Experiment Study Of Ultra-low Friction Phenomenon On Jointed Rock Mass

Rockburst is a nonlinear dynamic phenomenon,and its mechanism is closely related to the geomechanical environment in which the rock is located.According to the mechanical characteristics of the rock burst,it can be divided into strain rockburst and impact rockburst,and the ultra-low friction phenomenon in deep mining is one type of rockburst.In order to reproduce the phenomenon of ultra-low friction in the room,this paper,under the guidance of He Manchao,used the deep rock mechanics experiment system of the deep rock mechanics and the state key laboratory(Beijing),and the layered granite And the effects of different static load levels and different disturbing loads on the ultra-low friction phenomena were studied in this paper.The experiments were carried out under different experimental conditions.In the experiment,the digital speckle correlation method is introduced to measure the deformation and displacement of the rock surface.The vertical displacement of the falling block under the disturbance load and the treated drop block and the adjacent bedding block And the deformation data of the gap were analyzed and studied.In the analysis of ultra-low friction mechanism,the one-dimensional elastic stress wave propagation theory is introduced and the dynamic model of one-dimensional block ultra-low friction experiment is established.Finally,the numerical model of the same model with the physical model is established by 3DEC,and the numerical simulation is carried out.The numerical simulation results are compared with the experimental results.The geologic environment,which is distinct from the surrounding rock and the shallow surrounding rock,can be described by "three high and one disturbance",ie,high ground stress,high ground temperature,high karst water pressure and strong mining disturbance.The deep surrounding rock also exhibits characteristics different from shallow surroundings in this environment,such as ductility,high ductility and rheological properties of the rock.The bursting of the deep surrounding rock is also a scientific phenomenon that cannot be ignored,which has aroused the concern of many scholars.Many scholars through the in situ test method of the relevant research,that the deep partition of the phenomenon of fracture in a specific stress conditions,the results of the pull shear cycle.The deep rock also has a distinct tectonic level,and each structural level has its own structural plane,which is a weak surface of the rock,and many geomechanical disasters occur on these structural planes.The design of the experimental samples in the room to achieve the purpose of the surrounding rock and the rupture of the purpose,but also to meet the direct observation of ultra-low friction phenomenon as the key to the success of the experiment.Therefore,the design of the middle of the hole with the layer of granite samples,the size of the size of the test machine is based on the requirements of processing,indoor reproduction of the ultra-low friction phenomenon,by analyzing the hole above the vertical displacement of the block and the gap changes To study the effect of different experimental conditions on ultra-low friction.The experimental system of deep nonlinear rock mechanics is the experimental system based on multi-year engineering practice and theoretical basis.The system can realize three-way six-side loading,and can apply static load and disturbance load of different waveforms.The traditional stress and strain measurement methods are mostly point measurement and mostly contact measurement,and cannot reflect the overall force and deformation of the sample,with many limitations.According to the purpose of this experiment,the need for a non-contact,high precision and observable sample of the entire plane of the measurement means,so in a comprehensive comparison of the current application of a variety of test methods,select the digital image related method.The method has the advantages of full field,non-contact,automation and high precision,and the measurement result is intuitive and suitable for dynamic observation.According to the definition of ultra-low friction phenomenon,the direction of ultra-low friction phenomenon must be perpendicular to the direction of the disturbance load,when the falling block on the friction decreased or disappeared,the displacement of the block will have a corresponding feedback,this article Based on this and using the digital image correlation method,the vertical displacement of the falling block is used to characterize the occurrence of ultra-low friction phenomenon.On the basis of this principle,this paper designs the ultra-low friction experiment under the disturbance load under the action of the stratified granite specimen with the middle hole,and reproduces the ultra-low friction phenomenon under the disturbance load.In the analysis of ultra-low friction test results,this paper focuses on the vertical displacement of the block and the variation of the gap width as the research object.On this basis,the ultra-low friction experiments under different disturbance load amplitude and different static load levels are carried out,and some laws are tried to be found.In both experiments,the vertical displacement and gap width of the falling block are also Parameters to study.In the analysis of the ultra-low friction results,it is found that the fluctuation load of the falling block is not linearly falling,and the local data can be enlarged.It can also observe that the drop curve has the characteristic of sticky and slippery curve,Cycle consistent.Whether it is the vertical displacement of the falling block or the gap width of the adjacent block,the ultra-low friction phenomenon also shows a significant stage.Under different disturbing load amplitudes,the number of stages of ultra-low friction phenomena and the time of divergence at each stage are different,and the relevant parameters representing ultra-low friction phenomena are defined,and the ultra-low friction phenomena of different disturbance loads are Summary.The effect of different static load levels on the ultra-low friction phenomenon is obvious,especially in the final vertical displacement of the falling block.In this paper,the experimental results show that the static load level is much higher than that of the ultra-low friction experiment,and the static load level is not higher than that of the ultra-low friction experiment.The vertical load of the block is expressed as the critical friction force of the block,and the variation law of the critical friction force under different disturbance loads is studied.During the experiment,the vertical displacement and gap width of the falling block were recorded by digital speckle correlation equipment.The effect of friction weakening was observed directly in the experiment.The experimental results show that the effect of disturbance load on the friction.The effect is obvious,the greater the amplitude of the disturbance load,the greater the proportion of friction reduction.In the analysis of the mechanism of ultra-low friction,due to the propagation of the disturbance in the medium is the stress wave,so the introduction of one-dimensional elastic stress wave in the stratigraphic surface and the variable cross section of the propagation law,found that the greater the amplitude of disturbance The larger the projection coefficient of the wave of the stress wave through the nonlinear joint,the greater the force acting on the falling block.From this point of view,the greater the amplitude of the disturbance load,the more the ultra-low friction phenomenon is The model is discretized into rigid blocks and deformed blocks,in which the deformed blocks are used to characterize the inter-block bedding,and the rigid blocks are used to characterize the non-deformable Granite block,the motion equation of the rigid block is established and the displacement of the rigid block is obtained by finite difference method,which is compared with the experimental resultThe numerical simulation of the same size was established by using 3DEC software.The numerical simulation results were compared with the experimental results.The results of numerical simulation were mainly concerned with the vertical displacement of the falling block and The fluctuation velocity of the falling block is calculated,and the characteristics of the stage are consistent with the vertical displacement.The numerical simulation results show that in the numerical simulation,the vertical displacement of the falling block shows a similarity to the experiment.