Study On The Damage Evolution Law And Risk Level Evaluation Of Helankou Site Carrier Rock

There are a large number of complex and culturally rock paintings distributed in the Helankou Site,which is an important part of northern rock paintings and holds an important position in the world.However,cracks,peeling,collapse,salt stains,and other diseases appear on the surface of rock paintings,and even some rock paintings are on the brink of disappearance,because of long-term outdoor exposure,corrosion by aqueous chemical solutions,extreme temperature changes,and long-term repeated loading.Therefore,this article conducts a statistical investigation of the diseases in the Helankou Site,collects rock painting carrier rocks for indoor simulation deterioration tests,uniaxial/triaxial compression acoustic emission tests,scanning electron microscopy tests,and X-ray diffraction tests,compares the differences in the degree of rock deterioration under different degradation environments,analyzes the deterioration laws of physical and mechanical properties of rocks and the micro damage characteristics,and conduct weathering assessment research based on the statistical results of disease investigation.The main research results of this article are as follows:Firstly,a survey was conducted on three typical diseases of cracks,spalling,and collapse in the site area.The statistical analysis revealed that crack diseases can be divided into two types based on their impact on rock paintings:weathered cracks and non weathered cracks,with a certain positive correlation between their crack densities.There are five forms of spalling disease,which are in descending order of weathering degree:layered peeling,flaky peeling,scaly peeling,granular peeling,and powder peeling.The collapse risk of rock paintings can be measured by rebound value,joint inclination,and the nearest collapse distance.Secondly,in indoor simulation deterioration tests,under the same deterioration environment and confining pressure,as the number of cycles increases,the quality of rock decreases,the porosity increases,wave velocity decreases,rebound value decreases,peak stress decreases,and residual stress decreases.After experiencing a long-term deterioration process,the degree of deterioration in each environment is as follows:dry group<pH=7 group<NaCl group<CaCl2 group<Na2SO4 group<pH=2 group.The process of deterioration and confining pressure lead to a transition from brittleness to plasticity in rock.The linear function can better fit the change of physical and mechanical properties of rock in dry,neutral and acid water environments.The quadratic function without a linear term can better fit the change of physical and mechanical properties of sandstone under three salt solution environments of NaCl,CaCl2 and Na2SO4.Thirdly,in the acoustic emission test,the ringing count and energy count change are divided into five stages,corresponding to the stress change process.The peak values of ringing count and energy count increase with the increase of confining pressure and decrease with the increase of deterioration degree.The 3D positioning can accurately capture the generation,development,and expansion of cracks and pores in rocks during compression process.Under high cycles,severe deterioration of the environment,and low confining pressure,the main fracture mode of rock samples is tensile failure with single fracture surface.Under high cycles,severe deterioration of the environment,and high confining pressure,the main fracture mode of rock samples is shear failure with multi fracture surface.Under low cycles or gentle deterioration of the environment,the main fracture mode of rock samples is shear failure with single fracture surface.Finally,establish a fuzzy tomographic analysis evaluation model,with the weathering degree ranking as follows:collapse>environment=peeling>cracks.In the evaluation of the weathering degree of rock paintings,the number of moderately weathered and highly weathered rock paintings is the highest,while the number of low weathered and extremely low weathered rock paintings is relatively small.There is currently no rock painting in a highly weathered state,and the evaluation results are consistent with the on-site investigation results.The research results of this article provide a theoretical basis for evaluating the preservation status of cultural relics,and have practical significance for formulating precise prevention and management decisions of cultural relics protection.