基桩桩身完整性检测中的影响因素浅析

近年来,桩基础的广泛应用带动了检测技术的进一步发展,基桩检测技术也越来越受到人们的重视.本文从反射波理论出发介绍了反射波法的基本原理,指出了桩身完整性的判定标准,并系统的分析了基桩检测中的多种影响因素.本文通过分析和总结,指出了反射法测桩存在的不足,并提出了相应的注意事项及解决办法.     

模糊关系数据库中数据的特点和完整性研究

从模糊集合的基本理论出发,分析了模糊关系数据库的数据特点,给出了模糊关系的形式化描述,对由于模糊关系将传统关系的范围由二值逻辑论扩展到模糊集合论而引起的问题进行了探讨,特别对模糊数据库数据的完整性作了较深入的研究。     

Structural health monitoring of bridges in the State of Connecticut

A joint effort between the Connecticut Department of Transportation and the University of Connecticut has been underway for more than 20 years to utilize various structural monitoring approaches to assess different bridges in Connecticut. This has been done to determine the performance of existing bridges, refine techniques needed to evaluate different bridge components, and develop approaches that can be used to provide a continuous status of a bridge＇s structural integrity. This paper briefly introduces the background of these studies, with emphasis on recent research and the development of structural health monitoring concepts. This paper presents the results from three different bridge types： a post-tensioned curved concrete box girder bridge, a curved steel box-girder bridge, and a steel multi-girder bridge. The structural health monitoring approaches to be discussed have been successfully tested using field data collected during multi-year monitoring periods, and are based on vibrations, rotations and strains. The goal has been to develop cost-effective strategies to provide critical information needed to manage the State of Connecticut＇s bridge infrastructure.     

生物完整性在时间尺度趋势分析中的偏差和校正研究——以松花江流域为例

以松花江流域为对象,利用2012-2015年底栖动物调查数据及生物完整性指数(index of biotic integrity,IBI)评价结果,定量分析并阐释了IBI(基于参照位点法)在时间尺度趋势分析中产生的偏差和影响,提出采用校正系数r(r表示参数赋分计算中,比较年参数基础值相对初始年参数基础值的倍数)及初始年数据对IBI结果进行校正的方法.研究表明,正向参数(干扰越大分值越低的参数)参照组2013-2015比较年的值较初始年(2012年)呈现不同程度升高,反向参数(干扰越大分值越高的参数)受损组值呈现下降.同时,正向参数和反向参数的r值分别分布在1.1～4.9和0.7～0.8之间,参照组/受损组参数的95th年度间变化显著,参数赋分环节的记分偏差不可忽略.在评价标准划分环节中,最差及优良区域占比的差异达10.0%～13.4%,偏差对趋势分析的干扰显著.2012-2015各年度IBI经校正后,评价达良好-优状态的区域占比较校正前高4.3%～13.3%,评价为很差状态的区域占比较校正前低6.7%～30.0%.完整性评价中关键环节产生的偏差可显著影响时间尺度趋势的分析和判定,基于校正的评价方法可以初步解决完整性评价在趋势分析中产生的偏差干扰问题.     

3维GIS在管道完整性管理中的应用

介绍了大庆油田工程有限公司在管道完整性管理信息化系统建设方面的成果,重点介绍3维GIS技术在完整性管理中的应用,以3维GIS作为工具进行工程地质灾害风险分析与预测的实现方法。     

柳州市白云岩区钻孔取芯判断岩体完整性研究

建筑岩基的岩体完整性划分是否准确直接影响到建筑物的安全性、施工的可行性及经济性,文章通过钻孔取芯观察岩石破裂面,研究岩质坚硬程度,结合辅助钻进速度、进尺、压力及返水情况,综合判断岩体的完整性,即不要进行统计又无需做测试,具有直观、快速、易行等特点,经２８个工程实例开挖检验吻合率达１００％,准确率高。     

Alteration processes of cement induced by CO2-saturated water and its effect on physical properties: Experimental and geochemical modeling study

The objective of this study is to understand cement alteration processes with the evolution of porosity and hardness under geologic CO₂ storage conditions. For this study, the cylindrical cement cores (class G) were reacted with CO₂–saturated water in a vessel (40 °C and 8 MPa) for 10 and 100 days. After the experiment, the CO₂ concentration and Vickers hardness were measured in the hydrated cement core to estimate the carbonation depth and to identify the change in hardness, respectively. Diffusive-reactive transport modeling was also performed to trace the alteration processes and subsequent porosity changes. The results show that cement alteration mainly results from carbonation. With alteration processes, four different reaction zones are developed: degradation zone, carbonation zone, portlandite depletion zone, and unreacted zone. In the degradation zone, the re-dissolution of calcite formed in the carbonation zone leads to the increase of porosity. In contrast, the carbonation zone is characterized by calcite formation resulting mainly from the dissolution of portlandite. The carbonation zone acts as a barrier to CO₂ intrusion by consuming dissolved CO₂. Especially in this zone, although the porosity decreases, the Vickers hardness increases. Our results show that cement alteration processes can affect the physical and hydrological properties of the hydrated cement under CO₂-saturated conditions. Further long-term observation is required to confirm our results under in-situ fluid chemistry of a CO₂ storage reservoir. Nonetheless, this study would be helpful to understand alteration processes of wellbore cements under CO₂ storage conditions.     

Mechanism of Underground Fluid Injection Induced Seismicity and Its Implications for CCS Projects

CO₂ capture and storage projects must consider the potential possibility ofinjection induced seismicity. Moderate earthquakes and strong earthquakes may endanger human life and property, and even felt earthquakes and microquakes also pose a threat to seal integrity of CO₂ reservoir and increase the risk of leakage. Underground fluid injection induced seismicity usually happens in some geoengineering projects such as waste fluid disposal, EOR and EGS, and it occurs when fluid is injected along the fault. Therefore, it can be studied through stress analysis. The density of supercritical CO₂ is smaller than water, which may develop density flow in the deep strata or water-rock interactions in pre-existing structures, and cause the variation in permeability and pressure to induce a seismic activity. In this paper, we reviewed the mechanism of underground fluid injection induced seismicity with the focus of CCS, combined with fluid injection projects and seismic monitoring analysis in both commercial scale and experimental scale, to investigate its impact on the integrity of the cap rock of the reservoir. Finally, we summarized the appropriate site selection, injection methods and monitoring programs to prevent the occurrence of induced seismicity.     

基于GNSS的地基增强系统信号质量监测阈值设计

针对载噪比和码/载波分歧监测量在信号质量监测(SQM)过程中出现的非高斯性导致阈值模型过于保守的问题,提出一种基于稳定分布的SQM监测量参数阈值算法。首先给出2种监测量基于高斯分布的阈值模型,然后推导基于稳定分布的监测量阈值模型,最后通过实测数据对稳定分布的阈值算法进行评估与验证。结果表明,稳定分布可更加准确地描述载噪比和码/载波分歧监测量,使阈值更加紧致地包络监测量参数,从而解决传统阈值模型过于保守、精确低的问题,降低系统风险,提升GBAS系统的完好性。     

Experts talk the future Reflections on the Bonn Seminar of Governmental Experts, 16–17 May 2005: a view from Europe

Abstract

This article provides a first-cut estimate of the potential impacts of the clean development mechanism (CDM) on electricity generation and carbon emissions in the power sector of non-Annex 1 countries. We construct four illustrative CDM regimes that represent a range of approaches under consideration within the climate community. We examine the impact of these CDM regimes on investments in new generation, under illustrative carbon trading prices of US$ 10 and 100/t C. In the cases that are most conducive to CDM activity, roughly 94% of new generation investments remains identical to the without-CDM situation, with only 6% shifting from higher to lower carbon intensity technologies.We estimate that the CDM would bolster renewable energy generation by as little as 15% at US$ 10/t C, or as much as 300% at US$ 100/t C.

A striking finding comes from our examination of the potential magnitude of the “free-rider” problem, i.e. crediting of activities that will occur even in the absence of the CDM. The CDM is intended to be globally carbon-neutral—a project reduces emissions in the host country but generates credits that increase emissions in the investor country. However, to the extent that unwarranted credits are awarded to non-additional projects, the CDM would increase global carbon emissions above the without-CDM emissions level. Under two of the CDM regimes considered, cumulative free-riders credits total 250–600 MtC through the end of the first budget period in 2012. This represents 10–23% of the likely OECD emissions reduction requirement during the first budget period. Since such a magnitude of free-rider credits from non-additional CDM projects could threaten the environmental integrity of the Kyoto protocol, it is imperative that policy makers devise CDM rules that encourage legitimate projects, while effectively screening out non-additional activities.