## 4 Kelly Pile Production System  
The Kelly drilling method used for pile production uses a rotary drill rig (\"rig\" in short) with different attachment tools and additional equipment to drill piles up to 3 m in diameter and more than 100 m deep [39] (Figure 3). The application of activity recognition requires the subdivision of the production process into recurring standard activities. Therefore, we next describe the most common steps in the pile production process using the Kelly drilling method. We are aware that these steps vary depending on the construction project. The results are based on interviews conducted in previous work by the authors [36]. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sensor** & **Unit** & **Sensor** & **Unit** \\ \hline Depth & m & Main winch rope speed & cm/min \\ Torque of rotary drive & kNm & Pressure pump 1–4 & bar \\ Speed of rotary drive & Rpm & Torque of Kelly bar & \% \\ Main winch rope force & t & Auxiliary winch rope force & t \\ Crowd force & t & Crowd depth & m \\ Casing length & m & Boring threshold & m \\ Status rig & - & Torque steps & - \\ Main winch gear mode & - & Inclination X, Y & deg \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Sensor data available from the Kelly drill rig. Figure 3: Rotary drilling rig at the test site of Bauer Group in Schrobenhausen, Germany (pictures by [PERSON]); components (number in white circle) and sensors (black circles): (1) under carriage; (2) upper carriage (pressure pumps); (3) main winch (force, speed, and tool depth); (4) auxiliary winch (force); (5) crowd winch (force); (6) kinematic system; (7) mast (inclination); (8) mast head; (9) Kelly bar; (10) rotary drive (torque, speed); (11) bucket drill tool; (12) auger drill tool; (13) casing string; and (14) casing shoes. Kelly pile production consists of three main steps: (1) drill, (2) reinforce, and (3) concrete (Figure 4). Once the rig and any needed auxiliary equipment such as drilling tools, casings, and concrete delivery pipes are set up, the alternating steps of the drilling process start. The equipment picks up the appropriate tool, e.g., an auger (Figure 3 middle), then slews and positions itself toward the drilling attachment point. Lowered with the help of the telescopic Kelly bar, the drilling tool drills as the rotary drive applies torque to the locked Kelly. Once the tool is filled with soil cuttings, it is pulled out and emptied, usually in a container, to ease soil removal from the site. In turn, a wheel loader takes the drill cuttings to a disposal site for further processing. Casing sections prevent the hole from collapsing. The rotary drive turns in casings separately and casings are manually fixed by workers (Figure 3 right). The first casing has teeth for better progress in the soil. The deeper the drilling tool, the lower the performance due to longer run-in/out times and higher surface friction. Thus, casing oscillators are used when additional torque force is needed. For reinforcement, the rebar cage is attached to the auxiliary cable of the rig and raised. The rig swivels to the drilling attachment point to lower the reinforcement cage in the drilled opening. Before concrete placement starts, the delivery pipes are assembled, lowered into the drill hole, and joined together. Concrete is placed directly through the concrete mixer discharge or a concrete pump/bucket (requiring additional steps). Casing and delivery pipes are removed in alternation, often requiring extra power from a casing oscillator. [PERSON] et al. [40] define three KPIs in pile production: (1) the pile length produced per day (or piles per day); (2) variations in the planned vs. actual output (process quality); and (3) the inclination of the piles (product quality). Pile production resembles a single-line production system. It is characterized by the use of highly specialized equipment and skilled operators [36]. Deep domain knowledge of geotechnical engineering and process technology is required to handle the complexity of the production system.