Study on the response of postside-grouted piles subjected to lateral loading in calcareous sand

The post-grouting technique has gradually become an effective approach to improve the bearing capacity of piles in calcareous sand due to its simple process, low cost and reliable reinforcement effect. In this paper, model tests were performed on horizontally loaded single piles under static pressure pile driving in a calcareous sand foundation. The responses of ungrouted piles and post-grouted piles subjected to lateral loads in calcareous sand were studied, the test results were compared with those of ungrouted piles and post-grouted piles in siliceous sand, and the influence of postside grouting on the horizontal bearing behavior of piles in calcareous sand was explored. The results show that due to the particularity of the calcareous sand, its horizontal restraint ability of ungrouted piles is weaker than that in siliceous sand. Post-grouting at the pile side has a significant effect on improving the horizontal bearing capacity and strengthening the deformation control ability of the pile in calcareous sand, while showing approximately the same characteristics as that of the post-grouted pile in siliceous sand under the same conditions. The ratio of the lateral resistance coefficient of ungrouted and post-grouted piles gradually tends to be consistent with the increase in the lateral displacement of the pile head, and the bending moment and lateral displacement of the pile shaft are mainly concentrated in the upper part of the pile shaft. The lateral bearing capacity of the pile is greatly affected by the upper level of soil, and grouting at the pile side can effectively increase the ability of the pile foundation to resist horizontal loads and control deformation by improving the physicomechanical properties of the upper soil layer. In addition, the distribution and microstructure of cement-stabilized soil are analyzed based on the excavation of a post-grouting single pile. It is found that the cement grout injected at the pile side moves upward, penetrates downward and diffuses horizontally along the pile shaft to form a stable structure of cement-stabilized soil with calcareous sand particles; therefore, the pile–soil system interaction enters a new structural equilibrium state, thereby improving the horizontal bearing capacity of the pile foundation in calcareous sand.