Study On Dynamic Mechanical Properties And Failure Mechanism Of Frozen Rock With Ice-rock Structural Plane Architecture And Civil Engineering

The mine construction of the western passes through the deep water rich fissure bedrock.The freezing shaft sinking method is the most commonly used scheme for shaft excavation in this kind of stratum.The frozen wall is an important guarantee for the safety of shaft construction.Water rich fractured bedrock forms ice-rock composite structure under freezing conditions.Due to ice and frozen rock have different dynamic responses under blasting shock,the blasting shock wave generated during construction will not only change the properties of ice-rock structural plane,but also affect the overall stability of frozen rock mass.In this paper,the dynamic uniaxial impact compression test of frozen rock with ice-rock structural plane at different angles is carried out by SHPB test system and the research is carried out from the perspectives of stress wave propagation,dynamic response,energy dissipation and failure mechanism.The main research work and conclusions are as follows:(1)Trace and analyze the path of multiple reflection of stress wave at rock-ice,ice-rock interface and structural plane,deduce the stress expression of stress wave transmission and attenuation,and define the variation law of reflection coefficient and transmission coefficient.When the stress wave passes through a large structural plane angle,the attenuation is obvious,the reflection effect is weak and the transmission ability is strong.The weakening of stress wave on the structural plane is much greater than the strengthening of strain rate.At low strain rate,the ability of stress wave passing through the structural plane is limited.The stress wave is superimposed by multiple transmittance and reflection between structural planes in a very short time,and the decrease of transmittance and reflection coefficient is in an unstable fluctuation state.(2)The effects of temperature,strain rate and structural plane angle on the dynamic characteristics of frozen rock with ice-rock structural plane are explored.The stress wave fluctuation,dynamic stress-strain and peak strength show obvious strain rate strengthening effect and structural plane deterioration effect.The rate sensitivity decreases gradually with the increase of angle,the deterioration effect increases gradually with the increase of air pressure,and the through structural plane significantly reduces the ultimate bearing capacity of rock.(3)The transmission mechanism of stress wave is analyzed from the perspective of energy,and the process of rock impact damage is summarized combined with high-speed photographic images and final failure morphology.The incident energy,reflected energy and dissipated energy increase linearly with the increase of strain rate,and the transmission energy changes in a weak power function.With the increase of structural plane angle,the reflected energy increases,the dissipated energy decreases,and the transmission remains low.Under the low strain rate of 0° specimen,only the ice crystal in the structural plane is compressed and destroyed,and both ends remain intact.The 15°,30° and 45° specimens shear slip and stagger along the structural plane.The large angle structural plane reduces the stability of rock mass and effectively disperses the force of impact load.(4)The failure of rock mass with single structural plane is determined by internal factors(inherent strength)and external factors(external load).The stress and deformation characteristics are jointly controlled by the orientation of structural plane and the strength of each part.The strength of rock mass is related to the strength parameters(cohesion,friction angle)and interface angle of structural plane.Based on the strength theory,the failure modes mainly include ice compression,ice shear,ice rock compression and ice rock compression shear failure.From the ice adhesion strength theory,it can be divided into ice shear,ice rock interface separation and composite failure.The influencing factors are liquid water content(strain rate)and interface pressure(structural plane angle).This paper mainly studies the propagation and attenuation characteristics of stress wave in ice rock structural plane,the dynamic response characteristics of frozen rock with ice rock structural plane,energy dissipation mechanism and failure mechanism.The corresponding research results can provide reference for the design of freezing parameters of water rich fractured rock stratum.It is of great significance to the design and construction of shaft blasting excavation in western mining area and the treatment of dynamic instability accidents of surrounding rock.