Earth Pressure and Earth-Retaining Structures

Sheet pile walls are flexible retaining structures that are used to hold the horizontal soil pressures behind them, especially in situations that cause stress changes such as excavation. They are divided into two as cantilever and externally supported. Cantilever walls are used in excavations with a maximum depth of 6 meters and are supported by anchors in excavations deeper than this. Some of the values to be calculated in the design of cantilever sheet pile walls are the embedment depth and the maximum bending moment that(Mmax) will occur in the cross-section of the wall. There are various approaches in analytical methods that have complex calculation steps such as determining earth pressures, solving second and third-order equations. In this study, the Mmax that will occur in the cross-section of a cantilever sheet pile wall penetrates in the sand is estimated by the expressions obtained with the help of multiple linear regression(MLR) analysis. The results showed that the Mmax may not be achieved by only MLR models but with the help of polynomial equations.

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Estimation of the maximum bending moment of cantilever sheet pile walls by using multiple linear regression analysis

Konsol Palplanş Duvarların Gömme Derinliklerinin Lineer Regresyon Analizi ile Tahmini

Objectives: The present study discuss estimation of active and passive earth pressure behind a smooth vertical retaining wall with horizontal backfill under linearly varying geotechnical properties, i.e., cohesion (c), angle of internal friction (φ) and unit weight (γ) of backfill vary linearly with depth.It is noted that the earth pressure behind the retaining wall is nonlinear and its variation can be established through regression analysis that follows 2nd order polynomial in the form of pa = -az2+bz+c; where z is the depth below the backfill surface, a, b & c are constants. Methods/Statistical Analysis: Regression analysis incorporating least square error approach option is available in Microsoft excel in data analysis tool pack. The total amount of thrust (active or passive ) estimated through non-linear distribution of earth pressure behind retaining wall is compared with the corresponding values computed through most widely used Rankine’s earth pressure theory in which average values of geotechnical parameters are taken. Findings: It is noted that there is 5-7% reduction in the active earth thrust although not much reduction is achieved in the moment. In passive case, the increase in passive thrust is almost 20%. Application/Improvements: Consideration of non-linear earth pressure distribution is useful in situations where base width of the retaining wall is controlled with respect to base shear. It will ultimately lead to reduction in the total cost of construction of the retaining wall and will help in achieving economy when the length of the retaining wall is large.

M. Malhotra

Papers

Earth Pressure behind a Retaining Wall under Linearly Varying Geotechnical Parameters