中文摘要：

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。

英文摘要：

Soft interlayer is a widely existing geological body in rock and soil mass. Due to its weak mechanical properties, it usually brings potential safety hazard to engineering construction. Based on the plastic limit equilibrium method, an ultimate-load formulation of soft interlayer is derived by using the modified Prandtl squeezing theory and assuming that the upper and lower layers close to the soft interlayer to be quasi-rigid. In the analysis, we suggests that under the limit state the soft interlayer between quasi-rigid layers displays plastically squeezing failure behaviors. Due to the inaccuracy of Prandtl’s shear stress solution in the x direction, new solutions of stress components and ultimate load of soft interlayer are determined with considering various boundary stress conditions. A simple formulation of the ultimate load on the soft interlayer is derived, which could reflect the comprehensive effects of dead weight, boundary stress conditions, as well as friction condition of boundaries on the ultimate load of soft interlayer.Meanwhile, by comparing results from proposed method to other methods, it is shown that, if the dead weight of interlayer is ignored,the variation of ultimate load with thickness of soft interlayer in this text generally agree with what the Prandtl method predicts; when the dead weight is taken into account, the solutions of the proposed method yields results similar to the method in the construction code. For thick interlayer, however, the proposed method can more properly reflect the influence of width on the ultimate load. In addition, the effect of the boundary friction on the ultimate load varies with width-thickness ratio of soft interlayer, and a critical width is found to exist for the interlayer, which is hardly affected by the friction condition for the interlayer with a certain thickness.