Laboratory Study for Influence of Clay Content (CC) on Wave-Induced Liquefaction in Marine Sediments

In this artice, the influence of clay content on the wave-induced liquefaction in marine sediments was reported. The one-dimensional (1-D) equipment was setup with a vertical cylinder and 1.8–m–thick clayey sandy deposit and 0.2–m–thick water above the deposit. Unlike the previous experimental study for a single soil layer, this study used sand-kaolin mixtures, sand-illite mixtures, and sand-bentonite mixtures as the experimental samples. A series of experiments with 3,000 wave cycles in each test were conducted under numerous wave and soil conditions, which allowed us to examine the influence of clay content (CC) on wave-induced liquefaction in marine sediments. The experimental results showed that the clayey sandy deposit will become prone to liquefaction with the increase of CC when CC is less than a critical value, which depends on the type of clay. However, when CC is greater than the critical value, liquefaction depth will decrease as CC increases. Furthermore, when the CC value reaches a certain level, liquefaction will not occur. For example, no liquefaction occurs when CC ≥ 33% for both kaolin-sand and illite-sand mixtures and CC ≥ 16.36% for bentonite-sand mixtures.     

海啸灾害后印度尼西亚班达阿齐市的土地覆盖变化与海岸带区域规划

2004年12月26日,由于欧亚板块的碰撞,40年以来最大的地震灾害发生在印度洋。地震诱发的海啸影响到Nangroe Aceh Darussalam省的许多城市,包括省会城市班达阿齐。在这地区共有超过12万人死亡,100万人无家可归。基于遥感数据的分析表明,有12万亩的土地受到了灾害。在班达阿齐市,鱼塘、住宅用地和保护区的变化是这一地区最显著的土地利用/覆盖变化,受灾前后这些用地类型的面积相应的变化了61.5%、57.8% 和77.6%。目前,印度尼西亚中央政府正在计划一个新的海岸带土地利用规划,在原来密集的海岸带建立一个缓冲区（约距海岸带2 km）。政府已经要求许多海岸带的社区代表与非政府组织参与到决策的过程中。 为了选择并采取最佳的土地利用方式,海啸灾害后的海岸带规划应该包括一些重要的基本要素。本研究主要关注作为该省社会经济活动中心的班达阿齐市。检测了由于海啸灾害造成的土地利用/覆盖变化（包括物理破坏）,特别是农业用地和居住区用地的变化,并且分析了受灾村落的不同类型及灾害对社会经济活动造成的影响。此外,还为政府以及当地居民在灾后的规划中选择更为可持续的空间布局方案提出了建议。     

Design of shallow foundations under tensile loading for transmission line towers: An overview

Tensioned foundations are common in civil engineering applications such as transmission towers, harbors, offshore structures, basement slabs under pressure, industrial equipment, etc. Procedures for the design of tensioned foundations are discussed in this paper, including specific recommendations for more common transmission tower foundations. Starting from a distinction between shallow and deep modes of failure, the paper presents the most common failure mechanisms for shallow failure in tension, including procedures for calculation of foundation tensile capacity under vertical and inclined loading. Emphasis is given to the influence of the strength of the compacted backfill compared to the strength of the natural soil, including presentation of results of full-scale loading tests.     

Chemistry of snow and lake water in Antarctic region

Surface snow and lake water samples were collected at different locations around Indian station at Antarctica, Maitri, during December 2004–March 2005 and December 2006–March 2007. Samples were analyzed for major chemical ions. It is found that average pH value of snow is 6.1. Average pH value of lake water with low chemical content is 6.2 and of lake water with high chemical content is 6.5. The Na⁺ and Cl^? are the most abundantly occurring ions at Antarctica. Considerable amount of SO ₄ ^2? is also found in the surface snow and the lake water which is attributed to the oxidation of DMS produced by marine phytoplankton. Neutralization of acidic components of snow is mainly done by NH ₄ ⁺ and Mg²⁺. The Mg²⁺, Ca²⁺ and K⁺ are nearly equally effective in neutralizing the acidic components in lake water. The NH ₄ ⁺ and SO ₄ ^2? occur over the Antarctica region mostly in the form of (NH₄)₂SO₄.     

Spatio-temporal variation in some physical and chemical parameters over a 25-year period in the catchment of the river Adour

The catchment of the river Adour (SW France) has been examined in order to analyse spatio-temporal variations in a number of key variables (flow, suspended matter, nitrate and dissolved orthophosphate concentrations) over a 25-year period (1972–1996).

Within the catchment area, it has been possible to discern how hydroclimatic fluctuations have affected the watershed, with dry periods in 1972–1976 and 1983–1993 alternating with wetter phases in 1977–1982 and 1994–1995. The anthropogenic activity, primarily, involving the use of water for agricultural purposes, has also had a major impact during this period, particularly in the downstream areas of the catchment.

Suspended matter fluxes display regular downstream increases with significant erosion being evident in the mountainous region contrasting with retention in the floodplains area downstream. These fluxes exhibit temporal and spatial variations with peaks occurring every 3–5 years, 1975–1977, 1979, 1982, 1985, 1987 and 1992. Some of these peaks are suggested to be related to anthropogenic activity involving river management, including the cutting of meanders and the construction of dykes for flood prevention.

Nitrate concentrations evince a similar pattern to the suspended matter fluxes with enhanced levels of downstream. The confluence of the Adour with the Midouze appears not to have any major impact on the nitrate concentration. In the downstream areas, an uptake of nitrate is registered indicating the activity of the riparian vegetation. For the entire catchment, maximal nitrate concentrations are observed in 1979, 1982, 1987, 1991–1992 and 1995.     

Detecting significant sediment motion in a laboratory flume using digital video image analysis

A video analysis method for monitoring sediment transport and sorting processes in a laboratory flume is presented. Video taken through the glass side‐wall of a laboratory flume is captured using a digital CCD (charge‐coupled device) camera and significant movements between individual frames are detected using image analysis. This method involves direct subtraction of the brightness numbers of pixels in sequential video frames, followed by thresholding to produce binarized images of significant change, above the inherent level of system noise. Experimental results showing dilation of a gravel framework and rapid infiltration of fines just prior to entrainment are discussed. Copyright © 2000 John Wiley & Sons, Ltd.