深中通道沉管隧道基槽回淤及边坡稳定性研究

Back silting and slope stability of foundation trench in Shenzhen-Zhongshan immersed tunnel project

跨海沉管隧道因其回淤强度大、晾槽时间长等特点,大量累积的回淤物威胁到沉管隧道的安全性。以深中通道沉管隧道为背景,总结试挖槽试验中回淤时空变化规律,研究回淤对基槽边坡稳定性的影响,深入分析坡面回淤的局部稳定性影响因素,结果表明:①回淤平面分布差异明显,槽底、北坡、南坡的回淤量依次减小;回淤竖向分布不均,从上至下呈递减趋势;回淤全年分布不均,洪季时回淤量大,进入枯季后回淤量减小。②基槽边坡稳定性主要受坡面回淤控制,放坡清淤可明显改善坡面回淤的稳定性;回淤厚度、清淤坡率、基槽坡高、边坡坡率增大及回淤抗剪强度降低均不利于坡面回淤的稳定性,清淤坡率应考虑各影响因素和所处季节综合确定。

Due to the large intensity of back silting and long-term idleness of foundation trench,back silting will threaten the safety of immersed tunnel.Relying on Shenzhen-Zhongshan immersed tunnel project,the change rules of back silting with time and space in the trial trench tests are summarized.A numerical model is established to study the influences of back silting on the stability of foundation trench slope.The factors affecting the local stability of back silting are deeply analyzed.The results show that:(1)The horizontal distribution of back silting is obviously different,that is,the amount of back silting at the bottom,north slope and south slope decreases in turn.The vertical distribution of back silting is uneven,and the thickness of back silting from top to bottom decreases.The amount of back silting varies greatly through out the year,large in flood season but small in dry season.(2)The stability of foundation trench slope is mainly controlled by the back silting,and the stability of back silting can be significantly improved by desilting with slope.The safety factor of back silting decreases with the increase of thickness of back silting,desilting gradient,slope height,slope gradient or the decrease of shear strength of back silting.