跨铁钢箱梁架设临时支墩设计检算     

解海  任伟 《世界地震工程》2013,(1):98-101

针对基底软弱且临近既有线路的施工情形,建议采用大跨度组合钢箱梁跨越铁路线。介绍了采用扩大基础与钢管桩基础相结合的跨铁钢梁架设临时支墩基础的施工方法。  相似文献   

基于模糊故障树法的深基坑支护工程项目风险评估     

娄昊 《西部资源》2013,(3):162-165

深基坑工程施工中安全事故的发生给社会及施工企业带来了不良影响和巨大的经济损失,如何减少深基坑工程安全事故发生率,降低工程风险是一个值得研究的问题。本文通过将模糊理论与故障树分析方法相结合,建立了基于模糊故障树法的深基坑支护工程项目风险评估模型,克服了传统故障树方法忽略底事件发生概率的不确定性这一缺陷。通过对某深基坑工程实例的计算分析,说明了本文所建立的模型在深基坑工程风险评估中具有较好的理论价值与实际应用价值。  相似文献   

Demonstration and application of NMM‐based fractured porous medium flow model     

Qi‐Hua Zhang  Shao‐Zhong Lin  Hai‐Dong Su  Gen‐Hua Shi 《国际地质力学数值与分析法杂志》2021,45(1):132-153

In natural rock masses, the shapes of three‐dimensional (3‐D) blocks cut by arbitrary fracture networks may be very complex. Owing to the geometric complexity and difficulty of mesh discretization of 3‐D blocks and fracture facets, explicit consideration of fracture networks in flow analysis of fractured porous medium (FPM) is very challenging. Using the numerical manifold method based on independent covers (NMMIC), an FPM flow model was proposed that can deal with very complex 3‐D fracture networks. In this paper, the convergence of NMMIC was first demonstrated. The theoretical basis of the arbitrary refinement of computational meshes was proven. Moreover, three peculiarities of NMMIC meshes, that is, arbitrary shape, arbitrary connection, and arbitrary refinement of independent covers, were concluded. Finally, some two‐dimensional (2‐D) tunnel flow examples were analyzed and the numerical results were compared with the analytical results. 3‐D examples with complex fracture distributions were also analyzed. In addition, the computational scale of the developed program was tested by increasing the number of computational elements. The results show that our model can accurately analyze the groundwater flow of rocks surrounding tunnels with complex fracture distributions.  相似文献   

From cave geomorphology to Palaeolithic human behaviour: speleogenesis,palaeoenvironmental changes and archaeological insight in the Atxurra-Armiña cave (northern Iberian Peninsula)     

Martin Arriolabengoa  Inaki Intxaurbe  Mª Ángeles Medina-Alcaide  Olivia Rivero  Joseba Rios-Garaizar  Inaki LÍbano  Peru Bilbao  Arantza Aranburu  Hai Cheng  Richard Lawrence Edwards  Diego Garate 《第四纪科学杂志》2020,35(6):841-853

A detailed geomorphological study was performed in the Atxurra-Armiña cave system (northern Iberian Peninsula) to decode landscape evolution, palaeoenvironmental changes and human use of a cave within an Inner Archaeological Context. The results show an average incision rate of the river of <0.083 mm a^–1 for at least the last 419 ka, with interruptions due to sedimentary inputs. Moreover, allostratigraphic units comprising fluviokarstic deposits at the base and flowstone formation at the top have been shown to be climatically controlled, formed either during glacial–interglacial cycles or during interstadial cycles. Finally, when the cave was used by humans in the Late Magdalenian, the lower entrance was closed, and they must therefore have entered the cave through the upper entrance. To reach the sectors selected to decorate the panels, they probably travelled from the upper cave level, as the current crawlway was wider than today, according to our U/Th dating. Once these visitors reached the panels, the floor in the main gallery would have been around 15 cm lower than at present. However, the morphology of the conduit was similar; this has significant implications for understanding and interpreting the human use of the cave during the Palaeolithic.  相似文献   

A survey of trace element distribution in tissues of stone crabs (Menippe mercenaria) from South Carolina coastal waters     

Reed LA  Pennington PL  Wirth E 《Marine pollution bulletin》2010,60(12):2297-2302

The stone crab (Menippe mercenaria) is an important component of the estuarine food web as both predator and prey. Stone crabs live in sediment, primarily consume oysters, and as a result, have the potential to accumulate significant quantities of pollutants including metals. In South Carolina, the stone crab is becoming a targeted fishery as an ecologically sustainable seafood choice. To date, no studies have reported metals in stone crab tissues. This study examined the distribution of major and minor trace elements in chelae and body muscle, gill, and hepatopancreas. Crabs were collected from three tidal areas within Charleston County, South Carolina, with differing upland use. Results were compared by collection location and by tissue type. Concentrations of some metals associated with anthropogenic activities were up to three times higher in crabs from sites adjacent to more urbanized areas. Concentrations in edible tissues were below historical FDA levels of concern.  相似文献   

跨断层形变观测显示的断裂活动特征分析研究   总被引：4，自引：3，他引：1  

李杰  刘文义  楼关寿  唐廷梅  冯志军  荆强 《中国地震》2010,26(1)

系统分析了全国不同地区和断裂带的活动特征及其与地质构造和强震的关系,着重从逆断层、正断层和基岩标、土层标两方面讨论了断层活动速率。研究结果表明:断层形变活动速率的大小和方向与形变场地所处的地质构造位置有关;断层现今垂直和水平运动既具继承性也具有一定的新生性,既具阶段性又具有时空差异性;断裂活动与地震活动在时空上具有一致性;断层活动水平形变量大于垂直形变量;正断层的活动水平较逆断层高,它们对监测地震孕育过程引起的断层活动都是有效的,没有本质上的区别;土层标石场地的垂直和水平形变平均活动速率均比基岩标石场地的高,但两者均可监测到地震前兆异常。  相似文献   

Precise dating of abrupt shifts in the Asian Monsoon during the last deglaciation based on stalagmite data from Yamen Cave, Guizhou Province, China   总被引：1，自引：0，他引：1  

EDWARDS R. Lawrence 《中国科学:地球科学(英文版)》2010,(5)

Based on 33 U/Th dates and 1020 oxygen isotopic data from stalagmite Y1 from Yamen Cave, Guizhou Province, China, a record of the Asian Summer Monsoon (ASM) was established. The record covers the last deglaciation and the early Holocene (from 16.2 to 7.3 ka BP) with an average oxygen isotope resolution of 9 years. The main millennial-scale deglacial events first identified in Greenland (Greenland Interstadial Events: GIS 1e through GIS 1a) and later in China are clearly present in the Y1 record. By analogy to earlier work, we refer to these as Chinese Interstadials (CIS): CIS A.1e to CIS A.1a. The onset of these events in Y1 δ18O records are nominally dated at: 14750±50, 14100±60, 13870±80, 13370±80, and 12990±80 a BP. The end of CIS A.1a or the beginning of the Younger Dryas (YD) event is nominally at 12850±50 a BP and the end of the YD dates to 11500±40 a BP. The δ18O values shift by close to 3‰ during the transition into the Bφlling-Allerφd (BA, the onset of CIS A.1e) and at the end of the YD. Comparisons of Y1 to previously published early Holocene records show no significant phase differences. Thus, the East Asia Monsoon and the Indian Monsoon do not appear to have been out of phase during this interval. The Y1 record confirms earlier work that suggested that solar insolation and North Atlantic climate both affect the Asian Monsoon.  相似文献   

Catalytic Reduction of Hexaminecobalt(III) by Pitch‐based Spherical Activated Carbon (PBSAC)     

Yu Chen  Yan‐peng Mao  Hai‐song Zhu  Jing‐yi Cheng  Xiang‐li Long  Wei‐kang Yuan 《洁净——土壤、空气、水》2010,38(7):601-607

The wet ammonia (NH₃) desulfurization process can be retrofitted to remove nitric oxide (NO) and sulfur dioxide (SO₂) simultaneously by adding soluble cobalt(II) salt into the aqueous ammonia solution. Activated carbon is used as a catalyst to regenerate hexaminecobalt(II), Co(NH₃), so that NO removal efficiency can be maintained at a high level for a long time. In this study, the catalytic performance of pitch‐based spherical activated carbon (PBSAC) in the simultaneous removal of NO and SO₂ with this wet ammonia scrubbing process has been studied systematically. Experiments have been performed in a batch stirred cell to test the catalytic characteristics of PBSAC in the catalytic reduction of hexaminecobalt(III), Co(NH₃). The experimental results show that PBSAC is a much better catalyst in the catalytic reduction of Co(NH₃) than palm shell activated carbon (PSAC). The Co(NH₃) reduction reaction rate increases with PBSAC when the PBSAC dose is below 7.5 g/L. The Co(NH₃) reduction rate increases with its initial concentration. Best Co(NH₃) conversion is gained at a pH range of 2.0–6.0. A high temperature is favorable to such reaction. The intrinsic activation energy of 51.00 kJ/mol for the Co(NH₃) reduction catalyzed by PBSAC has been obtained. The experiments manifest that the simultaneous elimination of NO and SO₂ by the hexaminecobalt solution coupled with catalytic regeneration of hexaminecobalt(II) can maintain a NO removal efficiency of 90% for a long time.  相似文献   

沽源盆地大官厂铀钼多金属矿床成矿机理及成矿 预测   总被引：1，自引：0，他引：1       下载免费PDF全文

伍静  娄峰  李宏卫  肖成东  樊秉鸿  沈光银  薛清波 《地学前缘》2011,18(1):133-140

沽源火山盆地是中国华北地块北缘一条重要的铀钼多金属成矿带--燕辽成矿带的重要组成部分,长期以来受到地学界的广泛关注。由于该带矿床多数产于火山岩中,其成因一直被认为是与火山岩有关的矿床。文中根据花岗岩原地重熔理论及大官厂矿区地质、地球物理资料特征,提出大官厂矿区其下隐伏有花岗岩体,成矿作用主要与隐伏的花岗岩有关;同时分析出本区隐伏花岗岩体的重熔界面隆起部位,指出该位置(背斜核部)是成矿最有利部位,推测可能隐伏有斑岩型钼矿床,为本矿区的找矿指明了新的方向。  相似文献   

多次重熔的成矿作用:对甘肃中川岩体成岩成矿过程的再认识   总被引：2，自引：1，他引：1       下载免费PDF全文

李宏卫  娄峰  许冠军  陈震  陈小月 《地学前缘》2011,18(1):126-132

在花岗岩原地重熔成因理论的基础上,对甘肃中川岩体的地质、地球化学和成矿学资料进行重新“编码”,证实中川花岗岩体的形成是该区地壳于早中生代两次原地熔融或重熔的结果。陆壳的多次熔融(重熔)不但造成复式岩体的同心圆状构造和岩体化学成分的规律性变化,同时造成不同元素的成矿作用。富金地层被卷入的中生代早期的地壳熔融事件,使印支-燕山早期的成矿作用主要形成金或金多金属硫化物矿床。根据岩体内部发育的NNE向破裂体系特征及沿断裂发生的热液活动,推断该区深部在晚白垩世-古近纪尚发生过一次重熔事件或尚存在重熔岩浆。晚期的重熔岩浆具有较高的氧逸度f(O2),此为铀元素在热液中大量存在的必要条件,因而本阶段的成矿作用主要导致铀的富集,在岩体内部的断裂中形成脉状的“花岗岩型”铀矿床。  相似文献