Case Studies: Geosynthetics solve problem at Strubens Valley, South Africa

Urgent subgrade stabilisation for a construction site access road was economically and effectively solved with Kaytech’s geotextile and geogrid at a new development for the Chamberlain Hardware Distribution Centre in Strubens Valley, Roodepoort, in South Africa. Eco-friendly bidim geotextile in conjunction with TriAx, the innovative geogrid developed by Tensar International (and supplied locally by Kaytech), were the products of choice to solve the problem.

After discovering weak and waterlogged subgrade beneath a proposed temporary access road for plant and heavy machinery, Pierre Badenhorst Engineers approached Kaytech for a solution. The road was to be used for approxi-mately six months and although minimal groundwater was discovered in initial geotechnical reports, significant dam-age was anticipated.

A subsequent site inspection by Technical marketing engineer Byron de Cramer revealed that a crushed G5 material was available but with limited information gleaned at the time, an allowable bearing capacity was determined from an assumed CBR of 3. It was decided that two different proposals were required; a 30 mm premix surface for the future parking area to be utilised by mainly light motor vehicles, and a concrete hard stand surface for the access road that in future, will form the permanent road for delivery vehicles.

Due to concerns of damage to the access road during the 6 month construction and stocking period, it was decided to split this portion of the works into two phases. Tensar was consulted to provide indepth analysis using their software program, TensarPave to analyse the project requirements. The following layer works were specified:

Phase 1 would comprise a layer of bidim A2 to act as separator between the subgrade below and a layer of TriAx TX160 above. Two 150 mm layers of G5 (300 mm) for the premix area and three 150 mm layers of G5 (450 mm) for the hardstand area would follow.

After the initial construction of the building structure was completed Phase 2 would commence comprising bidim A2 as separator, and a layer of TriAx 130s covered with a layer of G2 material. A 170 mm 30 mPa concrete surface would complete the hard stand area and 30 mm of asphalt premix for the parking areas.

Bulk earthworks contractor, Zero Azania, was contracted for the stabilisation of the project. Completion of the project in June 2017 saw a total of 8 500 m² of both bidim A2 and TriAx TX160 used to reinforce and stabilise the access road. The same quantities apply to Phase 2.

Kaytech’s core product, bidim is a continuous filament, nonwoven, needlepunched geotextile manufactured from 100% recycled material. During the last decade, the company’s ISO 9001 registered facility has processed and converted almost 500 million discarded plastic cooldrink bottles into 26 million kilograms of high-grade polyester to create eco-friendly, A-grade bidim that meets the most stringent civil engineering and industrial specifications. As a sepa-rator, it maintains the integrity of selected fill material over very low CBR subgrades, thereby allowing dissipation of pore water pressure and resulting in accelerated consolidation. Up to 50% less fill material is required when using this geotextile as a separation layer. Highly versatile, it is suitable for use in various other applications including erosion control, reinforcing earth retaining structures, subsoil drainage and as liner protection in raw water dams.

Typical of top of layer works under bulk earth works (Left) & A part of the earthworks required further stabilisation due to ground water (Right)

Compared to bi-axial geogrids, the groundbreaking triangular design of TriAx imparts several advantages including near-uniform stiffness through 360o as well as high junction strength and efficiency. In trafficking applications, com-bined with a suitable aggregate, it outperforms all bi-axial geogrids and creates a mechanically stabilised layer with near isotropic properties.

By using two advanced products, time and money were saved in rendering the access road suitable for plant and heavy machinery to reach the construction site. Bidim A2 and TriAx will also form the base for the entire permanent road network and parking areas of the Distribution Centre development.

Further information

For more information on Kaytech products and systems, visit www.kaytech.co.za

Case Studies: Innovative access road design to reach Glenchamber Wind Farm (Scotland) on soft, peaty ground

Innovative access road design, employing Tensar’s TriAx geogrids, enabled lorries delivering turbine sections to reach the site of a new wind farm built on soft, peaty ground.

The 11 turbines of the Glenchamber Wind Farm in south west Scotland generate 27.5MW, enough to meet the demands of about 20,000 homes in Dumfries and Galloway.

Renewable energy company RES appointed main contractor Luce Bay Group to build the wind farm, which included widening 4.5km of local roads, plus construction of 5.9km of wind farm tracks and a new 2.8km access road across the peat bog surrounding the site.

The tracks and access road were on the critical path of the project, as they had to be ready in time for the arrival of the first turbine sections. As a result, they had to be economical and fast to build, plus they had to perform immedi-ately.

Excavating the thick, very soft peat and replacing it with site-won granular material to form a stable road foundation would have been time-consuming and expensive, so Luce Bay and its geotechnical consultant JNP Group worked with Tensar International to come up with an alternative solution.

This comprised Tensar’s TriAx TX170-GD geocomposite laid beneath the granular road base and TriAx TX160 ge-ogrid incorporated within it, to form a mechanically stabilised layer. The TriAx geogrid interlocked with the granular particles, confining and restraining them from moving laterally. This increased the aggregate’s bearing capacity and delivered roads able to carry the heavy construction loads.

Luce Bay Group Project Manager David McCracken commented: “Not only did the design ensure the access roads were ready for the arrival of the first turbine sections, but it will also enable the road to perform throughout the oper-ational life of the wind farm, with minimal maintenance.”

Client benefits:

  • Efficient access road design over deep, soft peaty ground
  • Minimising the use of site-won aggregate
  • Enabling on-time delivery of wind turbines
  • Construction and operational performance, with minimal maintenance.

Tensar TriAx geogrid was incorporated into the road’s granular surface to create a mechanically stabilised layer.

The access road had to be capable of supporting lorries bringing the turbine sections to site.

Further information

For more information visit www.tensar.co.uk

Case Studies: Temporary Slope Stabilisation, Wastewater Treatment Works Manchester, England

PROJECT SPECIFICATION

As part of a Wastewater Treatment Works upgrade, a 25m x 50m storm water retention tank was to be constructed. A formation level of 14m below existing ground level required a novel approach for stabilisation of the temporary batters. Typical solutions such as a secant pile wall or sheet pile wall were not appropriate due to the lack of flexibility to avoid existing infrastructure.

Slope reinforcement during excavation using Platipus anchors (Left) & Design showing anchor installation to stabilise slope (Right)

SOLUTION

The Designer, OGI Groundwater Specialists, proposed their Stable-Earth™ system which comprises of slope rein-forcement and erosion control using Platipus Percussion Driven Earth Anchors (PDEA®) together with groundwater management. The design approach was flexible and enabled OGI’s Engineer to adjust the placement and frequency of the Platipus anchors as necessary. The use of the PDEA® System and the OGI Stable-Earth™ system for this large-scale infrastructure project has demonstrated the viability of using cost effective materials to stabilise steep batters for temporary excavation works.

Completed temporary works with the retention tank in position

Further Information

For more information visit www.platipus-anchors.com or write to info@platipus-anchors.com

Case Studies: Subgrade Stabilization at Santa Ana, CA

THE CHALLENGE

Rancho Santiago Community College District performed a parking lot expansion in the Spring of 2014 at Santa Ana College located within the City of Santa Ana, California. The improvement projects associated with parking lot and fire lane pavements utilized Mirafi® RS380i woven geosynthetic in order to reduce pavement thickness thus avoiding any conflict between overexcavation/ grading and the existing underground utilities.

THE DESIGN

The Geotechnical Engineer, Geo-Advantec of San Dimas, California designed pavement sections for the parking lots and fire lanes. Both sections consisted of concrete pavers underlain by bedding sand and a geotextile. One paver section was installed on Asphalt Concrete (AC), and the other on Portland Cement Concrete (PCC) . The on-site native subgrade consisted of slightly sandy silty clays and/or clays. Pumping soils during the required compac-tion was expected because of the high moisture content of existing clayey soils. Geo-Advantec recommended a layer of Subgrade Enhancement Geotextile (SEG) . This geotextile layer, Mirafi® RS380i, was placed below the Class II base beneath the AC and PCC pavement sections. The intent of the Mirafi® RS380i was to provide sub-grade stabilization, separation between soft subgrade fines and base material, as well as decrease the total thick-ness of pavement sections. Mirafi® MiraSpec software was used to calculate the reinforced pavement sections us-ing subgrade strength and loading parameters.

THE CONSTRUCTION

Rancho Santiago Community College District hired McCarthy Building Companies, Inc. as the General Contractor. McCarthy subcontracted to Southern California Grading for the earthwork and paving. Southern California Grading procured the Mirafi® RS380i through WhiteCap Construction Supply. WhiteCap delivered approximately 65 rolls that were 15 feet wide by 300 feet long. For the pavement sections with pavers on PCC pavement, the Mirafi® RS380i was installed on compacted native soil. Eight inches of Class II base was placed directly on Mirafi® RS380i. For the pavement sections with pavers on AC pavement, the Mirafi® RS380i was again installed on compacted native soil. The thickness of Class II base ranged between 6 and 10 inches based on asphalt thicknesses of 3 and 4 inches. Therefore, for the AC pavement, the contractor was able to reduce required Class II base section by 2 inches which resulted in a cost savings.

THE PERFORMANCE

The inclusion of Mirafi® RS380i high strength woven geosynethic to the structural section of the parking lot improve-ments resulted in a cost savings for the Rancho Santiago Community College District. This cost savings was asso-ciated with reduced aggregate base requirements that avoided relocation of shallow utilities and faster compaction, which expedited construction. In addition, the new pavement structure will require less maintenance as it will be less suspectible to cracking and failures because of the subgrade reinforcement, separation, confinement and filtration associated with Mirafi® RS380i, the superior geosynthetic.

Project site native subgrade preparation (Left) & Placing Mirafi® RS380i over native soil and applying base material over RS380i (Right)
Compacting base material over Mirafi® RS380i (Left) & Completed asphalt parking area at Santa Ana College (Right)

Further Information

For more information visit www.mirafi.com

Case Studies: Subsidiary Revetment Construction of Desilting Tunnel Zengwun Reservoir, Tainan, Taiwan, ROC

Application

Zengwun reservoir had suffered from a large amount of sediment after every typhoon disaster, which seriously affects the reservoir operation. A new desilting tunnel is constructed to be the suitable dredging approach, and it brings about subsidiary revetment construction in response to spoil disposal. Also, the overflow prevention during discharge needs to be taken into consideration.

The Conventional Solution

The common countermeasures for riverbank protection are high durability, rigid concrete structures, but coupled with higher energy consumption as well as carbon emission, and its inability to dispose spoil results in additional cost in earthwork cleaning. Both explicit cost and implicit cost of the whole construction will increase. It stands to reason that an economical approach to reuse the spoil and construct revetments simultaneously is in demand.

ACE Solution

A composite system is applied to revetment construction, and it can be divided into two parts: concrete retaining wall under the water level to resist water flow impact and a geosynthetic reinforced structure above it, both including drainage systems. ACEGrid® geogrid is a product with a high modulus which is made of polyester with a durable polymer coating. By suitable installation and compaction, proper ACEGrid® can be interlocked with soil and compen-sate for the tensile strength of soil mass, constituting a reinforced structure with safety and stability. The total height of whole structure is 13m approximately, that consists of 8m-height concrete retaining wall and about 5m-height wrap-around reinforced structure. Spoil from the tunnel is the major fill in the reinforced zone, and few deposits in the river are also used to offset the lack. Around 60,000 sqm ACEGrid® are used for 780m-length revetment.

With the tunnel construction process, the revetment structure finished one after another, and 165,000m3 of spoil is reused, that both dispenses with earthwork cleaning and saves the cost of reinforced fill. The hydroseeding after construction takes on good vegetation effect 3 months later, and the water level would not exceed the top of concrete wall even while the sluice is open. These revetments not only solve the problems of spoil disposal and overflow, but also reduce the carbon emission in case the structures are originally all made of concrete. Also, the effects on land-scape and ecology are clearly displayed.

Further information

For more information about ACE Geosynthetics, visit www.geoace.com or contact sales@geoace.com.

Report on Corporate Committee Meeting at GeoAfrica 2017 Marrakech, Morrocco, 7 October 2017

The Corporate Committee (CC) would like to take this opportunity to update you on its recent activities. The compo-sition of the current Committee membership is as follows:

As a general point, please do not hesitate to contact the chairman or secretary at any time with any queries/questions on Corporate Member issues. The CC recently held a committee meeting in October in Marrakech, Morocco just prior to the 3rd GeoAfrica IGS Regional Conference and the following provides a brief report on the issues discussed.

Membership

  • Currently we have about 190 Corporate Members which marks a strong increase over the past few years. This growth strongly supports the overall strategic plan of the IGS to grow its individual membership and promote the appropriate use of geosynthetics.
  • Please note that whilst the vast majority of members pay subscriptions on time we always have a few who are late. Some of the problems of late payment seem to be associated with lack of clear communication on due dates etc so we will be implementing a clearer and more rigorous system in this regard in order to be fair to the majority of on-time payers.

Conferences & Exhibitions

  • Committee is discussing a range of initiatives aimed at improving the Corporate Member experience with IGS Conferences and Exhibitions.
  • We previously mentioned the provision of guidelines to organisers of regional and international conferences en-suring ease of access for ‘exhibition only’ visitors. This access is preferably to be provided free of charge or, at worst, for a nominal fee (eg to cover catering). We see this as a vehicle to encourage visitors from related profes-sions who perhaps would not attend the full conference but can be introduced to geosynthetics via the exhibition. Clearly this could facilitate member exhibitors being able to issue invitations to customers and partners and hope-fully generate a wider audience for our exhibitions and industry.
  • We will also be making a slight change to the IGS Corporate Member Plaques that we issue at International and Regional Conferences. These plaques will now highlight 40, 30, 20 and 10 year members. We consider this a small but important acknowledgement of those Corporate Members who have consistently supported the IGS over time.

Marketing & Communication

  • From January 2018 we will be publishing a Corporate Members Bulletin Board on regular basis. This will be a short ‘one page’ communication containing concise information and links to all IGS and related activities that we believe may be of interest to Corporate Members. We hope that you will find this useful and will welcome your feedback once this starts.
  • We will be asking all Corporate Members to provide contact details for two further individuals – in addition to the primary contact to receive the above Bulletin Board and other communications. Hopefully this will provide a com-munication ‘safety net’ to ensure that all Corporate Members do not miss out on any important information or op-portunities.
  • Please note that the list of current Corporate Members on the IGS now has a logo for each member. Members are strongly encouraged to check their logo and provide us with an updated version if they wish.

Other Business

  • The Corporate Member case history contest previously mentioned is in planning so please look out for further information on the first Bulletin Board in January.
  • The Corporate Committee has established an official liaison with the European Association of Geosynthetic Man-ufacturers to promote communication. We would be keen to hear from Corporate Members who have ideas on other similar bodies with whom liaison might be beneficial.

Next Meeting

The next meeting of the Corporate Committee is planned for 22nd November 2017 via teleconference. Please do not hesitate to contact us with any matters you wish to raise.

We hope that you found this update useful and are reminded that if you have any queries please do not hesitate to contact the CC at any time.

Reported by

Kent von Maubeuge, Corporate Committee Chair

Geotextiles and Geomembranes: Best papers in 2016

Following the Editorial Board meeting held in Yokohama in September 2006 it was decided that it would be desirable to recognise some of the best papers published in Geotextiles and Geomembranes. We started with Volume 23 and have selected the Best paper in each subsequent year. This year the Editorial Board were charged with selecting what they considered to be the “Best Paper” published in Geotextiles and Geomembranes in 2016. Papers were considered for their contribution to the discipline in terms of providing significant new insights and/or of being of high potential impact on the discipline. All Technical Articles, except those co-authored by the Editor, were eligible. The selection of wining papers was decided based on a vote of the Editorial Board members.

Following a rigorous review of the papers I am pleased announce that the winner for the Best Paper for 2016 was:

Electrokinetic strengthening of slopes Case history

  1. Lamont-Black, C.J.F.P. Jones, D. Alder, Geotextiles and Geomembranes, 44(3):319-331 Two papers were selected for Honourable Mention

Investigations of geomembrane integrity within a 25-year old landfill capping

Eugene M. Gallagher, David M. Tonks, John Shevelan, Andrew R. Belton, Ria E. Blackmore, Geotextiles and Geomembranes, 44(5):770-780

and

A review of the performance of geosynthetics for environmental protection

  1. Touze-Foltz, H. Bannour, C. Barral, G. Stoltz, Geotextiles and Geomembranes, 44(5):656-672

as runners-up and hence being judged to be amongst the three best papers published in Geotextiles and Geomembranes in 2016. Congratulations to all of the authors for their very significant contribution to the geosynthetics discipline.

Geosynthetic Application EtE Event organized by the Indonesian Chapter of IGS

EtE Program

ETE logoEducate the Educators (EtE) is an event held in the form of workshops, to provide teaching, lecture sessions, and preparations for the course’s curriculum. The topic for this year’s event is Geosynthetics Application.

International Geosynthetics Society (IGS) is an organization that initiated the EtE events in the form of geosynthetics learning workshop. The IGS itself has educational programs that are being developed around the world. The aim for this EtE program is to educate people about the usage of geosynthetics, especially in the field of Civil Engineering projects.

Through this event, IGS also wants to develop an SN-Dikti curriculum in Indonesia based on competency due to the need for Civil Engineering graduates to understand the latest technology in construction. It is necessary to have experts who are excellent at their own fields sharing their knowledge to complete the knowledge of future Civil Engineering graduates.

The EtE event in the form of workshop, is aimed at lecturers as well as new civil engineering graduates, as practi-tioners and academics in Civil Engineering. After this event is done, it is hoped that the participants are able to share their knowledge to all students about geosynthetics technology and application in Civil Engineering. Through this workshop, it is also hoped that the geosynthetics application as an educational program, will be more developed in the future. This is supported by the number of Civil Engineering graduates who have a good understanding regarding to geosynthetics applications in Civil Engineering projects.

Implementation of the EtE Program

The Educate the Educators (EtE) event, for the first time, was held in Indonesia and was organized by the Indonesian Chapter of the International Geosynthetics Society (INA-IGS). INA-IGS also cooperates with MY IGS (Malaysian Chapter of International Geosynthetics Society), Krida Wacana Christian University and University of Science Ma-laysia in organizing the EtE event.

Through discussions in the event, it was discovered that only a small number of campuses have made some kind of introduction regarding geosynthetics and an even smaller number of them have a subject on geosynthetics. The common problem was that the subjects were electives and due to the general interest being low, its impact is very limited. The general consensus was that geosynthetics needs to be included in subjects such as soil improvement, thus ensuring every Civil Engineering graduates knows that geosynthetics is an available alternative instead of just some special product that manufacturers are trying to sell.

The event took place on October 2nd 2017 at Hotel Century Senayan, Jakarta. The EtE event was then continued with a geosynthetics international seminar with the theme “Quality in Construction Using Geosynthetics” on October 3rd 2017 at the same place.

The EtE Lectures were Delivered by:

  • Amelia Makmur, S.T., M.T., Topic 1: Introduction on types and functions of geosynthetics materials.
  • Sam Allen, Topic 2: Fundamental properties and related tests on geosynthetics materials.
  • Prof Dr. Fauziah Ahmad, Topic 3: Indroduction on the application of geosynthetics for soil reinforcement.
  • Ir. Gouw Tjie Liong M.Eng., ChFC, Topic 4: Introduction on geosynthetics application in in roadway system.
  • Michael Dobie, Ceng, FICE, FCIHT, Topic 5: Introduction on geosynthetics application on soft soil.
  • Mike Sadlier, Topic 6: Introduction on geosynthetics for environmental application.

The Participants

Total participants are 28 participants from:

  • PT Summarecon (10 participants)
  • PT TGU (3 participants)
  • Atma Jaya Yogyakarta University (1 participant)
  • PT MRP (2 participants)
  • PT Sakarna (2 participants)
  • National Defence University of Malaysia (1 participant)
  • PT Hilon (1 participant)
  • Dinas PU Merauke (1 participant)
  • Polytechnic of Jakarta (1 participant)
  • PT Hakaaston (1 participant)
  • Bina Nusantara university / PT Tetrasa Geosinindo (1 participant)
  • PT GSI (1 participant)
  • Sri Kanti (personal)
  • Krida Wacana Christian University (1 participant)
  • Maranatha Christian University (1 participant)
Participants of the EtE Workshop 2017 in Jakarta

Reported by

David Saputra and Amelia Makmur, Chairperson of conference and EtE

Geosynthetic Materials and their Use in Infrastructure Projects Heraklion, Greece, 08 November 2017

The informative meeting entitled “Geosynthetic Materials and their use in Infrastructure Projects” organized by Thrace Nonwovens & Geosynthetics on 8 November 2017, in Heraklion, Crete completed in success. The meeting was held in collaboration with Technical Chamber of Greece – Eastern Crete Department, under the auspices of the Hellenic Geosynthetic Society (HGS).

On behalf of HGS, Mr. Stratakos (Member of the Administration Council of HGS and Technical Director of “NAMA Lab S.A”) made a brief opening speech in which he high-lighted the advancements made in implementing Geosynthetics Engineering in modern Greek infrastructure projects. Through his following presentation Mr. Stratakos analyzed the benefits of incorporating geosynthetics in asphalt pavements.

In a series of presentations made by Mr. Morvakis (Greece Geosynthetics Sales Manager, Thrace NG) and his partners, four main objectives were developed:

  • the contribution of Thrace NG as a supplier in the latest infrastructure breakthroughs in Greece
  • the main functions which geosynthetics serve in civil engineering projects and the procedures that are used for their production
  • the importance of CE Marking and the Quality Control procedures and methods
  • the use of geosynthetics in flexible pavements

Reported by

Kollios Anastasios, Hellenic IGS Chapter President