水泥土搅拌桩的桩径分析

针对搅拌桩施工会引起周围土体的位移及产生很高的超静孔隙水压力的工程现象,首先分析了搅拌桩施工中固化剂的注入体积与膨胀压力、成桩直径的关系。结果表明,5%~10%的注入浆液的体积可以对周围土体产生1.8~3.0倍不排水抗剪强度的膨胀压力,成桩直径比搅拌叶片的名义直径大5%~10%。然后量测室内模型桩、现场搅拌桩的成桩直径,分析了注入浆液的体积与成桩直径的关系。结果表明,对于深度不太大的水泥土搅拌桩,有约45%的注入体积会通过上浮隆起的土体损失掉;大约5%的注入体积通过劈裂裂缝渗入到周围土体中;大约50%的注入体积会转化为成桩直径,使桩体膨胀5%~10%,即实测桩径比搅拌叶片的名义直径大5%~10%。

On the Diameter of Deep Mixed Column

Installation of deep mixing columns causes lateral displacement and induces high excess pore pressures in surrounding soils.The relationship among the injected volume of cement slurry,the expanding pressure,and the column diameter was analysed.The result indicates that 5%-10% injected slurry volume can induce expanding pressure of 1.8 to 3 times the undrained shear strengths,and the diameter of column expands 5% to 10%.Then,the relationship between the injected slurry volume and the real diameter was presented after investigating diameters of the model column in laboratory test and the diameters of the field mixed column.For short columns(diameter/length <10),it shows that about 45% injected slurry volume was lost due to soil heaving during mixing,about 5% injected slurry volume penetrated into the surrounding soils through fractures,and about 50% injected slurry volume was transformed to the column diameter and made the column expanding 5% to 10% of its original diameter.These results indicate that the expansion makes the real diameter 5% to 10% greater than the nominal diameter of mixing blades.