Rapid equivalent dose estimation for eolian dune sands using a portable OSL reader and polymineralic standardised luminescence growth curves: Expedited sample screening for OSL dating     

《Quaternary Geochronology》2014

Portable optically stimulated luminescence (OSL) readers are robust devices that allow rapid determination of luminescence signals of polymineralic coarse-grained samples. To date, however, the utility of portable OSL readers has largely been confined to the construction of luminescence profiles that depict variations of luminescence signal intensities with depth. Because the luminescence signals used to construct such profiles are uncalibrated, it is neither practical to quantitatively compare portable OSL data from different sites nor is it possible to approximate sample ages. Such comparisons could be facilitated by converting portable OSL signals into equivalent doses (D_e). However, determining D_e requires the construction of unique growth curves for each sample; a laborious procedure that negates the rapidity associated with portable measurements. To circumvent that limitation, we construct standardised growth curves (SGCs) using normalized regeneration dose signals obtained using a portable OSL reader from the feldspar component of polymineralic sands from five disparate eolian dune sites in Alberta, Canada. Comparison of SGCs from different samples indicates general congruence and we merge these to construct a regionally applicable curve which we test by comparing the D_e obtained from given samples with that obtained using conventional OSL dating protocols. Results show that, though the uncertainties associated with the portable OSL data are high, the D_e values from the two approaches are linearly proportional. This direct variation enables portable OSL SGC D_e values to be used independently in reconnaissance studies that aim to screen samples for more detailed analysis using standard OSL methods. The affordability of portable OSL readers suggests that the approach could be attractive to researchers who do not have ready access to conventional OSL readers.  相似文献   

城镇有限场地条件下的物探找水试验     

周磊  曹创华  邓专  谭佳良  龙霞 《城市地质》2019,14(1):97-102

为在城区强干扰环境、有限场地条件下进行物探方法找水,特利用等值反磁通瞬变电磁法,在湖南郴州市某城镇进行了野外试验。在地表调查和周边人文环境基础上,常规电测深等找水有效手段在城镇区域难以施工,面对这个难题利用等值反磁通瞬变电磁法进行试验,其利用对偶中心耦合装置消除了收发线圈感应耦合来消除干扰。首先根据地质信息设计了近似南北向的4条剖面,然后进行了发射频率试验并进行单点连续探测,最后利用探测结果绘制了多测道曲线和二维模拟断面等值线图并设计了钻孔。钻探验证结果表明:等值反磁通瞬变电磁法在强干扰、场地受限的城镇区域找水效果较好,是一种值得推广的新方法。  相似文献   

Relating equal smectite content and basal spacing to the residual friction angle of soils     

Abidin Kaya   《Engineering Geology》2009,108(3-4):252-258

The residual shear strength of soils is increasingly becoming an active research area, as landslides occur almost daily all over the world. Since Skempton published his landmark paper in 1964, several researchers proposed correlations between soil index properties and residual friction angle of soils for preliminary estimates. However, recent data gathered from Japanese colluvium soils indicate that previously proposed charts correlating soil index properties with residual friction angle yield very poor estimates. In this study, first previously published Japanese data are reevaluated to establish a theoretical foundation for such correlations. Then, it is shown that equivalent smectite content (ESC) largely controls the residual friction angle of soils. In the second stage of the paper using the data of several researchers, it is shown that there is piecewise linear correlation between the equivalent basal spacing (EBS) and the residual friction angle. This study lays down a foundation for theoretical correlation between EBS and residual friction angle of soils.  相似文献   

Influence of soil non-linearity on the dynamic response of high-speed railway tracks     

Pedro Alves Costa  Rui Calçada  António Silva Cardoso  Anders Bodare 《Soil Dynamics and Earthquake Engineering》2010

The main objectives of this paper are the evaluation of the relevance of the non-linear behaviour of the soil on the track response and the validation of a methodology, which includes these effects through an equivalent linear analysis. The proposed numerical model is based on 2.5D finite/infinite elements method, coupled with an iterative procedure in order to obtain an agreement between the strain levels and the dynamic properties of the materials. In order to validate the model, the case study of Ledsgard was simulated, and the experimental and numerical results of displacements of the track were compared, considering several circulation speeds for the X2000 train. From the results, it is possible to recognize that the stiffness degradation, function of the strain level, plays a relevant role for the case of high-speed railway lines on soft ground. Moreover, the simulations developed with the proposed methodology provided similar results to those observed, independently of the train speed, contrary to what was obtained when the elastic linear model was used.  相似文献   

运用防屈曲支撑的混凝土框架结构的抗震性能研究          下载免费PDF全文

赵杰  孙晓艳  霍林生 《地震工程学报》2015,37(1):100-105

简要介绍地震安全社区的实现途径以及防屈曲支撑的构成和性能参数。运用ABAQUS软件对有无安装防屈曲支撑的钢筋混凝土框架模型进行动力时程分析,总结分析防屈曲支撑对钢筋混凝土框架结构的减震效果。结果表明,防屈曲支撑能大大降低钢筋混凝土框架结构在罕遇地震作用下的层间位移角,提高建筑物抗震性能,使地震安全社区中抗震设防烈度为Ⅶ度的建筑物能够抵御Ⅷ度罕遇地震。  相似文献   

大地等效电容量及其测量方法     

朱旭 《地震》2015,35(4):76-82

在脉冲供电和正弦交流供电地电阻率观测研究中, 大地容性效应会引起测量误差。 本文按照电子学等效电路的方法提出了大地等效电容量的概念, 研究了大地等效电容量的测量方法, 为合理确定脉冲供电参数和减小交流地电阻率测量误差奠定了基础。  相似文献   

深基坑内撑式支护结构计算的综合刚度和双参数法     

陈林靖  戴自航 《岩土力学》2010,31(3):891-895

将吴恒立提出的用于合理计算桩顶作用水平集中荷载的推力桩的综合刚度原理和双参数法,延伸应用于作用有水平分布荷载（土压力）的深基坑围护结构上,提出其杆系有限元数值解法,对一深基坑内支撑式支护结构实例的开挖和支护过程中的各个工况进行了数值模拟分析,由实测位移试算反分析得到了合理的墙-土的综合刚度和地基土抗力双参数,与现有方法计算结果对比表明,该方法能使所得结果更接近实测值。从而说明,综合刚度原理和双参数法的杆系有限元数值解能更为可靠的计算深基坑内支撑式支护结构,具有参考应用价值。  相似文献   

带隅撑胶合木梁-双肢柱框架结构节点抗震性能试验研究     

王柳  陈伯望  刘哲  谢亚孜  刘帅  王怀 《地震工程与工程振动》2022,42(1):210-221

针对胶合木梁-柱节点抗弯能力弱的问题,提出了一种带隅撑的胶合木梁-双肢柱框架结构节点,以提高节点的转动刚度,改善梁柱结构框架的抗侧性能.对3组6个足尺胶合木梁-双肢柱框架结构节点进行了单调和低周反复加载试验以研究节点的抗震性能.结果表明:无隅撑节点类似于铰接,抗弯承载力很小,增设隅撑后显著提高了节点的转动刚度和抗弯承载...  相似文献   

THE EQUIVALENT SLOPE - A NEW METHOD FOR CALCULATING SOIL LOSS FROM IRREGULAR SLOPES     

XiaoguangZHAO HuiSHI Ming＇anSHAO 《国际泥沙研究》2004,19(3):202-209

he slopes in field conditions are always irregular, but the supposed uniform slopes are used in most erosion models. Some studies used several uniform slopes to approximate an irregular slope for estimating soil erosion. This approximation is both time-consuming and weak in physical insights. In this paper, the concept of equivalent slope is presented based on that runoff potential on uniform slope is equal to that of irregular slope, and the equivalent uniform slope is used to estimate soil erosion instead of the irregular slopes. The estimated results of slope-length factors for convex and concave slopes are consistent with those from the method of Foster and Wischmeier, The experiments in the southern part of the Loess Plateau in China confirmed the applicability of the present method. The method is simple and has, to some extent, clear physical meanings, and is applicable for estimating soil erosion from irregular slopes.  相似文献   

消能减震结构设计参数研究与试验验证   总被引：10，自引：1，他引：9  

翁大根  吕西林 《地震工程与工程振动》2004,24(2):150-157

本文就消能减震结构设计参数,即消能部件的支撑刚度、层间最大阻尼力与结构层间屈服力比值等恢复力模型参数的选取进行了讨论。通过对消能装置的耗能特性理论分析,导出了消能装置产生的层间等效阻尼比与这些参数的关系曲线,建议了这些参数的合理取值范围。同时通过对两个消能减震试验结果的分析,验证了本文建议的参数取值的合理性。  相似文献