荒漠植被根系增强土体抗剪强度性能研究

Study on shear strength performance of soil mass enhancedby root system of desert vegetation

为研究塔里木河干流上游岸坡荒漠植被根系对土体抗剪强度的增强作用,在初步分析流域植被覆盖现状基础上,对上游6个典型河岸进行了现场勘查,对骆驼刺(Alhagi sparsifolia.)、红柳(Tamarix ramosissima.)和芦苇(Phragmites australias.)三种典型植被覆盖的根-土复合体和无植被覆盖原状土体分别进行了12组和11组的对比取样,并进行了室内土工试验。试验结果表明:根-土复合体与原状素土相比平均黏聚力由8.04 kPa增加到16.86 kPa,增加了110%,平均内摩擦角由32.59°增加到33.76°,增加了3.6%。结合摩擦加筋原理,建立了植被根系增加土体抗剪强度的力学计算模型,通过模型计算了骆驼刺、红柳和芦苇三种植被不同根体积密度对应的根-土复合体抗剪强度,并与实测结果进行对比。结果表明:16组实测值中只有一组数据小于其相应的理论值范围(2.47<2.6 kPa),其余实测值全部大于理论计算最小值,充分说明建立的力学计算模型完全可以用于上述三种典型荒漠植被根系影响下的土体抗剪强度计算,为定量评价荒漠植被根系的固土能力提供一定的参考。

In order to study the strengthening effect from the root system of desert vegetation along the upstream bank-slope of the main stream of Tarim River on the shear strength of the soil mass therein,the site investigations on 6 typical river banks of the upper reach of the river are carried out;in which the root-soil composites covered by three typical vegetations,i.e.Alhagi sparsifolia,Tamarix ramosissima and Phragmites australias,and the undisturbed soil mass without the coverage of vegetation are comparatively sampled in 12 groups and 11 groups respectively,and then the relevant indoor geotechnical experiments are made.The experiment results show that compared with the undisturbed plain soil,the mean cohesion of the root-soil composite is enhanced from 8.04 kPa to 16.86 kPa with the increment of 110%,while the mean internal friction angle is enhanced from 32.59°to 33.76°with the increment of 3.6%.Combined with the principle of friction reinforcement,a mechanical calculation model for the enhancement of the shear strength with roots is established;from which the shear strengths of the root-soil composites corresponding to different root volume densities of the three vegetations,i.e.Alhagi sparsifolia,Tamarix ramosissima and Phragmites australias,are calculated and then compared with the relevant measured results.The results indicate that within 16 groups of the measured values,only one group of data are less than the relevant theoretical value range(2.47<2.6 kPa),all the others are larger than the minimum theoretical calculation values,thus it is fully verified that the established model can be fully applied to the calculation of the soil mass shear strengths under the effects of the root systems of the three desert vegetations mentioned above,which can provide a certain reference for quantitatively evaluating the soil consolidation capacity of the desert vegetation root system.