Abstract
Owing to salt erosion, the sandstone of Yungang Grottoes has widespread weathering diseases. The soluble salt develops reciprocating crystallization pressure under the action of dry and wet cycles to diminish the sandstone strength. Finally, several pore-like and powder-like weathering phenomena are formed. To explore the change in sandstone strength during this process, the sandstone of Yungang Grottoes was taken as the research object. Herein, the uniaxial compression test, XRD test, and other methods were employed to study the samples under different salt erosion cycles. As the number of salt damage cycles increased, the phenomenon of sand particles on the sandstone surface gradually amplified. The compressive strength, tensile strength, and elastic modulus of sandstone decreased with the increase in erosion cycles. The curve was divided into two stages, and the macroscopic and microscopic damage equations of sandstone after erosion were established. During the entire damage process, erosion damage served as the basis of load damage and was affected by different cycles, impacting the development process of load damage. Through the establishment of numerical simulation meso-parameter evolution equations, the PFC2D particle flow model was used to conduct uniaxial simulation tests, and the simulation results were close to the macroscopic test results. Using the particle flow simulation test parameters under salt erosion, the development of the distribution of “displacement-force chain-crack” was analyzed under different salt erosion cycles. These results further revealed the meso-fracture damage characteristics of the Yungang Grottoes sandstone under the action of salt damage and provided a theoretical basis and a novel method for the protection of Yungang Grottoes against weathering.
Highlights
Salt damage is the leading cause of sandstone weathering [1, 2]
When the soluble salt enriches the pores of sandstone, the soluble salt undergoes repeated crystallization under the alternating action of dry and wet cycles
Under the repeated action of dry and wet cycles for a long duration, the tensile strength of the surface rock is greatly reduced, gradually forming flakes, pores, and powder weathering, which severely threatens the preservation of the cultural relics of Yungang Grottoes
Summary
Salt damage is the leading cause of sandstone weathering [1, 2]. When the soluble salt enriches the pores of sandstone, the soluble salt undergoes repeated crystallization under the alternating action of dry and wet cycles. Under the repeated action of dry and wet cycles for a long duration, the tensile strength of the surface rock is greatly reduced, gradually forming flakes, pores, and powder weathering, which severely threatens the preservation of the cultural relics of Yungang Grottoes Sun et al [14] (2019) investigated the weathering of rocks under the combined action of freeze-thaw cycles and salt crystallization cycles They found that the crystallization pressure of salt and the frost heave of ice reduces the cohesive force between the particles and cause the particles to fall off, which is the most important factor causing sandstone damage. The Yungang Grottoes antiweathering protection path provides a novel method and theoretical basis [19,20,21,22,23]
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