Geotechnical & retaining wall glossary (A-Z).

A

AASHTO LRFD - American Association of State Highway and Transportation Officials Load and Resistance Factor Design. The US bridge / highway design framework, occasionally cited on Malaysian projects with North American consultants. Section 11.10 covers MSE wall design.

Active earth pressure - The lateral earth pressure exerted by retained soil on a wall that yields slightly outward, allowing the soil to mobilise its shear strength. The minimum lateral pressure case. Coefficient KA per Rankine or Coulomb theory. See backfill mechanics.

Anchored MSE wall - The AnchorSOL variant of Mechanically Stabilized Earth wall, where pullout resistance is concentrated at a discrete deadman anchor block at the back of each tendon rather than distributed along the full reinforcement length. Allows the wall to run on crusher run instead of premium granular fill. See anchored vs reinforced soil.

AVIF / WebP - Modern image formats; not geotechnical, but they make web pages load faster.

B

Backfill - The granular material placed and compacted behind the wall facing during construction. The MSE wall's structural mass. See backfill mechanics and granular fill.

Bearing capacity - The maximum vertical load the foundation soil can sustain without shear failure. Critical for MSE wall foundation design. See foundation design.

Bishop method - The simplified Bishop method of slope stability analysis, using circular slip surfaces with horizontal interslice forces. Standard for slope-stability checks on Malaysian hillside projects. See slope stability analysis.

BS 8006-1:2010 - British Standard "Code of practice for strengthened/reinforced soils and other fills". The primary design code for MSE walls adopted by JKR for Malaysian federal-road projects.

C

Cantilever wall - Reinforced-concrete retaining wall that resists overturning by self-weight and structural action of its stem-and-base geometry. Typical RC alternative to MSE for short walls. See RC retaining wall design.

CIDB - Construction Industry Development Board Malaysia. Registers contractors and certifies site personnel (the "Green Card" + safety officer cards).

Coefficient of earth pressure (K) - Ratio of lateral to vertical effective stress. KA = active, KP = passive, K0 = at-rest. Drives the magnitude of lateral pressure on the wall.

Compaction - The mechanical densification of fill material during placement. Specified as a percentage of Modified Proctor MDD (Maximum Dry Density), typically 95% for MSE backfill.

Compound stability - A failure mode where the slip surface passes partly through the reinforced soil mass and partly through the retained earth or foundation. Checked alongside internal and external stability.

Connection strength - The capacity of the joint between the facing panel and the reinforcement to transfer load. A specific limit-state check per FHWA NHI-10-024.

Counterfort wall - A tall RC retaining wall with vertical stiffening ribs (counterforts) on the back face. Used when the stem-flexure of a plain cantilever becomes excessive. See counterfort RC wall.

Crusher run - Crushed-stone aggregate at angular gradation, friction angle ≥34°, locally available across Malaysia. The preferred backfill for anchored MSE walls. See crusher run as MSE backfill.

D

Deadman anchor block - A precast concrete block buried at the back end of each tendon in an anchored MSE wall. Provides discrete bearing resistance against pullout, transferring tendon tension into competent retained soil.

Design life - The intended service period for which the wall is engineered. Standard values: 75, 100, or 120 years. Drives the sacrificial-thickness corrosion allowance on galvanised tendons. See design life and corrosion.

Diaphragm wall (D-wall) - Cast-in-place reinforced-concrete wall constructed in a slurry-supported trench. The most expensive engineered retaining wall, used for deep urban basement perimeters. See the retaining wall comparison.

Differential settlement - The difference in settlement between two points along (or across) a structure. MSE walls tolerate larger differential settlement than rigid RC walls because the composite mass yields elastically.

Drainage blanket - A geocomposite or granular layer placed behind the wall facing to relieve pore-water pressure and prevent saturated-fill failure modes. See drainage design.

E

Earth pressure - The lateral force exerted by soil against a retaining structure. Magnitude depends on soil properties, wall geometry, and wall movement.

Eurocode 7 (EN 1997-1) - The European geotechnical design framework. Increasingly cited on Malaysian projects with European-influenced consultant teams.

Eurocode 8 (EN 1998-5) - European seismic-design code. Part 5 covers foundations, retaining structures, and geotechnical aspects. Adopted in Malaysia as MS EN 1998-5. See seismic design.

External stability - Stability checks on the reinforced-soil mass treated as a rigid body: overturning, sliding, bearing capacity, eccentricity.

F

FHWA NHI-10-024 - US Federal Highway Administration design manual "Design and Construction of Mechanically Stabilized Earth Walls and Reinforced Soil Slopes". The principal US reference for MSE wall design, parallel to BS 8006.

Friction angle (phi) - The angle whose tangent equals the soil's friction coefficient. For granular fill, drives the active and passive earth-pressure coefficients. Crusher run typically achieves ≥34°.

G

Galvanising (hot-dip) - The process of coating steel with a sacrificial zinc layer for corrosion protection. Tendons in MSE walls are typically hot-dip galvanised, with the zinc thickness selected per the design-life corrosion allowance.

GBI (Green Building Index) - Malaysian green-building rating system. MSE walls contribute to credit through lower embodied carbon vs RC. See embodied carbon.

Geocomposite - A composite drainage material combining a geotextile filter with a drainage core (typically polymer mesh or cuspated sheet). Used behind MSE wall facings for drainage.

Geogrid - A polymer-grid reinforcement material (HDPE or PET) used in friction-based MSE / RS walls. Engages soil through aperture interlock.

Geotextile - A permeable polymer fabric (woven or non-woven). Used as a filter (separating fine soils from drainage layers) and occasionally as primary reinforcement in wrapped-face walls.

Global stability - The overall stability of the wall + retained soil + foundation against a deep-seated slip-circle failure. Checked separately from external stability. See slope stability analysis.

Granular fill - Cohesionless soil (sand, gravel, crusher run) with adequate friction angle for use as MSE backfill. See granular fill.

GRS-IBS - Geosynthetic Reinforced Soil Integrated Bridge System. The FHWA-codified true-abutment system using closely-spaced geosynthetic reinforcement. See true vs false bridge abutment.

Ground improvement - Techniques to strengthen soft foundation soil: prefabricated vertical drains (PVDs) + preload, stone columns, jet grouting, deep mixing, vibro-replacement.

I

IEM - The Institution of Engineers, Malaysia. Professional body for chartered engineers.

Inclinometer - A drilled vertical casing with a probe lowered to measure lateral ground movement at depth. Standard MSE wall monitoring instrument. See instrumentation and monitoring.

Internal stability - Stability checks on the reinforcement within the MSE wall mass: tensile failure, pullout failure, connection failure. Separate from external stability checks.

J

Jet grouting - A ground-improvement technique using high-pressure cement-grout jets to mix or replace in-situ soil. Used to create stiff columns supporting MSE wall foundations on soft ground.

JKR - Jabatan Kerja Raya (Public Works Department), Malaysia. The federal infrastructure authority responsible for trunk roads, federal buildings, and other federal works.

L

Lateral earth pressure - The horizontal pressure exerted on a retaining wall by retained soil. See active and passive earth pressure.

LLM - Lembaga Lebuhraya Malaysia (Malaysian Highway Authority). Oversees federal expressway concessions.

LRFD - Load and Resistance Factor Design. The limit-state design approach with partial factors on both load and resistance.

M

MASMA - Manual Saliran Mesra Alam, the Malaysian urban stormwater design manual published by JPS.

MBI / MBSA / MBPJ / MBPP / MBJB / etc. - Majlis Bandaraya (City Council) for various Malaysian cities. MBI = Ipoh, MBSA = Shah Alam, MBPJ = Petaling Jaya, MBPP = Penang Island, MBJB = Johor Bahru, MBSJ = Subang Jaya, MBIP = Iskandar Puteri, MBMP = Miri.

Mononobe-Okabe - The pseudo-static seismic earth-pressure method extending Coulomb theory with horizontal and vertical seismic coefficients. The standard simplified seismic check for MSE walls per Eurocode 8 Annex E.

MSE wall - Mechanically Stabilized Earth wall. A composite retaining structure where granular fill is reinforced with horizontal layers (strips, grids, or anchored tendons) tied to a facing. See what is an MSE wall.

N

Newmark method - A displacement-based seismic analysis method for slopes and walls, treating the sliding mass as a rigid block. Less conservative than Mononobe-Okabe for moderate seismicity.

O

Overturning - The failure mode where the wall rotates about its toe under lateral earth pressure. One of the external stability checks.

P

Partial factor - The multiplier applied to characteristic loads or resistances in limit-state design to produce design values. Specified in design codes (BS 8006, Eurocode 7, AASHTO LRFD).

Passive earth pressure - The maximum lateral pressure exerted by soil compressed against a wall (wall moves toward the soil). Coefficient KP.

Piezometer - An instrument measuring pore-water pressure in the soil. Standard MSE wall monitoring instrument, especially on soft-ground sites.

PGA (peak ground acceleration) - The maximum horizontal ground acceleration during a design earthquake, expressed as a fraction of gravitational acceleration g. Malaysian Peninsular typically 0.02-0.10g, Sabah Ranau corridor up to 0.20g.

PLUS - PLUS Malaysia Berhad. The largest Malaysian expressway concessionaire, operating the North-South Expressway and several other corridors.

Pullout capacity - The maximum tensile force a reinforcement can sustain without being pulled out of the retained soil. One of the internal-stability limit states. See pullout testing.

PVD (prefabricated vertical drain) - A pre-fabricated drainage strip driven vertically into soft soil to accelerate consolidation under preload. Standard ground-improvement technique for MSE walls on soft-ground sites.

R

Rankine method - A classical earth-pressure theory assuming a smooth vertical wall and horizontal backfill. Simpler than Coulomb but more restrictive in scope.

RE wall (Reinforced Earth) - The original MSE wall variant (Henri Vidal, 1963) using steel-strip reinforcement and cruciform precast facing. See reinforced earth wall.

Residual soil - Soil formed by in-place weathering of bedrock. The dominant Malaysian inland soil type (granitic residual soil in the Klang Valley, sedimentary residual soil in Pahang east).

RS wall (Reinforced Soil) - Modern MSE variant using geosynthetic (geogrid, geotextile) reinforcement. Lighter and faster than steel-strip RE but with shorter design life. See reinforced soil wall.

S

Sacrificial-thickness allowance - Additional steel or zinc thickness added to tendons to allow for corrosion loss over the design life. Sized per FHWA NHI-10-024 or BS 8006 Annex B.

Seismic coefficient (kh, kv) - The pseudo-static accelerations used in Mononobe-Okabe analysis. kh = horizontal, kv = vertical. Derived from PGA and soil-profile factor S per Eurocode 8.

Settlement plate - A horizontal steel plate at foundation level with a vertical riser pipe. Survey the riser elevation over time to measure foundation settlement.

Sheet pile wall - A driven-in retaining wall of interlocking steel or precast sheets. Standard for waterfront and temporary works. See MSE vs sheet pile.

Slope stability analysis - Engineering analysis verifying that a slope (or wall + retained slope) is stable against failure. See slope stability analysis.

Soil nailing - A cut-slope stabilisation technique using drilled-and-grouted steel bars (nails) with shotcrete face. See soil nailing vs MSE.

SPT (Standard Penetration Test) - The standard in-situ soil test. Drops a 63.5 kg hammer 760 mm onto a sampler; the blow count to drive 300 mm is the "SPT N-value", a proxy for soil density and strength.

SRW (Segmental Retaining Wall) - A dry-stacked modular-block wall variant. North American terminology equivalent to "modular block retaining wall".

Stone column - A ground-improvement technique using vibro-replacement to create granular columns through soft soil, reducing settlement and increasing bearing capacity.

Surcharge - Additional vertical load applied on the retained-soil surface (traffic, slab loading, stockpiled material). Increases lateral earth pressure on the wall.

T

TBM (Tunnel Boring Machine) - A large mechanical excavator that bores tunnels in a single pass. Launched and retrieved from shafts; portal walls retain the approach embankment.

Tendon - The reinforcement element in an anchored MSE wall: hot-dip galvanised steel rod, connecting the facing panel to a deadman anchor block at the back of the reinforced mass.

True abutment - A bridge abutment configuration where the bridge bearings sit directly on the reinforced soil mass. The MSE wall both retains the embankment and supports the bridge. See true vs false bridge abutment.

U

ULS / SLS - Ultimate Limit State / Serviceability Limit State. The two main check categories in limit-state design. ULS = collapse / failure prevention; SLS = function / deformation under normal service.

W

Wire-faced MSE wall - An MSE wall variant using welded wire mesh as the facing rather than precast concrete panels. Used for temporary works and fast-build approach embankments. See wire-faced MSE wall.