The dynamic plate load test with the Medium Heavy Falling Weight Deflectometer is used to check the soil and base courses applied using loads similar to traffic. A dynamic deformation modulus Evd,M is used as the measurement variable. The test is similar to the familiar method with the Lightweight Deflectometer (ZORN ZFG); with the difference that the maximum normal stress under the loading plate of the Medium Heavy Falling Weight Deflectometer is 0.2 MN/m² (0.1 MN/m² on the ZFG). The maximum impact force produced by a 15 kg falling weight is double that of the Lightweight Deflectometer at 14.140 kN.
Technical test specification:
The Medium Heavy Falling Weight Deflectometer is suitable, as per the technical test specification (TP Gestein-StB Part 8.2.1), for testing the load-bearing capacity of courses without binding agent according to ZTV SoB-StB, i.e. for frost protection courses, gravel and ballast courses, wearing courses without binding agent as well as for other courses with similar load-bearing capacity. The measuring range is specified between 30 and 150 MN/m².
Permissible limits or instructions for the implementation of comparative tests (for instance to the static plate load test according to DIN 18134 or to the Lightweight Deflectometer according to TP BF-StB, Part 8.3) are expressly not part of the test specification.
Tests by our measuring device experts on the ZORN test site have shown that there is good comparability with measurement values from the Lightweight Deflectometer in heavily compacted quarrystone in particular. (E.g. chippings or ballast, Evd ≧50 MN/m²)
For less compacted materials it was not possible to establish such a relationship. With gravel/sand mixtures the material may be disturbed during the test. The deformation modulus measured drops correspondingly. ZORN INSTRUMENTS recommends experienced testers use the Medium Heavy Falling Weight Deflectometer. The device is particularly suitable for well-compacted base courses made of crushed rock and for courses after qualified soil improvement.
The dynamic plate load test with the Medium Heavy Falling Weight Deflectometer ZFG-M is a comparatively new method. It is imperative you talk to a ZORN measuring instrument expert before use.