Ultimate bearing capacity of geogrid-reinforced sand composite
XU Chao1, 2, LIANG Cheng2
1. Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092, China; 2. Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China
Abstract：The differential settlement generated between the bridge deck and the approaching road willn be eliminated and bridge jump will also be prevented if geosynthetic-reinforced soil abutment is employed. To calculate its safety redundancy in the design, the ultimate bearing capacity of the geosynthetic-reinforced soil composite needs to be computed. Firstly, the model for calculating the ultimate bearing capacity of the geosynthetic-reinforced soil mass proposed by Wu and Pham is analyzed, and whether this model has the capability to predict the ultimate bearing capacity of geosynthetic-reinforced fine grained soil is questioned. To verify this problem, five geogrid-reinforced sand model tests and one unreinforced soil model test are then conducted under plain strain condition. The effects of reinforcement spacing and strength on the ultimate bearing capacity of the geosynthetic-reinforced soil are considered in the model tests. A comparison is made between the test results and those calculated using the model proposed by Wu and Pham. It is found out that the model proposed by Wu and Pham underestimates the ultimate bearing capacity of the geogrid-reinforced sand. Finally, a new analytical model is put forward based on the failure criterion of Mohr-Coulomb and the assumption of Rankine failure surface. The results calculated using the proposed model are coincident well with those obtained from the model tests.
 ADAMS M T, NICKS J E, STABILE T, et al.Geosynthetic reinforced soil integrated bridge system interim implementation guide[R]. Final Report, FHWA-HRT-11-026. McLean: Federal Highway Administration, 2011.  ADAMS M T, NICKS J E, STABILE T, et al.Geosynthetic reinforced soil integrated bridge system synthesis report[R]. Final Report, FHWA-HRT-11-027. McLean: Federal Highway Administration, 2011.  SAGHEBFAR M, ABU-FARSAKH M, ARDAH A, et al.Performance monitoring of geosynthetic reinforced soil integrated bridge system (GRS-IBS) in Louisiana[J]. Geotextiles and Geomembranes, 2017, 45(2): 34-47.  HELWANY S M B, WU J H T, FROESSL B. GRS bridge abutments-and effective means to alleviate bridge approach settlement[J]. Geotextiles and Geomembranes, 2003, 21(3): 177-196.  BERG R R, CHRISTOPHER B R, SAMTANI N.Design and construction of mechanically stabilized earth walls and reinforced soil slopes-Volume Ⅰ[R]. Washington D C: Dept. of Transportation, 2009.  ELTON D J, PATAWARAN M A B. Mechanically stabilized earth reinforcement tensile strength from tests of geotextile-reinforced soil[R]. Washington D C: Transportation research record 1868, Transportation research board, 2005.  ADAMS M T, KETCHART K, WU J T H. Mini pier experiments: geosynthetic reinforcement spacing and strength as related to performance[C]// Geosynthetics in Reinforcement and Hydraulic Applications, Geotechnical Special Publication 165, Geo-Denver 2007, ASCE. Reston, 2007.  WU J T H, LEE K Z Z, PHAM T. Allowable bearing pressures of bridge sills on GRS abutments with flexible facing[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2006, 132(7): 830-841.  WU J T H, PHAM T Q. Load-carrying capacity and required reinforcement strength of closely spaced soil-geosynthetic composites[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2013, 139(9): 1468-1476.  LADE, P V, LEE K L.Engineering properties of soils[R]. Report UCLA-ENG-7652, Department of Civil Engineering, University of California. Los Angeles, 1976.  ADIB M E.Internal lateral earth pressure in earth walls[D]. University of California. Berkeley, 1988.