干湿循环会导致压实黄土的严重恶化,从而影响填方边坡的安全性。离散元方法(DEM)可以考虑非均匀、不连续,和岩土介质的各向异性性质,更能够反映边坡稳定性分析中失稳的机理和过程。因此,本文提出利用DEM分析干湿循环条件下压实黄土边坡的稳定性。首先,为了解决DEM模型中宏观和介观参数之间复杂的校准问题,通过引入基于sigmoid加速系数的混沌粒子群算法(CPSOS),提出了一种高效的参数优化方法。其次,在参数校准期间,一个新的指标,粘结比(BR),提出了表征干湿循环过程中压实黄土中孔隙和裂缝的发展,以反映干湿作用对黄土骨料间粘结降解的影响。最后,根据参数校准的结果,建立了干湿循环作用下压实黄土边坡的稳定性分析模型。结果表明,所提出的优化标定方法能够准确反映干湿循环下实际试验结果的应力-应变曲线和强度的变化趋势,BR也反映了干湿循环对压实黄土的降解作用。边坡稳定性分析表明,DEM反映了干湿循环对压实黄土边坡安全系数的负面影响,以及干湿循环逐渐稳定的趋势。通过与有限元分析结果的对比,验证了离散元边坡稳定性分析的准确性。
Dry-wet cycles can cause significant deterioration of compacted loess and thus affect the safety of fill slopes. The discrete element method (DEM) can take into account the non-homogeneous, discontinuous, and anisotropic nature of the geotechnical medium, which is more capable of reflecting the mechanism and process of instability in slope stability analysis. Therefore, this paper proposes to use the DEM to analyze the stability of compacted loess slopes under dry-wet cycles. Firstly, to solve the complex calibration problem between macro and mesoscopic parameters in DEM models, an efficient parameter optimization method was proposed by introducing the chaotic particle swarm optimization with sigmoid-based acceleration coefficients algorithm (CPSOS). Secondly, during the parameter calibration, a new indicator, the bonding ratio (BR), was proposed to characterize the development of pores and cracks in compacted loess during dry-wet cycles, to reflect the impact of dry-wet action on the degradation of bonding between loess aggregates. Finally, according to the results of parameter calibration, the stability analysis model of compacted loess slope under dry-wet cycling was established. The results show that the proposed optimization calibration method can accurately reflect the trend of the stress-strain curve and strength of the actual test results under dry-wet cycles, and the BR also reflects the degradation effect of dry-wet cycles on compacted loess. The slope stability analysis shows that the DEM reflects the negative effect of dry-wet cycles on the safety factor of compacted loess slopes, as well as the trend of gradual stabilization with dry-wet cycles. The comparison with the finite element analysis results verified the accuracy of the discrete element slope stability analysis.