Experimental study on pile-soil bearing behavior and thickness-diameter ratio of composite foundation with long and short piles

The bearing behavior of long pile and short piles, load sharing ratio of soil between piles, pile-soil stress ratio and mobilization factor of bearing capacity are measured in indoor model tests on piles with constant thickness-diameter ratio. The bearing capacity of long piles, short piles and the soil between piles cannot be fully mobilized at the same time. Besides, the bearing capacity of short piles is mobilized more than that of long piles. By analyzing the test results of the constant thickness-diameter ratio, the design of long-short rigid pile composite foundation with varying thickness-diameter ratios is investigated. It is believed that the varying thickness-diatmeter ratio, reduction of thickness-diameter of long piles and increase of thickness-diameter of short piles are suitable for the long-short rigid pile composite foundation. The varying thickness-diameter ratios can be realized by constant cushion thickness and varying pile diameters, in which the diameter of long piles is bigger. Otherwise it can be realized by constant pile diameter and varying cushion thicknesses, in which the thinner cushion of long piles is selected.