含根量对根-土石复合体的抗剪强度影响试验初探——以垂丝海棠为例

Experimental study on the influence of root content on the shear strength of root-soil-rock composite——taking Malus halliana koehne as an example

根据现场剖面得到垂丝海棠根系沿土层的分布规律,基于数字图像处理技术量化剪切面上的含石量,结合现场根面积比和含石量的分布特征,分别在50,100,150,200k Pa四级正应力下进行改进的直接剪切试验,探究不同含根量对根-土石复合体抗剪强度的影响,分析根-土石复合体黏聚力和内摩擦角的变化规律。结果表明:(1)土石混合体抗剪强度随含石量的增大而增高,在同一正应力下,土石混合体抗剪强度变化幅度随含石量的增加呈现由缓到陡再到缓的变化规律;(2)垂丝海棠根系可提高根-土复合体、根-土石复合体的抗剪强度,二者的抗剪强度随着根面积比的增大均呈现先增高后降低的趋势,且均在根面积比为0.2%时达到最大值;(3)当含石量为30%时,含根量的变化对根-土石复合体的抗剪强度影响不大,根系主要起阻裂和增强作用;当含石量为50%时,在根面积比为0.2%时抗剪强度有明显增长,且在剪切过程中,根系附近的块石产生绕根弧形滑移,部分块石出现挤压破损现象;(4)根-土石复合体的抗剪强度符合库伦强度准则,其内摩擦角主要受含石量控制,随着含石量的增大,内摩擦角也相应增大;黏聚力主要受含根量控制,黏聚力随着根面积比的增加呈现先增大后减小的趋势,且在根面积比为0.2%时达到最大值。研究结果有助于进一步认识根系与土石混合体之间的相互作用,同时为植物加固土石混合体浅表层边坡提供一定的理论依据。

In order to investigate the effect of root content on the shear strength of the root-soil-rock composite and analyze the variation rules of the cohesion and internal friction angle of the root-soil-rock composite,the root distribution rule of the Malus halliana Koehne with the increase of buried depth was obtained according to the field profile,and the rock content along the shear surface was quantified based on the digital image analysis technique,and the modified direct shear tests were conducted under four different normal stresses(50,100,150,200 kPa)combined with the distribution characteristics of the root area ratio and rock content in the field.The results showed that:(1)The shear strength of the soil-rock mixture increases with the increase of rock content,the increment shows a change rule of“slow-steap-slow”for increasing rock content under the same normal stress.(2)The shear strength of the root-soil composite and the root-soil-rock composite can be improved with the root of the Malus halliana Koehne,and both of them increase first and decrease later with the increase of root area ratio and the maximum value is reached when the root area ratio is 0.2%.(3)When the rock content is 30%,the root content has little effect on the shear strength of root-soil-rock composite,and the roots mainly play a role in crack resistance and reinforcement.When the rock content is 50%,the shear strength increases significantly when the root area ratio is 0.2%,and the rocks around the roots produce arc slip and some rocks subject to extrusion damage during the shear process.(4)The shear strength of the root-soil-rock composite conforms to Coulomb strength criterion,and the internal friction angle is mainly controlled by the rock content,i.e.,it increases with the increase of the rock content.The cohesion is mainly controlled by the root content,i.e.,it increases firstly and then decreases with the increase of the root area ratio,and the maximum value is reached when the root area ratio is 0.2%.The results are helpful to further explore the interaction between the root system and the soil-rock mixture,and provide some theoretical basis for the plant reinforcement of the soil-rock mixture shallow slopes.