Experimental Study On Freeze-thaw Damage Of High-cold Surface Coal Mine Road Based On Geopolymer Modification

During the mining and transportation of open-pit coal mines,the structure of temporary non-hardened mine roads is mainly a mixture of soil and rock,which is prone to dust hazards due to rolling and wind blowing.The geopolymer is used to consolidate the soil-rock mixture in the road to meet certain strength requirements and meet the short-term use of the mine.However,in the high-cold open-pit coal mine,affected by weather changes,freezing and thawing will affect the long-term use and normal use of the road safe operation.Based on this,the Yimin Open-pit Coal Mine was used as the research object of the alpine open-pit coal mine to explore the changes in the mechanical properties of the modified mine road materials under different freezing temperatures and different cycles of freezing and thawing,and to study its microscopic changes.According to the initial test design,plan A29 was selected for the on-site road construction test of Yimin Coal Mine.After 28 days of curing,the uniaxial compressive strength can reach 20.96MPa,which meets the requirement of 15MPa for the mine temporary road strength.The on-site test results have passed the mining vehicle rolling inspection,On this basis,conduct a freeze-thaw test.As the freezing temperature decreases,the strength of the sample decreases first and then tends to be stable.Specifically:the uniaxial compressive strength decreases after fitting and shows a quadratic function curve,which decreases from 21.62MPa without freezing and thawing.To 13.19MPa at-35℃,the strength is reduced to 61%;after fitting,the tensile strength is reduced by a quadratic function curve,from 2.43MPa without freezing and thawing to 1.19MPa at-35℃,and the strength is reduced It is49%,which is greater than the uniaxial compressive strength loss;after fitting,the cohesion of the sample decreases in a linear function,from 4.35MPa under no freeze-thaw to 2.31MPa under-35℃,and the internal friction angle changes irregularly.With the increase in the number of freeze-thaw cycles,the strength of the sample shows a linear decline.Specifically:the uniaxial compressive strength decreases linearly after fitting,from 21.62MPa under no freeze-thaw cycles to 11.63 under 50cycles.MPa,the strength is reduced to 54%;after fitting,the tensile strength decreases in a linear function,from 2.43 MPa without freezing and thawing to 1.09 MPa under50 times,and the strength is reduced to 45%,which is greater than the uniaxial compressive strength Loss:The cohesion of the sample decreases linearly after fitting,from 4.35 MPa under no freeze-thaw to 1.82 MPa under 50 times,and the internal friction angle changes irregularly.Through the use of SEM electron microscope scanning test,the microscopic morphology of the sample after failure is analyzed,specifically:as the number of freeze-thaw cycles increases,the internal structure of the sample gradually becomes looser,and the fracture mode changes from ductile fracture to transgranular fracture.It becomes intergranular fracture,and the energy consumption during failure is gradually reduced,that is,the maximum load during failure is reduced;the energy spectrum analysis of the fracture zone of the sample shows that the main elements are changed from O,Si,Al without freezing and thawing It is the O,Ca,and Si after freezing and thawing.According to the high content of Ca O in the slag and the high content of Al₂O₃in the fly ash,it can be obtained that the rupture area of the sample before freezing and thawing is dominated by the accumulation of fly ash,and the test after freezing and thawing The sample fracture area is dominated by slag accumulation,which means that the degradation of slag after freezing and thawing is higher than that of fly ash.The paper has 83 pictures,30 tables,and 93 references.