Experimental Study On Mechanical Performance And Frost Heave Force Of Pile-soil Interface In Seasonal Frozen Area

The interaction between soil and structure is an important research in the field of geotechnical engineering.The contact problem is reflected in many engineering practices and contains different types of soil surface effects.Such as piles in various types of projects,ground-connected walls in foundation pits,culvert tunnel supports,cut-off walls,retaining walls,and various types of building foundations,etc.During the freezing process of soil in seasonal frozen soil area,the freezing strength between structural foundation and soil is a key index to evaluate its anti-jacking-up performance.It is usually measured by the interfacial shear strength between the foundation material under the freezing state and the soil.Therefore,this paper redefines a roughness algorithm which is suitable for geotechnical field by introducing the concept of“extended surface ratio”.Based on the improved roughness algorithm,the shear stress-displacement relationship,shear strength and shear strength index are used as evaluation indexes,and roughness,temperature,water content and normal stress are regarded as influencing factors,evolution law of mechanical properties of structural soil-structure interface and the low of freezing and pulling of rough piles were studied and analyzed.Through the experimental research,the following results are obtained:?1?The roughness algorithm is improved by introducing the concept of"extended surface ratio".It is defined thatR=R₀+R_S is the roughness of the geotechnical structure surface,₀R is the roughness of the smooth structure surface,which is the basic roughness,and _SR is the"extended surface ratio"of the structural surface.?2?The shear stress-displacement curve of the soil-structure interface exhibits a strain hardening mode under normal temperature conditions,while the strain softening mode appears under freezing conditions,and the lower the temperature,the more pronounced the softening characteristics.?3?Under different normal stress,temperature and water content,the shear strength,cohesive force and internal friction angle all showed a linear growth trend with the increase of roughness.Among these factors,the temperature effect is particularly significant.?4?Under the same normal stress and roughness conditions,the decrease of temperature and the increase of water content will greatly improve the shear strength of the soil-structure contact surface.Different from the shear strength of the contact surface under normal temperature.The shear strength of the soil-structure contact surface under the frozen state mainly comes from the contribution of the cohesive force,which is the cementation of the ice crystal.?5?The difference in roughness have a different impact on the freeze-drawing performance of the pile.Specifically,the greater the roughness of the same type of pile,the greater the freezing force,the effect of smooth piles on the freezing force is more obvious.At the same time,the difference in the type of groove on the pile side has different effects on the freezing and pulling of the pile.For the piles with the same roughness within the scope of the test,the greater the groove depth,the greater the strength of the soil on the pile side and the greater the freezing force.