# The Development of the Pipe Jacking Guidance Technology
## 1 Introduction  
In recent years, the development and utilization of underground space have received more and more attention, and the construction of underground pipeline networks is crucial for urban construction [1, 2]. Pipe jacking construction causes little damage to rivers, plants, buildings and traffic facilities, generates low noise, works efficiently and can complete the laying of underground pipelines with high quality [3]. In the jacking process, the cutter head has some problems such as uneven force, mechanical oscillation and uneven grouting, which lead to the jacking trajectory deviating from the design route [4]. Therefore, it is necessary to obtain the attitude and position information of pipe jacking in time to correct the current pipe jacking machine to avoid further deviation from the design route. The quality of guidance is contingent upon the pipe jacking machine's capacity to advance efficiently and safely according to the pre-designed plan line, and it is also pivotal to whether the pipe jacking machine can reach the receiving shaft smoothly and finally realize the penetration. With the densification of urban underground pipelines, the new pipeline lines are no longer just short-distance straight lines, and the construction of long-distance and curved lines has become one of the important requirements of pipe jacking construction, which has more stringent requirements for the guidance system of pipe jacking [5, 6, 7]. Especially in the long-distance curve jacking construction, as the pipeline needs to advance along the complex curve, the measurement path must be calculated accurately to ensure that the pipeline can be jacked in accordance with the radius and length of the curverequired by the design. This not only ensures the construction quality of the pipeline but also avoids damage to the surrounding environment and underground pipelines during the construction process. By measuring the path accurately, the construction personnel can accurately grasp the attitude and position information of the pipe jacking machine, which can help the construction personnel find and deal with the potential safety hazards in time and ensure the construction safety.  
At present, the traditional pipe jacking guiding methods include the manual visual inspection method, the prism method and the laser target method. In recent years, the inertial guidance method has been widely studied without considering the bending and distance of the construction pipeline. However, in practical engineering applications, when the construction conditions are more demanding, such as small diameters, curves and long distances, it is difficult for a single method to meet the accuracy and adapt to all construction environments in the research of pipe jacking guidance methods. Therefore, a hybrid method using the above methods is proposed. At the same time, the idea of multi-source data fusion based on multiple sensors has a remarkable effect on improving the guidance accuracy and has been paid attention to by many researchers.  
The research of the pipe jacking guidance system is of great significance to the development and utilization of urban underground space. Therefore, this paper will summarize the current technical status of the pipe jacking guidance system in order to help researchers in the follow-up research in this field.