Integrated Rehabilitation of Qanat-Induced Water Leakage in a Cast-in-Place Concrete Underpass: A Case Study from Tehran, Iran

Water ingress is a major serviceability and durability concern in underground concrete structures, especially where permanent groundwater pathways or traditional subsurface water channels intersect the project alignment. This paper presents the rehabilitation of a cast-in-place reinforced-concrete underpass connecting the old and new sections of Behesht-e Zahra Cemetery in Tehran, Iran. During the final stages of construction in ۲۰۱۱, water intrusion was detected in the tunnel sections passing beneath the old Tehran-Qom Road, between Bab al-Zahra and Bab al-Heydari. Field inspections and source investigations identified an east-west qanat running parallel to the roadway as the principal water source. Leakage occurred through cracks, inadequately sealed construction joints, local connection zones, and porous or honeycombed concrete. The observed water manifestations ranged from superficial dampness and seepage to dripping and localized water flow. A staged repair strategy was implemented to address the different leakage mechanisms. First, active leakage paths were treated by high-pressure injection of hydrophilic polyurethane resin, CARBOPUR WFA, using No. ۱۰ packers spaced at ۱۵۰-۳۰۰ mm and injection pressures of ۹۰-۱۲۰ bar. Localized areas affected by fine cracking, concrete porosity, and honeycombing were subsequently repaired using a crystalline waterproofing mortar applied by trowel. Finally, Radcon #۷ was spray-applied over the treated surfaces as a final waterproofing treatment. Active flow and dripping stopped after polyurethane injection, residual seepage was eliminated after crystalline mortar application, and visible dampness disappeared after the final treatment and curing. One year of monitoring showed no recurrence of active leakage or dripping, with only limited minor damp traces in isolated locations. The case confirms the effectiveness of an integrated repair approach combining polyurethane injection, localized crystalline treatment, and final surface waterproofing for underground concrete structures exposed to qanat-related and seasonal water ingress.

کلیدواژه ها:

underground structure ، water leakage ، polyurethane injection ، crystalline waterproofing ، qanat seepage ، concrete rehabilitation ، underpass ، Radcon #۷