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为提高我国公路及城市道路的透水性能及吸音功能,特介绍德国透水沥青路面的级配、路肩设计、施工要点及有关试验。 相似文献
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拱坝坝肩稳定性的地质力学模拟研究 总被引:8,自引:1,他引:8
李天斌 《岩石力学与工程学报》2004,23(10):1670-1676
为了论证和评价澜沧江小湾水电站拱坝坝肩岩体的稳定性,特别是软弱面(带)对坝肩稳定性的影响,采用相似材料三维嵌合块体地质力学模型试验,对坝肩岩体在开挖、工程荷载和超载条件下的变形破坏特征以及破坏机制进行研究,并评价坝肩岩体的稳定安全度和超载能力。 相似文献
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某机场道肩混凝土损伤原因分析 总被引:1,自引:0,他引:1
某刚建成1年左右的机场道肩混凝土表面出现了开裂和剥落,为分析道肩混凝土损伤的原因,同时进行了现场和试验室的研究工作.根据现场取回的混凝土芯样的外观检查、岩相分析、孔结构分析、抗渗性试验结果,发现道肩混凝土内部粘结不良,结构疏松,密实性较差.对混凝土芯样和按照道肩混凝土配合比,采用工程所用原材料在试验室中成型的混凝土试件进行抗冻性分析,结果发现,混凝土芯样和试验室试件抗冻性均表观不良.故推断此道肩混凝土由于内部粘结疏松、密实性和抗冻性较差,在北方严酷环境作用下,混凝土发生冻融破坏而产生了膨胀开裂和剥落. 相似文献
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焊具是搅拌摩擦焊的核心,对焊接质量起至关重要的作用. 利用不旋转轴肩焊接系统对6061-T6铝和AZ31B镁合金进行连接,重点分析传统和不旋转轴肩焊接系统下接头成形和力学性能等. 结果表明,与传统工艺相比,采用不旋转轴肩工艺的接头表面成形更加光滑,焊核区以典型铝镁混合的叠层结构为主,且铝镁冶金结合界面呈弯曲状,有效地增强了铝镁异种材料的机械咬合效果;焊缝区金属间化合物层明显减小,其主要是由不旋转轴肩增强焊核区材料的搅拌效果并起到“热沉”的作用所致. 采用不旋转轴肩的接头最大抗拉强度为137 MPa,较传统工艺提高了28%. 相似文献
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《Ergonomics》2012,55(5):637-648
The objective of this prospective cohort study was to evaluate if peak or cumulative musculoskeletal discomfort may predict future low-back, neck or shoulder pain among symptom-free workers. At baseline, discomfort per body region was rated on a 10-point scale six times during a working day. Questionnaires on pain were sent out three times during follow-up. Peak discomfort was defined as a discomfort level of 2 at least once during a day; cumulative discomfort was defined as the sum of discomfort during the day. Reference workers reported a rating of zero at each measurement. Peak discomfort was a predictor of low-back pain (relative risk (RR) 1.79), neck pain (RR 2.56), right or left shoulder pain (RR 1.91 and 1.90). Cumulative discomfort predicted neck pain (RR 2.35), right or left shoulder pain (RR 2.45 and 1.64). These results suggest that both peak and cumulative discomfort could predict future musculoskeletal pain. 相似文献
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《Ergonomics》2012,55(12):1657-1670
AbstractWork-related shoulder joint disorders contribute considerably to absenteeism in the workplace. To identify the tasks that are stressful to the shoulder joint, a strain index was formulated based on the concept of concavity compression—a shoulder stabilizing mechanism. The magnitude and direction of the shoulder joint reaction forces were used in formulating the strain index. A two phase experiment was conducted. In Phase 1, participants performed 30 different manual handling tasks. The tasks were categorized into low, medium and high strain tasks based on their strain index values. In Phase 2, out of the 30 tasks, repetitive exertions of three tasks (low, medium and high strain index values) were simulated using three external loads (0.91, 1.81 and 2.72?kg). The muscle activity data recorded from eight shoulder muscles showed that tasks with higher strain index values induced significantly greater activation and muscle fatigue than tasks with lower strain index values.Practitioner Summary: The strain index developed in this study is a conclusive estimation of the concavity compression required for shoulder joint stabilization. It can be used to identify the activities that may contribute to the risks of shoulder disorders. Abbreviation BLS Bureau of the Labor Statistics 相似文献
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《Ergonomics》2012,55(10):1226-1239
This paper combines epidemiological data on musculoskeletal morbidity in 40 female and 15 male occupational groups (questionnaire data 3720 females, 1241 males, physical examination data 1762 females, 915 males) in order to calculate risk for neck and upper limb disorders in repetitive/constrained vs. varied/mobile work and further to compare prevalence among office, industrial and non-office/non-industrial settings, as well as among jobs within these. Further, the paper aims to compare the risk of musculoskeletal disorders from repetitive/constrained work between females and males. Prevalence ratios (PR) for repetitive/constrained vs. varied/mobile work were in neck/shoulders: 12-month complaints females 1.2, males 1.1, diagnoses at the physical examination 2.3 and 2.3. In elbows/hands PRs for complaints were 1.7 and 1.6, for diagnoses 3.0 and 3.4. Tension neck syndrome, cervicalgia, shoulder tendonitis, acromioclavicular syndrome, medial epicondylitis and carpal tunnel syndrome showed PRs > 2. In neck/shoulders PRs were similar across office, industrial and non-office/non-industrial settings, in elbows/hands, especially among males, somewhat higher in industrial work. There was a heterogeneity within the different settings (estimated by bootstrapping), indicating higher PRs for some groups. As in most studies, musculoskeletal disorders were more prevalent among females than among males. Interestingly, though, the PRs for repetitive/constrained work vs. varied/mobile were for most measures approximately the same for both genders. In conclusion, repetitive/constrained work showed elevated risks when compared to varied/mobile work in all settings. Females and males showed similar risk elevations. This article enables comparison of risk of musculoskeletal disorders among many different occupations in industrial, office and other settings, when using standardised case definitions. It confirms that repetitive/constrained work is harmful not only in industrial but also in office and non-office/non-industrial settings. The reported data can be used for comparison with future studies. 相似文献