In-situ Friction Testing for Estimating the Bearing Capacity of Friction Piles

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Experimental tests were carried out to study the possibility of estimating the frictional factor of the bearing capacity of piles with the use of a Lateral-stress-sensing cone penetrometer.1. The characteristics of lateral stress acting of the cone penetrometer in sandy soil were examined with the results of the friction tests in pressurized artificial grounds and inーsitu tests at reclaimed grounds.The change of horizontal stress was measured during the penetration of the cone penetrometer into the pressurized artificial ground. The relative density of the sand was found to be influential to the lateral stress acting on the friction sleeve. The results of in-situ tests at reclaimed sandy grounds showed that the location of the pore water pressure transducer has an important role on the test results.In-situ friction tests were carried out at soft and stiff clayey grounds, Frictional resistance from the cone penetration tests were studied in comparison with the frictional resistance from the loading tests of piles.From the test results in the soft clayey ground, it was found that neither the location nor the roughness of friction sleeve has evident influence on the frictional resistance measured by the cone penetrometer. From the test results in the stiff clayey ground, it was found that the frictional resistance measured by friction sleeve is closer to the frictional resistance from the loading tests of piles than the value estimated from the point resistance of the cone penetrometer.3. Problems were identified on the apparatus and procedure of the in-situ tests by the lateral-stress-sensing cone penetrometer. It will become necessary to solve these problems to establish a concrete method for estimating the frictional resistance of piles from the results of cone penetration tests.