Reinforced Earth Wall (RE Wall)

Reinforced Earth Wall (RE Wall) serves the critical function of supporting soil laterally, retaining it at different levels on both sides of a roadway. This construction method involves a combination of earth and linear reinforcements, such as strips, grids, rods, or mesh, designed to withstand substantial tensile stress.

Elements of Reinforced Soil Wall:

1.Facia Panel/RE Panel:

– Concrete grade: Minimum M35.
– Facia panel thickness: 180mm.
– Spacing maintained using Ethylene Propylene Diene Monomer (EPDM) Pads.

2.Reinforced Fill:

– Borrowed material with specific geotechnical properties.
– Properties include the absence of organic material, specific grain size, plasticity index, bulk density, and drained shear strength.

3.Drainage Media/Filter Media:

– Typically 600 mm width for drainage behind RE panel.
– May use profiled blocks for facia with drainage provisions.

4.Reinforcement:

– Metallic or polymeric elements extending beyond the Rankine zone for proper anchorage.
– Quality control tests include tensile strength, installation damage, creep, pullout tests, carboxyl end group, and molecular weight.

5.Crash Barrier:

– Integral for impact resistance.

Reinforced Earth Wall Construction Sequence:

1.Excavation:

– Adherence to construction drawings.
– Compaction to prevent settlement.

2.Levelling Pad:

– Initial 150mm thick M20 concrete pad below the first fascia layer.

3.Facia Placement:

– Careful alignment of facing elements during the first layer placement.

4.Drainage Material:

– Compacted layer-wise.

5.Reinforced Soil Placement:

– Compacted to 95% density in layers not exceeding 200mm thickness.

6.Reinforcement Placement:

– Avoid direct movement of construction equipment over reinforcement.
– No protrusion of reinforcement from facia.

Construction Tolerances:

– Dimensions of precast RCC facia panel within ±5mm.
– Front face evenness ±5mm over 1500mm.
– Maximum difference between diagonal lengths: 5.00mm.
– Thickness of RS Wall facia panel within ±5mm.

Causes of Failure:

1. Inadequate Levelling Pad Construction
2. Compaction and Reinforced Fill Properties
3. Abnormal Drainage System
4. Improper Connection to Facia
5. Variations to Specifications/Drawings
6. Proximity of Heavy Compaction Equipment
7. Filter Material Non-compliance
8. Missing Primary Batter in Panels

Potential Failures:

– Excessive settlement and facia panel bulging.
– Distortion/leaning of the wall and uneven riding surface.
– Clogging of drainage.
– Leaning and eventual collapse of panels/blocks leading to local failures.

This construction method involves a series of intricate steps to ensure the stability and longevity of the reinforced earth wall. Excavation is performed according to detailed construction drawings, followed by careful compaction to prevent any settlement in the foundation soil.

An initial levelling pad of 150mm thickness, made of M20 grade plain cement concrete, is crucially placed below the first row of the facia layer.

The facia placement is a meticulous process, especially during the initial layer, requiring utmost care to maintain the alignment of the facing elements. Drainage material, or filter media, is then introduced and compacted layer by layer to ensure effective drainage behind the RE panel.

The reinforced soil fill is subsequently placed and compacted to achieve a density of 95%, with each layer not exceeding 200mm in thickness.

The reinforcement material, whether metallic or polymeric, undergoes stringent quality control tests such as tensile strength, installation damage, creep, pullout tests, carboxyl end group, and molecular weight checks.

Proper placement of the reinforcement is essential, with construction equipment strictly avoiding direct movement over the reinforcement, and ensuring no protrusion of reinforcement from the facia.

Construction tolerances are carefully adhered to, with dimensions of precast RCC facia panels, front face evenness, diagonal lengths, and facia panel thickness all maintained within ±5mm. These tolerances are crucial for achieving the desired structural integrity.

Failures in reinforced earth walls can be attributed to various factors, including inadequate levelling pad construction, issues with compaction and reinforced fill properties, abnormal drainage systems, improper connection to facia, variations to specifications or drawings, proximity of heavy compaction equipment, filter material non-compliance, and the absence of a primary batter in panels.

These failures can lead to consequences such as excessive settlement and bulging of facia panels, distortion or leaning of the wall, uneven riding surfaces, clogging of drainage, and even the collapse of panels or blocks, resulting in local failures.

Understanding and addressing these potential failure points is essential for the successful implementation of reinforced earth walls, emphasizing the importance of quality control measures, precise construction sequences, and adherence to specified tolerances.

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