基于NbS结构的黄土填方边坡降雨物理模型试验

Rainfall Physical Model Test of Loess Filling Slope Based on the NbS Structure

黄土高原地区,在“平山造城”“固沟保塬”“治沟造地”等计划开展过程中产生了大量的填方工程边坡,存在着巨大的地质灾害隐患。为了对黄土高原地区填方边坡治理提供新的解决思路,本文将黄土-古土壤层状自稳结构引入黄土填方边坡的灾变防控中,利用生石灰以及改性纤维素对黄土进行改良,提出了基于自然的解决方案(natural-based solutions,NbS)理念的黄土填方边坡控水结构,并开展人工降雨物理模拟实验,探究了有无控水结构下填方边坡渗流场、应力场和形变场变化规律、低渗场性质对边坡的影响,最终得出边坡失稳破坏模式。结果表明:1)改良黄土具有良好的工程性质,与重塑黄土相比,其液限、塑限均提高,抗剪强度增强,饱和渗透系数大幅下降,其中,改性纤维素改良黄土渗透系数降低88.59%,石灰改良黄土渗透系数降低95.18%,有控水结构边坡水分运移速度较慢,低渗层起到了良好的隔水效果;2)抗侵蚀面层的存在提高了边坡的抗侵蚀能力,有控水结构坡面的侵蚀量仅为无控水结构的28.43%;3)有控水结构边坡变形破坏模式为渐进式剪切滑移失稳,无控水结构边坡变形破坏模式为突发式溃散流滑破坏。本研究成果可为黄土高原地区填方边坡的生态治理及灾变防控工作提供理论参考。

The increasing number of filling engineering slopes in the loess plateau area over three major projects,“building a city on leveled mountain”“consolidating the ditch and protecting the plateau”and“managing the ditch and creating land”are causing enormous potential geohazard.To provide a new solution for the treatment of the filling slopes in the loess plateau,a loess-paleosol layered self-stabilizing structure is introduced into the disaster prevention and control of loess filling slopes using quicklime and modified cellulose to improve the loess and a new water control structure of loess filling slopes is proposed based on the natural-based solution concept.Through physical model tests,the changes in the seepage field,stress field,and deformation field of filling slopes with or without water control structure are explored,and the final failure mode of slope instability is obtained.The results showed that:1)compared to the remodeled loess,the improved loess has a better liquid limit,an increased plastic limit,an increased shear strength,a significantly decreased saturated coefficient of permeability,of which the modified cellulose improved loess coefficient of permeability decreased by 88.59%and the lime improved loess coefficient of permeability decreased by 95.18%,and a slower water migration speed in slopes with a water control structure.Besides,the low-permeability layer plays a good effect of water insulation;2)the existence of anti-erosion surface layer improved the anti-erosion ability of the slope,and the erosion amount of the slope with water control structure was only 28.43%of that without water control structure;3)the deformation and failure mode of the slope with water control structure was progressive shear slip instability,while the deformation and failure mode of the slope without water control structure was sudden collapse flow slip failure.The results of this study can provide a theoretical reference for ecological management and disaster prevention of filling slopes in the loess plateau.