Noninsulated electrodes

In the framework of a land reclamation project, electrokinetics was applied in combination with preloading and prefabricated vertical drains to improve the mechanical strength of marine sediments intermittent current and noninsulated electrodes were adopted (Lo et al, 2000). The results showed that the mechanical properties of sediment were signiflcantly improved in the vicinity of the electrodes after 22-34 days, by applying voltage gradients ranging between 9.5 and 28.2V/m. 

The electrode was made up of two 210-mm iron rods of 1 mm diameter. The lower 30 mm of the elec-trode was divided into insulated and noninsulated areas in the following way 0-7, 10-17, and 20-27 mm and from 30 mm up to the connection points were insulated areas, while the areas between were noninsulated. Teflon was used as insulating material. Figure 1 demonstrates how the electrode was placed in the measming cell. 

Figure 6.9 shows the needle surface current density as a function of depth, normalized with J = 1 at the electrode tip. If such a noninsulated needle is used for nerve excitation, most of the current will be injected from the shaft, but at threshold the excitation occurs only at the tip. 

The frequently used ionisation probe is the so-called pin ionisation probe (Figure 4.11). The electric conductor inserted into the explosive charge parallel with the charge s longitudinal axis serves as a common electrode. It is actually a noninsulated copper wire (or strip) 1 mm in diameter. The other two electrodes are steel pins placed perpendicularly to the common electrode at a distance 0.5-3.0 mm from it. When the detonation wave arrives at the pin, the electric contact between the common electrode and the pin is restored, due to the ionisation effect in the detonation wave. 

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