NOVELTY - The method involves introducing a drill tube (1) into soil (100) in a drilling motion, where the drill tube is provided with a drill head (2) at a lower end of the drill tube. A liquid (6) i.e. bentonite mixture, is supplied through a space formed within the drill tube during drilling motion. An elongated element i.e. tubular geothermal heat exchanger, in the space is introduced within the drill tube. The drill tube is detached from the drill head. The drill tube is retracted when keeping the elongated element in the soil.    USE - Method for introducing an elongated element i.e. tubular geothermal heat exchanger (claimed), into a borehole made in soil. Can also be used for a drainage pipe, exploration pipe, gas supply line and a gas extraction line.    ADVANTAGE - The method ensures integrity of the borehole during tile introduction of the elongated element i.e. tubular geothermal heat exchanger. The method enables making the elongated element not to make contact with the borehole wall during lowering of the elongated element, thus reducing risk of external damage of the elongated element during introduction. The method enables introducing the elongated element into the borehole made in soil in an easy manner. The drill head can be urged axially from the drill tube end, and is pressed deeper into the soil before and during uncoupling, so that the uncoupling is accelerated and/or the drill head is attached into the soil firmly. The method enables utilizing coupling units to be designed double diametrically with respect to each other, thus enhancing stability of the drill head in the drill head holder.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following:    (1) a drill head assembly comprising a drill head and a drill head holder to be attached to a drill tube    (2) an anchor for anchoring an elongated element such as geothermal heat exchanger, in a borehole made in soil    (3) a tube assembly comprising an inner tube bounding a passage for a flowing heat exchanger fluid    (4) a device for moving a tubular element.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of an elongated element.    Drill tube (1)    Drill head (2)    Drill tube holder (3)    Liquid (6)    Soil (100)