RETAINING STRUCTURES
Retaining Structures
Berlin Shoring Walls
Berlin shoring walls consist of steel soldier H beams installed at regular spacing with horizontal wood or concrete lagging in-between. The designation “Berlin Wall” originates from its use for the Berlin subway prior to the Second World War.
Berlin Shoring Walls are widely used in the Kingdom, especially where excavation depths are not excessive and where nearby structures and potential dewatering requirement allow it. The soldier piles may be driven or installed in a predrilled borehole. In most cases the wood lagging is extracted while backfilling is carried-out around the structure being built and soldier piles are extracted once construction reaches ground level. Exceptions occur when the structure being built reaches the shoring wall, in which case the latter is left in place.
Diaphragm Walls
A Diaphragm Wall is a structural system, which can provide lateral retention, load bearing capacity and waterproofing to a foundation while becoming part of the permanent structure. It can be built with zero clearance to existing structures, act as under-pinning of superficial foundations and, in conjunction with pre-founded columns, constitute the perimeter wall in top-down construction schemes. Diaphragm Walls are very versatile: they can assume any shape in plan, with thickness varying from 45 cm to 120 cm through every imaginable soil
condition. Circular Diaphragm walls permit unbraced excavation while post-tensioned Diaphragm Walls allow for greater unsupported spans.
Diaphragm walls can be cast-in-situ or, when ground water is not a concern, precast. Solid slabs or prestressed hollowcore slabs may be used in the latter case.
Contiguous Piles Walls
Contiguous pile walls provide an economical solution for shoring works, alone or in combination with a berlin shorin wall when the excavation depth becomes excessive for the latter. This system is constructed by drilling a series of bored piles next to each other with a clear gap of up to 30cm. The gap may be sprayed with shotcrete according to site specific need while excavation progresses.
Contiguous bored piles walls can be used where ground water is not a hazard to the adjacent structure and can be controlled through a dewatering system.
Secant Pile Walls
Secant pile walls are used as a watertight retention system where conditions make it a competitive alternative to other retention systems.
By drilling in between the previously concreted piles cutting a portion of them in the process, a structural wall can be constructed by overlapping circular sections. Diameter of the piles, amount of overlap, depth and reinforcement can vary to suit design requirements.
Sheet Pile Walls
Sheet Piles are prefabricated re-usable steel elements driven into the ground and interlocking with each other in such way to form an impervious retaining wall. Individual sheet piles typically have a “U” or “Z” shape and are driven into the ground with a vibro-hammer. In most cases sheet pile walls have a temporary function and are extracted at completion of the work. Sheet pile walls are often an efficient and economical solution for applications such as cofferdams or shoring for deep excavations extending below ground water table.
Bracings
Bracings are normally used as an alternative to tie-back anchors when the latter cannot be executed, due to the nature of the prevailing subsoil formations, presence of adjacent building basements or site specific constraints. Bracings generally consist of either steel tubular struts or H beams fixed to a shoring wall segment at each end. Strut levels are designed in such way to match the structure staged construction as they are later on dismantled in sequence with the slabs execution.
Ground and Rock Anchors
The anchor technique employing high tensile steel strands and bars in foundation engineering has been developed at the same time as the reinforced and pre-stressed concrete structures. Ground anchors are widely applied in Saudi Arabia, and TASC provides broad expertise in the installation of anchors in all kinds of soil conditions, under specific requirements and in combination with different type of retaining structures.
Anchors can also play important roles as “rock bolts” by keeping a rock mass stable as well as stabilizing an unstable rock. Rock and soil anchors have opened a variety of new possibilities in the design for rock stability and underground works, and they can be utilized as temporary or permanent elements.
Soil Nailing
Soil nail walls are built by installing closely spaced steel reinforcing bars into a slope or excavation in such way to create a reinforced stable soil mass behind the wall facing. Construction is performed in vertical steps, with construction starting at the top of the excavation and proceeding downward. Once an excavated level is reinforced with soil nails, a permanent or temporary facing is applied to retain the soil, typically consisting of shotcrete with mesh wire reinforcement.
Berlin shoring walls consist of steel soldier H beams installed at regular spacing with horizontal wood or concrete lagging in-between. The designation “Berlin Wall” originates from its use for the Berlin subway prior to the Second World War.
Berlin Shoring Walls are widely used in the Kingdom, especially where excavation depths are not excessive and where nearby structures and potential dewatering requirement allow it. The soldier piles may be driven or installed in a predrilled borehole. In most cases the wood lagging is extracted while backfilling is carried-out around the structure being built and soldier piles are extracted once construction reaches ground level. Exceptions occur when the structure being built reaches the shoring wall, in which case the latter is left in place.
Diaphragm Walls
A Diaphragm Wall is a structural system, which can provide lateral retention, load bearing capacity and waterproofing to a foundation while becoming part of the permanent structure. It can be built with zero clearance to existing structures, act as under-pinning of superficial foundations and, in conjunction with pre-founded columns, constitute the perimeter wall in top-down construction schemes. Diaphragm Walls are very versatile: they can assume any shape in plan, with thickness varying from 45 cm to 120 cm through every imaginable soil
condition. Circular Diaphragm walls permit unbraced excavation while post-tensioned Diaphragm Walls allow for greater unsupported spans.
Diaphragm walls can be cast-in-situ or, when ground water is not a concern, precast. Solid slabs or prestressed hollowcore slabs may be used in the latter case.
Contiguous Piles Walls
Contiguous pile walls provide an economical solution for shoring works, alone or in combination with a berlin shorin wall when the excavation depth becomes excessive for the latter. This system is constructed by drilling a series of bored piles next to each other with a clear gap of up to 30cm. The gap may be sprayed with shotcrete according to site specific need while excavation progresses.
Contiguous bored piles walls can be used where ground water is not a hazard to the adjacent structure and can be controlled through a dewatering system.
Secant Pile Walls
Secant pile walls are used as a watertight retention system where conditions make it a competitive alternative to other retention systems.
By drilling in between the previously concreted piles cutting a portion of them in the process, a structural wall can be constructed by overlapping circular sections. Diameter of the piles, amount of overlap, depth and reinforcement can vary to suit design requirements.
Sheet Pile Walls
Sheet Piles are prefabricated re-usable steel elements driven into the ground and interlocking with each other in such way to form an impervious retaining wall. Individual sheet piles typically have a “U” or “Z” shape and are driven into the ground with a vibro-hammer. In most cases sheet pile walls have a temporary function and are extracted at completion of the work. Sheet pile walls are often an efficient and economical solution for applications such as cofferdams or shoring for deep excavations extending below ground water table.
Bracings
Bracings are normally used as an alternative to tie-back anchors when the latter cannot be executed, due to the nature of the prevailing subsoil formations, presence of adjacent building basements or site specific constraints. Bracings generally consist of either steel tubular struts or H beams fixed to a shoring wall segment at each end. Strut levels are designed in such way to match the structure staged construction as they are later on dismantled in sequence with the slabs execution.
Ground and Rock Anchors
The anchor technique employing high tensile steel strands and bars in foundation engineering has been developed at the same time as the reinforced and pre-stressed concrete structures. Ground anchors are widely applied in Saudi Arabia, and TASC provides broad expertise in the installation of anchors in all kinds of soil conditions, under specific requirements and in combination with different type of retaining structures.
Anchors can also play important roles as “rock bolts” by keeping a rock mass stable as well as stabilizing an unstable rock. Rock and soil anchors have opened a variety of new possibilities in the design for rock stability and underground works, and they can be utilized as temporary or permanent elements.
Soil Nailing
Soil nail walls are built by installing closely spaced steel reinforcing bars into a slope or excavation in such way to create a reinforced stable soil mass behind the wall facing. Construction is performed in vertical steps, with construction starting at the top of the excavation and proceeding downward. Once an excavated level is reinforced with soil nails, a permanent or temporary facing is applied to retain the soil, typically consisting of shotcrete with mesh wire reinforcement.