A simple prediction model for wall deflection caused by braced excavation in clays     

《Computers and Geotechnics》2015

Deep excavations particularly in deep deposits of soft clay can cause excessive ground movements and result in damage to adjacent buildings. Extensive plane strain finite element analyses considering the small strain effect have been carried out to examine the wall deflections for excavations in soft clay deposits supported by retaining walls and bracing. The excavation geometry, soil strength and stiffness properties, and the wall stiffness were varied to study the wall deflection behavior. Based on these results, a simple Polynomial Regression (PR) model was developed for estimating the maximum wall deflection. Wall deflections computed by this method compare favorably with a number of field and published records.  相似文献   

鞍本地区早前寒武纪地质体铅同位素组成及铀源条件定量计算方法研究     

韩军  李林强  李月湘  夏毓亮 《矿物岩石地球化学通报》2011,30(2):172-179

本文对比了鞍本地区前寒武纪铅-锌-银矿区和铀矿区的硫化物矿石和花岗岩长石Pb同位素组成,分别用矿石铅二阶段普通铅法、铅构造模式图解和全岩铅同位素组成三阶段拟合法计算了年龄和全岩原始铀含量。结果表明,矿石铅和长石铅模式年龄约为2000 Ma,在铅构造模式图上投影于2000~1600 Ma间,花岗岩和辽河群全岩拟合年龄为2000~1800 Ma;铅同位素组成显示铅-锌-银来自早元古代辽河群地层,连山关地区明显为放射性成因Pb同位素组成,源于富铀花岗岩。连山关矿石铅年龄和全岩三阶段年龄与该区铀矿床沥青铀矿的年龄基本一致;花岗岩原始铀的得失计算表明,该地区不同地质体均经历了约2000~1800 Ma花岗岩重熔改造,花岗质岩石发生了铀的丢失,是连山关地区铀矿的主要来源。  相似文献   

基于广义极值分布的设计波高推算   总被引：1，自引：0，他引：1  

陈子燊  刘曾美  路剑飞  于吉涛 《热带海洋学报》2011,(3)

简介了广义极值分布函数及其3种参数估计方法,包括极大似然(ML)、线性矩(LM)和间隔最大积(MPS)估计的计算方法。使用广义极值分布函数推算了北部湾涠洲岛海域3个波向的年波高极值序列设计波高,并与Weibull分布、Gumbel分布和皮尔逊Ⅲ型分布的推算结果加以对比。分析表明,涠洲岛海域极值波高服从于广义极值Ⅲ型分布,拟合优度检验结果表明广义极值分布能更好地拟合极值波高;MPS方法是一种优良的参数估计法,推算的设计波高可作为海岸环境工程设计的首要参考值。  相似文献   

Governance fit for climate change in a Caribbean coastal-marine context     

《Marine Policy》2015

Coastal-marine systems in small island developing states of the Caribbean are highly vulnerable to both current and future climate change. Societies navigate these changes in part through processes of governance and the institutions through which governance takes place. The concept of institutional adaptive capacity is used to explore how governance processes and institutional arrangements can be adapted to match the scale and extent of climate change in a case study of the Soufriere Marine Management Area, St. Lucia. Institutional adaptive capacity is analyzed based on the following factors: institutional variety, analytical deliberation and nesting and networks. The analysis is based on 36 semi-structured interviews conducted with key informants from NGOs, cooperatives, management authorities and government agencies. The findings suggest that governance to address climate change in the case study is contingent upon developing holistic, integrated management systems, improving flexibility in existing collaborative decision making processes, augmenting the capacity of local management authorities with support from higher-level government, exploring opportunities for private–social partnerships, and developing adequate social–environmental monitoring programs. These findings have potential implications and lessons for similar settings throughout the Caribbean.  相似文献   

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杨厚丽  邹彤  郭唐永  刘延飞 《大地测量与地球动力学》2015,35(2):346-348

?????????????????????????????????????????????????????????????????????и??????????????????????????????λ??????????????????????????÷??????????????????????g?????????????????÷?????????????10^??3?? μGal??????????????  相似文献   

An improved segmentation approach for planar surfaces from unstructured 3D point clouds     

Tarek M.  Awwad  Qing  Zhu  Zhiqiang  Du  Yeting  Zhang 《The Photogrammetric Record》2010,25(129):5-23

The extraction of object features from massive unstructured point clouds with different local densities, especially in the presence of random noisy points, is not a trivial task even if that feature is a planar surface. Segmentation is the most important step in the feature extraction process. In practice, most segmentation approaches use geometrical information to segment the 3D point cloud. The features generally include the position of each point (X, Y and Z), locally estimated surface normals and residuals of best fitting surfaces; however, these features could be affected by noisy points and in consequence directly affect the segmentation results. Therefore, massive unstructured and noisy point clouds also lead to bad segmentation (over-segmentation, under-segmentation or no segmentation). While the RANSAC (random sample consensus) algorithm is effective in the presence of noise and outliers, it has two significant disadvantages, namely, its efficiency and the fact that the plane detected by RANSAC may not necessarily belong to the same object surface; that is, spurious surfaces may appear, especially in the case of parallel-gradual planar surfaces such as stairs. The innovative idea proposed in this paper is a modification for the RANSAC algorithm called Seq-NV-RANSAC. This algorithm checks the normal vector (NV) between the existing point clouds and the hypothesised RANSAC plane, which is created by three random points, under an intuitive threshold value. After extracting the first plane, this process is repeated sequentially (Seq) and automatically, until no planar surfaces can be extracted from the remaining points under the existing threshold value. This prevents the extraction of spurious surfaces, brings an improvement in quality to the computed attributes and increases the degree of automation of surface extraction. Thus the best fit is achieved for the real existing surfaces.  相似文献   

A generalized conditional intensity measure approach and holistic ground‐motion selection     

Brendon A. Bradley 《地震工程与结构动力学》2010,39(12):1321-1342

A generalized conditional intensity measure (GCIM) approach is proposed for use in the holistic selection of ground motions for any form of seismic response analysis. The essence of the method is the construction of the multivariate distribution of any set of ground‐motion intensity measures conditioned on the occurrence of a specific ground‐motion intensity measure (commonly obtained from probabilistic seismic hazard analysis). The approach therefore allows any number of ground‐motion intensity measures identified as important in a particular seismic response problem to be considered. A holistic method of ground‐motion selection is also proposed based on the statistical comparison, for each intensity measure, of the empirical distribution of the ground‐motion suite with the ‘target’ GCIM distribution. A simple procedure to estimate the magnitude of potential bias in the results of seismic response analyses when the ground‐motion suite does not conform to the GCIM distribution is also demonstrated. The combination of these three features of the approach make it entirely holistic in that: any level of complexity in ground‐motion selection for any seismic response analysis can be exercised; users explicitly understand the simplifications made in the selected suite of ground motions; and an approximate estimate of any bias associated with such simplifications is obtained. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

东太平洋多金属结核分布的二维趋势面分析   总被引：1，自引：0，他引：1  

章伟艳  张富元  马维林 《海洋学研究》2001,19(1):27-34

对规则网的 469个测站的多金属结核丰度和 93个测站的 Mn、 Cu、 Co、 Ni元素进行趋势面分析 ,经 F检验 ,各变量的变异性显著 ,拟合度较低 ,表明多金属结核丰度及 Mn、Cu、Co、Ni金属元素的控制因素比较复杂。趋势面分析结果与相关分析结果一致 ,Mn、Cu、Ni元素有极相似的趋势特征 ,有两个轴向分布 ,一个为东西向轴 ,高值区在东部 ,另一个为北西向轴 ,高值区在北西部 ;结核丰度与 Co也有极相似的趋势特征 ,高值区在西部。应用逐次趋势面分析的结果将结核丰度的地质特征分解成各种简单控制因素的叠加 ,使对多金属结核的控矿因素、分布规律和物质来源的研究方法多样化  相似文献   

Investigation of gas content of organic-rich shale:A case study from Lower Permian shale in southern North China Basin,central China     

Wei Dang  Jin-Chuan Zhang  Xuan Tang  Xiao-Liang Wei  Zhong-Ming Li  Cheng-Hu Wang  Qian Chen  Chong Liu 《地学前缘(英文版)》2018,9(2):559-575

Measuring gas content is an essential step in estimating the commerciality of gas reserves. In this study,eight shale core samples from the Mouye-1 well were measured using a homemade patented gas desorption apparatus to determine their gas contents. Due to the air contamination that is introduced into the desorption canister, a mathematical method was devised to correct the gas quantity and quality.Compared to the chemical compositions of desorbed gas, the chemical compositions of residual gas are somewhat different. In residual gas, carbon dioxide and nitrogen record a slight increase, and propane is first observed. This phenomenon may be related to the exposure time during the transportation of shale samples from the drilling site to the laboratory, as well as the differences in the mass, size and adsorptivity of different gas molecules. In addition to a series of conventional methods, including the USBM direct method and the Amoco Curve Fit(ACF) method, which were used here for lost gas content estimation, a Modified Curve Fit(MCF) method, based on the 'bidisperse' diffusion model, was established to estimate lost gas content. By fitting the ACF and MCF models to gas desorption data, we determined that the MCF method could reasonably describe the gas desorption data over the entire time period, whereas the ACF method failed. The failure of the ACF method to describe the gas desorption process may be related to its restrictive assumption of a single pore size within shale samples. In comparison to the indirect method, this study demonstrates that none of the three methods studied in this investigation(USBM, ACF and MCF) could individually estimate the lost gas contents of all shale samples and that the proportion of free gas relative to total gas has a significant effect on the estimation accuracy of the selected method. When the ratio of free gas to total gas is lower than 45%, the USBM method is the best for estimating the lost gas content, whereas when the ratio ranges from 45% to 75% or is more than 75%, the ACF and MCF methods, are the best options respectively.  相似文献   

Internal testing of a numerical model of hillslope–channel coupling using laboratory flume experiments     

Katerina Michaelides  John Wainwright 《水文研究》2008,22(13):2274-2291

The numerical model COUP 2D simulates the hydrological coupling between hillslopes and the river channel during a rainfall event. In order to test the numerical model, a 1:100 scaled laboratory flume which was modified to incorporate lateral hillslope elements, was used to run a series of experiments in which hillslope angle, channel angle, hillslope discharge and channel discharge were the varying parameters. Overall, there were 18 different experimental configurations with three replicates carried out for each condition, leading to a total of 54 experiments. These conditions were then used to parameterize and run COUP 2D. Internal model outputs of flow depth and flow velocity at four cross‐sections in the channel were compared to the measurements made in the physical model for the same parameter conditions. Statistical comparisons of the measured and modelled data were carried out for each experiment and across all experiments, using two goodness‐of‐fit measures—root mean square error and Nash–Sutcliffe coefficient of efficiency—in order to assess the performance of the model over an entire simulation as well as over all the simulations. The main effects on the goodness‐of‐fit measures for flow depth of each experimental variable, as well as the interactions between variables, were evaluated using statistical modelling. The results show that the model captures flow‐depth variations in response to changing channel and hillslope parameters. Statistical modelling suggests that the main effects on model error are cross‐section position, channel angle and channel discharge. Significant interactions also occur between all the channel variables and between the channel variables and hillslope discharge. The results of the testing procedure have significant implications for the consideration of different model components and for the interaction between data‐ and model evaluation. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献