Progressive vector compression for high-accuracy vector map data

With the increase in the number of applications using digital vector maps and the development of surveying techniques, a large volume of GIS (geographic information system) vector maps having high accuracy and precision is being produced. However, to achieve their effective transmission while preserving their high positional quality, these large amounts of vector map data need to be compressed. This paper presents a compression method based on a bin space partitioning data structure, which preserves a high-level accuracy and exact precision of spatial data. To achieve this, the proposed method a priori divides a map into rectangular local regions and classifies the bits of each object in the local regions to three types of bins, defined as category bin (CB), direction bin (DB), and accuracy bin (AB). Then, it encodes objects progressively using the properties of the classified bins, such as adjacency and orientation, to obtain the optimum compression ratio. Experimental results verify that our method can encode vector map data constituting less than 20% of the original map data at a 1-cm accuracy degree and that constituting less than 9% at a 1-m accuracy degree. In addition, its compression efficiency is greater than that of previous methods, whereas its complexity is lower for close to real-time applications.     

PROGRESSIVE COALESCENCE MODEL FOR BRITTLE FAULT FORMATION AND ITS MECHANISM

In shallow crust, faults often consist of a series of secondary fractures. Based on experimental micro-features in rock mechanics and macro-structures in field, the progressive coalescence model, in which a brittle fault evolved from micro-crack, stylolitic fracture, large fault to super-large fault, is founded, and its forming mechanism is discussed by variation of stress field. At last the undulation,branches of faults and the phenomenon that the angle between fractures and the principal stress axis decreases gradually are explained by the G. C. Sih model.     

辽河(岩)群变形期次再讨论

辽河（岩）群在辽宁省为十分重要的地层,不仅蕴藏着丰富的矿产,还存在诸多有争议的问题,变形期次就是其中重要问题之一.辽河（岩）群中最主要的构造形迹就是东西向展布的区域上透入性面理,它是纵向置换作用形成的,在微观上残留了较多置换过程的痕迹.从辽河（岩）群的的原岩建造来看,它至少经历了类似"大西洋阶段"和"太平洋阶段",不会是夭亡的裂谷.通过全方位构造解析认为,洋盆闭合挤压造山过程是一个漫长的递进变形过程,在这一漫长的递进变形过程中形成的所有构造形迹皆属同一期构造,即辽河（岩）群可归纳为一期构造.     

多核处理器的机载激光雷达点云并行三角网渐进加密滤波方法

滤波是机载LiDAR点云数据处理的关键步骤之一,点云数据的海量化特性使得一般的串行化滤波处理方法无法满足快速成图的应用需求。提出一种基于多核计算技术的并行三角网渐进加密滤波方法,将串行方法中最耗时的三角网构建与脚点判别过程进行了并行化改造。三角网构建算法的并行化基于分治法实现,脚点判别算法的并行化采用一种随机分配策略将三角网划分为多个离散分布的三角形子集合来实现负载均衡。并行滤波方法在8核环境下多次渐进加密的实际加速比达到3.1左右。试验证明,该方法可以充分发挥多核计算优势,并且对不同分布形态点云数据具有良好的适应性。     

东营凹陷营26断层调节带特征及其对油气分布的控制作用

为揭示复杂断块油田小型断层调节带的特征并明确其对油气分布的控制作用,笔者利用高精度三维地震资料结合油田地质资料分析了营26块内断层的几何学、运动学和动力学特征,认为其为近东西向展布的对向叠覆—同向叠覆复合型断层调节带。西侧主断层(营1断层)与调节断层在剖面上呈多级反"Y"字形组合样式,东侧主断层(营8断层、营31断层)与调节断层为包心菜状组合;营1断层活动性减弱时,将位移量传递给营8断层、营31断层和调节断层,使区域位移有规律变化;通过力学分析认为营26北部断层调节带是在左旋张扭构造应力场作用下形成的,营26南部断层调节带是在右旋张扭构造应力场作用下形成的。结合营26块油气分布、油气来源及断裂活动性与封闭性研究,阐明了主断层沟通烃源灶和储集层,成为油源断层;调节断层停止活动时间早,封闭性好形成断块圈闭,是遮挡断层;建立了营26断层调节带油气成藏模式,预测营13井、营24井和营26井附近为有利滚动勘探开发区。     

加筋砂土挡墙面板刚度效果的数值分析

为了对加筋砂土挡墙面板的刚度效果有一个合理、定量的把握,利用非线性硬化-软化弹塑性有限元方法对相关的一系列室内模型试验结果进行了系统全面的数值分析。有限元解析中所采用的砂土本构模型是以修正塑性功为基本状态量的弹塑性硬软化模型,该模型可以较为精确地模拟砂土的应力路径效应。结果表明,利用这种较高精度的有限元方法对加筋砂土挡墙的变形破坏进行解析,不仅能较好地模拟加筋砂土挡墙基础底面的平均压力与沉降之间的关系,同时也能较好地再现由于面板刚度变化对加筋砂土挡墙基础的承载力以及渐进性变形破坏的影响。随着面板刚度的增加,面板对剪切带的抑制作用将随之增加,具体表现在砂土围压σ3增大所带来的砂土强度σ1的提高,进而使得加筋砂土挡墙的峰值承载力也随之增大。     

不同类型滑坡渐进破坏过程与稳定性研究

滑坡的类型一般可分为牵引式滑坡、推移式滑坡和复合式滑坡,根据其滑面的发展形态,依次表现为前进式渐进破坏模式、后退式渐进破坏模式和复合式渐进破坏模式。基于岩土体应变软化特性,揭示了滑坡渐进破坏过程的本质是滑带力学参数弱化的过程,初步探讨了3种类型滑坡渐进破坏过程的远动特点和力学特征和滑坡渐进演化过程。以不平衡推力法和3种类型滑坡的演化特征为基础,提出3种类型滑坡渐进破坏过程中临界状态条块确定方法,通过建立滑坡渐进破坏稳定性计算模型和计算公式,提出滑坡随着渐进演化过程的滑带参数取值方法,并阐述了渐进破坏过程的稳定性计算实现过程,实现不同类型滑坡渐进破坏过程的稳定性分析。以3个典型滑坡为例,分析得出滑坡渐进破坏过程中牵引式滑坡和复合式滑坡稳定性降低速率由大到小再到大和推移式滑坡稳定性降低速率由小到大的过程,3种类型滑坡在渐进破坏过程中不同部位对稳定性的贡献不同,验证了不同类型滑坡的变形规律。研究结论可对不同类型滑坡的稳定性发展进行初步预测和为滑坡治理提供指导意义。     

Discussion of “formation mechanism of large pockmarks in the subaqueous Yellow River Delta”

Abstract

The excess pore pressure accumulation is a key factor when estimating the formation mechanism of large pockmarks, as it determines the liquefaction potential of marine sediments due to water waves. The governing equations for excess pore pressure may have different forms for various types of sediments and then shall reflect the cyclic plasticity of the soil. For water waves propagating over a porous seabed, the liquefaction area induced by waves is generally progressive, which indicates that the liquefaction area will move forward following the wave train. Therefore, the excess pore pressure accumulation can be used to explain the occurrence of the large pockmarks, but the dimension of the pockmark may be related to the heterogeneity of sediment or the wave properties affected by the topography in the subaqueous Yellow River Delta.     

砂土中等截面桩的上拔机制分析

桩的上拔承载性能的宏观力学现象与桩周土细观结构变化相关,应用细观力学的颗粒流（PFC2D）数值模拟方法对承受上拔荷载作用的桩基进行了分析,数值模拟了上拔荷载作用的桩及桩周土的细观力学特征,研究了桩侧摩阻力的分布、桩周土剪切带的形成过程,较好的再现了桩的荷载－位移关系的实验结果,并与宏观物理实物试验的位移实测结果作了对比分析。分析了土体中剪切带形成过程中的颗粒间的细观变化及其形成过程,当上拔荷载达到极限时,上拔桩的剪切带形成原因是密砂的应变软化效应;颗粒流数值模拟的颗粒接触力与实物物理试验桩侧摩阻力是同一的,数值模拟的荷载-位移曲线与实物物理试验的荷载-位移曲线一致;桩侧摩阻力、桩上拔过程中剪切带的形成过程、桩上拔荷载-位移关系与颗粒流数值模拟的颗粒分布、速度、接触力的细观参数的变化密切相关。桩承受荷载过程中土颗粒细观结构变化的颗粒流仿真,是关于细观力学特征与宏观力学响应的初步研究。     

华北板块南缘的变形分解:洛南-栾川断裂带与秦岭北缘强变形带研究

秦岭洛南-栾川断裂带具有左旋斜向俯冲的运动学特征,其产状一般为107°/N∠65°。华南板块的俯冲方向为80°,俯冲角度为42°;华南板块运动方向为42°,运动方向与华北板块南部边界的夹角为65°,汇聚角25°。秦岭北缘强变形带内褶皱枢纽延伸方向为290°,与洛南-栾川断裂带存在15°的夹角。逆冲断层走向与褶皱的枢纽方向基本一致,大多数断层与洛南-栾川断裂带有相同的运动学极性,性质为左行平移逆断层。平移正断层走向主要为NE SW,断层性质、展布方向、运动学特征与板块汇聚的应力作用方式吻合;片理、片麻理走向117°,与洛南-栾川断裂带走向夹角为10°。在垂直剪切带的剖面上,系统观察岩石变形特征,测量面理产状,进行岩石有限应变测量,岩石非共轴递进变形分析结果表明:秦岭北缘强变形带内由南向北面理走向与剪切带走向的夹角逐渐增大,岩石剪应变量依次递减,造山带变形具有“三斜对称”特点。