Loading Rate Effects on Axial Pile Capacity in Clays

In order to design more efficient and reliable structures, axial load tests are performed on foundation piles. Traditionally, static tests with an average duration of approximately twenty-four hours have been performed on test piles to obtain their axial capacity. These static tests require multiple piles used as anchors in addition to the test pile. Static tests are both expensive and time consuming. An alternative to static testing is dynamic testing which requires sophisticated interpretation, can damage the pile and may not produce accurate results. There is a relatively new testing method called the Statnamic Testing Method which tests foundation piles at a very fast rate, but still slower than with dynamic tests. As the rate at which load is applied to a test pile increases, the axial capacity also increases, particularly in clay. Research suggests that shear strength of soil typically increases 10% per log cycle increase in strain rate. Strain rate effects can vary widely and may be influenced by many factors including plasticity index, structure, ageing, overconsolidation ratio, temperature, etc. Statnamic testing was performed for this work. Nine static tests were performed on six different piles identical to the Statnamic test pile and driven through the same soil profile. The static tests had times to failure ranging from ten seconds to eighteen hours. Failure load increased by 13.7% per log cycle increase in velocity. Statnamic tests need more careful analysis when performed in clay to avoid over predicting pile capacity. A factor of 0.55 should be applied to Statnamic capacity to predict static capacity.

Name thesis:degree_name

MS

Grantor dc:publisher

Brigham Young University - Provo

Author dc:creator

• Garner, Michael Paul

• pile testing
• shear strength
• rate effects
• strain rate
• statnamic
• clay
• Civil and Environmental Engineering

Language dc:language

English

Repository record dc:identifier

https://scholarsarchive.byu.edu/etd/1434

OAI identifier oai:identifier

oai:scholarsarchive.byu.edu:etd-2433