Performance of pullout resistance of anchored earth system by field pullout test

Abstract

Anchored Earth System had been developed from combination of the techniques used in reinforced earth and soil anchoring. Instead of using steel strip as a reinforcement, Anchored Earth System consist of round steel bar (tendon) with precast concrete block attached at the free end of each of the reinforcing steel bars, and it is backfilled with granular material or suitable earth fill. This research project can be considered a case study of anchored reinforced soil wall which investigates the performance of Anchored Earth System due to its pullout capacity. In this study, pullout resistance which contributed by friction between the backfill material and the shaft surface of reinforcing tendon, and the passive earth pressure against the concrete anchor block, can be evaluated through pullout tests. The main problems to be studied in this project are the results obtained from field pullout test are different from the calculated theoretical values and there is a non-zero intercept at relationship of pullout force against overburden pressure. The field pullout tests were carried out in three conditions: i) with reinforcing tendon only; ii) with anchor block only; and iii) with both reinforcing tendon and anchor block together in order to determine the sharing of resistance in the system. The pullout test was also done under soaked condition. The average interaction coefficient a’ = 1.99 and bearing factor ß = 6.32 were determined by back analysis. It was found that the sharing of load between the tendon and the anchor block in anchored earth system is not equal, but most of the resistance is contributed by the bearing passive of anchor block where approximately 30 % of resistance contributed by residual frictional resistance and 70 % contributed by peak bearing passive resistance. The pullout resistance in soaked condition observed to be lower than in unsoaked condition due to the increase in pore water pressure that reduced the shear resistance.