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Shotcrete is an all-inclusive term for spraying concrete or mortar with either a dry or wet mix process. However, shotcrete may also sometimes be used to distinguish wet-mix from the dry-mix method. The term shotcrete was first defined by the American Railway Engineers Association (AREA) in the early 1930s. [6]
The primary advantages of fibre-reinforced shotcrete are: Addition of steel fibers into the concrete improves the crack resistance (or ductility) capacity of the concrete. Traditional rebars are generally used to improve the tensile strength of the concrete in a particular direction, whereas steel fibers are useful for multidirectional ...
Recently Conco has taken a role in the developing field of sculpted shotcrete, which is the use of concrete as a canvas to create shotcrete walls that have structural integrity but are aesthetically pleasing. Shotcrete provides an excellent alternative to traditional cast-in-place walls, and since it is pneumatically placed, greatly reduces ...
The use of sheet piles, diaphragm walls or bored piles to construct a square or rectangular braced shaft; The use of segmental lining installed by underpinning or caisson sunk to form a circular shaft; Incremental excavation with a shotcrete circular or elliptical lining
Trapped air will leave voids that allow water to collect and degrade (rust) the steel. Modern practice often includes spraying the mixture at pressure (a technique called shotcrete) or some other method of driving out trapped air. Older structures that have failed offer clues to better practices.
Drilling of the tunnel face anchors, Val di Sambro Tunnel, Italy. The Analysis of Controlled Deformation in Rocks and Soils, translated from Italian Analisi delle Deformazioni Controllate nelle Rocce e nei Suoli (ADECO-RS), also known as The New Italian Tunneling Method (NITM), [1] is a modern tunnel design and construction approach.
Top-down method: Side support walls and capping beams are constructed from ground level by such methods as slurry walling or contiguous bored piling. Only a shallow excavation is needed to construct the tunnel roof using precast beams or in situ concrete sitting on the walls. The surface is then reinstated except for access openings.
A minimum of 2 inches (5 cm) thickness of wet mix shotcrete is applied around the exposed ground perimeter following each day’s advance. As cave dimensions and ground conditions require, additional layers of shotcrete and welded wire fabric follow on subsequent days. The shotcrete mix is a 4,000 psi (28 MPa) compressive strength design.