Cone tipped cylindrical probe for use in groundwater testing

• US 6,208,940 B1
• Filed: 06/25/1998
• Issued: 03/27/2001
• Est. Priority Date: 03/30/1998
• Status: Expired due to Term

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Kram, Mark L., Massey, James A.
• Primary Examiner(s): Williams, Hazron
• Assistant Examiner(s): WILSON, KATINA M
• Application Number:
  US09/111,629
• Time in Patent Office: 1,006 Days
• Field of Search: 73/84, 73/38, 73/152.41, 73/73, 702/11, 702/12, 702/2
• US Class Current: 702/12
• CPC Class Codes: E02D 1/06 Sampling of ground water
• CPC Class Codes: G01N 2203/0082 Indentation characteristics measured during load
• CPC Class Codes: G01N 33/24 Earth materials G01N33/42 takes precedence

Abstract

A piezocone for measuring the soil'"'"'s resistance to penetration and pore water pressure while being advanced into the ground by a rig. The piezocone includes a friction sleeve and a conical tip attached to the lower end of the sleeve. The conical tip develops the cone resistance. The friction sleeve is an isolated cylindrical sleeve which measures the resistance of the soil as the sleeve passes through the soil. The pore water pressure is measured by a porous element mounted in the conical tip of the piezocone and a pressure transducer mounted in the cylindrical friction sleeve of the piezocone. The measurements including pore water pressure, cone resistance and soil resistance are supplied to a computer which includes a Piezocone Dissipation Analysis program for processing data from the measurements to generate dissipation curves for each depth at which the piezocone provides hydrogeologic site characterization data. Soil classification is also provided from a data file stored within the computer. The Piezocone Dissipation Analysis program generates a Hydrostatic Pressure Profile curve and a Hydraulic Conductivity Profile Plot. A water depth below surface estimate is provided using the Hydrostatic Pressure Profile curve zero pressure intercept. The Hydraulic Conductivity Profile Plot may be generated using coefficients of Permeability from a soil classification table.

Claims

1. An in soil testing system for measuring soil parameters while being forcibly penetrated into the soil comprising:

a probe having a plurality of sensors for measuring said soil parameters;

said plurality of sensors including;

first and second strain gauge load cells mounted within said probe, said first strain gauge load cell measuring forces resisting tip penetration by said probe, said second strain gauge load cell measuring lateral forces resisting penetration by said probe; and

a pressure sensing device for measuring said pore water pressure in the soil at said plurality of depths of penetration, said pressure sensing device including a porous filter mounted in a conical tip of said probe and a pressure transducer mounted within said probe, said pressure transducer being connected to said porous filter;

said plurality of sensors of said probe generating electrical signals representative of said soil parameters;

means coupled to said probe for forcibly penetrating said probe into the soil;

a digital computer coupled to said plurality of sensors to receive said electrical signals from said plurality of sensors, said digital computers processing said electrical signals to provide a designation of a soil type for the soil, a pressure dissipation curve for said pore water pressure in the soil at each of said plurality of depths of penetration of said probe and a time T₅₀ required for a fifty percent pressure dissipation of said pressure dissipation curve at each of said plurality of depths of penetration of said probe;

said digital computer calculating a hydraulic conductivity for each of said plurality of depths of penetration of said probe using the formula;

$k=\frac{r^2}{279.12\times <br><br>t_{50}\times <br><br>\mathrm{\alpha <br><br>}\times <br><br>q_c}$

where r is a radius for said probe stored in said digital computer, a is an empirical average coefficient for said soil type, and q_c is an end bearing component of the forces resisting tip penetration by said probe;

said digital computer calculating a water depth below surface for each of said plurality of depths of penetration of said probe using the formula;

$\begin{array}{cc}\mathrm{WDBS}=\mathrm{MD}-\frac{p_p\times <br><br>144}{d_w}& \left(5\right)\end{array}$

where MD is a measured depth for said probe, p_p is a final pressure for said pressure dissipation curve and d_w is a density for fresh water which is approximately 62.4 pounds per cubic foot;

said digital computer generating a hydrostatic pressure profile which illustrates a final pressure point for the pressure dissipation curve of each of said plurality of depths of penetration of said probe;

said digital computer providing a best fit line for the final pressure point of only completed pressure dissipation curves for each of said plurality of depths of penetration of said probe;

a monitor coupled to said digital computer for displaying a penetrometer dissipation analysis window which includes the hydraulic conductivity and the water depth below surface calculated by said digital computer for each of said plurality of depths of penetration of said probe, said monitor displaying said hydrostatic pressure profile and said best fit line;

said digital computer containing a Piezocone Dissipation Analysis computer software program, said Piezocone Dissipation Analysis computer software program calculating said hydraulic conductivity and said water depth below surface for each of said plurality of depths of penetration of said probe, said Piezocone Dissipation Analysis computer software program generating said hydrostatic pressure profile and said best fit line;

said Piezocone Dissipation Analysis computer software program including an option program module, said option program module having an option which allows a user of said in soil testing system to select said option, said option when selected by said user providing a Coefficient of Permeability from a soil classification lookup table for each of said plurality of depths of penetration of said probe;

said Piezocone Dissipation Analysis computer software program using said Coefficient of Permeability from said soil classification lookup table for each of said plurality of depths of penetration of said probe to generate a hydraulic conductivity profile, said hydraulic conductivity profile appearing on said monitor.

2. The in soil testing system of claim 1 wherein said means for forcibly penetrating said probe into the soil comprises:

a three axil truck having a plurality of hydraulic rams mounted inside a rear compartment of said three axil truck; and

a string of steel pipes having one end extending vertically downward from an underside of said three axile truck into the soil, said probe being attached to the opposite end of said string of steel pipes, said string of steel pipes being pushed into the soil at a constant penetration rate of two centimeters per second.

3. The in soil testing system of claim 1 wherein said string of steel pipes comprises a plurality of steel pipes, each of said plurality of steel pipes having a length of approximately one meter.

4. The in soil testing system of claim 1 wherein said soil classification lookup table comprises a Robertson cone penetration test soil classification lookup table having coefficients of permeability for a variety of soil types, said coefficients of permeability for said variety of soil types ranging from 10⁻

1 cm/sec to 10<sup>−

7</sup> cm/sec.

5. The in soil testing system of claim 4 wherein said variety of soil types includes sensitive, fine grained soils;

organic soils;

peats; and

very stiff sands to clayey sands, each of said variety of soil types having a coefficient of permeability of 10<sup>−

5</sup> cm/sec.

6. The in soil testing system of claim 4 wherein said variety of soil types includes silt mixtures;

clayey silts to silty clays; and

very stiff, fine grained soils, each of said variety of soil types having a coefficient of permeability of 10<sup>−

6</sup> cm/sec.

7. The in soil testing system of claim 4 wherein said variety of soil types includes sand mixtures;

and silty sands to sandy silts, each of said variety of soil types having a coefficient of permeability of 10<sup>−

4</sup> cm/sec.

8. The in-soil testing system of claim 4 wherein said variety of soil types includes clays to silty clays, each of said variety of soil types having a coefficient of permeability of 10⁻

7 cm/sec.

9. The in soil testing system of claim 4 wherein said variety of soil types includes sands to clean sands to silty sands, each of said variety of soil types having a coefficient of permeability of 10⁻

2 cm/sec.

10. The in soil testing system of claim 4 wherein said variety of soil types includes gravelly sands to sands, each of said variety of soil types having a coefficient of permeability of permeability of 10⁻

1 cm/sec.

11. The in soil testing system of claim 1 further 27-t, comprising a printer connected to said digital computer, said printer providing a printout of the water depth below surface and the hydraulic conductivity for each of said plurality of depths of penetration of said probe.

12. A method for investigating soil parameters and collecting data and information relating thereto comprising:

positioning a probe located at one end of a string of steel pipes, on a soil surface, said probe including a plurality of sensors for measuring said soil parameters;

applying a force to the other end of said string of steel pipes to forcibly penetrate said probe into the soil below said soil surface at a constant penetration rate;

measuring pore water pressure in the soil with one of said sensors at a plurality of depths of penetration of said probe in said soil;

measuring forces resisting tip penetration by said probe with a second of said sensors at a plurality of depths of penetration of said probe in said soil;

measuring lateral forces resisting penetration by said probe with a third of said sensors at a plurality of is depths of penetration of said probe in said soil;

recording in digital form the analog output of all of said plurality of sensors of said probe in a repetitive manner while said probe is being penetrated into said soil;

processing said data and information relating to said soil parameters for each of said plurality of depths of penetration of said probe to generate a pressure dissipation curve for said pore water pressure in the soil at each of said plurality of depths of penetration of said probe and a hydrostatic pressure profile which illustrates a final pressure point for the pressure dissipation curve of each of said plurality of depths of penetration of said probe; and

plotting a best fit line for the final pressure point of only completed pressure dissipation curves, said best fit line being used to determined a water depth below surface for the soil said probe is penetrating.

13. A method for investigating soil parameters and collecting data and information relating thereto comprising:

positioning a probe located at one end of a string of steel pipes, on a soil surface, said probe including a plurality of sensors for measuring said soil parameters;

applying a force to the other end of said string of steel pipes to forcibly penetrate said probe into the soil below said soil surface at a constant penetration rate;

measuring pore water pressure in the soil with one of said sensors at a plurality of depths of penetration of said probe in said soil;

measuring forces resisting tip penetration by said probe with a second of said sensors at a plurality of depths of penetration of said probe in said soil;

measuring lateral forces resisting penetration by said probe with a third of said sensors at a plurality of depths of penetration of said probe in said soil;

recording in digital form the analog output of all of said plurality of sensors of said probe in a repetitive manner while said probe is being penetrated into said soil;

processing said data and information relating to said soil parameters for each of said plurality of depths of penetration of said probe to generate a pressure dissipation curve for said pore water pressure in the soil at each of said plurality of depths of penetration of said probe and a hydrostatic pressure profile which illustrates a final pressure point for the pressure dissipation curve of each of said plurality of depths of penetration of said probe;

plotting a best fit line for the final pressure point of only completed pressure dissipation curves, said best fit line being used to determined a water depth below surface for the soil said probe is penetrating;

calculating a hydraulic conductivity for each of said plurality of depths of penetration of said probe whenever sufficient data exists to calculate said hydraulic conductivity; and

generating a hydraulic conductivity profile which includes the hydraulic conductivity calculated for each of said plurality of depths of penetration of said probe.