13 the load shoe 10 comprises web plate part 10a and branch parts 10b 1 10b 2 extending therefrom the seat 13 comprises a web plate part 13a and branch parts 13b 1 13b 2 and at ends of the branch parts inwardly directed edges 13d 1 13d 2 in the approximate center point of the web plate part 13a a neck part 13c is attached so that spaces e 1 and e 2 are defined between the neck 13c and the side walls 13b 1 13b 2 the side branches 10b 1 10b 2 of load shoe 10 are disposed in a respective one of the spaces e 1 e 2 a medium preferably water is conducted by pressure via channel 15 in neck 13c into a space defined between the neck 13c of the seat 13 and the load shoe 10 which is chamber d the medium is passed or flows from the space d onward via a channel 16 in web plate part 10a into a groove 17 on the front surface 10 39 of the load shoe the medium is liquid preferably water or an aqueous mixture the groove 17 is arranged to extend over substantially.