Investigation of the Degradation Mechanism of the Tensile Mechanical Properties of Sandstone under the Corrosion of Various pH Solutions.

The research aimed to examine the impact of different pH solutions on the tensile mechanical properties of saturated and natural sandstone specimens. The study utilized the WHY-300/10 microcomputer-controlled pressure testing machine to conduct Brazil splitting tests and employed acoustic emission and local dynamic strain testing techniques. The results indicated the tensile strength and split tensile modulus of the sandstone specimens gradually decreased with the polarisation of the solution pH, and the acoustic emission signal ring number monitoring values showed an increasing trend. The pH of the soaking solution followed an exponential decay pattern over time, eventually tending towards weak alkalinity. A new damage variable based on the cumulative ring count after chemical corrosion was defined to indirectly analyze the degree of corrosion degradation. It was discovered that in acidic or alkaline environments, the internal crystals of the rock are dissolved, weakening the mineral interconnections and causing a deterioration in tensile stress and strength. These findings can provide valuable insights for ensuring the safety and stability of the Denglou Mountain Tunnel in Yunnan Province.

Research of Dynamic Tensile Properties of Five Rocks under Three Loading Modes Based on SHPB Device.

The validity of calculating the dynamic tensile strength of rock materials based on dynamic Brazilian tests is problematic. In order to gain a deeper understanding of the effects of three typical loading methods on the damage mechanism of rock specimens in the dynamic Brazilian tests, five different rocks were selected for the study. In the constant incident energy dynamic Brazilian test, the loading modes had a significant effect on the loading rate and dynamic tensile strength of the specimen, with the highest loading rate and tensile strength of the specimens under mode-III loading, followed by mode-I loading and mode-II loading. A high-speed camera and the digital image correlation (DIC) technique were used to successfully capture the rupture process of the Brazilian disc during impact loading. The evolution of the displacement and strain fields of the specimen was obtained by DIC technique, and four typical failure patterns and two rupture characteristics in the dynamic Brazilian test were summarized. The loading mode determined the crack initiation position of the specimen in the dynamic Brazilian test. The results showed that the mode-III loading is the most consistent with the Brazilian test theory, while the mode-II loading violates the test principle.