h/Deq Ratio in Geocells
What is the h/Deq Ratio?
The h/Deq ratio is a dimensionless geometric parameter defined as:
- h = geocell height (depth)
- Deq = equivalent diameter of the geocell pocket (based on area equivalence)
It represents the proportion between cell depth and plan geometry, allowing different geocell configurations (non-circular cells) to be compared using a common parameter.
Engineering significance
The h/Deq ratio is an important geometric index influencing the confinement efficiency of geocell systems. It affects how effectively the geocell mobilizes:
- Lateral restraint of infill
- Passive resistance along cell walls
- Load distribution to the subgrade
However, it does not directly measure lateral stress. Instead, it influences the ability of the system to develop confinement under loading.
Role in confinement mechanism
Geocell reinforcement works primarily through:
- Lateral restraint of infill material
- Development of apparent cohesion
- Load spreading (slab effect)
The h/Deq ratio affects these mechanisms as follows:
- Low h/Deq (shallow cells / large pockets):
- Limited wall contact area
- Reduced confinement
- Higher chances of lateral spreading
- High h/Deq (deep cells / smaller pockets):
- Increased wall interaction
- Improved confinement
- Reduced lateral deformation
Practical behaviour
Increasing h/Deq generally:
- Improves stiffness and load distribution
- Reduces rutting and deformation
However:
- Beyond an optimal range, additional increase gives diminishing returns
- Performance becomes controlled by material properties and subgrade conditions, not geometry alone
Typical design insight
Although values depend on application:
- Very low h/Deq (< ~0.5) → insufficient confinement
- Moderate range (~0.5–1.5) → effective performance
- High values (> ~1.5–2) → marginal improvement vs cost
(Ranges are indicative and must be validated by testing or guidelines)
Applications
1. Pavements
- Influences aggregate confinement and rut resistance
- Higher h/Deq → better performance on weak subgrades
2. Railways
- Helps reduce ballast movement and degradation
- Improves resistance to cyclic loading
3. Slopes and Embankments
- Enhances shear resistance and stability
- Improves anchorage of infill
4. Hydraulic Structures
- Controls erosion and particle washout
- Improves stability under hydraulic forces
5. Retaining Systems
- Affects facing stability and deformation behavior
Limitations
The h/Deq ratio cannot be used independently for design. Its effectiveness depends on:
- Infill material properties (gradation, friction angle)
- Compaction quality
- Geocell stiffness and material
- Subgrade strength
- Loading conditions (static vs cyclic)
Design considerations
A rational design should:
- Select h/Deq based on application-specific performance requirements
- Ensure compatibility between:
- Cell size and aggregate size
- Cell depth and expected stress level
- Consider constructability and cost efficiency
- Validate using:
- Laboratory tests
- Field performance data
Key takeaway
The h/Deq ratio is a useful geometric design parameter, not a standalone performance indicator. It helps optimize geocell design by balancing:
- Confinement efficiency
- Material usage
- Structural performance