Research On The Protective Effect Of Anchored Reinforced Vegetation System On Expansive Soil Slope Surface

The protection and treatment of expansive soil slope has been one of the difficult problems in the field of geotechnical engineering. The expansive soil slope surface is easy to generate large deformation. The traditional rigid protective measures are easy to be destroyed by the large deformation. The flexible slope protection measures can not only withstand a certain slope deformation but also restrain the deformation to develop. So, it is suitable for the protection of expansive soil slope. Anchored Reinforced Vegetation System (ARVS) is a new type of flexible protection system which is composed of high performance turf reinforcement mats (HPTRM) and percussion driven earth anchor (PDEA). HPTRM is a kind of high strength geotechnical material of three-dimensional which has high tensile strength and low elongation and the ability to constrain the deformation of expansive soil. But the research on the applicability of ARVS in protection of expansive soil slope surface is almost blank. So, it is particularly necessary to research the protective effects of ARVS for expansive soil slope.Aiming at the problem of flexible protection of expansive soil slope, the effects of ARVS constraining to the deformation of expansive soil are studied through the model test of indoor ARVS. The expansion force of the soil sample is simulated by the numerical simulation method, and the feasibility of the numerical simulation method is verified by means of the relationship between the micro deformation expansion force and the micro deformation of the expansive soil and the deformation of the expansive soil in the model test. Furthermore, the study on the protective effect of ARVS on expansive soil slope surface was conducted in this paper, which was used to determine the applicability of ARVS and the influencing factors of protection effect.The main conclusions are as follows:(1) After the mixing of the roots in the expansive soil, the expansion force will reduce. When the dry density and initial water content of expansive soil are constant, the micro deformation expansion force with different expansive potential decreases exponentially with the increase of the micro deformation rate.(2) The maximum deformation of expansive soil with ARVS constraint reduces greatly compared to the maximum deformation of unconstrained. Considering the effect of vegetation which is contained in ARVS, the deformation of expansive soil will be further reduced, but the decrease range is not very large.(3) Expansive soil expands after absorbing water, due to the constraint of ARVS, there will be expansion force generated on HPTRM, which will pass a portion of the expansion force to the anchor. And finally the expansion force is transferred to the soil layer.(4) With the rise of free expansion rate, the deformation of expansive soil also increase. What’s more, at low free expansion rate, the deformation of expansive soil with different free expansion rate is close; at high free expansion rate, the deformation increases larger with the free expansion rate rise. ARVS is more adapted to the expansive soil slope with medium and lower swell-shrink grade.(5) Anchor space, anchor arrangement, vegetation and other factors will affect the protective effect of ARVS on expansive soil slop protection. The results show that the medium expansion of expansive soil under the protection of ARVS with vegetation,1.5m anchor space can guarantee the slope surface deformation within 100mm and the deformation of HPTRM is within the elastic range.