SUPPORTING WELDED BEAM WITH SECTIONAL STEM

Technical field

The invention concerns a supporting welded beam with a sectional stem, the beam being formed by a couple of flanges, where there is the stem mounted between them.

Actual state of technique

In the Earth crust there are going on processes, which result from the action of various forces variables in space and time. A part of stable forces is gravitation, forces of geophysical and geochemical processes and these with them bind temperature cha,rigea _l r-:iιnf!uences! _. pfr!prces _l acting in the Earth corn and terrestrial forces. These are facilitating us to make clear the states of tension in a rock pillar.

;.Frpmfth% phenomenological point of view, we take the rock pillar for an assembly composed from many parts (quasi-homogenous units), which are in a. mutual state ;, and _; in. certain given, system, both in strengths one and in structural one. We.can account to the quasi-continuum the parts of assembly of the rock surrounding and the reinforced or unreinfoxςed underground work, as well.

.^By _t resplyiηg.pf tension-deformation states in the underground worfejsufjioundiηgewejf before , the, undergrpiUndvyprk≤; primaFy tension, state.; The: coπηppsedi from, the; rock sequences is from the static point of view in an equilibrium tenseness state, e.g. the geostatic primary tenseness. By exhausting a hole in the rock surrpundingy^ the,- primary tenseness behind the. walls of the stope changes*. as , a, consequence, pf disturbing: the equilibrium tenseness state. A: new. fprQe;.sy,stem J&. creating _; that evokes in the. rock surrounding, around the unequipped exhausted, par^ sp- called secondary tenseness, In these .conditions the equilibrium tenseness state can ber ensured: by _. supports (the term supports in mining work corresponds to the term furniture in the building construction), because the internal (protective) forces of the rock are. not ,

match for that. The mining supports help to the rock to secure the required stability of the underground work during its lifetime. Functionally, it takes effect as an indivisible construction element in the static system of the ,,rock surrounding - reinforcing". Its mechanical stress is a function of changing tensions in the rock surrounding around the stope, of physical and. mechanical rocks characteristics in situ and of the time, and of the active influence of the supports as well.

In mining and in the underground building construction as well, there are and had been used wood, steel, concrete and combination of them as the basic materials for supports of underground works. From the recent, the most widespread technological methods of securing the underground burst parts supports, it is the fabrication of coipier^te; aπd.reJπfprced; conorete^linings^ underground .works,, driven, by, convectional methpdsy _;i e!tg. atg tunjiejao.biβetsv.the stability, of the stope, is secured, by -.a two-surface armored .concrete} lining that _i; : frp,m _: the functional point, of _. view,, is divided to primary- ancL secondary, (de|initiyeymiηg. _r:

The primary. lining; of the underground worK serves as ar supporting structure, thatn du/ing the buHding works, is assuring the stope by all, the time till the secpndary -Jiniηg pf the-unde/g round work is.fmished. To ₁ the prirnary lining,, a temporary Hfetim%is= imp _ι u.|ed _?, ι Thatrpηe, is,many times Jpngeηthaη -the, operating period _; pf, the bui^ lining is made,.by the shptcrete, technology, where the lining is created by a shotcrete layer reinforced by wire, messes < and _f f rames,;, pi- pnly ^■ >■ W _{. <} porrnal^. concrete , of fiber, , reinforced; , concrete^ <Thef supp,prti.ng _j €pnstructipn; _; pf:the ppiφa^ stppe^ yjeinity. and pnλhe way of the; driving, work. Wire meshes at both surfacesj.pf; i$e ₍ construction; ace, a common supporting of the lining; they are fitted before the concreting at the frames fit together from the sections of the space truss reinforcement (so called BRETEXes).. The frames are fitted . in the proposed step of the drivjngi mostly, j _. n the

spacing at 1 ,0 m. The reinforcement becomes a bearing capacity one after being concreted and after a time delay necessary for concrete strength rising.

At driving works with a high overburden or in loamy and clayey pressing rocks, the supporting frames are formed by sections made from steel bended rolled profiles of the type HEB. To insure the contact with the stope (activation by sprinkle), the frames are immediately carrying ones and are capable to transfer as much as 35 to 40 % of the total load at the primary lining. The rolled profiles are made of the steel S235. This ductile material is characterized by a long deformation trace and makes possible a plastic deformation of the primary lining, without which the construction would be hardly sizable. The bending of the rolled profiles, as to their rigidity and dimensions, is very laborious and in addition, it requires a special technique.

A problem is the fact that the interaction of the rolled profiles together with the concrete is disputable, when having limit stresses, from the reason of quite different properties of the materials. Concrete in combination with the rolled profiles behaves as an imperfect composite construction (there are missing the elements of coupling, e.g. the pins). More, by application of shotcrete the concrete cleaves hardly at the rolled profiles, it comes to great fallout and there are created so called shadows, i.e. areas not covered by concrete.

The secondary lining fulfills a function of definitive lining for transfer of earth pressures coming from the rock, together with insurance of requirements of durability, resistance of the lining to the environmental influences and the surface quality requirements. The secondary lining is made after a partial appeasement of the primary lining deformations and it is possible to divide it technologically at the foot-wall and vault construction. The vault lining is fabricated from the cast-in situ concrete to a formwork. A current reinforcement of the lining is made by wire meshes by both surfaces of the construction, which are mounted at the frames built-up from the sectors made from the space truss reinforcement (so called BRETEXes). By high overburden and not itself stabilizing deformations of the primary lining, there is a possibility to use the supporting

frames made from steel bended rolled profiles of the HEB-type, with the same utility properties as in the primary lining.

Subject matter of the invention

The purpose of the invention is to propose a new construction of the supporting welded beam that, in interaction with the concrete, will insure an optimal lining behavior of the stope, as a reaction from the loading by the continuum rock pressure in the stope surrounding. The main goal is to increase the interaction of the beam with the concrete an also to optimize the total static carry capacity of the lining and at the same time to simplify the fabrication and to reduce the weight of individual welded beams. Further also to improve the properties of the composite beam construction and shotcrete structure.

The here-above mentioned purpose is achieved by supporting welded beam with a sectional stem, the beam being formed by a couple of flanges, where there is the stem mounted between them, the subject matter of the beam consisting in the fact that that it is formed by at least two, in distance from each other mounted flanges mutually connected by a system of in distance from each other mounted stems in parallel with the longer dimension of the flanges, where the distance between the two neighbor stems is permanently connected by at least one diagonal.

The main advantage of the welded beam is its easy forming according to the given profile of the drived underground work, where only the flanges are formed and they are welded after that with other elements, from which the welded beam is created. At fabricating the supporting welded beam it comes to inconsiderable savings against the welded beam of the HEB-type. One of the savings is a sinking of the steel consumption of until 15 % and the second saving concern reduction of the technological exigency at the flanges bending. The technology used at this beam fabrication ensures a minimal material salvage above all at the flanges bending and mainly a keeping the limit geometrical deviations determined by the project of the work. Insignificant is neither the fact that the beam of such construction will ensure a lot greater cohesion with the

shotcrete, by its constructional mounting it makes possible a plastic deformation, which it is possible unambiguously and in the concrete to specify at the construction proportioning, and the last not the least, it is minimizing a creation of not concreting spheres, by which losses of quality concrete used in the shotcrete technology are markedly reduced.

To increase the profile rigidity and to keep a sufficient skid action at the supposed lining deformation it is convenient, when the supporting welded beam with sectional stem has flanges in the form of a chord bended to an arch and mutually connected by the sectional stem fitted by diagonals formed by rebars made from the steel class B500B, minimally one end of the beam being fitted by a mounting flange. An indispensable advantage is the possibility of a proposal of flexible rigidity along the beam length (considering the course of charge) by the influence of the sectional stems ordering, distance between two edges of neighbor stems being in the interval of <min. b/2, max. 2h>, where b is the width of the stem and h is the total height of the welded beam in its cross section.

To increase the static resistance of the supporting welded beam with sectional stem it is favorable, if the flange is fabricated from the tension or compression chord made from the weldable steel class S235 or S275.

To keep a sufficient rigidity of the supporting welded beam with sectional stem it is favorable, if the flanges together with the stems and/or mounting flanges are mutually connected by welds.

To create the space truss construction it is favorable, if the supporting welded beam with sectional stem has each diagonal lead crossways across the free space between two neighbor stems and if each diagonal is welded to each stem in the touch point with the stem area. It is favorable as well that the carry capacity of the weld in the touch point of the diagonal and the stem would be higher than the carry capacity of the diagonal itself.

For an easy mutual mounting of the supporting welded beam with sectional stem it is favorable, when the mounting flange is equipped by a system of holes.

To increase the static resistance of the supporting welded beam with sectional stem it is favorable, when the mounting flange is equipped by a stiffening rib lead upright at its area and at the area of the adjacent flange.

Review of figures at the drawings

The technical solving according to this invention is more closely clarified at examples of its practical performance introduced at enclosed figures, where at the fig. 1 there is the side view at the supporting welded beam in its basic execution. At the fig. 1a there is shown the cross section of the beam by the plane A-A, at the fig. 2 there is shown the bended supporting welded beam in a side view, at the fig. 3 there is shown a view at one of mounting flanges is a section by the plane B-B according to the fig. 2 and at the fig. 4 there is a view at the second mounting flange in the section by the plane C-C according to the fig. 2.

Examples of the invention realization

The supporting welded beam with sectional stem designed to reinforce underground works lining will be explained but not limited by several example executions.

The basic execution of the module of supporting welded beam with sectional stem designed to reinforce exceptionally loaded plate ferro-concrete constructions is displayed at the fig. 1 and fig. 1a. The supporting beam consists of mounted sections formed by a couple of flanges 1, where there are between them fixed the stems 2, mutually permanently connected with the aid of diagonals 3. In the touch point of the flanges 1 and the stems 2 there is made a weld. Always the neighbor stems 2 are mutually connected with the aid of the diagonals 3.

The supporting welded beam designed to support the primary underground work lining, is shown at the fig. 2, .3 and 4. The welded beam shown at the fig. 2 is formed by two, in distance one from other mounted and to an arch bended flanges ±. The flanges i in the form of chords are bended to the arch and mutually connected by the sectional stem 2. This one is provided with the diagonals 3 formed e.g. by rebars with a diameter of 10 mm to 16 mm and the steel class 10505. Hereat the mutual distance I between two neighbor stems 2 lays in the extent from 150 mm to 500 mm, whereat these stems 2 are arched by at least one diagonal 3. Each one of the diagonals 3, through the free area between two neighbor stems 2, is led diagonal and is welded to each stem 2, partly at the place of the their joints, partly at all touch place with the plane of the stem 2. At both ends of the welded beam there are used two diagonals 3, each one from one side of the welded beam. In the remaining part of the welded beam, one diagonal 3 only is used, fixed by welding in turns at both sides of the sectional stem 2. Further the welded beam is at both ends fitted by the mounting flanges 5 that are equipped by the system 4 of mounting holes. These holes serve to connect the individual welded beams to the construction of frame support by the aid of fasteners. For higher rigidity of the joints of the frame supporting construction, the mounting flange 5 can be equipped by the reinforcing rib 6, as seen from the fig. 2 and fig. 3. In this execution, the supporting rib 6 is led perpendicular to the mounting flange 5 plane and to the plane of the adjacent flange 1, as well.

The flanges λ_ are fabricated with advantage as chords from a bright strip steel of the class 11500.0 or 11375, with dimension of 200x15 mm. The stems 2 can be fabricated from the same steel, but can have an inferior thickness, namely in the limits from 6 mm to 12 mm. For diagonals 3 can be used with advantage the reinforcement, e.g. material of the class B500B, with the diameter of 12 mm, e.g. All the welded beam could be fabricated with advantage by welding in the welding fixture, whereat the mounting flanges 5 are welded to the needed position even after taking of the welded beam out of the welding fixture.

With advantage, each the mounting flange 5 is connected not only by the aid of flanges i, but also with the adjacent stem 2, which also increases the stiffness of the welded beam and the connection strength of two neighbor welded beams, as well. The slope of the mounting flange 5 against the flanges i is given by the form of the stope, into which the frame steel support is used.

Industrial usability

The objective welded beam with sectional stem is designed to equip the line underground works tunnelled by classical technology in loamy and clayey unstable rocks, above all for highly loaded primary lining of the underground works. It is possible to use it everywhere, where it is possible to replace the original supporting beams made from rolled profiles, e.g. of the HEB-type, but it is possible to use it for other purposes as well, as are e.g. highly loaded secondary linings of the underground works, constructions of bridge panels, ceiling constructions, etc.

List of the relating marks

1 flange

2 stem

3 diagonal

4 system of through holes

5 mounting flange

6 reinforcing rib

7 joint

12