Influence of wall friction on Active Earth Pressure in Model Test

Abstract

Earth pressure theories occupy a paramount position in the field of geotechnical engineering. The knowledge of active earth pressure under static condition is essential in designing a retaining wall as the damage to such retaining structures may lead to disastrous failure. A retaining wall helps in maintaining the ground surface at different elevations on either side of it. Without such a structure, the soil at higher elevation would tend to move down till it acquires its natural, stable configuration. Laboratory model tests in geotechnical engineering are being performed in small steel test tanks to examine the lateral earth pressure on retaining walls.
In present study laboratory model of retaining wall is cantilever type, having model tank of MS (1810 x 1210 mm) in plan and 1000 mm height. The MS plate (1210 x 1000 x 5 mm) acts as a retaining wall. Present work consists of evaluation of active earth pressure by conducting 18 tests on model with different frictional surfaces namely jute, geotextile, thick plastic sheet, cement bag and uniform surcharge of 2.0 kN/m2. All the tests are conducted on dry, cohesionless backfill. Test results show that, when frictional surfaces are attached on the side walls and retaining wall, the deflection of the retaining wall reduces and hence active earth pressure is also reduced. Earth pressure slightly reduces in case of frictional surfaces on side wall as well as on retaining wall as compared to that with frictional surface only on retaining wall. Further it is observed that the reduction of the active earth pressure depends on to the wall friction angle () of frictional surface. Increase in wall friction angle () of surface results in decrease in deflection and thereby corresponding decrease in active earth pressure. Earth pressure obtained in the present work agrees well with Culmann’s graphical method whereas earth pressure by coulomb method is slightly higher than that obtained experimentally.