Considering the delay effect of initial lining and revising the Winkler elastic foundation model,an analytical approach based on Pasternak elastic foundation beam theory for pipe roof reinforcement was put forward. Wi...Considering the delay effect of initial lining and revising the Winkler elastic foundation model,an analytical approach based on Pasternak elastic foundation beam theory for pipe roof reinforcement was put forward. With the example of a certain tunnel excavation,the comparison of the values of longitudinal strain of reinforcing pipe between field monitoring and analytical approach was made. The results indicate that Pasternak model,which considers a more realistic hypothesis in the elastic soil than Winkler model,gives more accurate calculation and agrees better with the result of field monitoring. The difference of calculation results between these two models is about 7%,and Pasternak model is proved to be a better way to study the reinforcement mechanism and improve design practice. The calculation results also reveal that the reinforcing pipes act as levers,which increases longitudinal load transfer to an unexcavated area,and consequently decreases deformation and increases face stability.展开更多
为提高相变屋面的性能,本文提出了一种冷却塔-内嵌管式相变屋面复合降温系统。基于焓法,建立了系统的数值计算传热模型,数值研究了该系统在福州地区的热性能及节能潜力,探讨了相变材料相变温度、相变材料导热系数以及内嵌管间距的影响,...为提高相变屋面的性能,本文提出了一种冷却塔-内嵌管式相变屋面复合降温系统。基于焓法,建立了系统的数值计算传热模型,数值研究了该系统在福州地区的热性能及节能潜力,探讨了相变材料相变温度、相变材料导热系数以及内嵌管间距的影响,并与传统的无内嵌管相变屋面进行了对比分析。研究发现,相变温度越高,复合降温系统的相变材料越容易完成凝固,但潜热利用率随相变温度的升高呈现先增加后降低的趋势。当相变温度由35℃升高到41℃时,屋面的累计冷负荷由383 k J/m^(2)增大到400 k J/m^(2),增加了4.4%。相变材料导热系数越高、内嵌管间距越小,复合降温系统相比于传统无内嵌管相变屋面的潜热利用优势越显著。当导热系数由0.2 W/(m·K)增加到0.8 W/(m·K)时,复合降温系统的潜热利用率和屋面累计冷负荷分别增加了36.3%和5.1%,而无内嵌管相变屋面的潜热利用率和屋面累计冷负荷分别升高了33.1%和6.3%。当内嵌管间距由500 mm减少到100 mm时,复合降温系统比传统无内嵌管相变屋面的潜热利用提高率由2.7%增大到16.3%,累计冷负荷降低率由3.8%升高到10.9%。研究结果可促进建筑节能和双碳目标的实现。展开更多
为研究“管幕冻结法”这一新型工法中“钢管-冻土”复合结构接触面剪切强度的影响因素及规律,基于港珠澳大桥拱北隧道工程,通过变角剪切试验方法设计不同剪切角度的试验,对温度和粗糙度2个维度进行探究,试验结果拟合出-5、-10、-15、-20...为研究“管幕冻结法”这一新型工法中“钢管-冻土”复合结构接触面剪切强度的影响因素及规律,基于港珠澳大桥拱北隧道工程,通过变角剪切试验方法设计不同剪切角度的试验,对温度和粗糙度2个维度进行探究,试验结果拟合出-5、-10、-15、-20、-25℃5种温度条件以及R=0.0、0.3、0.5 mm 3种粗糙度条件下的剪切面剪切强度包络线。试验结果表明:温度对钢管-冻土接触面内摩擦角影响不大;对接触面黏聚力,在-15℃之前,黏聚力近似呈线性增长,在-15℃达到峰值,在-20℃达到波谷,继而随温度的降低而增加。钢管-冻土接触面粗糙度的增加对结构面剪切强度的提高具有正向促进作用,但粗糙度过大会对接触面处的冻土体结构(如冰颗粒和土颗粒间隙等)造成一定的内部损伤,导致剪切强度下降。试验给出最优剪切强度下的温度及粗糙度取值区间。展开更多
基金Project(IRT0518) supported by the Program of Innovative Research Team of Ministry of Education of China
文摘Considering the delay effect of initial lining and revising the Winkler elastic foundation model,an analytical approach based on Pasternak elastic foundation beam theory for pipe roof reinforcement was put forward. With the example of a certain tunnel excavation,the comparison of the values of longitudinal strain of reinforcing pipe between field monitoring and analytical approach was made. The results indicate that Pasternak model,which considers a more realistic hypothesis in the elastic soil than Winkler model,gives more accurate calculation and agrees better with the result of field monitoring. The difference of calculation results between these two models is about 7%,and Pasternak model is proved to be a better way to study the reinforcement mechanism and improve design practice. The calculation results also reveal that the reinforcing pipes act as levers,which increases longitudinal load transfer to an unexcavated area,and consequently decreases deformation and increases face stability.
文摘为提高相变屋面的性能,本文提出了一种冷却塔-内嵌管式相变屋面复合降温系统。基于焓法,建立了系统的数值计算传热模型,数值研究了该系统在福州地区的热性能及节能潜力,探讨了相变材料相变温度、相变材料导热系数以及内嵌管间距的影响,并与传统的无内嵌管相变屋面进行了对比分析。研究发现,相变温度越高,复合降温系统的相变材料越容易完成凝固,但潜热利用率随相变温度的升高呈现先增加后降低的趋势。当相变温度由35℃升高到41℃时,屋面的累计冷负荷由383 k J/m^(2)增大到400 k J/m^(2),增加了4.4%。相变材料导热系数越高、内嵌管间距越小,复合降温系统相比于传统无内嵌管相变屋面的潜热利用优势越显著。当导热系数由0.2 W/(m·K)增加到0.8 W/(m·K)时,复合降温系统的潜热利用率和屋面累计冷负荷分别增加了36.3%和5.1%,而无内嵌管相变屋面的潜热利用率和屋面累计冷负荷分别升高了33.1%和6.3%。当内嵌管间距由500 mm减少到100 mm时,复合降温系统比传统无内嵌管相变屋面的潜热利用提高率由2.7%增大到16.3%,累计冷负荷降低率由3.8%升高到10.9%。研究结果可促进建筑节能和双碳目标的实现。
文摘为研究“管幕冻结法”这一新型工法中“钢管-冻土”复合结构接触面剪切强度的影响因素及规律,基于港珠澳大桥拱北隧道工程,通过变角剪切试验方法设计不同剪切角度的试验,对温度和粗糙度2个维度进行探究,试验结果拟合出-5、-10、-15、-20、-25℃5种温度条件以及R=0.0、0.3、0.5 mm 3种粗糙度条件下的剪切面剪切强度包络线。试验结果表明:温度对钢管-冻土接触面内摩擦角影响不大;对接触面黏聚力,在-15℃之前,黏聚力近似呈线性增长,在-15℃达到峰值,在-20℃达到波谷,继而随温度的降低而增加。钢管-冻土接触面粗糙度的增加对结构面剪切强度的提高具有正向促进作用,但粗糙度过大会对接触面处的冻土体结构(如冰颗粒和土颗粒间隙等)造成一定的内部损伤,导致剪切强度下降。试验给出最优剪切强度下的温度及粗糙度取值区间。
