| Fractured rock mass is a kind of complex heterogeneous medium which is common in underground engineering.Within the action of external load,the small defects of rock extend,then eventually causes material damage evolution and failure,and fissure water pressure influenced on deformation and strength characteristics of rock mass is also very significant.Now many big projects have very important significance,which related to the rock mass fissure water.Fissure water pressure acts on the crack initiation and propagation of the rock,and the influence of solving the problem on underground engineering security is notified.At present,because the underground engineering is mostly based on the bidirectional stress state,it is necessary to study the initiation of crack and expansion law of the fractured rock mass.For fissure water pressure and axial compression is under the same indoor test,and most of the samples belong to three-dimensional internal cracks,and the observation of experimental phenomena is not very inconvenience.This paper includs two-dimensional fracture of the cement mortar specimens,and is conducted in axial compression.It also studies the propagation of the crack under different water pressure,and researches on compression fissure water pressure characteristic parameters of the aid in the process of change with the utility of acoustic emission testing technology.The relevant work and conclusions are as follows:1.Uniaxial and biaxial compression experiments are carried out without fissure water pressure by using prefabricated crack specimens,the corresponding stress strain curve is obtained and the initiation and propagation of cracks are analyzed,and the influence of fracture angle.number and the lateral pressure on crack initiation stress and peak strength is discussed.The crack angle is between 69°?72° under uniaxial compression,and the crack initiation stress is between 40%?50%of the peak intensity.The crack stress and peak intensity decrease with the increase in the number of fractures,and the peak intensity decreases firstly and then increases with the increase of the crack tip.The crack initiation and expansion of the tip of the crack in the biaxial compression are blocked,the ultimate failure mode of the specimen is the shear failure along the secondary cracks,and when the side pressure is added,the connect between the two cracks occurs on the crack surface instead of the tip,the larger the lateral pressure is,the greater the crack specimen stress and peak strength of the enhanced,what's more,the peak intensity enhancement is particularly obvious when the fissure angle is 45 °.2?In order to research the rock crack propagation mechanism of two-dimensional fissure specimens under water-rock coupling,a set of water-rock interaction mould was designed and developed,which can effectively prevent the water out of joints,so as to ensure the smooth progress of the experiment.3?The compression experiment results of 2D crack specimens under water-rock coupling show that the crack fissure water pressure reduce the crack stress and crack angle,the existence of water pressure makes the normal stress the normal which is on the crack surface is reduced,and the effective shear force on the crack surface is increased,the initiation and propagation of cracks are increased as well,which makes the peak strength of specimens decrease,The failure of the specimen is mainly tensile failure,and the crack morphology is dominated by the wing crack,and the crack propagation path is closer to the axial pressure as the water pressure increases.4.In this paper,the effect of fracture water pressure on crack propagation and acoustic emission characteristic parameters is studied by using the acoustic emission monitoring technology.The larger the crack water pressure is,the smaller the peak intensity of the specimen is.The process of the acoustic emission under different water pressure have been through the initial pressure peak area,rose area,area and falling area four stages,the existence of fissure water pressure makes the pressure phase is longer,and this stage acoustic emission activity is relatively dense,acoustic emission event rate and acoustic emission energy peak before specimen reached the peak stress,and the water pressure,the greater the peak of acoustic emission activity more significantly than the moment before,can be used as a sign of rock damage omen.5?The particle flow PFC2D program can simulate the compression fracture experiment of the fracture sample with different inclinations and several purposes,and the expansion process of the crack initiation is straightforward.. |
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