wilmington tunnel fill slide

Tunnel Abandonment

By applying unique solutions to increase the safety and longevity of our environment.

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Facing a tunnel abandonment challenge?  CJGeo specializes in long run and high volume tunnel abandonment grouting.  We can generate up to 1000CY/day of CJFill cellular grout from bulk cement. This lets us work in remote sites, and avoid the logistical constraints associated with ready mix or aggregate-based mixes.

The Mechanics

Mix Design

25PCF wet cast density CJFill is the most common tunnel abandonment mix.  This yields an average compressive strength of 70psi at 28 days.  Higher densities can be used to achieve higher break strengths if required by project conditions.  However, cost increases with density. The lower the density, the longer runs are achievable per placement point, and the lower the cost per cubic yard in place.  Unlike sanded flowable fill mixes, cellular concrete does not segregate. Therefore, high factors of safety aren’t required to ensure adequate bearing capacity and/or long term stability.

Placement Method for Tunnel Abandonment

Depending on the tunnel size, slope, and existing access points, cellular concrete is usually pumped via sacrificial pipes.  Tremmie placement into shafts or access holes is the most economical method, however relies on gravity to ensure complete fill, so is rarely used.  Cellular concrete can easily be pumped 3000+ feet through abandoned pipes.  Therefore, cellular concrete requires far fewer injection points than traditional flowable or pumpable fill.

We install both prepolymer grouts (expansive) and acrylic grouts (non-expansive).

The Advantages

Risk Reduction

There are two typical risks associated with traditional methods of tunnel abandonment: incomplete fills due to the physical limitations of flowable fill, and those associated with access point excavation, such as utility strikes.

The risk from incomplete fills is primarily related to the difficulty of pumping flowable fill. Since flowable fill relies heavily upon water content to ensure flowability, it is particularly prone to segregation. This segregation can lead to aggregate settling out and blocking a pipe. The higher the pump pressure, the more it packs the aggregate, making it impossible to overcome.

Since utilities being abandoned are typically colocated with other utilities, reducing excavation is almost always advantageous. Using cellular concrete virtually eliminates access point excavations due to very long pumping distances.

Cost Reduction

Because cellular concrete reduces the need for digging access points and the time it takes to perform abandonments, it tends to be significantly less expensive than traditional methods.

We perform turnkey abandonments; there’s no need for our customers to coordinate pump services, ready mix companies, etc.

Increase Speed

Our customers are almost always amazed by how quickly abandonments happen compared to self-performing with flowable fill. That 3000LF of 8″ that the owner said needed an access point every 200LF? It’s just 18 minutes of pumping with 25lb/cuft cellular concrete from a single point.

Speak With An Expert

Facing a challenge? Give us a shout or shoot us a text. Click the state marker for the location of the project for contact info for the appropriate rep.

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