Leak Detection from Large Storage Tanks Using Seismic Boundary Waves

Abstract

This research investigates and develops the seismic boundary wave concept for leak detection in large soil‐supported storage tanks. Mathematical models are developed for the propagation of seismic boundary waves (i.e., Stoneley waves) along a liquid‐solid‐(tank‐bottom‐) soil boundary. These models augment the standard Stoneley wave (liquid‐solid‐boundary) formulation with the addition of a thin but stiff intermediate layer representing the tank bottom plate. These models are used to determine the effect of tank bottom on the propagation of boundary waves. Results show that the boundary‐wave velocity is essentially independent of wavelength, except at small wavelengths. The constant value of this velocity is about 4–6% higher than the Stoneley wave velocity that would exist in the absence of the tank‐bottom plate. Numerical examples and experimental results have also been presented to demonstrate the sensitivity of this technique to leakage from tank bottoms. The technique senses the effect of leakage as they manifest themselves in soil property changes under the tank bottom. The theoretical study as well as the field tests have shown that moisture infiltration in the soil produces a measurable change in the boundary wave velocity.