芯吸效应与非饱和土柱试验

介绍了非饱和土柱试验构造技术,重点介绍了芯吸技术的应用,结合研究实际,给出了此方面的初步研究成果,研究显示芯吸技术是一种构造非饱和土柱试验的较好技术,但仍需进一步开展工作。     

荒漠下垫面陆面过程和大气边界层相互作用敏感性实验

建立了一个研究荒漠下垫面陆面物理过程与大气边界层相互作用的模式. 模拟了荒漠下垫面的土壤环境物理、地面热量通量、蒸发、蒸散及大气边界层结构特征.并对主要的环境物理参数进行了敏感性实验.结果表明,本模式能合理地模拟荒漠下垫面地表热量平衡、土壤体积含水量、地表植被蒸发散阻抗、地表水汽通量日变化和湍流交换系数、湍流动能、位温和比湿廓线等.该模式还可进一步应用于研究区域陆面物理过程与大气边界层相互作用机制,及与中尺度大气模式耦合用于区域环境生态和气候的研究.     

Stokoe扭转剪切／共振柱仪性能及试验

本文简介了Stokoe扭剪/共振拄仪的结构、性能、原理、方法及通过各种试验方法所获得的部份成果。     

Determination of soil impedance functions from vibration-test response of a circular foundation

The paper presents the results of the determination from vibration tests of impedance functions for a concrete basemat of a one-quarter scale model of a nuclear power-plant containment building. The tests were designed to excite all rigid-body modes of the foundation. In addition to the impedance functions for all the rigid-body degrees of freedom, natural frequencies and damping for the fundamental modes were estimated. Comparison of the test-determined modal characteristics with corresponding analytical ones based on the Lysmer analog shows that though the latter gives natural-frequency estimates of the right order of magnitude, it does not give acceptable estimates of the damping coefficient. Analytical impedance functions based on a model of a rigid-plate on an elastic half-space were found to have the sam trend as the test-determined ones at lower frequencies, but not at higher frequencies. The utility of test data for verification of analysis is discussed.     

Dynamic poroelastic soil column and borehole problem analysis

The one-dimensional dynamic column and borehole problems of soil mechanics formulated on the basis of the poroelastic theory of Vardoulakis and Beskos are solved analytically-numerically. The quasi-static counterparts of these problems are analysed as special cases of the dynamic ones. Use of Laplace transform with respect to time reduces the column and borehole problems to ordinary differential equations with constant and variable coefficients, respectively. The transformed solution of these problems is obtained analytically for the column and by finite differences for the borehole problem, and after, a numerical Laplace transform inversion produces the time domain response. Both a suddenly applied and a harmonically varying with time load are considered. It is concluded that the significance of inertial effects depends on the kind of loading and that the degree of saturation for the nearly saturated case greatly affects the response.     

Chi-square tests for markov chain analysis

Markov chain analysis has become a popular and useful technique for the evaluation of stratigraphic information. Field data on frequencies of facies transitions are first assembled in a transition count matrix. Observed frequencies can be compared statistically with frequencies expected if no order, or memory, exists in the stratigraphic sequence. Two chi-square (²) tests have been proposed for this purpose. One of the previously proposed ² tests was observed to give anomalously large values of the test statistic during another study. This unsatisfactory behavior is verified here. Limiting values of the two ² tests (from tables) are compared with the distribution of values for both test statistics obtained by analyzing many random matrices generated by a simple computer program. In all cases, the logarithmic ² test, suggested by several previous authors, fails to provide any meaningful assessment of the presence or absence of order in stratigraphic sequences evaluated. Further use of this test should therefore be avoided.     

砂-粉混合料剪切波速的弯曲元及共振柱试验对比试验研究

为探讨测试方法、试验条件以及级配特征对砂-粉混合料剪切波速的影响，对具有不同细粒含量FC，相对密度D_r以及初始有效围压$\sigma_{3 \mathrm{c}}^{\prime}$的砂-粉混合料进行弯曲元和共振柱试验。结果表明:当D_r =35%或50%时，剪切波速V_s随FC的增大先减小后增大；当D_r =60%时，V_s随FC的增大而减小；弯曲元试验测得的V_s明显大于共振柱试验测得的V_s，随着FC的增大，弯曲元试验与共振试验得到的V_s差值逐渐减小，而当FC＞20%时，两种试验得到的V_s基本相同。在考虑V_s弥散性之后，不同FC的混合料弯曲元与共振柱试验得到的V_s结果具有较好的一致性。基于Hardin模型建立的砂-粉混合料V_s预测方法具有较好的预测效果。     

An annual wet sulfate deposition index

 Averages of annual wet deposition data are often used as an indicator of acid amounts in the atmosphere. From the view point of statistics, the average is a meaningful estimator only for identically distributed data with specific types of probability distribution. Wet deposition data usually carry seasonal trends. To learn about year-to-year concentration changes, a more accurate summary information accommodating the trend is thus necessary. This paper suggests a quantity (index) describing the annual wet deposition of SO₄ and formulas for its calculation. The formulas are in some sense optimal in case the data can be considered independent, lognormally distributed and have a time dependent trend. Generalization of these assumptions is also discussed. The index is derived from specific features of the average applied to data with lognormal distribution. The theory is utilized to analyze a set of SO₄ precipitation concentrations observed in the Ontario region. A work sponsored by the Atmospheric Environment Service in Toronto and the Canadian NSERC. I want to thank the Ontario Ministry of the Environment for provision of the data used in this study and the anonymous referee for a number of comments that resulted in improvement of the final presentation.     

A Semi-active Oleodynamic Damper for Earthquake Control. Part 1: Design, Manufacturing and Experimental Analysis of the Device

Within an experimental research project financed by the European Union, a prototype semi-active oleodynamic damper has been conceived and manufactured in Italy starting from technology today currently adopted for passive energy dissipation devices. The new device was obtained by just adding two identical electrovalves and an external oleodynamic circuit to a commercially available silicon oil damper. Static and dynamic tests performed on the damper allowed to determine its stiffness and energy dissipation characteristics when passively operating (both electrovalves are always closed or open) as well as to measure the release and insertion times of the electrovalves during opening and closing tests. The experiments indicated a non-linear quadratic viscous constitutive law for the damper as well as operating times of electrovalves in good agreement with specifications given by the manufacturer. A semi-active assembly composed by the prototype damper and external flexible steel plates was then mounted and subjected to further tests in order to definitively characterize through a simple mathematical model the entire system and to completely identify its operating delays and their physical sources. This revised version was published online in July 2006 with corrections to the Cover Date.