束浆挤扩钢管桩竖向抗拔承载力计算方法

Calculation of uplift capacity of steel pipe pile with constrained grouting

随着城市地下空间的开发,深厚黏性土地区的基础抗浮问题愈发凸显。钻孔预制桩因环境友好,得到了广泛的应用,但钻孔过程削弱了预制桩的抗拔性能。拟开发一种新型的约束注浆挤扩钢管桩,为了准确评估束浆挤扩桩的承载力,分析了抗拔桩的破坏模式。基于对数螺旋线,提出局部滑裂面理论。采用经典案例,验证了抗拔承载力公式的有效性。基于正交试验设计理念,研究了束浆挤扩桩承载力的影响因素。结果表明,桩径和桩-土界面强度,对抗拔承载力的贡献最大。开展束浆挤扩桩的现场抗拔试验,与同直径钢管桩相比,束浆挤扩工艺可提高抗拔承载力达到70%。使用简化计算公式,计算基桩的抗拔承载力,误差控制在5%以内,更为准确安全。研究结果为约束注浆挤扩钢管桩承载力的设计和优化,提供了理论和技术参考。

With exploiting of the urban underground space,the problem of anti-floating foundation becomes prominent in the soft soil areas.Bored and precast piles are widely used due to their environmental friendliness,but drilling process typically reduces the shaft resistance.Thus a constrained grouting pile is proposed.In order to accurately evaluate the uplift capacity of steel pipe pile with constrained grouting,the failure mechanism is analyzed,and the logarithmic spiral curve is adopted to fit the local slip surface.The simplified calculation formula is derived,and its effectiveness is verified by a classic case study.Based on the design concept of orthogonal experiment,the influencing factors of uplift capacity are compared.The results show that the diameter of pile and the strength of pile-soil interface control the uplift capacity.Field test on the steel pipe pile with constrained grouting is carried out.The test shows that the uplift capacity of the pile is increased by 70%.It is more accurate and safer to use the theoretical formula proposed to calculate the uplift capacity of foundation pile.The research results provide reference for the uplift capacity design of the constrained grouting piles.