国家大剧院深基坑地下水控制设计及施工技术

国家大剧院基坑地下水控制是大剧院工程的三大难题之一,也是专家们讨论的焦点。经过水文地质试验和充分论证,确定了地下水控制方案和施工方法,即采用反循环成井工艺施工引渗井,将上层滞水和潜水引渗到第一层承压含水层中消纳,保证第一步基坑开挖至-15 7m;在-15 7m位置采用连续墙阻隔第一层承压水,并使用旋挖钻机在槽内施工降水井,疏干槽内承压含水层并进行越流补给控制,保证基坑开挖至-26m;在歌剧院台仓局部加深部份(-32 5m),采用封闭布设减压井,解决基坑开挖和台仓地下结构施工时基坑突涌的问题;最后采用特殊的封井技术,将井管内高于槽底约10m的承压水头封堵在槽底以下0 5m,安全截断井管,保证了基础施工。

Design and construction techniques of controlling groundwater in the deep foundation pit of the National Grand Theatre

Controlling groundwater is one of the three most difficult problems in the construction of the National Grand Theatre. It is also the focus that experts discuss. By conducting hydrogeologic tests and thorough discussions, the design project and construction method of controlling groundwater for the foundation pit were determined. Firstly, groundwater in the perched aquifer was led to the first confined aquifer by self absorbing wells, in order to guarantee the excavation of the foundation pit to a depth of 15.7m. Secondly, at the depth of 15.7 m, a continuous ground wall was adopted to separate the first confined aquifer. Dewatering wells were used to drained the groundwater in the confined aquifers and control the leakage in order to guarantee the excavation of the foundation pit to a depth of 26.0 m. At the deepest part (-32.5m) of the opera house,using the decompression well lowered 10 meters water head of the second-floor confined water to avoid destroying the construction of the foundation pit. Finally, sealed the decompression well by special technique and safely cut off the well tube and guaranteed the safe construction of the foundation pit. In the deepest part of the pit where the storehouse of the stage is locate, special well-filling techniques are finally employed to protect the potentiometric head of the confined aquifer, which is 10 m higher than the bottom of the pit, from rising to a level of 0.5m lower than the bottom of the pit. As a result, the construction of the foundation were safely carried out.