共查询到20条相似文献，搜索用时 16 毫秒
1.
M. Kavvadas A. Giolas G. Papacharalambous 《Geotechnical and Geological Engineering》1992,10(2):141-157
Summary The paper provides the approximate closed-form expressions for the estimation of the amount of ground water infiltration, the seepage exit gradient and the hydraulic pressure distribution on the cutoff elements in the case of sheeted excavations below the water table. The expressions are obtained by a multiple regression-type fitting of the results of an extensive parametric finite-element analysis for the two-dimensional steady-state flow in the soil around a sheeted excavation. In addition to the problem geometry, the effects of an impermeable base and a thin low permeability layer penetrated by the sheeting are also studied. The predictions of the approximate expressions deviate from the corresponding finite-element results by less than 15%, for a wide range of geometries and soil characteristics. It is shown how shape factors might be used to adapt the semi-empirical formulae for the case of excavations with limited length (circular and rectangular). 相似文献
2.
传统的参数化多元组合算子模型因取极大极小运算丢失太多信息,而且不能普适通用。若适当设定水安全评价各指标参照值和指标值的规范变换式,使规范变换后的不同指标的同级标准规范值差异很小,从而可以认为用规范值表示的不同指标皆"等效"于某个规范指标。因此,用规范值表示的水安全评价的参数化多元组合算子指数公式可以用该"等效"指标的水安全评价的参数化多元组合算子指数公式替代。在满足一定优化目标准则条件下,应用免疫猴王进化算法对公式中的参数进行优化,得到优化后对任意m项指标组合都适用的水安全评价的参数化组合算子普适指数公式。对公式的可靠性进行了理论分析,并对公式的实用性进行了效果检验。结果表明:水安全评价的参数化组合算子普适指数公式具有形式简洁、直观,计算简便和普适通用的特点。 相似文献
3.
宋家营勘查区位于河北唐山丰南区,存在着新生界厚度大,流沙层、卵石层、砂砾层松散破碎,部分钻孔漏失严重;煤层埋藏深、层数多、层位变化大等问题,给提高钻探施工质量和效益带来了不便。为解决这些问题,作者从钻孔设计人手,针对不同的地层采用相适应钻探工艺和技术措施,对长期沿用钻探方法进行改进,使钻进方法更具有针对性;对不同的地层配制了不同的冲洗液,对地层漏失根据情况采用恰当的堵漏方法,大大减少了因堵漏增加的成本。从而使钻进效率由过去的287m／台月,提高到440m／台月,台月效率提高了53．3％,大大降低了钻探成本。 相似文献
4.
Downhole microseismic data has the significant advantages of high signal-to-noise ratio and well-developed P and S waves and the core component of microseismic monitoring is microseismic event location associated with hydraulic fracturing in a relatively high confidence level and accuracy. In this study, we present a multidimensional DIRECT inversion method for microseismic locations and applicability tests over modeling data based on a downhole microseismic monitoring system. Synthetic tests inidcate that the objective function of locations can be defined as a multi-dimensional matrix space by employing the global optimization DIRECT algorithm, because it can be run without the initial value and objective function derivation, and the discretely scattered objective points lead to an expeditious contraction of objective functions in each dimension. This study shows that the DIRECT algorithm can be extensively applied in real downhole microseismic monitoring data from hydraulic fracturing completions. Therefore, the methodology, based on a multidimensional DIRECT algorithm, can provide significant high accuracy and convergent efficiency as well as robust computation for interpretable spatiotemporal microseismic evolution, which is more suitable for real-time processing of a large amount of downhole microseismic monitoring data. 相似文献
5.
基于ImPACT等式的人类活动环境影响分析——以甘肃省虚拟水消费为例 总被引：2，自引：0，他引：2
应用ImPACT等式,分析了甘肃省1990—2003年虚拟水消费中人类活动对环境的影响.结果表明:相比1990—1995年,1996—2000年和2001—2003年甘肃省收入显著提高,而使用强度(单位GDP的农产品消费量)和效率(单位农产品消耗的虚拟水量)大幅度改善,对环境影响(虚拟水消费量)起到了调节作用.收入弹性分析表明,收入增加1%将引起人均农产品消费量增加0.13%,使用强度下降0.87%,而环境影响增加0.14%.2000年甘肃省城镇和农村虚拟水消费对比分析表明,农村的虚拟水强度(0.706 m3·元-1)显著高于城镇(0.051 m3·元-1),合理改善消费结构能降低虚拟水强度从而减轻对环境的影响.应用ImPACT等式设置环境目标并检验其可行性,结果表明:在1990—2003年的基础上,使用强度降低1.5倍,效率提高1倍,能够保障经济的增长,并在合理的时间范围内(28 a)实现虚拟水消费量减少到2003年的50%,是一种可行的选择方案. 相似文献
6.
三维反演在磁数据定量解释中具有重要作用。常用的空间域三维反演方法通常需要大量的正演和反演计算,因此对大规模数据的反演效率较低。三维成像是另一种定性和定量解释磁数据的重要方法。文中给出了一种磁异常与梯度三维成像的频率域迭代方法,该方法可以提高成像效率,适用于大规模数据的快速成像。笔者推导了磁总场异常和异常梯度频率域正演公式和成像公式,并将一种深度尺度因子引入成像公式中,提高了深度精度;笔者采用了迭代优化算法,减小了拟合误差,进一步提高了成像精度。通过理论模型数据试验和中国新疆某金属矿床实测数据,验证了本文方法的有效性、可行性。 相似文献
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8.
在《矿产资源综合勘查评价规范》（GB／T25283-2010）附录Q疑点讨论的基础上,提出了关于矿产资源综合评价品位计算公式的正确推导及应用。《规范》附录Q存在问题是：重要术语有误,公式参数有误,不合市场规则。本文试按“等价原则”的评价思路,对矿产资源综合评价品位计算公式重新进行推导,详细讨论了各公式的适用条件和内在联... 相似文献
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10.
在研究岩石变形破坏时,现在采取的弹塑性分析,多是根据岩石在不同的应力状态下的典型破坏现象,提出强度理论(破坏准则),进而在导出岩石的本构关系基础上进行分析计算的。一般说来,岩石在不同应力状态下,基本破坏形式可分下面三类:(1)脆性拉伸破坏,(2)剪切破坏,(3)塑性流动破坏。这三种破坏类型,基本上可以归结为流动和断裂(拉断和剪断)两种破坏形式。 相似文献
11.
瞬态横向振动桩的Winkler参数 总被引：3，自引：0，他引：3
应用Fourier变换,推导了瞬态横向振动桩桩周土阻力在频率域中的Baranov公式,并得到瞬态横向振动桩Winkler参数k和c的表达式。该式因计算复杂不便于桩瞬态横向振动的计算,笔者应用Hankel函数渐近展开式得到k和c的简化式。对桩的瞬态横向振动的计算表明,简化式的精度满足要求,且大大提高了计算速度。 相似文献
12.
初值射线追踪方法是现代射线追踪方法中的一个很重要的理论,它克服了两点法射线追踪方法耗时的计算效率问题。以程函方程为基础,对初值射线追踪方法进行改进,即利用平方慢度来替换模型中的速度参数,使得程函方程产生解析解,从而进一步导出当射线遇到界面时的反射和透射慢度向量的计算表达式,以及反射、透射系数的函数表达式。通过对简单的两层界面向斜模型及复杂的多层盐丘模型的射线追踪,表明该初值射线追踪方法的改进相比于以往的龙格库塔离散数值解法,不但使射线追踪效率得到了大幅度提高（10倍左右）,且也扩大了射线法使用范围。 相似文献
13.
William G. Pariseau 《国际地质力学数值与分析法杂志》1985,9(3):277-283
The vibrating wire stress gauge is a borehole device for measuring stress changes in situ. Three gauge arrays are required for determining changes in the secondary principal stresses. Standard data reduction formulae that use the principal axes for reference are in error because of possible changes in the principal directions. Data reduction formulae that allow for such changes and for arbitrary gauge orientations within an array are presented here. This is of considerable practical importance when installing gauges because of scheduling restrictions and hole irregularities that may preclude installation at the planned angles for which data reduction formulae exist. Linearization and thus direct inversion of the resulting system of equations, is achieved in a fixed but otherwise arbitrarily oriented Cartesian system of reference. 相似文献
14.
横向各向同性介质中群速度的计算 总被引：2，自引：0，他引：2
各向异性走时计算和走时反演常需计算群速度，群速度的表达式通常在弱各向异性假设下给出。本文就横向各向同性介质中几种常见的群速度表示法进行了研究，给出了相应的计算方法，用数值例子讨论了它们所能近的各向异性强度，并比较了相互的优劣，这对各向异性人是质走时计算和走时反演无疑很有意义。 相似文献
15.
The procedure of fitting an ellipsoid to vitrinite reflectance anisotropy is described. Several authors on this subject use
incorrect fitting formulae. The correct formulae are given and a least- squares procedure is developed to give confidence
regions for the principal reflectances and their orientations. A FORTRAN program is offered that computes the principal reflectances
using the correct formulae. A test is constructed for whether the principal reflectance orientations are the same at two locations.
Because of the ellipsoid shape, the reflectance anisotropy can be compared to the strain ellipsoid. As an example, the methods
are used to compare two coal blocks from an openpit mine in Alberta, Canada. The test shows that the principal reflectances
of the two blocks have different orientations, indicating that the orientation of the principal strain axes is different at
the two sites. 相似文献
16.
The main objective of this study was to discuss the efficiency of agricultural land suitability for assessing land use types in rural areas. In this research, El-Nubariya area west of Nile Delta was selected as a case study site, which considers one of the high priority regions for future development in Egypt. As input, a total of ten representative soil profiles and number of observations points were used for collecting soil samples. Based on the field survey, laboratory analysis, and satellite image interpretation in cooperation with geographic information system (GIS), the physiographic map was executed. Three main landscape units were identified as follow: marine deposits, eolian deposits, and river terraces. The soils were classified mainly as Typic Torripsamments, Typic Paleorthids, and Typic Calciorthids. Land suitability assessment was done to define maps of the suitable areas for agricultural production using MicroLEIS microcomputer program and ALESarid-GIS system as well. According to the crop suitability results, the most suitable crops to grow in the study area were maize, melon, potato, sunflower, onion, garlic, olive, and date palm in the order indicated. Generally, the data on land suitability resulting from the evaluation models indicated that 56.1 % of the area is considered as suitable, 30.8 % is moderately to marginally suitable, and 13.1 % is not suitable. The main limitation factors for land suitability are the excess of salts, shallow soil depth, and inadequate drainage conditions. The output results are presented as georeferenced soil suitability maps using GIS utilities. 相似文献
17.
C. O. Okagbue 《Geotechnical and Geological Engineering》1995,13(3):157-168
Summary The permeability of graded sands was studied in the laboratory to determine the influence, if any, of stratification order on permeability (i.e. the position in which finer or coarser layers occur in the flow path). The evidence suggests that the order of stratification does not influence the order of magnitude of permeability of a sand. This order of magnitude is determined by the fine fraction of the sand. However, the order of stratification does have an influence on the finer details (i.e. variation within the same order of magnitude) of permeability. In this regard, an unsorted sand (all fractions mixed together) has the lowest permeability while a sorted one that has the fine fraction at the end of the sequence has the highest vertical permeability. It is also concluded that empirical formulae that use only the effective size, D
10, to estimate permeability yield results that are comparable with those that incorporate sorting in their formulae. However, experimental results show that these formulae do not yield reliable results when used for more denser sands. 相似文献
18.
为考察不同的各向异性抗剪强度表达式对于数值计算结果的影响,以一个假定的位于层状岩体中的矩形地下洞室为背景,分别使用笔者和Pietruszczak各自提出的材料摩擦系数和黏聚力随方向变化的公式,进行3种工况的弹塑性二维有限元模拟,对比了围岩中的应力、位移及塑性区。结果显示,笔者提出的经验表达式与和相应的Pietruszczak一阶表达式在计算中的精度基本相当,而与Pietruszczak的二阶表达式相比有较明显的差别。 相似文献
19.
Haosheng Wu Roman Bttger Frdric Couffignal Jens Gutzmer Joachim Krause Frans Munnik Axel D. Renno Ren Hübner Michael Wiedenbeck Ren Ziegenrücker 《Geostandards and Geoanalytical Research》2019,43(4):531-541
Although electron probe microanalysis and secondary ion mass spectrometry are widely used analytical techniques for geochemical and mineralogical applications, metrologically rigorous quantification remains a major challenge for these methods. Secondary ion mass spectrometry (SIMS) in particular is a matrix‐sensitive method, and the use of matrix‐matched reference materials (RMs) is essential to avoid significant analytical bias. A major problem is that the number of available RMs for SIMS is extremely small compared with the needs of analysts. One approach for the production of matrix‐specific RMs is the use of high‐energy ion implantation that introduces a known amount of a selected isotope into a material. We chose the more elaborate way of implanting a so‐called ‘box‐profile’ to generate a quasi‐homogeneous concentration of the implanted isotope in three dimensions, which allows RMs not only to be used for ion beam analysis but also makes them suitable for EPMA. For proof of concept, we used the thoroughly studied mineralogically and chemically ‘simple’ SiO2 system. We implanted either 47Ti or 48Ti into synthetic, ultra‐high‐purity silica glass. Several ‘box‐profiles’ with mass fractions between 10 and 1000 μg g?1 Ti and maximum depths of homogeneous Ti distribution between 200 nm and 3 μm were produced at the Institute of Ion Beam Physics and Materials Research of Helmholtz‐Zentrum Dresden‐Rossendorf. Multiple implantation steps using varying ion energies and ion doses were simulated with Stopping and Range of Ions in Matter (SRIM) software, optimising for the target concentrations, implantation depths and technical limits of the implanter. We characterised several implant test samples having different concentrations and maximum implantation depths by means of SIMS and other analytical techniques. The results show that the implant samples are suitable for use as reference materials for SIMS measurements. The multi‐energy ion implantation technique also appears to be a promising procedure for the production of EPMA‐suitable reference materials. 相似文献
20.
Michael S. Cherkiss Stephanie S. Romañach Frank J. Mazzotti 《Estuaries and Coasts》2011,34(3):529-535
Intensive crocodile monitoring programs conducted during the late 1970s and early 1980s in southern Florida resulted in an
optimistic outlook for recovery of the protected species population. However, some areas with suitable crocodile habitat were
not investigated, such as Biscayne Bay and the mainland shorelines of Barnes and Card Sounds. The objective of our study was
to determine status and habitat use of crocodiles in the aforementioned areas. Spotlight and nesting surveys were conducted
from September 1996 to December 2005. The results revealed annual increases in the number of crocodiles. Crocodiles preferred
protected habitats such as canals and ponds. Fewer crocodiles were observed in higher salinity water. The distribution and
abundance of crocodilians in estuaries is directly dependent on timing, amount, and location of freshwater delivery, providing
an opportunity to integrate habitat enhancement with ongoing ecosystem restoration and management activities. 相似文献