲灌区为研究区域,通过MODFLOW建立地下水流数值模型,模拟了现状及限额供水后的预测结果,并根据灌区的实际情况提出合理的地下水开采方案,以达到有效调控地下水位的目的。此方案下地下水开采量为1.14×108m3/a,并在全区范围内合理控制地下水位,为防治土壤盐碱化、减少无效蒸发和区域水资源的优化配置提供了有益参考。     

Influence of uncertainty in the initial groundwater table on long-term stability of reservoir landslides

The seepage calculation of water fluctuation is the crucial precondition for landslide stability evaluation. It is controlled by the initial condition, boundary condition, and soil or rock structure as well as geotechnical parameters. Although the geotechnical parameters and boundary condition have greater influence on seepage and the stability of landslides, the role of the initial groundwater position cannot be ignored. To investigate the influence of an initial groundwater table on landslides, especially the influence of cyclical reservoir water fluctuation on their long-term stability, seven different methods to determine the initial groundwater table were proposed in the presented study, among which one is the actual groundwater table, and the other six are obtained with simplified methods. According to the results of the calculations, at the beginning, there is some difference in the factor of safety among different initial groundwater tables. The maximum value of relative tolerance reduces to less than 1.0 % 160 days later. After a filling–drawdown cycle, the relative tolerance of all methods reduces to less than 0.8 %, which could be ignored. It is also observed that, the closer the hydraulic gradient of the proposed initial groundwater table is to the actual condition, the smaller is the relative tolerance. Therefore, to study the influence of cyclical reservoir water fluctuation on landslide long-term stability, the initial groundwater table could be proposed as (1) equal to reservoir water level and (2) on a straight line with the hydraulic gradient equal to the weighted average of actual groundwater table for simplification.     

地下水位上升对土体震陷的影响

地震作用是产生震陷的主要动荷因素 ;多种自然、人为因素引起的温室效应会造成地下水位上升 ,而地下水位上升又会对震陷产生较大的影响。在给出地震作用下考虑地下水位上升而影响震陷的简化分析方法的同时 ,指出了地下水位上升对震陷量影响的规律。     

Infiltration und Grundwasserströmung in geklüftet-porösen Buntsandsteingrundwasserleitern im Osten des Thüringer Beckens

In the eastern Thuringian Basin, the low precipitation rate of 585?mm/y limits the groundwater resources in the sandstone aquifer system. The aim of this study was to develop a groundwater flow model for the region in order to forecast the impacts of different climate scenarios on the groundwater balance. Since recharge is of high relevance for the numerical model, a time series of groundwater levels were investigated to obtain the recharge input function. In the sandstone aquifer it could be shown that groundwater flow is characterised by flow in the fracture network as well as in the matrix. The largest fraction of recharge reaches the water table very quickly via the fracture network. However, both the thickness of the unsaturated zone and the low hydraulic conductivity of the sandstone matrix control the time lag of groundwater recharge. The time lag of the slow component to reach the water table is in the order of several years.     

Quantitative assessment of intrinsic groundwater vulnerability to contamination using numerical simulations

Intrinsic vulnerability assessment to groundwater contamination is part of groundwater management in many areas of the world. However, popular assessment methods estimate vulnerability only qualitatively. To enhance vulnerability assessment, an approach for quantitative vulnerability assessment using numerical simulation of water flow and solute transport with transient boundary conditions and new vulnerability indicators are presented in this work. Based on a conceptual model of the unsaturated underground with distinct hydrogeological layers and site specific hydrological characteristics the numerical simulations of water flow and solute transport are applied on each hydrogeological layer with standardized conditions separately. Analysis of the simulation results reveals functional relationships between layer thickness, groundwater recharge and transit time. Based on the first, second and third quartiles of solute mass breakthrough at the lower boundary of the unsaturated zone, and the solute dilution, four vulnerability indicators are extracted. The indicator transit time t₅₀ is the time were 50% of solute mass breakthrough passes the groundwater table. Dilution is referred as maximum solute concentration C_max in the percolation water when entering the groundwater table in relation to the injected mass or solute concentration C₀ at the ground surface. Duration of solute breakthrough is defined as the time period between 25% and 75% (t_25%-t_75%) of total solute mass breakthrough at the groundwater table. The temporal shape of the breakthrough curve is expressed with the quotient (t_25%-t_50%) / (t_25%-t_75%). Results from an application of this new quantitative vulnerability assessment approach, its advantages and disadvantages, and potential benefits for future groundwater management strategies are discussed.     

Responses of calcareous sand foundations to variations of groundwater table and applied loads

The long-term settlement of calcareous sand foundations caused by daily periodic fluctuations has become a significant geological hazard, but effective monitoring tools to capture the deformation profiles are still rarely reported. In this study, a laboratory model test and an in situ monitoring test were conducted. An optical frequency domain reflectometer (OFDR) with high spatial resolution (1 mm) and high accuracy (±10^-6) was used to record the soil strain responses to groundwater table and varied loads. The results indicated that the fiber-optic measurements can accurately locate the swelling and compressive zones. During the loading process, the interlock between calcareous sand particles was detected, which increased the internal friction angle of soil. The foundation deformation above the sliding surface was dominated by compression, and the soil was continuously compressed beneath the sliding surface. After 26–48 h, calcareous sand swelling occurred gradually above the water table, which was primarily dependent on capillary water. The swelling of the soil beneath the groundwater table was completed rapidly within less than 2 h. When the groundwater table and load remain constant, the compression creep behavior can be described by the Yasong-Wang model with R² = 0.993. The daily periodically varying in situ deformation of calcareous sand primarily occurs between the highest and lowest groundwater tables, i.e. 4.2–6.2 m deep. The tuff interlayers with poor water absorption capacity do not swell or compress, but they produce compressive strain under the influence of deformed calcareous sand layers.