Ajalooliste rajatiste mõju tänapäevasele hoonestusele Kaitseliidu Peastaabi hoone näitel [Magistritöö. Juhendaja: H. Soosalu]

The aim of this Master’s thesis is to analyse the impact of historic structures on modern day buildings using the example of the Headquarters of the Estonian Defence League located in Tallinn at Toompea street 8. Cracks started to develop in the B-wing of the Headquarters building during the year 2015. The whole building complex of the Defence League is situated in the medieval earthen fortification zone of the Toompea Hill. Furthermore, the Wismar ravelin runs under the modern day Headquarter complex.

The results of the thesis are based on geotechnical and geodetic investigations. Special focus is on the possible collapse of the Wismar ravelin, consolidation of filling material under the foundation, hydrogeological conditions, and washout of filling material into the ravelin.

It is found that the cracks in the Headquarters B-wing were caused by washout of soil from under the shallow foundation of the building. In addition, cyclical subsidence of the B-wing can be observed. The greatest total subsidence of the B-wing is 3.5 mm, as shown by geodetic measurements. However, it is not considered as a threat to the structural durability of the building. The results indicate that the Wismar ravelin is structurally sound under the modern building complex and no abrupt subsidence was observed. Periodical survey of the subsidence behaviour is recommended, as it would provide information on dynamics of subsidence features in the future.

This Master’s thesis provides aid in understanding deformation or other problems that may occur in modern day buildings located in the medieval earthen fortification zone. It also provides insight into better planning of survey methods suitable for geotechnical investigations helping in avoiding future problems related to cracks or deformation of new buildings.