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本提出了一种离散元和边界元法相耦合的数值法，将粒状土层模拟为二维圈片状集合体来研究，在正常固结和超固结圆片状集合体材料中做了一系列锥顶角为６０°的模拟触探测试。可以从这个模拟试验的微观分析以及传统的连续介质力学角度评价静力触探的机理。试验结果表明，土的加载历史影响了土的破坏机制和剪胀性，但对锥头底部以后的侧压力没有明显影响。此外还发现较细颗粒承受了较高的接触应力，因此更容易在贯入过程中被压碎。 相似文献
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本文利用龙陵地区自1958年至1983年进行的一、二等水准测量结果,对该区地震前、地震时和地震后的地面垂直运动情况进行了分析,发现在地震发生前十多年震中区周围自澜沧江向西已出现了一缓慢的抬升趋势,累计值达46毫米,特别在团田至龙陵区段内变化尤为突出。重力测量结果也出现明显减小,二种手段所获得的前兆现象是一致的。地震后八年,由于地下物质发生了新的调整,形变逐渐趋于平稳,重力变化与垂直形变正好与震前相反,呈现整体下沉,留下了震后永久形变的痕迹。作者认为该区的地震形变周期已接近结束,附近地区所出现的新的变化是另一周期的开始。总结这次龙陵地震的垂直形变和重力变化结果,其变化模式如下:膨胀(上升)——突变(震时)——收缩(下沉)——新的膨胀(上升)。 相似文献
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Conceptual geological models based on geophysical data can elucidate aquifer architecture and heterogeneity at meter and smaller scales, which can lead to better predictions of preferential flow pathways. The macrodispersion experiment (MADE) site, with >2000 measurements of hydraulic conductivity obtained and three tracer tests conducted, serves as an ideal natural laboratory for examining relationships between subsurface flow characteristics and geophysical attributes in fluvial aquifers. The spatial variation of hydraulic conductivity measurements indicates a large degree of site heterogeneity. To evaluate the usefulness of geophysical methods for better delineating fluvial aquifer heterogeneities and distribution of preferential flow paths, a surface grid of two-dimensional ground penetrating radar (GPR) and direct current (DC) resistivity data were collected. A geological model was developed from these data that delineate four stratigraphic units with distinct electrical and radar properties including (from top to bottom) (1) a meandering fluvial system (MFS); (2) a braided fluvial system (BFS); (3) fine-grained sands; and (4) a clay-rich interval. A paleochannel, inferred by other authors to affect flow, was mapped in the MFS with both DC resistivity and GPR data. The channel is 2 to 4 m deep and, based on resistivity values, is predominantly filled with clay and silt. Comparing previously collected hydraulic conductivity measurements and tracer-plume migration patterns to the geological model indicates that flow primarily occurs in the BFS and that the channel mapped in the MFS has no influence on plume migration patterns. 相似文献
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1 INTRODUCTIONThe tUrbidity maximum with suspended sediment concentrations, which exhibits higher concentrationthan either in the river or in the adjoining sea, gommonly occurs in many tidal estUaries. It often ingrateseither toward the land or toward the sea due to the change in the runoff in the high and low dischargeseasons or over a tidal cycle (Alien, 1980; Gelfenbaum, 1983; Uncles et. al., 1994). ms phenomenonaffects the siltation both in the harbor and navigation channel (Dbereine… 相似文献
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Borja A Josefson AB Miles A Muxika I Olsgard F Phillips G Rodríguez JG Rygg B 《Marine pollution bulletin》2007,55(1-6):42-52
The European Water Framework Directive (WFD) establishes a framework for the protection and improvement of transitional and coastal waters; its final objective is to achieve at least 'good water status' for all waters, by 2015. The WFD requires Member States (MSs) to assess the Ecological Status (ES) of water bodies. This assessment will be based upon the status of the biological, hydromorphological and physico-chemical quality elements, by comparing data obtained from monitoring networks to reference (undisturbed) conditions, and then deriving an Ecological Quality Ratio (EQR). One of the biological quality elements to be considered is the benthic invertebrate component and some structural parameters (composition, diversity and disturbance-sensitive taxa) must be included in the ES assessment. Following these criteria, several approaches to benthic invertebrate assessment have been proposed by MSs. The WFD requires that these approaches are intercalibrated. This contribution describes the comparison of the different methodologies proposed by United Kingdom, Spain, Denmark and Norway. Results show a high consistency between the approaches, both with regard to determining the EQR and boundary settings for the ES. 相似文献
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Costa AB Novotny EH Bloise AC de Azevedo ER Bonagamba TJ Zucchi MR Santos VL Azevedo AE 《Marine pollution bulletin》2011,62(8):1883-1890
The impact of human activity on the sediments of Todos os Santos Bay in Brazil was evaluated by elemental analysis and 13C Nuclear Magnetic Resonance (13C NMR). This article reports a study of six sediment cores collected at different depths and regions of Todos os Santos Bay. The elemental profiles of cores collected on the eastern side of Frades Island suggest an abrupt change in the sedimentation regime. Autoregressive Integrated Moving Average (ARIMA) analysis corroborates this result. The range of depths of the cores corresponds to about 50 years ago, coinciding with the implantation of major onshore industrial projects in the region. Principal Component Analysis of the 13C NMR spectra clearly differentiates sediment samples closer to the Subaé estuary, which have high contents of terrestrial organic matter, from those closer to a local oil refinery. The results presented in this article illustrate several important aspects of environmental impact of human activity on this bay. 相似文献
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一种新的空间模型表达式由表述地震样本的点集组成。该方法基于全集合形态测量，称为明科夫斯基函数。它包含了拓扑化特征和几何描述，以确定空间集的含量、形状和连通性。该方法对小样本、独立统计假定，全球以及区域形态数据的量额也是有效的。以东天山地震目录为例说明此方法 相似文献
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