Structural fill solutions are evolving—and R-Shield® Geofoam is leading the way with lightweight, high-performance alternatives to traditional materials. One of the most important aspects of using geofoam in structural and civil engineering applications is selecting the correct grade for the expected load.

R-Shield's Technical Team has provided three detailed calculation examples to help engineers understand how to evaluate vertical stresses in geofoam and verify that the selected product is suitable for real-world conditions. Let’s explore what each example illustrates.

Example 1: Single Point Load over Geofoam

This first scenario models a straightforward case: a single 12.5 kip point load applied over a layered pavement system (pavement, base, and 6 feet of geofoam). The goal is to verify that the selected EPS 22 Geofoam, with a compressive resistance of 7.3 psi at 1% strain, can withstand the combined dead and live loads.

⇒ View Full Calculation Example 1 Document

Key Takeaways:

• Dead load and live load calculations are performed at both the top and bottom of the geofoam.
• The maximum stress calculated at the top of the geofoam is 6.42 psi, safely within the compressive resistance of EPS 22.
• This example demonstrates a basic stress distribution method from a single vertical load, using standard slope assumptions based on NCHRP guidelines.

Result: EPS 22 is suitable for this single-load application.

Example 2: Dual Wheel Loads and Stress Overlap

This second scenario increases complexity by analyzing two adjacent 12.5 kip loads (simulating dual tires), introducing load overlap as a critical factor. The model incorporates both transverse and longitudinal load distributions, reflecting real-world wheel loading on roadways or parking decks.

⇒ View Full Calculation Example 2 Document

Key Takeaways:

• Load overlap at various depths is calculated to reflect how vertical stress patterns interact between the two loads.
• Multiple stress zones are examined:
  • Top of Geofoam
  • Beginning of Load Overlap
  • Bottom of Geofoam
• Maximum stress remains 6.42 psi, even with overlapping load zones.

 Result: EPS 22 still passes, proving its performance under more dynamic and complex loading conditions.

Example 3: Four-Wheel Load Configuration

In this advanced scenario, four 12.5 kip loads are placed in both transverse and longitudinal configurations—mimicking real-world conditions like truck or equipment loading on a geofoam-supported surface. This significantly increases the demand on the geofoam and emphasizes multi-load interaction at depth.

⇒ View Full Calculation Example 3 Document

Key Takeaways:

• All four loads interact at the bottom of the geofoam, requiring a full-area stress distribution analysis.
• Total vertical stress at the bottom reaches 4.29 psi, still well below the 7.3 psi limit of EPS 22.
• This example shows how R-Shield Geofoam manages complex, compounded loading across both planes.

Result: EPS 22 continues to perform, even in a high-demand, multi-load scenario.

Why These Examples Matter

These examples are more than just theoretical—they reflect common project scenarios like:

• Roadway or bridge deck construction
• Load-bearing fill in urban infrastructure
• Structural backfill behind retaining walls

They illustrate how to apply NCHRP-based simplified stress distribution models to calculate load suitability for geofoam. While simplified, they provide a solid starting point and reinforce the importance of:

• Understanding load interactions at different depths
• Selecting the correct ASTM D6817-compliant geofoam grade
• Involving qualified engineers in final design decisions
  
  

🏗️ Build with Confidence Using R-Shield® Geofoam

Whether you're designing for transportation, infrastructure, or commercial construction, R-Shield Geofoam offers a lightweight yet strong alternative to traditional fill materials. These load calculation examples highlight not only the performance of EPS 22 Geofoam, but also the engineering rigor behind proper material selection.

Need assistance selecting the right grade? R-Shield is here to help your team navigate design and specification with confidence. Contact us today!