Method and apparatus for measuring in-place density and moisture content

• US 6,215,317 B1
• Filed: 04/27/1999
• Issued: 04/10/2001
• Est. Priority Date: 04/27/1999
• Status: Active Grant

• Current Assignee: Purdue Research Foundation (Purdue University)
• Original Assignee: Purdue Research Foundation (Purdue University)
• Inventors: Drnevich, Vincent P., Siddiqui, Shafiqul I.
• Primary Examiner(s): Metjahic, Safet
• Assistant Examiner(s): KERVEROS, DEMETRIOS C
• Application Number:
  US09/300,208
• Time in Patent Office: 714 Days
• Field of Search: 324/642, 324/643, 324/690, 324/637
• US Class Current: 324/643
• CPC Class Codes: G01N 27/223 for determining moisture content, e.g. humidity rain detectors on vehicle windows B60S1/0825
• CPC Class Codes: G01N 33/246 for water content for control of watering A01G25/167

Abstract

A method and apparatus for measuring in-place soil density and moisture content. A cylindrical cell is disclosed which may be used to measure the density and the dielectric constant of a soil sample placed within the cylindrical cell. Also disclosed is a multiple rod probe which is designed to contact spikes driven into the ground to measure the in-place dielectric constant of soil. The multiple rod probe includes adjustable studs which ensure complete contact with the spikes. Both measurements are performed using time domain reflectometry. The present invention develops equations for determining the density of the soil in-place from the measured dielectric constant of the soil in-place and the measured density and dielectric constant of the soil in the cylindrical cell.

Claims

1. A method of installing an apparatus for measuring a dielectric constant of an in-place soil sample, comprising the steps of:

(a) providing a template having a central hole therethrough and a plurality of peripheral holes therethrough, the plurality of peripheral holes being substantially equidistant from the central hole;

(b) laying the template on a surface of the in-place soil sample;

(c) driving a plurality of conductive spikes into the soil through the central hole and each of the peripheral holes of the template;

(d) removing the template;

(e) providing a probe head, comprising;

an annular conductive body;

a plurality of conductive peripheral studs mounted to a bottom surface of the body;

a conductive central stud; and

an annular non-conductive insert coupling the body to the central stud;

wherein a first spacing between the central stud and the peripheral studs is substantially the same as a second spacing between the central hole and the peripheral holes, such that each stud is aligned with a respective spike when the probe head is placed over the spikes after they have been driven into the soil sample; and

(f) placing the probe head onto the conductive spikes, such that each stud is aligned with a respective spike.

2. A method of installing an apparatus for measuring a dielectric constant of an in-place soil sample, comprising the steps of:

(a) providing a template having a central hole therethrough and a plurality of peripheral holes therethrough, the plurality of peripheral holes being substantially equidistant from the central hole;

(b) laying the template on a surface of the in-place soil sample;

(c) driving a plurality of conductive spikes into the soil through the central hole and each of the peripheral holes of the template; and

(d) removing the template.

3. A method of installing an apparatus for measuring a dielectric constant of an in-place soil sample, comprising the steps of:

(a) providing a probe head, comprising;

an annular conductive body;

a plurality of conductive peripheral studs mounted to a bottom surface of the body;

a conductive central stud; and

an annular non-conductive insert coupling the body to the central stud;

wherein the central stud and the peripheral studs are arranged in a first pattern;

(b) driving a plurality of conductive spikes into the soil, wherein the spikes are arranged in the first pattern; and

(c) placing the probe head onto the conductive spikes, such that each stud is aligned with a respective spike.