Hydraulic Heave – Design Charts and Design Formula for the Required Embedded Length

For the determination of the required embedded length for the safety against hydraulic heave several approximate solutions exist. However, most of these solutions do not take into account the geometrical boundary conditions such as width B and length L of the excavation as well as the thickness of the aquifer S. Thus, values obtained by such simplified approximate solutions can easily lead to either uneconomical or unsafe design. For this reason investigations on the safety against hydraulic heave have been carried out at the Chair of Geotechnical Engineering at RWTH Aachen University. Based on the results of numerous calculations dimensionless design charts have been generated. With the help of these design charts the required embedded length T can be determined quite easily taking into account the difference of the ground water level H, the Thickness of the aquifer S, the geometrical dimensions B and L of the excavation and the unit weight of submerged soil γ′. In addition to these design charts a formula has been developed. By use of this design formula the required embedded length can directly be determined taking into account the before mentioned boundary conditions.