Loading Rate Dependence And Generalized Relaxation Behaviors Of Rocks

In many underground structures,rock mass is neither subjected to pure creep or pure relaxation,but to a stress-strain synchronously varies with the lapse of time.It displays time-dependence,rock mass will be failured,it is hard to exhaustively explain this phenomenon by creep and relaxation.Loading rate dependence tests of strength,Young's modulus and generalized relaxation for Class rocks ? and ? were carried by self-made,servo-controlled testing system,which are controlled by stress-feedback method.This study quote the properties of generalized relaxation to explain this rheological phenomenon by the ways of experimental method in laboratory,theoretical analysis,numerical simulation and engineering application,and rheological behaviors and mechanical mechanism were systemic investiaged.This investigation explounds time-effect of rocks under different conditions,and provides theoretical basis for tunnel rock wall,rock burst and landslides et al.Constitutive equation of variable-compliance-type,which is time-dependence,is proposed by author.loading rate dependence tests of strength,Young's modulus and general relaxation were numerical simulated by proposed constitutive equation.This research is useful to forecast life of engineering,investigate engineering significance of general relaxation under complex stress contions.Mainly contents of this paper are as follows:1)Based on sevro-controlled theory,servo-controlled machines were successfully developed by stress feedback method,in which a linear combination of stress and strain,is used as the feedback signal in a closed-loop,servo-controlled testing machine.It provides a new method to investigate general relaxation behavious of rocks by general relaxation tests.2)Loading rate dependence tests of strength,Young's modulus for Class ? rocks(Tage tuff,Ogino tuff)and Class ? rocks(Sanjome andesite,Jingkou sandstone)were carried out under different loading conditons.From results,for loading rate dependence of strength,Young's modulus,there are the similiarity under uniaxial compression,indirectly tension and directly tension.The character of stress-strain curves between Class ? and Class ? rocks were showed,failure mode under compressive,tensile condition also were further investigated.3)Generalized relaxation tests for Class ? rocks(Tage tuff)and Class ? rocks(Jingkou sandstone,Granite)were carried out by stress feedback method.The author investigated rheological behaviors and mechanical mechanism of generalized relaxation,also analyse and contrast behavious of generalized under different stress level,different direction coefficient constant,different rocks.Finally,preparatory process,generating mechanism and dynamic effect of rock burst for Granite,the law of “Rheology-Failure” were illustrated.Engineering significance of general relaxation under complex stress contions also were sought and analysed.4)Based Maxwell model,Variable-compliance-type constitutive equation,which are time-dependence,were proposed,the author solved these equations,and model of failure strength,Young's modulus were obtained,the value of parameters were solved by testing methods.5)Loading rate dependence tests of failure strength,Young's modulus,and generalized relaxation tests were numerical simulated by non-linear viscoelastic constitutive equation.The author expounded loading rate dependence of Young's moduls,contrast and analyse time-dependence for Class ? and Class ? rocks,the purpose is to forecast engineering lifetime.