The American Society of Civil Engineers (ASCE) developed the 20-96 standard to fill a critical void: a unified, industry-consensus guideline covering both the structural design and field installation of buried utilities.
For a project engineer designing a new 36-inch storm drain or a 12-inch gas main, here is the practical workflow dictated by ASCE 20-96:
Step 1: Geotechnical Investigation The standard requires a soil classification per the Unified Soil Classification System (USSC). A minimum of one soil test per 500 linear feet of trench is recommended. The American Society of Civil Engineers (ASCE) developed
Step 2: Determine Pipe Stiffness Calculate the pipe stiffness factor (PS) or D-Load for rigid pipes. Compare this to the required strength based on depth of cover.
Step 3: Select Installation Type Choose Installation Type 1 through 4 based on available bedding materials and required long-term deflection. (Type 4 is rarely used today due to cost; Type 3 is the industry gold standard for critical utilities). The standard provides detailed tables for:
Step 4: Calculate Deflection (for Flexible Pipes)
Use the Iowa Deflection Formula (modified by ASCE 20-96):
Δy (%) = (DL * K * Wc * 100) / (144 * PS + 0.061 * E')
Where E' is the soil modulus of reaction (depends on bedding type). The standard provides lookup tables for E' values.
Step 5: Specify Trench Geometry The guideline explicitly prohibits a trench width exceeding the pipe outside diameter plus 24 inches, unless structural reinforcement is added. Wider trenches impose higher loads on the pipe. Unlike earlier guidelines
These shortcomings led to ASCE 20-02, which was later withdrawn entirely as deep foundation design migrated into:
Unlike earlier guidelines, ASCE 20-96 dedicates significant space to pile group efficiency:
ASCE 20-96 emphasizes a load and resistance factor design (LRFD) approach, though it was published when Allowable Stress Design (ASD) was still common. Key formulas include:
The standard provides detailed tables for: