The New North-South Underground Line Cologne 

The project was divided into four planning and two con­struc­tion lots. CDM Smith led a con­sor­tium in the design and per­mis­sion planning as well as ten­der­ing for the two southern planning lots, in­clud­ing the two Kartäuserhof and Bonner Wall un­der­ground stations.

The northern section involved the Breslauer Platz (main station) stop to be built using the top-down method. The excavation pit was secured using diaphragm, bored and soldier pile walls, some with multiple bracing; the pit intersected with existing structures in places, and included two launching shafts for the tunnel boring machines (TBM) launchs. In addition, an excavation pit at 25 m depth was excavated and secured by diaphragm walls with multiple bracing at Kurt-Hackenberg-Platz as the receiving shaft for the TBMs from the southern lot and launching shaft for compressed air propulsion underneath the philharmonic concert hall. This involved a highly complex process of determining pressure levels due to repeatedly changing dependencies between construction, stability specifications and costs. 

CDM Smith was re­spon­si­ble for tech­ni­cal prepa­ra­tions for all of the spe­cialised ex­ca­va­tion en­gi­neer­ing work in the northern section, which involved di­aphragm, bored and soldier pile walls with wood and shot­crete lagging, Jet grouted shafts, in­jec­tion grouting un­der­pin­ning and sealing blocks, el­e­va­tion and pore grouting, and de­wa­ter­ing measures.

The Rathaus, Sev­erin­straße, Chlod­wig­platz und Karthäuserhof un­der­ground stops were partly mined out using piling, in­jec­tion grouting and ground freezing as pro­tec­tion between tunnels ex­ca­vated by TBMs. Wa­ter­tight ex­ca­va­tion en­case­ment with di­aphragm walls down to depths of around 45 m were required for build­ings to be con­structed using open con­struc­tion tech­niques; these ex­ca­va­tion trenches required complex de­wa­ter­ing planning and mod­el­ling in­volv­ing regular con­sul­ta­tion with the com­pe­tent au­thor­i­ties. CDM Smith provided as­sess­ment and con­sul­ta­tion services in all of the deep foun­da­tion en­gi­neer­ing and tun­nelling work during con­struc­tion phase for the southern section of the north-south route of the Cologne Stadt­bahn light-rail service, es­pe­cially as experts in jet grouting and ground freezing. In addition, CDM Smith studied the en­vi­ron­men­tal, ge­ot­ech­ni­cal and hy­dro­log­i­cal effects in prepa­ra­tion for the project using a 3D ground­wa­ter model, and obtained official per­mis­sion for ground­wa­ter ex­trac­tion as based on German water pro­tec­tion law.