Towed Time Domain Electromagnetic (t-TEM)

Methods › Electromagnetic › Towed Time Domain Electromagnetic (t-TEM)

The Towed Time Domain Electromagnetic (t-TEM) system is a recent adaptation of the traditional ground-based TEM geophysical tool designed for rapid acquisition of high-resolution images of the shallow subsurface. The t-TEM method provides critical insights for various subsurface investigations. One of the significant advantages of t-TEM is its ability to collect subsurface geophysical data quickly and cost-effectively. It is particularly beneficial for large-scale surveys needing detailed 3D geological mapping capabilities and short field deployment times, making it a preferred choice for many large-scale applications.

t-TEM is beneficial for large-scale surveys needing detailed 3D geological mapping capabilities and short field deployment times.

How does it work?

The t-TEM system involves cycling a primary electrical current through a wire in a transmitter loop (Tx), generating a static primary magnetic field. When the current in the TX loop is turned off, secondary electrical currents are induced in the earth, moving outward and downward, decaying over time. When the secondary electrical field decays, a secondary magnetic field is measured by a receiver (Rx) loop towed behind the Tx loop (See diagram below) The Rx loop measures the decay of the secondary magnetic field as it varies with time. The decay of the secondary electrical field is influenced by the resistivity distribution beneath the ground surface. Measured TEM signals at the receiver are converted to apparent resistivity and inverted to understand the depth-varying resistivity structure of the earth.

Applications of t-TEM

The t-TEM system is widely used for groundwater investigations, helping map aquifers and effectively assess water resources. It is also used in environmental and engineering applications, such as contamination assessment and infrastructure planning. The system’s ability to quickly provide comprehensive images of large areas makes it a vital tool.

  • Groundwater Exploration: Locating and Mapping Aquifers

    The t-TEM system is used to locate and map aquifers to help identify the depth, extent, and properties of aquifers, providing important data for water resource management. This is especially useful in areas where water scarcity is a concern, allowing for planning and sustainable use of groundwater resources.

  • Recharge Basin Characterization: Understanding Recharge Basins

    Recharge basins are characterized using t-TEM to identify subsurface features influencing water infiltration and storage. This method helps determine locations best suited for high-quality infiltration basins, optimizing their design and functionality. t -TEM creates images of the subsurface, which helps determine the most effective locations for recharge basins, which is crucial for enhancing groundwater recharge and managing water supplies.

  • Tailings Storage Facilities: Geotechnical Investigations

    t-TEM is used for geotechnical investigation of tailings storage facilities to assess the stability and integrity of the storage structures. It provides a better understanding of the subsurface, allowing engineers to identify potential weak points, monitor changes over time, and ensure the safe containment of mining waste materials.

  • Levee and Embankment Dam Investigations: Geotechnical Investigations

    Levees and embankment dams can have structural challenges, such as voids, piping, or areas of weakness, that could compromise their stability. t-TEM is used to investigate structural integrity by imaging the subsurface and detecting anomalies. This information is critical for maintenance, repair, and ensuring the safety of flood protection systems.

  • Environmental Applications: Detecting Contaminants and Monitoring Cleanup Projects

    By providing subsurface images, t-TEM can detect and map many subsurface contaminants and help monitor environmental cleanup projects. The methodology can identify contamination plumes and track their movement over time. This capability helps assess the extent of the pollution, guides remediation efforts, and helps understand the effectiveness of cleanup activities.

  • Engineering Applications: Assessing Suitability for Construction Projects

    In infrastructure development, t-TEM is crucial in assessing land suitability for construction projects. It provides information about the subsurface structural conditions, helping engineers determine the best locations for foundations, identify potential hazards, and design safe and stable structures. This application of t-TEM ensures that construction projects are built on solid ground, reducing the risk of structural failure and enhancing the longevity of the infrastructure.

Technical Specifications

The t-TEM system is designed for shallow subsurface mapping, typically up to 150 meters deep. It features advanced technical components, including a high-resolution transmitter and receiver, which ensure accurate data collection. These specifications enable detailed and reliable subsurface imaging, essential for various subsurface investigations. Hydrogeophysics (HGI) offers comprehensive t-TEM services, from initial consultation to data acquisition and processing. Our team is ready to provide high-quality, reliable geophysical surveys tailored to your needs.

Learn the Applications of t-TEM