上海软土地区大直径钻孔灌注桩承载力偏低原因浅析

Analysis on Lower Bearing Capacityof Bore Cast - in - place Pile with a Major Diameter in Shanghai Soft Soil Area

就上海软土地区大直径(设计直径≥800mm)钻孔灌注桩承载力普遍低于按规范计算的极限承载力的原因进行了分析,认为大直径尺寸效应、编制规范时引用的资料存在一定的局限性以及成桩工艺时间长短等对大直径钻孔灌注桩承载力充分发挥都有不同程度的影响。建议在设计取值时,以取f_i和f_p的低限值为宜;同时,施工队伍应加强管理,缩短成桩时间;并应视具体情况适当增大泥浆比重。

the paper has asalysed the reason why the bearing capacity of bore cast-in-place pile with major diameter in Shanghai soft soil area has always been lower ultimate bearing capaci-ty which calculated in the standard.The cause has been considered as the size effects of major di-ameter,the limiatationof data cited in comiling standard and also the influence of different pile-forming time on the bearing capacity of bore cast-in-place pile with major diamnater.It has been suggested that when designing,it is suitable to take the low limited value of fi and fp.At the same time.the management of the construction team should be enhanced,the time of pile form-ing also should be shortened and moreover,cement specific gravity should be increasted to the specific siltation.