A rotary-shear low to high-velocity friction apparatus in Beijing to study rock friction at plate to seismic slip rates

This paper reviews 19 apparatuses having highvelocity capabilities,describes a rotary-shear low to highvelocity friction apparatus installed at Institute of Geology,China Earthquake Administration,and reports results from velocity-jump tests on Pingxi fault gouge to illustrate technical problems in conducting velocity-stepping tests at high velocities.The apparatus is capable of producing plate to seismic velocities（44 mm/a to 2.1 m/s for specimens of 40 mm in diameter）,using a 22 kW servomotor with a gear/belt system having three velocity ranges.A speed range can be changed by 103 or 106by using five electromagnetic clutches without stopping the motor.Two cam clutches allow fivefold velocity steps,and the motor speed can be increased from zero to 1,500 rpm in 0.1-0.2 s by changing the controlling voltage.A unique feature of the apparatus is a large specimen chamber where different specimen assemblies can be installed easily.In addition to a standard specimen assembly for friction experiments,two pressure vessels were made for pore pressures to 70 MPa;one at room temperature and the other at temperatures to 500 °C.Velocity step tests are needed to see if the framework of rate-and-state friction is applicable or not at high velocities.We report results from velocity jump tests from 1.4 mm/s to 1.4 m/s on yellowish gouge from a Pingxi fault zone,located at the northeastern part of the Longmenshan fault system that caused the 2008 Wenchuan earthquake.An instantaneous increase in friction followed by dramatic slip weakening was observed for the yellowish gouge with smooth sliding surfaces of host rock,but no instantaneous response was recognized for the same gouge with roughened sliding surfaces.Instantaneous and transient frictional properties upon velocity steps cannot be separated easily at high velocities,and technical improvements for velocity step tests are suggested.     

Ambient noise as the new source for urban engineering seismology and earthquake engineering: a case study from Beijing metropolitan area

In highly populated urban centers, traditional seismic survey sources can no longer be properly applied due to restrictions in modern civilian life styles. The ambient vibration noise, including both microseisms and microtremor, though are generally weak but available anywhere and anytime, can be an ideal supplementary source for conducting seismic surveys for engineering seismology and earthquake engineering. This is fundamentally supported by advanced digital signal processing techniques for effectively extracting the useful information out from the noise. Thus, it can be essentially regarded as a passive seismic method. In this paper we first make a brief survey of the ambient vibration noise, followed by a quick summary of digital signal processing for passive seismic surveys. Then the applications of ambient noise in engineering seismology and earthquake engineering for urban settings are illustrated with examples from Beijing metropolitan area. For engineering seismology the example is the assessment of site effect in a large area via microtremor observations. For earthquake engineering the example is for structural characterization of a typical reinforced concrete high-rise building using background vibration noise. By showing these examples we argue that the ambient noise can be treated as a new source that is economical, practical, and particularly valuable to engineering seismology and earthquake engineering projects for seismic hazard mitigation in urban areas.     

盾构隧道实测土压力分布规律及影响因素研究

以大量现场实测土压力为基础,分析了影响盾构隧道衬砌土压力的一些主要因素,总结出不同地层地铁盾构隧道长期稳定土压力的分布规律,并探讨了盾构施工期土压力随时空的变化情况。研究得出,地下水位高低对稳定土压力大小及分布影响较大;作用在管片上的长期土压力大小与地层衬砌刚度系数有关,当地层衬砌刚度系数为1.5时,管片竖向及水平土压力都较小;盾构施工期临时荷载对管片土压力影响不可忽视,无论是黏土地层还是砂土地层,大的注浆压力及注浆率将导致作用在管片上的稳定土压力分布不均;管片土压力可按时空分为4个阶段,拼装阶段、同步注浆阶段、浆液凝固阶段及后期稳定阶段,其中同步注浆阶段管片周边最大土压力为稳定阶段的2～3倍。     

干旱区尾矿污染环境的植物修复技术研究进展

干旱区矿业废弃地（尤其是尾矿及其污染环境）的治理面临着水资源短缺、土壤贫瘠、盐碱化、植物资源相对匮乏等不利因素的制约,很大程度上阻碍了该区域的生态恢复进程。基于目前国内外在干旱区尾矿污染环境治理方面所开展的研究,本文从植物修复的理论及技术方面进行了初步的综述,重点对比分析了植物提取技术和植物固定技术的优势和不足,并对相关典型应用实例进行了分析评价,最后对国内干旱区尾矿污染环境的治理研究和技术给出建议。     

环境公共物品的私人补偿:农业遗产保护的试点项目(英文)

在一次性支付中,某种环境物品真正价值或许更容易如果它能以捐赠的方式加入私人物品中。我们研究了人们的购买行为并与问卷调查中所阐明的购买行为相对比。我们检验了条件价值法(Contingent Value Method,CVM)的效标效度,例如(检验)当捐赠被附加时人们所表现出与规定值的差异程度。结果表明价格上涨对商品的总销量有任何影响。把捐赠附加到私人物品中可能是种很有效的收集捐款形式。这些捐款被用于保护具有非排他性和非竞争性的景观或者作为景观一部分的农业遗产。此外,我们还可以表明,资金可以在不改变销售数量被收集。这种方法在其他环保活动也是很有效的。     

2011年春末夏初长江中下游地区旱涝急转成因初探

选用NCEP/NCAR、NOAA、国家气候中心(NCC)提供的各要素资料及NOAA-Hysplit模型,对2011年春末夏初发生在中国长江中下游地区旱涝急转的降水异常事件及其影响机制进行初步分析,并建立天气学概念模型.结果表明:(1)长江中下游地区,尤其是(27°N～～32°N,l10°E～120°E)区域在6月第1候...     

线状自然灾害风险地图的自动综合——以铁路承灾体为例

在地理学与地图学的基础上,从灾害系统的角度,探讨了图层约束(LC)和道格拉斯-普克(DP)相结合的线状地图自动综合问题。以铁路线为例,构建了基于地震长期烈度区划、滑坡危险性、泥石流灾害活动程度、多年平均最大积雪深度、水灾频次、沙尘暴年最大日数和湖泊分布等图层信息的约束源数据库,结合铁路密度与综合致灾强度风险矩阵,实现了分区、分段铁路承灾体的自动综合,揭示了多尺度下铁路密度分布的区域规律。     

大数据开创地学研究新途径:查明相关关系,增强研究可行性

人类已经进入大数据时代,大数据研究的思想、方法在地学领域也备受关注。笔者认为,大数据研究的对象是数据,研究的工具是计算机,研究的方法、手段是查明数据间相关关系,研究的特点是取向高概率做出决策。大数据是通过对大量数据的挖掘,查明数据间的相关关系,研究问题并做出正确决策的思想、方法。本文提出大数据是应用“归纳法”开展科学研究的思想、方法,以及高性能计算机和大数据计算技术使“归纳法”得以升华的观点。文章通过对统计学、机器学习算法的深入探讨,得出大数据将改变人们对自然的理解和认知方式,改变科学研究的思想和方法,改变长期以来人们通过查找因果关系开展科学研究的习惯。大数据必将开创一条跨越复杂的因果关系、直接获得研究结果的全新的科学研究途径。随着数据爆发式增长,随着高性能计算机的普及和计算技术的迅猛发展,统计分析方法将很大程度地突破数据体量的限制,统计分析预测模型以其真实可靠的处理结果、对条件和结果良好的解释能力、结合机器学习算法对半结构化与非结构化数据的处理优势,将推动地质科学进入定量化研究的新高度。     

城镇有限场地条件下的物探找水试验

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。