柴达木盆地盐湖区盐生植物根土复合体抗剪强度试验研究

本研究选取柴达木盆地内大柴旦盐湖南岸5种优势草本盐生植物，即赖草（Leymus secalinus （Georgi）Tzvel．）、海韭菜（Triglochin maritimum L．）、毛穗赖草（Leymus paboanus （Claus）Pilger）、芦苇（Phragmites australis （Cav．）Trin．ex Steud）、无脉苔草（Carex enervis C．A．Mey．）等作为试验供试种，采用由地表向下分层制取根土复合体试样的方法，分别对区内5种植物根土复合体和不含根系素土试样进行了直剪试验．试验结果表明，根土复合体的粘聚力c值由地表向下呈逐渐降低趋势，且赖草、毛穗赖草、无脉苔草3种草本植物平均粘聚力 c 值由表层的14．83 kPa 逐渐降至下层的6．23 kPa，海韭菜、芦苇2种草本植物平均粘聚力 c 值则由表层的15．62 kPa 逐渐降至下层的11．83 kPa；根土复合体的粘聚力c值由表层至下层呈逐渐降低，其主要与根土复合体中的根面积比和含根量由表层至下层呈逐渐降低具有密切关系；5种草本植物根土复合体内的摩擦角φ值未表现出一定的规律性．根土复合体在50 kPa、100 kPa、200 kPa、300 kPa垂直压力下的抗剪强度均大于相应素土的抗剪强度，与不含根素土相比，5种草本根系在地表以下的上层、中层、下层等3层对土体粘聚力增幅为40．7％～875．6％，体现了5种草本植物对浅层土体具有显著加筋作用．

An experimental research on shear strength of halophytes root-soil complexes in salt lake area of Qaidam basin

Five dominant species of halophytes growing in the south bank of Da Qaidam Salt Lake were chosen as experimental species.They were Leymus paboanus (Claus)Pilger,Triglochin maritimum L.,and Leymus angustus (Trin.)Pilger,Phragmites australis (Cav.)Trin.ex Steud,and Carex enervis C.A.Mey.The root-soil complexes,related salinized soil of the above-mentioned five species and root-free soils were tested on direct shear equipment,and then the roots were analyzed.Root-soil complex samples from surface to bottom were taken and tested on direct shear equipment,and then the characteristics of roots were analyzed.Experimen-tal results show that the cohesion (c)of root-soil complexes decreases from surface to bottom,for L.paboanus, L.angustus,and C.enervis,with average c gradually decreasing from 14.83 kPa at the surface to 6.23 kPa at the bottom,and for T.maritimum and P.australis,the average c gradually decreasing from 15.62 kPa at the surface to 1 1 .83 kPa at the bottom.The gradual decrease of c from surface to bottom is closely related to the gradual decrease of root area ratio (RAR)or roots contents from surface to bottom.There is no obvious varia-tion in the internal friction angle (φ)of the five halophytes root-soil complexes.Under the vertical pressure of 50,100,200 and 300 kPa,the shear strength of all the five kinds of root-soil complexes is stronger than that of the root-free soils.Compared to salinized root-free soils,the increase rate of c of the surface layer,middle layer and bottom layer of the root-soil complexes of the five halophytes is 40.7%~875.6%,showing that the five halophytes have obvious reinforcement effect on shallow soils.