复杂条件下隧道断面形状和支护参数优化   总被引：1，自引：0，他引：1  

韩现民  孙明磊  李文江  朱永全 《岩土力学》2011,32(Z1):725-0731

通过有限差分法（FLAC3D）数值计算和现场试验对马蹄形断面和大曲率边墙、似圆形断面形式下隧道的支护受力和围岩变形特征进行了对比分析,得出采用似圆形断面可以有效地控制围岩的变形量和变形速率,尤其是水平收敛变形;现场变形量测时的丢失位移所占总位移比例较大,其中下台阶丢失位移比例最大;通过现场试验,对不同支护刚度下围岩压力、锚杆受力、钢架、混凝土应力以及二次衬砌分担的围岩压力和模筑混凝土受力情况进行分析,结合洞室变形的现场量测,得出二次衬砌接触压力及分担围岩压力比呈现出随着初支刚度增大而增大的规律,并综合确定了板岩段合理的支护参数。该结论对在构造应力发育的软岩地区修筑隧道提供了有益的工程经验  相似文献   

Geophysical implications of Izu–Bonin mantle wedge hydration from chemical geodynamic modeling     

Laura B.  Hebert  Michael  Gurnis 《Island Arc》2010,19(1):134-150

Using two-dimensional dynamic models of the Northern Izu–Bonin (NIB) subduction zone, we show that a particular localized low-viscosity (η_LV =  3.3 × 10¹⁹ − 4.0 × 10²⁰ Pa s), low-density (Δρ ∼ −10 kg/m³ relative to ambient mantle) geometry within the wedge is required to match surface observations of topography, gravity, and geoid anomalies. The hydration structure resulting in this low-viscosity, low-density geometry develops due to fluid release into the wedge within a depth interval from 150 to 350 km and is consistent with results from coupled geochemical and geodynamic modeling of the NIB subduction system and from previous uncoupled models of the wedge beneath the Japan arcs. The source of the fluids can be either subducting lithospheric serpentinite or stable hydrous phases in the wedge such as serpentine or chlorite. On the basis of this modeling, predictions can be made as to the specific low-viscosity geometries associated with geophysical surface observables for other subduction zones based on regional subduction parameters such as subducting slab age.  相似文献   

A macroscopic damage‐plastic constitutive law for modeling quasi‐brittle fracture and ductile behavior of concrete     

P. J. Sánchez  A. E. Huespe  J. Oliver  G. Diaz  V. E. Sonzogni 《国际地质力学数值与分析法杂志》2012,36(5):546-573

A new phenomenological macroscopic constitutive model for the numerical simulation of quasi‐brittle fracture and ductile concrete behavior, under general triaxial stress conditions, is presented. The model is particularly addressed to simulate a wide range of confinement stress states, as also, to capture the strong influence of the mean stress value in the concrete failure mechanisms. The model is based on a two‐surface damage‐plastic formulation. The mechanical behavior in different domains of the stress space is separately described by means of a quasi‐brittle or ductile material response:

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利用垂线偏差计算大地水准面中央区效应的改进方法     

李厚朴  边少锋 《测绘学报》2011,40(6):730-735

为提高利用Molodensky公式反演测高大地水准面中央区效应的精度,视中央区为矩形域,将垂线偏差分量表示成双二次多项式插值形式,引入非奇异变换,推导出了大地水准面的计算公式。垂线偏差理论模型下的分析表明本文导出公式误差为零,而传统公式的误差与纬度以及垂线偏差子午分量与卯酉分量之间的比值有关;以中纬度区域分辨率为2'*2'的垂线偏差数据为背景场进行了实际计算,结果表明在反演计算点本身所在的1个网格对大地水准面的贡献时,传统公式与本文导出公式计算结果差值的最大值达数厘米。本文导出公式可为测高大地水准面的高精度反演提供理论依据。  相似文献   

区域似大地水准面精化模型算法的优选     

雷伟伟  张锋 《测绘工程》2011,20(1):33-36

建立高精度、高分辨率的区域似大地水准面模型是GPS高程测量在实际应用中必须解决的首要问题,分别介绍BP神经网络、曲面拟合的模型及算法,并基于焦作市GPS测量数据,通过MATLAB编程计算和分类实验,验证几种算法的有效性与可靠性,结果证明神经网络算法要优于其它算法,最后给出有益的结论.  相似文献   

水平面代替水准面对两井贯通的影响     

杨英伟 《北京测绘》2011,(4):84-85

理论结合实际,用详实的数据说明了在两井贯通时,把水准面当作水平面处理的界限,避免了盲目应用而产生严重后果.  相似文献   

新疆全区域似大地水准面的建立   总被引：1，自引：0，他引：1  

陈合忠 《测绘与空间地理信息》2011,(6):221-223

简述了大地水准面精化的方法、原理及新疆似大地水准面确定的过程。  相似文献   

热带海气相互作用对大气BSISO年际振荡的影响     

林爱兰  LITim  李春晖  梁建茵  LUOJing-Jia 《海洋学报(英文版)》2011,30(4):62-73

利用卫星观测OLR资料以及海气耦合数值模拟试验结果,从每年波-频分析结果提取了各种传播模态的强度指数序列,分析了热带北半球夏季季节内振荡(BSISO)各种传播模态的年际变化谱特征,探讨了热带各海区海气相互作用对其影响。主要结果如下:赤道外西传波和印度洋北传波以准2 a为显著振荡周期,赤道东传波、南海北传波和西太平洋北传波则都包含准2 a和准5 a两种周期,南海北传波是5种指数中惟一以准5 a为最主要周期振荡的模态。热带印度洋、西太平洋、东太平洋各海区海气相互作用对各指数准2 a振荡、准5 a振荡既有加强作用,也有削弱作用。各海区比较而言,对赤道东传波准2 a和准5 a振荡、南海北传波准2 a和准5 a振荡起最大加强作用的是西太平洋海区海气相互作用;对赤道外西传波准2 a振荡、西太平洋北传波准2 a和准5 a振荡起最大加强作用的是印度洋海区海气相互作用。  相似文献   

High-precision geoid determination in small areas: A case study in Doñana National Park (Spain)     

M. A. Núñez  A. Martín  J. A. Gili  A. B. Anquela 《Studia Geophysica et Geodaetica》2008,52(3):361-380

Doñana National Park is an area of approximately 500 km² located on the SW coast of Spain that shows one of the greatest geoid gradients on the entire Iberian Peninsula, due to its peculiar tectonic characteristics. So, it is necessary to elaborate an accurate geoid model that can be used with GPS for precise surveying, since the existing ones are insufficient, due to their poor resolution and their limited adaptation to a small area with such a strong gradient. The least squares prediction method was tested in order to obtain the undulation from GPS/orthometric points. The results obtained were unsatisfactory because of the strong geoid gradient. In order to improve accuracy the remove-restore technique was used. Global geopotential model EIGEN-CG01C and a Digital Elevation Model (DEM) with a 25 × 25 m resolution and an accuracy better than 3 m were used. Thus, the final geometrical geoid obtained reaches the precision required by other disciplines (3 cm in any point within the Park). Particularly, the geoid model has allowed for the acquisition of a precision DEM that is essential to formulate a hydrodynamic model for the Doñana marsh functions.  相似文献   

Contributions of terrestrial and GRACE data to the study of the secular geoid changes in North America   总被引：1，自引：0，他引：1  

Elena Rangelova  Michael G. Sideris 《Journal of Geodynamics》2008,46(3-5):131

This paper tests and discusses different statistical methods for modelling secular rates of change of the geoid in North America. In particular, we use the method of principal component/empirical orthogonal functions (PC/EOF) analysis to model the geoid rates from Gravity Recovery and Climate Experiment (GRACE) satellite data. As demonstrated, the PC/EOF analysis is useful for studying the contributions from different signals (mainly residual hydrology signals and leakage effects) to the GRACE-derived geoid rates. The PC/EOF analysis leads to smaller geoid rates compared to the conventional least-squares fitting of a trend and annual and semi-annual cycles to the time series of the spherical harmonic coefficients. This is because we filter out particular spatiotemporal modes of the regional geoid changes.We apply the method of least-squares collocation with parameters to combine terrestrial data (GPS vertical velocities from the Canadian Base Network and terrestrial gravity rates from the Canadian Gravity Standardization Net) with the GRACE-derived vertical motion to obtain again the geoid rates. The combined model has a peak geoid rate of 1.4 mm/year in the southeastern area of Hudson Bay contrary to the GRACE-derived geoid rates that show a large peak of 1.6–1.7 mm/year west of Hudson Bay. We demonstrate that the terrestrial data, which have a longer time span than the GRACE data, are important for constraining the GRACE-derived secular signal in the areas that are well sampled by the data.  相似文献