# The Efficiency of Large Hole Boring (MSP) Method in the Reduction of Blast-Induced Vibration
## 2 Project Description
### Characteristics of the MSP Method  
The characteristics of the most commonly used traditional methods and the MSP method are compared in Table 1. V-cut and cylinder-cut, which are mainly used for cut blasting, have no free face or small scale before blasting. One of the most important features of the MSP method is the formation of a large empty hole of 382 mm, which is approximately 3.7 times larger than that for the cylinder-cut before blasting. This method provides a larger initial space for moving breaking rocks through a large empty hole, and then a new free face is created sequentially through the movement of the breaking rocks [24]. In particular, vibration reduction and breaking efficiency can be maximized when constructing multi-MSP with two or more holes, and this method can use both short- and long-hole blasting. In addition, the large hole serves as a groundwater discharge hole as well, and the amount of groundwater for a 50 m section ahead of the tunnel face can be predicted. The MSP method includes a real-time boring data monitoring system equipped with the high-performance boring machine, and a borehole alignment tracking and ground exploration system. The monitoring system measures the feed pressure, torque pressure, percussion pressure, advance speed, and percussion vibration during construction. This system can increase boring efficiency and minimize several problems, including damage or loss of equipment caused by contact with geological anomalies or the carelessness of operators. The large empty hole is not only used as a free face but also plays an important role as a guide hole. The borehole alignment tracking and ground exploration system is placed into the hole after boring is completed to observe the geological features ahead of the tunnel face. Images inside a hole are captured using a machine vision camera or 360\({}^{\circ}\) camera to investigate the conditions of the rock mass, joints, groundwater, and fractured zones. Figure 4 shows a case of exploring the inside of a hole in a tunnel construction site in the Gangwon region, Korea, where limestone is dominantly distributed. The image on the left shows the system equipment, and the image on the right shows a large amount of groundwater leaking from the left side of the roof at 30 m, and it can be realized that a confined aquifer exists in this section. These data provide important information for \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{2}{c}{**General Blasting (B)**} & \multicolumn{1}{c}{**Single-MSP**} & \multicolumn{1}{c}{**Multi-MSP**} \\ \hline \multirow{4}{*}{Site image} & \multirow{4}{*}{\begin{tabular}{c} 0 or 1–3 \\ (Small scale) \\ \end{tabular} } & \multirow{4}{*}{\begin{tabular}{c} 1 \\ (Large scale) \\ \end{tabular} } & \multirow{4}{*}{\begin{tabular}{c} 2–3 \\ (Extremely large scale) \\ \end{tabular} } \\ \cline{3-4} \multirow{4}{*}{Characteristics} & - & \begin{tabular}{c} Traditional cut method \\ (V-cut, Cylinder-cut) \\ \end{tabular} & - & High vibration reduction efficiency & - & Combining low-vibration explosive \\  & - & Relatively simple & - & Increases blasting & maximizes vibration \\  & & process compared with & efficiency of cut area & reduction & reduction \\  & & other methods & - & Additional process and & - & Increased construction \\  & - & Limitation of vibration & cost required for boring & cost due to combination & cost due to combination \\  & & reduction exists & a large hole & of methods & \\ \hline \multirow{4}{*}{Application target areas} & - & \begin{tabular}{c} Suitable for short-hole \\ blasting (\(L\leq 1.5\) m) \\ \end{tabular} & - & \
\begin{tabular}{c} Suitable for long-hole \\ blasting (\(L\geq 2.0\) m) \\ \end{tabular} & - &
\begin{tabular}{c} Suitable for short- and \\ long-hole blasting \\ \end{tabular} \\  & - & Suitable for hard rock & - & Suitable for soft rock & - \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of characteristics of cut blasting methods.