Research on Pile-Soil Stress Ratio Algorithm for Composite Foundation of Micro-Split Grouting Pile

Split grouting technology is a common technique for strengthening loess foundations. When calculating the settlement of composite foundations formed by split grouting piles, a reasonable pile-soil stress ratio formula is needed as a theoretical support. According to the principle of loess split grouting, the soil around the pile is divided into grouting compaction area and original foundation soil area. The soil in the grouting compaction area exhibits the characteristics of cement-soil. Considering the interaction between the split grouting pile and the grouting compaction interval is affected by the split branch, based on the assumption of the linear distribution of the pile side friction, a calculation method for the side friction of the split grouting pile is established. Combined the interaction of pile-soil under the coordination of stress and displacement, the calculation formula of pile-soil stress ratio is obtained. By comparing the field test results and the calculation results, it is found that the relative error between the two is about 20%, which meets the engineering practicability and provides theoretical guidance for engineering practice. Finally, the single-variable method is used to analyze the results: the increase of the split branch length increases the load shared by the pile, and the increase of the compressive modulus in the grouting compaction area can significantly share the pile stress.