Instrumented Static Load Test on Micropile Socketed into Limestone

摘要

Many researchers have investigated the behavior of rock-socketed piles and related the uniaxial compressive strength of "intact" rock to pile shaft resistance without considering rock mass quality. 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 about 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 RQD values.