Diaphragm Wall

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Diaphragm Wall (Strip Piles)Ahmed Osama Khattab Ahmed Hussien Moharram Mohamed Hatem Shams Mohamed Osama Amin Mohamed Yousry Mohamed

Contents Introduction to the sites Problems faced. Sequence of Construction. Diaphragm wall construction. Soil injection (plugging). Excavation and Dewatering. Slab Construction.

Introduction to The Sites

The SitesThe two sites we covered are: The Ventilator in Khalifa El-Maamoun ElStreet (Diaphragm Wall work was done) The Station in Marghany Street (Diaphragm Walls are under construction)

Ventilator Plans

Problems

Problems Very deep construction (up to 35 m in depth) High water table (3 m below ground level) Connecting the slabs reinforcement to the smooth diaphragm walls Slab construction sequence: Bottom to top Top to bottom

Building Sequence

Construction Sequence Diaphragm wall construction Injection Excavation and dewatering Slab construction

Diaphragm Wall ConstructionEquipment:

Diaphragm Wall ConstructionThe Hydrofraise The hydrofraise is used to dig deep rectangular walls The Hydrofraise suspends the excavated soil into the bentonite slurry The boring is guided by the guide walls Dimensions range from (2.1*0.6) to (2.1*2.1)m

Diaphragm Wall ConstructionThe Hydrofraise

Diaphragm Wall ConstructionThe Hydrofraise

Diaphragm Wall ConstructionThe De-sander De The de-sander separates the excavated desoil from the bentonite slurry The slurry fit for recirculation is reused, the polluted slurry is stored in the dumping silos Excavation product is separated to be carried away on dump trucks

Diaphragm Wall ConstructionThe De-sander De-

Diaphragm Wall ConstructionThe De-sander De-

Diaphragm Wall Construction

Diaphragm Wall ConstructionAnother System:

Diaphragm Wall ConstructionThe Process:

Diaphragm Wall Construction Construction of Guide Walls Bore the primary walls Dropping the Steel Cage Pouring the Primary Walls Repeat with Secondary Walls

Diaphragm Wall ConstructionConstruction of Guide Walls

Diaphragm Wall Construction

Diaphragm Wall Construction

P-9

Diaphragm Wall Construction

P-9

Injection (Plugging) To overcome the GWT problem, a grout/gel plug should be injected to seal the bottom before excavation and dewatering starts The plug can be permanent (grout) Or temporary (gel) until the raft level is reached, then a permanent raft is constructed

Excavation and Dewatering After the construction domain is sealed, excavation can start for the remaining activities to proceed During the excavation, the water must be drained

Injection Excavation and Dewatering

Slabs The final stage in finishing the ventilator is casting the slabs. Slabs are cast from top to bottom unlike the usual sequence.

Slabs Locations of the slabs are determined before the reinforcement cage is prepared. Slab reinforcement is placed in the cage and ended with the mechanical splice The mechanical splices are protected from the concrete using foam When casting the slab, the splices are located and exposed to be connected to the diaphragm wall.

Slabs

Slabs

Slabs And then the steel is connected via the mechanical splice. Concrete is cast. A vertical shaft is made to allow working in the lower floors

Slabs The level under construction is accessed using the floors cast above Pouring and excavation equipment are kept on the ground level. Access to the floor under construction is through the working shaft