不均匀淤泥地层多室沉井挖土下沉方案研究
Study on Excavation Scheme of Multi Chamber Open Caisson in Uneven Silt Stratum

合理的挖土下沉方案能够有效控制沉井下沉姿态及结构应力，减小对周围环境的影响。以深圳市固戍水质净化厂沉井工程为背景，结合现场施工条件，设计12种不同挖土下沉方案，通过数值模拟的方法，得出了不均匀淤泥地层中多室沉井不同挖土下沉方案对沉井下沉姿态，结构应力及周围管道的影响规律。结果表明：不同挖土方案会导致沉井结构受力出现“简支效应”、“悬臂效应”和“扁担效应”；研究发现“简支效应”对沉井结构受力最为有利；对称挖土方案中先开挖中间区域土体对沉井下沉姿态控制效果最好，沉井结构应力也能得到较好控制；各挖土下沉方案对周围管道影响程度不同，挖土方案B3对管道影响最小。
Reasonable excavation scheme of open caisson can effectively control the subsidence posture and structural stress of open caisson, and reduce the impact on the surrounding environment. Based on the open caisson project of Shenzhen Gushu water purification plant and the construction conditions, 12 excavation and subsidence schemes are considered. The influence law of different excavation schemes on the subsidence posture and structural stress of open caisson, as well as surrounding pipeline were obtained based on the numerical simulations. The results show that these excavation schemes probably induce the “simple support effect”, “cantilever effect” and “carrying pole effect” in the multi chamber open caisson. However, the “simple support effect” is beneficial to the stress states of the open caisson. In the symmetrical excavation, excavation of the middle area firstly is the best scheme for the subsidence posture and the structural stress of open caisson; each excavation scheme has different influence on the surrounding pipeline. The impact of scheme B3 on the surrounding pipeline is minimal.