Leakage-induced pipeline stressing and its potential detection by distributed fiber optic sensing

The paper aims to develop an approximated analytical solution to model the bending moment profile in a sewage pipe, buried within an unsaturated soil, which occurs as a result of a leak. The solution involves evaluation of the greenfield displacements due to a buried point source, and its use as an input to a soil-pipeline interaction problem. The solution is extended for a general wetted sphere (having different degree of saturation with the radial distance). The final model is tested against finite element simulations of the coupled problem without the simplified assumptions and approximations, and is found to be satisfactory. The work may be considered a first step towards realization of a distributed fiber optic sensing system that, together with an appropriate spatial signal analysis, could identify leaks at their early stage. The current analysis indicates that the developed strain signal (and its profile) could be detectable for leaks having liquid loss as little as 300 to 500 liters.