The invention discloses a combined advanced detection method based on borehole transient
electromagnetism and direct-current resistivity, and the method comprises the steps: laying an advanced borehole in a tunnel face in a
tunneling direction, carrying out the collection of borehole transient electromagnetic data, and carrying out the inversion, and obtaining a borehole transient electromagnetic inversion result; according to an inversion result and a corresponding
estimation method, calculating to obtain
Gaussian variation models in three main axis directions, and expanding the
Gaussian variation models to any direction; then, the
Gaussian variation model in any direction is substituted into a
covariance calculation formula, a
covariance value between any
two grid units in the area needing to be detected is obtained through calculation, and a
covariance constraint matrix is assembled; and finally, introducing the matrix as a regularization item into an inversion objective function of direct-current resistivity advanced detection to realize covariance constrained direct-current
resistivity inversion, so that the inversion stability and the inversion imaging precision of the direct-current resistivity advanced detection are remarkably improved, and the method is suitable for scenes such as tunnel face or
coal mine underground tunneling advanced detection and the like.