Diaphragm wall could be a continuous concrete wall made within the ground to support major construction activities just like the construction of dams, tunnel approaches, deep basements and enclosures. They act as a wall, support for the underground structure, as a foundation or facilitate interrupt provision so as to support deep excavation.
The construction sequence and therefore the varied options of a diaphragm wall are explained during this article.
Features of Diaphragm Wall
A diaphragm wall forms an oblong section made unchanged underneath the soil. Hence, this is often Associate in Nursing underground concrete wall. These walls are made panel-by-panel every interlocked to confirm structural stability and water tightness.
The diaphragm walls will have a thickness starting from 60cm to 150cm with a dimension of two.0 to 3.5m. The diaphragm walls may be made up to a depth of 60m.
How to construct a Diaphragm Wall?
The construction sequence principally has 3 steps:
Construction of Guide Wall
Excavation of the panel
Fig.1.Construction Stages of Diaphragm Wall
Image Courtesy: www.railsystem.net
1. Construction of Guide Wall
Guide walls are 2 temporary parallel beams made on the facet of the wall up order to guide the excavation tool and stabilize the highest portion. The implementation of guide walls before diaphragm-wall construction helps to keep up the horizontal alignment and continuity of the diaphragm walls made. Guide walls also:
Avoid Soil collapse
Help mark the panel positions
Support the reinforcement steel cages
Fig.2.Guide Wall Constructed To Prevent Soil Collapse during Trenching
As the suspension levels of soil vary for the most part, it’s necessary to possess a brief support like guide wall. the size of the guide wall made changes with the kind of topsoil. In case, the groundwater level level within the space is just too high, the guide wall is built at a height on top of the bottom level to guide the development.
2. Excavation of Panel
This stage includes soil-removal and stabilization. an oblong excavation tool is employed to excavate the panel section. A clam-shell or grab is employed to excavate the ditch in traditional soil. Grab suspended by a crane or cable simply moves into the soil. If any obstruction is encountered, it’s broken by the means that of a gravity hammer and brought out by means of the grab.
The on top of procedure should be conducted with adequate excavation support, otherwise, the edges of the excavated trench will collapse. to guard the edges, clay suspension is employed. The suspension helps in manufacturing lateral pressure that’sample to retain the vertical soil.
3. Wall Concreting
This stage involves the concreting of the panel excavated. Initially, the reinforcement cage is inserted into the ditch. If the depth of the diaphragm wall is a lot of, 2 or a lot of steel reinforcement cages need to be inserted to hide the depth and these cages are lapped.
Once the reinforcement is placed, the concrete is poured into the ditch with the assistance of tremie pipes. the employment of tremie pipes helps to avoid segregation of concrete. The poured concrete replaces the clay clay within the trench. The density of clay is low compared to concrete thence is replaced throughout the concreting. The clay displaced is collected and reused.
Diaphragm Wall Connections
Mainly 2 kinds of joint style are utilized in diaphragm walls. they’re by using:
Stop finish Pipes
1. Stop finish Pipes
In this methodology, 2 steel pipes are inserted into the ditch before concreting, in order that once concreting a semi-circular finish section panel is obtained. The panel shaped with pouch like ends forms the first panel. instead, Associate in Nursing intermediate section is made wherever the secondary panel is built. Once the first panel is created, the secondary panels are dead.
Fig.3. Diaphragm Joints by Stop end Pipes; Image Courtesy: http://soilmec.com.au
2. Disposable PVC Pipes
In this methodology, 2 pipes are organized at the ends of the steel reinforcement cage of the panel. The concreting is performed for the first panel departure the pipes with suspension. throughout the concreting of the secondary panel employing a dedicated tool, the separation is broken as shown in figure -4 below. A spherical indentation is created within the primary panel in reference to secondary. whereas concreting the secondary panel, the indentation too is stuffed therefore creating a joint with the first panel.
Fig.4. Diaphragm Joints by Disposable PVC Pipes; Image Courtesy: http://soilmec.com.au