EFFECT OF REINFORCED EARTH ON DYNAMIC EARTH PRESSURE

Abstract

Economical 1mlpr•ovement of' mechanical properly of' the sol i Is one of the aim of a Geotechnical engineering. Reinforced earth technique is a method by which overall stability of the soil can be improved. Reinforced earth soil is a composite material which is formed by the association of' soil and tension resistant reinforcing elements. The reinforcement suppresses the normal tensile strength in the soil mass through frictional interaction. Due to its economy, ease in construction and flexibility in nature, such a material has varied application in civil engineering construction like retaining walls, slabs, and water front structures to industrial and special structure. • In present the application of reinforced soil in retaining wall has been •Investigated.- Where the lateral pressure on the conventional retaining wall are sought to reduce by reinforcing the backfill by unattached horizontal strips or mesh or meshes. Cheap reinforcing material like Mosquito mesh could be employed as reinforcement. The experiment were conducted on masonry retaining wall constructed in a steel tank of size 1.05m x 0.6m x 0.4m mounted on steady state vibration table, excited by a 3 phase, 3 H.P. AC motor through crack mechanism for changing the. rotary motion into sinusoidal motion. Effect of two parameter on the dynamic earth pressure was studied (1) Acceler•al.ion level (li)t.ype of reinforcement(different hole size of mesh). Mesh reinforcement having size 70cm x 60 cm were placed in three layer behind the 40 cm high retaining wall. 3 Nos. of pressure cell were embedded In the wall to record the earth pressure at different elevation. The tank was excited at a frequency of 3.5 cps with acceleration 0.07188 g t.o 0.2418g. It has been observed from the experiment that in static condition with plain backfill, pressure distribution is almost hydrostatically and is very close to that given by Jacky formula. In case of reinforced earth static pressure are reduced significantly while dynamic earth pressure are reduced comparatively less as compare to static earth pressure. The use of smaller hole size of reinforcement mesh cause aapppreciable reduction in static earth pressure but simu!taneous1y dynamic increment are more with heavy reinforcement because of inertia of the backfill. Reduction in static earth pressure are more as compare to the dynamic increment, and therefore it.cause reduction in dynamic earth pressure with smaller size of reinforcement. It was observed that dynamic earth pressure with plain backfill or with reinforced backfill is increase with increasing of acceleration level of the dynamic, force but reduction in dynamic earth pressure due to reinforced backfill was constant with acceleration level of dynamic force. The point of action of' total dynamic earth pressure was shift. towards bottom due to provision of reinforcement in the backfill. IV