论三峡永久船闸中隔墩北倾变形机制

三峡永久船闸中隔墩在开挖期间出现了北倾变形现象。针对这一问题,从岩石力学基本思想的角度将其定位成一个结构面控制的局部问题。据此对现场地质条件、监测资料、开挖和加固与变形之间可能的关系进行了综合分析,论证了北倾变形的局部性和结构面控制特点,认为在闸室开挖初期阶段,两侧闸室的不均匀开挖是引起北倾变形的主要因素。在开挖中期,不均匀开挖起作用的同时,普遍存在的北倾结构面开始发挥重要作用;后期在对北倾结构面控制的中隔墩北侧潜在不稳定块体进行加固的同时,也把一部分荷载转嫁给南侧岩体,成为导致北倾变形的主要因素。针对变形的非连续特点,建立了三峡船闸基于非连续力学的三维离散远模型,论证了这一机理的可能性。

STUDY ON NORTHWARD DEFORMATION MECHANISM OF CENTRAL PIER OF PERMANENT SHIPLOCK OF THREE GORGES PROJECT

Northward deformation is monitored during the excavation period with various devices installed on the surface and inside the rock mass of the central pier between the double chambers of the permanent shiplock of the Three Gorges Project in China.In terms of the fundamental understanding of rock deformation for such a slope in hard rock,the northward deformation is believed to be linked to local factors such as presence of north-dipping geological structures in the pier,excavation and support sequences during the construction period.In details,the advanced proceeding in the north chamber in the early excavation stage did result in the northward deformation in general,but at a small magnitude with a few millimeters,thus it was not the major factor causing the occurrence of the northward deformation.With the proceeding of excavation to greater depths in the middle stage,dominant north-dipping geological structures started to play an important role in the northward deformation.In the later stage,the reinforcement on the potentially instable rock blocks controlled by the northward structures transfers partial loads to the southern rock mass simultaneity,which turns to be the main factor that induces the northward deformation.Based on the discontinuous mechanics,a three-dimensional distinct element code(3DEC) model was accordingly established and numerically validated the northward deformation.