Assessment of the stress-strain state of pile foundations of a multi-story building with possible water saturation of loess soil

The increase in the density of buildings leads to the need to set aside for development areas that were previously considered unfavorable from the point of view of the quality of the geological conditions. Deposits of loess rocks cover almost 80% of the territory of Ukraine. Such soils are characterized by a negative feature - the ability to rapidly reduce their mechanical properties in contact with liquid and to cause additional subsidence deformations. Based on this, a significant part of buildings and structures is erected in conditions of the possible occurrence of uneven deformations due to water saturation of subsidence soils. Therefore, the foundation structures of these structures must be designed with taking into account the occurrence of subsidence of loess soils. 
In their natural state, loess soils have sufficiently high mechanical characteristics due to structural connections. However, as the moisture content increases, the resistance to compression rapidly decreases, structural bonds are destroyed, and soil subsidence is observed. 
The modern level of foundation structures design involves the search for a reliable and cost-effective foundation option. This is especially relevant in the conditions of construction on soils that have the property of settling with possible increase in moisture content. 
The paper presents the results of a comparison of foundation options, taking into account the influence of possible water saturation of loess soils on the stress-strain state of foundation structures. Different schemes of possible water saturation of loess soils were considered depending on their size and location. 
This publication is a continuation of the previously published work [4]. It was about the results of the research, which was devoted to the variant design of foundations using numerical simulation of the joint work of the elements of the "soil base - foundation - above-ground structures" system. According to the results of the study, the choice of a rational option of foundations was substantiated, based on its indicators of reliability and economic efficiency. The conducted research confirms that the size and location of the soaking zones of the subsiding soil affect the nature of the stress distribution in the foundation structures. It is shown that the variant design of foundations, taking into account the negative factors related to the soil conditions of the construction site, as well as man-made situations that may arise during the operation of the building, make it possible to design a reliable and at the same time cost-effective option of the foundations.