| Summary: | 碩士 === 國立成功大學 === 土木工程學系碩博士班 === 94 === Four preliminary compression tests of bored piles with two different post-grouting methods of single-stage and multi-stage respectively in one project of Taiwan High Speed Rail are studied to explore the effectiveness of post grouting in this study. Nine methods recommended by Fellenius (1980) to determine the ultimate bearing capacity of four tested piles are applied. The t-z curve and q-z curve methods are also employed to study the loading distribution behavior and loading settlement behavior at pile tip under vertical loading so that the skin friction and end bearing can be otained and the effectiveness of post grouting can be understanded accordingly.
The bearing capacity, skin friction, end bearing, t-z curve, q-z curve and soil stiffness are discussed for single- and multi- stage of post grouting, rspectively. The following conclusions are made after thorough evaluation,
(1). The bearing capacity of pile applied single- stage post grouting is only half of prediction value. The caking effect caused by stabilizing agent in the shaft due to longer constrution period of pile significantly reduced the skin friction, especially for the cohesionless soil. The end bearing capacity is also lower than the expect value. The performance of this method is poor.
(2). The improved post grouting method, namely multi-stage grouting, is more significantly effective than single stage in the aspect of end bearing capacity, t-z curve, q-z curve and soil stiffness.
(3). The contribution proportion of end bearing under vertical loading is increased due to the improvement of q-z curve so that the design of pile can be proceeded economically.
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