Empingham Dam—design, construction and performance

Empingham Dam is an earthfill embankment 37 m high, 1200 m long. The dam foundation is Upper Lias clay extensively sheared and brecciated by valley bulging and periglacial disturbance. The weak foundation was the controlling factor in design and made a wide cross-section with extensive berms necessary. Determination of the reliable strength of the foundation was difficult and was to be confirmed at full scale by a trial bank placed early in construction and incorporated within the dam. The tender design allowed for the uncertain strength by indicating a range of dam volumes corresponding to the likely range of foundation strength values. Various measures, including 10800 vertical sand drains and zoning of fills incorporating an inclined core, were utilized to minimize the volume of earthfill required. The bulk of the 5 Mm of fill was Upper Lias clay excavated from borrow pits upstream of the dam, and was placed over three summer seasons. The performance of the dam is monitored by a comprehensive range of instruments, including a movement monitoring system. Finite-element methods were used to predict early movements. The instrumentation records show the behaviour of the dam to be satisfactory.

• Introduction

• Site investigation

• Geology

• Principal features of the design

• Design calculations

• Sand drain design, construction and performance

• The trial embankment and borrow pit slips

• Fill

• Final design

• Construction, plant and materials

• Internal drainage

• Instrumentation

• Surveys

• Slopes and crest protection

• Programme and progress

• Performance of the embankment

• Acknowledgements

• References