Lower Risk Installation
Concrete pipe far outperforms plastic or metal. Concrete’s rigidity and mass allow for easy and secure placement in the ditch, without disrupting line or grade. Plus, precast concrete pipe joints are easily assembled, which helps minimize the time needed for installation. When installation time matters, or when the soil poses challenges to installation, precast concrete pipe is quite simply the most logical and responsible option. Since concrete pipe is a rigid pipe system that is over 85% dependent on the pipe strength and only 15% dependent on the strength derived from the soil envelope, installation is made easy. In many situations, the installation of plastic or metal pipes can take longer than precast concrete pipe. That’s because the structural and hydraulic integrity of flexible pipes rely heavily on how well you prep the surrounding soil at installation, rather than on their own inherent brute strength. Making sure all conditions are right and installing per national specifications can be a costly and time-consuming proposition when installing flexible pipe.
Concrete pipe has an unlimited range of pipe strengths from which to choose, and strength is demonstrated prior to installation. By specifying concrete pipe:
- The designer has more control over pipe strength than any other facet of the project
- There is less reliance on quality installation by the installer
- There is lower embedment material cost
- There is less compaction required
- It is easier to maintain grade and alignment
- There are no excess deflection concerns
- There is a lower life cycle cost of the project
- There is a lower maintenance cost over the design life of the project
- There is a reduced likelihood of failure
- A lower risk for the specifier, designer and owner of the project, and reduced overall liability to the public after the project has been commissioned
Standard Installations is a term for a technology used for precast concrete pipe beddings. Design of the pipe wall – its thickness and amount of reinforcement – is based on the stresses and strains in the pipe. This approach is more precise and can result in pipes that require less material. In addition, the standard installations approach permits greater choice of backfill materials, from granular materials to clay, and needs less compaction of the backfill.
Standard Installations were adopted by the American Society for Civil Engineers (ASCE) as Specification 15-93-Standard Practice for Direct Design of Buried Precast Concrete Pipe Using Standard Installations. It was adopted later in the 1996 (16th) Edition of the American Association of State Highway and Transportation Officials (AASHTO) Standard Specification for Highway Bridges, Section 17, Soil-Reinforced Concrete Structure Interaction Systems.
Standard Installations provide several benefits when using concrete pipe:
- Provides flexibility to meet design requirements and site conditions
- Allows for narrower excavation limits
- Less expensive backfill materials may be used
- Can reduce the level of compaction
- Increases contractor productivity in installing reinforced concrete pipe
There is a choice of Types of Standard Installations that provide versatility to adapt to field conditions.
- Type 1: Highest Quality installation using select granular soils with high compaction requirements for haunching and bedding.
- Type 2: Allows silty granular soils with less compaction required for haunching and bedding.
- Type 3: Allows use of soils with less stringent compaction requirements for haunching and bedding.
- Type 4: Allows use of onsite native material for haunching and bedding with no compaction required. (6 inches of bedding is required if rock foundation)
The short lengths of concrete pipe make it easier to work with around existing municipal services. Concrete pipe installations using trench boxes do not require special attention to sliding the trench box and disturbing the bedding and backfill in the process, referenced by all installation standards and recommendations of manufacturers. Using standard lengths of concrete pipe, line and grade can be checked frequently for accuracy.
