In this study, a series of experimental tests was carried out to investigate the effect of polyurea type spraying membrane (SM) interlayer on load bearing capacities of the concrete slabs with the size of 600 mm × 600 mm × 100 mm. Different concrete slabs with SM interlayer, with conventional membrane geotextile interlayer and without a membrane interlayer were casted to compare their load bearing capacities and deformation characteristics under both static and dynamic (impact) loading. According to the result of this study, SM interlayers were found to be advantageous in comparison with the conventional membrane textiles against both static and dynamic loading. From the static load tests, the best bearing capacity was obtained with the concrete slabs without membrane layer. On the other hand, the concrete slabs with SM interlayer exhibited the best impact resistance performance. In addition to having a significant increase in load bearing capacity, the ductility of the concrete slabs was found to improve using the polyurea type SM interlayer.
The concrete linings of tunnels excavated by conventional methods are usually designed to have doubleshell, a temporary concrete lining (primary lining) to stabilize the opening after excavation and a permanent lining (secondary lining) casted for long-term purposes of serviceability and stability.
During the last two decades, important progresses were made in shotcrete technology, using different water-proof engineering materials being sprayed by robots instead of setting by hand. The conventional geo-membrane products are not practical and not convenient to be used on rough surfaces resulting from blasting operations, edges, junction parts of tunnels/underground opening, cross-sections with complex geometries. To prevent the tearing of the geomembranes, some additional textile materials like felts are used which cause an important time consuming during the water resisting system setting. The conventional geo-membranes could not adhere to the concrete surface and have bonding problems preventing the two concrete linings to work together.
The conventional membrane textiles heated to be bonded each other are not practical to set continuous water resisting liners, whereas it takes a short time to set continuous liners applying spraying membrane (SM) materials which allow for composite behavior supplying two-sided bond with primary and secondary concrete linings.