ENGINEERING AND GEOLOGICAL PROBLEMS OF PRESERVATION OF THE BOIM IN LVIV CHAPEL

Abstract

The article presents the results of a comprehensive study of the geological environment and the state of structural elements of the architectural monument of national importance. It has been established that the chapel building is located on the gentle slope of the valley of the Poltva River. The geological section in the sphere of its influence is composed of a thick layer of heterogeneous, unstable artificial soils with a thickness of up to 4.2 m, covered with medium-grained and gravel sands, which lie on a thick layer of Upper Cretaceous marls and products of their weathering. The basis of the foundations is medium-grained sands with high mechanical properties. There is no groundwater. On the building stone of the buried premises, composed of Middle Bulk lithotamnium limestones, well-expressed microcrystalline efflorescences of white colour were found. According to X-ray diffraction analysis, a small amount of gypsum and tenardite was found in their composition. On the other hand, chemical analysis of aqueous and hydrochloric acid extracts from soils where the foundations are located showed their practical sterility from lightly and moderately soluble salts. This indicates that the crystallisation of artificial minerals is not related to the composition of the geological environment but is mainly due to the intake of sulphur compounds from polluted atmospheric air.The study of the building material used for the decoration of the façade wall of the chapel and its microscopic examination showed that it is an organogenic-detritus moss-crinoid limestone. It is characterised by low density, high porosity, and the ability to absorb significant moisture. The leading factors in the development of destructive processes are the physical and chemical weathering of limestone, which is caused by climatic factors and a high level of transport pollution of the atmosphere. Chemical analysis of rainwater has shown its aggressiveness to calcium carbonate, which causes the destruction of limestone and works of art made from it.At the entrance to the chapel, an active development of mechanical sufosis, found in the formation of a sufosis failure, was recorded. The process of leaching fine soil from the soil layer took place in the cavity formed by the underground entrance to the crypt of the chapel and the hole arranged in the foundation. They found artificial soil with well-defined horizontal layering, which indicates sufficiently high gradients of infiltration water pressure, which pose a threat of suffocation and destruction of soils under the sole of the foundations.Prevention of physical and chemical weathering of limestone of the ground part of the building and the development of sulfosis processes requires proper drainage of atmospheric waters from the structural elements of the chapel and the area of the earth's surface adjacent to it. To replace the destroyed fragments of the thread, conducting a detailed petrographic study of the limestones of the Polyana deposit is advisable.