考虑应变强化与扩容效应的深埋软岩隧洞时效变形解析理论研究

发布时间：2018-05-26 01:53

本文选题：软岩隧洞 + 应变强化　；参考：《华侨大学》2017年硕士论文

【摘要】：在隧洞开挖过程中,两帮收敛和底板向上鼓起等成为常见的工程灾害。通过围岩性质、力学特性和变形机制等,进行深埋软岩隧洞围岩力学状态的解析研究。本文基于幂强化-理想塑性本构模型和平面应变理论下考虑扩容性能的岩土体中主应力计算式,求解出Drucker-Prager强度准则下软岩隧洞的三维弹塑性解。在恒定应力场作用下,借助非关联流动法则、Burgers蠕变模型计算深埋软岩隧洞黏弹塑性蠕变解,从理论上阐释了软岩隧洞变形机制并深化了侯公羽的求解。将计算结果与软岩(粘土岩)隧洞的实测数据进行对比,发现本研究结果可较好的反映深埋软岩隧洞长期时效变形。最后考虑有水条件下软岩隧洞出现的吸水膨胀现象,基于改进Burgers模型初步探讨了软岩隧洞吸水失稳的力学问题。得出以下结论:1.幂强化-理想塑性模型能较好的描述深埋软岩隧洞围岩的力学状态,再考虑围岩中主应力与扩容的影响,结果发现不考虑扩容效应的体积不可压缩理论存在物理意义上的错误,具有一定的局限性。2.随着扩容角的增加,深埋软岩隧洞的围岩应力逐渐增大,塑性区半径呈递增的趋势,这与参数的物理意义一致。隧洞围岩位移明显增加且发展变快,隧洞周边位移对幂强化参数的敏感性越高。3.应变强化效应和扩容特性二者对深埋软岩隧洞围岩的应力状态具有一定的协同作用,增大扩容角或幂强化指数,隧洞围岩位移的敏感性随之增强,考虑扩容或应变强化效应的软岩隧洞变形明显大于不考虑的情况。4.不论是否考虑吸水效应的影响,对于深埋软岩隧洞围岩的长期时效变形,随着幂强化指数值的增大,应变强化效应加强,洞壁蠕变位移量增大,且隧洞围岩的蠕变行为对时间的敏感性越高。扩容角越大,洞壁位移明显增加且发展变快。在富水条件下,顾及吸水率影响的深埋软岩隧洞变形明显大于不考虑的情况,对围岩长期稳定不利。本文针对深埋软岩隧洞的围岩力学问题,基于理论研究了该类隧洞的变形机制,探索了不同遇水条件下隧洞长期时效变形。解析结果可作为修筑软岩隧洞的数学、物理和力学理论依据。
[Abstract]:In the process of tunnel excavation, the convergence of two sides and the upwelling of bottom plate become common engineering disasters. Based on the properties of surrounding rock, mechanical properties and deformation mechanism, the mechanical state of surrounding rock in deep buried soft rock tunnel is studied. Based on the power hardening ideal plastic constitutive model and the plane strain theory the three dimensional elastoplastic solution of soft rock tunnel under Drucker-Prager strength criterion is obtained. Under the action of constant stress field, the viscoelastic-plastic creep solution of deep buried soft rock tunnel is calculated by the Burgers creep model with the aid of non-associated flow rule, and the deformation mechanism of soft rock tunnel is explained theoretically and the solution of Hou Gongyu is deepened. By comparing the calculated results with the measured data of soft rock (clay rock) tunnels, it is found that the results of this study can well reflect the long-term aging deformation of deep buried soft rock tunnels. Finally, considering the phenomenon of water absorption and expansion in soft rock tunnel under the condition of water, the mechanical problems of water absorption instability of soft rock tunnel are discussed based on the improved Burgers model. Draw the following conclusion: 1. The power-hardening ideal plastic model can well describe the mechanical state of the surrounding rock in deep buried soft rock tunnel, and then consider the influence of principal stress and expansion in surrounding rock. The result shows that the volume incompressibility theory without considering the expansion effect has a physical error. Has some limitations. With the increase of expansion angle, the surrounding rock stress of deep buried soft rock tunnel increases gradually, and the radius of plastic zone increases, which is consistent with the physical meaning of the parameters. The displacement of surrounding rock of tunnel increases obviously and develops faster, and the sensitivity of surrounding displacement of tunnel to power strengthening parameter is higher. 3. The strain strengthening effect and the expansion characteristic have some synergistic effect on the stress state of the surrounding rock of the deep buried soft rock tunnel. The sensitivity of the surrounding rock displacement of the tunnel increases with the increase of the expansion angle or the exponent of power strengthening. The deformation of soft rock tunnel considering capacity expansion or strain strengthening effect is obviously larger than that without consideration. Whether or not the effect of water absorption is considered or not, for the long-term aging deformation of the surrounding rock of deep buried soft rock tunnel, with the increase of power strengthening exponent, the strain strengthening effect is strengthened, and the creep displacement of tunnel wall increases. The creep behavior of tunnel surrounding rock is more sensitive to time. The larger the expansion angle, the more the wall displacement increases and the development becomes faster. Under the condition of rich water, the deformation of deep buried soft rock tunnel considering the influence of water absorption is obviously larger than that without consideration, which is unfavorable to the long-term stability of surrounding rock. In this paper, the deformation mechanism of the deep buried soft rock tunnel is studied based on the theory, and the long-term aging deformation of the tunnel under different water conditions is explored. The analytical results can be used as the theoretical basis of mathematics, physics and mechanics for the construction of soft rock tunnel.
【学位授予单位】：华侨大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U451.2

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