西宁盆地黄土区草本植物边坡电阻率与土体物理力学性质关系研究

Relationship between resistivity and soil physical and mechanical properties of herbaceous slopes in the loess area of Xining Basin

为研究高寒干旱-半干旱环境黄土区种植不同类型草本植物边坡土体电阻率与其物理力学性质之间的定量关系,探讨电阻率数值反映边坡土体物理力学性质及其变化特征,在西宁盆地长岭沟流域自建试验区选取未种植裸坡以及种植生长期为3年的垂穗披碱草(Elymus nutans Griseb.)、老芒麦(Elymus sibiricus Linn.)、细茎冰草(Agropyron trachycaulum Linn.Gaertn.)、高羊茅(Festuca arundinacea Schreb.)的边坡共5种类型边坡为研究对象。通过开展边坡土体密度、含水率、含根系与不含根系土体直剪试验,对比不同草本植物根系对边坡土体物理力学性质的影响。在此基础上,利用二维电阻率层析成像方法建立不同边坡土体物理力学性质指标与土体电阻率间的定量关系。结果表明:(1)与未种植裸坡相比较,种植老芒麦边坡上层(0~10 cm)土体含水率增幅最大为26.53%;种植高羊茅边坡上层(0~10 cm)土体平均密度降幅最大为18.30%;种植垂穂披碱草边坡上层(0~10cm)土体黏聚力附加值最大,且为未种植裸坡的2.75倍。(2)5种类型边坡的电阻率受根系分布和边坡位置因素的共同影响,电阻率随着深度增加逐渐降低。4种草本边坡坡面以下0~20cm处土体电阻率均较裸坡大,该深度为根系分布大致范围。(3)5种边坡土体物理力学性质与电阻率数据之间存在拟合方程式(相关系数R2为0.48~0.77),且通过Pearson相关性分析得到边坡土体黏聚力c与电阻率间的相关性相对最高,相关系数R2为0.765。上述研究结果反映出可通过电阻率层析成像技术反映边坡土体物理力学性质,以及边坡土体中植物根系分布特征,可为研究区及其周边地区采用植物有效防治水土流失、浅层滑坡等灾害提供理论依据和实际指导意义。

This study aims to investigate the quantitative relationship between resistivity and the physical and mechanical properties of soil in different types of herbaceous slopes in the alpine arid and semi-arid loess area.The research is conducted in the self-built test area of Changlinggou Basin in Xining Basin.Five types of slopes,including Elymus nutans Griseb.,Elymus sibiricus Linn.,Agropyron trachycaulum Linn.Gaertn.,Festuca arundinacea Schreb.,and bare slopes are selected as the research objects.These slopes have been planted for 3 years.The study compares the effects of different herbaceous roots on the physical and mechanical properties of the soil by conducting tests of soil density and water content,and direct shear test on the soils with and without root systems.Based on these tests,a quantitative relationship between the physical and mechanical properties of different slope soils and resistivity data is established using 2D electrical resistivity tomography.The results show that:(1) Compared with the bare slope without planting,the maximum increase of soil moisture content in the upper layer(0–10 cm) of the Elymus sibiricus Linn.slope is 26.53%.The average soil density of the upper layer(0–10 cm) of the Festuca arundinacea Schreb.slope was 18.30% lower than that of the bare slope.The maximum added value of soil cohesion in the upper layer(0–10 cm) of the Elymus nutans Griseb.slope is 2.75times that of the bare slope.(2) The resistivity characteristics of five types of slopes are affected by root distribution and slope position factors,and the resistivity value decreases with the increase of depth.The soil resistivity value of the four herbaceous slopes is larger than that of the bare slope at 0–20 cm,which is the approximately range of root distribution.(3) There are fitting equations between the physical and mechanical properties and resistivity data of five kinds of slope soils(with correlation coefficients R2ranging from 0.48 to 0.77),and the Pearson correlation analysis shows that the cohesion c value of the slope soil has the highest correlation with resistivity,with an R2 value of 0.765.The results of this study demonstrate that 2D resistivity tomography technology can reflect the physical and mechanical properties of slope soil,as well as the distribution characteristics of plant roots.This provides a theoretical basis and practical guidance for effectively preventing and controlling soil erosion,shallow landslides,and other disasters in the study area and its surrounding areas.