干湿循环脆性红砂岩的孔隙及声发射特征研究

为研究脆性红砂岩在干湿循环条件下,孔隙率变化情况、变形破坏特征以及声发射特征,进行了10次干湿循环试验。结果表明,最初的孔隙变化主要是小开孔隙过渡为大开孔隙,随循环进程小开孔隙呈小幅度波动,但大开孔隙呈对数增长;干燥、饱和的单轴抗压强度均呈对数降低趋势;而结合声发射特征曲线可以更合理地把脆性红砂岩单轴压缩过程划分为3个显著阶段:裂隙压密阶段、弹性变形阶段、宏观破坏阶段。随干湿循环次数的增多,因孔隙的逐渐扩大、增多,压密阶段的声发射事件有逐渐增多的趋势;累计计数的突变可以作为弹性变形阶段后岩石内部关键断裂初始扩展、贯通的依据;宏观破坏阶段声发射累计计数占比随循环次数有降低趋势,脆性红砂岩低次干湿循环的变形破坏高度集中在宏观破坏阶段,随着循环次数的增加,孔隙的增大、增多,变形破坏有提前发生的趋势,大量声发射活动逐渐提前,且破坏形式有脆性破坏向延性破坏的过渡趋势。     

大气干湿循环作用下高液限土微观结构研究

高液限土边坡在降雨历时、雨后多呈浅层破坏工况。为探明不同干湿循环条件对原状高液限花岗岩残积土微观结构的影响，选取惠龙高速高液限土原状样开展干湿循环及扫描电镜试验，探究干湿循环作用前后原状高液限花岗岩残积土微观结构变化，定量分析定向度、丰度、面积孔隙率与面积孔隙比、等效直径、平均圆形度等微观特征参数变化规律。结果表明：干湿循环作用对高液限花岗岩残积土的损伤效应在微观上表现为孔隙裂隙的扩张，整体孔隙率增大；片状颗粒破碎严重，颗粒尺寸变小，原先较大的团粒分散成了更小的团粒，粒间黏聚力降低；颗粒不断向长扁状演化。该结果可为干湿循环作用下高液限花岗岩残积土强度衰减机制及边坡失稳破坏机理提供一定理论依据。     

干湿循环作用下红砂岩堆石料力学性能研究

为研究红砂岩堆石料在干湿循环作用下的力学性能,以干湿循环次数为主要变量,开展常规三轴压缩试验。研究结果表明:不同干湿循环次数下,红砂岩堆石料应力-应变曲线变化规律基本一致,整体呈现出明显的应变软化。应力-应变曲线在初期快速增加,直至出现峰值,而后开始降低,最后趋于稳定;相同干湿循环次数下,试样破坏强度随围压增大而逐渐增长;相同围压,破坏强度随干湿循环次数增加而逐渐降低,破坏强度与干湿循环次数呈现指数关系;当干湿循环次数增加时,试样强度指标黏聚力逐渐减小,从125.9 kPa降低到62.3 kPa,黏聚力降幅约50%,且黏聚力与干湿循环次数之间成负线性关系;与之相似,另一强度指标内摩擦角逐渐减小,但降低幅度较小,减小幅度为15%左右,与干湿循环次数呈现指数关系。     

侧限条件对干湿循环过程中膨胀土强度的影响

文章通过对合肥地区膨胀土进行侧限和无侧限的干湿循环条件下的直接剪切试验,探讨了试验过程中强度侧限条件对土样干湿循环后的强度衰减情况的影响。研究结果表明:每次干湿循环后,有侧限试样的强度都高于无侧限试样的强度,其中,侧限条件在前3次干湿循环中对膨胀土强度的影响较为明显,在第4、第5次干湿循环后,无侧限试样与有侧限试样的内聚力及内摩擦角基本接近,表明随着循环次数的增加,侧限条件对膨胀土干湿循环条件下强度的衰减影响明显减弱,直至可以忽略;在膨胀土地区工程实践中,考虑安全因素,对于易受外界条件影响而产生干湿循环的膨胀土层,其强度应采用原状土样强度的1/3。     

干湿循环下红砂岩强度衰减规律及工程应用

干湿循环作用下红砂岩岩体强度衰减是导致红砂岩边坡失稳的重要原因.针对这一现象,选取湖南省某在建高速公路具有代表性的红砂岩,采用烘干-浸泡的方式模拟岩石及结构面干湿循环过程,对干湿循环作用下红砂岩岩体抗劈裂强度及抗剪强度进行试验.试验结果表明,随着干湿循环作用次数的增加,岩石抗劈裂强度降低了55.7%,内摩擦角及粘聚力分...     

基于声发射监测循环载荷下岩石损伤过程

应用声发射技术对循环载荷下岩石损伤过程进行了实验研究.基于加卸载响应比理论和损伤力学理论建立了循环载荷下岩石破坏过程中的内部损伤和声发射关系的数学模型,分析了循环加载方式下的岩石损伤演化过程和岩石失稳破坏的前兆.实验结果表明,岩石加载的声发射活动规律反映了其损伤过程;在循环加载条件下,随着载荷的增加,岩石在卸载过程中的损伤逐步增大,声发射数加卸载响应比Y值逐渐减小;对于大多数岩石试样而言,在其处于弹性变形后期时,声发射数加卸载响应比Y值达到(或接近)1并在小范围内波动,可以作为岩石失稳破坏的前兆,这对于循环载荷下岩石失稳破坏具有预测意义.     

离散元对加固尾砂在干湿循环作用下的细观力学分析

为探究加固尾砂在干湿循环作用影响下力学性能、力链和尾砂颗粒运动的变化,通过对加固尾砂进行三轴试验和离散元颗粒流(PFC2D)模拟试验,分析其力学性能变化趋势,并且探究尾砂颗粒间受力传力和颗粒运动的演变。试验结果表明:加固尾砂峰值应力随着干湿循环次数增加而逐渐递减,但是其峰值应力相较于原状尾砂至少提升2.13倍;在干湿循环作用下,加固尾砂内部力链逐渐加粗,网状粗力链区域增多,且网状粗力链区域发生位置变化;试样破坏碎片数量随循环次数增加而增加,碎片集中区随着循环进行,从试样下部向上部移动;干湿循环造成尾砂颗粒位移情况发生改变,颗粒不同位移区域增加,并在试样上端产生大量不同位移区域,造成试样上端更容易被破坏。     

路用红砂岩碎石土湿化变形特性试验

针对湿热地区红砂岩碎石土用作路基填料易发生湿化崩解,导致路基刚度软化及其耐久性能降低的问题,采用自行研制的大型干湿循环压缩剪切仪,开展不浸水条件与反复浸水下红砂岩碎石土的一维大型压缩试验,揭示红砂岩填料在干湿循环条件下的湿化压缩变形规律。研究结果表明:湿化变形量随浸水次数增加而增加,压缩模量在前2次干湿循环过程中衰减幅度较大,第3次后逐渐趋于稳定;地基土附加湿化变形量随浸水时间增加而增大,变形模量随含水率增加而减小。试验结果可为红砂岩填筑路基的安全施工及其长期沉降预测提供依据。     

旱区陡坡黄土的低压力抗剪强度特性试验研究

黄土强度指标的准确确定是地质体稳定性分析的基础依据。以延安地区某边坡上更新统黄土为研究对象,利用改进的直剪仪,开展不同初始含水率、密度、干湿循环条件下原状与重塑黄土的低压力抗剪强度试验,研究原状与重塑黄土的低压力抗剪强度及抗剪强度指标随初始含水率、密度及干湿循环次数的变化规律,建立黄土的低压力抗剪强度指标与初始含水率、密度及干湿循环次数之间的函数关系。结果表明,黄土的低压力抗剪强度与初始含水率的关系可采用指数函数描述,与土体密度和干湿循环次数的变化关系可采用线性函数描述;原状与重塑黄土的黏聚力、内摩擦角与初始含水率之间呈负相关,且原状黄土抗剪强度指标高于重塑黄土;黄土的抗剪强度指标随土体密度增加而显著提高,随干湿循环次数增加呈明显减小趋势。     

混凝土声发射信号频率特征与强度参数的相关性试验研究

对不同强度指标的混凝土试块进行抗压试验,应用声发射及其定位技术对抗压试验全过程进行同步监测,分析混凝土受载破坏过程中声发射频率特征参数与混凝土强度指标的关系,研究混凝土受载破坏过程中内部裂纹的三维空间演化规律。研究结果表明:混凝土强度指标影响混凝土声发射信号频率特征参数。结合荷载-位移曲线对声发射振铃计数率和能率进行分析,发现C10和C20混凝土(低强度混凝土)声发射信号主要集中于弹性阶段初期和中期;C30和C40混凝土(中等强度混凝土)声发射信号处于受压全过程,声发射活跃期处于极限荷载处。通过对混凝土声发射事件进行空间三维定位,从微观上探明受载混凝土裂纹的萌生、发展和贯通的演化规律,对受载混凝土内部结构的变化有了直观的认识。     

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.