# Vibration Analysis and Empirical Law Definition for Different Equipment in a Civil Construction
## 3 Results and Discussion
### Historical Site Analysis  
Figure 9 shows different machinery working in the initial trench for the cut and cover tunnel. The ground vibrations were recorded with a seismic station located close to the foundation of the historical building while machinery was working. The measurements were carried out when the machinery was working on the side nearest to the building to control vibrations under the most unfavorable conditions, having a practically constant distance to the building. On the other hand, the excavation depth did not vary too much during the whole monitoring period. The whole data set from the historical site foundation is included in Figure 10 regarding the maximum velocity. The distance during the recording period is around 100 m, which is the minimum distance during the excavation period. The maximum velocities only exceed 0.04 mm/s on five days. These days with the higher values correspond to the usage of, at least, the vibrating ripper and vibrating roller simultaneously, working the two types of equipment with the higher potential of vibration. Values are especially high when the vibrating roller is working. The excavation equipment was used on all the operating days, while the  
Figure 10: Maximum daily velocities recorded in the foundations of the historical site. Figure 9: Machinery working in the trench. bulldozer was used on all the days with a registration of 0.03 mm/s or higher. When the vibrating roller is added, the maximum vibration is doubled. On the other hand, days with a value around 0.01 mm/s coincide with the weekend or situations with no simultaneous activities and without the usage of the bulldozer and/or the vibrating roller. Besides, some abnormal situations have also been detected: measurement 23 corresponds to an earthquake more than 100 km away, while measurement 34 is related to a landslide close to the construction site. A completely vibration-free excavation is unachievable [48], therefore background vibration will be always present, varying from the area of study. In this case, it reached around 0.005 mm/s. Moreover, what also have to be considered are other elements influencing the background that can increase it to around 0.01 mm/s. In this regard, the location of the historical site, close to the Cantabrian Sea, can suffer strong wind and high tidal conditions that increase the background values. Other elements, like agricultural activity around the area, were also identified, reaching occasional values around 0.066 mm/s. A specific analysis of the equipment, either individual or combined, was also done to know the maximum potential vibration. The data collected in the historical site were correlated with the type and number of machines working, taking into account the time. Table 5 gathers different combinations of the maximum vertical vibration velocity associated with the usage of equipment at the same time, which was daily known. The abnormal values obtained due to the specific conditions detailed in the previous paragraphs have been filtered. These abnormal peaks were easily identified, being isolated maximums, while peaks related to the machine's activity are repeated many times along the day or working period. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**V Bucket** & **Ripper** & **Vibration Ripper** & **Bulldozer** & **Vibrating Roller** & **Velocity** \\ \hline
1 & 0 & 0 & 1 & 0 & 0.006 \\
1 & 1 & 0 & 1 & 0 & 0.008 \\
0 & 0 & 0 & 0 & 0 & 0.005 \\
1 & 1 & 0 & 1 & 0 & 0.006 \\  
Assuming the superimposition principle, the maximum vibration of the day can be expressed by Equation (6). This approach is considered acceptable because the vibration periods are for an order of magnitude of milliseconds, compared with the daily measurements. In short, if two machines work the same day, their vibrations coincide many times along the day.