A Study of the t-z and q-z Curves of Shaft Socketed in Soft Rock

• Main Authors: Cheng-Chan Pan, 潘成展
• Other Authors: Chih-Sheng Ku
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/68691280664675960778

碩士 === 義守大學 === 土木與生態工程學系碩士班 === 95 === The bearing capacity of pile socketed into soft rock was still not understood well nowadays. In this thesis, compression and tension pile loading tests of the instrumented bored piles were conducted at the soft rock formation site. The unconfined compression strength of soft rock range from 441 kPa to 1297 kPa, its average is about 903 kPa. The test site was located at Hsinchu County, Taiwan. The test data of those two load tests, tensile and compressive loading, were used to investigate the bearing capacity and mechanism of shaft socketed into soft rock. The compression and tension test piles dimension are 800 mm in diameter and 24 m in length. The results of those two pile tests show that the instrumented data of rebar stressmeter of pile sockted into soft rock were significant difference under tension and compression loading conditions. Beside, the elastic modulus of concrete Ec of pile were discussed in detail. Strain-dependent Ec were recommended to calculate the load transfer of pile. The unit skin friction is conducted based on the load distribution along the pile shaft. These curves are the so called t-z curves. The analysis results of the compression pile showed that the unit skin friction of the soft rock could be divided into three distinct phases: a linear phase, nonlinear phase (transition phase) and strain hardening phase. The maximum unit skin friction of this soft rock was about 16 t/m2. According to the q-z curve, a significant mobilization of the base resistance was observed in this test pile. A maximum end resistance of 749 t/m2 was observed under the maximum applied load of 1000 ton. The tension pile analysis results indicated that the t-z curves were with the similar trend. The maximum unit tension skin friction of this soft rock was about 17.4 t/m2.