Experimental Study On Creep Behavior Of Anchorage Rock Mass Under Stress-seepage Coupling Environment

Based on the anchorage rock mass as the research object,the creep characteristics of anchorage rock mass under stress-seepage coupling environment are studied and analyzed from three aspects of macro-micro-data mining.The specific research contents are as follows:Firstly,a set of experimental system is designed to study the creep characteristics of anchorage rock mass under stress-seepage coupling environment.The anchorage rock mass samples are made by using similar materials and porous water pressure pipes,and the hydrostatic heads with different sizes are provided by adjusting the water level height in the water pressure pipes suspended from the top of the experimental building.Secondly,the uniaxial compression test and uniaxial compression creep test of anchorage rock mass under different hydrostatic pressure are carried out.The compressive strength and creep characteristics of anchorage rock mass under stress-seepage coupling environment are compared and analyzed,and the long-term strength variation law is analyzed by ' Chen ' method and ' isochronous curve method '.At the same time,the creep test process of the anchoring rock sample was monitored by the electrochemical workstation,and the change law of the internal microstructure in the creep test process and the influence of the osmotic pressure on the internal fracture development were analyzed by the electrochemical test data.Finally,based on the creep test data,the BP neural network prediction model between stress,time,osmotic pressure and creep strain is established by MATLAB,and the test data are predicted and analyzed to excavate the hidden law of test data.The results show that:(1)The internal microstructure of the anchoring rock sample will be destroyed by the seepage pressure,resulting in the damage of its compressive strength.The higher the seepage pressure is,the greater the damage rate is.(2)The total strain value,elastic strain cumulative value and creep strain cumulative value of the anchoring rock sample increase with the creep test.The elastic strain cumulative value of the four groups of samples is greater than that of the creep strain cumulative value,and the growth rate of the creep strain cumulative value increases with the increase of the osmotic pressure,and the growth rate of the elastic strain cumulative value decreases with the increase of the osmotic pressure.(3)The long-term strength of the anchorage rock sample is affected by the osmotic pressure.The greater the osmotic pressure,the smaller the long-term strength of the sample.(4)With the creep test,the impedance value of the anchoring rock sample gradually decreases,and the phase angle value gradually increases,and the change rate increases with the creep test.In other words,the internal cracks of the anchoring rock sample continue to expand with the creep test,and the expansion rate gradually accelerates.(5)Under the action of different sizes of osmotic pressure,the four groups of anchoring rock samples have different performances in the same electrochemical detection times.The impedance value with high osmotic pressure is significantly smaller,and the phase angle value is significantly larger,that is,the osmotic pressure has a promoting effect on the development of internal pores of anchoring rock samples,and the greater the osmotic pressure is,the more obvious the promoting effect is.(6)Based on the creep test data,the BP neural network prediction model between stress,time and osmotic pressure and creep strain is established.The experimental data are predicted and analyzed,and the predicted results are in good agreement with the experimental results.The research results can provide reference for the long-term safety and stability of related anchorage projects and the creep characteristics of anchorage rock mass under stress-seepage coupling environment.