DISPLACEMENT ANALYSIS OF RETAINING WALLS WITH REINFORCED BACKFILLS

Abstract

Displacement analysis is proposed by replacing the reinforced earth backfill with the independent elastic springs fixed to the back of retaining wall at different locations and other ends of the springs are fixed to an immovable support. The spring constant of soil, backfill spring is calculated by treating the retaining wall as a beam simply supported on these springs. The loading on this beam is triangular as the soil modulus varies with depth for cohesionless soil. Similarly the reinforcement is also replaced with the springs of high stiffness which can be calculated for the reinforcing material. The value of limiting strain for each spring may be specified as per location of the spring. When al•l springs attain this limiting strain at particular displacement of wall, the analysis will give pressure equal to Rankine active earth pressure. Initially the soil springs are assumed to be in precompressed state representing soil in ko condition and the total earth pressure is computed. Now for any displacement at a given limiting strain the spring forces are determined in soil springs as well as in reinforcement springs. Soil spring forces are subtracted from initial forces which. are due to soil in Ko condition and thus in unreinforced soil total lateral earth force is calculated. This analysis is done for many assumed value of limiting strain and from there yield strain at which total lateral earth pressure just equals to Rankine's earth pressure in unreinforced backfill Retaining Wall is determined. At this yield strain, total lateral earth pressure is calculated by reinforcing the backfill with different size and type of reinforcement. Now by substracting the reinforcement spring force from Rankine's active earth pressure the total lateral earth pressure is determined for three modes of wall movement (Translation, Rotation about bottom, Rotation about top). In this analysis the pressure distribution for reinforcing member is plotted and it is linear for above three modes of wall movement. Area of this pressure distribution diagram gives the total reduction made in earth pressure due to adding of reinforcement in backfill.