The design, construction and performance of Cow Green embankment dam

The 25 m high Cow Green embankment dam has been constructed in the upper Pennines on a deep boulder clay foundation with the aid of sand drains. The design of the core and filter received special attention following erosion of the rolled clay core of a neighbouring dam. The embankment design was based on a conventional factor of safety of 1·5. The sand drains did not achieve the predicted performance and the factor of safety in terms of effective stress approached 1·0 at completion. This condition does not represent failure in boulder clay, which is nonbrittle in undrained shear, but rather the onset of relatively large displacements. The performance of the embankment supports the view that under these circumstances construction stability may best be monitored by measurements of deformation. The failure of the sand drains to attain the degree of consolidation anticipated in the design is discussed, as is the control of placing of the boulder clay core and the behaviour of the gravel fill.

• Site Investigation, Geology and Soil Properties

• Design of the Embankment Section

• Embankment Instrumentation

• Embankment Construction

• Embankment and Foundation Performance

• Discussion of the Performance of the Embankment Foundation

• Acknowledgements

• References