| Fissured composite rock mass is a common surrounding rock mass in underground engineering construction.The safety and reliability of roadway or chamber is closely related to the stability of the surrounding rock.Fissured composite surrounding rock mass are particularly sensitive to the blasting vibration or mechanical disturbance that often occur,and the phenomenon of exfoliation or even collapse of surrounding rock of roadway is appeared,which seriously affects the smooth construction of the project.Therefore,it is necessary to study the mechanical properties and deformation failure of fissured composite rock mass.On the basis of static and dynamic mechanical tests of composite rock samples with different combined forms.The mechanical,deformation-failure and energy dissipation characteristics of fractured combination specimens under different fracture parameters and impact velocities are discussed in detail.The conclusions are as follows:(1)The basic mechanical parameters,such as strength,modulus of elasticity,Poisson ratio,and tensile strength of three kinds of specimens are obtained through the basic mechanical tests of remolded coal,mortar and combination specimens.Radial strains of combination specimens at different positions are different.The tensile strength of mortar is the largest,and the tensile strength at the joint surface of the combination is slightly larger than that of remolded coal.(2)The deformation and failure process of specimens under impact load is divided into three stages: elastic deformation stage,unsteady fracture development stage and post-failure stage.The peak strain of mortar is slightly smaller than that of the combinations and remolded coal at the same strain rate,and the latter two are similar when the strain rates are lower,and the coal monomer is larger when the strain rates are high.(3)The strengths of remolded coal,mortar monomers and complete combination specimens increase in a logarithmic manner with the increase of strain rates.Under the same fracture position and inclination angle,the strengths of combination specimens at three fracture positions are increase with the increase of strain rates.Under the same fracture position and strain rate,the strengths of the combination specimens at 90°inclination should be greater than that at 30°and 60°,and uncertain at 30°and 60°.The strengths of specimens which the crack is located in the mortar are the largest at the same fracture angle and strain rate.(4)The mortar part of the combination specimens has "strength extension effect".Fractures induced the failure of combination bodies,the fracture propagation modes of specimens with different fracture positions and angles are different.The two components of the combination specimens are more broken under the higher strain rates.(5)According to the dynamic stress-strain relationship of remolded coal and mortar monomers,a new damage constitutive model was established through further simplification and improvement based on ZWT model,and found that the model can well reflect the stress-strain relationship before peak stress of remolded coal and mortar.(6)The energy composition and dissipation characteristics of all kinds of specimens are analyzed.The absorption energy ratio and dissipation energy density of specimens are effected by the angle and position of fracture.Compared with complete combinations specimens,the absorption energy of specimens with cracks in mortar is larger,and close when cracks located in coal,and smaller in the joint surface.The gap among them decrease with the increase of fracture angle.The gap among the dissipative energy density of specimens at the same angle and different fracture positions are increase with the increase of strain rates,and the angle of 90 ° crack inclination has relatively little effects on the dissipative energy density of the combination specimens.The energy dissipation density of specimens with fissures in the coal body and the joint plane are smaller,and larger with fissures in the mortar. |
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