不同地质后注浆钻孔灌注桩承载力试验研究

Experimental Study on Bearing Capacity of Post-grouted Bored Piles under Different Geological Conditions

为了研究不同地质土层对后注浆钻孔灌注桩的桩端承载力和桩侧摩阻力的影响和作用机理,通过3根桩端后注浆钻孔灌注桩的静载荷试验和内力测试,取得了注浆前后单桩承载力、桩身轴力和桩顶的沉降数据,推算出桩端承载力和各土层的桩侧摩阻力。通过分析荷载-沉降曲线、桩身轴力分布图,探讨了不同桩端土层强度的桩端后注浆对桩端承载力和桩侧摩阻力影响的作用机制,进一步研究不同地质条件钻孔灌注桩后注浆技术的承载力改善性状,分析承载力提高的机理和效果各不相同的原因。对比不同地质条件桩端后注浆对桩端承载力和桩侧摩阻力的影响程度,验证了桩端承载力和桩侧摩阻力在不同桩端土层强度条件下会产生不同的相互作用和影响。试验结果表明:钻孔灌注桩后注浆技术的应用可以有效地提高钻孔灌注桩的单桩承载力,明显地减少桩顶的沉降。不同地质土层的桩端后注浆可以不同程度地提高桩端承载力和桩侧摩阻力,桩端承载力和桩侧摩阻力的提高幅度均与桩端土的力学性质密切相关,粗粒土提高幅度大于细粒土。实际工程中,为充分利用注浆后单桩承载力所能提高的潜力储备,可根据桩端地质条件不同,合理调整端阻力、侧阻力增强系数取值。

In order to study the influence and mechanism of action of different geological soil layers on the bearing capacity of pile-end and the frictional resistance of pile-side post-grouted bored piles,we obtained the data of bearing capacity of single pile,axial force of pile and settlement of pile-top before and after grouting through the static load test and internal force test of 3 pile-end post-grouted bored piles,and calculated the bearing capacity of pile-end and the frictional resistance of pile-side for each soil layers. Through the analysis of the load-settlement curve and the distribution curve of axial force of the pile,we discussed the mechanism of influence of pile-side post-grouting with different soil strengths on the bearing capacity of pile-end and frictional resistance. We further studied the improvement of the bearing capacity of post-grouting technology of bored piles under different geological conditions,analyzed the improvement mechanism and reason of different effects of bearing capacity. We compared the influence degrees of pile-end post-grouting on the bearing capacity of pile-end and the frictional resistance of pile-side under different geological conditions,and verified that the bearing capacity of pile-end and the frictional resistance of pile-side would produce different interactions and influences with different soil strengths at pile-end. The test result shows that（ 1） theapplication of the post-grouting technology of bored piles can effectively improve the bearing capacity of single bored pile,and obviously reduce the settlement of pile-top;（ 2） the bearing capacity of pile-end and the frictional resistance of pile-side in different geological soil layers can be improved after pile-end post-grouting,their increasing ranges is closely related to the mechanical property of the soil at the pile-end,and the increasing range of coarse-grained soil is larger than that of fine-grained soil. To make full use of the potential reserves of single pile bearing capacity to be improved after post-grouting,we can reasonably adjust the enhancement coefficients of pile-end resistance and pile-side resistance according to different geological conditions of the pile-end in actual engineering.