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71.
帷幕注浆技术能实现岩溶水矿山的安全开采,而注浆(即隔障带)厚度一般是利用经验公式计算所得,存在较大的误差。本文应用流固耦合理论,对矿体开采条件下顶板注浆隔障带的稳定性问题进行了分析。采用数值模拟的方法,定量地模拟了矿房开挖过程中围岩(即隔障带)应力场的分布、破坏场的发展及位移场的变化规律。模拟表明由于顶板发生破坏,经验公式计算的隔障带不能满足隔水的要求,应增大隔障带厚度保证安全开采。根据采动影响范围为大水矿床顶板注浆及矿房参数设计提供依据,对防治岩熔水矿山突水有一定的指导意义。 相似文献
72.
Jan Atle Knutsen Halvor Knutsen Eli Rinde Hartvig Christie Torjan Bodvin Einar Dahl 《Ambio》2010,39(2):148-158
For many years, the planning and management of terrestrial areas has been supported by a detailed knowledge of the distribution
of habitats and their associated species. However, the detailed mapping of biological resources in extent coastal areas, such
as the Norwegian coastal zone, is unrealistic due to its enormous coastline. Here, we present a useful and feasible approach
and a set of simple, cost-effective methods which are suitable for providing a broad-scale overview of marine habitats and
fish resources. This approach was developed in conjunction with a pioneer study conducted along the southern coast of the
Skagerrak, where we combined knowledge gathered from local fishermen with scientific knowledge of important species and nature
types to establish a coastal sea mapping program. GIS modeling tools were used in both the mapping program and to integrate
local and scientific knowledge into digital maps made available to local area management. This multi-faceted approach, which
combines local knowledge and scientific methods, provides valuable information with respect to marine biodiversity, and has
been used extensively by local environmental management. 相似文献
73.
The study focuses on evaluating factors that farmers consider relevant in adopting cassava production in five semi-arid zone
of West African countries. The study is based on primary data randomly collected as part of collaborative study of cassava
in semiarid zones of Africa (COSCASSA) village level survey from five West African countries namely: Nigeria, Ghana, Chad,
Niger and Burkina Faso. This study models effects of farm, farmer and technology specific factors on the decision of semi
arid farmers to adopt cassava into their farming system. By way of threshold decision models—Probit and Logit models, the
estimation of each country and the pooled data adoption models reveal different adoption models for the countries considered.
For each country, different variables appeared as major adoption shifters. Comparatively, the adoption models for Nigeria
and whole region appear to have the highest significance variables, being seven in number. This is followed by Chad (6), Ghana
(4), and Burkina Faso and Niger with three each. For the variables considered, distance to nearby urban market appears a major
adoption shifter in all the country, except for Niger. This is closely followed by contact with extension, variety, pest/disease
resistance and livestock feeds, which appear significant in four of the countries. Membership of cooperative societies appears
as the least adoption predictor, which is only significant in Chad republic. The study therefore recognizes the importance
of varietial characteristics and farmers’ characteristics in acceptance of cassava as a major root tuber crop in the semi
arid region of West Africa.
Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue. 相似文献
74.
传统开发区内,资源的流动是一些相互不发生关系的线性物质流的叠加,出入系统的物质流远远大于内部交互的物质流,因而造成经济活动的"高开采、低利用、高排放"特征,即"大量生产、大量消费和大量废弃"[1]。而发展循环经济,是我国贯彻落实科学发展观、建设资源节约型和环境友好型社会的重大战略选择[。2]目前新型开发区产业发展,则要求按照循环经济的理念,积极探索发展循环经济之路。本文以昌吉市高新技术产业开发区为例,研究其循环经济模式,为其他开发区设计和发展提供有益的经验和建议。 相似文献
75.
某矿区土壤和地下水重金属污染调查与评价 总被引:3,自引:0,他引:3
为了解湘南某矿区土壤和地下水重金属污染状况,对该矿区东河流域附近重金属污染源进行了调查,同时,对地下水和土壤样品进行了采样分析,结果表明:(1)该矿区东河流域附近的主要污染源有18个,其中有色金属选厂、尾矿库、采矿场和冶炼厂是排放重金属较多的污染源;(2)20个采样点中土壤重金属Pb、Cd、Zn、As和Hg大部分超过国家土壤环境质量标准(GB15618-1995),综合污染指数P综〉1,该矿区主要的重金属污染元素为Cd、As和Hg,且土壤中Cd、Zn和As的含量两两之间存在着极显著的正线性相关关系;(3)重金属元素在土壤中的纵向迁移不明显,该矿区附近20个采样点的地下水并未受到污染,综合污染指数P综〈1。20个采样点地下水Pb、Cd、Zn、As、Hg浓度均能达到地下水质量标准(GB/T14848.9)中的Ⅲ类标准。 相似文献
76.
77.
Almost half (354) of all fish kills (805) in South Carolina, USA, between 1978 and 1988 occurred in the coastal zone. These
kills were analyzed for causative, spatial, and temporal associations as a distinct data set and as one integrated with ambient
water quality monitoring data. Estuarine kills as a result of natural causes accounted for 42.8% followed by man-induced (35.1%)
and undetermined causes (22.1%).
Although general pesticide usage was responsible for 53.9% of man-induced kills, weed control activities around resorts and
municipal areas accounted for slightly more kills (20.9%) than did agricultural (19.8%) or vector control (13.2%) uses. A
dramatic decline in agricultural-related kills has been observed since 1986 as the integrated pest management approach was
adopted by many farmers. When taken with the few kills (12.0%) resulting from wastewaters, this suggests that these two land-use
activities have been successfully managed via existing programs (IPM and NPDES, respectively) to minimize their contributions
to estuarine fish kills.
Ambient trend monitoring data demonstrated no coastal-wide dispersion of pesticide pollution. These data confirmed the nature
of fish kills to be site-specific, near-field events most closely associated with the contiguous land-use practices and intensities.
Typically, fish kill data are considered as event-specific data limited to the bounds of that event only. Our analysis has
shown, however, that a long-term data set, when integrated with ambient water quality data, can assist in regulatory and resource
management decisions for both short- and long-term planning and protection applications. 相似文献
78.
在则木河断裂带宏观研究的基础上,结合岩石破裂实验成果,对包括1850年大震变形带在内的断裂产物进行定向原态采集、固结、制片和镜下系统观测,从复杂纷呈的变形遗迹中鉴别出微观粘滑与蠕滑标志。最后就有关问题进行了简要讨论. 相似文献
79.
Jirka ;imnek Diederik Jacques Martinus Th. Van Genuchten Dirk Mallants 《Journal of the American Water Resources Association》2006,42(6):1537-1547
Abstract: The transport of reactive contaminants in the subsurface is generally affected by a large number of nonlinear and often interactive physical, chemical, and biological processes. Simulating these processes requires a comprehensive reactive transport code that couples the physical processes of water flow and advective-dispersive transport with a range of biogeochemical processes. Two recently developed coupled geochemical models that are both based on the HYDRUS-1D software package for variably saturated flow and transport are summarized in this paper. One model resulted from coupling HYDRUS-1D with the UNSATCHEM module. While restricted to major ion chemistry, this program enables quantitative predictions of such problems as analyzing the effects of salinity on plant growth and the amount of water and amendments required to reclaim salt-affected soil profiles. The second model, HPI, resulted from coupling HYDRUS-1D with the PHREEQC biogeochemical code. The latter program accounts for a wide range of instantaneous or kinetic chemical and biological reactions, including complexation, cation exchange, surface complexation, precipitation dissolution and/or redox reactions. The versatility of HP1 is illustrated in this paper by means of two examples: the leaching of toxic trace elements and the transport of the explosive TNT and its degradation products. 相似文献
80.
构造运动与中国沿岸平原的地质灾害 总被引:3,自引:1,他引:3
中国海岸穿过构造沉降带和隆起带,沉降带及隆起带断陷盆地的持续下降吸引了源远流长的大河在此人海,而隆起带内入海的河流多为近源小河,从而引起河流泥沙沿岸分配的不均和海岸沉积物的差异。沉降带内每公里海岸线接受的沉积物是隆起带的数十倍,且以砂质沉积物为主.隆起带河流泥沙来量少.而且砂质沉积物占了压倒的优势.河流泥沙沿岸分配的不均决定了中国沙质和淤泥质海岸的基本类型和分布格局、沉降带和隆起带松散沉积层的厚度和结构,山此产生了中国沿岸与第四纪沉积层有关的灾害和环境问题的有规律的分布。地面沉降主要分布于沉降带内,而地下海水入侵多出现在依赖地下水的隆起带内,底辟构造、浅层天然气往往在大河三角洲构成灾害和潜在的地质灾害.沉降带和隆起带断陷盆地内的海岸低地通常是海平面上升的主要脆弱地区.此外,丰富的河流泥沙使中国海岸对全球海平面上升的响应也不相同,如海岸湿地的再生和海岸侵蚀原因的复杂性等. 相似文献