Abstract:

Buckling instability may occur when pile foundation passes through large caves, and the critical buckling load is the ultimate bearing capacity of pile foundation. To solve the buckling problem of pile foundation crossing single layer karst cave in karst area, a total potential energy equation of pile foundation crossing single layer karst cave is established according to the principle of energy method. According to the catastrophe characteristics of pile foundation buckling, the cusp catastrophe theory is introduced, and a cusp catastrophe model of pile foundation instability under the condition of elastic embedding at the top and fixity at the bottom is established. The bifurcation set equation of the system is derived, and then by analyzing its instability conditions, the method of calculation of buckling critical load of pile foundation crossing single-layer karst cave is developed. In order to verify the rationality of the proposed method, laboratory model tests of pile foundation crossing karst caves with different heights are carried out. Some conclusions are drawn. 1) The compression failure and buckling failure are main forms. When the height of the cave is less than 6d, the foundation pile fails due to material compression failure. When the height of the cave is greater than or equal to 6d, the buckling occurs in pile foundation. The maximum displacement point is observed to be located at the midpoint of the karst cave section. 2) The critical buckling load of pile foundation decreases linearly with the increase of cave height. The proposed method is suitable for the buckling of pile foundation, and it is in good agreement with the experimental results. 3) The small cave height, thick roof, great elastic modulus of the pile foundation, and rough pile-rock interface can result in a great critical buckling load, and not vice versa.

Key words: karst pile foundation, buckling failure, experimental study, catastrophe theory, critical cave height