1st Croatian Conference on Earthquake Engineering 1CroCEE 2021

The foundation soil is the last structural element to which seismic forces are transmitted and is an unavoidable factor of stability, but also a threat to some buildings. Many years of experience in testing and repairing the foundations of buildings in the urban area of Zagreb and Banovina has shown that the soil is degraded in many cases, primarily by secondary influences. Among the most pronounced are the impacts of water resulting from outdated water supply and sewerage infrastructure and climate change causing long droughts and heavy rains. Such soil has poorer geomechanical properties than those according to which the building was designed before construction, and thus does not provide sufficient load-bearing capacity of the building located on it. This problem is even more pronounced during seismic oscillations because it creates an additional load on the foundation soil, resulting in greater displacement of objects, and thus greater risks to people and structures of objects.

In this paper, through mathematical models, but also examples from practice, the impact of earthquakes on buildings with degraded foundation soil, and also the impact on those where foundation soil is strengthened or rehabilitated by the method of expanding resin injection, will be presented. Regardless of the method of improving the foundation soil, each of them contributes to the stability of the building, and thus to seismic resistance; especially in cases where there has been degradation of the foundation soil after its construction.