FIELD INVESTIGATION OF THE INITIAL SETTLEMENTS OF PILE NOT CONNECTED TO THE RAFT IN A COMBINED RAFT-PILE FOUNDATION

Problem statement. The patented useful model for the design of the combined raft-pile foundation (CRPF), consisting of a raft part and piles, with a gap of height Δ is made between the raft part and the piles. That is, the distribution of settlements (resistances) of the soil base under the raft and then under the piles (after the hinged connection of the piles with the raft) is assumed, based on the condition of not exceeding the maximum allowable settlement su of the building or structure. The initial settlement of the piles, which arises from the effect of the additional loading (negative) friction force acting on their lateral surface within the compressible layer during the pressure loading of the soil base raft part, must additionally be taken into account to correct the value of the gap Δ. The purpose of the article is to conduct field investigation of the piles initial settlements under the action of additional loading (negative) friction forces acting along their lateral surface in a large-scale combined raft-pile foundation to identify new dependencies and generalize them. Conclusions. On the basis of field studies, a qualitatively new dependence of the pile deformation on the action of additional ground friction forces has been revealed, which shows the "pile up-slip effect" due to the excess of resistance forces on its lateral surface with manifestation of inverse (elastic) deformations of the ground base of the pile. On the basis of field investigation, a qualitatively new dependence of the pile deformation on the effect of soil additional loading (negative) friction forces was revealed, which shows the “effect of the pile slipping upwards” due to exceeding the negative friction forces the resistance forces on its lateral surface with the manifestation of reverse (elastic) deformations of the pile soil base, which indicates the need to take this phenomenon into account when determining the gap between the raft part and the piles in projects of similar CRPF.