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Do steel tubes installed by a vibrator have bearing capacity?

 

Of course! But the real question is: How much? And what will be the load displacement behavior? For a project of TenneT such piles have been tested near Breukelen (NL). The chosen proof load test method was Rapid Load Testing. Typically a job for the Rapid Load Tester of Allnamics, the StatRapid.

 

The steel tubular piles were part of the temporary foundation for a Mammoet mega crane. The load to be lifted over the railway line Amsterdam-Utrecht was a 325 ton transformer. Because insufficient load bearing capacity and/or large deformations could lead to disastrous consequences for the stability of the crane, it was vital to test the piles in advance.

 

It was requested to test as many piles as possible during a normal working day. At 7 am the work could be started with setting up the StatRapid device and at 5 pm testing had to be finished. During this 10 hour period as many as five piles were subjected to multi-cycle load tests. After testing the last pile, the StatRapid device was disassembled and well before dark all the equipment and testing and support teams had left the site.

 

Photo 1 : The assembly of the StatRapid device with the optical displacement monitoring system Reyca in the front

 

Video of setting up the StatRapid for the first test pile.

 

Photo 2 : Testing piles near the railway track

 

In conclusion, thanks to the good cooperation between Allnamics, Gebr. Van 't Hek, VROOM Funderingstechnieken, Joulz and Mammoet, five piles could be tested in one day, all with a positive result. The lifting operation of the transformer was carried out successfully two weeks later.

Photo 3 : The ‘real' test whether the piles where able to carry the full load.(Source: Light at Work Photography, Jorrit Lousberg c.b. TenneT)

 

Do you want to learn more about this project? Click one of the links below.

 

http://www.tennet.eu/nl/nieuws/nieuws/spectaculair-transport-van-loodzware-transformator-naar-breukelen/

 

http://www.tennet.eu/fileadmin/user_upload/Our_Grid/Onshore_Netherlands/Factsheet_Breukelen_SEP2016_web.pdf

 

Do you want to know more about Rapid Load Testing? Please contact Allnamics.

 

Vibration monitoring research project at Terneuzen, NL

 
On August 8th and 9th, 2016 Allnamics performed, together with Fugro and Fides, vibration monitoring at a test location in Terneuzen NL.
 

At the test location several abandoned buildings were available for monitoring the vibrations caused by a test drive of 3 large diameter steel tube piles. The piles were vibrated in up to refusal and then driven to final penetration with a large hydraulic hammer. This presented the researchers the opportunity to examine the buildings while being exposed to large vibrations and assess whether the building showed any resulting damage.
 
The vibration monitoring was carried out with 24 monitoring systems with 3 channel geophones on 4 separate buildings. The results of the measurements have been submitted to the SBRCUR committee updating the guidelines on vibration nuisance.

Photo 1 : The Vibro hammer PVE 2350 VM

Photo 2 : Vibration Monitoring during impact driving.

Photo 3 : Vibration monitoring on 4 different buildings with 24 systems.

Photo 4 : Vibration Monitoring at ground level

Photo 5 : Monitoring at corner of building at roof level

 

 


 
More information about vibration monitoring.
 
Or
 
Contact our office in Heemskerk
 


 

Crack monitoring Dutch home in Alphen aan den Rijn

 

In a home in the Dutch city of Alphen aan den Rijn cracks developed in the masonry due to the previous construction of an adjacent building. On July 31, 2017 a new crack was noticed and Allnamics was asked to ascertain whether any corrective action was required.

 

Initially  a visual inspection was performed and a plastic crack meter was installed.

 

Photo 1 Can you see the crack in the masonry?

Photo 2 The installed plastic crack meter.

Since this crack meter showed no obvious change in the crack width it was decided to carry out more precise measurements with Leiderdorp Instruments digital crack meters, which can detect displacements of 0.0061 mm (0.00025 in) and take a measurement as often as once every minute.  The meters were installed on March 16, 2017 and since that time the data logger sends daily reports with the measurements that are carried out every 15 minutes.

Photo 3 Step 1 : Installing anchors for the electronic crack meters.

Photo 4 Step 2 : Installing the electronics crack meters.

Photo 5 Step 3 : Placement of a protective case.

Photo 6 Step 4 : Connecting the sensors on the logger.

Photo 7 Step 5 : The closed protective case.

Graphic 1 The first measurements.

 

Graphic 2 The last days the temperature is showing a more day night pattern and the crack is responding to this.

 

If you are interested in crack monitoring please feel free to contact us.

 

PDR-system used for special bridge project in Cartagena, Colombia

 

For the highway from Cartagena to Barranquila, Colombia, the approx. 6 km long bridge “Viaducto Gran Manglar” is built just north of Cartagena through a shallow lagoon with mangroves.

 

Mangroves are protected vegetation and therefore a construction method with minimal environmental impact was required. The contract was awarded to the Italian contractor Rizzani de Eccher who proposed to build the bridge from a launching gantry, using precast concrete elements.

 

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This very special construction method – developed by Canadian piling & equipment company Berminghammer - has a minimal impact on the surroundings, because the footprint of the construction work is the same as for the bridge itself: the gantry rests on the front end of the already completed part of the bridge and cantilevers to the location of the next pier. At the front of the gantry the piles for the next pier are installed, while at the back the main girders of the bridge deck are installed. These girders (just as all other construction materials) are transported over the already completed part of the bridge instead of through the lagoon, further reducing the environmental impact.

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Essential for this construction method is the verification of the foundation piles’ bearing capacity for each of the 129 piers within hours after installation, because the piles will have to bear their maximum design load 72 hours after driving. For this reason Rizaani chose to purchase Allnamics PDR-systems and AllWave software, and have their staff trained on site by Allnamics. This enabled Rizzani to perform PDA and subsequent signal matching themselves, with Allnamcis support (both on site & remote). Rizzani also contracted Allnamics to perform the dynamic monitoring of the test piles and the development and implementation of the pile driving and acceptance criteria.

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The construction method with the launching gantry allows the entire bridge to be built with precast pre-stressed concrete elements. For production of these elements – piles, pier caps and bridge girders – a complete precast yard has been built next to the northern abutment of the bridge. All elements are then transported to the rear of the gantry, using the already constructed part of the bridge.

 

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The launching gantry consists of 2 parallel truss bridges, and  rests on 2 main support beams that are placed on already installed piers.  From there the gantry cantilevers approx. 50 m, just past the loacation of the next pier.  Running over the top of the gantry are 2 cranes and at the front there is a leader system, equipped with a Berminghammer B6505-HD diesel hammer.

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The hollow concrete piles with a diameter of 1,0 m and a length of up to 55 m are driven in 2 sections that are jointed together with a custom designed mechanical splice . The cranes move the pile sections from the rear to the front of the gantry where it is placed into the leader. Next the leader  is erected vertically, after which the pile section is driven. Once the pile section is installed the leader is lowered back to the horizontal position sothe next pile section can be accepted.

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After all 6 piles for the pier have been installed, they are cut off and a precast concrete cap is mounted over the pile heads. Once a temporary support is placed between this pile cap and the gantry, the front main support can be moved to this new pile cap and the rear main support is also moved up one pier. Then when both main supports are in their new position, the whole gantry is moved one span forward (approx. 37 m), with the leader ending up just past the location of the next pier to be constructed. But before the piles for that pier are driven , the girders for the bridge deck are mounted up to the just finished pier.

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With the launching gantry working at its normal pace, this installation cycle takes 3 days. For that reason the piles will get their maximum design load after 72 hours, when the gantry with leader cantilevers just passed the freshly installed pier cap. In each cycle, the pile bearing capacity needs to be verified in time for that.

 

Rizzani started piling at the north end of the bridge in August 2016 and will soon start with a second gantry at the south end.

 

For dynamic pile monitoring on two fronts Rizzani has purchased a second PDR-system.

 

 

Video of Berminghammer.

 

Static Pile Testing on an existing wooden pile foundation in Amsterdam

 

In March 2017 Allnamics performed SLT-monitoring for a client in Amsterdam. The timber piles under an existing building were presumed to have inadequate static bearing capacity and therefore needed to be tested.

 

Most buildings in the center of Amsterdam have wooden piles foundations with approx. 12 m long timber piles that are driven into the so-called first sand layer.  However, at some locations this first sand layer is not there and in that case piles of that length will have inadequate (toe) bearing capacity.

 

To testing an existing wooden pile foundation specialized monitoring equipment is required.  The process begins by creating a small excavation pit to expose the top of the timber pile and given the high water table continuous dewatering is necessary to keep the pile top exposed.

 

The pile head is then cut off and prepared so a steel plate can be placed to ensure that the pressure applied by the hydraulic jack is equally distributed over the pile head.  On top of that steel plate a load cell and a hydraulic jack are placed, while below the plate a special reference frame is constructed to mount potential sensors that will monitor the displacement.

 

The load cell and the potential sensors are connected to a PDR (either a Quad-PDR or a standard PDR) that is connected to a laptop with the Allnamics-SLT software. The software is able to show all test data both in tabular and graphical format.

 

During the test, the pile load is controlled manually in accordance with the client specification and local regulations.  Typical test results are shown in the graphs below.

 

The ultimate load capacity can be then determined as specified by the client.  This is commonly defined as the load that causes a displacement of 10% of the pile diameter, but it can also be defined in accordance with various other methods, such as Chin-Kondner, Davisson, Van Delft, or Van der Veen.

 

Allnamics developed for this type of Static Load Test a monitoring equipment set with a load cell that has a very high accuracy (+0.23kN) over the relatively small operating range (up to 1 MN), which is more than adequate considering the actual loads on these timber piles.   

 

 

Photo 1 : The load cell with cable and USID connector for connection on the PDR

 

Inside the load cell’s connector is a memory chip that contains information on the load cell such as calibration data and various information for checking the proper functioning of the load cell.

The load on the pile can also be checked using a pressure sensor attached to the hydraulic system. For this purpose Allnamics selected a sensor capable of monitoring hydraulic pressures up to 70 MPa (700 Bar) with an accuracy of 28 kPa.

 

 

Photo 2 : The pressure sensor with cable and USID connector for connection to a PDR

 

Apart from monitoring the force on the pile head accurate monitoring of the pile head movement is essential. For this purpose Allnamics selected potential sensors with a range of 200 mm and an accuracy of 0.15 mm.

 

Photo 3 : The potential sensor for monitoring the movements during the pile test

Photo 4 : The wooden pile cut off and 4 plates for the potential meters are placed around the pilehead.

 

 

Photo 5 : The pile with steel plate, load cell and yellow piston with the pressure sensor on the hydraulic system.

Photo 6 : The pile with reference frame and potential meters installed

Photo 7 : Overview of the Static Load Test underneath an existing building

Photo 8 : The Quad-PDR with at the background the test location underneath the existing building.

Photo 9 : The measuring specialists behind the monitoring software.

Graph 1 : The measured force of the load cell in time

Graph 2 : The measured positions of the potential measurements in time

Graph 3 : The calculated average settlement of the pilehead in time

The results indicate that the creep criterion was not yet met at the end of load step no. 5. In this case it was decided to calculate the final set of this step by extrapolation and proceed to the next load step.

Graph 4 : The load – settlement diagram of the wooden pile

 

 

If you are interested in Static Load Testing please contact us.
 

PDA monitoring for new Blue Piling hammer with 4000 ms samples

 

In spring of 2016 Allnamics was involved in monitoring the performance of a prototype of the new developed Blue Piling hammer. The performance tests were done in the Caland Canal in the Rotterdam Harbor, on a dedicated 140 m long test pile. This pile has sufficient resistance for pile driving hammers with a large energy output. In January 2013, at the same location, Allnamics was also involved in a PDA test for the acceptance of the (at that time) largest hydraulic hammer in the world, the Menck MHU 3500 S.

 

The Blue Piling hammer type is developed by Fistuca. Its working principle is explained on the website of Fistuca and is different from traditional hydraulic hammers or diesel hammers. One of the differences is the much longer load cycle duration of a single hammer blow.

 

The monitoring had some special requirements. First, next to the pile, also the housing of the hammer had to be monitored. Second, because full loading cycles had to be monitored, measurement samples of 4000 milliseconds had to be recorded. For the 140 m long test pile, this corresponds to approx. 70 stress wave periods (2*L/c). For standard PDA monitoring, international standards (ASTM, Eurocode) require a minimum sample duration of 6-8 stress wave periods, at a sample rate of at least 10 kHz. With the Allnamics PDR-system and Allnamics-PDADLT software, it was possible to monitor pile and hammer simultaneously for 4000 ms at 12.5 kHz sample rate during each blow. A new milestone!

 

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Photo 1 The Blue Hammer from Fistuca

 

Fistuca2

Photo 2 PDA Measurement with the PDR and sensors on the pile and hammer housing.

 

After instruction and training by Allnamics staff during the first day, engineers from Fistuca performed the PDA measurements themselves. For a period of 1 month the equipment was continuously exposed to humid and salty weather conditions, performing 100% of the time. This was another milestone in endurance of the equipment.

 

 

 

In case you are interested in more information on Pile Driving Analysis, Hammer monitoring or the PDR-system, please feel free to contact us.

 

Research project DOT500 – Vibratory Driving Prediction and Analysis

 

On May 6th 2016 a monopile foundation has been vibratory driven into the ground for a full-scale test of a newly developed wind turbine.

 

Allnamics performed vibratory driving predictions in order to quantify the required vibro hammer (CV320). During actual installation Allnamics performed so-called VDA monitoring. The Vibratory Driving Analysis results in records of strain and acceleration in the pile. This offers the possibility to verify assumptions made for the prediction and consequently effectively close the double loop of the learning system.

 

The time-lapse presented below offers an impression of the monopile installation.

 

 
 
If you want more info about VDP or VDA?  Contact us!
 
More info about the CV320 or Cape Holland ?
 
More info about the DOT500 ?

 
 

StatRapid testing at Yara Sluiskil

 

On the 4th of July 2016 Allnamics checked the capacity and stiffness of 4 production piles (Fundex-type), commissioned by contractor Ballast Nedam Industriebouw BV.

 

The piles are part of the tank foundation for the UREA Granulation 8 Project on the production yard of Yara in Sluiskil, the Netherlands. Rapid Load Testing system StatRapid has been deployed, with which, following CUR guideline 230, the load-displacement behaviour of the piles has been determined.

 

The proof load testing was a contractual requirement and the (positive) results are regarded as representative for the entire tank foundation. Consequently the foundation slab has been cast with high confidence in the foundation design.

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Dynamic Pile Testing for Amstel Towers Hotel in Amsterdam

 

In April 2016 Allnamics has performed PDA-monitoring and DLT-testing for our client Voorbij Funderingstechniek BV, for the Amstel Towers Hotel near Amstel station in Amsterdam. The tests were done on 51 m long precast concrete piles, driven in sections, with a mechanical joint.

 

PDA monitoring (Pile Driving Analysis) was done during full installation cycles of selected production piles. Main goal of the test was to check the tensile stresses during driving, in particular at the location of the mechanical joint.

 

DLT-monitoring (Dynamic Load Testing) was done during restrike (approx. 10 blows) on piles that had been installed a couple of days earlier. Main goals of this test were to check the strength of pile shaft and joint and the static bearing capacity  of the pile.

 

Both tests were performed with the in-house developed Allnamics PDR-system, fitted with combined strain and acceleration sensors, which were mounted near the pile head. The PDR reads and stores the monitoring data real time and transmits them with a wireless connection (by WiFi) to the field computer of the monitoring engineer. The wireless connection offers great advantages during upending and positioning of the pile and makes it possible for the monitoring engineer to do his monitoring job on a good location, at a safe distance from the pile and without traditional worries about the long cable getting stuck or damaged during handling or piling.

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Photo 1 : Monitoring with WiFi connection, at a safe distance from the pile

The tests showed that the tension stresses during driving were acceptable and that the available static bearing capacity is sufficient for the design loads of the piles.

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Photo 2 : no trouble with long cables during upending of the pile

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Photo 3 : pile and monitoring equipment at end of PDA

Recorder function of PDR used for offshore PDA-test

 

In september 2015, Allnamics was asked to monitor stresses in the flange and on the inside of a monopile for an offshore windfarm, during installation of the pile with an impact hammer. Special challenge was that all the instrumentation had to be mounted on the inside of the pile, with limited space AFoto01available for placing sensors and equipment. On top of that, drilling and welding were not allowed and the test had to be completed within 3 weeks after the first enquiry. The recorder mode of the Allnamics PDR, ingenuity and improvisation made it possible!! AFoto02

 

The instrumentation consisted of 2 acceleration sensors placed vertically, 2 horizontal strain gauges on the flange and 4 vertical strain gauges on the inside of the pile wall; this setup also incorporated a “normal” PDA (Pile Driving Analysis) setup. 2 PDR-systems were used for data acquisition of these 8 channels, with the acceleration sensors used for triggering.

 

Challenges

Main challenge for this project was that the instrumentation had to be installed on the inside of the pile, because of the hammer sleeve. Obviously this would make it impossible to establish a wireless connection to a computer on the vessel. But a cabled connection was also not possible, because the pile did not contain a cable outlet hole or snorkel hole near the pile head and below the hammer sleeve.Measuring on the inside of a pile without any communication from the outside was solved by using the Allnamics-PDR in recorder mode. All monitoring data were saved and stored in the PDR-systems during pile installation and transferred to a computer after they were retrieved from the pile.

 

Figure 1 : Configuration D: PDR operating in recorder mode

Figure 1 : Configuration D: PDR operating in recorder mode

 

The required battery life time of the PDR needed to be approximately 12 hours. The installation cycle was expected to be around 3000 blows By using an external battery the monitoring time could be extended to 12 hours. The standard memory is already able to record 10.000 blows.

 

Positioning of sensors

Next challenge was the restrictions imposed by the space that was needed for the grippers of the upending tool and an airtight platform that had to be mounted inside the pile, before removal of the equipment. This required mounting of the instrumentation above the platform, less than 1 m below the pilehead. All in all very little space for positioning the sensors and recorders was left.

 

Photo 1 : The gripping tool just before pile upending

Photo 1 : The gripping tool just before pile upending

 

 

Photo 2 : airtight platform in mobilization port

Photo 2 : airtight platform in mobilization port

 

Photo 3 Finding space to place sensors and monitoring equipment (pile in horizontal position)

Photo 3 Finding space to place sensors and monitoring equipment (pile in horizontal position)

 

Mounting of sensors

The next challenge was the way to mount the acceleration sensors and the PDR-systems without drilling holes in the pile or welding on the pile. For the strain gauges (and their tension relief) this was solved by glueing them on the pile. For the acceleration sensors this was solved by adapting their housing, so they could be bolted to the earthing stubs that were already inside the pile.

 

hoto 4 : Earthing stub used for mounting the acceleration sensor and the strain gauge glued directly on the pile

Photo 4 : Earthing stub used for mounting the acceleration sensor and the strain gauge glued directly on the pile

 

For suspension of the PDR-systems this was solved by placing wooden stub between the flange and the platform ring. The stubs were kept in position by using the bolt holes in the flange and the stiffener plates of the platform mounting ring. Each PDR was suspended between 2 stubs, with elastic bands.

 

Photo 5 : One of the 2 PDR’s mounted between 2 wooden stubs (pile in horizontal position)

Photo 5 : One of the 2 PDR’s mounted between 2 wooden stubs (pile in horizontal position)

 

Execution of the project

Next challenge was to prepare and monitor the project within 3 weeks from the first enquiry. The mounting of the sensors had to be done outdoors, in the mobilization port prior to pile installation on site. Conditions were quite hostile that day, cold and very windy!

 

 

 

Photo 6 Installing the sensors from a cherry picker: 2 acceleration gauges & 6 strain gauges

Photo 6 Installing the sensors from a cherry picker: 2 acceleration gauges & 6 strain gauges

 

But al sensor mounting and glueing went smooth and successful. After all these challenges were solved, there was one more left: Allnamics had no monitoring specialist available in the planned time frame for the offshore testing campaign….  Luckily our German partner company Fichtner could provide us with one of their specialists to do the job offshore!  The PDR’s were successfully retrieved and had recorded all blows, giving the client valuable information of the pile during driving without disturbing the production process.

 

Photo 7 : The piles on deck of the installation vessel

Photo 7 : The piles on deck of the installation vessel

 

Photo 8 : Bringing the pile in position

Photo 8 : Bringing the pile in position

 

Photo 9 : Hammering down the pile down

Photo 9 : Hammering the pile down

 

Photo 10 : Exciting moment: just after lifting the hammer

Photo 10 : Exciting moment: just after lifting the hammer

 

Photo 11 : The equipment after pile installation and installation of the airtight platform.

Photo 11 : The equipment after pile installation and installation of the airtight platform.

 

In case you are interested in more information on Pile Driving Analysis or the PDR, please feel free to contact us.