Theoretical Calculation of Crack Performance in Continuous Track Slab in Severe Cold Area
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摘要: 为了研究严寒地区连续式道床板的裂缝性能及其影响因素，基于严寒地区连续式道床板的实际工作状态，修正了前人关于连续式道床板裂缝计算的假设条件和力学模型，并通过理论推算和试验验证提出了不同工况的连续式道床板裂缝性能计算方法，总结了连续式道床板的开裂规律及其裂缝性能随温度变化的发展趋势. 研究结果表明：连续式道床板的裂缝性能与温降幅值和相邻裂缝间距密切相关，连续式道床板在温降5 ℃左右将产生集中批量式的首次开裂现象，道床板的固定区长度随着温降幅值的增大将随即降低至0，道床板的二次开裂则以单一零星的方式呈现，且相邻裂缝间距越小，其间道床板二次开裂对应的温降幅值越大，试验表明相邻裂缝间距小于3.25 m时，其间道床板在温降幅值小于37 ℃的地区将不会产生二次开裂现象；单一裂缝的产生仅对其左右滑动区范围内轨道结构力学性能有影响，若新老裂缝的滑动区部分相重叠，则新裂缝的产生将引起相邻既有裂缝钢筋应力和裂缝宽度幅值的突降.Abstract: In order to study the crack performance and its influencing factors in the continuous track slab in severe cold area, previous assumptions and mechanical models for the calculation of cracks in continuous track slab were modified according to their actual working states in severe cold area. Based on theoretical derivation and experimental verification, a methodology for calculating the crack performance in continuous track slab in different working conditions was proposed; the cracking law of the continuous track slab and the development trend of cracks with temperature drop were summarized. Results show that the crack performance in continuous track slab is closely related to the temperature drop amplitude and the spacing between adjacent cracks. The continuous track slab undergoes a primary cracking phase in a concentrated manner at a temperature drop of about 5 ℃. As the temperature drops further, the fixed zone length of the track slab will decrease to 0, and a secondary cracking phase occurs to the track slab in a single and sporadic manner; what’s more, the smaller the spacing between adjacent cracks is, the larger the temperature drop magnitude to initiate the secondary cracking of the track slab is. Tests show that when the spacing between adjacent cracks is smaller than 3.25 m, the track slab will not cause the secondary cracking at a temperature drop less than 37 ℃. The generation of a single crack only affects the mechanical properties of the track structure in the range of its left and right sliding zones, and if the sliding areas of the new and old cracks partially overlap, the new crack will cause a sudden decrease in the reinforcement stress and crack width amplitude of the adjacent existing cracks.
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Key words:
- severe cold area /
- continuous track slab /
- crack width /
- reinforcement stress /
- theoretical derivation
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图 3 裂缝间钢筋混凝土应力分布
Figure 3. Stress distribution in reinforcement and concrete between penetrating cracks
图 4 裂缝间钢筋混凝土应力分布
Figure 4. Stress distribution in reinforcement and concrete between penetrating cracks
图 5 温降增加引起的钢筋混凝土应力分布改变
Figure 5. Change in stress distribution in reinforcement and concrete caused by further drop of temperature
图 6 裂缝间钢筋混凝土应力分布（工况3）
Figure 6. Stress distribution in reinforcement and concrete between penetrating cracks (working condition 3)
图 9 道床板开裂处裂缝宽度和钢筋应力变化曲线
Figure 9. Variations of crack width and steel bar stress at crack position of track slab
表 1 温降过程中的轨道结构性能
Table 1. Track structure performance during temperature drop
结构性能项目 状态 1 状态 2 状态 3 状态 4 状态 5 支承层应力/MPa 0.56 0.58 0.66 0.81 0.91 锚固区长度/m 0.14 0.16 0.20 0.39 0.44 钢筋应力/MPa 90.35 97.56 125.48 244.68 277.56 裂缝宽度/mm 0.06 0.07 0.12 0.47 0.62 
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