Lateral deformation and acoustic emission characteristics of dam bedrock under various river flow scouring rates

Abstract

To investigate the lateral deformation characteristics of dam bedrock scoured by river flow environments, standard specimens were prepared using cored sandstone from the barrage bedrock at the Sanhekou Water Conservancy Dam. The mechanical parameters, microstructure, and mineral fractions of the sandstones were analyzed after water scouring at five different rates (0, 200, 400, 600, and 800 mm⋅s−1) for 49 days. Scanning electron microscopy (SEM), electron energy spectroscopy (EDS), and X-ray diffraction (XRD) techniques were employed to track the changes. Laboratory tests including uniaxial compression, acoustic emission (AE), and digital image correlation (DIC) were conducted to elucidate the deformation damage mechanism of the scoured sandstones. The results indicate the following: (1) During the crack closure and compaction stage, the deformation of the rock samples primarily involves axial compression with minimal lateral deformation. However, as the crack propagates unstably and expands after the peak load, the lateral strain of the specimens accelerates. The lateral-axial ratio of the samples remains relatively low during the initial scouring period but increases rapidly after the first drop in axial stress until the end of the test. Higher scouring rates and longer durations weaken the strength and exacerbate the deformation of the sandstone. Under a flow rate of 800 mm⋅s−1, the elastic modulus decreases by 45.67%, while Poisson's ratio increases by 73.67%. (2) The acoustic emission process exhibits distinct phases, including a calm phase, growth phase, and rapid rise phase. As the flow rate increases, the internal crack types in the sandstone transition from shear cracks to tensile cracks, corresponding to the shift from shear failure to cleavage failure. The sandstone's damage variables show progressive abrupt changes under flow rates of 0, 200, and 400 mm⋅s−1, while segmented growth is observed under flow rates of 600 and 800 mm⋅s−1. (3) After absorbing water in a dynamic water environment, the interparticle cementation capacity of the sandstone weakens due to softening, water-rock interactions, and swelling reactions of clay minerals. The overall structure becomes destabilized, ultimately leading to failure through deformation. These findings provide a basis for predicting destruction and analyzing the stability of rock masses during water absorption and expansion deformation under dynamic water conditions.

Keywords

• Sandstone
• Dynamic water scouring
• Lateral deformation
• Mechanical properties damage
• Acoustic emission