南京长江漫滩区某超大深基坑支护与监测结果分析

Analysis of support and monitoring results of a super large deep foundation pit in the floodplain area of the Yangtze River in Nanjing

以南京长江漫滩区某超大深基坑工程为背景,根据地质和周边环境条件、基坑支护方案,对基坑开挖过程中支护结构和周边环境进行监测和分析。结果表明:超大深基坑支护结构具有明显的空间效应,开挖深度越大,空间效应越明显;随着施工的进行,各层锚索轴力逐渐增大,其中第1层锚索轴力普遍大于第2、3层锚索轴力,第1层锚索轴力平均值为206.7 kN,该值为设计值的71.3%;由于第2、3层锚索轴力没有得到充分发挥,且施工过程中出现漏水、漏砂,需采取坑外应急降水措施,虽然能保证锚索的正常施工,但对基坑周边道路造成严重的影响,降水期间坑外道路最大沉降达209 mm,占总沉降的86.2%。

Based on a super large deep foundation pit in the floodplain area of the Yangtze River in Nanjing,according to the geological and surrounding environmental conditions,and the foundation pit retaining scheme,the retaining structure and surrounding environment in the process of foundation pit excavation were monitored and analyzed.Results showed that the retaining structure of the super large deep foundation pit had obvious spatial effect,and the deeper the excavation depth,the more obvious the spatial effect was.With the progress of the construction,the axial force of each layer of the anchor cable increased gradually.The axial force of the first layer was generally greater than those of the second and third layers,and its average value was 206.7 kN,which was 71.3%of the design value.Because the axial forces of the second and third layer anchor cables were not fully exerted,water and sand leakage occurred during the construction process,the emergency dewatering outside foundation pit measures were taken.Although the normal construction of the anchor cable was ensured,it had a serious impact on the roads around the foundation pit.During the dewatering period,the maximum settlement of the road outside the pit was 209 mm,accounting for 86.2%of the total settlement.