A study on dynamic shear strength on frozen soil-concrete interface

Using newly developed dynamic shearing devices, the dynamic sheafing strength of frozen soil-conerete interface was studied experimentally. By placing concrete blocks in the lower half of the shear box and frozen soil sample in the upper part, a series of dynamic shear tests on their interfaces were carried out. The obtained results are summarized and the main influencing factors are revealed.

Testing and modeling of frozen clay-concrete interface behavior based on large-scale shear tests

The shear behavior of the frozen soil-structure interface is important for accurately predicting the interface responses of structures adopted in the cold regions.The purpose of this study is to experimentally and theoretically investigate the shear behavior of frozen clay-concrete interface under engineering conditions.A large-scale direct shear apparatus with a temperature-controlled shear box is used to test the interface behavior.Test specimens consisting of a cement concrete block and frozen soil with initial water content ranging between 14.6%and 24.6%were prepared at different conditions of temperatures(15.4 to-9.8℃),shear rates(0.03-0.9 mm min^(-1)),and normal stresses(50-200 kPaj.It is found that the peak shear strength is linear developing with increasing of normal stress,initial water content,and temperature.It increased from 67.7 to 133.3 kPa as the initial water content increased from 14.9%to 24.6%at temperature of-6.8 to-6.6℃,and it increased from 51.2 to 80.6 kPa with temperature decreasing from 15.4 to-9.8℃at initial water content of 14.6%-14.9%,furthermore it has a power law relationship with shear rate.The final vertical displacement increases with the decreasing temperature,and increasing initial water content.While,it is slight or could be ignored at lower shear rates(e.g.0.03 mm min^(-1) and 0.15 mm min^(-1))and it is-0.25 mm and-0.28 mm at shear rate of 0.3 mm min^(-1) and 0.9 mm min^(-1),respectively.In addition,the evolution of vertical displacement also varies with test condition,the growth rate at beginning increases with increasing initial water content and decreasing temperature or ice content,which is because of the ice film effects the particle size.Moreover,a disturbed state concept model combined with linear and nonlinear characteristics is developed to describe the interface shear behavior.The disturbance D reflects the interface mechanical response and responds differently trend for different test conditions,increasing faster with increasing temperature and decreasing initial water content or shear rate.The testing results,including the test and model results,can be used to simulate the performance of engineered geotechnical assets such as earth dams or irrigation channels with concrete linings in cold regions.

Elastoplastic behavior of frozen sand-concrete interfaces under cyclic shear loading

The resilient modulus,accumulated plastic strain,peak shear stress,and critical shear stress are the elastoplastic behaviors of frozen sand–concrete interfaces under cyclic shear loading.They reflect the bearing capacity of buildings(e.g.highspeed railways)in both seasonal frozen and permafrost regions.This study describes a series of direct shear experiments conducted on frozen sand–concrete interfaces.The results indicated that the elastoplastic behaviors of frozen sand–concrete interfaces,including the resilient modulus,accumulated plastic strain,and shear strength,are influenced by the boundary conditions(constant normal loading and constant normal height),initial normal stress,negative temperature,and cyclic-loading amplitude.The resilient modulus was significantly correlated with the initial normal stress and negative temperature,but not with the cyclic-loading amplitude and loading cycles.The accumulated plastic shear strain increased when the initial normal stress and cyclic-loading amplitude increased and the temperature decreased.Moreover,the accumulated plastic shear strain increment decreased when the loading cycles increased.The accumulated direction also varied with changes in the initial normal stress,negative temperature,and cyclic-loading amplitude.The peak shear stress of the frozen sand–concrete interface was affected by the initial normal stress,negative temperature,cyclic-loading amplitude,and boundary conditions.Nevertheless,a correlation was observed between the critical shear stress and the initial normal stress and boundary conditions.The peak shear stress was higher,and the critical shear stress was lower under the constant normal height boundary condition.Based on the results,it appears that the properties of frozen sand–concrete interfaces,including plastic deformation properties and stress strength properties,are influenced by cyclic shear stress.These results provide valuable information for the investigation of constitutive models of frozen soil–structure interfaces.

Frozen sand-concrete interface direct shear behavior under constant normal load and constant normal height boundary

The shear strength properties of the frozen sand–structure interface are critical for evaluating the serviceability of pile foundations in frozen ground.The shear characteristics of the frozen sand–concrete interface were studied with two boundary conditions(constant normal load(CNL)and constant normal height(CNH)),at three normal stresses(100,200,and 300 k Pa),and at three temperatures(-2,-5,and-8℃).A detailed comparative analysis was performed to explore the principal factors affecting the shear/normal-shear displacement.The results showed that the shear behavior of the frozen sand–concrete interface under CNL was similar to that under CNH.The shear stress–shear displacement exhibited strain softening.The temperature and normal stress were the major influences on normal properties.The lower the temperature and the higher the normal stress,the greater was the elastic shear modulus.The peak shear stress and critical shear stress exhibited a dependence on normal stress.An exponential growth in the peak shear stress was observed as the temperature decreased.Critical shear stress was dependent on temperature.The value and percentage of peak ice-cementation in peak shear stress was affected by temperature and normal stress.