基坑施工对邻近振冲灌注桩基础房屋的影响分析

Analysis of the influence of foundation pit construction on the adjacent buildings with vibrating cast-in-situ piles

从基坑施工降水、土方开挖和桩间支护、锚索施工等3个方面评价分析了某项目基坑施工对邻近振冲灌注桩基础房屋造成的影响,结合场地普遍分布的松散砂土对原房屋振冲灌注桩的施工可能造成的桩身缩颈及可能存在无法直接核验桩端持力层性状的隐患分析,同时参考基坑施工期间原房屋的沉降观测等资料进行了综合分析。结果表明:原房屋振冲灌注桩存在缩颈和桩尖未进入中密卵石层的质量缺陷和隐患,基坑施工加剧了邻近振冲灌注桩基础房屋的裂缝及变形的发展。并提出了基坑周边存在桩周土层为松散砂层的振冲灌注桩基础房屋的时候,基坑支护设计时邻近建筑物宜按水平位移敏感建筑物考虑,即建议了控制基坑施工引起的邻近建筑物水平位移不超6 mm。

This paper evaluated and analyzed the impact of a project’s foundation pit construction on the adjacent buildings with vibrating cast﹣in﹣situ piles from three aspects of foundation pit construction dewatering,earthwork excavation and pile support,and anchor cable construction. Combined with the analysis of the possible pile shaft shrinkage caused by the construction of vibro replacement piles in the original building due to the loose sandy soil widely distributed on the site and the possible hidden danger that the behavior of the bearing layer at the pile end cannot be directly verified,at the same time,referring to the settlement observation data of the original house during the foundation pit construction,the comprehensive analysis shows that the vibroflotation pipe sinking cast﹣in﹣situ pile of the original house has the quality defects and hidden dangers of necking and the pile tip not entering the medium dense pebble layer,the construction of foundation pit aggravates the development of cracks and deformation of buildings adjacent to vibro replacement pile foundation. It was also proposed that when there was a vibro replacement pile foundation house with loose sand layer around the pile,the adjacent buildings should be considered as horizontal displacement sensitive buildings in the design of foundation pit support,that was,it was suggested that the horizontal displacement of adjacent buildings caused by the construction of foundation pit should not exceed 6 mm.