Test Study And Numerical Analysis On The Static And Dynamic Characteristics Of Eco-reinforced Earth Retaining Wall

Eco-reinforced earth retaining wall is a new type support structure which is combined with the technology of reinforced soil and bioengineering techniques for slope protection, and widely used in actual engineering. However, the relevant research has not been done sufficiently and traditional theory of reinforced earth retaining wall was adopted for design. The theoretical study of eco-reinforced earth retaining wall dropped far behind its practice which restricted its popularization.Supported by the transportation scientific research project of Hunan province-"Application Technique and Demonstration Engineering of Highway Reinforced Soil Structure"(No.200612) and transportation scientific research project of Zhejiang province "Special Study on Application of Flexible Ecology Retaining Wall in Highway"(No.2010H08), and based on the projects of the green reinforced gabion retaining wall and reinforced earth retaining wall with geogrid and eco-bag in Shaozhu Expressway, the reinforcement mechanism, failure mechanism, dynamic property, stability analysis method and durability of eco-reinforced earth retaining wall was studied systematically by the means of theoretical analysis, laboratory and field test and numerical simulation in this paper.The main research conclusions and innovation points were as follows:1. Based on the triaxial test, direct shear test and pullout test of reinforced clay with different reinforcements, the characteristics of shear strength and interface relationship between clay and reinforcement have been studied. The formula for calculating shear strength of reinforced clay, which considers the influence of water content and reinforced spacing, and the friction coefficient of clay with different reinforcements has been gotten, which provides parameters for engineering design.2. By the model tests, the dynamic characteristics of eco-reinforced earth retaining wall in different working conditions (common type and digging and stowing one) and structure forms (green gabion reinforced earth retaining wall and reinforced earth retaining wall with geogrid and eco-bag) under traffic load were studied. It has been gotten that the laws of acceleration, dynamic earth pressure, vertical and horizontal accumulated deformation, accumulated tensile strain of reinforcement under cyclic loading with different amplitudes and frequencies.3. The static characteristics of eco-reinforced earth retaining wall in different working conditions and different structure forms were studied by model tests and numerical analysis. The laws of deformation, tensile strain of reinforcement, ultimate bearing capacity and failure models of walls were obtained.4. The dynamic response characteristics of eco-reinforced earth retaining wall under traffic load had been studied by numerical analysis where green gabion reinforced earth retaining wall in the section K38+325-k38+485of Shaozhu Expressway was taken for prototype.5. Based on the analysis of durability injury law of gesynthetics, the durability influence factors of reinforced earth retaining wall were studied, its evaluation criterions were provided according to reinforcement strain controlling and lateral deformation controlling of the reinforced soil structure respectively, and the lifetime prediction method for reinforced soil structure has been set up.6. Based on the upper bound method of plastic limit analysis theory, the failure mechanisms of eco-reinforced retaining wall in common conditions and cutting with filling conditions have been studied, and the respective calculation formulas for their bearing capacity have been gotten.7. Based on the system reliability theory, the limit state equations of various failure models of reinforced soil retaining wall were set up and their logical relationships were analyzed, and the structural system reliability calculation model was established and a practical project was analyzed.8. The point safety factor method for reinforced soil structure stability analysis was proposed. The formulas for point safety factor of rock and soil, reinforcement unit and interface were derived out. The calculation method for anti-breack and anti-pullout factors of reinforcement were provided. The steps and FISH command flow for the method to implement in FLAC3D were analyzed and a practical project was analyzed.9. Field test was implemented for green gabion reinforced earth retaining wall. Its earth pressures in different directions in bottom of the base, vertical and horizontal earth pressures in wall, tensile strain of reinforcement and its lateral deformation were monitored during construction. 10. Some rationalization proposals for the application of eco-reinforced earth retaining wall were put forward according to the results of test studies, in-situ test and field investigation.