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331.
332.
土体渗流固结参数识别方法 总被引:6,自引:1,他引:6
根据土体固结过程中超孔隙水压力观测资料,建立了基于遗传算法的土体渗流团结参数非线性识别方法,解决了经典高斯-牛顿极小化问题所存在的局部极小问题和最小二乘法所存在的当初始值选择不合适时迭代过程发散的问题,提出了根据观测仪器的精度,建立 工终止条件的方法,数值计算结果表明,本文所提出的非线性反演方法适合于土体团结参数识别等类似的反问题。 相似文献
333.
块状硫化物矿石中硫化物的压溶和增生及成矿意义——以加拿大西部矿床为例 总被引:7,自引:0,他引:7
加拿大西部块状硫化物矿石普遍地发生过硫化物的压溶和增生。增生作用根据增生体的成分可以分为同质增生和异质增生,根据动力环境可以分为静态增生和动态增生。三晶嵌接结构可以是静态增生的产物。压溶和增生是块状硫化物矿床成岩和变质过程中的重要作用。脉石矿物的压溶可使原生矿石就地加富,硫化物的压溶可使成矿物质发生再活化。增生可促进矿质沉淀。富含硫化物的地层之所以能成为地球化学障而有利于后期热液叠加和层控矿床的形成,硫化物晶芽的增生是一种重要机制。 相似文献
334.
川东地区碳酸盐岩超压与天然气富集关系研究 总被引:7,自引:2,他引:7
地层流体超压的形成、演化及分布与油气成藏的主要石油地质过程有着千丝万缕地联系。由于碳酸盐岩本身的复杂性,其超压的成因及研究方法不能简单地借用“欠压实”的原理。本文从对比砂泥岩和碳酸盐岩在成压机理上的差异性入手,详细探讨了川东地区碳酸盐岩成压的各种机理,指出成烃作用是造成区域性超压的最主要因素;并结合该区超压平面上的分区性及纵向上的分带性,论述了各区、带超压与气藏分布的内在联系,总结出该区超压与天然气富集的关系。 相似文献
335.
Generation of Deccan Trap magmas 总被引:1,自引:0,他引:1
Gautam Sen 《Journal of Earth System Science》2001,110(4):409-431
Deccan Trap magmas may have erupted through multiple centers, the most prominent of which may have been a shield volcano-like
structure in the Western Ghats area. The lavas are predominantly tholeiitic; alkalic mafic lavas and carbonatites are rare.
Radioisotope dating, magnetic chronology, and age constraints from paleontology indicate that although the eruption started
some 68 Ma, the bulk of lavas erupted at around 65–66 Ma. Paleomagnetic constraints indicate an uncertainty of ± 500,000 years
for peak volcanic activity at 65 m.y. in the type section of the Western Ghats. Maximum magma residence times were calculated
in this study based on growth rates of “giant plagioclase” crystals in lavas that marked the end phase of volcanic activity
of different magma chambers. These calculations suggest that the > 1.7 km thick Western Ghats section might have erupted within
a much shorter time interval of ∼ 55,000 years, implying phenomenal eruption rates that are orders of magnitude larger than
any present-day eruption rate from any tectonic environment. Other significant observations/conclusions are as follows: (1)
Deccan lavas can be grouped into stratigraphic subdivisions based on their geochemistry; (2) While some formations are relatively
uncontaminated others are strongly contaminated by the continental crust; (3) Deccan magmas were produced by 15–30% melting
of a Fe-rich lherzolitic source at ∼ 3–2 GPa; (4) Parent magmas of the relatively uncontaminated Ambenali formation had a
primitive composition with 16%MgO, 47%SiO2; (5) Deccan magmas were generated much deeper and by significantly more melting than other continental flood basalt provinces;
(6) The erupted Deccan tholeiitic lavas underwent fractionation and magma mixing at ∼ 0.2 GPa. The composition and origin
of the crust and crust/mantle boundary beneath the Deccan are discussed with respect to the influence of Deccan magmatic episode. 相似文献
336.
337.
Masayuki Hyodo Noritaka Aramaki Masayuki Itoh Adrian F.L. Hyde 《Soil Dynamics and Earthquake Engineering》1996,15(5):331-336
Cyclic triaxial tests have been carried out on a skeletal carbonate sand from the west coast of Eire. Results are presented for undrained cyclic shear tests on samples with 80% of relative density consolidated under both isotropic and anisotropic conditions. Failure was defined as a 5% double amplitude cyclic strain and a 5% peak axial strain for stress-reversal and non-reversal stress conditions, respectively. Using this definition the cyclic strength for isotropically consolidated samples was affected by the confining pressure although the angular platey nature of the sand resulted in higher cyclic strengths than for a comparable silica sand. For anisotropically consolidated samples the cyclic strength increased with increasing initial static shear stress while on the other hand the cyclic strength normalised in the usual way with respect to the initial confining pressure decreased as this pressure increased. 相似文献
338.
土压力问题的变分解答 总被引:1,自引:0,他引:1
用变分学方法导出了与朗肯土压力公式和库伦土压力公式完全一致的土压力计算公式,并且一般情况下的极值曲线线不同一条直线,而是比较复杂的曲线,在 倾斜边坡情况下的伦公式仅仅是一个特解。 相似文献
339.
A complete spectrum of Lyapunov exponents (LEs) is obtained from 1970— 1985 daily mean pressuremeasurements at Shanghai by means of a correlation matrix analysis technique and it is found that there exist LEs≥0,and <0. with their sum 0λ_i=K=0.110405 whereuponT=1 /K =9 is obtained as the predictable time scale, a result close to that acquired by the dynamic-statistical approachin early days and also in agreement with that present by the authors themselves(1991). 相似文献
340.