Abstract
In order to study the influence of steep slope-karst coupling on the vertical bearing characteristics of pile foundation, the orthogonal simulation tests of pile foundation under 4 different roof thickness and 5 different slope are carried out by using Marc finite element software, and the correction coefficient of vertical partial bearing capacity of pile foundation according to roof thickness and slope is put forward. The test results show that when the thickness of the roof is more than 3 times the pile diameter, the ultimate bearing capacity of the pile foundation tends to be stable, and the value is about 19% when the slope is 45°; the ultimate bearing capacity of the pile foundation decreases gradually with the increase of the slope, and the reduction reaches 29.83% when the slope is greater than 45°. According to the calculation results, the variation law of vertical partial bearing capacity of pile foundation is analyzed, and the calculation formula of standard value of vertical ultimate bearing capacity of pile foundation in steep slope karst area considering both roof thickness and slope is put forward, and the correction coefficients αi and β are put forward.
Highlights
With the continuous construction of China's highway network, karst strata and passing through steep slopes are becoming more and more common in engineering, and the requirements for the bearing capacity of pile foundation are getting higher and higher
When the rock-socketed depth and roof thickness are constant, the degree of lack of rock and soil on the side of the pile increases with the increase of the slope, the load at the top of the pile is mainly borne by the resistance at the end of the pile, and the exertion of the resistance on the side of the pile decreases significantly, indicating that the slope has an important influence on the vertical bearing characteristics of bridge pile foundation in the karst development area of steep slope. when the slope is greater than 45°, the influence of rock and soil loss on the bearing characteristics of pile foundation should be considered
(1) when the steep slope is constant, the ultimate bearing capacity of pile foundation increases with the increase of roof thickness, and the bearing capacity tends to be stable when the roof thickness is more than 3 times the pile diameter
Summary
With the continuous construction of China's highway network, karst strata and passing through steep slopes are becoming more and more common in engineering, and the requirements for the bearing capacity of pile foundation are getting higher and higher. Based on the solid project of Guang Na Expressway in Yunnan Province, this paper uses Marc finite element software to design orthogonal numerical simulation test, systematically studies the influence of roof thickness and steep slope on the bearing characteristics of pile foundation, and puts forward the partial bearing capacity correction coefficient according to the calculation results, which has certain theoretical significance and engineering application value for further perfecting the current design code of pile foundation in steep slope karst area. Marc finite element software is selected to design orthogonal simulation test for practical engineering simulation In this test, the linear elastic constitutive model is used for the pile, and the elastic-plastic constitutive model is used for rock and soil, and the design is carried out according to the Mohr-Coulomb yield criterion.
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