separation & reinforcement temp. roads
TRANSCRIPT
Geotextile Separation & Geogrid Reinforcement
P.O.Box 87532 Mombasa 80100, Kenya | Moushmi Complex, Ground Fl, Nyoka Road, Nyali+254 (0) 722 410 221 / +254 (0) 733 711 781 | [email protected]
www.geotextileseastafrica.com
GeotextileDefinition:
A permeable geosynthetic comprised solely of textiles. Geotextiles are used with foundation, soil, rock, earth, or any other geotechnical engineering-‐related material as an integral part of a human made project, structure, or system (ASTM D4439).
Functions of Geotextiles:Separation,
Filtration,
Drainage
Reinforcement
Protection
Why do we use Geotextiles in separation?
To prevent mixing of constructionLayers
To increase bearing capacity byavoiding material loss into theSubgrade
To improve the compaction propertiesof the aggregate layer
To provide long-‐term stability offoundation layers
?
Fibertex Geotextiles FunctionsSeparation
Loss of Aggregate
Aggregate Retained
Elongation Tensile strength
Mechanical propertiesSeparation
Puncture Resistance
Mechanical propertiesSeparation
Required Hydraulic propertiesSeparation
Cost savings from using Separation
0.00 0.50 1.00 2.502.001.50 3.000
20
40
100
80
60
120
% o
f Des
ign
Aggr
egat
e Th
ickn
ess
CBR
Aggregate loss to weak subgrade(FHWA 1989)
Heavy-‐Grade Nonwoven Geotextile Over a Low-‐Bearing Capacity Soil (marshland)
Geotextile Separation : Examples
Temporary Site Access Example: Geotextile used as separation & reinforcement over low-‐bearing capacity soil (swamp)
GeogridDefinition:
a structurally sound and stable grid for soil reinforcement, manufactured of extruded and drawn bars, laid and welded solid together.
Applications of Geogrids:Geogrids provide tensile reinforcement for base courses in:
-‐ Roads (paved & unpaved), airports & runways, railway and highway foundation engineering
-‐ steep sided soil embankments and retaining walls, foundation reinforcement of earth embankments
-‐ load transfer of overlying soil masses, spanning voids and sink holes, sludge lagoon closures, trench covers and beds.
base course reinforcement roads
Combigrid + Secugrid geogrids
140 MW windfarm in Dobrogea , SE of Romania
Case Study Salbatica II windfarm Romania
Quelle: REpower Systems AG
Access road to site; low-‐bearing capacity soils...
(without geotextile for soil separation & geogrid for soil reinforcement)
The crushed stone is dumped from the trucks , spreaded and compacted
Geosynthetic Solution: Combigrid (2-‐in-‐1 solution; a composite product of a Secugrid geogrid, with a nonwoven geotextile firmly welded between the reinforcement bars for soil stabilisation, separation and filtration applications)
Flensburg
FüssenNesselwang
Füssen
BAB A7:Flensburg Nesselwang
945,6 km= the longest
german Highway
Case Study German Autobahn
The soil and foundation conditions of the project were as follows:
flat willow areas with in-situ peat and sea cretaceous withpulpy to soft consistency beneath
high moor areas/moor willows with thicknesses of upto 4m, under the top ground surface there were layers of pulpy to soft sea cretaceous.
groundwater appx. 0.1m above top ground surface
Year of construction 2003/2004
Subsoil improvement with geosynthetics
The project included the preparation of the drainage trenches, foundation of the dams and noise barriers and subsoilimprovement.
Due to the subsoil with its low bearing capacity in large depths, the dams and the subsoil improvement were reinforced withgeosynthetics and built as a floating mattress.
For levelling and the reduction of the expected long-‐term settlements of the peat, the peat was completely removed in certain areas and the subsoil was improved with crushed stone of the grain size 2/150mm.
Examples of geogrids rolled out over various soil conditions:
NAUE Tragschichtbewehrungen
Advantages of Geogrids:
cost saving alternative to conventional construction methods
very high strength at low strains
immediate interlocking effect
low creep characteristics (PET)
high angles of friction due to the structured geogrid surfaces
high resistance against installation damage
4.75 m wide rolls
made from uniformly extruded solid PET or PP bars
high resistance against biological and chemical attack
biaxial geogrid strengths up to 80 kN/m
uniaxial geogrid strengths up to 400 kN/m
quick and easy to install
Alternative solutions for temporary roads:
GREENCELLS: made up of alternately joined geotextile strips to form a continuous square cellular mat section which is filled with earth, gravel or concrete & used to stabilize embankments, river banks, sand dunes, base courses & canals
P.O.Box 87532 Mombasa 80100, Kenya | Moushmi Complex, Ground Fl, Nyoka Road, Nyali+254 (0) 722 410 221 / +254 (0) 733 711 781 | [email protected]
www.geotextileseastafrica.com
Thank you !