Instability Analysis of Damaged Pile Due to Static or Dynamic Overload

ABSTRACT

Instability of a damaged pile due to a statically or dynamically applied overload is studied in this work using the finite element method. A damage parameter from such a pile is calculated using fracture mechanics concepts. The parameter is used to modify the beam element at the cracked or damaged location. Soil samples were obtained from the site of the pile and were subjected to laboratory tri-axial tests to obtain shear strength parameters c and  . Other soil parameters

such as Young’s modulus E and Poisson’s ratio  were also obtained from the tri-axial tests. These were used to cal- culate shear strength  and sub-grade modulus k for the soil. The parameters , E,  and k were later used together with the damage parameter  in the finite element simulation of the strength of the damaged pile using Eigen value

analyses. The layered soil modulus is approximated by taking the mean value and is denoted by K f . The discrete ele- ment matrices are assembled into a system  Eigen-value equation, the solution of which provides the stability or instability loads for the damaged pile. The results obtained for a pile without damage, that is, when   0 , are in good agreement with those published in the literature. It has also been found that higher soil resistance is needed to support the damaged pile. It is concluded that the proposed model is a good candidate for use in the analysis and repair of damaged piles due to earthquake overload by soil stabilization methods.

Keywords: Damaged Piles; Earthquake Overload; Instability Analysis; Layered Soil Support