## 3 Analysis and Interpretation of Measurement Results  
### Soil Properties  
Based on soil investigation, the ground at the location of the Cathedral consists of low-plastic clay which extends to a depth of about 18 to 20 m and is cut at a depth of about 9 to 9.5 m with a 1.8 to 2 m thick layer of sand. Based on laboratory tests, the compressibility of clay, at a depth between 2.5 to 5.0 m, because of the effect of pre-consolidation, reaches the highest values, of a range between 7.0 and 9.0 MPa. At other depths, the modulus is significantly smaller, between 3.1 and 4.8 MPa. According to the analysis, the weight of the individual tower is up to \(V\) = 32.0 MN, and the height of the centre of gravity is about \(Z_{t}\) = 15.0 m. The average pressure below the quadratic foundation footing \(B\) = 8.0 m is \(q\) = 500 kPa. When the pressure on the ground is known, the settlement of the tower can be determined through the method of one-dimensional deformation, and since the foundation is rigid, the settlement is determined by the equivalent point of the foundation. The soil compressibility modules were adopted by the correlation with one penetration resistance, using a simplified diagram of mean values on Figure 10. The calculated settlement is about \(s\) = 25 cm. For further analysis, using the calculated settlement of the tower, the average modulus of elasticity was determined by the following analytical expression [12]:  
\[s=qB\frac{1-\
u^{\prime 2}}{E^{\prime}}\left(I_{3}+\frac{1-2\
u^{\prime}}{1-\
u^{ \prime}}I_{2}\right)I_{1}\,\
u^{\prime}=0.3 \tag{1}\]  
\[\frac{H}{B}=1.63,\ \frac{D}{B}=0.25\]  
corresponding modulus of compressibility of the layer of \(D^{\prime}\) = 4.3 MPa was determined by the following well-known expression:  
\[D^{\prime}=E^{\prime}\bigg{(}1-\frac{2\
u^{\prime 2}}{(1-\
u^{\prime})}\bigg{)} \tag{3}\]  
An important data for the analysis is the eccentricity of the towers center of gravity (\(e_{x},e_{y}\)) in relation to the foundation joint, which is determined based on the height of the centre of gravity \(Z_{t}\) and geodetically measured inclination of the towers \(\theta\) (Table 1). In the next step, based on the inversely calculated modulus of elasticity \(E^{\prime}\) = 3.2 MPa of the soil layer and measured eccentricities of the towers (\(e_{x},e_{y}\)), the inclinations (\(\theta_{x},\theta_{y}\)) of the towers can be calculated by analytical expression [13], as shown in Table 2.  
\[\theta_{x,y}=\frac{1-{\
u^{\prime}}^{2}}{E^{\prime}}\frac{V\cdot e_{y,x}}{B^{2 }L}l_{\theta},l_{\theta}=4.17 \tag{4}\]  
When the divergence of the towers at the height of the frontage is calculated, by applying data from Table 2, the value \(\Delta X=27(2.41/1000+3.21/1000)=0.154\) m is obtained, which is a very good approach to the geodetically determined size \(\Delta X\) = 13.8 cm and the approximate sum of measured crack widths at the crown of the frontage of about 15.0 cm. The previous analysis shows good agreement between measured and calculated displacements. Ultimately, this indicates that, with the parameters of soil modulus determined in the laboratory and from field tests, the interaction of the object and the foundation soil can be reliably modelled. It is also interesting to analyse the critical height of the centre of gravity of the tower, which can be estimated based on the following expression [14]:  
\[Z_{t,cr}=\frac{E^{\prime}}{\Big{(}1-{\
u^{\prime}}^{2}\Big{)}I_{\theta}}\frac{ B^{2}L}{V},I_{\theta}=4.17 \tag{5}\]  
The calculated critical height is about 13.5 m, which is close to \(Z_{t}\) = 15.0 m. The critical height of the structure centre of gravity is the height at which even a very small, horizontal force, relative to the structure weight, causes a large increase in stress and deformation in the ground, and thus endangers the stability of the structure. This is corroborated by the measured and visually noticeable damages on the Cathedral, based on cracks in the front facade wall, on the longitudinal facade walls of the Cathedral wave, arches, etc.