WO2020032811A1

WO2020032811A1 - Method for strutting and relieving struts in an earth-retaining structure of an excavation support system, and a system of intercoupled elements used for purposes of this method

Info

Publication number: WO2020032811A1
Application number: PCT/PL2019/000062
Authority: WO
Inventors: Paweł KWARCIŃSKI; Marcin GIERSZAL
Original assignee: Isps Sp. Z O.O.
Priority date: 2018-08-07
Filing date: 2019-08-01
Publication date: 2020-02-13
Also published as: PL426583A1

Abstract

The method for strutting and relieving struts of brace legs in an excavation support system consists in that at least one non-permanent support point is formed for the strut placed between the brace legs, whose positioning on the brace leg is controlled by means of an adjustable anchoring piece catching on another support point on the same brace leg. The force component produced by the strut's thrust, affecting the brace leg, is controlled by adjusting the anchoring piece's tensioning force. The force component is relieved by breaking the anchoring piece's continuity. In the system for strutting and relieving of struts, on the surface of each of the pair of intercoupled corner brace legs (11), supporting corner retaining walls (12) of the excavation, a retaining element (13) and, at a certain distance from it, a corner lug (15) are installed. The retaining element (13) and the corner lug (15) are coupled by means of corner anchoring pieces (16) terminated with corner working nuts (17) on both sides. Both corner lugs (15) are connected with each other with a comer strut (19). Corner induction winding (18) is coiled about the corner anchoring pieces (16). In the invention variation, on the outer surface of each of two coupled side brace legs (21), supporting side retaining walls (22), at a certain distance from each other, there are two side lugs (23). The lugs are intercoupled by means of side anchoring pieces (24) terminated with side working nuts (25) on both sides. Spreading struts (26), whose other ends are connected with the main strut (27), are attached to both side lugs (23). Side induction winding (28) is coiled about the side anchoring pieces (24).

Description

Method for strutting and relieving struts in an earth-retaining structure of an excavation support system, and a system of intercoupled elements used for purposes of this method

The subject of the invention is a method for strutting and relieving struts in an earth-retaining structure of an excavation support system, and a system of intercoupled elements used for purposes of this method.

There is a known method for strutting brace legs in an earth-retaining structure of an excavation support system using corner struts as well as struts perpendicular to excavation walls, where the force clamping the brace leg against the earth-retaining structure’s sheet piles is generated by means of a hydraulic spreader with a pitch of ca. 60-70 cm as well as intercoupled rigid strutting beams, also coupled with the spreader, with a length of 0.5 m, 1 m, 2 m, etc. Depending on the excavation shoring variant, these elements are mounted between brace legs which support the excavation’s retaining walls, and they are fixed to the latter by means of removable strut lugs seated on l-section type brace legs. Each time the brace leg is set out at a specific location, these lugs are secured against uncontrolled travel along the brace leg with travel locking elements welded to them. Using the struts according to the known method to secure a specific excavation consists in initially determining their length values, which correspond to the distances between individual points at which struts and brace legs are connected, which is performed by adjusting the slide-out of a piston tied in the hydraulic spreader’s strut, while after all struts have been coupled with strut lugs, working pressure is delivered at the same time to all hydraulic spreaders, the effect of which is uniform thrust of sheet piles against the soil forming excavation walls. The thrust of struts against brace legs is relieved by simultaneously reducing working pressure in all hydraulic spreaders.

A model solution making use of the method in question has been presented in a description of a shoring device according to patent US4787781.

A flaw of the known method is the necessity to join new travel locking elements in by welding in different brace leg locations, if they have been changed, in the event that the same brace legs are to be used multiple times. This makes it necessary to perform some additional activities when removing old elements, cleaning the brace leg surface of paint, welding new locking elements and painting them. Another flaw of the known method is the necessity to leave the hydraulic spreader in the strut structure for the entire excavation shoring time, which not only increases costs, since many struts are typically used in the same excavation, but also entails a risk of oil leakage from spreader cylinders which may consequently weaken the entire excavation shoring structure as time passes.

Furthermore, there is a method, known from Polish patent description PL183464, for coupling a strut in an earth-retaining structure, and especially in an excavation support system, which consists in using a deformable element, composed of a box enclosure and loose material, preferably sand, which fills the housing, to couple the strut in the earth-retaining structure. The deforming element is placed in the strut’s longitudinal axis, preferably between the strut’s tensioning wedges and the strut itself. In order to dismantle the strut, the loose material is removed from inside the deforming element’s enclosure through a hole located behind a valve, thus causing deformation of this element as well as uniform relieving of the strut, which allows for the strut tensioning wedges to be removed easily.

The essential feature of the method according to the invention is that, on the surface of each of the two intercoupled l-section brace legs supporting the Opposite excavation retaining walls, at least one non-permanent support point is formed for the rigid strut placed between the brace legs, whose positioning on the brace leg is controlled by means of at least one adjustable metal anchoring piece catching on another support point on the same brace leg. By that means it is possible to compensate for the force component of the strut’s thrust, directed longitudinally along the brace leg, while the value of the force component triggered by this thrust, directed perpendicularly to the brace leg, is controlled by adjusting the anchoring piece’s tensioning force. The force component perpendicular to the brace leg is relieved by reducing the said tensioning force, preferably by breaking the anchoring piece’s continuity.

The anchoring piece’s continuity is broken by locally plasticising and rupturing the piece’s material, preferably by induction heating.

The essential feature of the system according to the invention is that, on the outer surface of each of the two coupled l-section corner brace legs supporting the corner retaining walls of the excavation, a retaining element is placed from the excavation corner side, preferably comprising a limiter plate welded to the outer surface of the corner brace leg and a detachable block, supported on the corner brace leg, embracing the outer part of the corner brace leg section, while at a certain distance from the retaining element, there is a detachable corner lug embracing the outer part of the section of the same brace leg. The retaining element and the corner lug, each of the two, preferably feature a pair of identical and mutually facing corner straight-through holes penetrated by bilaterally threaded oblong corner anchoring pieces having on their ends, on the outer side of the retaining element and the corner lug, corner working nuts. Both corner lugs, embracing the outer part of the sections of both coupled corner brace legs, are non-permanently connected with each other by means of a rigid corner strut using corner mounting catch pawls combined with corner lugs. The corner anchoring pieces are tied in two internally threaded corner blocks, preferably cuboidal, joined together by means of bilaterally threaded corner.

The essential feature of the system’s variation according to the invention is that on the outer surface of each of the two coupled l-section side brace legs, supporting the retaining walls on the opposite sides of the excavation, at a certain distance from each other, there are two symmetrically positioned side lugs embracing the outer part of the section of the same side brace leg, while at the same time, each of them preferably features one pair of identical mutually facing side straight-through holes. The side holes are penetrated by bilaterally threaded oblong side anchoring pieces having side working nuts at their ends, on the outer side of both side lugs. Identical rigid spreading struts, the length of which preferably corresponds to the distance between the side lugs, are non-permanently connected on one end with both side lugs by means of side mounting catch pawls combined with the struts. The other ends of the spreading struts are non-permanently connected with the main strut which is non- permanently connected on the other side with ends of the second pair of spreading struts tied in the side brace leg supporting the opposite retaining wall of the excavation. The side anchoring pieces are tied in two internally threaded side blocks, preferably cuboidal, joined together by means of bilaterally threaded side connector pipes screwed in them, with side induction winding coiled about the pipes.

The invention has been shown in sample variations on a number of drawings, where fig. 1 provides a schematic diagram of the invention for an earth-retaining structure of the excavations corner, while fig. 2 illustrates a set of strut’s tensioning elements for this variation of the invention. Further drawings illustrate its individual components, i.e. fig. 3 shows the detachable block in an axonometric projection, fig. 4 is a projection of the entire retaining element, fig. 5 provides an end view of the block attached to the brace leg, fig. 6 is an axonometric projection of the corner lug, while fig. 7 provides an end view of the corner lug attached to the brace leg. Furthermore, fig. 8 is a general schematic diagram of the invention variation for an earth-retaining structure stabilising excavation side walls, while fig. 9 schematically illustrates a system of intercoupled brace leg and struts for a single excavation side wall, fig. 10 illustrates a set of strut’s tensioning elements for this variation of the invention. Further drawings illustrate its individual components, i.e. fig. 1 1 is an axonometric projection of the side lug, while fig. 12 provides an end view of the side lug attached to the brace leg. As demonstrated in the example of execution, on the outer surface of each of the two intercoupled l-section corner brace legs 1 1 , supporting corner retaining walls 12 of the excavation, retaining element 13 is placed on the excavation corner side, preferably comprising a steel plate of limiter 13a welded to the outer surface of corner brace leg 1 1 and detachable block 13b, supported on corner brace leg 1 1 and embracing the outer part of its section. Block 13b is formed by locking mechanism base plate 14a made of steel, whose width is larger than the width of the outer surface of corner brace leg 1 1 , on both sides of which there are locking mechanism mounting holes 14b used for bolt fixing of two locking mechanism pressure plates 14d, where the pressure plates are set in place from underneath via locking mechanism spacing plates 14c. On the upper surface of locking mechanism base plate 14a, there is lateral locking mechanism pressure plate 14e, with two symmetrically positioned locking mechanism straight-through holes 14f, as well as four locking mechanism brackets 14g perpendicular to the plate, all combined with the base plate. Once it has been mounted to corner brace leg 1 1 , block 13b embraces the outer T-section of corner brace leg 1 1 with its locking mechanism pressure plates 14d, being set against it in such a manner that lateral locking mechanism retaining plate 14e rests on the outer side of retaining element 13. At a certain distance from retaining element 13, on corner brace leg 1 1 , there is detachable corner lug 15 embracing the outer part of the brace leg’s section. Corner lug 15 is formed from steel corner lug base plate 15a, whose width is larger than the width of the outer surface of brace leg 1 1 , on both sides of which there are corner lug mounting holes 15b used for bolt fixing of two corner lug pressure plates 15d, where the pressure plates are set in place from underneath via corner lug spacing plates 15c. On the upper surface of corner lug base plate 15a, there is lateral corner lug pressure plate 15e combined with the said base plate, with two symmetrically positioned corner lug straight-through holes 15f, as well as two corner lug brackets 15g perpendicular to the plate and two corner lug catch pawls 15h with corner lug catch holes 15i. Once it has been mounted, corner lug 15 embraces the outer part of the l-section of corner brace leg 1 1 with its corner lug pressure plates 15d, being set against it in such a manner that lateral corner lug retaining plate 15e rests on the outer side of corner lug 15. Locking mechanism straight-through holes 14f and corner lug straight- through holes 15f, respectively, are penetrated by the threaded ends of two corner anchoring pieces 16, tightened on both sides to locking mechanism pressure plate 14e and to corner lug pressure plate 15e by means of corner working nuts 17. Each comer anchoring piece 16 consists of two corner lateral rods 16a joined together by means of two threaded hexagonal corner blocks 16b, symmetrically screwed on the rods, and threaded corner connector pipe 16c, positioned between the rods, where the connector pipe is coiled about with corner induction winding 18. Between corner lugs 15 set on coupled corner brace legs 1 1 , rigid corner strut 19 is mounted, and the latter’s ends are connected with the said lugs by means of corner mounting catch pawls 15h using their corner catch holes 15i. Strut 19 is composed of a specific number of intercoupled corner strutting beams 19a of varying lengths, the total length of which is adjusted to the distance between coupled corner lugs 15.

Using the solution according to the invention consists in that, once an appropriate number of brace leg components have been assembled, as required to support the excavation sheet piles and to raise them to the assumed height vis-a-vis the height of the excavation walls, on the outer sections of each of corner brace legs 11 that come together, in front of the steel plate of limiter 13a, if viewed from the excavation corner, block 13b is attached by bilaterally bolting locking mechanism base plate 14a with locking mechanism pressure plates 14d via locking mechanism spacing plate 14c. At a certain distance from block 13b, on the outer section of each corner brace leg 1 1 , corner lug 15 is installed by bilaterally bolting corner lug base plate 15a with corner lug pressure plates 15d via corner lug spacing plate 15c. Next, corner lateral rods 16a, terminated with corner working nuts 17, are put through pairs of locking mechanism straight-through holes 14f and corresponding pairs of lug straight-through holes 15f, and the rods are then joined in pairs in the middle by means of bolted together corner blocks 16b and corner connector pipe 16c. Before corner connector pipe 16c is installed, it is coiled about with corner induction winding 18. Then corner lugs 15, placed on both coupled corner brace legs, are connected by joining them with rigid strut 19 using corner catch pawls 15h. Strut 19 is composed of an adequate number of bolted standard corner strutting beams 19a, and its length is individually adjusted to match the dimensions of the given excavation’s sides. The operation performed once the strutting elements have been installed in all excavation corners consists in increasing the thrust of struts 19 against all brace legs 1 1 mounted along the excavation perimeter. This is accomplished by successively tightening corner working nuts 17 of all corner anchoring pieces 16, thus moving corner lugs 15 towards blocks 13b locked in placed by means of limiters 13a and cooperating with the lugs. Consequently, struts 19 are evenly moved towards excavation corners and the thrust against brace legs 1 1 increases. The thrust of struts 19 against brace legs 1 1 is relieved gradually or, optionally, at the same time at all excavation comers by connecting coils of corner induction winding 18 to a high power source of alternating current. By that means, eddy currents are induced in steel corner connector pipes 16c as an effect of the variable magnetic field, consequently heating the connector pipes up to a high temperature and either plasticising them or rupturing. Once corner connector pipes 16c have been ruptured, corner lugs 15 are relieved, and so are the forces of thrust acting against brace legs 1 1. In the invention variation, on the outer surface of each of the two coupled l-section side brace legs 21 , supporting opposing side retaining walls 22 of the excavation, at a certain distance from each other, there are two symmetrically positioned side lugs 23 embracing the outer part of the section of the same side brace leg 21. Each side lug 23 is formed by steel side lug base plate 23a, whose width is larger than the width of the outer surface of side brace leg 21 , on both sides of which there are side lug mounting holes 23b used for bolt fixing of two side lug pressure plates 23d, where the pressure plates are set in place from underneath via side lug spacing plates 23c. On the upper surface of side lug base plate 23a, there is lateral side lug pressure plate 23e combined with the said base plate, with two symmetrically positioned side lug straight-through holes 23f, as well as two side lug brackets 23g perpendicular to the plate and two side lug catch pawls 23h with side lug catch holes 23i. Once it has been mounted, side lug 23 embraces the outer part of the l-section of side brace leg 21 with its side lug pressure plates 23d, being set against it in such a manner that lateral side lug retaining plate 23e rests on the outer side of side lug 23. Threaded ends of two side anchoring pieces 24, attached on both sides to side lug pressure plates 23e by means of side working nuts 25, are placed through mutually facing side straight-through holes 23f of both side lugs 23. Each side anchoring piece 24 consists of two lateral side rods 24a joined together by means of two threaded hexagonal side blocks 24b, symmetrically screwed on the rods, and threaded side connector pipe 24c, positioned between the rods, where the connector pipe is coiled about with side induction winding 26. Rigid spreading struts 27 of identical length, corresponding to the distance between the side lugs, are non-permanently connected on one end with both side lugs 23 by means of side mounting catch pawls 23h combined with the struts. The other ends of spreading struts 27 are non-permanently connected with main rigid strut 28. On the other end, the strut is non-permanently connected with ends of the second pair of spreading struts 27 tied in side brace leg 21 whose function is to support side retaining wall 22 on the opposite side. Main strut 28 is composed of a specific number of intercoupled side strutting beams 28a of varying lengths, the total length of which is adjusted to the distance between opposite spreading struts 27.

Using the solution according to the invention consists in that, once an appropriate number of brace leg components have been assembled, as required to support side retaining walls 22 and to raise them to the assumed height vis-a-vis the height of the excavation walls, two side lugs 23 are installed on the outer sections of opposite side brace legs 21 , at a certain distance from each other on these brace legs. This is accomplished by bilaterally bolting their side lug base plates 23a with side lug pressure plates 23d by means of side lug spacing plates 23c, while at the same time, both side lugs 23 are facing each other with their side catch pawls 23h. Next, side lateral rods 24a, terminated with side working nuts 25, are put through pairs of straight-through side holes 23f of both side lugs 23, and the rods are then joined in pairs by means of bolted together side blocks 24b and side connector pipe 24c. Before side connector pipe 24c is installed, it is coiled about with side induction winding 26. Next, spreading struts 27, whose other ends are connected with one end of main strut 28, are mounted to both side lugs 23 using the struts’ side mounting catch pawls 23h. The other end of main strut 28 is connected with two spreading struts 27 which belong to a similar assembly of elements coupled with brace leg 21 on the opposite side. Main strut 28 is composed of an adequate number of standard side strutting beams 27a bolted together, and its length is individually adjusted to match the dimensions of the given excavation’s sides. The operation performed once all strutting elements have been installed along both opposing excavation walls consists in increasing the thrust of main struts 28 along with spreading struts 27 against all side brace legs 21 mounted along the excavation walls. This is accomplished by tightening side working nuts 25 of all side anchoring pieces 24, thus causing side lugs 24 to move towards each other and generating a force clamping side brace legs 21 against retaining walls 22. The thrust produced by main struts 28 along with spreading struts 27 against side brace legs 21 is relieved either gradually or, optionally, at the same time along the entire length of excavation walls by connecting individual coils of side induction winding 26 to a shared high power source of alternating current. By that means, eddy currents are induced in steel side connector pipes 24c as an effect of the variable magnetic field, consequently heating the connector pipes up to a high temperature and either plasticising them or rupturing. Once side connector pipes 24c have been ruptured, side lugs 23 are relieved, and so are the forces of thrust acting against side brace legs 21.

The main advantage of the method proposed for strutting brace legs in an excavation earth-retaining structure according to the invention is that one is not forced to use hydraulic spreaders which, according to known solutions, formed an integral part of the strut which remained in operation over the entire excavation shoring period.

The new solution assumes that their function, which consisted in applying pressure against brace legs, has been taken over by the system of screw-type elements cooperating with rigid struts. This advantage not only makes it possible to significantly reduce the costs related to the strutting structure by taking expensive hydraulic spreaders out of the equation, but it has also enabled a considerable increase in terms of reliability, mainly by eliminating the risk of oil leakage from the spreader cylinder during excavation works. With regard to the corner strut, another advantage of the solution according to the invention is that only one universal travel limiter plate of the block is used, welded to the brace leg and supporting the screw-type anchoring piece, while a variation of the invention makes it possible to completely avoid using welded travel locking elements in the brace leg as well as to use the same brace legs multiple times for shoring of numerous successive variants of excavations without the labour and cost intensive operation of removing old locking elements welded to brace legs.

Yet another advantage of the invention is the manner in which struts are relieved, making it possible to trigger the force reduction process either gradually in steps or remotely at the same time to relieve the thrust of struts against all excavation brace legs by induction plasticising of the anchoring pieces tensioning these struts.

Claims

1. The method for strutting and relieving struts in an earth-retaining structure of an excavation support system using retaining elements installed on brace legs as well as strut mounting elements, along with rigid strutting beams comprising the strut, where the brace legs are affected by vectors of components of the strut’s force of thrust acting in directions both perpendicular and longitudinal towards the brace legs, characterized in that, on the outer surface of each of two coupled I- section brace legs supporting excavation retaining walls, at least one nonpermanent support point is formed for the rigid strut placed between the brace legs, whose positioning on the brace leg is controlled by means of at least one adjustable metal anchoring piece catching on another support point on the same brace leg, whereby it is possible to compensate for the force component of the strut’s thrust, directed longitudinally along the brace leg, while the value of the force component triggered by this thrust, directed perpendicularly to the brace leg, is controlled by adjusting the anchoring piece’s tensioning force, while the said force component, perpendicular to the brace leg, is relieved by reducing the tension force in question, preferably by breaking the continuity of the anchoring piece.

2. The method according to claim 1 , characterized in that, the anchoring piece’s continuity is broken by locally plasticising and rupturing the piece’s material, preferably by induction heating.

3. The system of intercoupled elements used for strutting and relieving of brace legs in an earth-retaining structure of an excavation support system containing retaining elements installed on the brace legs as well as strut mounting elements, and further containing rigid strutting beams comprising the strut, characterized in that, on the outer surface of each of two coupled l-section corner brace legs (11), supporting corner retaining walls (12) of the excavation, a retaining element (13) is placed on the excavation corner side, preferably comprising a limiter plate (13a) welded to the outer surface of the corner brace leg (11) and a detachable block (13b), supported on the corner brace leg, embracing the outer part of the corner brace leg (11) section, while at a certain distance from the retaining element (13), there is a detachable corner lug (15) embracing the outer part of the section of the same brace leg (11), while at the same time, the retaining element (13) and the corner lug (15), each of the two, preferably feature a pair of identical and mutually facing locking mechanism straight-through holes (14f) and corner straight-through holes (15f) respectively penetrated by bilaterally threaded oblong corner anchoring pieces (16), having on their ends, on the outer side of the retaining element (13) and the corner lug (15), comer working nuts (17), and furthermore, both corner lugs (15), embracing the outer part of the sections of both coupled comer brace legs (11), are non- permanently connected with each other by means of a rigid corner strut (19) using corner mounting catch pawls (15h) combined with corner lugs (15).

4. The system according to claim 3, characterized in that, the corner anchoring pieces (16) are tied in two internally threaded corner blocks (16b), preferably cuboidal, joined together by means of bilaterally threaded corner connector pipes (16c) screwed in them.

5. The system according to claim 3 or 4, characterized in that, between the retaining element (13) and the corner lug (15), corner induction winding (8) is coiled about the corner anchoring pieces (16).

6. The system of intercoupled elements used for strutting and relieving of brace legs in an earth-retaining structure of an excavation support system containing retaining elements installed on the brace legs as well as strut mounting elements, and further containing rigid strutting beams comprising the strut, characterized in that, on the outer surface of each of two coupled l-section side brace legs (21), supporting side retaining walls (22) opposing each other in the excavation, at a certain distance from each other, there are two symmetrically positioned side lugs (23) embracing the outer part of the section of the same side brace leg (21), while at the same time, each of them preferably features one pair of identical mutually facing side straight-through holes (23f) penetrated by bilaterally threaded oblong corner anchoring pieces (24), having side working nuts (25) on their ends, on the outer side of both side lugs (23), and furthermore, identical rigid spreading struts (26), whose length preferably corresponds to the distance between the side lugs (23), are non-permanently connected on one end with both side lugs (23) by means of side mounting catch pawls (23h) combined with the struts, whereas the other ends of the spreading struts (27) are non- permanently connected with the main rigid strut (28) non-permanently connected on the other side with ends of the second pair of spreading struts (27) tied in the side brace leg (21) whose function is to support the opposite side retaining wall (22).

7. The system according to claim 6, characterized in that, side anchoring pieces (24) are tied in two internally threaded side blocks (24b), preferably cuboidal, joined together by means of bilaterally threaded side connector pipes (24c) screwed in them.

8. The system according to claim 6 or 7, characterized in that, between both side lugs (23), corner induction winding (26) is coiled about the side anchoring pieces (24).