| Underground engineering in soft stratum, the deformation of wall rock does not instant finished, but sustains long time, and when the deformation continuously develops, a part of wall rock will reach plastic yield. Under this condition, the field measuring displacement actually reflects the viscoelastic-plastic character. If still carried on the counter- analysis based on elastic or the viscoelasticity supposition, obtained the result inevitably will not be able the very good reflection actual rock mass deformation mechanics characteristic, not to be able to achieve monitored the counter- analysis the goal. And under the function in such factors as water and weathering, etc. some mechanical parameters of rock body such complicated material change obviously over time, for example such parameters as Young's modulus and intensity reduce with growth of time, this fact has already proved to test in door.This article uses non-stationary creep constitutive model instead of the stationary model, considering the plastic flow of rock mass compiles non-stationary visco-elastic-plastic positive finite element procedure, and through calculated example confirms the reliability of this procedure; unifying the non-stationary viscoelastic-plastic procedure and the compound law optimization technology, compiles non-stationary visco-elastic-plastic displacement anti-analysis finite element procedure, and through calculated example confirms the reliability of this procedure, and does displacement back analysis of soft tunnel project.The result indicates that the creep model with non-stationary parameters can reflect the aging character of rock mass viscosity objectively, and will more accurately predict the aging deformation character of rock mass in later days, and considers the plasticity rock flows, making the results of the anti-analysis as a basis for the calculation of parameters do viscoelastic-plastic analysis, can predict the development of surrounding rock plasticity zone. |
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