Method and apparatus for measuring in situ density and fabric of soils

• US 4,219,776 A
• Filed: 08/25/1978
• Issued: 08/26/1980
• Est. Priority Date: 08/25/1978
• Status: Expired due to Term

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Arulanandan, Kandiah
• Primary Examiner(s): Strecker, Gerard R.
• Application Number:
  US05/936,836
• Time in Patent Office: 732 Days
• Field of Search: 324/1, 324/2, 324/10, 324/11, 324/13, 324/30 B, 324/57 R, 324/61 P, 324/65 P, 324/62, 324/60 R
• US Class Current: 324/323
• CPC Class Codes: G01N 33/24 Earth materials G01N33/42 takes precedence
• CPC Class Codes: G01R 27/26 Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
• CPC Class Codes: G01V 3/06 using ac

Abstract

A method and implementing apparatus for measuring in situ the electrical capacitance and resistance of soils and determining therefrom the density and fabric thereof. The apparatus includes a self-contained probe adapted to be driven into the soil to be measured. The probe has a soil sensor element and a measuring circuit such as a capacitance and resistance bridge. The measuring circuit employs radiofrequency current to enable direct measurement at the probe of the resistance and capacitance of the soil sample and of the pore liquid. A remote indicator and control unit in communication with the probe is provided with indicators such as meters or displays which provide direct readout of measured resistance and capacitance, and which may also enable the bridge in the probe to become balanced. Alternatively, the probe may include a computer for automatically balancing the bridge and calculating critical soil properties. The apparatus can automatically register such engineering properties as density, porosity, friction angle, elastic and secant modulus, coefficient of dynamic settlement, stress ratio required to cause liquefaction, and permeability coefficient. The probe and measuring equipment can, alternatively, be manually balanced and the engineering properties and related properties can be hand calculated. The concept outlined and apparatus can be extended or modified for a wide variety of other uses also.

Claims

1. Apparatus for measuring in situ the resistance and capacitance at radio frequency of soils, including sands and silts, to enable evaluation of the density and fabric thereof, comprising:

probe means adapted to be driven into the soil to be measured in situ to a fixed depth so that said probe means comes into physical proximity and electrical contact with a sample of said soil to be evaluated, said probe means having

a first pair of electrodes for measuring in situ the electrical resistance and capacitance of said soil sample along a horizontal direction,

a second pair of electrodes for measuring in situ the electrical resistance and capacitance along a vertical direction,

a pore-liquid chamber in said probe means having an inlet and means for relieving gas,

a third pair of electrodes in said pore liquid for measuring in situ the electrical resistance and capacitance of pore liquid in said chamber,

filter means at the inlet to said probe means for admitting pore liquid to said chamber and excluding the soil therefrom,

means for applying radio-frequency voltage to each said pair of electrodes,

resistance measurement indicator means in communication with said probe means for indicating said measured resistance of said soil sample along said horizontal direction and along the vertical direction and for indicating the measured resistance of said pore liquid, and

capacitance measurement indicator means connected to said probe means for indicating said measured capacitance of said soil sample along the horizontal direction and along the vertical direction and for indicating the measured capacitance of said pore liquid.

2. The apparatus of claim 1 wherein said probe means includes,

a radio-frequency bridge adapted for simultaneous in situ measurement of capacitance and resistance of said soil sample, and

balancing means for balancing said bridge while it is in place in situ for making said measurements.

3. The apparatus of claim 2 wherein said bridge is a radio frequency capacitance bridge.

4. The apparatus of claim 1 having temperature sensing means in said probe means and indicator means in communication therewith for indicating the sensed temperature.

5. Apparatus for simultaneous measurement in situ of the resistance and capacitance of soils, sands, silts, and the like to enable evaluation of density and fabric thereof, said apparatus comprising probe head means, measurement point means, and interconnection means for electrically interconnecting said probe head means with said measurement point means,

said probe head means being adapted to be driven into the soil to be tested to a fixed depth, and including:

a sensor element of plural electrodes for physically engaging a soil sample of the soil to be tested at said fixed depth,

an oscillator outputting a signal at a predetermined radio frequency,

an impedance bridge including;

a first coil having a primary winding connected to said oscillator and a center tapped secondary winding with one end thereof connected to one of the electrodes of said sensor element,

a second coil having a center tapped primary winding with the center tap thereof connected to the center tap of the secondary winding of said first coil, and with one of the ends of said center tapped primary winding being connected to another of the electrodes of said sensor element, said second coil having a secondary winding providing an output of said probe head means,

a variable resistance element of adjustable value connected between the other end of said first coil and the other end of said second coil,

a variable capacitance element of adjustable value connected between the other end of said first coil and the other end of said second coil,

said measurement point means being remote from said probe head means, and including;

signal converting means connected through said interconnection means to said secondary winding of said second coil, for converting said radio frequency signal into a rectified and amplified signal proportional in magnitude to said radio frequency signal,

filter means connected to said converter means for smoothing said rectified signal into d.c. voltages,

analog to digital converter means connected to said filter means for converting said d.c. voltages into digital values,

digital computer means connected to said analog to digital converter means for automatically repeatedly determining from said digital values changes of value of said variable resistance element and said variable capacitance element to provide a null point in said bridge, and providing a digital output change signal,

said probe head means further including;

output decoder means connected through said interconnection means to said digital computer means for decoding said digital output change signal,

resistance switching means in said variable resistance element connected to said output decoder means, for increasing and decreasing the resistance of said variable resistance element in accordance with said decoded change signal, and

capacitance switching means in said variable capacitance element connected to said variable capacitance element connected to said output decoder means for increasing and decreasing the capacitance of said variable capacitance element in accordance with said decoded change signal,

said measurement point means further including;

resistance indicator means connected to said digital computer means for indicating soil sample resistance in accordance with the status of said variable resistance element at null point of said bridge,

capacitance indicator means connected to said digital computer means for indicating soil sample capacitance in accordance with the status of said variable capacitance element at null point of said bridge,

whereby when said probe head means is driven into the soil to be tested and said sensor element comes into physical proximity and electrical contact with a sample of said soil at said fixed depth, and said bridge is then automatically nulled by operation of said computer, resistance and capacitance of said soil sample may thereupon be measured in situ and be read remotely therefrom, thereby enabling evaluation of density and fabric of said soil.

6. The apparatus of claim 5 wherein said plural electrodes comprise one pair of electrodes disposed in horizontal relation to each other and a pair of electrodes disposed in vertical relation to each other, and switching means for placing one said pair at a time in the operation mode, whereby both resistance and capacitance of said soil are determined in both a horizontal direction and in a vertical direction.

7. The apparatus of claim 5 or 6 wherein said probe means includes pore-liquid sensor means for measuring in situ resistance and capacitance of a pore-liquid sample collected at said pore-fluid sensor, said pore-liquid sensor means comprises filter means for passing pore liquid and blocking particulate material and structure defining a chamber having an opening communicating with said filter means, and pore-liquid electrode means in said chamber for contacting said pore liquid collected therein, and thereby enabling measurement by said probe means of resistance and capacitance of said pore-fluid sample, said probe means including switch means for switching between said soil sample measuring plural electrodes and said pore-liquid electrode means.

8. The apparatus of claim 7 wherein said structure includes vent means for venting gas in said chamber to the outside of said probe means, as said pore fluid sample enters said chamber.

9. The apparatus of claim 7 wherein said structure includes an expandable enclosure connected to said chamber and into which gas may pass from said chamber.

10. The apparatus of claim 7 wherein said filter means comprises porous stone material.

11. The apparatus of claim 7 wherein said filter means comprises cotton padding.

12. The apparatus of claim 5 wherein said probe means includes temperature sensor means for measuring in situ the temperature of said soil sample and means connecting said sensor means to said computer.

13. Apparatus for measuring in situ the resistance and capacitance at radio frequency of soils, including sands and silts, to enable evaluation of density and fabric thereof, said apparatus comprising probe head means, control point means, and interconnection means for electrically interconnecting said probe head means with said control point means,

said probe head means adapted for being driven into the soil to be tested to a fixed depth and including:

a sensor element,

an oscillator providing a radio-frequency current output signal at a predetermined frequency and amplitude,

a bridge circuit connected to said sensor element and to said oscillator,

said bridge including a variable resistor and a variable capacitor in electrical connection therewith, remotely controllable resistor adjusting means for adjusting said resistor, and remotely controllable capacitor adjusting means for adjusting said capacitor,

said control point means including;

resistance setting means connected through said interconnection means to said remotely controllable resistor adjusting means for setting the adjustment of said resistor,

capacitance setting means connected through said interconnection means to said remotely controllable capacitor adjusting means for setting the adjustment of said capacitor,

null point indicator means connected through said interconnection means to said capacitance bridge, for indicating a null point of said bridge,

resistance indication means correlated to the setting of said resistor for indicating soil sample resistance in accordance with the setting of said resistor upon indication of null point of said bridge,

capacitance indication means correlated to the setting of said capacitor for indicating soil sample capacitance in accordance with the setting of said capacitor upon indication of null point of said bridge,

whereby when said probe head means is driven into the soil to be tested and said sensor element comes into physical proximity and electrical contact with a sample of said soil at said fixed depth, and said bridge is balanced by adjustment at said control point means of said variable resistor and said variable capacitor, the resistance and capacitance of said coil sample at radio frequency may be measured in situ, thereby enabling evaluation of density and fabric thereof.

14. Apparatus for simultaneous measurement in situ of the resistance and capacitance at radio frequency of soils, including sands and silts, to enable evaluation of density and fabric thereof, said apparatus comprising probe head means, control point means, and interconnection means for electrically interconnecting said probe head means with said control point means,

said probe head means being adapted to be driven into the soil to be tested to a fixed depth and including:

a sensor element,

an oscillator providing a radio-frequency current output signal at a predetermined frequency and amplitude,

a capacitance bridge circuit connected to said sensor element and to said oscillator,

said bridge including an incrementally variable resistance element and an incrementally variable capacitance element in electrical connection therewith,

radio-frequency current detector means connected to said bridge for detecting the magnitude of radio-frequency current therein,

incremental resistance adjustment means connected to said detector means and to said resistance element for automatically incrementing and decrementing said resistance element in accordance with the magnitude of detected alternating current in said bridge until a null point is reached whereupon said resistance adjustment means ceases action,

incremental capacitance adjustment means connected to said detector means and to said capacitance element for automatically incrementing and decrementing said capacitance element in accordance with the magnitude of said detected alternating current in said bridge until a null point is reached whereupon said capacitance adjustment means ceases action,

said control point means being remote from said probe head means and including;

automatic control means for automatically controlling simultaneously said incremental resistance adjustment means to bring about said null point and then cease control,

resistance measurement indication means connected to said incremented resistance adjustment means for indicating soil resistance when said bridge is at null point,

capacitance measurement indication means connected to said incremental capacitance adjustment means for indicating soil capacitance when said bridge is at null point,

whereby when said probe head means is driven into the soil to be tested and said sensor element comes into physical proximity and electrical contact with a sample of said soil at said fixed depth, and said bridge is automatically balanced, the resistance and capacitance at radio frequency of said soil sample may thereupon be measured in situ and be displaced remotely therefrom, thereby enabling evaluation of density and fabric of said soil.

15. The apparatus of claim 14 further comprising manual override control means at said control point means, said manual control means being engageably connected to said incremental resistance adjustment means and to said incremental capacitance adjustment means for enabling manual adjustment thereof to a null point, and null point monitor means at said control point means in connection with said detector means for indicating said null point.

16. Apparatus for simultaneous measurement in situ of the resistance and capacitance of soils, sands, silts, and the like to enable evaluation of density and fabric thereof, said apparatus comprising probe head means, measurement point means, and interconnection means for electrically interconnecting said probe head means with said measurement point means,

said probe head means being adapted to be driven into the soil to be tested to a fixed depth, and including:

a sensor element of plural electrodes for physically engaging a soil sample of the soil to be tested at said fixed depth,

a first oscillator outputting a signal at a predetermined radio frequency,

a second oscillator outputting a signal at a predetermined modulating frequency,

a modulator connected to said first oscillator and to said second oscillator for modulating said radio frequency signal with said modulating frequency signal, to provide a modulated radio frequency signal as output,

an impedance bridge including;

a first coil having a primary winding connected to said modulator and a center tapped secondary winding with one end thereof connected to one of the electrodes of said sensor element,

a second coil having a center tapped primary winding with the center tap thereof connected to the center tap of the secondary winding of said first coil, and with one of the ends of said center tapped primary winding being connected to another of the electrodes of said sensor element, said second coil having a secondary winding providing an output of said probe head means,

a variable resistance element of incrementally adjustable value connected between the other end of said first coil and the other end of said second coil,

a variable capacitance element of incrementally adjustable value connected between the other end of said first coil and the other end of said second coil,

said measurement point means remote from said probe head means, and including;

radio frequency amplifier means connected through said interconnection means to said secondary winding of said second coil, for amplifying said modulated radio frequency signal,

rectifier means connected to said radio frequency amplifier means for rectifying said modulated radio frequency signal to recover said modulating signal,

filter means connected to said rectifier means for smoothing said rectified modulating signal into d.c. voltages,

analog to digital converter means connected to said filter means for converting said d.c. voltages into digital values.

digital computer means connected to said analog to digital converter means for automatically repeatedly determining from said digital values incremental changes of value of said variable resistance element and said variable capacitance element to provide a null point in said bridge, and providing a digital output change signal,

said probe head means further including;

output decoder means connected through said interconnection means to said digital computer means for decoding said digital output change signal,

incremental resistance switching means in said variable resistance element connected to said output decoder means, for incrementing and decrementing said variable resistance element in accordance with said decoded change signal,

incremental capacitance switching means in said variable capacitance element connected to said output decoder means, for incrementing and decrementing said variable capacitance element in accordance with said decoded change signal,

said measurement point means further including;

resistance indicator means connected to said digital computer means for indicating soil sample resistance in accordance with the status of said variable resistance element at null point of said bridge,

capacitance indicator means connected to said digital computer means for indicating soil sample capacitance in accordance with the status of said variable capacitance element at null point of said bridge,

whereby when said probe head means is driven into the soil to be tested and said sensor element comes into physical proximity and electrical contact with a sample of said soil at said fixed depth, and said bridge is then automatically nulled by operation of said computer, resistance and capacitance of said soil sample may thereupon be measured in situ and be read remotely therefrom, thereby enabling evaluation of density and fabric of said soil.

17. The apparatus of claim 16 further comprising manual override control means at said measurement point means, said manual control means being engageably connected to said incremental resistance switching means and to said incremental capacitance switching means for enabling manual adjustment thereof to a null point, and null point monitor means at said measurement point means in connection with said rectifier means for indicating said null point.

18. The apparatus of claim 16 wherein said sensor comprises two pairs of electrodes, one disposed in horizontal relation to each other and the other diposed in vertical relation to each other.

19. The apparatus of claim 16 wherein said probe means includes pore-liquid collection means for collecting soil-free pore liquid and pore-liquid sensor means for measuring in situ the resistance of the collected pore liquid.

20. The apparatus of claim 19 wherein said pore-liquid collection means comprises filter means for passing pore fluid and blocking particulate material and structure defining a chamber having an opening communicating with said filter means and said pore-liquid sensor means comprises electrodes in said chamber for contacting said collected pore liquid, thereby enabling measurement by said probe means of the resistance and capacitance of said collected pore liquid.

21. The apparatus of claim 20 wherein said structure includes vent means for venting gas in said chamber to the outside of said probe means, as said pore liquid enters said chamber.

22. The apparatus of claim 20 wherein said structure includes an expandable enclosure for receiving gas and relieving it from said chamber as said pore liquid enters said chamber.

23. The apparatus of claim 20 wherein said filter means comprises porous stone material.

24. The apparatus of claim 20 wherein said filter is cotton padding.

25. The apparatus of claim 19 wherein said probe means includes switch means for switching between said soil sample measuring electrodes and said pore liquid sensor means.

26. The apparatus of claim 16 wherein said probe means includes temperature sensor means for measuring in situ the temperature of said soil sample.

27. Apparatus for simultaneous measurement in situ of the resistance and capacitance of soils, sands, silts, and the like to enable evaluation of density and fabric thereof, said apparatus comprising probe head means, measurement point means, and interconnection means for electrically interconnecting said probe head means with said measurement point means,

said probe head means being adapted to be driven into the soil to be tested to a fixed depth, and including:

a sensor element of plural electrodes for physically engaging a soil sample of the soil to be tested at said fixed depth,

a first oscillator outputting a signal at a predetermined radio frequency,

an impedance bridge including;

a first coil having a primary winding connected to said first oscillator and a center tapped secondary winding with one end thereof connected to one of the electrodes of said sensor element,

a second coil having a center tapped primary winding with the center tap thereof connected to the center tap of the secondary winding of said first coil, and with one of the ends of said center tapped primary winding being connected to another of the electrodes of said sensor element, said second coil having a secondary winding providing an output of said probe head means,

a variable resistance element of incrementally adjustable value connected between the other end of said first coil and the other end of said second coil,

a variable capacitance element of incrementally adjustable value connected between the other end of said first coil and the other end of said second coil,

a second oscillator outputting a frequency lower than that of said first oscillator by a frequency difference between about 50 to about 500 kHz,

mixing means connected to the output from said second oscillator and to the secondary winding of said second coil for mixing the signals therefrom and for producing a difference signal between about 50 to about 500 kHz,

amplifier means connected to said mixing means for amplifying said difference signal, and

detector means connected to said amplifier means for isolating and putting out said difference frequency,

said measurement point means remote from said probe head means, and including;

rectifier means connected through said interconnection means to said detector means for rectifying said difference signal,

filter means connected to said rectifier means for smoothing said rectified difference signal into d.c. voltages,

analog to digital converter means connected to said filter means for converting said d.c. voltages into digital values,

digital computer means connected to said analog to digital converter means for automatically repeatedly determining from said digital values incremental changes of value of said variable resistance element and said variable capacitance element to provide a null point in said bridge, and providing a digital output change signal,

said probe head means further including;

output decoder means connected through said interconnection means to said digital computer means for decoding said digital output change signal,

incremental resistance switching means in said variable resistance element connected to said output decoder means, for incrementing and decrementing said variable resistance element in accordance with said decoded change signal,

incremental capacitance switching means in said variable capacitance element connected to said output decoder means, for incrementing and decrementing said variable capacitance element in accordance with said decoded charge signal,

said measurement point means further including;

resistance indicator means connected to said digital computer means for indicating soil sample resistance in accordance with the status of said variable resistance element at null point of said bridge,

capacitance indicator means connected to said digital computer means for indicating soil sample capacitance in accordance with the status of said variable capacitance element at null point of said bridge,

whereby when said probe head means is driven into the soil to be tested and said sensor element comes into physical proximity and electrical contact with a sample of said soil at said fixed depth, and said bridge is then automatically nulled by operation of said computer, resistance and capacitance of said soil sample may thereupon be measured in situ and be read remotely therefrom, thereby enabling evaluation of density and fabric of said soil.

28. The apparatus of claim 27 further comprising manual override control means at said measurement point means, said manual control means being engageably connected to said incremental resistance switching means and to said incremental capacitance switching means for enabling manual adjustment thereof to a null point, and null point monitor means at said measurement point means in connection with said rectifier means for indicating said null point.

29. The apparatus of claim 27 wherein said probe means includes pore-liquid collecting means for collecting soil-free pore liquid from said soil and pore-liquid sensor means for measuring in situ the resistance of the collected pore liquid.

30. The apparatus of claim 29 wherein said pore-liquid collecting means comprises filter means for passing pore fluid and blocking particulate material and structure defining a chamber having an opening communicating with said filter means and said pore-liquid sensor means comprises electrodes in said chamber for contacting said collected pore liquid, thereby enabling measurement by said probe means of the resistance and capacitance of said collected pore liquid.

31. The apparatus of claim 30 wherein said structure includes vent means for venting gas in said chamber to the outside of said probe means, as the pore-liquid sample enters said chamber.

32. The apparatus of claim 30 wherein said structure includes an expandible second chamber for receiving gas and relieving the gas from said first-named chamber as said pore liquid enters said first-named chamber.

33. The apparatus of claim 30 having an electrically actuated, normally closed valve for admitting pore liquid from said soil into said chamber.

34. The apparatus of claim 29 wherein said probe means includes switch means for switching between said soil sample measuring electrodes and said pore-liquid sensor means.

35. The apparatus of claim 27 wherein said probe means includes temperature sensor means for measuring in situ the temperature of said soil sample.

36. The apparatus of claim 27 wherein said sensor comprises two pairs of electrodes, one disposed in horizontal relation to each other and the other disposed in vertical relation to each other.

37. A method of evaluating in situ mechanical properties of soils, including sands and silts, from certain electrical properties thereof, comprising

forcing into said soil two pairs of spaced-apart electrodes, so that some of the in situ soil to be measured lies between said electrodes, one said pair of electrodes being disposed horizontally and the other being disposed vertically in said soil,

sending a radio-frequency current across said electrodes,

measuring at said radio frequency the electrical resistance and capacitance of the soil across each said pair of said electrodes to obtain the horizontal resistance, vertical resistance, horizontal capacitance and vertical capacitance of said soil in situ,

filtering in situ pore liquid from said soil at a locus adjacent said electrodes to obtain a soil-free pore-liquid sample at that locus, `sending said radio-frequency current through said pore liquid,

measuring at said radio frequency the electrical resistance of said soil-free pore liquid, and

calculating from said in situ obtained resistances and capacitances the desired mechanical properties.

38. A method of evaluating in situ mechanical properties of soils, including sands and silts, from certain electrical properties thereof, comprising

forcing into said soil two pairs of spaced-apart vertically extending electrodes, so that some of the in situ soil to be measured lies between said electrodes, one said pair of electrodes being disposed horizontally and the other being disposed vertically in said soil,

sending a radio-frequency current across said electrodes and through the soil in between them,

measuring at said radio frequency the electrical resistance and capacitance of the soil across both said pairs of said electrodes to obtain the horizontal resistance, vertical resistance, horizontal capacitance and vertical capacitance of said soil in situ,

filtering in situ pore liquid from said soil at a locus near said electrodes to obtain a soil-free pore-liquid sample at that locus,

sending said radio-frequency current through said soil-free pore liquid,

measuring at said radio frequency the electrical resistance of said soil-free pore liquid, and

calculating from said in situ obtained resistances and capacitances the density, friction angle, and structural index of said soil.

39. A method of evaluating in situ certain mechanical properties of a selected wet soil, comprising the steps of:

inserting to a predetermined depth into the soil to be tested a probe having spaced-apart soil-sensing electrodes and having a pore-liquid chamber with a soil-filtering inlet thereinto and spaced-apart liquid-sensing electrodes therein,

driving said soil-sensing electrodes into said soil to be evaluated so that some of the soil lies in between said soil-sensing electrodes,

filling said pore-liquid chamber with filtered pore liquid obtained from said soil near said electrodes,

measuring both the resistance and the capacitance of the wet soil in between said soil-sensing electrodes,

converting the measured resistance and capacitance of said in-situ soil into the conductivity and the dielectric constant E'"'"' therefor,

measuring the conductivity and the dielectric constant Es of the pore liquid in said chamber,

determining the dielectric constant Er of the dry soil particles,

determining the dielectric constant Es of the pore liquid,

determining the formation factor F of the wet soil in accordance with the formula;

##EQU7## then determining the soil porosity n from the formula;

##EQU8##

40. The method of claim 39 including the step of calculating the in situ density n by the formula:

space="preserve" listing-type="equation">n=(2/1+F).

41. The method of claim 40 including the step of calculating a factor X related to the shape of the said particles, using the formula:

space="preserve" listing-type="equation">X=Fn-1/1-n.

42. The method of claim 41 including the step of calculating the friction angle φ

of the soil from the formula;

space="preserve" listing-type="equation">φ

=13.33 FX-10.33.

43. The method of claim 39 including the step of calculating the relative density in the field, D_r as from the formula:

space="preserve" listing-type="equation">D.sub.r =F-3/1.8.

44. The method of claim 39 wherein a coefficient of anisotropy A is obtained by

determining the conductivity of the soil between said sensing electrodes along an horizontal plane,

determining therefrom a value F_H,

determining the conductivity of the soil between soil-sensing electrodes along a vertical plane, determining therefrom a value F_V and then calculating

45. The method of claim 44 including the step of calculating the relative density D_r from the formula:

space="preserve" listing-type="equation">D.sub.r =F-3/1.8,

and then calculating a structural index I_D.sbsb.r from the formula;

space="preserve" listing-type="equation">D.sub.D.sbsb.r =D.sub.r A.sup.-16.

46. A method of evaluating in situ certain mechanical properties of a selected wet soil, of which the dielectric constant Er of the dry soil particles and the dielectric constant Es of the pore liquid thereof are known, comprising the steps of:

emplacing into said selected soil, in situ, spaced-apart soil-sensing electrodes, so that some of said soil lies in between said soil-sensing electrodes,

emplacing into said selected soil, in situ and near said electrodes, a pore-liquid chamber having a soil-filtering inlet thereinto and having spaced-apart liquid-sensing electrodes therein,

filling said pore-liquid chamber with filtered pore liquid so that pore liquid lies in between said liquid-sensing electrodes,

sending radio-frequency current across the soil-sensing electrodes,

measuring both the resistance and the capacitance of the wet soil in between said soil-sensing electrodes,

converting the measured resistance and capacitance of said in situ wet soil into the conductivity and the dielectric constant E'"'"' therefor,

sending radio-frequency current across the liquid-sensing electrodes,

measuring the resistance of the pore liquid in said chamber,

converting the measured resistance of the pore liquid into the conductivity thereof,

determining the formation factor F of the wet soil in accordance with the formula;

##EQU9## and then determining the soil'"'"'s porosity n from the formula;

##EQU10##

47. The method of claim 46 wherein the frequency of the radio-frequency current is about one megaHertz.

48. The method of claim 46 including the step of calculating in situ said density n by the formula:

space="preserve" listing-type="equation">n=(2/1+F).

49. The method of claim 48 including the step of calculating a factor X related to the shape of the said particles using the formula:

space="preserve" listing-type="equation">X=Fn-1/1-n.

50. The method of claim 49 including the step of calculating the friction angle φ

of the soil from the formula;

space="preserve" listing-type="equation">φ

=13.33 FX-10.33.

51. The method of claim 46 including the step of determining the relative density in the field, D_r from the formula:

space="preserve" listing-type="equation">D.sub.r =F-3/1.8.

52. The method of claim 46 wherein a coefficient of anisotropy A is obtained by

determining the conductivity of the soil between soil-sensing electrodes along an horizontal plane,

determining therefrom a value F_H,

determining the conductivity of the soil between soil-sensing electrodes along a vertical plane,

determining therefrom a value F_V and then calculating

53. The method of claim 52 including the step of calculating the relative density D_r from the formula:

space="preserve" listing-type="equation">D.sub.r =F-3/1.8,

and

then calculating a structural index I_D.sbsb.r from the formula;

space="preserve" listing-type="equation">I.sub.D.sbsb.r =D.sub.r A.sup.-16.

54. The method of claim 46 wherein there is the step of determining the degree of saturation of the in situ soil by

determining F for a withdrawn sample of soil that has been 100% saturated with said pore liquid,

determining the actual F for the in situ soil, and

comparing the in situ soil F with the saturated soil F on a logarithm basis.