Abstract: To investigate the effectiveness of Wenner AMN & MNB joint inversion imaging in the division of rock contact zones, a geoelectric model of soft and hard rock with integral and local surface highresistance bodies is constructed, and the response characteristics of different highdensity electrical arrays to the inversion resistivity are analyzed. Furthermore, the ability of Wenner AMN & MNB joint inversion imaging to identify the contact zone of rock strata under varying overburden resistivity and thickness is discussed, and the response characteristics of the resistivity section are investigated by changing the dip angle of the contact zone. The results reveal the following: (1) The interference of the local highresistance body on the inversion section is stronger than that of the whole high-resistance body, but the influence depth is shallow. (2) The inversion fracture surfaces of different arrays are consistent with the preset models, but the Wenner AMN & MNB joint inversion has a larger detection depth and a more detailed description of the dip angle. (3) With a decrease in overburden resistivity or an increase in overburden thickness, the identification ability of Wenner AMN & MNB joint inversion to dip angle decreases. (4) The Wenner AMN & MNB joint inversion can track the change of rock dip angle, but the highresistance overlying strata are prone to false lowresistance anomalies in the contact zone. Based on the application of rock stratum division of diversion tunnel at Si′an reservoir, the occurrence and position of contact zone obtained by Wenner AMN & MNB joint inversion imaging are more consistent with the actual exposure than those obtained by conventional electrical method device.

Key words: rock contact surface, soft and hard rock, highdensity electrical method, Wenner AMN &, MNB, combined resistivity imaging