微波暗室三轴仿真转台旋转中心测量     

刘鹏军  王策  刘敏  马孝尊 《测绘科学》2015,(8):135-139

针对表述微波暗室三轴仿真转台位置与姿态特征的三轴旋转中心以及偏航轴、俯仰轴、横滚轴等元素均为虚交点、虚轴线的特点,该文提出了基于全站仪MetroIn的高精度微波暗室转台中心测量方法。针对微波暗室特殊的测量环境,结合转台自身特殊的结构特征与运动特性,制定了相应的设备布站与测量实施方案,实现了对微波暗室三轴仿真转台虚拟旋转中心的测量。  相似文献   

Garnet-bearing Xenoliths from Salt Lake Crater, Oahu, Hawaii: High-Pressure Fractional Crystallization in the Oceanic Mantle     

Keshav  Shantanu; Sen  Gautam; Presnall  Dean C. 《Journal of Petrology》2007,48(9):1681-1724

The focus of this study is a suite of garnet-bearing mantlexenoliths from Oahu, Hawaii. Clinopyroxene, olivine, and garnetconstitute the bulk of the xenoliths, and orthopyroxene is presentin small amounts. Clinopyroxene has exsolved orthopyroxene,spinel, and garnet. Many xenoliths also contain spinel-coredgarnets. Olivine, clinopyroxene, and garnet are in major elementchemical equilibrium with each other; large, discrete orthopyroxenedoes not appear to be in major-element chemical equilibriumwith the other minerals. Multiple compositions of orthopyroxeneoccur in individual xenoliths. The new data do not support theexisting hypothesis that all the xenoliths formed at 1 6–22GPa, and that the spinel-cored garnets formed as a consequenceof almost isobaric subsolidus cooling of a spinel-bearing assemblage.The lack of olivine or pyroxenes in the spinel–garnetreaction zones and the embayed outline of spinel grains insidegarnet suggest that the spinel-cored garnets grew in the presenceof a melt. The origin of these xenoliths is interpreted on thebasis of liquidus phase relations in the tholeiitic and slightlysilica-poor portion of the CaO–MgO–Al₂O₃–SiO₂(CMAS) system at pressures from 30 to 50 GPa. The phase relationssuggest crystallization from slightly silica-poor melts (ortransitional basaltic melts) in the depth range 110–150km beneath Oahu. This depth estimate puts the formation of thesexenoliths in the asthenosphere. On the basis of this study itis proposed that the pyroxenite xenoliths are high-pressurecumulates related to polybaric magma fractionation in the asthenosphere,thus making Oahu the only locality among the oceanic regionswhere such deep magmatic fractional crystallization processeshave been recognized. KEY WORDS: xenolith; asthenosphere; basalt; CMAS; cumulate; oceanic lithosphere; experimental petrology; mantle; geothermobarometry; magma chamber  相似文献   

Stresses from linearly distributed pressures over rectangular areas     

Halil Murat Algin 《国际地质力学数值与分析法杂志》2000,24(8):681-692

This paper presents a general algebraical formula to determine the vertical stresses resulting from a linearly distributed surface pressure resting on an elastic medium. This problem and its various derivations has received considerable attention because of its applications in foundation engineering [1–5]. The equation presented in this paper has been determined by the integration of the Boussinesq [6] equation with respect to the general surface function of a linearly distributed loading regime. The equation can be applied to the case of an optimally designed rectangular footing subjected to biaxial bending. Unlike the current design formulae [1–7], it provides the flexibility of having various contact pressures at each of the four corners of the rectangular area. This may enable more accurate design procedures for pad foundations in the future. This paper explains the validity of the new formula by comparing its results with those produced by classical methods. It shows how it can be applied to determine the vertical stress distributions resulting from all types of linearly distributed surface pressures which occupy a rectangular area on an elastic mass. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

A general method for defining the number of cycles of repeated loading     

M. D. Liu  J. P. Carter 《国际地质力学数值与分析法杂志》2001,25(1):71-81

In geotechnical engineering designs and safety checks, the number of cycles of repeated loading N is frequently used as a parameter for calculating the response of soil structures under the repeated loading. However, there appears to be a lack of rational methods for calculating N for repeated loadings along general stress paths. A new method for defining N is proposed in this paper, based on the assumption that a yield surface may be identified for the material. It is demonstrated that the proposed method provides a rational and useful means for engineering calculation of soil deformations under repeated loadings. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

桩土相互作用分析中的动力Winkler模型研究评述   总被引：10，自引：0，他引：10  

孔德森  栾茂田  杨庆 《世界地震工程》2005,21(1):12-17

Winkler地基梁集中参数模型在桩一土动力相互作用分析中得到了普遍应用,在现有研究成果的基础上,对桩一土相互作用分析中的动力Winkler模型进行了较全面的综述,指出了各种模型的优缺点,并对有待于深入探讨的问题及发展动向进行了简要评述,为今后深入研究提供了基础。  相似文献   

Vertically loaded piles in non-homogeneous media     

Wei Dong Guo  Mark F. Randolph 《国际地质力学数值与分析法杂志》1997,21(8):507-532

Analytical methods for the axial responses of piles can be classified under three broad categories of (1) simple but approximate analytical solutions, (2) one-dimensional numerical algorithms, (3) full axisymmetric analyses using boundary or finite element approaches. The first two categories rely on the so-called load transfer approach, with interaction between pile and soil determined by independent springs distributed along the pile shaft and at the pile base. The non-linear spring stiffness is related to the elastic–plastic properties of the actual soil partly by empirically based correlations and partly by theoretical arguments based on simplified models of the pile–soil system. This paper presents new closed-form solutions for the axial response of piles in elastic–plastic, non-homogeneous, media. The solutions fall in the first of the three categories above, and have been verified through extensive parametric studies using more rigorous one-dimensional and continuum analyses. The effect of non-homogeneity and partial slip on the load and displacement profiles along the pile shaft is explored, and comparisons are presented with experimental data. © 1997 John Wiley & Sons, Ltd.  相似文献   

地图切片技术分析与简单实现   总被引：8，自引：0，他引：8  

赵大龙  孙恒宇 《测绘与空间地理信息》2010,33(1):116-118

地图切片(MapTile)技术是目前大多数电子地图网站、3维地图网站使用的预先生成栅格地图,并由客户端接口呈现出无缝拼接地图的浏览技术。地图以链接图片的方式快速定位,访问速度要快于传统的WebGIS,同时,对地图服务器的负载也相应小一些。本文介绍了地图切片技术的相关步骤并对主流电子地图网站做了分析。笔者利用Flash作为地图客户端开发工具,实现了地图切片的实时加载和不同比例尺的漫游。  相似文献   

大跨度钢桁架模板在地下硐室中的研究与应用          下载免费PDF全文

朱爱山  郭红里  周慧鹏  费益滨 《探矿工程》2020,47(12):66-71

以江苏省某人防坑道工程为背景,通过实际工程应用,结合安全性、经济性和可操作性综合比较,研究融合了钢模台车、承重脚手架、钢桁架和定型钢模等施工方法,形成硐室大跨度钢桁架模板施工技术。对该系统在地下硐室中的施工做了技术研究和应用探讨,重点介绍了工艺原理、模架设计及受力分析、工程应用等。该施工方法能够提高工效,节省成本,提高施工质量。  相似文献   

循环荷载下非饱和结构性黏土的弹塑性双面模型     

李潇旋  李涛  李舰  张涛 《岩土力学》2020,41(4):1153-1160

非饱和黏土的结构性能够显著影响其力学特性。基于非饱和土经典模型BBM（Barcelona basic model）和一种可描述循环塑性的硬化法则,引入体积破损率的作为标准土体结构破损的参数,建立了一个描述常吸力下非饱和结构性黏土静态及动态力学特性的弹塑性双面模型。模型在应力空间中包含与重塑非饱和土屈服面几何相似的结构性边界面和加载面,采用径向映射法则和可移动的记忆中心原理,通过结构性边界面和加载面在应力空间中的演化来反映循环加载过程中非饱和结构性黏土的循环塑性特征和结构损伤过程。通过与相关非饱和黏土控制吸力试验数据的比较,表明该模型能够较好地反映静态加载下非饱和结构性黏土的力学特性,而模型预测的循环荷载下的应力?应变特征也具有一定的合理性。  相似文献   

冲击损伤砂岩动静组合加载力学特性研究     

闻磊  梁旭黎  冯文杰  王伟  王亮  常江芳  袁维 《岩土力学》2020,41(11):3540-3552

利用霍布金森压杆试验装置对灰砂岩试样进行预加静载的循环冲击,使试样产生初始损伤,并分析此过程中试样的损伤演化规律。使用能够施加轴压的霍布金森压杆进行预损伤试样动静组合加载试验,获得试样破坏模式、动态应力-应变关系等指标。基于应变等价原理分析预损伤试样动静组合加载条件下的总损伤变量,建立相应的损伤演化方程及损伤本构关系,并与完整试样进行对比。研究结果表明：循环冲击过程中试样损伤变量分为快速上升、低速发展、高速发展3个阶段,预加轴压越大低速发展阶段损伤变量平均值越小;相同动静组合加载条件下预损伤试样动态强度较小,完整试样应变率增强效应更加显著;循环冲击预损伤变量 、预加静载损伤变量 对于应力-应变关系的影响是较为复杂的, 、 值之和可能为负值;建立的本构关系与试验曲线具有较好的一致性,得到的总损伤变量曲线不仅能够解释试样宏观破坏与细观损伤过程的一致性,并且能够反映循环冲击和预加静载两种因素对岩石总损伤发展的非线性影响。  相似文献