Experimental Study On The Strength And Deformation Characteristics Of T-shaped Fractured Rock Mass

Discontinuous fractured rock masses are very common in rock mass engineering.It is of important theoretical and practical significance to study the deformation and failure mechanism and strength characteristics of discontinuous fractured rock masses.In this paper,the uniaxial compression test and triaxial compression test of the T-shaped fractured rock mass are carried out to study the mechanical properties and failure modes of the T-shaped fractured rock mass,and the constitutive model of the T-shaped fractured rock mass is established.The main research results and conclusions are as follows:(1)A uniaxial compression test was carried out to study the strength characteristics and deformation characteristics of the T-shaped fracture specimen,and the influence of the T-shaped fracture on the peak strength,elastic model,residual strength,and stress-strain of the rock mass was analyzed.The results show that the peak strength,residual strength,and elastic modulus of the fractured rock mass increase with the increase of the inclination of the single fracture.For T-shaped fractured rock mass,when the main fissure is 0°,the peak strength and elastic modulus of the sample increase with the increase of the angle between the primary and secondary fissures of the T-shaped fissure;when the main fissure is 45°,90°,With the increase of the angle between the primary and secondary cracks of the T-shaped crack,the peak strength and elastic modulus of the sample decrease.The failure modes of rock with single fissure and T-shaped fissure are shear failure and tensile failure;(2)A triaxial compression test was carried out to study the influence of confining pressure on the peak strength,elastic model,residual strength,and stress-strain of the T-shaped fractured rock mass.The results show that as the confining pressure increases,the peak strength of the sample increases.It is found that when the triaxial compression test increases from 0 MPa to 4 MPa,the peak strength of the sample increases greatly;as the confining pressure increases,The elastic modulus of the sample also gradually increased,but the rate of increase slowed down;the residual strength of the sample also increased with the increase of the confining pressure,when the confining pressure of the triaxial compression test increased from 0 MPa to 4 MPa,except Except for single-crack and T-shaped crack specimens with a crack inclination angle of 90°,the residual strength sensitivity of other specimens is generally higher;(3)With the increase of confining pressure,the T-shaped fractured specimens undergo shear failure first,and then the failure mode changes to tensile failure.Under the condition of uniaxial compression,for the specimens with the inclination of the main cracks of 0° and 90°,the secondary cracks participate in the destruction of the specimens,and the T-shaped crack specimens with the inclination of the main cracks of 45°,and the secondary cracks do not participate in the destruction of the specimens..Under triaxial compression conditions,when the confining pressure is greater than 4MPa,for the T-shaped fractured rock sample,the second fracture participates in the destruction of the sample,and the T-shaped fracture sample with the main fracture inclination angle of 90°,and the secondary fracture Destruction plays a leading role;(4)Under uniaxial compression,the specimen first undergoes shear failure,and then evolves into tensile failure.When the confining pressure is 4 MPa,it is found that for the 0°main crack sample,the secondary crack participates in the damage of the sample,while under uniaxial compression,for the 0° main crack sample,the secondary crack does not participate in the damage of the sample.As the confining pressure increases,for the 45° T-shaped crack specimen with the main crack specimen,the second crack begins to participate in the destruction of the specimen.For the T-shaped fracture specimen with the main fracture of 90°,the second fracture plays a leading role in damage;(5)Based on the Wei-bull distribution model,power function distribution model,and normal distribution model,a constitutive model of the T-shaped fractured rock mass is established,and the power function distribution model is more suitable for the T-shaped fractured rock mass.A good understanding of the applicability of the statistical distribution model.Under uniaxial compression,the experimental data of single fracture and T-shaped fractured rock mass are compared with the theoretical value of the constitutive model.The fitting effect of the power function constitutive model is ideal.Prove the rationality and applicability of the constitutive model.At the same time,the relationship between the parameter m,the parameter and the inclination angle of the T-shaped fracture specimen is analyzed.When the inclination angle of the main fracture is 0°,the parameter m decreases with the increase of the angle between the primary and secondary fractures.When the inclination angle of the main fracture is 45° and 90°,The parameter m increases with the increase of the angle between the primary and secondary cracks;the relationship between the parameter and the inclination angle of the T-shaped fracture specimen is that when the angle of the primary fracture is 0°,the parameter increases with the increase of the angle between the primary and secondary cracks When the inclination angle of the main fissure is 45° and 90°,the parameter decreases with the increase of the angle between the primary and secondary fissures.