Detection of two anomalies behind the Eastern face of the Menkaure Pyramid using a combination of non-destructive testing techniques

The Menkaure Pyramid is the smallest of the three main pyramids on the Giza Plateau. Recently, the possibility of a second entrance to the Pyramid has been hypothesized by Van den Hoven [1], based on similarities between the polished granite blocks covering the Eastern face and the blocks around the main entrance on the Northern face. To test this hypothesis, measurement campaigns using three non-destructive techniques, Electrical Resistivity Tomography (ERT), Ground Penetrating Radar (GPR), and Ultrasonic Testing (UST), were carried out on the Eastern face of Menkaure Pyramid. ERT data was obtained from measurements of four long parallel profiles using stainless steel mesh electrodes and inverted using a three-dimensional inversion algorithm. These ERT results guided the more focused grid measurements of a dual-frequency GPR instrument (200/600 MHz antenna) and a 16-channel UST array device. Image Fusion (IF) was utilized to merge the reconstructed ERT, GPR, and UST images, allowing for precise correlation of the detected features from each technique. The images revealed two anomalies directly behind the polished granite blocks, which would indicate the presence of air-filled voids. This interpretation was supported by a series of numerical simulations that considered various possible scenarios under real-world conditions.