Tunnels, Pipelines & Other Underground Infrastructure

Exponent’s multidisciplinary scientific and engineering staff is ideally suited for investigations related to risk assessment, construction, performance, and failure of elements of underground infrastructure. Our mechanical and materials engineers and metallurgists can evaluate the integrity of materials used for constructing underground structures. Our structural engineers have extensive expertise in the design and overall structural integrity of these structures. Our engineering geologists and geotechnical engineers use their education, training, and expertise to investigate pertinent aspects of the soil, rock, and groundwater that surround and interact with underground structures.

The performance of tunnels and pipelines relies on their material and structural integrity and their ability to resist external forces. Aging pipelines, like other elements of our infrastructure, are increasingly susceptible to failure. Material integrity factors often associated with pipeline failures include material defects, improper installation (e.g., welding defects), internal erosion due to a high-energy flow environment, and corrosion—an electrochemical reaction that can manifest as uniform thinning of a pipe wall or as localized pitting. Structural integrity factors include insufficient pipe rigidity or tunnel-support strength to accommodate external soil and traffic loads. Geologic and geotechnical factors that govern soil-structure interaction between a tunnel or pipeline and the surrounding soil and rock include the corrosivity of soil and groundwater, and external forces resulting from unanticipated overburden pressures, improper tunnel or trench shoring, unsuitable pipe bedding or trench backfill, inadequate compaction, soil erosion and piping, and ground movement.

Exponent’s services include:

  • Emergency response and evaluation of imminent hazards posed by failure of tunnels, pipelines, or other underground structures
  • Pre- and post-construction evaluation of the effects of underground construction on adjacent structures
  • Field investigation of underground structures, including: 
    • Pipeline video surveys 
    • Confined-space inspections 
    • Surface and underground geologic mapping, emphasizing ground stability, soil corrosivity, and groundwater pathways 
    • Documentation of ground movement indicators 
    • Collection of subsurface boring, CPT, and test-pit data 
    • Installation and monitoring of instrumentation to detect ground movement 
    • Geotechnical laboratory testing for measuring rock and soil engineering properties
  • Engineering analyses of tunnel stability, pipeline integrity, and underground structure conditions
  • Pipe stress modeling, pipe material and weld evaluation, non-destructive and destructive pipe testing, corrosion and biochemical testing, collection and preservation of pipeline-failure evidence, fracture analysis
  • Condition assessment of pipe in distribution systems
  • Service life modeling of distribution/collection systems
  • Analysis of the causes of tunnel, pipeline and underground infrastructure failures, including: 
    • Evaluation of earthquake hazards 
    • Evaluation of erosion and flood hazards 
    • Evaluation and substantiation of, and response to, differing site-condition claims