Appendix Q

Appendix Q Electrode Experiment In Dry Soil

The following tests were performed in undisturbed dry soil in north central Nevada. The soil was dry silty sand with sagebrush growing nearby. Two holes were dug for reference electrodes. No indication of moisture was encountered at any depth in the holes. The bottom of each hole was light colored, dusty extremely dry soil.

The two holes were 1.5 meters (4.5 feet) apart. Half-inch reinforcing rod (rebar) electrodes were inserted 0.6 meter (2 feet) into the soil at the bottom on the holes and eight liters of water added to the bottom of each hole. After about ten minutes the resistance between the two electrodes settled to 11.5 ohms. The two electrodes were connected together to form a reference electrode. The resistance of the two connected electrodes was then somewhat LESS than 11.5 ohms; about 6 ohms.

Two different electrodes were tested: the first was a pointed stainless steel 3/8-inch diameter 10-inch long rod. The rod was inserted into the soil to greater and greater depth and the decrease in resistance recorded.

The second electrode tested was a cadmium plated 18-inch long steel rod with a blunt end. The results of those tests follow.

These resistances are higher than those of the stainless electrodes. The difference is significant. It is possible that the pointed end compacts the soil near the point, thus enhancing the electrical contact. The blunt end of the steel rod "rattled" in the ground and pushed the dirt away from the metal. Electrodes with pointed ends seem to give better electrical contact for the same depth of penetration and are also easier to insert.

The effect of the two reference electrodes that were tied together probably adds about six ohms to the total resistance of the reference electrodes plus the test electrodes. Thus the test electrode values as given above are slightly higher than actual value.

Home Additional Information MiniRes