Study On Space-time Evolution Law And Mechanism Of Deformation-cracking Of Deep Rock Mass

The rock of deep roadway is in a complex geological mechanics environment with high ground stress, temperature, mining disturbance and osmotic pressure. The temporal evolution law and mechanism of rock cracking around deep roadway is a key scientific problem in relation to stability control principle and technology of deep engineering. As the material in actual engineering or the current physical models are not transparent, the direct observation of rock deformation is limited to the surface of the model. Interior deformation of the model is limited only by local, indirect observation method, which has been restricted for comprehensive and detailed research on rock deformation and rupture process and its complex mechanical behavior. Therefore, based on the transparent rock similar material, the methods were adopted such as digital photography measurement method, numerical simulation and theoretical analysis method. On the basis, the internal deformation and rupture laws and mechanism during the excavation of deep circular roadway were studied without tectonic stress.（1） Around existing transparent geotechnical experiment method, the transparent rock similar material and experimental method were further studied. The transparent rock similar material meeting test requirement was successfully researched. Experimental and excavation equipment for roadway model used transparent rock was developed, as well as multifunctional loading test system for motor loading. The artificial filling spot method and three-dimensional digital photogrammetry method were put forward, which provided a new idea in order to obtain the interior data for deformation and rupture.（2） Through the research on the related algorithm of three-dimensional digital photogrammetry, the object-oriented programming language Delphi combined by Matlab database was adopted. Eventually, the three-dimensional digital photogrammetry system called Photogram₃D was developed, which contained four modules such as image preprocessing, feature point detection, plane calibration of camera, three-dimensional coordinate.（3） The temporal evolution laws of interior deformation and cracking in roadway model used transparent rock were obtained: At first, with the propelling of excavation face, the rock around the roadway deformation had come through three stages: basically invariability, abrupt increasing and gradual decrease of deformation rate. While, cracking development can be roughly divided into six stages: non-rupture, appearance, intercourse from the upper and lower, the beginning to substantially of coalescence and alternating and deflection consolidation. Secondly, the rock radial displacement everywhere was exponential attenuation relationship with the distance from the roadway surface. Thirdly, the number and overall length of macroscopic crack, the width and central angle of failure zone at the cross-section of model increased with an exponential decay in excavation time and the top load. Finally, with the increase of top load, integrity shear slip occurred at roadway roof, resulting in instable failure.（4） PFC3 D, discrete particle flow code software, helped reconstruct the spatio-temporal evolution process of rock deformation and cracking around deep roadway. On this basis, the paper further analyzed the influence of the lateral pressure coefficient, embedded depth and single fissure distribution patterns on rock deformation and cracking. The conclusions are as follows: At first, the high lateral pressure coefficient was the main reasons for zonal disintegration around the roadway. At second, as formation depth of roadway grew, horizontal interlaced separation phenomenon occurred around the roadway. Moreover, the two obvious main cracks happened near the two diagonals, forming an "X" type burst. Finally, the cracking azimuth and crack width were the most important factor for surface convergence deformation of roadway. Besides, the cracking azimuth and crack length played a decisive role in the cracking extension of the cross section of roadway.（5） The elastic-plastic model and sliding instability failure model of deep circular roadway were established, considering time effect of roadway excavation and dilatancy function of plastic zone. To a certain extent, the two models can represent and illustrate the spatio-temporal evolution law of rock deformation and cracking around the roadway.（6） The rock deformation and rupture mechanism of deep circular roadway without tectonic stress were as follows: Firstly, the deformation of roadway reflected results superimposed by unloading, dilatancy and sliding deformation. Secondly, the multiple sudden unloading of rock radial stress was the main reason for crescent type rupture in roadway side and extension to the great depth, roof and bottom of the roadway. Finally, the cracking and extension of the side rock in roadway would lead to the decrease of bearing and skid resistance capacity, resulting in the unstable base of rock at the roof and bottom. In turn, global sliding occurred along with "X" type rupture appeared.