滨海软土沉管隧道结构性能演化规律及成因分析

ANALYSIS ON EVOLUTION LAWS AND CAUSES OF STRUCTURE PERFORMANCES FOR COASTAL IMMERSED TUNNELS IN SOFT SOIL

鉴于我国沉管隧道运营期服役安全鉴定和进一步维修养护决策亟需相应技术支撑和参考依据,为研究沉管隧道结构长期性能演化的规律及其成因,对上海外环隧道长期沉降、接头水压及裂缝、渗水、露筋、覆土厚度等多项数据进行对比分析,揭示了沉管隧道病害的主要分布特征、结构性能的发展规律及各类常见病害的成因。结果表明:外环隧道存在显著的不均匀沉降,部分区段至今未达稳定;止水损伤的接头内存在水压,水压随温度季节性变化的现象反映了接头的伸缩;上海外环隧道结构性能存在"地基垫层、覆土荷载—不均匀沉降—结构受力变形—荷载裂缝开展—渗水、露筋锈蚀"的劣化链。

In view of the urgent need of dependably technical supports and guidance in safety appraisals and further maintenance decisions for immersed tunnels in operation in China,to explore the long-term evolution laws and causes of structural performances for immersed tunnels,an analysis comparison was conducted on investigated data from Waihuan Tunnel in Shanghai involving long-term subsidence,water pressure in gaskets between segment joints,cracks in segments,quantities of water seepage and bare rebars,and thickness of overlaying soil,the main distribution characteristics of damage,evolution laws of structural properties,and causes of common damage were revealed.The results showed that subsidence was significant uneven along Waihuan Tunnel in Shanghai,in which the subsidence in some sections was not steady yet.Water pressure was measured in gaskets between segment joints of being damaged in waterproof,the seasonal variations of water pressure by temperature reflected the expansion and contraction of segment joints.A main chain of the performance deterioration for Waihuan Tunnel in Shanghai was revealed,that was the poor foundation and heavier loads from overlaying soil caused the uneven subsidence and then led to a series of quality issues that were the deformation of the structure,the evolution of cracks,the water seepage,the exposure and corrosion of rebars in series.