REINFORCED EARTH RETAINING STRUCTURES SUBJECTED TO EARTHQUAKES

Abstract

Earth retaining structures are used in road and railway embankments and for abutments of bridges which are termed as lifeline structures in earthquake engineering to highlight their importance to the economy of the region. As such, they are important. The soil is strong in taking compression and week in tension,whereas,the soil reinforcements are strong in tension but week in compression. Therefore, the composite reinforced earth is strong in compression as well as tension. Reinforced earth shows ductile behaviour when tension failures are avoided. It is also ready for use immediately after construction which makes the material ideal for use in disaster mitigation works immediately after the earthquakes. There are few published investigations dealing with dynamic behaviour of reinforced earth retaining walls (RE walls) and an the determination of frictional resistance of reinforcements burned in soil under static and dynamic conditions. However, available reports indicate that the frictional resistance under dynamic conditions is less than that under static conditions. Dynamic laboratory tests on RE walls confirm occurrences of Mononobe--Okabe rupture wedges within RE walls. Moreover, dynamic earth forces predicted by the Mononobe-Okabe theory are in reasonable agreement with the experimental data. Hence, it is appropriate to adopt pseudostatic method of analysis using Mononobe-Okabe rupture wedge for internal as well as external stability of the RE wall in the proposed investigation. The distribution of dynamic active earth pressures required for the analysis is obtained by using the numerical amalysis of Joshi and Prajapati (1982) together with modifications. proposed by Das (1988).The analysis is in plastic domain. All the soil and reinforcement material properties required may be obtained by suitable laboratory test. The study of elastic behaviour of RE walls is outside the scope of this investigation.