Quantified effects of fixing soil by root system of Broussonetia papyrifera based on experiment and model
BO Shengnan, WANG Yunqi, MA Chao, LI Yaguang
1. Jinyun Forest Ecosystem Research Station, School of Soil and Water Conservation, Beijing Forestry University, 100083, Beijing, China;
2. Beijing Engineering Research Center of Soil and Water Conservation(Beijing Forestry University), 100083, Beijing, China
Abstract：[Background] Roots of vegetation play an important role in slope stability, and increase soil strength. To study and quantify the effect of the root system on soil reinforcement, taking the Broussonetia papyrifera as the research object, the reinforcement effect of the root system of the B. papyrifera was determined by two methods of experimental determination and model calculation.[Methods] We used root-soil samples of B. papyrifera with different root diameters and volumes, and measured the pull strength of root-soil samples. Direct shear instrument was used to determine the shear strength of the root-soil and soil blocks. Wu model was to calculate the root shear strength increment of the root-soil samples. Compared measured values with the calculated values by Wu model, the effect of the diameter and the number of roots on the increment of shear strength were analyzed.[Results] 1) The tensile strength and pull strength of B. papyrifera root decreased with the increase of diameter. Two strengths intersected at a diameter of 1.3 mm. The root's pull strength was greater than the tensile strength when the diameter was < 1.3 mm; the tensile strength was higher than the pull strength when the root system was > 1.3 mm. 2) The results of the direct shear test showed that when the positive pressure on the shear surface was smaller, the shear strength of the soil-root blocks increased with the increase of the root diameter and the number of roots. As the positive pressure increased, the relationship between the shear strength and root diameter and the number of roots was no longer a simple incremental relationship. The maximum shear strength of root-soil complexes with the same number of roots migrated toward the smaller diameter of the average root diameter. 3) Wu model overestimated the effect of roots on soil reinforcement, and high valuation increased as the number of roots and root diameter increases.[Conclusions] There is a threshold between the tensile strength and the pull strength, and it is 1.3 mm. Under a certain range of root cross-sectional area ratio, the influence of the increase in shear strength of smaller diameter roots is more significant than the number of roots. For soil of Jiufeng and the root of B. papyrifera, we revised the k' value as 0.45. In addition, how to improve the simulation accuracy of the model and explore the numerical model of strength suitable for the failure of different plant roots is still a direction in this field.
孛胜男1, 王云琦1,2, 马超1,2, 李亚光1,2. 基于试验与模型的构树根系固土效果量化的研究[J]. 中国水土保持科学, 2019, 17(1): 24-30.
BO Shengnan, WANG Yunqi, MA Chao, LI Yaguang. Quantified effects of fixing soil by root system of Broussonetia papyrifera based on experiment and model. SSWC, 2019, 17(1): 24-30.
李建兴,何丙辉,谌芸,等.不同护坡草本植物的根系分布特征及其对土壤抗剪强度的影响[J].农业工程学报, 2013, 29(10):144. LI Jianxing, HE Binghui, CHEN Yun, et al.Root distribution features of typical herb plants for slope protection and their effects on soil shear strength[J]. Transactions of the CSAE, 2013, 29(10):144.
[2]
郭翚,王云琦,王玉杰,等.根系逐渐破坏过程中固土效果研究[J].北京林业大学学报, 2015, 37(6):85. GUO Hui, WANG Yunqi, WANG Yujie, et al. Change of fixation effects in process of gradual damage[J]. Journal of Beijing Forestry University, 2015, 37(6):85.
[3]
WU T H. Investigation of landslides on prince of Wales Island, Alaska[M]. Columbus:Ohio State University, USA, 1976.
[4]
WALDRON L J. The shear resistance of root-permeated homogeneous and stratified soil[J]. Soil Science Society of America Journal, 1977, 41(5):843.
[5]
MATTIA C, BISCHETTI G B, GENTILE F. Biotechnical characteristics of root systems of typical Mediterranean species[J]. Plant and Soil, 2005, 278(1/2):23.
[6]
LOADES K W, BENGOUGH A G, BRANSBY M F, et al. Planting density influence on fibrous root reinforcement of soils[J]. Ecological Engineering, 2010, 36(3):276.
[7]
及金楠,张志强,郭军庭,等.黄土高原刺槐和侧柏根系固坡的有限元数值模拟[J].农业工程学报, 2014, 30(19):146. JI Jinnan, ZHANG Zhiqiang, GUO Junting, et al. Finite element numerical simulation of black locust (Robinia pseudoacacia) and arborvitae (Platycladus orientalis) roots on slope stability on Loess Plateau of China[J]. Transactions of the CSAE, 2014, 30(19):146.
[8]
GRAY D H, SOTIR R B. Biotechnical and soil bioengineering slope stabilization:A practical guide for erosion control[M]. New York:John Wiley & Sons, 1996:54.
[9]
GENET M, STOKES A, SALIN F, et al. The influence of cellulose content on tensile strength in tree roots[J]. Plant and Soil, 2005, 278(1/2):1.
[10]
POLLEN N, SIMON A. Estimating the mechanical effects of riparian vegetation on stream bank stability using a fiber bundle model[J]. Water Resources Research, 2005(41):7025.
[11]
FAN C C, SU C F. Role of roots in the shear strength of root-reinforced soils with high moisture content[J]. Ecological Engineering, 2008, 33(2):157.
[12]
DOCKER B B, HUBBLE T C T. Quantifying root-reinforcement of river bank soils by four Australian tree species[J]. Geomorphology, 2008, 100(3):401.
[13]
朱锦奇,王云琦,王玉杰,等.基于试验与模型的根系增强抗剪强度分析[J].岩土力学, 2014, 35(2):449. ZHU Jinqi, WANG Yunqi, WANG Yujie, et al. Analysis of root system enhancing shear strength based on experiment and model[J]. Rock and Soil Mechanics, 2014, 35(2):449.
[14]
PRETI F. On root reinforcement modeling[R]. Geophysical Research Abstracts, 2006(8):4555.
[15]
POLLEN N. Temporal and spatial variability in root reinforcement of stream banks:Accounting for soil shear strength and moisture[J]. Catena, 2007, 69(3):197.
[16]
张秋玉,李远发,梁芳.构树资源研究利用现状及其展望[J].广西农业科学, 2009, 40(2):217. ZHANG Qiuyu, LI Yuanfa, LIANG Fang. The research and utilization status of Broussonetia papyrifera resources and its prospect[J]. Guangxi Agricultural Sciences, 2009, 40(2):217.
[17]
WALDRON L J, DAKESSIAN S. Soil reinforcement by roots:Calculation of increased soil shear resistance from root properties[J]. Soil Science, 1981, 132(6):427.
[18]
OPERSTEIN V, FRYDMAN S. The influence of vegetation on soil strength[J]. Proceedings of the Institution of Civil Engineers-Ground Improvement, 2000, 4(2):81.
[19]
CAZZUFFI D, CRIPPA E. Contribution of vegetation to slope stability:An overview of experimental studies carried out on different types of plants[C]//Briaud J L, Bhatia S K. Erosion of Soils and Scour of Foundations. Reston:ASCE, 2005:130.
[20]
HUBBLE T C T, DOCKER B B, RUTHERFURD I D. The role of riparian trees in maintaining riverbank stability:A review of Australian experience and practice[J]. Ecological Engineering, 2010, 36(3):292.
[21]
朱锦奇,王云琦,王玉杰,等.基于两种计算模型的油松与元宝枫根系固土效能分析[J].水土保持通报, 2015, 35(4):277. ZHU Jinqi, WANG Yunqi, WANG Yujie, et al. An analysis on soil physical enhancement effects of root system of Pinus tabulaeformis and Acer truncatum based on two models[J]. Bulletin of Soil and Water Conservation, 2015, 35(4):277.
[22]
BENNETT S J, SIMON A. Riparian vegetation and fluvial geomorphology[M]. Washington:AGU, 2004:125.
[23]
朱锦奇,王云琦,王玉杰,等.根系主要成分含量对根系固土效能的影响[J].水土保持通报, 2014, 34(3):166. ZHU Jinqi, WANG Yunqi, WANG Yujie, et al. Effect of root main component content on its soil-binding capacity[J]. Bulletin of Soil and Water Conservation, 2014, 34(3):166.
[24]
管世烽,夏振尧,张伦,等.水平荷载作用下多花木兰根系拉拔试验研究[J].长江科学院院报, 2016, 33(6):24. GUAN Shifeng, XIA Zhenyao, ZHANG Lun, et al. Pull-out test of Indigofera amblyantha Craib root under horizontal load[J]. Journal of Yangtze River Scientific Research Institute, 2016, 33(6):24.
[25]
THOMAS R E, POLLEN-BANKHEAD N. Modeling root-reinforcement with a fiber-bundle model and Monte Carlo simulation[J]. Ecological Engineering, 2010, 36(1):47.
[26]
POLLEN N. Temporal and spatial variability in root reinforcement of stream banks:Accounting for soil shear strength and moisture[J]. Catena, 2007, 69(3):197.
[27]
FRYDMAN S, OPERSTEIN V. Numerical simulation of direct shear of root reinforced soil[J]. Proceedings of the ICE-Ground Improvement, 2001, 5(1):41.
[28]
栗岳洲,付江涛,余冬梅,等.寒旱环境盐生植物根系固土护坡力学效应及其最优含根量探讨[J].岩石力学与工程学报, 2015, 34(7):1370. LI Yuezhou, FU Jiangtao, YU Dongmei, et al. Mechanical effects of halophytes roots and optimal root content for slope protection in cold and arid environment[J]. Chinese Journal of Rock Mechanics and Engineering, 2015, 34(7):1370.
[29]
胡其志,周政,肖本林,等.生态护坡中土壤含根量与抗剪强度关系试验研究[J].土工基础, 2010, 24(5):85. HU Qizhi, ZHOU Zheng, XIAO Benlin, et al. Experimental research on relationship between root weight and shearing strength in soil[J]. Soil Engineering and Foundation, 2010, 24(5):85.
2019, Vol. 17 
