Analysis Of Soil Consolidation Mechanism And Slope Stability Of Herbaceous Plant Roots In Ecological Slope Protection In Dalian Area

As an emerging slope support and restoration technology,ecological slope protection is widely used in slope management.However,due to the comprehensive,complex and regional characteristics of ecological slope protection,its theoretical research lags far behind the engineering practice.In this paper,relying on the project funded by Dalian Distinguished Young Scientists,we comprehensively use data collection,outdoor planting experiments,indoor geotechnical tests,theoretical analysis,numerical simulation and other methods to reveal soil consolidation mechanism,establish soil consolidation model,quantify soil consolidation capacity,analyze slope effect from multiple scales such as single root,root bundle,plant body and slope body,so as to provide some theoretical basis for the promotion of eco-slope protection in Dalian area.The main achievements are as follows:(1)Root-soil composite experimental research was carried out.Outdoor planting experiments,root tensile tests,physical properties of substrates,in-situ soil direct shear tests,and remodeled soil direct shear tests were designed and conducted to study the physical and mechanical properties of root systems,substrates,and root-soil complexes.The study shows that: the growth patterns of ryegrass radicle,tall fescue radicle and alfalfa main root can be fitted by logistic Stiffy equation.The maximum tensile strength of the root system is a power function positively related to the diameter of the root system,and the tensile strength is a power function negatively related to the diameter.The base material used can meet the requirements of ecological slope protection for rocky slopes.The presence of roots improves the shear strength and ductility of the soil.The roots have a greater influence on the cohesion of the soil and less influence on the internal friction angle.The shear strength of root-soil complex increases with increasing root content.The shear strength of the root-soil composite tends to increase and then decrease with the water content,i.e.,there is an optimum water content.(2)A study on the mechanism of root consolidation was carried out.In view of the defects of Wu model and Waldron model,an improved reinforcement model was proposed considering the angle between root system and shear direction,anchorage length and effective root number,and the contribution value of single reinforcement was analyzed by using the improved model.The study shows that: the improved model proposed in this paper can fit the experimental results well.With the increase of the angle between the root system and the shear surface,the reinforcement contribution of the inverse oblique root system to the soil increases and then decreases,and the reinforcement contribution of the oblique root system to the soil is first zero,then increases and finally decreases.With the increase of the root system diameter,the reinforcement contribution of the root system to the soil increases.(3)Research on the stability of ecological slope protection was carried out.A theoretical model of herbaceous plant roots reinforcing the shallow slope was established,and the influence of the roots on the stability of the shallow slope under different kinds of plants and different slope conditions was compared and analyzed.FLAC 3D was used to simulate the actual ecological slope protection situation and analyze the effect of thick substrate spraying ecological slope protection technology on the overall stability of slopes,and the model was used to analyze the effect of different plant states and different support parameters on the overall stability of slopes.The study shows that: the plant root system can significantly improve the shallow stability of the slope.The deeper the potential slip surface and the larger the width of the slider body,the smaller the shallow stability of the slope.When the width of the slider body is constant,the larger the width to length ratio of the slider,the greater the shallow stability of the slope.When the depth of the slip surface is constant,the shallow stability of the slope decreases and then increases with the increase of the slope.The thick substrate spraying technology can effectively improve the overall safety coefficient of slope.The slope safety coefficient is related to the plant growth state.With the growth of plants,the safety factor shows a slow-fast-slow growth trend.With the increase of plant density and bolt length,the safety factor shows a fast-slow growth trend.The thickness of the substrate has little effect on the slope safety factor.When adopting thick layer substrate spraying ecological slope protection technology,it should ensure that the slope is in a stable state when the plant growth state is the worst.