Study on the effects of double-pipe grouting in silt-sand composite strata on surrounding soil and bridge substructures

This study proposed a new "grouting-soil-pier interaction transmission model", using work done on soil per linear meter to reflect the impact of soil displacement on the bridge pier. Exploring the relationship between grouting volume, soil displacement, and bridge pier displacement, the relationship between bridge pier horizontal displacement and grouting volume is divided into three zones: linear, nonlinear, and ineffective. A continuous transition from linear to nonlinear behavior is formulated, thereby elucidating the entire progression of pier displacement. For the present project, In the range of grouting distance [0, 5] meters and volume [0, 120] cubic meters, a proportional relationship is observed. Field tests show that the error between derived and measured slopes of pier displacement is under 10%, validating the model. Further exploration reveals that the maximum bending moment and maximum soil displacement occur at the same depth, which corresponds to the silt layer. Under different pile deflection conditions, the ratio of work done on soil per linear meter to pile strain energy varies, indicating different energy transfer efficiencies.