水泥土搅拌桩复合地基承载力折减系数a和b的试验研究

 《建筑地基处理技术规范》分别给出含有折减系数a的单桩承载力计算公式和含有系数β的复合地基承载力计算公式，为了得到适用于本地区的a和b的取值范围，为今后规范的修订提供参考数据，对珠三角地区有代表性的淤泥质土地基采用水泥土搅拌桩进行加固处理，进行单桩、天然地基以及设置4种厚度褥垫层的水泥土搅拌桩四桩复合地基的静载荷试验。通过对试验数据的分析和反算，对规范给出的承载力计算公式中折减系数a和b的取值范围进行修正，给出详细的取值建议。同时分析褥垫层厚度对复合地基承载力的影响，并建议褥垫层厚度取200～400 mm，为珠三角地区水泥土搅拌桩复合地基的设计提供参考。

EXPERIMENTAL STUDY OF REDUCTION COEFFICIENTS α AND β OF CEMENT-SOIL PILES COMPOSITE FOUNDATION

The calculational formula for bearing capacity of single pile with coefficient α and bearing capacity of composite foundation with coefficient β are shown in Technical Code for Construction Foundation Treatment. In order to get the value scopes of α and β which are suitable for this region and provide revision data for future code revision,the reinforcement treatment of representative silt soil foundation is carried out by means of cement-soil mixing pile in the Pearl River Delta area. And then,the load test is performed on single pile,natural foundation and four cement-soil mixing piles composite foundation,which is set with four kinds of thickness cushions. Based on analysis and calculation of the test data,the value ranges of the reduction coefficient α and β in the bearing capacity formula in the code are modified. Finally,the influence of cushion thickness on the bearing capacity of composite foundation is analyzed. It is suggested that the value range of cushion thickness is 200-400 mm,which can provide reference for design of cement-soil mixing pile composite foundation in the Pearl River Delta area.