The shear stress strain characteristics of weakly cemented soft rock under roadway excavation stress path and its non-coaxial characteristics
To investigate the evolution law of principal stress rotation path caused by tunnel excavation and the resulting deformation in rock masses,a numerical model has been developed to explore the evolution of principal stress rotation paths and resultant rock mass deformations due to tunnel excavation,with a focus on weakly cemented soft rock tunnels.This model examines the changes in magnitude and direction of principal stresses surrounding the tunnel,induced by the excavation process.Parameters for loading states in excavation-disturbed rotational stress path experiments are determined through this investigation.Nine kinds of excavation disturbance stress rotation paths tests were conduct by using hollow torsional shear tests on weakly cemented soft rock.The spatial curve characteristics of shear stress-strain excavation distance law and non-coaxial angle variation in the stress(σz-σθ)-2τzθ plane was researched.Significant changes were observed in the magnitude and direction of principal stresses in the surrounding rock of the tunnel,including its floor,roof,andsidewalls,as excavation progressed.Particularly within the 2D range of the tunnel,strong stress rotation and abrupt stress magnitude changes occurred.Shear stress-strain curves at monitoring points in the surrounding rock,influenced by excavation disturbance stress,were observed to develop in patterns resembling V,Z or N shapes.Excavation disturbance in weakly cemented soft rock induced principal stress rotation,resulting in a non-coaxial angle between strain increment and stress directions.The non-coaxial angles peaked at 52.8°,-22.3° and30.6° forthe tunnel floor,roof and sidewalls,respectively,influenced by stress path variations.This research results light on the non-coaxial plastic deformation in rock masses,a result of principal stress rotation from tunnel excavation.The design level and disaster prevention capability of underground engineering are enhanced.
mining engineeringrock mass mechanicsexcavation disturbanceprincipal stress valueprincipal.stress directionnon-coaxial angle
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