论文部分内容阅读
通过室内试验与现场水泥稳定碎石基层裂缝监测试验,采用分布式BOTDA光纤监测技术,研究了传感光纤的应变与裂缝宽度的关系、半刚性基层早期裂缝扩展规律以及裂缝发展速率。研究结果表明:当裂缝宽度分别为3、6、9mm时,聚氨酯封装的传感光纤应变分别为5.9×10~(-3)、7.7×10~(-3)、10.3×10~(-3),金属基封装的传感光纤应变分别为1.5×10~(-3)、1.6×10~(-3)、2.1×10~(-3),光纤应变随着裂缝宽度的增加而增大;当裂缝宽度为9mm时,聚氨酯与金属基封装的光纤应变分别为内定点铝合金铠装光纤平均应变的33.2、6.8倍,因此,聚氨酯与金属基封装的传感光纤裂缝监测效果较好;在现场基层施工完成后第13d,80m长的路段出现了3处微裂缝,此期间最大温差为2.1℃,说明基层裂缝的产生和发展主要在第1个月,且主要是干缩裂缝,干缩应力是裂缝产生及裂缝间距的主要影响因素;在施工完成后第20、77、139d,基层底面温度分别为10.3℃、2.5℃、9.4℃,基层底面K24+656位置裂缝处光纤应变分别为4.2×10-4、9.5×10-4、4.3×10-4,在139d之内,没有新的裂缝出现,说明温缩应力对早期裂缝间距的影响较小,主要影响裂缝宽度,温缩裂缝主要出现在干缩阶段干缩应力较大的位置;当上、下基层连铺时,基层上表面与底面的裂缝位置一致,表明水泥稳定碎石基层横向裂缝为贯穿裂缝;基层上表面裂缝发展速率分别是基层中间和底面的3.8、2.8倍,基层上表面的裂缝发展速率最大。
Through the monitoring test of the cracks in the basement of cement stabilized gravel in laboratory and on the spot, the relationship between the strain and the width of the crack in the sensing fiber, the law of the early crack growth in the semi-rigid base and the crack growth rate were studied by the distributed BOTDA fiber monitoring technology. The results show that when the crack widths are 3, 6, and 9 mm respectively, the strain of the sensing fiber in the polyurethane package is 5.9 × 10 -3, 7.7 × 10 -3, 10.3 × 10 -3 ), And the sensing optical fiber strain of the metal-based package is 1.5 × 10 -3, 1.6 × 10 -3 and 2.1 × 10 -3, respectively. The strain of the optical fiber increases with the increase of the crack width ; When the crack width is 9mm, the optical fiber strain of polyurethane and metal-based package is 33.2,6.8 times of the average strain of the internal fixed aluminum alloy armored fiber, therefore, the detection effect of the sensing fiber crack in polyurethane and metal-based package is better; Three cracks occurred on the 13th and 80m long sections of the site after the construction of the site was completed. The maximum temperature difference during this period was 2.1 ° C, indicating that the primary crack generation and development were mainly in the first month and were mainly shrinkage cracks and dry At the 20th, 77th, and 139th days after the completion of the construction, the base temperature of the base layer was 10.3 ℃, 2.5 ℃ and 9.4 ℃, respectively. The optical fiber strains at the cracks at the base K24 + 656 were 4.2 × 10-4,9.5 × 10-4,4.3 × 10-4, within 139d, no new cracks appear, indicating that the thermal stress on the early crack spacing Which mainly affects the crack width and temperature shrinkage cracks mainly in the place where the shrinkage stress in dry shrinkage phase is larger. When the upper and lower grassroots are connected, the crack location on the upper surface and the bottom surface of the grassroots is consistent, indicating that the cement is stable and broken The horizontal cracks in the base course are through the cracks. The development rates of the surface cracks in the base course are 3.8 and 2.8 times of those in the middle and bottom of the grass roots, respectively. The rate of crack growth in the upper surface of the grass roots is the highest.