管棚挠度及内力在超浅埋暗挖工程中的计算研究

Calculation and Research on deflection and internal force of pipe shed in ultra shallow buried and concealed excavation engineering

超浅埋暗挖管棚及小导管注浆是超前支护中的主要支护结构,其受力、变形复杂,缺少有效计算方法,为此结合某城市道路下地下商业街超浅埋暗挖工程,依据Winkler弹性地基梁理论,对超前支护中的管棚进行了结构受力变形分析,建立了管棚结构受力变形力学模型,进而推导出管棚挠度和内力计算方法。研究结果表明:计算得到的挠度曲线与实测数据曲线变化比较一致,挠度值均小于20 mm,最大偏差幅度39.5%。进一步通过推导得到的计算方法对超浅埋暗挖管棚弯矩进行求值,弯矩值先增大后减小并逐步趋于0,在钢管弯曲的允许范围之内。在距管棚与钢架连接端0.75 m处出现反弯点,弯矩值达到最大,模型1较模型2的弯矩小32.7%,故模型1的计算结果优于模型2,与实际监测结果更接近。

The super shallow buried and concealed excavation pipe shed and small conduit grouting are the main support structures in the advanced support,and their stress and deformation are complex and lack of effective calculation methods.Therefore,combined with the super shallow buried and concealed excavation project of an underground commercial street under an urban road,according to the Winkler elastic foundation beam theory,the structural stress and deformation of the pipe shed in the advanced support were analyzed,and the mechanical model of the stress and deformation of the pipe shed structure was established.Then the calculation method of deflection and internal force of pipe shed was deduced.The results show that the calculated deflection curve is consistent with the measured data curve,the deflection values are less than 20 mm,and the maximum deviation range is 39.5%.Further,the bending moment of the ultra shallow buried and concealed excavation pipe shed is evaluated through the calculation method derived.The bending moment first increases and then decreases,and gradually tends to zero.Within the allowable bending range of the steel pipe,there is a reverse bending point at 0.75 m away from the connecting end of the pipe shed and the steel frame,and the bending moment reaches to the maximum.The moment of model 1 is 32.7%smaller than that of model 2.Therefore,the calculation result of model 1 is better than model 2 and closer to the actual monitoring result.