Vibro compaction

Under testing conditions the fuel element to be tested is placed at the stand. Then it is moved into the control unit and gripped with a collet. First the density distribution of the vibro-compacted fuel along the total length of the fuel element is tested. Proceeding from the obtained data the section to be investigated in detail is chosen and a tomogramm of this section is obtained. 

Type of soil Vibro-compaction Vibro-replacement... 

Large concrete pipes can be vibrocast. Vibro-compaction. Vibration and pressure are applied simultaneously, to density powder mixtures. The usual techniques produce particle accelerations of some 50g, and require an appropriate particle size distribution to obtain dense compaction. To density mixed powders whose components differ greatly in density, very strong vibrations (accelerations c. 20 OOOg) have been studied. 

Lowering the 0/M ratio to 1.97-1.98 by incorporating metallic getters inside the pin is a promising way to do this. Cr, Nb, V, Ti and U have been tested in the BOR 60 vibro-compacted fuel rods [7.31] the best results were obtained with fine granular metallic Uranium. Figure 7.20 illustrates the reduction of corrosion layer (less than 20 mm for bum-up levels up to 15 at %). 

Research by Massarsch has led to an improved energy transmission using resonance vibro-compaction. The key features of the resonant compaction technique are the use of a specially designed compaction probe (double Y with adapted impedance) and a heavy vibrator with variable operating frequency on top of the probe. After probe insertion, the frequeney of the vibrator is adjusted to the resonance frequency of the soil layer, thereby amplifying the ground response (Massarsch, 2002). 

The grain size distribution envelope in Figure 7.22 indicates when vibro-replacement should be used instead of vibro-compaction. 

Wehr, W.J. Influence of the carbonate content of sand on vibro compaction, 6th Conf on Ground Improvement techniques, Coimbra, Portugal, 2005. 

Until satisfactoty experimental data are obtained this model is the only one available for treating the behavior of vibro-compacted fuel. 

Vibro-flotation Density by horizontal vibration and compaction of backfill material... 

Conveyor (4) can be reversed to clean out individual bins or the entire chip storage facility into transport containers (17). During start-up, optimization trials, or towards the end of a run, unsatisfactory compacts may be produced. In this case, the vibro-screen feeder (13) can be turned to remove the off-spec material from the system via vibro-feeder (14) and conveyor (15), which is reversed to transport the material into a dumpster. 

Vibrating Table. A table which oscillates rapidly to remove air and compact a refractory castable placed on it. Vibro-casting. Pouring concrete into a mould, and densifying by vibration. 

Typical execution methods are based on the vibro-replacement technique or on the insertion of a closed-ended casing by vibration or driving. During extraction of the probe or casing the gravel is compacted and a further enlargement of the column diameter is realised. Only the more frequently used vibro-replacement technique will be further discussed in this section. 

Various methods exist to eonstruct stone eolumns over water. Traditionally a blanket of gravel with a thiekness typically varying between 2 to 3 m is placed on the seabed. The vibro-probe penetrates the layer to its final depth. As with the top feed method, the hole is supported by water jets and gravel drops in the annular space between the existing ground and the probe to the bottom of the hole. The gravel is compacted by the probe. 

Soil improvement methods include techniques such as surcharging (in combination with vertical drains), compaction, deep soil mixing and vibro replacement (see Chapter 7). 

Vibro-flotation the surrounding soil is compacted with a horizontally vibrating motor attached to the end of the probe, sometimes aided by water sprayed from the nozzle tip end. 

Vibro-rod compaction is achieved using vertical vibratory penetration to the top of the probe or rod. 

---