Abstract：By field sliding resistance test of the retaining structure both with and without key wall in the soft clay ground，the effect of key wall on the retaining structure is studied. The field test results are analyzed by means of non-linear FEM. The conclusions are as follows. The effect of the key wall on sliding resistance is quite great in spite of shorter key wall length，and the sliding resistance is in direct proportion to the key wall length in the range of testing key wall length. The earth pressure in front of the key wall reaches the passive pressure and the earth pressure behind the key wall is close to zero while the retaining structure is in limit equilibrium condition. The FEM predictions are in good agreement with the experimental results. Finally，the critical length of the key wall is studied by means of FEM.
