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    The way the market of underground mining has evolved is a direct consequence of the recent appearance of electric drills with high rotary coring power (borehole lengths between 800 and 1,000 metres).

    This machinery, as well as being useful in mineral research, opens up an important range of possibilities in terms of geotechnical research on underground infrastructure.

    With these kinds of drills which are versatile and easily positioned in fields, horizontal or highly inclined borehole exploration can be carried out, which allows infrastructure such as tunnels, piling, diversion dams, etc.…, to be researched on a design level which until now had been studied through expensive geotechnical campaigns carried out vertically, which obtained limited information on the terrain that was subject to interpretation.
    The drill frame allows boreholes to be made in any orientation and inclination (even boreholes in negative inclination – ascending), up to depths/ lengths between 800 and 1000 metres.
    The boreholes are made via rotation with water circulation, with continuous rotary coring and in varying diameters, generally between HQ and NQ (core diameter varying between 63.5 and 47.6 mm respectively).
    The length as well as the deviation of a borehole are very dependent on the terrain that is to be perforated, therefore these lengths and deviations will be what the existing technology allows.
    For the measurement of borehole deviation a REFLEX® gyroscope can be used, which allows measurements to be taken in all kinds of environments, whether they are magnetic or not, as well as inside perforation rods.
    Over 6,000 m of horizontal boreholes have been made for geotechnical exploration.

    In Spain, GEONOR is the company that has carried out the largest volume in metres of this kind of perforation for geotechnical studies and during the completion of civil construction.