Objects that have a high historical or cultural value are often threatened by natural aging and destruction – just like all other buildings. However, objects that are recognised as a part of national or world cultural heritage, must be conserved, restored or reconstructed in a way that allows to reduce damage to their elements to minimum, no matter whether minor repairs of the walls and floors, or raising and reinforcement of the foundation are performed. Damage caused to historical buildings can be minimised by using URETEK’s geopolymer technology.
Similar to other historic buildings in Riga, Riga Cathedral is supported by oak piles, rammed into the shores of River Daugava centuries ago. Alas, groundwater level has dropped over the past few decades. This is partially due to Riga hydroelectric power plant built on the River Daugava, which closes the locks that adjust river surface according to season and need. Therefore, water level in the river varies and surface water level of the city drops. Due As a result of major drop in the surface level, oak piles exposed to air started to decompose, which in turn caused subsidence of the building.
Subsidence of that magnificent cathedral was seen in many cracks in the walls and it was only a matter of time until it would need large-scale renovation.
Latvian Evangelic Lutheran Church addressed URETEK team for consultation when searching for alternative solutions. In the course of test assignment, URETEK technology was used for injecting geopolymer resin under the building at the depth of 4 m, thus compacting the soil around piles. This stopped further subsidence of the building, preserving this great cathedral for future generations.
Besides improving soil, geopolymer formed a protective layer around piles that were still intact, thus preserving their original load-bearing structure.
As the cathedral has been built on former cemetery, there are lots of human remains under it, that need to be protected and preserved. Considering that out of all methods used today, URETEK method represents the least disruptive towards the environment surrounding the work area, it was decided to use URETEK solution for performing the job.
Riga Cathedral represented a unique object that required very high responsibility from URETEK Baltic OÜ, because the cathedral belongs to UNESCO World Heritage List and soil density tests carried out later on proved that the test assignment was successful.
URETEK solution is the first choice in case of subsidence of historic buildings. The reason for that is simple: it does not generate vibration, does not endanger surrounding historic buildings and does not interfere with life and business in the building.
In former grain drier of Mooste Manor, water had eroded the base of the chimney at the depth of 1.5 m, resulting in subsidence of the chimney by 5 cm which would have probably continued. Surveys revealed that chimney flues had shifted within permitted tolerance, so it was decided to omit lifting and URETEK technology was used to stabilise subsoil under the chimney and restore load-bearing capacity of soil.
Entire duration of works was 4 hours, whereas client was convinced that it was impossible and too expensive to stabilise the base of the chimney by using traditional methods.
When restoring a historic tavern building, the designer added extra load to the building, causing suspicion of subsidence. A responsible team promptly stopped construction works and started to inspect potential subsidence, ascertained that it was highly probable and that the building required additional support. The subsidence was considered dangerous because one corner of the house rested on former city wall that definitely did not sink. Such uneven situation caused quick breaking of the house. Moreover, house foundation consisted in simple stone wall typical to the time when it was built, which caused some stones to shift out from the wall. Thus, foundation lost part of its load-bearing capacity.
URETEK technology was used to stabilise the area adjacent to stone wall in order to support and bind existing foundation. Only after that, URETEK team started stabilisation of the subsoil under stone wall.
URETEK team cannot estimate the extent of money and time saved for the client, because the client had excluded the option of excavating the foundation for stabilisation purposes since the very beginning.
Pirogov Park and Toome Hill in Tartu are among most important park areas in Tartu. A few years ago, park underwent renovation, but in the course of construction, one side of the monument erected to Nikolai Pirogov, former professor of Tartu University, started to sink. Considering that there was no building documentation available regarding the monument, its stabilisation and lifting was a challenge for URETEK team, because they had to work by trial and error. Besides absence of documentation, performance of works was complicated by the fact that in pre-war years, Pirogov Park was the location of cinema Central and a café that were bombed and their ruins formed a base for hillslope. This in turn meant that the slope contains old foundations, cellars, passages and storages.
However, soil under the monument was stabilised and sunken side lifted to its former height.
Three-storey nobility building built in Toompea quarter in Tallinn in 1776 started to sink in the 2000s. Remarkable cracks occurred in the façade and partition walls, and new owner of the building started to look for a solution to his problem and contacted URETEK team. It was known that the building stands on former moat, which meant challenging soil conditions.
The first stage of work involved making a binding new load-bearing pad between and around the wooden rafts directly under the foundation in order to evenly distribute the weight of the building to soil.
Stage two comprised penetration of previously created load-bearing pad and injection of a stronger and wider pad.
Stage three involved penetrating both pads and reaching load-bearing soil, where URETEK polymer resin was injected by pull method. This method was used to fill the soil evenly from load-bearing soil to previously supported pads.
URETEK Baltic OÜ team injected geopolymer resin at the depth of 7 m and special geopolymer resin was also injected in already rotten rafts, to capsulate the logs that were still intact and replace decomposed logs with stronger resin and soil mixture.
URETEK team prepared work schedule and progress plans. They started compilation of additional and new geology reports. It was also discovered that the building is erected on wooden rafts that were inevitably past their expected life and completely rotten. As the foundation of the house was laid as stone wall on wooden rafts, it was urgent to replace rotten wood with a new load bearing “raft”. Special URETEK polymer resin was chosen for that purpose.
Entire duration of work was six business days and the residents of the house could stay in the house and not move out for the time of works; a business venue operating in the building also continued its daily activities.
