Earthwork check tests

The compaction of loose soils and building infill materials are a central activity of day to day operations on the building site. Many construction defects can be attributed retrospectively to an insufficient load-bearing capacity or inadequate compaction of the subsurface. Only when unambiguous verification of the quality of the earthwork exists are you protected against expensive remedial work. Professionally conducted earthwork check tests protect you from ruts forming in road surfaces or subsidence occurring in excavation pits.

To determine the load-bearing capacity of soil, we conduct a static plate load test in accordance with DIN 18134. In confined conditions, for instance on small plots or in pipeline trenches, we can perform dynamic plate load tests pursuant to TP BF-StB Part 8.3, if you require. And we are available at any time and any place for determining densities in accordance with DIN 18125 and light dynamic probing pursuant to DIN EN ISO 22476-2. With earthwork check tests from GTC-Nord, you will always have solid ground beneath your feet.

Static plate load testing

To test the load-bearing capacity or close-to-surface density of the soil, most building constructors trust in the static plate load test pursuant to DIN 18134. Due to its detailed standardisation, this is the most precise earthwork test with the highest level of reproducibility. The static plate load test involves applying repeated incremental levels of stress and relief to a circular plate by means of a pressure assembly and measuring the subsidence of the plate in the subsurface. A truck or excavator is used as a counterweight; at GTC-Nord we usually use our own cone penetration vehicles.

In the case of the static plate load test, not only are the applied pressure and the depth to which the load plate sinks measured, but also the easing of the pressure in the soil following the pressure load. The deformation modulus Ev2 is then calculated from the data; this is a mathematical value that takes into account both stress and subsidence and is used to classify the load-bearing capacity of the soil. Static plate load tests in accordance with DIN 18134 enables conclusions to be drawn about a variety of soil parameters, as well as allowing indirect determination of the Proctor density. It also serves as verification of the suitability of soils and subsurfaces as building ground or for use in the entire field of earthwork, foundation engineering, and road construction.

Dynamic plate load testing

Dynamic plate load testing pursuant to TP BF-StB Part 8.3 can be employed in rail construction, deep pipeline trenches or any other confined locations that do not allow static plate load testing due to the necessity of a counterweight. However, the considerably smaller load on the building ground brought about by the lightness of the drop weight tester means that the test volume is considerably smaller than with static plate load tests.

The lightweight drop weight tester comprises a guide rod, at the upper end of which a 10kg plate is disengaged. An electronic measuring module determines the value of the dynamic deformation modulus Evd in MN/m², which can, if preferred, be converted into Ev2 quantities by means of correlation values.

Density determination

The determination of soil density is an important factor for evaluating soil properties of importance to building engineering. Density determination in the field pursuant to DIN 18125-2 involves samples being taken and the soil sample’s mass and volume being determined. To ascertain the volume, we use either a cutting cylinder or a densitometer (balloon method).

To determine soil density using a cutting cylinder, we drive a standardised cylinder into the soil. Any protruding sample material is removed, the faces compared, and the cylinder sealed tight to prevent the soil from drying out. In the laboratory, we weigh the content of the cylinder to determine the moist mass; the exact volume of the soil sample is determined from the dimensions of the cylinder. Determining densities with the cutting cylinder is particularly suitable for fine-grained soils (sands, silts and clays).

To measure density using a densitometer (balloon method), a metal annulus disc is placed on the soil, after first removing the grass cover. We then take away the loose rock through the hole in the metal ring down to 1-1.5 times the internal diameter of the ring. The volume of the sample is determined on site with a rubber balloon filled with water, which is pushed into the hole by the densitometer. A scale is attached to the densitometer that shows the volume of water used. The moist mass of the soil sample is determined in the laboratory. Density determination using the densitometer is suitable for both cohesive and non-cohesive soils. The method is particularly recommended for fine-grained soils with embedded gravel and stones and for coarse soils with no sharp-edged stones.

Light dynamic probing

Das Verfahren der Rammsondierung gemäß DIN EN ISO 22476-2 dient vor allem der Überprüfung von Graben- oder Gebäudeverfüllungen. Dabei wird eine Sondierstange mit einer leichten Ramme bei gleichbleibender Fallhöhe  in den Untergrund getrieben, wobei wir die Schlagzahl für eine definierte Eindringtiefe festhalten. Aus der ermittelten Schlagzahl lassen sich wichtige Rückschlüsse auf die Verdichtung und Tragfähigkeit des Bodens ziehen. Leichte Rammsondierungen belegen zweifelsfrei die Belastbarkeit eines verfüllten Baugrundes und schützen Sie so vor teuren Nachbesserungen.

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