CN113356223A - Asynchronous decoupling construction method for large foundation pit coupling inner support system - Google Patents
Asynchronous decoupling construction method for large foundation pit coupling inner support system Download PDFInfo
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Abstract
The invention relates to the technical field of building construction, in particular to an asynchronous decoupling construction method for a large foundation pit coupling inner support system, which comprises the following steps: and (3) working condition analysis: analyzing the structural working condition of the basement according to a building construction scheme; decoupling design: setting decoupling models according to the corresponding settings of the support systems at different positions; decoupling and reinforcing measure construction: reinforcing construction is carried out aiming at the weak position of a bearing system of the supporting structure; and (3) carrying out underpinning construction of collision points: performing collision inspection on the basement structure and the inner support lattice column by using a BIM technology, providing a underpinning construction scheme according to the collision inspection result of the lattice column and the structural beam, and performing construction according to the underpinning construction scheme; and (4) removing the inner support in the comprehensive method. The method overcomes a plurality of factors restricting the construction period of dismantling the coupling inner support, accelerates the construction efficiency, saves energy, protects the environment and improves the resource recovery benefit.
Description
Technical Field
The invention relates to the technical field of building construction, in particular to an asynchronous decoupling construction method for a large foundation pit coupling inner support system.
Background
In recent years, large-scale underground spaces have been more developed and utilized. Underground works for various purposes, such as basements, underground malls, parking lots, and the like, are gradually being built more and more. In various foundation pit supporting structure forms, an inner supporting and supporting system is often used in a deep and large foundation pit. The inner support supporting system has high rigidity and small foundation pit deformation, is not limited by insufficient surrounding fields, and can ensure the safety of basement construction, foundation construction and surrounding public facilities close to buildings, subways, roads, underground pipelines and the like. The ring support system is a support arrangement form commonly used in foundation pit engineering, has the advantages of large area of an unsupported area, contribution to earth excavation and underground structure construction, easiness in avoiding vertical members of a main structure and the like, is particularly suitable for foundation pit engineering with an ultra-large area, and can select a specific ring arrangement form according to the shape of a foundation pit and the arrangement of a building plane in practice. When the construction project is two or more high-rise buildings or the foundation pit has different plane shapes, a double-circle or multi-circle coupling system is adopted. The double-ring coupling body is a combined supporting system formed by two ring supports under the common stress action.
The existing circular ring support system has the problem of low demolition efficiency when the concrete inner support is demolished, the next step work cannot be carried out at all before the current work is not finished, the high-speed continuous construction cannot be realized, the construction period is greatly prolonged, the requirement of a construction unit for continuously improving the construction period cannot be met, the existing inner support demolition method has the potential safety hazards of the surrounding environment of a foundation pit caused by the stagnation of main body construction, and the harmful effects restrict the development of the field of inner support demolition to a great extent.
Disclosure of Invention
Features and advantages of the invention will be set forth in part in the description which follows, or may be obvious from the description, or may be learned by practice of the invention.
In order to overcome the problems in the prior art, the invention provides an asynchronous decoupling construction method which can realize high-speed continuous construction, can meet the requirement of continuously improving the construction period of a construction unit and has small influence on the surrounding environment for a large foundation pit coupling inner support system.
An asynchronous decoupling construction method for a large foundation pit coupling inner support system adopts a circular ring support system, and comprises the following steps:
and (3) working condition analysis: analyzing the structural working condition of the basement according to a building construction scheme;
decoupling design: setting decoupling models according to the corresponding settings of the support systems at different positions;
decoupling and reinforcing measure construction: reinforcing construction is carried out aiming at the weak position of a bearing system of the supporting structure;
and (3) carrying out underpinning construction of collision points: performing collision inspection on the basement structure and the inner support lattice column by using a BIM technology, providing a underpinning construction scheme according to the collision inspection result of the lattice column and the structural beam, and performing construction according to the underpinning construction scheme;
removing an inner support in a comprehensive method: and according to different support structures of the support system, performing demolition operation in the formed closed underground chamber by adopting at least one of rope saw demolition, mechanical demolition and blasting demolition methods.
Preferably, the working condition analysis further comprises the steps of establishing a correct foundation pit working condition model by selecting reasonable foundation pit design parameters, and calculating the stress according to the most unfavorable working condition.
Preferably, the setting of the decoupling model comprises the following steps:
respectively analyzing the stress condition of the support system before and after the removal and the deformation condition of the support system after the removal of the support system supported by the support beams at different positions to be removed;
and setting corresponding support dismantling assumed conditions according to the results of the stress condition analysis and the deformation condition analysis.
Preferably, the support removal assumption conditions are as follows:
when the supporting beams are bottom supporting beams, pouring of the raft plates corresponding to the bottom supporting beams is finished, the designed strength is 85%, and the supporting effect of the indwelling supporting system is not influenced after the raft plates are dismantled;
when the supporting beam is an upper supporting beam arranged above the bottom supporting beam, two layers of floor slabs which are arranged below the upper supporting beam and adjacent to the upper supporting beam are poured to reach 85% of the designed strength, and the supporting effect of the indwelling supporting system is not affected after the supporting beam is dismantled.
Preferably, the underpinning construction scheme comprises the following steps:
s1 designing a underpinning structure;
s2, determining the distance B between the underpinning structure and the longitudinal central axis of the lattice column in the BIM model, and determining the B values of the underpinning structures at different positions;
s3, manufacturing a underpinning structure on the ground;
s4, establishing quality assurance measures for the connection and fixation of the underpinning structure;
s5, hoisting the underpinning structure to the working surface of the lattice column to be underpinned, and welding and fixing according to the quality assurance measures.
Preferably, the underpinning structure comprises two main frames which are symmetrically arranged at two sides of the lattice column along the central axis of the lattice column and are arranged in parallel, at least two connecting beams which are used for connecting the two main frames, and lifting lugs arranged at the top of the main frames.
Preferably, because the lattice column is in a stressed state, the underpinning structure and the lattice column are strictly polished and derusted before being welded so as to ensure that the welding is free of impurities; welding from one end of the position to be welded to the other end of the position to be welded in a sectional skip welding mode; the segmented skip welding mode is that each segment of welding line is welded for 100mm, welding is not carried out at intervals of 100mm, and each welding interval is 3-5 min, so that the temperature of the lattice column base metal is ensured to be less than or equal to 100 ℃; and the welding line of the underpinning structure and the lattice column adopts a single welding line so as to reduce the heat input.
Preferably, the rope saw removal is applied to a support beam with a small cross section, and a stirrup is arranged below the support beam before the rope saw removal construction.
Preferably, the mechanical dismantling is applied to lattice column joints of the inner support and positions of the ring beam and the surrounding purlin which cannot be cut; before the ring beam is crushed, a knife is cut at the middle position of the ring support to remove the internal force of the ring support; the mechanical dismantling is to adopt a small and medium pick machine to protect the large bottom plate, and simultaneously, a steel plate is laid on a walking line of the pick machine to protect the raft, and a steel plate is laid below a part to be dismantled, and a wood fragment is laid on the steel plate to protect the structural concrete; the diameter of a concrete block generated by mechanical dismantling is less than or equal to 30 cm; when the enclosing purlins are dismantled, vertically and obliquely crushing the enclosing purlins which are 30cm away from the ground connecting wall, and vertically crushing the enclosing purlins which are 30cm away from the ground connecting wall; when the crushing and dismantling are carried out, special staff need to carry out side station, and the distance between the staff in the side station and the construction position is 10 m.
Preferably, the blasting demolition is applied to demolition of the inner support at a narrow position of the working face; the blasting demolition is implemented in the formed closed underground chamber by adopting a millisecond delay blasting technology; the blasting demolition construction comprises the following steps: 1) arranging blast holes in the construction process of the basement main body structure in an inserting manner; 2) checking the blast hole after the construction of the basement structure is completed; 3) cutting a shock insulation seam; 4) filling explosives into the blast hole; 5) connecting a millisecond delay blasting line control device; 6) detonating and dismantling and clearing the dregs.
The invention has the beneficial effects that:
1. according to the construction method, reasonable design parameters of the foundation pit are selected, a correct foundation pit working condition model is established, stress calculation is carried out according to the most unfavorable working condition, construction is carried out through decoupling and reinforcing measures, the existing coupling inner support system is split into the non-coupling inner support systems with two independent working conditions, the problem that other constructions are carried out after the construction of the coupling inner support system in the prior art is completed is solved, and the construction of the inner support of the foundation pit and the construction of a main body structure can be carried out synchronously.
2. The method is suitable for the removal of various large-scale deep foundation pit coupling inner support systems, is particularly suitable for the removal of foundation pit enclosure reinforced concrete horizontal supports for projects in urban areas with high support concrete strength grade, large square amount and tight construction period, greatly reduces potential safety hazards and quality risks in the construction process of removing the inner supports in the foundation pits, avoids construction period delay caused by site transfer and other difficult conditions, and ensures that the removal construction of the inner supports in the foundation pits and the construction of a main structure can be synchronously carried out.
3. The invention can randomly specify the dismantling amount and the dismantling position of the coupling inner support system, and is convenient and flexible. The method is suitable for the demolition construction of all ultra-deep foundation pit supports, not only can be used for high-efficiency construction in a narrow space, but also can be used for saving the construction cost, and therefore, the method has a great application prospect in the demolition construction of the foundation pit support of the coupling inner support system.
4. The method overcomes a plurality of construction period restricting factors for dismantling the coupling inner support, reduces labor consumption, accelerates construction efficiency, reduces environmental influence and improves resource recovery benefit. The supporting and replacing structure and the comprehensive method inner support dismantling technology are adopted to carry out asynchronous decoupling, 100% recovery of steel materials and reinforcing steel bars used in the original coupling inner support is achieved, the construction efficiency is greatly improved, the construction period is shortened, meanwhile, labor consumption and protection cost are reduced, and the engineering cost is reduced.
Drawings
The advantages and realisation of the invention will be more apparent from the following detailed description, given by way of example, with reference to the accompanying drawings, which are given for the purpose of illustration only, and which are not to be construed in any way as limiting the invention, and in which:
fig. 1 is a flowchart of an asynchronous decoupling method for a large foundation pit coupling inner support system according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a main frame in an asynchronous decoupling construction method for a large foundation pit coupling inner support system according to an embodiment of the present invention;
fig. 3 is a schematic diagram of a main structure partition of an asynchronous decoupling construction method of a large foundation pit coupling inner support system in the embodiment of the invention;
fig. 4 is a cross-sectional view of a south district basement structure of an asynchronous decoupling construction method of a large foundation pit coupling inner support system in an embodiment of the invention;
fig. 5 is a flowchart of a rope saw dismantling method of an asynchronous decoupling method for a large foundation pit coupling inner support system in the embodiment of the invention.
Detailed Description
The embodiments of the present invention will be described in further detail with reference to the drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
In the description of the present invention, "a plurality" means two or more unless otherwise specified; the terms "upper", "lower", "inner", "outer", "top", "bottom", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are simply used for simplifying the description of the present invention, and do not indicate or imply that a particular orientation, configuration, and operation are necessary, and thus, the present invention should not be construed as being limited.
In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "connected" and "connected" are to be interpreted broadly, e.g., as being fixed or detachable or integrally connected; may be mechanically coupled, may be directly coupled, or may be indirectly coupled through an intermediary. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
Detailed description of the preferred embodiment 1
As shown in fig. 1, the invention provides an asynchronous decoupling construction method for a large foundation pit coupling inner support system, wherein the large foundation pit coupling inner support system adopts a ring support system, and the asynchronous decoupling construction method comprises the following steps:
working condition analysis 100: analyzing the structural working condition of the basement according to a building construction scheme;
decoupling design 200: setting decoupling models according to the corresponding settings of the support systems at different positions;
decoupling and reinforcing measure construction 300: reinforcing construction is carried out aiming at the weak position of a bearing system of the supporting structure;
collision point underpinning construction 400: performing collision inspection on the basement structure and the inner support lattice column by using a BIM technology, providing a underpinning construction scheme according to the collision inspection result of the lattice column and the structural beam, and performing construction according to the underpinning construction scheme;
According to the invention, the double-ring or multi-ring inner support system is disassembled into two or more inner support systems through the working condition analysis 100, the decoupling design 200 and the decoupling and reinforcing measure construction 300, so that the technical intermittence time is reduced, the construction efficiency is improved, social resources are saved, the inner support dismantling 500 technology is adopted to accelerate the inner support dismantling construction progress on the premise of ensuring the safety of a foundation pit and the quality safety of a main structure, and the smooth construction of an underground structure is ensured. Through the screening and underpinning construction technology of the BIM technology, collision points between a large number of structural beams and lattice columns in the foundation pit are solved, and potential safety hazards and quality risks in the construction process of removing the inner support of the foundation pit are reduced.
Further, the working condition analysis 100 further includes establishing a correct foundation pit working condition model by selecting reasonable foundation pit design parameters, and performing stress calculation according to the most unfavorable working condition, thereby ensuring construction safety and reducing construction risks. And then, constructing 300 by decoupling and reinforcing measures, and splitting the existing coupling inner support system into two non-coupling inner support systems with independent working conditions, so that the problem that other constructions are carried out after the construction of the removal of the coupling inner support system in the prior art is completed is solved, and the removal construction of the inner support of the foundation pit and the construction of the main body structure can be synchronously carried out.
Further, the setting of the decoupling model comprises the following steps:
respectively analyzing the stress condition of the support system before and after the removal and the deformation condition of the support system after the removal of the support system supported by the support beams at different positions to be removed;
and setting corresponding support dismantling assumed conditions according to the results of the stress condition analysis and the deformation condition analysis.
Further, the support removal assumption conditions are as follows:
when the supporting beams are bottom supporting beams, pouring of the raft plates corresponding to the bottom supporting beams is finished, the designed strength is 85%, and the supporting effect of the indwelling supporting system is not influenced after the raft plates are dismantled;
when the supporting beam is an upper supporting beam arranged above the bottom supporting beam, two layers of floor slabs which are arranged below the upper supporting beam and adjacent to the upper supporting beam are poured to reach 85% of the designed strength, and the supporting effect of the indwelling supporting system is not affected after the supporting beam is dismantled.
Further, the underpinning construction scheme comprises the following steps:
s1 designing a underpinning structure;
s2, determining the distance B between the underpinning structure and the longitudinal central axis of the lattice column in the BIM, namely the parallel distance between the underpinning structure and the longitudinal central axis of the lattice column, and determining the B values of the underpinning structures at different positions;
s3, manufacturing a underpinning structure on the ground;
s4, establishing quality assurance measures for the connection and fixation of the underpinning structure;
s5, hoisting the underpinning structure to the working surface of the lattice column to be underpinned, and welding and fixing according to the quality assurance measures.
Further, the quality assurance measures include the steps of:
(1) all welding sections are kept to be continuously welded as far as possible, and multiple arc blowout and arc starting are avoided; when the connector passes through the fabrication hole at the connecting plate, the connector is required to be conveyed to the center of the connecting plate as far as possible, and the positions of the connector are required to be staggered;
(2) when the welding seam of the same layer stops once or for a plurality of times and needs to be welded again, an initial welding head needs to start arc at a position which is 15mm behind the original arc quenching position, and direct arc starting at the original arc quenching position is forbidden; when the CO2 gas shielded arc is extinguished, the welding gun can be removed after the supply of the shielding gas is completely stopped and the welding seam is completely condensed; prohibiting the electric arc from stopping burning and removing the welding gun to expose the red hot molten pool to the atmosphere to lose CO2 gas protection;
(3) priming a bottom layer: igniting electric arcs on an arc striking plate 50mm in front of the starting point of the welding seam, and then carrying out arc operation for welding construction; when the arc is extinguished, the arc is prevented from being extinguished at the joint, the arc is brought to the arc extinguishing plate which exceeds the joint by 50mm to be extinguished, an arc pit is filled, the arc is transported by adopting a reciprocating arc transporting method, and the arc is slightly stopped at two sides, so that an included angle between the welding meat and the groove is avoided, and the purpose of gentle transition is achieved;
(4) filling layer: before filling welding, a convex part on a first layer of welding bead and a redundant part caused by arc striking are removed, splashes and dust adhered to a slope wall are removed, whether the edge of a groove is not fused or a concave included angle exists or not is checked, and an angle grinder can be used for removing the splashes and the dust if necessary; during CO2 gas shielded welding, the CO2 gas flow is preferably controlled to be 40-55 (L/min), the outer extension of a welding wire is 20-25 mm, the welding speed is controlled to be 5-7 mm/s, a molten pool is kept in a leveling state, a bevel circle drawing method is adopted in a welding method, and when a surface layer of a filling layer is welded, the depth of 1.5-2 mm is required to be uniformly reserved, so that the bevel edge can be conveniently seen when the surface layer is covered;
(5) surface layer welding: because the surface layer welding directly relates to whether the appearance quality of the welding seam meets the quality inspection standard, the whole welding seam is repaired before the welding is started, the concave-convex part is eliminated, the unqualified part is repaired firstly, and the continuous and uniform molding of the welding seam is kept; during the welding of the last welding seam, the undercut defect of the edge of the welding seam of the surface layer is avoided;
(6) in the welding process: the interlayer temperature of the welding seam is controlled to be 100-150 ℃ all the time, the welding process is kept to have the maximum continuity, when the conditions of repairing defects and welding stopping for cleaning welding slag occur in the welding process, the temperature is reduced due to welding stopping, heating treatment is carried out firstly when the welding is continued until the specified value is reached, and then the welding can be continued so as to ensure the welding quality.
Further, the underpinning structure comprises two main frames 410 which are symmetrically arranged at two sides of the lattice column along the central axis of the lattice column and are arranged in parallel, at least two connecting beams which are used for connecting the two main frames 410, and lifting lugs arranged at the top of the main frames 410. The underpinning structure is made of recyclable section steel, all welding seams are connected by fillet welds, and the height of fillet weld leg is 12 mm. After the main frame 410 is assembled, the main frame 410 is lifted to the working surface of the lattice column to be underpinned by a tower crane, and a two-point lifting method is adopted for lifting so as to ensure that the main frame 410 is stable in the lifting process. The underpinning structure of single installation can solve the collision problem of two layers of structural beams.
Further, the main frame 410 includes two vertical rods 411 disposed in parallel, a main beam 412 disposed at two side ends of the vertical rods 411 and connected to the two vertical rods 411, and at least one tie beam 413 disposed in a middle portion of the vertical rods 411. The main frame 410 is made of profile steel so as to be recycled.
Furthermore, because the lattice column is in a stressed state, the underpinning structure and the lattice column are strictly polished and derusted before being welded so as to ensure that the welding is free of impurities; welding from one end of the position to be welded to the other end of the position to be welded in a sectional skip welding mode; the segmented skip welding mode is that each segment of welding line is welded for 100mm, welding is not carried out at intervals of 100mm, and each welding interval is 3-5 min, so that the temperature of the lattice column base metal is ensured to be less than or equal to 100 ℃; and the welding line of the underpinning structure and the lattice column adopts a single welding line so as to reduce the heat input.
Further, the rope saw removal is applied to a support beam with a small cross section, and a stirrup is arranged below the support beam before the rope saw removal construction.
Further, mechanically dismantling lattice column joints applied to the inner supports and positions of ring beams and surrounding purlins which cannot be cut; before the ring beam is crushed, a knife is cut at the middle position of the ring support to remove the internal force of the ring support; the mechanical dismantling is to adopt a small and medium pick machine to protect the large bottom plate, and simultaneously, a steel plate is laid on a walking line of the pick machine to protect the raft, and a steel plate is laid below a part to be dismantled, and a wood fragment is laid on the steel plate to protect the structural concrete; the diameter of a concrete block generated by mechanical dismantling is less than or equal to 30 cm; when the enclosing purlins are dismantled, vertically and obliquely crushing the enclosing purlins which are 30cm away from the ground connecting wall, and vertically crushing the enclosing purlins which are 30cm away from the ground connecting wall; when the crushing and dismantling are carried out, special staff need to carry out side station, and the distance between the staff in the side station and the construction position is 10 m.
Further, the blasting demolition is applied to demolition of the inner support at a narrow position of the working face; the blasting demolition is implemented in the formed closed underground chamber by adopting a millisecond delay blasting technology; the blasting demolition construction comprises the following steps: 1) arranging blast holes in the construction process of the basement main body structure in an inserting manner; 2) checking the blast hole after the construction of the basement structure is completed; 3) cutting a shock insulation seam; 4) filling explosives into the blast hole; 5) connecting a millisecond delay blasting line control device; 6) detonating and dismantling and clearing the dregs. The millisecond delay blasting circuit control device is the prior art and is not described in detail herein. Compared with the conventional blasting technology, the millisecond time-delay blasting technology is implemented in the formed closed underground chamber, and compared with the conventional blasting technology, protective steel plates and other protective measures are not required to be arranged independently, stress waves generated by the explosives are transmitted to the interface of concrete and reinforcing steel bars to be reflected and refracted in the millisecond time-delay blasting process, the reinforcing steel bars and the concrete are completely separated due to the fact that the propagation speeds of the stress waves are different due to different medium densities, the reinforcing steel bars are enabled to be exposed completely without damage, residues are uniformly distributed and dispersed on a lower floor slab, the structural floor slab is hardly affected, the stress waves generated by instantaneous explosion amount of the explosives in the millisecond time-delay blasting process are extremely small, and safety of a high-rise dense area and a civil insurance building around a foundation pit is guaranteed successfully. Because the invention carries on the blasting construction of the internal support beam of concrete in the formed basement, and blast the harmful effect is instantaneous, not only has avoided the noise and vibration that the time produced while mechanically demolishing the internal support is long, have reduced the influence of the peripheral environment, and while carrying on the clear transportation construction to the muck after blasting, all mechanical equipment also carry on the operation in the enclosed space, further avoided the influence of the construction noise after blasting to the peripheral environment, more environment-friendly, compare with traditional internal support demolition process of concrete, the influence to the peripheral environment has been reduced to the minimum; meanwhile, the influence of flying stones and shock waves in conventional support blasting construction is avoided, the pollution of noise and dust is greatly reduced, and the construction period of the main body structure cannot be influenced.
Furthermore, in the support dismantling process, the surrounding environment, the foundation pit deformation, the blasting vibration rate and the blasting vibration frequency are monitored to ensure the safety and the stability of the foundation pit in the implementation process, and warning values shown in the following table 1 are set to strengthen the monitoring and timely know the working condition change in the construction process.
TABLE 1 Foundation pit monitoring content and warning value
Specific example 2
A certain construction project is located in the central core area of an urban area, and the project consists of 2 super high-rise skyscrapers and a high-end business center. The excavation depth of the foundation pit is 22.7m, the total area is 3.4 ten thousand square meters, the perimeter is 810m, and the foundation pit belongs to a deep and large foundation pit. Because the depth of the foundation pit is large, the foundation pit is built near the river, the underground water of the field is rich, the field is positioned in a luxurious zone in the center of a city, and the periphery of the field is provided with the basement of a high-rise building and a subway tunnel, in order to ensure the peripheral environment and the safety of the foundation pit, a double-ring coupling supporting system is adopted, and the asynchronous decoupling construction method of the large foundation pit coupling inner supporting system provided by the invention is adopted for asynchronous decoupling.
Further, operating condition analysis 100: as shown in fig. 3, the construction project is divided into a north area and a south area, and is divided according to the plane of the basement structure and the principles of post-cast strip and the like, and the plane of each area is divided as shown in fig. 3. The area A is a north area, the area D is a south area, the area C is an underground power transformation room, and the area T is a tower. The north area comprises internal support systems A1-A7 and corresponding main towers T1 and D5; the south area comprises an inner support system corresponding to the auxiliary towers T2 and D1-D4.
Further, decoupling design 200: decoupling assumptions are firstly carried out according to support systems at different positions, a decoupling model is set, working conditions of a south area and a north area are respectively combed according to the actual conditions of the construction project to be analyzed, corresponding assumed support detaching conditions are set according to the corresponding working conditions, and the south area is taken as an example for explanation, as shown in table 2 and fig. 3 to 4.
TABLE 2 decoupling design analysis chart
Further, decoupling reinforcement measure construction 300: according to the construction scheme of the construction project, the position of the trestle in the whole north area needs to be subjected to horizontal reinforcement construction, so that the rigidity reduction and the restraint relaxation of the weak position of the stress system of the rest support body supporting structure after decoupling are compensated, and a restraint support is erected at the position 7 of the midspan position of the trestle. In addition, because the bending moment of the ring support of the third support is too large, a reinforcing measure needs to be arranged at the weak position of the third support to restrict the lateral displacement of the third support, and the purpose of reducing the bending moment in the ring support is achieved. And secondly, based on the condition of the completion of the structure of the bottom plate, the bottom plate is used as an inclined throwing support which is arranged on the side part of a third support corresponding to the trestle area.
Further, the collision point underpinning construction 400: the method comprises the steps of performing collision inspection on a basement structure and an inner support lattice column by using a BIM technology, identifying collision types and number, and providing a profile steel underpinning construction scheme aiming at the collision condition of the lattice column and a structural beam; through design calculation, the section steel specification, the installation sequence, the welding requirement and the acceptance standard of the underpinning node are determined, after acceptance, the cutting of the corresponding collision point of the original inner support lattice column at the collision part is started, the cutting principle needs to be strictly controlled according to the range of the design calculation, and the cutting and the strict monitoring need to be carried out simultaneously. The underpinning structure mainly utilizes the high-strength performance and the flexible machinable characteristic of steel, and the welding becomes the substitute member of transmission vertical load on the lattice column rather than colliding, after guaranteeing that the substitute member satisfies the acceptance condition, can cut or open a hole to the lattice column in the former, and the structural beam reinforcing bar can link up smoothly, has guaranteed the integrality of structural beam reinforcing bar and concrete.
Further, the underpinning structure comprises two main frames 410 which are symmetrically arranged at two sides of the lattice column along the central axis of the lattice column and are arranged in parallel, at least two connecting beams which are used for connecting the two main frames 410, and lifting lugs arranged at the top of the main frames 410. All components of this underpinning structure all adopt shaped steel material, and the preferred Q235B of model of shaped steel, and all welds all adopt the fillet weld to connect, and the fillet weld leg height is 12 mm. The main frame 410 includes two parallel vertical rods 411, a main beam 412 disposed at both side ends of the vertical rods 411 and connected to the two vertical rods 411, and at least one connecting beam 413 disposed at the middle portion of the vertical rods 411, and the corresponding section steel specifications are [36a channel steel, [40a channel steel, [14a channel steel.
Further, in order to facilitate the underpinning construction 400 of the interpenetration collision points in the construction process of the basement structure, the installation time of the profile steel underpinning structure needs to be reduced, and the cross influence of working faces is avoided. The profile steel underpinning structure is designed into two main frames 410 which are connected through a connecting beam and symmetrically arranged, the two main frames 410 are named as an A piece and a B piece for facilitating understanding, the two main frames 410 are assembled on the ground and welded well respectively, and the two main frames are hoisted to an operation point after being folded into grids empirically. It should be noted that, the distance between the two main frames 410 and the central axis of the lattice column is B, and the width of the B value at each collision point needs to be measured in the BIM model and the actual positioning, so that the width and size of the section steel at each underpinning position are different, and the stable structure is ensured, and at the same time, the construction space for beam reinforcement installation and beam formwork erection at each collision point is ensured. Hoisting the underpinning structure to a preset position, and after the correction is finished, welding the topmost and bottommost parts of the underpinning structure with the lattice columns to realize temporary fixation; and after the A/B sheets are installed, installing a connecting beam to connect the A sheet and the B sheet into a whole.
Further, the whole installation sequence of the underpinning structure is as follows: determining the B value in the plane and the BIM model → processing the ground of the A/B sheet → hoisting and temporarily fixing the A sheet → hoisting and temporarily fixing the B sheet → installing the A sheet and the B sheet connecting beam → welding the main welding seam.
Further, the overall assembling sequence of the main frame 410 is as follows: erecting an ultra-flat assembled jig frame → installing a vertical rod 411 → installing a main beam 412 → installing a tie beam 413 → acceptance.
Further, support removal 500 in the integrated method: according to the arrangement of engineering construction nodes, the support dismantling belongs to the project of non-critical lines, but because the support system of the double-ring coupling system is complex, the workload of inner support dismantling is large, and if the arrangement cannot be reasonably arranged, the progress of the main structure construction is easily influenced, at least one of rope saw dismantling, mechanical dismantling and blasting dismantling methods is adopted for dismantling operation, so that the progress of the main structure construction is not influenced by the inner support dismantling. Comprehensively analyzing the aspects of working conditions, construction period, environment and the like to obtain an inner support dismantling scheme, namely mechanical dismantling is mainly applied to inner support lattice column nodes, ring beams and surrounding purlins which cannot be cut; the rope saw is dismantled and applied to the whole supporting beam with a smaller section; demolition blasting is applied in locations where access to large mechanical demolition is not available. Different dismantling modes are alternated, as shown in the following table 3, or staggered, or synchronous, or jointly complete the support dismantling operation.
TABLE 3 demolition work method selection and determination
Further, as shown in fig. 5, the construction work of removing the wire saw is performed, and before the construction, the cutting and support removing construction can be performed after stirrups are erected on the lower portions of all the support beams, and the overall support removing sequence is smoothly consistent with the main structure construction. And each concrete support is dismantled by adopting a rope saw cutting and hoisting method to combine construction, and the rope saw cutting, forklift lightering and truck crane outward transportation methods are adopted on the large surface of the support dismantling, so that the size of a cutting unit can be reduced at a local position in order to accelerate the construction period.
The method of mechanical demolition and blasting demolition in this embodiment is the same as the method of embodiment 1, and is not described here again.
The asynchronous decoupling technology provided by the invention overcomes a plurality of construction period limiting factors for detaching the coupling inner support, reduces the labor consumption, accelerates the construction efficiency, reduces the environmental influence and improves the resource recovery benefit; the method solves a series of problems of collision of the coupling inner support on a main body structure, influence of inner support dismantling on the surrounding environment and the like, realizes asynchronous decoupling through optimization of all construction links, realizes 100% recovery rate of the steel bar used by the section steel material and the original coupling inner support, greatly improves construction efficiency, saves construction period, and reduces labor consumption and protection cost.
While the preferred embodiments of the present invention have been illustrated in the accompanying drawings, those skilled in the art will appreciate that various modifications can be made to the present invention without departing from the scope and spirit of the invention. For instance, features illustrated or described as part of one embodiment, can be used with another embodiment to yield a still further embodiment. The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the scope of the present invention, which is defined in the appended claims.
Claims (10)
1. An asynchronous decoupling construction method for a large foundation pit coupling inner support system, wherein the large foundation pit coupling inner support system adopts a ring support system, and is characterized by comprising the following steps:
and (3) working condition analysis: analyzing the structural working condition of the basement according to a building construction scheme;
decoupling design: setting decoupling models according to the corresponding settings of the support systems at different positions;
decoupling and reinforcing measure construction: reinforcing construction is carried out aiming at the weak position of a bearing system of the supporting structure;
and (3) carrying out underpinning construction of collision points: performing collision inspection on the basement structure and the inner support lattice column by using a BIM technology, providing a underpinning construction scheme according to the collision inspection result of the lattice column and the structural beam, and performing construction according to the underpinning construction scheme;
removing an inner support in a comprehensive method: and according to different support structures of the support system, performing demolition operation in the formed closed underground chamber by adopting at least one of rope saw demolition, mechanical demolition and blasting demolition methods.
2. The asynchronous decoupling construction method for the large foundation pit coupling inner support system according to claim 1, wherein the working condition analysis further comprises the steps of establishing a correct foundation pit working condition model by selecting reasonable foundation pit design parameters, and carrying out stress calculation according to the most unfavorable working condition.
3. The asynchronous decoupling construction method for the large foundation pit coupling inner support system according to claim 1, wherein the step of setting the decoupling model comprises the following steps:
respectively analyzing the stress condition of the support system before and after the removal and the deformation condition of the support system after the removal of the support system supported by the support beams at different positions to be removed;
and setting corresponding support dismantling assumed conditions according to the results of the stress condition analysis and the deformation condition analysis.
4. The asynchronous decoupling construction method for the large foundation pit coupling inner support system according to claim 3, wherein the assumed support dismantling condition is as follows:
when the supporting beams are bottom supporting beams, pouring of the raft plates corresponding to the bottom supporting beams is finished, the designed strength is 85%, and the supporting effect of the indwelling supporting system is not influenced after the raft plates are dismantled;
when the supporting beam is an upper supporting beam arranged above the bottom supporting beam, two layers of floor slabs which are arranged below the upper supporting beam and adjacent to the upper supporting beam are poured to reach 85% of the designed strength, and the supporting effect of the indwelling supporting system is not affected after the supporting beam is dismantled.
5. The asynchronous decoupling construction method for the large foundation pit coupling inner support system according to claim 1, wherein the underpinning construction scheme comprises the following steps:
s1 designing a underpinning structure;
s2, determining the distance B between the underpinning structure and the longitudinal central axis of the lattice column in the BIM model, and determining the B values of the underpinning structures at different positions;
s3, manufacturing a underpinning structure on the ground;
s4, establishing quality assurance measures for the connection and fixation of the underpinning structure;
s5, hoisting the underpinning structure to the working surface of the lattice column to be underpinned, and welding and fixing according to the quality assurance measures.
6. The asynchronous decoupling construction method for the large foundation pit coupling inner support system according to claim 5, wherein the underpinning structure comprises two main frames which are symmetrically arranged on two sides of the lattice column along the central axis of the lattice column and are arranged in parallel, at least two connecting beams which connect the two main frames, and lifting lugs arranged at the top of the main frames.
7. The asynchronous decoupling construction method for the large foundation pit coupling inner support system as claimed in claim 6, wherein the underpinning structure and the lattice column are strictly polished and derusted before being welded due to the fact that the lattice column is in a stressed state, so that welding is ensured to be free of impurities; welding from one end of the position to be welded to the other end of the position to be welded in a sectional skip welding mode; the segmented skip welding mode is that each segment of welding line is welded for 100mm, welding is not carried out at intervals of 100mm, and each welding interval is 3-5 min, so that the temperature of the lattice column base metal is ensured to be less than or equal to 100 ℃; and the welding line of the underpinning structure and the lattice column adopts a single welding line so as to reduce the heat input.
8. The asynchronous decoupling method for the large foundation pit coupling inner support system according to any one of claims 1 to 7, wherein the rope saw removal is applied to a support beam with a smaller cross section, and a stirrup is erected below the support beam before the rope saw removal is performed.
9. The asynchronous decoupling construction method for the large foundation pit coupling inner support system according to any one of claims 1 to 7, wherein the mechanical dismantling is applied to lattice column joints of the inner support and positions of ring beams and surrounding purlins which cannot be cut; before the ring beam is crushed, a knife is cut at the middle position of the ring support to remove the internal force of the ring support; the mechanical dismantling is to adopt a small and medium pick machine to protect the large bottom plate, and simultaneously, a steel plate is laid on a walking line of the pick machine to protect the raft, and a steel plate is laid below a part to be dismantled, and a wood fragment is laid on the steel plate to protect the structural concrete; the diameter of a concrete block generated by mechanical dismantling is less than or equal to 30 cm; when the enclosing purlins are dismantled, vertically and obliquely crushing the enclosing purlins which are 30cm away from the ground connecting wall, and vertically crushing the enclosing purlins which are 30cm away from the ground connecting wall; when the crushing and dismantling are carried out, special staff need to carry out side station, and the distance between the staff in the side station and the construction position is 10 m.
10. The asynchronous decoupling construction method for the large foundation pit coupling inner support system according to any one of claims 1 to 7, wherein the blasting demolition is applied to demolition of the inner support at a narrow position of a working face; the blasting demolition is implemented in the formed closed underground chamber by adopting a millisecond delay blasting technology; the blasting demolition construction comprises the following steps: 1) arranging blast holes in the construction process of the basement main body structure in an inserting manner; 2) checking the blast hole after the construction of the basement structure is completed; 3) cutting a shock insulation seam; 4) filling explosives into the blast hole; 5) connecting a millisecond delay blasting line control device; 6) detonating and dismantling and clearing the dregs.
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