| Jointed rock mass is a complex rock mass.Generally,it appears in the geotechnical engineering and environmental engineering,and structural plane form is different,such as fault,joint and fracture.This has brought a lot of trouble to the security implementation and maintenance of geotechnical engineering projects in China.Because fractured rock mass suffers a variety of geological structure movement,so the geological environment and stress environment of the fractured rock mass are very complex.Fracture is a kind of original damage,the form in the rock mass is random,so the strength of fractured rock mass can be greatly reduced,and the original characteristics of rock mass is changed.In recent years,the study,which jointed rock mass is effected by external loads,the connection and transfixion mode between the expansion of cracks and multiple fractures,has attracted more and more attention.By reading the relevant literature,the paper gets th following views: the root of macroscopic failure and instability of jointed rock mass is the opening,closing,expanding and penetrating of the discontinuities.In other words,local instability and failure leads to macroscopic instability and failure.When external load is definited,joint,crack propagation and transfixion mode of jointed rock mass have a close relationship with the state(the length,quantity,dip angle and so on).Many researchers have studied a lot of factors,such as the fracture rock mass and fracture length,but in the case of large size square specimens with cracks under the external load conditions,there is not much laboratory test research on the instability and failure characteristics of rock mass.In this paper,based on the previous studies,the following aspects are done:1 In this paper,by consulting the relevant literature and books,the experimental study is carried out on the basis of the different inclination angles and the number of variables.The research contents include the local instability of rock mass with different crack angles under uniaxial conditions and global failure characteristics.In the process of studying local instability,standard sample(50mm* 100mm)of jointed rock mass and the samples with 70 mm * 70 mm * 140 mm and 70 mm * 90 mm * 150 mm.In this paper,the sample with 150 mm * 150 mm * 300 mm size is used to do simulation study.The crack depth ratio(d/T)is 1,crack length is 50 mm,parallel fracture is selected from multi-fracture specimen,and the spacing between fracture is 50 mm.2 Suitable similarity material is selected to simulate rock,to make sample mold and prefabricated crack.And in accordance with the design,the samples are completed and maintained.Then samples are added in numbers,uniaxial compression tests are performed on specimens of different conditions.The stress-strain curves of the specimens are compared and analyzed.In addition,the crack initiation,propagation path and the failure characteristics of the specimens are taken with the high pixel camera to provide the basis for the following analysis.Acoustic emission PCI-2 system is used in the compression process to ensure the test reliability.3 The numerical simulation is carried out by using RFPA2 D numerical simulation software.The initiation of simulated fractured specimen,propagation,coalescence and failure characteristics of specimens with crack are observed,and the results are compared with the experimental results.After the completion of the above work,the local instability and failure characteristics of fractured rock mass are analyzed by simulation and experiment,and the some simple rules of crack propagation and transfixion mode are summarized.It can provide some reference value and guiding significance for engineering practice. |
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