Study On Deterioration Effect Of Limestone Under Dry-wetting Cycle In Acidic Environment

Due to the extensive existence of water in nature,water-rock interaction can be said to be the most common and extensive influence on rocks,and water-rock interaction is also one of the most popular and basic research topics in the field of geotechnical engineering.Water-rock action causes physical,chemical and mechanical damage to rock mass and degrades its various physical and mechanical parameters.And in recent years due to oil,coal and so on in the human production and living of the fuel emissions,cities and regions acid rain district formation,water-rock action gradually shift to acid conditions in aqueous environment,at the same time in the sun and rain,under the action of rock under dry-wet circulation state for a long time,thus aggravate the deterioration process of rock,while the degradation to a certain extent,geological disasters such as landslides,rock slope instability began to happen.In view of the above problems,this paper analyzes and explores the deterioration law and mechanism of mechanical and physical parameters of limestone through the experimental study of dry-wetting cycle in acidic environment of limestone.The main contents and results of the study are as follows:1)The hydroscopicity test,nuclear magnetic resonance test and immersion solution ion concentration detection test of limestone under different acting environments and different wetting and drying cycles were carried out,and the relationship between its mass loss rate,saturated water absorption rate,porosity and immersion solution ion concentration and the corresponding wetting and drying cycles was obtained.The results showed that the mass loss rate,saturated water absorption rate,porosity and ion concentration of soaking solution increased with the increase of drying and wetting cycles,and the increase was obvious in the early stage of the cycle but decreased in the late stage,the pore structure has also changed in different ways.2)Uniaxial compression tests of limestone under different operating environments and different dry-wet cycles were carried out to obtain the corresponding stress-strain curves,average uniaxial compressive strength and elastic modulus of limestone.Results showed that,on average,the uniaxial compressive strength and elastic modulus of different levels with the increase of dry-wet cycles decreases,and the degradation effects of limestone water can reflect on the deformation characteristics,especially the acid environment for limestone mechanical characteristics influence is bigger,can appear at the same time,the failure pattern of rock sample changes,mainly embodied in the cracks,and the function of the late cycle corrosion resulting in stripping vulnerable part of the sample surface.3)The Brazilian splitting test of limestone under different operating environments and different wetting and drying cycles was carried out,and the average uniaxial tensile strength of limestone was obtained.The results show that the average tensile strength is negatively correlated with the number of wetting and drying cycles,and positively correlated with the pH value.With the increase in the number of wetting and drying cycles,the vertical fracture becomes a lateral deflection fracture.,and the failure mode increases with the number of dry-wet cycles,and the vertical fracture turns into one with lateral deflection.4)The fitting formulas of the five parameters of water absorption,porosity,compressive strength,elastic modulus and tensile strength of limestone were normalized,and the deterioration degree of the physical and mechanical parameters under different action environments and different wetting and drying cycles was analyzed and compared.The results show that under the condition of pH=3,the deterioration degree law is porosity > water absorption > compressive strength > elasticity modulus >tensile strength;Under the conditions of pH=5 and pH=7,the deterioration degree is porosity > water absorption >elasticity modulus > compressive strength > tensile strength;Under different acting environments,the deterioration rule of the five parameters was pH=3 > pH=5 > pH =7.