真空预压法中渗流体力和压差面力联合作用机理浅析

从渗流问题的基本方程出发，导出了真空预压的固结解析解，认为在地基中存在负压边界引起的瞬时稳定渗流与固结渗流2种不同特性的渗流、瞬时稳定渗流体力使膜下地基竖向拉伸、侧向受压，接近纯剪切应力状态，体积压缩变形较小，难以有效地加固地基．柔性膜上压差面力产生的偏应力与渗流体力的偏应力方向相反，大致可以互相抵消，使地基处于接近球应力状态．因此，膜上压差是加固地基的主要荷载，对地基的固结特性和最终加固效果起着控制作用．     

真空联合变堆载预压下竖井地基固结分析

为了得到真空联合变堆载预压下竖井地基沉降随时间的发展规律,考虑真空度沿竖井线性减小,堆载单级线性施加,还考虑了地基的径竖向渗流以及扰动区土体水平渗透系数呈抛物线变化,推导了真空联合变堆载预压下竖井地基固结度的一个解析解.并分析了地基固结性状.结果表明,荷载逐渐施加时,采用真空联合堆载预压比只采用堆载预压固结要快,真空度越大,沿深度衰减越慢,固结越快.在地基井径比和水平渗透系数与竖向渗透系数之比较小时,地基的竖向渗流对地基的固结度有较大的影响.     

真空堆载联合预压法加固软基的现场试验

结合山东日照港集装箱码头辅建区的软基处理工程,开展了现场真空-堆载联合预压试验和监测资料分析研究,并对其加固机理和加固效果进行了探讨.研究结果表明真空预压明显地加快了地基的沉降速率,加速其固结过程,同时产生向内的水平位移,从而使真空-堆载联合预压比超载预压具有更强的抗失稳能力.土体侧向位移量和位移速率与加荷方式及大小密切相关.真空预压的加固深度主要是地表以下竖向排水体范围内受荷载影响的土层.     

真空预压机理模拟装置及典型示范结果

为了解释广泛应用于软土地基加固的真空预压技术的加固机理中关于影响深度这一困惑工程界多年的疑难问题，研制了一套真空预压机理的演示模型装置，通过该装置可以直观演示真空预压过程中孔隙水与地基土骨架应力的相互转换和传递过程，可以解释和解决真空预压的影响深度问题，实验结果和相关分析可以有力地证明真空预压的有效加固深度大于10m．     

基于ABAQUS的软土地基加固有限元分析

文章采用等效砂墙地基法,以某软基加固工程为算例,用ABAQUS软件对真空预压加固软基中的负压分布及竖向与水平位移的影响范围进行有限元分析.计算结果和实测值比较吻合,能准确地反映出真空预压加固软基土体变形的实际情况,计算结果可为地基处理的设计提供参考.     

真空预压在轨道列车中的应用

路基是承受有轨电车上部荷载的重要构筑物,应具有足够的强度、稳定性和耐久性,以保证列车的安全运行.真空预压排水固结法是加固软土地基有效方法之一,在加固大面积软土地基时,具有造价低、工期短、加固效果好等优点.基于南京河西江东南路真空预压现场试验,通过表层沉降、分层沉降、孔压、水位和深层水平位移监测数据来分析真空预压的加固效果.研究结果表明:在抽真空过程中,孔隙水压力逐渐减小,深层水平位移变化速率逐渐减小;随着深度的增加,土体的分层沉降量逐渐减小.抽真空70 d后,表层沉降速率维持在1 mm/d左右,表明土体固结接近完成.表层总沉降量为476 mm,与设计沉降量(450 mm)相比,误差约为6%.由此表明真空预压在短时间内可以取得很好的加固效果,为控制工后沉降奠定了良好的基础.     

真空联合堆载预压技术在现代公路工程施工中的应用

随着我国公路建设的进一步发展,将不可避免地要在软土地基上修建越来越多的高速公路。真空联合堆载预压加固施工是一种快速、简便、文明的加固地基的有效方法,能够有效地加速深厚软土地基的排水固结,减少工后沉降.水平向位移是真空预压施工中容易出现的问题,为此,本文在分析真空联合堆载预压法加固机理的基础上,探讨了真空联合堆载法施工中的关键技术与具体施工工艺。     

真空预压的有效应力原理浅论

通过分析有效应力原理解释固结过程的前提条件，并结合真空预压机理的再分析，阐述了真空预压过程中固结产生的有效应力原理是加固土体作为“地基”，在抽真空所产生的“负压荷载”以及其较大渗流力所产生的“摩擦荷载”等外荷变化的共同作用下使其孔隙压力减小，有效应力增大而使土体固结的。此种解释将能为完善真空预压设计、施工和监测产生较大的影响。     

塑料排水板结合真空预压法的径向固结解析解

塑料排水板结合真空预压的软土地基加固方法是一种经济高效并被逐渐广泛应用的地基加固方法,该方法不仅可以减少堆载预压坝体的高度,还能减少土体的侧向位移.推导的塑料排水板与真空预压结合的非线性径向固结解析解可以较好地用于该种地基加固的预测和分析.求解过程认为软土在一维固结条件下孔隙比与平均有效应力、水平渗透系数成对数线性关系,而非以前认为的一维线性关系,因排水板周围土体被扰动,所以涂抹区中水平渗透系数采用抛物线分布形式,同时还考虑真空预压对固结的作用.退化提出的解析解与前人解析解进行对比验证、完成解析解与试验结果验证,证明了该解析解的正确性.最后,分析了参数κ和C_k/C_c对固结的影响,结果表明C_k/C_c值越大,固结时间越短,κ值增大,固结时间增长.     

地基加固深度对矩形综合管廊力学性能的影响分析

为反映地基加固深度对软土地基综合管廊结构受力性能的影响,以广州大学城综合管廊为例,通过对加固综合管廊断面宽度范围内的土体进行仿真模拟,研究了地基加固深度(0~4.8 m)对软土地基综合管廊结构受力性能的影响。分析表明:综合管廊结构竖向位移和宽度范围内的地表土体竖向位移随地基加固深度的增加而线性减小;地表竖向位移受地基加固深度的影响较大,而在综合管廊宽度范围外,地表竖向位移随地基加固深度的增大而减小,但其受地基加固深度的影响较小。     

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).     

Wuhan University Journal of Natural Sciences TOTAL CONTENTS

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