experimental investigation of vertical bearing characteristics of composite post-grouting piles in sandy soil

As a novel technology for strengthening the bearing capacity of bridge piles, related research on composite post-grouting at pile ends is still underdeveloped. to reveal the reinforcement mechanism and bearing characteristics of composite post-grouting piles, indoor model tests were implemented in sandy soil, which applied different grouting methods, including non-grouting, open post-grouting, and composite post-grouting methods on three pile-ends, and static load compression tests were conducted. the load–settlement curves, grouting curing performance, axial force of the pile, frictional resistance of the pile side, pile-soil relative displacement, and pile-end resistance were compared and investigated. the experimental results show that the load–settlement curves indicated the same pattern of steep variation. compared to the pile without grouting, the ultimate compressive bearing capacity of the model pile was improved by 67.2% and 101.6% using the open post-grouting and composite post-grouting methods at the pile end, respectively. compared to s1 pile without grouting, the average frictional resistance of the pile side in the slurry up-return zones under the ultimate condition for s2 (open post-grouting) and s3 (composite post-grouting) increased by 109.3% and 129.3%, respectively. in contrast, the pile-end resistance increased 2.3 times and 2.9 times, respectively. therefore, the bearing capability of piles can be improved more effectively when using the composite post-grouting technique in sandy soil rather than the traditional open post-grouting technique. these findings can be used as references for the optimized design and application of composite post-grouting bridge-pile foundations. © the author(s), under exclusive licence to the iran university of science and technology 2023.