Research on Bearing Characteristics of Modified Variable Diameter Micropile Based on Pile Group with Uniform-section

In order to improve the load bearing characteristics of micropile and to study the deformation mechanism of variable diameter micropile. On the basis of the real type test of group pile foundation with uniform-section in plateau mountainous area, combined with the load transfer mechanism of variable diameter micropile, FLAC3D was used to numerically simulate the horizontal and vertical loads of three kinds of single micropiles, and to compare with the real type test of group pile foundation of uniform-section, the results show that: Due to the influence of bearing platform and pile group effect, the compressive and pull-out bearing capacity of pile group foundation is greater than and less than the sum of the corresponding single micropile bearing capacity, respectively; The ultimate pullout and compressive capacity of double diameter-extended micropile are about 4.4 times and 3.8 times of the uniform-section micropile. The soil deformation is concentrated on the expanding part and the value is larger, which shows the characteristics of frication & end-bearing pile characteristic of multi fulcrums; the vertical bearing capacity of double diameter-extended micropile is close to group pile foundation with uniform-section (2x2 micropile), but its horizontal bearing capacity is less than pile group foundation, which can be improved by adding a bearing platform to the pile top. It is feasible to improve the performance of single micropile to the level of pile group with uniform-section expanding the diameter, which has engineering significance for power transmission and transformation engineering.