深厚杂填土场地地基处理实例分析

Case study of ground treatment for thick miscellaneous fill site

以北京市朝阳区某处于深厚杂填土场地的项目为例,介绍该项目地基处理方案及特点,并对处理效果进行了评价。杂填土中含有大量的建筑垃圾和生活垃圾,基底以下最大厚度超过22 m。勘察时重点加强杂填土层性状、回填年限、力学性质等参数评价,并通过填土沉降观测评价其固结状况和稳定性,作为地基处理设计的依据。采用柱锤冲扩桩+CFG桩长短桩结合的复合地基处理方案,根据杂填土性状、回填年限、承载力要求、附加应力大小等条件,考虑工程造价因素,采用柱锤冲扩桩不穿透杂填土层深厚区域的设计方案。柱锤冲扩桩填料采用现场再生碎石,处理效果优于常规填料,且可减少填料用量。地基处理与基坑支护方案协同设计,在基坑坡面增加注浆微型桩作为地基处理范围边界,可缩小地基处理外扩范围,节约造价。复合地基检测及建筑沉降观测结果均满足设计要求,说明该地基处理方案可行,可为类似场地地基处理方案提供参考。

The ground treatment scheme was presented, based on a project in Chaoyang district, Beijing, which sitting on thick miscellaneous fill, and its effectiveness was also investigated in this paper. The miscellaneous fill contains a lot of construction waste and household waste, and the maximum thickness of the foundation is more than 22 meters. The emphasis of investigation is to evaluate the properties of the miscellaneous fill such as the age of backfilling, mechanical parameters, etc. The paper evaluates the consolidation and stability of the miscellaneous fill by settlement monitoring,which is the basis for ground treatment design. The impact displacement column+CFG pile is used to form the composite foundation. According to the characteristics of miscellaneous fill, the age of backfilling, subsoil bearing capacity requirments, additional stress condition, and the cost of the project, the design scheme of impact displacement column without penetrating the deep area of miscellaneous fill layer are considered. The filling material of impact displacement columns are recycled crushed stones, which can provide better effect and reduce the total amount. Combined design of ground treatment and excavation, which using grouting micropiles at the slope of the excavation as the boundary of the ground treatment, can reduce the scope of ground treatment and save the cost. The results of detection and settlement monitoring meet the requirements, showing that the scheme is applicable, which can provide reference for similar projects.