TY - JOUR
T1 - Instrumented static load test on rock-socketed micropile
AU - Seo, Hoyoung
AU - Prezzi, Monica
AU - Salgado, Rodrigo
PY - 2013
Y1 - 2013
N2 - Rock-socketed piles are often used to transfer heavy loads from a superstructure to competent underlying rock layers. The loads are transferred by the pile to the surrounding rock mass through shaft and base resistance. Several researchers have investigated the behavior of rock-socketed drilled shafts and related the uniaxial compressive strength of intact rock to pile-shaft resistance. However, the loadtransfer behavior and load-settlement response of micropiles are different from those of drilled shafts because of the large slenderness ratio (pile length=pile diameter) of micropiles. This study presents results from a fully instrumented field-scale load test on a 0.2-m-diameter micropile socketed 4.2 m into limestone layers (2.7 m into weathered limestone and 1.5 m into hard limestone). The results show that practically no base resistance is mobilized until the pile-head settlement reaches approximately 7% of the diameter of the test micropile. The measured limit shaft resistance values are compared with values predicted using methods available in the literature. The comparison indicates that use of the intact strength of the rock for estimation of limit shaft resistance may lead to an unconservative design when the rock mass quality is very poor, as indicated by, for example, low rock-quality designation values.
AB - Rock-socketed piles are often used to transfer heavy loads from a superstructure to competent underlying rock layers. The loads are transferred by the pile to the surrounding rock mass through shaft and base resistance. Several researchers have investigated the behavior of rock-socketed drilled shafts and related the uniaxial compressive strength of intact rock to pile-shaft resistance. However, the loadtransfer behavior and load-settlement response of micropiles are different from those of drilled shafts because of the large slenderness ratio (pile length=pile diameter) of micropiles. This study presents results from a fully instrumented field-scale load test on a 0.2-m-diameter micropile socketed 4.2 m into limestone layers (2.7 m into weathered limestone and 1.5 m into hard limestone). The results show that practically no base resistance is mobilized until the pile-head settlement reaches approximately 7% of the diameter of the test micropile. The measured limit shaft resistance values are compared with values predicted using methods available in the literature. The comparison indicates that use of the intact strength of the rock for estimation of limit shaft resistance may lead to an unconservative design when the rock mass quality is very poor, as indicated by, for example, low rock-quality designation values.
KW - Load-bearing capacity
KW - Micropiles
KW - Pile load tests
KW - Rocks
UR - http://www.scopus.com/inward/record.url?scp=84887981834&partnerID=8YFLogxK
U2 - 10.1061/(ASCE)GT.1943-5606.0000946
DO - 10.1061/(ASCE)GT.1943-5606.0000946
M3 - Article
AN - SCOPUS:84887981834
SN - 1090-0241
VL - 139
SP - 2037
EP - 2047
JO - Journal of Geotechnical and Geoenvironmental Engineering
JF - Journal of Geotechnical and Geoenvironmental Engineering
IS - 12
ER -