柴达木盆地大柴旦盐湖区盐生植物根-土复合体力学强度试验研究

摘要

以柴达木盆地大柴旦盐湖区作为试验区,分别筛选出5种优势盐生植物,即海韭菜(Triglochin maritimum Linn.)、芦苇(Phragmites australis Trin.)、赖草(Leymus secalinus Tzvel.)、毛穗赖草(Leymus paboanus Claus.)和无脉苔草(Carex enervisC.A.Mey.)作为试验供试种,分别对5种盐生植物根-土复合体试样和不合根系素土试样进行了室内直接剪切试验和三轴压缩试验,对比了不合根系素土试样与根-土复合体试样的抗剪强度指标;在此基础上,评价了5种盐生植物根系增强土体抗剪强度作用.试验结果表明:(1)当含水量和密度值分别为29.01％和1.65 g/cm3时,5种盐生植物根-土复合体试样的抗剪强度指标粘聚力c值为10.38 ～ 19.19 kPa,且显著大于素土试样的粘聚力c值5.95 kPa,内摩擦角φ值未表现出变化规律;(2)相对于不合根系的素土试样,由直剪试验和三轴试验得到的5种盐生植物根-土复合体试样的粘聚力增长幅度分别为16.8％ ～ 108.7％、19.2％ ～ 113.6％;(3)由直剪试验与三轴试验结果表明,区内5种盐生植物根-土复合体试样抗剪强度大小变化顺序表现出一致的规律性,即由大至小依次为,芦苇、海韭菜、赖草、毛穗赖草、无脉苔草和素土.该项研究结果为区内进一步开展盐生植物增强土体抗剪强度机理等方面的研究具有理论研究价值和实际指导意义.%Da Qaimdam salt lake and surrounding areas have been selected as the test sites and 5 predominant halophytes (Triglochin maritimum Linn.,Phragmites australis Trin.,Leymus secalinus Tzvel.,Leymus paboanus Claus.,and Carex enervis C.A.Mey.) have been selected as the test species.Direct shear tests and triaxial compression tests have been performed to rooted soil samples for the five halophytes as well as non-rooted soil samples to compare shear strength indices for these samples.Based on these,contributions by roots for the 5 halophytes in increasing shear strength of soil have been evaluated,and the following results have been achieved:(1) As moisture content and soil density remain constant,shear strength indices,cohesion forces (c) of rooted soil for the five halophytes are 10.38 kPa ～ 19.19 kPa,markedly greater than that for non-rooted soil,while the internal frictional angle (φ) exhibit no marked regularity;(2)In contrast to non-rooted soil,incremental rates of cohesion force rooted soil for the five halophytes obtained by direct shear tests and triaxial compression tests are 16.8％ ～ 108.7％,and 19.2％ ～ 113.6％,respectively;(3)Direct shear test and triaxial compression test results show variability of shear strength values of non-rooted and rooted soil for the five halophytes obtained by direct shear test are in according well with what obtained by triaxial compression test,and value magnitude of shear strength of rooted soil for the five halophytes from larger to smaller are P.australis,T.maritimum,L.secalinus,L.paboanns,and C.enervis,and non-rooted soil has minimum value in shear strength.The conclusion has a great significance and real value in implementing studies in the mechanism of soil shear strength reinforcement by halophyte roots in the test site.