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IIT Tirupati Navavishkar I-Hub Foundation Website
Problem Statement
Optical Fiber Cables (OFCs) form the backbone of digital connectivity, but their non-metallic composition and installation within plastic conduits make them extremely difficult to detect with conventional geophysical tools. In wet soil conditions, where radar signal attenuation is high, mapping such cables becomes even more challenging. A non-destructive technique was required to attempt detection of OFC alignments while simultaneously assessing subsurface soil conditions for site planning.
Overview
A 3D Ground Penetrating Radar (GPR) survey was carried out at the IIT Tirupati campus using 250 MHz and 500 MHz ultra-wideband antennas to investigate the presence of buried OFC cables, while also mapping surrounding soil strata and embedded obstructions.
Engineering Impact
Provided valuable insights into soil stratigraphy and boulder distribution for geotechnical planning.
Demonstrated the limitations of GPR in detecting deep, non-metallic OFC cables in wet soil environments.
Reinforced the need for integrated geophysical methods for comprehensive underground utility detection.
Conclusion
While GPR effectively mapped soil layers and buried obstructions, the detection of non-metallic OFC cables within plastic conduits at 5 m depth proved infeasible under wet soil conditions. This study underscores both the capabilities and limitations of GPR, highlighting the necessity of multi-technique surveys for complete underground utility mapping in complex environments.
Methodology
System Configuration: Dual-frequency acquisition with 250 MHz (deep penetration) and 500 MHz (higher resolution) antennas.
Survey Design: Dense 3D grid acquisition to enhance imaging and provide volumetric subsurface visualization.
Site Conditions: Wet soil environment, posing challenges due to high dielectric losses and signal attenuation.
Key Findings
Subsurface Stratigraphy: Distinct layering of soil strata was mapped, along with reflections from embedded boulders and heterogeneities.
OFC Cable Response: Due to the non-metallic nature of the OFC and installation within plastic conduits at ~5 m depth, clear GPR signatures could not be obtained.
Depth Limitations: Signal attenuation in wet soils further restricted the visibility of thin dielectric targets at such depths.
Complementary Potential: The survey highlighted the importance of multi-method approaches, such as combining GPR with electromagnetic induction (EMI) or ground-truthing techniques, for reliable detection of non-metallic utilities.
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