## 5 Conclusions  
This study investigated the mechanical deformation behavior of a model shaft lining under simulated non-uniform ground pressure by applying differential loads in the X and Y directions. Distributed fiber optic sensing based on OFDR technology was utilized to explore strain transfer characteristics in the model test. Key findings are summarized below:  
Figure 16: Comparison between fiber optic measurements and numerical simulations at the outer edge of the NO. 3 shaft lining model: (**a**) X = 0.48 MPa, Y = 0.8 MPa; (**b**) X = 0.96 MPa, Y = 0.1.6 MPa; (**c**) X = 1.44 MPa, Y = 2.4 MPa; (**d**) X = 1.92 MPa, Y = 3.2 MPa; (**e**) X = 2.4 MPa, Y = 4 MPa; (**f**) Specific point numbering of the shaft lining model.  
(1) Comparison demonstrates strong agreement between OFDR technology and strain gauge measurements in axial strain monitoring of shaft linings.  
OFDR technology enabled full cross-section monitoring of the inner and outer edges of the shaft lining, with generally accurate results.  
(2) OFDR technology has the ability to detect some cracks in shaft lining that cannot be identified by the human eye.  
(3) The composite filling of a PTFE plate and fine sand at the interface between the model shaft lining and the surrounding rock can produce model shaft linings whose deformation characteristics closely match those of the prototype.  
(4) During fiber installation, adhesive-sealed plastic tubes are used at the inter-face between the shaft lining and air to protect the fibers from environmental effects and prevent signal attenuation or damage caused by bending or compression. Additionally, the bending radius of the fibers can be maintained above 1 cm to ensure proper functionality. Embedding distributed fibers in the shaft lining mold allowed comprehensive monitoring of axial, circumferential, and radial strains, providing precise data for structural health monitoring and maintenance.  
The test results have some errors in the crack location range, and the optical fiber measurement has a certain weakening in the location of the stress concentration in the shaft lining, this is a limitation of the study. How to use optical fiber to measure the three-dimensional strain at any point of the well wall and realize the quantitative analysis of random cracks is the future development direction of this technology. Automation methods have become an indispensable part of modern engineering testing, significantly improving testing efficiency, coverage, and reliability. Adopting automation methods is highly beneficial for the analysis of inclined shaft lining test results, representing a future trend in testing research. We will strive to apply automation methods in subsequent studies [49; 50].  
Conceptualization, W.Y. ([PERSON]) and Z.Y.; methodology, T.L. and Z.Y.; validation, W.Y. ([PERSON]) and [PERSON] ([PERSON]); formal analysis, [PERSON] ([PERSON]), T.L. and Z.Y.; investigation, [PERSON] ([PERSON]); resources, [PERSON] ([PERSON]); data curation, [PERSON] ([PERSON]), T.L. and Z.Y.; writing--original draft preparation, [PERSON] ([PERSON]), T.L.and Z.Y. writing--review and editing, T.L., [PERSON] ([PERSON]) and Z.Y.; visualization, [PERSON] ([PERSON]) and T.L.; supervision, [PERSON] ([PERSON]) and Z.Y.; project administration, [PERSON] ([PERSON]); funding acquisition, [PERSON] ([PERSON]). All authors have read and agreed to the published version of the manuscript.  
This study was supported by the National Key Research and Development Program of China (grant NO. 2016 YFC0600904).  
Not applicable.  
The data presented in this study are available on request from the corresponding author.  
The authors declare no conflict of interest.