Abstract
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.
Highlights
For the determination of the required embedded length for the safety against hydraulic heave several approximate solutions exist
With the help of these design charts the required embedded length T can be determined quite 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′
Extensive numerical flow calculations were performed to develop numerous dimensionless design charts. These can be used to directly read off the required embedded length for the safety against hydraulic heave depending on the decisive boundary conditions e.g. difference of the water level, thickness of the aquifer, width and length of the excavation and location in the excavation and depending on the soil conditions
Summary
For the determination of the required embedded length for the safety against hydraulic heave several approximate solutions exist. Neglecting the geometry unsafe results can be obtained for narrow excavations For this reason, systematic investigations on the safety against hydraulic heave have been carried out. In addition to the design charts a formula has been developed allowing the straight determination of the required embedded length under considering the before mentioned boundary conditions. EN 1997-1 universally specifies that for every relevant soil column safety shall be verified, whereas DIN 1054 recommends that in case of a vertical seepage flow in front of a retaining wall a body of soil should be investigated which’s width generally is half of the embedded length.
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