加拿大、澳大利亚铀矿勘查活动的特点及其成功经验

自上世纪80年代中期以来，世界铀市场就一直处于低迷状态，极大地影响了世界铀矿勘查的投入和勘查成果。但是加拿大、澳大利亚这2个世界上铀资源大国和产铀大国在此期间在铀矿勘查上仍取得不小的进展。究其原因是2个国家都坚持把铀矿勘查工作的重点放在已知成矿单元和初步查明的远景区，把勘查的目标矿床类型锁定在成矿单元内成熟的矿床类型，并长期不懈地投入工作量。我国的铀矿勘查正处于新的发展时期，借鉴他们的成功经验应当是有益的。     

泥石流入汇条件下交汇区的流动特性

根据动量原理,引入了输运流量和淤积流量以及输运率和淤积率等概念,研究了泥石流入汇主河道后,主河道交汇口附近水位壅高以及交汇区泥沙淤积等问题,分析了泥石流进入主河道后流量、容重等的变化。研究了交汇区复杂条件下的动量传递关系,推导了综合反映交汇后下游水力条件关系和交汇区淤积情况的弗劳德数计算公式,并应用试验数据对其进行了验证,结果表明只要参数选取得当,用所提出的公式计算可达到较高的预测精度。     

Hydrodynamics and sediment flux of hoa in an Indian Ocean atoll

Detailed hydrodynamic and sediment ?ux measurements are reported from 11 hoa (shallow cross‐reef channels) in the Cocos (Keeling) Islands, Indian Ocean. All hoa exhibit unidirectional oceanside reef to lagoon ?uxes. These currents are driven by tides, wave set‐up and incident waves, and the presence of islands that generate alongshore gradients so that currents ?ow toward the topographic low points of hoa entrances in the reef rim. Two functional groups of hoa are identi?ed that extend Chevalier's typology of hoa and possess different process signatures. Sediment‐limited hoa (SLH) are ef?cient conduits of sediment transport. They are located close to the reef rim where incident wave energy propagates across the reef crest into the hoa and is able to entrain sediment. Transport‐limited hoa (TLH) are characterized by low rates of sediment transport because incident wave energy is negligible as they are located much further from the reef edge than SLH. In the absence of an entrainment mechanism the oceanside reef ?at is laden with sediment. Storm energy increases transport ef?ciency through hoa. However, the net sedimentation response differs between the two hoa types. Proximity to the reef edge means that frequent storms ?ush sediment from SLH increasing hoa depth and enhancing the potential for erosion of the conglomerate boundary. In contrast, the greater reef width fronting TLH means that sediment transport from reef ?ats to the lagoon is only activated during infrequent storms. The contrasting process signatures account for morphological differences between sediment‐limited hoa (lagoonward decrease in depth and increase in width), and transport‐limited hoa (lagoonward increase in depth). The number and type of functional hoa are found to have signi?cant implications for the rate of lagoon sedimentation in enclosed atolls. In general, an increase in frequency of functional hoa and increased proportion of SLH will promote more rapid rates of lagoon in?ll. Copyright © 2004 John Wiley & Sons, Ltd.     

井液电阻率法在井管故障探测中的应用

通过对井液电阻率方法与技术的研究和测试仪器的改进,将其运用于井管故障的检测。能简便、快捷、准确地探明井管破损的位置、大小以及由于成井工艺不良而引导的渗漏问题,为修井和故障处理提供了可靠的依据,从而扩大了这种方法的应用领域。     

渝怀铁路圆梁山隧道桐麻岭背斜东翼岩溶涌水突泥灾害与整治方案比选

圆梁山隧道是在建铁路重庆至怀化线的关键性控制工程,隧道全长11.068km,最大埋深约780m。隧道施工穿越桐麻岭背斜东翼时,遇到了水平循环带岩溶强烈发育地段,该地段岩溶十分发育,且连通性好;加之数次强降雨,DK361 764、DK360 873等段多次突发大规模的涌水突泥砂、块石灾害,造成部分施工机具掩埋损毁,施工掘进严重受阻,蒙受巨大的经济损失,初步分析认为涌水突泥与地下暗河或岩溶泉群的主管道网络发生较为密切的联系,可以直接接受大气降水补给。为了确保隧道施工和运营安全,针对背斜东翼段岩溶发育情况、涌水突泥特征及其降雨影响程度,进行了泄水洞排水、平导排水、封堵和堵排结合4个整治方案比选,最终采用了泄水洞方案;2003年5～9月雨季,背斜地区多次普降(特)大暴雨,DK361 764、DK360 873等地段又再次突发大规模的涌突水(泥、砂、块石),都通过兴修的泄水洞排泄掉了,隧道及其村砌结构安然无恙,表明采用泄水洞方案整治背斜东翼段的岩溶涌水突泥灾害是正确的选择。     

地铁车站主体结构渗漏及堵漏

地铁工程建设中，结构渗漏的堵漏工作非常重要，实际施工十分复杂，对整个工程质量有重大影响。该文总结了长期项目施工中的有效经验，并以某车站主体结构工程为例，详细介绍了该车站主体结构自防水设计及施工工艺，对结构渗漏的原因及具体的堵漏施工方法进行了探讨。     

Phytoplankton subsidies to the inter‐tidal zone are strongly affected by surf‐zone hydrodynamics

The size of bottom‐up subsidies, food and larvae, from the ocean has a profound impact on inter‐tidal communities and populations. Alongshore variations in subsidies are attributed to variation in coastal conditions, but also might be due to variations in surf‐zone hydrodynamics. We tested this hypothesis by comparing surf‐zone phytoplankton concentrations to surf‐zone hydrodynamics as indicated by the width of the surf zones. To minimize the potential effects of alongshore variation in phytoplankton abundance in the coastal ocean, we sampled closely spaced sites (median separation 1 km) over short periods (3 days). Surf‐zone concentrations of coastal phytoplankton taxa (e.g. Chaetoceros spp., Pseudo‐nitzschia spp. and dinoflagellates) varied with surf‐zone width; 65% to 94% of the variability in their concentration is explained by surf‐zone width. Where surf zones were narrow and more reflective, phytoplankton concentrations were one to several orders of magnitude lower than in wider, more dissipative surf zones. The most closely spaced stations were 30 m apart, but represented distinct habitats – a reflective and a more dissipative surf zone. Phytoplankton concentrations in the reflective surf zone were an order of magnitude or more lower than in the adjacent more dissipative surf zone. A reanalysis of a published study on phytoplankton subsidies found similar results. Alongshore variation in surf‐zone hydrodynamics appears to be an important driver of phytoplankton subsidies to the inter‐tidal zone.     

黏弹性叠前时间偏移:陡倾角构造成像与实际应用

黏弹性叠前时间偏移通过在偏移过程中补偿地球介质的吸收衰减,恢复被衰减的高频成分,进而获得较常规叠前时间偏移更高分辨率的偏移成像结果.相比于常规叠前时间偏移,该方法实现环节包含的频率域积分产生的巨大计算量,需要基于GPU加速实现才能满足工业应用对其计算效率的需求.本文针对黏弹性叠前时间偏移算法实现的这一特点,提出了修正其走时计算方法精度和应用分时段的频率域成像策略,在进一步提升计算效率的同时,改进了该方法对陡倾角构造和断层的成像效果.我们将改进的黏弹性叠前时间偏移方法应用于三维陆上地震资料,与现行的商业偏移软件对比表明,该方法不仅获得了更高分辨率的成像结果,也实现了对断层和陡倾角构造的清晰成像,而新方法的计算耗时也较改进前减少了三分之一以上.     

西康铁路大瓢沟隧道工程控制网测量中问题的探讨

对西康铁路大瓢沟隧道工程施工控制网的布设方案和观测技术进行了讨论,较准确地估算隧道的贯通误差,得出该隧道的平面施工控制网的测量成果,并详细探讨了精密工程控制网的等级划分、网形、点位、边长和角度。     

强透水砂卵石复杂地层的高压旋摆喷灌浆处理技术

通过对复杂地层的结构和各种防渗材料进行深入研究,选择合适的施工机具,改进工艺。在试验分析的基础上,根据不同的地层确定科学的施工控制参数,进一步对两层强透水带采取简单易行的深层充填堵漏工程措施,达到理想防渗效果。经对嘉陵江和白龙江流域砂卵（砾）石地层多个工程实例统计分析,其防渗系数 >1×10-4 cm/s,而复杂强透水地层经试验分析计算和抽水验证, <5×10-5 cm/s。介绍了采用单排孔替代2双排或三排高喷孔在复杂地层中的施工过程控制措施和充填式堵漏工程处理措施,应用实例可供类似工程借鉴。