Patent ID: 6497282
Filing Date: 2002-12-24
Classification: E21B,G01B

Abstract:
A method of monitoring the diameter of columns made in the ground by jet grouting, the method comprising the following steps:forming a column using a material that sets; providing a measuring instrument, wherein said measuring lent comprises a tubular element having a length substantially equal to that of said column, said tubular element being fitted with a plurality of emission electrodes for creating an electric field, and with a plurality of measurement electrodes for measuring potential differences created by said electric field, wherein at least one of said emission electrodes is connected to a source of electricity and at least one of said emission electrodes is connected to a measuring means; making a reference borehole in the ground close to the location where said at least one column is to be made; acquiring voltage measurements by placing said measuring instrument into said reference borehole, wherein said voltage measurements are representative of the physical characteristics of the ground at different depths of said reference borehole so as to obtain a series of reference measurements for said depths; boring an axial borehole in said column to be tested, with the diameter of the axial borehole being much smaller than the diameter of said column; acquiring voltage measurements by inserting said measuring instrument into said borehole made in said column, wherein said voltage measurements correspond to different depths, thus obtaining actual measurements of voltages representative of a physical characteristic associated with said column and with the surrounding ground at different depths; and processing said actual measurements with reference to said reference measurements so as to obtain information representative of the diameter of said column at said different depths.