2015 Volume 1 Issue 6 Pages 41-46
The Quaternary alluvial deposits was widely distributed in the field of hydropower station, composed of the silty sand with mud, the silty sand and the gravel. The Quaternary alluvial was with the low average standard compaction number and the loose structure, high compressibility and low bearing capacity, particularly its saturated silty sand had the potentiality of liquefaction. According to these characteristics, the single mixed pile foundation was used to improve its bearing performance. There were series of static loading tests in situ with the different conditions including the three different pile’s length and the two different bearing stratums.Combined with the data of numerical analysis, its failure modes were analyzed and both of the vertical ultimate bearing capacity and the characteristic value of bearing capacity were obtained. Study showed that: 1)when bearing stratums was the compacted sands or the gravel, the P-S curve was the gradually falling type with no steep drop and the P-Δs/ΔP curve had plain stage or sharp, 2)when pile length was 14.0m and 19.0m respectively, the pile failuer was resulted by the pile flaw，their ultimate bearing capacity by the static loading test was lower than the ultimate strength value of core of pile and the one calculated by the minimum combination, when pile length was 11.0m, it was controlled by the ultimate bearing capacity by the resistance from the soil surround pile and the resisitance from the pile’s tip. The study was the foundation for the follow up tests of grid structure mixed pile composite foundation and as the reference for the similar engineering.
