Unified elasto-plastic solution for deep-buried circular tunnels considering the swelling characteristics of surrounding rock
Addressing the challenge of quantifying variations in stress and displacement fields induced by surrounding rock swelling due to water absorption in tunnels and underground engineering, this study develops a unified elastic-plastic solution for deep-buried circular tunnels. The solution considers the intermediate principal stress effect and swelling characteristics of the surrounding rock, employing elastic-plastic theory and humidity stress field theory. Firstly, stress and displacement solutions under elastic conditions of the surrounding rock are derived by integrating equilibrium and constitutive equa-tions considering humidity changes. Secondly, a method for determining the elastic-plastic state of sur-rounding rock is proposed, and an analytical solution under plastic conditions is then obtained based on the unified strength theory and non-correlated flow rule. Finally, the accuracy of the proposed unified solution is verified by the example comparison and analysis. Further, the study investigates the influ-ence of intermediate principal stress, humidity swelling coefficient, and water content changes on sur-rounding rock stress fields and plastic zone radius. Results indicate that comparative analysis with lit-erature demonstrates a negligible 0.136％ deviation in the plastic zone radius, validating the rationale of the proposed unified solution. Incorporating swelling characteristics increases the plastic zone radius and hoop stress at the elastic-plastic interface by 1.06 times under equivalent support resistance condi-tions. Increasing the unified strength theoretical parameter from 0.0 to 1.0 results in a 6.6％ increase in hoop stress, a 13.9％ decrease in plastic zone radius, and a 16.0％ reduction in tunnel wall displace-ment. Moreover, varying the humidity swelling coefficient from 0.0 to 0.1 leads to 17.98％ and 27.4％ increases in hoop stress and plastic zone radius, respectively. Similarly, increasing the maximum wa-ter content from 0.0 to 0.06 results in a 16.9％ increase in hoop stress, a 23.1％ expansion in plastic zone radius, and a 100％ increase in tunnel wall displacement. These findings provide theoretical in-sights for the design of swelling rock tunnel structures.
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维普
