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501.
基于岩体开挖卸荷过程中力学参数变化理论的分析研究,建立卸荷岩体有限元分析模型,运用ADINA有限元分析软件对岩体进行一维卸荷数值仿真研究。根据有限元数值分析计算成果得到岩体力学参数与主卸荷方向累计开挖卸荷量间的变化关系曲线。结果表明:岩体开挖卸荷过程中,岩体力学参数变形模量、泊松比、粘聚力和内摩擦角等呈现出随开挖卸荷量的变化而发生变化的特征,随卸荷量的增大有减小的趋势,但它们不是从初始值一直减小到零,而是随卸荷量的增大减小到一定的量值后,岩体的裂隙张开、结构面的扩展到一定的程度,岩体的力学参数保持一定的量级不再减小。 相似文献
502.
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505.
20世纪重大自然灾害评析 总被引:24,自引:8,他引:16
人类在科学技术上取得了辉煌成绩的同时,在认识自然和改造自然方面也得到了才识和新的认识,这一教训主要是来自自然灾害。根据收集到的全球自然灾害有关数据,对20世纪全球主要自然灾害特征分布特点进行了分析,并对其成因提出了看法。 相似文献
506.
传统概念的地气测量是指地下上升到地表并扩散到大气空间的天然状态气体 ,如CO2 、CH4 、Rn、Hg、H2 等。近十多年的研究证实地气还包含着新的内涵 ,即地壳岩石以及地表土壤中还存着痕量的金属与非金属气体 ,通过捕集这些气体 ,可以获得更多的深部地质构造、矿床信息。据报导 ,国内外的研究主要是在已知矿床上做的正演研究。本文是在已知隐伏断层构造上方地表 ,试验金属与非金属地气存在的可能性。 相似文献
507.
Multivariate Analysis of Interactions Between Phytoplankton Biomass and Environmental Variables in Taihu Lake, China 总被引:1,自引:0,他引:1
Phytoplankton variation in large shallow eutrophic lakes is characterized by high spatial and temporal heterogenity. Understanding
the pattern of phytoplankton variation and the relationships between it and environmental variables can contribute to eutrophic
lakes management. In this study Taihu Lake, one of the largest eutrophic fresh water lake in China, was taken as study area.
The water body of Taihu Lake was divided into five regions viz. Wuli bay (WB), Meilian Bay (MB), West Taihu Lake (WTL), Main
Body of Taihu Lake (MBTL) and East Taihu Lake (ETL). Concentrations of chlorophyll-a and the related environmental variables
were determined in each region in the period 2000–2003. Factor analysis and multivariate analysis were applied to evaluate
the interactions between phytoplankton variation and environmental variables. Results showed that the highest average concentrations
of TN, TP and Chl-a were observed in WB, followed in a descending order by MB and WTL, and the lowest concentrations of TN,
TP and Chl-a were observed in MBTL and ETL. Chl-a and TP concentrations in most regions (except ETL) declined during the study
period. It suggested that to some extent the lake was recovering from eutrophication. However, persistent ascending of TN
and NH4–N in all five regions indicated the deteriorating of water quality in the study period. Results of multivariate showed that
the relationships between phytoplankton biomass and environmental variables varied among regions. TP illustrated itself a
controlling role on phytoplankton in WB, MB, WTL and MBTL according to the significant positive relations to phytoplankton
biomass in these regions. Nitrogen could be identified as a limiting factor to phytoplankton biomass in ETL in view of the
positive correlations between TN and phytoplankton and between NH4–N and phytoplankton. Spatial variation of interactions between phytoplankton and environmental parameters suggested proper
eutrophication control measures were needed to restore ecological system in each region of Taihu Lake. 相似文献
508.
Demirel Z 《Environmental monitoring and assessment》2007,132(1-3):15-23
In this study, heavy metal contents of groundwater from the Mersin aquifer were determined with photometric methods and used
to determine the main factors controlling the pollution of groundwater in the area. Using MapInfo GIS software, spatial analysis
and integration were carried out for mapping drinking water quality in the basin. From the photometric heavy metal analysis,
it is inferred that the excess concentration of Fe, Ni, Mn, Mo and Cu at some locations is the cause of undesirable quality
for drinking purposes. Similarly, the EC thematic map shows that considerable areas in the basin are having high salinity
hazards. The reason for excess concentration of various heavy metals is the industrial activities and petroleum pipelines
and salinity levels show the sea water intrusion. 相似文献
509.
In order to investigate the distribution pattern of individual organochlorine compounds in soil samples collected from the sites (Canary Island – Spain, China, Germany, India, Romania, Russia, Serbia, Swiss, UK) affected by industrial activities to the more remote areas, principal component analysis was performed on the data taken from literature. Loading plots pointed out the strong correlation among the variables. Score plots revealed similar PCB- and OCP-soil patterns for majority of the investigated sites. Nevertheless, the temporal differences of PCB-soil loads have been identified: the late 1990s and early 2000s concentrations are similar to those of the early 1940s, and they are below the levels existed in 1980. The most pronounced PCB concentrations characterized the soil from 1966. For OCPs the influence of sites location on the detected concentration has been revealed: China and India were characterized by comparably higher loads of DDX (DDT and its metabolites) and of HCH-isomers, respectively. 相似文献
510.
Effects of sewage sludge blending on the coal combustion: a thermogravimetric assessment 总被引:3,自引:0,他引:3
Combustion of urban sewage sludge together with coal in existing infrastructures may be a sustainable management option energetically interesting for these materials, usually considered wastes. Thermogravimetric analysis was used to study the combustion of a semianthracite coal and the modifications undergone when adding a small percentage (2%, 5%, 10%) of sewage sludge. Both Differential Scanning Calorimetric analysis and Differential Thermogravimetry burning profiles showed differences between coal and sewage sludge combustion. However, the effects of adding a percentage of sewage sludge equal or smaller than 10% was hardly noticeable in terms of heat release and weight loss during the coal combustion. This was further proved by non-isothermal kinetic analysis, which was used to evaluate the Arrhenius activation energy corresponding to the co-combustion of the blends. This work shows that thermogravimetric analysis may be used as an easy rapid tool to asses the co-combustion of sewage sludge together with coal. 相似文献