CN119121962A

CN119121962A - Steel-concrete composite support structure for large-span deep foundation pit and its construction method

Info

Publication number: CN119121962A
Application number: CN202411518605.XA
Authority: CN
Inventors: 何均; 韩磊; 江帅; 张洪宽; 柴小明; 王修璞; 倪晨
Original assignee: China Construction Eighth Engineering Division Co Ltd
Current assignee: China Construction Eighth Engineering Division Co Ltd
Priority date: 2024-10-29
Filing date: 2024-10-29
Publication date: 2024-12-13
Anticipated expiration: 2044-10-29
Also published as: CN119121962B

Abstract

The invention relates to a steel-concrete combined supporting structure of a large-span deep foundation pit and a construction method thereof, wherein the steel-concrete combined supporting structure comprises steel purlins arranged at the edge of the foundation pit, concrete side truss structures arranged at two opposite sides of the foundation pit, steel supports connected between the concrete side truss structures arranged oppositely, a plurality of steel corner supports arranged at the corners of the foundation pit in an inclined manner, the end parts of the steel corner supports are connected with the corresponding steel purlins and the concrete side truss structures, and an axial force servo system connected to the steel supports and the steel corner supports is used for applying axial force to the steel supports and the steel corner supports. The concrete side truss structure adopted by the invention has better deformability control, is used as a force transmission buffer belt between the prestressed steel support and the envelope structure capping beam, and avoids the problems of cracking, bending, tilting and the like of a foundation pit caused by overlarge centralized axial force.

Description

Steel-concrete combined supporting structure for large-span deep foundation pit and construction method thereof

Technical Field

The invention relates to the field of foundation pit construction engineering, in particular to a steel-concrete combined supporting structure of a large-span deep foundation pit and a construction method thereof.

Background

Along with the rapid promotion of urban progress in China, the number of deep foundation pit projects is also increased sharply, and the deformation control requirements of the foundation pit are also more and more strict. In order to ensure the safety of underground engineering construction, a reasonable and efficient foundation pit engineering supporting scheme is important. The deep foundation pit has the advantages of high water level outside the pit, large supporting span and high deformation control requirement, and the foundation pit supporting requirement is higher than that of other types of deep foundation pits. The traditional reinforced concrete support has strong rigidity, is suitable for different foundation pits, but has poor flexibility and economy, is non-reusable in materials, and is easy to generate safety and environmental problems in the process of installation and dismantling.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, provides a large-span deep foundation pit steel-concrete combined supporting structure and a construction method thereof, and solves the problems that the existing reinforced concrete supporting structure is poor in flexibility and economy, materials are not reusable, safety, environment and the like are easy to generate in the installation and dismantling processes.

The technical scheme for achieving the purpose is as follows:

the invention provides a steel-concrete combined supporting structure of a large-span deep foundation pit, which comprises the following components:

The profile steel surrounding purlin is arranged at the edge of the foundation pit;

concrete edge truss structures arranged on two opposite sides of the foundation pit;

The section steel supports are connected between the oppositely arranged concrete edge truss structures in a supporting way;

the inclined supports are arranged at the corners of the foundation pit and are connected with corresponding steel purlins and concrete side truss structures at the ends of the steel gussets;

and the axial force servo system is connected with the section steel support and the section steel angle support and is used for applying axial force to the section steel support and the section steel angle support.

The invention further improves a large-span deep foundation pit steel-concrete combined supporting structure, which also comprises a plurality of pairs of supporting columns driven into the foundation pit along the arrangement positions of the profile steel supports and the profile steel gussets, wherein a supporting cross beam is connected between the pair of supporting columns, and the supporting cross beam supports the corresponding profile steel supports and profile steel gussets.

The invention further improves a large-span deep foundation pit steel-concrete combined supporting structure, which is characterized in that the concrete side truss structure is provided with a concrete triangular structure corresponding to the section steel support and the section steel angle support, and one side surface of the concrete triangular structure is in butt joint connection with the end parts of the corresponding section steel support and section steel angle support.

The invention further improves a steel-concrete combined supporting structure of a large-span deep foundation pit, which is characterized in that a pair of diagonal braces are arranged at the end part of the section steel support close to the end part of the concrete side truss structure, and the pair of diagonal braces are obliquely supported between the section steel support and the concrete side truss structure.

The invention further improves a steel-concrete combined supporting structure of a large-span deep foundation pit, which is characterized in that a steel triangular structure is arranged on the steel surrounding purlin corresponding to the steel angle brace, and one side surface of the steel triangular structure is in butt joint connection with the end part of the steel angle brace.

The invention also provides a construction method of the steel-concrete combined support structure of the large-span deep foundation pit, which comprises the following steps:

installing a profile steel purlin at the edge of the foundation pit;

Casting concrete edge truss structures on two opposite sides of the foundation pit;

providing a section steel support, and connecting the section steel support between oppositely arranged concrete edge truss structures;

Providing a profile steel angle brace, obliquely supporting the profile steel angle brace at the corner of a foundation pit, and connecting the end part of the profile steel angle brace with a corresponding profile steel enclosing purlin and concrete side truss structure;

And providing an axial force servo system, connecting the axial force servo system on the profile steel support and the profile steel angle support, and applying axial force to the profile steel support and the profile steel angle support by using the axial force servo system.

The invention relates to a construction method of a large-span deep foundation pit steel-concrete combined supporting structure, which is further improved in that before a section steel support and a section steel angle brace are arranged, supporting columns are provided, and the supporting columns are driven into a foundation pit in pairs along the arrangement positions of the section steel support and the section steel angle brace;

And providing a supporting beam, connecting the supporting beam between a pair of supporting columns, and supporting the corresponding profile steel support and profile steel angle support by using the supporting beam.

The invention relates to a construction method of a large-span deep foundation pit steel-concrete combined supporting structure, which is further improved in that when a concrete side truss structure is formed by pouring, steel bars of a concrete triangular structure are arranged at corresponding positions of the side parts of the concrete side truss structure, embedded parts which are in butt joint connection with corresponding section steel supports and the end parts of section steel gussets are arranged at corresponding side surfaces of the concrete triangular structure,

The construction method of the large-span deep foundation pit steel-concrete combined supporting structure is further improved in that a pair of diagonal braces are arranged between the section steel supports and the concrete side truss structure when the section steel supports are arranged.

The invention relates to a construction method of a large-span deep foundation pit steel-concrete combined supporting structure, which is further improved in that when a steel purlin is installed, a steel triangular structure is arranged at a position corresponding to a steel angle support on the steel purlin, and the arranged steel triangular structure is used for connecting the steel angle support.

The steel-concrete combined supporting structure for the large-span deep foundation pit and the construction method thereof have the beneficial effects that:

The concrete side truss structure adopted by the invention has better deformability control, is used as a force transmission buffer belt between the prestressed steel support and the envelope structure capping beam, and avoids the problems of cracking, bending, tilting and the like of a foundation pit caused by overlarge centralized axial force.

According to the invention, the concrete triangular structure is arranged on the side truss structure and is connected with the section steel support, so that the safety coefficient of the joint of the section steel support and the support is increased, and the axial force servo system is arranged on the section steel support, so that the functions of automatically compensating low pressure and automatically alarming high pressure are realized.

The steel-concrete combined supporting structure for the large-span deep foundation pit and the construction method thereof effectively improve the work efficiency, shorten the construction period, save the cost and achieve the purposes of safe and efficient construction.

Drawings

FIG. 1 is a flow chart of a construction method of the steel-concrete combined support structure of the large-span deep foundation pit.

FIG. 2 is a cross section of the connection of a medium-sized steel support and a concrete side truss structure of the large-span deep foundation pit steel-concrete combined support structure.

Fig. 3 is a top view of the steel-concrete composite support structure of the large-span deep foundation pit of the present invention.

FIG. 4 is a schematic layout of axial force servo systems in the steel-concrete combined support structure of the large-span deep foundation pit.

Fig. 5 is a schematic diagram of connection between the concrete triangle structure and the corresponding part of the side truss structure in the steel-concrete combined support structure of the large-span deep foundation pit.

Fig. 6 is a schematic diagram of the arrangement of the reinforcing steel bars inside the concrete triangular structure in the steel-concrete combined support structure of the large-span deep foundation pit.

Fig. 7 is a schematic structural view of an embedded part arranged at a concrete triangle structure in the steel-concrete combined support structure of the large-span deep foundation pit.

Fig. 8 is a model diagram of a steel-concrete combined supporting structure for a large-span deep foundation pit and a bracket arranged in the construction method of the steel-concrete combined supporting structure.

Fig. 9 is a model diagram of a steel-concrete combined supporting structure for a large-span deep foundation pit and an enclosing purlin with installation steel in the construction method thereof.

Fig. 10 is a model diagram of a steel-concrete combined support structure for a large-span deep foundation pit and a method for constructing the same, wherein support columns and cross beams are installed.

FIG. 11 is a cross-sectional view of a support column butt joint in the steel-concrete combined support structure for a large-span deep foundation pit and the construction method thereof.

Fig. 12 is a schematic diagram of a formwork and reinforcement layout of a concrete side truss structure in a large-span deep foundation pit steel-concrete composite supporting structure and a construction method thereof.

Fig. 13 is a schematic view of a steel-concrete combined support structure for a large-span deep foundation pit and a construction method thereof, in which a steel angle brace is installed.

Fig. 14 is a schematic structural view of a steel-concrete combined support structure for a large-span deep foundation pit and a construction method thereof, in which an axial force servo system is installed.

Fig. 15 is a model diagram of a steel-concrete composite support structure for a large-span deep foundation pit of the present invention.

FIG. 16 is a flow chart of installation, use and removal of axial force servo systems in the steel-concrete combined support structure of the large-span deep foundation pit and the construction method thereof.

Detailed Description

The invention will be further described with reference to the drawings and the specific examples.

Referring to fig. 1, the invention provides a steel-concrete combined supporting structure of a large-span deep foundation pit and a construction method thereof, aiming at the construction pain points of the deep foundation pit such as near pipelines, high water level, large span and the like, the traditional technology adopts reinforced concrete support, but has poor flexibility and economy, materials are not recycled, and safety and environmental problems are easy to generate in the process of installation and dismantling. The concrete side truss structure has better deformation control capability, is used as a force transmission buffer belt between the prestress steel combination support and the support beam of the building envelope, avoids the problems of cracking, bending, tilting and the like of a foundation pit caused by overlarge central axial force, adopts single-split vertical second-split steel support for effectively solving the problem of larger deformation of the middle area of the building envelope, is connected with the concrete side truss structure through a force transmission piece, is provided with a concrete triangular structure at the anchoring end of the surrounding purlin and the force transmission piece along the stress direction, increases the safety coefficient of a joint part of the steel support and the support, combines the steel combination support with the axial force servo system, accurately applies prestress, simultaneously applies the second-split steel support up and down, and realizes the functions of low-pressure automatic compensation and high-pressure automatic alarm through 24-hour real-time monitoring of the axial force servo system. The construction method of the steel-concrete combined support for the large-span deep foundation pit effectively improves work efficiency, shortens construction period, saves cost and achieves the aims of safe and efficient construction. The steel-concrete combined supporting structure for the large-span deep foundation pit and the construction method thereof are described below with reference to the accompanying drawings.

Referring to fig. 3, a top view of the steel-concrete composite support structure of the large-span deep foundation pit of the present invention is shown. Participating in FIG. 4, a layout diagram of axial force servo system in the steel-concrete combined support structure of the large-span deep foundation pit is shown. Referring to fig. 15, a model diagram of a large-span deep foundation pit steel-concrete composite support structure of the present invention is shown. The steel-concrete composite support structure for the large-span deep foundation pit of the present invention will be described with reference to fig. 3,4 and 15.

As shown in fig. 3, 4 and 15, the large-span deep foundation pit steel-concrete combined supporting structure comprises a steel purlin 21, a concrete side truss structure 22, steel support 23, steel angle supports 24 and an axial force servo system 25, wherein the steel purlin 21 is arranged at the edge of a foundation pit, the steel purlin 21 is arranged at one side of the foundation pit, the concrete side truss structure 22 is arranged at two opposite sides of the foundation pit, the steel support 23 is arranged at two sides of the steel support 23, the steel support 23 is connected between the oppositely arranged concrete side truss structures 22, the steel angle supports 24 are provided with a plurality of steel angle supports, the steel angle supports 24 are obliquely arranged at corners of the foundation pit, the ends of the steel angle supports 24 are connected with the corresponding steel purlin 23 and the concrete side truss structure 22, and the axial force servo system 25 is connected with the steel support 23 and the steel angle supports 24 and is used for applying axial force to the steel support 23 and the steel angle supports 24.

As shown in fig. 2, before the foundation pit is excavated, an enclosure structure 10 is arranged around the foundation pit, the enclosure structure 10 can adopt structures such as a diaphragm wall or a waterproof curtain, a capping beam 11 is arranged at the top of the enclosure structure 10, a first concrete side truss structure 22 can be constructed after the foundation pit is excavated to a certain depth, and the first concrete side truss structure 22 is connected with the capping beam 11. When the foundation pit is dug to the position of the second support, a concrete enclosing purlin 12 is arranged on the inner side of the enclosing structure 10, and the second concrete edge truss structure 22 is connected with the concrete enclosing purlin 12. The effective secure connection is preferably achieved by implanting the rebar portions of the concrete edge truss structure 22 into the corresponding capping beam 11 and concrete purlin 12.

In one embodiment of the present invention, as shown in fig. 8 and 9, before installing the steel purlin 21, the bracket support 212 is installed on the inner side of the capping beam 11, then the steel purlin 21 is installed on the bracket support 212, and the steel triangle 211 is provided on the steel purlin 21 at the connection position corresponding to the steel gusset 24, and as shown in fig. 13, one side surface of the steel triangle 211 is butt-connected with the end of the steel gusset 24.

In one embodiment of the present invention, as shown in fig. 12 and 15, when constructing the concrete side truss structure, reinforcing bars are bound at corresponding positions and form plates are supported, and then concrete is poured to form the concrete side truss structure.

Further, as shown in fig. 3, the concrete side truss structure 22 is provided with a concrete triangle structure 222 corresponding to the section steel support 23 and the section steel gusset 24, and one side surface of the concrete triangle structure 222 is in butt joint connection with the end parts of the corresponding section steel support 23 and section steel gusset 24.

Referring to fig. 5 and 6, the concrete triangle 222 and the concrete side truss structure 22 are integrally cast, when the formwork and the steel bar of the concrete side truss structure 22 are arranged, the formwork and the steel bar of the concrete triangle 222 are in butt joint with the formwork and the steel bar of the concrete side truss structure 22, specifically, the concrete triangle 222 comprises a plurality of triangular bars 2223, bending angles of the triangular bars 2223 are matched with angles of the concrete triangle 222, the triangular bars are arranged at intervals along the thickness direction of the concrete triangle 222, the concrete triangle 222 further comprises a plurality of U-shaped stirrups 2221, the U-shaped stirrups 2221 are clamped on the triangular bars 2223 and partially extend into the concrete side truss structure 22, the concrete triangle 222 further comprises a plurality of closed stirrups 2222, the closed stirrups 2222 are arranged on the triangular bars 2223 and the U-shaped stirrups 2221, and the setting directions of the closed stirrups 2222 are perpendicular to the setting directions of the U-shaped stirrups 2221.

An embedded part 2224 is arranged on one side surface of the concrete triangular structure 222 connected with the steel angle support 24, and the embedded part 2224 is correspondingly connected with a triangular rib 2223, a U-shaped stirrup 2221 and a closed stirrup 2222 in the concrete triangular structure 222 through a connecting rib 2225. Referring to fig. 7, the embedded parts 2224 are connected with the bolts 2227 by the side plates, the ends of the bolts 2227 are connected with the steel bar connectors 2226, the steel bar connectors 2226 are connected with the embedded bars 2225, and thus the embedded bars 2225 extend into the concrete triangular structure 222.

After the templates and rebars of the concrete delta structure are set, concrete is poured to form the concrete side truss structure 22 and the concrete delta structure 222.

Still further, in order to improve the structural stability of the concrete side truss structure 22, vertical lattice columns 221 are further disposed in the foundation pit, and the vertical lattice columns 221 are provided with a plurality of channels and are propped against the beams corresponding to the concrete side truss structure 22.

In one embodiment of the present invention, as shown in fig. 10 and 15, before the section steel support 23 and the section steel gusset 24 are installed, a plurality of pairs of support columns 261 are driven into the foundation pit along the installation positions of the section steel support 23 and the section steel gusset 24, the support columns 261 are arranged on both sides of the section steel support 23 and the section steel gusset 24 to be installed, and a support cross beam 262 is connected between the pair of support columns 261, and the support cross beam 262 is used for supporting the corresponding section steel support 23 and the section steel gusset 24. I.e. the section steel support 23 and the section steel gusset 24 are arranged, the section steel support 23 and the section steel gusset 24 are placed on the corresponding support beams 262.

Referring to fig. 11, when the support column 261 is driven, the driving depth of the support column 261 needs to be deep to a certain distance below the pit bottom of the foundation pit, so that the support column 261 is formed by butt welding a plurality of steel columns, and when welding is performed, corresponding connecting plates are arranged at joints and meet the welding quality requirement. The support column 261 is formed by connecting a plurality of steel columns, and when the support column 261 is driven in, the welding joint is not formed at the position above the bottom plate elevation of the foundation pit.

In one embodiment of the present invention, as shown in fig. 3, 4 and 15, a pair of diagonal braces 231 is provided at the end of the section steel support 23 near the end of the concrete side truss structure 22, and the pair of diagonal braces 231 are supported between the section steel support 23 and the concrete side truss structure 22 in an inclined manner. The ends of the diagonal braces 231 are fixedly connected with the embedded parts on the corresponding concrete triangular structures 222.

When the section steel support 23 is arranged, the end part of the section steel support 23 is vertically connected with the beam corresponding to the concrete side truss structure 22. The diagonal braces 231 are provided in a direction consistent with the diagonal chords provided on the concrete truss structure 22 to ensure uniformity of force transfer.

In a specific embodiment of the present invention, as shown in fig. 14 and 15, the axial force servo system 25 includes a monitoring station, an operation station, a field control station, a hydraulic servo pump station system, a bus system, a power distribution system, a communication system, a mobile diagnosis system, a compensation section (servo combined booster jack), a wireless distributed numerical control hydraulic station junction box device and a software system (operation platform), and the axial force servo system can be divided into a plurality of wireless distributed numerical control pump stations according to the number of the servo hydraulic jacks, wherein independent control of each numerical control pump station is not affected.

Each numerical control pump station is provided with 4 independent oil path channels, 4 groups of support independent control is realized, and 6 servo oil jack can be controlled by one path channel. The numerical control oil pump of each servo oil jack is internally provided with an oil pressure and displacement sensor so as to realize double control of oil pressure and stroke and achieve the purpose of regulating and controlling the axial force.

The foundation pit is provided with two layers of prestress steel combined supports, a first layer of single-spliced supports and a second layer of double-spliced supports. The prestress steel combination supporting first layer of the servo system is provided with 2 groups, and the second layer is provided with 4 groups. And 6 jacks are used for combined support of the prestress section steel of each group by adopting a servo system. And the support pre-loading axial force is determined empirically according to design values during the construction of each group of supports, and the support axial force is adjusted according to the axial force and deformation monitoring data during the excavation of the foundation pit.

The invention also provides a construction method of the steel-concrete combined support structure of the large-span deep foundation pit, and the construction method is described below.

As shown in fig. 15, the construction method of the present invention includes the steps of:

installing a profile steel purlin at the edge of the foundation pit;

Providing a profile steel angle brace, obliquely supporting the profile steel angle brace at the corner of the foundation pit, and connecting the end part of the profile steel angle brace with a corresponding profile steel enclosing purlin and a concrete side truss structure;

and providing an axial force servo system, connecting the axial force servo system on the profile steel support and the profile steel angle support, and applying axial force to the profile steel support and the profile steel angle support by utilizing the axial force servo system.

The large-span deep foundation pit steel-concrete combined supporting structure is applied to building construction projects at the junction of Qian pond river and Beijing Hangzhou great canal, the construction projects comprise 3 sewage main pipes outside a pit at one side close to the Qian pond river, the bearing state is near 50% of the daily sewage quantity, the distance between the sewage pipes and the excavation edge of a foundation pit is less than 6m, precipitation is forbidden outside the pit for guaranteeing the settlement, the water pressure outside the pit is high, the foundation pit deformation requirement is high, foundation pits of carrier projects are regular, the span reaches 134.5m, the average excavation depth is 14.95m, the pit in part of the pits reaches 6m, the foundation pit span is large, and the excavation depth is deep.

As shown in FIG. 1, the construction method comprises the steps of preparing construction, carefully familiarizing with design drawings, organizing professional subcontracting units to make drawing examination work and obtain intersection summary, carrying out refined design of section steel support by the professional subcontracting units according to the demonstrated intersection summary of the support drawings and the drawings, rechecking the deviation of the constructed vertical building envelope by combining the construction condition of the vertical building envelope before the section steel support is refined, and combining the actual deviation condition to comprehensively plan the section steel support refined design so as to ensure accurate size and reduce closing difficulty during support installation.

The lattice column can be used for the engineering pile, and the section steel column can be inserted on site without the engineering pile.

The bracket mounting and the support column inserting can be synchronously performed.

And the support column is inserted, wherein the support column is made of profile steel, such as I-steel, and needs to be welded in a butt joint mode, so that no welding joint exists at the position above the bottom elevation of the bottom plate. The section steel is directly inserted by a mechanical arm, and the insertion depth, angle, verticality and the like of the section steel are strictly controlled in the construction process, so that the connection of a subsequent bracket and a beam is facilitated. After the pile is inserted into the pile body, two theodolites are mutually intersected to form 90 degrees so as to detect the perpendicularity of the pile body, and the perpendicularity deviation of the pile inserted into the soil is not more than 1% of the pile length. And (3) configuring an S3 level gauge during pile delivery, and marking marks on a pile delivery rod in advance to control pile top elevation (pile top elevation error is controlled to be about +2 cm) and strictly prohibiting overdriving post pulling-up actions. When the section steel upright post pile is inserted, if the section steel upright post pile is not aligned with the pile position, the upright post pile is pulled up and inserted, if the section steel upright post pile is deviated from the pile position due to the underground obstacle, the upright post pile is immediately pulled up, the underground obstacle is cleared, and after the hole is backfilled, the section steel upright post pile is lofted again and inserted. If the section steel can be easily inserted and beaten to the elevation of the designed pile bottom (especially the project of a mucky soil layer), the supervision unit should be reported for the first time, the supervision unit is connected with the support design unit and takes measures for lengthening the upright post, so that the bottom of the section steel upright post is ensured to enter a better soil layer (so as to reduce the sinking of the section steel upright post).

Bracket mounting: the bracket brackets are arranged along the periphery of the foundation pit, the positions and the elevations of the bracket brackets are determined according to the design drawing, the plane elevations (the elevation deviation is not more than +/-2 mm), the profile steel surrounding purlin (central line) on the steel frame is ensured to be in the same horizontal plane and straight and beautiful. Before welding, the bracket needs to thoroughly clean the connection parts (such as embedded parts, H-shaped steel and the like) of rust, greasy dirt, concrete residues and other impurities within the range of not less than 200mm multiplied by 200 mm. The welded bracket support must ensure firm and reliable connection, has enough stability, does not have the phenomenon of torsion and cold joint, and has the elevation controlled within 2mm and the elevation controlled not less than 90 degrees and not exceeding 95 degrees. When the steel bracket is welded, the excavator is required to be used for firmly hanging, positioning and welding, and the hanging can be stopped after the supporting point at the lower part or the upper part is fully welded so as to ensure the operation safety.

And (3) installing the profile steel surrounding purlin, namely setting a datum point and positioning a pull line. Before the purlin is installed, an axis datum point is required to be determined, a total station or a theodolite is used for measuring and measuring the base points on the inner sides of two adjacent corners of the foundation pit through coordinate calculation, and plane installation and positioning are carried out through the base points by adopting a line hanging method. The actual mounting axis deviation is required to be not more than + -10 mm. The wire for pulling is generally a string or cotton wire, the diameter is preferably 0.8-1.0 mm, the distance between the wires is determined on site, the wire plummet is used for centering, the specification is indefinite, the diameter is preferably 25-50 mm, and the falling tip of the wire plummet is accurate so as to aim at the center point. And firmly arranging a hinge bracket at a place beyond the reference center point, hanging a string or cotton thread, straightening the string or cotton thread by using a tensioning force (the tensioning force is 40% -60% of the line breaking force is proper), and marking on the bracket after positioning so as to control the mounting position of the enclosing purlin. The unilateral positioning line of the purlin of the inner side wall of the foundation pit needs to meet the basic requirement of being in a straight line, and the aim is to ensure that the outer side enclosing structure is uniformly stressed after the prestressing force is applied. The installation of the enclosing purlin should follow the principle of 'length before length, reducing the number of joints and staggering joints', and the longer enclosing purlin is preferentially used to reduce the number of joints. The purlin is hoisted section by section along with the erection sequence of the support, the steel purlin is placed on the bracket support by manually matching with the crane, and whether the steel bracket loosens due to collision or not is checked after the purlin is in place, and if the steel bracket loosens, the steel bracket is immediately repaired and welded for reinforcement.

Bracket and beam installation, wherein the installation of the bracket is necessary to control the horizontal elevation of the bracket, and the horizontal elevation of the top surface of the bracket is reversely pushed by the positioning elevation of the angle brace, the opposite support and the H-shaped steel, and the bracket elevation=the central elevation of the supporting structure- (1/2+the height of the beam of the supporting piece). The deviation of elevation of the bracket surface (the deviation of elevation is not more than +/-2 mm) ensures that the elevation of the beam surface supported by the corresponding channel is on the same plane, and the bracket and the steel upright post are fastened by adopting at least 6 high-strength bolts (note that the installation direction of the upright post and the bracket connecting bolt is required to be consistent). The mounting of the bracket requires strict control of perpendicularity, even if the section steel upright is deviated, the bracket must meet the perpendicularity requirement by the addition of a steel plate. If the elevation positioning of the steel upright post deviates, the steel channel can be used for replacing a bracket (a temporary adjustment mode) to be connected with the supporting beam, when the supporting beam and the original bracket are used for forming holes on site by using oxygen acetylene, the size of the aperture is controlled, the slipping of the bolt after being stressed is avoided, the bracket piece after being installed is firmly fastened with the steel upright post pile, and the torque of the friction type high-strength bolt is required to meet the specified requirement. The elevation deviation of the bracket surface of each steel upright post must not exceed 5mm. After the bracket is installed and the elevation of the surface is rechecked, the beam can be installed, the specification of the beam meets the requirement of a design drawing, butt joints (the materials are checked and accepted one by one when entering the field), and the span of the beam cannot be increased without permission when the positioning and the adjustment of the profile steel upright posts (the members such as structural beams, walls and columns are avoided).

The construction of the concrete side truss structure comprises the construction of a capping beam (enclosing purlin), a concrete triangle and a steel support according to a detailed view of a connecting node. And pouring after the reinforcement is bound, the installation of the reinforcement embedded part is completed and the experience is passed.

And (3) installing the section steel support and the section steel angle support, wherein before installing each section steel combined support beam, the section steel combined support beam is pre-spliced on the ground and the straightness of the pre-spliced support is checked, the eccentricity of the central lines of two ends (including a jack and a TO component) of the spliced support is controlled within 2cm, and the section steel combined support beam is integrally hoisted into position according TO the position after being checked TO be qualified. The project without pre-splicing condition on site should adopt total station (theodolite) to locate, and make control line of supporting beam on the crossbeam, then from one end (over 100m, from both ends) along the control line to make pre-splicing, and must ensure that the sectional steel combined supporting beam is straight in plane. In the pre-splicing process, WA components, special jacks, TO components and the like are firmly connected through high-strength bolts, and cross locks of the special jacks are arranged in the middle, namely three wire spaces are reserved in the front and the rear, so that the pre-stress is conveniently removed during the dismantling process. In the assembly process of the section steel combined support beam, if the SC is placed in a neutral gear and redundant space exists, a steel plate pad with corresponding thickness is required to be closely attached, so that the whole support system is prevented from being eccentric after being stressed. The section steel combined support beam is assembled in place, and is temporarily connected with the cross beam by adopting a hoop before pressurization, and after the section steel combined support beam is inspected to be qualified, the joint bolt can be fastened.

The installation, use and dismantling flow of the axial force servo system is shown in figure 16, and equipment debugging is carried out, namely after the system is electrified, the system is respectively tested for upward pressure, pressure maintaining, electromagnetic valve switching, manual loading, automatic loading, communication distance and the like, so that the normal equipment of the pump station is ensured.

Lifting and installing a jack, namely, supporting section steel related to axial force servo, and assembling according to the node structure requirement of a servo part during the installation of the support, and after the following requirements are met, positioning the jack at the center of a pressurizing piece:

① A cross beam (generally realized by a cross beam of a cross frame) is arranged below the support piece of the servo node part, so that the support node part is ensured not to sink under the action of dead weight;

② The pressurizing piece at the servo node part is naturally contacted with the force-retaining box or the gap is not more than 5mm (the width of the force-retaining box is 400mm, the size of the servo oil jack is phi 455 multiplied by 359 mm), and the force-retaining box is connected with the pressurizing piece by bolts with the length not less than 200mm (all bolts cannot be fastened and the same large telescopic space should be kept);

③ The joints of other supports except the servo nodes are tight (gaps exist, and wedge iron is plugged before pressurization) so as to avoid unbalanced stress of the support parts caused by the gaps during pressurization;

④ The horizontal supporting piece is connected with the beam part by adopting a hoop (so as to avoid lateral deflection of the beam when the beam is pressurized), and other supporting pieces (including channel steel and cover plates) are fastened in place by bolting.

And the oil pipe data line is connected with the data line, and the oil pipe and the data line are connected from the corresponding oil way and the data interface on the pump station and reach the jack part along the side edge and the supporting side edge of the vertical enclosure structure. And installing an ultrasonic sensor, enabling the end face of the ultrasonic sensor to be flush with the installation end face, then connecting a displacement line, and observing whether an indicator lamp of the ultrasonic sensor is normal or not. And then connecting an oil pipe, connecting an oil inlet pipe with the lower cavity of the jack, connecting an oil return pipe with the upper cavity of the jack, and adding a gasket. The displacement line and the oil pipe are then tied up on the support head by the tie-up so that the joint is not in a stressed state.

After the jack is in place and before the axial force is applied, the two sides of the jack in the 0 stroke state are firmly attached with pressing pieces (the gap is not more than 5mm, and the condition of insufficient pressing in the maximum stroke is easily caused when the gap is overlarge), the oil pressure is regulated to enable the piston of the jack to prop against the pressing pieces until the axial force is generated, and at the moment, when the stroke of the piston is larger, the piston is regulated through wedge iron.

Setting a shaft force control value, namely after pressurization is carried out to a design preset value, setting a shaft force design value, an upper limit design alarm value, and the like under each design working condition in a central monitoring system according to design requirements, and setting the upper limit value and the lower limit value according to the design requirements when the design has the requirements. When the design has no requirement, the upper limit alarm value is set to 1.05-1.1 times of the support preset value (the upper limit is set to 1.3-1.5 times of the support preset value when the support preset value is used for the muddy soil layer), and the lower limit alarm value is set to 0.85-0.95 times of the support preset value (the lower limit is set to 1.0 times of the preset value when the support preset value is used for the muddy soil layer).

And in the field measurement and control, the system measurement and control adopts closed-loop continuous measurement and control, and if the measurement and control mode is changed, approval of a design unit is required. And the system is monitored and controlled by manual monitoring, and monitoring in a monitoring room and manual inspection are carried out. The monitoring room ensures 24 hours of personnel duty (or remote on-line duty) and reacts to the first time of data abnormality.

And releasing pressure and returning to the field, namely releasing pressure after the support dismantling instruction is obtained, wherein a step-by-step unloading mode is adopted to avoid local deformation and cracking of the structure caused by excessive instantaneous prestress release, the unloading is divided into three steps, and the jack piston is retracted when the pressure is released to 0.

Support is dismantled, demolishs the principle:

(1) The side truss is removed according to the principle of 'first support replacement and then support removal', the support replacement structure strength reaches 100%, and support removal can be carried out.

(2) According to the principle of 'first angle brace, then opposite support and first length and then short' of angle brace, each support is totally dismantled by adopting the principle of 'symmetrically dismantling, first secondary component and then primary component', gradually retreating from small to large and sequentially proceeding from the middle to two ends.

(3) And the side close to the subway tunnel and the sewage main pipe is dismantled by adopting a static cutting method in order to ensure the safety of the foundation pit and reduce disturbance to the surrounding environment.

Support and release pressure:

(1) The support pressure relief is carried out slowly and in batches (50% of the pressure relief is carried out firstly, and then the pressure relief is carried out to zero after 1 hour of stabilization), and the rapid pressure relief is forbidden.

(2) If the abnormal conditions such as the cracking of the floor slab force transmission belt or the capping beam are found during the pressure relief, the pressure relief should be stopped, and if the monitoring data is abnormal, the pressure should be temporarily restored.

In one embodiment of the invention, the support columns are provided before the section steel supports and the section steel gussets are arranged, and the support columns are driven into the foundation pit in pairs along the arrangement positions of the section steel supports and the section steel gussets;

In one specific embodiment of the invention, when the concrete side truss structure is formed by pouring, reinforcing steel bars of the concrete triangular structure are arranged at corresponding positions of the side parts of the concrete side truss structure, embedded parts which are in butt joint connection with corresponding section steel supports and the end parts of the section steel angle supports are arranged at corresponding side surfaces of the concrete triangular structure,

In one embodiment of the invention, when the section steel support is provided, a pair of diagonal braces are provided between the section steel support and the concrete edge truss structure.

In one specific embodiment of the invention, when the profile steel purlin is installed, a steel triangular structure is arranged on the profile steel purlin corresponding to the position of the profile steel angle support, and the arranged steel triangular structure is used for connecting the profile steel angle support.

The present invention has been described in detail with reference to the embodiments of the drawings, and those skilled in the art can make various modifications to the invention based on the above description. Accordingly, certain details of the illustrated embodiments are not to be taken as limiting the invention, which is defined by the appended claims.

Claims

1. The utility model provides a long-span deep basal pit steel-thoughtlessly makes up bearing structure which characterized in that includes:

2. The long-span deep foundation pit steel-concrete composite supporting structure of claim 1, further comprising a plurality of pairs of support columns driven into the foundation pit along the arrangement positions of the section steel supports and the section steel gussets, wherein a support cross beam is connected between the pair of support columns, and the support cross beam supports the corresponding section steel supports and section steel gussets.

3. The long-span deep foundation pit steel-concrete combined supporting structure according to claim 1, wherein the concrete side truss structure is provided with a concrete triangle structure corresponding to the section steel support and the section steel angle brace, and one side surface of the concrete triangle structure is in butt joint connection with the end parts of the corresponding section steel support and section steel angle brace.

4. The long-span deep foundation pit steel-concrete composite supporting structure of claim 1, wherein the end of the section steel support is provided with a pair of diagonal braces near the end of the concrete side truss structure, and a pair of diagonal braces are supported between the section steel support and the concrete side truss structure in an inclined manner.

5. The long-span deep foundation pit steel-concrete combined supporting structure according to claim 1, wherein the steel triangular structure is arranged on the steel section enclosing purlin corresponding to the steel section angle support, and one side surface of the steel triangular structure is in butt joint connection with the end part of the steel section angle support.

6. The construction method of the steel-concrete combined supporting structure of the large-span deep foundation pit is characterized by comprising the following steps of:

installing a profile steel purlin at the edge of the foundation pit;

7. The construction method of the long-span deep foundation pit steel-concrete combined supporting structure according to claim 6, wherein the supporting columns are provided before the section steel supports and the section steel gussets are arranged, and the supporting columns are driven into the foundation pit in pairs along the arrangement positions of the section steel supports and the section steel gussets;

8. The construction method of the large-span deep foundation pit steel-concrete combined supporting structure according to claim 6, wherein when the concrete side truss structure is formed by pouring, steel bars of a concrete triangular structure are arranged at corresponding positions of the side parts of the concrete side truss structure, and embedded parts which are in butt joint with corresponding section steel supports and the end parts of the section steel corner supports are arranged at corresponding side surfaces of the concrete triangular structure.

9. The method of constructing a steel-concrete composite support structure for a large-span deep foundation pit according to claim 6, wherein a pair of diagonal braces are provided between the section steel support and the concrete side truss structure when the section steel support is provided.

10. The construction method of the large-span deep foundation pit steel-concrete combined supporting structure according to claim 6, wherein when the steel purlin is installed, a steel triangular structure is arranged on the steel purlin corresponding to the steel angle support, and the steel angle support is connected by the arranged steel triangular structure.