石质陡边坡构树根系抗拉特性研究

Characteristics of Tensile of Root System of Broussonetia papyrifera Growing on Lithosol Steep Slopes

通过对构树根系进行室内单根拉伸试验,从根系生长方位和根系分级角度,系统分析了上、下坡向,一、二、三级侧根的抗拉强度和应力-应变曲线。试验研究结果表明:根系的抗拉强度随着根径的增大而减小,有着很好的幂函数关系,并且随着根径的增大,它们的抗拉强度值越来越接近;根系的应力-应变曲线与其自身的生长方位、根径大小、根系分级存在一定的关系;上、下坡向根系的抗拉强度之间存在显著性差异,其中下坡向根系的抗拉强度大于上坡向根系的抗拉强度;一、二、三级根系的抗拉强度之间不存在显著性差异,三级侧根抗拉强度平均值最大、二级侧根次之、一级侧根最小。由此可见,细根或毛根抗拉强度大,对保持边坡稳定的贡献较大。不同生长方位和分级根系对护坡的贡献也不相同,其中下坡向根系的贡献要大于上坡向根系,随着根系级别的增加,根系对护坡的贡献率也在增加。

The paper systematically analyzes the tensile strength and stress-strain curve of up slope direction,down slope direction and lateral roots of grades 1,2 and 3 from the view points of growing location and grade of root system based on indoor single-root tensile tests of root system of Broussonetia papyrifera.The outcomes show that a) the tensile strength of root system decreases along with the increase of root diameter,showing a good relationship of power exponent.Their tensile strength values are getting closer and closer along with the increase of root diameter;b) the stress-strain curve of root system has a certain relationship with its growing location,size of root diameter and grade of root system;c) there is obvious difference existed between tensile strength of root system of up slope direction and down slope direction,of which,the tensile strength of root system of down slope direction is greater than that of the up slope direction and;d) there is no obvious difference existed among root systems of grade 1,2 and 3.The average value of tensile strength of the lateral root of grade 3 is the maximum,then the grade 2 and the grade 1 the minimum.It can be seen that the tensile strength of fine root or very thin root is great,having greater contribution to the stability of slopes.The contribution of root system with different locations and different grades is also different.The contribution of root system of down slope direction is greater than that of the up slope direction and the contribution rate of root system to slope protection increases along with the increase of root system grade.