Building site monitoring

The advantage of SOCOTEC is that we work completely independently. In addition, our knowledgeable staff is on site to relate the influence of the subsurface to the results of pile installation. In case of piling or drilling problems, a geotechnical consultant is immediately involved in the project in order to get the work back on track quickly. 

Plate printing tests 

Does your foundation conform to the design? SOCOTEC can carry out plate pressure tests to verify the compaction of a rubble or mixed aggregate package and determine its subsidence constant. 

When performing a plate pressure test, increasing pressure is applied to a circular plate (Ø300 mm or Ø762 mm). By accurately measuring the applied pressure and the settlement the plate undergoes at this pressure, statements can be made about the bedding constant and degree of compaction in accordance with DIN-18132. 

The advantage of plate pressure testing is that it shows immediately whether the test requirements are met. 

SOCOTEC provides plate compression tests both at home and abroad and is directly involved in the realization of wind farms and distribution centers.

Acoustic testing of foundation piles 

Although building a concrete-pile foundation is a well-known process in the Netherlands, there are various factors that might lead to the reduced functionality of a pile. 

SOCOTEC offers you a cost-effective and fast method to check the integrity of your concrete-pile foundation: acoustic testing. We have over 30 years’ experience in this. 

Concrete foundation piles are acoustically tested using a handheld, plastic hammer to create a shockwave in the pile. We accurately measure the shockwave with a sensor on the head of the pile, so that we determine the integrity of the foundation pile. 

SOCOTEC ill often communicate the results to you the next working day. 

We carry out the measurements in accordance with CUR Recommendation 109:2013 “Acoustic testing of concrete foundation piles”. (CUR-Aanbeveling 109 (cur-aanbevelingen.nl)) 

Concrete foundation piles that have been poured in the ground cannot undergo acoustic testing until the concrete used has completely hardened after five days. 

If the aforementioned waiting period of at least five days is a problem, you can consider testing the integrity of your concrete-pile foundation using a thermal inspection of the piles. The advantage of this method is that after just 18 hours it is possible to determine any possible distortions in the pile. 

For thermal inspection, temperature sensors are attached to the reinforcement before the foundation pile is poured. Accurately measuring the temperature whilst the concrete hardens reveals any temperature differences, making it possible to determine whether there are constrictions or other defects. Since concrete starts to harden as soon as it is mixed, it is possible to decide on whether or not there are defects in the pile after as little as 18 hours. 

If you wish to have even better control of the work, in addition to the aforementioned quality control measures, SOCOTEC can also supervise your pile-driving or drilling work. 

Soil improvement test 

Soil improvement is generally done using sand, rubble or concrete and brick granulate in the Netherlands. The aim of soil improvement is to avoid the construction involved (a building, a spot to install a crane, etc.) requiring a more expensive pile foundation rather than a foundation on steel.

When improving the soil, it is important that the soil improvement has sufficient bearing capacity and that this is checked and guaranteed, so that no unexpected damage or distortion can occur. Soil improvement using rubble or concrete and brick granulate can be tested using a plate load test.

Soil improvement using sand can also be tested using manual probing tests. Theoretically or if desired, soil improvement using sand can also be tested using a plate load test, but it should be noted that carrying out a plate load test is a lot more cumbersome than testing by hand. 

Manual testing

For manual testing, cones with a surface area of 1 cm², 2 cm², 3.5 cm² or 5 cm² are pressed into the ground by hand using probing rods to a maximum depth of 1.0 m. During manual testing, the resistance that occurs is read off on a manometer and written down. Whilst carrying out the manual testing, SOCOTEC will also carry out manual drilling.

This achieves two things:

• The foundation is verified using visual identification
• By placing a manual sound in the drilling hole, it is possible to achieve insight in the underground at a greater depth

In this way, a manual test can in general be carried out down to the phreatic zone or a maximum depth of 3 m to 5 m under the surface.

In addition to a handheld probing device, use can also be made of a hand penetrometer. In contrast to the handheld probing device, the hand penetrometer does not have probing rods but has a standard length of 0.8 m. In addition, the hand penetrometer automatically makes a digital record of the resistance measured.

SOCOTEC can provide measurements using both the handheld probing device and a hand penetrometer.

Automated measurement of settlement rods

Settlement as a result of embankment is usually measured with so-called traditional settlement rods whose height is periodically measured so that the settlement can be determined. The manual measurement of settlement rods is relatively time consuming and human error is possible. The use of automatic settlement rods means that the settlement occurring can be measured remotely, at high measurement frequencies and measurement accuracy  and the measurement data can be made available online. 

How does the automatic settlement rod work? 

Before work can start on making the embankment, a bar is pressed down into the hard Pleistocene sand layer with the aid of a truck. After that, a settlement rod is placed on top of the bar. An automatic telemeter is then attached between the bar that is not subject to settlement and the settlement rod. The telemeter is attached to a datalogger with a modem.

SOCOTEC presents the measurement data on a web portal. Using your login, you can see the data yourself real-time and export it for your own use and analysis. 

Use of automatic settlement rods creates a reliable, accurate (1 mm) and continuous series of data. This makes it faster and easier to determine the residual and final settlement, since the high data density and accurate measurements permit faster and more reliable recalculation of the progression of the settlement over time. As a result, it can be determined faster whether the assumptions with regard to the soil parameters, the necessary settlement/preloading time and the amount of preloading required were correct. In the end, this can prevent too much residual settlement from occurring in the underground. 

Advantages of automatic settlement rods 

Use of automatic settlement rods creates a reliable continuous series of data with a high degree of measuring accuracy of 1 mm and a high measuring frequency. This makes it faster and easier to determine the residual and final settlement, since the high data density and accurate measurements permit faster and more reliable recalculation of the progression of the settlement over time. As a result, it can be determined faster whether the assumptions with regard to the soil parameters are correct and whether the points of departure such as the necessary settlement/preloading time and the amount of preloading required were correctly assumed in the design phase. Too much residual settlement of the underground can thus be prevented. 

Ground resistance measurement 

The determination of electrical resistance in the soil is carried out with geoelectric equipment (Sonel MRU120). 

For this purpose, the Wenner method is used, in which 4 electrodes (metal pins with length of 30 cm and diameter of 1 cm) are pressed into the ground at a certain interval. The electrodes are connected with a cable to a resistance meter. The resistance is measured and noted. After this, the pins are placed at increasing distances apart.