生态护坡中根系对土体抗剪强度的影响
|
摘要
在护坡工程中,植被发达的根系能对边坡土体产生一定程度的加筋作用,从而可提高边坡的浅层稳定性。为探究植物根系对土体抗剪强度的影响,采用常规三轴不固结不排水试验,测定不同含根量、含水率对重塑粉质黏土抗剪指标的影响,结果表明:①根土复合体与素土的应力-应变变化趋势相同,说明摩尔-库仑强度准则同样适用于根土复合体,其不同主要体现在黏聚力大小上;素土和根土复合体均大约在轴向应变2%处出现主应力差峰值,然后逐渐趋于破坏。②根土复合体的抗剪强度明显大于素土,并且在含水率为9%时黏聚力增加显著,说明根能起到加筋作用,能够用来约束土体变形、增加抗剪强度。③在一定条件下,黏聚力和含根量成线性正相关关系;黏聚力和含水率对数成反比关系,即在一定条件下随着含水率增大,黏聚力降低。通过拟合得到根系加筋效应公式τ_f=c+σtan φ=c_0+a+bx+σtan φ,只要给定含水率和含根量,就能初步计算出抗剪强度。
In the slope protection project,the developed root system can reinforce the slope soil to a certain extent,so as to improve the shallow stability of the slope. In order to study the influence of plant root system to the shear strength of soil,it used the conventional three axis unconsolidated undrained tests to determine the effect of different root contents and water contents on remolded silty clay shear index. The results show that a) the variation trends of reinforced soil and soil are the same,showing that Mohr-Coulomb strength criterion is also applicable to the root soil complex and mainly is reflected in the different of cohesion. The peak values of soil and reinforced soil all appear at about 2% of the strain and then tend to destroy; b) the shear strength of reinforced soil is significantly greater than that of soil and the cohesion is increased significantly when the moisture content is 9%,showing that the roots can play a reinforcing effect which can be used to increase the shear strength of soil deformation constraints and; c) the cohesion and the root content are positively correlated and show a linear distribution under certain conditions. The cohesion and water content logarithm are in inverse proportion,i.e. under certain conditions,the cohesion is decreased along with the increase of water content. The root reinforcement effect formula of is obtained by fitting,i.e. τ_f= c+σtan φ =( c_0+a+bx) +σtan φ. The shear strength can be preliminarily estimated as long as the water content and root content are given.
In the slope protection project,the developed root system can reinforce the slope soil to a certain extent,so as to improve the shallow stability of the slope. In order to study the influence of plant root system to the shear strength of soil,it used the conventional three axis unconsolidated undrained tests to determine the effect of different root contents and water contents on remolded silty clay shear index. The results show that a) the variation trends of reinforced soil and soil are the same,showing that Mohr-Coulomb strength criterion is also applicable to the root soil complex and mainly is reflected in the different of cohesion. The peak values of soil and reinforced soil all appear at about 2% of the strain and then tend to destroy; b) the shear strength of reinforced soil is significantly greater than that of soil and the cohesion is increased significantly when the moisture content is 9%,showing that the roots can play a reinforcing effect which can be used to increase the shear strength of soil deformation constraints and; c) the cohesion and the root content are positively correlated and show a linear distribution under certain conditions. The cohesion and water content logarithm are in inverse proportion,i.e. under certain conditions,the cohesion is decreased along with the increase of water content. The root reinforcement effect formula of is obtained by fitting,i.e. τ_f= c+σtan φ =( c_0+a+bx) +σtan φ. The shear strength can be preliminarily estimated as long as the water content and root content are given.
引文
[1] 周德培,张俊云.植被护坡工程技术[M].北京:人民交通出版社,2003:5-7.
[2] 张兴玲,胡夏嵩,毛小青,等.植物根系固土护坡力学机理研究现状与进展[J].人民黄河,2009,31(6):88-90,92.
[3] 赵丽兵,张宝贵,苏志珠.草本植物根系增强土壤抗剪切强度的量化研究[J].中国生态农业学报,2008,16(3):718-722.
[4] 胡其志,周一鹏,肖本林,等.根土复合体的抗剪强度研究[J].湖北工业大学学报,2011,26(2):101-104.
[5] 封金财,王建华.植物根系的存在对边坡稳定性的作用[J].华东交通大学学报,2003,20(5):42-45.
[6] 封金财,王建华.乔木根系固坡作用机理的研究进展[J].铁道建筑,2004(3):29-31.
[7] 卢海静,王磊,翟国良,等.植物根-土复合体原位剪切试验研究现状及其进展[J].中国水土保持,2013(7):42-46.
[8] 格日乐,张成福,蒙仲举,等.3种植物根—土复合体抗剪特性对比分析[J].水土保持学报,2014,28(2):85-90.
[9] 廖晶晶,罗绪强,罗光杰,等.三种护坡植物根—土复合体抗剪强度比较[J].水土保持通报,2013,33(5):118-122.
[10] 张峰,凌贤长,吴李泉,等.植被须根护坡力学效应的三轴试验研究[J].岩石力学与工程学报,2010,29(增刊2):3979-3985.
[2] 张兴玲,胡夏嵩,毛小青,等.植物根系固土护坡力学机理研究现状与进展[J].人民黄河,2009,31(6):88-90,92.
[3] 赵丽兵,张宝贵,苏志珠.草本植物根系增强土壤抗剪切强度的量化研究[J].中国生态农业学报,2008,16(3):718-722.
[4] 胡其志,周一鹏,肖本林,等.根土复合体的抗剪强度研究[J].湖北工业大学学报,2011,26(2):101-104.
[5] 封金财,王建华.植物根系的存在对边坡稳定性的作用[J].华东交通大学学报,2003,20(5):42-45.
[6] 封金财,王建华.乔木根系固坡作用机理的研究进展[J].铁道建筑,2004(3):29-31.
[7] 卢海静,王磊,翟国良,等.植物根-土复合体原位剪切试验研究现状及其进展[J].中国水土保持,2013(7):42-46.
[8] 格日乐,张成福,蒙仲举,等.3种植物根—土复合体抗剪特性对比分析[J].水土保持学报,2014,28(2):85-90.
[9] 廖晶晶,罗绪强,罗光杰,等.三种护坡植物根—土复合体抗剪强度比较[J].水土保持通报,2013,33(5):118-122.
[10] 张峰,凌贤长,吴李泉,等.植被须根护坡力学效应的三轴试验研究[J].岩石力学与工程学报,2010,29(增刊2):3979-3985.