红层软岩高边坡的时效变形特性

Time-dependent Deformation Characteristics of High Slope in Red Layer Soft Rock

红层地区的工程建设日益增多,红层软岩边坡在其整个寿命期内是一个逐渐“衰老”的过程,开挖边坡在运营5~10 a以后常出现各种严重地质病害和安全风险,而在前期边坡稳定性评价中都采用传统的极限平衡法计算,但其无法根据红层特性预判边坡的长期稳定性和时效变形特征,无法指导工程设计制定出既经济又安全可靠的针对性预加固措施,因此为日后的长期安全运营留下了较大隐患。为了研究边坡工程的长期稳定性受红层特殊工程地质特性的影响,以西南红层山区某快速通道项目隧道改路基的深挖路堑100 m级高边坡工程为例,通过FLAC 3D建立了包含特殊节理裂隙单元的复杂数值模型,计算获得了边坡潜在变形范围、潜在滑面位置、深度等,对比分析了边坡刚开挖完成时、未加支护工程蠕变20 a和增加支护工程蠕变20 a后这3种工况下的长期稳定状态、位移及应力变化等时效变形特性。计算结果表明:红层地区高边坡在长期服役环境下会发生蠕变、应力松弛、软化破坏等复杂变形,其普遍存在于实际工程中,后期针对性的支护方案应高度重视红层软岩高边坡的时效变形问题。计算结果成功应用于最终工程设计中,填补了传统计算方法难以分析解决此类问题的空白,以期为今后红层地区这类高达100 m量级的软岩高边坡开挖后的时效变形特性研究和加固设计提供一定的参考和借鉴作用。

The special engineering geological characteristics of red beds,the red beds soft rock slope is a gradual“aging”process in its whole life.After 5 to 10 years of operation,excavated slopes often appear various serious geological diseases and safety risks.Although the traditional limit equilibrium method is often used to calculate the stability of slope in the early stage,owing to the characteristics of red beds,the method can not predict the long-term stability and time-dependent deformation characteristics of slope,and can not guide engineering design to formulate economic,safe and reliable targeted pre-reinforcement measures,thus leaving a greater hidden danger for the long-term safe operation in the future.In order to study the long-term stability of slope engineering,affected by the special engineering geological characteristics of red bed,Taking the 100 m magnitude deep excavation cutting high slope engineering of a fast-track project in southwest red beds mountainous area as an example,a complex numerical model including special joint and crack elements is established by FLAC 3D.The potential deformation range,potential sliding surface location and depth of the slope are calculated and obtained.The creep of the slope at the completion of the first excavation,20 years without additional support engineering and additional support workers are compared and analyzed.After 20 years of creep,the long-term stability,displacement and stress changes under these three conditions are analyzed.The results show that:Creep,stress relaxation,softening failure and other complex deformation behaviors of high slopes in red beds will occur under long-term service environment.They are ubiquitous in practical projects.The time-dependent deformation of high slopes in red beds should be paid great attention to in later supporting schemes.The research findings have been successfully applied to the final engineering design,filling in the blank of the traditional statistical calculation method which is difficult to analyze and solve such problems,and is hoped to provide some references for the future research and reinforcement design of the time-dependent deformation characteristics of such high soft rock slopes up to 100 m magnitude in the red bed area.