UNDERGROUND CONSTRUCTION OF AN UNDERGROUND STATION WITH LIMITED COVER

A 600 M LONG CONTRACT SECTION OF THE URBAN RAILWAY SYSTEM AT BOCHUM WAS CONSTRUCTED BY TUNNELLING METHODS BETWEEN 1975 AND 1976. THIS INCLUDED THE CONSTRUCTION OF AN UNDERGROUND RAILWAY STATION AS WELL AS SINGLE AND DOUBLE TRACK TUNNEL SECTIONS. THE HEIGHT OF OVERBURDEN VARIED BETWEEN 8 AND 3 METRES, AND THE ENTIRE TUNNEL SECTION LAY UNDER STREETS OR BUILDINGS. THE SUB-SURFACE CONSISTED OF MARLS OF WIDELY VARYING STRENGTHS AND FINE SAND-SILT AND GRAVEL OF LOW COHESION. IN PARTS OF THE TUNNELLING, THE REMAINS OF OLD FOUNDATIONS AND BOMB DEBRIS WAS ENCOUNTERED. THE TUNNELLING WAS CARRIED OUT IN ACCORDANCE WITH THE PRINCIPLES OF THE NEW AUSTRIAN TUNNELLING METHOD AND WAS CONTROLLED BY MEANS OF AN EXTENSIVE MEASUREMENT PROGRAMME. AT NO POINT DID DAMAGE TO BUILDINGS OCCUR. THE SETTLEMENTS LAY IN GENERAL IN THE REGION OF 20 MM. PARTICULAR CARE WAS REQUIRED FOR THE FIRST APPLICATION OF THIS METHOD OF CONSTRUCTION FOR UNDERGROUND RAILWAY STATION CONSTRUCTION. THUS TWO TUNNEL TUBES RUNNING PARALLEL TO ONE ANOTHER WERE DRIVEN SUCCESSFULLY, THESE INTERSECTED ONE ANOTHER IN THE ABUTMENT REGION, AND THE ABUTMENT LOADS WERE TAKEN UP BY A COMMON CENTRE WALL. THE NECESSARY CONSTRUCTION PATTERN AND MEASURES, AS WELL AS THE MEASUREMENTS CARRIED OUT BOTH UNDERGROUND AND OVERGROUND ARE DESCRIBED HERE AND DISCUSSED.