Light Weight Deflectometer (Part 1)

Light Weight Deflectometer (LWD) with Geophone

Light Weight Deflectometer is not like Light Weight Deflectometer. Watch out for the differences between two types of eqipment. It is a non destructive test (NDT) equipment for dynamic load testing of load bearing capacity. Light Weight Deflectometers are offering the most economic way to do non destruction test (NDT) of compaction quality of unbound or partially bound material in earthworks, road constructions, canal construction, railway constructions and utility trenches, all as one single solution. The one person test procedure is done in less than two minutes and still provides full results. No counterweight (truck or roller) is required and tests can be done in places hard to enter. The equipment has no radioactive sources and all tests can be done by one single person.

There are two different types of Light Weight Deflectomete in existence: One type is operating via a Geophone and one type is operating via an acceleration meter. TERRATEST® is the only manufacturer in the world producing both types. And there are many more differences of facilities between these two types of test instruments. The acceleration meter Light Weight Deflectometer (german dynamic load plate test) was invented in Germany several decades before. It meets the german specification TP BF-StB Part B8.3, the ASTM E2835-11, the Austrian specification RVS 08.03.04, the Spanish specification UNE 103807-2:2008, the cChinese specification TB 10102-2010, J338-2004 (standard for soil testing in railway construction), the Czech specification CSN 736192-1996 and the RIL 836 for track laying of Deutsche Bahn (German railway). The geophone type meets the ASTM E2883-07, UK standard IAN 73 and Italian standard UNI 11531-1.

Terratest as the leading manufacturer of Light Weight Deflectometer is asked frequently by customers from all over the world, which type is the best for which requirements. An answer is not as easy as it seems.

First of all customers have to follow the required specification of their specific project in their country. According to the required specification they have to choose the corresponding type. If no specification is required, the type should be chosen according the operation area.

The accelaration model is far easier to use. But it gives the user even less features than the geophone one. Following the instruction manual, one single person can handle the gauge immediately, no training is necessary. The test procedure does not require a counterweight like a truck or roller and the test procedure needs less than two minutes. Immediately after the test procedure users can printout a test protocol and will have the result in their own hands. In Germany results can be used according to the specifications ZTVA and ZTVE as an official compaction proof.

Thanks to the short time needed for each single test the compaction quality of all layers can be tested all over the construction site, even on natural ground before starting the earthworks.

It provides an immediate method to the workers in the construction site before, during and after the compaction process to determine the load bearing capacity of unbound soil to make a statement about the compaction quality. Moreover the compaction process can be managed directly at any stage of the procedure The Light Weight Deflectometer is used for self monitoring and even to provide official proofs.

Light Weight Deflectometer for Safe Foundation

The construction boom in Germany is continuously growing. Comfortable prefabricated houses and solid buildings are in progress all around. The bearing capacity of the soil is an imperative condition to be evaluated beforehand - particularly below the foundation plate, as this element represents the interface between house and subsoil. It is the purpose of the foundation plate to distribute the weight of the building in a homogeneous manner and to protect the building from heat/cold and vibrations of the ground. The available ground however is often not strong enough to carry the foundation plate without additional earthwork. Therefore besides deep sounding, analysis of the bearing capacity of the grown soil is required. A light weight deflectometer is an adequate instrument, since it is able to perform a measurement within only two minutes. The simple service as well contributes to a quick establishment of comprehensive measurement sequences. This way, a qualified assessment concerning the entire field is possible in no time. In the case of cohesive soil or inclination of the site, soil replacement has to be carried out. Sometimes several meters can be involved. For these works, it is important that the new soil is inserted by layers and that these layers are individually compacted by vibratory plate. Thickness of each layer should not exceed 30 cm, and evidence of qualified compaction must be provided each time. For this inspection, a light weight deflectometer is an ideal instrument. Minimum requirement for the bearing capacity of soil for private homes usually amounts to 30-40 MN/m² for the layer directly below the foundation plate.

„During each construction project, we carefully examine the quality of the earthwork for cellars and foundation plates. Compaction work and subsequent compaction control is of major importance. Particularly in places with difficult access, there is no alternative to light weight deflectometers. They do not need a counterweight, and the assessment is easy to perform “, declares project manager Kai Wolts. Mr. Wolts and his company recently invested in 14 light weight deflectometers produced by TERRATEST from Berlin. From now on, each construction gang disposes of its own measuring equipment and can immediately provide itself evidence for the compaction of the soil. „This fact ensures our independence from external geotechnical experts, thus saving time and money.”

All around Germany, light weight deflectometers make themselves indispensable, as settlement damages turned out to be a serious topic for several companies, causing major follow-up costs. Particularly for foundation plates, insufficient compaction of the subsoil gives rise to exorbitant expenses, as the whole building may be subjected to cracks. Therefore before pouring the foundation plates, measurement of the bearing capacity of the subsoil is imperative. „Since many years, we trust in light weight deflectometers, and are continuously in action in the vicinity of Berlin with three of them”, emphasizes construction engineer Norbert Wenzel from Frankfurt (Oder). „Besides prescribed core sounding, we are carrying out also measurements by means of light weight deflectometers, to ensure homogeneous bearing capacity and sufficient compaction quality of the soil, before pouring the foundation plate. This is an essential element of responsible construction management”, so his opinion.

The essential benefits of light weight deflectometers are obvious: 

• Measurements can be carried out by each capable member of the team in no time.
• Large measurement sequences are possible even under tight deadlines, as each measurement takes only two minutes.
• Counterweights like road rollers are not necessary.
• Compaction work for each layer can be accompanied by measurements.
• Homogeneity of bearing capacity can be checked already during insertion of the layers.

Light Weight Deflectometer at Bauma 2019

This was the fourth time in a row that we presented our light weight deflectometer for dynamic load plate test at BAUMA in Munich, since its market launch in the year of 2010. Also this year, the BAUMA broke all records with 620,000 visitors and 3,700 exhibitors from 63 countries – the best result in the 65-year history of this trade fair. Particularly the huge number of visitors from abroad (250,000 were counted) was remarkable. This became visible also at the TERRATEST® booth. “Again we could sell some light weight deflectometers to clientele from China and India, the Chinese client even ordered a set of several items”, resumes Frank G. Schulz, CEO of TERRATEST. ”Orders from Eastern Europe were received as well, and for the first time we did business with a company in Malawi (South Africa). That’s one more country in our list!”

The rush of professional visitors from numerous sectors like road, track and channel construction, civil engineering, gardening and landscaping exceeded all our expectations. Access to our booth sometimes proved to be difficult. Falko Weiß, sales manager of TERRATEST® mischievously smiles: ”A particular highlight was the complaint of one of our competitors. He asked from the fair management to cover our prices, because they were so low that he could not tolerate.”

One fact that our competitor did not take into consideration was the curiosity that covered price tags incite from visitors. “Oh, what kind of secret is hidden over here?” Finally visitors of course found out that our prices are so favorable, that ordering could not be a wrong decision, and the number of sold light weight deflectometers broke all records. TERRATEST this way achieved the highest turnover during a fair participation ever.

Fabrizio Schulz, the son of the company founder, was present as well.” I already belonged to the staff during the BAUMA in Delhi, but BAUMA Munich was far beyond my expectations. I even sold some instruments myself, and will definitely participate in the next BAUMA as well.” TERRATEST® presented the well-known light weight deflectometer for compaction tests of soil, available with cable and Bluetooth. The Bluetooth model was launched to the markets during a previous BAUMA fair, and meanwhile exists in an upgraded version with Bluetooth Low Energy (TERRATEST® 6000 BLE). Bluetooth models can be used with iPhone as well as with Android APP, so that measuring electronics do not need to be transported anymore to the construction site. These models can completely be operated via smartphone.

During this event, our new Light Weight Deflectometer TERRATEST 9000 LWD was also presented for the first time in Germany. This instrument features one central and up to two additional geophones (available upon request), furthermore a load cell which allows falling weight and falling height to be modified. The falling weight of 10 kg this way can be increased by two times five kg, i.e. to 15 and to 20 kg, to carry out the compaction test. This model has been developed mainly for exportation into countries with corresponding test specifications, i.e. for clients in UK, Italy, Korea, India, Saudi Arabia and many African countries.

Our staff is meanwhile preparing the next trade fair, because “After the BAUMA is before the BAUMA.” And thanks to our helpful competitor, we found a new slogan: ”Our prices should be forbidden!”                

Light Weight Deflectometer with Geophones and Load Cell

Four years of intense development work have been crowned with success. TERRATEST® on the bauma Shanghai is proud to present its new high-tech model of Light Weight Deflectometer TERRATEST 9000 LWD for the first time, thus reaching the top in the field of light weight deflectometers. This device for measurement uses a central geophone instead of an acceleration sensor, thus significantly increasing the precision in the case of high rigidity. “Meanwhile we are in contact with dealers in Saudi Arabia and Korea, ready to offer our devices in these countries”, explains Sven Krone, CEO of TERRATEST LWD GmbH. “This model is produced particularly for export, as no test specification in Germany for this type of instrument exists. The situation in USA, Canada, Great Britain, Italy, India and South East Asia however is different, so there is a strong demand.”< The configuration enables two external geophones to be attached additionally, in order to measure settlement at a distance of up to 60 cm. An integrated load cell is provided as well, so that falling height, plate diameter and mass of the falling weight can be optimized by the user whenever needed. The four plate diameters amount to 100, 150, 200 and 300 mm; falling weights with a mass of 10, 15 and 20 kg can be used. The load measurement is correspondingly taken into consideration for the calculation.

Production enhanced by Synergy Effects

For the production, TERRATEST® can exploit synergies, which becomes obvious by the optical appearance of the device, hexagonal shape of the falling weight and the inclined load plate handles. Development of smartphone App and software is based on proven resources as well.

The new light weight deflectometer TERRATEST 9000 LWD has been conceived for international markets, and results from a development phase of four years. The instrument features a central geophone and a load cell; two external geophones can be attached as well.