Load Transfer Curve Analyses of Drilled Shafts Using Crosshole Sonic Logging Test

The erroneous load transfer curve calculated using the nominal cross-sectional area ($A_C$) and elastic modulus of a concrete specimen ($E_{\mathrm{CU}}$) was modified by considering the nonuniform cross-sectional area ($A_{\mathrm{CR}}$) and nonhomogeneous elastic modulus ($E_{\mathrm{CV}}$) of concrete. A drilled shaft instrumented with strain gauges and pipes for a crosshole sonic logging (CSL) test was constructed as the test pile. To estimate $A_{\mathrm{CR}}$, the incremental volume of the placed concrete was recorded. After curing the concrete, the CSL test was performed to estimate $E_{\mathrm{CV}}$ based on the compressional wave (P-wave) velocity. In addition, a bidirectional load test was conducted, and the load transfer curve was calculated. The results of the analyses demonstrated that although the erroneous load transfer curve was partially modified by considering either $A_{\mathrm{CR}}$ or $E_{\mathrm{CV}}$ individually, the modification was enhanced further by adopting both $A_{\mathrm{CR}}$ and $E_{\mathrm{CV}}$. This study demonstrates that the estimation of $A_{\mathrm{CR}}$ and $E_{\mathrm{CV}}$ may be used to calculate reasonable load transfer curves for drilled shafts.