A Para-Whole Space Model for Underground Magnetic Resonance Sounding Studies

Determining the presence of water ahead of a tunnel face or mine well is important for preventing accidents and ensuring higher efficiency in underground engineering. The surface magnetic resonance sounding (SMRS) technique can provide more direct and quantitative estimates of subsurface water variations than other geophysical methods. However, MRS is more complicated when it is performed in underground conditions (UMRS), i.e., interference water often exists and produces an SMRS signal in the opposite direction to the detection direction. Therefore, para-whole space theories are proposed to apply MRS in underground engineering to identify interference water. Singular value decomposition (SVD) inversion algorithms and a model resolution matrix in SMRS were implemented in UMRS. By using a para-whole space model, the impact of the hollow area of the tunnel is effectively removed from the calculation results to distinguish the interference water in the aquifer. A comparison of the inversion results from half space and whole space models shows that the para-whole space model can produce more accurate inversion results of the location and amount of subsurface water. Our research provides a theoretical foundation for MRS detection in tunnels or mines.