基于卸荷和抗震分析理论的大岗山坝肩边坡锚固优化研究     

刘杰  李建林  宛良朋  蔡健  肖蕾 《岩土力学》2012,33(Z2):275-282

基于卸荷岩体的理论和方法,对大岗山水电站坝肩边坡进行研究。以大型通用有限元程序ADINA为计算平台,对比分析坝肩边坡卸荷后,不同地震加速度及不同锚固长度和锚固吨位在卸荷条件下关键点的位移和应力以及塑性区的变化规律,认为边坡开挖变形由两部分组成,一部分为卸荷回弹,另一部分是由于大吨位锚索施加后产生的朝向坡内的压缩变形。研究表明,由于锚索穿过V岩体底部界线,在可能的滑坡剪出口形成强大的阻滑键,增加锚索长度或吨位均可有效地减小坝肩塑性区,地震加速度为0.1g和0.15g时,在各加固吨位下均可能形成塑性区的贯通;在不同的地震加速度下,受不同锚固长度和锚固力影响,不同关键点处水平向位移呈现线性变化和非线性变化,非线性关系中的拐点应重点关注;若要减少岩体塑性区,相同比例下增大锚固长度效果更好。为了有效减少在高地震烈度时边坡塑性区的发育,建议采用增加120%的锚固长度。  相似文献   

滑动面倾斜时抗滑桩弹塑性区临界高度的计算     

周春梅  殷坤龙  简文星 《岩土力学》2008,29(7):1949-1954

探讨了三峡库区滑坡治理滑面倾斜时抗滑桩桩前岩土体弹塑性区临界高度的计算模式。介绍了常用的确定抗滑桩嵌岩深度的工程地质法和强度控制法,剖析了抗滑桩设计的弹性理论和弹塑性理论,利用空间楔形体极限平衡理论,得出了滑面倾斜时桩前岩土体弹塑性区的临界高度计算公式,并且讨论了弹塑性区临界高度与滑面倾斜角度及岩体的强度参数之间的关系。以三峡库区万州区某滑坡为例,计算了桩前弹塑性区的临界高度,并总结出临界高度与滑面倾角及岩体的黏聚力呈指数分布关系,与岩体的抗力及岩体的内摩擦角呈线性分布关系的规律。根据这些规律可以对抗滑桩嵌岩深度进行修正,并适当地控制抗滑桩嵌岩段岩土体弹塑性区临界高度。  相似文献   

刚性承台下考虑有效桩长的柔性桩复合地基沉降计算方法研究   总被引：2，自引：0，他引：2  

孙林娜 《岩土力学》2008,29(Z1):663-666

试验研究和理论分析表明,柔性桩存在有效桩长。考虑刚性基础对桩顶部桩-土相对位移的限制,假定桩侧摩阻力为双折线三角形分布,根据桩-土协调变形,推导出复合地基中柔性桩的有效桩长,并在此基础上提出将柔性桩复合地基压缩层分为三层进行沉降计算。通过实例验证该方法是有效且可行的。  相似文献   

汶川M_S 8.0地震地表破裂带北端位置的修订   总被引：6，自引：1，他引：5       下载免费PDF全文

李传友  魏占玉 《地震地质》2009,31(1):1-8

对汶川MS8.0地震地表破裂石坎乡以北段的野外地质调查显示,这一段地表破裂仍然十分明显。地表破裂并未沿地质填图所标定的位置发育,而是在走向上稍有变化,但清楚的地貌显示它在此段并不是一条新生断裂。与前期工作相比,可观察到的地表破裂又往NE方向延长了约12km。该段破裂位于平武县石坎乡至青川县马公乡窝前村之间,走向为15°～45°,运动学性质主要为右旋走滑逆冲。地震地表破裂显示的同震垂直位移与石坎乡一带相近,为1～2m左右;右旋水平位移略有增加,为2.0～3.0m之间。地表调查的情况显示,地表破裂在北端可能消失在红光乡东河口一带。  相似文献   

Hg, Zn and Cu levels in the muscle and liver of tiger sharks (Galeocerdo cuvier) from the coast of Ishigaki Island, Japan: relationship between metal concentrations and body length     

Endo T  Hisamichi Y  Haraguchi K  Kato Y  Ohta C  Koga N 《Marine pollution bulletin》2008,56(10):1774-1780

We analyzed Hg, Zn and Cu concentrations in the liver and muscle of tiger sharks (Galeocerdo cuvier) from the coast of Ishigaki Island, Japan. The Hg concentration in the muscle increased proportionally with body length in the tiger sharks, whereas that in the liver increased rapidly after maturity (defined by a length of over 2.7 m). Muscle Hg levels were higher than liver concentrations in immature sharks, with the inverse trend observed in mature sharks. Notably, the Zn and Cu concentrations in the liver tended to decrease with increasing body length. This rapid increase in hepatic Hg concentration concurrent with the onset of maturity in sharks may result from the continuous intake of Hg via food and the slower growth of mature sharks. The high concentrations of the essential metals Zn and Cu in immature sharks may be explained by the physiological demands related to rapid growth.  相似文献   

3种驼绒藜属植物种子萌发期耐盐性试验研究   总被引：13，自引：8，他引：5  

李得禄  王继和  李爱德  刘虎俊  安富博 《中国沙漠》2006,26(6):1009-1014

用0.3％,0.6％,0.9％,1.2％,1.5%、1.8%的NaCl溶液对3种驼绒藜属植物种子进行处理,观测它们的发芽率、发芽势、幼苗长度指标来研究驼绒藜属3种植物种子的耐盐性。试验研究表明:以1.2%或1.5%的NaCl溶液鉴定驼绒藜属植物耐盐性较为合理,3种驼绒藜属植物种子耐盐性存在明显差异。以NaCl溶液为培养液,随着浓度的增加,种子发芽率降低,种子发芽高峰的出现延迟,同时幼苗长度随盐分浓度的递增而呈减小趋势。综合分析发芽率、发芽势及幼苗长度,认为3种驼绒藜属植物种子的耐盐顺序为:华北驼绒藜最强、绵毛优若藜次之,驼绒藜最差。  相似文献   

根据静载荷试验成果讨论深层搅拌桩复合地基桩长设计的合理性   总被引：1，自引：0，他引：1  

张继诚  刘婕 《水文地质工程地质》2000,27(2):57-58

本文通过按理论公式计算与根据静载荷试验结果确定深层搅拌桩复合地基承载力标准值的结果数据的对比分析,提出了在实践中合理设计深层搅拌桩桩长的必要性。  相似文献   

Sensible Heat Flux-Radiometric Surface Temperature Relationship Over Sparse Vegetation: Parameterizing B-1   总被引：1，自引：0，他引：1  

J. P. Lhomme  A. Chehbouni  B. Monteny 《Boundary-Layer Meteorology》2000,97(3):431-457

In the bulk formulation of vegetation-atmosphere transfer, theparameter B^-1 is needed for evaluating the sensible heatflux from radiometric surface temperature. An excess resistance,expressed as a function of B^-1 (r_rB^-1/u_*, whereu_* is the friction velocity), shouldbe added to the aerodynamic resistance calculated between thelevel of apparent sink of momentum and the reference height.Over sparse vegetation, B^-1 (and consequently the excessresistance) can be very large and variable. A one-dimensionaltwo-layer model of the canopy-atmosphere interaction is used toinvestigate the behaviour of this fitting parameter and to derive anoperational parameterization in terms of structural and viewingcharacteristics. Besides canopy structural characteristics andradiometer viewing angle, input variables include weather data,stomatal and substrate resistances. B^-1 varies with almostall the input variables; however, the leaf area index (LAI) andthe view angle of the radiometer appear as the most significantfactors of variation. Using a set of weather data and componentresistances randomly generated between fixed limits, `average'curves representing B^-1 as a function of LAI for differentview angles are inferred from the model and polynomial expressionsare fitted to the simulated curves. This set of parameterizations isobtained from ranges of input data wide enough to be representativeof a large variety of experimental conditions. It is successfully testedagainst other parameterizations, using both simulated data andmeasurements made over contrasted surfaces in Niger, France andCalifornia. As the formulations proposed depend on the range ofvalues prescribed in the simulation process for each input data, theyare modifiable and adjustable to any experimental conditions.  相似文献   

Modelling The Mean Velocity Profile In The Urban Canopy Layer   总被引：19，自引：18，他引：1  

R. W. Macdonald 《Boundary-Layer Meteorology》2000,97(1):25-45

A simple model originally derived for meanwind speed profiles in vegetative canopy flows ismodified for application to arrays ofthree-dimensional surface obstacles (cubes), whichcould be representative of a simple urban-typesurface. It is shown that for cube arrays that arenot too densely packed, the predicted exponentialvelocity profile provides an adequate fit to thespatially averaged velocity profile (u(z))within the obstacle canopy. Application of the model to a set of wind-tunnel dataallows for the evaluation of an empirical fittingparameter called the attenuation coefficient. This isrelated to the turbulence length scale, which can befound by manipulating the results of thegradient-diffusion model used to derive the velocityprofile. The results show a reduction of theturbulence length scale with increasing obstaclepacking density. By assuming a linear transition fromthis length scale at the top of the canopy to theclassical Prandtl length scale in the overlyinginertial sublayer, an acceptable model is obtained forthe full velocity profile within simple obstaclearrays, from the ground up to the overlyingsemi-logarithmic region.  相似文献   

SLC Analysis on Earthquake Activity in the Regions of Sichuan and Yunnan of China     

Gao Yuan  Zhou Huilan  Ma Yanlu 《中国地震研究》2000,14(3):277-283

Using the method of Single-link Cluster(SLC),analyzing the pattern of time sliding of SLCparameters,the earthquake activity in the western Sichuan-Yunnan of China is studiedcombining with the regional earthquake catalogue since 1970 and the tectonic background.Comparing with the high level of earthquake activity in 1970’s and the low in 1980’s,theearthquake activity is in general at the middle level in 1990’s.This paper suggests that SLCmethod,which considers the temporal and spatial relationship among earthquake events,could be adopted to analyze the trend of regional earthquake activity,it is very useful forstudying seismic activity.  相似文献