The Experimental Study On Mechanical Characteristics Of Geogrid Reinforced Soil Retaining Wall

Because of its incomparable advantages, reinforced soil retaining wall is widely used in the projects. With the rapid development of geosynthetics, geosynthetics (geogrid especial) retaining wall is one of light supporting constructure that has been the most prospective since 1970s.At present, the theory and application of the geogrid reinforced soil retaining wall(H<10m) are reliable. However, the theory and application of the geogrid reinforced soil retaining wall(H>10m) are very unreliable. So, a large number of geogrid reinforced soil retaining walls(H>10m) are designed with reference to the similar projects, instead of the reliable design method.Considering the reasons mentioned above and to solve the problems during the design and construction of highways in the mountain areas, this paper aims to study the mechanical behavior of the geogrid reinforced soil retaining walls. This study is conducted through the field test and the numerical simulation by finite element method. The main contents and conclusions in this paper are:1)The experimental results on the vertical basal pressure of the geogrid reinforced soil retaining wall(1)The measured normal stresses at the basement of the wrapping and panel geogrid reinforced soil retaining walls are nearly uniformly distributed and they are larger than the value ofγ·H.(2)The measured normal stresses at the basement of the compound geogrid reinforced soil retaining walls (with concrete rigid face) are larger than the value ofγ·H and they are not uniformly distributed. It is observed that the normal stress is larger near the toe of the retaining wall. This may be due to the strong supporting effect of the gravity retaining wall.(3)The measured normal stresses at the basement of the geogrid reinforced soil retaining walls remain stable at the stage of"quasi-operation". This illustrates that the formation and variation of the normal stresses are almost completed at the construction stage. (4)As the measured normal stresses at the basement of the geogrid reinforced soil retaining walls are larger thanγ·H, it is suggested that the calculated normal stresses at the basement should be enlarged by K (K= 1.2-1.4) when the height of the wall is larger than 10 m. This is to ensure the bearing capacity is high enough.2)The experimental results on the geosynthetics deformation of the geogrid reinforced soil retaining wall(1)With the increment of the height of the earth fill, the deformation of the geogrid inside the retaining walls is not uniform (looks like a double-peak). This implies a potential failure surface exists inside the retaining wall.(2)During the rainy season, the·deformation of the geogrid inside the retaining walls is quite large (due to the soil settlement by saturation and nonuniform compression). This should be considered during the design and construction to prevent unfavorable effects.(3)After the construction, the·deformation of the geogrid inside the retaining walls is becoming smaller with time and tends to be stable. This illustrates the most unfavorable condition for the high geogrid reinforced soil retaining walls occurs at the end of the construction (i.e., the subgrade is formed and the filling project is completed).(4)The measured largest tension force of the geogrid inside the wrapping and panel geogrid reinforced soil retaining walls is larger than the designed value. The one in the central part is larger than the designed value by 40%-50%. Thus the code is reasonable and necessary to take a material reduction factor (>5) and to maintain a high safety factor (>1.3).3)The potential failure surface of the geogrid reinforced soil retaining walls(1)The potential failure surface of the wrapping geogrid reinforced soil retaining walls is similar to the theoretical prediction by the Coulomb method. The only difference is the area of the soil wedge.(2)The measured failure surface of the panel geogrid reinforced soil retaining walls is similar to the theoretical prediction by the"0.3H"method and the classic Rankine's method(3)There are two potential failure surfaces in compound geogrid reinforced soil retaining.The above one is consistent with the distribution of the number of spiral,and the below one is alittle complicated. It is quite different from the theoretical prediction by the "0.3H"method and the Coulomb method.The shape and location are mainly affected by combination of retaining walls and reinforced soil.4)The FEM results of the geogrid reinforced soil retaining wall Two panel geogrid reinforced soil retaining walls at the K68+698 and K68+798 of the Shui-Ma Highway are investigated by the field testing. Also, numerical simulations are conducted by the strength reduction finite element method and some conclusions can be given as follows:(1)The calculated and measured normal stresses at the basement are consistent. Both of them are larger than and uniformly distributed.(2)The calculated tensional force of the geogrid is almost consistent to the measured value in the field testing.(3)The simulated potential failure surface of the panel geogrid reinforced soil retaining walls is close to the real measured result and similar to the theoretical prediction by the"0.3H"method.(4)According to sensitivity analysis by FEM, the intensity index and the geosynthetics length have more influence over the stability factor of the geogrid reinforced soil retaining wall.This study is a key component of the research for the project of the west traffic construction <The study of supporting constructure in mountainous areas>. This pape introduced the applying of geogrid reinforced soil retaining walls and the topics reason for doing prototype test research The main works include:introducing the site prototype test plan,analyzing the data results,studying the vertical pressure distribution,reinforced soil's pull,deformation & the failure surface's shape ,and revealling the mechanical properties. With this research,the construction of the high geogrid reinforced soil retaining walls and the prototype test,which are synchronized with project's construction on the highway,get success first.The research results point out the accordance or difference with the studied conclusion of the failure surfaces's shape, pressure distribution and the biggest pull of geogrid reinforced soil retaining walls at home and abroad,enrich and develop the technology of the geogrid reinforced soil retaining walls greatly. The research results are useful to the later design,construction and study,and to perfect the theory and the design standard of the geogrid reinforced soil retaining wall.