The method for restoring an underwater wood, concrete or steel piling or other underwater structure includes the steps of: placing a jacket around a portion of a piling to be restored; securing the jacket in place around the piling so as to create a closed, annular space between the piling and the jacket; injecting, in at least one location at the lower end of the annular space, an epoxy resin composition into the annular space while at the same time venting the annular space in at least one location at the upper end of the annular space until the epoxy resin composition begins to escape from the upper end of the annular space. The underwater injection jacket comprises a sheet of flexible material having an upper edge and a lower edge and which is coilable into a generally cylindrically shaped jacket about an underwater piling with first and second mating edges of the sheet adapted to be secured in place relative to each other to form the jacket about the piling. A first sealing strip is provided along the lower edge of the sheet and a second sealing strip is provided along the upper edge of the sheet for establishing lower and upper annular seals between the jacket formed by the sheet and the piling when the mating edges are secured in place thereby forming a closed annular space within the jacket. A clamping system is provided for securing the mating edges in place relative to each other and in a sealed manner. The jacket also has inlet ports for the injection of epoxy resin into the annular space and venting ports for venting water from the annular space. Additionally, two semi-annular space portions can be formed so that epoxy resin composition can be injected into one side of the jacket while a vacuum is drawn on the other side of the jacket to seal cracks within the piling.

A plurality of hollow prop casings are provided which are each composed of at least two telescopable sections. These sections are erected by putting them upright and are then telescoped apart until they bear upon the roof to be supported. They are then temporarily arrested in this position and filled with a hardenable substance in flowable condition which, when it hardens, forms a solid column that is able to support the roof. Reinforcing bars or similar elements may be provided in the interior of the prop casings to become embedded in the hardenable substance. Measures may be taken for facilitating disassembly of the prop casings with the solid columns therein, under circumstances in which the casings are subjected to downward pressure by the roof.

A method and an arrangement are disclosed for supporting a roof of an underground excavation. A hollow prop casing of two or more telescopable sections is erected and telescoped apart until it bears on the floor and the roof. The sections are then biased against the floor and the roof and the prop casing is filled with a hardenable substance which upon hardening forms in the casing a solid column capable of supporting the roof.

A method of making on site a ground anchor having at least double corrosion protection about the anchor element, comprises locating a number of fixed lengths of corrosion proof sleeve about the element, applying a cap to the sleeve at the end of the element, and supplying a self-setting composition into the sleeve via the cap to fill an annular clearance between the sleeve and the element. The cap may be left in place on the end of the anchor to protect the anchor during insertion thereof into a borehole. The sleeve preferably comprises an outer plastics layer, an inner metal layer, and an intermediate layer of set filler.

A method of reinforcing a hollow underwater member of an offshore platform which includes drilling and tapping holes at substantially opposite ends of the member, injecting air into the member to determine leak holes, cleaning the outside of the member near the holes, patching the holes on the outside of the member, and injecting grout into the patched member.