垂穗披碱草根系力学特性统计分析

Statistical Analysis on Mechanical Characteristics of Roots of Elymus nutans

垂穗披碱草作为一种适应性强、分布广泛的优良水土保持植物,广泛应用于各类山区生态恢复/修复工程。为合理评估垂穗披碱草在水土保持工程中的力学作用,本文对生长于青海省河南县的多年野生垂穗披碱草(ElymusnutansGriseb.)根系进行单根拉伸试验,测定其单根根径、抗拉力、抗拉强度、拉伸率和拉伸模量等五项力学指标;通过数理统计模型(正态分布、瑞利分布、伽马分布和威布尔分布)对五项力学指标分布特性进行统计分析;采用卡方检验(χ^2检验)和柯尔莫哥洛夫-斯米洛夫检验(K-S检验)对五项指标在不同分布函数中的显著性进行了检验;对比了两种检验方法的优劣,确定各指标的最优分布函数。研究结果表明:垂穗披碱草根系力学五项指标表现出巨大的变异性,变异系数为37.01%~76.00%;四种分布函数均可定性描述根系各指标的分布特征,但不同指标在不同分布函数下表现出一定程度的差异;相较于χ^2检验,K-S检验由于其更适用于小样本数据,其检验结果更具有可信性;五项指标中,根径和拉伸率最优分布函数均为伽马分布,抗拉力和抗拉强度最优分布函数均为威布尔分布,拉伸模量最优分布函数为正态分布。该研究结果对于深入认识垂穗披碱草根系力学特性,揭示垂穗披碱草在水土保持工程中的力学机制具有重要的理论价值。

Due to the extensive adaptability in water and soil conservation, Elymus nutans Griseb. has been introduced extensively and successfully into ecological recovery and re-establishment engineering for deserted land reclamation and ecosystem restoration for the past decades. To sufficiently understand mechanical performance and properly assess the role of E. nutans roots in soil and water conservation application, roots of uncultivated perennial E. nutans sampled at field sites of Henan county, Qinghai Province, China were taken as targeted objects. The mechanical property indexes(diameter, tensile resistance, tensile strength, tensile strain and tensile modulus) were determined using indoor tension tests. Built on these mechanical property indexes, four statistical functions, i.e., Normal distribution, Rayleigh distribution, Gamma distribution, and Weibull distribution, were adapted to describe the distribution of these mechanical indexes of E. nutans. Subsequently Chi-square test(Χ^2 test) and Kolmogorov-Smirov test(K-S test) were applied to test the goodness of fitting of these distribution functions to the five mechanical indexes. Based on the goodness of fitting, the optimal distribution functions of the mechanical indexes was determined. The results showed that great variability in root mechanical indexes was discovered. And nearly all the distribution functions could be used to describe the distribution of root mechanical indexes. In contrast to Χ^2 test, the testing results based on K-S test were more reliable due to its advantages in testing small sample. Of the five mechanical indexes, the optimal distribution functions for diameter and tensile strain were Gama distribution, tensile strength/resistance’s optimal functions were Weibull distribution, and tensile modulus’ optimal distribution was Normal distribution. The findings improve our understandings on the mechanical properties of herbaceous root and could be useful for slope protection using herbaceous roots.