基桩穿越大型溶洞时可能发生屈曲失稳，屈曲临界荷载即为基桩极限承载力。针对岩溶区穿越单层溶洞基桩屈曲问题，依据能量法原理建立了穿越单层溶洞基桩总势能方程。根据基桩屈曲的突变特性，引入尖点突变理论，建立了基桩在顶部弹嵌、底部嵌固情况下失稳的尖点突变模型，导出了该体系的分岔集方程，进而通过分析其失稳条件，提出了穿越单层溶洞基桩屈曲临界荷载计算方法。为验证理论方法的合理性，进行了基桩穿越不同高度溶洞的室内模型试验，研究表明：（1）基桩主要发生桩身压缩破坏和屈曲破坏，洞高小于6 d 时基桩发生材料压缩破坏，洞高大于等于6 d 时基桩发生屈曲，位移最大点位于临空段的中点；（2）基桩屈曲临界荷载随洞高增大呈线性减小，理论方法适用于基桩发生屈曲的情况，且与试验结果吻合较好；（3）洞高越小、顶板越厚、基桩弹性模量越大、桩−岩界面越粗糙，则基桩屈曲临界荷载越大，反之则越小。Buckling instability may occur when pile foundationpasses through large caves

and the critical buckling load is the ultimatebearing capacity of pile foundation. To solve the buckling problem of pilefoundation crossing single layer karst cave in karst area

a total potentialenergy equation of pile foundation crossing single layer karst cave isestablished according to the principle of energy method. According to thecatastrophe characteristics of pile foundation buckling

the cusp catastrophetheory is introduced

and a cusp catastrophe model of pile foundationinstability under the condition of elastic embedding at the top and fixity atthe bottom is established. The bifurcation set equation of the system isderived

and then by analyzing its instability conditions

the method ofcalculation of buckling critical load of pile foundation crossing single-layerkarst cave is developed. In order to verify the rationality of the proposedmethod

laboratory model tests of pile foundation crossing karst caves withdifferent heights are carried out. Some conclusions are drawn. 1) Thecompression failure and buckling failure are main forms. When the height of the cave is less than 6d

the foundation pile fails dueto material compression failure. When the height of the cave is greater than or equal to 6d

the buckling occurs in pilefoundation. The maximum displacement point is observed to be located at themidpoint of the karst cave section. 2) The critical buckling load of pilefoundation decreases linearly with the increase of cave height. The proposedmethod is suitable for the buckling of pile foundation

and it is in goodagreement with the experimental results. 3) The small cave height

thick roof

great elastic modulus of the pile foundation

and rough pile-rock interface canresult in a great critical buckling load

and not vice versa.