植物根系倾角对土体抗剪强度影响试验研究

Shear Test for Root Reinforced Soil Samples Considering the Inclination of Roots

植物是天然的工程师,拥有防止浅层滑坡和地表侵蚀的潜能,并具备低投入、低养护、绿色环保和生态平衡等优点。植被护坡技术在西南地区浅层滑坡的预防及治理中有着广泛的应用前景,因此深入了解植被护坡机理具有重要的工程意义。影响植被护坡效应的因素有很多,根-土体系的协同作用机制是当前研究的重点。由于根系的分布模式及倾角不同,根-土体系的强度和变形会有较大差异,因此采用人工根系(草根和灌木根)制备试样并设定根系与剪切面的夹角α值为变量,对比不同试样的强度和变形差异。通过直剪试验研究草本根系倾角对土体抗剪强度的影响,通过三轴剪切试验研究灌木根系倾角对土体抗剪强度的影响。试验结果表明:含根系土样的峰值强度及残余强度均明显高于素土,具有τ_(p素土)<τ_(p90°)<τ_(p45°)<τ_(p135°)的规律;直剪试验中在α值等于135°时土样抗剪强度最高且表现出应变硬化,其余含根系试样应变软化特征均得到不同程度的抑制;三轴试验中当α值为135°时根系对土体抗剪强度的提高最为明显,其残余强度也最大,其余含根系试样抗剪强度也有不同程度提高。恰当的植物根系倾角能够加强根-土体系的协同作用,从而提高土体抗剪强度。同时由于根-土体系表现出延性破坏的特征,从而保证了土坡安全。研究结果可应用于生态护坡实践。

Plants are sophisticated and intelligent natural construction materials,which can be used for enhancing the stability of shallow soil slopes and minimizing surface erosion.It is evident that the use of plants can be low-cost,sustainable(almost maintenance free)and environmentally friendly.Vegetation used in shallow slope protection has a wide application prospect in southwest China,so it is important to understand the mechanism of vegetation in slope engineering stabilization.The stabilized mechanism is influenced by a lots of factors,in which the synergistic effect of root-soil mass is the focus of current research.Due to the different inclination of roots,the shear strength of root-soil system becomes complicated.Direct and triaxial shear test were performed on soil sample with different inclinations of artificial roots to investigate the reinforcement effect.Test results indicated that the peak shear strength and the residual shear strength of roots reinforced soil were obviously larger than soil without roots,and followed the laws of τ_(p pure)< τ_(p90°)<τ_(p45°)<τ_(p135°).In the direct shear test,the largest shear strength was detected and strain hardening was observed when the inclination of roots was 135°,and strain softening tendency of soil samples with roots was controlled at different levels.When the inclination of roots was 135°,the root reinforcement effect was the most obvious and the residual strength was also the largest.It was indicated that proper inclination of roots may enhance the synergistic effect between roots and soil,then the strength of root-soil mass could be improved.The ductile deformation characteristics of root-soil system could help improve the safety of the slope.This research results is valuable for vegetated slope engineering practice.