双排型钢等厚水泥土墙在深大基坑中的应用分析

Application and analysis of double-row constant thickness steel cement-soil walls on a large-scale deep excavation

以中冶39大街项目为例,介绍双排型钢等厚度水泥土搅拌墙在武汉地区深大基坑中的应用。本项目基坑面积约52145m2,普遍挖深7.15~7.45m,周边环境复杂,软弱土层深厚,地下水量充沛,工期极其紧张。针对项目特点,基坑普遍采用双排型钢等厚度水泥土搅拌墙的围护形式。分别采用规范方法和有限元法预测双排桩围护与单排桩+支撑围护的侧向位移。计算结果表明,基坑工程完成时,双排桩围护的侧移-深度曲线呈“弯剪型”,单排桩+支撑围护的侧移-深度曲线呈“弯曲型”,两种围护形式的最大侧移均发生在桩顶处,双排桩围护的最大侧移明显小于单排桩+支撑,而在坑底附近两者侧移大致相当,两种围护形式的侧移均满足规范要求。现场监测数据与理论计算结果吻合,印证了预测方法的有效性。最终基坑工程在汛期前完工,总工期仅约六个月。

Based on the 39th Avenue project of China Metallurgical Group Corporation,application of double-row constant thickness steel cement-soil walls on a large-scale deep excavation in Wuhan area is introduced in this paper.The excavation was 7.15~7.45m in depth and 52145 m2 in area.Besides of the thick soft soil and the abundant underground water,the surroundings were complex while the construction period was extremely tight.In consideration of these characteristics,double-row constant thickness steel cement-soil walls were employed as retaining structures.Specification approach and finite element method was respectively utilized to predict the lateral displacements of double-row piles and single-row piles with struts.Calculation results indicated the form of the final lateral displacement-depth curve of double-row piles was“bending-shear”while the form of the curve of single-row piles with struts was“pure bending”.The maximum displacements of double-row piles were apparently smaller than those of single-row piles with struts,which occurred at the top of piles of each type.The displacements of both types met the specification requirements and were roughly equivalent at the bottom of excavation.The field monitoring data were consistent with the theoretical calculation results,which verified the validity of the prediction methods.The excavation was accomplished before the flood season.The total construction period was about six months.