Study On The Mechanism Of Bearing Deformation Of Bamboo Geogrid Reinforcement In Digging And Filling Roadbed In Mountainous Areas

Non-uniform settlement on both sides of digging and filling boundary in mountain area has been one of the major problems in subgrade engineering field.In the past,scholars have adopted the method of excavating the steps at the junction of digging and filling subgrade and laying geogrid at the steps to solve the problem of uneven settlement on both sides of the junction of digging and filling.However,as a kind of non-renewable chemical synthetic material,geogrid has high production cost,which will pollute the environment in the process of production,and the complex mountainous terrain restricts the transportation of geogrid.For this reason,this paper will introduce bamboo reinforcement as a new type of reinforcement material,its raw material is widely distributed in the mountains of China,the original ecological and environmental protection,not only can ensure the reinforcement effect,but also easy to obtain local materials in the mountains.Firstly,the distribution of bamboo was summarized.on this basis,the structure and mechanical properties of bamboo were considered from macro and micro perspectives respectively.at the same time,the durability and economy of bamboo were analyzed.The results showed that the content of bamboo fiber played a decisive role in the mechanical properties of bamboo.The use cost of bamboo is lower than that of other reinforced materials,and the durability of bamboo can be enhanced by boric acid solution immersion method.Then,the tensile,compressive,shear and bending mechanical properties of bamboo bars in Xiangxi were tested by indoor test.the comparison between the mechanical properties of bamboo bars and the requirements of reinforced materials in the code shows that the mechanical properties of bamboo bars meet the requirements of the code.at the same time,the development process of tensile failure surface and compressive failure crack of bamboo bars was analyzed based on the test results.On the basis of the results of laboratory tests and in-situ drawing tests,the interfacial characteristics of bamboo bars and grids under different normal stresses are studied,and the formulas for calculating the pullout stress in previous drawing tests are optimized.Thirdly,based on the mechanical characteristics of bamboo grille in practical work,the mechanism of bearing deformation of bamboo grille is studied from two aspects.First,based on the tensile properties of bamboo grating,its bearing mechanism is divided into friction reinforcement mechanism,cohesive force mechanism,passive anchoring mechanism and tension film mechanism.Secondly,based on the bending performance of bamboo grating,combined with paster nak two-parameter subgrade model,the reinforced digging and filling subgrade of bamboo grating is simplified.the bending deformation of reinforced bamboo grating is studied,and the specific calculation method is given.at the same time,the accuracy and effectiveness of the method are verified by numerical simulation.Finally,FLAC 3d finite difference software is used to establish the three dimensional model of the excavated and filled subgrade.the settlement,stress and horizontal displacement of the top surface of the subgrade at the interface of the excavated and filled subgrade under three working conditions of no reinforcement,geogrid and bamboo grille are compared and analyzed,and the laying layers of bamboo grille of the reinforced excavated and filled subgrade with bamboo grille are discussed.The results show that the bamboo grating can obviously control the differential settlement on both sides of the digging and filling interface,reduce the horizontal displacement of subgrade and stress concentration of subgrade.it is suggested that the bamboo grating be laid above the middle layer of the digging and filling interface.