挡土墙主动土压力极限上限分析

为了计算墙背倾斜粗糙、填土面倾斜且作用均布荷载条件下的挡土墙主动土压力,采用摩尔-库仑屈服准则,建立三角形破坏机构,推导了挡土墙主动土压力上限解计算公式,使用粒子群算法搜索最危险滑裂面并获得主动土压力最优解.通过与经典朗肯土压力理论和模型试验结果对比分析可知:该计算方法包含了朗肯土压力理论并与模型试验实测结果比较符合.在此基础上分析了墙背倾角、填土面倾角、墙土外摩擦角和填土内摩擦角对滑裂面倾角和主动土压力系数的影响规律,相关计算数据可用于工程计算.     

有荷载作用时挡土墙主动土压力的计算

在工程中计算挡土墙的主动土压力,朗肯土压力理论和库仑土压力理论因其简单实用仍得到较多的应用,但两者却存在着一定的局限性,即对于实际工程很难严格满足其假设条件。基于库仑理论的平面滑裂面假定,考虑滑裂面上填土的粘聚力及填土与墙背接触面上的粘着力等因素的影响,分析了有荷载作用时滑动土楔体的极限平衡状态,并利用力矢多边形推导出了有荷载作用时主动土压力（粘性土、无粘性土）的计算公式。分析表明：提出的对粘性土主动土压力计算方法,可以不受传统朗肯理论和库仑理论较为苛刻的假设条件的限制,具有普遍的适用性。     

黏性土被动土压力计算的库仑数值解

针对库仑土压力理论中图解法计算黏性土被动土压力过程繁琐及精度较低的问题,应用库仑平面滑裂面假定,考虑填土黏聚力及其与挡土墙墙背接触面上的黏着力,建立了可用于编程试算的黏性填土挡土墙的被动土压力计算公式.算例分析表明:对符合朗肯或库仑理论假设条件的情况,公式的计算结果与经典的朗肯或库仑公式相同;考虑与不考虑墙背上的黏着力,计算结果差异较大,该差异随着墙背上的黏着力增大而增大;公式计算简便快捷,精度可靠,易于在工程中推广应用.     

刚性挡土墙后粘性土土压力研究

经典朗肯和库伦土压力理论在实际工程中有着广泛应用,但它们的适用范围也十分明显．基于土体的极限平衡理论,考虑了粘性填土、墙土间的粘着力、连续均布超载等因素对挡土墙土压力的影响,并利用力矢量多边形法,推导出适用多种复杂条件下的粘性土土压力计算式,给出了极限状态下滑动楔体临界破解角的显式解答．该公式适用的范围较广,在朗肯或库伦理论假设条件下能够得到与之完全一致的解答,对刚性挡土墙的设计计算具有一定的应用价值．     

基于PSO搜索潜在滑裂面非极限状态土压力计算

作用于刚性挡土墙侧土压力的计算一直沿用经典的朗肯或库仑土压力理论,这两种理论只能求得极限状态的土压力,而在许多实际情况下,挡土墙的土压力处于非极限状态.本文将潜在滑裂面视为一任意曲线,改进水平层分析法,同时基于摩擦角随位移的变化关系,对平动模式下墙后填土进行分析,推导出非极限状态下主动方向土压力分布、合力大小及作用点的理论公式.以各薄层微元的滑裂面倾角为变量,利用PSO(粒子群算法)对潜在滑裂面进行搜索从而获得土压力最优解.分析了内摩擦角、刚性挡土墙位移量对非极限状态主动方向土压力分布、土压力合力大小、土压力合力作用点高度以及潜在滑裂面的影响.本文提出的计算方法得出的结果与试验数据的大小及变化趋势基本吻合,具有推广应用价值.     

考虑土拱效应和平移的刚性挡土墙被动土压力

根据土拱效应原理,得到考虑填土内摩擦角和墙土摩擦角的平移模式下挡土墙的被动滑裂面倾角和侧向被动土应力系数,并将其用于水平微分层法的平移模式下的刚性挡土墙墙背被动土应力的分析中,得到被动土应力、被动土压力及其作用点的计算公式,并与朗肯理论、库仑理论、吴明法、侯键法、模型试验数据进行比较分析.结果表明:本文方法得到的平移模式下刚性挡土墙墙背被动土应力分布与模型试验结果吻合最好,且偏于安全的;被动土应力随填土内摩擦角的增加而增加,在墙顶附近随墙土摩擦角的增加而减小,在墙中下部却随墙土摩擦角的增加而增加;被动滑裂面倾角随墙土摩擦角增大而增大,随填土内摩擦角增大而减小.     

墙背粗糙且填土面倾斜情况下的土压力解析解

基于数学方法对斜单元体进行力和力矩的平衡分析,得到了墙背粗糙且填土坡面倾斜情况下的土压力解析解,并进一步分析了墙土之间摩擦角及填土坡面倾角对土压力的影响。对比分析表明,经典朗肯土压力理论可看作是本文解析解在墙背光滑、填土坡面水平情况下的特例。该文中的求解方法还可进一步拓展至探求填土为黏性土情况下挡土墙上土压力的解析解。     

考虑第二破裂面的折线墙背挡土墙的地震主动土压力

应用极限平衡原理和库伦土压力思想,研究地震荷载作用下折线墙背挡土墙的主动土压力问题.采用拟动力法对地震荷载进行描述,考虑地震荷载作用下第二破裂面的产生条件,推导折线墙背挡土墙的地震主动土压力计算公式.通过算例分析各参数对折线墙背挡土墙的地震主动土压力的影响,预测墙后填土滑裂面的位置.     

基于墙后土体滑裂面的朗肯被动土压力的探索

摘要：基于前人从极限平衡理论出发而提出的朗肯土压力作用下的极限土体会出现滑裂面这一前提,推导了墙背与土体之间的摩擦力作用下墙背垂直的挡墙和仰斜式挡墙的朗肯被动土压力的公式,列表分析了墙背垂直挡墙的外摩擦角 对墙后土体破裂角 和朗肯被动土压力 的影响,并对比分析了仰斜式挡墙的倾角 对墙后土体破裂角 和朗肯被动土压力 的影响,在举例过程中也侧面印证了通过求导数计算被动土压力 时应该取破裂角 变化范围内的极小值。另外,通过公式对比及理论分析,提出了墙背与土体之间外摩擦角 的两种简便可行的理论测定方法。     

临近地下室边墙挡土墙主动土压力解析解

随着工程建设的需要,特别是在临近地下室边墙修筑挡土墙时以半无限土体为基本假设的传统土压力计算公式不再满足需求。针对此类问题,以平面滑裂面为假设,将墙后土体分为上下两个隔离体,采用薄层单元法推导了临近地下室边墙挡土墙主动土压力计算的解析公式。公式考虑了墙土间黏聚力和摩擦角的影响,在特定条件下现行的土压力公式为特解,从而论证了计算方法的正确性。计算得到的黏性土极限破裂角不为定值;随着计算参数的变化而呈现不同的变化特征,因此在土压力求解时须重新计算破裂角。通过算例分析表明:在考虑墙土内聚力和摩擦角情况下,主动土压力明显小于朗肯解和文献解,其结果对实际工程有一定的参考价值。     

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.     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

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.