Combined land-use and environmental factors for sustainable groundwater management

Sustainable groundwater management must take into consideration pollution sources and the potential of fluid percolation which could convey pollutants to the aquifer. The objective of this paper is to highlight the relationship between environmental factors and land-use types, and the adverse effects upon groundwater quality which may stem from that relationship. A clear understanding of the significant impact of land-use can generate guidelines for sustainable groundwater management. Appropriate conservation and remediation measures, could then be suggested, taking in consideration land-use and intensity of percolation potential from the ground surface to the water table. Guidelines for operational measures can be suggested to mitigate and correct adverse trends in groundwater quality. Integrated with such guidelines, planned land-use activities should harmonize with needs of both ecological and sustainable groundwater management. Two study areas located in different regions of Israel's coastal aquifer have been considered in this paper. Erez-Shiqma represents a pristine region, whilst the Ra'anana area represents a region suffering from significant eco-hydrological stress.     

Integrated tool for risk assessment in agricultural management of soil erosion and losses of phosphorus and nitrogen

In recent years, increased attention has been focused on models for risk assessment of source areas in agricultural landscapes. Among the simplest of such models are index tools, which have been developed particularly for phosphorus (P) and to some extent nitrogen (N). However, only a few studies have considered the development of an integrated management strategy that includes erosion and losses of both P and N. Accordingly, the major objective of this study was to initiate the development of an integrated risk assessment tool, consisting of indices for erosion, P and N. The strategy used to create the integrated tool was based on the assumption that all input data at field scale should be readily available either from ordinary agricultural statistics or from the farmer. The results from using the indices in a pilot case study catchment illustrated that losses of P and N had often different critical source areas. The P index was highest for fields with manure application and/or high soil P status or with autumn ploughing, and the N index was highest for fields with excessive N application. The integrated risk was greatest for areas with manure application and some areas with a high erosion risk in combination with high nutrient application rate. Additionally, four different management options were assessed: (1) reduced fertilisation, (2) catch crops, (3) autumn ploughing, and (4) no autumn ploughing. The results verified that reduced nutrient application and stubble during autumn and winter led to the largest decrease in index values, and it was also apparent that management changes in high-risk areas had the greatest impact on the indices. Overall, our findings indicate that the present integrated risk assessment tool with readily available input data can be used to rank farm fields according to risk of soil erosion and losses of P and N.     

灾难损失与灾难管理

从2008年5月12日14点28分那一刻起,十几亿中国人经历了巨大悲痛的和无数的感动.灾难现场惨烈的景象令观者动容,抗震救灾的每一瞬间震撼着人们的心灵.痛定思痛,为了将灾难带来的损失降到最小,我们需要对灾难造成的损失有一个清楚的认识,震撼的瞬间也仅仅是我们重建家园的一个片断,谋定而动,我们需要考虑到灾后恢复的方方面面.将悲痛埋在心底,将感动化作理性,试从经济学的视角分析诸如地震、洪水、台风等灾难的损失以及灾后的恢复,希望能为当前和以后的减灾救灾工作提供一些帮助.     

Experimental investigations on suffusion characteristics and its mechanical consequences on saturated cohesionless soil

The characteristics of suffusion and its mechanical consequences on saturated cohesionless soil with different initial fines contents at various stress states are presented in this paper. A series of seepage tests is performed by constant-flow-rate control mode with the measurement of the induced pore water pressure difference between the top and bottom of the tested specimen under the isotropic confining pressure. Back pressure is maintained constant in the tested soil specimen to ensure fully saturated soil condition. Cumulative eroded soil mass is continuously recorded by a consecutive monitoring system. Suffusion induced axial strain and radial strain of the 70mm-in-diameter and 150mm-in-height specimen is recorded during the seepage tests. The gap-graded cohesionless soil, which are assessed as internally unstable by existing evaluation methods, are tested. The mechanism of suffusion is demonstrated by the variation of hydraulic gradient, hydraulic conductivity, percentage of cumulative fines loss and volumetric strain during suffusion. The parametric study on the influence of two variables, effective stress level and initial fines content, on the mechanism of suffusion is elaborated. The mechanical consequences of suffusion are evaluated by conducting monotonic drained compression tests on the eroded specimens. Companion specimens without suffusion are tested for comparison purpose. The test results reveal that with the progress of suffusion, hydraulic gradient would drop and hydraulic conductivity would increase. Large amounts of fines are eroded away and correspondingly, contractive volumetric strain occurs. The larger effective confining pressure would lead to the less extent of suffusion. With larger initial fines content, more fines would be eroded away. The monotonic compression tests indicate that suffusion would cause the reduction of the soil strength at the major stage of drained shearing.     

Dissolved organic carbon losses from grazed grasslands under different management regimes

Dissolved organic matter (DOM) is fundamental to many biogeochemical processes in soils and natural waters. Despite the large number of studies reporting on DOM losses from forest soils and in surface waters there is little published data on exports from managed grasslands. The objective of our study was to determine the extent of short-term exports of dissolved organic carbon (DOC) from managed grazed grasslands and to evaluate the influence of fertilizer management and drainage regime. DOC discharged from grazed grassland plots, with a range of management strategies. was determined over 2 months. Total export varied from 42 to 118 kgCha(-1), and was greater from some plots than literature estimates for annual losses from all catchment types. There was a significant (P = 0.048) positive correlation between DOC export and rates of nitrogen application for treatments with no artificial drainage. Increased dry matter production arising from increased fertilizer-N inputs is suggested as an important factor in this relationship. DOC export was significantly (P = 0.032) reduced by artificial drainage and adsorption of DOC to soil surfaces and the restriction of decomposition due to waterlogging are suggested as two possible explanations.     

土地利用管理信息系统的建设与实现研究

对土地利用规划管理工作的主要内容、特点和ArcObjects组件库及其应用开发方式做了深入分析，以实例详细阐述了基于ArcObjects组件库开发土地利用规划管理信息系统的实现方法和过程，在相关专业的GIS系统建设中具有一定的参考作用。     

An integrated GIS-based analysis system for land-use management of lake areas in urban fringe

Lake areas in Chinese urban fringes are under increasing pressure of urbanization. Consequently, the conflict between rapid urban sprawl and the maintenance of water bodies in such areas urgently needs to be addressed. An integrated GIS-based analysis system (IGAS) for supporting land-use management of lake areas in urban fringes was developed in this paper. The IGAS consists of modules of land-use suitability assessment and change/demand analysis, and land evaluation and allocation. Multicriteria analysis and system dynamics techniques are used to assess land-use suitability and forecast potential land-use variation, respectively. Cost approximation and hypothetical development methods are used to evaluate land resource and market values, respectively. A case study implementing the system was performed on the Hanyang Lake area in the urban fringe of Wuhan City, central China, which is under significant urbanization pressure. Five categories of suitability were investigated by analyzing 11 criteria and related GIS data. Two scenarios for potential land-use changes from 2006 to 2020 were predicted, based on a systematic analysis and system dynamics modeling, and a hierarchical land-use structure was designed for the conservation of aquatic ecosystems. The IGAS may help local authorities better understand and address the complex land-use system, and develop improved land-use management strategies that better balance urban expansion and ecological conservation.     

工程机械液力传动损失与特性

分析了液力传动的各种损失,结合工程机械的工况对其特性作了分析,提出冲击损失是液力传动的主要损失。     

Nonlinear soil mechanics and prospects for its development

Conclusions 1. In substantiating technical solutions applicable to earth structures, it is expedient to use positions and conclusions of nonlinear soil mechanics. 2. The principal trend in the development of basic positions of nonlinear soil mechanics should be the expansion of experimental investigations to establish the most significant parameters affecting the behavior of soils in the sublimiting and limiting states under both static and dynamic effects. 3. It is necessary to orient design engineers in the use of computer programs in design practice. In developing algorithms and computer programs, the multiphase character of the soils, their real properties, and the technology and sequence of building earth structures should be considered. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 5, pp. 28–31, September–October, 1982.     

连续级配土的级配方程及其适用性研究

提出了一个描述连续级配土的级配方程,研究了方程的基本性质、对不同土体级配曲线的反映能力,验证了方程对各种连续级配土的普适性。研究表明:该级配方程能够描述出双曲线形、反S形和近乎直线等三种典型的土体级配曲线,而且对于黏土、粉土、砂土和粗粒土等不同土料的级配都具有广泛的适用性。方程参数分析得知b主要决定级配曲线的形状,即双曲线形或反S形,而且,当m较小时,曲线很缓,近似于直线。参数m主要决定曲线的倾斜程度,且曲线主体部分的斜率与m成正相关。和Swamee提出的级配方程相比,本文的级配方程有明显的优越性和更宽广的适用性。对6座国内外土石坝人工爆破堆石料的级配研究表明,级配参数b和m大致在-0.28~0.64和0.45~0.75范围。     

The influence of soil moisture content variations on heat losses from earth-contact structures: an initial assessment

An initial investigation of the influence of varying ground moisture content beneath buildings on the heat losses through ground floor slabs is presented. A range of finite element analyses have been performed that indicate that soil moisture content changes can have a significant effect on soil thermal conductivity and hence on ground heat transfer. The work is undertaken for conditions of static moisture content distributions. For the particular problems considered, the results obtained show that total heat flux to the ground can increase significantly with decreasing ground water table depth. Steady-state heat conduction analyses were performed for three test problems; a one-dimensional problem, a two-dimensional shallow earth-contact structure and a two-dimensional “deep” earth-sheltered structure. Each problem was analysed for water table depths ranging from 10 m to zero (i.e. the ground surface). The resulting increase in soil moisture content was found to cause a 60% increase in heat flux in the one-dimensional problem, a 20% increase for the two-dimensional shallow structure and 40% for the deep structure. The variation between types of analysis is due to the heat flow path geometry available in each case. The work is viewed as a further step towards a more complete understanding of the influence of ground moisture content on heat transfer problems. The conclusions drawn should be viewed as a first indication of the significance of this aspect of the problem and need to be considered separately from other work on the influence of ground water flow beneath the water table. The results also suggest that transient effects and coupling of heat and moisture transfer processes merit further attention.     

软土地区深基坑工程监督与管理探析

介绍了软土地区深基坑工程特征,从施工准备、基坑降水控制、基坑监测、环境保护四方面论述了软土深基坑工程的监督与管理措施,以便保障工程的安全性,提高工程质量。     

Comprehensive assessment of soil quality for landscape and urban management

Approaches to measuring air and water quality are well established, but soil quality assessment protocols to be used in landscape monitoring efforts are largely non-existent. The concept of soil quality represents the integration of the physical, biological, and chemical aspects of soils. Limited attention has been given to the holistic assessment of soil quality in landscape and urban planning, as it is typically addressed only through chemical analyses. We describe the process used for the selection of soil quality indicators that are being offered as part of the new Cornell Soil Health Test. Over 1500 samples were collected from agricultural landscapes, including controlled experiments, and analyzed for 39 potential soil quality indicators. Four physical and four biological soil indicators were selected based on sensitivity to management, relevance to functional soil processes, ease and cost of sampling, and cost of analysis. Seven chemical indicators were selected as they constitute the standard soil fertility test. For potentially contaminated sites, additional chemical indicators were considered through a total elemental analysis. Test reports were developed to allow for overall soil quality assessment and the identification of specific soil constraints that may be remedied through management practices. The use of the new soil quality test is exemplified for three landscape scenarios in New York State: a vegetable farm, a town park, and a vacant urban lot. The protocol provides a comprehensive assessment of the soil’s ability to perform critical environmental functions at a relatively modest cost, and it helps target management and remediation approaches.     

土力学综合性实验教学探索与实践

针对目前土力学验证性实验教学中存在的一些问题,探讨了开设土力学综合性实验及实验教师的有效指导方法,指出土力学综合性实验教学对提高实验教学质量,培养学生的实际动手能力、综合分析能力有积极的作用。     

公路膨胀土地质问题常用的处置方法及评价

介绍了膨胀土的地质特征及地质问题表现，并对置换法、土性改良法及防水土工布等几种处理膨胀土不良地质问题的方法作了总结，指出膨胀土的防治和处理须配合合理的防水措施，才能发挥最好的效益。     

Investigations on air pressure and air losses in compressed air tunneling through saturated clayey soil

Determination of air pressure and assessment of air losses in clayey soil are of great importance to implementation of compressed air tunneling. In the present work, a series of air flow tests were performed to provide a more reasonable method based on flow characteristics of snap-off pressure and the dissolution/diffusion. Results showed that, the nonlinear air flow behavior and gas breakthrough were presented with the increase in air pressure. After that, the excessive pressure decreased continuously to reach an equilibrium termed as the snap-off. For the tested clayey soil, snap-off pressures around 250 kPa could be adopted as the air pressure, which was significantly lower than the gas breakthrough pressures. Diffusion coefficient of 1.5 × 10^-11 m²/s could be determined in the followed dissolution/diffusion stage, which bring 3 orders of decreasing magnitude in air losses compared to the capillary flow occurred after gas breakthrough. As a conclusion, the adoption of snap-off pressure in compressed air tunneling could effectively prevent the continuous air/water flow in clayey soil and create a more human-friendly environment. Additionally, less air losses could be presented compared to that using gas breakthrough pressure, indicating tremendous energy savings in field implementation.     

Three-dimensional gaseous transfer within cellular plastic insulation and its consequences

The authors present a 3D gaseous transfer model and a simplified mechanical model. Thermal ageing and average volume change of ozone depletion potential foams with different facings are addressed. A formula has been suggested to correlate the elastic modulus and the reduced density of rigid foams over the whole foam density range. Les auteurs presentent un modele tridimensionnel de transfert gazeux et un modele mecanique simplifie. Ils traitent du vieillissement thermique et de la modification volumique moyenne de produits mousse a pouvoir d'appauvrissement de la couche d'ozone, en fonction de leur revetement; et proposent une formule permettant d'etablir une correlation entre le module elastique et la densite reduite des mousses rigides sur la plage complete de densite de mousse.