Research On The Mechanical Behaviour Of The Buffer Backfill Material Based On The UH Model

Buffer backfill material plays an very important role in the high-level radioactive waste disposal.In recent years,more and more attention has been paid to the study on the mechanical properties of the buffer backfill material.In this paper,based on the deformation characteristics of the GMZ bentonite,the constitutive model which is suitable for the unsaturated expansive soils is proposed.After that,the model is applied to the calculation of the finite element software.1)UH model for unsaturated expansive soilsOn the basis of UH model for unsaturated soils,UH model for unsaturated expansive soils is proposed introducing an expansion volumetric strain coupled with the original plastic volumetric strain.The Model is capable of describing the high expansion and the effect of initial dry density and overconsolidation on expansion of the unsaturated expansive soils.2)The application of the model in finite element applicationAfter the UH model for unsaturated expansive soils is proposed,it is introduced into the finite element calculation through the UMAT subroutine of ABAQUS.In this paper,the UMAT subroutine of the UH model for unsaturated soils is extended to which can consider the effect of temperature of unsaturated soil,and is carried out by using the finite element simulation of three axis test.Then the expansion strain of expansive soil is added to the model subroutine,which can consider the effect of unsaturation,temperature and expansion effect.The subroutine is tested by the finite element simulation of swelling pressure test.3)Finite element simulation of the China-Mock-UpThe temperature field and the flow field of the China-Mock-Up test device are simulated by using ABAQUS finite element software.The subroutine for unsaturated expansive soils which can also considering the effect of temperature is used to calculate the swelling pressure of the bentonite.The changes of temperature,saturation and expansion pressure of the China-Mock-Up in 3 years has been obtained.