Experimental Study On Vegetation Reinforcement System Of Expansive Soil Slope In Nanning City

In recent years, road construction in Guangxi has been developing rapidly, and many roads pass through expansive soil areas. With the improvement of people’s experimental awareness, it has been an urge to reinforce vegetation recovery of expansive soil slop under the condition of stabilization. This research is a preliminary work for the project "Mechanism Study on the Improvement of Expansive Soil Rock with High Performance Turf Reinforcement Mats". The main focus is vegetation recovery under the HPTRM system on expansive soil slope. The research conducts nutriment testing of expansive soil, as well as vegetation survey on expansive soil and its cover soil, in order to guide the plantation on expansive soil.The major conclusions are as following:(1) From the perspective of Soil Science, expansive soil belongs to clay soil. It has low contents of organic material, total nitrogen, rapid available nitrogen, and extremely low rapid available nitrogen, all of which are below the average level of planting soils in Guangxi; but its potassium is sufficient. Its pH is neutral, or alkalescency, different from the common acid soil in Guangxi. It has low constitutive property, dry density larger than general clay; small porosity, and more non-activity pores; less capillary pores, various air holes, which leads to the difficulty for vegetation rooting, as well as the solution of hydrosphere conflicts. Therefore, expansive soil is not suitable. for direct plantation; it needs proper reformation before plantation, and mixed sowing of high stress resistance plants is recommended.(2) HPTRM has high intensity and good durability. Compared with3D Geomat EM5, Green-HPTRM has the same3D structure and approximate mass area ratio, but ten times higher strength of extension, and strong radiation proof which lasts for more than50years.(3) With the same condition of water, fertilizer, light, heat and other factors, the germination rate of ryegrass is not influenced by gradient, but affected by buried depth. Under the same condition, compared with that in EM5, biomass of ryegrass in Green-HPTRM is relatively lower, but very close.(4) Prepare four expansive soil tubs whose initial moisture content are all30%, then put them outdoors for48days. Afterwards inspect the moisture content in the center of each tub. The increase of moisture: cover soil5cm+HPTRM+ryegrass only0.8%, cover soil10cm4.4%, cover soil5cm5%, and no cover soil6.3%.(5) The runoff shear force of HPTRM can be calculated. This thesis puts forward calculation formula of runoff shear force, and provides the basis for washout experiment.