Possibility for stabilization of grounds and foundations of two valuable ancient cathedrals on weak soils in Baltic Sea region with grouting

Abstract

In this paper are analysed deformations of ancient churches in Vilnius and in Koenigsberg (Kaliningrad) and possibilities for stabilization of its grounds with grouting. Foundations of both Cathedrals were constructed on weak soils. Deformations of Vilnius Cathedral foundations are reflected by cracks in structures. Underpinning with bored piles of Vilnius cathedral in years 1931–1937 improved situation. Settlements of Koenigsberg cathedral reached approximately 2.0 m during 6 centuries. This cathedral is not underpinned but rebuild after Second World War demolitions. Results of laboratory tests with sandy soils from Vilnius Cathedral stabilized with solutions of organic polymers are given. Comparison was done of properties of conventional polymer resins with properties of modified resins. Such properties of solution of resins have been investigated: density, viscosity, pH (alkalinity level), evaporation of components from solution in water and air. During the next stage of investigations properties of alluvial medium dense sand stabilized with conventional and modified resins have been compared. Such properties of reinforced soil have been investigated: compressed strength, evaporation of formaldehyde from stabilized soil, time dependent strength of soil in air and water medium. Addition of active components to polymer resins increase density and pH of solution of organic polymers, decrease viscosity. Compressed strength of sands from Vilnius Cathedral stabilized with polymer resins is time dependent and increased from 2.2 MPa after 7 days to 2.9 MPa after 3 months. 12 to 19 times less formaldehyde is liberated into the air from soil stabilized with the modified resins than from the soil stabilized with the unmodified resins. Test with stabilization for peaty and clay soils from Kaliningrad Cathedral was unsuccessful.