CFG桩复合地基沉降计算探讨   总被引：8，自引：0，他引：8  

潘星 《岩土力学》2005,26(Z1):248-251

CFG桩（水泥粉煤灰碎石桩）复合地基是新近发展起来的一项地基处理技术,具有承载力提高幅度大,地基沉降小,适用范围广,造价低,施工方便等特点。阐述了CFG桩复合地基加固机理及沉降模式,详细讨论了其沉降计算,包括它的计算厚度、影响因素、压缩模量选取及附加压力计算等。提出按变形控制理论进行变形计算有其优点,但仍有很多工作要做。  相似文献   

Modelling of the retreat process of composite riverbank in the Jingjiang Reach using the improved BSTEM          下载免费PDF全文

Quanli Zong  Junqiang Xia  Meirong Zhou  Shanshan Deng  Yi Zhang 《水文研究》2017,31(26):4669-4681

Bank retreat in the Jingjiang Reach is closely related not only to the near‐bank intensity of fluvial erosion but also to the composition and mechanical properties of bank soils. Therefore, it is necessary to correctly simulate bank retreat to determine the characteristics of fluvial processes in the Jingjiang Reach. The current version of bank stability and toe erosion model (5.4) was improved to predict riverbank retreat, by inputting a dynamic water table, and calculating the approximation of the distribution of dynamic pore water pressure in the soil near the river bank face, and considering the depositional form of the failed blocks, which is assumedly based on a triangular distribution, with the slope approximately equalling the stable submerged bank slope and half of collapsed volume deposited in the bank‐toe region. The degrees of riverbank stability at Jing34 were calculated using the improved bank stability and toe erosion model. The results indicate the following trends: (a) the degrees of riverbank stability were high during the dry season and the rising stage, which led to minimal bank failure, and (b) the stability degrees were low during the flood season and the recession stage, with the events of bank collapse occurring frequently, which belonged to a stage of intensive bank erosion. Considering the effects of bank‐toe erosion, water table lag, and the depositional form of the collapsed bank soil, the bank‐retreat process was simulated at the right riverbank of Jing34. The model‐predicted results exhibit close agreement with the measured data, including the total bank‐retreat width and the collapsed bank profile. A sensitivity analysis was conducted to determine the quantitative effects of toe erosion and water table lag on the degree of bank stability. The calculated results for toe erosion indicate that the amount of toe erosion was largest during the flood season, which was a primary reason for bank failure. The influence of water table lag on the degree of stability demonstrates that water table lag was an important cause of bank failure during the recession stage.  相似文献   

Three‐dimensional dynamic response of ground with a poroviscoelastic interlayer to a harmonic moving rectangular load          下载免费PDF全文

S.‐J. Feng  Y.‐C. Li  Z.‐L. Chen  H.X. Chen 《国际地质力学数值与分析法杂志》2017,41(7):1055-1076

Stratification is a basic characteristic of ground. Due to the influence of ground water, saturated weak interlayers widely exist, particularly in soft soil area. An interlayer of high compressibility and low strength has a substantial effect on dynamic response of the ground, especially under high speed moving load. Thus, a comprehensive investigation in the influence of interlayer is essential and useful in geotechnical and transportation‐related engineering. This paper presents a three‐dimensional semi‐analytical approach to study the dynamic response of a layered ground with a soft saturated interlayer. The ground is modelled as a half‐space consisting of three parts: a viscoelastic upper layer, a saturated poroviscoelastic interlayer governed by Biot's theory and a viscoelastic half‐space. An ‘adapted stiffness matrix’ is proposed to obtain the semi‐analytical solution to the system. Comprehensive parametric study is conducted to investigate the influences of existence, geometrical and physical properties of the interlayer. Depth, thickness, hydraulic permeability of the interlayer, load speed and frequency significantly influence the dynamic response of the ground, among which the interlayer depth plays a dominant role. Resonant frequency exists, which is highly affected by the interlayer thickness, especially in low speed regime. Both hydraulic permeability and boundary conditions of the interlayer influence the characteristics of pore pressure distribution. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

An analytical model for vapor‐phase volatile organic compound diffusion through landfill composite covers          下载免费PDF全文

Haijian Xie  Huaxiang Yan  Hywel R. Thomas  Shijin Feng  Qihua Ran  Peixiong Chen 《国际地质力学数值与分析法杂志》2016,40(13):1827-1843

One‐dimensional mathematical models for vapor‐phase volatile organic compound (VOC) diffusion through composite cover barriers are presented. An analytical solution to the model was obtained by the method of separation of variables. The results obtained by the proposed solution agree well with those obtained by a numerical analysis. Based on the proposed analytical model, the VOC breakthrough curves of five different composite covers are compared. The effects of degree of saturation of geosynthetic clay liner (GCL) or compacted clay liner (CCL) on VOC migration in the composite covers are then presented. Results show that the composite cover barriers provide much better diffusion barriers for VOC than the single CCL. The top surface steady‐state flux for a composite barrier, consisting of a 1.5 mm geomembrane (GM) and a 20 cm CCL, can be 8.3 times lower than that for a 30 cm CCL. The surface steady‐state flux for the case with (1.5 mm GM + 6 mm GCL) was found to be 2.3 times lower than that for the case with (1.5 mm GM + 20 cm CCL). The degree of saturation S_r of the CCL has a great influence on VOC migration in composite covers when S_r is larger than 0.5. The steady‐state flux at the surface of GM for the case with S_r = 0.7 can be 1.8 times lower than that for the case with S_r = 0.2. The proposed analytical model is relatively simple and can be used for verification of complicated numerical models, analysis of experimental data and performance assessment of composite cover barriers. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

宁波海雾特征和预报着眼点   总被引：4，自引：3，他引：1  

周福  钱燕珍  金靓  孙军波 《气象》2015,41(4):438-446

本文用1971—2011年石浦站资料及NCEP再分析资料,统计分析宁波各种强度海雾特征和合成分析其出现的天气背景。统计表明：海雾多发生于4—6月,主要出现在23时至次日11时,其中23时至次日02时最多,11时后消散。风力在2~3级的西南或东北风有利于海雾的发生。相对湿度在90%~95%,本站气压在990~1002 hPa时,海雾发生概率随着湿度的增加及气压的减小而增加,但对于能见度≤50 m的强浓雾来说,相对湿度和本站气压范围分别为92%~95%和990~999 hPa,且强浓雾随湿度及气压的增加而增加。宁波海雾通常出现在江淮气旋、冷空气影响前和梅雨锋中低涡东移前。合成分析表明：锋面雾一般形成于系统过境前2～3 d,局地上空西南暖湿气流影响时;或静止锋南侧,局地上空风速较小,且前期有充足水汽汇聚并导致湿层增厚;平流雾形成时上空位于西南涡前部,长时间西南暖湿气流输送,形成一定厚度和范围的湿度层,在该天气背景下,下垫面的气 海温差维持在0~1.5℃左右,露点 海表温差在-0.5~0℃上下。浓雾（强浓雾）的形成需在稳定的大气层结下,长时间深厚的暖湿气流里,同时来自北方的冷海流不断注入宁波沿海。此外,雾的强度与暖平流及海表冷平流的强度有较大关系。这些对宁波海雾及其强度的预报有较好指导作用。  相似文献   

Characterization and source apportionment of volatile organic compounds in urban and suburban Tianjin,China   总被引：1，自引：0，他引：1  

Meng Han  Xueqiang Lu  Chunsheng Zhao  Liang Ran  Suqin Han 《大气科学进展》2015,32(3):439-444

Tianjin is the third largest megacity and the fastest growth area in China, and consequently faces the problems of surface ozone and haze episodes. This study measures and characterizes volatile organic compounds(VOCs), which are ozone precursors, to identify their possible sources and evaluate their contribution to ozone formation in urban and suburban Tianjin,China during the Ha Chi(Haze in China) summer campaign in 2009. A total of 107 species of ambient VOCs were detected,and the average concentrations of VOCs at urban and suburban sites were 92 and 174 ppbv, respectively. Of those, 51 species of VOCs were extracted to analyze the possible VOC sources using positive matrix factorization. The identified sources of VOCs were significantly related to vehicular activities, which specifically contributed 60% to urban and 42% to suburban VOCs loadings in Tianjin. Industrial emission was the second most prominent source of ambient VOCs in both urban and suburban areas, although the contribution of industry in the suburban area(36%) was much higher than that at the urban area(16%). We conclude that controlling vehicle emissions should be a top priority for VOC reduction, and that fast industrialization and urbanization causes air pollution to be more complex due to the combined emission of VOCs from industry and daily life, especially in suburban areas.  相似文献   

新疆阿尔泰库卫铜镍硫化物-钛铁氧化物复合型矿化镁铁-超镁铁质杂岩体成因   总被引：3，自引：2，他引：1  

李强  柴凤梅  杨富全  杨俊杰 《岩石学报》2015,31(8):2211-2229

库卫镁铁-超镁铁质杂岩体位于新疆阿尔泰南缘,兼具铜镍矿化岩体和钒钛铁矿化岩体的双重特征,主要组成岩石类型有中粒辉长岩、条带状橄榄辉长岩、橄榄苏长辉长岩、角闪辉长岩和含橄辉长岩等。本文采用LA-ICP-MS锆石U-Pb定年法,获得中粒辉长岩、橄榄苏长辉长岩和含橄辉长岩的加权平均年龄分别为398.7±3.7Ma、397.5±2.3Ma和385.2±1.6Ma,表明库卫岩体是早中泥盆世构造-岩浆活动的产物。岩体的主量元素显示其属亚碱性系列,并具有向拉斑系列岩石演化的趋势。具有Ba、U、Ta、Pb、Sr、Ti和Eu的正异常,Th的负异常,显示了相似的LREE相对富集的右倾型配分模式,表明它们可能为同源岩浆演化的产物。结合地球化学特征和区域地质背景,推测库卫岩体为早中泥盆世俯冲消减环境的产物,其原始岩浆可能来源于受俯冲物质交代的地幔楔和软流圈的混合体,不同的岩石类型是相似来源的岩浆经强烈分异的结果。库卫岩体兼具铜镍矿化岩体和钒钛铁矿化岩体的双重特征,但形成铁钛矿床的潜力略显不足。  相似文献   

关于金刚石钻头胎体硬度分布的试验研究          下载免费PDF全文

汤凤林  Чихоткин В.Ф.  彭莉  李晓磊  赵俊彩 《探矿工程》2015,42(9):65-71

钻头胎体硬度是一项重要技术指标,应与所钻岩石的硬度（可钻性）和研磨性相适应。胎体硬度直接影响钻探技术经济指标的提高和钻进工艺参数的选择。试验研究表明,钻头胎体硬度分布很不均匀,差别很大。首先应从胎体烧结工艺上找原因,烧结压力偏小（5 MPa）可能是首要原因。钻头、工艺参数、操作技术等都很重要,缺一不可。钻进技术经济指标低,不一定都是钻头质量问题,要从多方面进行研究。提倡把经验打钻提高到科学打钻上来。  相似文献   

基于土地利用格局变化的胶东半岛生境质量时空演变特征研究   总被引：1，自引：0，他引：1  

王超  常勇  侯西勇  刘玉斌 《地球信息科学学报》2021,23(10):1809-1822

生境质量受人类活动引起的土地利用变化影响日益严重,因此,对于生境质量的监测与评估具有重要意义。基于2000、2005、2010、2015和2020年土地利用数据,利用GIS空间分析技术和InVEST-Habitat Quality模型,对胶东半岛土地利用和生境质量时空特征进行定量化描述,甄别生境质量变化的热点区域,探究胶东半岛土地利用格局变化对生境质量的影响。结果表明：耕地一直是胶东半岛的主要土地利用类型,该地区整体土地转移的速率呈缓慢上升趋势,建设用地的转入和耕地的转出尤为突出;胶东半岛5个年份的生境质量平均值分别为0.565、0.560、0.552、0.548、0.545,总体上呈下降趋势;不同等级区域的面积占比大小依次为：中等、高、低、较高、较低;中等生境质量区域面积减少最多,而低等生境质量区域面积增加最多,内陆区域生境质量高值区面积小且分散,而生境质量低值区分布相对集中且呈块状、片状;生境质量指数变化速率在减缓;不同区域中,生境质量对于土地利用变化的响应不同,建设用地增加是胶东半岛地区生境质量整体下降的主要原因,而滨海湿地增加提高了局部区域的生境质量。本研究将为胶东半岛地区土地的规划管理和生态环境保护提供相关科学参考。  相似文献   

一种基于NDISI的复合权重波段双差值不透水面提取指数     

黄菲  刘正才  谢婷  何永红 《地球信息科学学报》2021,23(10):1850-1860

针对现有遥感指数提取不透水面取结果中混有沙地、裸土等噪声的问题,本文在传统NDISI的形式基础上,提出一种新型的复合权重双差值不透水面指数（Composite-Weighted Double-Difference Impervious Surface Index, CWDDISI）。通过波段的2次差值扩大不透水面和裸地的光谱表现差距,并以植被指数和夜光灯数据作为约束权重,以此提高热红外波段中的不透水面信息比重的同时降低噪声地物的干扰。本文利用Landsat8 OLI-TIR、Landsat7 ETM⁺以及Sentinel-2A光谱数据,结合珞珈一号、DMSP-OL以及VIIRS/DNB夜光数据,选取广州市、西安市、咸阳市以及深圳市、北京市为实验区展开对比实验。研究结果：① CWDDISI具有很好的多区域适用性。在2018年的数据集上,相较于NDISI,CWDDISI在以山地为主的广州市试验区和以平原为主的西安市、咸阳市实验区中,其不透水面提取总精度分别提高了6.02%和7.56%,Kappa系数提高了0.078和0.104; ② CWDDISI具有很好的多时相数据适用性。实验选取2002年和2016年的Landsat7 ETM⁺多时相数据,以深圳市和北京市为实验区展开对比;相较于NDISI,CWDDISI的不透水面总精度分别提高了1.74%和2.13%,Kappa系数分别增加了0.028和0.076。通过实验对比结果可证明,CWDDISI能够克服传统不透水面指数难以区分不透水面信息和裸土区域的问题,为后续不透水面指数的研究提供参考价值。  相似文献