Effect Of Reinforcement And Anchorage Of Plant Roots On Slope Stability

In recent years,our country's economy is in high speed development,and all kinds of infrastructure construction are also being built rapidly.At the same time,we also have more and more influence on nature when we build a lot.According to statistics,about50% of large landslides are directly or indirectly related to human activities.The occurrence of geological disasters is becoming more and more important to us,in 2016,the national geological disaster caused a direct economic loss of 3 billion 170 million yuan,and the number of deaths of 405 people,an increase of 27.3% and 41.1% over the previous year.To take the road of sustainable development,harmony with nature is our only choice.As far as the current slope protection is concerned,engineering protection measures are mainly used,and the use of plant slope protection is far from enough.With the increasing emphasis on environmental protection and green development,plant slope protection has been recognized by more and more people.It is particularly important to study the mechanism of plant slope protection and support the actual project based on theory.This paper summarizes the theoretical basis of plant slope protection,mainly the Mohr-Coulomb law,the reinforcement and anchorage theory of the root system,and the hydrological effect of the plant slope protection.The analysis method of slope stability is analyzed,and the finite element method and the rigid body limit equilibrium method in the quantitative analysis method are emphatically expounded.Under the premise of reading a large number of literatures and related theories,the use of triaxial compression tests combined with unconfined compression tests to study the effect of root volume,single root length,and the placement of distribution on the strength of soil mass,and to use simulation analysis to explore the influence of herbaceous and woody roots on slope stability.The main research contents are as follows:(1)The roots of herbaceous plants were replaced with the main veins of S.shuishanensis,and the triaxial compression test and the unconfined compression test were performed by adding soil samples made from the soil.Using the cohesion and internal friction angle as indicators of strength evaluation,the effects of root volume,single root length and distribution pattern on the strength of the sample were investigated.At the same time,the reason why the main vein of Metasequoia was used to replace the plant root and the feasibility of alternative roots were also analyzed.(2)Effect of surface reinforcement of simulated herbaceous plants on slopestability.It is divided into two cases: surface reinforcement only on the water surface and reinforcement on all slopes.Set three kinds of reinforced thicknesses 1,2,and 3 m.The two types of slope heights are 15 and 30 m,and the three slope rates are 1:2.1:1,2:1,using safety factor as an indicator,to study the changes of slope stability under different working conditions.(3)Effects of simulated woody plant roots on slope stability.It is divided into two situations: planting only on the slope above the water surface and planting on all slopes.Set three kinds of main root lengths of 4,6,and 8 m.The two types of slopes are 15 and30 m high.The three slopes are 1:2,1:1.,2:1,using the safety factor as an indicator,combined with the slip line,to study the changes in slope stability under different conditions.In order to further explore the effect of the main root on the slope,another simulation was performed to remove the main root and only the lateral root reinforcement.The main conclusions are as follows:(1)The shear strength of the reinforced soil samples increased significantly compared with plain soil,indicating that the root system can significantly improve the soil strength.Among them,the root strength of the sample increases the shear strength of the sample.With the increase of the root content,the cohesion of the soil increases continuously,the maximum increase is 277.59%,but the internal friction angle does not change significantly,basically within 3%.In addition,in the case of a certain amount of roots,the influence of the length of a single root on the cohesion of the sample is small,and the effect of the distribution on the cohesion is even greater.The cohesion of the layer distribution sample is obviously larger than that of the uniform distribution sample,which indicates that the smaller the included angle between the root system and the potential landslide deformation direction is,the better the slope protection effect is.In the absence of confining pressure,in the unconfined compression test,the increase of the main stress difference is far greater than the three axis compression test.The smaller the confining pressure is,the lighter the soil is,indicating that the reinforcement effect of the plant roots to the surface of the soil is more significant.(2)With the increase of the thickness of the herb planting reinforcement or the length of the main root of the woody plant,the safety factor of the slope is increasing.When simulating planting of herbs or woody plants on slopes,the slope safety factor increases by 15 m at a slope of 30 m.When planting herbs,the greater theslope,the more obvious the safety factor increases;When planting woody plants,the safety factor of the slope is increased when the slope ratio is 1:1.In general,planting herbaceous plants or woody plants near the foot of the slope is the best to improve the stability of the slope,but in the actual situation,when there is water at the foot of the slope,when the tree can not be planted,it can be replaced by the engineering slope at the foot of the slope and the slope protection on the water surface will bring better slope protection effect.In addition,when woody plants are planted,the anchor effect of the main roots is not as effective as the lateral reinforcement effect on the safety factor.Woody plants have a higher safety factor than herbaceous plants.Taking into account the hydrological effects of plants,the combination of the two can achieve better slope protection.In summary,plant roots can significantly increase soil strength and enhance slope stability.Plant revetment is an environment-friendly slope protection method.Scientific planting methods can bring better slope protection effects.