长钻孔灌注桩后注浆深度及数值模拟研究

Numerical study on depth of post-grouting in-situ of length bored pile

对钻孔灌注桩后注浆深度时的桩顶位移进行了数值计算。当桩端和桩侧注浆的浆液上升55 m时,桩顶荷载为700t时的未注浆桩桩顶位移为9.357 mm,桩侧注浆的桩顶位移为6.99 mm,桩端注浆的桩顶位移为7.11 mm。未注浆桩的计算极限承载力为1 300 t,桩侧注浆桩的极限承载力为1 800 t,桩端注浆桩的极限承载力为1 700 t。2种注浆方法提供桩基承载力的比例分别为38.5%和30.8%。数值结果表明:后注浆技术是减小深厚软土地区桩基沉降的有效手段之一。对深厚软土地区的超长钻孔灌注桩,宜优先选用桩侧压力注浆为主的方法减小桩基沉降,即可简化后注浆装置,又可方便注浆施工;当承载力要求较高、桩较长且桩端有较好的持力层时,可采用桩端桩侧联合注浆。

The pile top displacement of bored pile was analyzed by numerical simulation. Numerical analysis is performed on ultimate bearing capacity of bored pile. The results show that, when the load at pile top is equal to 700 t, the pile top displacement of un - grouting pile is 9. 357 mm, while that of pile - side. grouting is 6.99 mm, pile - tip grouting is 7.11 mm （ serum migrating up to 55 m） , and that of combined grouting is 6.78 mm. Furthermore, the pile top displacement declines by 2. 367, 2. 247 and 2. 577 mm respectively. The calculational ultimate bearing capacity of un - grouting pile is 1 300 t, that of pile - side grouting is 1 800 t, and that of pile - tip grouting is 1 700 t （ serum migrating up to 55 m）, whereas, that of combined grouting of pile side and tip goes up to 1 900 t. The bearing capacity of pile foundation provided by these three grouting methods is 38.5%, 30.8% and 46.2%, respectively. Post - grouting technology is an effective method to decrease the pile founda- tion settlement in deep soft soil foundation. As for overlength bored pile in deep soft soil foundation, pile -side grouting is effective to reduce the pile foundation displacement, in this way, not only the grouting installation is simlified, but also make the construction of grouting more convenient; besides, combined grouting is suitable for the piles which need high bearing capacity or long -piles supporting by a fine supporting course.