Foundations over Piles

Product catalog summary

Overview: The document details the construction and performance of Enhanced Arch Load Transfer Platforms (LTP) at the Second Severn Crossing, UK, focusing on the use of Tensar geogrids to reinforce granular layers, improve load distribution, and minimize settlement over weak ground supported by piles or vibro concrete columns (VCCs).

Specifications: Enhanced Arch LTPs involve installing Tensar geogrids within granular layers to increase the angle of load distribution, transferring most embankment load directly to pile heads, which act as inverted pedestals for continuous support.

Procedures: Construction includes placing, spreading, and compacting granular fill with 2 or 3 layers of Tensar geogrids. Dead weight compaction is applied to the cushion layer under the bottom grid, with overlapping or tying adjacent grids for continuity.

Performance: Monitoring at the Second Severn Crossing showed similar settlement above VCCs and mid-way between them, with minimal stress at subgrade level, indicating effective load transfer and minimal settlement.

Applications: Enhanced Arch LTPs are suitable for supporting embankments over soft ground where minimal settlement is critical, such as in highway construction and support of concrete ground floor slabs.

Recommendations: Tensar International advises consulting experienced engineers for design and construction advice, with the use of Tensar products determined by a professional with full project knowledge.

Limitations: LTPs are unsuitable for certain ground treatment techniques like vibro stone columns, emphasizing the need for professional assessment to determine Tensar product suitability.

Contact Information: Tensar International Limited offers support services and literature on their products and applications, providing guides and specifications for various geosynthetic applications.

Introduction to Tensar Load Transfer Platforms (LTPs): Tensar LTPs support embankments and ground-bearing slabs over weak soils, providing an alternative to traditional surcharge methods and accommodating poorer quality fill.

Specifications and Applications: LTPs are useful where minimal settlement is critical, distributing loads efficiently onto piles or VCCs, eliminating the need for concrete rafts or ground beams.

Types of Load Transfer Platforms:

Tensioned Membrane LTP: Uses high-strength geotextiles to span between piles, transferring loads through tension.
Enhanced Arch LTP: Incorporates Tensar geogrids within granular layers to enhance load distribution, acting as inverted pedestals.

Construction and Performance: LTP construction involves placing multiple layers of Tensar geogrids within granular layers above supports, demonstrating excellent load spreading capabilities and minimal settlement.

Support and Services: Tensar International offers comprehensive support services, including design and construction advice, with literature and guides to assist engineers and contractors.

Conclusion: Tensar LTPs provide a practical solution for constructing over weak ground, ensuring stability and minimizing settlement, leading to significant cost and time savings in civil engineering projects.

Ground Stabilisation: Discusses the reinforcement of unbound layers in roads and trafficked areas using geosynthetics to improve stability and longevity.

TriAx™ Geogrid Technology: Highlights the innovative properties and performance benefits of Tensar TriAx™ geogrids for enhanced support and stabilization.

Asphalt Pavements: Focuses on reinforcing asphalt layers in roads to increase durability and reduce maintenance needs.

Tensartech Earth Retaining Systems: Covers solutions for constructing bridge abutments, retaining walls, and steep slopes, emphasizing stability and structural integrity.

Railways: Discusses mechanical stabilization of track ballast and sub-ballast for safe and reliable railway operations.

Foundations over Piles: Describes methods for constructing over weak ground without settlement issues using advanced geosynthetic solutions.

Basal Reinforcement: Explains the use of Basetex high strength geotextiles for reinforcing foundations and preventing settlement.

Tensartech Geocell Mattress System: Introduces a system for soil stabilization and erosion control, particularly on slopes.

Erosion Control: Provides strategies for controlling erosion on soil and rock slopes, ensuring environmental protection and structural stability.

Catalog excerpts

Contact Tensar International or your local distributor to receive further literature covering Tensar products and applications. Also available on request are product specifications, installation guides and specification notes. The complete range of Tensar literature consists of: • Tensar Geosynthetics in Civil Engineering A guide to products, systems and services • Ground Stabilisation Reinforcing unbound layers in roads and trafficked areas • TriAx™ A Revolution in Geogrid Technology The properties and performance advantages of Tensar TriAx™ geogrids • Asphalt Pavements Reinforcing asphalt layers in roads and trafficked areas • Tensartech Earth Retaining Systems Bridge abutments, retaining walls and steep slopes Small pile caps being cast prior to constructing the Enhanced Arch Load Transfer Platform. Construction of an Enhanced Arch Load Transfer Platform Once the supporting piles/VCCs have been installed the simple construction process involves the inclusion of 2 or 3 layers of Tensar geogrids in the granular layers above the supports. Dead weight compaction of the cushion layer of fill under the bottom grid, and the layer of fill between the bottom two grids, is the only deviation from standard embankment placement and compaction operations. Overlapping, or tying, of adjacent grids provides the continuity required. • Railways Mechanical stabilisation of track ballast and sub-ballast • Foundations over Piles Constructing over weak ground without settlement • Basal Reinforcement Using Basetex high strength geotextiles • Tensartech Geocell Mattress System • Erosion Controlling erosion on soil and rock slopes Your local distributor is: Tensar International Limited Cunningham Court Shadsworth Business Park A grid layer is placed. The design thickness of granular fill is placed, spread and compacted. Blackburn BB1 2QX United Kingdom Second Severn Crossing, UK The Toll Plaza area for the Second Severn Crossing in the UK was built over compressible soils supported on VCCs. Load from the embankment and pavement above was transmitted to the VCCs using a Tensar geogrid reinforced Enhanced Arch Load Transfer Platform (LTP). The graphs summarise the performance from monitoring this LTP. Settlement above the VCCs and mid-way between them is almost the same, whereas stress measured at subgrade level between the VCCs is almost zero. These results show how well the design assumptions have been realised in practice. The Enhanced Arch LTP has performed as a stiff raft, transmitting loads from the pavement and embankment directly to the VCCs using the excellent load spreading capability of a granular layer reinforced with Tensar biaxial geogrids. Second Severn Crossing Enhanced Arch Load Transfer Platform performance. Details of Enhanced Arch LTP at Second Severn Crossing. ©Copyright Tensar International Limited Printed August 2010 Issue 11, SDA: 583090 The information in this brochure is supplied by Tensar International free of charge. Tensar International do not assume any duty of care to you or any third party. No liability for negligence (other than for death and personal injury) can arise from any use of or reliance on the information in this brochure or use of any Tensar International product mentioned. Tensar International will not be liable if this brochure contains any misrepresentation or misstatement. Determination of the suitability for any project of the information and any Tensar International product mentioned in it must be made by your engineer or other professional advisor who has full knowledge of the project. You, together with any such engineer or advisor, must assume all risk of loss and damage of any kind arising from use of the information or any product of Tensar International other than the risk of death and personal injury. If you or any third party subsequently purchases a product referred to in this brochure or any other Tensar International product the entire terms of the contract of purchase and the entire obligation of Tensar International relating to the product or arising from its use shall be as set out in Tensar International's Standard Conditions in force at the time of purchase, a copy of which may be requested from Tensar International. Tensar and Tensartech are trade marks of tensar International Limited. Foundations over Piles Constructing Load Transfer Platforms over weak ground with piled foundations

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Load Transfer Mechanisms 2 Enhanced Arch Load Transfer Platform Tensar Technology - proven practical solutions and the know-how to get them built Based on the characteristic properties of Tensar geogrids and geotextiles, Tensar Technology is widely adopted for ground stabilisation and soil reinforcement problems, delivering real savings in cost and time. We can help you apply Tensar Technology to improve the bottom line on your project. The inclusion of Tensar geogrids within granular layers has been shown to increase the angle of load distribution considerably in comparison with the unreinforced...

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