Experimental Study On Shear Mechanical Properties Of Cured Silty Soil-concrete Interface

Since soft soils have undesirable engineering properties such as high water content,high compressibility,and low bearing capacity,they frequently need to be cured in practical engineering to meet the requirements of pile foundations and construction machinery for foundation stability.As the main material required for pile foundation construction,the mechanical properties of the contact surface between concrete and cured soft soil have a noticeable impact on the quality of the pile foundation construction.In order to investigate the shear mechanical properties of the interface between cured soft soil and concrete,this paper selects silty soil as the original sample soil,cures it with different types of curing agents,and investigates the effects of factors such as the type and content of curing agents,the age of specimen curing and the roughness of the interface on the shear mechanical behavior of the cured silty soil-concrete interface using indoor uniaxial compression test and direct shear test.The main work and results are as follows:（1）Mg O and Si O₂were selected as the two main curing agents,and quicklime,cement and triathlon were used as admixtures to cure the silt soil.The cured silt soil was cured for 7d,14d and 28d,followed by a uniaxial compression test and a direct shear test to analyze the resulting test data and observe the apparent characteristics of the cured silt-concrete interface after the shear test.（2）The results of uniaxial compression tests found that the compressive strength of the cured silt soil increased with the increase of curing age under the combined effect of curing agent and admixture,followed by the highest compressive strength of 12%Mg O cured silt soil,then 12%and 6%Si O₂cured treated silt soil in order,and the lowest compressive strength of6%Mg O cured silt soil.It shows that 12%Mg O has the best curing effect on silt soil,while6%Mg O is the weakest.Curing agent type,content,and curing environment can affect the rate of hydration reaction of the curing agent,which in turn affects the mechanical properties of the cured silt soil.（3）By observing the apparent characteristics of the concrete interface,and the higher the degree of curing of the silt soil with the extension of the curing age,the less the residual amount of water and soil stains within the shear interface.As the surface roughness of the concrete increases,the amount of residual water and soil stains in the interface increases.After28 days of curing,there were varying amounts of water and soil stains at the shear interface between the silty loam and the concrete.（4）The shear strength and shear strength indexes increase with the increase of interfacial roughness and curing agent content;variation in interfacial shear strength with curing age is affected by the type and content of the curing agent;the cohesion tends to decrease and then increase with age,while the inner friction angle increases with age;the shear strength and cohesion of the interface between Si O₂cured silt and concrete is slightly higher than that of Mg O;the internal friction angle of the interface is positively correlated with the degree of curing of the silt.（5）An orthogonal test was designed to investigate the influence of various test factors on the shear mechanical properties of the cured silt-clay-concrete interface by using the analysis of extreme differences.It was found that the normal stress had the greatest influence on the shear mechanical properties,followed by the curing age of the cured silt,the roughness of the interface and the type of the curing agent,with the least influence coming from the curing agent content.（6）According to Duncan-Zhang theory,combined with the results of the application of hyperbolic model in shear test,the initial tangential deformation modulus is simplified,and based on the test data,the modified hyperbolic model is established under different maintenance age conditions,and the model parameters are solved to verify the applicability of the model to the shear test of cured silt-concrete interface.