Effect of Dry–Wet Cycling on the Degradation Characteristics and Mechanisms of Red Sandstone

Abstract

The physical and mechanical parameters and degradation mechanisms of red sandstone in the Mount Wuyi scenic area were studied under the action of dry–wet cycles. Dry–wet cycle, acoustic wave velocity, water saturation rate, and triaxial compression tests were conducted, aided by scanning electron microscopy and X-ray diffraction testing techniques. The study’s results show that the dry–wet cycle effect on red sandstone is a major factor in the degradation of its physical and mechanical parameters and that its microstructural characteristics are significantly affected. The P-wave velocity, peak strength, elastic modulus, internal friction angle, and cohesion decreased, the water content and peak strain increased, and the elastic modulus was the most sensitive to dry–wet cycles. A dry–wet cycle’s action severely damages the microstructural integrity of the red sandstone. After 15 dry–wet cycles, the interstitial fillings between the skeletal grains are dissolved over a large area, microfractures are interwoven throughout, and the structure is severely fragmented. The microstructural degradation of the red sandstone by dry–wet cycles mainly manifests in the dissolution of the interstitial filler, and the relative content of calcite as an interstitial filler is reduced by 46.6% after 15 dry–wet cycles. The proposed strength decay prediction equation has reference significance for the strength prediction of the red sand conglomerate in the project. This study’s results can provide theoretical support for the landscape protection of rock masses and the prevention of engineering geological hazards.

Experimental Study on Erosion Modeling of Architectural Red Sandstone under the Action of the Natural Environment

“…Using the water-absorbing properties of sponge sheets to simulate the external erosive environment, wet and dry cycle tests were carried out on two types of red sandstone. Following the test method described in references [23,29], all specimens processed were dried in a drying oven at a temperature of 80 • C for 24 h and cooled for 1 h. The sponge sheet saturated with sulfate solution was placed on top of the machined specimens to erode the specimens for 24 h, which is one dry and one wet cycle. The experiment found that after one cycle, the ultrasonic data change is small, so take every two cycles to measure and record the ultrasonic velocity of the specimen and twenty wet and dry cycles to obtain ten sets of data.…”