The “high-standard micro-piles method” which is also possible at a narrow space, low altitude head condition and low cost has been developed as a new construction method for reinforcing existing foundation structures. Micro-piles are constructed with double tube excavation using by boring machine. After inserting a steel pipe into the hole, grouts are filled both inside and outside of pile.
This paper describes the results of adhesion tests between pile and grout, field tests, compression loading tests, pull-out loading tests, and trail digging of compression loading test pile. By these test results, the following things could be confirmed. 1) It is possible that maximum adhesion stress between piles and grouts was estimated from unconfined compression strength of grouts, 2) It was confirmed that end improved soils were satisfied with diameters and strengths, 3) Covering depth of grout was more than 20mm, 4) Ultimate bearing capacity was evaluated the bearing capacity formula of micro-piles by cast in place pile in specifications for highway bridges.
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