Performance of Trenchless Rehabilitations for Culvert, Sewer, and Maintenance Hole Structures
Deterioration and rehabilitation impacts on buried infrastructure were explored using experimental methods. Deterioration studies included the effects of erosion voids (in the immediate backfill) on steel and reinforced concrete pipe behaviour. Additionally, the voids were rehabilitated using simple trenchless solutions and the impact on pipe capacity was explored. Furthermore, rehabilitation is also commonly performed on access structures (i.e. maintenance holes) to restrict leaks rather than restore structural capacity; and this ability of the repaired system to sustain further leaks was also explored. A corroded steel pipe buried with an erosion void simulated on one side, was tested under simulated service loads. This revealed that the void appeared to compromise the stability of the structure. Rehabilitation of the culvert with a high density polyethylene slip liner and a low density, low strength grout lowered the strains in the host pipe. Strains measured before 300 kN applied load suggests that the grout had not fractured, and the steel pipe, liner, and grout responded as a composite system. After 300 kN, the grout appeared to fracture, and the strains in the steel pipe and liner accelerated with applied load. The impact of erosion voids and rehabilitated voids (filled with low strength, low density grout), of varying sizes, on the live load responses of reinforced concrete pipes were also studied. The changing pipe responses were quantified using modified bedding factors (Bf). Erosion voids increased the overall pipe bending moments, especially at the invert; grouting both the larger and smaller voids reduced the increases in invert moment. For sprayed liners installed within maintenance holes, the primary loads result from groundwater infiltration. Testing protocols and equipment were developed to monitor leakage resistance of the sprayed liners, simulating different sized areas with poor bond between the liner and the substrate. For the specific liner system investigated, circular zones with poor bond resulted in water loss after ‘peeling’ failure (water pressure acted to lift the circular zone with poor bond off the substrate around its circumference). The peeling per unit circumference was found to be a constant, independent of the diameter of the circular area with poor bond.