One of the most effective methods of laying engineering networks is HDD.

Factors contributing to the success of HDD include the building of the mining hole, minimisation of time expenses and the prevention of failures related to the stability of drilled soils. The correct choice of the boring solution and the use of special reagents also influences the process of HDD.

In the Ukraine the high cost of drilling fluids, imported from the Czech Republic, France and even the USA, has had a negative effect on the uptake of HDD.

It is necessary to point out that the Ukraine has its own deposit of bentonite clays, the Cherkassky deposit, developed by the corporation Dashukovsk Bentonites.

According to the results of laboratory research, the characteristics of clays from the Cherkassky deposit are very close to those of the imported products. This is why it was decided to use Ukrainian bentonites for the execution of an HDD project in the Pechersk region near Kiev.

The job site was a residential area with a complex ground conditions and restricted approach. The distance from the privately owned land varied from 5 - 8 metres, and the road width was from 2.5 - 3.5 metres. The area had many utilities installed including gas, telephone, water supply and sewerage. The task was to lay over four kilometres of engineering communications without disrupting the existing ones and inconveniencing the owners of the adjoining private property. The pipelines laid included PE water pipes of diameter 110 – 225 mm in casings 400 mm in diameter, of a total length of 2, 217 metres, and sewerage pipes, diameter 225 mm, with a total length of 1,963 metres.

The soils in the vicinity of the Narodnicheskaya ravine near the job site were represented by the following layers:

1. Modern technogenic formations: made ground – sand, partially clay — dark grey and yellowish grey — with inclusions of small rock, bricks, debris, consolidated soil. The thickness of this layer is 0.3 – 1.8 metres.

2. Upper Quaternary and modern diluvium formations: pulverulent clay – grey, dark-grey, greyish-yellow , 0.2 – 1.7 metres thick; fine sand – grey, yellowish grey, 0.3 – 0.5 metres thick; pulverulent loam, 1.8 metre.

3. Upper Quaternary diluvium formations: pulverulent loess, red-yellow, jonquil grey, depth up to 4.7 metres.

4. Middle Quaternary, proglacial lake formations: light pulverulent loam, grey with a blue tint, brownish-grey, yellowish-grey, with spots and layers of clay. Layer thickness is 1.4 metres.

The HDD works on an experimental section of 115 metres were conducted with the use of the boring solution which was prepared using the Dashukovsk clays. The field control after the execution of works revealed the specificity of the Dashukovsk bentonites, namely that the time required for the preparation of the solution is longer than required for standard imported solutions. Furthermore, the viscosity of the used solution appeared to be higher, which resulted in an insignificant load increase on the engine ensuring the rotation of the rods and circulation of the solution.

The above drawbacks of the Dashukovsk bentonites, however, do not reduce their obvious advantages, which do not stop at their low cost. The solution preserves its working properties without additional interfusion for a long period of time. Also, the preparation of a solution using Dashukovsk clays requires a smaller quantity of dry powders, compared with imported products, resulting in additional savings.

The conducted research makes it possible to arrive at the following conclusions; the experiment has proven the possibility of using Dashukovsk bentonites for HDD. For commercial production of Ukrainian bentonites on the basis of Dashukovsk clays it will be necessary to conduct a complex research program to identify the additives available in the market so as to optimise the composure of the solutions required for different conditions and equipment.