Abstract
Post-grouted piles, as a foundation form for large-span and large-scale structures on calcareous sand, are expected to provide a high bearing capacity, but research on the response of post-grouted piles subjected to axial load in calcareous sand is still in the exploratory stage. In this paper, a model test is constructed for static pressure piles in calcareous sand under axial loading. The response of axial compressive piles, with and without post-grouting, in calcareous sand were investigated, and the test results were compared with those of axial compressive piles, with and without post-grouting, in siliceous sand. The influence of post-side-grouting on the response of a single pile subjected to axial compressive load in calcareous sand and its bearing mechanism were further analyzed. The results show that the change in shaft resistance, caused by the lateral extrusion of calcareous sand, is less than the negative effect caused by particle breakage during pile driving, so single piles without post-grouting in calcareous sand exhibit weaker axial bearing behavior than that in siliceous sand. A single pile with post-side-grouting in calcareous sand can provide a higher bearing capacity by increasing the shaft resistance and tip resistance compared with a single pile without post-side-grouting, and the increased ratio of the bearing capacity of piles, after grouting in calcareous sand, is better than that of piles in siliceous sand. Post-side-grouting can not only strengthen the surrounding soil by the solidification effect of injected cement grout, but it can also have a strengthening effect on the tip resistance. In addition, ideal-geometry grouting has more obvious advantages in improving the bearing behavior of pile foundations than annular point grouting, and higher stability in improving the bearing properties of pile foundations is evident for ideal-geometry grouting. Therefore, it is suggested that a directional grouting device should be adopted in actual projects in the future to form a more stable pile-soil interaction system and to expand the application prospect of pile foundations in calcareous sand.
Highlights
Given that most of the deposition process of calcareous sediments, without long-distance transport, retains the characteristics of a more native biological skeleton, it presents the characteristics of porosity, easy cementation, and easy breakage, resulting in obvious differences from the mechanical properties of terrestrial sediments [2,3]. This has caused the traditional pile analysis approach for terrestrial sediments to be unsuitable for calcareous sediments; pile foundations in calcareous sand have gradually become an issue of great concern in engineering and academia
The test results have proven that the post-grouting technique can increase the bearing capacity of a pile in calcareous sand by enhancing the shaft resistance and tip resistance, and calcareous sand formations can be effectively improved by injected cement grout
This paper presents a model test of an axially loaded single pile in a calcareous sand foundation
Summary
Introduction published maps and institutional affilCalcareous sediments are an important component of applications in coral reef engineering and are mainly carbonate sediments formed by the physical, biological, and chemical processes of the remains of marine organisms [1]. Given that most of the deposition process of calcareous sediments, without long-distance transport, retains the characteristics of a more native biological skeleton, it presents the characteristics of porosity, easy cementation, and easy breakage, resulting in obvious differences from the mechanical properties of terrestrial sediments [2,3]. This has caused the traditional pile analysis approach for terrestrial sediments to be unsuitable for calcareous sediments; pile foundations in calcareous sand have gradually become an issue of great concern in engineering and academia.
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