# Monitoring the Impact of the Large Building Investments on the Neighborhood
## 4 Discussion
In the case of smaller objects (e.g., single family houses), additional settlements and inclinations, regardless of the measured values, are not too much of a problem. This is due to the compact and rigid building structure and lower requirements (compared to large buildings) in terms of the serviceability limit state. Yet, the problem may involve the deterioration of the technical conditions of such buildings as a result of impacts from the construction site. Hence, it is essential to measure the vibration amplitudes, which in such cases are the decisive factor. It is also essential to observe the development of cracks and damage, which can be extremely helpful when choosing the technology of work execution. A detailed report on the rise of damage may also be helpful in resolving claims for compensation. It is important to have the inventory of damages prior to the commencement of works, so that the investor is not forced to pay for the damage incurred prior to the commencement of works. The results of the monitoring presented above indicate that in the case of earthworks, in particular those carried out below the groundwater level, it is essential to measure the current water level with piezometers. It can be roughly assumed that the reduction of water level by 1 m can result in additional settlements of about 1 mm (assuming an active depth of 5 m and an average modulus of elasticity of the subsoil 50 MPa, the above value may be slightly different depending on the type of soil). With the lowering of up to a few meters, this is not a big problem for the condition of the building structure, but when the lowering is larger, additional settlements may contribute to a failure. In the case of the construction of the roundabout in Katowice, the change in ground water level did not exceed 2 m, because of the proper operation of the diaphragm walls, although they were not brought to impermeable soil. The frequency of measurements (see Table 1) was adjusted to the work schedule. In the periods of higher intensity of construction works, measurements were carried out  
Figure 20: An example of a crack was created as a result of uneven settlement of the building (at the window and under the ceiling). more often, while at the time when the impact of these works on the resulting settlement was smaller, measurements were carried out less often. Generally, in the case of large construction investments with typical soils in Poland, there is no need for measurements more frequent than once every 2 weeks. It should not be forgotten that more frequent measurements are more expensive, which can be a problem in some countries. The accuracy of the measurements of displacements (including settlements), as well as the amplitudes and frequencies of vibrations mentioned in Section 2, turned out to be sufficient to assess the impact of the works on the neighborhood. In the case of the construction of the tunnel under the roundabout, the greatest concern was the fall of the groundwater level, which was predicted over a large area. Deep excavations could also be dangerous, but they were secured by diaphragm walls. The monitoring results showed that although some settlements and horizontal displacements were found, there was no greater threat to the safety of the structures of adjacent buildings. It also turned out to be beneficial that no mining deformation occurred during the construction works, which would constitute an additional risk of failure. The location of the investment (the center of a large city) was essential here, because there is no mining activity causing large deformations of the land surface, as well as the final phase of coal extraction in Upper Silesia in Poland. In the case of the construction of the Debowe Tarasy estate, the main problem was vibrations and their destructive impact on the neighborhood. The vibrations caused by use of the heavy ramming method to soil improvement. Fears were intensified by the poor technical condition of the adjacent buildings.