# A Review of Vertical Shaft Technology and Application in Soft Soil for Urban Underground Space
## 4 Technological Advancements in Mechanized Systems
### Advancement in (PIAUS) Construction Technologies
#### 4.3.2. Actively Controlled Prefabricated Caisson Construction Technology (ACPP)
\begin{table}
\begin{tabular}{p{56.9 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Technology** & **Description** & **Advantages** & **Limitations** & **Applications** \\ \hline \multirow{4}{*}{**Shaft boring system (SBS)**} & Mechanized excavation system for deep vertical shafts in hard rocks; includes rock curting, muck removal, and shaft support & High excavation efficiency; widespread geological adaptability in urban settings & Limited efficiency in soft grounds; requires & Underground parking \\ \hline \multirow{4}{*}{**Shaft boring machine (SBM)**} & Established by [PERSON] (up to 12 m diameter, 2000 m depth); uses rotating cutter wheel with disc cutters & High efficiency, automation, and modularity; simultaneous drilling and support operations & Inflexible for non-linear drilling; high cost-per-meter for shorter depths; requires stable ground conditions & Deep shaft construction; mining; infrastructure projects \\ \hline \multirow{4}{*}{**Blind shaft boring**} & Mechanized excavation of large-diameter vertical shafts without a pilot hole; excavated material is transported to the surface & Highly automated; no personnel in the shaft during operation & Limited access for ground superstillation; requires precise rock mass conditions & Metro access tunnels; ventilation shafts \\ \hline \multirow{4}{*}{**Raise boring machine (RBM)**} & Mechanized construction method for shafts using a pilot hole and reaming; suitable for stable rock conditions. & High efficiency; reduced construction time; minimal rock mass damage & Limited to stable rock diameters; restricted diameter (up to 6 m); limited access for remedial support & Ventilation shafts; mining; hydropower hydropers \\ \hline \multirow{4}{*}{**Shaft boring road header (SBR)**} & Mechanized excavation of a soft to medium-hard rock (up to 120 MPa compressive strength); uses a road header boom and rotating cutting drum & Safe operation with no personnel at the shaft bottom; efficient excavation in soft to medium-hard rock conditions & Limited to soft to medium-hard rock; not suitable for hard rock conditions & Service and production shafts; urban infrastructure \\ \hline \multirow{4}{*}{**Shaft boring cutterhead (SBC)**} & Mechanized excavation of deep blind shafts in hard rock (up to 2000 m depth, 7–12 m diameter); uses a conical full-faced cutterhead with disc cutters & High progress rate personnel at the shaft bottom; efficient excavation in soft to medium-hard rock conditions & Limited case histories in soft ground; high cost and complexity & Deep shaft construction; mining \\ \hline \multirow{4}{*}{**Vertical shaft construction (VSM)**} & Mechanical excavation of deep blind shafts in hard rock (up to 2000 m depth, 7–12 m diameter); uses a conical full-faced cutterhead with disc cutters & Suitable for soft and heterogeneous conditions, operates in submerged conditions; remote-controlled operation; waterproofing layers for jointed or water-bearing rocks & Limited to shallow shafts; prior to remedial work requires dewatering for conditions & Shallow shafts in urban areas; soft ground conditions \\ \hline \multirow{4}{*}{**Vertical shaft construction (VSM)**} & In situ assembled caisson technology for soft grounds; deploy underwater robots and an intelligent propulsion system to complete excavation; uses non-draining sinking and automated mud sleeve injection & Active sinking control and unmanned construction; prefabricated wall linings; reduced environmental impact & Escape shafts and ventilation shafts; underground parking; pumping stations \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Description of mechanized shaft technologies including their advantages and limitations.