CN116043867A - Prepositioned steel support system suitable for small ultra-deep foundation pit - Google Patents

Abstract

The invention discloses a front-mounted steel support system suitable for a small ultra-deep foundation pit, which comprises a plurality of lattice columns, a plurality of connecting devices, a front-mounted steel support, a plurality of steel strands, a plurality of penetrating jacks, a plurality of servo cylinders and a hydraulic system, wherein the front-mounted steel support comprises a steel enclosing purlin and a plurality of corner horizontal inclined struts arranged at four corners of the steel enclosing purlin, the plurality of servo cylinders are arranged on the outer side surface of the steel enclosing purlin at intervals along the circumferential direction of the steel enclosing purlin, the plurality of servo cylinders stretch out and draw back under the action of the hydraulic system to realize active deformation control of an underground diaphragm wall, and the plurality of penetrating jacks realize lifting of the front-mounted steel support through synchronously retracting corresponding steel strands under the action of the hydraulic system.

Description

Prepositioned steel support system suitable for small ultra-deep foundation pit

Technical Field

The invention belongs to the technical field of constructional engineering machinery, and particularly relates to a preposed steel support system suitable for a small ultra-deep foundation pit.

Background

The small ultra-deep foundation pit (such as a subway end well) has the characteristics of small area, large depth, high deformation control requirement and the like, and a supporting scheme of adding a steel support (or a concrete support) to the underground diaphragm wall is generally adopted.

The underground diaphragm wall is supported by simply using the traditional steel support (or concrete support), and the defects that the super-excavation has long support time, the deformation of the underground diaphragm wall cannot be actively controlled, the construction concrete support needs to be excavated after the strength of the underground diaphragm wall reaches the standard, the construction period is influenced and the like exist.

Disclosure of Invention

The invention aims to invent a front-mounted steel support system suitable for a small ultra-deep foundation pit, and solves the problems that the ultra-excavation has long support time, the deformation of an underground diaphragm wall cannot be actively controlled, and the construction period is influenced by excavation after the strength of the construction diaphragm wall reaches the standard after the construction diaphragm wall is supported in the prior art.

In order to solve the technical problems, the invention provides the following technical scheme:

the front-mounted steel support system suitable for the small ultra-deep foundation pit comprises a plurality of lattice columns, a plurality of connecting devices, a front-mounted steel support, a plurality of steel strands, a plurality of through jacks, a plurality of jack foundations, a plurality of steel strand guide frames, a plurality of servo cylinders and a hydraulic system, wherein the front-mounted steel support comprises a steel enclosing purlin and a plurality of corner horizontal diagonal braces arranged at four corners of the steel enclosing purlin, the inner side of each corner of the steel enclosing purlin, which is positioned at the innermost corner horizontal diagonal brace, is correspondingly provided with one lattice column, the lattice column is pressed into a soil layer in advance according to a design position, each corner of the steel enclosing purlin is connected with the corresponding lattice column through the corresponding connecting device, and the jack foundations are respectively arranged at the four corner positions of a continuous wall head layer ring beam; the penetrating type jack is arranged on the corresponding jack foundation; the steel strand guide frames are arranged on the corresponding jack foundation or the ring beam at the first layer of the continuous wall; the steel strands are erected on the corresponding steel strand guide frames; the steel encloses the medial surface of purlin and the both sides face of the horizontal bracing of bight equidistant a plurality of adjustable supporting angles that set up respectively through bolted connection mode, hydraulic system sets up on diaphragm wall first floor girth or ground or leading-type steel support, a plurality of servo cylinders set up on the lateral surface of steel encloses the purlin along the circumference interval of purlin, a plurality of servo cylinders and a plurality of jack-in type jack are connected with hydraulic system respectively, a plurality of servo cylinders stretch out and draw back under hydraulic system effect, realize the initiative deformation control to the diaphragm wall, a plurality of jack-in type steel support's four bight through corresponding steel strand wires and leading-in type steel support respectively, a plurality of jack-in type steel support's lift is realized through synchronous receipts corresponding steel strand wires under hydraulic system's effect.

Preferably, in the foregoing front-mounted steel support system suitable for a small ultra-deep foundation pit, the front-mounted steel support is located inside the underground diaphragm wall, and the front-mounted steel support is assembled below the diaphragm wall first-layer ring beam.

Preferably, in the foregoing front-mounted steel support system suitable for a small ultra-deep foundation pit, the connection device includes a load-bearing tripod, a tripod support plate, two connection angles, a plurality of weld nuts, a plurality of adjusting bolts, an adjusting support plate, two lattice column U-bolts, two lattice column connection plates, four lattice column connection nuts, a horizontal diagonal connection plate, two horizontal diagonal U-bolts and four horizontal diagonal connection nuts, the load-bearing tripod is a right-angle triangle structure, the load-bearing tripod has a horizontal plane and a vertical plane, the horizontal diagonal connection plate is fixedly arranged on the horizontal plane, the tripod support plate is fixedly arranged on the vertical plane, the horizontal diagonal connection plate is mutually perpendicular to the tripod support plate, the two connection angles are respectively vertically arranged on the left and right sides of the tripod support plate, the upper and lower parts of the two connecting angle steels are respectively provided with a first through hole for the passing through of a lattice column U-shaped bolt, the two lattice column U-shaped bolts are connected with the lattice column connecting nuts through corresponding lattice column connecting plates after hooping the lattice column, two sides of the horizontal diagonal bracing connecting plates are respectively provided with a row of second through holes for the passing through of corresponding horizontal diagonal bracing U-shaped bolts along the longitudinal direction of the two horizontal diagonal bracing connecting plates, the two horizontal diagonal bracing U-shaped bolts connect the horizontal diagonal bracing connecting plates with the corner horizontal diagonal bracing through corresponding horizontal diagonal bracing connecting nuts, the upper and lower parts of the tripod supporting plates are respectively provided with a third through hole, threaded holes matched with the adjusting bolts are arranged at the third through holes, one end of each adjusting bolt is hinged with the adjusting supporting plate through a spherical hinge mode after passing through the corresponding threaded holes in the tripod supporting plates, the adjusting bolts can be rotated to correspondingly adjust the supporting plates, so that the adjusting support plate is attached to the side surface of the lattice column.

Preferably, in the foregoing front-mounted steel support system suitable for a small ultra-deep foundation pit, the bearing tripod comprises two tripod vertical rods, two tripod horizontal rods, two tripod diagonal rods and three tripod cross rods, the tripod vertical rods, the tripod horizontal rods and the tripod diagonal rods are connected to form a tripod structure, the end parts of the two tripod structures are respectively connected through the three tripod cross rods, the horizontal diagonal connecting plates are arranged on the upper parts of the bearing tripod, the horizontal diagonal connecting plates are respectively and rigidly connected with the tripod horizontal rods and the tripod cross rods, and the tripod vertical rods and the tripod cross rods are rigidly connected with the tripod support plate, so that the bearing tripod is supported on the tripod support plate.

Preferably, in the foregoing front-mounted steel support system suitable for a small ultra-deep foundation pit, each adjusting support plate is hinged with three adjusting bolts, and the three adjusting bolts are arranged at equal intervals along the horizontal direction.

Preferably, in the foregoing front-mounted steel support system suitable for small-size super deep foundation pit, the steel purlin that front-mounted steel supported encloses includes a plurality of straightness section girder steel and four L shape bight girder steel, a plurality of straightness section girder steel pass through bolted connection mode equipment and form four strip girder steel, and the tip of four strip girder steel passes through L shape bight girder steel and connects and form the steel purlin that is the rectangle, and strip girder steel and corresponding L shape bight girder steel pass through bolted connection mode and connect, the both ends of bight horizontal bracing are connected with the inside wall that the steel encloses the purlin through bight horizontal bracing linkage segment respectively, and every bight that the bight was enclosed to the steel sets up a plurality of bight horizontal bracing that parallels, and two bight horizontal diagonal bracing that parallels that are located the inboard set up a plurality of tie beams, the bight horizontal diagonal bracing upper berth scaffold board of bight serves as the operation platform.

Preferably, in the foregoing front-mounted steel support system suitable for a small ultra-deep foundation pit, the tie beam comprises a tie beam steel beam and two tie beam end connection plates, the two tie beam end connection plates are fixedly arranged at two ends of the tie beam steel beam, through holes for the tie beam U-shaped bolts to pass through are formed in the two tie beam end connection plates, and the corresponding corner horizontal diagonal braces of the tie beam U-shaped bolt hoops are fixed on the corresponding tie beam end connection plates through tie beam connection nuts.

Preferably, in the foregoing front-mounted steel support system suitable for a small ultra-deep foundation pit, the corner horizontal diagonal bracing includes a gusset steel beam, two gusset end connection plates, and a plurality of gusset leg connection channels, the two gusset end connection plates are respectively fixedly disposed at two ends of the gusset steel beam, the gusset leg connection channels are symmetrically disposed on two sides of the gusset steel beam in pairs at equal intervals along a longitudinal direction of the gusset steel beam, bolt holes for connecting corresponding corner horizontal diagonal bracing connection sections are formed in the two gusset end connection plates, and a plurality of bolt holes for connecting corresponding adjustable gussets are formed in the gusset leg connection channels at intervals; the horizontal bracing linkage segment of bight includes linkage segment girder steel, linkage segment gusset connecting plate and linkage segment steel and encloses the purlin connecting plate, linkage segment gusset connecting plate and linkage segment steel enclose the purlin connecting plate and just connect respectively in the both ends of linkage segment girder steel, the linkage segment steel encloses purlin connecting plate slant setting, the vertical setting of linkage segment gusset connecting plate, the linkage segment steel encloses the bolt hole that is used for connecting the steel and encloses the purlin on the purlin connecting plate, the linkage segment gusset connecting plate is offered and is used for connecting the bolt hole of the horizontal bracing of bight that corresponds.

Preferably, in the foregoing front-mounted steel support system suitable for a small ultra-deep foundation pit, the cross section of the straight section steel beam is in a double-web H shape, and is formed by fixedly connecting a straight section steel beam web with straight section steel beam flange plates at two sides; the cross section of the L-shaped corner steel beam is double-web H-shaped, and the L-shaped corner steel beam is formed by fixedly connecting an L-shaped corner steel beam web with L-shaped corner steel beam flange plates on the inner side and the outer side; and a hole is formed in the web plate of the L-shaped corner steel beam, a steel strand anchor is arranged at the hole, and stiffening plates are respectively arranged at two sides of the steel strand anchor.

Preferably, in the foregoing front-mounted steel support system suitable for a small ultra-deep foundation pit, the servo oil cylinder comprises an oil cylinder sleeve, an adjusting cushion block, sleeve hook rollers and an oil cylinder body, the oil cylinder body is arranged in the oil cylinder sleeve, one end of the oil cylinder sleeve is provided with a vertical end plate, an adjusting cushion block for adjusting total elongation of the servo oil cylinder is arranged in the oil cylinder sleeve, the adjusting cushion block is located between the vertical end plate and the oil cylinder body, the upper end of the vertical end plate is provided with a sleeve hook which is downwards opened and is used for being hung against a steel purlin, a plurality of sleeve hook rollers are arranged between the vertical end plate and the sleeve hook, and a bolt hole for connecting the steel purlin is formed in the vertical end plate.

Compared with the prior art, the technical scheme disclosed by the invention has the following beneficial effects:

the invention discloses a front-mounted steel support system suitable for a small ultra-deep foundation pit, which comprises a plurality of lattice columns, a plurality of connecting devices, a front-mounted steel support, a plurality of steel strands, a plurality of through jacks, a plurality of jack foundations, a plurality of steel strand guide frames, a plurality of servo cylinders and a hydraulic system, wherein the front-mounted steel support comprises a steel enclosing purlin and a plurality of corner horizontal diagonal braces arranged at four corners of the steel enclosing purlin, the inner side of each corner of the steel enclosing purlin, which is positioned at the innermost corner, of the steel enclosing purlin is correspondingly provided with one lattice column, the lattice column is pressed into a soil layer in advance according to a design position, each corner of the steel enclosing purlin is connected with the corresponding lattice column through the corresponding connecting device, and the jack foundations are respectively arranged at the four corner positions of a continuous wall head layer ring beam; the penetrating type jack is arranged on the corresponding jack foundation; the steel strand guide frames are arranged on the corresponding jack foundation or the ring beam at the first layer of the continuous wall; the steel strands are erected on the corresponding steel strand guide frames; the steel encloses the medial surface of purlin and the both sides face of the horizontal bracing of bight equidistant a plurality of adjustable supporting angles that set up respectively through bolted connection mode, hydraulic system sets up on diaphragm wall first floor girth or ground or leading-type steel support, a plurality of servo cylinders set up on the lateral surface of steel encloses the purlin along the circumference interval of purlin, a plurality of servo cylinders and a plurality of jack-in type jack are connected with hydraulic system respectively, a plurality of servo cylinders stretch out and draw back under hydraulic system effect, realize the initiative deformation control to the diaphragm wall, a plurality of jack-in type steel support's four bight through corresponding steel strand wires and leading-in type steel support respectively, a plurality of jack-in type steel support's lift is realized through synchronous receipts corresponding steel strand wires under hydraulic system's effect. The front-mounted steel support system provided by the invention can realize a construction method of being arranged in front of a concrete support or a steel support along with the excavation and the descent and the support, effectively shortens the construction period and the super-excavation non-support time, and has the advantages of high mechanization degree, high construction safety, high turnover utilization rate and the like; the front-mounted steel support is integrally lifted by adopting the penetrating jack to be matched with the steel strand, so that the lifting device has the advantages of stable descending, safety, reliability and good synchronism; the adjustable angle brace is arranged on the steel support, so that dead weight of the front-mounted steel support and dead weight of the upper pouring concrete can be effectively transferred to the ground, the front-mounted steel support is kept horizontal, and the servo oil cylinder can be prevented from being subjected to vertical torsion when the servo oil cylinder supports the underground continuous wall in the horizontal direction, so that construction safety and equipment stress rationality are improved.

Drawings

FIG. 1 is a three-dimensional view of a construction state of a front-end steel support system suitable for a small ultra-deep foundation pit.

Fig. 2 is a plan view of a construction state of a front-end steel support system suitable for a small ultra-deep foundation pit.

Fig. 3 is a three-dimensional view of a front-end steel support system suitable for use in a small ultra-deep foundation pit.

Fig. 4 is a three-dimensional view of a lattice column.

Fig. 5 is a front view of the connection device.

Fig. 6 is a top view of the connection device.

Fig. 7 is a side view of the connection device.

Fig. 8 is a three-dimensional view of the connection device.

Fig. 9 is a three-dimensional view of a straight section steel beam.

Fig. 10 is a three-dimensional view of an L-shaped corner steel beam.

FIG. 11 is a three-dimensional view of a servo cylinder.

Fig. 12 is a three-dimensional view of an adjustable foot.

Fig. 13 is a three-dimensional view of a corner horizontal diagonal bracing connection segment.

Fig. 14 is a plan view of a corner horizontal diagonal bracing connection segment.

Fig. 15 is a three-dimensional view of a corner horizontal diagonal brace.

Fig. 16 is a three-dimensional view of a tie beam.

Fig. 17 is a schematic structural view of a method for using a front-end steel support system suitable for small ultra-deep foundation pit in step 1.

Fig. 18 is a schematic structural view of a method for using a front-end steel support system suitable for small ultra-deep foundation pit at step 2.

Fig. 19 is a schematic structural view of a method for using the front-end steel support system for a small ultra-deep foundation pit at step 3.

Fig. 20 is a schematic structural view of a method for using a front-end steel support system suitable for small ultra-deep foundation pit at step 4.

Fig. 21 is a schematic structural view of a method for using a front-end steel support system suitable for small ultra-deep foundation pit in step 5.

Fig. 22 is a schematic structural view of a method for using a front-end steel support system suitable for small ultra-deep foundation pit in step 6.

In the figure:

1. underground continuous wall,

2. A continuous wall first layer ring beam,

3. Lattice column, 31 lattice column angle steel, 32 angle steel connecting plate,

4. The device comprises a connecting device, 401, a tripod supporting plate, 402, connecting angle steel, 403, welding nuts, 404, adjusting bolts, 405, adjusting supporting plates, 406, a lattice column U-shaped bolt, 407, a lattice column connecting plate, 408, a lattice column connecting nut, 409, a tripod vertical rod, 410, a tripod horizontal rod, 411, a tripod diagonal rod, 412, a tripod cross rod, 413, a horizontal diagonal connecting plate, 414, a horizontal diagonal U-shaped bolt, 415, a horizontal diagonal connecting nut, a horizontal diagonal connecting rod, a vertical rod and a horizontal diagonal rod

5. Front-mounted steel support,

51. Straight section steel girder, 511, straight section steel girder web, 512, straight section steel girder flange plate,

52.L-shaped corner steel beam, 521.L-shaped corner steel beam web, 522.L-shaped corner steel beam flange plate, 523.steel strand anchor, 524.stiffening plate,

53. Servo oil cylinder, 531, oil cylinder sleeve, 532, adjusting cushion block, 533, sleeve hook roller, 534, oil cylinder body, 535, vertical end plate, 536, sleeve hook,

54. Adjustable support foot 541, support foot connection board 542, support foot,

55. The corner horizontal diagonal bracing connecting section, 551, connecting section steel girder, 552, connecting section angle brace connecting plate, 553, connecting section steel purlin connecting plate, connecting section steel ring,

56. Corner horizontal diagonal bracing, 561, gusset steel girder, 562, gusset end connecting plate, 563, gusset supporting leg connecting channel steel,

57. Connecting beams, 571, connecting beam steel beams, 572, connecting beam end connecting plates,

58. A U-shaped bolt of a connecting beam,

59. A connecting beam connecting nut,

510. A scaffold board,

6. Steel strand wires,

7. A penetrating jack,

8. Jack foundation,

9. A steel strand guide frame,

10. A concrete support or a steel support,

11. Soil layer,

12. And a concrete cushion layer.

Detailed Description

The invention is described in further detail below with reference to the drawings and the specific examples. The technical contents and features of the present invention will be described in detail below with reference to the attached drawings by way of the illustrated embodiments. It should be further noted that the drawings are in a very simplified form and are all to a non-precise scale, merely for convenience and clarity in aiding in the description of embodiments of the invention. For convenience of description, the "upper" and "lower" described below are consistent with the upper and lower directions of the drawings, but this should not be construed as a limitation of the technical scheme of the present invention.

Referring to fig. 1 to 16, the present embodiment discloses a front-mounted steel support system suitable for a small ultra-deep foundation pit, which comprises a plurality of lattice columns 3, a plurality of connecting devices 4, a front-mounted steel support 5, a plurality of steel strands 6, a plurality of through jacks 7, a plurality of jack foundations 8, a plurality of steel strand guide frames 9, a plurality of servo cylinders 53 and a hydraulic system, wherein the front-mounted steel support 5 comprises a steel enclosing purlin and a plurality of corner horizontal diagonal braces 56 arranged at four corners of the steel enclosing purlin, the inner side of the corner horizontal diagonal brace 56 positioned at the innermost side on each corner of the steel enclosing purlin is correspondingly provided with a lattice column 3, the lattice column 3 is pressed into a soil layer 11 in advance according to a design position, the corner horizontal diagonal brace 56 positioned at the innermost side on each corner of the steel enclosing purlin is connected with the corresponding lattice column 3 through the corresponding connecting devices 4, and the jack foundations 8 are respectively arranged at four corner positions of a continuous wall head layer collar beam 2; the penetrating jack 7 is arranged on the corresponding jack foundation 8; the steel strand guide frames 9 are arranged on the corresponding jack foundations 8 or the continuous wall first layer ring beams 2; the steel strand 6 is erected on a corresponding steel strand guide frame 9; the inner side of steel enclosing purlin and the both sides face of angle portion horizontal bracing 56 pass through bolted connection mode equidistant a plurality of adjustable supporting angles 54 that set up respectively, and hydraulic system sets up on diaphragm wall first floor girth beam 2 or ground or leading type steel support 5, a plurality of servo cylinder 53 set up on the lateral surface of steel enclosing purlin along the circumference interval of steel enclosing purlin, a plurality of servo cylinder 53 and a plurality of through jack 7 respectively with hydraulic system is connected, a plurality of servo cylinder 53 stretches out and draws back under hydraulic system effect, realizes the initiative deformation control to diaphragm wall 1, a plurality of through jack 7 are connected with four angles of leading type steel support 5 through corresponding steel strand wires 6 respectively, a plurality of through jack 7 realize leading type steel support 5's lift through synchronous receipts putting corresponding steel strand wires 6 under hydraulic system's effect. The front-mounted steel support 5 system provided by the invention can realize a construction method of being arranged in front of a concrete support or a steel support 10 along with excavation, descending and supporting, effectively shortens construction period and super-excavation non-supporting time, and has the advantages of high mechanical degree, high construction safety, high turnover utilization rate and the like; the front-mounted steel support 5 is integrally lifted by adopting the penetrating jack 7 and the steel stranded wire 6, so that the lifting device has the advantages of stable descending, safety, reliability and good synchronism; the adjustable angle brace 54 is arranged on the steel support, so that the dead weight of the front-mounted steel support 5 and the dead weight of the upper casting concrete can be effectively transferred to the ground, the front-mounted steel support 5 is kept horizontal, and the servo oil cylinder 53 can be ensured not to bear vertical torsion when supporting the underground continuous wall 1 in the horizontal direction, so that the construction safety and the equipment stress rationality are improved.

Preferably, in the foregoing front-mounted steel support system suitable for a small ultra-deep foundation pit, the front-mounted steel support 5 is located inside the underground diaphragm wall 1, and the front-mounted steel support 5 is assembled below the diaphragm wall first layer ring beam 2, and specifically, the bolt assembly type mounting and dismounting is adopted, so that the mounting and dismounting convenience and the turnover use rate are improved.

Preferably, referring to fig. 5 to 8, in the foregoing front-mounted steel support system suitable for a small ultra-deep foundation pit, the connecting device 4 includes a load-bearing tripod, a tripod support plate 401, two connecting angles 402, a plurality of welding nuts 403, a plurality of adjusting bolts 404, an adjusting support plate 405, two lattice column U-bolts 406, two lattice column connecting plates 407, four lattice column connecting nuts 408, a horizontal diagonal connecting plate 413, two horizontal diagonal U-bolts 414 and four horizontal diagonal connecting nuts 415, the load-bearing tripod is a right-angled triangle structure, the load-bearing tripod has a horizontal plane and a vertical plane, the horizontal diagonal connecting plate 413 is fixedly arranged on the horizontal plane, the tripod support plate is fixedly arranged on the vertical plane, the horizontal diagonal connecting plate 413 is mutually perpendicular to the tripod support plate 401, the two connection angles 402 are vertically disposed on the left and right sides of the tripod support plate 401, the upper and lower parts of the two connection angles 402 are respectively provided with a first through hole (not shown) through which the U-shaped bolt 406 of the lattice column passes, the U-shaped bolts 406 of the two lattice columns are connected with the lattice column connecting nuts 408 through corresponding lattice column connecting plates 407 and lattice column connecting plates 3 after the lattice column 3 is held, the two sides of the horizontal diagonal bracing connecting plates 413 are respectively provided with a row of second through holes (not shown) through which the corresponding U-shaped bolts 414 of the horizontal diagonal bracing pass along the longitudinal direction of the horizontal diagonal bracing connecting plates 413, the two horizontal diagonal bracing U-shaped bolts 414 connect the horizontal diagonal bracing connecting plates 413 with the corner horizontal diagonal bracing 56 through corresponding horizontal diagonal bracing connecting nuts 415, the upper and lower parts of the tripod support plate 401 are respectively provided with a third through hole (not shown), and threaded holes matched with the adjusting bolts 404 are disposed at the third through holes, one end of the adjusting bolt 404 passes through a corresponding threaded hole on the tripod support plate 401 and then is hinged with the adjusting support plate 405 in a ball hinge mode, and the adjusting support plate 405 corresponding to the abnormal movement of the adjusting bolt 404 can be rotated, so that the adjusting support plate 405 is attached to the side face of the lattice column 3. Considering the possibility that the lattice column 3 may have torsion and vertical deflection, the connection is firstly performed by preliminary positioning, so that the horizontal diagonal bracing connecting plate 413 is attached to the bottom surface of the corner horizontal diagonal bracing 56; then the connecting device 4 is rotated, the adjusting bolt 404 is rotated, the two adjusting support plates 405 are attached to the side surfaces of the lattice column 3, and then the connecting device 4 and the lattice column 3 are connected and fixed by adopting the lattice column U-shaped bolts 406, the lattice column connecting plates 407 and the lattice column connecting nuts 408; and then the two horizontal diagonal bracing U-shaped bolts 414 hoop the corner horizontal diagonal bracing 56 and are fastened by the horizontal diagonal bracing connecting nuts 415, so that the connection between the corner horizontal diagonal bracing 56 and the lattice column 3 is realized.

On the other hand, since the horizontal diagonal brace 56 and the connecting device 4 are connected by the horizontal diagonal brace U-shaped bolt 414, after the horizontal diagonal brace connecting plate 413 is attached to the bottom surface of the horizontal diagonal brace 56, the connecting device 4 is rotated to ensure the connection between the lattice column 3 and the connecting device 4 when the lattice column 3 has a torsion deviation and a horizontal position deviation, and since the horizontal diagonal brace connecting plate 413 is provided with a plurality of holes, i.e., two rows of second through holes, the connecting device 4 can be rotated to select the appropriate second through holes to insert the corresponding horizontal diagonal brace U-shaped bolt 414, thereby realizing the connection between the horizontal diagonal brace 56 and the connecting device 4.

On the other hand, because the screws at the two ends of the U-shaped bolt 406 of the lattice column can freely rotate in the corresponding first through holes of the corresponding connecting angle steel 402, and one end of the adjusting bolt 404 passes through the corresponding threaded holes on the tripod support plate 401 and then is hinged with the adjusting support plate 405 in a ball hinge mode through the adjusting bolt 404, the adjusting bolt 404 is rotated, the two adjusting support plates 405 can be attached to the side surfaces of the lattice column 3, the effective force transmission connection, namely the effective supporting connection, of the lattice column 3 and the horizontal diagonal bracing is ensured when the perpendicularity deviation exists in the lattice column 3, and the connecting device 4 can always be in effective supporting connection with the lattice column 3 by means of the adjusting support plate 405, so that the connecting device 4 has high adaptability and can adapt to the embedded errors such as the deviation of the horizontal distance, the plane torsion, the vertical inclination and the like of the lattice column 3.

Moreover, because the adjusting support plate 405 is attached to the side surface of the lattice column 3, the vertical force of the corner horizontal diagonal brace 56 supported by steel can be well transmitted to the lattice column 3, and because the connection between the connecting device 4 and the corner horizontal diagonal brace 56 adopts a U-shaped bolt hoop mode, the connecting device 4 is not restrained in the horizontal direction, the corner horizontal diagonal brace 56 can be effectively prevented from transmitting the horizontal force to the lattice column 3, and the safety is ensured.

In order to improve the rigidity and the bearing performance of the bearing tripod, the bearing tripod comprises two tripod vertical rods 409, two tripod horizontal rods 410, two tripod diagonal rods 411 and three tripod cross rods 412, the tripod vertical rods 409, the tripod horizontal rods 410 and the tripod diagonal rods 411 are connected to form a tripod structure, the end parts of the two tripod structures are respectively connected through the three tripod cross rods 412, the horizontal diagonal connecting plates 413 are arranged on the upper part of the bearing tripod, the horizontal diagonal connecting plates 413 are respectively and rigidly connected with the tripod horizontal rods 410 and the tripod cross rods 412, and the tripod vertical rods 409 and the tripod cross rods 412 are rigidly connected with the tripod support plates 401, so that the bearing tripod is supported on the tripod support plates 401.

Preferably, in the foregoing front-mounted steel support system suitable for a small ultra-deep foundation pit, each adjusting support plate 405 is hinged with three adjusting bolts 404, and the three adjusting bolts 404 are arranged at equal intervals along the horizontal direction, so that the adjusting support plates 405 are tightly attached to the side surfaces of the lattice columns 3, and the force transmission performance between the two is improved.

Preferably, in the foregoing front-mounted steel support system suitable for a small ultra-deep foundation pit, the steel purlin of the front-mounted steel support 5 comprises a plurality of straight section steel beams 51 and four L-shaped corner steel beams 52, the straight section steel beams 51 are assembled to form four strip steel beams in a bolt connection mode, the ends of the four strip steel beams are connected to form a rectangular steel purlin through the L-shaped corner steel beams 52, the strip steel beams and the corresponding L-shaped corner steel beams 52 are connected in a bolt connection mode, two ends of the corner horizontal diagonal braces 56 are respectively connected with the inner side wall of the steel purlin through corner horizontal diagonal brace connecting sections 55, each corner of the steel purlin is provided with a plurality of parallel corner horizontal diagonal braces 56, two parallel corner horizontal diagonal braces 56 positioned on the inner side are provided with a plurality of connecting beams 57, so that the overall stability of the front-mounted steel support 5 is improved, and a scaffold 510 is laid on the corner horizontal diagonal braces 56 to serve as a working platform, so that a constructor can conveniently carry out working construction.

Preferably, in the foregoing front-mounted steel support system suitable for a small ultra-deep foundation pit, the integral platform plate can be arranged on the front-mounted steel support 5, so that the front-mounted steel support system can be used as an operation platform to bear side templates of operators, engineering materials and concrete supports and can be used as a bottom die for pouring the concrete supports on the upper part, thereby avoiding frequent assembly and disassembly of the die carrier, effectively improving the turnover use efficiency of the die carrier, further improving the construction efficiency of the foundation pit and shortening the construction period.

Referring to fig. 4, the lattice column 3 is formed by connecting four lattice column angle steels 31 through a plurality of angle steel connecting plates 32.

Preferably, in the foregoing front-mounted steel support system suitable for a small ultra-deep foundation pit, please refer to fig. 9, the cross section of the straight steel beam 51 is in a double-web H shape, and is formed by fixedly connecting a straight steel beam web 511 with straight steel beam flange plates 512 on both sides; referring to fig. 10, the cross section of the L-shaped corner steel beam 52 is a double-web H-shape, and is formed by fixedly connecting an L-shaped corner steel beam web 521 with L-shaped corner steel beam flange plates 522 on the inner side and the outer side; the L-shaped corner steel beam web 521 is provided with a hole, and a steel strand anchor 523 is arranged at the hole so as to form effective connection between the penetrating jack 7 and the steel purlin, thereby finally realizing stable lifting of the steel purlin and improving construction safety.

Preferably, in the foregoing front-mounted steel support system suitable for a small ultra-deep foundation pit, please refer to fig. 11, the servo cylinder 53 includes a cylinder casing 531, an adjusting pad 532, a casing hanger roller 533, and a cylinder body 534, the cylinder body 534 is disposed in the cylinder casing 531, one end of the cylinder casing 531 is provided with a vertical end plate 535, an adjusting pad 532 for adjusting the total elongation of the servo cylinder 53 is disposed in the cylinder casing 531, the adjusting pad 532 is disposed between the vertical end plate 535 and the cylinder body 534, the upper end of the vertical end plate 535 is provided with a casing hanger 536 which is opened downwards and is used for being hung against the steel purlin, a plurality of casing hanger rollers 533 are disposed between the vertical end plate 535 and the casing hanger 536, and bolt holes for connecting the steel purlin are formed in the vertical end plate 535. Through setting up the cover case couple gyro wheel 533, can make things convenient for servo cylinder 53 to enclose the purlin along the steel, reduce the friction force between the two, after servo cylinder 53 reaches the preset position, can enclose purlin fixed connection with the steel through set up the bolt hole that is used for connecting the steel on the vertical end plate 535.

Preferably, referring to fig. 12, in the foregoing front-mounted steel support system suitable for a small ultra-deep foundation pit, the adjustable support leg 54 includes a support leg connecting plate 541 and a support leg body 542, the support leg connecting plate 541 is fixedly disposed on an upper portion of the support leg body 542, the support leg connecting plate 541 is vertically disposed, and a plurality of bolt holes for adjusting a height of the adjustable support leg 54 are vertically disposed on the support leg connecting plate 541 along a vertical interval, so as to realize a support height of the adjustable support leg 54.

Preferably, in the foregoing front-mounted steel support system suitable for a small ultra-deep foundation pit, please refer to fig. 15, the corner horizontal diagonal brace 56 includes a gusset steel beam 561, two gusset end connection plates 562, and a plurality of gusset-leg connection channels 563, the two gusset end connection plates 562 are respectively and fixedly disposed at two ends of the gusset steel beam 561, the gusset-leg connection channels 563 are symmetrically disposed on two sides of the gusset steel beam 561 at equal intervals along a longitudinal direction of the gusset steel beam 561, the two gusset end connection plates 562 are provided with bolt holes for connecting the corresponding corner horizontal diagonal brace connection sections 55, and the gusset-leg connection channels 563 are provided with a plurality of bolt holes for connecting the corresponding adjustable angle brace 54 at intervals; referring to fig. 13 to 14, the corner horizontal diagonal bracing connecting section 55 includes a connecting section steel beam 551, a connecting section gusset connecting plate 552 and a connecting section steel purlin connecting plate 553, the connecting section gusset connecting plate 552 and the connecting section steel purlin connecting plate 553 are respectively and just connected at two ends of the connecting section steel beam 551, the connecting section steel purlin connecting plate 553 is obliquely arranged, the connecting section gusset connecting plate 552 is vertically arranged, a bolt hole for connecting the steel purlin is formed in the connecting section steel purlin connecting plate 553, and a bolt hole for connecting the corresponding corner horizontal diagonal bracing 56 is formed in the connecting section gusset connecting plate 552, so that detachable connection between the corner horizontal diagonal bracing connecting section 55 and the corner horizontal diagonal bracing 56 and detachable connection between the steel purlin are realized, and the dismounting convenience and turnover use rate are improved.

Preferably, in the foregoing front-mounted steel support system suitable for a small ultra-deep foundation pit, please refer to fig. 16, the tie beam 57 includes a tie beam steel beam 571 and two tie beam end connection plates 572, the two tie beam end connection plates 572 are fixedly disposed at two ends of the tie beam steel beam 571, through holes for passing through the tie beam U-shaped bolts 58 are disposed on the two tie beam end connection plates 572, and after the corresponding corner horizontal diagonal braces 56 are held by the tie beam U-shaped bolts 58, the tie beam end connection plates 572 are fixed on the corresponding tie beam end connection plates 572 through tie beam connection nuts 59, thereby realizing detachable connection between the tie beam 57 and the corner horizontal diagonal braces 56, and improving the convenience of assembly and disassembly and turnover use rate.

The application method of the preposed steel support system suitable for the small ultra-deep foundation pit comprises the following steps:

step 1, please refer to fig. 17 with emphasis, finish the pouring construction of the diaphragm wall 1 and the diaphragm wall first layer ring beam 2, press the lattice column 3 into the soil layer 11 according to the design position, excavate the soil layer 11 to a certain depth, pour the concrete cushion layer 12 on the soil layer 11, set up the jack foundation 8 on the diaphragm wall first layer ring beam 2; and a through jack 7 and a steel strand guide frame 9 are arranged. Further, in the process of excavating the soil layer 11 to a certain depth, earth excavation is performed according to the excavation sequence of the periphery after the middle, and more lattice columns 3 are excavated, so that the connecting device 4 of the horizontal diagonal bracing and the lattice columns 3 is installed, and meanwhile, the earth excavation amount is increased, and the construction safety of a foundation pit is improved.

Step 2, please refer to fig. 18 with emphasis, hang the constituent members of the front-mounted steel support 5 to the concrete cushion 12 through the gap of the ring beam 2 of the first layer of the continuous wall, and finish the assembly of the front-mounted steel support 5, the steel strand anchors 523 are distributed at four corners of the steel purlin of the front-mounted steel support 5, each penetrating jack 7 is connected with the corresponding steel strand anchor 523 on the front-mounted steel support 5 through the corresponding steel strand 6, the plurality of servo cylinders 53 and the plurality of penetrating jacks 7 are connected with the hydraulic system respectively, adjust the adjustable feet 54 to extend and support on the concrete cushion 12, fine tune the adjustable feet 54 to enable the front-mounted steel support 5 to be horizontal, and drive the servo cylinders 53 to extend through the hydraulic system to apply a certain pressure to the underground continuous wall 1, so as to actively control the deformation of the underground continuous wall 1. The steel support is integrally leveled more conveniently and reliably through the arrangement of the adjustable supporting feet 54, dead weight of the front-mounted steel support 5 can be effectively transferred to the ground, the phenomenon that the servo oil cylinder 53 is subjected to vertical force to twist and damage when the underground continuous wall 1 is horizontally supported is avoided, and construction safety and equipment stress rationality are guaranteed.

Step 3, please refer to fig. 19 with emphasis, a concrete support or a steel support 10 is arranged above the front-mounted steel support 5 according to the design position, meanwhile, the soil layer 11 is continuously excavated, the support-following excavation is realized through the front-mounted steel support 5, and the construction efficiency of the foundation pit is improved;

Step 4, please refer to fig. 20 with emphasis, excavate the soil layer 11 to a certain depth, and pour the concrete cushion layer 12 on the upper part of the soil layer 11;

step 5, please refer to fig. 21 with focus, the servo cylinder 53 is driven by the hydraulic system to shrink, the descending path of the front steel support 5 is checked to ensure no obstacle, the penetrating jack 7 is driven by the pressing system, the front steel support 5 is lowered to a certain distance above the current concrete cushion 12, the front steel support 5 is leveled by the penetrating jack 7, the adjustable support 5454 is adjusted to be supported on the concrete cushion 12, the servo cylinder 53 is driven by the hydraulic system to stretch out, a certain pressure is applied to the underground diaphragm wall 11, the active control of the deformation of the underground diaphragm wall 1 is carried out, each lattice column 3 and the corresponding corner horizontal diagonal brace 56 are connected by the connecting device 4, the construction efficiency of the foundation pit excavation support is improved by using the front steel support 5 as the following support, the excessive excavation non-support time is reduced, and the construction safety of the foundation pit is improved;

and 6, referring to fig. 22, repeating the steps 3 to 5 until the excavation supporting construction of the small ultra-deep foundation pit is completed, and disassembling the front steel support 5 at the bottom layer to hoist the components from the foundation pit.

The principle and effect of the prepositive steel support system suitable for the small ultra-deep foundation pit are as follows: the front-mounted steel support 5 is matched with the underground diaphragm wall 1 and the traditional concrete support or the steel support 10 to form a small ultra-deep foundation pit support system; the front-mounted steel support 5 is arranged in front of the traditional concrete support or the steel support 10, and is supported along with the excavation and the descent, so that the super-excavation unsupported time can be shortened, and the construction safety is enhanced; the servo cylinder 53 is integrated on the front-mounted steel support 5, so that pressure can be applied to the inner wall of the underground diaphragm wall 1, and active control of foundation pit deformation is realized; the front-mounted steel support 5 is integrally slid down by using the through jack 7 and matching with the steel stranded wire 6, so that the stability and safety of landing can be improved; the corner horizontal diagonal braces 56 of the front-mounted steel support 5 are connected by adopting the detachable high-adaptability connecting device 4, so that the overall stability and the construction efficiency are improved; the front steel support 5 is provided with the adjustable supporting feet 54, so that the overall stability can be improved; the working platform is arranged at the upper part of the front-mounted steel support 5, so that the construction convenience is enhanced; the front-mounted steel support 5 members are all of standard modularized design and are assembled, so that the convenience in assembly and disassembly and the turnover utilization efficiency of the members can be effectively improved.

In summary, the servo oil cylinders 53 are arranged around the steel purlin of the front-mounted steel support 5 to realize active control of deformation of the underground diaphragm wall 1, the turnover utilization rate is improved by adopting a modularized assembly design, the construction method of the front-mounted concrete support or the steel support 10 along with the excavation and the descending and the support is adopted to shorten the construction period and the super-excavation and support-free time, and the invention has the advantages of high mechanical degree, high construction safety, high turnover utilization rate and the like. Moreover, (1) the corner horizontal diagonal braces 56 of the front-mounted steel support 5 are connected with the lattice columns 3 by adopting special connecting devices 4, and the connecting devices 4 can adapt to the position errors of the lattice columns 3, can descend along with the front-mounted steel support 5 and can be quickly installed and removed; (2) The penetrating jack 7 is matched with the steel strand 6 to integrally lift the front-mounted steel support 5, so that the lifting device has the advantages of stable descending, safety, reliability and good synchronism; (3) The steel support is provided with the adjustable angle brace 54, so that the dead weight of the front-mounted steel support 5 and the dead weight of the upper casting concrete can be effectively transferred to the ground, the front-mounted steel support 5 is kept horizontal, and the servo oil cylinder 53 can be ensured not to bear vertical torsion force when supporting the underground continuous wall 1 in the horizontal direction, thereby improving the construction safety and the equipment stress rationality; (4) The integral platform plate is arranged on the front-mounted steel support 5, so that the front-mounted steel support can be used as an operation platform for bearing operators, engineering materials and side templates of the concrete support and can be used as a bottom die for casting the concrete support on the upper part, frequent assembly and disassembly of the die carrier can be avoided, the turnover utilization efficiency of the die carrier is effectively improved, the construction efficiency of a foundation pit is further improved, and the construction period is shortened.

The above description is only illustrative of the preferred embodiments of the present invention and is not intended to limit the scope of the present invention, and any alterations and modifications made by those skilled in the art based on the above disclosure shall fall within the scope of the appended claims.

Claims (10)

1. The front-mounted steel support system is characterized by comprising a plurality of lattice columns, a plurality of connecting devices, a front-mounted steel support, a plurality of steel strands, a plurality of through jacks, a plurality of jack foundations, a plurality of steel strand guide frames, a plurality of servo cylinders and a hydraulic system, wherein the front-mounted steel support comprises a steel enclosing purlin and a plurality of corner horizontal diagonal braces arranged at four corners of the steel enclosing purlin, the inner side of each corner of the steel enclosing purlin, which is positioned at the innermost corner, is correspondingly provided with one lattice column, the lattice column is pressed into a soil layer in advance according to a design position, each corner of the steel enclosing purlin is connected with the corresponding lattice column through the corresponding connecting device, and the jack foundations are respectively arranged at the four corner positions of the continuous wall head layer beam; the penetrating type jack is arranged on the corresponding jack foundation; the steel strand guide frames are arranged on the corresponding jack foundation or the ring beam at the first layer of the continuous wall; the steel strands are erected on the corresponding steel strand guide frames; the steel encloses the medial surface of purlin and the both sides face of the horizontal bracing of bight equidistant a plurality of adjustable supporting angles that set up respectively through bolted connection mode, hydraulic system sets up on diaphragm wall first floor girth or ground or leading-type steel support, a plurality of servo cylinders set up on the lateral surface of steel encloses the purlin along the circumference interval of purlin, a plurality of servo cylinders and a plurality of jack-in type jack are connected with hydraulic system respectively, a plurality of servo cylinders stretch out and draw back under hydraulic system effect, realize the initiative deformation control to the diaphragm wall, a plurality of jack-in type steel support's four bight through corresponding steel strand wires and leading-in type steel support respectively, a plurality of jack-in type steel support's lift is realized through synchronous receipts corresponding steel strand wires under hydraulic system's effect.

2. The front-end steel support system for a small ultra-deep foundation pit of claim 1, wherein said front-end steel support is located inside a diaphragm wall, said front-end steel support being assembled below a diaphragm wall head ring beam.

3. The front-mounted steel support system for a small ultra-deep foundation pit according to claim 1, wherein the connecting device comprises a bearing tripod, a tripod support plate, two connecting angles, a plurality of welding nuts, a plurality of adjusting bolts, an adjusting support plate, two lattice column U-shaped bolts, two lattice column connecting plates, four lattice column connecting nuts, a horizontal diagonal connecting plate, two horizontal diagonal U-shaped bolts and four horizontal diagonal connecting nuts, the bearing tripod is a right-angle triangle structure, the bearing tripod has a horizontal plane and a vertical plane, the horizontal diagonal connecting plate is fixedly arranged on the horizontal plane, the tripod support plate is fixedly arranged on the vertical plane, the horizontal diagonal connecting plate is mutually perpendicular to the tripod support plate, the two connecting angles are respectively vertically arranged on the left side and the right side of the tripod support plate, the upper and lower parts of the two connecting angle steels are respectively provided with a first through hole for the passing through of a lattice column U-shaped bolt, the two lattice column U-shaped bolts are connected with the lattice column connecting nuts through corresponding lattice column connecting plates after hooping the lattice column, two sides of the horizontal diagonal bracing connecting plates are respectively provided with a row of second through holes for the passing through of corresponding horizontal diagonal bracing U-shaped bolts along the longitudinal direction of the two horizontal diagonal bracing connecting plates, the two horizontal diagonal bracing U-shaped bolts connect the horizontal diagonal bracing connecting plates with the corner horizontal diagonal bracing through corresponding horizontal diagonal bracing connecting nuts, the upper and lower parts of the tripod supporting plates are respectively provided with a third through hole, threaded holes matched with the adjusting bolts are arranged at the third through holes, one end of each adjusting bolt is hinged with the adjusting supporting plate through a spherical hinge mode after passing through the corresponding threaded holes in the tripod supporting plates, the adjusting bolts can be rotated to correspondingly adjust the supporting plates, so that the adjusting support plate is attached to the side surface of the lattice column.

4. The front-mounted steel support system suitable for the small ultra-deep foundation pit according to claim 3, wherein the bearing tripod comprises two tripod vertical rods, two tripod horizontal rods, two tripod diagonal rods and three tripod cross rods, the tripod vertical rods, the tripod horizontal rods and the tripod diagonal rods are connected to form a tripod structure, the end parts of the two tripod structures are respectively connected through the three tripod cross rods, the horizontal diagonal connecting plates are arranged on the upper part of the bearing tripod, the horizontal diagonal connecting plates are respectively connected with the tripod horizontal rods and the tripod cross rods, and the tripod vertical rods and the tripod cross rods are respectively connected with the tripod support plate in a rigid manner, so that the bearing tripod is supported on the tripod support plate.

5. A front-end steel support system for a small ultra-deep foundation pit as claimed in claim 3, wherein each of the adjusting support plates is hinged with three adjusting bolts which are disposed at equal intervals in a horizontal direction.

6. The preposed steel support system suitable for the small ultra-deep foundation pit according to claim 1, wherein the preposed steel support steel enclosing purlin comprises a plurality of straight section steel beams and four L-shaped corner steel beams, the straight section steel beams are assembled to form four strip steel beams in a bolt connection mode, the end parts of the four strip steel beams are connected to form a rectangular steel enclosing purlin in the L-shaped corner steel beams, the strip steel beams are connected with the corresponding L-shaped corner steel beams in the bolt connection mode, two ends of the corner horizontal diagonal bracing are connected with the inner side wall of the steel enclosing purlin through corner horizontal diagonal bracing connecting sections respectively, each corner of the steel enclosing purlin is provided with a plurality of parallel corner horizontal diagonal bracing, two parallel corner horizontal diagonal bracing positioned on the inner side are provided with a plurality of connecting beams, and a scaffold board is paved on the corner horizontal diagonal bracing to serve as an operation platform.

7. The prepositive steel supporting system suitable for a small ultra-deep foundation pit according to claim 1, wherein the connecting beam comprises a connecting beam steel beam and two connecting beam end connecting plates, the two connecting beam end connecting plates are fixedly arranged at two ends of the connecting beam steel beam, through holes for the connecting beam U-shaped bolts to pass through are formed in the two connecting beam end connecting plates, and the corresponding corner horizontal diagonal bracing of the connecting beam U-shaped bolt hoops is fixed on the corresponding connecting beam end connecting plates through connecting beam connecting nuts.

8. The prepositive steel support system suitable for the small ultra-deep foundation pit according to claim 1, wherein the corner horizontal diagonal bracing comprises a gusset steel beam, two gusset end connection plates and a plurality of gusset and support foot connection channel steels, the two gusset end connection plates are respectively fixedly arranged at two ends of the gusset steel beam, the gusset and support foot connection channel steels are symmetrically arranged on two side surfaces of the gusset steel beam in pairs at equal intervals along the longitudinal direction of the gusset steel beam, bolt holes for connecting corresponding corner horizontal diagonal bracing connection sections are formed in the two gusset end connection plates, and a plurality of bolt holes for connecting corresponding adjustable gussets are formed in the gusset and support foot connection channel steels at intervals; the horizontal bracing linkage segment of bight includes linkage segment girder steel, linkage segment gusset connecting plate and linkage segment steel and encloses the purlin connecting plate, linkage segment gusset connecting plate and linkage segment steel enclose the purlin connecting plate and just connect respectively in the both ends of linkage segment girder steel, the linkage segment steel encloses purlin connecting plate slant setting, the vertical setting of linkage segment gusset connecting plate, the linkage segment steel encloses the bolt hole that is used for connecting the steel and encloses the purlin on the purlin connecting plate, the linkage segment gusset connecting plate is offered and is used for connecting the bolt hole of the horizontal bracing of bight that corresponds.

9. The prepositive steel support system suitable for a small ultra-deep foundation pit according to claim 1, wherein the cross section of the straight section steel beam is in a double-web H shape and is formed by fixedly connecting straight section steel beam webs with straight section steel beam flange plates at two sides; the cross section of the L-shaped corner steel beam is double-web H-shaped, and the L-shaped corner steel beam is formed by fixedly connecting an L-shaped corner steel beam web with L-shaped corner steel beam flange plates on the inner side and the outer side; and a hole is formed in the web plate of the L-shaped corner steel beam, a steel strand anchor is arranged at the hole, and stiffening plates are respectively arranged at two sides of the steel strand anchor.

10. The prepositive steel support system suitable for a small ultra-deep foundation pit according to claim 1, wherein the servo oil cylinder comprises an oil cylinder sleeve, an adjusting cushion block, sleeve hook rollers and an oil cylinder body, the oil cylinder body is arranged in the oil cylinder sleeve, one end of the oil cylinder sleeve is provided with a vertical end plate, an adjusting cushion block for adjusting the total elongation of the servo oil cylinder is arranged in the oil cylinder sleeve, the adjusting cushion block is arranged between the vertical end plate and the oil cylinder body, the upper end of the vertical end plate is provided with a sleeve hook which is downwards opened and is used for being hung against a steel purlin, a plurality of sleeve hook rollers are arranged between the vertical end plate and the sleeve hook, and bolt holes for connecting the steel purlin are formed in the vertical end plate.

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