结合南水北调工程SG14标的端夯扩碎石桩施工,根据现场静载、静力触探和动力触探试验以及室内土工试验对端夯扩碎石桩复合地基的桩土应力比、承载力以及桩间土的挤密效果进行了分析。试验表明:带有桩端扩大头的夯扩碎石桩的桩土应力比一般碎石桩大,试验所得桩土应力比一般在[4.2,7.4]之间;桩土应力比值随荷载的增加呈现先增后减,并逐渐趋于稳定,桩土应力比值随桩长的增大而增大;夯扩碎石桩复合地基的沉降曲线(P-S曲线)呈渐变型,没有明显的拐点或变化点出现;单桩复合地基承载力随着桩长的增大,承载力也逐渐增大;夯扩碎石桩施工能有效提高桩间土的强度,同时,对改善地基的不均匀沉降也有很好的效果。
According to measured results of in-situ static load test, static cone penetration test(CPT), heavy dynamic penetration test(DPT), and indoor soil test, we analyze three mechanical parameters of composite foundation of ram-compaction gravel pile, namely pile-soil stress ratio, bearing capacity, and soil’s compacted effect with piles. We take the construction of ram-compaction gravel pile in the 14th bid of South-to-North Water Transfer Project, located in Handan, Hebei province, as an example. Results show that, pile-soil stress ratio of composite foundation of ram-compaction gravel pile with expanding head is bigger than that of normal gravel pile, which is from 4.2 to 7.4; pile-soil stress ratio first increases and then decreases with the increase of load, and gradually tends to be stable, and the ratio increases with the pile length; then, the gravel pile’s curve of load vs. settlement (P-S curve) exhibits gradual change, without obvious inflection point or abrupt change point; furthermore, bearing capacity of composite foundation of ram-compaction gravel pile increases with pile length. According to the results of CPT and DPT, we find that the rammed gravel pile can effectively improve the strength of soil among piles, and decrease uneven settlement of the foundation.
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