Horizontal boring

Horizontal boring is similar to traditional raise boring where a pilot hole is drilled in a horizontal position. An excellent method in urban construction projects where drilling and blasting is restricted or forbidden and tunnel boring machines are too bulky. First, a horizontal pilot hole is drilled, with the aid of a directional drilling system if necessary. When the pilot bit breaks through, it is removed and replaced with a reaming head. Because the hole is horizontal, the reamer must be equipped with a special cuttings removal system.

Typical diameters for horizontal reaming are from 0.6 to 4.5 m. Horizontal boring requires good rock stability.

Applications

★Mining sector: HRB is used where a horizontal excavation is required and a chamber is available at both ends. Typically, such tunnels are bored in a block cave mining layout, or on a undercut or production level where the ring tunnel is first established.

★Civil sector: In urban infrastructure, HRB is used for excavating tunnels through mountains/hills, for connecting parallel metro or rail tunnels, as well as tunnels required under roads.

★Energy sector: HRB is used in the energy industry, for nuclear storage tunnels or short tail races in hydro-electric plants.

Advantages

★Similar to that of traditional Raise Boring it shows potential for lower support requirements than tunnels excavated by means of explosives.

★It is a continuous excavating cycle, and the structure of the tunnel is stronger due to the circular profile of the tunnel.

★In certain locations it is impossible to assemble a TBM due to its length and size. In these locations the plant for raise boring is smaller and easier to transport.

★A raise boring is more cost effective, and in some cases a more reliable system, when compared to a TBM system.