Using Steel Plates for Trench Crossings with a Mini Excavator

[MikePhua]

The Role of Steel Plates in Compact Excavation
In utility work and small-scale excavation, leaving trenches open for inspection or bedding placement is often unavoidable. When operating compact equipment like the John Deere 35G mini excavator—an 8,800 lb machine with a 1,508 lb side-lift capacity at a 10-foot radius—crossing trenches safely becomes a logistical challenge. Steel plates offer a practical solution, acting as temporary bridges that support the machine’s weight while maintaining access to the trench below.
Steel plates are commonly used in roadwork, demolition, and urban excavation to span voids and protect surfaces. For compact machines, the key is selecting a plate that balances strength, weight, and maneuverability.
Terminology Annotation
- Trench Plate: A steel sheet used to span open trenches, allowing equipment or vehicles to pass safely.
- Heel Planting: A technique where the excavator bucket is pressed against the ground to reduce load on the plate during crossing.
- Fast-Lok Plate: A steel plate with integrated lifting points for secure rigging and placement.
- A514 T1 Steel: A high-strength alloy with a yield strength of 100,000+ PSI, used in structural applications.
- Picking Eye: A welded or bolted lifting point used for rigging and handling heavy plates.
Selecting Plate Thickness and Material
For trench spans of 18 to 36 inches, a ¾-inch thick mild steel plate is generally sufficient to support a mini excavator and a loaded bucket. However, operators often consider reducing thickness to ⅝ inch to save weight and improve handling. This trade-off depends heavily on the steel grade.
Standard A36 mild steel has a yield strength of around 36,000 PSI. In contrast, A514 T1 plate offers a yield strength of 110,000 PSI and tensile strength of 118,000 PSI. By using A514, a ⅝-inch plate can perform comparably to a thicker A36 plate while weighing less—approximately 919 lbs for a 6' x 6' sheet.
For non-road use, such as trench crossings on private sites, the plate does not need to meet DOT standards. However, durability and safety remain paramount. QT100 and other high-tensile steels are also viable options, offering long-term resistance to bending and fatigue.
Handling and Placement Techniques
Moving steel plates with compact machines requires finesse. One effective method involves pinching the plate between the excavator’s blade and bucket, allowing precise placement without swinging loads. This approach minimizes risk and improves control, especially when working perpendicular to the trench.
For more permanent rigging, operators often weld or bolt picking eyes to the plate. A ¾-inch center hole with a threaded nut allows for secure lifting using a Crosby-style rigging system. Some prefer coil rod nuts welded into the plate for quick attachment and removal.
When crossing, heel planting the bucket reduces the center load on the plate until the track frame spans the trench. This technique distributes weight and prevents flexing or deformation.
Design Considerations and Plate Dimensions
A 6' x 6' plate is ideal for machines like the 35G, which has a track width of 67 inches. This size provides adequate coverage while remaining manageable for transport and placement. It can also accommodate wider machines like the 79-inch John Deere 50 in a pinch.
Key design features include:

• Rounded corners to reduce edge damage
  
• Center and side lifting holes for balanced rigging
  
• Welded lifting eyes rated for at least 2x the plate weight
  
• Anti-skid surface treatment if used in wet or sloped conditions
  

Operators should avoid placing plates over trenches wider than 36 inches without additional support or thicker material. For road use, DOT guidelines recommend a 12-inch overlap and 1-inch thickness for speeds under 35 mph.
Field Anecdotes and Practical Lessons
One operator in Washington used a 5/8-inch A514 plate on a jobsite and reported excellent performance. The plate was easy to pick and set, and showed no signs of bending after repeated crossings with an 800 lb bucket of pea gravel. He noted that the seller allowed him to torch custom lifting holes, which simplified rigging and transport.
Another technician in British Columbia recommended QT100 plate for similar applications, citing its durability and resistance to edge wear. A mechanic in Pennsylvania emphasized the importance of avoiding swinging loads when placing plates, especially near utilities or fragile trench walls.
Recommendations for Long-Term Use
To maximize plate lifespan and safety:

• Inspect lifting eyes and welds before each use
  
• Store plates on flat surfaces to prevent warping
  
• Avoid dropping plates or dragging them across abrasive surfaces
  
• Use protective coatings to reduce corrosion in wet environments
  
• Label plates with weight and steel grade for quick reference
  

Operators should also maintain a log of plate usage, noting any signs of fatigue or deformation. Plates used in high-cycle environments may require periodic re-leveling or reinforcement.
Conclusion
Steel plates are indispensable tools for trench management in compact excavation. With the right material, thickness, and handling technique, operators can cross trenches safely and efficiently—even with machines like the John Deere 35G. Whether fabricated from A514 or QT100, a well-designed plate becomes more than a bridge—it’s a foundation for productivity, safety, and precision in the field.