泸州长江二桥非对称大跨连续刚构的施工控制

泸州长江二桥为大跨度非对称连续刚构,采用悬臂浇筑施工.由于施工过程复杂,结构的内力和变形变化较大,必须对其进行施工过程的控制.主要介绍了施工监控技术的原理和方法.通过有效地施工控制,给出了线形和应力控制的结果,为提高桥梁施工质量和安全可靠提供科学保证.     

柔性吊桥缆索吊装施工技术

依据我国桥梁施工技术规范、缆索吊装施工技术资料和柔性吊桥施工实践,在总结柔性吊桥施工经验的基础上,探讨柔性吊桥缆索吊装索道施工的施工方案、施工准备、施工工艺、施工方法和施工控制,系统提出柔性吊桥缆索吊装施工过程的关键技术,为山区和景区等复杂地形条件下柔性吊桥施工提供科学依据。     

浅谈斜拉桥施工

斜拉桥的施工包括索塔施工、主梁施工和拉索施工,文章对其施工方法进行了详细的阐述。     

混凝土施工缝的质量控制

就控制施工缝的留置位置进行分析,得出按照施工规范与要求留置和处理施工缝,施工缝处的混凝土强度不会低于设计强度要求,施工缝的质量也能得到较好的控制和保证。     

环保生态袋在景观工程施工中的应用

介绍了环保生态袋的特点、结构和功能,并通过沙河三期Ⅱ标段湖心岛边坡施工的具体事例,充分论证了作为新产品的环保生态袋在施工中的环保、节能、易于施工等优点和功用,对提高施工效率和降低施工成本具有无可比拟的实用性,提倡将该产品进行系统推广并充分运用在施工中尤其是边坡绿化施工中,以解决边坡施工不可实现的技术难题。     

高速公路绿化工程施工探讨

针对高速公路绿化施工的特点,就如何从多方面控制施工工期和施工成本、提高苗木成活率,并结合作者的施工经历探讨了一些技术要领和操作方法.     

关于公路路基施工技术的研究

公路路基施工是公路施工质量保障的基础,也是公路的主体,因此路基施工的重要性在整个施工过程中应受到施工单位的高度重视。其中保证施工质量,认真监管路基施工是施工环节中应重点考虑的问题。本文主要从施工放样、路基施工和施工程序三个方面,结合多年来的经验对其进行了较详细的阐述。     

民用建筑工程项目的质量管理探讨

简要分析民用建筑工程项目施工质量,着重讨论探讨施工材料和施工工序,同时就施工过程中要注意的事项提出建议。     

建筑工程模板施工技术控制要点

在高层建筑施工中,带有转换层的高层建筑施工的关键,在于对转换层施工方案的确定,这是直接影响施工阶段结构安全和工程质量的重要环节。对高层建筑工程转换层的特点、转换层结构的施工特点进行了详细介绍,并重点对模板工程进行了分析和研究。     

高速公路路基施工技术

在分析高速公路路基施工质量要求的基础上,对路基施工中的路基填土与路基压实施工技术、路基排水施工技术和路基裂缝防治的施工技术作了阐述。     

Effect of Drought on Growth and Mortality of Actively Growing Norway Spruce Container Seedlings Planted in Summer

Survival, root egress and height growth of 13-month-old actively growing Norway spruce ( Picea abies (L.) Karst.) container seedlings exposed to preplanting drying treatments (0, 4, and 8 days) and postplanting drought periods (1, 2, 3, and 4 weeks) were studied in the field between 5 July and 18 August 1999. The mortality of seedlings increased and the height growth and root egress decreased throughout the postplanting drought period. Postplanting performance was also affected by preplanting drying treatments. The results indicate that no risk of excessive mortality and growth restrictions occurs when actively growing seedlings are planted in summer, provided that seedlings are well watered before planting and the drought period does not exceed 3 weeks.     

Repair and strengthening of timber cantilever beams

This research aims to study the feasibility of repair and strengthening of timber cantilever beams used in historic buildings. It is conducted to investigate the feasibility of using different valid materials and techniques to repair and strengthen timber cantilever beams in new and historic timber buildings. The study is performed in terms of structural performance as well as historic and architectural values. An experimental program of several different materials and techniques is executed. The results are driven in terms of initial cracking load, crack propagation for the tested samples at different loading stages, deflection values, and failure load for each repaired or strengthened material and technique. The main variables are timber types (new and historic), repair and strengthening materials (steel plates, Glass Fiber Reinforced Polymer wrap, and Carbon Fiber Reinforced Polymer laminates), repair or strengthening techniques (near surface mounted and externally bonded system), and cantilever length (1000 and 1250?mm). Test results indicated that using steel plates, glass fiber wrap, and carbon fiber laminates increases the value of failure loads and decreases the deflection at both; repaired and strengthened timber cantilever beams compared to control beams.     

坚持和完善森林资源管理制度 保障和促进林业持续快速发展

概要阐述了森林资源在维护生态平衡、促进可持续发展中的重要作用,简要分析了当今全球和我国森林资源状况,全面总结了建国以来我国森林资源管理取得的成绩和经验,深入揭示了当前我国森林资源及其保护管理存在的问题和原因,系统介绍了我国森林资源管理的基本政策和制度。按照《中共中央国务院关于加快林业发展的决定》要求,对今后一个时期我国森林资源管理的思路、目标、任务提出了一些设想和建议。     

竹大片刨花板对竹材生物学特性的适应性

以云南四种典型材用丛生竹（龙竹、甜龙竹、黄竹和油勒竹）宏观构造、组织结构、主要物理力学性质和化学组份等竹材主要生物学特性的研究分析结果为依据,提出了竹大片刨花板的结构、制板工艺和设备与原料竹材生物学特性之间应有的适应性关系。继而,通过实验室系列化试验和工厂试生产,确定了竹大片刨花板的应有性能和最佳工艺条件包括竹大片刨花的最佳质量指标及其最佳制备条件。     

Comparison of tree growth and undergrowth development in aerially seeded and planted Pinus tabulaeformis forests

Direct seeding is a less expensive practice than planting and has the potential to become a viable alternative to transplanting for afforestation and regeneration purposes. As an effective and a less costly regeneration method, aerial seeding has been applied with several tree species. As early as 1956, Chinese people engaged in aerial seeding and stands with a total of 2.97×10⁷ hm² have been developed up to 2004. Our study tested whether the growth of planted Chinese pine (Pinus tabulaeformis Carr.) seedlings and its undergrowth development in northwest aspects differ from that of aerially sown seedlings on the northern and northwestern aspects of slopes. In 2007, we collected data such as height, diameter at breast height (DBH), clear bole height and canopy widths of trees, abundance, coverage, and frequency of shrubs and herbs from 21-year-old planted Chinese pine stands on a northwestern aspect (PNW), aerially sown stands in a northwest aspect (ANW) and aerially sown stands in a northern aspect (AN). Results showed that the relation of crown area and mean DBH was best fitted by a double inverse model for the ANW and AN forests and by a quadratic model for the PNW forest. There was no difference in the growth between ANW and AN forests, while growth was significantly higher in the PNW forest than in the ANW and AN forests. That was consistent with the Sorenson diversity indices in the shrub and herb layers, indicating that there was a large number of the same species in both aerially seeded stands, although their locations were different. Both the number of species in the undergrowth and the Shannon-Wiener index in the shrub layer were higher in the PNW stands than in the ANW and AN stands. Dominant families for all three stands were Rosaceae and Compositae in the shrub and herb layer, respectively. The dominant species for all three stands was Spiraea pubescens in the shrub layer, while the dominant species was different from each other in the three stands. The discrepancy in diversity and composition of species in the herb layer show that herbs are sensitive to shrubs in the three forests. High mortality and skewed diameter distributions reflect severe competition and too high a density in the aerially seeded forests. Thus, aerial seeding is a viable and effective regeneration technique, but management practices, such as thinning, should be applied to these forests.     

Diversity,regeneration status and population structure of gum- and resin-bearing woody species in south Omo zone,southern Ethiopia

South Omo Administrative Zone in Ethiopia is home to 18 indigenous ethnic groups whose livelihood is vulnerable due to recurrent drought and degradation. Despite the preliminary observation showing the rich dry-forest resource base that, if sustainably managed could enhance livelihoods and biodiversity conservation, there is lack of empirical data on its current status. We conducted a study aiming at quantifying the population status of gum- and resin-bearing species in two randomly selected districts, Hamer and Bena-Tsemay. Seventy-five quadrats(35 at Hamer and 40 at Bena-Tsemay) each measuring 400 m2 were established along line transects to assess species diversity and equitability, density, frequency, dominance, importance value and population structure. We recorded a total of 27 woody species of 12 families and 14 genera. Fifteen species(9 at Hamer and 14 at Bena-Tsemay) of the genera Acacia, Boswellia, Commiphora and Sterculia, were identified as either major sources of commercial gums and resins or their adulterants. Gum- and resin-bearing species comprised 56% and 57% of species richness, 48% and 50% of total density per ha, 95% and 98% of basal area, and 64% and 56% of importance values at Hamer and Bena-Tsemay, respectively. Diversity of the entire woody species assemblage and of the gum- and resin-bearing species was slightly higher at Bena-Tsemay(H= 2.61, 1.4) than at Hamer(H′= 2.48, 1.28), respectively. The diversity and abundance of the resource base suggest potential for development of value-added commercialization of gum and resins to enhance livelihoods and encourage sustainable management of the forest at these study areas. We recorded, however, declining natural regeneration of most gum- and resin-bearing species, and this calls for integrated and participatory species management and landscape rehabilitation.     

Forest Utilization in Oaxaca

Abstract

Two communities, Ixtlan and Chalchijapa, located in the Mexican state of Oaxaca, are compared based on their utilization of local forests. The long-settled community of Ixtlan, with its pine-oak forests, is compared to the recently established village of Chalchijapa which is located in rain forest on the edge of the Chimalapas nature reserve. Constraints such as forest type and management, land ownership and tenure, and current and future plans for timber extraction and utilization are examined, as are methods of wood processing and milling. The degree and type of wood utilization carried out by these two timber-dependent communities is greatly reflective of the local forest type and social structure.     

Effects of thinning on growth of six tree species in north-temperate forests of Lithuania

This paper summarises the results from 35 years-observed thinning experiments on 256 permanent sample plots in 10–60 year-old stands of ash, aspen, birch, oak, pine and spruce in Lithuania. Thinning enhanced crown projection area increment of residual trees. The largest effect was observed in stands of aspen and birch (growth increase by 200%), followed by ash and oak (over 100%), and spruce and pine (about 80%). Thinning also promoted dbh increment, especially in younger stands, and the increase of dbh increment was positively correlated with the thinning intensity. The strongest reaction was exhibited by oak and aspen, while ash, birch and conifers reacted to a lower extent. Low and moderate intensities of thinning stimulated volume production in younger stands while the opposite was observed in older stands with increasing removals. Spruce stands exhibited relatively strongest increase of volume increment and pine, –the weakest, while the effect on deciduous species was intermediate. The results demonstrate that significant increase in volume increment is achievable with thinning of only young forest stands, e.g. 10–20 year-old pine, birch and ash, or 10–30 year-old oak, aspen and spruce.     

气候变化背景下森林资源发展的机遇

气候变化的影响多被认为是负面的,甚至是毁灭性的,然而对林业生产也存在着正面作用。文中借助3个例子来说明降雨量和气温的变化可能对林木生长潜势的影响,以及在气候变化和发展森林资源中如何予以善用。气温升高和降雨量增加,在一定范围内能够提高森林生态系统的林木生长量,特别在生长明显受温湿度约束的温带、寒温带、高海拔、干旱和半干旱地区;改变各地区引种树木的种植分布,扩大生长快、效益好树木的种植范围;改变树木受温湿度所制约的边缘分布区,使其逐步变成适生区或种植区。可以利用现有气候、生物地理、引种、遗传改良等知识,结合进一步的系统试验研究,在林业实践中把气候变化变成机遇,提高森林生态系统的生产力。     

采伐作业对长白山阔叶红松林林下植被影响的研究(英文)

森林采伐是森林经营中的一个关键环节。采伐对树木天然更新的影响直接关系到森林的结构、组成及森林的可持续经营。本文以长白山阔叶红松林为研究对象,对择伐5 年后不同作业迹地(集材道、楞场和采伐后林窗)的幼苗更新及灌木、草本的多样性进行研究,并以没有进行采伐干扰的林地作为对照。共设计样地23 块,在各个小样地内调查幼树的种类、树木、高度;灌木和草本植物的种类、树木、高度和盖度,应用SPSS 软件进行一元方差分析。结果表明,择伐作业影响幼苗的更新,灌木和草本的多样性在作业迹地增加,尤其在林隙处的多样性最高。适当采伐能促进幼苗的更新,特别是阔叶树种的更新。集材道对幼苗密度的影响比对幼苗高度的影响大,幼苗密度在集材道上密度最高;采伐作业对针叶树种有严重的影响,在三种作业迹地上针叶树种的密度都比对照低。为了维持森林的结构和组成,在森林收获和楞场的建立时,必须采取科学措施保护针叶树种。此外,采伐林窗和楞场的面积都应该减小。为了确保采伐迹地建群树种的更新,经营中应该在保护生物多样性的前提下,适当控制过于旺盛的灌木和草本层的生长。本研究结果将为采伐后作业迹地的恢复和森林的可持续经营提供科学的依据。图1 表4 参14。