jobsite report yerseke, stabilisation with geocrete® of ......dosing unit and the wirtgen ws220 was...

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Where: Yerseke, NETHERLANDS, Seashore area. What: National Sea dikes, stone carpet with sandy clay underneath. M2 / M3: 35.000m2, depth: 0,40m and 14.000 m3 Used: GeoCrete® Mix ST03 with Cement CEM I, 52,5R Cliënt: Head contractor: F.L. Liebregts B.V. / Rijkswaterstaat bureau Zeeweringen

JOBSITE REPORT YERSEKE, Stabilisation with GeoCrete® of silty clay in a coastal protection dike.

P.Box: Postbus 49 5740AA, Beek en Donk

Netherlands Phone: (0031)492 – 351077

Fax: (0031)492 – 352508 Mailbox: [email protected]

A stabilized foundation for a “stone” construction on a sea wall with GeoCrete® .

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SITUATION :

The seawall at the Oosterschelde near Yerseke should be reinforced with a construction on a stabilized foundation bed with a thickness of 40 cm. Between the stabilized base course and the construction is a water-permeable geotextile with a so-called “filter / street layer” of +/- 14cm. To this the setting stones are layed automatically. PROBLEM: Over almost the entire route length of the clay dike is in such a bad strength and

stability that it should be replaced by a foundation material on which a special stone construction can be placed. In addition, the silty clay allows easy water to flow through allowing the stone construction may be endangered. With the traditional method, the silty clay layer had to be excavated and replaced by a layer of granulated blast furnace slag from 80 cm. The excavated clay must first be put in depot prior to further processing and deposition. This leads to extra time / removal and processing costs. Sales of the silty clay is an additional problem for the customer “Rijkswaterstaat” and due to the enormous volume of transport movement a lot of damage is to be expected in the immediate vicinity of the village and business park Yerseke. PURPOSE:

The stabilization method had previously been used in a pilot project in 2010 in which the naturally occurring clay was stabilized with binders / excipients in such a way that the use of the stone construction was possible without reducing the sealing function of the dike. The stabilizing clay was treated in 2010 in a layer thickness of +/- 45 cm The client is examined in conjunction with the administrator Rijkswaterstaat if the stabilization method could be optimized within the new dike improvement project . For this project in total between the 12,000 – 15.000 m3 needed to be excavated and disposed. Costs for transportation and disposal / storage of these silty clay would have become unacceptably high. In addition, this entire logistics operation would give an enormous burden for the local village and industrial area where a large part of the transport went through.

Photo 1: Sketch of the Dike and Yerseke with the surroundings .

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The ramp surface on which the ( bottom ) stabilization had to be carried out was 25% To 28% ( slope gradient 1 : 4). The work had to be done in the tidal zone , and there is talk of ebb & flood of the sea - level. Free period for consecutive could be stabilized was set for +/- 5 hours.

Research :

Given the nature and urgency of this work, there was not time to have extensive pre work testing in laboratory conditions. We have chosen the dose of the binders used in the pilot project in 2010 and where the experience and expertise of the specialists were decisive. Beginning in mid- April 2015 from the existing embankment soil samples were taken at several places and then tested for water permeability (K - value). The water permeability test is done by FUGRO in six consecutive days. The K- value indicated that the displacement by stabilized cylinder +/- 5 cm and 4 cm is within 24 hours.

Photo 2: The stone construction , the street layer , beneath geotextiles and stabilizing layer of Geocrete® .

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Equipment used :

The stabilization was performed according the so-called in-situ method in which the binders, with special equipment suitable for this purpose, are directly milled into the existing soil. Because of the strong slope gradients are this used equipment powered by caterpillars. Was the deposition of the binders at the start done with a caterpillar propelled spreaders with a cargo capacity of 10 tons. However, due to the steep slope the machine, in combination with the poor bearing capacity of the soil, could only be loaded for 50 %. Additionally, it could only spread the binders driving backwards. There was a reasonable amount of dust. The reason for this was the presence of wind on the coast and the fact that the caterpillar was scattering the Geocrete in two paths needing to drive through the first path while depositing in the second path. After a few weeks the caterpillar was therefore replaced by a Streumaster SW3FC fronts scatterer to which on the boom a 35 tons crawler crane is mounted. This custom spread dosing unit and the Wirtgen WS220 was constructed done by Terrastab BV by for these conditions. Under these stray -unit was also a cultivator mounted so that the clay could be ripped open, whereby the scattered binders remained to stay in place, which gives a more accurate dosage method and the dust has now also a great deal reduced.

Photo 3 + 4: The Automated deployment

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For the routing in the clay - layer of the binders, the use was made of a caterpillar driven tractor Challenger MT 665B with a Wirtgen WS2200 milling unit. This combination may easily achieve a milling depth of 45 cm. For optimum depth control it is important that the machine will not sink into the bad unstable substrate. Especially for this pupose Terrastab BV adapted the Wirtgen WS2200 with a track powered cradle. After the ramping of the binders, the clay layer was compacted with a crawler crane and, with the use of a GPS surveying system, brought to the correct profile.

BINDERS :

As a special additive the use was made of the excipient GeoCrete® This auxiliary substance can be adapted to all different circumstances and, therefore, the GeoCrete® is tuned to salt water conditions. The Geocrete type ST03 variant is more suitable for saline / brackish water conditions. The GeoCrete® is mixed with the cement type : CEM I , 52.5 R which were delivered in bulk trucks . This type of cement is chosen because of its increased initial strength in combination with a relatively high hydration speed. On the working place the active binders GeoCrete® and the cement are delivered as a a turnkey pre-mix and could be processed DIRECT through the spreader. There is therefore no need ( extra ) or separate mixing activities needed . The total quantity of pre-mix : 8% (Cement and GeoCrete® together ) Per m3 ground = 168 kgs Pre mix processed. Per m2 = 65-70 kgs Pre - mix processes

Photo 5 + 6: In Situ milling on a 28 % slope

IMPLEMENTATION of the soil stabilization.

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The implementation of this soil stabilization was accompanied by a number of aggravating circumstances. □ Slope of 25 %. □ Extremely short processing time because of tides (max. 5 hours). □ A salt water saturated clay subsoil. The binders are in two ( 2 x 34 kgs / m2) swaths scattered and milled areas, this is to prevent spreading of the binders as much as possible. Occasionally the stabilization machines needed help if they could not drive back up the slope on its own.

Verification and results:

Despite the short processing time and the curing under saltwater conditions the stabilization held up well. Because the processing time is relatively short in order to apply the stabilization, any kind of time gain is of great importance. The fact that the Geocrete excipient was pre/mixed ex factory, this could be seen as a significant advantage in this project. The cement / additive comes as "ready to use" pre-mix to the work, and can be directly spread and processed.

The hydraulic crawler excavator is always checked during construction if the treated layer thickness was achieved. The check moments are also recorded by GPS. Every day samples were taken from the milled mixture that are compressed in a proctormal. There are two proctor cylinders per production day at the work site. Every fifth day of production at least one cylinder is brought to an external laboratory to test the permeability. On the request of the client on May 18, 2015 a chunk out of the Geocrete stabilized layer was removed. It was observed that the stabilization was sufficiently bounded and the molded foundation layer was mixed sufficiently homogeneous.

Picture 7 + 8 : Verification of the layer thickness and under the compound proctor cylinders.

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Design .

I the report of Infram No : 07i128 date of Jan. 14 . 2009 called "design methodology for the use of of GeoCrete®” ( client report : Project Zeeweringen ) one can find the principles for dike design and stabilization techniques using Geocrete®

Photo 9: The extracted fragment of May 18, 2015 whereby the mixing result is visible.

jobsite report yerseke, stabilisation with geocrete® of ......dosing unit and the wirtgen ws220 was...

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