Using Shotcrete for Steep Slope Stabilization

November 30, 2016

A report from the National Cooperative Highway Research Program classifies about 75 percent of U.S. roads as “low-volume” roads created and maintained by local rather than state or federal agencies. Unfortunately, these agencies often omit an important engineering step when they build these roads, reasoning that it’s unnecessary because the roads experience minimal traffic. This step is called surface slope protection, and it’s important to the integrity of road stability.

What Is Steep Slope Stabilization?

Steep slope stabilization is the practice of shoring up and reinforcing infrastructure to minimize the risk of road collapse. On both paved and unpaved roads that lack surface slope protection, gravity, temperature fluctuations and precipitation change a road’s slope over time. Steep slopes that aren’t adequately stabilized are at risk of collapsing and causing dangerous mudslides and rock slides that threaten motorists, render roads impassable, and result in the need for expensive and complex repairs.

What Is Shotcrete/Gunite?

Shotcrete, also known as gunite, is concrete that is sprayed in wet form through a hose onto a surface at a very high velocity. The material conforms to the profile of whatever it’s being sprayed onto (dirt, rocks, wood, etc.) When it dries, it leaves behind a strong, hard, impenetrable surface. Shotcrete/gunite adheres to any surface, dries quickly and can be used in the absence of forms. When hardened, shotcrete exhibits similar properties to conventional cast-in-place concrete. In fact in some cases, including susceptibility to cold-joint issues, shotcrete delivers an end result that is far superior to cast-in-place applications.

How Shotcrete Is Used in Infrastructure

Shotcrete is an invaluable tool for stabilizing infrastructure, including roads and tunnels. It’s as hard as cast-in-place concrete but is far more versatile. It’s the ideal solution for repairing and retrofitting infrastructure in challenging environments in which cast-in-place methods aren’t feasible. Stabilizing precariously steep road slopes is one prime example. Other uses of shotcrete besides stabilizing roadways when it comes to addressing infrastructure challenges include shoring up deteriorating piers, berth faces, dams, bridges and hydraulic structures in marine applications.

Modern shotcrete technology gives local agencies with limited budgets a cost-effective, durable option for building new and stabilizing existing infrastructure.