Engineering Design

1. HEADWORKS AND APPURTENANT STRUCTURES

1.1 DAMS

1.1.1 DESIGN AND STRUCTURE ANALYSIS

1.1.1.1 CONCRETE GRAVITY DAM

The following considerations are made for the case of a concrete gravity dam. However they can be applied to concrete dams in general, such as rollcrete and roller-compacted concrete dams as well as arch dams and buttress dams. While the geometry of the latter mentioned is more sophisticated, the basic design guidelines explained in the following text are also valid and needed. For this reason, given explanations in this paragraph will deal with the case of concrete gravity dam.

The design of a dam generally requires that:

• Foundation and material properties and applied loads be determined

• Layout be prepared, considering spillway and structural requirements

• Analyses be performed to assure that the layout provides adequate structural performance in terms of stability factors, stress conditions and material properties

The layout and shape has to be adjusted until a suitable design is achieved. While the non-overflow section is often the typical design section and principal water barrier, appurtenant elements and service needs are often made an integral part of the dam.

The basic design of a gravity dam is generally shaped with a vertical or near-vertical upstream face, providing the stabilising mass as far upstream as possible. A roadway on top of the dam may establish the crest width. The base of the dam is thoroughly keyed into rock formations along the foundation and abutments. The concrete is homogeneous and uniformly elastic in all parts of the structure. Construction joints should be properly grouted under adequate pressure and open slots should be properly filled with concrete to ensure a monolithic structure. To reduce the uplift pressures which may develop along areas of contact between the concrete and foundation, sufficient drains should be installed.

Uncontrolled cracks in gravity dams are undesirable and may endanger the monolithic structure of the dam with early deterioration of the concrete. Therefore joints, such as contraction