Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
  • G01N33/24—Earth materials
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
  • G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
  • G01N15/082—Investigating permeability by forcing a fluid through a sample
  • G01N15/0826—Investigating permeability by forcing a fluid through a sample and measuring fluid flow rate, i.e. permeation rate or pressure change

Definitions

• the present invention relates to a method for determining the hydraulic permeability of a material, in particular, a soil with little or very little permeability, by electro-osmotic method and a device for determining the hydraulic permeability of a material, in particular , soil with little or very little permeability, by electro-osmotic method.
• the hydraulic permeability of a material is a determining factor in the use made of the material, in particular in the context of its possible selection as a sealing element for a dam or in a nuclear storage site for example.
• fine porous soils or materials are materials which are not very permeable to liquids, especially with regard to clays.
• ⁇ w represents the density of water
• A represents the surface
• a first object of the present invention is to provide a method for determining, in the laboratory and / or in situ, the hydraulic permeability of a material which is faster.
• the potential difference of said material is measured between two points in a uniform part of said electric field
• the flow rate of the moving water in said material is measured under the action of said imposed electrical gradient, which corresponds to the electro-osmotic flow rate of said material and
• the hydraulic permeability of said material is calculated from the measured values of said potential difference, said pressure difference and said water flow rate.
• A represents the surface (in m 2 )
• k e represents the coefficient of electro-osmotic permeability (in m 2 .s "1 N " 1 )
• A represents the surface
• ⁇ x represents the distance between the measurement points ⁇ e represents the electrical conductivity of the material
• the electrical conductivity of the material ⁇ e can be either measured using an impedance meter, or determined from the measurement of the current and the difference in electrical voltage.
• said electric field is imposed by imposing either an electric voltage or an electric current in said material using supply electrodes.
• imposing a current all the problems of polarization of the electrodes are advantageously eliminated.
• a cathode is placed inside said material and an anode is either inside said material, or on the surface of said material.
• the supply electrodes it is more or less easy to introduce the supply electrodes inside the material and it may then be preferable to place the cathode on the surface, which does not change the application of the electric field within the material.
• a hollow anode is used to saturate said material with water.
• the water circulating from the positive pole to the negative pole it suffices to fill the anode (positive pole) with water and to keep the filling level constant.
• one of the supply electrodes can be used to recover the water which has migrated through the material.
• a hollow cathode is advantageously used to measure said water flow rate.
• two measurement electrodes are used to measure said potential difference, either inside said material, or on the surface of said material.
• the user will take care to place the measuring electrodes in a homogeneous part of the electric field.
• at least one hydraulic pressure probe is placed inside said material.
• We will either choose to place two pressure probes in two different measurement points, i.e. to place a single pressure probe. In the latter case, it is preferable to use a differential hydraulic pressure sensor which will directly indicate the pressure difference.
• the moving water is also advantageously filtered in said material, before measuring the flow rate, which makes it possible to avoid any measurement error, in particular, when the measurement of the water flow rate is made. by weighing.
• a second object of the present invention is to propose a device which is simpler to implement for determining the hydraulic permeability of a material by electro-osmotic method, and which can be easily transportable for carrying out measurements in situ.
• the device comprises:
• the device comprises two pressure probes connected to a differential pressure sensor. So that the measurement of the water pressure is correct, the two pressure probes are placed at two different points in a homogeneous electric field.
• the device also advantageously comprises a filter, which makes it possible to eliminate any pollution of the water whose flow rate is measured by particles for example. This precaution is obviously preferable, in the case where the flow measurement is made by weighing the water circulating in the material.
• the anode and the cathode are either continuous electrodes or discontinuous electrodes, which can be either planar or cylindrical.
• Continuous electrodes usually in the form of metal grids, have the advantage of allowing water to pass through.
• Discontinuous electrodes for their part, allow better management of the electric field, since they can be in the form of several portions which are just plugged into the material in a judiciously spaced manner depending on the zone in which one wishes to make measurement. These electrodes are particularly advantageous in situ, when the soil is not of homogeneous composition, since their location makes it possible to define the measurement area.
• said anode is hollow to saturate said material with water and said cathode comprises a water recovery device.
• the device advantageously comprises a water extraction device which can be placed in the water collector to facilitate the measurement of the flow rate.
• the device also advantageously comprises insulating elements intended to limit the electro-osmosis zone in said material.
• FIG. 1 is a perspective view of the device according to the invention
• FIG. 2 is an enlargement of FIG. 1 showing the paired electro-osmosis zone
• FIG. 3 is a schematic sectional view of the device in FIG. 1,
• FIG. 4 is a schematic perspective view of a variant of supply electrodes and,
• FIG. 1 represents a device for determining the hydraulic permeability of a material 10 placed in a parallelepipedic test box 12.
• the nature of the material 10 can be diverse, permeable soil, clays, medicated paste, etc.
• the test box 12 comprises two opposite compartments 14A and 14C between which the material 10 is placed connected to the electrical supply electrodes 16A and 16C which will make it possible to generate an electric field within the material between two points 16'A and 16 'C any on the power supply electrodes 16A and 16C.
• the anode compartment 14A, anode side 16A is filled with water and serves as a saturator; its level is kept constant so that constantly be able to saturate the material 10 with water.
• the anode 16A is flat and continuous, consisting of a metal grid or a carbon fabric, so that the water from the anode compartment 14A passes through it to the material 10.
• the cathode compartment 14C, cathode side 16C forms a water recuperator having migrated through the material 10.
• the cathode 16C is flat and continuous, made up of a metal grid, so that the water which migrates into the material 10 passes through it to the cathode compartment 14C. Indeed, under the action of the electric field imposed between the anode
• the water will migrate from the anode compartment 14A to the cathode compartment 14C. It then suffices to take the water from the cathode compartment 14C to determine the flow rate.
• Two measurement electrodes 18 and 20, as well as two hydraulic pressure probes 22 and 24, are placed inside the material 10 between the supply electrodes 16A and 16C.
• the two pressure probes 22 and 24 are each connected to a differential pressure sensor 23 or to independent pressure sensors.
• the supply electrodes 16A and 16C are each connected to the terminals of an electric generator 26.
• the electric generator 26 will be used. current or voltage generator.
• the potential difference is measured using a voltmeter connected to the measurement electrodes 18 and 20.
• the water extraction device 30 comprises a probe 32 disposed in the cathode compartment 14C connected to a water pump 34 to suck the water that has migrated into the material 10 to a container 36 and measure the flow rate by weighing, for example.
• the measuring electrodes 18 and 20 are placed at two points 18 'and 20', shown in FIG. 3, in an area where the electric field is uniform. The same goes for hydraulic pressure sensors
• this area may vary slightly.
• the user will take care to take account of the field lines, specific to the types of supply electrodes used 16A and 16C, to place the measurement electrodes 18 and 20 and the pressure probes 22 and 24 in a uniform field area.
• he will choose the depth of insertion of the measurement electrodes 18 and 20 and of the pressure probes 22 and 24, according to the layer which one wishes to examine, in particular, during in situ tests.
• Filters 38 and 40 can be arranged, respectively against the anode 16A and the cathode 16C to filter the water before and after its passage through the material 10.
• the supply electrodes 16A and 16C can also be discontinuous, depending having, for example, in the form of bars which have just been inserted into the soil whose material 10 is to be analyzed.
• the supply electrodes 16A and 16C can be flat and in this case, they can be placed either on the surface of the material or in depth, or else cylindrical in which case they are necessarily inserted inside the material 10.
• the supply electrodes 16A and 16C can be in the form of a grid or a fabric, preferably according to a geometry of revolution. Furthermore, it may be advantageous to choose them hollow so as to be able to circulate water through them, either for supplying the material 10, that is to recover the water which has migrated into the material 10 under the effect of the electric field imposed by the supply electrodes 16A and 16C.
• the cathode 16C When the cathode 16C is intended to recover the water which has migrated through the material 10, it is necessary for it to be inserted into the material 10, the anode 16A being able, for its part, even if it supplies the material 10 with water, be placed on the surface of the material 10, as shown in FIG. 4.
• test box 12 In the context of in situ measurements, the test box 12 is not generally used, especially in the case of an underlay measurement, to supply the material with water, it is preferable to choose a hollow 16A anode which contains the water saturator 14A whose level is kept constant and a hollow cathode 16C containing the water collector 14C, to recover the water having migrated through the material 10.
• a limitation of the area electro-osmosis is necessary.
• the area is technically limited by the very geometry of the electrodes.
• the cathode 16C is placed in the anode 16A, preferably centered, both inserted in the ground, so that the water coming from the anode 16A can only saturate the material contained in the anode 16A and migrates towards the cathode 16C.
• an electric field is generated within the material 10 (in voltage or direct current) using the supply electrodes 16A and 16C judiciously arranged and the material 10 is saturated with water with the water saturator 14A.
• the electrical conductivity ⁇ e of the material 10 is determined from the potential difference ⁇ (-V) and the electrical intensity I, measured in the material 10.
• the hydraulic pressure ⁇ (-P) is measured in the same way. , with two pressure probes 22 and 24 also placed between the two supply electrodes 16A and 16C in a homogeneous zone of the electric field spaced apart by a distance ⁇ x and connected to a differential voltage sensor 23.
• the flow rate of the water Q t which migrates through the material 10 from the anode 16A to the cathode 16C is measured, by weighing the amount of water withdrawn by the probe 32 in the recuperator 14C or else by measuring its level in the recuperator 14C for a given duration.

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• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Health & Medical Sciences (AREA)
• Physics & Mathematics (AREA)
• Immunology (AREA)
• Pathology (AREA)
• Analytical Chemistry (AREA)
• Biochemistry (AREA)
• General Health & Medical Sciences (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Environmental & Geological Engineering (AREA)
• Fluid Mechanics (AREA)
• Dispersion Chemistry (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geology (AREA)
• Remote Sensing (AREA)
• Food Science & Technology (AREA)
• Medicinal Chemistry (AREA)
• Investigation Of Foundation Soil And Reinforcement Of Foundation Soil By Compacting Or Drainage (AREA)
• Analysing Materials By The Use Of Radiation (AREA)

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Citations (5)

• 2001
  • 2001-11-13 FR FR0114632A patent/FR2832218B1/fr not_active Expired - Fee Related
• 2002
  • 2002-11-12 AU AU2002361315A patent/AU2002361315A1/en not_active Abandoned
  • 2002-11-12 WO PCT/FR2002/003863 patent/WO2003042688A2/fr not_active Application Discontinuation
• 2003
  • 2003-07-08 NO NO20033121A patent/NO20033121L/no unknown

Patent Citations (5)

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