Reference · Glossary · 65+ terms

Geosynthetics and geotechnical glossary for Malaysian engineers.

A working glossary covering 65+ terms used in geosynthetics design, specification, and construction in Malaysian conditions. Geotextile, geogrid, geocell, geomembrane, geocomposite, soil mechanics, slope stabilisation, retaining walls, test methods, and standards. Each entry includes a definition plus the relevant test standard or code reference. Free reference for consulting engineers, QS, spec writers, authority reviewers, and procurement teams.

65+

Terms defined

Topic categories

Free

No registration

CIDB G7

Working reference

Geotextile Geogrid Geocell Geomembrane Geocomposite Soil mechanics Slope stabilisation Retaining wall Test methods Standards & codes

Category 01

Geotextile terms

Geotextile: Permeable textile material used in geotechnical applications for one or more of five functions: separation, filtration, drainage, reinforcement, or protection. Woven (intersecting yarns) or nonwoven (randomly bonded fibres). Made from polypropylene (PP) or polyester (PET) polymer. Specified per AASHTO M288, BS EN 13249-13257, ASTM D-series, or BS EN ISO 10319. Mass per unit area typically 100 to 800 gsm.
Woven geotextile: Geotextile formed by interlacing two perpendicular sets of yarns (warp and weft). Higher tensile strength per gsm than nonwoven, lower elongation, lower in-plane drainage capacity. Used for separation, basal reinforcement on soft ground, and high-strength reinforcement. Two sub-families: slit-film (woven from flat polymer ribbons, lower cost) and woven monofilament or multifilament (higher performance, used for high-strength geotextile like StrataTex HSR).
Nonwoven geotextile: Geotextile formed by randomly oriented fibres bonded by needle-punching, thermal bonding, or chemical bonding. Higher elongation, better in-plane drainage and filtration than woven. Used for filtration behind drains, separation under light loading, drainage trench wrap, and protection of geomembrane. Typical mass 100 to 800 gsm.
AOS (Apparent Opening Size): Geotextile filtration property indicating the largest soil particle size that will pass through the fabric. Measured by glass-bead sieving test (ASTM D4751) reporting the O95 value (95 percent of beads finer than this size will pass). BS EN ISO 12956 reports an equivalent O90. Lower AOS retains finer soils. Filter design rule of thumb: AOS less than D85 of the protected soil for stable cohesionless soils.
Permittivity: Geotextile property quantifying water flow perpendicular to the plane per unit head gradient. Units: 1/s (per second). Higher permittivity means greater drainage capacity. Filter design rule: geotextile permittivity should pass water at least one order of magnitude faster than the protected soil's hydraulic conductivity to avoid acting as a flow bottleneck.
Transmissivity: Geocomposite or thick nonwoven geotextile property quantifying in-plane water flow capacity per unit width and head gradient. Units: m squared per second. Critical for drainage geocomposites (StrataDrain) used behind retaining walls or in basement waterproofing.
Wide-width tensile strength: Geotextile or geogrid ultimate tensile capacity measured by stretching a 200 mm wide specimen at controlled strain rate. Units: kN/m. Reported as MD (machine direction) and CD (cross-machine direction). Used as the starting point for reinforcement design, before applying reduction factors per ISO 13431.
CBR puncture resistance: Geotextile resistance to puncture by a 50 mm cylindrical plunger. Units: N. Indicates survival under aggregate placement and compaction during construction. AASHTO M288 specifies CBR puncture minima per separation class (Class 1 highest for severe conditions, Class 3 for mild).
Grab tensile: Geotextile tensile strength measured on a 100 by 200 mm specimen with 25 by 50 mm grip area (the "grab" pattern). Used in separation and filtration specifications. Lower numerical value than wide-width tensile because gripping concentrates stress.
Trapezoidal tear strength: Geotextile resistance to tear propagation. Specimen cut in trapezoidal shape with notch; force to propagate tear measured. Critical for in-service durability under cyclic loading and resistance to damage from sharp aggregate edges.
Gradient ratio: Soil-geotextile filter compatibility test. Soil column with candidate geotextile at bottom subjected to head; ratio of head loss in the bottom 25 mm (with geotextile) over head loss in 50 mm of soil above. Values below 3 indicate the system is not clogging significantly. Critical for high-fines Malaysian residual soils.

Category 02

Geogrid terms

Geogrid: Open-aperture polymeric mesh used for soil reinforcement. Three main families: uniaxial (tensile capacity in one direction, used for MSE walls, RSS, basal reinforcement), biaxial (equal capacity in two directions, used for road base reinforcement), triaxial (three-direction load transfer, used in advanced subgrade stabilisation).
Uniaxial geogrid: Geogrid with primary tensile strength in one direction (typically machine direction). Made from polyester (PET) yarns with PVC coating, e.g. StrataGrid range, 30 to 1000 kN/m tensile strengths. Used for MSE walls, reinforced soil slopes (RSS), basal reinforcement on soft ground, segmental retaining walls.
Biaxial geogrid: Geogrid with equal tensile strength in both machine and cross-machine directions. Made from polypropylene (PP) via punched-and-drawn process. Used for road base reinforcement, working platform on soft subgrade, sub-base stabilisation. Aperture typically 30 to 50 mm for granular interlock with crushed aggregate.
Triaxial geogrid: Advanced PP geogrid with triangular aperture geometry providing three-direction load transfer. Higher stiffness at low strain than biaxial. Used in critical road and rail subgrade applications, working platforms for heavy cyclic loading.
RF_ID (Installation Damage Reduction Factor): Strength reduction factor applied to ultimate tensile (T_ult) to account for mechanical damage during aggregate placement and compaction. Typical PET uniaxial in granular fill: 1.05 to 1.30. Higher in angular fill or thin first lift.
RF_CR (Creep Reduction Factor): Strength reduction factor for long-term tensile capacity loss under sustained load. PET typically 1.40 to 1.80 for 100-year design; PP biaxial higher. Combined with other factors to convert T_ult to long-term design tensile T_d.
RF_CH (Chemical / Biological Reduction Factor): Strength reduction for long-term degradation in soil chemistry and biological environment. Neutral Malaysian residual soils: 1.00 to 1.20 typical. Higher in aggressive chloride-rich, low-pH, or sulphate-bearing ground.
Pullout coefficient (Ci): Soil-geogrid interaction coefficient measured by pulling a geogrid embedded in soil. Used in MSE wall and RSS design to verify pullout capacity behind the active wedge. Typical Ci: 0.6 to 0.8 for geogrid in well-graded granular fill.

Category 03

Geocell terms

Geocell: Three-dimensional cellular confinement system made from HDPE strips welded into a honeycomb structure. Expanded on site and filled with soil, aggregate, or concrete. Provides confinement that enhances bearing capacity, prevents lateral spread, and stabilises slopes. STRATA's range is StrataWeb. Cell depths 75 to 200 mm typical.
Cell depth: Geocell vertical dimension, typically 75, 100, 150, or 200 mm. Selection depends on application: 75 mm for shallow erosion-only slope facings, 100 mm for standard vegetated facings, 150 mm for steeper slopes or channel lining, 200 mm for very steep slopes or high-shear hydraulic applications.
K-factor (Modulus Improvement Factor): Manufacturer-published ratio of effective modulus of geocell-confined aggregate vs unconfined aggregate at same density. Used in pavement design (AASHTO LRFD) and unpaved road design (Giroud-Han 2004 method) to compute reduced aggregate thickness. Typical K-factor for StrataWeb 100 to 150 mm filled with crushed aggregate: 1.5 to 3.0.
Stress Crack Resistance: HDPE durability metric measuring time to failure under sustained tensile load with notch. Higher values indicate longer service life. STRATA published values exceed 400 hours, corresponding to 75 to 120 year design life in buried Malaysian conditions.
Perforated vs non-perforated cells: Perforated cells (small slots in the cell walls) allow lateral water flow and root growth, used for vegetated slope facings and drainage applications. Non-perforated cells used for concrete-filled channel lining where lateral flow is not needed.

Category 04

Geomembrane terms

Geomembrane: Continuous polymer sheet used as a low-permeability barrier in containment applications. Materials: HDPE (most common, highest chemistry resistance), LLDPE (more flexible, used for caps and irregular slopes), PVC (water-only applications), EPDM (specialty UV-exposed water features). Thickness 0.75 to 2.5 mm typical.
HDPE (High-Density Polyethylene): Geomembrane material with highest chemical resistance and stress crack resistance. Default choice for landfill basal liner (1.5 to 2.5 mm), mining tailings storage facility liner, hazardous waste containment. Smooth or textured surface variants for slope stability applications.
LLDPE (Linear Low-Density Polyethylene): More flexible geomembrane than HDPE, used where the liner must accommodate settlement, irregular subgrade, or steep slopes. Common for landfill cap liners and aquaculture pond liners. Slightly lower stress crack resistance than HDPE.
GCL (Geosynthetic Clay Liner): Composite barrier with bentonite clay layer encapsulated between two geotextile layers. Hydraulic conductivity below 1E-11 m/s. Used as primary or secondary barrier in landfill basal liner systems, often combined with HDPE for composite liner systems per DOE Garis Panduan.
Hot-wedge seam: Primary geomembrane seam type. Dual-track weld with central air channel for non-destructive pressure testing. Made by automated walking welder. Standard for HDPE and LLDPE production seams. Tested per ASTM D5820 (air pressure) for 100 percent NDT coverage.
Extrusion fillet seam: Secondary geomembrane seam type. Hand-extruded HDPE bead at seam edge or repair patches. Used for detail work, repair, and pipe penetrations. Tested per vacuum box (ASTM D5641) for NDT.
Geoelectric leak detection: Post-installation testing method that energises the geomembrane with low-voltage current and detects current leakage at any pinhole or seam defect. Locates leaks across entire installed area before final backfill. Increasingly specified for stringent DOE compliance.
Interface friction: Shear strength of contact between geomembrane and adjacent layers (subgrade, cover soil, geotextile). Critical for slope stability of liner-on-slope geometries. Smooth HDPE typical 0.4 to 0.5 coefficient; textured HDPE 0.6 to 0.8. Textured HDPE specified on slopes steeper than 1V:3H.

Category 05

Geocomposite terms

Geocomposite: Multi-layer geosynthetic combining two or more polymer functions in one product. Common combinations: drainage geocomposite (geotextile wrap on plastic drainage core), reinforcement composite (woven core plus nonwoven facing), barrier composite (geomembrane bonded to geotextile).
Drainage geocomposite: Geocomposite with drainage core (typically perforated polymer mesh or cuspated sheet) wrapped in nonwoven geotextile filter. Used behind retaining walls, in basement waterproofing, beneath landfill caps. STRATA range is StrataDrain. Transmissivity sized per ASTM D4716.
PVD (Prefabricated Vertical Drain): Pre-manufactured drainage strip (typically 100 mm wide x 4 mm thick) installed vertically through soft ground to accelerate consolidation by shortening drainage path. Standard pairing: PVD plus basal woven PET geotextile for embankment over peat or marine clay. Spacing typically 1.0 to 2.0 m square or triangular grid.

Category 06

Soil mechanics terms

CBR (California Bearing Ratio): Soil strength index measured by penetration of a piston into compacted soil sample. Reported as percentage. Used in pavement design and subgrade assessment. Malaysian residual soils typically CBR 5 to 15 percent in optimum moisture; soft clays below 2 percent.
Residual soil: Soil formed in place by weathering of parent rock without transport. Malaysian tropical residual soils are typically reddish-brown, high in fines (silt and clay greater than 30 percent), with weathered structure inherited from parent rock. Common in hilly West Malaysia.
Saprolite: Highly weathered residual soil retaining the original rock structure but mineralogy converted to clay. Typically Grade IV or V weathering classification. Strength variable; care needed in slope cuts where original rock joints control failure.
Peat: Highly organic soil formed by accumulation of partially decomposed plant material in waterlogged conditions. Malaysian peatlands extensive in Pahang, Sarawak, Sabah. Very low shear strength (sᵤ typically 5 to 15 kPa), very high compressibility, requires basal reinforcement plus PVD for embankment construction.
Soft marine clay: Soft clay deposited in marine or estuarine conditions. Typical undrained shear strength 10 to 25 kPa. Found in west coast alluvial belts (Klang, Selangor coast) and east coast estuarine areas. Major foundation challenge for reclamation, highway, and rail embankments.
Undrained shear strength (sᵤ): Shear strength of cohesive soil under undrained loading (water cannot drain during load application). Measured by vane shear test, triaxial UU test, or unconfined compression. Key parameter for soft-ground stability analysis. Typical Malaysian soft clay: 10 to 25 kPa; peat: 5 to 15 kPa.
Consolidation: Time-dependent volume change in saturated cohesive soil under load, as pore water dissipates and soil skeleton takes the stress. Critical design consideration for embankment on soft ground. Accelerated by PVD installation.
Bearing capacity: Maximum load per unit area that soil can support without shear failure of the soil mass. Computed per Terzaghi, Meyerhof, or Eurocode 7 methods depending on geometry and code. Factor of safety typically 2.5 to 3.0 for permanent works.

Category 07

Slope stabilisation terms

Soil nailing: Slope stabilisation technique using passive steel bars (nails) drilled at engineered angles into a slope face and grouted in place, locking the soil mass against sliding. Face finished with shotcrete and welded mesh. Standard for hillside cut slopes and distressed-slope remediation.
RSS (Reinforced Soil Slope): Steepened earth slope (slope angle 30 to 70 degrees from horizontal) with horizontal geogrid reinforcement layers, allowing greater slope angles than the soil's natural angle of repose. Faced with vegetation, geocell, or wrapped geotextile.
MSE wall (Mechanically Stabilised Earth wall): Vertical or near-vertical earth retaining wall reinforced with horizontal geosynthetic layers (geogrid or geotextile) and faced with modular blocks, precast panels, gabion baskets, or wrapped geosynthetic. Heights up to 25 m practical with appropriate reinforcement.
Factor of safety (FoS): Ratio of resisting forces to driving forces on a slip surface. Target FoS depends on code and application: permanent slopes typically 1.5 minimum (BS 8006), temporary 1.3. Reinforced slopes use partial factor approach in Eurocode 7.
Slip circle (Bishop, Spencer methods): Limit equilibrium method for slope stability analysis assuming circular slip surface. Bishop method: simpler, common for short slopes. Spencer method: more rigorous, accounts for interslice forces, used for complex geometries. Critical slip surface located by iterative search.
Horizontal drain (sub-horizontal drain): Drilled sub-horizontal pipe drain installed into a slope to lower the groundwater table by gravity. Single most effective slope stabilisation when groundwater drives failure. Designed per BS 6031 and JKR Slope Engineering Manual.

Category 08

Retaining wall terms

RC cantilever wall: Reinforced concrete retaining wall with L-shaped or T-shaped cross-section. Stem cantilevers from base slab. Designed per BS 8002, BS EN 1997, or AASHTO LRFD. Standard for tight urban sites where wall footprint must be minimised.
Gabion wall: Gravity retaining wall built from rectangular wire-mesh baskets (gabion boxes) hand-packed with hard angular stone. Permeable, flexible, tolerates differential settlement. Heights 1 to 8 m without geogrid; taller with geogrid tail-back. Designed per BS 8002, BS EN 1997, USACE EM 1110-2-2502.
Modular block (segmental retaining wall): Dry-stacked precast concrete blocks (typical 200 mm tall) with geogrid reinforcement extending into backfill. Designed per NCMA SRW Design Manual. Architectural finish through textured block face. Heights up to 8 m typical with proven connection systems.
Sheet pile wall: Earth retaining wall formed from interlocking steel sheet piles driven or vibrated into ground. Used for excavation support, marine works, riverside walls. Cantilever for short heights, anchored or strutted for deeper excavations.
Ground anchor: High-strength steel bar or strand drilled and grouted into ground, post-tensioned to deliver active retention force. Used for tieback walls, slope stabilisation, dam stabilisation. Contrasts with passive soil nailing where load develops only when soil tries to move.
Active earth pressure: Lateral earth pressure on a retaining wall when the wall moves slightly away from the retained soil, allowing the soil to mobilise its full shear strength. Lower than at-rest pressure. Computed per Coulomb (BS 8002) or Rankine theory. Used in active wall design.

Category 09

Test methods

SPT (Standard Penetration Test): In-situ soil strength index test using 63.5 kg hammer falling 760 mm onto a sampler driven into the borehole base. Reports N value (blows per 300 mm penetration). Standard parameter for foundation design. Correlations to phi, sᵤ, modulus depend on soil type.
CPT (Cone Penetration Test): In-situ test using a cone tip pushed into ground at controlled rate. Reports cone tip resistance (qc), sleeve friction (fs), and pore pressure (u). More repeatable than SPT, particularly for soft soils. Increasingly specified for Malaysian soft-ground sites.
Vane shear test: In-situ undrained shear strength test for soft clays using a cruciform vane rotated at depth. Direct measurement of sᵤ without sample disturbance. Standard for assessing soft marine clay and peat parameters in reclamation and embankment design.
Triaxial compression test: Laboratory soil strength test where a cylindrical sample is loaded axially while confined at controlled radial pressure. Variants: UU (unconsolidated undrained, fast for sᵤ), CIU (consolidated isotropically undrained, for effective stress parameters), CID (consolidated drained, for drained shear strength).
Oedometer test (consolidation test): Laboratory test on cylindrical soil sample loaded incrementally with lateral confinement. Reports compressibility parameters (Cc, Cα, mv, cv) for consolidation analysis. Standard for soft-ground design.
UV resistance: Geosynthetic durability test measuring strength retention after controlled UV exposure (typically 500 hours xenon-arc). Critical for any geosynthetic exposed during installation or in service.

Category 10

Standards & codes

BS 8006: British Standard Code of Practice for strengthened/reinforced soils and other fills. BS 8006-1 (MSE wall, RSS, basal reinforcement, embankments on piles). BS 8006-2 (soil nailing). Primary design code for geosynthetic reinforcement in UK and Commonwealth practice including Malaysia.
Eurocode 7 (BS EN 1997): European geotechnical design code, partial factor LRFD framework. Two parts: BS EN 1997-1 (general rules), BS EN 1997-2 (ground investigation and testing). Used in parallel with BS 8006 for Malaysian federal works.
FHWA-NHI design references: US Federal Highway Administration reference manuals widely cited in Malaysian practice. FHWA-NHI-14-007 (Soil Nail Walls), FHWA-NHI-10-024 (MSE Walls and Reinforced Soil Slopes), FHWA-NHI-07-092 (Geosynthetics), FHWA-HEC-23 (Bridge Scour Countermeasures).
JKR-SPJ Section 7: Jabatan Kerja Raya Standard Specification for Public Works, Section 7 (Earthworks and Slope). Federal works specification applying to JKR, federal highway, federal building, and government infrastructure projects. References ASTM, BS, AASHTO for material properties.
AASHTO M288: American Association of State Highway and Transportation Officials standard specification for geotextile in highway applications. Defines separation Classes 1, 2, 3 (with class-specific strength minima) and filtration class. Widely cited in Malaysian highway and federal works specifications.

Related references