基础工程施工的发展方向

基础专业承包商在美国是第三大专业承包商，总货币工作量达１０亿美元，仅次于电子和机械专业。本文简略回顾了基础施工业的发展历史；然后详细介绍了基础施工技术的最新发展，包括挡土结构（连续墙、深层搅拌墙、桩墙、土钉墙、土层锚固和加固）、地下开挖和支护（顶管、新奥法、水平定向钻进）、垂直支护结构（打入桩、钻孔灌注桩和微桩）、地下水隔墙（防渗墙、旋喷和压密灌浆）、以及桩的加载试验和检测（奥斯特伯格加载元件、假     

在均质中等密度砂层中桩的承载能力

在砂层中，桩承载能力的预测仍是岩土工程各种参数计算中最不精确的一种。本文作者将静载和动载的估算值在与纽约沿岸的几个工程中实测的桩承载能力进行了比较，找出了各种桩型在砂层中承载能力与桩长之间的关系，对在类似的地层选取合适的桩型及桩的基本参数具有一定的参考意义。     

浅谈岩土锚固技术的应用前景

岩土锚固技术是岩土工程领域的一个重要分支。本文着重介绍了锚固技术在岩土工程中的应用，主要涉及隧道与地下工程、坝基工程、边坡工程、深基坑支挡工程、结构抗浮抗倾、以及载简试验等。     

Analysis of recharge-induced geochemical change in a contaminated aquifer

Recharge events that deliver electron acceptors such as O2, NO3, SO4, and Fe3+ to anaerobic, contaminated aquifers are likely important for natural attenuation processes. However, the specific influence of recharge on (bio)geochemical processes in ground water systems is not well understood. The impact of a moderate-sized recharge event on ground water chemistry was evaluated at a shallow, sandy aquifer contaminated with waste fuels and chlorinated solvents. Multivariate statistical analyses coupled with three-dimensional visualization were used to analyze ground water chemistry data (including redox indicators, major ions, and physical parameters) to reveal associations between chemical parameters and to infer processes within the ground water plume. Factor analysis indicated that dominant chemical associations and their interpreted processes (anaerobic and aerobic microbial processes, mineral precipitation/dissolution, and temperature effects) did not change significantly after the spring recharge event of 2000. However, the relative importance of each of these processes within the plume changed. After the recharge event, the overall importance of aerobic processes increased from the fourth to the second most important factor, representing the variability within the data set. The anaerobic signatures became more complex, suggesting that zones with multiple terminal electron-accepting processes (TEAPs) likely occur in the same water mass. Three-dimensional visualization of well clusters showed that water samples with similar chemical associations occurred in distinct water masses within the aquifer. Water mass distinctions were not based on dominant TEAPs, suggesting that the recharge effects on TEAPs occurred primarily at the interface between infiltrating recharge water and the aquifer.     

Seasonal nitrogen and phosphorus dynamics during benthic clam and suspended mussel cultivation

Effects of suspended mussel and infaunal clam cultivation on sediment characteristics, and benthic organic and inorganic nitrogen and phosphorus fluxes were compared in a shallow coastal lagoon. The two species had different impacts on sediment features, but both created “hotspots” of nutrient fluxes with annual N and P regeneration rates being 4.9 and 13.5 (mussel) and 4.5 and 14.9 (clams) fold greater than those of unfarmed control sediments. Mussel farming also caused considerable nutrient regeneration within the water column with the mussel ropes contributing ∼25% of total inorganic N and P production and at times dominating the sediments (e.g. 95% of SRP production in summer and 45% of DIN production in winter). Such nutrient regeneration rates seriously question the proposal that suspension-feeding bivalves act as a eutrophication buffer, especially during summer when nutrient regeneration rates are maximal, but other nutrient sources (freshwater run-off and unfarmed sediments) are at their lowest.     

2013年非开挖行业统计分析

2013年,受世界经济复苏乏力、国内经济下行压力加大等不利因素影响,国内非开挖市场在经历了黄金十年后增速明显回落,市场需求萎缩,行业竞争更为激烈,企业之间的分化也进一步加剧。本文回顾了2013年对我国非开挖行业发展具有较大影响的十大重要事件,详细介绍和分析了中关两国非开挖行业的统计情况。     

Macroalgal bioindicators (growth, tissue N, delta(15)N) detect nutrient enrichment from shrimp farm effluent entering Opunohu Bay, Moorea, French Polynesia

Nutrient enrichment from shrimp aquaculture poses an increasing environmental threat due to the industry's projected rapid growth and unsustainable management practices. Traditional methods to monitor impacts emphasize water quality sampling; however, there are many advantages to bioindicators, especially in developing countries. We investigated the usefulness of three bioindicators -- growth, tissue nitrogen content and nitrogen stable isotope signature (delta(15)N) -- in the tropical red macroalga Acanthophora spicifera. Algae were collected, cultured, and deployed in a spatial array around the outflow from a shrimp farm in Moorea, French Polynesia, to detect nitrogenous wastes. All three parameters were highest adjacent to the shrimp farm indicating nutrient enrichment, and delta(15)N values confirmed the shrimp farm as the dominant nutrient source (5.63-5.96 per thousand). Isotope ratios proved the most sensitive indicator, as delta(15)N signatures were detected at the most distant sites tested, confirming their usefulness in tracing nutrients and mapping the spatial extent of enrichment.     

一种新型的微型水平定向钻机的研制

一种新型的微型水平定向钻机已经开发出来,并用于几个工程施工中。这种新型钻机能够铺设１５０ｍｍ直径的管线,上下左右的精度极高,因而可用于铺设重力管道。本文比较了几种不同的定向钻进技术的特点,并给出Ｔｒｕ－Ｇｒａｄｅ微型定向钻机的一些特点。在由作者主持的项目评定工程,该钻机成功地铺设了一条内径为１００ｍｍ的高密度聚乙烯和,上下左右的偏差均在２５ｍｍ以内。     

非开挖管线施工技术的发展及我国对策

非开挖技术是指利用探矿工程的技术手段,在地表不挖槽的条件下进行各种地下管线施工的新技术,是地下管线施工的一项技术革命,它以独特的技术优势和广阔的市场前景而得到世界各国的极大重视,其发展极为迅猛,业成为一门新兴的产业。同时,非开挖技术又是探矿工程应用领域的进一步拓宽,是继岩土工程这后,又一个潜在的巨大市场。本文拟对国外非开挖技术的重大进展作详细的分析和介绍,并对发展我国的非开挖技术与设备提出了若干有