高速铁路无砟轨道地基泥岩膨胀性分类分级研究     

薛彦瑾  王起才  马丽娜  张戎令  代金鹏  王强 《岩土力学》2020,41(9):3109-3118

红层泥岩是一种典型侏罗系沉积岩，其含有微量黏土矿物，易遇水软化、失水崩解，具有一定膨胀性，是引起兰新高速铁路路基持续上拱变形的一个重要因素，故重新判定该种土体膨胀性对高速铁路无砟轨道设计和施工具有重要意义。为此，选取等效蒙脱石含量、阳离子交换量、自由膨胀率和液限为泥岩膨胀性判别指标，通过兰新高速铁路上拱地段大量钻孔实测资料，提出了泥岩膨胀等级分级标准，采用改进层次分析法、基尼系数法和直觉模糊理论确定了判别指标组合权重，基于逼近理想解排序法(TOPSIS法)建立了泥岩膨胀性直觉模糊综合评价模型。结果表明：直觉模糊综合评价模型将泥岩膨胀性进行了定量化，克服了同一试样不同指标属于不同等级判别缺陷；室内膨胀量试验验证了膨胀等级分级标准和直觉模糊综合评价模型对兰新高铁地基泥岩适用性和准确性。研究成果对地基红层泥岩高速铁路路基长期持续上拱变形风险评估和工程控制措施提供技术支撑。  相似文献   

Single subduction zone for the generation of Devonian ophiolites and high‐P metamorphic belts of the Variscan Orogen (NW Iberia)     

Rubn Díez Fernndez  Ricardo Arenas  Sonia Snchez Martínez  Irene Novo‐Fernndez  Richard Albert 《地学学报》2020,32(4):239-245

Within the Variscan Orogen, Early Devonian and Late Devonian high‐P belts separated by mid‐Devonian ophiolites can be interpreted as having formed in a single subduction zone. Early Devonian convergence nucleated a Laurussia‐dipping subduction zone from an inherited lithospheric neck (peri‐Gondwanan Cambrian back‐arc). Slab‐retreat induced upper plate extension, mantle incursion and lower plate thermal softening, favouring slab‐detachment within the lower plate and diapiric exhumation of deep‐seated rocks through the overlying mantle up to relaminate the upper plate. Upper plate extension produced mid‐Devonian suprasubduction ocean floor spreading (Devonian ophiolites), while further convergence resulted in plate coupling and intraoceanic ophiolite imbrication. Accretion of the remaining Cambrian ocean heralded Late Devonian subduction of inner sections of Gondwana across the same subduction zone and the underthrusting of mainland Gondwana (culmination of NW Iberian allochthonous pile). Oblique convergence favoured lateral plate sliding, and explained the different lateral positions along Gondwana of terranes separated by Palaeozoic ophiolites.  相似文献   

Nanpanjiang basin: A window on the tectonic development of south China during Triassic assembly of the southeastern and eastern Asia     

《Gondwana Research》2020

As the largest siliciclastic sink in the South China block, the Triassic Nanpanjiang basin is generally thought of as a foreland basin related to Indosinian collision between the South China and Indochina blocks. Our basin analysis, spanning an eight years period, provides details of Lopingian to Middle Triassic stratigraphic fill and tectonic subsidence of the basin. Field observation and sedimentological analyses reveal that the basin was not filled by a monotonous turbidite system and suggest instead the development of five primary depositional units constituted by deep-water turbidite systems, mass-transport deposits, condensed drapes, shallow-water isolated carbonate platforms, and volcano-volcaniclastic rocks. The stratigraphic completeness of the basin, the coexistence of widespread but localized carbonate platforms within axially filled deep-water basin, tectonically generated cyclothems of transverse mass-transport deposits along intrabasinal faults and basin fill of extrusive rocks of bimodal composition together apparently call in question the claim that crustal shortening prevailed during the Late Permian to pre-Norian Triassic. Patterns of basin fill, differential tectonic subsidence and very high subsidence rate of the region adjacent to master fault are more closely match the pattern expected for extensional to transtensional basin in a back-arc setting. The crustal extension in the southwestern South China was not consistent with hypothesized Indosinian collision between South China and Indochina blocks, but more likely developed in response to northwestward subduction of the paleo-Pacific plate. Our results, combined with regional considerations, lead to a new model for the Triassic tectonic evolution of South China during Triassic assembly of the southeastern and eastern Asia.  相似文献   

蚀变岩帽的特征、成因以及在华南的分布探讨     

陈静  周涛发  张乐骏  孙艺  WHITE Noel C  李旋旋 《岩石学报》2020,36(11):3380-3396

Sillitoe（1995）蚀变岩帽（Lithocap）的定义为大范围富黄铁矿的硅化、高级泥化和泥化蚀变，在地质环境上位于古地表和浅成中-酸性岩浆侵入体之间。蚀变岩帽往往显示为突出的正地形，有助于寻找隐伏的斑岩矿化体。但蚀变岩帽在地表的范围往往多达几十个平方千米，又常常掩盖下覆斑岩矿床的蚀变矿化特征及其地球化学印记，因此大型的蚀变岩帽又给勘探工作带来一定的挑战。蚀变岩帽相关矿床的勘探需以地质填图为基础，结合近红外光谱分析（SWIR）进行蚀变填图，以及全岩地球化学以及矿物地球化学表现的元素或元素组合异常，来帮助定位热源或深部斑岩体。遥感和地球物理中的激电响应，也可以辅助定位岩体。华南地区的蚀变岩帽主要分布于长江中下游成矿带和东南沿海火山岩带。前人对安徽庐枞盆地中的矾山蚀变岩帽进行了系统研究，确定了矾山蚀变岩帽形成于白垩纪，与围岩砖桥组火山岩年龄一致。同位素和流体包裹体工作证明了形成矾山蚀变岩帽的流体主要为深部岩浆热液中的酸性气体与浅部大气降水的混合，在浅部高渗透率的火山岩及其岩性界面反应，广泛发育了一套硅化和高级泥化蚀变，指示与矾山相关可能存在斑岩和高硫型浅成低温热液铜金矿床。福建紫金山地区有中国最大的高硫型浅成低温热液矿床，主要赋存于紫金山蚀变岩帽中。紫金山蚀变岩帽的地质特征和蚀变分带已经研究的较为详细，但目前深部的侵入体还没有发现。浙江的蚀变岩帽是中国非金属矿产的重要来源，包括明矾石矿、地开石矿和红柱石矿等，这些蚀变岩帽与金属矿化的关系尚未有相关研究。根据目前的资料总结，有较多的蚀变岩帽分布在中国华南，这些蚀变岩帽特征典型，但目前的研究程度尚浅。现有的研究结果表明，华南的蚀变岩帽的成矿潜力巨大，可能存在一条巨型的斑岩-浅成低温矿床成矿带，具有广阔的找矿勘查前景，建议加强蚀变岩帽及相关矿床的找矿与研究工作。  相似文献   

Analysis and Comparison for Fusion Algorithms of Time Transfer     

WANG Wei-xiong  DONG Shao-wu  WU Wen-jun  GUO Dong  ZHANG Jian 《Chinese Astronomy and Astrophysics》2021,45(2):224-235

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The recognition of former melt flux through high‐strain zones          下载免费PDF全文

Catherine A. Stuart  Sandra Piazolo  Nathan R. Daczko 《Journal of Metamorphic Geology》2018,36(8):1049-1069

High‐strain zones are potential pathways of melt migration through the crust. However, the identification of melt‐present high‐strain deformation is commonly limited to cases where the interpreted volume of melt “frozen” within the high‐strain zone is high (>10%). In this contribution, we examine high‐strain zones in the Pembroke Granulite, an otherwise low‐strain outcrop of volcanic arc lower crust exposed in Fiordland, New Zealand. These high‐strain zones display compositional layering, flaser‐shaped mineral grains, and closely spaced foliation planes indicative of high‐strain deformation. Asymmetric leucosome surrounding peritectic garnet grains suggest deformation was synchronous with minor amounts of in situ partial melting. High‐strain zones lack typical mylonite microstructures and instead display typical equilibrium microstructures, such as straight grain boundaries, 120° triple junctions, and subhedral grain shapes. We identify five key microstructures indicative of the former presence of melt within the high‐strain zones: (a) small dihedral angles of interstitial phases; (b) elongate interstitial grains; (c) small aggregates of quartz grains with xenomorphic plagioclase grains connected in three dimensions; (d) fine‐grained, K‐feldspar bearing, multiphase aggregates with or without augite rims; and (e) mm‐ to cm‐scale felsic dykelets. Preservation of key microstructures indicates that deformation ceased as conditions crossed the solidus, breaking the positive feedback loop between deformation and the presence of melt. We propose that microstructures indicative of the former presence of melt, such as the five identified above, may be used as a tool for recognising rocks formed during melt‐present high‐strain deformation where low (<5%) volumes of leucosome are “frozen” within the high‐strain zone.  相似文献   

文莱-沙巴盆地深水褶皱冲断带构造变形特征及成因机制          下载免费PDF全文

唐武  赵志刚  张功成  谢晓军  刘世翔  王一博  宋双  王龙  孙瑞  郭佳 《地球物理学报》2018,61(10):4281-4295

为揭示活动陆缘深水褶皱冲断带的特征及成因，本文利用地震和区域地质资料的综合分析，系统阐述了文莱—沙巴盆地深水褶皱冲断带的构造变形特征，并结合盆地演化动力学特点，探讨其构造变形机制及其对深水区油气成藏的影响.研究结果表明，文莱—沙巴盆地深水褶皱冲断带具有"垂向分期、平面分段"的特点，垂向上，以中中新统底界面为界可划分为下部（始新世-早中新世）和上部（中中新世-现今）两套逆冲褶皱冲断体系，其中下部逆冲褶皱冲断带的形成与古南海的俯冲作用密切相关，上部逆冲褶皱冲断带是中中新世以来三角洲前缘重力滑动与苏禄海扩张造成的区域挤压应力远程效应共同作用的结果，且苏禄海扩张造成的远程挤压效应主控平面上南北段褶皱冲断带变形的差异性，导致北段褶皱变形强度大于南段，具有背斜褶皱数量多、褶皱间距离短、逆冲断层倾角陡的特点，南段反之；且晚上新世以来北段深水区地层缩短量大于陆架区伸展量，两者之差为2~6 km，而南段两者相当，仅受三角洲前缘重力滑动影响.整个褶皱冲断带发育断弯、断展、断滑褶皱等3种断层相关褶皱以及叠瓦扇和冲起构造2种逆冲构造组合，是多期NW向挤压应力作用下形成的大型逆冲推覆构造，以前展式向盆地扩展.此外，由于中中新世以来逆冲断层的持续活动，研究区深水褶皱冲断带发育众多构造圈闭，油气成藏条件优越，且南段优于北段，靠近陆坡的近端优于远端，可作为勘探部署重点.  相似文献   

The effects of floods on the temperature of riparian groundwater          下载免费PDF全文

Jeffery A. Watson  M. Bayani Cardenas  Stephen B. Ferencz  Peter S.K. Knappett  Bethany T. Neilson 《水文研究》2018,32(9):1267-1281

The transition area between rivers and their adjacent riparian aquifers, which may comprise the hyporheic zone, hosts important biochemical reactions, which control water quality. The rates of these reactions and metabolic processes are temperature dependent. Yet the thermal dynamics of riparian aquifers, especially during flooding and dynamic groundwater flow conditions, has seldom been studied. Thus, we investigated heat transport in riparian aquifers during 3 flood events of different magnitudes at 2 sites along the same river. River and riparian aquifer temperature and water‐level data along the Lower Colorado River in Central Texas, USA, were monitored across 2‐dimensional vertical sections perpendicular to the bank. At the downstream site, preflood temperature penetration distance into the bank suggested that advective heat transport from lateral hyporheic exchange of river water into the riparian aquifer was occurring during relatively steady low‐flow river conditions. Although a small (20‐cm stage increase) dam‐controlled flood pulse had no observable influence on groundwater temperature, larger floods (40‐cm and >3‐m stage increases) caused lateral movement of distinct heat plumes away from the river during flood stage, which then retreated back towards the river after flood recession. These plumes result from advective heat transport caused by flood waters being forced into the riparian aquifer. These flood‐induced temperature responses were controlled by the size of the flood, river water temperature during the flood, and local factors at the study sites, such as topography and local ambient water table configuration. For the intermediate and large floods, the thermal disturbance in the riparian aquifer lasted days after flood waters receded. Large floods therefore have impacts on the temperature regime of riparian aquifers lasting long beyond the flood's timescale. These persistent thermal disturbances may have a significant impact on biochemical reaction rates, nutrient cycling, and ecological niches in the river corridor.  相似文献   

Spatio‐temporal tracer variability in the glacier melt end‐member — How does it affect hydrograph separation results?          下载免费PDF全文

Jan Schmieder  Jakob Garvelmann  Thomas Marke  Ulrich Strasser 《水文研究》2018,32(12):1828-1843

Geochemical and isotopic tracers were often used in mixing models to estimate glacier melt contributions to streamflow, whereas the spatio‐temporal variability in the glacier melt tracer signature and its influence on tracer‐based hydrograph separation results received less attention. We present novel tracer data from a high‐elevation catchment (17 km², glacierized area: 34%) in the Oetztal Alps (Austria) and investigated the spatial, as well as the subdaily to monthly tracer variability of supraglacial meltwater and the temporal tracer variability of winter baseflow to infer groundwater dynamics. The streamflow tracer variability during winter baseflow conditions was small, and the glacier melt tracer variation was higher, especially at the end of the ablation period. We applied a three‐component mixing model with electrical conductivity and oxygen‐18. Hydrograph separation (groundwater, glacier melt, and rain) was performed for 6 single glacier melt‐induced days (i.e., 6 events) during the ablation period 2016 (July to September). Median fractions (±uncertainty) of groundwater, glacier melt, and rain for the events were estimated at 49±2%, 35±11%, and 16±11%, respectively. Minimum and maximum glacier melt fractions at the subdaily scale ranged between 2±5% and 76±11%, respectively. A sensitivity analysis showed that the intraseasonal glacier melt tracer variability had a marked effect on the estimated glacier melt contribution during events with large glacier melt fractions of streamflow. Intra‐daily and spatial variation of the glacier melt tracer signature played a negligible role in applying the mixing model. The results of this study (a) show the necessity to apply a multiple sampling approach in order to characterize the glacier melt end‐member and (b) reveal the importance of groundwater and rainfall–runoff dynamics in catchments with a glacial flow regime.  相似文献   

天津滨海爆炸事件检测与相对定位研究     

邓莉  谭毅培  刘双庆  马婷  卞真付  曹井泉 《地震》2018,38(3):158-169

2015年8月12日发生在天津滨海新区的化学品爆炸事故造成了严重的人员伤亡和财产损失。 基于区域地震台网记录的数字化连续地震波形资料, 对爆炸发生过程的精细分析是深入调查爆炸事故发生原因、 快速估计事故所造成灾害与损失的重要手段之一。 本文首先利用震相到时和质点运动轨迹信息对记录波形中能量较强的震相性质进行分析, 再通过模板匹配算法检测爆炸过程中是否存在两次大爆炸以外的小爆炸事件, 并对检测方法的效能进行检验, 最后依据波形互相关得到的震相到时差估计两次较大爆炸的相对位置。 计算结果显示区域台网记录波形中能量最大的体波震相可能为沿沉积层顶部传播的Pg震相, 垂直向能量最强的面波震相为Rg震相, 而能量较弱的初至震相可能为结晶基底首波; 爆炸过程中除了两次能量较大的爆炸以外还能检测到两次较小的爆炸事件, 其当量相当于约M_L0.5的地震; 基于两次大爆炸Pg震相相对到时信息得到第二次大爆炸发生在第一次大爆炸的北西侧, 两次爆炸位置距离约50~55 m。 本文研究结果为爆炸事故的调查分析提供了地震学依据。  相似文献