硬质合金内衬的组合超高压筒体优化设计

研究了硬质合金内衬的多层组合超高压筒体的强度优化设计。以等强度理论为设计原则,建立了以各外层径比(外径与内径的比值)为变量,容器总径比为约束,弹性承压能力最大为目标的优化设计数学模型。应用Lagrange乘子法进行优化,得到了各层最优径比公式及最大内压公式。在此基础上,从叠加原理出发,推导了不同材料多层容器的层间缩套压力及过盈量的最优精确解。最后通过实际算例与分析表明,硬质合金内衬的组合容器需要更大的缩套压力,对于三层容器,中间层和内衬主要承担径向压应力,而外层主要承担周向拉应力。     

在加变炉中内衬轻质混凝土的应用

在加变炉内衬矾土水泥胶结剂、陶粒和蛭石为骨粉材料的轻质混凝土，能收到隔热好、寿命长、成本低的效果．     

一种修正的Miner法则在疲劳寿命预测中的应用

鉴于传统的线性累积损伤理论即 Miner 法则中存在的不足之处,对预测疲劳寿命有着较大的误差。考虑了低于疲劳极限下的小载荷所造成的损伤,同时考虑了工程中实际的"α"值不等于"1"的因素,计算相应的α值,在考虑了这2个相关因素的前提下,并引入了模糊数学,建立了修正的 Miner 公式。通过实例分析表明,所建立的修正 Miner 公式较好的提高了疲劳寿命预测的精度,在工程应用中具有一定的价值。     

等离子束硬化处理气缸套内壁的应用研究

介绍了采用等离子束对内燃机气缸套进行熔凝淬火硬化处理的基本原理及实际应用。利用等离子束对原先无法进行常规热处理的气缸套内壁进行超快速的加热熔凝淬火,在气缸套内表面形成白口及马氏体类的高硬度组织,提高了气缸套的耐磨性和使用寿命,这一新型的实用 内燃机行业有着广阔的应用前景。     

应变硬化垃圾堆体抗局部沉陷研究

通过三种不同材料堆体的局部沉陷模型试验发现局部沉陷条件下应变硬化材料可能产生"自支撑"现象。利用模型试验和退化情况下的解析解验证了数值分析模型模拟应变硬化材料堆体局部沉陷问题的有效性。在此基础上比较了采用不同垃圾应力应变模型的分析结果,考虑堆体材料应变硬化的复合指数模型和线弹性模型计算得到的沉陷区土压力明显小于与之对应的摩尔-库伦模型计算结果,采用传统摩尔-库伦模型计算得到的沉陷区衬垫系统挠曲变形和应变值偏大,因而针对砂土材料的Giroud(1990)Trapdoor土拱效应理论应用于垃圾堆体局部沉陷分析时存在一定的局限性。进一步分析了各种参数对衬垫系统表面土压力和变形的影响,发现沉陷区衬垫系统最大挠度和最大应变随垃圾堆体高度的增加而增加,随垃圾堆体模量和加筋体刚度的增加而减小。最后提出应变硬化垃圾堆体在局部沉陷条件下衬垫系统土工膜的应变计算和加筋层的设计方法,对于垃圾填埋场衬垫系统抗局部沉陷设计具有一定的指导意义。     

Numerical investigation on hydraulic and gas flow response of MSW landfill cover system comprising a geosynthetic clay liner under arid climatic conditions

Municipal solid waste (MSW) landfill cover systems are designed to minimize the infiltration of rainwater into waste and to mitigate the biogas emissions to the atmosphere. In the present study, the efficacy of such a landfill cover system consisting of a Geosynthetic clay liner (GCL)in mitigating the hydraulic flow and gas emissions under arid climatic conditions was investigated critically. For this purpose, the water retention curve (WRC), hydraulic conductivity function, and gas flow characteristics of the chosen GCL were studied through experimental methods in the laboratory. The unsaturated transient state seepage analysis utilizing coupled hydraulic and gas flow mechanisms was performed in the study to assess the performance of the cover system. The results obtained from the experiments were used as input parameters. The effect of drying/desiccation and the self-healing nature of GCL due to climatic changes were also analyzed by exposing the GCL directly to the climatic boundary for one year. It was observed that the GCL present in the chosen cover system effectively functions as a hydraulic barrier in arid climatic conditions. However, during the summer and winter seasons, an increase in gas flow from 0.02 g/h/m² to 24.7 g/h/m² was observed, probably due to the drying anddesiccation of GCL. Interestingly, due to the self-healing nature of the GCL, gas flow through the cover system was substantially reduced to 0.02 g/h/m² during the rainy season. The effect of drying was more pronounced when the GCL was exposed to the climatic condition, leading to an early gas breakthrough and an increase in gas flow from 0.02 g/h/m² to 957 g/h/m². The percolation through the cover system remains considerably low throughout the year, mostly due to the unsaturation and low hydraulic conductivity in GCL. A cumulative percolation close to 0.1 m³ was observed at the end of one year in arid climatic conditions.     

Cyclic shear behavior of GMB/GCL composite liner

The composite liner system consisting of geomembrane (GMB) and geosynthetic clay liner (GCL) has been widely used in landfills. Although there have been a lot of studies on the monotonic shear behavior of GMB/GCL composite liner, the dynamic test data are still very limited and consequently, the dynamic shear mechanism is not clear. A series of displacement-controlled cyclic shear tests were conducted to study the shear behavior of GMB/GCL composite liner, including the shear stress versus horizontal displacement relationships, backbone curves, and shear strengths. Hysteretic loops in the shape of parallelogram were obtained and equivalent linear analyses revealed that the secant shear stiffness decreased and the damping ratio increased with the rise in loading cycles. According to the test results, it is generally acceptable to predict the dynamic peak strength of a GMB/GCL composite liner with its static strength envelope. Furthermore, the dynamic softening mechanism and rate-dependent shear stiffnesses were well described by the proposed equations, which also facilitate the accurate modeling of the cyclic shear behavior.     

预应力混凝土空心板梁电动液压落梁施工工艺

预应力混凝土空心板梁电动液压落梁施工工艺在时间上．由传统工艺的8小时操作完成缩短到1小时以内完成。将操作工人由原来的9人减少到现在的4人;同时把人工手摇千斤顶改成电动控制,降低了工人的体力消耗,减轻了劳动强度,改变了传统施工方法的千斤项在大负荷、长时间的工作后客易出现失灵或经常性损坏,需要经常雏修等问题;费用方面仅增加了液压泵和液压缸一次性投入,节省了大量的人工费、材料损耗和千斤顶购置与维修费,成本大大降低。本文通过对空心板梁电动液压落梁的工艺原理的介绍,证明了其具有较强的安全性、实用性、经济性,能显著节省工程造价和缩短工期,具有明显的经济效益和社会效益,因此获得了国家实用新型专利。     

Seismic performance of small earth dams with sloping core zones and geosynthetic clay liners using full-scale shaking table tests

In Japan, a large number of old small earth dams are in critical need of repair due to leakage and poor earthquake resistance. In addition to cohesive soils, geosynthetic clay liners (GCLs) are used as impervious materials to repair such dams. This paper discusses the seismic performance of small earth dams, with reservoirs on their upstream side, repaired with a sloping core zone and a GCL on the basis of the results of full-scale shaking table tests performed at the E-Defense facility. The main focus is on the differences in mechanical behavior between the upstream and downstream sides of the dam. The results elucidate that the effective stress of the upstream embankment materials increased because of the undrained shear behavior of the compacted soils, although the deformation on the upstream side was larger than that on the downstream side. A large phase difference in the measured accelerations between the upstream slope and the downstream slope was also observed. Therefore, it is concluded that significant differences occurred in the dynamic behavior of the upstream side and the downstream side.     

Development of geomembrane strains in waste containment facility liners with waste settlement

The development of tensile strains in geomembrane liners due to loading and waste settlement in waste containment facilities is examined using a numerical model. Two different constitutive models are used to simulate the waste: (a) a modified Cam-Clay model and (b) a Mohr-Coulomb model. The numerical analyses indicate the role of the slope inclination on the maximum geomembrane liner strains for both short-term loading (immediately post closure) and long-term waste settlement. A geosynthetic reinforcement layer over the geomembrane liner is shown to reduce the maximum geomembrane liner strains, but the strain level of the geosynthetic reinforcement itself may become an engineering concern on steeper slopes (i.e., greater than 3H:1V) for cases and conditions examined in this paper. The paper considers some factors (e.g., slope inclination, use of a high stiffness geosynthetic over the geomembrane liner) and notes others (e.g., the designer selection of interface characteristics below and above the geomembrane, use of a slip layer above the geomembrane) that warrant consideration and further investigation to ensure good long-term performance of geomembrane liners in waste containment facilities.