基于修正西原模型与Lade-Duncan准则的隧道围岩蠕变效应研究

Study on Creep Effect of Tunnel Surrounding Rock Based on the Modified Visco-elastoplastic Model and Lade-Duncan Criterion

为探究软岩隧道围岩变形的蠕变时效性,采用非定常黏滞体对西原模型进行修正。基于Lade-Duncan准则,分析了围岩黏弹性和塑性阶段隧道围岩变形过程,推导得到了隧道围岩黏弹塑性解。以某高速公路隧道为工程研究对象,计算了蠕变时效过程的围岩位移值;并通过现场拱顶沉降监测的方法,实测了隧道围岩的蠕变变形,通过对比理论计算值与现场实测值,验证了理论计算的准确性。理论计算显示,当t=0时,隧道围岩将发生蠕变现象,此时围岩位移值为17.890 mm;当t为常数时,围岩位移随着时间的变化逐渐增大;当t=∞时围岩发生充分蠕变,围岩位移达到极值为26.451 mm。现场监测结果显示,围岩变形第一次稳定拱顶累计变形为19.1 mm,此后进入蠕变阶段,达到第二次稳定拱顶累计变形为29.3 mm。初始蠕变变形的理论计算与实际监测结果之间的误差为6.76%,最终蠕变变形的理论计算与实际监测结果之间的误差为10.77%,两者误差较小,反映了理论计算具有较高的准确度。在理论层面,考虑蠕变效应后围岩变形增加了47.85%;在实际层面,考虑蠕变效应后围岩变形增加了53.4%,皆反映了蠕变效应举足轻重的作用。由此可见,对于软岩隧道在进行支护设计时,必须考虑蠕变效应,避免因后期围岩蠕变效应导致初支失效进而影响隧道的整体稳定性。

In order to study the influence of creep timeliness on tunnel,the non-stationary viscous body was adopted to revise the visco-elastoplastic model. Combining with the Lade-Duncan criterion,both the deformation process of tunnel surrounding rock in the viscoelasticity phase and plastic phase were analyzed. Based on the engineering of the tunnel in the freeway,the displacement value of surrounding rock in the creepprocess was calculated.Additionally,through the vault subsidence monitoring method,the creep deformation of tunnel surrounding rock was measured. And by comparing the theoretical calculated values and measured values the accuracy of theoretical calculation was verified. The theoretical calculation shows that,when t = 0,the creep phenomenon of tunnel surrounding rock will occur,the surrounding rock displacement value of 17. 890 mm; When t is constant,the displacement of surrounding rock as the change of time gradually increase; When t = ∞,the surrounding rock has the full creep,and the displacement of surrounding rock to extreme value is 26. 451 mm. The monitoring results show that,the first deformation stable arch accumulative deformation of surrounding rock is 19. 1 mm. Since then,stepped into the stage of creep,achieve stable second vault accumulative deformation is 29. 3 mm. Initial creep deformation of the error between the theoretical calculation and the actual monitoring results is 6. 76%,the final creep deformation of the error between the theoretical calculation and the actual monitoring results is 10. 77%,the error is small,reflects the theoretical calculation with high accuracy. In the theoretical level,after considering the creep effect of surrounding rock deformation increased by 47. 85%,and at the practical level,increased by 53. 4% after considering the creep effect of surrounding rock deformation,creep effect reflects the important role. Thus,in supporting design for soft rock tunnel,creep effect,must be considered to avoid late surrounding rock creep effect cause early failure will affect the overall stability of the tunnel.