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391.
基于断裂力学、损伤力学和路面破坏的原理,对水泥混凝土路面损伤断裂的产生、扩展直至破坏的全过程进行分析,并指出每个阶段混凝土路面裂缝形成的根本原因,为板开裂防治提供了一种新思路。 相似文献
392.
大体积混凝土表面易出现纵横裂缝,影响混凝土质量。分析大体积混凝土裂缝产生的原因,介绍防止裂缝发生的一些措施,包括选择合适的水泥、骨料,掺加粉煤灰,掺入外加剂和纤维材料,完善施工工艺,加强温度控制等措施。 相似文献
393.
LI Qing-fen FU Yu-dong and XU Xiao-xueSchool of Mechanical Electrical Engineering Harbin Engineering University Harbin China 《船舶与海洋工程学报》2005,(2)
1 INTRODUCTIONThe linear elastic fracture mechanics provides auseful means of determining a material’s toughness.However, deeply cracked standard laboratory speci-mens those have high level of constraint may not alwaysbe representative of those found in structural compo-nents. Structural components often exhibit compara-tively shallowand surface-breaking.We have previously shown that shallow crackshave greater COD andJ-integral values at initiationthan deeply cracked specimens in EPFM… 相似文献
394.
为解决阳城煤矿-650南翼轨道大巷断层破碎带支护中出现的围岩变形大和变形持续时间长等问题,采用室内实验、理论计算和支护实践相结合的方法,对-650南翼轨道大巷围岩地质进行测试研究,揭示巷道原有支护变形破坏机制,提出断层破碎带巷道承压环强化支护设计方法,并由此设计基于钢管混凝土支架的复合支护设计方案。实验及理论分析得出: 钢管混凝土支架支护反力为0.92 MPa,基于钢管混凝土支架的复合支护体总体承载力达到1.37 MPa,超过预估围岩压力。支护实践表明: 基于194 mm×8 mm浅底拱圆形钢管混凝土支架复合支护方案能够有效控制巷道变形,抑制底鼓,保证了-650南翼轨道大巷的长期稳定。 相似文献
395.
Zarir Hafiz Zulkipli Siti Atiqah Mohd Faudzi Abdul Rahmat Abdul Manap Noor Faradila Paiman 《国际交通安全学会研究报告》2018,42(3):121-127
This study aims to determine spinal injury patterns and identify crash factors commonly associated with serious spinal injury as a result of motorcycle crashes. Data was retrospectively collected from motorcyclists sustaining spinal injuries from road crashes treated at Kuala Lumpur Hospital, Malaysia, over the 5-year period from 2005 to 2009. Each patient's injuries were analyzed by reviewing his or her medical records for radiographic imaging and computed tomography scans.A total of 151 patients were included in this study, of which, males accounted for over 87%. The first lower lumbar (L1) was the most commonly injured vertebral level, followed by the adjacent thoracic vertebra (T12). Fracture to the vertebral body without dislocation was found to be the most frequently observed spinal injury pattern. Injury severities for a majority of patients (65%) were measured at Maximum Abbreviated Injury Scale (MAIS) of 2. Serious spinal injury was associated with thorax or upper-extremity injury.Prevalence of lumbar spinal injury in the study reflects a predominantly low-speed crash among the motorcyclist in the region. Motorcyclists are at greater odd to sustain severe spinal injury when directly striking an object compare to striking the ground during the crash event. 相似文献
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Field evidence has shown that large-scale and unstable discontinuous planes in the rock mass surrounding tunnels in rich water region are probably generated after excavation. The tunnel surrounding rock was divided into three zones, including elastic zone, plastic damage zone and shear fracture zone fof assessing the stability of the tunnel surrounding rock. By local hydrogeology, the stresses of surrounding rock of Jinshazhou circular tunnel was analyzed and the stress solutions on the elastic and plastic damage zones were obtained by applying the theories of fluid-solid coupling and elasto-plastic damage mechanics. The shear fracture zone generated by joints was studied and its range was determined by using Mohr-Coulomb strength criterion. Finally, the correctness of the theoretical results was validated by comparing the scopes of shear fracture zones calculated in this paper with those from literature. 相似文献
399.
An improved ductile fracture criterion for fine-blanking process 总被引:3,自引:0,他引:3
In order to accurately simulate the fine-blanking process, a suitable ductile fracture is significant.So an evaluation strategy based on experimental and corresponding simulation results of tensile, compression, torsion and fine-blanking test is designed to evaluate five typical ductile fracture criteria, which are widely-used in metal forming process.The stress triaxiality and ductile damage of each test specimen are analyzed.The results show that none of these five criteria is sufficient for all tests.Furthermore, an improved fracture criterion based on Rice and Tracey model, taking the influence of both volume change and shape change of voids into account, is proposed.The characterization of this model for fine-blanking process is easily done by the tensile test and the prediction result shows good. 相似文献
400.
文章针对福州魁岐2号特大断面小净距隧道工程特点,以Ⅴ级围岩为研究对象,利用离散单元法对节理岩体中断层存在时初始围岩应力分布特征以及断层与隧道不同相对位置情况下围岩变形特征进行了定性分析。结果表明,当节理岩体中有断层存在时,初始围岩应力不再呈水平层状分布,而是出现一定程度的应力集中现象;围岩变形在断层附近区域显著增大,而距断层较远处基本不受影响;对于小净距隧道,当中间岩柱中存在断层时更不利于隧道和中间岩柱的整体稳定。 相似文献