Punching settlement of raft-pile foundation under cyclic loading
Problem statement. The purpose of the study is to identify the patterns of development of punching settlement of raft-pile foundations. During cyclic loading, the raft-pile foundation settlement consists of three components: the conditional foundation settlement, the settlement due to compression of the pile and the pile punching settlement. The draft of the raft-pile foundation significantly changes the load distribution on the piles in the raft-pile foundation. Under cyclic loading, the regularities of the precipitation of raft-pile foundations are insufficiently studied. Results. The main results of the study include the fact that the author established a method for determining punching settlement of raft-pile foundation under cyclic loading. This process is considered in a spatial formulation, taking into account the joint deformation of all elements of the system «pile cap - piles - soil of inter-pile space - soil below the toe of the pile». The redistribution of forces between the system elements in the process of cyclic loading due to the development of deformation of the soil, pile cap and piles in the associated conditions is considered. The stresses in certain specific zones of the system are determined by solving 4 quasistatic equations together. The precipitation of the raft-pile foundation punching occurs when the stress under the fifth pile exceeds the fatigue strength of the soil during triaxial cyclic compression. Conclusions. The significance of the results for the construction industry is that the proposed method allows more accurate assessment of the stress-strain state of individual elements and the draught of the punching plate-pile foundations under cyclic loading with account of redistribution of efforts between the elements of the system «slab raft foundation -pile - soil mismanage space and the soil below the pile toe», which is a significant contribution to the theory of calculation of piled raft foundations and provides saving of concrete up to 15 % compared to existing methods.