考虑层面滑移条件的软弱夹层极限荷载分析

Ultimate Load Analysis of Soft Interlayer Considering Slip Plane Conditions

针对现有岩土体中软弱夹层的极限荷载计算理论无法全面考虑层面滑移条件,且多数理论采用金属材料屈服准则,并不适用于具有内摩擦特性的岩土材料的问题,基于Prandtl塑性挤出破坏模式,采用主应力法和摩尔-库仑屈服准则,分析了3种层面滑移条件下软弱夹层极限荷载的变化规律及3种滑移条件的适用范围,得到了相应的极限荷载计算公式,并将其与薄层挤压理论及Prandtl理论进行了对比,指出了所述方法适用的夹层宽厚比范围。结果表明:软弱夹层的极限荷载随夹层宽厚比、强度参数、摩擦因数的增加而增大,但摩擦因数高于一定值以后极限荷载不再随之变化;夹层面滑移条件在强度较低时对极限荷载的影响不明显,极限荷载主要受夹层材料强度参数控制;软弱夹层强度逐渐提高时,夹层面的滑移条件对极限荷载的影响逐步变大,尤其在夹层宽厚比较大时更为显著;提出的极限荷载计算公式能较明确地反映夹层面滑移条件对极限荷载的影响,可以为岩土体中软弱夹层的稳定性分析提供参考。

Aimed at the problems that some available calculation theories of ultimate load to soft interlayer could not fully take into account of the slip plane conditions and most of these theories adopted metal yielding criteria, not suit for geo-materials with internal friction characteristics, based on Prandtl＇s plastic extrusion failure mode, the variation law of ultimate load of soft interlayer under three slip conditions and the applicable scopes of these slip conditions were analyzed with the main stress method and the Mohr-Coulomb yielding criteria. Meanwhile, the relevant formulas for ultimate load were also deduced. The solutions were contrasted with those of thin-layer extrusion theory and Prandtl＇s squeezing theory, and the appropriate scope of flakiness ratios of the proposed method was also suggested. The results show that the ultimate load of soft interlayer is enhanced with the increment of flakiness ratio, strength parameter and friction coefficient. However, as the friction coefficient increases to a certain value, the ultimate load will not be varied anymore. The effect of slip conditions on ultimate load is not obvious when the strength parameter is low, and the ultimate load is controlled mainly by strength parameters. While the strength of soft interlayer increasing gradually, the influence of slip conditions on ultimate load is enhanced steadily, it is even more significant especially with a higher value of flakiness ratio. The proposed formula can reflect the effect of surface slip conditions to the ultimate load of soft interlayer more definitely, and can contribute references to the stabilization analysis of soft interlayer in rock-soil mass.