Evaluation of Compression Behavior for Pre-bored P.C. Piles in Drained Soils

• Main Authors: Chung-Hung Chen, 陳俊宏
• Other Authors: Yit-Jin Chen
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/49561360869992005069

碩士 === 中原大學 === 土木工程研究所 === 98 === ABSTRACT This study collected 50 load tests for pre-bored P.C. piles in drained soils to evaluate the axial compression behavior. The evaluation includes interpretation criteria, side resistance, and tip resistance. First, representative interpretation criteria were applied to these load test data to observe their relative merits and interrelationships. Then, the interpretation results were used to examine the analytical models of side resistance and tip resistance. For interpretation criteria, L1 occurs at about 0.53%B (B = shaft diameter) with mean displacement of 3.4 mm. The results indicate that the initial linear region is in a very small displacement. The ratios of representative interpretation criteria, all compared to L2, range from 0.78 to 1.28. The displacements of these criteria locate at between 15 and 47 mm, and the Chin method is greater than 64.6 mm. Among these criteria, the Chin method is upper bound, DIN 4026 method is lower bound, and Hirany and Kulhawy (L2) method is in the reasonable middle range. For axial capacity, the mean ratio of measure tip resistance to predicted tip resistance is between 0.15 and 0.18, while the mean ratio of measured side resistance to predicted side resistance is about 1.39-1.60. Based on the back-calculation from these load tests, the suggested K/Ko is 1.65 for pre-bored P.C. piles, which is much greater than the suggested values in drilled shafts. In addition, the ratio of measured/predicted side resistance is convergent to 1.0 when the shaft length increases. Finally, the measured results also compare with related codes using the SPT-N empirical formula. It is found that the "Architectural Institute of Japan Recommendations for Design of Building Foundation" is closer to the measured results. Based on these analyses, the suggested unit side resistance and unit tip resistance are (0.4 ± 0.03) N (t/m2) and (10 ± 0.14) N (t/m2), respectively.