基于应变软化特征的含软弱层公路边坡稳定性研究

Stability Evaluation of Highway Slope with Soft Layer Based on Strain Softening Characteristics

西部山区高速公路建设过程中经常由于边坡开挖而容易导致失稳事故。研究发现,大量公路边坡内的软弱夹层的岩体强度具有显著的应变软化特征。为了研究应变软化后对边坡稳定性的影响程度,以沪蓉西高速公路某典型含软弱夹层边坡为实例,对应变软化模型和理想弹塑性模型进行了对比研究。结果表明:①2种模型计算所得出的最大不平衡力、水平位移、塑性区和塑性剪应变的变化规律基本相同,每次开挖后均累计增大,但是采用应变软化模型计算的累计值和范围均大于理想弹塑性模型;②每次开挖的瞬间会产生最大不平衡力峰值,随后迅速减小,拉应力带主要分布于开挖卸荷面附近以及坡顶面附近10 m内;③软弱夹层的分布位置对边坡的稳定性影响很大,坡脚前缘软弱夹层易发生剪破坏,边坡后缘软弱夹层易发生拉破坏。应变软化模型的稳定系数比理想弹塑性模型的稳定性系数小,综合得出,影响含软弱夹层边坡稳定性的关键是开挖后软弱夹层的强度参数劣化程度,采用应变软化模型反映了这一渐进性的破坏过程,与实际情况相符,而理想弹塑性模型未反映出这一劣化特征,计算结果偏危险。

In the process of highway construction in western mountain area in China, slope excavation often leads to instability accidents. The practice shows that the strength parameters of the weak interlayer in a large number of highway slopes has a significant strain softening characteristics, which greatly influence the slope stability. In order to study the effect of strain softening on slope stability, this paper takes a typical slope with the weak interlayer to compare the two models.The results show that: ①The changes of the maximum unbalance force, horizontal displacement, plastic zone and plastic shear strain obtained by the two models are basically the same, and increase accumulatively after each excavation, but the accumulative value and range calculated by the strain softening model are larger than the ideal elastic-plastic model. ②The maximum unbalanced force peak is generated at the moment of each excavation, and then decreases rapidly.The tensile stress zone is mainly distributed within 10 meters near the excavation unloading surface and the slope top surface. ③The distribution of weak interlayer has a great impact on the stability of the slope. The weak interlayer at the front edge of the slope is prone to shear failure, while the weak interlayer at the back edge of the slope is prone to tensile failure. The stability coefficient of strain softening model is smaller than that of ideal elastoplastic model. It is concluded that the key affecting factor on the stability of the slope with weak interlayer is the deterioration degree of the strength parameters of the weak interlayer after excavation.