Study On Bearing Capacity And Calculation Method Of Rock-socketed Pile Through Single Layer Karst Cave In Karst Area

With the advancement of construction to the western region,the landforms in the western region are mostly karst topography.When building bridges in this area,it is difficult to avoid encountering karst areas.The existence of the karst zone has brought many difficulties to the construction,and if it is not handled properly,it will bring many problems.Therefore,many experts and scholars have studied the problems of foundation piles in karst areas,and put forward two ideas for the treatment of foundation piles in karst areas.The first method is to use the self-supporting capacity of the top slab of the pile tip,and the second method is to adopt The bored cast-in-place rock-socketed pile passes through the karst cave,and the pile end is embedded in the stable rock mass at the bottom of the karst cave.The first method needs to meet certain conditions for the roof of the karst cave and its theoretical research is systematic and relatively complete,while the research on the second method is rarely reported.There is still a lack of systematic research and practical methods for the ultimate bearing capacity of rock-socketed piles that pass through a single-layer karst cave in a karst area.Therefore,this article combined with the National Natural Science Foundation of China "Research on the Vertical Bearing Mechanism and Design Calculation of Rock-Socketed Piles Through Karst Cave"（Project No.51878270）The bearing characteristics of rock-socketed piles in karst caves and the calculation method of bearing capacity have been preliminary explored.The main research contents are as follows:（1）According to the similar principle,the bearing characteristics test of rock-socketed piles crossing a single-layer karst cave in a karst area was carried out.In the test,the pile top load,pile end load,pile top settlement,pile strain and pile displacement of the model pile were measured.The law of load transfer was analyzed,and the failure modes of foundation piles and cave roofs were observed.（2）According to the experimental phenomenon,the ultimate bearing capacity of the three possible failure modes of the cave roof is calculated and compared with the experimental results.It is concluded that the failure mode of the cave roof mainly depends on the value of the side friction resistance between the foundation pile and the roof.The failure of the cave roof varies with the size of the side friction resistance,and there may be combined failures.（3）When studying the calculation method of the ultimate bearing capacity of rocksocketed piles passing through small caves and high karst caves in the karst area,the ultimate bearing capacity value of the material damage of the pile body and the material damage of the base rock of the pile end were carried out according to the different types of material failures.The ultimate bearing capacity value is calculated and compared with the test results.The small value of the two results is regarded as the ultimate bearing capacity of rock-socketed piles that pass through small caves and high karst caves in karst area.（4）Based on the principle of the total potential energy of foundation piles,the catastrophe theory is introduced to derive and calculate the ultimate bearing capacity method of karst areas crossing large caves and high karst caves.The stability factor of foundation piles in the code is analyzed.