Full-scale tests on the grouting effectiveness of offshore bored piles with various bearing strata

Abstract

The bearing capacity of the post-grouted bored piles in sea-crossing bridges is greatly impacted by the kind of bearing stratum. Engineers are urgently concerned with the reinforcement effectiveness, improvement mechanism, and grout diffusion mechanism of tip-grouting of offshore bored piles in various bearing strata. Two groups of core-drilling inspections and six groups of full-scale static load tests were performed in this research. According to the test results, post-grouting significantly improved the load-settlement response of bored piles with various bearing strata. The improvement mechanism of tip-grouting included the formation of an enlarged pile tip, the pre-mobilization effect, and the improvement of bearing strata and soil–pile interface. The reinforcement effect of post-grouting in a coarse-grained soil bearing stratum was better than that of a fine-grained soil bearing stratum. The diffusion range of upward-flowing cement mortar in the coarse-grained soil bearing stratum and fine-grained soil bearing stratum was 14–15 m and 5–7.5 m respectively, and the diffusion range was significantly affected by the type of bearing stratum. The grout exhibited spherical penetration diffusion in the coarse-grained soil bearing stratum and splitting diffusion in the fine-grained soil bearing stratum, respectively. The investigation findings provided references for amending the existing construction method of post-grouted offshore bored piles in sea-crossing bridges.