Study On Disturbance Creep Damage And Fracture Law Of Shale Under Seepage Water Pressure

In recent years,the mining of coal and other resources has been extending to the deep.The deep rock shows significant rheological properties under complex geological conditions,which makes the stability control of roadway surrounding rock extremely difficult.Ensuring production safety is the top priority.When tunneling or blasting activities are carried out in underground engineering,the rock under long-term stable stress state will be affected by external disturbance.At this time,small disturbance may seriously damage the mechanical properties of rock.In addition,in some coal mines with rich water,the seepage of groundwater will accelerate the deformation of surrounding rock of the roadway,and the cracks inside the surrounding rock body develop rapidly to form a macro permeable channel,which leads to the groundwater flowing into the roadway,which causes the mine water inrush disaster.Therefore,it is of great significance to study the seepage creep mechanics of rock under disturbance.In this paper,the seepage creep test system is designed and improved by combining experimental research and theoretical analysis.The shale seepage creep test under different disturbance amplitude,frequency and permeability pressure is carried out with the study object of shale roof of coal seam.The seepage creep test is studied from macro and micro scale by SEM test system based on the fractional calculus theory,the seepage creep model is proposed.The main achievements as follows:(1)Triaxial compression experiments were carried out on shale under different confining pressures,and basic mechanical parameters such as peak strength,elastic modulus,Poisson's ratio,cohesion and internal friction Angle were obtained.On this basis,to carry out the different disturbance amplitude and frequency disturbance,different osmotic pressure of rock triaxial hierarchical load creep experiments,to analyze the creep curve,found 4 under the action of axial compression,shale axial strain for disturbance disturbance frequency,amplitude,the relationship between the sensitivity of seepage water pressure is: the osmotic pressure>disturbance amplitude >disturbance frequency.At the same time,the permeability characteristics of shale in the creep process are analyzed,and the variation law of permeability characteristics with the permeability water pressure,disturbance amplitude and disturbance frequency is analyzed,including the variation law of the permeability water collected by experiment,the calculated permeability rate,permeability coefficient and permeability.(2)The macroscopic failure characteristics of shale after seepage creep failure were analyzed,such as failure mode,crack propagation on fracture surface;combined with SEM scanning electron microscope test,the micro view fracture morphology of shale under different conditions was analyzed,and the variation law of fracture mode of shale with disturbance factors and osmotic pressure was analyzed;the local micro view fracture and macro view fracture of shale were analyzed.The creep fracture law of shale under seepage is expounded.(3)Based on the creep theory of rock and fractional-order calculus theory,the fractional-order element Abel is introduced and the improved nonlinear viscoplastic creep element(NVPB)is introduced on the basis of the basic creep mechanics element,and the NVPB is connected in series with other elements,thus the fractional-order nonlinear creep model of rock is established.Based on the data of rock seepage and creep test,the model parameters were determined by the least square method,and the model was verified.The paper has 48 figures,8 tables and 89 references.