Analysis Of Long-term Characteristics Of Geogrid Reinforced Earth Retaining Wall By Nonlinear Finite Element Method

The reinforced earth retaining wall has been paid enormous attention and widely used because of its superiority in many categories like the convenience in construction,inexpensiveness,beauty and high adaptability to the deformation of foundation.However,the current recognition and research on the long-term characteristics of reinforced earth retaining wall lag behind by the engineering practice,affecting the development of reinforcement technology.Therefore,it has practical and engineering significance to develop the research of the long-term working characteristics of geogrid reinforced earth retaining wall.Based on the Nanchang to Ningdu expressway project,the method of combining test and numerical analysis is adopted in this paper.The creep characteristics of the HDPE geogrid before and after aging process are both studied by the accelerated UV aging test and the laboratory creep test;and then the viscoelastic constitutive model of the geogrid is established.The creep test at different stress levels and the direct shear tests are carried out on the grave soil filler used in the actual engineering;and then the viscoelastic-plastic constitutive model of gravel soil is established.On this basis,the long-term characteristics and its influencing factors of geogrid reinforced earth retaining wall are theoretically analyzed by nonlinear finite element method.The failure modes of reinforced earth retaining wall are further analyzed.The results show that:(1)The lateral displacement of panel and geogrid strain along the wall height show nonlinear change law which decreases after the first increasing.The strain of each layer of geogrid along the length direction shows variation of first increasing and then decreasing.The maximum strain at the bottom geogrid is near to the panel.And the maximum strain of the geogrid is gradually removed away from the panel along with the increasing of the geogrid layer.The settlement of the filler surface along the surface increases first and then decreases,and finally tends to be stable.The maximum settlement area is located in the non reinforced area.The wall of horizontal earth pressure along the wall depth shows variation of first increasing and then decreasing and then increasing.The maximum pressure is located in the lower zone.The interlaminar shear stress and the vertical earth pressure show different laws with the different layer of the geogrid.(2)The creep properties of filler and geogrid will result in the increase of lateral displacement,vertical displacement,geogrid strain,horizontal earth pressure;and it will also make earth pressure and interlaminar shear stress produce stress relaxation.The aging of geogrid will further increase the rheology of the retaining wall.(3)The stability characteristics of retaining wall increases with the increase of the internal friction angle and cohesion;and the increase of the internal friction angle is more significant to improve the stability characteristics of the wall.With the decrease of the reinforcement spacing and the increase of the length of reinforcement,the overall stability characteristics of the wall is enhanced.(4)Both the potential local fracture surface and the whole fracture surface of the reinforced earth retaining wall appear zigzag distribution.