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http://dx.doi.org/10.7843/kgs.2012.28.6.19

Skin Friction Mobilized on Pack Micropiles Subjected to Uplift Force  

Hong, Won-Pyo (School of Civil & Environmental Engineering, Urban Design & Study Chung-Ang Univ.)
Cho, Sam-Deok (Korea Institute of Construction Technology)
Choi, Chang-Ho (Korea Institute of Construction Technology)
Lee, Choong-Min (Dept. of Civil Engineering, Chung-Ang Univ.)
Publication Information
Journal of the Korean Geotechnical Society / v.28, no.6, 2012 , pp. 19-29 More about this Journal
Abstract
Pack micropiles were recently developed to improve pile capacity of general micropiles. Pack micropiles were made by warping thread bar or steel pipe of general micropile by geotexlile pack and grouting inside the pack with pressure. According to the pressure, the boring hole could be enlarged. A series of pile uplift tests were performed on three micropiles. Two out of the three piles were the pack micropiles and the other was the general micropile, in which a thread bar was used in the boring hole. According to the pressure applied to the pack micropiles, the diameter of boring hole was enlarged from 152 mm to 220 mm. Unit skin friction mobilized on side surfaces of micropiles increased with displacement of pile head and reached on a constant value, which represents that the relative displacement between piles (or thread bar) and soils was reached on critical state. And the uplift resistance of pack micropile was higher than that of general micropile. Two reasons can be considered: One is that the frictional surface increases due to enlarging diameter of boring holes and the other is that the unit skin friction could increase due to compressing effect of surrounding soils by soil displacement as much as the enlarging volume of boring hole. The compression effect appeared at deeper layer rather than surface layer. The unit skin friction mobilized on micropiles with small diameter was higher than the ones on large bored piles.
Keywords
Geotextile; Load transfer; Micropile; Pack; Pile uplift test; Skin friction; Uplift force;
Citations & Related Records
Times Cited By KSCI : 2  (Citation Analysis)
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