Vertical cyclic loading response of geosynthetic-encased stone column in soft clay

Dynamic responses of the geosynthetic-encased stone column (GESC) supported embankment under traffic loads have become a hot topic. This study investigates the responses of GESC improved ground under vertical cyclic loading. A series of laboratory tests in a designed model test tank have been carried out with different loading parameters (varied loading amplitudes and frequencies), different column dimensions (varied encasement lengths and column diameters). In the tests, the soil-column stress distribution, accumulated settlement of loading plate, excess pore water pressure in the surrounding soil and lateral bulging of the stone column are monitored. Experimental results indicate that the vertical stress on the stone column increases with the increment of encasement length, and decreases with the increment of column diameter, loading amplitude and loading frequency. The increasing stress on the surrounding soil leads to a greater accumulated settlement of the loading plate and excess pore water pressure, while the increasing stress on the column leads to larger lateral bulging of the column. Excess pore water pressure dissipates effectively through vertical and horizontal drainage channels provided by the stone column and the sand bed. The geosynthetic encasement prevents the clay from obstructing the drainage channel by filtration and guarantees the drainage effect.     

一种分析碳酸盐岩孔隙系统数字图像的新方法

碳酸盐岩的孔隙类型多，孔径变化范围大，孔隙系统结构复杂，研究难度大。长期以来，是利用光学显微镜法、毛细管压力分析法、岩石孔隙系统复制法和图像分析仪法等方法或其中几种方法配合来研究碳酸盐岩孔隙系统。随着计算机图像技术的迅速发展和日益完善，借助该项技术通过碳酸盐岩孔隙系统数字图像来研究碳酸盐岩孔隙系统已经成为现实。文章提出一种研究碳酸盐岩孔隙系统数字图像的新方法。通过样品光薄片的光学显微镜（OM）数字图像和环境扫描电子显微镜（ESEM）数字图像二值化识别孔隙；构造孔隙度、孔隙贡献率和孔隙形状参数的计算公式用于数字图像分析，得到孔隙大小分布和孔隙形状分布。在此基础上，总结碳酸盐岩孔隙参数对其渗透率的控制作用。与传统的孔隙系统研究方法相比，该方法与计算机图像技术紧密结合，具有定量、快速的明显优势。     

论四川盆地天然气勘探前景

中石油及其前身已在四川盆地从事天然气勘探开发工作50余年,截至2005年底累计探明天然气地质储量逾8400×10⁸m³,累计生产天然气超过2300×10⁸m³,年产量现已超过120×10⁸m³,已成为国内目前最大的产气区。对于该盆地进一步勘探前景如何的命题,从以下4个方面给予了论证：一是资源丰富、勘探成果持久不衰，近期仍有大发现；二是要辩证地认识盆地油气地质的复杂性，探索新规律，解放新领域；三是寻求地质认识和勘探技术进步是勘探突破的关键；四是继续以盆地两大地质体系（海相古隆起体系及陆相前陆盆地体系）和8套裂缝-孔隙性储集层（中上寒武统白云岩、石炭系白云岩、上二叠统长兴组生物礁白云岩、下三叠统飞仙关组鲕状白云岩、下三叠统嘉陵江组粒屑白云岩、中三叠统雷口坡组藻粒白云岩、上三叠统须家河组长石岩屑石英砂岩和中上侏罗统红层砂岩）为对象获取更多的天然气资源量及优质储量。据此得出结论：四川盆地天然气勘探前景是广阔的，但勘探难度会逐步加大。     

工程建设的新特点与中国三峡总公司的可持续发展

本文介绍了三峡工程进入2002年后工程建设的新特点,并对工程下一步两个重点项目三期截流和碾压混凝土围堰的技术难点和工期安排做了深入分析。另外,作者根据国家电力体制改革的重要内容,以及中国三峡总公司自身情况,对公司未来的可持续发展之路亦做了深入探讨。借助中国三峡总公司的品牌优势和资本实力,吸收其它形式的能源,优化能源结构;进一步降低工程造价,提高三峡电价在电力市场的竞争力;依靠科学管理,实现电力生产利润最大化,深化内部改革等措施,促进中国三峡总公司可持续发展。     

APPLICATION OF COMPUTER NUMERICAL METHOD IN PORE STRUCTURE CALCULATION

This paper compares the results Of calculat-ing pore structure and graphing differential and integralpore size distribution by hand and Computer,and presents thatlagrangian interpolation uesd by calculating pore structure issuitable and reliable.     

利用T2分布进行岩石孔隙结构研究

测井地层评价的基本任务除了要研究储层参数外，还要研究岩石孔隙结构。核磁共振测井技术和出现和应用，为测井解释研究孔隙结构提供了一种有效方法。通过研究泥质砂岩岩心核磁共振T2分布与压汞毛管压力曲线之间的关系，建立起二者之间的相互计算方法，从而为利用T2分布进行岩石孔隙结构研究提供了理论和方法的支持。     

Efficient Parallel Algorithms for Some Graph Theory Problems

In this paper,a sequential algorithm computing the aww vertex pair distance matrix D and the path matrix Pis given.On a PRAM EREW model with p,1≤p≤n^2,processors,a parallel version of the sequential algorithm is shown.This method can also be used to get a parallel algorithm to compute transitive closure array A^* of an undirected graph.The time complexity of the parallel algorithm is O(n^3/p).If D,P and A^* are known,it is shown that the problems to find all connected components,to compute the diameter of an undirected graph,to determine the center of a directed graph and to search for a directed cycle with the minimum(maximum)length in a directed graph can all be solved in O(n^2/p logp)time.     

Microscopic and Macroscopic Growth Rates of Fatigue Cracks in Steels and Alloys under the Influence of Crack Closure

On the basis of the experimental data, we show that the difference between the macroscopic and microscopic fatigue crack growth rates in the second section of the kinetic diagram of fatigue fracture is caused by the effect of crack closure within the limits of its existence. We establish the relationships between the macroscopic and microscopic fatigue crack growth rates and the structure of the material in the second section of the diagram for various values of the load ratio with regard for the effect of crack closure and propose a procedure of examination of the fracture processes in structural materials based on the analysis of microscopic and macroscopic fatigue crack growth rates.     

三峡地下电站变顶高尾水洞水动力特性

在国内首次应用模型水轮发电机组对三峡地下电站变顶高尾水洞方案进行水力过渡过程试验研究。对水轮机导叶实行分段关闭 ,并求出了二段关闭的最佳拐点 ,试验证实了二段关闭对减小尾水管进口的负压和机组转速上升有明显的作用。通过有关水力参数的测试 ,认为变顶高尾水洞可以满足各项技术要求 ,是一个减少山体开挖、节省投资的新型设计方案。在地下电站中具有广泛的应用前景     

关于混凝土四面体截流材料的探讨

通过对比混凝土四面体与特大块石这两种截流材料的抗冲稳定性和施工的方便性,分析了混凝土四面体截流材料在工程应用中存在的问题。指出:①混凝土四面体密度、综合稳定系数、化引球形粒径都偏小,在龙口的抗冲稳定性不如特大块石;②混凝土四面体制作麻烦,成本高,占地面积大,装运困难,抛投强度低,施工不如特大块石方便;③在截流施工中宜优先使用特大块石,慎用混凝土四面体。