强度折减法在三种坡度下的植物护坡应用

以均质黄土和油松根系组成的根土复合坡体为研究对象,在植物固土护坡力学原理的基础上,利用有限元软件ANSYS进行分析。在三种不同坡度下不断植树,采用强度折减法分析滑动面的安全系数,定量分析边坡的稳定性变化情况,从而获得最优的植树方案。由安全系数变化情况可得出:边坡为25°时,前2棵(从坡脚起)油松对于边坡稳定性的提升作用较为显著,最佳树距为3 m;边坡为35°时,为前4棵和2.5 m;边坡为45°时,为前5棵和2 m。结果表明:(1)坡度越大,种植棵数越多,离坡脚越远的树对边坡稳定性的贡献越少(安全系数增幅不断减小);(2)坡度越大,种植间距越小,但不是越小越好,有最佳值;(3)三种坡度下,坡脚处最易失稳,第一棵树根系所承受的拉应力最大,对稳定性的贡献也最大(安全系数增幅最大)。研究结果为植物护坡的植树栽植提供理论支持。

Application of strength reduction method to plant-slope protections with three kinds of slope gradients

By taking the simulated composite slope that consists of homogeneous loess and root system of Pinus tabuliformis Carrière as the study object，an analysis with the finite element software———ANSYS is made on the basis of the dynamic principle of the plant-soil reinforcement and slope protection; i. e. plantation is continuously carried out with three different slope gradients，and then the strength reduction method is adopted for analyzing the safety coefficient of the sliding plane，afterwards，the variation of the slope stability is quantitatively analyzed as well，thus an optimal plantation scheme is obtained. It can be obtained from the variation of the safety coefficient that when the slope gradient of the slope is 25°，the enhancing effect from the first two ( from the slope toe) trees ( Pinus tabuliformis Carrière) on the slope stability is more significant with the optimal tree spacing of 3 m，while the enhancing effect is from the first four trees with the optimal tree spacing of 2. 5 m when the slope gradient is 35° and from the five trees with the optimal tree spacing of 2 m when the slope gradient is 45°. The result shows that ( 1) the larger the slope gradient is，the more the tree to be planted are to be，while the farer the distance to the slope toe is，the less the contribution of the tree to the stability of the slope is to be ( the increasing amplitude is continuously decreased) ; ( 2) the larger the slope gradient is，the smaller the planting spacing is to be. However，it is not the smaller the better，as an optimal value is there. ( 3) With the three slope gradients，the instability is prone to occur at the slope toe，and then the tensile stress borne by the root system of the first tree is the largest，from which the contribution to the stability is the largest as well ( the increasing amplitude of the safety coefficient is the largest) . The result can provide a theoretical support for the plantation made for the plantslope protection.