Geophysical Exploration

Where We Make a Difference

Building Tomorrow – assessing roads, bridges, and tunnels for safer infrastructure.

Smart Cities – locating utilities before a single trench is dug.

Water & Environment – tracing aquifers, mapping soil health, identifying contamination zones.

Heritage – protecting archaeological treasures without disturbing them.

Mines & Energy – scanning for voids, shallow deposits, and safe operations.

Security – detecting tunnels, UXOs, and hidden threats.

Join the Journey

At GeoIntel, it’s a vision of exploration without destruction. Whether you are an industry partner, a researcher, or an innovator, let’s collaborate to uncover what lies beneath.

What Makes GPR Unique?

Unlike drilling or excavation, GPR provides a non-destructive window into the Earth. From concrete bridges to ancient ruins, from hidden pipelines to aquifers, GPR reveals what lies beneath — quickly, safely, and in high resolution.  

Our Edge

Dual-Antenna Power – 250 MHz for depth, 500 MHz for detail.

3D Mapping & Visualization – transform profiles into volumetric models.

Smart Processing – advanced filters, imaging, and AI-powered insights.

Integrated Approach – combine with seismic, electrical, and magnetic methods for a complete picture.

Experienced Geophysicists and Geologists. 

Problem Statement 

Reinforced concrete culverts are critical components in transportation and drainage infrastructure, ensuring safe water conveyance and load transfer. Over time, these structures are subjected to traffic loading, environmental exposure, moisture ingress, chloride penetration, and material fatigue, which may lead to deterioration, corrosion of reinforcement, void formation, and loss of serviceability.

Conventional inspection methods such as visual surveys or coring are often invasive, time-consuming, and limited in scope, failing to capture the internal condition of the culvert in a holistic manner. As a result, there is a pressing need for non-destructive, high-resolution, and rapid assessment techniques that can provide actionable insights into the structural health and durability of culverts for asset management and preventive maintenance planning.

Overview

Ground Penetrating Radar (GPR) was deployed for a non-destructive evaluation (NDE) of a reinforced concrete culvert to assess its structural integrity and support preventive maintenance planning. The survey covered 144.5 m² with a high-density 10 cm grid spacing, ensuring comprehensive coverage and fine-scale resolution.

Methodology

A GPR system with a 500 MHz central frequency and 250–750 MHz bandwidth was employed to optimize the depth–resolution tradeoff required for infrastructure investigations. A total of 260 radargrams were acquired and processed using advanced 2D and 3D imaging workflows, including filtering, migration, amplitude analysis, and volumetric reconstruction.

Key Findings

• The processed dataset yielded critical insights into culvert condition and performance:

• Rebar Mesh Mapping: High-resolution imaging of embedded reinforcement, including rebar spacing assessments and concrete cover thickness estimation.

• Interface Characterization: Clear delineation of the asphalt–concrete contact zone.

• Material Degradation Mapping: Identification of localized deterioration zones, voids, and delamination features within the slab.

• Corrosion Potential Zones: Detection of anomalous reflections indicative of possible moisture ingress and early-stage corrosion risks.

• Structural Elements: Precise localization of abutments and supporting walls, aiding in load-bearing capacity assessment.

Engineering Impact

This investigation enabled:

• Condition-Based Monitoring (CBM): Establishing baseline structural health data for future comparative studies.

• Serviceability Evaluation: Verifying functionality of structural components relative to design intent.

• Life-Cycle Extension Planning: Providing data-driven recommendations for targeted rehabilitation and preventive maintenance strategies.

• Compliance with Standards: Workflow aligned with ASTM D6087 guidelines for GPR in concrete evaluation.

Conclusion

The study demonstrates GPR’s effectiveness as a non-invasive diagnostic tool for civil infrastructure. By integrating structural integrity assessment with quantitative deterioration mapping, the methodology enhances decision-making for long-term asset management and infrastructure resilience.

Problem Statement 

Reinforced concrete culverts are critical components in transportation and drainage infrastructure, ensuring safe water conveyance and load transfer. Over time, these structures are subjected to traffic loading, environmental exposure, moisture ingress, chloride penetration, and material fatigue, which may lead to deterioration, corrosion of reinforcement, void formation, and loss of serviceability.

Conventional inspection methods such as visual surveys or coring are often invasive, time-consuming, and limited in scope, failing to capture the internal condition of the culvert in a holistic manner. As a result, there is a pressing need for non-destructive, high-resolution, and rapid assessment techniques that can provide actionable insights into the structural health and durability of culverts for asset management and preventive maintenance planning.

Overview

Ground Penetrating Radar (GPR) was deployed for a non-destructive evaluation (NDE) of a reinforced concrete culvert to assess its structural integrity and support preventive maintenance planning. The survey covered 144.5 m² with a high-density 10 cm grid spacing, ensuring comprehensive coverage and fine-scale resolution.

Methodology

A GPR system with a 500 MHz central frequency and 250–750 MHz bandwidth was employed to optimize the depth–resolution tradeoff required for infrastructure investigations. A total of 260 radargrams were acquired and processed using advanced 2D and 3D imaging workflows, including filtering, migration, amplitude analysis, and volumetric reconstruction.

Key Findings

• The processed dataset yielded critical insights into culvert condition and performance:

• Rebar Mesh Mapping: High-resolution imaging of embedded reinforcement, including rebar spacing assessments and concrete cover thickness estimation.

• Interface Characterization: Clear delineation of the asphalt–concrete contact zone.

• Material Degradation Mapping: Identification of localized deterioration zones, voids, and delamination features within the slab.

• Corrosion Potential Zones: Detection of anomalous reflections indicative of possible moisture ingress and early-stage corrosion risks.

• Structural Elements: Precise localization of abutments and supporting walls, aiding in load-bearing capacity assessment.

Engineering Impact

This investigation enabled:

• Condition-Based Monitoring (CBM): Establishing baseline structural health data for future comparative studies.

• Serviceability Evaluation: Verifying functionality of structural components relative to design intent.

• Life-Cycle Extension Planning: Providing data-driven recommendations for targeted rehabilitation and preventive maintenance strategies.

• Compliance with Standards: Workflow aligned with ASTM D6087 guidelines for GPR in concrete evaluation.

Conclusion

The study demonstrates GPR’s effectiveness as a non-invasive diagnostic tool for civil infrastructure. By integrating structural integrity assessment with quantitative deterioration mapping, the methodology enhances decision-making for long-term asset management and infrastructure resilience.

Problem Statement

Underground manholes and inspection chambers are vital for drainage, utility access, and maintenance. However, their depth, extent, and connectivity are often poorly documented, posing risks during construction, retrofitting, or urban expansion. Conventional intrusive methods are disruptive, whereas a non-destructive, high-resolution approach is essential for safe and precise infrastructure assessment.

Overview

At IIT Tirupati campus, a Ground Penetrating Radar (GPR) survey was conducted to investigate two different manholes and their surrounding subsurface conditions. The study aimed to map the depth, extent, internal structure, and connecting utilities, while also characterizing the geotechnical layers around the chambers.

Methodology

• System Configuration: A 250 MHz ultra-wideband antenna was employed, providing deeper penetration and wide-frequency coverage.

• Survey Design: Data acquisition was performed on 3D grids with 25 cm line spacing, enabling detailed volumetric imaging and depth slicing.

• Processing Workflow: Advanced 2D/3D imaging, time-slicing, and amplitude analysis were applied to highlight manhole geometry, utilities, and surrounding strata.

Key Findings

• Manhole Geometry: Both manholes were clearly mapped in terms of depth and lateral extent, with volumetric estimates generated.

• Utilities and Connectivity: Subsurface pipelines connecting the manholes were identified, including utilities located beneath concrete reinforcement layers, which are typically difficult to detect.

• Material Stratigraphy: Multiple subsurface layers were distinguished, including reinforced concrete, unsettled soil, and underlying bedrock at greater depths.

• Airwave Reflections: Strong reflections from nearby building walls were recorded, producing distinct patterns due to indoor signal propagation.

• Depth-Slice Imaging: The dense 3D grid and ultra-wideband configuration enabled clear visualization of manholes, chambers, and connecting utilities in successive depth slices.

Engineering Impact

• The survey demonstrated the ability of GPR to:

• Deliver accurate mapping of manholes and chamber volumes.

• Detects deep-seated and hidden utilities beneath reinforced concrete layers.

• Provide layer-specific geotechnical insights for soil and foundation conditions.

• Support infrastructure planning, rehabilitation, and safe excavation.

Conclusion

This case study establishes GPR as a powerful tool for non-invasive investigation of underground manholes and chambers, offering detailed information on geometry, connectivity, and surrounding materials. The combination of 250 MHz ultra-wideband antenna and 3D grid survey design proved particularly effective for resolving complex subsurface conditions within a campus infrastructure setting.

Problem Statement

Accurate determination of concrete slab thickness and assessment of underlying conditions are critical for evaluating the structural integrity and service life of built infrastructure. Traditional coring methods are invasive, time-consuming, and often compromise the structure. A non-destructive and high-resolution approach was required to measure slab thickness, detect reinforcement, and identify potential voids beneath the structure.

Overview

A Ground Penetrating Radar (GPR) survey was conducted using a 500 MHz broadband antenna (250–750 MHz) to measure the thickness of a reinforced concrete slab and assess subsurface anomalies.

Methodology

• System Configuration: 500 MHz antenna with ultra-wide bandwidth for shallow, high-resolution imaging.

• Survey Design: Closely spaced parallel profiles were collected to generate 2D sections and depth slices.

• Processing Workflow: Standard GPR data processing, including filtering, migration, and amplitude analysis, was applied to refine thickness estimation and anomaly mapping.

Key Findings

• Slab Thickness Measurement: Clear reflection signatures allowed accurate estimation of concrete slab thickness.

• Rebar Detection: Strong hyperbolic signatures of reinforcement bars were visible due to the high-frequency content in the shallow region of the slab.

• Underlying Strata: Distinct layering below the slab was imaged, providing insights into subgrade composition.

• Cavity Detection: Possible voids or cavities were detected beneath the reinforcement slab, indicating potential risk zones.

Engineering Impact

• Enabled non-destructive thickness measurement of reinforced concrete structures.

• Identified reinforcement conditions and spacing with high clarity.

• Provided early detection of subgrade cavities, supporting preventive maintenance and rehabilitation planning.

• Reduced the need for invasive coring, saving time and preserving structural integrity.

Conclusion

This study highlights the effectiveness of GPR with a 500 MHz broadband antenna for slab thickness evaluation and subsurface assessment. The ability to resolve reinforcement, underlying strata, and cavities establishes GPR as a reliable tool for condition monitoring and structural health evaluation in civil infrastructure.

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.

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.

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.

Problem Statement

Understanding root architecture is essential for assessing tree health, stability, and ecological impact. Traditional root studies rely on trenching and excavation, which are invasive, labor-intensive, and often damage the tree or surrounding environment. A non-destructive, high-resolution approach was required to visualize the spatial extent, depth, and complexity of root systems in young trees at IIT Tirupati.

Overview

A Ground Penetrating Radar (GPR) survey was carried out on four different tree species—Neem, Mango, Teak, and Eucalyptus—located within the IIT Tirupati campus. The objective was to map their root distribution and compare variations in structure and growth patterns. The survey employed a 500 MHz broadband antenna, suitable for shallow, high-resolution imaging of root networks, with a maximum depth setting of 4 meters.

Methodology

• System Configuration: A 500 MHz ultra-wideband antenna was used to balance penetration depth with high-resolution imaging for near-surface root mapping.

• Survey Design: Data were collected in a grid format with 10 cm line spacing, enabling generation of detailed 2D profiles and depth-slice images of the root zone.

• Processing Workflow: Standard GPR data processing steps, including dewow filtering, background removal, migration, and amplitude/depth-slice analysis, were applied to highlight root structures and their spatial patterns.

Key Findings

• Complex Root Networks: All four tree species exhibited dense and intricate root systems, with lateral roots spreading extensively within the top 2 meters.

• Species-Specific Characteristics:

• Neem Tree: Produced a unique depth-slice pattern, showing vertically oriented strong root signatures extending deeper than other species, suggesting robust anchorage development.

• Mango Tree: Displayed a balanced root distribution with both lateral and vertical components, typical of fruit-bearing species in early growth stages.

• Teak Tree: Showed relatively linear and directional root growth, possibly influenced by soil stratigraphy.

• Eucalyptus Tree: Demonstrated an extensive lateral root network dominating the upper 1.5 meters, aligning with its fast-growing nature.

• Depth Variability: Root reflections were visible up to the 4 m survey depth, although most strong responses were concentrated between 0.5–2.5 m.

• Anomalous Zones: Areas of high-amplitude reflections suggested zones of root clustering or soil heterogeneity influenced by root activity.

Engineering & Ecological Impact

• Provided non-destructive mapping of root systems, supporting ecological and campus landscape management.

• Helped compare root distribution among different species, valuable for urban forestry and stability assessments.

• Identified unique Neem root patterns that may inform species-specific growth studies.

• Demonstrated the potential of GPR for tree health monitoring, soil–root interaction studies, and ecological research without harming vegetation.
  
  

Conclusion

This study highlights the potential of 500 MHz GPR for root mapping in younger trees, with 10 cm line spacing ensuring high-resolution detection of root complexity. The comparative assessment of Neem, Mango, Teak, and Eucalyptus revealed distinct root growth patterns, with Neem exhibiting particularly unique depth-slice features. GPR proves to be a powerful, non-invasive tool for studying below-ground biomass, offering significant benefits for forestry, urban planning, and ecological research.

Problem Statement

Characterizing regolith layers is essential for understanding ground stability, soil–rock interactions, and construction suitability. Conventional borehole methods provide only point-specific information and often miss lateral variability. A non-invasive, high-resolution technique was required to map regolith thickness, detect lithological variations, and identify subsurface features such as boulders and air pockets near construction sites at IIT Tirupati.

Overview

A Ground Penetrating Radar (GPR) survey was conducted in selected construction zones of IIT Tirupati campus to assess regolith distribution and subsurface heterogeneity. A 250 MHz antenna was employed using the reflection method, balancing penetration depth with resolution to investigate the regolith cross-section up to several meters.

Methodology

• System Configuration: 250 MHz antenna, optimized for medium-depth penetration and subsurface imaging.

• Survey Design: Reflection profiling method was adopted to capture continuous subsurface cross-sections across target areas.

• Processing Workflow: Advanced GPR data processing steps including background removal, bandpass filtering, migration, and amplitude/depth-slice analysis were applied to refine imaging of regolith thickness and internal structures.

Key Findings

• Regolith Thickness: Distinct reflections allowed mapping of variable regolith thickness across the surveyed areas. Layer changes were evident based on compaction and material properties.

• Layer Compactness: Upper regolith layers showed relatively loose packing, while deeper layers displayed increased compactness and stronger reflection contrasts.

• Boulder Detection: Medium- to large-scale boulders were imaged after migration, providing evidence of subsurface heterogeneity and rock–soil interaction.

• Air Pockets & Loose Zones: Possible voids or air pockets were inferred near shallow layers where reflection discontinuities and low-amplitude zones were present.

• Soil–Rock Transition: Gradual changes from loose regolith to compact layers were well-resolved, supporting stratigraphic interpretation.

Engineering Impact

• Enabled non-destructive mapping of regolith thickness and variability.

• Provided critical insights into subsurface stability for construction site planning.

• Identified boulders and packing variations, important for excavation and foundation design.

• Detected potential air pockets that could pose risks for structural settlement.

Conclusion

The 250 MHz GPR survey effectively characterized regolith distribution and subsurface heterogeneity in IIT Tirupati construction zones. The ability to resolve compactness variations, boulders, and potential voids demonstrates the utility of GPR in geotechnical and construction-related investigations. This non-invasive approach provided valuable input for site evaluation, reducing reliance on invasive drilling and enhancing subsurface understanding.

Problem Statement

In transportation and pavement engineering, accurate knowledge of asphalt overlay thickness is essential for structural capacity assessment, maintenance planning, and rehabilitation design. Traditional coring is destructive and provides only point-specific data. A non-destructive, high-resolution solution was required to evaluate the asphalt layer and underlying concrete slab, along with potential anomalies at their interface.

Overview

A Ground Penetrating Radar (GPR) survey was performed using a 500 MHz broadband antenna (250–750 MHz) to measure the thickness of asphalt overlay placed over a concrete base and to assess the condition of underlying strata.

Methodology

• System Configuration: 500 MHz broadband antenna for shallow high-resolution imaging of pavement layers.

• Survey Design: Parallel lines with dense spacing were acquired for both 2D radargrams and 3D volumetric reconstruction.

• Processing Workflow: Filtering, migration, amplitude analysis, and depth conversion techniques were applied to quantify layer thicknesses and highlight anomalies.

Key Findings

• Asphalt Thickness Measurement: The asphalt overlay thickness was mapped with high accuracy based on clear dielectric contrast between asphalt and concrete interface.

• Concrete Slab Imaging: Underlying concrete slab thickness was also estimated, providing a complete pavement profile.

• Interface Characterization: The asphalt–concrete contact zone was clearly delineated, allowing detection of potential debonding or moisture ingress.

• Anomaly Detection: Reflections indicated possible air gaps, voids, or material deterioration at localized points within the slab system.

Engineering Impact

• Delivered non-destructive thickness evaluation of both asphalt and concrete layers.

• Provided a continuous pavement profile beyond point-specific coring methods.

• Enabled early detection of debonding and voids, supporting preventive maintenance planning.

• Reduced investigation time and preserved pavement integrity.

Conclusion

This case study demonstrates the utility of GPR for layer thickness measurement and interface assessment in asphalt-over-concrete pavements. The ability to resolve asphalt thickness, concrete slab conditions, and potential anomalies makes GPR a powerful diagnostic tool for pavement engineering and infrastructure management.

Problem Statement

The performance and durability of reinforced concrete structures depend heavily on the correct placement and alignment of rebar meshes. Misalignments, improper spacing, or cover variations can compromise load-bearing capacity and accelerate deterioration through corrosion. Conventional inspection methods such as coring are destructive and limited in scope, necessitating a non-destructive, high-resolution technique for rebar quality verification.

Overview

A Ground Penetrating Radar (GPR) survey using a 500 MHz ultra-wideband (UWB) antenna was carried out to assess rebar placement within a reinforced concrete slab. The primary objective was to detect rebar misalignments, spacing irregularities, and cover depth variations in the embedded mesh.

Methodology

• System Configuration: 500 MHz UWB antenna with a bandwidth of 250–750 MHz, optimized for shallow, high-resolution imaging.

• Survey Design: High-density parallel scans with close line spacing to capture fine-scale anomalies in rebar geometry.

• Processing Workflow: Application of filtering, migration, and amplitude enhancement to highlight rebar hyperbolas and measure spacing accurately.

Key Findings

• Rebar Mesh Visualization: Strong, shallow reflections enabled clear identification of reinforcement patterns.

• Misalignments Detected: Deviations in bar spacing and alignment were observed compared to expected mesh geometry.

• Concrete Cover Assessment: Variations in rebar cover thickness were detected, indicating inconsistent placement during construction.

• Structural Implications: Misaligned reinforcement may influence load transfer efficiency, crack propagation, and long-term durability.

Engineering Impact

• Enabled non-destructive detection of rebar misalignments, offering rapid feedback on construction quality.

• Provided digital records for as-built verification against design specifications.

• Supported structural health monitoring (SHM) and preventive maintenance planning.

• Reduced reliance on invasive methods, saving both time and structural integrity.

Conclusion

This study demonstrates the capability of 500 MHz UWB GPR to accurately detect rebar misalignments, spacing irregularities, and cover variations in reinforced concrete. GPR proves to be a valuable diagnostic tool for quality assurance, construction verification, and long-term monitoring of civil infrastructure.

Problem Statement

Coring through reinforced concrete requires precise avoidance of reinforcement, tendons, and embedded services. Inadequate targeting risks structural damage, costly repairs, and safety incidents. A non-destructive, high-resolution method was needed to quantify rebar spacing, cover depth, and bar layout to define a safe coring window.

Overview

A high-frequency UWB GPR survey (≈500 MHz bandwidth ~250–750 MHz) was performed over the proposed coring zone. Objectives: (i) map rebar grid geometry, (ii) measure bar spacing and concrete cover, (iii) confirm absence of utilities/tendons in the intended core footprint, and (iv) designate a safe, centered coring location with tolerances.

Methodology

• Survey design: Dense parallel lines (≤5–10 cm spacing) in two orthogonal directions for true grid reconstruction.

• Processing: Background removal, bandpass, migration, attribute/amplitude analysis; time–depth conversion via dielectric calibration (from known slab thickness or on-site calibration target).

• Analysis: Hyperbola fitting to estimate bar positions/diameters, compute center-to-center spacing, cover depth, and produce plan-view depth slices marking bar centrelines and no-core zones.

• Screening: Focused passes to rule out post-tension (PT) ducts, conduits, or anomalies within the proposed core diameter + safety buffer.

Key Findings

• Rebar layout: Orthogonal mesh resolved with consistent spacing (e.g., ~150–200 mm c/c typical; site-specific values reported) and cover depth variability quantified (±5–10 mm).

• Clear windows: Multiple rebar-free corridors identified; the optimal coring point centered mid-span between adjacent bars with ≥1.5× core radius clearance to nearest bar.

• No services detected: No GPR signatures indicative of PT tendons or utilities within the buffered core footprint.

• Tolerance box: A marked core window (e.g., Ø100 mm) with ±15 mm placement tolerance defined on the slab surface; relocation rules provided if tolerance exceeded.

Engineering Impact

• Enables safe, non-destructive core extraction while preserving structural capacity.

• Provides as-built rebar map and measurements for QA/QC and records.

• Reduces risk of striking reinforcement/services, minimizing downtime and repair costs.

• Supplies inputs for material testing (e.g., compressive strength, chloride) with documented structural clearance.

Conclusion

High-density UWB GPR reliably resolved rebar spacing, cover, and clear zones, allowing a precisely located, low-risk core cut. The workflow couples quantitative spacing/cover metrics with a field-marked tolerance window, offering a repeatable, audit-ready approach to coring in reinforced concrete.

Problem Statement
Road durability depends on the integrity of subsurface layers and uniform compaction beneath the asphalt. Conventional inspection methods often miss hidden discontinuities and early signs of soil subsidence, which later lead to cracks and structural failures. A non-destructive, high-resolution survey was required to detect hidden joints, subsurface discontinuities, and potential zones of weakness in a newly constructed road at IIT Tirupati.

Overview
A Ground Penetrating Radar (GPR) survey was conducted over a 150 m² road section in the North Campus of IIT Tirupati to assess the condition of subsurface layers and detect hidden joints. A 500 MHz ultra-wideband antenna with a depth setting of 4 meters was used to capture both shallow and moderately deep structural features.

Methodology

• System Configuration: 500 MHz broadband antenna (250–750 MHz) for high-resolution road subsurface imaging.

• Survey Design: Dense grid survey with 10 cm line spacing in both directions, enabling detailed 2D cross-sections and 3D depth slices.

• Processing Workflow: Advanced GPR data processing including dewow, background removal, migration, and amplitude slice analysis was applied to resolve hidden transverse/longitudinal joints and potential subsidence zones.
  
  

Key Findings

• Hidden Joints: Subtle transverse and longitudinal reflection patterns were identified below the asphalt, indicating possible construction-induced joints or discontinuities.

• Soil Subsidence: Localized low-amplitude anomalies and undulating reflector patterns suggested early signs of soil subsidence from shallow depths (<1.5 m).

• Cracking Indicators: Areas with subsidence corresponded to shallow cracking patterns observed on the asphalt surface. The severity was assessed as low to medium.

• Continuity of Layers: Most of the road base showed uniform layering, but isolated weak zones were identified as potential risks in the long term.
  
  

Engineering Impact

• Enabled non-invasive detection of hidden transverse and longitudinal joints beneath the road.

• Identified zones of soil subsidence before severe damage, supporting preventive maintenance planning.

• Provided critical inputs for site monitoring, reducing future repair costs and improving road service life.

• Suggested specific areas for long-term observation and priority-based repair interventions.

Conclusion
The dense-grid GPR survey with a 500 MHz ultra-wideband antenna successfully identified hidden discontinuities and early subsidence beneath the road in IIT Tirupati North Campus. Although the severity is currently low to medium, these anomalies represent potential risk zones for future asphalt cracking and should be monitored for preventive repairs. This case demonstrates the value of GPR for road condition assessment and long-term infrastructure monitoring.

Problem Statement

Locating utilities beneath reinforced concrete structures is one of the most challenging tasks in subsurface investigations. The dense rebar mesh often produces strong reflections that mask deeper anomalies, making conventional detection methods unreliable. A non-destructive, broadband geophysical technique was needed to penetrate the reinforcement layer and identify underlying utilities without damaging the structure.

Overview

A Ground Penetrating Radar (GPR) survey was carried out using a 250 MHz ultra-wideband (UWB) antenna to detect utilities beneath a reinforced concrete slab. The aim was to resolve the interference caused by rebar signatures while still imaging deeper subsurface utilities.

Methodology

• System Configuration: 250 MHz UWB antenna offering deeper penetration and wide frequency coverage.

• Survey Design: Data collected in dense 3D grids to enable depth-slice visualization of utilities masked by rebar clutter.

• Processing Workflow: Advanced processing including background removal, migration, and frequency filtering was applied to suppress rebar responses and enhance deeper reflections.

Key Findings

• Rebar Mesh Imaging: Clear, shallow hyperbolic patterns from reinforcement were recorded, confirming the presence and spacing of rebar.

• Utility Detection: Despite rebar interference, utilities beneath the slab were successfully identified in depth slices, thanks to the penetration capability of 250 MHz UWB.

• Subsurface Clarity: Volumetric visualization enabled separation of shallow rebar reflections from deeper utility responses.

• Structural Insight: In addition to utilities, layering beneath the slab was imaged, supporting a more comprehensive structural health assessment.

Engineering Impact

• Demonstrated GPR’s ability to detect utilities hidden under rebar mesh—a task often considered infeasible.

• Provided a non-invasive, reliable alternative to coring or destructive investigations.

• Enhanced safety during renovation, retrofitting, and drilling works.

• Added value to facility management and infrastructure monitoring by offering precise digital subsurface records.

Conclusion

The use of 250 MHz UWB GPR with dense 3D survey design proved effective for utility detection beneath reinforced concrete slabs. This case study highlights GPR’s potential in addressing complex subsurface imaging challenges in civil and structural engineering contexts.

Problem Statement
Efficient irrigation systems rely on well-laid underground pipelines, which are often difficult to detect once covered by soil and vegetation. Traditional pipe location methods require excavation or rely on as-built drawings, which may be inaccurate or unavailable. A non-invasive, high-resolution approach was needed to map the underground pipe network supporting the sprinkler system in a newly constructed lawn at IIT Tirupati.

Overview
A Ground Penetrating Radar (GPR) survey was conducted on the lawn area in front of Academic Building 1, IIT Tirupati to identify and map the subsurface pipe network responsible for the sprinkler irrigation system. A 500 MHz ultra-wideband antenna was used to capture shallow subsurface features with high clarity.

Methodology

• System Configuration: 500 MHz broadband antenna, suitable for high-resolution shallow imaging of utility networks.

• Survey Design: A grid-based survey with 20 cm line spacing was carried out to ensure adequate coverage and accurate reconstruction of the pipe network.

• Processing Workflow: Standard GPR data processing including filtering, background removal, migration, and amplitude slice analysis was applied to highlight linear anomalies consistent with pipelines.

Key Findings

• Pipe Network Detection: Continuous linear hyperbolic signatures corresponding to small-diameter pipes were clearly visible in both 2D profiles and depth slices.

• Depth Estimation: The pipes were imaged at shallow depths (<1.5 m), consistent with irrigation infrastructure placement.

• Network Mapping: The dense survey grid enabled reconstruction of the pipe layout, showing connectivity and distribution across the lawn.

• Infrastructure Confirmation: The detected network matched the expected layout of the sprinkler system, validating the survey approach.

Engineering Impact

• Successfully provided a non-invasive method for locating small-diameter irrigation pipes.

• Enabled precise mapping of the sprinkler pipeline network for maintenance and future landscaping work.

• Reduced reliance on excavation or incomplete as-built documentation.

• Demonstrated GPR’s effectiveness for shallow utility detection in landscaped environments.

Conclusion
The 500 MHz GPR survey with 20 cm line spacing successfully detected and mapped the underground pipe network in the newly constructed lawn area in front of Academic Building 1, IIT Tirupati. The ability to resolve small-diameter pipelines at shallow depths highlights the utility of GPR for non-destructive utility detection, supporting both infrastructure maintenance and planning.