| Rock is not only a kind of natural aggregate widely distributed in underground engineering,but also an important material widely used in engineering construction.Under the action of external forces,the defects distributed in the rock form the initiation and development of cracks,which affects the mechanical properties of the rock in varying degrees and has a great impact on the construction quality and the safety of the project in the engineering application.The study of mechanical properties such as strength and deformation damage of rock with holes is of great significance to ensure the safety and stability of many projects.In this paper,the rock-like model test is used,the indoor uniaxial compression test of gypsum specimen with holes is carried out firstly,the deformation and fracture characteristics of rock with holes are analyzed,the damage degree of initial defects is evaluated quantitatively by the initial damage coefficient k,and then the meso-damage evolution of rock is further analyzed by simulating the specimen with holes by PFC2D.Furthermore,the influence law of pore on rock macroscopic mechanical parameters and the law of mesoscopic and macroscopic fracture evolution are obtained.Through the comparison of laboratory experiments to verify the feasibility of rock modeling with holes,the research results of this paper are as follows:(1)Taking the gypsum specimen as the research object,the rock specimens with holes with different pore sizes,double rows of holes and different three-hole arrangement are prepared by designing reasonable mix ratio.Through indoor uniaxial compression tests,the mechanical parameters and deformation and fracture laws of rock-like specimens under different single-hole sizes,double-row holes and different three-hole arrangement are obtained.the results show that the three groups of experiments have different effects on the strength,elastic modulus and strain energy mechanical parameters of rock-like specimens,and the mechanical parameters decrease with the increase of the pore diameter of single-hole and the number of double-row holes.On the other hand,the reduction of mechanical parameters of three-hole triangular gypsum specimens is greater than that of single-hole and double-row holes gypsum specimens,and the geometric shape of hole arrangement has the greatest influence on the mechanical parameters of the specimens.(2)Considering the influence of initial macro-meso defects on rock mechanical parameters,an acoustic emission constitutive model is established in this paper.The initial defects are quantitatively evaluated by defining the initial damage variable k.Through comprehensive comparative analysis,the apparent defects can not determine the degree of damage.Through the fitting of acoustic emission data,it is concluded that the geometric shape of holes has a greater influence on mechanical parameters than single holes of different sizes and different numbers of holes.(3)The uniaxial compression simulation test is carried out by using the mesoscopic parameters calibrated by PFC,and the consistency of stress-strain curve,strength and deformation law and results of the model specimens with single-hole,double row holes and three holes are obtained and analyzed,which verifies the feasibility of PFC2D for modeling rock with holes.On this basis,the microcrack development process,meso-displacement field,meso-contact force chain and meso-energy evolution of porous specimens are studied,and the mechanical properties,macro-meso-deformation damage and energy evolution of rock-like with holes are further studied. |
