Identification of soil parameters in the calcu-lation of high-rise buildings on pile foundation

Abstract

The results of numerical modeling of the interaction of bored piles with the soil environment are presented. The process of identifying soil parameters according to static tests of piles was studied. The parameters of the soil, which have the greatest influence on the change in the graph of the dependence of the pile settlement on the load, are singled out.
 The research process can be divided into the following stages: creation of a numerical model of the interaction of the pile with the volumetric soil array in the PC «LIRA-Sapr». The size of the array is 30x30x40 m, based on the research of scientists [1]. The pile is defined be a rod finite element (pile length 30 m, diameter 0.82 m). The array is defined by non linear finite elements with characteristics according to data from engineering and geological studies. The load is applied step by step (10 steps) with a maximum value of 600 ton-forces. 4 variants of the volumetric soil massif with different values of the modulus of elasticity were considered. In the first variant, the modulus of elasticity is unchanged, in the second it is increased by 2 times, in the third by 3 times and in the fourth variant by 4 times. The modulus of elasticity increased simultaneously in all elements of the soil massif. According to the calculation, it was established that when the elasticity modulus is increased by 4 times, the graph of the dependence of the settlement on the load is close to the graph of field tests. Further, the identification of the angle of internal friction was carried out, with an increased modulus of elasticity by 4 times. It was established that in the soil model with the angle of internal friction taken with a factor of 0.5, the settlement graph of the test pile is very close to the test graph. Therefore, for the calculation of the «base – foundation – above-ground structures» system, it is customary to increase the elasticity modulus by 4 times and take the angle of internal friction with a factor 0.5.
 The calculation of the «base – foundation – above-ground structures» system for a high-rise building with identified soil parameters and with parameters that were before identification was performed. The stress- strain state of foundation structures for two variants of soil conditions was investigated. Redistribution of forces in foundation structures with both variants of soil parameters is given