MSE wall tendon variants: steel strip, deformed bar, geogrid, welded mesh.

The pullout mechanism determines the tendon choice

Every MSE wall tendon must provide pullout resistance equal to or greater than the design tensile load at every layer. The mechanism by which the tendon develops this resistance is what distinguishes the families:

The first five all rely on friction or passive bearing distributed along the embedded length L_e. The last (anchored MSE) concentrates the pullout resistance at a single point. The economic consequence: friction-based tendons need premium granular fill at phi 36 degrees and above to achieve adequate alpha sigma_v tan(phi); anchored MSE works on phi 34 degrees because K_p dominates the resistance.

1. Galvanised flat steel strip (original Reinforced Earth)

The Henri Vidal original. A flat galvanised steel strip 40 to 100 mm wide and 3 to 5 mm thick. Smooth surface produces interaction coefficient alpha approximately 0.4 to 0.6 with granular fill. Typical design tensile capacity 30 to 100 kN per strip.

Where it suits

• Projects with premium granular fill (phi at least 36 degrees, low fines)
• Long design life (100 to 120 years) with BS 8006 Annex B sacrificial-thickness allowance
• Standard MSE wall geometry where reinforcement length 0.7 H is acceptable

Limitations

• Lower interaction coefficient than ribbed or welded mesh variants
• Premium granular fill cost premium versus crusher run
• Single-strip pullout sensitive to backfill quality variation

2. Ribbed (deformed) steel strip

An evolved Vidal-style strip with surface ribs to increase the interaction coefficient. Alpha rises to 0.8 to 1.4 depending on rib geometry. Allows shorter reinforcement length than smooth strip for the same design load.

Where it suits

• Same applications as flat strip but where shorter reinforcement length is advantageous
• Sites with marginal granular fill where higher alpha compensates for lower phi

3. Carbon-steel deformed bar with deadman block (anchored MSE / AnchorSOL)

A different mechanism entirely. The tendon (typically T20 to T32 deformed bar, hot-dip galvanized) does not rely on distributed friction. It connects the facing panel to a discrete precast concrete deadman block at the tendon end. The deadman mobilises passive earth pressure against the surrounding compacted backfill.

Pullout capacity

For a deadman of dimensions h_block by w_block at depth z below wall top: P_r approximately (K_p minus K_a) gamma z h_block w_block

For typical Malaysian conditions (phi 34 degrees, gamma 20 kN per m^3, K_p approximately 3.5, deadman 500 by 500 mm), pullout capacity at 5 m depth approximately 60 to 80 kN per tendon. Sufficient for typical MSE wall design loads.

Where it suits

• Crusher run backfill (phi 34 degrees and above)
• Hillside cut-and-fill platforms where competent in-situ ground sits close behind facing
• Cyclic loading applications (rail, dynamic)
• Tall walls where reinforcement length economics matter
• Malaysian conditions broadly

The AnchorSOL specialty

AnchorSOL is the Malaysian-developed anchored MSE system. 500+ projects, 1,000,000+ m^2 delivered since 1999. The tendon-deadman geometry is project-specific, with the deadman size and position optimized for the actual backfill and wall geometry at hand.

4. HDPE geogrid

Polymeric reinforcement: high-density polyethylene sheet punched to a regular pattern and stretched (drawn) to develop tensile strength. Junctions are integral (not welded). Short-term tensile strength 30 to 150 kN per metre width.

Where it suits

• Medium-height MSE walls (3 to 10 m) on residential, commercial, township projects
• Combined with segmental retaining wall (SRW) modular block facing
• Geosynthetic-friendly soil environments (low chemical aggressivity)

Design considerations

Creep is the principal long-term concern. The design code requires a creep-reduction factor (typically 0.4 to 0.6) applied to short-term strength to get the long-term design strength over a 100-year design life. Result: a geogrid with short-term strength of 100 kN per m might have long-term design strength of 40 to 60 kN per m.

5. PET woven geogrid

Polyester fibre yarns woven into a grid, coated with PVC or HDPE for UV and abrasion protection. Higher initial stiffness than HDPE geogrid. Short-term tensile strength 50 to 300 kN per metre width.

Where it suits

• Higher-load MSE walls where HDPE creep is limiting
• Combined with precast concrete facing on architectural walls

Design considerations

More creep-sensitive than HDPE in elevated temperature. pH-sensitive in highly alkaline backfill. Both are accounted for via additional reduction factors in design.

6. Welded steel wire mesh

Galvanised steel wires welded into a grid. Combines tensile capacity with high interaction coefficient (passive bearing on transverse wires gives alpha 1.0 to 1.6).

Where it suits

• North American welded-wire-mesh MSE practice
• Less common in Malaysia but feasible on projects following FHWA design standards
• Tall walls where the high alpha allows shorter reinforcement length

7. Polymeric strip composite (PET in HDPE)

A composite tendon: PET fibre core enclosed in an HDPE sheath. Combines PET strength with HDPE durability. Short-term tensile strength 50 to 200 kN per strip.

Where it suits

• Modern architectural MSE walls with precast facing
• Sites where steel is undesirable (specific industrial or aesthetic contexts)

The decision matrix for tendon choice