# Stabilization Methodology in Foundation Soils by ERT-3D Application in Estepona, South Spain
## 3 Case Study
### Damaged Building Analysis  
The most common deformations in a building are related to foundation differential movements. These alterations result in structural deformations in the building and angular distortions in its foundation [3; 65]. This provokes stress throughout the construction, and when this stress limit is exceeded, cracking or breakages occur. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Depth (m)** & **Hit N20** & **Consistency** &
\begin{tabular}{c} **Admissible Stress** \\ **(KN/m2)** \\ \end{tabular} \\ \hline
**0.00–1.00** & **4** & **Soft** & **30** \\
**1.00–2.00** & **3** & **Soft** & **20** \\
**2.00–3.00** & **6** & **Slightly hard** & **40** \\
**3.00–4.00** & **7** & **Slightly hard** & **50** \\
**4.00–4.40** & **10** & **Slightly hard** & **70** \\
4.40–6.00 & 19 & Moderately hard & 120 \\
6.00–7.00 & 52 & Hard & 310 \\
7.00–8.00 & 63 & Hard & 350 \\
8.00–8.60 & 84 & Hard & 440 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of the consistency and admissible stress of the soil according to the rotary probes. Measurements were taken at the height of the main facade of the most affected building. Figure 1: Aerial picture.Red circle: building location. April 2012.Source: geographical application Googlemaps/[[https://www.google.com/maps/place](https://www.google.com/maps/place)]([https://www.google.com/maps/place](https://www.google.com/maps/place)) (accessed on 25 April 2012), coordinates 36.461094, \(-5.160498\). The Spanish Building Technical Code (2006) defines the maximum angular distortion values for a building's ultimate limit of state and service, conditioning this value to the type of structure. In the service limit state, the allowable angular distortion value is L/500 for reticulated structures, and L/300 for isostatic structures and for load-bearing walls (the studied case). For L, the length in a straight line between the axes of the footings is analyzed. However, the structure's ability to assume these deformations will depend, among other factors, on the stiffness of each element comprising it, so any fixed distortion value could be conservative or give rise to non-tolerable deformations [66; 67; 68; 69]. According to current urban regulations, the rural house examined in this study would be difficult to demolish and rebuild. Therefore, a major challenge to this research and methodology was finding a solution to recover the building without having to demolish it. The main building in this study was a rectangular two-story building, 17.15 m long and 12.05 m wide, with a surface area of approximately 206.66 m\({}^{2}\) per floor and a total building area of 413.32 m\({}^{2}\) (Figure 2). This was a residential building and was used as a rural house (country holiday house); hence, guest and owner safety was paramount. The distribution comprised two building components: two floors, with an open area on the ground, and an upper, noble floor (Figure 2). Both the main building and the entrance foyer were designed in the late 1980s and completed in the early 2000s.The building's structure consisted of load-bearing walls and solid brick pilasters on the facade's main porch (vertical structure); these rested on a shallow foundation base of a reinforced concrete simple wall footing, formed by three parallel simple wall footings (A, B, C) (Figure 2). The horizontal structures of the building were24 cm thick unidirectional slabs formed of semi-resistant joists, supported in three spaces by load-bearing walls and pilasters resting on a shallow foundation composed of three longitudinal foundations in a trench. From the previous geotechnical and structural analysis of the building illustrated in Figures 2 and 3, a problem of support in the foundation for differential seats was deduced. Of the A, B, and C foundations, B and C had become unstable (sunk downward) with respect to A (Figure 4).