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含冰率影响下冻结道砟集料的三点弯曲试验研究
Experimental study on three-point bending test of frozen ballast aggregate under different ice contents
投稿时间:2022-04-01  修订日期:2022-05-30
DOI:
中文关键词:  寒区铁路  冻结道砟  三点弯曲  含冰率  断裂能
英文关键词:cold region railway  ice-bonded ballast  three-point bending  ice content  fracture energy
基金项目:国家自然科学基金(面上项目)(11572067, 11872136)
作者单位邮编
黎旭 大连理工大学 116081
严颖 大连交通大学 116028
薛一桢 大连理工大学 116081
季顺迎 大连理工大学 116024
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中文摘要:
      寒区有砟轨道中碎石道床在低温冰冻条件的力学性能与常温明显不同,其中冻结强度是冻结道砟颗粒影响道床动力学特性的一个重要参数。为进一步探究级配碎石在冻结条件下弯曲力学性能,设计并制备了不同含冰率的冻结碎石集料试样并开展了室内低温三点弯曲试验。研究了含冰率对冻结试样加载力曲线及力学性能的影响,分析了冻结试样的断裂行为及断裂耗能情况。试验结果表明,试样的弯曲断裂失效过程可以分为脆性断裂和二次断裂两部分,加载力-挠度全曲线在脆性断裂时出现明显加载力跌落现象,而在二次断裂过程中曲线下降趋势平缓。含冰率的提高显著增大了试样的弯曲强度及弯曲模量,两者可近似线性表示。高冰率试样在弯曲破碎过程中,脆性断裂时在试样中部下方可观察到明显的受拉裂纹,并沿着道砟接触面向上不断扩展。含冰率较低时,试样脆性断裂耗能略高于二次断裂耗能,其耗能占总消耗能量的70%以上,试样以脆性断裂为主;随着含冰率增大,试样脆性断裂能占比急速下降,二次断裂已占主体且不容忽视。
英文摘要:
      Compared with normal temperature environment, the mechanical properties of railway ballast bed in cold region are obviously different under freezing condition. The freezing strength is an important parameter of ice-bonded ballast particles affecting the dynamic characteristic of ballasted railway track. To further explore the bending mechanical properties of grading railway ballast under freezing condition, ice-bonded ballast aggregate specimen with different ice content were prepared and indoor three-point bending test was carried out at low-temperature environment. The effect ice content on loading force curve and mechanical properties were studies. Meanwhile, fracture behaviour and the dissipated fracture energy of specimen was analyzed. The experimental results show that the failure process of bending fracture can be divided into brittle fracture and secondary fracture. The loading-deflection curves appear obvious loading force drop when brittle fracture happens, after that the curve present a gentle downward trend in second fracture process. With the increasing ice content, the bending strength and bending elastic modulus increase significantly, which can be expressed linearly approximately. In the process of bending fracture, an obvious tensile crack can be observed at the bottom of specimen with high ice content and expand upward along the contact face between ballast particles. When the ice content is low, the energy consumption of brittle fracture is slightly higher than that of secondary fracture, accounting for more than 70% of the total energy consumption. The specimen is manly brittle fracture. With the increasing the ice content, the proportion of brittle fracture energy decreases rapidly, and the secondary fracture is the main part of the specimen failure and cannot be ignored.
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