太行山区林木根系单根固土生物力学及疲劳特性研究

Study on the Biomechanics and Fatigue Characteristics of Single Root Soil and Soil of Tree Roots in Taihang Mountain

为了揭示河北太行山区崇陵小流域林木根系固土能力,选取太行山区崇陵小流域内的20年生油松(Pinus tabulaeformis)和侧柏(Platycladus orientalis)人工林为研究对象,采用室内单根拉伸试验的方法,测定3、5、7mm 3个径阶下最大抗拉力平均值和平均抗拉强度,对根系疲劳前后固土的力学特性及根系疲劳过程进行研究。结果表明:1)疲劳前后油松和侧柏根系的最大抗拉力与根径呈正相关关系,回归曲线采用幂函数拟合;2)疲劳前后油松根系最大抗拉力平均值和平均抗拉强度均高于侧柏,疲劳后2种林木根系抗拉强度随根径的变化规律与疲劳前一致;3)疲劳后不同径阶油松和侧柏最大抗拉力和抗拉强度均有提升,疲劳后油松和侧柏根系3个径级(3、5、7mm)的极限抗拉力比疲劳前分别增加了69.2%、36.5%、37.7%和13.7%、12.9%、32.9%,疲劳后油松和侧柏根系的平均抗拉强度分别是疲劳前的1.50倍和1.19倍;4)林木根系滞回曲线表现出明显的周期循环特征,最初几个周期"滞回环"饱满且间隙明显,"滞回环"间距随着循环周期的增加越来越密集,几乎形成闭合曲线,逐渐趋于稳定。

In order to reveal the Hebei Taihang mountain Chongling watershed forest root soil fixation ability,this study selected taihang mountain chung ling in the small watershed of Pinus tabulaeformis and Platycladus orientalis plantation 20 years as the research object,using the method of indoor single tensile test,the mechanical properties of solid soil before and after the fatigue of root and root system to research the fatigue process.The results show that:1)The maximum tensile strength and root diameter of the P.tabulaeformisand P.orientalis root system were positively correlated with the root diameter before and after fatigue,and the regression curve was fitted with power function;2)The maximum tensile strength of the P.tabulaeformis root system(368.50 N;518.75 N)is higher than the average of the P.orientalis(305.18 N;374.82 N)before and after fatigue.The average tensile strength of the P.tabulaeformis root system before the fatigue(17.35 MPa)was greater than the average tensile strength of the P.orientalis(14.25 MPa)before the fatigue.After fatigue,the root diameter of the two trees was consistent with the change of root diameter before fatigue,the tensile strength of the P.tabulaeformis root system(25.90 MPa)is still higher than that of the P.orientalis(16.93 MPa);3)The maximum tensile strength and tensile strength of P.tabulaeformis and P.orientalis were both improved after fatigue.Among them,the ultimate tensile strength of the various diameters of the P.tabulaeformis and P.orientalis roots increased by69.2%,36.5%,37.7%and 13.7%,12.9%,32.9%respectively,the average tensile strength of P.tabulaeformis and P.orientalis root was 1.50 times and 1.19 times before fatigue;4)Tree root hysteresis curve showed obvious cycle characteristics,beginning'sluggish loopback'full and arrangement sparse,with the increase of cycling times,'sluggish loopback'spacing is more and more intense,and gradually close to the closing,the last phase of the hysteresis loop is almost repeated on the same hysteretic ring.