Method of and apparatus for supporting an overburden

An arrangement for supporting a roof, particularly a roof of an underground exacavation such as a mine, comprising a hollow prop casing composed of at least two telescopable sections which can be telescoped apart subsequent to erection of the prop casing so as to bear upon the roof and a floor beneath the same, said sections having sufficient strength to be self-supporting but not to support the roof;

• means for biasing said sections in their telescoped-apart condition against the floor and the roof, respectively, so that the sections are thereby held in position without, however, supporting any load;
• and means for filling the prop casing with a hardenable substance in flowable condition so that the prop casing acts as a form which contains said substance until the latter, upon hardening thereof, forms a solid column which by itself is able to support said roof.

In an arrangement for supporting a roof, particularly of an underground excavation, with a pit prop which bears upon the roof and the floor of the excavation, a device for removing the pit prop while the same is under pressure, comprising an upright tubular element having a circumferential wall of non-loadbearing sheet material provided with an upper open end dimensioned to receive a bottom end portion of a pit prop, and also having a lower end engageable with the floor, said wall also having at least two oppositely located holes;

• and a wedge member received in said holes extending across the interior of said element and adapted to support the pit prop, said wedge member having a wider end and also having a narrower end which projects from one of said holes so that on application of an inwardly directed force said wedge member may be expelled from at least said one hole, thereby permitting a pit prop to descend toward said lower end of said tubular element.

In an arrangement for supporting a roof, particularly of an underground excavation, with a pit prop which bears upon the roof and the floor of the excavation, a device for removing the pit prop while the same is under pressure, comprising an upright tubular element having a circumferential wall of non-loading sheet material;

• a slidable support for the lower end of a pit prop received in the interior of said tubular element and subdividing the interior into an upper compartment for accommodating the lower pit prop end, and a lower compartment;
• an elastically distendable bladder accommodated in said lower compartment;
• and valve means communicating with the interior of said bladder for filling the same with hydraulic fluid which in use carries said support and a pit prop resting on the same, and for venting hydraulic fluid from said bladder to permit the support and pit prop to descend when the pit prop is to be removed.

In an arrangement for supporting a roof, particularly of an underground excavation, with a pit prop which bears upon the roof and the floor of the excavation, a device for protecting the pit prop against roof pressure in excess of its load-bearing capacity, comprising an upright tubular element of non-loadbearing sheet material having a lower end adapted to engage the floor, and an upper open end in which a lower end portion of a pit prop is receivable;

• and means in said tubular element supporting the pit prop therein and yieldable axially of said element in direction to the floor in response to roof pressures upon the pit prop which are lower than the load-bearing capacity of the same by a preselected extent.