In some tunnels of railway lines located in water-rich region, due to the long-term water leakage and erosion, the foundation of railway lines showed large uneven settlement deformation, so the above concrete roadbed slabs also experienced uneven settlement accordingly. The smoothness of railway tracks diminished, and the speed of passing trains had to be limited to ensure safety. To restore the smoothness of the tracks, a dedicated polymer injection technology for quick uplift rehabilitation of uneven settlement concrete roadbed slabs was studied on site just within the specified daily skylight time (about 3 hours every day) of the railway lines. A hydrophobic polymer with low-viscosity, quick-setting and high-strength properties was used for injecting, filling and uplifting the concrete slabs in water-rich foundations. The high-precision electronic levels were adopted to monitor rising height of the tracks in real time. After rehabilitation, the filling quality of polymer injection under roadbed slabs was examined using Φ50 mm core samples and the strength of hardened polymer was verified by compressive strength test. Results indicated that the polymer could uplift the concrete roadbed slabs effectively and restore the smoothness of railway tracks accurately even in the water-rich environment. The research can provide some valuable references for quick rehabilitation of uneven settlement concrete roadbed slabs in water-rich tunnels.
Small molecular monomer and initiator were added to cement mixture, in situ polymerization had occurred under the action of initiator with the cement hydration, and polymer network was produced, and thus the toughness of cement paste was improved. The toughness of in situ toughening mortar had been measured through flexural/compressive ratio, and modification mechanism had been revealed through MIP, SEM and TG-DTG. The results show that, flexural/compressive ratio of in situ toughening mortar has been enhanced greatly compared with reference; Many polymer films are formed in hardened cement mortar, and hydrolysis product of polymer can react with cement hydration product Ca(OH)2. Physical adhesion between polymer films and cement hydration products and chemical bonding between polymer and cement hydration products are primary causes to improve toughness of cement mortar.
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