Plate load test
|
DIN 18134 |
|---|---|
| Area | Building ground |
| title | Experiments and experimental devices - plate pressure test |
| Brief description: | Experiment to determine the compressive strength of soils and materials |
| Latest edition | 2012-04 |
| ISO | - |
The static plate load test or static load plate test , also called load plate pressure test , is an experiment to determine the compressive strength and load-bearing capacity of floors and materials. It serves as evidence of the suitability of soils and subsoils (bulk layers) as building ground according to DIN 1054, as well as in the entire earthworks, foundation and road construction.
execution
The implementation is in the DIN standard DIN 18134 subsoil; Experiments and experimental devices - plate pressure test regulated and can be carried out as a field test with the plate pressure device. A circular, standardized load plate is repeatedly loaded and unloaded by a pressure device on the substrate with a certain pressure and interval . A truck, excavator or similar heavy device is used as a counterweight (the weight of which influences the maximum load that can be applied.)
Not only the pressure applied and the sinking depth of the load plate are recorded, but also the relaxation of the material that begins after the pressure load. The determined relationship between pressure and settlement of the soil of the successive passages is plotted as a pressure settlement line in a diagram. The deformation modulus E v can be determined from this diagram . The values are given in M N / m². In addition to the absolute value of the pressure required for a certain deformation, the ratio of the pressure values determined for successive passes is decisive for the classification of the suitability of the material.
For the control of compaction, for example in road construction, a load plate with a diameter of 30 cm is usually used (according to DIN 18134, those with 60 cm and 76.2 cm are also used) and the load in steps up to a maximum value (often 0.5 MN per square meter for the 30 cm slab) and then relieved again, whereby the settlement is measured in each case. According to DIN 18134, it may be used for coarse and mixed-grain soils and fine-grain soils whose consistency is stiff to firm. Disturbed surface layers (e.g. softening) must be removed, the load plate must lie completely on the test surface, for which a layer of sand or gypsum a few mm thick may be applied. Grains that are more than a quarter of the diameter of the load plate must be removed. With a plate diameter of 30 cm, a preload of 0.01 MN per square meter is applied. According to DIN, the load increase takes place in at least six roughly equal steps up to the maximum value and the relief in three steps (to half, then to a quarter and finally to 2% of the maximum voltage). DIN 18134 also specifies the timing of loading and unloading. After the first exercise, a second exercise cycle is carried out (but only up to the penultimate stage of the first cycle). The calculated deformation modules are given indices 1 and 2, depending on whether they were calculated in the first or second cycle.
When calculating the modulus of elasticity, the load-settlement curve is approximated by a polynomial of the second degree using the method of least squares (formulas for this can be found in DIN 18134). Before the calculation, the settlement measured on the dial gauge must be corrected by multiplying it by the lever ratio of the measuring device.
Through the experiment, you can divide the subsoil into load levels (soil groups). In addition, there are requirements for various layers in public road construction in Germany as an indirect proof of compaction (ZTV E-StB).
Dynamic plate load test
Alternatively, other methods such as B. the dynamic plate load test, the dynamic modulus of elasticity E vd (according to TP BF-StB Part 8.3) can be determined. This can also be done by small construction companies with a hand tool and lets a weight of 10 kg fall from a height of about 70 cm on a rod (the weight is thrown back by a spring on the base plate and is latched again at the top) and shows the behavior of the floor with an accelerometer in the plate. It does not require any heavy counter loads and can also be used in confined spaces. It is primarily used for self-monitoring of compaction in road and path construction and does not have the same reliability as the more complex static plate load test. The load is lower than in the static test, the values are more scattered and can only be used to a limited extent or not at all for soils with coarse gravel and stones and with higher water contents. It is not regulated in a DIN , but is partially recognized by road construction administrations in additional technical contract conditions such as that for earthworks (ZTV E-StB). For the conversion to deformation modules, it is usually recommended to check the results by means of a static plate load test.
Web links
Individual evidence
- ↑ According to DIN 18134, the counterweight must be at least 10 kN heavier than the maximum load. Regarding the order of magnitude: with a plate diameter of 30 cm (0.07 square meter area), a maximum pressure of 0.5 MN per square meter corresponds to a load of around 3.6 tons.
- ↑ Diameters of 76.2 cm are generally used in accordance with DIN 18134 to determine the bedding module for ceiling structures in road and airport construction
- ↑ According to DIN, if 5 mm settlement is reached beforehand, the associated load value is taken as the maximum value.
- ↑ P. Mair on the plate printing test, script Fachschule für Agrarwirtschaft Landshut-Schönbrunn, 2005, pdf ( memento of the original from July 21, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
