非对称卸荷条件下逆作地下结构回弹变形特征

Rebound Deformation Characteristics of Reverse Underground Structure under Asymmetric Unloading Conditions

依托北京城市副中心站综合交通枢纽工程01标段超大深基坑,结合工程设计方案及场地的地质条件,对站房核心区部分建立三维有限元数值模型,研究了基坑在非对称卸荷开挖条件下,逆作“凹”字型底板的位移和应力分布规律,并根据开挖卸荷特征,提出有针对性的开挖方案和控制措施。结果表明:B1层底板在法向方向的位移以向上为主,回弹变形在南北方向上呈现类似“驼峰”的形态,在除去中空洞口的东西方向上呈现出一种反转的“对勾”形态;B1层底板在南北方向的水平位移是由两端指向基坑内部,位移为零的位置大致在底板的中部;应力较大的区域集中在柱子与底板相接的位置;对比分析得出按照整体由西向东推进,中间优先,两侧同步跟进的方式开挖,对B1层底板造成的影响最小。

Based on the ultra-large deep foundation pit of the No.01 section of the comprehensive transportation hub project of Beijing Sub-center Station,combined with the engineering design scheme and the geological conditions of the site,a three-dimensional finite element numerical model is established for the core area of the station(B24-B38 axis position).The displacement and stress distribution of the inverted’concave’type bottom plate under the condition of asymmetric unloading excavation are studied.According to the characteristics of excavation unloading,the targeted excavation scheme and control measures are put forward.The results show that the displacement of B1 floor in the normal direction is mainly upward,and the rebound deformation shows a similar“hump”shape in the north-south direction,and a reverse“hook”shape in the east-west direction after removing the hollow hole.The horizontal displacement of B1 floor in the north-south direction is from both ends to the inside of the foundation pit,and the position of zero displacement is roughly in the middle of the floor.The area with large stress is concentrated in the position where the column and the floor are connected.The comparative analysis shows that the excavation method of advancing from west to east as a whole,priority in the middle and synchronous follow-up on both sides has the least impact on the B1 floor.