| It is very important theoretical value and practical significance is that carry out the rockrheological mechanical properties and models research for which correct prediction andeffective control of the security and stability of rock engineering under different waterconditions. carbonaceous slate in wooden village ridge tunnel of Lan-Yu railway were takenfor research object, the research methods combined with the experiment, theoretical analysisand numerical calculation are used, based on the mechanical properties and creep law in dryand saturated state of the carbonaceous slates, Nonlinear rheological constitutive model ofcarbonaceous slate rock were established, identified the rheological parameters combinedwith particle swarm optimization (PSO) and nonlinear least square method, and accomplishedsecondary development in the FLAC3Dnumerical program, all of these are vital for predictionlong-term stability of tunnel engineering. The paper mainly focused on the following:(1) It is grasp the instantaneous mechanical properties of dry and saturated statecarbonaceous slate in which carry out uniaxial and triaxial compression test, wedge shear test,brazilian spilt test, as well as uniaxial cyclic loading and unloading instantaneous mechanicalproperties test. It is mainly focused on the mechanical property differences of two states ofrock, and also provide test base for creep test of rock; The test shows that water bring aboutsignificant influence to strength and deformation of carbonaceous slates, especially in uniaxialcyclic loading and unloading test conditions;(2) It is launched step load and circular increment step load and unload creep test of thedry and saturated carbonaceous slates in automatic servo rheometer, the mainly researchedcreep characteristics of two conditions of carbonaceous slates, and the influence of watertowards on the creep value and creep rate under all levels of pressure.The test resultsindicated that creep deformation mainly presents attenuation creep and steady-state creep inmost stress level, and the deformation has increased dramatically, performance acceleratingcreep stage when the stress level is higher. The mainly influence of water towards on rock isthat instantaneous plastic value in instantaneous deformation and the visco-elastic strain increep deformation;(3) According to the creep characteristics of carbonaceous slates in dry and saturatedstate, put forward a nonlinear viscoplastic body, combined with Burgers rheological model,established an improvement Burgers nonlinear viscoelastic-plastic rheological model, and thecreep equation, unloading equation and three dimensional form of creep model is deducedfrom the rheological constitutive model model; (4) Considered the defect of parameter identification in rheological model, based on theimprovement particle swarm optimization (PSO), combined with linear decreasing weightparticle swarm optimization and Levenberg-Marqud nonlinear least squares method, a newparameter inversion method is proposed，which proceeds as:1) the model parmeters areinverted using PSO;2) L-M nonlinear least square is used to invert the model parameterswith initial values from step1). A case demonstrates that the PSO—L-M method could beeffectively used in inverting the parameters of rock creep models;(5) By means of classic element combination modeling ideas, put forward a newnonlinear viscoelasto-plastic rheological model that contained component of fractionalcalculus and a nonlinear visco-plastic body of power function, and given constitutive equationand creep equation of the model. The fitted results of the test data showed that nonlinearrheological model that contained soft-matter element and nonlinear visco-plastic body can beeffectively depicted the creep properties of rocks, efficiently reduced the number ofcomponents and parameters of combination model;(6) Rock creep process is the result that constantly adjusts internal stresses of rock,hardening and damage effect gradually growth and mutual affect. By means of classicelement combination modeling ideas, the rock initial yield strength is regarded as the stressthreshold of the creep hardening, and rock’s long-term strength served as the stress thresholdof damage softening, introduced hardening function and damage variable that can reflectedthe effect of rock hardening and damage effect, established nonlinear creep model of rock thatcan comprehensively reflected the creep mechanism. The fitted results of the test data showedthat nonlinear rheological model not only can be effectively described the creep process ofrocks, but also can reflected creep hardening and damage softening mechanism in the creepprocess of rocks;(7) On the basis of the constitutive model code and the finite difference form of Burgerscreep model in FLAC3D, deduced the three dimensional difference form of improvementBurgers nonlinear creep model,and compiled into the dynamic link library in FLAC3Dby C++language, finished secondary development of the constitutive model. Uniaxial compressioncreep simulation test is implemented, the simulation test manifested that it is fitted for theindoor creep test curves, verified the correctness of the secondary development. |
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