A simple prediction model for wall deflection caused by braced excavation in clays     

《Computers and Geotechnics》2015

Deep excavations particularly in deep deposits of soft clay can cause excessive ground movements and result in damage to adjacent buildings. Extensive plane strain finite element analyses considering the small strain effect have been carried out to examine the wall deflections for excavations in soft clay deposits supported by retaining walls and bracing. The excavation geometry, soil strength and stiffness properties, and the wall stiffness were varied to study the wall deflection behavior. Based on these results, a simple Polynomial Regression (PR) model was developed for estimating the maximum wall deflection. Wall deflections computed by this method compare favorably with a number of field and published records.  相似文献   

A stabilized single-point finite element formulation for three-dimensional dynamic analysis of saturated soils     

《Computers and Geotechnics》2015

  相似文献   

Geochemical constraints on the contribution of Louisville seamount materials to magmagenesis in the Lau back-arc basin,SW Pacific     

Zheng-Gang Li  Yan-Hui Dong  Ji-Qiang Liu  Ling Chen 《International Geology Review》2015,57(5-8):978-997

Seamounts are an integral part of element recycling in global subduction zones. The published trace element and Pb-Sr-Nd isotope data for basaltic lavas from three key segments (Central Lau Spreading Ridge (CLSR), Eastern Lau Spreading Ridge (ELSR), and Valu Fa Ridge (VFR)) of the Lau back-arc basin were compiled to evaluate the contribution of Louisville seamount materials to their magma genesis. Two geochemical transitions, separating three provinces with distinct geochemical characteristics independent of ridge segmentation, were identified based on abrupt geochemical shifts. The origin of the geochemical transitions was determined to be the result of drastic compositional changes of subduction components added into the mantle source, rather than the transition from Indian to Pacific mid-ocean ridge basalt (MORB) mantle, or due to variable mantle fertilities. The most likely explanation for the drastic shifts in subduction input is the superimposition of Louisville materials on ‘normal’ subduction components consisting predominantly of aqueous fluids liberated from the down-going altered oceanic crust and minor pelagic sediment melts. Quantitative estimation reveals that Louisville materials contributed 0–74% and 21–83% of the Th budget, respectively, to CLSR and VFR lavas, but had no definite contribution to the lavas from the ELSR, which lies farthest away from the subducted Louisville seamount chain (LSC). The spatial association of the subducted LSC with the Louisville-affected segments suggests that the Louisville signature is regionally but not locally available in the Tonga subduction zone. Besides, the preferential melting of subducted old Cretaceous LSC crust instead of the old normal Pacific oceanic crust at similar depths implies that elevated temperature across the subduction interface or seamount erosion and rupture were required to trigger melting. A wider implication of this study, thus, is that seamount subduction may promote efficiency of element recycling in subduction zones.  相似文献   

新疆东天山突出山铜铁矿床地球化学特征与地质意义          下载免费PDF全文

尚海军  张志欣  李卫东  张耀选  仇银江  刘锋  周可法  李强  王金林 《地质科学》2015,(4):1102-1119

突出山铜铁矿床是东天山雅满苏石炭纪弧前-岛弧带中代表性的铁多金属矿床, 矿体呈透镜状、脉状、似层状赋存于上石炭统底坎尔组下亚组火山岩中。矽卡岩阶段包裹体均一温度为151℃~>380℃, 盐度为1.91%~23.18% NaCl_eq, 密度为0.76~1.09 g/cm³, 热液硫化物阶段包裹体均一温度为101℃~280℃, 盐度为0.35%~23.05% NaCl_eq, 密度为0.74~1.13 g/cm³, 表明成矿流体属于中-高温、中-低盐度、中-低密度的NaCl-H₂O体系。(绿泥石)绿帘石矽卡岩、磁铁矿(镜铁矿)矿石、含磁铁矿灰岩的稀土配分模式均为轻稀土相对富集的右倾型(LREE/HREE=2.85~9.21), 以出现负铕异常(δEu=0.22~1.09)和铈异常不发育为特征, 与底坎尔组火山岩相似, 表明成矿物质来源于底坎尔组火山岩。矿区矽卡岩可能是火山热液交代碳酸盐岩形成的, 成矿条件为中-高温、较为宽广的氧化还原环境, 矿床成因属火山热液交代型。  相似文献   

探测仪器特性曲线异常分析     

敬颖  闵锦忠  刘立辉  吴恒  徐爽 《气象科技》2015,43(4):601-606

探测仪器感应曲线发生变化,造成升速异常、等压面的温度、湿度错误、雷达〖CD*2〗气压高差偏大、时间〖CD*2〗高度线曲变化异常造成的规定高度上的风误差偏大,使部分资料或整份资料失真,影响探测准确性。本文主要从仪器的感应曲线变化后对各气象要素产生的影响进行分析,得出结论：不同的元件变性对气象要素产生的影响不同,气压变化的影响侧重于高差和升速,温度变化则侧重于规定等压面的温度绝对误差和规定等压面高度的偏差。采用绝对误差计算、加密气象要素计算等方法,结合图形、数据对比,可以确定感应曲线变化时间,从而及时、有效的对探测数据做出合适的处理,进一步提高探测数据的精准度。  相似文献   

地理国情要素数据成果的一致性检查方法     

李海  周进  闫庆庆  陈春希 《测绘通报》2021,(12):115-119

本文结合全国地理国情要素数据成果过程质量控制、质量复核工作,以及地理国情要素数据成果自身、与地表覆盖分类数据成果、与外业调查核查数据、与专题资料的一致性要求,通过分析检查中发现的质量问题,提出了地理国情要素数据成果的质量控制方法。该方法为国情要素数据成果的质量控制提供了技术参考,为质检工作提供了方法依据。  相似文献   

云南马关火山角砾岩及其包体岩石岩相学和元素地球化学特征及其地质意义   总被引：1，自引：0，他引：1  

李春辉  刘显凡  赵甫峰  陶专  吴冉  楚亚婷  王艳艳  肖继雄  宋祥峰 《地质科技情报》2011,30(3):48-56

对云南马关地区的爆破火山角砾岩及其中各类包体岩石开展了系统的岩相学和元素地球化学研究.结果表明,与爆破火山角砾岩有成因联系的岩石有3类:①以爆破火山角砾岩胶结物形式产出的碧玄岩和钾玄岩.②作为寄主岩的碧玄岩和钾玄岩中包含(携带)的尖晶石相地幔橄榄岩包体,进一步划分为两类:一类是具原始地幔性质的岩石,成分较单一,地幔交代...  相似文献   

长江口外海域表层沉积物微量元素地球化学特征   总被引：1，自引：1，他引：0  

蓝先洪  张志殉  李日辉  王中波  陈晓辉  侯方辉 《现代地质》2011,25(6)

对采自长江口外海域187个表层沉积物的25个微量元素含量进行了标准差系数、相关分析及R型因子分析,探讨了微量元素的来源和分布特征。长江口外海域沉积物微量元素Li、V、Cr、Co、Ni、Ga、Cu、Zn、Th和Rb分布基本相似;Sr分布与Li、Cu、Pb、Zn、Th和Rb相反;研究区东南部Sr分布与生物作用有明显关系;Cd和Mo分布与粒度之间的相关性较差,主要受氧化还原环境的控制;Zr分布反映了长江物源的影响。相关分析和R型因子分析结果表明,沉积作用、粒度控制效应、海洋生物作用、氧化还原环境和源区地质背景等对长江口外海域表层沉积物中微量元素分布起着主要控制作用。  相似文献   

冀中南平原土壤氟地球化学特征及其控制因素   总被引：1，自引：0，他引：1  

谷海峰  栾文楼  杜俊  陈志贤  蔡奎  李超 《物探与化探》2011,35(3):388-392

详细研究了冀中南平原土壤氟的地球化学特征,并探讨其控制因素。冀中南平原整体氟含量较高,且分布不均匀,具有明显分带性,分别出现4个高氟带和4个低氟带。氟在该区的分布明显受自然地理、地质因素和人为因素控制,且以自然地理、地质因素为主。在自然地理、地质因素中地貌起主导作用,而在人为因素中化肥为主导因素。  相似文献   

A Kinematic Thermal Model for Descending Slabs with Velocity Boundary Layers: A Case Study for the Tonga Subducting Slab   总被引：3，自引：0，他引：3  

ZHANG Keliang an  WEI Dongping 《《地质学报》英文版》2011,85(1):211-222

For the purpose of investigating the influence of metastable olivine (MO) phase transformations on both deep seismicity and stagnation of slabs, we constructed a 2-dimensional finite element thermal model for a 120 Ma-old 50o dipping oceanic lithosphere descending at 10 cm/yr with velocity boundary layers, which would mitigate the interference of constant velocity field for the slab. The resulting temperatures show that most of intermediate and deep earthquakes occurring within the Tonga slab are occurring inside the 800oC and 1200oC isotherm, respectively. The elevation of olivine transformation near ~410 km and respective persistence of metastable olivine and spinel within the transition zone and beneath 660 km would thus result in bimodal positive, zonal, negative density anomalies, respectively. These results together with the resulting pressure anomalies may reflect the stress pattern of the Tonga slab: (i) slab pull force exerts above a depth of ~230 km; (ii) MO existence changes the buoyancy force within the transition zone and facilitates slab stagnation at a depth of 660 km; (iii) as the subducting materials accumulated over 660 km, deepest earthquakes occur due to MO transformation; (iv) a flattened ‘slab’ may penetrate into the lower mantle due to the density increment of Sp transformation.  相似文献