An adjustable lattice girder includes a first lattice girder portion having a first end and a second end positioned opposite the first end, with the first lattice girder portion having a first connection member, and a second lattice girder portion having a first end and a second end positioned opposite the first end, with the second lattice girder portion having a second connection member configured to engage the first connection member. The first connection member is slidable relative to the second connection member between a first position corresponding to a first distance between the second end of the first lattice girder portion and the first end of the second lattice girder portion, and a second position corresponding to a second distance between the second end of the first lattice girder portion and the first end of the second lattice girder portion. The first distance different than the second distance.

An adjustable lattice girder includes a first lattice girder portion having a first end and a second end positioned opposite the first end, with the first lattice girder portion having a first connection member, and a second lattice girder portion having a first end and a second end positioned opposite the first end, with the second lattice girder portion having a second connection member configured to engage the first connection member. The first connection member is slidable relative to the second connection member between a first position corresponding to a first distance between the second end of the first lattice girder portion and the first end of the second lattice girder portion, and a second position corresponding to a second distance between the second end of the first lattice girder portion and the first end of the second lattice girder portion. The first distance different than the second distance.

A self-supporting reinforcement system for the concrete lining of the inner shell of a tunnel construction. At least one object is that of supporting the outer shell or rock wall of a tunnel construction. According to an embodiment of the invention, this is achieved by tension brackets or tension rings, formed from one or more bracket segments made of individual reinforcing steel bars. M-shaped tensioning support bodies having a connecting region to the tension brackets, and support arms for the supporting bracing, establishing the spacing with respect to an outer shell or rock wall, of the bracket and spacers on the tensioning support bodies and between the outer layer and an inner layer of the reinforcement.

A self-supporting reinforcement system for the concrete lining of the inner shell of a tunnel construction. At least one object is that of supporting the outer shell or rock wall of a tunnel construction. According to an embodiment of the invention, this is achieved by tension brackets or tension rings, formed from one or more bracket segments made of individual reinforcing steel bars. M-shaped tensioning support bodies having a connecting region to the tension brackets, and support arms for the supporting bracing, establishing the spacing with respect to an outer shell or rock wall, of the bracket and spacers on the tensioning support bodies and between the outer layer and an inner layer of the reinforcement.

An adjustable lattice girder includes a first lattice girder portion having a first end and a second end positioned opposite the first end, with the first lattice girder portion having a first connection member, and a second lattice girder portion having a first end and a second end positioned opposite the first end, with the second lattice girder portion having a second connection member configured to engage the first connection member. The first connection member is slidable relative to the second connection member between a first position corresponding to a first distance between the second end of the first lattice girder portion and the first end of the second lattice girder portion, and a second position corresponding to a second distance between the second end of the first lattice girder portion and the first end of the second lattice girder portion. The first distance different than the second distance.

An adjustable lattice girder includes a first lattice girder portion having a first end and a second end positioned opposite the first end, with the first lattice girder portion having a first connection member, and a second lattice girder portion having a first end and a second end positioned opposite the first end, with the second lattice girder portion having a second connection member configured to engage the first connection member. The first connection member is slidable relative to the second connection member between a first position corresponding to a first distance between the second end of the first lattice girder portion and the first end of the second lattice girder portion, and a second position corresponding to a second distance between the second end of the first lattice girder portion and the first end of the second lattice girder portion. The first distance different than the second distance.

A self-supporting reinforcement system for the concrete lining of the inner shell of a tunnel construction. At least one object is that of supporting the outer shell or rock wall of a tunnel construction. According to an embodiment of the invention, this is achieved by tension brackets or tension rings, formed from one or more bracket segments made of individual reinforcing steel bars. M-shaped tensioning support bodies having a connecting region to the tension brackets, and support arms for the supporting bracing, establishing the spacing with respect to an outer shell or rock wall, of the bracket and spacers on the tensioning support bodies and between the outer layer and an inner layer of the reinforcement.

A self-supporting reinforcement system for the concrete lining of the inner shell of a tunnel construction. At least one object is that of supporting the outer shell or rock wall of a tunnel construction. According to an embodiment of the invention, this is achieved by tension brackets or tension rings, formed from one or more bracket segments made of individual reinforcing steel bars. M-shaped tensioning support bodies having a connecting region to the tension brackets, and support arms for the supporting bracing, establishing the spacing with respect to an outer shell or rock wall, of the bracket and spacers on the tensioning support bodies and between the outer layer and an inner layer of the reinforcement.

A telescopic device includes a first U-shaped connector with a plurality sets of adjustment slots defined in two sides thereof and arranged along an adjustment direction; a second U-shaped connector defining first through holes in two sides thereof, the second U-shaped connector being inserted into the first U-shaped connector with U-shaped openings thereof opposite to each other to define an accommodating space; a first spring located in the accommodating space and abutting against the first and second U-shaped connectors, respectively; an elastic pin with two ends thereof extending through the first through holes and engaging into one of the plurality sets of adjustment slots; and an initial fixing pin being detachably connected to the first and second U-shaped connectors. A telescopic annular tunnel steel arch includes an upper arch, two lower arches and two telescopic devices connecting two ends of the upper arch to the two lower arches, respectively.

A telescopic device includes a first U-shaped connector with a plurality sets of adjustment slots defined in two sides thereof and arranged along an adjustment direction; a second U-shaped connector defining first through holes in two sides thereof, the second U-shaped connector being inserted into the first U-shaped connector with U-shaped openings thereof opposite to each other to define an accommodating space; a first spring located in the accommodating space and abutting against the first and second U-shaped connectors, respectively; an elastic pin with two ends thereof extending through the first through holes and engaging into one of the plurality sets of adjustment slots; and an initial fixing pin being detachably connected to the first and second U-shaped connectors. A telescopic annular tunnel steel arch includes an upper arch, two lower arches and two telescopic devices connecting two ends of the upper arch to the two lower arches, respectively.