Development and Validation of Pulse-Echo Methods for the Detection of Buried Objects

Abstract

The undergrounding of electrical cables is a promising strategy for improving the reliability and resilience of the U.S. energy grid; however, widespread adoption is hindered by the risk of utility strikes during installation, which cause an estimated $30 billion in damages an- nually. Current pre-construction survey methods carry residual positional uncertainty and require dedicated survey campaigns that limit contractor productivity for a period of time. This work explores the viability of using high-frequency seismic pulse-echo signals to detect buried objects ahead of a horizontal directional drilling (HDD) drill head at laboratory scale. A key novelty of this work is the subsurface, ahead-of-drill sensor configuration, in which the seismic source and receivers are buried at the drill head level rather than deployed at the sur- face. This configuration has not been previously reported in the utility detection literature, and would streamline undergrounding projects by enabling detection during active drilling operations. To evaluate the viability of this approach, the wave propagation characteristics of the soil medium were first characterized, including signal-to-noise ratio, coherence, source directivity, wave speed, and dispersion. These measurements represent a contribution in their own right, as they establish the operating envelope of high-frequency seismic sensing in a granular soil medium at the scale relevant to utility detection. Target detection ex- periments were then conducted using steel and PVC pipes buried at distances ranging from 0.50 m to 1.50 m. The system achieved mean signal-to-noise ratios of 5.86 and 6.16 for steel and PVC, respectively, both exceeding the established detection threshold of SNR ≥ 3, and an imaging algorithm successfully localized both materials at all tested distances. Notably, comparable detection performance was achieved for both metallic and non-metallic targets, a capability that distinguishes the seismic approach from electromagnetic methods such as ground penetrating radar. Additionally, an in-depth analysis was conducted on the reference seismic signals using cross-correlation techniques to study how the soil changes as it is altered by following the experimental sequence of placing and removing buried targets. Together, these findings establish a physical and experimental foundation for future development of a real-time, imaging-while-drilling sensing system.