冲击钻冲孔埋钻事故的处理

该文详细的介绍了简便可行的钻孔灌注桩施工中埋钻事故的处理方案。 即先用钻井法提取被埋钻颈,原地回填后再重新造孔、这样可以不修改设计方案节省费用,在一般中小型施工中可以实施。     

某引水隧洞围岩变形探讨

某引水隧洞主要采用双护盾式TBM施工。在穿越高埋深的区域性断裂带时,采用绕行导坑人工钻爆法施工。本文对采用绕行导坑的围岩变形情况进行分析,指出在隧洞开挖过程中围岩变形的时间效应,为修改设计与指导施工提供理论依据。     

城市地下浅埋暗挖隧道小导管注浆加固措施探讨

随着我国经济和社会的发展,地铁这一交通方式因其运量大、快速、正点、低能耗、少污染、乘坐方便等优点,被越来越多的城市所采用.城市地铁工程一般位于城市的繁华地段,一旦沉降事故发生,将可能造成建筑物开裂、倾斜,地下管线断裂等事故.文章结合莞惠城际轨道交通项目隧道工程实际,对城市地下浅埋暗挖隧道的小导管注浆加固措施进行分析阐述...     

城市管网工程中管道施工水土流失问题探讨

由于城市管网是城市的"生命线",在城市基础设施建设中发挥着重要作用,但其管线施工过程中不可避免造成地表破坏和水土流失等问题。以上海市某污水处理厂排海管工程为例,分析了开槽埋管施工和顶管施工两种施工工艺的地表扰动特点和水土流失问题,并提出了相应的水土保持措施:其中开槽埋管施工应注重施工作业面沿线的临时排水、沉沙措施和堆土坡面的保护措施,顶管施工应注重钻渣、泥浆的处置和防护,为城市管网工程施工中水土流失的防治提供参考。     

基于胡杨年轮的塔里木河下游地下水埋深历史重建

【目的】采用树木年轮技术重建塔里木河下游地下水历史变化动态过程,以期弥补塔里木河下游地下水埋深历史数据资料的不足,为干旱区内陆河流域地下水埋深重建研究提供一个新方法。【方法】以荒漠河岸林建群植物胡杨为对象,于2015年9月在塔里木河下游英苏断面共钻取胡杨年轮样芯58个,经Cofecha交叉定年程序和Arstan软件,选用48个样芯建立胡杨年轮宽度年表。采用滑动t-检验、M-K趋势检验、累积曲线分析胡杨轮宽指数和地下水埋深变化趋势,采用频率分布、方差分析、相关分析和线性回归,分析轮宽指数与气温、降水量、径流和地下水埋深关系。【结果】塔里木河下游英苏断面的胡杨树龄为40~80年,超过60年的树木均有不同程度的心腐现象,未发现100年以上木质部保存完好的胡杨;塔里木河下游胡杨年表突变时间分别为1957,1967,1975和2000年;区域气温和降水量对胡杨年轮宽影响并不显著;采用胡杨年轮宽度重建了塔里木河下游英苏断面近83年来的地下水埋深历史变化,其重建结果与区域水文记录基本一致。【结论】塔里木河下游胡杨年轮的形成受气温和降水量的影响不显著;胡杨年轮可作为研究塔里木河下游地下水位变化过程的一个新生态指标。     

螺旋钻成层土拔钻力的研究

为实现长螺旋钻回转动力头及绞车参数的控制,考虑成层土参数的影响,对拔钻过程的钻具进行力学分析,得到了成层土回转拔钻力的计算公式,并对3种实际拔钻过程的拔钻力进行了计算。计算结果与实测结果吻合,说明了该计算公式的正确性。在工程实际参数的变化范围内应用此公式,分析了螺旋角、回转速度以及拔钻速度对拔钻力的影响。以上结果对长螺旋钻钻具的设计以及动力头、绞车的参数设计具有重要指导意义。     

深栽高效牵引式植树机钻主轴的有限元分析

应用有限元分析软件 Patran/Nastran,分析高效深栽牵引式植树机钻主轴的受力情况、固有频率及振型,参考俞国胜教授研制的植树机钻的结构参数,通过受力分析及计算,得出主轴的最优参数并完成了钻主轴的有限元建模及静力与自由模态分析.结果表明,主轴整体变形量非常小,最大应力产生于钻主轴与翼片焊接处的最下端,小于主轴的强度极限,可对钻主轴做进一步结构优化;钻的各阶固有频率远高于其工作频率,不会发生共振,满足工作要求     

多层混合结构房屋浅基础埋深问题探讨

通过对多层混合结构房屋浅基础埋深问题分析,使我们在设计、施工过程中合理选择埋深和根据实际情况确定基础的埋深.     

钻夹头提高输出夹紧力矩的研究

根据钻夹头的工作原理,对其进行了力学分析和计算,导出了钻夹头夹紧力和输出夹紧力钜的计算公式。通过调整钻夹头的某些几何尺寸和材料间的摩擦系数,能够提高夹紧力和输出夹紧力矩。     

霸王种子出苗的沙埋需求

沙埋是荒漠植物自然更新中种子萌发及成苗过程的重要环境因子。为研究霸王种子出苗对沙埋的需求，设置5个沙埋处理深度，分析霸王出苗率及幼苗株高生长。结果表明：不同深度沙埋处理下霸王幼苗出苗率及株高差异有效，随着沙埋深度的增加，其幼苗的出苗率和株高均呈先升高后降低的趋势，埋深3 cm时达到最大值，分别为80.7%和2.30 cm。总之，霸王种子出苗对沙埋的需求范围为埋深1～7 cm，最适沙深为1～3 cm。     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。     

Natural Regeneration in Clear-cuts: Effects of Scarification,Slash Removal and Clear-cut Age

The effects of soil scarification (mounding), slash removal and clear-cut age on the natural regeneration in clear-cuts was evaluated using data from four sites in southern Sweden. The treatments were carried out during a good seed and establishment year for birch ( Betula pubescens Ehrh. and B. pendula Roth). Scarification had the strongest positive effect on the density of naturally regenerated seedlings, especially in birch, but also in pine ( Pinus sylvestris L.) and spruce [ Picea abies (L.) Karst]. Slash removal had a positive effect on birch density. No statistically significant effect of clear-cut age was found. In addition, no statistically significant interactions between clear-cut age and scarification or slash removal were found. The ingrowth of field vegetation was the fastest in areas that were not scarified, less rapid in areas scarified on old clear-cuts, and the slowest after scarification in fresh clear-cuts. In conclusion, it may be possible to control the density of birch during a good establishment year for birch. If birch is desired, the best combination of treatments is to remove the slash and scarify; otherwise, these treatments should be avoided.     

Risk Perception Among Non-industrial Private Forest Owners

Based on an enquiry, risk perception among non-industrial private forest owners is described in relation to climate change and forestry hazards. Of the respondents, 11% took action to remedy the effects of climate change. Out of a given set, hazards were ranked according to each respondent's experience of recent substantial financial loss to the estate and in relation to his or her willingness to make investments aimed at risk reduction. For each hazard, the respondent assessed the risk in four classes ranging from very high to negligible risk. Six hazards were considered most problematic in all three aspects: browsing damage, falling timber prices, damage by wind, spruce bark beetle, root rot and pine weevil. A majority of the respondents claimed to take action to reduce the risk associated with at least one hazard, while 35% did not know whether they did. Excluding climate change, the need for decision support was the largest in relation to damage by wind owing to a combination of perceived high risk and a high level of ignorance in relation to whether risk-reducing measures were taken.     

Interactions in decomposition and N mineralization between tropical legume residue components

In situ produced plant residues contain a mixture of different plant components of varying quality. To assess synergistic or antagonistic interactions occurring during the decomposition and mineralization of such mixtures, individual plant parts (stems, leaves, leaf litter and roots) or the mixture of stems, leaves and leaf litter of the agroforestry species pigeonpea (Cajanus cajan) or of crop residues of peanut (Arachis hypogaea) or of the weed hairy indigo (Indigofera hirsuta) were incubated in pots for 19 weeks. Periodically, remaining plant residues were sieved out (>2 mm), weighed and N content as well as soil mineral N determined. Above- and below-ground residues of peanut decomposed fastest and showed the largest N release in agreement with their high N concentration and low-acid detergent fibre (ADF) : N ratio. Hairy indigo was hypothesized to be of lower quality than pigeonpea because of its high-polyphenol content. However, it decomposed faster than pigeonpea, largely because of the higher N and lower lignin concentration of its components. Ranking of individual plant components for N mineralization resulted in the following pattern, leaves > leaf litter > roots > stems. In mixtures of the different plant components a similar species order in decomposition was obtained, e.g. peanut > hairy indigo > pigeonpea. The amount of N released from the mixture was dominated by stem material that comprised 46–61% of the mixture. The interactions in mixtures were relatively small for peanut (generally high-quality components) as well as for pigeonpea (low proportion of high-quality components, i.e. N rich leaf material). However, a positive interaction occurred during later stages of N mineralization in the mixture of hairy indigo as it had a significant proportion of N rich components and absence of highly reactive polyphenols. Thus, for plants with low to intermediate chemical quality attributes, manipulating plant composition (e.g. by varying harvest age, affecting stem and leaf proportions) will be important to obtain significant interactions during decomposition when its components are mixed.     

Pasture production and tree growth in a young pine plantation fertilized with inorganic fertilizers and milk sewage in northwestern Spain

The use of organic waste materials such as milk sewage as an organic fertilizer could have the dual advantages of organic-waste disposal and reduced dependence on inorganic fertilizers. The effects of fertilization with (1) conventional mineral fertilization, (2) milk sewage sludge at 40 kg N ha⁻¹ target rate and (3) no fertilization on pasture production and tree growth were examined in an experiment consisting of two pasture mixtures under a one-year-old Pinus radiata plantation with a density of 2500 trees ha⁻¹. The two pasture mixtures were: (1) Dactylis glomerata L. var. saborto (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹); (2) Lolium perenne L. var. Tove (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹). The experiment began in the spring of 1995 using a randomized block design with three replicates in Castro Riberas de Lea (Lugo, Galicia, north-western Spain). Plot size was 12 × 8 m², with a 1 m buffer strip between plots. Two-year data showed that fertilization with either material had a positive effect on pasture production, with no significant difference between the two fertilization treatments. Tree growth in the milk sewage sludge plot was significantly higher than in the control plots. Inorganic fertilization increased pasture production, but affected tree growth negatively. The results show that milk sewage sludge could be used as a fertilizer in silvo-pastoral systems. This revised version was published online in June 2006 with corrections to the Cover Date.