频率－初速测桩法的应用与提高

本文对频率-初速测拉法的理论和实践作了进一步阐述,并针对测桩资质考核中存在的问题,提出若干技术对策。     

频率－初速测桩法的应用与提高

本文对频率－初速测拉法的理论和实践作了进一步阐述，并针对测桩资质考核中存在的问题，提出若干技术对策。     

2011年3月10日盈江5.8级地震诱发砂土液化灾害特征研究

2011年3月10日中缅边境附近的云南省德宏傣族景颇族自治州盈江县发生Ms5.8级地震,震源深度10km,造成25人死亡,250人受伤,13万人口受灾,众多构(建)筑物损毁,砂土液化广泛发育,约19km长的盈江河堤开裂.5.8级地震诱发如此大的次生灾害是近年来少有的.通过对本次地震地质背景和地质灾害调查分析,初步认识到...     

静力触探法对巴楚地震液化判别的适用性

2003年2月24日新疆巴楚-伽师地区发生的6.8级地震中出现了自1996年唐山大地震以来我国大陆境内最为严重的砂土液化现象。以此地震液化调查为基础,检验包括我国规范液化判别方法、Robertson方法和Olsen方法的国内外现有静力触探试验为指标的液化判别方法的适用性。结果表明,我国规范、Robertson方法、Olsen方法在对巴楚地震液化场地判别中,总体上非液化场地判别成功率高于液化场地判别成功率,非液化场地的判别成功率分别为88%、71%和88%,但对液化场地判别成功率分别为55%、73%和45%,明显偏于危险,原因需要进一步查明,建立适合局部地区的液化判别方法应是未来必须进行的工作。     

频率测深的拟地震解释法

电磁波和弹性波的复反射函数无论从数学表达形式上,还是从物理意义上都有一定的相似性。通过对拟地震解释法中反射系数q_n的求取,将频率测深曲线转换成v_p－t₀曲线及时间剖面,并对均匀介质及2层、3层、4层断面的理论模型和实例做了正反演计算。结果表明,频率测深拟地震解释法作为一种新的解释手段具有较好的应用前景。     

循环加载频率对饱和珊瑚砂液化特性的影响

人们对循环加载频率f对饱和石英砂液化特性的影响已进行大量的不排水循环试验研究,但循环加载频率f对饱和珊瑚砂液化特性的影响尚未引起重视。为探究f对饱和珊瑚砂液化特性的影响,针对中密、均等固结的饱和珊瑚砂试样,开展了f=0.01～1.00 Hz、循环主应力路径90°跳转的系列不排水循环剪切试验。试验表明：孔压比ru和广义剪应变γg的增长速率随f增大而降低,到达初始液化所需的液化次数N_L随f增大而增大;不同循环加载方式引起的广义剪应变幅值γ_ga与峰值孔压比r_umax存在事实上的唯一性关系,且γga可表示为以r_umax为自变量的正切函数;f的增大会减弱试样的剪胀性。引入单元体循环应力比USR作为施加于试样的循环应力水平指标,USR-N_L关系曲线随f的增大而移向右上侧,不同f的USR-N_L关系曲线均服从相同形式的负幂函数。这意味着饱和珊瑚砂的抗液化强度随f的增大而增大。     

最近20年地震中场地液化现象的回顾与土体液化可能性的评价准则

回顾了1994年美国Northridge地震、1995年日本阪神地震、1999年土耳其Kocaeli地震、1999年台湾集集地震、2008年中国汶川地震、2010年智利Maule地震、2010～2011新西兰Darfield地震及余震、2011年东日本地震中大量的、不同类型的液化实例调查与研究,发现这些地震的液化具有以下特点：（1）罕见的特大地震（Mw9.0）使远离震中300～400 km的新近人工填土发生严重的大规模液化;（2）特大地震（Ms8.0、Mw8.8）使远离震中的低烈度Ⅴ～Ⅵ度地区发生严重液化;（3）海岸、河岸附近地区的新近沉积冲积、湖积土,填筑时间不到50年的含细粒、砂砾人工填土,容易发生严重液化;（4）天然的砂砾土层液化发生严重液化;（5）发生了深达20 m的土层液化现象;（6）松散土层液化后可以恢复到震前状态并再次发生液化;（7）高细粒（粒径≤75 ?m）含量≥50%或高黏粒（粒径≤5 ?m）含量≥25%的低-中塑性土严重液化,对介于类砂土与类黏土之间的过渡性态土,有时地表未见液化现象;（8）液化土层的深度较深或厚度较小时,容易出现地面裂缝而无喷砂现象;有较厚的上覆非液化土层时,场地液化不一定伴随地表破坏。液化实例证明,第四系晚更新世Q3地层可以发生严重液化;黏粒含量不是评价细粒土液化可能性的一个可靠指标;低液限、高含水率的细粒土易发生液化,采用塑性指数PI、含水率wc与液限LL之比作为细粒土液化可能性评价的指标是适宜的。综合Boulanger和Idriss、Bray和Sincio、Seed和Cetin等的液化实例调查与室内试验研究成果,建议细粒土液化可能性的评价准则如下：PI ＜12且wc/LL＞0.85的土为易液化土,12＜PI≤20和/wc/LL≥0.80的土为可液化土;PI ＞20或wc/LL＜0.80的土为不液化土。     

地震历史对砂土抗液化性能影响的试验研究

为探讨地震历史对饱和砂土抗液化性能的影响,通过离心机动力模型试验,观测了遭受过不同强度地震的饱和砂土水平场地在再次地震荷载作用下的响应,包括超静孔隙水压力的发展和土体的变形。研究表明,小地震有利于增强砂土颗粒之间的咬合及结构的稳定性,极大地提高了其抗液化能力,而遭受强地震并且发生液化的砂土,由于在沉积过程中形成的不稳定结构,则可能在将来强度相对较小的地震中再次液化。试验结果说明了地震历史对砂土液化性能有重大影响及进一步开展砂土细观结构研究的重要性。     

防水措施对堤坝地震液化影响的数值分析

通过基于有效应力的完全耦合动力分析方法,研究了混凝土面板坝在地震作用下的动力响应,详细地讨论了堤坝迎水面斜坡上铺设的防水毯对堤坝地震液化的影响。计算中土体采用Cyclic mobility本构模型,该模型通过在修正剑桥模型上增加应力诱导各向异性、超固结和结构性的概念及其相关发展准则,可以很好地描述可液化土体的动力特性。计算结果表明防水毯的存在可以有效降低坝体的地下水位浸润线,增加坝基的初始有效应力,从而降低坝基地震液化发生的可能性,同时坝体的变形明显减小。     

1989～2011期间8次强地震中抗液化地基处理成功案例的回顾与启示

回顾了1989年美国Mw6.9级Loma Prieta地震、1993年日本Ms7.8级Kushiro-Oki地震、1994年日本Mw8.2级Hokkaido Toho-Oki地震、1995年日本Ms7.2级阪神地震、1999年台湾集集地震、1999年土耳其Mw7.4级Kocaeli地震、2001年美国Mw6.8级Nisqually地震以及2011年Mw9.0级东日本地震中场地抗液化工程措施的成功案例,初步分析了各种抗液化工程措施的有效性与优劣性,可以给出如下工程场地抗液化处理的经验：（1）对于易液化的沿海及填海造陆场地,采用适宜的抗液化工程措施应成为地基处理不可缺少的环节;（2）应基于场地条件、经济条件及环境要求,综合考虑场地抗液化地基处理措施的选择;（3）挤密砂桩法和碎石桩法运用广泛、技术成熟且比较经济,宜优先选择作为抗震设防烈度Ⅷ度及以下地区的场地抗液化地基处理措施;（4）强夯法使用机具简单、费用低廉,适宜选择作为抗震设防烈度Ⅷ度及以下地区大面积场地的抗液化地基处理措施;（5）注浆法、深层搅拌法、旋喷法作为抗震设防烈度Ⅸ度及以下地区的场地抗液化地基处理措施是有效的;（6）多种抗液化地基处理措施联合使用的处理效果往往优于单一措施单独使用的处理效果,在条件许可的情况下,宜选择多种抗液化地基处理措施联合使用,以期达到更好的处理效果。     

新西兰城市防震减灾

本文介绍了新西兰的地震背景以及城市防震减灾工作的组织机构、动作及相关措施。     

基于静力触探试验的液化判别新方法

近来地震液化灾害频发,再次成为研究重点,发展具有良好应用前景的基于静力触探试验（CPT）的液化判别方法对预防液化灾害具有重要意义。以Boulanger数据库171组数据为回归样本,分析既有方法存在的问题,提出了基于CPT液化判别的双曲线模型和计算公式,并通过提取2011年新西兰地震147组液化新数据,对该方法进行对比检验。研究表明,我国岩土工程勘察规范的CPT液化判别方法对浅埋砂层偏于保守,对深层土又明显偏于危险,而国际上具有代表性的Robertson方法,其液化临界线存在低烈度区不合理回弯、高烈度区又偏于保守的问题。提出的新公式在不同地震动强度和砂层埋深下均可给出合理判别结果,克服了国内外既有方法的缺点,并纳入到具有样板规范性质的《建筑工程抗震性态设计通则》修订稿中,可为我国相关规范修订和工程应用提供支持。     

Boulders of MIS 5 age deposited by a tsunami on the coast of Otago, New Zealand

A series of elevated imbricated boulders were investigated on the Otago coastline, southeast New Zealand, through field surveying and optical luminescence dating. By using established hydrodynamic relationships of sediment transport the energy required to move the clasts was calculated and compared to the historic record of marine inundations of that coast. The boulders are platy in shape and are over 2 m long in some cases, and are sourced from a locally outcropping conglomerate unit which appears to be the only lithology on this section of coast that erodes to produce clasts of this size. It is estimated that the boulders were deposited by a tsunami between 2 and 3 m high during the latter part of Marine Isotope Stage 5. They therefore represent the first pre-Holocene tsunami deposit and one composed of large boulders described on the New Zealand coastline.     

Rhizocarpon calibration curve for the Aoraki/Mount Cook area of New Zealand

Development of Rhizocarpon growth curve from the Aoraki/Mount Cook area of New Zealand provides a means to assess Little Ice Age glacier behaviour and suggests approaches that have wider application. Employing a sampling strategy based on large populations affords the opportunity to assess which of various metrics (e.g. single largest, average of five largest, mean of an entire population) best characterise Rhizocarpon growth patterns. The 98% quantile from each population fitted with a quadric curve forms a reliable representation of the growth pattern. Since this metric does not depend on the original sample size, comparisons are valid where sample strategy must be adapted to local situations or where the original sample size differs. For the Aoraki/Mount Cook area a surface 100 years old will have a 98% quantile lichen diameter of 34.3 mm, whereas a 200‐year‐old surface will have a lichen diameter of 73.7 mm. In the Southern Alps, constraints from the age range of calibration points, the flattening of the quadric calibration curve and ecological factors limit the useful age range to approximately 250 years. Copyright © 2005 John Wiley & Sons, Ltd.     

The consumption of space: Land, capital and place in the New Zealand wine industry

Geographers have developed a keen interest in the social production of space - in the way meanings and values are ascribed to places as a result of changing social, cultural and political processes. There is a need to explore this approach further, seeing how social and economic values of places are inter-related and how these values are constructed in often deliberate and concerted ways. There is also a need to explore how such values are consumed: how the values in place are traded, appropriated and redistributed, both through the products of places and in land markets. This paper examines the New Zealand wine industry where certain wine regions have been identified and developed in ways which attempt to emphasise their distinctiveness in terms of wine quality and thus enhance the value of the wine produced. Different strategies have been employed in this process of place construction and this reflects the differential role of capital, striving on the one hand to increase the price and marketability of the products of distinctive places but, on the other, careful not to over-inflate land values and thus restrict further expansion. The paper suggests that the issue of consumption of space, involving a complex relationship amongst land, capital and place, is worthy of further exploration.     

Calibration of the in situ cosmogenic 14C production rate in New Zealand's Southern Alps

In situ cosmogenic ¹⁴C (in situ ¹⁴C) analysis from quartz‐bearing rocks is a novel isotopic tool useful for quantifying recent surface exposure histories (up to ～25 ka). It is particularly powerful when combined with longer‐lived cosmogenic isotopes such as ¹⁰Be. Recent advances in the extraction of in situ ¹⁴C from quartz now permit the routine application of this method. However, only a few experiments to calibrate the production rate of in situ ¹⁴C in quartz have been published to date. Here, we present a new in situ ¹⁴C production rate estimate derived from a well‐dated debris flow deposit in the Southern Alps, New Zealand, previously used to calibrate ¹⁰Be production rates. For example, based on a geomagnetic implementation of the Lal/Stone scaling scheme we derive a spallogenic production rate of 11.4 ± 0.9 atoms ¹⁴C (g quartz)^?1 a^?1 and a ¹⁴C/¹⁰Be spallogenic production rate ratio of 3.0 ± 0.2. The results are comparable with production rates from previous calibrations in the northern hemisphere. Copyright © 2012 John Wiley & Sons, Ltd.     

Occurrence of Almandine, and Its Implications for Ancient High Temperature Activity of the Orakeikorako Geothermal Field, Taupo Volcanic Zone, New Zealand

Abstract: Exploration drilling at Orakeikorako provides information on the hydrologic and thermal regime of the geothermal system, which is presently as high as 265C. The presence of almandine in Drillhole OK–1, at 1312. 5m drilled depth, is the only known occurrence of hydrothermal garnet in an active geothermal system from New Zealand. The formation temperature of the almandine, is not consistent with measured (bore) temperatures, but does coincide with fluid inclusion data and temperatures inferred from other secondary minerals, which suggest it formed at >240C, and possibly as much as 310C. Almandine is an important mineral geothermometer in active hydrothermal systems, and implications for its occurrence should not be discounted in fossil (mineralised) epithermal-type hydrothermal systems.     

隧道含水构造频域激发极化法超前探测研究

隧道前方含水构造的超前预报是地下工程领域中亟待解决的难题。基于频域激发极化法中频散率参数对水体响应敏感的特点,将其引入到隧道含水体超前探测研究工作中。从理论正演、物理模拟、解译方法等方面入手对频域激发极化超前预报技术进行了系统的研究。利用三维有限元数值模拟技术解决了隧道中频域激发极化超前探测的数值正演难题,并通过对典型含水体的正演研究得到了视频散率对含水构造的响应规律,发现视频散率曲线的极大值是表征掌子面前方含水构造存在的重要特征;基于大量数值正演的结论,提出了一种利用两次探测的视频散率曲线极大值联合判断含水构造位置的方法;物理模型试验和现场实际应用表明,频域激发极化法预报的含水体位置与实际情况基本一致,验证了该方法用于隧道含水构造超前探测的有效性,为解决隧道含水构造超前探测这一难题提供了可行的途径。     

坑道掘进瞬变电磁超前探水技术应用分析

坑道掘进前方含水体一直是影响安全生产的主要因素之一,瞬变电磁法在超前探水预报中发挥了重要作用。由于坑道全空间探测条件的特殊性,其测试布置方式对探测结果判断产生一定影响,主要表现在干扰因素剔除、电阻率深度计算、异常体空间判断等内容。为了获得较为可靠的探测结果,通过改进测试布置方式,增加中心线方向竖直测试剖面,与坑道迎头顶板、顺层、底板剖面一起形成四断面法超前测试,增强了对前方含水异常体的空间判断能力。通过与瞬变电磁超前常规探测方式相对比,认为四断面法利用横断面与纵剖面相结合,对地质体判断的优越性较强。现场应用结果表明,该方法在预报测区前方地质异常体时,以低于10 ?•m为低阻异常区判断标准,具有一定的可靠性,能为坑道掘进安全生产提供有效指导。     

矿井瞬变电磁法超前探测研究

本文通过实例介绍了矿井瞬变电磁法超前探测的基本原理及井下施工技术。实际应用表明,该方法对解决巷道掘进迎头方向的水害隐患及确保巷道安全是一种快捷、有效的勘查手段,可以为煤矿地质保障系统提供重要的技术依据。