泥石流堆积物中细颗粒含量与渗透系数关系试验研究     

杨进兵  陈兴长  汪惠  田小平  贾利蓉 《岩土力学》2016,37(11):3184-3190

泥石流拦砂坝通常建造在沟床堆积物上。泥石流堆积物的渗透性是影响坝底扬压力的关键因素。目前关于土体渗透性的研究主要集中于无黏性粗粒土,对泥石流堆积物这种宽级配土体渗透性的研究比较缺乏。选择北川县泥石流沟床堆积物作为试验材料,通过渗透试验,确定了影响宽级配土渗透性的细颗粒上限粒径;在此基础上,通过试验研究了细颗粒含量与渗透系数的关系。结果表明,泥石流堆积物中粗颗粒仅起骨架作用,细颗粒才是决定其渗透性能的关键;显著影响宽级配土渗透性的细颗粒上限粒径为0.1 mm;细颗粒（<0.1 mm）含量与渗透系数呈负指数关系,并且当细颗粒含量超过20%以后,泥石流堆积土的渗透性趋于稳定。  相似文献   

时间二阶积分波场的全波形反演   总被引：4，自引：4，他引：0       下载免费PDF全文

陈生昌  陈国新 《地球物理学报》2016,59(10):3765-3776

通过对波场的时间二阶积分运算以增强地震数据中的低频成分,提出了一种可有效减小对初始速度模型依赖性的地震数据全波形反演方法—时间二阶积分波场的全波形反演方法.根据散射理论中的散射波场传播方程,推导出时间二阶积分散射波场的传播方程,再利用一阶Born近似对时间二阶积分散射波场传播方程进行线性化.在时间二阶积分散射波场传播方程的基础上,利用散射波场反演地下散射源分布,再利用波场模拟的方法构建地下入射波场,然后根据时间二阶积分散射波场线性传播方程中散射波场与入射波场、速度扰动间的线性关系,应用类似偏移成像的公式得到速度扰动的估计,以此建立时间二阶积分波场的全波形迭代反演方法.最后把时间二阶积分波场的全波形反演结果作为常规全波形反演的初始模型可有效地减小地震波场全波形反演对初始模型的依赖性.应用于Marmousi模型的全频带合成数据和缺失4Hz以下频谱成分的缺低频合成数据验证所提出的全波形反演方法的正确性和有效性,数值试验显示缺失4Hz以下频谱成分数据的反演结果与全频带数据的反演结果没有明显差异.  相似文献   

Vertical acceleration demands on column lines of steel moment‐resisting frames          下载免费PDF全文

Lukas Moschen  Ricardo A. Medina  Christoph Adam 《地震工程与结构动力学》2016,45(12):2039-2060

In this paper, vertical peak floor acceleration (PFA_v) demands on elastic multistory buildings are statistically evaluated using recorded ground motions. These demands are applicable to the assessment of nonstructural components that are rigid in the vertical direction and located at column lines or next to columns. Hence, PFA_v demands of the floor system away from column lines and their effects on nonstructural components are not addressed. This study is motivated by the questionable general assumption that typical buildings are considered to be relatively flexible in the horizontal (lateral) direction but relatively rigid in the vertical (longitudinal) direction. Consequently, only few papers address the evaluation of vertical component acceleration demands throughout a building, and there is no consensus on the relevance of vertical accelerations in buildings. The results presented in this study show that the vertical ground acceleration demands are amplified throughout the column line of a steel frame structure. This amplification is in many cases significant, depending on the vertical stiffness of the load‐bearing system, damping ratio, and the location of the nonstructural component in the building. From these outcomes it can be concluded that the perception of a rigid‐body response of the column lines in the vertical direction is highly questionable, and further research on this topic is required. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

低解吸气量页岩气组分校正方法探讨          下载免费PDF全文

赵立鹏 《中国地质调查》2016,3(6):75-78

通过现场解吸试验,采用气相色谱等测试方法,对低解吸气量页岩气组分测定结果校正方法进行了研究。在常规现场解吸试验操作基础上增加校正实验,结合理想气体状态方程,总结归纳出校正参数及适用性研究。结果显示,当解析气量较少时,解吸罐内残留空气对组分测定结果的影响较大,排除解吸罐中空气的影响后,解吸气组分甲烷体积分数普遍增加12.23%~54.44%。研究表明,对低解吸气量页岩气组分结果进行校正十分必要。  相似文献   

基于核主成分元胞模型的城市演化重建与预测   总被引：3，自引：1，他引：2  

冯永玖  刘妙龙  童小华  刘艳  韩震 《地理学报》2010,65(6):665-675

通过元胞自动机(CA)模拟和重建城市演化的复杂非线性过程,对于城市土地利用规划和决策具有指导意义。利用传统线性方法获取的地理CA转换规则,较难刻画城市演化的时空动力学过程。基于核主成分分析方法(KPCA),通过核函数映射,在高维特征空间下不仅能够对多重共线的空间变量进行非线性降维,且由此建立的地理元胞模型KPCA-CA参数物理意义明确,能够较好地体现城市化过程的非线性本质。基于GIS环境下自主研发的地理模拟框架SimUrban,利用该KPCA-CA模型模拟和重建了快速城市化区域上海市嘉定区1989-2006年城市演化过程,并预测了研究区2010年的城市空间格局。模拟结果显示,嘉定区城市主要沿中心区域及主干道路而扩展,体现了KPCA方法提取的前两个主成分的作用,与城市实际发展情况相符。利用混淆矩阵和面积控制精度等指标,对模拟结果进行了评价,得到总体精度为80.67%、Kappa系数为61.02%,表明模拟结果与遥感分类结果及统计结果符合程度较好;与传统基于线性方法的地理CA模型比较,KPCA-CA模型模拟结果精度更高。  相似文献   

基于中国规范的剪力墙构件性能指标限值初探     

劳晓春  韩小雷  黄超 《地震工程与工程振动》2010,30(4)

本文主要论述了基于中国规范的剪力墙构件性能指标限值的研究思路和方法。首先根据规范的相关震害概念,提出小震、中震、大震三种地震水准下剪力墙构件的基本性能要求,然后通过对剪力墙构件的破坏形态及其影响因素的分析,给出剪力墙构件的分类及其性能指标限值的确定方法,并讨论了对结构中的剪力墙进行构件划分的方法,最后对剪力墙构件性能指标限值合理性的检验进行了论述。  相似文献   

Parameter variability of the observed periodic oscillations of polar motion with smaller amplitudes     

J. Höpfner 《Journal of Geodesy》2003,77(7-8):388-401

Compared to the Chandler and annual wobbles, the higher-frequency components of polar motion (PM) have substantially smaller amplitudes. Therefore, their study has had to wait until higher-quality time series with high temporal resolution, as measured by space geodetic techniques, have become available. Based on the combined Earth orientation series SPACE99 computed by the Jet Propulsion Laboratory (JPL) from 1976 to 2000 at daily intervals, the periodic PM terms, in particular at the quasi-biennial, 300-day, semi-Chandler, semi-annual, 4-month, 90-day, 2-month and 1.5-month periods, have been separated by band-pass filtering and it has been found that the persistence of oscillations becomes less with increasing frequency. In order to quantify and better describe the parameter variability of these PM components over time, the radii, direction angles and period lengths were computed from the periodic terms filtered out from the time series. The results clearly show the characteristics and time evolution of the periodic PM components. The largest elliptic oscillation is the semi-annual wobble with a maximum semi-major axis of up to 13 mas (milliarc seconds). The other wobbles are smaller. They have maximum semi-major axes of between 3 and 8 mas. If the oscillations have period lengths of 4 months and less, then they are elapsed not only progradly, but also retrogradly. AcknowledgementsThis paper was presented at the 27th General Assembly of the European Geophysical Society in Nice, France, 22–26 April 2002. Thanks go to Kevin Fleming for his linguistic advice. The author would also like to thank Barbara Koaczek for suggesting some valuable improvements.  相似文献   

Comparison of taste components between triploid and diploid oyster   总被引：1，自引：0，他引：1  

Lin?HongEmail author  Wang?Xiaoxue  Zhang?Bin  Tang?Haiqing  Xue?Changhu  Xu?Jiachao 《中国海洋大学学报(英文版)》2002,1(1):55-58

The main taste components of triploid and diploid oyster (Crassostrea gigas) were compared. Free amino acids, inosine monophosphate, succinate, trimethylamine oxide and betaine in fresh and boiled extractives were analyzed. The protein, lipids, glycogen, moisture and ash, which may affect the flavour, were evaluated. In boiled extractives, the amino acids were 394.1 mg(100 g)⁻¹ in diploid and 183.5 mg(100 g)⁻¹ in triploid. However, in fresh oyster extractives, they were 320.0 mg(100g)⁻¹ and 147.3 mg(100g)⁻¹ respectively. The inosine monophosphate in triploid was 44% more than that in diploid, and a little difference existed in the content of trimethylamine oxide between them. The contents of these taste components were the basis for taste flavour pattern determination.  相似文献   

Quadratic covariance estimation and equivalence of predictions     

Ronald Christensen 《Mathematical Geology》1993,25(5):541-558

This article illustrates the use of linear and nonlinear regression models to obtain quadratic estimates of covariance parameters. These models lead to new insights into the motivation behind estimation methods, the relationships between different methods, and the relationship of covariance estimation to prediction. In particular, we derive the standard estimating equations for minimum norm quadratic unbiased translation invariant estimates (MINQUEs) from an appropriate linear model. Connections between the linear model, minimum variance quadratic unbiased translation invariant estimates (MIVQUEs), and MINQUEs are examined and we provide a minimum norm justification for the use of one-step normal theory maximum likelihood estimates. A nonlinear regression model is used to define MINQUEs for nonlinear covariance structures and obtain REML estimates. Finally, the equivalence of predictions under various models is examined when covariance parameters are estimated. In particular, we establish that when using MINQUE, iterative MINQUE, or restricted maximum likelihood (REML) estimates, the choice between a stationary covariance function and an intrinsically stationary semivariogram is irrelevant to predictions and estimated prediction variances.  相似文献   

Some properties of principal component scores     

J. Trochimczyk  F. Chayes 《Mathematical Geology》1978,10(1):43-52

Commonly used methods for calculating component scores are reviewed. Means, variances, and the covariance structures of the resulting sets of scores are examined both by calculations based on a large set of electron microprobe analyses of melilite (supplied by D. Velde)and by a survey of recent geological applications of principal component analysis. Most of the procedures used to project raw data into the new vector space yield uncorrelated scores. In exceptions so far encountered, correlations between scores seem to have been occasioned by the use of unstandardized variables with components calculated from a correlation matrix. In a number of cases substantive interpretations of such correlations have been proposed. A different set of correlations results for the same data if scores are computed from standardized variables and components based on the covariance matrix. If unscaled components are rotated by the varimax procedure, the result is a return to the original space. In the work reported here, nevertheless, scores calculated from varimax-rotated scaled vectors are uncorrelated.  相似文献