Method for strutting brace legs in an earth-retaining structure of an excavation support system, and system of elements used for purposes of this method

Abstract

The method is used for strutting brace legs in a quadrangular setup of a rim of brace legs. The method consists in that a spreader (3) is attached to one end of each brace leg (2), while an extendable tensioning unit (4) is attached to the other end of the same brace leg (2). Next, the brace legs (2) are set inside the excavation in such a manner that, in the excavation corners, the ends of the brace legs (2) terminated with spreaders (3) become coupled with the ends of the subsequent brace legs (2) terminated with tensioning units. Once all the brace legs (2) have been coupled with each other, the ends of the brace legs (2), with the spreaders (3) attached to them, are pressed against the sheet piles (1) in the excavation corners by means of tensioning units (4) attached to subsequent brace legs (2).

Claims

1. A method for strutting brace legs in an earth-retaining structure of an excavation support system using a setup, comprising: a rim of brace legs and spreaders, wherein a spreader, is attached to one end of each brace leg, thus forming a brace leg extension, while an extendable tensioning unit with a spread locking feature is attached to an other end of each said brace leg, further forming the brace leg extension, wherein, after the distance between opposite excavation sheet piles has been measured, and a length of the brace legs thus prepared has been pre-set according to the measurement results obtained, the brace legs are set inside the excavation at a pre-assumed depth in such a manner that, in the excavation corners, the ends of the brace legs terminated with spreaders become coupled with the ends of the subsequent brace legs terminated with tensioning units, and then, once all the brace legs have been coupled with each other, using pins, the brace legs are pressed against the sheet piles in the excavation corners, and a position of the ends of the brace leg, with the spreaders attached to the brace leg, and fixed by the tensioning units attached to subsequent brace legs.

2. A system of elements for strutting of brace legs in an earth-retaining structure of an excavation support system, comprising: spreaders and two pairs of opposite brace legs, forming a quadrangular rim and supporting excavation sheet piles, distinctive in that a spreader, telescopic and terminated with a spreader mounting lug, is attached to one end of each brace leg, forming a brace leg extension, while an extendable tensioning unit is attached to an other end of the brace leg, providing the brace leg extension, where the tensioning unit comprises an I-section with an axially arranged lug mounted at its one end and a retaining block, featuring a centrally positioned straight-through block hole, rigidly mounted at the other end of the I-section, while between the axially arranged lug and the retaining block, seated on the I-section, there is a sliding panel composed of a base plate, protruding beyond the I-section outline, and two limiting plates attached to the base plate's sides by spacing plates, where the limiting plates are attached to the base plate, while upon being tightly fixed together, the base plate, the spacing plates and the limiting plates loosely embrace the I-section flanges; and wherein, welded to the base plate, is a transverse retaining element with a centrally positioned straight-through tensioning hole and two parallel lateral lugs, with the block hole and the tensioning hole being penetrated by a tensioning stud with working nuts on both its ends, while in each of the four corners of the rim of brace legs, attached to the brace leg of a first pair of brace legs of the two pairs of opposite brace legs, the spreader is coupled with the tensioning unit attached to the brace leg of a second pair of brace legs of the two pairs opposite brace legs with a pin inserted into a overlapping holes of the spreader mounting lug and of the pair of lateral lugs.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An example of the invention has been depicted in a series of figures, where:

(2) FIG. 1 shows a fragment of a rim of brace legs supporting the excavation sheet piles,

(3) FIG. 2 provides a magnified view of one of the corners of the rim of brace legs, and

(4) FIG. 3 is an axonometric projection of the tensioning unit, while FIG. 4 provides a partial longitudinal section of the tensioning unit.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

(5) As demonstrated in the example of the invention execution variation, the quadrangular rim which supports excavation sheet piles 1 features two pairs of opposite brace legs 2. Telescopic spreader 3, terminated with mounting lug 31, is attached to one end of each brace leg 2, thus providing its extension. At the other end of the same brace leg 2, tensioning unit 4 is attached, also extending the former. Tensioning unit 4 comprises I-section 41 to which axially arranged lug 42 is mounted at one end, and retaining block 43, featuring centrally positioned straight-through block hole 44, is rigidly mounted on the opposite side. Between axially arranged lug 42 and retaining block 43, there is sliding panel 5 seated on I-section 41. Panel 5 is composed of base plate 51, protruding beyond the outline of I-section 41, and two limiting plates 53 attached to the base plate's sides by means of spacing plates 52. Limiting plates 53 are fixed to base plate 51 by means of two rows of mounting bolts 54, while after base plate 51, spacing plates 52 and limiting plates 53 have been tightly fixed together, and loosely embrace the flanges of I-section 41. Welded to base plate 51, there is transverse retaining element 55 with a centrally positioned straight-through tensioning hole 56 and two parallel lateral lugs 57. Block hole 44 and tensioning hole 56 are penetrated by tensioning stud 7 with working nuts 71 on both its ends. In each of the four corners of the rim of brace legs, attached to brace leg 2 of the first pair of brace legs, spreader 3 is coupled with tensioning unit 4 attached to brace leg 2 of the second pair of brace legs. The coupling between spreader 3 and tensioning unit 4 in the corner of the rim of brace legs is provided by pin 8 inserted into the overlapping holes of spreader mounting lug 31 and the pair of lateral lugs 57.

(6) According to invention, the distance between the most protruding surfaces of opposite sheet piles 1 in the excavation corners is measured before brace legs 2 are set up inside the excavation, whereupon individual brace legs 2 are assembled, using an adequate number and unit lengths of the segments forming each brace leg, along with spreader 3 and tensioning unit 4, both mounted at the brace leg ends, so that their total lengths fall within the range established by the measurement results. At this point, the extent to which spreader 3 is to be spread is approximately pre-set in such a manner as to enable spread adjustment after brace leg 2 has been set in the excavation. Furthermore, in tensioning unit 4, nuts 71 on stud 7 are screwed off as much as possible so that panel 5 with lugs 57 can be moved away as far as possible from retaining block 43. Once all four brace legs 2 are set up in the excavation at an appropriate height matching sheet piles 1, in individual corners, mounting lugs 31 of spreader 3 and lateral lugs 57 of tensioning unit 4 are coupled using pins 8, whereupon the lengths of brace legs 2 are pre-adjusted to match the dimensions of excavation walls by extending the telescopic rods of spreaders 3. Then, using working nuts 71 to reduce the length of tensioning stud 7, the end of adjacent brace leg 2 is pressed against the sheet pile being supported. This procedure is repeated successively in all excavation corners, thus obtaining uniformly distributed pressure force applied by the entire rim of brace legs 2 on all sheet piles 1.

(7) One advantage of the solution according to the invention is that it does not require the use of expensive telescopic spreaders, featuring built-in hydraulic cylinders of high load capacity and long travel, to obtain a sufficient force of pressure applied on sheet piles by brace legs. Another advantage of this solution is that it ensures improved structural safety, since the earth pressure is transferred to elements whose load capacity results from tensioning a stud instead of compressing a hydraulic cylinder, as in conventional solutions where the potential loss of the cylinder integrity may lead to structural failure or even collapse. It should be emphasized that, considering the solutions currently available in the market and commonly applied, every case of hydraulic cylinder integrity loss causes contamination of soil and groundwater. With regard to the foregoing, the solution according to the invention also reduces the risk of natural environment pollution as well as the costs of removing potential contaminants.