测氡在滑坡研究中的应用

测氡是一种放射性地球物理方法,利用滑坡体与其周边岩土体的结构差异,应用测氡可对滑坡进行勘探,对滑坡的结构特征进行研究,达到节约投资,缩短勘探时间的目的,并可与地质分析相互验证,为工程应用提供依据。     

基于新息正交性自适应滤波的惯性/地磁组合导航方法

针对量测值存在野值以及量测噪声统计特性发生变化导致基于滤波的惯性/地磁组合导航系统滤波精度和稳定性下降的情形,提出一种基于新息正交性自适应滤波的惯性/地磁组合导航方法。首先通过新息过程正交性是否丧失进行量测值的野值辨识,然后对含野值量测值加权以减弱野值对系统滤波的不利影响,随后设置滑动窗口实时监测滤波器新息的动态变化以修正量测噪声方差,进而调整滤波器增益,提高系统的适应能力。仿真结果表明:在量测值存在野值以及噪声统计特性发生变化时,该方法能够抑制惯导系统的累积误差,并且得到的标准差指标相比标准EKF缩减至1/4左右,提高了组合导航系统的稳定性和适应性。     

红外热像法快速确定45#钢的疲劳性能

红外热像法作为一种无损、实时及非接触的测试技术,在疲劳研究领域得到广泛的应用.该方法克服了传统试验方法周期长、所需试验试件和费用多的困难.本文利用红外热像仪测量了疲劳试验中45#钢试件表面温升变化,根据红外疲劳极限快测法得到疲劳极限,并由累积塑性功和塑性温升之间的相关假设,推导出了试件疲劳寿命的计算公式.试验结果表明,红外热像法可以快速、准确地确定材料的疲劳极限和S-N曲线.     

北秦岭地带断裂活动性氡气测试成果分析评价

采用断层气体测试方法, 对北秦岭地带主要断裂及其活动性进行了测试, 首次提出了该区断裂活动性测氡成果判别的相对标准。进而对区内典型的氡气测试成果剖面作了解释分析, 并判别了断裂 (带)的相对活动强弱与活动水平等有关断裂活动性问题。最后, 简要地探讨了在北秦岭地区未来可持续发展中断裂 (带)对其模式及格局的影响。     

基于模糊自适应强跟踪滤波的惯性/地磁组合导航方法

针对在量测噪声统计特性发生变化时,基于滤波算法的惯性/地磁组合导航系统存在精度下降甚至发散的问题,提出了一种基于模糊自适应强跟踪滤波算法的惯性/地磁组合导航方法,该方法通过制定模糊规则,实时监控系统残差变化,自适应地调整柔化因子的大小,即增强了滤波器对时变噪声的跟踪能力又保证了滤波器处理当前信息的能力.仿真结果表明:该方法能够很好地抑制纯惯性导航系统随时间累积的误差,而且在量测噪声统计特性发生变化时,系统误差没有出现明显的跳变,保证了整个导航系统的精度,提高了系统的鲁棒性.     

光测力学的研究现状和展望

光测力学是实验力学的一个重要分支,在工程中得到了广泛的应用。本文简要地回顾了上海光测力学三十来年的进展情况,内容涉及普通的光弹性以及现代的光测力学在基本原理、测试技术与方法的研究和在工程、生物力学、断裂力学中应用的情况,并讨论了目前研究的重点与前景。     

第一讲 应变计和应变电测技术

电测技术是实验应分析方法中的一种最基本的方法,也是应用最广泛的一种。电测技术对科学技术和工业的发展,起着十分重要的作用。为了帮助读者提高电测技术的水平和了解其发展动向,自本期起,连载电测技术系列讲座。讲座共分六讲,包括应变计和应变电测技术,应变仪,数据处理技术,静、动态测量基本技术,工程应用和在新学科中的应用。每讲都由编辑部聘请专家撰写,希望对广大读者有所助益,并欢迎来自读者的反应。     

中国实验力学进展

本文试图对我国实验力学工作者在基础研究和应用研究方面所取得的成就作个简要的回顾。本文将涉及我国下列几方面近期内的工作;应变电测技术、光测力学、图象处理技术、声学方法、实验力学在断裂力学和生物力学中的应用。     

GPS测姿技术在航天测量船的应用分析

简要介绍了航天测量船测姿系统的特点,概要分析了GPS测姿技术的原理,着重论述了GPS测姿技术在测量船上应用的可行性。     

平面刚体系统的参数预调节保辛算法

保辛积分方法在约束哈密顿系统中有着重要的应用,是因为其在长时间仿真中表现出极好的稳定性。然而随着仿真时长增加,保辛格式通常具有较大的相位误差累积。本文提出了一种平面多刚体系统的参数预调节保辛积分方法。通过推导具有待定参数的改进的拉格朗日方程,并将其与已有保辛格式相结合并预先调节相关参数取值,可以大幅降低数值解的相位误差。理论分析与数值结果表明参数预调节保辛积分方法不仅保持了辛结构,而且具有很低的相位误差累积。因此,参数预调节保辛积分方法可应用于长时间仿真分析。     

氡射气测量在西安地裂缝勘察中的应用研究

为了避免大量开挖揭露工作量, 加快地裂缝的勘察速度, 研究出一种简便易行的探测方法是目前西安地裂缝勘察中迫切需要解决的问题。本文研究了氡射气测量在西安地裂缝勘察应用的地质基础, 结合近十几年工程勘察实践, 讨论了氡射气异常的特征, 分析了氡射气的探测效果, 结果认为：氡射气测量在西安地裂缝探测中的有效率为：８０％左右。     

Laboratory,Field and Modeling Studies of Radon‐222 as a Natural Tracer for Monitoring NAPL Contamination

The recently developed natural radon tracer method has potential as a rapid, lowcost, nondestructive, and noninvasive method for quantifying NAPL contamination. In the subsurface, radon222 (radon) is produced by the decay of naturally occurring radium226 contained in the mineral fraction of aquifer solids. In groundwater radon occurs as a dissolved gas, with a halflife of 3.83 days. In the absence of NAPL, the radon concentration in groundwater quickly reaches a maximum value that is determined by the mineral composition of the aquifer solids, which controls the rate of radon emanation. In the presence of NAPL, however, the radon concentration in the groundwater is substantially reduced due to the preferential partitioning of radon into the organic NAPL phase. A simple equilibrium model and supporting laboratory studies show the reduction in radon concentration can be quantitatively correlated with residual NAPL saturation. Thus, by measuring the spatial distribution in radon it may be possible to identify locations where residual NAPL is present and to quantify the NAPL saturation. When the basic processes of partitioning, radon emanation from the aquifer solids, and firstorder decay are incorporated into an advective/dispersive transport model, good agreement is obtained with the results of laboratory and field experiments. Model sensitivity analyses shows many factors can contribute to the radon concentration response, including the length of the NAPL zone, NAPL saturation, groundwater velocity, porosity, and radon emanation. Thus, care must be taken when applying the radon method to locate and quantify NAPL contamination in the subsurface.     

The removal of radon from CO2 for use in14C age measurements

Summary It is shown that traces of radon can be extracted from carbon dioxyde by pumping off from solid CO₂. Since the volatility of radon is smaller than the volatility of CO₂, special care has to be taken during condensation in order to avoid occlusion. Enrichment of radon at the wall where the CO₂ condenses is avoided by stirring the gas. An estimate of the fraction of radon, adsorbed on the wall, demonstrates the necessity of performing the condensation at about −80°C. At −180°C the greater part of the radon is adsorbed; consequently it is occluded if CO₂ is added. The method can be used only in those cases where the volatility of the contaminant is not too much lower than of CO₂, and where the molecules of the contaminant do not fit well into the lattice of solid CO₂. The present purification is much faster than the chemical purification described previously 1) 2). Our thanks are due to Drs Ir H. Boerboom and Mr F. Monterie, Laboratory of Massspectrometry, Amsterdam, for adapting the mass-spectrometer to the problem and for the measurement of the samples.     

Identification of radon transfer velocity coefficient between liquid and gaseous phasesIdentification de la vitesse de transfert de radon entre une phase liquide et une phase gazeuse

Radon transfer between a liquid phase and a gaseous phase is modelled by a Robin's condition (radon flux at the common interface is expressed as function of radon concentrations in the two phases). This condition involves two constants: Ostwald's coefficient (α) and the transfer velocity coefficient (β). Assuming the value of α is known, a method is proposed to determinate the value of β, by studying the radon transfer phenomenon at the laboratory scale. Knowing the initial radon concentrations, the experiment consists in measuring how long the radon flux passes through the common interface. In this stabilisation time radon transport is governed in each phase by diffusion and disintegration. Then, determination of β is equivalent to solving an inverse problem formulated using measured data. A numerical procedure is developed to solve this problem. To cite this article: D.-G. Calugaru, J.-M. Crolet, C. R. Mecanique 330 (2002) 377–382.     

Comparison Between Equivalent Continuum and Discrete Crack Models of Transient Radon Transport at the Soil–Building Foundation Crack Interface Using TOUGH2/EOS7Rn

In the framework of radon risk management in France, it is necessary to enhance knowledge on radon transfer from its source to exposure areas (e.g., buildings) by developing simple, accurate, numerical models for transient radon transport in three-dimensional (3D) unsaturated porous materials. The equivalent continuum model (ECM) of flow and transport at the interface between the soil and cracks (fissures) in a building foundation (e.g., slab on grade, basement) is attractive, since equivalent (effective) continuum properties assigned to model cells can represent the combined effect of individual cracks and solid matrix of the cracked concrete of the foundation (slab and blocks walls). Although the ECM approach based on the volume averaging method has been used to model flow and transport through cracks at the soil–building interface, it has never been verified numerically. Thus, the goal of the present work is to develop an ECM using this averaging method and to quantify its uncertainties based on its comparison to an accurate numerical discrete crack model (DCM) for flow and transport in the crack. As a first step, the DCM implemented in the TOUGH2/EOS7Rn module has been verified numerically through a comparison to a reference 3D steady-state numerical solution for radon transport into a house with basement under constant negative pressure. Then, 3D results of the DCM and ECM approaches were compared, under time-dependent indoor–outdoor pressure differentials conditions, for two crack line configurations in the basement slab floor and two different soil configurations with different soil permeability and radium \(^{226}\)Ra mass content values. Results of this comparison show that, for a homogeneous soil configuration, discrepancies between ECM and DCM simulated indoor radon activity concentrations decrease with the increase in soil permeability, regardless crack line configuration in the slab floor and soil radium mass content. However, ECM uncertainties were not within the range of absolute errors on measured radon concentration for the higher soil permeability \((1\times 10^{-9}, 1\times 10 ^{-8} \hbox { m}^{2})\) and the higher \(^{226}\hbox {Ra}\) mass content values (4500 \(\hbox {Bq\;kg}^{-1})\), especially for high radon pics induced by sudden increase in indoor air pressure drop. Regardless soil \(^{226}\hbox {Ra}\) mass content and crack line configuration in the slab floor, the ECM showed to be conservative for the two-layered soil configuration with the presence of aggregates beneath the slab foundation, generally practiced in buildings constructions.     

Diffusion of Randon in Porous Media Saturated with Gels and Emulsions

The effective diffusion coefficient of radon was determined in polymer/silicate gels and clay suspension used as sealing materials in environmental protection. On the basis of the experimental findings, it was concluded that both materials drastically decrease the convective mass transport in porous media. Simultaneously, the effective diffusion coefficient was reduced significantly. Thus, the radon flux might be decreased by 5 to 6 orders of magnitude in porous systems originally having gas or low water saturation by injection of gel-forming materials or placement of clay suspensions. At high water saturation, however, the diffusion transport of radon can be slightly restricted in consolidated and unconsolidated porous media. The laboratory studies may firmly allow us to conclude that hydrogels and clay suspensions are prospective candidates in an integrated environmental technology to be used for restriction of radon migration in subsurface regions.     

汶川地震震后大成都地区断裂带活动性氡气测量分析评价

本文运用活动断裂剖面上的土壤氡气浓度测量,对大成都地区断裂的位置、范围和活动性进行监测,监测结果表明汶川地震对大成都地区断裂带有较大的影响。通过对北川断裂虹口剖面、彭灌断裂小渔洞剖面、彭灌断裂中坝剖面、彭灌断裂白鹿剖面以及新津-蒲江断裂剖面进行监测,从测量结果分析可知：断裂剖面土壤氡浓度背景高于无断裂带地区,且受地震影响较大,距汶川地震震中越近,断裂剖面土壤氡浓度值越高;断裂剖面氡浓度异常阈值与背景值之比均不大于3,最大值与背景值之比均小于5。结合测量地点的地形、表层土壤结构等地质条件,对大成都地区震后活动断裂的相对活动性的强弱进行科学评价,认为目前大成都地区并无活动性极强的断裂,且北川断裂与新津-蒲江断裂的活动性高于彭灌断裂。     

某区放射性环境地质评价研究

在某区拟建隧洞沿线的条带状区域进行了放射性环境地质调查。共采集和分析岩土(芯)放射性核素镭、钍、钾样品111组,地下水和地表水样品5组;现场测定岩土放射性样品392组。结果表明,在该区域内,某煤矿巷道中煤层和砂岩接触带煤、砂岩中镭-226比活度出现高值异常,相应的内照射指数和外照射指数也超过相关标准中规定的放射性核素限量,该异常带环境γ辐射剂量率也较高。镭-226的富集可能源于煤中有机质对放射性核素的吸附和解吸过程。建议在隧道选线过程中尽力避让这一地段。