Experimental And Numerical Study On Mechanical Properties Of Rock-Like Materials Containing Holes

Rock is a complex natural aggregate,after a long geological tectonic movement,there are not only a large number of joints and fissures,but also a variety of scale and shape of the hole defects in it.Under the action of external forces,these defects are easy to cause the initiation and development of cracks,which affect the mechanical properties of rocks to varying degrees.In actual life,they have a great impact on the quality of engineering and construction safety.Therefore,it is of great engineering significance to study the mechanical properties of rock with holes,such as strength and deformation failure,to ensure the safety and stability of underground geotechnical engineering.Because it is difficult to sample the original rock,and the process of directly processing holes in the original rock will cause new damage and affect the test results,the model test of rock similar material was adopted in this paper.Firstly,the uniaxial compression test of single-hole rock specimens was carried out in laboratory.Then,through the sensitivity analysis of PFC³DD meso-parameters,the influence law of the change of meso-parameters on the macro-mechanical parameters of rock was obtained,and the calibration of the meso-parameters of PFC³DD model was realized.Finally,the calibrated meso-parameters were used to carry out numerical simulation,and the feasibility of PFC³DD in the modeling of rock with holes was verified by comparing with laboratory tests.Based on this,the mechanical properties of rock samples with double holes were further studied.The specific research work is as follows:（1）Taking slate as the research object,the rock similar materials were determined based on the previous design ratio of the rock,and the single-hole rock specimens with different pore sizes and distribution positions were prepared.Through uniaxial compression tests in laboratory,the strength,deformation and failure of rock-like specimens with different pore sizes and locations were obtained.The results show that the pore size and location have obvious effects on the mechanical strength and deformation parameters of rock-like specimens.（2）According to the rock standard uniaxial compression particle flow model,for the mesoscopic parameters of the main particles in PFC^3D,the relationship between macro-and meso-parameters in rock particle flow model was obtained through a large number of uniaxial compression simulation tests.The mesoscopic parameter that affects poisson’s ratio is the stiffness ratio of flat-joints（k_n/k_s）,which has a power function growth relationship with poisson’s ratio.The main mesoscopic parameters affecting the elastic modulus are the flat-joint modulus（E_c）and the stiffness ratio（k_n/k_s）,and the effect of E_c is more obvious,showing a linear growth relationship with E_c,and an approximate power function decrease relationship with k_n/k_s.There are many mesoscopic parameters affecting compressive strength,mainly including flat-joint tensile strength（σ_b）,cohesion（C_b）,internal friction angle（φ_b）and stiffness ratio（k_n/k_s）,The influence of C_bandσ_b is greater.The overall trend is that the compressive strength increases with the increase of both,while bothφ_b and k_n/k_s have an effect on it which increases first and then decreases.（3）According to the relationship between macro and micro parameters of rock particle flow model,the calibration of micro parameters of rock PFC³DD model was realized,and the uniaxial compression numerical simulation was carried out by using the calibrated mesoscopic parameters.The stress-strain curves,strength and deformation law,microcrack development process and displacement field of single-hole model specimens with different pore sizes,different pore distribution locations and different specimen widths were obtained.By comparing the numerical simulation results with laboratory tests,the reliability of PFC³DD in rock modeling with holes was verified.On this basis,considering the interaction between holes and holes,the influence of the distance between holes and the inclination angle between holes on rock strength,deformation characteristics and fracture process was further studied.