It comprises at least one substantially elongated pin associated with a wind turbine tower and at least one corresponding substantially elongated pile to be inserted into a surface and adapted for receiving at least one portion of the pin. A chamber is defined between the pin and the pile for receiving grout. At least one of the pin and the pile is provided with connecting plates extending inside the grouting chamber and provided with holes through which the grout passes. The connecting plates may extend radially inside the grouting chamber, aligned or not to each other or with the center of the pin or the pile.