Automated-Precision Pressure Meter

Abstract

A pressure meter includes a probe ( 1 ) and a piece of surface equipment ( 2 ), an inflatable sleeve ( 11 ), a non-deformable reservoir ( 4 ) containing a gas (G) and a liquid (L), a pressurized-gas source ( 21 ), various ducts ( 31, 32 ), gas-flow control elements ( 220 - 222 ), a pressure sensor ( 5 ), and a volume sensor. According to the invention, the reservoir ( 4 ) is supported by the probe, the gas flow is controlled by a nozzle ( 221 ) and a valve ( 222 ), and this pressure meter additionally includes pressure control members ( 7, 8 ) designed to open the valve ( 222 ), when establishing each new pressure level at a setpoint pressure (Kpi), for a time period (Tpi) corresponding to this setpoint.

1 . Pressure meter intended to enable evaluation of a geotechnical property of the subsoil, this pressure meter comprising, as sub-assemblies, a bottom tool ( 1 ) intended to be inserted into a borehole (F), surface equipment ( 2 ), and connecting means ( 30 - 33 ) adapted to at least connect the tool to the equipment, these sub-assemblies themselves comprising at least a first inflatable sleeve ( 11 ) held by the bottom tool ( 1 ), a substantially non-deformable reservoir ( 4 ) containing complementary volumes (Vg, VI) of gas (G) and liquid (L), a pressurized gas source ( 21 ), a first duct ( 31 ) connecting the gas source ( 21 ) to the gas volume (Vg) of the reservoir ( 4 ), a second duct ( 32 ) connecting the liquid volume (Vi) of the reservoir ( 4 ) to the first inflatable sleeve ( 11 ), flow control means ( 220 - 222 ) interposed on the first duct ( 31 ), a pressure sensor ( 5 ) adapted to provide a signal (Sp) related to the pressure of the liquid inside the reservoir ( 4 ), and a volume sensor ( 6 ) adapted to provide a signal (Sv) related to the volume (VI) of the liquid inside the reservoir ( 4 ), characterised in that the reservoir ( 4 ) is supported by the bottom tool ( 1 ), in that the flow control means ( 220 - 222 ) include a nozzle ( 221 ) and a valve ( 222 ), in that the surface equipment ( 2 ) further includes pressure control means ( 7 ,  8 ) wherein are stored a plurality of pressure set points (Kpi) of increasing values, a program (PROG) for successive application of these set points (Kpi) over time, and a law of correspondence (CORR) associating at least these set points (Kpi) with corresponding respective time periods (Tpi), and in that these pressure control means ( 7 ,  8 ) are designed to selectively open the valve ( 222 ) for the purpose of applying each new pressure set point (Kpi) in accordance with the program (PROG), during the time period (Tpi) corresponding to this set point. 
   
   
       2 . Pressure meter of  claim 1 , characterised in that the pressure control means ( 7 ,  8 ) are preferably connected to the pressure sensor ( 5 ) and are further designed to open the valve ( 222 ) during a predefined time period (T 0 ), in response to a deficit in the pressure signal (Sp) in relation to a set point pressure (Sp), when this deficit appears during an increment of this set point pressure (Kpi) and when it exceeds a predetermined threshold. 
   
   
       3 . Pressure meter as claimed in  claim 1 , characterised in that the pressure control means ( 7 ,  8 ), for example, include a control unit ( 7 ). which actuates the valve ( 222 ) and a computer ( 8 ) wherein the pressure set points (Kpi), program (PROG), and law of correspondence (CORR) are stored, said computer (B) being connected to the control unit ( 7 ) and controlling same. 
   
   
       4 . Pressure meter as claimed in  claim 1 , characterised in that the flow control means ( 220 - 222 ) include a solenoid valve ( 220 ) holding both the nozzle ( 221 ) and the valve ( 222 ). 
   
   
       5 . Pressure meter as claimed in  claim 1 , characterised in that the volume sensor ( 6 ) includes a liquid level detector ( 61 ) housed inside the reservoir ( 4 ) and in that the connecting means ( 30 - 33 ) include a transmission link ( 30 ) connecting the level detector ( 61 ) to the surface equipment ( 2 ). 
   
   
       6 . Pressure meter as claimed in  claim 1 , characterised in that in the operating configuration of the bottom tool ( 1 ) inside a borehole (F), the reservoir ( 4 ) is arranged above the first inflatable sleeve ( 11 ). 
   
   
       7 . Pressure meter as claimed in  claim 5 , characterised in that the volume signal (Sv) is of an electrical type and in that the transmission line ( 30 ) comprises an electrical transmission line. 
   
   
       8 . Pressure meter as claimed in  claim 1 , characterised in that the reservoir ( 4 ) is cylindrical. 
   
   
       9 . Pressure meter as claimed in  claim 5 , characterised in that the liquid (L) has a relatively low electrical resistivity, in that the level detector ( 61 ) includes at least one resistive element ( 610 ) which is connected to an electric power generator ( 60 ) and partially submerged in the liquid (L), in that the resistive element ( 610 ) has a shape that is elongated in the heightwise direction of the reservoir ( 4 ) and a relatively high electrical resistivity, and In that the liquid (L) and the resistive element ( 610 ) partially shunted by the liquid (L) form a resistive load (CR) for the generator, the resistance of which depends on the level of said liquid inside the reservoir ( 4 ). 
   
   
       10 . Pressure meter of  claim 9 , characterised in that the electric power generator ( 60 ) delivers an alternating current. 
   
   
       11 . Pressure meter as claimed in  claim 1 , characterised in that the bottom tool ( 1 ) further includes second and third inflatable sleeves ( 12 ,  13 ), and a third duct ( 33 ) connecting the volume (Vg) of gas of the reservoir ( 4 ) to the second and third sleeves ( 12 ,  13 ). 
   
   
       12 . Pressure meter as claimed in  claim 2 , characterised in that the pressure control means ( 7 ,  8 ), for example, include a control unit ( 7 ). which actuates the valve ( 222 ) and a computer ( 8 ) wherein the pressure set points (Kpi), program (PROG), and law of correspondence (CORR) are stored, said computer (B) being connected to the control unit ( 7 ) and controlling same.