# Study on Representative Parameters of Reverse Engineering for Maintenance of Ballasted Tracks
## 4 Case Study
### Evaluation Experiment for 3D Scan Data and BIM Model  
In the evaluation experiment conducted for this study, the shape expression possibilities for the ballasted track and railroad maintenance damage types were examined using the representative parameters selected by comparing the 3D scanning point cloud data for the testbed with the BIM model (Table 2). The following five damage types and representative parameters of maintenance were verified in this experiment: \"track gauge,\" \"ballast refill (sleeper exposure),\" \"ballast refill (reduction of ballast shoulder width),\" \"ballast refill (reduction of ballast shoulder fill),\" and \"sleeper irregularities (interval irregularity and right-angle irregularity).\" The other representative parameters were reviewed simultaneously. To closely examine the representative parameters, the BIM model and scan data for the testbed, with nine concrete sleepers were installed, were divided into the same nine components, based on the sleeper and the center of a sleeper, as shown in Figure 8.  
Figure 8: Extraction of the values of representative parameters for the sleeper scan data (1). Figure 9: Testbed 3D scanning BIM model. Based on the results of the testbed verification experiment conducted in this study, for track gauge, the distance of a point 14 mm below the rail head of the sleeper (1) was used, as shown in Figure 10. The track gauge was measured as 1435 mm for the sleeper (1) of the testbed, confirming that no track gauge irregularity occurred. Second, considering the sleeper exposure in the ballast refill, the sleeper exposure was measured for sleeper (1) using the representative parameters as shown in Figure 11. The measured values of the sleeper exposure parameters were H\({}_{\rm SR}\) = 50 mm and H\({}_{\rm GL}\) = 13 mm. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Representative** & **Description** & **Shape** & **Track Irregularities** \\
**Parameters** & **Description** & **Expression** & **Management Criteria** \\ \hline \multirow{3}{*}{H\({}_{\rm 1R},\)H\({}_{\rm 1L}\)} & Height from floor level (F.L) & \multirow{3}{*}{Possible} & Ballast refill (reduction of ballast \\  & to surcharge fill (ballast shoulder peak) & & shoulder fill) occurs \\  & (R: right, L: left) & & \\ \hline H\({}_{\rm 2R},\)H\({}_{\rm 2L}\) & Ballast shoulder height (R, L) & Possible & Ballast refill (reduction of ballast \\  & & & shoulder fill) occurs \\ \hline H\({}_{\rm 3R},\)H\({}_{\rm 3L}\) & ballast height excluding ballast shoulder (R, L) & Possible & - \\ \hline H\({}_{\rm 4R},\)H\({}_{\rm 4L}\) & Rail height (R, L) & Possible & - \\ \hline H\({}_{\rm 5R},\)H\({}_{\rm 5L}\) & Sleeper exposure (R, L) & Possible & Ballast refill (sleeper exposure) occurs \\ \hline W\({}_{\rm 1}\) & Total ballast width & Possible & - \\ \hline W\({}_{\rm 2R},\)W\({}_{\rm 2L}\) & Ballast width excluding sleeper length (R, L) & Possible & - \\ \hline W\({}_{\rm 3R},\)W\({}_{\rm 3L}\) & Width from surcharge fill (ballast & \multirow{2}{*}{Possible} & Ballast refill (shoulder width reduction) \\  & shoulder peak) to ballast end (R, L) & & occurs \\ \hline W\({}_{\rm 4R},\)W\({}_{\rm 4L}\) & Width from surcharge fill (ballast & \multirow{2}{*}{Possible} & Ballast refill (shoulder width reduction) \\  & shoulder peak) to sleeper end (R, L) & & occurs \\ \hline W\({}_{\rm 5}\) & Sleeper length & Possible & - \\ \hline W\({}_{\rm 6}\) & Track gauge & Possible & Track gauge does not occur \\ \hline W\({}_{\rm 7R},\)W\({}_{\rm 7L}\) & Rail base width (R, L) & Possible & - \\ \hline W\({}_{\rm 8R},\)W\({}_{\rm 8L}\) & Rail head width (R, L) & Possible & - \\ \hline L\({}_{\rm 1}\) & Rail length & Possible & - \\ \hline L\({}_{\rm 2}\) & Sleeper thickness (width) & Possible & - \\ \hline L\({}_{\rm 3R},\)L\({}_{\rm 3L}\) & Interval between the sleeper edges (R, L) & Possible &
\begin{tabular}{c} Sleeper irregularities (interval \\ irregularity and right-angle \\ irregularity) occur \\ \end{tabular} \\ \hline L\({}_{\rm 4}\) & Ballast length & Possible & - \\ \hline \hline \end{tabular}
\end{table}