基于缩尺降雨模型的狗牙根-锚杆框格梁组合护坡效应试验研究

Experimental study on combined slope protection effect of cynodon dactylon- anchor rod frame beam based on reduced-scale rainfall model

摘要

为解决生态-工程组合护坡稳定性维持机理研究不足、忽视植物根系作用的问题,依托云南昆明某边坡工程,以根系发达的狗牙根-锚杆框格梁为研究对象,基于相似理论,按照几何相似比50∶1以及密度等相似比1∶1构建坡率1V:0.4H及1V:0.6H两种边坡模型,通过在室内开展最大降雨工况150 mm·d^-1、34 h单次独立人工降雨模型试验,分别监测裸露与植被边坡孔隙水压力、土压力及边坡变形,研究组合护坡效果。结果表明:在本次试验条件下,狗牙根-锚杆框格梁加固能有效降低边坡孔隙水压力与土压力34 h终值,相较于裸露边坡,1V:0.4H植被边坡坡顶、坡中、坡脚处孔隙水压力终值分别降低约8%、7%、8%,土压力终值分别降低约10%、9%、11%,1V:0.6H植被边坡坡顶、坡中、坡脚处孔隙水压力终值分别降低约6%、6%、7%,土压力终值分别降低约7%、7%、9%;狗牙根根系对土体有加筋作用,可延缓裂缝发育并提升边坡稳定性,植被边坡裂缝出现时间及破坏时间均晚于裸露边坡且缓坡效果更明显。本研究可为植被-工程组合护坡技术应用研究提供数据与方法支撑。

Abstract

To address the research gaps in the stability maintenance mechanism of ecological-engineering combined slope protection systems and the neglect of the role of plant root systems, this study takes a slope engineering project in Kunming, Yunnan as the research background, with the cynodon dactylon-anchor rod frame beam system featuring well-developed root systems as the research object. Based on the similarity theory, two slope models with gradient ratios of 1V:0.4H and 1V:0.6H are constructed according to a geometric similarity ratio of 50∶1 and a density similarity ratio of 1∶1. By conducting indoor artificial rainfall model experiments under the maximum rainfall condition of 150 mm·d^-1 for a single independent duration of 34 hours, the pore water pressure, earth pressure and slope deformation of both bare and vegetated slopes are monitored respectively to investigate the combined slope protection effect. The results show that under the experimental conditions of this study, the reinforcement of cynodon dactylon-anchor frame beams can effectively reduce the final values of pore water pressure and earth pressure in slopes after 34 hours. Compared with the bare slope, for the 1V:0.4H vegetated slope, the final pore water pressure at the slope crest, middle slope and slope toe decreases by approximately 8%, 7% and 8%, respectively, and the final earth pressure decreases by about 10%, 9% and 11%, respectively. For the 1V:0.6H vegetated slope, the final pore water pressure at the slope crest, middle slope and slope toe reduces by roughly 6%, 6% and 7%, respectively, and the final earth pressure reduces by around 7%, 7% and 9%, respectively. The cynodon dactylon roots exert a soil reinforcement effect, which can delay crack development and improve slope stability. The crack initiation time and failure time of vegetated slopes are later than those of bare slopes, and the effect is more significant on gentle slopes. This study provides data and methodological references for the application research of vegetation-engineering combined slope protection technology.To address the insufficient research on the stability maintenance mechanisms of ecological-engineering combined slope protection and the neglect of the plant root effects, this study is based on a slope engineering project in Kunming, Yunnan. Taking the deeply rooted Bermuda grass (Cynodon dactylon)-anchor frame beam system as the research object, two slope models with gradient ratios of 1V:0.4H and 1V:0.6H were constructed according to similarity theory, with a geometric similarity ratio of 50∶1 and a density similarity ratio of 1∶1. Indoor single-event artificial rainfall model experiments were conducted under a maximum rainfall intensity of 150 mm·d^-1 for a duration of 34 hours, during which pore water pressure, earth pressure and slope deformation were monitored for both bare and vegetated slopes to evaluate the combined protection effect. The results show that under the experimental conditions of this study, the reinforcement with the Bermuda grass-anchor frame beam system effectively reduces the final values of pore water pressure and earth pressure after 34 hours. Compared with the bare slope, for the 1V:0.4H vegetated slope, the final pore water pressure at the slope top, middle slope and toe decreased by approximately 8%, 7% and 8%, respectively, and the final earth pressure decreased by about 10%, 9% and 11%, respectively. For the 1V:0.6H vegetated slope, the final pore water pressure at the slope top, middle slope and toe decreased by roughly 6%, 6% and 7%, respectively, and the final earth pressure decreased by around 7%, 7% and 9%, respectively. The root system of Bermuda grass exerts a soil-reinforcing effect, which retards crack development and enhances slope stability. The occurrence time of cracking and the failure time of vegetated slopes were both later than those of the bare slopes, with the effect being more pronounced on the gentler slope. This study provides data and methodological references for the application research of vegetation-engineering combined slope protection technologies.

关键词

边坡 / 室内模型试验 / 孔隙水压力 / 土压力 / 变形特征

Key words

slope / indoor model experiment / pore water pressure / earth pressure / deformation characteristics

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基金资助

国家自然科学基金项目(12462033)