Patent ID: 7483791

Claim:
A method for determination of soil stiffness levels of a soil area, whereas one and the same self-propelled apparatus ( 1 ) is used not only to determine the absolute soil stiffness level (k B ) when located on at least one predetermined soil subarea ( 3 ) of the soil area but also to determine a plurality of relative soil stiffness levels(s) while crossing over a plurality of soil subareas of the soil area, comprising: in order to determine an absolute soil stiffness level (k B ), moving a vibration unit ( 5 ) of the apparatus ( 1 ) into a predetermined soil subarea ( 3 ), and a first time-variable excitation force being produced as a periodic first force with a maximum first oscillation level, which is directed at right angles (with the exception of an adjustment tolerance) against the soil surface, is applied by means of the vibration unit ( 5 ) in permanent contact with the soil surface, whereas the vibration unit ( 5 ) and the predetermined soil subarea ( 3 ) represent a single oscillating system, and first data items of a first oscillation response of the oscillating system and second data items of the first time-variable excitation force are determined, and an absolute soil stiffness level (k B ) of the predetermined soil subarea ( 3 ) is determined from the first and second data items; and in order to determine a plurality of relative soil stiffness levels(s) of a plurality of soil subareas, moving the vibration unit ( 5 ) to the soil surface of one of the soil subarea of the soil area, whereas a second time-variable excitation force acts on the vibration unit ( 5 ) in such a way that the vibration unit ( 5 ) is lifted off the soil surface ( 2 ) and can thus be moved in a jumping manner to a plurality of the soil subarea, whereas third data items representing a lowest subharmonic frequency of a second oscillation response of the oscillation of the vibration unit ( 5 ), caused by the second excitation force, and fourth data items representing the oscillation of the second excitation force are determined, and relative soil stiffness levels (k B ) of the soil subareas are determined successively and continuously over the soil area from the third and fourth data items.