The settlement monitoring devices are used to determine the settlement of different soil layers beneath foundations at various depths through time with high precision. The main functions of the system are to: • Verify the soil criteria and the geotechnical investigation which the project designer anticipated in the design • Measure the differential settlement at critical points in the project’s foundation • Determine the appropriate time for closing any settlement strip which is conceived between the various structures of a project For the Sama Beirut Project, five boreholes of 10cm diameter were drilled at the four corners and the center of the raft with a 40m depth beneath foundations subgrade. Within each borehole, four measuring devices (extensometers) made of flexible stainless steel, were inserted and respectively grouted at depths of 1.5m, 7.5m, 15m, and 40m. Readings are correlated from the zero reference set at 40m outside the bulb pressure curve beneath foundations where the soil is theoretically not influenced by the tower exerted stresses. All five points are electrically connected to a digital data logger which collects the readings at a precision of 0.05mm. Monthly readings are taken, and actual dead and superimposed loads (concrete and finishing works) are provided periodically to the project’s structural consultant for review and verification. In addition, due to the presence of a settlement strip at the foundation and all basement slab levels which separate the tower (8 basements + GF + 52 floors) from the podium, the actual values of settlement at the aforementioned five points are monitored and analyzed in order to determine the settlement strip closure time.

Sami Mekanna - Sama Beirut Project Manager