Investigation on the Micro-structure Evolution and Mechanical Damage Characteristics of 3D Printed Rock with Prefabricated Defects under Freeze-Thaw Cycles
Freeze-thaw damage of rocks is a significant factor leading to the loss of stability and destruction of in-service geotechnical engineering structures in cold regions.Macroscopic rock failure often goes through a damage process of micro-crack initiation,development,coalescence,and penetration at the microscale,which is the fatigue damage that occurs to the rock's initial defects(pore-fracture struc-ture)under the action of cyclical freeze-thaw expansion forces.To investigate the microstructural evolu-tion and mechanical property degradation characteristics of 3D printed rocks with initial defects under freeze-thaw cycles,uniaxial compression test and SEM imaging test were conducted to analyze the me-chanical property degradation characteristics and microstructural evolution patterns of 3D printed rocks un-der different freeze-thaw conditions.The CT scanning three-dimensional reconstruction technology was used to obtain and reconstruct the equivalent pore network model of the samples,and the variation of the microstructural parameters such as porosity,permeability,and pore throat number of the samples with the number of freeze-thaw cycles were quantitatively analyzed.A freeze-thaw damage variable defined by pore structure parameters was established,and the evolution rule of the freeze-thaw damage variable with the increase of freeze-thaw cycles was analyzed.The results show that the presence of prefabricated cracks significantly increases the brittleness of 3D printed rocks.With the increase of freeze-thaw cy-cles,the original cementation between sand grains is destroyed under the influence of cyclical freeze-thaw expansion,micro-cracks begin to initiate,the arrangement of particles gradually becomes disorder-ed,and both the number and size of pores increase.The development of the freeze-thaw damage varia-ble goes through three stages:slow increase,stable growth,and rapid development.The research findings of this paper provide a non-destructive and quantitative research method for revealing the intrinsic relation-ship between the macroscopic mechanical property degradation of rocks and microstructural evolution un-der freeze-thaw cycles.It can provide theoretical guidance for the prevention and control of freeze-thaw damage in geotechnical engineering in cold regions.
3D printingFreeze-thaw cycleCT scanMicroscopic structureDamage variable
万方数据
维普
