Research On Energy Evolution Law And Constitutive Model Of High-strength Concrete In The Process Of Deformation And Failure Under Different Confining Pressure Conditions

With the rapid development of infrastructure,the height of ground buildings and the depth of underground structures are increasing.This makes the bearing capacity of concrete,which is the main structure of the building,higher requirements are put forward.However,whether in the ground structure or underground structure engineering,the concrete structure is often in a complex multi-directional stress state.It is of great significance to study the deformation and failure characteristics of concrete under multi axial loading to ensure the safety and stability of buildings.In this paper,the uniaxial and conventional triaxial compression tests of C60 and C70 high strength concrete under different confining pressures are carried out.According to the test,the deformation and failure characteristics of concrete in the compression process are analyzed.Based on the thermodynamic principle,the energy evolution law of the whole process of high strength concrete from the beginning to the failure under different stress states is studied.Finally,the statistical damage variable based on dissipative energy density is derived by using Weibull statistical law.Finally,based on the effective stress principle and hook’s law,the statistical damage constitutive model of high strength concrete is obtained,and the model is verified according to the test results.The results show that:(1)With the increase of confining pressure,the peak stress and the axial strain corresponding to the peak stress of concrete samples increase,and the failure mode of concrete samples transits from tension shear failure to shear failure with the increase of confining pressure.(2)During the compression process of concrete samples,the input energy of the test system to concrete samples is mainly stored in the form of elastic strain energy before the peak value of axial stress.In the post peak stage,the input energy is mainly released by elastic strain energy,which is transformed into various forms of energy dissipation with the destruction of concrete samples.(3)At the peak stress,the corresponding input energy density,elastic strain energy density and dissipation energy density have obvious confining pressure effect.The three energy densities increase with the increase of confining pressure,and the corresponding input energy density and dissipation energy density at the peak stress meet the good exponential function relationship with the confining pressure,and the corresponding elastic strain energy density and confining pressure at the peak stress meet a good linear relationship.(4)The shape change coefficient increases with the increase of axial stress,while the volume change coefficient decreases with the increase of axial stress.When the peak stress is reached,the volume change coefficient is smaller than the shape change coefficient.The experimental results are compared with the theoretical results calculated by the damage constitutive model of concrete.The results show that the damage constitutive model results established in this paper are in good agreement with the experimental results.Because the failure of materials is a state instability phenomenon driven by energy,and the transformation and transmission of energy are the essence of deformation and failure of materials,so the damage constitutive model based on energy method can better reflect the characteristics of concrete samples in the process of stress.Figure[33]Table[12]Reference[92]...