shell is produced of the same material as the tubular shell and if a maintenance free corrosion protection is required it is made of highly alloyed stabilized high quality steel a screw collar ring of the same material is screwed onto this cover shell after the production of the parallel wire bundle and the closely enveloping tubular shell at the construction site is complete a two part double longitudinally threaded outer jacket of the same material is placed around the end of the tubular shell whereby a circular small gap of a few mm must be provided a few rings with distributed spacers take care of a uniform spacing at all points the spacers must leave openings free for the later injection of the synthetic material by means of the above mentioned screw ring the tubular shell is solidly connected with the cover jacket and thus with the anchor head the jacket is shaped so that it can grip around the 34 welding lock 34 and the 34 expansion corrugation 34 with a small spacing at the end of the jacket which is away from the anchor head it is crimped so that it lies closely against the tubular shell any gap which remains is plugged with small 34 teflon 34 wedges a closing circular projection holds a fitted two part rubber ring which is pressed together by means of a tightly drawn band of high quality steel and is rigidly pressed onto the end of the jacket and onto the tubular shell in such a manner that the gap at the end is covered the length of the jacket must be a function of the largest possible expansion of the parallel wire bundle so that even when.