Performance of two cast-in-place box culverts under high embankments

摘要

Two cast-in-place reinforced concrete box culverts (Longs Creek and McBean Brook culverts) with similar geometry were instrumented to monitor earth pressures. The Longs Creek structure is a 7.30 m wide by 4.53 m high double-cell box under 14.10 m of fill, constructed using the positive projection installation (PPI) method. The McBean Brook structure is a 6.75 m wide by 4.65 m high double-cell box culvert under 25.10 m of fill, constructed using the induced trench installation (ITI) method. Earth pressures were monitored as the fill height above the culvert was increased for both structures. Data from the McBean Brook culvert at a fill height of 14.40 m are compared with the data from the Longs Creek culvert. The similar geometries of these two prototype culverts provide a unique opportunity to compare their performance based on the two different installation methods. For a comparable height of soil cover, measured vertical earth pressures on the roofs were 0.94 and 0.56 times the overburden pressures for the Longs Creek (PPI) and the McBean Brook (ITI) culverts, respectively. The average measured lateral earth pressure was 0.32 times the overburden pressure at the Longs Creek culvert (PPI), and 0.46 times the overburden pressure at the McBean Brook culvert (ITI). Data from the McBean Brook culvert pertaining to base contact pressure are also presented, but could not be compared directly with the Longs Creek culvert, as base pressures were not measured. Measured pressures at the base of the McBean Brook culvert show the presence of drag forces developed on the sidewalls of box culverts. Results from centrifuge model testing are also presented and compared with the field-measured pressures.