Study on positioning of trenchless drill bits based on the principle of acoustic resonance

Trenchless Technology is widely used in underground pipelines installation for communication, energy, and other applications. To avoid accidents such as the drill bits' sliding and deviating to obtain the pilot path, the typical positioning method depended on electromagnetic signals requires an inner probe and is easily disturbed in the urban electromagnetic environment. This paper introduces a new method for positioning metal drill bits at shallow depth based on the principle of acoustic resonance. In a simulated trenchless experiment, the hammering method and the fast Fourier transform algorithm were used to analyze the resonant characteristics of the un-derground drill bit. Measured by acoustic sensors set on the surface, the resonant wave was analyzed by acoustic spectrum and spectral analysis to obtain its capability to position. It is found that the underground drill bit is an oscillation system whose resonance could be excited by an aboveground acoustic generator at the resonant frequency, and the resonant sound intensity can be used to position. The calculation model was proposed with the linear algorithm and the least square method, which was studied on the lab scale simulation. The average positioning error is less than 0.083 m, which can meet the accuracy at the operational depth of urban trenchless projects. This pioneer method is based on the resonance principle to eliminate the inner probe and remedy the weak robustness of electromagnetic signals in urban mini trenchless projects, which provides a new way to design positioning systems for underground space.