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作者结合实践,分析了地下工程渗漏水的原因往往是由于设计不合理及施工不规范而造成的,并提出了相应的防治措施。 相似文献
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The effects of j-rooting on water stress and growth of loblolly (Pious taeda L.) and eastern white pine (Pious strobus L.) were examined over three growing seasons in the field. Seedlings were planted in an area with severe herbaceous competition with either their roots planted straight or bent into a j shape. All seedlings were planted with their root collars placed at the soil surface. During the first year j-rooted seedlings consistently had lower water potentials but never statistically significant. Since both treatments were planted with the root collar at the soil surface, this trend was likely due to an initial shallower root system in j-rooted seedlings. In year three no differences in water potential were significant and no trends were evident. Growth did not differ significantly by treatment at any time but, by year three, j-rooted plants were consistently larger for both species. 相似文献
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Compressive deformation of wood impregnated with low molecular weight phenol formaldehyde (PF) resin II: effects of processing parameters 总被引:1,自引:0,他引:1
To obtain high-strength phenol formaldehyde (PF) resin-impregnated compressed wood at low pressing pressure, the effects of resin content, preheating temperature, pressing temperature, and pressing speed on the compressive deformation of oven-dried low molecular weight PF resin-impregnated wood was investigated. With an increase of PF resin content, the Youngs modulus of the cell wall perpendicular to the fiber direction decreases, and collapse-initiating pressure decreases linearly with the Youngs modulus. This indicates that the occurrence of cell wall collapse is strain-dependent. By increasing preheating temperatures, the collapse-initiating pressure increases due to the increment of the Youngs modulus of the cell wall. An increase in pressing temperature results in the thermal softening of the cell wall and causes collapse at a lower pressure. The wood is compressed effectively despite accelerated resin curing. The pressing speed significantly affects the viscoelastic deformation of the cell wall and the wood is well deformed with decreasing pressing speed, although the differences in density and mechanical properties are relatively small after a pressure-holding period of 30min. In all the parameters examined in this study, the Youngs modulus and bending strength increase with increasing density. 相似文献
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CHEN Peng ZHAO Guangjie College of Material Science Technology Beijing Forestry University Beijing P.R.China 《中国林业科技(英文版)》2007,(2)
There are many advantages of bended wood,such as good-looking shape,simple process and low cost.The product,however,is easy to get recovery,which is urgent to be dealt with.This paper concludes the features of deformation and recovery of bended wood and wood-based composites and summarizes four treating methods to keep dimensional stability.Compared to bended solid wood,some elementary perspectives on the research of bended wood-based composites are presented.The purpose of this paper is to suggest:1)to investigate the optimum heating time and temperature that bended wood and wood-based composites need from the formation of deformation to the recovery and to the permanent fixation,according to its changes of dimensional stability such as curvature radius;2)to measure the composites comprised of wood and adhesives on the changes of stress relaxation,dynamic viscoelasticity and crystal1ization field;3)to quantitatively analyze changes of the major components in wood cell wall polymers as well as the composites under heat/steam treatment and untreated conditions.It will be helpful for subsequent research to clarify on the mechanisms of permanent fixation of bended wood and also contribute to that of wood-based composites. 相似文献
7.
李军伟 《林业机械与木工设备》2015,(1)
阐述了三层实木复合地板的结构特点,对其产生弯曲变形的原因进行分析,并结合生产实际提出了三层实木复合地板的质量控制措施。 相似文献
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【目的】研究混凝土面板砂砾石坝防渗墙的应力变形及实际防渗效果,为高寒地区深厚覆盖层类似工程的设计与施工提供依据。【方法】以青海省纳子峡混凝土面板砂砾石坝为研究对象,在防渗墙施工及运行初期(2012-05-2018-01)对其进行应力监测、变形监测、渗流监测,对所得监测数据进行统计分析,进而评价防渗墙的实际工作状态。【结果】纳子峡混凝土面板砂砾石坝防渗墙各测点应力及变形表现稳定,在施工期防渗墙钢筋的应力变化因受地面施工等因素影响主要承受拉应力,且向上游侧倾斜;在水库运行期间(2014-09-2018-01),墙体受到来自上游的水压力,主要承受压应力,且向下游侧倾斜;布置在墙体上游侧的渗压计渗透压力远大于下游侧各测点,表明防渗墙防渗效果良好,渗透压力受测孔孔内水位影响,且随库水位表现出一定的周期性变化规律,库水位每抬升(或下降)1 m,墙体下游侧各测点渗透压力增加(或减小)约0.6 kPa。【结论】纳子峡大坝混凝土防渗墙在其施工及运行初期应力变形较为稳定,防渗效果良好,能为大坝的安全提供保障。 相似文献
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The dynamic behavior of a fish cage collar in waves was investigated using a numerical model based on the finite element method. The floating collar and mooring system were divided into a series of line segments modeled by straight massless model segments with a node at each end. To verify the validity of the numerical model, research data from other authors were cited and compared with the simulated results, the comparison of results showed a good agreement. The numerical model was then applied to a dynamic simulation of a floating cage collar in waves to analyze its elastic deformation and mooring line tension. The simulated results indicated that the greatest deformation of the collar taken place in the position of the mooring line connection point when incident waves were in the same direction. An increase in the length of mooring line would help to decrease the mooring line tension of the collar. Furthermore, the effects of collar dimension, including collar circumference, pipe diameter in cross-section, and pipe thickness, on the dynamic behavior of the floating collar were discussed. The results of this study provided a better understanding of the dynamic behavior of the fish cage collar. 相似文献
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对黄河宁夏境内具有连续弯道的大柳树一沙坡头河段的泥沙运移及河床变形等进行了平面二维数值模拟研究.建立了修正的平面二维RNGκ-ε紊流泥沙数学模型,其中水流模块采用修正的RNGκ-ε紊流模型,泥沙模块采用全沙模型,考虑了不同粒径组悬移质和推移质运移对河床变形的影响。数值模拟结果与实测结果比较吻合。表明该模型可以用于模拟具有连续弯道的多沙河流泥沙运移及河床演变过程;在4种典型工况下分别进行了数值模拟,研究了不同水沙条件对水沙运移及河床变形的影响;吸取了关于泥沙数学模型中水流模块和泥沙模块的耦合式算法和分离式算法的优点,建立了一种半耦合算法,其计算量比耦合式算法大大减小,计算精度上比分离式算法要高。 相似文献