Study On Reinforcement Effect Of Geosynthetic Cell Mattress

Object of this study was geocell, which is geotechnical construction material using subgrade material as the main body. Purpose of this study was to investigate the mechanism of reinforcement effect of geocell reinforced soil through the experimental research on the bearing capacity of geocell reinforced soil and characteristics of the interface between reinforcement and soil.In this study, PIV analysis images were obtained by the bearing capacity of indoor model test. Quantitative and qualitative analysis for internal sand movement of foundation and meso-structure images by using PIV image analysis method and digital image processing technology to get the change regularity of parameters, various stress and strain fields before and after reinforced in the strip of sand foundation under uniformly distributed loads. In model tests, displacement of reinforced foundation loading deformation and foundation internal local shear strain field image were analyzed using Deformation Measurement System to investigate the mechanism of reinforced foundation failure mode. Foundation internal local stress state results, stress field, stress path and stress variation were analyzed using Finite Element Simulation analysis. In this study, the basic model according to the actual same scaling was used in the test for reinforced soil interface charisteristics. Measuring process continuous change of internal displacement of soil by pull-out test device and displacement; comparing the pullout behavior of geocell and geogrid and studying displacement transfer mechanism of geocell and geogrid. Stress distribution determined by static bearing capacity tests and paper-like pressure sensor, in order to investigate the effect of stress dispersion and reinforcement mechanism. Discussing reinforced soil elastoplastic mattress effect, bending rigidity and stress dispersion effect by the stress measurement system. Finally, a simple site load test was used for comparison of reinforcement effect with different reinforcing material, and review similar theorem of geocell model and the prototype system.In this study, using above methods, tracked the progressive failure process and deformation of reinforced soil, captured deformation mode, sliding shear plane position shapes and shear zone of reinforced soil. Carried the measurement and quantitative analysis for the displacement occurred in drawing horizontal load of sand, development and evolution characteristics of the partial displacementPIV image analysis indicated that velocity vector distribution in the no geocell reinforced foundation showed obvious movement with high speed to the positive direction of the center beneath the load plate, which means that the stress concentration below the load board; while in occasion of geocell reinforced foundation, velocity vector distribution showed cross direction movement with small and uniform speed, which means that the phenomenon of stress concentration were dispersed. Deformation Measurement System analysis showed that in occasion of pure sand or no reinforcing, the maximum shear strain direction was almost at about10°rupture line for foundation internal sand in shear process. While Geogrid reinforced soil shear strain contour line, that the maximum shear strain almost occurred in the horizontal direction, and the horizontal plane was consistent with reinforcement layout. Foundation internal local stress state results were analyzed using Finite Element Simulation Analysis and showed that high reinforcing effect in the local stress state is close to failure state and shown after the failure field diffusion. In pullout test, geogrid displacement weak segment came faster and directly into state of residual small strength; however for geogcell, displacement weak segment came later, first showed slightly higher maximum resistance than the former, after short displacement weak segment, finally showed residual strength. Internal displacement of geocell model spread beginning from the wall to the back, its progress was less significant than geogrid. Stress diffusion test showed that stress curve distribution of geogrid or geocell reinforcd soil was in the vicinity of the spire. Meanwhile, for geogrid combined geocell type, stress curve was distributed in wide range near the center. Foundation bearing capacity was improved when geogrid combined with geocel. When gravel used as filler, bearing capacity of gravel reinforced geocell was larger than that of geogrid combined with geocell.Main difference between geocell and geogrid is that geocell has a certain thickness and a certain bending ability, therefore can effective diffusion the vertical stress from the superstructure; at the same time play a role similar to the "deep foundation", greatly improved the bearing capacity of foundation.The results indicated that using Finite Element Simulation Analysis, the variety feature of micro-structure is consistent with the macroscopic mechanical response feature. Finite Element Simulation analysis is feasible for studying on bearing capacity and deformation characteristic of reinforced foundation. The variety feature of physical model test PIV images reflect macroscopic mechanical response feature of soil, that means the feasibility for response strength before and after failure and deformation of soil by the microscopic structure change. Comparing the relationship analysis of two types of micro-structure with the macroscopic test results indicated that PIV images of micro-structure is consistent with macroscopic mechanical response feature.Greocell as a new type of building material, that has good adaptability (adapt to variety filler), good economy (application of geocell can save up30%of investment) and good stability. Geocell method can effectively use the field soil, reduce earthwork, effectively reduce the environmental load and speed up the progress of works. Study on the mechanism of geocell reinforced structure remains to be deepening. To propose a practical engineering design calculation method is a priority.