主直根系拉拔力的室内试验研究

乔灌木主直根系对边坡土壤的深层锚固作用能明显提高边坡的稳定性,但在降雨条件下是否能发挥良好的固坡作用却存在争议,这给主直根系在降雨条件下锚固作用效果发挥的判断造成了一定的阻碍.为研究影响主直根系拉拔力的因素,本文以山矾根系为研究对象,分别在4种土壤含水率条件和3种竖向压力条件下开展单条主直根系的单次拉拔试验和循环拉拔试验,以此来研究主直根系拉拔力的问题.研究结果表明:1)根系拉拔力随根系表面压力的增大而增大,并有趋于稳定的趋势;2)根系拉拔力随土壤含水率的增加呈先增后减的趋势;3)在黏土条件下,山矾单根系的最大拉拔力所对应的土壤含水率约为22％;4)在低应力状态下,根系表皮组织完整度对根系拉拔力的影响大,而高应力状态下,根系内部组织完整度对根系拉拔力的影响大.试验证明,土壤性质及含水率,根系表面压力及完整度将对主直根系拉拔力产生影响.并且,只要保证土壤含水率不超过最优值,则主直根系的锚固作用将得到充分发挥.

Study on pull-out force in taproot by indoor test

Background] The deep anchoring effect of trees taproot and shrubs taproot on soil of slope can significantly improve the stability of slope.But in the rainfall conditions,whether the plant can play a favorable role in the stabilization of slope is controversial.Therefore,this has caused obstacles to judgement of pull-out force of taproot in rainfall conditions.Methods] To study the factors that affect the pull-out force of taproot,the Symplocos sumuntia taproot was selected as the research object in this paper,and was used to study on the problem of pull-out force of taproot.Among them,pull-out tests were carried out under 4 soil water content conditions (10％,15％,20％,and 25％) and 3 vertical stress conditions (3.06 kPa,6.13 kPa,and 9.19 kPa),and pull-out tests contains two parts:single pull-out test and cyclic pull-out test.The pull-out test device was designed as in Figure 2 by our own laboratory.Results] 1)The taproot pull-out force increased with the increase of stress on the taproot surface and gradually became stable.The single pull-out test results showed that,taking soil water content of 11.74％ of the situation as an example,when the vertical stress was 3.06 kPa,6.13 kPa and 9.19 kPa,the taproot average pull-out stress was 42.61 Pa,71.52 Pa and 91.36 Pa.2) With the increase of soil water content,the taproot pull-out force increased firstly and then decreased.The single pull-out test results showed that,taking vertical stress of 3.06 kPa of the situation as an example,when the soil water content was 11.74％,16.02％,21.11％ and 26.53％,the taproot average pull-out stress was 42.61 Pa,61.79 Pa,70.35 Pa and 63.11 Pa.3) When the soil was clay,the corresponding soil water content of the greatest pull-out force of Symplocos sumuntia taproot was 22％.4) In the low state of stress,taproot external organizational integrity had a greater effect on the pull-out force;while in the high state of stress,taproot internal organizational integrity had a greater effect on the pull-out force.Taking soil water content of 16％ of the situation as an example,when the vertical stress was 3.06 kPa and 9.19 kPa,the average pull-out stress obtained by the cyclic pull-out test was 40.79 Pa and 101.03 Pa.And the average pull-out stress obtained by the single pull-out test was 61.79 Pa and 109.01 Pa.Conclusions] Experiments show that the soil properties and water content,root surface stress and integrity will have a significant effect on the pull-out force of taproot.And,as long as the soil water content does not exceed the optimal value,the anchoring effect of the taproot will be fully exerted.