Analysis of the effectiveness of the use of short piles as part of a columnar pile foundation

Abstract

The realization of the operation of the grid and piles as a part of the columnar pile foundation, depending on the length of the piles, the method of arranging the piles, the distance between the piles and the type of soil with a constant number of piles, has been studied. The degree of implementation of the load-bearing capacity of the piles and the degree of implementation of the grid work as part of the pile foundation were analyzed. To solve the tasks set in this work, mathematical modeling by the finite element method of the joint operation of the pile foundation elements with the soil base and the separate operation of the pile and grid as a shallow foundation was performed in the "Plaxis 3D Foundation" software complex. It was established that the implementation of the load-bearing capacity of piles in the composition of the foundation with a large distance between the piles is much better. The length of the piles also affects the degree of their implementation. When the length increases, the bearing capacity of the piles is realized less. The greatest implementation of the load-bearing capacity of piles in the composition of the foundation is observed for short piles. The realization of the pressure under the sole of the grid with an increase in the pitch of the piles also improves, the realization of the load-bearing capacity of the grid is from 8 to 50%, which allows to raise the load-bearing capacity of the foundation. For sandy and clay soils, the nature of the redistribution of forces between the elements of the columnar pile foundation is similar. For foundations made of drilled piles, the degree of realization of pressure under the sole of the grate, as well as the degree of realization of the load-bearing capacity of the piles, is higher than for foundations made of driven piles. The guiding factor is the length of the piles. The economic efficiency of the transition in homogeneous soils from a bush made of long piles with a standard minimum step to a bush made of short piles with an increased distance between the piles was investigated. By taking into account the joint operation of piles and grid, a bush made of short piles with larger dimensions of the grid provides the same bearing capacity as a bush made of long piles with a compact grid. Despite the significant increase in the volume of concrete grating and the number of fittings with an increase in the pitch of the piles, cost savings on the cost of piles provide an economic effect of using bushes from short piles with wide gratings up to 35%.