Abstract: The ultimate bearing capacity of a strip footing on the reinforced sand is studied based on both the limit equilibrium slice method and the critical slip field method. It is assumed that friction of the interface between the soil and reinforcements is uniform when the reinforced foundation soil is in the limit equilibrium state. Based on the limit equilibrium equations of soil slice, a recursion expression of slice force is derived. Firstly, the borders of the soil mass with potential sliding are determined, then soil mass is divided into a series of slices, and the state points is distributed on interfaces between the slices. Secondly, the recursion expression is used to calculate the parameters of all state points and search the critical slip surface. Finally, the bearing capacity can be determined according to the critical slip surface which meets the balance of forces and moments. The reliability of calculation results is shown by comparing with the results in literature. Effects of distance from footing bottom to top reinforcement, layer numbers and length of reinforcement on bearing capacity and slip surface are also presented. The results show that the bearing capacity increases firstly and then decreases as the depth increases, or it increases firstly and becomes stable lastly as layer number and length increase. It is also shown that the slip surface changes mainly in the vertical and horizontal ranges. Because the proposed method is easy to understand and numerically implement, it provides a new idea to calculate the bearing capacity of strip footing on reinforced sand, and it extends the critical slip field method to the calculation of bearing capacity.

Key words: strip footing, reinforced foundation, ultimate bearing capacity, limit equilibrium method, slice method