Robust weighted-mean approach for the evaluation of ground improvement columns using surface wave analysis

This paper demonstrates the application of surface wave analysis specifically for the evaluation of ground improvement columns, and considers the susceptibility of phase measurements to noise associated with this technique. This is addressed by introducing a robust approach of calculating the phase velocity based upon a weighted-mean approach that uses the signal-to-noise ratio SNR of the signal as a variable cost function to obtain an optimal phase velocity estimation. Experimental data was collected from a laboratory scale setup of a 0.1 m diameter × 0.15 m depth gravelly-sand column installed within a 0.6 m × 0.3 m × 0.3 m block of homogenous kaolinite-clay. Results from the measurements indicated Rayleighwave phase velocities of 59 m/s and 110 m/s for the clay and column respectively. The weighted-mean approach demonstrated consistently more accurate phase estimation as compared to the case of a rigid threshold approach.