Method for calculating collapsible compressive stress of loess tunnel foundation
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摘要: 黄土隧道地基湿陷变形产生的不均匀沉降是导致衬砌结构破坏的重要影响因素。首先,在应用松散介质围岩压力的Terzaghi公式和松散岩柱公式确定隧道围岩压力的基础上,考虑衬砌结构自重荷载,得到了衬砌结构基底压力的两种计算方法。然后,应用半无限弹性空间解答,考虑衬砌结构基底压力和隧道两侧上覆地层土自重压力,得到了隧道地基土竖向压缩应力的解析解,从而提出了一种黄土隧道地基湿陷压缩应力的解析计算方法。利用隧道基底压力的两种解答,比较分析了不同埋深隧道的基底压力和自重应力的差异;利用隧道地基土竖向压缩应力计算方法,比较分析了隧道地基土竖向压缩应力和场地自重应力的差异,得到了地基土竖向压缩应力和场地自重应力比值沿深度的分布变化规律。并与数值计算结果比较,表明解析计算方法确定的湿陷压缩应力安全可靠,为合理评价黄土隧道地基的湿陷性提供了压缩应力条件。Abstract: The differential settlement produced by collapsible deformation of loess tunnel foundation is an important factor to cause failure of lining structures. Firstly, two methods for calculating base pressure of the lining structures are derived based on the Terzaghi formula from loose medium surrounding rock pressure and the loose rock pillar formula considering the dead load of lining structures. Then, the analytical solution of vertical compressive stress of tunnel foundation is got when that elastic half-space answer is applied and the base pressure of lining structures and the self-weight stress of at both sides of tunnel overburden soil are considered. Thereby an analytic method for collapsible compressive stress of loess tunnel foundation is proposed. The difference between different buried depths of tunnel foundation pressure and self-weight stress is analyzed by using the two methods for tunnel base pressure, and the difference between the vertical compressive stress of tunnel foundation and the field self-weight stress is analyzed by using the proposed method. The distribution variation laws of foundation compressive stress of vertical and field self-weight stress with the increase of depth are obtained. Compared with the numerical results, the proposed method is proved to be more reliable and safer. It may provide the compressive stress condition for reasonable evaluation of the collapsibility of loess tunnel foundation.
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Keywords:
- loess tunnel /
- foundation /
- collapsibility /
- compressive stress
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