In general

the calculation of earth pressure existing in the back of retaining wall employs the classical earth pressure theory; and the earth pressure distribution along the wall back is linear. In practical engineering

however

the earth pressure distribution usually is nonlinear. In order to enhance the accuracy of earth pressure calculation

it was assumed that the potential slip surfaces of backfill soils were composed of log-spiral surface and plane. Based on the existing researching works

the formulae for calculating active earth pressure were obtained by utilizing thin-layer element method. Since the calculation value of earth pressure is relevant to the location of slip surface; in the search for the most dangerous potential slip surfaces

a new hybrid genetic algorithm

called complex genetic algorithm (CGA)

was developed by introducing complex method into simple genetic algorithm to enhance the calculation efficiency. CGA was used to determine the potential slip surfaces and calculate the corresponding active earth pressure. Finally

the earth pressures of the laboratory model retaining wall and in situ retaining wall were analyzed and the results show that the calculation values given by the presented method are very consistent with the measured values. It is indicated that the presented method is feasible and reliable.