共查询到20条相似文献，搜索用时 15 毫秒
1.
根据理想模型中土颗粒和孔隙水之间的几何关系、热力学原理和土力学基本理论,研究了土的非饱和性在非饱和土中引起的力系。给出了张力吸力和吸力比的定义,并在考虑基质吸力作用面积的基础上定义了等效吸力的概念。按照孔隙水弯液面是否与土颗粒表面搭接,将非饱和土分为搭接非饱和土和不搭接非饱和土两类。进而根据搭接状态将搭接非饱和土细分为水封闭非饱和土和搭接双开敞非饱和土,根据孔隙气状态将不搭接非饱和土细分为不搭接双开敞非饱和土和气封闭非饱和土。在搭接非饱和土中,出现张力吸力并对土体的强度产生增强作用;在不搭接非饱和土中,表面张力只是沿着液面传播,不对土的强度产生效应。另外,张力吸力只对强度问题有贡献,它不是渗流问题的驱动力。 相似文献
2.
《International Geology Review》2012,54(7):932-938
Current definitions of "geologic structure" are considered along with definitions of structure in the various fields of knowledge (petrography, "crystallography, chemistry, mathematics and philosophy). Structure of a complex and very complex geologic body with non-conditional boundaries is defined as the "relative arrangement of its structural elements." Differences between "structural elements" and inclusions are pointed out, along with definitions of the order and nature of geologic structure. The concept of disjunctive etructure is introduced. -- Author. 相似文献
3.
Eli Borukhov 《GeoJournal》1991,2(1):71-80
Residential density (dwelling units per area) affects the quality of life in urban environments in many direct and indirect ways. Determining the optimal level of density requires in each case, balancing all the relevant factors and influences, and should depend on the preferences of the potential residents and their financial resources.A residential neighborhood has many characteristics. Usually people trade off one characteristic against another. For instance: people can trade off density against cost or accessibility against space. The aim of good planning is to find the combination of characteristics that will give maximum level of satisfaction to the residents of a neighbourhood subject to the limitations of their budgets. Density standards should, therefore, be adapted to the preferences of the potential residents and their preferred compromise between the various attributes of their environment.To make things more complicated, the concept of density has many definitions, and different definitions are relevant when analysing the various effects of density. It seems that people do not perceive the gross residential density as it is measured, but are influenced by variables such as set-back distances, the percentage of building coverage and the like.Evidence is cited from an investigation in Kiryat-Gat which suggests that the perception of density is affected by other factors except the density itself.If people do not perceive the density as such but are affected by other factors, then modification of these factors is very important. If planners are to design neighborhoods according to the residents' preferences, they should have quantitative estimates of the residents' relative evaluation of these characteristics, including possible savings in the price of housing. The problems of investigating residential preferences are discussed, and examples of studies addressed to these questions are described. 相似文献
4.
首次报道青海东昆仑中段早寒武世小壳动物化石，计有Ａｎａｂａｒｉｔｅｓｔｒｉｓｕｌｃａｔｕｓ，Ｈｙｌｉｔｈｅｌｕｓｔｅｎｕｉｓ，Ｈｙｌｉｔｈｅｌｕｓｓｐ．，Ｃｏｎｏｔｈｅｃａｓｐ．，Ｐａｌａｅａｃｍａｅａｓｐ．以及Ｌａｔｏｕｃｈｅｌａｓｐ．。这些化石的发现丰富了该区早古生代古生物资料，对于万宝沟群和纳赤台群的定义、层序和时代归属具有重要意义。 相似文献
5.
Essaieb Hamdi Jean du Mouza 《Fragblast: International Journal for Blasting and Fragmentation》2000,4(3):238-245
The efficiency of a blast depends very widely on three groups of parameters: rock mass, blast geometrical parameters and energy distribution in space (borehole bottom, column energy) and time (delays between holes and rows). According to the expected results from a blast, there are several definitions for the term efficiency. The criterion for the block size reduction in the muck pile is often considered as important, because generally it has a great influence on the efficiency of all the operations after the blast. In this paper, a new parameter for the assessment of the blast efficiency is proposed, based on the relative comparison of area delimited by the Rosin-Rammler curves of the in situ rock mass and of the muck pile. This parameter is then compared to others previously established, namely the fragmentation index (Aler et al. 1996) and the surface energy ratio (Hamdi et al. 2001). 相似文献
6.
Dr. Eli Borukhov 《GeoJournal》1978,2(1):71-80
Residential density (dwelling units per area) affects the quality of life in urban environments in many direct and indirect ways. Determining the optimal level of density requires in each case, balancing all the relevant factors and influences, and should depend on the preferences of the potential residents and their financial resources. A residential neighborhood has many characteristics. Usually people trade off one characteristic against another. For instance: people can trade off density against cost or accessibility against space. The aim of good planning is to find the combination of characteristics that will give maximum level of satisfaction to the residents of a neighbourhood subject to the limitations of their budgets. Density standards should, therefore, be adapted to the preferences of the potential residents and their preferred compromise between the various attributes of their environment. To make things more complicated, the concept of density has many definitions, and different definitions are relevant when analysing the various effects of density. It seems that people do not perceive the gross residential density as it is measured, but are influenced by variables such as set-back distances, the percentage of building coverage and the like. Evidence is cited from an investigation in Kiryat-Gat which suggests that the perception of density is affected by other factors except the density itself. If people do not perceive the density as such but are affected by other factors, then modification of these factors is very important. If planners are to design neighborhoods according to the residents' preferences, they should have quantitative estimates of the residents' relative evaluation of these characteristics, including possible savings in the price of housing. The problems of investigating residential preferences are discussed, and examples of studies addressed to these questions are described. 相似文献
7.
The lack of adequate water supply and sanitation services is a major issue related to sustainable development in many parts
of the developing world. New strategic planning approaches which directly address users’ needs and demand—often referred to
as demand-responsive, community-based or household-centred approaches—are regarded as a crucial step towards improving the
situation. This paper investigates household needs and demand for improved water supply and sanitation services in peri-urban,
low-income settlements, known as “ger areas”, in the city of Darkhan, Mongolia. The paper is based largely on a household
survey conducted in a selected ger area subdistrict in Darkhan. The results reveal a complex picture. Even if the existing
situation can be regarded as largely “improved” in terms of the definitions stipulated by the Joint Monitoring Programme for
water supply and sanitation, it is shown that there is a need for action nonetheless. The paper also argues that the household
survey is a useful method for assessing users’ needs and demand and for meeting the requirements of demand-responsive sanitation
planning approaches. 相似文献
8.
9.
给出了真空预压区四周开敞式与封闭式边界定义、两者的不同,分析了开敞式边界加固效果优于封闭式边界的原因并以三个实例说明之,给出如何将封闭式转化为开敞式的方法;柔性与刚性密封膜同样可构成开敞式与封闭式边界,讨论了此时两种边界下差别;给出了密封墙和支挡墙的定义、功能、应用范围;讨论了水泥搅拌与旋喷桩单体墙与格栅墙的定义、功能、应用范围,前者只能作为密封墙,后者既可作密封墙也可作支挡墙. 相似文献
10.
Philip J. Potts 《Geostandards and Geoanalytical Research》2012,36(3):231-246
The Joint Committee for Guides in Metrology (JCGM) has introduced a revised third edition of the International Vocabulary of Metrology – basic and general concepts and associated terms ( VIM: 2008 ) that replaces the second edition which was published in 1993. This article includes a table containing the terms and definitions that are most relevant to geoanalysis, designed to extend awareness and to promote best practice in the use of this terminology. Comparison is made, where appropriate, with definitions from the earlier 1993 definitions, to demonstrate the way in which thinking in metrological concepts has evolved over this time period. 相似文献
11.
水系连通的定义决定其科学技术和工程技术层次,如何科学概括现有科学研究和工程实践,研究水系连通的定义及分类具有重要的理论和生产应用价值。应用形式逻辑学的相关方法和规范,结合水利行业现有名词定义的主要问题分析,论述给名词下定义的意义和重大作用,系统论证应用"水系连通"替代"河湖水系连通"的必要性和科学性,评析现有多种水系连通定义存在的主要问题,给出水系连通的定义"研究相连水系连接通道的形成、水系的演化、水体转移的影响的科学技术",以及水系连通工程的定义"利用水工程、河流及湖泊等构成水系之间水体转移通道的工程",并论述了2个定义的内涵及其分类。该定义不仅比现行各种定义更科学、更简洁合理,而且能科学地处理概念定义适应性与分类完整性的关系。 相似文献
12.
Progresses and Prospects of the Research on Soil Erosion in Karst Area of Southwest China* 总被引：1，自引：0，他引：1
The karst area of Southwest China is suffering from serious ecological and environmental problems due to soil erosion while the research on soil erosion is not sufficient. Primary achievement was systematically reviewed in this paper in three aspects: erosion characteristics, current researches about erosion on different spatial scales, and key scientific problems. Based on the review, the authors figured out the shortcomings of the existing studies and pointed out the directions on erosion study in southwest China karst region. The results showed that: ① Due to the existence of a dual structure in karst environment including ground and underground erosion, the process of runoff and sediment production on slope scale and confluence and sediment transportation processes on catchment scale were more complex under the unique geological and hydrological backgrounds; ② At present, most researches about erosion mechanism in karst area focus on slope scale and some achievements on quantitative evaluation of erosion factors have been made. Continuous data with high quality about relationship between water and sediment on catchment scale is limited. When data is scarce, river sediment data can be used as an effective way to study soil erosion intensity and spatial-temporal variation in karst area; ③ It is more reasonable to use 50 t/(km2·a) as the grading standard of soil loss tolerance than the previous grading standard of soil erosion intensity. Given the complex relationship between rocky desertification and soil erosion, more quantitative studies about the effects of rocky desertification on soil erosion are still necessary. There are different viewpoints on soil leakage definitions, leakage mechanism and leakage ratios, and new breakthroughs could be achieved by combining different methods and matching multi-scales. In conclusion, in order to further reveal soil erosion laws and establish and revise available regional soil erosion forecasting models for Southwest China karst areas, synchronous test and monitoring on slope, watershed, and channel spatial scales are urgently needed. The results can provide theoretical and technical support for promoting soil and water conservation work for the karst area of Southwest China. 相似文献
13.
Hugh Rollinson 《Journal of African Earth Sciences》1999,28(4):903-910
Quality is an elusive concept — hard to define, but you recognise it when you come across it. This paper reviews the meaning of quality as applied in Higher Education and shows that there are, of necessity, a number of workable definitions of quality in Higher Education. The assessment of quality in Earth Science Higher Education in England during 1994–1995 is described. A number of general features of quality in Earth Sciences Education are drawn from this case study and the future direction of quality assurance is mapped. Three principles drawn from the definitions of quality and from the English teaching quality assessment exercise are applied to Earth Science Education in Africa. It is argued that different definitions of quality will apply in different societal contexts in Africa and that these may be used to shape the relevance of Geoscience Education. Increasing mobility of labour means that comparability of academic standards between African countries within a region is desirable and should be worked for. Finally, research in the UK shows that teaching quality is not necessarily dependent upon the size or research potential of a department, indicating that Africa can deliver high quality Earth Science Education. 相似文献
14.
在扫描电镜法（SEM）图像二值化基础上,建立了以颗粒体面积为变量的面积累计曲线表示方法,进而建立了该曲线的曲率系数和颗粒体面积分布特点的不均匀系数。基于瓜州砂质粉土和天津黏土的SEM图像,分析了不同面积比对应的颗粒体特征。研究表明,砂质粉土和黏土的颗粒体面积累计曲线、曲率系数和不均匀系数具有明显的差异性。砂质粉土的颗粒体面积累计曲线是一条平滑的曲线,表现为不良级配土的粒径分布特点;而黏土的颗粒体面积累计曲线具有明显的台阶,表现为某粒组缺失的粒径分布特点。另外,砂质粉土的颗粒体面积累计曲线曲率系数和不均匀系数均明显大于黏土的对应系数。该分析方法可以用来量化不同土的SEM照片之间的差异,从而为岩土微结构的定量化研究提供了一条新的思路。 相似文献
15.
16.
Groundwater sensitivity (Ray and O’dell in Environ Geol 22:345–352, 1993a) refers to the inherent ease with which groundwater can be contaminated based on hydrogeologic characteristics. We have developed
digital methods for identifying areas of varying groundwater sensitivity for a ten county area of south central Kentucky at
a scale of 1:100,000. The study area includes extensive limestone karst sinkhole plains, with groundwater extremely sensitive
to contamination. Digitally vectorized geologic quadrangles (DVGQs) were combined with elevation data to identify both hydrogeologic
groundwater sensitivity regions and zones of “high risk runoff” where contaminants could be transported in runoff from less
sensitive to higher sensitivity (particularly karst) areas. While future work will fine-tune these maps with additional layers
of data (soils for example) as digital data have become available, using DVGQs allows a relatively rapid assessment of groundwater
sensitivity for Kentucky at a more useful scale than previously available assessment methods, such as DRASTIC and DIVERSITY.
Geographic definitions: United States of America, Kentucky, Barren River Area Development District. 相似文献
17.
The definitions of the term “geological environment” that were given by different scientists previously are considered. An expanded interpretation of the content of the “geological environment” concept is suggested; it should contain not only anthropocentric and not only ecological meanings as the living environment, but also a broader “noospheric” meaning as a sensibly organized environment for human life and a habitat. Based on this fact, the term “geological environment” is given a new definition in respect to the noospheric concepts. 相似文献
18.
Climatological drought in Nigeria 总被引：1，自引：0，他引：1
Peter Kwabenah Acheampong 《GeoJournal》1990,20(3):209-219
In this paper, the definitions of drought are reviewed and evaluated for Nigeria. Drought in Nigeria is thought of as a purely climatological or meteorological phenomenon, that is, a temporary abnormal rainfall deficiency over the country, the result of some unfavourable meteorological conditions such as persistent widespread subsistence and the absence or weakness in the atmospheric rain-generating systems during the rainfall season. 相似文献
19.
Stephen R. H. Worthington Pierre-Yves Jeannin E. Calvin AlexanderJr Gareth J. Davies Geary M. Schindel 《Hydrogeology Journal》2017,25(5):1237-1240
It is generally considered that karst aquifers have distinctly different properties from other bedrock aquifers. A search of the literature found five definitions that have been proposed to differentiate karst aquifers from non-karstic aquifers. The five definitions are based upon the presence of solution channel networks, hydraulic conductivities >10?6 m/s, karst landscapes, channels with turbulent flow, and caves. The percentage of unconfined carbonate aquifers that would classify as ‘karst’ ranges from <1 to >50%. 相似文献
20.
Wind scale or earthquake magnitude is easier to remember and to be understood by the community. Although many systems of classifying
debris flows are presently available, it is necessary to propose an index as simple as wind scale or earthquake magnitude
for measuring debris flows. Based on the principles used in wind scale and earthquake magnitude calculation, this paper presents
the concepts of debris flow magnitude and disaster intensity as well as a new numerical calculation method. Debris flow magnitude
is a quantitative index describing the scale of a debris flow. The disaster intensity of a debris flow is a quantitative index
describing the severity of the damage to society caused by a debris flow. With their explicit definitions and simple concepts,
both indices are considered to be important both practically and theoretically. 相似文献