The most popular use of a diaphragm wall is for the construction of multilevel basements and for top –down building construction method. The trenching process of this diaphragm wall system is aided by bentonite fluid support. During the excavation process bentonite is introduced and recycled during the construction process. Bentonite is used during the excavation process to facilitate the removal of the cuttings when using the trench cutter, until reaching desired depth. This is later replaced by placing concrete in the trench via the tremie method. Bentonite is returned to holding tanks on site to undergo treatment and reuse.
The diaphragm wall system is a fantastic solution compared to any other conventional retaining wall systems because of increased water tightness by minimizing vertical joints. The use of the diaphragm wall system is to alleviate issues in constructing underground tunnels along heavy public presence, deep basements without endangering the stability of the foundations of the nearby buildings. Diaphragm wall system can be applied to water storage, sewage disposal shafts, security vaults, pits, and wharves, containment of contaminated area and control of toxic effluents travelling underground.
Diaphragm wall ancillary structure comprises of de-sanding equipment, silos, holding tanks, transfer pumps, mixer tanks and compressors.
- Ideal for top down construction projects.
- Can be installed in virtually all soil conditions including high strength rock.
- Reduced noise and vibration compared with other shoring techniques such as sheet piling.
- Very accurate method of construction with high tolerance levels.
- Removes the requirement for dewatering the site.
- Can be used in the immediate vicinity of existing buildings.
- Can be designed to carry structural loads thereby reducing the foundation costs.
Scope of Works
Diaphragm Wall Construction for the proposed residential development at 330 Church Street, Parramatta, NSW. The proposed development will comprise two residential towers over a common podium level and four levels of basement carparking over the main rectangular portion of the site with the footprint of the basement extending to the eastern, western and southern boundaries, and set back between about 9m and 12m from the northern site boundary. The site is located within near level terrain on the south bank of the Parramatta River. Bulk excavations to a maximum depth of about 12m below existing surface levels to be carried out following the completion of the Diaphragm wall.
The work was carried out for Karimbla Construction Services Pty Ltd (Meriton Group)
Scope of Works
Design and construction of the diaphragm wall system with two rows of temporary rock anchors through the wall, which include:
Diaphragm wall: 49 panels x 640mm wide x 2800mm-7000mm length x 12m–13m depth
Temporary anchors: 2 rows x 243 rock anchors x approx. 14m-23m length
- Design works for the diaphragm wall.
- Removal of 40 existing old reinforced concrete piles from the location of the diaphragm wall.
- Design and construct Guide Wall.
- Supply and installation of all concrete, reinforcing steel, anchor blockouts and couplers.
- Supply and installation of Inclinometer system.
- Design, install and test all anchors.
- Installation of standpipe piezometers and monitoring of groundwater levels.
- Monitoring the performance of the southern boundary shoring using the inclinometers and survey monitoring points.
- De stress the temporary anchors.
Concrete used: 50MPa for DW panels (volume 2,650m3)
25MPa for Guide Wall (volume 370m3)
Reinforcement: 200 ton
Diaphragm Wall construction for Stage 4 (Project 145) for a fourth Dump Station and associated conveyor infrastructure at the Port Waratah Coal Services (PWCS) Kooragang Coal Terminal (KCT).
The work was carried out for Bechtel on behalf of PWCS.
The project included the following relevant elements:
- A dump station which is approximately 15 m deep, 12 m wide and 66 m long. The walls were formed using diaphragm wall construction with a jet-grouted base plug.
A conveyor exits the base of the dump station through a tunnel which slopes up to a surface exit point about 200 m to the east and was constructed using a similar methodology to the main dump station.
Scope of Works
All construction associated with the diaphragm wall system and supporting base plugs (jet Grouting Plug) between the walls for both the dump station and the tunnel.
Dump Station area was divided by cross DW panels into 3 cells. Tunnel area was divided by (Jet Grouting) cross cut-off walls into 4 equal cells.
No. of Cells: 3
No. of Diaphragm Wall Panels: 25
Size of Panels: 11nos.x800mm wide x (2800mm-7000mm) length x 20m-28m depth.
24nos.x640mm wide x (2800mm-7000mm) length x 14m-21m depth.
No. of Cells: 4
No. of Diaphragm Wall Panels: 48
Size of Panels: 48nos.x640mm wide x (2800mm-7000mm) length x 11.3m-17m depth.
- Design and Construct Guide Wall.
- Supply and installation of all concrete, reinforcing steel, hold-down bolts, couplers, embeds and ferrules.
- Supply and installation of Inclinometer pipes.
- Installation of A base block plug (Jet Grouting Plug) throughout both the dump station and the tunnel to limit the inflow of water as specified.
- Jet Grouting Cut-off Walls to separate the Tunnel into 4 sections.
- Water Tightness Testing for all 7 Cells in the dump station and Tunnel.
Concrete used: 40MPa for DW panels (volume 4,673.8m3)
25MPa for Guide Wall (volume 476.2m3)
Reinforcement: 522.75 ton
Diaphragm Wall construction for Stage 4 (Project 145) for a fourth Dump Station and associated conveyor infrastructure at the Port Waratah Coal Services (PWCS) Kooragang Coal...