Study On Nonlinear Visco-elastic-plastic Rheological Model Of Soft Rock With Unstable Parameters

With western development and the fast growth of national economic,more and more projects in deep soft-rock have been constructed in the areas of mining,water-electric and transportation.But there is also a rather critical problem in these constructions-the large and continue creep deformation in surrounding rocks-which will have a great challenge on the security of configuration and at the same time the use-life.Based on the NNSF program-the study on creep constitutional model of soft-rock by Unsteady fractional calculus method and the deformation-controlling of tunnel in deep soft-rock body,this paper researches the creep characteristic of soft-rock under long-time loads by using the theoretical and experimental methods,and some results have been attained:(1)Since the mechanical parameters of rock will be weakened during the creep experimental process,this paper proposes one time-attenuating format based on the experimental results of soil-rock under the action of different creep time and stresses.(2)By considering the attenuation regularity of the rock elastic modulus in the creep process and the Maxwell creep model,one viscoelastic constitutive model with inconstant parameters was set,and then checked by experiments which shows that this model has a good fit with the uniaxial pressed creep deformation process of soil-rock,but unfit with the three-dimensional case under constant-speed and inconstant-speed pressed process.(3)By redefining a new nonlinear viscoelastic component and combining with the Bingham creep model,this paper gives one unidimensional nonlinear viscoelastic constitutive model which will have a good prediction of the attenuating,steady and speedy creep phase deformation of soil-rock under uniaxial creep compression process.(4)By proposing the improved Bingham creep model into three-dimension and then comparing with the experimental results of three-dimensional creep deformation experiments of soil rock,the correction and rationality of this model have been proved,which means that the model in this paper have a very practical evaluation.(5)Some new advantages and disadvantages of the model proposed by this paper have been analyzed by comparing the experimental results under same situation among the improved Bingham model,the traditional Bingham model,the model with inconstant parameters,the advanced Xiyuan model and the Hohai model.