Table 1 Creep curve fitting equation.

From: Solution of plastic zone range in soft rock tunnel surroundings considering joint damage

Curve

Fitting curve equation

R2

Part I fitting curve equation

\(\varepsilon = 0.23125 + 0.01226 \times (1 - e^{ - 2.61837 \times t} ) + 0.00426 \times (1 - e^{ - 2.56863 \times t} )\)

0.9984

Part II fitting curve equation

\(\varepsilon = 0.2041 + 0.00341 \times t^{2}\)

0.9979

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