Methods or apparatus for making or lining tunnels, galleries or large underground chambers, using underground mining methods only, i.e. not involving disturbance of the ground surface.

Techniques and tools for stabilising such underground constructions against the pressure of the surrounding soil or rock.

Vertical excavation of shafts from the surface and removal of cuttings:

Shafts can also be used as a starting point for the excavation of tunnels or for the excavation of galleries or horizontal bores for the production of hydrocarbons. Only the specific technical details disclosed relative to each part of the operative sequence should be classified in the corresponding groups.

Shafts starting from a gallery at a lower level, and which can be made by a single boring machine of by drilling multiple boreholes:

Methods, materials and apparatuses for lining a shaft, regardless of the method of excavation:

Equipment installed permanently or removably in the shaft other than excavating or lining equipment

Shafts characterised by features other than the excavation form or the lining installed, such as by a particular layout:

Methods or apparatus for excavating tunnels. This includes the stabilisation of the soil prior to the excavation, and the constructive details of the tunnel boring machines:

Making by using a driving shield, i.e. advanced by pushing means bearing against the already placed lining; Tunnel boring machines featuring driving shields with a cutting action or for protection against collapse of the tunnel:

Tunnel boring machines for which no driving shield is mentioned:

Materials, methods and machines for lining the surface of an excavated tunnel:

E21D 9/06 has several subgroups relative to a combination of driving shield and devices for lining the tunnel. The specific details of the lining operation are also classified in the corresponding subgroup under E21D 11/00.

Documents mentioning aspects of lining, but focussing on the details covered by groups E21D 15/00 - E21D 23/00 are classified only in those groups.

Underground chambers having a three-dimensional volume, in contrast with vertical linear cavities (shafts) or with horizontal linear cavities (tunnels)

Props: elongated supports to prop the roof of tunnels or galleries.

Chocks: roof support formed by fillable bags or stapled cribs:

Props forming part of supports for step-by-step movement are classified in E21D 23/00. If one such prop contains specific details not covered by E21D 23/00, then it should also be classified in E21D 15/00.

A cap is understood as the roof or top piece in a three-piece , support or beam set used for tunnel support. A piece of plank, timber, support or beam placed on top of a prop, stull, or post. The horizontal member of a set of timber, support or beam used as a roadway support:

Means for protecting a work area from rocks falling from the roof or tunnels other than the final lining. This temporary roof support can be in the form of movable shields, caps or covers, of mobile or temporary roof supports, or of linings fixed to the walls and intended to be supplemented by additional lining at a subsequent stage:

Documents mentioning aspects of provisional support by way of a driving shield for tunnels, or of mine roof supports for step-by-step movement, are classified instead in E21D 9/06 and in E21D 23/00 respectively.

Methods and machines for installing anchoring bolts or rock bolts, including machines for drilling a hole and inserting an bolt in combination. Under this main group is also classified the use of resins or mortars for fixing anchoring-bolts:

Anchoring bolts, also known as rock bolts or roof bolts, characterised by their construction or by additional elements forming part of them, such as washer or anchoring heads.

Hydraulic jacks and frame for supporting the roof of the coal seam, as in longwall mining. A shearer cuts the coalface ahead of the support, and the support moves forward as the cutting progresses. The overburden collapses behind the support after passage of the same: