Download - Pertemuan 04 GEOGRIDS/GEONETS
![Page 1: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/1.jpg)
Matakuliah : S0522/ Aplikasi Geosintetik Dalam Teknik Sipil
Tahun : Juli 2005
Versi : 01/01
Pertemuan 04
GEOGRIDS/GEONETS
![Page 2: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/2.jpg)
Learning Outcomes
Pada akhir pertemuan ini, diharapkan
mahasiswa akan mampu :
• Mahasiswa mampu menghitung dan mendesain aplikasi pemakaian geogrid/geonet sesuai kondisi lapangan dan kebutuhan. C3 , C5
• Mahasiswa mampu membandingkan pemakaian geogrid/geonet sesuai dengan analisa desain bagi perbaikan tanah. C4
![Page 3: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/3.jpg)
Outline Materi
• Pendahuluan mengenai material Geogrids dan Geonets
• Fungsi dan properties
• Metoda desain dan pemilihan material
• Perhitungan dan perencanaan
• Metoda Konstruksi pemasangan
• Analisa desain dengan dan tanpa material geosintetik
Sebagian Materi ini diambil ari :No. 8 of 19Reinforced Soil – Embankments on Soft Foundations by Jim PaulTensar International
![Page 4: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/4.jpg)
Lecture Outline.The problem.
• Analysis & design.
• Requirements of geosynthetics.
• Types of geosynthetics.
• Examples / case studies.
Reinforced SoilEmbankments on Soft Foundations
![Page 5: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/5.jpg)
The Problem• Construction of embankments on soft ground
can lead to:- Deep seated foundation failure- Excessive settlements
![Page 6: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/6.jpg)
Example of Failure
Failure by rotational movement of very soft mud due to small differential loading
![Page 7: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/7.jpg)
• removal of soft material and replacement with quality fill
• displacement of soft material• piling• staged construction• toe berms• elevated structure• lightweight fill• ground improvement• geosynthetics
Solutions to the Problem
![Page 8: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/8.jpg)
Geosynthetics
• Structurally sound solution at a lower cost
• Faster than traditional methods
• In its simplest form geosynthetics tie the potentially failing area back into the stable zone
![Page 9: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/9.jpg)
Example of Basal Reinforcement Using Geogrids
• High tensile strength required to maintain stability and prevent failure
• As the foundation shear stress increases the required geosynthetic tensile force reduces
![Page 10: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/10.jpg)
Analysis and Design
• Established geotechnical and stability methods used
• Soil parameters generally considered in total stress terms
• Three main failure mechanisms considered
- Rotational Stability- Lateral Sliding- Bearing Capacity
![Page 11: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/11.jpg)
Rotational Stability
Common form of analysis: • Simplified Bishop Method for circular surfaces• Failure can be deep seated or shallow
Reinforcement: Full width or localised areas
Soft Clay Foundation
Embankment Fill
Reinforcement tension develops as a vector of these forces
TrTr
Beware of ditches in this area!!!
![Page 12: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/12.jpg)
Lateral Sliding
• Resistance to lateral sliding determined from active driving force
• Geosynthetics/soil interface should be obtained from testing
Reinforcement
Soft Clay Foundation
Embankment fill
Reinforcement tension develops in the plane of the reinforcement
TrTr
Horizontal movement of fill, driven by active wedge
![Page 13: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/13.jpg)
Foundation Extrusion
• If soft soil thickness > embankment base width, a bearing capacity analysis will be required
• If soft soil layer thickness < than the embankment base foundation width extrusion occurs at the toe.
Soft Clay Foundation
Embankment fillLateral extrusion of foundations due to settlement of fill
The solution to this mode of failure is to reduce the settlement by making the base stiffer (Geocell mattress)
ReinforcementReinforcement
![Page 14: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/14.jpg)
7.
Geocell Mattresses..
Example of a Geocell Mattress
![Page 15: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/15.jpg)
Use of a Slip Line Field
•
• Based on bearing capacity theory
• Tensile forces determined from stresses acting on the base of the mattress
![Page 16: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/16.jpg)
Soft Clay Foundation
Embankment fillSettlement
Serviceability Limit States
• Both ultimate limit state and serviceability to be considered
Geosynthetic
![Page 17: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/17.jpg)
• Stiff Reinforcement may alter the failure surface shape
• Computer programs can consider non-circular failure surfaces
Failure Surface
![Page 18: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/18.jpg)
Embankment Over Voids
• Collapse due to abandoned mine workings or natural voids
• Geosynthetics perform either short-term or long-term function
• Case History: Ripon By-Pass (Paralink)
![Page 19: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/19.jpg)
Case History: Ripon By-Pass
![Page 20: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/20.jpg)
View of Ripon By-Pass
![Page 21: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/21.jpg)
Load Transfer Platforms
![Page 22: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/22.jpg)
Load Transfer Platform:Duffryn Link
![Page 23: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/23.jpg)
Requirements of Geosynthetics
• High tensile strength, at least in roll direction
• Ability to carry high loads for several years• Ability to transfer loads from soils to
geosynthetic, by interlock or friction• High resistance to damage during
installation• Durable against UV, chemical and
biological effects
![Page 24: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/24.jpg)
Basal Reinforcement using Geotextiles
Requirements of Geosynthetics
![Page 25: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/25.jpg)
Types of Geosynthetics
• Woven or knitted geotextiles- Normally polyester Tult to 1250 kN/m
• Extruded geogrids- Many uses, where ultra high strength not
needed
• Woven or welded geogrids- Mix of the properties of both geotextiles
and extruded geogrids
![Page 26: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/26.jpg)
Woven or Knitted Geotextiles
![Page 27: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/27.jpg)
Extruded Geogrids
![Page 28: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/28.jpg)
Woven or Welded Geogrids
![Page 29: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/29.jpg)
Case Studies
• High strength Geotextiles- Lok Ma Choa Highway, Hong Kong
• Load Transfer Platform- Toll Plaza Second Severn Crossing
• Geocell Foundation Mattress- Went Landfill Access Road, Hong Kong
![Page 30: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/30.jpg)
Lok Ma Chao Highway, Hong Kong
Embankment constructed over swamps and fishponds. Soft clay foundations, 10 m deep, strength as low as 3 kPa
![Page 31: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/31.jpg)
Lok Ma Chao Highway, Hong Kong
Geotextile avoided need for long preload or replacement of soft soils
![Page 32: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/32.jpg)
Lok Ma Chao Highway, Hong Kong
Geosynthetic Band drains were installed to increase the rate of consolidation. Five sections were set up with instruments to monitor :
• Geotextile strains
• Settlement
• Porewater pressure
• Lateral displacements
![Page 33: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/33.jpg)
Second Severn Crossing
Soils cross section showing extensive deposits of estuarine mud underlain by peat.
![Page 34: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/34.jpg)
Second Severn Crossing
Vibro concrete columns (VCCs) being formed using a modified vibroflot
![Page 35: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/35.jpg)
Second Severn Crossing
Geosynthetic used to transfer loads from the embankment fill to the VCCs
Full scale testing shows good load transfer at low imposed loads.
![Page 36: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/36.jpg)
Second Severn Crossing
Construction is quick, with placing of the geogrid and the granular layer keeping pace with the construction of the VCCs.
![Page 37: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/37.jpg)
Second Severn CrossingAerial View of Works
![Page 38: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/38.jpg)
Second Severn CrossingCompleted Bridge
![Page 39: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/39.jpg)
WENT, Landfill Access Road, HK
The access road crosses an alluvial plain on an embankment which is up to 10m high
The embankment is founded on soft clay 6m thick, strength 10kPa to 25kPa.
![Page 40: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/40.jpg)
WENT, Landfill Access Road, HK
The solution was to install band drains to increase the rate of consolidation, with a Geocell mattress as the foundation to the embankment
![Page 41: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/41.jpg)
WENT, Landfill Access Road, HK
The Geocell mattress consists of transverse grids with a triangular honeycomb structure formed by interlacing other sheets of uniaxial geogrid into the mesh.
![Page 42: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/42.jpg)
WENT, Landfill Access Road, HK
Construction of the geocell mattress is rapid and easily outpaces the infilling with granular fill
![Page 43: Pertemuan 04 GEOGRIDS/GEONETS](https://reader033.vdokumen.com/reader033/viewer/2022050909/56814f59550346895dbd07a5/html5/thumbnails/43.jpg)
WENT, Landfill Access Road, HK
Filling takes place from one edge, once an area is filled, delivery trucks can run on the surface of the geocell.
Lateral extensions in the geocell were less than 1% and the mattress acted as a ‘stiff’ foundation.