In the world of heavy lifting, site conditions often dictate equipment selection more than any other factor. When operating on soft, unstable, or low-bearing-capacity ground, choosing the correct crane is critical—not only for efficiency, but for safety, stability, and long-term structural integrity of the worksite.
Two of the most commonly considered crane types in such conditions are crawler cranes and rough terrain (RT) cranes. Each has its own operational strengths, but when it comes to performance on soft ground, the differences are significant.
Understanding the Design Fundamentals
Crawler cranes are mounted on a pair of continuous tracks, which distribute the machine’s weight over a much larger surface area than conventional wheeled cranes. This design inherently results in significantly lower ground-bearing pressure, making them ideal for work on soft or saturated soil conditions.
In contrast, rough terrain cranes are four-wheeled, self-propelled hydraulic cranes designed specifically for pick-and-carry operations in confined or uneven areas. Their high ground clearance and all-wheel drive allow them to navigate rugged terrain, but their point load distribution is considerably higher, especially when outrigger pads are not supplemented with load-distributing mats.
Ground Pressure: The Deciding Factor
From a geotechnical standpoint, ground pressure is a primary factor in crane selection for soft terrain. The ground pressure exerted by crawler cranes typically ranges from 1.0 to 3.0 psi, depending on load and track configuration. This is significantly lower than that of rough terrain cranes, which may exceed 10 psi at the tires or outrigger contact points, especially under heavy load conditions.
For comparison, many soft or muddy soils may have a safe bearing capacity below 2,000 psf (13.9 psi). Without adequate matting or ground preparation, a rough terrain crane can easily exceed this threshold and become immobilized or worse—experience a structural failure due to ground subsidence.
Load Mobility and Stability on Site
One of the operational advantages of crawler cranes is their ability to walk with a suspended load. This feature is crucial on undeveloped sites where surface preparation is minimal or roadways are incomplete. With proper rigging and load management, the crane can reposition materials without requiring a full breakdown or repositioning by transport.
Rough terrain cranes, although mobile within the site when unladen, cannot travel with suspended loads in most scenarios. Their stability relies heavily on the use of outriggers, which must be fully deployed and leveled before lifting. In soft ground scenarios, these outriggers often require steel mats or cribbing to prevent sinking, which adds to setup time and logistical complexity.
Site Preparation and Logistical Considerations
It’s important to acknowledge that crawler cranes do require more in terms of transport logistics. They are typically disassembled and moved in parts via flatbed trailers, then reassembled on-site using assist cranes. However, once mobilized, they offer excellent lifting capacity and reach, particularly for long-duration projects where daily relocation is not necessary.
Conversely, rough terrain cranes offer rapid mobilization and deployment, often arriving fully assembled and ready to lift. This makes them favorable for shorter-duration work or sites with variable tasks requiring frequent repositioning—assuming the ground is suitably firm or reinforced.
Practical Case Observations
In past projects involving low-lying industrial developments or pipeline installations over marshland, crawler cranes have consistently outperformed their wheeled counterparts. Their ability to traverse inconsistent soil profiles without compromising stability has proven invaluable. In contrast, RT cranes deployed without sufficient ground prep have resulted in delays, recovery operations, and in one instance, structural compromise of the outrigger supports due to insufficient load spread.
Conclusion: Making the Right Choice
For operations on soft or unstable ground, crawler cranes provide superior performance, safety, and operational reliability. Their low ground pressure, high lifting capacity, and mobility under load make them the preferred solution in most geotechnically challenging environments.
Rough terrain cranes, while versatile and cost-effective in suitable conditions, require significant site preparation to be viable in soft ground applications. When time, budget, and safety are non-negotiable, investing in the right crane from the start can prevent costly overruns and avoidable incidents.
