Mesoscopic Simulation Research On Calcareous Cemented Sandstone Under The Action Of Water Chemical Solution Based On Discrete Element Numerical Method

Water chemical solutions are widely present in rock mass engineering,and damage the physical and mechanical properties of rocks,such as reduced strength and cracks.Especially in the rapid development of industrialization,environmental problems such as river pollution and acid rain have exacerbated the degree of rock degradation,which has buried potential safety hazards for the normal use and operation of rock mass engineering,so it is of great engineering significance to study the mechanical properties of rock under the coupling of chemistry and mechanics.The macroscopic mechanical properties of rocks are controlled by their microstructures.Most rocks have the following microscopic features:(1)composed of mineral particles and crystalline or cemented connections between particles;(2)contains a large number of microdefects.When the rock in the water chemistry environment,the chemical solution will enter the interior through the cracks and holes in the rock,and react with the rock's mineral composition or the chemical substances between the particles,weakening the connection between the particles and changing the microstructure of rock.As the chemical reaction continues,the connection between the particles will become weaker and weaker,which leads to an increasing degree of rock corrosion degradation.This article takes calcareous cemented sandstone as an example,from a microscopic perspective,it mainly analyzes the mechanism of damage and deterioration of sandstone under acidic chemical environment and the change of microstructure before and after chemical corrosion.And a particle flow numerical simulation method that can quantitatively simulate the chemical corrosion process of rock over time by changing the bonding contact parameters is introduced,in order to study the damage and deterioration effect of rock in chemical solution by numerical experiment instead of laboratory experiment.The main research contents and results are as follows:(1)According to the existing laboratory test data,the damage of water chemistry on sandstone and the characteristics of its microstructure change were analyzed,and the chemical kinetic analysis of sandstone degradation was given.The dissolution and loss of soluble cement between sandstone particles is regarded as the main cause of sandstone water chemical damage.Based on the chemical reaction rate of cement,the amount of cement dissolved in sandstone during chemical corrosion is quantitatively counted.(2)Combined with the microstructure change of sandstone during corrosion,the particle flow code and the flat joint model that are more suitable for simulating chemical corrosion of rock were selected.The chemical corrosion process of sandstone changing with time was equivalent to the process of continuous dissolution of the soluble cement between mineral particles in sandstone,and finally converted into a process of continuously reducing the size of the bonding contact between particles in the particle flow code.In this way,chemical corrosion is introduced into discrete element model,and the calculation formula of the radius multiplier in the particle flow code under the action of water-rock chemistry was derived based on the dissolution rate of the soluble cement.(3)According to the laboratory corrosion test,a calibrated discrete element model was established,and the change rule of the parameter radius multiplier under the action of water chemistry was added to the flat joint contact of the particle flow code.The process of chemical corrosion and degradation of macro-mechanical properties of calcareous cemented sandstone was successfully simulated by numerical experiment and compared with the laboratory corrosion test.(4)Combined with the introduction of chemical corrosion in the particle flow code,a parameter sensitivity analysis is performed on the mesoscopic parameters that may have an impact on the simulation process,and the contact bond strength and contact elastic modulus were also used to simulate and reproduce the damage and degradation process of sandstone in water chemical solution.