Study and application of side-grouting uplift piles

Compared to the usual bored uplift piles, the side-grouting bored uplift piles are more effective in providing the uplift resistance by changing the interface property between the pile and the soil. The main features of the side-grouting system, construction technology and pile parameters are presented. Based on the full-scale tests, centrifugal model tests and shear tests, comparisons among the side-grouting uplift piles, base-enlarged uplift pile and straight shaft uplift pile are carried out. Some initial acknowledgement is attained, such as the bearing capacity, characteristics of load-displacement relation, interface mechanics between the pile and the soil and the strengthening mechanism of grouting. According to the engineering practice, two methods to calculate the bearing capacity of the side-grouting uplift piles are introduced, that is, grouting-strengthening empirical method and load-transfer method. The application cases of the side-grouting uplift piles in Shanghai EXPO 500 kv underground transformer substation and the project of Baiyulan Square are introduced.