岩溶区穿越溶洞桩基极限承载力及破坏模式试验研究

iming at the bearing mechanism and failure mode of the pile foundation passing through karst caves,laboratory model tests of ultimate bearing capacity and failure mode of pile foundation passing through karst caves were carried out to reveal the law of ultimate bearing capacity of pile foundation varying with the height of karst caves,and the failure modes of pile foundation and cave roof were classified when pile foundation passing through different cavern heights.According to the test results,the stability coefficient of pile foundations passing through different high karst caves was given.Finally,the pile tip resistance ratio of pile foundation passing through cavern of different heights in the limit state was analyzed,and the ratios of pile side resistance and pile tip resistance in the bearing process of 10d cavern height test were analyzed.The results show that:1)When the bending resistance of the cave roof is insufficient,the lateral friction resistance of the pile-rock interface is large,and the integrity of the roof and surrounding rock mass is good,the flexural failure of fixed plate occurs; when the integrity is poor,the flexural failure of the simple-supported plate occurs; when the lateral friction resistance of the pile-rock interface is small,the shear failure or the combined failure of shear and punching occurs.2)The minimum cave height of pile foundation buckling is 6d.When the uniaxial compressive strength of pile foundation is less than the ultimate resistance of pile tip and pile side,the pile material compression failure occurs in the pile foundation passing through small cavern; otherwise,the bedrock of pile tip will be damaged.When the buckling bearing capacity of pile foundation is less than the ultimate resistance of pile tip and pile side,the pile body buckling failure occurs in the pile foundation passing through large cavern,and the bedrock of pile tip will be damaged otherwise,and the buckling bearing capacity of pile foundation decreases linearly with the increase of cavern height.3)The ultimate bearing capacity of pile foundation passing through karst cavern depends on many factors,such as pile material strength,cavern height and strength of rock around pile.The minimum value of ultimate bearing capacity of pile material compression failure,pile foundation buckling failure,and pile tip bedrock failure is the ultimate bearing capacity of pile foundation passing through the karst cave.4)In the limit state,the pile tip resistance ratio of pile foundation passing through karst cavern decreases with the increase of cavern height,but the decrease is small.The greater the load on the top of the pile passing through karst cavern,the greater the pile tip resistance ratio and the smaller the pile side resistance ratio.