There are various health issues associated with the different stages of long-distance pipeline transportation. These issues pose potential risks to environmental pollution, resource waste, and the safety of human life and property. It is essential to have real-time knowledge of the overall health status of pipelines throughout their entire lifecycle. This article investigates various health-monitoring technologies for long-distance pipelines, providing references for addressing potential safety issues that may arise during long-term transportation. This review summarizes the factors and characteristics that affect pipeline health from the perspective of pipeline structure health. It introduces the principles of major pipeline health-monitoring technologies and their respective advantages and disadvantages. The review also focuses on the application of Distributed Acoustic Sensing (DAS) technology, specifically time and space continuous monitoring technology, in the field of pipeline structure health monitoring. This paper discusses the process of commercialization development of DAS technology, the main research progress in the experimental field, and the open research issues. DAS technology has broad application prospects in the field of long-distance transportation pipeline health monitoring.

Facing increasingly large and discontinuous structural evolution under the influence of extensive mining activities, some traditional geophysical technical methods of monitoring overburden deformation have become of restricted use. As an advanced sensing technology, the distributed optical fiber sensor has been introduced into rock deformation monitoring by virtue of its good adaptability and high precision. In this paper, an overburden stratum deformation monitoring experiment was performed within a physical model test to explore the deformation characteristics of mining-induced overburden stratum based on distributed optical fiber sensing. The results indicate that distributed optical fiber monitoring is effective, and the Brillouin frequency shift (BFS) variation distribution reflects every aspect of the space-time and movement laws of overburden stratum. The comparison of measurements of distributed optical fiber, fiber Bragg gratings (FBG), and dial gauges (DG) proved the feasibility and reliability, and revealed the ability of optical fiber measurement to monitor large-scale macroscopic deformation, and capture subtle deformation along the entire overburden stratum. More importantly, the BFS variation distribution present a three-step form, which explicitly identifies the zoning development of overburden stratum. In turn, a conceptual model for describing the overburden deformation process is provided; it illustrates the inversion mechanism of the BFS variation distribution in reaction to the typical overburden deformation structure. This study aims to provide a theoretical and methodological foundation for the application of distributed optical fiber sensing (DOFS) measurement in mining ground control research.

Energy evolution process of rock deformation is conducive to essentially reveal the rock failure mechanism and is of great significance to uncover the breeding of dynamic disasters in rock engineering. To characterize the damage evolution of energy dissipation during rock failure, the digital image correlation (DIC) technique is proposed to describe the rock failure mechanics and its energy evolution process. The uniaxial compression experiment of sandstone specimen was carried out, and the whole field deformation and failure characteristics of the rock had been captured by the DIC system. Measurement accuracy was verified by the fiber Bragg grating (FBG) sensor, the elastic region of the specimen was divided according to the location of strain localization band (SLB), and the evolution process of elastic strain energy of the rock was analyzed. The results show that the time history development of rock strain obtained by the FBG and DIC system matches identically, and the deviation of peak axial strain of both means is less than 5%, which verifies the applicability of DIC system. The uncoordinated evolution of rock deformation displacement field is discussed to reveal the crack development and failure form of the sandstone specimen under uniaxial compression. The energy evolution of the elastic region of the specimen is revealed, and the development of releasable elastic strain energy would be divided into three stages, which correspond to the stress–strain characteristics of rock failure mechanics. This study could provide an alternative analytical method for the experimental rock mechanics research studies.

The evolution of overburden deformation is crucial for safety and environmental efficiency and its monitoring is becoming a key scientific issue. The use of an optical fiber sensor (OFS) for mining engineering is now receiving praise by virtue of its distinct abilities of distribution, high accuracy, and anti-interference measurement. Nevertheless, the dynamic response of OFS monitoring on overburden deformation still needs to be characterized in detail. This paper analyzed the characterization pattern of overburden deformation based on distributed optical fiber sensing (DOFS) by means of an analogue model test. Then, we discuss the influence of rules of optical fiber embedding on a model test in a numerical simulation. The results show that the DOFS monitoring demonstrates the time-space evolution of overburden deformation and the development of three horizontal areas and three vertical zones. A standardization DOFS characterization model is proposed to expound the characterization mechanism of the overburden structure zoning process; the influence of optical fiber embedding on rock displacement in the model test is revealed, and it is found that the displacement error will increase sharply when the fiber diameter is larger than 2 mm. These findings could provide an effective solution for a monitoring method in intelligent mining from the perspective of a theoretical basis and technological system.

The expected extraction efficiency of coalbed methane (CBM) depends significantly on the laws considered to govern its gas flow. This study applies a non-Darcy gas flow model to describe the CBM migration in mine gobs; by mine gob, we mean that it is a fractured zone along with massive cracks and the primary place where gas flows after mining activities. A permeation experiment involving crushed sandstone is first conducted to prove the CBM undergoes Forchheimer-type non-Darcy flow. Subsequently, the three-dimensional continuous distribution functions of the permeability parameters are determined. The non-Darcy flow model includes the influence of inertial force on the gas flow, which is neglected in the Darcy model. A coupling model is established based on the experimental results and the gas flow characteristics in different regions. Thereafter, the model and distribution functions are applied to a series of numerical simulations of CBM extraction at the Sihe coal mine in China, to ascertain the most appropriate location for a ground borehole. These simulations involve boreholes placed in three different zones: the natural accumulation zone (NAZ), the load affected zone (LAZ), and the compaction stable zone (CSZ). The simulation results show that the total extraction quantity expected from the borehole in the NAZ is 2.4 and 13.5 times that from the boreholes in the LAZ and CSZ, respectively. This confirms that the NAZ is the most suitable zone for a borehole. This research ultimately provides a realistic gas flow model for CBM extraction from mine gobs.