Multiphysics monitoring of leakage-induced soil wetting and localized deformation around buried water pipelines: a physical model study with implications for mining-affected areas

Buried water pipelines in mining-affected areas may be exposed to pre-existing ground deformation and fracture conditions that can aggravate the consequences of leakage. The present physical model, however, does not directly reproduce mining-induced displacement or stress redistribution. To characterize leakage-induced moisture migration and localized deformation, a laboratory platform integrating fiber Bragg grating (FBG) strain sensing with parallel direct-current resistivity monitoring was developed. Under a constant internal pipe pressure of 0.16 MPa and a leakage rate of approximately 0.45 mL/s, strain responses from 28 FBG sensing points distributed across four channels, apparent resistivity distributions along two monitoring profiles, and water-content variations within the leakage core zone were recorded synchronously. Based on coincident changes in the temporal responses of water content, apparent resistivity, and FBG strain, the test was divided into four observational response stages: rapid wetting and localized response (0–700 s), wetting expansion and structural adjustment (700–5,900 s), sustained coupled anomaly and nonuniform deformation (5,900–7,000 s), and quasi-stable coupled response (>7,000 s). Using ρ <50 Ω m as an experiment-specific operational threshold, the low-resistivity area in the STUV profile increased from 0.0048 m 2 at 700 s to 0.098 m 2 at 7,000 s, whereas that in the OPQR profile increased from 0.0049 to 0.395 m 2 . The locations and dominant propagation directions of the low-resistivity zones were broadly consistent with the elevated FBG strain-response bands in the EADH and FBCG core regions and corresponded to stabilization of the core-zone water content at approximately 22%. FBG sensing was more sensitive to localized strain-response concentration, whereas resistivity imaging was better suited to delineating moisture anomalies and preferential seepage pathways. Their spatiotemporal correspondence therefore provides complementary evidence of leakage-induced ground weakening. A strain–resistivity coupling response index was further developed for retrospective within-test stage comparison, together with a model-scale coupled-anomaly interpretation framework. These results demonstrate leakage-induced soil wetting and localized deformation under the tested condition and provide monitoring implications for mining-affected areas; they do not constitute direct evidence of subsurface void formation or surface collapse. Repeated tests, direct geotechnical observations, coupled mining–leakage experiments, and field monitoring are required before engineering thresholds or warning criteria can be established.