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

MECHANICAL EFFECTS OF HALOPHYTES ROOTS AND OPTIMAL ROOT CONTENT FOR SLOPE PROTECTION IN COLD AND ARID ENVIRONMENT

以大柴旦盐湖区及其周边地区为例,选取海韭菜、赖草、毛穗赖草、无脉苔草4种优势盐生植物,对其单根进行单根拉伸试验以及4种植物根–土复合体抗剪强度试验。分别获得4种植物单根抗拉力和单根抗拉强度;通过对4种盐生植物根–土复合体在不同含根量梯度下的直接剪切试验,探讨根系对土体抗剪强度增强作用以及根–土复合体的最优含根量。由单根拉伸试验结果表明,4种植物平均单根抗拉力值为4.67~10.97 N,平均单根抗拉强度值为12.32~49.99 MPa,且4种植物平均单根抗拉强度由大至小依次为赖草、毛穗赖草、无脉苔草、海韭菜;4种植物根–土复合体扰动试样黏聚力值为10.44~27.42 k Pa,不含根素土试样黏聚力值为8.10 k Pa,与不含根系素土相比,根–土复合体的黏聚力增长量为2.34~19.32 k Pa,其增幅为28.89%~238.52%;根系增强土体抗剪强度存在最优含根量,根–土复合体试样中的含根量处于最优含根量时,4种植物根–土复合体的抗剪强度为相对最大值,其黏聚力值为17.94~27.42 k Pa,黏聚力由大至小依次为海韭菜、赖草、毛穗赖草、无脉苔草。该研究成果对大柴旦盐湖区以及与该区地质条件相似的其他地区开展利用盐生植物增强土体抗剪强度,且对于开展有效防治土体侵蚀和地表水土流失等地质灾害的发生具有理论价值和实际意义。

The area of experimental research is Da Qaidam salt lake region and the surrounding areas. The tension tests of single root as well as the shear strength test of the root-soil composite system of the four dominant halophytes(Leymus secalinus Tzvel.,Leymus paboanus Claus.,Carex enervis C. A. Mey. and Triglochin maritima Linn) were performed. The tensile resistance and the corresponding tensile strength for 4 species were determined. In addition,the effect of roots on the shear strength of soil and the optimal root content were studied through the direct shear test on root-soil systems of four halophytes. The results of single root tensile test showed that the average tensile resistance of single root for four halophytes was 4.67–10.97 N and the average tensile strength of single root for four halophytes was 12.32–49.99 MPa. The descending order of the average tensile strength for the 4 halophytes was Leymus secalinus>Leymus paboanus>Carex enervis>Triglochin maritima. The direct shear test showed that the cohesion force of the root-soil system for the disturbed samples of the four halophytes ranged in 10.44–27.42 k Pa and that of soil without root was 8.10 k Pa. Compared with that of soil without roots,the cohesion force of four root-soil system increased by 2.34–19.32 k Pa and with a percentage of increase 28.89%–238.52%. Roots improved the shear strength of soil and there's an optimal root content for shear strength to reach the peak value. At the optimal root content,the corresponding cohesion force of the root-soil system for the 4 halophytes ranged in 17.94–27.42 k Pa and the descending order was Triglochin maritima>Leymus secalinus>Leymus paboanus>Carex enervis.