深基坑开挖及降水诱发邻近建筑物变形破坏机理及影响因素

为分析深基坑开挖及降水诱发地表不均匀沉降而引发邻近建筑变形、破坏机理,以广州某深基坑开挖—降水—开挖为例,从理论角度分析了同时考虑开挖和降水前后土体自重应力变化、渗流动水压力引起的有效应力变化以及止水帷幕对土体沉降约束作用时坑外土体沉降机理;借助三维渗流有限元模型分析土层-地下水-承台-桩相互平衡协调问题,探究建筑开裂原因并分析了多种影响因素。结果表明：坑外建筑物变形主要由井点降水超采所致,开挖影响较小;建筑物距基坑越近桩基变形越大,间距大于降水深度时可显著减小建筑变形;桩基刚度越大,桩体位移越小但弯矩越大;止水帷幕越深,建筑物沉降越小,一定深度后防沉降效果显著降低;分次降水能有效减小建筑物沉降,且此方式成本较低,具有很好的现实意义。

Influencing Factors of Deformation and Failure of Adjacent Buildings Induced by Deep Foundation Pit Excavation and Precipitation

In order to analyze deformation and failure mechanism of adjacent buildings caused by uneven surface settlement induced by deep foundation pit excavation and precipitation, taking a deep foundation in Guangzhou as an example, we considered the change of soil gravity stress and effective stress caused by seepage hydrodynamic pressure, and the constraint effect of waterproof curtain on soil settlement. Through numerical simulation, we verified the theoretical and analyzed the influencing factors of building deformation caused by precipitation. The research shows that excessive precipitation caused mainly the deformation of buildings outside the pit and the excavation has little effect on it. The closer the building is to the foundation pit, the greater the pile foundation deformation is, and its deformation can be significantly reduced when the distance is greater than the precipitation depth. The greater the pile stiffness is, the smaller the pile displacement is, the greater the pile bending moment is. The deeper water tight screen is, the smaller the building settlement is, however the anti settlement effect is reduced significantly after a certain depth. The fractional precipitation can effectively reduce the settlement of buildings at low cost, which has great practical significance.