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岩土体中的软弱夹层是一种广泛存在的地质体,由于其力学性质较差,容易给工程建设带来安全隐患,对其稳定性的研究逐步引起重视。根据塑性极限平衡分析方法,针对软弱夹层的承载稳定问题,将软弱夹层上下土层当作准刚性层,基于修正Prandtl挤压理论解答对软弱夹层的极限荷载进行了计算。分析过程中认为,准刚性层间的软弱夹层在极限状态下发生塑性挤出破坏,考虑到Prandtl挤压理论的剪应力解答在x方向上的不足,结合不同的边界应力条件,对软弱夹层中的应力分量和夹层表面的极限荷载进行了重新求解。推导的极限荷载实用计算式能综合考虑软弱夹层面的摩擦条件、土层自重及夹层周围的受力状态等因素,并与其他理论计算式的结果进行了对比分析。计算结果分析表明,不考虑土重时,该方法计算的夹层极限荷载随厚度变化规律与Prandtl方法基本一致;考虑土重影响时,该方法计算结果与规范法相似,但在夹层较厚时能更明确地反映宽度对极限荷载的影响。此外,夹层上下边界的摩擦条件对极限荷载的影响程度随夹层宽厚比的不同而变化,对于一定厚度的夹层存在几乎不受摩擦条件影响的临界宽度。其研究结果可为软弱夹层的承载稳定分析提供参考。
The weak interlayer in rock and soil body is a kind of widespread geological body. Because of its poor mechanical property, it is easy to bring potential safety hazard to engineering construction, and the research of its stability is gradually paid more attention. According to the plastic limit equilibrium analysis method, considering the bearing stability of soft interlayer, the upper and lower layers of the soft interlayer are considered as the quasi-rigid layer, and the ultimate load of the weak interlayer is calculated based on the modified Prandtl squeezing theory. It is considered in the analysis that the soft interlayer between the quasi-rigid layers undergoes plastic extrusion failure under the limit state. Considering the deficiency of the shear stress solution of Prandtl’s extrusion theory in the x direction, in combination with different boundary stress conditions, The stress components and the ultimate load on the mezzanine surface have been re-solved. The deduced practical formula of ultimate load can comprehensively consider such factors as the friction condition of soft interlayer, the weight of soil and the stress state around the interlayer, and compared with other theoretical calculation results. The calculation results show that the method of calculating the ultimate load of the sandwich with the Prandtl method is basically consistent with the Prandtl method when the soil weight is not taken into account. When the soil weight is considered, the calculated result is similar to the normal method. However, More clearly reflect the impact of width on the ultimate load. In addition, the influence of the friction condition of the upper and lower boundary layers on the ultimate load varies with the ratio of the width to thickness of the interlayer, and there is a critical width that is hardly affected by the friction condition for a certain thickness of the interlayer. The results of this study can provide reference for the bearing stability analysis of soft interlayer.