Abstract

Based on the Kachanov damage theory and elastic wave theory, considering the long-term creep damage from time dimension and instantaneous disturbance damage from space dimension, we presented a 3D damage creep model and converted it to difference expressions in order to write into the finite difference software FLAC3D. Then, according to the results of creep tests, we conducted parameter inversion of our damage creep model with the help of the particle swarm optimization (PSO) method. Finally, the damage creep model was applied in a railway tunnel project in Yunnan to simulate the tunnel deformation. Compared with the Burgers model and the model considering only creep damage, our model which considers both creep damage and disturbance damage yielded more reasonable results.

Highlights

  • Any material under long-term load tends to creep, and rock is no exception, especially if it contains many internal flaws which could exacerbate such process

  • The creep property of rock has been widely studied in the past 80 years, including lots of mechanic experiments [1,2,3,4,5] and constitutive models [1, 6,7,8,9]. ere are many component creep models such as Kelvin, Maxwell, and Burgers which have been applied for simulating the mechanical behavior of rock masses under long-term load, and many improvements were carried out on these traditional creep models in order to improve their accuracy and applicability

  • From 2003 to 2010, Shao et al [22,23,24] presented a constitutive model for creep deformation considering the progressive degradation of elastic modulus and failure strength and it coupled with a second-order damage tensor for the description of induced anisotropic damage in brittle rocks

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Summary

Introduction

Any material under long-term load tends to creep, and rock is no exception, especially if it contains many internal flaws which could exacerbate such process. When the stress σ is lower than the long-term strength σs, the model is the same as the Burgers model, and when σ is beyond the long-term strength σs, the damage element will start to work E S-curve is monotonically increasing which means E is increasing and damage is decreasing, until the distance away from the excavation surface is large enough to ignore the disturbance damage and the curve tends to be stable It can be seen from the curve that the increase rate changes from high to low, so we can use equation (5) to fit the S-curve, and E can be written as equation (6): vp A􏼒1 − Be− 􏼓, e(x− C/D). Where new means the new value in a time step and old means the old value in a time step

Creep Tests
Parameter Inversion Based on PSO
50 MPa 70 MPa 90 MPa
Application and Discussion
Findings
Conclusions

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