Patent ID: 6499239
Filing Date: 2002-12-31
Classification: E02F

Abstract:
A method for extracting and grading or sizing sand, gravel or a mixture thereof, from a pit formed in untouched ground, comprising spraying a liquid into the ground, resulting in a fluidized state in the said ground, in which state sand or gravel with a relatively high relative density and/or relatively large dimensions moves downwards, and sand or gravel material with a relatively low relative density and/or relatively small dimensions moves upwards, in which a pit is formed in the ground which contains fluidized sand or gravel, in such a manner that a layered state is obtained, sucking out the layer of sand or gravel with a specific relative density and/or size, while the remaining fluidized material remains behind in order to stabilize the wall of the pit, and feeding the material which has been sucked out to a grading device or sizing device.