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461.
软土地基偏斜管桩检测及纠偏处理实例 总被引:1,自引:0,他引:1
软土地基的PHC管桩若施工不当,较易出现偏斜和断裂的现象。本文通过工程案例分析了事故原因,介绍了偏斜管桩的检测方法和顶推纠偏法的施工方法和结果。处理后的桩基经检测承载力和结构完整性满足设计要求,证明了该施工方法的有效性,为类似工程提供了参考价值。 相似文献
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土壤样品分别采于山西省大同、太原和临汾3个地区。实验分成吸附解吸、竞争吸附和运移实验3个部分。其中吸附实验又分成砂粒土壤和粘粒土壤2个粒级分别实验。结果表明:在常温常压下,3种土壤对Cd的吸附用Langmuir模式来拟合较合适,土壤粘粒的吸附能力大于土壤砂粒的吸附能力。Zn^2+与Cd^2+共存时,Cd的吸附受到抑制,在本实验浓度下,腐殖酸对土壤吸附Cd的抑制作用不明显。解吸过程显示土壤对Cd离子的解吸与有机碳、阳离子代换量成负相关。Cd在土壤中的穿透曲线是Cd在土壤中吸附、解吸、络合、迁移等作用的综合体现.Cd在各种土壤中的运移时间顺序为:大同土壤〉临汾土壤〉太原土壤,从而得出Cd在壤质砂土中运移得最快、在粉土中运移得最慢的结论。 相似文献
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M. F. Bransby 《国际地质力学数值与分析法杂志》1999,23(15):1909-1926
Two-dimensional finite element analysis has been used to find load–transfer relationships for translation of an infinitely long pile through undrained soil for a variety of soil-constitutive models. It has been shown that these load–transfer curves can be used as p–y curves in the analysis of single piles undergoing lateral pile head loading in undrained soils with non-linear stress–strain laws. Lateral pile response deduced from 2-D analysis input to the subgrade reaction method has been compared to the behaviour of a single pile analysed using three-dimensional finite element analysis. Good agreement between the two methods for non-linear soils suggests that the 2-D analysis may form a useful design method for calculation of p–y curves. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
464.
松散沉积物中的断层常常未留下明显的宏观形迹,单靠肉眼观测往往难以确定断层是否存在,即使判断出有断层亦常难以确定其活动性质和活动方式。大量资料表明,微观分析是探讨松散沉积物中断层和古地震事件的行之有效的方法。文中通过对采自顺义-前门-良乡断裂的顺义油库探槽样品的微观分析,探寻松散沉积物中宏观形迹不明断层的显微沉积学和显微构造标志,并据此判断是否伴随古地震事件。研究结果表明,松散沉积物中的断层在微观上表现为明显的滑移错动面、微破碎带、变形条带、泥质充填条带、黏土矿物集中和定向的带、铁质物集中的带以及碎屑颗粒集中和定向的带等。显微沉积学研究则表明,断层及其附近的地层中显微纹层常发生扰动现象,断层内样品碎屑颗粒粒度分布的粗尾段降低而细尾端增高,棱角状颗粒含量明显增加;扫描电镜分析表明这些碎屑颗粒有新的破裂产生,而分形研究获得了断层内样品较高的分维值(D约为2.5)。上述特征可以作为松散沉积物中宏观形迹不明断层的微观判断标志。此外,本研究还发现了与震击物的一些宏观标志,如球状体或枕状体、负荷构造、流体流、固体物质流以及有机物的悬浮等非常相似的微观特征。显然,它们可以作为判断古地震事件的微观标志。上述结果表明,微观分析是 相似文献
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468.
现行《岩土工程勘察规范》(GB50021-2001)及《建筑地基基础设计规范》(GB50007-2002)规定,确定岩石地基承载力特征值常用方法有取岩样作室内试验和现场原位载荷试验等。软质岩的岩石试样作室内试验时,因环境条件与实地有明显的差异,试验结果多不理想,现场静载试验在实际环境条件下进行,能更好地挖掘软质岩石地基承载力特征值的潜力,减少基础工程造价。 相似文献
469.
Evaluation of seismic displacement demands from the September 19, 2017 Puebla‐Morelos (Mw = 7.1) earthquake in Mexico City 下载免费PDF全文
This short communication presents the assessment of seismic inelastic and elastic displacement demands computed from earthquake ground motions (EQGMs) recorded in Mexico City during the intermediate‐depth intraslab Puebla‐Morelos earthquake on 19 September 2017 (Mw = 7.1). Evaluation is conducted by means of peak elastic and inelastic displacement demand spectra, inelastic displacement ratio, CR, spectra, and generalized interstory drift spectra computed for selected recording stations located in different soil sites of Mexico City, including those located in areas of reported collapsed buildings. Results of this study confirm previous observations made from interplate (subduction) EQGMs that peak inelastic displacement demands are greater than corresponding elastic counterparts for short‐to‐medium period structures, while the opposite is true for medium‐to‐long period structures. Possible basin site effects were identified from generalized interstory drift spectra. It is also shown that an equation introduced in the literature to obtain estimates of CR developed from interplate EQGMs provides also a good estimate for mean CR computed from the intermediate‐depth intraslab EQGMs. 相似文献
470.
Evaluating spatial variation of suspended sediment rating curves in the middle Yellow River basin,China 总被引:1,自引:0,他引:1 下载免费PDF全文
Abstract The suspended sediment load in the middle Yellow River basin (YRB) cannot be well predicted by capacity‐based transport formulas because a large fraction of suspended sediment load is composed of wash load. This study evaluated the spatial variations of sediment rating curves (SRCs) in the middle YRB. Both power and linear SRCs were used to fit daily flow and suspended sediment concentration (SSC) historical data at 49 gauging stations throughout the middle YRB. The spatial variation in regression coefficients was investigated, and the relationship between regression coefficients and the physical characteristics of watersheds was discussed. The results indicate that SRC regression coefficients vary with drainage area and basin slope, but their responses to these parameters are remarkably different in watersheds with different underlying surfaces, which indicates the significance of sediment availability, erodibility, and grain size distribution. For power SRCs representing sediment transport in unsaturated flows, the regression coefficients are more closely correlated with the drainage area in loess regions and with the basin slope in rock mountain regions. For linear SRCs representing sediment transport in saturated flows, saturated SSCs vary with coarse (particle size > 0.05 mm) and fine (particle size < 0.01 mm) fractions in suspended sediment. The maximum saturated SSC among the different gauging stations is associated with the optimal grain size composition of suspended sediment, which has been proposed for loess regions in previous studies. This study provides theoretical support for estimating the regression parameters for sediment transport modelling, especially in ungauged basins. 相似文献