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101.
火山渣丘,是火山区内的一种特殊的地质现象,以前地其成因国内外尚无详细探讨和描述,有的学者曾经统称为副火山。笔者通过实地调查,对这一结论提出新的见解,认为火山渣丘的形成是一复杂的地质现象,其成因具有多元性。这对探讨火山喷发规律,对火山地质地貌的准确描述与具有积极作用。 相似文献
102.
含煤层地质环境下地震波场的数值模拟 总被引:3,自引:2,他引:1
本文对含低速煤层地质环境下弹性波场多波多分量地震资料进行了二维数值模拟研究,对人工边界反射进行了有效处理,频散效应得到了有效的压制,对几种不同激发与观测排列方式下的弹性波资料进行了模型计算与分析。 相似文献
103.
104.
Ján Boďa 《Studia Geophysica et Geodaetica》1992,36(2):139-150
Summary Our discussion is concerned with the common effect of the non-uniformity of layer rotation and stratification. We have assumed a model of differential rotation with the upper part of the layer rotating more slowly, the bottom part more quickly. The upper part of the layer is stratified stably, the bottom part unstably.The thermal instabilities are preferred in the strong differential rotation case and they are the most easily excited by a strong magnetic field (102–103). The direction of its propagation is westward in the uniformly stratified layer and eastward in the non-uniformly stratified layer. 相似文献
105.
106.
107.
Not only the nutritional status and biological activity but also the soil ecological functioning or soil health has been impacted profoundly by land degradation in the karst area of southwest China where the karst ecosystems are generally considered as extremely vulnerable to land degradation under intensified land-use changes. The objectives of this study are to elucidate the changes in overall soil quality by a holistic approach of soil nutritional, biological activity, and soil health indicators in the karst area as impacted by intense cultivation and vegetation degradation. Topsoil samples were collected on selected eco-tesserae in a sequence of land degradation in a karst area of southwest Guizhou in 2004. The soil nutrient pools of organic carbon (Corg), extractable extracellular carbon (Cext), total soil nitrogen (Nt), alkali-hydrolyzable nitrogen (Nah), total phosphorus (Pt), available phosphorus (Pa) were analyzed by wet soil chemistry. The soil biological properties were studied by means of measurements of microbial biomass carbon (both by fumigation–extraction, FE-Cmic, and by calculation from substrate-incubation respiration, SIR-Cmic) of respiration [respiration without addition of substrates, basal respiration (BR), and potential respiration (PR) with substrate-incubation] and of soil enzyme activities (invertase, urease, and alkaline phosphatase). Soil health status was assessed by simple indices of Cmic/Corg and BR/Cmic in conjunction with bacterial community structures determined by polymerase chain reaction and denaturing gradient gel electrophoresis. While the nutritional pool parameters, such as Corg and Cext, described basically the changes in soil life-supporting capacity with cultivation interference and vegetation declined, those parameters of biological activity such as FE-Cmic, SIR, and SIR-Cmic as well as bacterial community structures measured by molecular method evidenced well the changes in soil functioning for ecosystem health with the land degradation. 相似文献
108.
Tracing leachates at landfills is usually carried out using either geophysical methods or chemical analyses of groundwater.
There are often problems with fingerprinting pollution sources or clarifying the spreading pattern due to a wide variety of
possibilities giving similar anomalies. The aims of the project were to evaluate the advantages of combining results from
multigeophysical modelling and statistical/chemical modelling in order to identify pollution sources and the spreading pattern
and to test a new technique for chemical fingerprinting. The project was carried out at a landfill in central Sweden using
geophysical measurements and modelling of CVES, GPR and VLF as well as chemical modelling using M3 (multivariate mixing and
mass balance calculations). The results indicate that by combining geophysical modelling and chemical calculations, the possibilities
of fingerprinting the origin of pollution as well as delineating the spreading pattern are significantly increased. 相似文献
109.
In ground improvement projects with prefabricated vertical drains, the duration of the preloading period is set in advance
based on the predetermined time rate of consolidation of the compressible layer. If prediction is accurately done, the required
degree of consolidation is met at the pre-determined preloading time. As such, there is a requirement for in-situ tests to be carried out just prior to the removal of surcharge to assess the degree of consolidation of the improved ground.
In-situ tests were carried out after 23 months of surcharge loading at the In-Situ Test Site within the Changi East Reclamation Project in the Republic of Singapore. In-situ testing works in this research study comprises the use of field vane shear, piezocone, flat dilatometer and self-boring pressuremeter.
The in-situ tests were carried out to determine the shear strength and degree of consolidation of the Singapore marine clay at Changi
after 23 months of surcharge loading. The In-Situ Test Site consisted of a Vertical Drain Area as well as an untreated Control Area. Both areas were located adjacent to each
other and were surcharged simultaneously to the same level and surcharge left in place for a period of 23 months. Comparison
was made between the in-situ test results of the Vertical Drain Area and the untreated Control Area. 相似文献
110.
以中国科学院盐亭紫色土农业生态试验站小流域为例,研究不同土壤侵蚀沉积地段(斜坡和沟谷不同部位)的土壤结构特征,以了解侵蚀沉积对土壤结构的影响。结果表明,在植被覆盖较好的坡体顶部,土壤侵蚀较弱,团聚度达到30.1%,MWD变化为3.4mm,土壤结构良好;沟谷底部由于沉积而有较多细土物质并具有适宜的水分条件,有利于土壤团聚体的形成,结构状况亦较好,团聚度达到50.3%,结构保持率为35.4%;而坡腰侵蚀较严重,团聚度仅为13.6%,结构保持率为14.1%,土壤结构状况较差。 相似文献