The effect of soaking on the pull-out forc in reinforced earth using different types of reinforcement materials.

The effect of soaking on the Pull-out Force in reinforced earth using different types of reinforcement materials has been studied in the Laboratory using Pull-out Tests. These tests were performed at constant rate of displacement of 0.60 mm/sec. and a constant vertical stress of 150KN/m2. In this study the different types of reinforcement materials used were (i) Flat bar (strip) and (ii) Round bar mesh (Grid) all made out of steel. Two types of soil fill materials were used in the study namely:- (i) River sand and (ii) Laterite soil. River sand was compacted in oven dry state at dry density (Yd) of 1.64 g/cm3 and voids ratio (e) of 0.604 using sand vibration method. The laterite soil was compacted (using 2.5kg rammer) to the maximum dry density (MDD) of 1.76 g/cm3 at an optimum moisture content (OMC) of 17 %. Tests were performed for both unsoaked and soaked soil conditions (in case of laterite soil., the soaking was of four days duration). The investigations indicated that: the maximum pull out forces vary with the type of reinforcement (higher for Grids than Flat bar). In addition it has been observed that the flat bar reinforcement showed a clear yield point (maximum pull out force) whereas there was no clear yield point for round bar mesh. It was also noted that River sand showed higher values of maximum pull-out forces as compared to the Laterite soil for both types of reinforcement materials and for both soil conditions (Soaked/Unsoaked). The investigation further indicated that for all types of soil fills tested and for both types of reinforcement materials used maximum pull out forces were lower for soaked condition as compared to unsoaked conditions. The average decrease in pull out forces on soaking is as follows: (a) River sand: (i) Flat bar 27.3% (ii) Round bar mesh 6.7% (b) Lateria soil (i) Flat bar 48% (ii) Round bar mesh 71.4% The values of maximum pull out forces are summarised as follows: (a) River sand (i) Flat bar: The values were 4.40KN and 3.20KN for unsoaked and soaked soil conditions respectively. (ii) Round bar mesh: The values were 5.96KN and 5.65KN for unsoaked and soaked soil conditions respectively. (b) Laterite soil (i) Flat bar: the values were 1.15KN and 0.60KN for unsoaked and soaked soil conditions respectively. (ii) Round bar mesh: The values were 2.91KN and 0.83KN for unsoaked and soaked soil conditions respectively.