无缝桥引板微型桩-土共同作用试验研究

利用MTS加载系统开展砂土中微型桩水平受荷室内足尺模型试验,对微型桩的桩身位移、桩身弯矩和桩周水平土抗力的分布进行研究,同时探讨了微型桩-土p-y曲线的特性.研究表明,桩身位移主要发生在桩顶下10倍桩径的范围,桩身弯矩主要集中在桩顶下15倍桩径的范围;采用双曲线模型拟合比抛物线模型拟合和双曲正切曲线模型拟合的p-y曲线精度更高.     

深厚软黏土地基中大直径单桩基础现场水平受荷试验及 p-y 曲线适用性研究

基于某海上风电场开展的单桩水平受荷特性现场试验,研究了深厚软黏土中2.4. m 大直径钢管桩荷载-位移响应、桩身挠度及桩身弯矩规律;探讨了m法、 API 规范法和双曲线型p-y曲线在软黏土地基中的适用性,并建立数值模型对不同直径单桩基础的水平承载力贡献因素进行分析。结果表明: API 规范法与双曲线型p-y曲线在浅层土中p-y曲线初始刚度与桩周土抗力偏大,双曲线型p-y曲线在一定深度下能够较好地预测土反力随位移的变化关系,m法与双曲线型p-y曲线计算得出的水平位移较实测值偏小,结果偏向不安全, API 规范法计算结果相比实测值较大,计算结果较为保守;随着桩径增大,单桩基础的侧摩阻力和基底抗力对水平承载力贡献也会随之增大,双曲线型p-y曲线会严重低估单桩的水平承载力。     

可液化地基处理前后单桩水平承载动力响应特征

为了研究可液化地基处理前后单桩水平承载动力响应问题,以宿迁金鹰工程可液化场地为依托,采用基于CPTU测试的p-y(土抗力桩挠度)曲线法,构建了单桩水平动力承载数值计算模型.分析了不同加载振幅和振动次数下的单桩水平循环加载特征,比较了可液化地基处理前后的单桩水平承载动力响应规律.结果表明:可液化地基处理后单桩水平动力承载能力增强,桩周土抗液化能力提升,桩身截面最大弯矩上移,桩顶荷载传递深度降低;在桩顶水平循环加载作用下,桩身变形和弯矩随加载振幅和振动次数的增加而增大;十字翼共振法处理可液化场地对提升桩基水平承载力具有显著效果.     

冲刷现象对海上风力机单桩基础水平承载性的影响

结合涠洲海域某风电场项目的工程实例,建立了海上风力机单桩基础的桩土有限元模型,采用p-y曲线法探讨了冲刷坑对单桩水平承载性的影响,分析了不同冲刷深度对支撑结构动力学特性的影响规律.研究结果表明,无冲刷现象时桩身的最大弯矩会出现在海床以下5 m左右;当冲刷深度为1 m时,桩身最大弯矩出现的位置也下降1 m.当冲刷深度小于1.3倍桩径时,基桩整体的位移、弯矩、应力均缓慢上升.当冲刷深度到达2倍桩径时,基桩的固有频率会降低1.8%.     

串珠状溶洞数量影响灌注桩顶部水平受拉特性试验研究

采用室内模型试验，对比研究串珠状溶洞数量对灌注桩顶部水平受拉特性的影响，为岩溶强发育区嵌岩桩的水平承载力设计提供试验依据. 结果表明：1）桩顶水平荷载相同时，上部土层段桩身水平位移、桩身弯矩（峰值）、桩侧土抗力随溶洞数量的增多而增大，单桩水平承载力随溶洞数量增多而明显减弱. 2）上部土层段桩身水平位移随桩顶水平荷载增大而增大，桩顶水平位移最大，嵌岩段很小甚至为0；弯矩M -深度z曲线整体呈抛物线形，桩身弯矩在土岩界面和上层溶洞与底板界面呈现2个峰值，弯矩的变化仅仅影响到上层溶洞及其底板，第2层溶洞及其以下的弯矩几乎为0，土岩界面弯矩最大、截面最危险；土抗力p-深度z曲线呈“凸肚”形. 3）溶洞数量增加，位置越高，p-y曲线越容易收敛，可以采用p/pub=α（y/y50）β拟合土层段的桩身p-y曲线. 溶洞数量对α与β值变化幅度的影响较小，α与β值变化幅度体现p-y曲线随深度变化的敏感度，两者敏感度随溶洞数量增多而增大. 4）工程桩刺穿串珠状溶洞时，为了提高单桩水平抗拉能力，建议采用注浆法改善上部岩土性质，加大土岩界面处桩身配筋率，并将桩身嵌入上层溶洞底板一定深度，防止基桩在土岩界面处发生弯曲破坏.     

输电塔基础斜桩非线性p-y曲线

为了解黏性土中斜桩对侧向荷载作用的响应规律,利用非线性p-y(土抗力-挠度)曲线法研究了斜桩特性.基于试验得到的斜桩土抗力分布曲线,将斜桩理想化为梁单元,土体离散为弹塑性弹簧单元,通过自编计算机程序对斜桩非线性p-y曲线进行了计算和分析.结果表明:计算得到的p-y曲线与试验结果吻合较好,轴向荷载引起的负斜桩沉降小于正斜桩;在相同侧向荷载作用下,负斜桩桩身挠度和内力均小于正斜桩;负斜桩具有侧向承载力大而变形小的工程特性,工程设计应尽量采用负斜桩布置形式.     

软粘土中水平荷载模型桩的试验研究

对水平静力荷载作用下软粘土中导管架海洋平台桩基的模型进行了试验研究.用多项式拟合法和加权残值法(WR)对试验数据进行处理,得到了土抗力的分布,并对两种方法进行了比较.将利用加权残值法得到的p-y曲线与API建议的软粘土p-y曲线进行了比较,并根据试验数据用折减系数法对API建议的软粘土p-y曲线进行了修正.研究结果表明,加权残值法比多项式拟合法得到的土抗力分布曲线更合理,试验软粘土的p-y曲线在泥面附近处低于API建议曲线,由修正的p-y曲线得到的模型桩的数值分析结果与试验值吻合较好.     

软粘土中水平荷载模型桩的试验研究

对水平静力荷载作用下软粘土中导管架海洋平台桩基的模型进行了试验研究。用多项式拟合法和加权残值法(WR)对试验数据进行处理,得到了土抗力的分布,并对两种方法进行了比较。将利用加权残值法得到的p-y曲线与API建议的软粘土p-y曲线进行了比较,并根据试验数据用折减系数法对API建议的软粘土p-y曲线进行了修正。研究结果表明,加权残值法比多项式拟合法得到的土抗力分布曲线更合理,试验软粘土的p-y曲线在泥面附近处低于API建议曲线,由修正的p-y曲线得到的模型桩的数值分析结果与试验值吻合较好。     

复杂荷载下斜坡上单桩水平承载特性研究

随着国家基础设施的不断完善,在实际工程中,建筑物桩基需要建立在倾斜的斜坡上,位于斜坡上的桩基的承载特性与平地上桩基的承载特性有明显的差别.利用自行研制的试验装置,采用粉土作为斜坡上的土体模型,进行了室内水平静载模型试验,得出斜坡上桩基在复杂荷载作用下的承载特性规律.运用ABAQUS有限元分析软件对斜坡上桩的承载特性进行数值模拟,计算结果与试验结果吻合较好,并进一步探讨了斜坡桩的桩承载因素的影响分析.研究结果表明:在水平推力较大时,桩顶位移随荷载呈现非线性变化,说明桩-土作用体系符合非线性模型规律;临坡距对桩身承载特性有一定的影响,斜坡上桩身距离坡顶越远,桩所受到的土体被动区土抗力越小,桩顶水平位移和桩身弯矩越小,在桩长和桩径不变的情况下,把桩设置在临近坡脚位置时可提高桩身的水平承载能力;增大桩周土体模量可以提高桩周土体对桩的嵌固作用,有效减小桩顶侧移和桩身最大弯矩.     

斜坡段桥梁基桩受力与变形分析的传递矩阵法

根据斜坡段桥梁基桩的水平承载特性,建立了考虑斜坡效应的桩-土相互作用模型及挠曲微分方程;基于m法和传递矩阵法,推导了桩身内力与位移分析的传递矩阵解答;通过模型试验,测得了黏土和砂土斜坡地基比例系数,拟合得到了斜坡地基比例系数与坡度间的关系式,验证了理论解答的合理性;以某工程实例为基础,分析了斜坡坡度和桩顶水平荷载对斜坡基桩受力与变形的影响.研究表明：斜坡地基比例系数随桩土交界面处桩身水平位移增大而呈非线性关系减小;黏土和砂土斜坡地基比例系数均随斜坡坡度增加而减小;基桩桩顶水平位移和桩身最大弯矩均随斜坡坡度和桩顶水平荷载增加而增大;当斜坡坡度由0°增加至60°时,桩顶水平位移约增大86.4%,桩身最大弯矩约增大4.6%,桩身最大弯矩位置约下移2.0 m;桩顶水平荷载每增加50 kN,桩顶水平位移平均增大48.5%,桩身最大弯矩平均增大41.6%.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with     

Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to     

《Chinese Science Bulletin》SUBJECT INDEX TO VOLUME 59(2014)

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An on-line scaling method for improving scalability of a database cluster

The explosive growth of the Internet and database applications has driven database to be more scalable and available, and able to support on-line scaling without interrupting service. To support more client's queries without downtime and degrading the response time, more nodes have to be scaled up while the database is running. This paper presents the overview of scalable and available database that satisfies the above characteristics. And we propose a novel on-line scaling method. Our method improves the existing on-line scaling method for fast response time and higher throughputs. Our proposed method reduces unnecessary network use, i.e. , we decrease the number of data copy by reusing the backup data. Also, our on-line scaling operation can be processed parallel by selecting adequate nodes as new node. Our performance study shows that our method results in significant reduction in data copy time.     

An improved R-tree based on childnode''s probability

R-Tree is a good structure for spatial searching. But in this indexing structure,either the sequence of nodes in the same level or sequence of traveling these nodes when queries are made is random. Since the possibility that the object appears in different MBR which have the same parents node is different, if we make the subnode who has the most possibility be traveled first, the time cost will be decreased in most of the cases. In some case, the possibility of a point belong to a rectangle will shows direct proportion with the size of the rectangle. But this conclusion is based on an assumption that the objects are symmetrically distributing in the area and this assumption is not always coming into existence. Now we found a more direct parameter to scale the possibility and made a little change on the structure of R-tree, to increase the possibility of founding the satisfying answer in the front sub trees. We names this structure probability based arranged R-tree (PBAR-tree).     

Integrating GIS Web services based on mediating architecture

The geographic information service is enabled by the advancements in general Web service technology and the focused efforts of the OGC in defining XML-based Web GIS service. Based on these models, this paper addresses the issue of services chaining,the process of combining or pipelining results from several interoperable GIS Web Services to create a customized solution. This paper presents a mediated chaining architecture in which a specific service takes responsibility for performing the process that describes a service chain. We designed the Spatial Information Process Language (SIPL) for dynamic modeling and describing the service chain, also a prototype of the Spatial Information Process Execution Engine (SIPEE) is implemented for executing processes written in SIPL. Discussion of measures to improve the functionality and performance of such system will be included.     

Tracking data management using topology of moving object database system for moving object constrained trajectory in LBS application

Advances in wireless technologies and positioning technologies and spread of wireless devices, an interest in LBS (Location Based Service) is arising. To provide location based service, tracking data should have been stored in moving object database management system (called MODBMS) with proper policies and managed efficiently. So the methods which acquire the location information at regular time intervals then, store and manage have been studied. In this paper, we suggest tracking data management techniques using topology that is corresponding to the moving path of moving object. In our techniques, we update the MODBMS when moving object arrived at a street intersection or a curved road which is represented as the node in topology and predict the location at past and future with attribute of topology and linear function. In this technique, location data that are corresponding to the node in topology are stored, thus reduce the number of update and amount of data. Also in case predicting the location,because topology are used as well as existing location information, accuracy for prediction is increased than applying linear function or spline function.