Dams are massive, complex structures built to impound water and create reservoirs. The construction of a dam requires careful planning, engineering expertise, and the use of specialized equipment and materials. One of the critical components of dam construction is the formwork system, which is used to shape and support the concrete during the pouring and curing process.
This system includes a unique way of connecting formwork to the structure, so it is permanently supported. The result is a virtually maintenance-free structure where no posts or columns must be installed and removed, no holes must be drilled and filled, and no steel forms are required. The process of building up the dam formwork system involves the following steps.
Site Surveying
Site surveying begins with preliminary research, a study of existing dams, and surveying to determine the needed location for excavation, soil and rock removal, new material placement, voids, and support beams. A detailed construction plan and project design drawings will follow that. The activities of site surveying for dam construction involve the following.
It establishes the boundary. This involves using surveying equipment such as GPS, total stations, and levels to measure and mark the boundaries.
Topographic survey. A survey is conducted to determine the shape and elevation of the construction site. This information is used in the design and engineering phase of the project.
Soil investigation. The investigation involves collecting soil samples from the construction site and analyzing them to determine the properties of the soil. This information is used in the design of the dam foundation and to assess any potential risks to the dam’s stability.
Hydrological survey. A survey is conducted to determine the water flow in the river where the dam will be constructed. This information is used to design the dam’s spillway and other water management systems.
Geotechnical survey. The survey involves drilling boreholes in the construction site to collect rock and soil samples beneath the surface. This information is used to design the foundation and support systems for the dam.
Environmental survey. An ecological survey is conducted to assess the potential impact of the construction on the surrounding area. This includes evaluating the presence of endangered species, wetlands, and other environmentally sensitive areas.
Site Preparation
Site preparation for formwork system construction refers to the setup of a firm foundation, generally in the form of compacted gravel or sand. The foundation must be large enough to support the weight of each piece that forms part of the dam.
In some cases, this may mean developing on an almost flat area. Where this is required, the formwork should be prepared with small amounts of balata or any other suitable material, covering approximately one-third to a half of the building site. Once erected at various locations on-site using temporary bracing, the formwork sections are then transported to their final assembly locations on concrete support beams.
Dry Laying the Formwork Layer
Pre-stressed horizontal steel and concrete formwork, used when building a dam or levee, is made in layers to support the primary structural forms. Typically, one or more layers must be dry before the next layer is placed to ensure accuracy and strength. Dry laying each layer of formwork allows for greater flexibility, as additional structural members can be added or removed. It also allows for easier finishing, extending the structure’s and the formwork’s lifespan.
Bearing in on Tensioning
Bearing tensioning involves placing a strip of metal under tension. This is done to attach the formwork system to its submerged foundation. The process uses small loads to anchor the formwork system. This occasionally includes monofilament and high-tensile manila.
Bearing in on tensioning is utilized to keep the formwork upright, and maintain its shape and position. Bearings are applied to the frame structures during construction or when smooth concrete is poured during completion.
After completing the dam formwork construction, the last thing is felling and cleaning up. This process includes the removal of debris from the ground, which can lead to poor performance of the dam-formed walls.