# The Development of the Pipe Jacking Guidance Technology
## 7 Analysis of Pipe Jacking Projects
### Analysis of Costs and Selection Experience  
The merits and demerits of the different methods of pipe jacking guidance systems are different, and they are closely related to the costs. As shown in Table 4, the manual visual inspection method utilizes a lesser quantity of measuring instrument hardware and exhibits the lowest cost, yet it demands a high level of operator skill. The laser target and prism methods for short-distance and straight pipe jacking construction conditions have reached a state of technological maturity and offer a reliable degree of accuracy. However, the laser target and prism methods for long-distance and curved pipe jacking construction conditions necessitate the augmentation of instrumentation within the pipeline, which in turn increases costs. The gyroscope used in the inertial guidance method is mature and has a relatively high cost. The hybrid method improves system accuracy based on the idea of redundancy, but the increase in measuring instruments increases the cost of the system. In the context of pipe jacking construction, the selection of a pipe jacking guiding system is a decision that must be made taking into consideration a number of factors. These include the construction conditions, cost and construction efficiency. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Methods** & **Merits** & **Demerits** & **Cost** \\ \hline Manual visual inspection method & Low amount of hardware & Limited construction conditions & + \\ \hline \multirow{3}{*}{Laser target method} & Reliable precision; & Deformation and dispersion of & \begin{tabular}{c} ++ \\ (Short distance straight pipeline) \\ \end{tabular} \\  & \begin{tabular}{c} Malet technology \\ \end{tabular} & Limited pipe diameter & \begin{tabular}{c} +++ \\ (Long distance curved pipeline) \\ \end{tabular} \\ \hline \multirow{3}{*}{Prism method} & Reliable precision; & Out-of-sync error; & \begin{tabular}{c} ++ \\ (Short distance straight pipeline) \\ \end{tabular} \\  & \begin{tabular}{c} Malet technology \\ \end{tabular} & Limited pipe diameter & \begin{tabular}{c} +++ \\ (Long distance curved pipeline) \\ \end{tabular} \\ \hline Inertial guidance method & \begin{tabular}{c} Small pipe diameter; \\ Continuous measurement \\ \end{tabular} & Error accumulation & \
\begin{tabular}{c} +++ \\ \end{tabular} \\ \hline Hybrid method &
\begin{tabular}{c} High precision; \\ Few construction restrictions \\ \end{tabular} & Multiple hardware & ++++ \\ \hline \hline \end{tabular}  
* The symbol “+” is used to denote the cost level. An increased numerical value of ‘+’ is indicative of a higher cost.  
\end{table} 
Table 4: Analysis of different methods. \begin{table}
\begin{tabular}{c c c c} \hline \hline
\begin{tabular}{c} Hyper valued \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Long-distance and curved-pipe jacking projects. Regarding construction conditions, the soil layers in engineering geology are divided into soft soil, mucky soil, sandy soil, loess and rock. Among them, the rock has high hardness. The soil layer has a serious impact on pipe jacking, such as ground settlement [32; 33; 34; 35; 36]. Additionally, no matter what kind of soil layer it is, it will affect the operation of the pipe jacking machine, and the higher the hardness, the greater the impact [37; 38]. The influence of the soil layer on the pipe jacking guide system is that vibration will be generated when the pipe jacking machine is advancing. For the manual visual inspection method, the engineering technicians are required to manually operate the laser equipment at the starting shaft or in the pipeline. The stability and stable support of the soil layers on the pipe segment must be ensured to prevent technical personnel from operating errors [39]. In addition, the target located at the pipe jacking machine will vibrate, affecting manual observation. The automation of the laser target method and the prism method avoids the influence of vibration on manual operation and observation.