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为研究卸荷效应对岩体强度变化的影响,以三峡地区砂岩为样本,通过三轴加载和卸荷试验,运用Hoek-Brown岩体破坏准则,探讨砂岩在不同卸荷速率条件下的强度损伤规律,并提出采用卸荷强度损伤因子来表征卸荷造成的强度变化。结果表明,卸荷条件下砂岩强度损伤明显,且与围压密切相关;随着围压的增大,卸荷效应造成的强度损伤量增大,最终趋于稳定。最后,基于工程设计最不利原则,修正了Hoek-Brown卸荷强度准则公式,为工程应用提供了建议和参考。
In order to study the effect of unloading on rock mass strength changes, taking the sandstone in the Three Gorges area as a sample, the Hoek-Brown rock mass failure criterion was used to investigate the strength damage of sandstone under different unloading rates by triaxial loading and unloading tests The law of unloading strength is proposed to characterize the strength change caused by unloading. The results show that the strength of the sandstone is obviously damaged under unloading condition and closely related to the confining pressure. With the increase of the confining pressure, the strength damage caused by the unloading effect increases and eventually becomes stable. Finally, based on the most unfavorable principle of engineering design, the formula of Hoek-Brown unloading strength criterion is revised, which provides suggestions and references for engineering application.