MSE wall method statement: step-by-step construction procedure.

1. Scope

This method statement covers the construction of an anchored MSE (Mechanically Stabilized Earth) wall using precast concrete facing panels, hot-dip galvanised tendons, discrete deadman anchor blocks, and crusher-run granular backfill, in accordance with JKR Standard Specification, BS 8006-1:2010, and FHWA NHI-10-024. The procedure is equally applicable to friction-based RE/RS wall variants with minor adjustments at tendon-installation steps.

2. Reference documents

• JKR Standard Specification for Road Works (current edition) - Malaysian federal-road materials and workmanship requirements.
• BS 8006-1:2010 Code of practice for strengthened/reinforced soils and other fills - primary design code adopted by JKR.
• FHWA NHI-10-024 Design and Construction of Mechanically Stabilized Earth Walls and Reinforced Soil Slopes - US reference for parametric design.
• AASHTO LRFD Section 11.10 - US-equivalent design code.
• Eurocode 7 (EN 1997-1) - European reference, applies on projects with European-influenced design platforms.
• Project-specific shop drawings issued by the wall designer.
• Approved geotechnical report for the site (soil parameters, ground water table, scour assessment if applicable).

3. Personnel, plant, materials

Personnel (typical 3-4 person erection crew + supervisor)

• 1 × site supervisor with MSE wall experience (CIDB Green Card holder, minimum 3 years MSE installation).
• 2 × erectors (CIDB Green Card holders).
• 1 × backfill operative (CIDB Green Card holder).
• 1 × surveyor (engaged at start-of-day for setting out and end-of-day for verification).
• 1 × safety officer (intermittent; CIDB Safety and Health Officer card).

Plant

• Mobile crane (10-20 tonne) for panel lifting.
• Mini-compactor (≤2 tonne plate compactor or ≤1.5 tonne vibratory roller) for compaction within 1 m of facing.
• Vibratory roller (8-15 tonne) for compaction beyond 1 m from facing.
• Excavator / loader for fill placement.
• Total station / theodolite for survey setting out.
• Hand tools: spanners, levels, tape measures, plumb bob.

Materials (per project shop drawing)

• Precast concrete facing panels - Grade 30 MPa minimum, dimensions per shop drawing.
• Hot-dip galvanised steel tendons - diameter and length per design.
• Deadman anchor blocks - precast concrete, dimensions per design.
• Crusher run granular backfill - minimum 34° friction angle, gradation per JKR Standard Specification and BS 8006 Annex A.
• Geocomposite drainage blanket - minimum 5 × 10⁻⁴ m/s transmissivity.
• Granular drainage bedding for toe collection pipe.
• Perforated UPVC or HDPE collection pipe - 100-150 mm diameter typical.
• Geotextile filter wrap for toe drain.

4. Construction procedure, step-by-step

Step 1 - Pre-construction setup

• Conduct toolbox talk + safety briefing covering manual handling, crane lift radius, fall protection at height, working with vibratory plant.
• Surveyor sets out wall alignment, vertical reference at the base, horizontal grid spacing for panel positions.
• Verify foundation level (concrete levelling pad) and tolerance - typical ±10 mm over wall length per JKR specification.
• Confirm panel and tendon delivery schedule. Reject damaged panels (chipped corners, cracks > 0.2 mm width, surface delamination).
• Set up storage area for panels, tendons, anchor blocks. Panels stored vertically on timber spacers; tendons stored off ground; anchor blocks stacked with timber dunnage.

Step 2 - Foundation preparation

• If pile foundation specified: complete piling and pile cap before wall starts.
• If ground improvement specified (PVDs + preload, stone columns, jet grouting): complete improvement, verify settlement plate readings stabilised within design tolerance.
• Cast in-situ concrete levelling pad - typically 300-600 mm wide, 150-200 mm thick, Grade 25 MPa, plain concrete. Cure 3 days minimum before panel placement.
• Verify levelling pad surface flatness with straight edge - ±5 mm over 3 m.

Step 3 - Bottom course panel placement

• Crane lifts panels using designed lifting points (typically lifting hooks cast in top of panel).
• Place each panel on the levelling pad in survey-set position.
• Set panel verticality with plumb bob - tolerance ±10 mm over panel height.
• Set panel-to-panel horizontal spacing (typically 10-15 mm joint) and stagger pattern per shop drawing.
• Use timber wedges or shims to maintain alignment during back-filling - remove progressively as fill builds up to mid-panel level.

Step 4 - Drainage installation

• Roll out geocomposite drainage blanket flat against the back of the facing panels, overlap 200 mm at joints.
• Excavate toe drain trench parallel to and ~500 mm behind facing.
• Wrap geotextile filter around granular bedding (typically 20-40 mm clean gravel).
• Place perforated collection pipe in trench. Connect to outlet positions at design intervals.
• Close geotextile wrap over pipe and bedding.

Step 5 - First lift of backfill

• Place crusher-run fill in lifts not exceeding 300 mm loose thickness, typically 200-250 mm.
• Within 1 m of facing: hand-tamp or mini-compactor only. Heavy vibratory plant prohibited in this zone to prevent panel displacement.
• Beyond 1 m from facing: vibratory roller, multiple passes (typically 6-8 passes for crusher run).
• Verify compaction to 95% Modified Proctor MDD on every layer - nuclear density gauge or sand-replacement test.
• Reject layer if compaction below specification; rework before next lift.

Step 6 - Tendon and anchor block installation

• Install tendons through pre-formed holes in facing panels.
• Set deadman anchor blocks at design distance behind facing (typically 0.7-0.9 × wall height for anchored MSE).
• Tighten tendon-to-anchor connection per shop drawing torque specification.
• For friction-based RE/RS variants, lay reinforcement strips horizontally on the compacted lift and extend the design length into the retained fill.

Step 7 - Repeat lift-by-lift

• Place next course of facing panels, with vertical alignment maintained from below.
• Extend drainage geocomposite upward.
• Place next backfill lift; compact; install tendons / reinforcement.
• Repeat until design wall height achieved. Typical erection rate: 30-80 m² of wall face per gang per day.

Step 8 - Top course and capping

• Place top course of facing panels.
• Cast in-situ capping beam if specified (typically 200-400 mm × wall thickness × wall length, Grade 30 MPa, reinforced).
• Connect drainage outlets to site drainage network.

Step 9 - Survey, instrumentation baseline, handover

• Surveyor records final facing position, verticality, level. Tolerances per JKR specification: ±10 mm horizontal, ±10 mm vertical over panel height, ±30 mm over total wall length.
• Take baseline readings from settlement plates and inclinometers (if specified).
• Issue handover documentation: as-built drawings, compaction test records, panel inspection records, instrumentation baseline.
• Defects-correction period: typically 12-24 months, with quarterly inspection of facing alignment and drainage outlets.

5. Safety / HSE

• Crane operations: exclusion zone within lift radius; trained banksman; daily crane inspection; load-test certificate current.
• Manual handling: tendons, anchor blocks, panel components weighing >25 kg require two-person handling or mechanical aid.
• Working at height: fall arrest harness above 1.8 m; edge protection at top of wall during construction; ladders inspected and tagged.
• Vibratory plant: hearing protection mandatory in 7 m radius around vibratory rollers; HAVS (hand-arm vibration syndrome) limits per DOSH guidelines.
• Confined space: not typically applicable to MSE construction; if soil-mixed columns or deep drainage chambers are involved, confined-space permit-to-work system applies.
• Adjacent traffic: staged traffic management plan, lane closures, signage; coordination with road authority.
• CIDB requirements: all site personnel hold valid Green Card; safety officer card current; toolbox talk records maintained.

6. Quality control checkpoints