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41.
42.
以松辽盆地地质资料为基础,介绍了应力场和张裂缝预测的计算方法。通过了各种岩性的张破裂概率隶属函数,预测松辽盆地酉部张裂缝区的分布。据此,为今后的油气勘探提出了几点认识和建议。 相似文献
43.
This article presents results from a series of Ko-consolidated compression and extension triaxial tests on specimens from undisturbed samples of Hong Kong Marine Deposits (HKMD). To investigate the strain-rate effects, a total of seven Ko-consolidated triaxial tests were conducted including four compression tests and three extension tests. After Ko-consolidation, the triaxial test specimens were sheared at step-changed axial strain rates under three different confining pressures of 50 kPa, 150 kPa, and 400 kPa, respectively. The step-changed strain rates were applied in the following order: +2%/h, +0.2%/h, +20%/h, -2%/h (unloading) and +2%/h (reloading) for the four compression tests and -2%/h, -0.2%/h, -20%/h, +2%/h (unloading) and -2%/h (reloading) for the three extension tests. The results are reported and analyzed in the paper. The results show that the strain rate effects, the stress-strain characteristics, and the effective stress paths of the specimens for tests in a compression state are different from those for tests in an extension stage. One order of magnitude increase in axial strain rate causes an average 8.6% increase in undrained shear strength for compression tests and a 12.1% increase for extension tests. It is also found that the failure mode of the specimens in compression is different from that in extension. The stress-strain behavior of specimens shows strain-softening and a clear shear band in compression tests, but strain-hardening without any clear shear band in extension tests for the same absolute value of axial strain. 相似文献
44.
-Combined refraction and diffraction models in the form of linear parabolic approximation are derived through smallparameter method. More strictly theoretical basis and more accuracy in the models than Lozano's (1980) are obtained. Some theoretical defects in Liu's model (1985) with consideration of current are not only found but also eliminated. More strict and accurate models are, therefore, presented in this paper.The calculation results and analysis in applying the models to actual wave field with consideration of bottom friction will be given in the following paper. 相似文献
45.
Jos Rafael García‐March Antonio Manuel García‐Carrascosa lvaro Luís Pea 《Marine Ecology》2002,23(3):207-217
Abstract. Pinna nobilis Linnaeus 1758 is an endemic bivalve mollusc in the Mediterranean Sea, where it inhabits seagrass meadows, especially Posidonia oceanica (L.) Delile. It is the largest bivalve in the Mediterranean, reaching lengths up to 120 cm. In its natural habitat, P. nobilis lives with the anterior part of the valve buried in the seabed, attached to Posidonia rhizomes by byssus threads. This habit makes it impossible to measure its total length directly in situ. As the only way to determine the individual age is the relationship between age and total length, several equations have been proposed to estimate total length by relating it to the unburied parts of the shell. Such measurements are essential to ecological studies that consider age, growth, and population dynamics, and that evaluate the environmental factors that affect this species.Accurately estimating total length depends on the accuracy and precision of the method employed to measure the unburied shell parts. In this paper, we point out the lack of precision of the instruments and methods used until now; we also demonstrate the reason for this imprecision. A new device to measure unburied parts of Pinna nobilis with a precision comparable to that obtained when measuring extracted valves is described. This device is unaffected by substratum type and reduces measurement time. The latter is a very important feature, because these procedures are usually performed whilst SCUBA diving. Finally, a growth equation has been fitted to the measurements obtained with the new device from a population located in Moraira (Alicante, western Mediterranean). 相似文献
46.
47.
黄河三角洲潮滩发育时空谱系 总被引:3,自引:0,他引:3
研究黄河三角洲潮滩发育的时空话系指出:在时间上,黄河三角洲潮滩系由不同时期河口滩发育而成,各段潮滩发育时间因素的差异在比较形态学上有清晰反映,在空间上,并存着处于不同发育阶段上的四种类型(阶段)。由此构成了黄河三角洲前沿所特有的湖滩形态时空体系。 相似文献
48.
49.
依据岩性岩相研究、孔隙度研究、物探测井解译等成果,对鄂尔多斯白垩系盆地含水层系统的结构进行了划分与研究。结果表明:盆地北部沙漠高原区为单一结构,表现为强富水与中等富水含水层在垂向上叠置与组合,无区域性连续稳定的隔水层,由下到上构成含水统一体;南部黄土高原区为多层结构,表现为含水层与隔水层上下叠置,垂向水文地质分层明显;盆地南、北含水层结构的结构类型明显不同。利用孔隙度、渗透系数、单位涌水量3个参数,对含水层的富水性级别进行了划分,盆地中共划分出7个强富水含水层、7个中等富水含水层和2个弱富水含水层。盆地南、北比较,北部含水层孔隙度大,富水性强,地下水主要富集于盆地北部地区。垂向上比较,盆地北部由上到下,孔隙度由大变小,富水性由强变弱,地下水主要富集于浅层和中层;南部上部罗汉洞组和下部洛河组孔隙度较大,富水性好,中部环河组相对较差,地下水主要富集于罗汉洞组和洛河组。 相似文献
50.
In northern Jiangsu coastal zone area, Guanhe River is the biggest river and has the best navigation conditions among rivers
which flow into the Yellow Sea. The grain sizes show gradual increase from the high intertidal zone to lower intertidal zone.
The heavy metal values have slight changes along both sides of the river mouth, but show an evident change perpendicular to
the tidal flat. In the latter case, they show a good correlation with grain size fluctuation, that is, the heavy metal values
gradually decline when the grain size increases from the high intertidal zone to the lower intra-tidal zone. Analyses of the
heavy metal elements show that on the Guanhe estuary surface sediment, the content of the elements Hg, As and Cu is above
background values; Pb and Zn contents are rather close to the background values; and Cd content is less than the background
values. The element Hg comes out to be harmful in a medium level to ecological environment, while the elements of Cr, As,
Cu, Pb, Zn and Cd fall in a safe range of MPL. On the whole, Guanhe estuary tidal flat is not very harmful to the ecology
in terms of the heavy metals.
__________
Translated from Marine Geology & Quaternary Geology, 2007, 27(5): 23–32 [译自: 海洋地质与第四纪地质] 相似文献