STATIC AND DYNAMIC PULLOUT RESISTANCE OF .SOIL-REINFORCEMENT

Abstract

Reinforce Earth is a combination of plain soil and reinforcements. Plain soil is good in taking the compression but weak in tension. So reinforcements which are good in taking tension are inserted in the plain soil to strengthen the soil. The strength is achieved through friction between reinforcement and soil. Therefore, pullout force mobilized is very important material property for the design of reinforced earth. Two types of apparatus are used to find the pullout force of soil-reinforcement. In both type of apparatus a test box similar to that of direct shear test with dimensions 300 mm X 300 mm X 120 mm is used. Strain control apparatus is the widely used apparatus. In this type of apparatus, soil-reinforcement is pulled out at constant strain under a normal stress, this dose not allow the full mobilization of pullout resistance. Hence, gives underestimated results which are dangerous.. Stress control type of apparatus allows enough time for the mobilization of pullout displacement. So it is better apparatus than strain control type of apparatus. Neeti Ranjan (2000) has modified instrument developed by Mehdi (1998), to find dynamic pullout resistance of soil-reinforcement. She has performed limited number of tests. Aterkar (2003) has performed number of tests to find static and dynamic pullout resistance of geosynthetics. Same instrument was used in this study with modification to reduce the dynamic friction. Tests were carried out with changed geosynthic, keeping all the parameters similar to that used by Aterkar. Parametric studies were also carried out changing density of soil and by changing the width of sample to find its effect on mobilized pullout resistance of soil-reinforcement. The main advantage is of controlled frequencies. The new power supply designed has worked wonderfully to give predetermined frequency which can be set before starting the motor.