Study On The Influence Of CMC And Peat On The Engineering Performance Of Thick-layer Substrates And Optimization Of Substrate Proportions

Exposed rock slopes have been formed due to mining in the Qinling Mountains.In order to restore the ecological environment of the Qinling Mountains,ecological reconstruction of the exposed slopes is required.Thick-layer base material spraying vegetation slope protection technology(TBS)is a common engineering method.The core of TBS is the base material ratio,so developing a thick-layer base material ratio suitable for use in the Qinling Mountains has important research value.Based on previous studies,this article uses CMC and peat as modifiers to reduce the alkalinity of thick layer substrates and improve their engineering properties.With CMC content of 0%,0.5%,1.0%,and 1.5%,and peat content of 10%,20%,30%,and 40%,16 groups of substrates were prepared for indoor planting tests,direct shear tests,and disintegration tests.The effects of CMC and peat on the planting performance,shear resistance,and water stability characteristics of thick substrate were analyzed.The optimal ratio of CMC and peat for comprehensive performance was selected through entropy weight method,and the appropriate spraying thickness of the optimal ratio of substrate under different slope ratios was determined through numerical simulation.The following research results have been achieved in this article:(1)The influence of CMC and peat on the growth performance was obtained through plant growth experiments.Appropriate CMC promoted the emergence rate,plant height,and total biomass,but showed inhibitory effects when the content exceeded a certain level.Turfy soil promoted seedling emergence rate,plant height,and total biomass as a whole,while it promotes root depth at low content and inhibits it at high content.The effect of CMC on the rooting depth of alfalfa is relatively complex.When the content of peat is low,excessive CMC content will be detrimental to root growth.When the content of peat is high,CMC will promote lateral root development,leading to an increase in CMC content,which first decreases and then increases in root depth.(2)The influence of CMC and peat on the shear properties was obtained through direct shear test.The shear displacement curves of 16 groups of base materials showed no obvious peak value and were of strain hardening type.CMC enhances the ductility of the substrate and reduces the internal friction angle of the substrate.Due to its high fiber content,peat increases the internal friction angle of the substrate.When the content of peat is 10% and 30%,CMC decreases the cohesion of the substrate;When the content of peat is 20% and 40%,the adhesive force of CMC to the substrate exhibits a trend of increasing at low concentration and decreasing at high concentration.When CMC content is 0%,1.0%,and 1.5%,with the increase of peat content,the cohesion decreases first and then increases.When CMC content is 0.5%,the cohesion increases in a convex shape.(3)The influence of CMC and peat on the water stability was obtained through disintegration experiments.CMC can improve the disintegration resistance of the substrate,while high content of peat has a negative impact on the water stability of the substrate.During the test,the overall disintegration degree of the substrate was low,CMC and peat had no significant impact on the disintegration amount and rate of the substrate.(4)The weights and optimal ratios of various indicators under the entropy weight method evaluation model was obtained.The order of index weight ratio from high to low was: plant height>cost>cohesion>internal friction angle>total biomass>maximum rooting depth>seedling emergence rate.When CMC content is 0.5% and peat content is 20%,the comprehensive performance of the substrate is the best.(5)The optimal spraying thickness for different slope ratios was obtained by combining numerical simulation.When the slope ratio is 1:1,the spraying thickness of the optimal substrate can be taken as 10-20 cm;When the slope ratio is 1:0.75,the spraying thickness can be taken as 10-14cm;When the slope ratio is 1:0.5,the spraying thickness can be taken as 10-12 cm.