植被护坡中根土复合土体抗剪强度分析
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摘要
针对植被护坡的稳定性难以界定和直剪仪大小限制试验素材大小的问题,为探索植被护坡中根土复合体的抗剪强度与树根和土体间组合方式的关系,选取乔木根和红黏土为材料,运用自行研制的大型直剪仪进行了大量根和土不同组合形式的直剪试验,并将根和土的力学模型推广到三维模型。结合试验数据和公式推导,研究发现:竖直布置根系并不能够让根土复合体的抗剪强度得到最大发挥;在设定的土质和含水量的条件下,试验结果和力学模型都显示,三维空间内单根沿滑坡方向呈62°时能更充分的发挥根系的作用,单根条件下提升根土复合体的强度最大为15.1%;根系穿过滑裂面时,将阻碍边坡的滑动,固坡效果明显。因此,树根能够限制边坡的侧向变形,使挡土墙内应力分布更平均,降低应力集中的可能。研究成果为拓展乔木根系对增强边坡抗剪强度的应用提供了依据。
Aiming at the problems of that the stability of vegetation revetment is difficult to be defined and the size of raw material for test is limited by the size of direct shear apparatus,the direct shear tests on large amount of different root-soil combination modes are carried out with self-developed large shear apparatus through selecting tree-root and red clay as the materials for the test,so as to explore the relationship between the shearing strength of the root-soil composite in vegetation revetment and the treeroot and soil mass combination mode,and then the root-soil mechanical model is also extended to a 3-D model. Combined with the test data and the relevant formula deduction,the study finds out that the vertical arrangement of root system cannot fully exert the shearing strength of the root-soil composite. Under the given conditions of soil property and water content,both the test result and mechanical model show that the role of root system can be more fully played when a single root presents a definite 62°within a 3-D space,while the strength of the root-soil composite can be enhanced by 15. 1% at the maximum under the condition of single root. When root system passes through sliding plane,the sliding motion therein is to be restricted,thus the effect of slop reinforcement is obvious. Therefore,root system can restrict the lateral deformation of slope and make the stress distribution inside of retaining wall more uniform,and then lower the possibility of stress concentration. The study result provides a basis for extending the application of tree root system to enhance the shearing strength of slope.
Aiming at the problems of that the stability of vegetation revetment is difficult to be defined and the size of raw material for test is limited by the size of direct shear apparatus,the direct shear tests on large amount of different root-soil combination modes are carried out with self-developed large shear apparatus through selecting tree-root and red clay as the materials for the test,so as to explore the relationship between the shearing strength of the root-soil composite in vegetation revetment and the treeroot and soil mass combination mode,and then the root-soil mechanical model is also extended to a 3-D model. Combined with the test data and the relevant formula deduction,the study finds out that the vertical arrangement of root system cannot fully exert the shearing strength of the root-soil composite. Under the given conditions of soil property and water content,both the test result and mechanical model show that the role of root system can be more fully played when a single root presents a definite 62°within a 3-D space,while the strength of the root-soil composite can be enhanced by 15. 1% at the maximum under the condition of single root. When root system passes through sliding plane,the sliding motion therein is to be restricted,thus the effect of slop reinforcement is obvious. Therefore,root system can restrict the lateral deformation of slope and make the stress distribution inside of retaining wall more uniform,and then lower the possibility of stress concentration. The study result provides a basis for extending the application of tree root system to enhance the shearing strength of slope.
引文
[1]杨秀元,姚亚辉,王爱军.云南鲁旬溶蚀堆积体滑坡研究:以龙头山镇葫芦桥滑坡为例[J].地震工程学报,2016,38(S1):138-143.
[2]郑力,谢春燕,李岩,等.强度折减法在三种坡度下的植物护坡应用[J].水利水电技术,2017,48(12):138-145.
[3]郭长宝,张永双,王涛,等.南北活动构造带中段地质灾害与重大工程地质问题概论[J].地质力学学报,2017,23(5):707-722.
[4]WALDRON L J.The shear resistance of root-permeated homogeneous and stratified soil[J].Soil science society of America journal,1977,41(5):843-849.
[5]WU T H,MCKINNELL W P,SWANSTON D N.Strength of tree roots and landslides on Prince of Wales Island,Alaske[J].Canadian journal of geotechical research,1979,16(1):19-33.
[6]POLLEN N,SIMON A.Estimating the mechanical effects of riparian vegetation on stream bank stability using a fiber bundle mode[J].Water resouces research,2005,41(7):226-244.
[7]赵记领,李光范,胡伟,等.不同降雨形式下植被边坡含水率变化对比试验研究[J].自然灾害学报,2017,26(3):193-199.
[8]周跃,徐强,络华松,等.乔木侧根对土体的斜向牵引效应Ⅰ原理和数学模型[J].山地学报,1999(1):5-10.
[9]周跃,徐强,络华松,等.乔木侧根对土体的斜向牵引效应Ⅱ野外直测[J].山地学报,1999(1):11-16.
[10]文伟,李光范,胡伟,等.浅层滑坡中的乔木根系阻滑效应及变形特性试验研究[J].防灾减灾工程学报,2016,36(4):587-594.
[2]郑力,谢春燕,李岩,等.强度折减法在三种坡度下的植物护坡应用[J].水利水电技术,2017,48(12):138-145.
[3]郭长宝,张永双,王涛,等.南北活动构造带中段地质灾害与重大工程地质问题概论[J].地质力学学报,2017,23(5):707-722.
[4]WALDRON L J.The shear resistance of root-permeated homogeneous and stratified soil[J].Soil science society of America journal,1977,41(5):843-849.
[5]WU T H,MCKINNELL W P,SWANSTON D N.Strength of tree roots and landslides on Prince of Wales Island,Alaske[J].Canadian journal of geotechical research,1979,16(1):19-33.
[6]POLLEN N,SIMON A.Estimating the mechanical effects of riparian vegetation on stream bank stability using a fiber bundle mode[J].Water resouces research,2005,41(7):226-244.
[7]赵记领,李光范,胡伟,等.不同降雨形式下植被边坡含水率变化对比试验研究[J].自然灾害学报,2017,26(3):193-199.
[8]周跃,徐强,络华松,等.乔木侧根对土体的斜向牵引效应Ⅰ原理和数学模型[J].山地学报,1999(1):5-10.
[9]周跃,徐强,络华松,等.乔木侧根对土体的斜向牵引效应Ⅱ野外直测[J].山地学报,1999(1):11-16.
[10]文伟,李光范,胡伟,等.浅层滑坡中的乔木根系阻滑效应及变形特性试验研究[J].防灾减灾工程学报,2016,36(4):587-594.
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