In this paper, based on the in-situ post-grouting single pile of the Wuqi-Dingbian Expressway in China, the bearing performance of the post-grouting pile groups in loess area were studied with the use of the centrifugal model test. Taking into consideration pile spacing and number of piles, nine working conditions of single pile, 2 × 2 pile group with different pile spacing and 3 × 3 pile group were designed. The settlement, ultimate bearing capacity, pile side resistance, and end resistance ratio of pile groups with different pile spacing and number of piles before and after grouting were compared and analyzed. Finally, based on the change in the group efficiency obtained before and after grouting through the model test, the group efficiency of non-grouting pile groups in code was modified and applied to the calculation of the ultimate bearing capacity of the grouting pile groups. The results show that the group efficiency will decrease after grouting, and the bearing capacity of grouting pile groups increases gradually with the increase of pile spacing, and reaches the maximum when the pile spacing is 5d. The proposed bearing capacity calculation method of grouting pile group was validated by the model test results, and the calculation results generally agree with the model results, which is valuable for pile foundation designs.

本文以吴起定边高速公路原位后灌浆单桩为基础，采用离心模型试验研究黄土地区后灌浆桩群的承载性能。考虑桩距和桩数，设计了单桩、不同桩距的2×2群桩和3×3群桩9种工况。对比分析了注浆前后不同桩距和桩数的桩群的沉降、极限承载力、桩侧阻力和端阻力比。最后，基于通过模型试验得到的灌浆前后组效率的变化，修改了代码中非注浆桩群的群效率，并将其应用于注浆桩群极限承载力的计算中。结果表明，注浆后群效率会降低，注浆桩群承载力随着桩距的增加而逐渐增加，在桩距为5d时达到最大值。模型试验结果验证了所提出的注浆桩群承载力计算方法，计算结果与模型结果基本吻合，对桩基设计具有参考价值。并在桩距为 5d 时达到最大值。模型试验结果验证了所提出的注浆桩群承载力计算方法，计算结果与模型结果基本吻合，对桩基设计具有参考价值。并在桩距为 5d 时达到最大值。模型试验结果验证了所提出的注浆桩群承载力计算方法，计算结果与模型结果基本吻合，对桩基设计具有参考价值。