Limit earth pressure under plane strain condition

Based on the strength criterion under plane strain condition and Rankine's theory, a simplified method for determination of limit earth pressure is proposed. The principal stress in the plane strain direction, which can be determined under the rigidity-plasticity assumption using static earth pressure coefficient, is the intermediate principal stress under the limit equilibrium condition. The relationship between major and minor principal stresses is obtained based on the strength criterion. Then the earth pressure coefficient can be determined. Although the proposed method is as simple as that of the Rankine's theory, it can obtain more reasonable calculation results, and accordingly improve the design methodology yielding output more economically. The results also show that the difference between the proposed method and the Rankine's theory is enlarged along with the increase of the friction angle of the material. The validity of this method is confirmed by observed data from the practical foundation engineering. Compared with the Rankine's theory, the proposed method can be more rationally used in soil-retaining structure designing.