港珠澳大桥岛隧工程沉管基槽开挖回淤强度研究

通过分析港珠澳大桥沉管隧道附近水沙条件及沉管开挖位置试挖槽回淤特征及影响因素,利用二维潮流及泥沙扩散数学模型模拟了沉管开挖前后水流变化及疏浚船舶施工溢流泥沙扩散淤积分布,综合考虑疏浚溢流因素及自然泥沙回淤因素,结合回淤公式对沉管基槽开挖回淤进行了分析研究和估算,结果显示挖槽后沉管基槽开挖位置流速减小40%～60%,流向更偏向垂直于挖槽基线;疏浚溢流泥沙扩散呈"窄条"型分布,泥沙扩散0.005 g/L浓度线最远范围不超过2 km,溢流泥沙主要沉淤至槽底内,两侧边坡也有所淤积,淤强低于挖槽底部。通过计算,基槽开挖后年淤积强度1.3～2.8 m/a。

Back-silting of trench excavation for the immersed tunnel in Hong Kong-Zhuhai-Macao bridge construction

This paper describes the flow & sediment conditions near the site of immersed tunnel of Hong Kong-Zhuhai-Macao bridge, and analyzes the back-silting characteristics and influential factors of the test excavated trench. Using a 2D flow and sediment transport model, this paper analyzes the change of flow due to the engineering implementation and the motion of dredging ship overflowed sediment. The model results show that the flow velocity decreases 40%~60%, the overflowed sediment of 0.005 g/L isolines spread away less than 2 km and distributes at a narrow strip. The overflowed sediments deposit mainly into the trench bottom, and a small part to the side slope. Under a comprehensive consideration of the dredging overflow sediment deposition and natural sediment deposition, and combining with the formula of back-silting, we estimate that the annual average strength of sediment back-silting is 1.3 ~2.8 m/a after the trench excavation .