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David J. Sanderson 《Mathematical Geology》1977,9(5):483-496
Arrays or rosettes of lines along which the extension or relative extension can be determined constitute finite strain gauge rosettes. Expressions for the principal strains and their orientation in terms of three nonparallel gauge extensions can be established in a suitable form for algebraic evaluation, thus replacing graphical methods based on Mohr construction. Three types of strain rosette problems, including one which utilizes angles, are particularly relevant to the study of deformed rocks. These, together with their relation to grid methods, are discussed and simple examples of their use given. Finally, an approach to the problem of finding best-fitting solutions to overdetermined regular strain rosettes is discussed. 相似文献
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考虑影响公路边坡稳定性信息的不完整性、随机性和模糊性,以最大熵原理和工程模糊集理论为基础,并采用综合赋权法确定指标权重,提出了一种改进的公路边坡稳定性模糊评价方法。该模型充分利用影响因素的信息,以广义加权距离表示待评价样本与标准样本的差异,从优化条件中获得相对隶属度,并依据加权平均原则对边坡样本等级进行识别。该模型应用于常吉和吉怀高速公路边坡稳定性评价中,将评价结果与模糊综合模型和属性识别模型的结果以及边坡实际情况进行对比验证,体现了其较好的一致性,并且结果更合理。同时,该模型具有较小的信息熵值,表明其评价的不确定性小,可靠性较高,是一种边坡稳定性评价分析新方法,可在相关工程领域中应用推广。 相似文献
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A formula for the thickness of a shear band formed in saturated soils under a simple shear or a combined stress state has been proposed. It is shown that the shear band thickness is dependent on the pore pressure properties of the material and the dilatancy rate, but is independent of the details of the combined stress state. This is in accordance with some separate experimental observations. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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针对常规数值模拟计算无法有效地反映锚杆对围岩的加固效果的缺陷,结合岩体变形在锚杆中产生的支护压力计算公式,提出了一种简单、有效的砂浆锚杆加固等效数值模拟方法。该方法首先在有锚杆支护隧道开挖的计算结果中提取每根锚杆的最大轴力;然后根据该轴力值按锚杆支护压力公式计算其所产生的等效均布力;最后将该均布力施加到相同计算工况下无锚杆支护的围岩表面进行模拟计算。将该方法应用于锦屏二级水电站地下厂房枢纽洞室及乌东德水电站4#导流洞0+ 550 m断面的开挖与支护计算,通过与现场实测数据对比,结果表明,该方法能较好地模拟锚杆支护对围岩的加固效果,其模拟结果可为隧洞的施工与支护设计提供可靠的参考依据。 相似文献
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柔性管线安全评价的简便方法 总被引:3,自引:2,他引:1
随着我国地铁建设的快速发展,地铁施工中邻近管线的安全评价是一项急待解决的关键技术问题。在地层移动基本规律认识基础上,提出了一种经验或半经验的基于变形控制的柔性管线的安全评价方法。该方法可应用于快速评估柔性管线的潜在损害,具体的管线细节一般不予考虑,涉及的参数少,更易于工程应用。该方法尤其适用于没有足够资料或者特殊敏感的条件下,需要对管线的接头单独考虑,需要采用保守估计的情况。 相似文献
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This study outlines an improved method, DIVERSITY, for delineating and rating groundwater sensitivity. It is an acronym for DIspersion/VElocity-Rated SensitivITY, which is based on an assessment of three aquifer characteristics: recharge potential, flow velocity, and flow directions. The primary objective of this method is to produce sensitivity maps at the county or state scale that illustrate intrinsic potential for contamination of the uppermost aquifer. Such maps can be used for recognition of aquifer sensitivity and for protection of groundwater quality. We suggest that overriding factors that strongly affect one or more of the three basic aquifer characteristics may systematically elevate or lower the sensitivity rating. The basic method employs a three-step procedure: (1) Hydrogeologic settings are delineated on the basis of geology and groundwater recharge/discharge position within a terrane. (2) A sensitivity envelope or model for each setting is outlined on a three-component rating graph. (3) Sensitivity ratings derived from the envelope are extrapolated to hydrogeologic setting polygons utilizing overriding and key factors, when appropriate. The three-component sensitivity rating graph employs two logarithmic scales and a relative area scale on which measured and estimated values may be plotted. The flow velocity scale ranging from 0.01 to more than 10,000 m/d is the keystone of the rating graph. Whenever possible, actual time-of-travel values are plotted on the velocity scale to bracket the position of a sensitivity envelope. The DIVERSITY method was developed and tested for statewide use in Kentucky, but we believe it is also practical and applicable for use in almost any other area. 相似文献
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Summary A linear algebraic model for the sequence-independent calculation of pyroxene components of microprobe analyses is presented. Assuming ideal stoichiometry, the theoretical Fe3+ is obtained by using charge balance criteria. The calculation of 11 linearly-independent endmember parameters (Jd, Ac, Ur, TiTs, CaTs, FeTs, CrTs, Pm, Fs, En, Wo) in conjunction with a rigorous mass balance enables the appreciation of the stoichiometry and the endmember definition. The presented method offers a normalized comparison base for a wide spectrum of pyroxene analyses. On the basis of the 11 linearly-independent endmember parameters other common pyroxene components (e.g. Di, Hd, Jh, FeATs, CrATs, MgTs, Fe2+Ts) may be calculated using exchange reactions.
Die Berechnung von Pyroxen-Endgliedern mit Methoden der Linearen Algebra
Zusammenfassung Unter Verwendung von Methoden der Linearen Algebra wird eine reihenfolgenunabhängige Berechnung von Pyroxen-Endgliedern aus Mikrosondenanalysen vorgestellt. Die Annahme idealer Stöchiometrie ermöglicht die Bestimmung des theoretischen Fe3+ aus einer Ladungsbilanz. Die Berechnung von 11 linear-unabhängigen Pyroxen-Endgliedern (Jd, Ac, Ur, TiTs, CaTs, FeTs, CrTs, Pm, Fs, En, Wo) erfolgt unter einer strengen Massenbilanz und gewährleistet eine theoretische Auswertung der auferlegten Bedingungen über die Stöchiometrie und die Endgliederdefinition. Darüber hinaus stellt diese Methode eine normierte Vergleichsbasis für ein breites Spektrum von Pyroxenanalysen dar. Ausgehend von den 11 linear-unabhängigen Endgliedern können weitere in der Natur auftretende Pyroxen-Endglieder wie z.B. Di, Hd, Jh, FeATs, CrATs, MgTs, Fe2+ Ts mittels Austauschreaktionen berechnet werden.相似文献
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To solve large deformation geotechnical problems, a novel strain-smoothed particle finite element method (SPFEM) is proposed that incorporates a simple and effective edge-based strain smoothing method within the framework of original PFEM. Compared with the original PFEM, the proposed novel SPFEM can solve the volumetric locking problem like previously developed node-based smoothed PFEM when lower-order triangular element is used. Compared with the node-based smoothed PFEM known as “overly soft” or underestimation property, the proposed SPFEM offers super-convergent and very accurate solutions due to the implementation of edge-based strain smoothing method. To guarantee the computational stability, the proposed SPFEM uses an explicit time integration scheme and adopts an adaptive updating time step. Performance of the proposed SPFEM for geotechnical problems is first examined by four benchmark numerical examples: (a) bar vibrations, (b) large settlement of strip footing, (c) collapse of aluminium bars column, and (d) failure of a homogeneous soil slope. Finally, the progressive failure of slope of sensitive clay is simulated using the proposed SPFEM to show its outstanding performance in solving large deformation geotechnical problems. All results demonstrate that the novel SPFEM is a powerful and easily extensible numerical method for analysing large deformation problems in geotechnical engineering. 相似文献
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A comparative error analysis of manual versus automated methods of data acquisition for algebraic strain estimation 总被引:1,自引:0,他引:1
This paper presents a statistical analysis of the algebraic strain estimation algorithm of Shimamoto and Ikeda [Shimamoto, T., Ikeda, Y., 1976. A simple algebraic method for strain estimation from deformed eillipsoidal objects: 1. Basic theory. Tectonophysics 36, 315–337]. It is argued that the error in their strain estimation procedure can be quantified using an expected discrepancy measure. An analysis of this measure demonstrates that the error is inversely proportional to the number of clasts used. The paper also examines the role of measurement error, in particular that incurred under (i) a moment based and (ii) manual data acquisition methods. Detailed analysis of these two acquisition methods shows that in both cases, the effect of measurement error on the expected discrepancy is small relative to the effect of the sample size (number of objects). Given their relative speed advantage, this result favours the use of automated measurement methods even if they incur more measurement error on individual objects. Validation of these results is carried out by means of a simulation study, as well as by reference to studies appearing in previous literature. The results are also applied to obtain an upper bound on the error of strain estimation for various studies published in the literature on strain analysis. 相似文献
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Ying Hongwei Cheng Kang Liu Sijie Xu Riqing Lin Cungang Zhu Chengwei Gan Xiaolu 《Acta Geotechnica》2022,17(12):5759-5771
Acta Geotechnica - Based on the 16 collected well-documented excavation cases of the Hangzhou metro basement, the standard parameters of the basement, the standard excavation process, and the... 相似文献
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Acta Geotechnica - This paper presents a risk evaluation model of excavation system. The model is developed based on extended TODIM method (TODIM is an acronym in Portuguese for Interactive... 相似文献
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近来地震液化灾害频发,再次成为研究重点,发展具有良好应用前景的基于静力触探试验(CPT)的液化判别方法对预防液化灾害具有重要意义。以Boulanger数据库171组数据为回归样本,分析既有方法存在的问题,提出了基于CPT液化判别的双曲线模型和计算公式,并通过提取2011年新西兰地震147组液化新数据,对该方法进行对比检验。研究表明,我国岩土工程勘察规范的CPT液化判别方法对浅埋砂层偏于保守,对深层土又明显偏于危险,而国际上具有代表性的Robertson方法,其液化临界线存在低烈度区不合理回弯、高烈度区又偏于保守的问题。提出的新公式在不同地震动强度和砂层埋深下均可给出合理判别结果,克服了国内外既有方法的缺点,并纳入到具有样板规范性质的《建筑工程抗震性态设计通则》修订稿中,可为我国相关规范修订和工程应用提供支持。 相似文献