Study On Bank Slope Stability And Bank Slope Protection In The Inner Mongolia Shisifenzi Reach Of The Yellow River Under Freeze-thaw Action

The rock and soil that is frozen in winter and completely melted in summer is called seasonal frozen soil.Seasonal frozen soil is distributed in all provinces and regions north of the Yangtze River in China,accounting for about 54 % of China territory.Affected by the periodic change of temperature,the soil of the bank slope in the Inner Mongolia section of the Yellow River will undergo repeated freezing-thawing processes,resulting in the attenuation of the physical and mechanical properties of the soil.Under the action of water erosion and ice impact,the bank slope will aggravate the destruction of the bank slope and increase the possibility of bank slope collapse.Therefore,it is of great significance to clarify the damage effect and law of freeze-thaw action on soil characteristics,study the influence of freeze-thaw action on bank slope stability,and explore the protection measures of bank slope in seasonal frozen area to maintain the safety of the Yellow River.Based on the freeze-thaw tests of the Yellow River bank slope soil under different freezing temperatures and freeze-thaw cycles,this thesis explores the mechanical changes of the bank slope soil under different confining pressures.According to the mechanical strength parameters of soil,the stability of bank slope soil is simulated and analyzed by ABAQUS finite element software.The influence of freeze-thaw erosion on the stability of bank slope is studied,and the protective effect of gabion cage protection measures on the stability of bank slope is explored.The main research results are as follows :(1)Through the data obtained from the soil moisture monitoring system,it is concluded that the freezing and thawing depth of the soil on the curved bank slope of the Yellow River is 160 cm.Based on the physical properties test of bank slope soil,it is determined that the soil of the Yellow River Shisifenzi bank slope is low liquid limit silt.(2)The more the number of freeze-thaw cycles,the lower the freezing temperature,the more obvious the softening effect on the stress-strain curve of the soil.Under high confining pressure,the softening effect of the stress-strain curve weakens the number of freeze-thaw cycles,and the freezing temperature has a certain attenuation effect on the mechanical parameters of the soil.After 10 freeze-thaw cycles,the attenuation range of cohesion,internal friction angle and elastic modulus of slope soil under different freezing temperatures is 9.24%-23.06%,3.33%-6.81% and 41.45%-63.91%,respectively.(3)The failure surface of the bank slope is an arc sliding surface.After the freeze-thaw cycle,the safety factors of the bank slopes with slopes of 30 degree,45 degree and 60 degree are attenuated by 4.8%,9.7% and 8.3%,respectively.The stability of the bank slope is reduced due to the damage effect of freeze-thaw action.The greater the slope gradient,the worse the stability.(4)Compared with the unreinforced bank slope,the safety factors of slope and wall gabion gabion reinforcement are increased by 24.1% and 26.2% respectively.Gabion stone cage has an important reinforcing effect on the stability of bank slope.