| The Wuyi Mountains are located in a subtropical monsoon humid climate zone with abundant rainfall,making it a typical acid rain area in China.The area also experiences hot and rainy periods simultaneously and has a well-developed surface water system.These natural environmental factors cause the rock formations in the scenic area to continuously experience acidic environmental dry-wet cycles,resulting in the deterioration of the rocks and gradual peeling of the rock surface,directly affecting the stability of the scenic rock formations.This article focuses on the study of the mechanical properties and deterioration mechanism of the red glutenite in the Wuyi Mountain Scenic Area.By using a combination of experimental research and theoretical analysis,the physical and mechanical properties of the red glutenite under different acidic environmental dry-wet cycles were analyzed,as well as the changes in its microstructure and chemical composition.The deterioration mechanism was then revealed from macroscopic and microscopic perspectives,and a damage constitutive model of the red glutenite considering the coupling effect of acidic environmental dry-wet cycles and loads was established based on the experimental data.The main research contents and results are as follows:(1)Density tests,ultrasonic longitudinal wave velocity tests,and uniaxial compression tests were carried out on the red glutenite under different acidic environmental dry-wet cycles to analyze the changes in density,ultrasonic longitudinal wave velocity,uniaxial compression strength,and elastic modulus of the red glutenite with changes in the p H value of the solution and the number of dry-wet cycles.The study found that these physical and mechanical parameters all decrease significantly with the increase in solution acidity and the number of dry-wet cycles.(2)Based on the experimental data,the sensitivity of the mechanical parameters to the p H value of the solution and the number of dry-wet cycles was analyzed.The results showed that the sensitivity of the uniaxial compression strength to the p H value of the solution and the number of dry-wet cycles is higher than that of the elastic modulus.A uniaxial compressive strength prediction model was obtained by regression fitting,which has a high fitting degree and can better reflect the relationship between uniaxial compressive strength and changes in the p H value of the solution and the number of dry-wet cycles.(3)Field emission scanning electron microscopy(FESEM)tests were carried out on the red glutenite under acidic environmental dry-wet cycles,and image processing software was used to perform image processing and quantitative identification of the microstructure of the red glutenite,as well as to quantitatively analyze its microstructural changes,revealing its damage characteristics from a microscopic perspective.(4)To explore the effects of acidic environmental dry-wet cycles on the mineral composition of the red glutenite,X-ray diffraction(XRD)mineral composition analysis was carried out,and the effects of acidic environmental dry-wet cycles on the mineral composition of the red glutenite were studied.The main mineral components of th red glutenite are quartz,calcite,sodium feldspar,illite,and zeolite.The relative content of calcite,sodium feldspar,and illite decreases significantly with the increase in the number of dry-wet cycles and the increase in solution acidity,while the chemical properties of quartz are relatively stable,and its relative content gradually increases with the increase in the number of dry-wet cycles and the increase in solution acidity.(5)By integrating the experimental results of FESEM and XRD,this study investigates the damage mechanism of red glutenite under the influence of acidic environmental dry-wet cycles.It is believed that the water-rock interaction and drying-wetting process are the main factors that cause the constant changes in the microstructure and mineral composition of red glutenite,ultimately leading to the alteration of its physical and mechanical properties.(6)Acoustic emission tests conducted on red glutenite under acidic environmental dry-wet cycles show that during the uniaxial compression test,the acoustic emission of red glutenite exhibits distinct stage characteristics.The impact and absolute energy evolution laws of each sample are roughly the same and can be divided into four stages: the compaction stage,the elastic stage,the plastic stage,and the failure stage.With the increase in the number of dry-wet cycles and the decrease in solution p H value,the cumulative absolute energy gradually increases.(7)The study on the energy evolution law of uniaxial compression tests of red glutenite treated by acidic environmental dry-wet cycles shows that the energy input from external factors to the rock system is mainly converted into dissipated energy and elastic energy,and there is a mutually exclusive relationship between dissipated energy and elastic energy.With the increase in the number of dry-wet cycles and the decrease in solution p H value,the total input energy and peak elastic energy of the sample both show a decreasing trend.(8)Based on the Weibull distribution of red glutenite microelement strength and introducing damage variables,a damage constitutive model of red glutenite under the influence of acidic environmental dry-wet cycles is established using the continuous medium damage mechanics theory and the Lemaitre strain equivalence hypothesis theory.The rationality of the model is verified by comparing it with experimental data.This research was supported by the Fujian Provincial Science and Technology Guiding Project(2020Y0092)“Development of Rock Mass Landscape Structural Surface Restoration Technology in Jiuqu River Scenic Area of Wuyi Mountain”.The research results provide a large amount of basic data and theoretical support for the project and have important practical significance for the restoration of rock mass structural surfaces in the Wuyi Mountain Scenic Area. |
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