MA Q, LIU Y, CUI Q,et al.Strength degradation and load-induced failure modes of fractured sandstone under freeze-thaw cycles[J].Journal of Henan Polytechnic University(Natural Science) ,2026,45(4):140-149.

doi:10.16186/j.cnki.1673-9787.2025100001

Received:2025/09/30

Revised:2025/12/23

Published:2026/06/17

Strength degradation and load-induced failure modes of fractured sandstone under freeze-thaw cycles

Ma Qiang1, Liu Yan1, Cui Qiang2, Liu Ran1

1.Economic and Technological Research Institute， State Grid Liaoning Electric Power Co.， Ltd.， Shenyang  110027， Liaoning， China;2.State Grid Electric Power Engineering Research Institute Co.， Ltd.， Beijing  102401， China

Abstract: Objectives To clarify the mechanical response of fractured sandstone under coupled freeze-thaw cycling and confining pressure conditions， the effects of freeze-thaw cycles and confining pressure on its mechanical properties and failure mechanisms were investigated.  Methods Gray sandstone was selected as the research material. Intact，  single-fractured， and cross-fractured specimens were prepared and subjected to 0， 30，  60， and 90 freeze-thaw cycles. Uniaxial compression tests and triaxial compression tests  under confining pressures of 5 MPa and 10 MPa were conducted.. Stress-strain curves were obtained， and characteristic stresses including crack closure stress， crack initiation stress， and peak stress were extracted. Combined with analyses fracture distribution and failure patterns， the mechanical evolution of different specimens under freeze-thaw and confining pressure coupling was systematically investigated. Results With increasing freeze-thaw cycles， the characteristic stresses of all specimen types decreased， and the overall stiffness was reduced. Intact specimens exhibited significant early-stage damage followed by a gradual stabilization. Single-fractured specimens showed rapid crack propagation in the initial stage and slower development thereafter. Cross-fractured specimens exhibited the most complex damage evolution due to interactions among fractures. Under low confining pressure， multiple crack types and complex failure patterns were observed. Under high confining pressure， the failure mode gradually transitioned from shear-dominated failure to shear-tensile composite failure. Freeze-thaw cycling intensified stress concentration at fracture intersections. Under uniaxial loading， failure tended to be tensile-dominated or disintegrative， while under triaxial conditions with low confining pressure， shear-tensile composite failure was dominant. Conclusions Freeze-thaw cycling and confining pressure jointly govern the mechanical evolution of fractured sandstone. Freeze-thaw cycling significantly weakens rock strength and promotes crack coalescence， while confining pressure partially suppresses deterioration and inhibits tensile cracking. Compared with intact specimens， cross-fractured specimens exhibit greater reductions in peak strength and characteristic stresses. Their fractures tend to propagate in multiple directions and form interconnected fracture networks， thereby enhancing the sensitivity of fractured sandstone to freez-thaw damage and mechanical loading. These results provide theoretical support for tunnel construction， slope stability evaluation， and disaster prevention in cold-regions engineering.

Key words:freeze-thaw cycle;fractured sandstone;failure mode;confining pressure effect