| Summary: | 碩士 === 國立宜蘭大學 === 土木工程學系碩士班 === 97 === In recent years, geosynthetic reinforced soil retaining structures have been increasingly constructed in Taiwan. However, because the good-quality backfilled materials are scarce and the principle of balancing cutting and filling is required to follow by the soil and water conservation legislation, the in-situ soils are used as the backfilled materials in civil engineering projects. Based on the reasons mentioned above, in the current technical manuals or design code, the basic requirement of backfilled materials has been relaxed and thus the backfilled materials in a range from GW to CL may be used. In this thesis, by utilizing two geosynthetic reinforced soil retaining walls constructed in the test site of National Ilan University in the summer of 2002, we carried out the long-term measurement of the stress and strain distributions in the geosynthetic reinforcements in order to understand the behavior of the model structures with various kinds of backfilled materials. In addition, with the aid of the finite element method program PLAXIS, we performed simulation analyses of stability, failure mode, elastic deformation, and the behavior of geogrid under tensile stress. From the comparison of the predicted results of the FEM model with the measured data of the model structures, we found that the simulation results are close to the measurements.
In addition to the investigation of two geosynthetic reinforced soil retaining walls, we performed numerical simulations of large-scale reinforced soil retaining structures with various property materials in Ilan County to further understand the interaction of the structure. From the investigation of the safety factor, potential failure surface, effect of additional loading, elastic deformation, and behavior of the geogrid under tensile stress, we found that the geosynthetic reinforced soil retaining structures in the Ilan County are stable structures. The largest tensile stress of the geodrid is in a range from 4.09 to 9.82 kN/m. Because clayey soils cover a wide area in the Ilan County, clayey soils are often used as a backfilled material for the geosynthetic reinforced soil retaining structures. In this thesis, we also investigated the creep behavior of the reinforced soil retaining structure by using a creep model of soft soils. The results indicated that the tensile stress of the geodrid is increasing with time. Although the creep behavior exists in the reinforced soil retaining structure, the creep is in the steady-state stage, the total creep is relatively small, and the tendency of creep is gradually slowing down; therefore, the creep will not result in a failure of the structure.
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