CN117027495A - Construction method for dismantling steel-concrete combined inner support of deep foundation pit - Google Patents

Abstract

The invention discloses a construction method for dismantling the inner support of a deep foundation pit steel-concrete combination, which includes the following steps: placing a temporary support under the reinforced concrete support in the foundation pit, using static cutting to remove the reinforced concrete support and hoisting it to a temporary stacking position; Unload the pre-loaded axial force of the steel supports step by step, and use gas cutting to cut off the steel supports from the vertical enclosure structure and hoist them to the temporary stacking position; use static cutting and demolition as the main method, supplemented by mechanical demolition. Method: Dismantle the middle partition wall structure layer by layer in a top-down order. This invention optimizes the removal process of steel-concrete composite internal supports in deep foundation pits, and uses static cutting to remove concrete supports, crown beams, pit connecting walls, and middle partition walls, thereby reducing the impact of vibration on the surrounding environment and ensuring construction It is safe and has high promotion value.

Description

Construction method for dismantling steel-concrete composite internal supports in deep foundation pits

Technical field

The invention relates to the technical field of foundation pit dismantling construction, and in particular to a construction method for dismantling steel-concrete composite internal supports in deep foundation pits.

Background technique

With the development and utilization of urban underground space, more and more underground civil air defense projects, underground garages, and urban infrastructure are being constructed. During the construction of underground engineering foundation pits, surrounding buildings and municipal facilities need to be protected to ensure that construction and municipal facilities are protected. For the normal and safe use of facilities, proper and effective support measures are required. Because the steel-concrete composite internal support has high stiffness, small deformation, and convenient construction, it is a commonly used support structure form for deep foundation pit support of underground projects in coastal soft soil areas. The reinforced concrete internal support in deep foundation pits is a temporary construction measure for the construction of the main structure of the underground project. It needs to be dismantled in time with the construction of the main structure of the underground project, and necessary "bracing replacement" is carried out to ensure the smooth construction of the main structure of the underground project. Engineering shows that the maximum deformation value of most deep foundation pit supporting structures is not during the excavation stage, but during the support removal stage. Previous studies only considered the deformation produced during the excavation stage of the foundation pit and ignored the impact of support removal on the deformation of the foundation pit, which in turn led to greater safety hazards in engineering construction.

At present, the commonly used foundation pit support removal technologies mainly include blasting and hydraulic hammer removal. Among them, blasting and demolition have hazards such as flying rocks, shock waves and vibrations, and can easily have a greater impact on the main body of the project and the surrounding environment. Therefore, safety measures are required. Protective racks require high manpower and material costs. At the same time, this technology is highly professional and requires approval from relevant departments, and the approval procedures are cumbersome. Hydraulic hammer demolition technology has a long construction period and is prone to continuous noise during the construction process, which has a great impact on surrounding residential areas. At the same time, the mechanical power is large, the vibration is strong, and the mechanical crushing is large, which will affect the reserved steel bars on the floor.

Contents of the invention

In order to overcome the defects existing in the prior art, the present invention provides an efficient construction method for dismantling steel-concrete composite internal supports in deep foundation pits, which improves the safety of support dismantling and avoids adverse effects on surrounding building facilities.

In order to achieve the above object, the present invention provides a construction method for dismantling the steel-concrete composite internal support of a deep foundation pit, which is used to dismantle the steel-concrete composite internal support system of a deep foundation pit. The internal support system includes a horizontal support on the deep foundation pit. A horizontal support structure in the foundation pit and a middle partition wall structure vertically supported in the deep foundation pit. The horizontal support structure includes a reinforced concrete support connected to the enclosure structure of the deep foundation pit and a reinforced concrete support fixedly connected to the reinforced concrete The supporting steel support, the dismantling construction method includes the following construction steps:

Place temporary supports under the reinforced concrete supports in the foundation pit, use static cutting to remove the reinforced concrete supports and hoist them to the temporary stacking position;

Unload the pre-loaded axial force of the steel support step by step, cut the steel support from the vertical enclosure structure, and hoist it to the temporary stacking position;

The middle partition wall structure will be dismantled layer by layer in a top-down order using a demolition method that mainly involves static cutting and demolition, supplemented by mechanical demolition.

Preferably, when the reinforced concrete support is dismantled, a gas cutting gun is used to cut off the steel bars on both sides of the reinforced concrete support.

Preferably, before the reinforced concrete support is dismantled, a steel wire rope is stretched on the upper part of the reinforced concrete support, the upper steel pipe protection is removed, and the cutting line is placed.

Preferably, the temporary support is a horse stool support bracket, and two horse stool support brackets are provided below each section of the reinforced concrete support, and the horse stool support bracket is in contact with the reinforced concrete support. A gap is reserved between them, and a filler is provided in the gap.

Preferably, when the steel support is dismantled, gas cutting is used to cut off the brackets and force transmission parts connecting the steel support and the vertical enclosure structure.

Preferably, when the middle partition wall structure is dismantled, the following steps are included:

Set bracing columns between both sides of the central partition wall structure and the frame columns of the main structure;

Remove the vertical support racks within the range from the middle partition wall structure to the frame columns of the main structure on both sides; use the jump method to connect the middle partition wall structure with the main structure on both sides in the order of first two sides to the middle, and then the middle to both sides. Floor slabs are cut;

The connecting floors are constructed in sections to connect the main structural floors on both sides of the middle partition wall structure, and the supporting columns are removed and replaced at each floor.

Due to the adoption of the above technical solutions, the present invention has the following beneficial effects:

1) By combining a variety of single internal support removal methods, the shortcomings of traditional single internal support removal in foundation pits are made up, and can be applied to a wider range of foundation pit projects. Compared with traditional construction methods, the There is less construction waste and noise, and the steel supports can be recycled after being dismantled to avoid waste of resources, meet the green construction concept advocated by the country, and have the advantages of safety, economy and speed.

2) Carry out local, graded and segmented demolition of the internal supports of the deep foundation pit steel-concrete combination, and use static cutting methods to remove the concrete supports, crown beams, sub-pit ground connecting walls and middle partition walls, and use diamond chains The saw is used with a drilling machine to cut concrete, and a gas cutting gun is used to cut the steel bars on both sides of the support to avoid adverse effects of vibration on surrounding construction facilities.

3) When dismantling the steel support, use a step-by-step unloading method to unload the pre-loaded axial force, which can effectively avoid local deformation and cracking of the structure caused by excessive instantaneous pre-loaded stress release.

4) Use a manual hoist to lift the bracket, then take out the high-strength bolts, and use the hoist to place them on the floor and transport them to the temporary storage area. This has a high degree of automation and is conducive to shortening the construction period.

5) Use gas cutting to cut off the brackets and force transmission parts welded to the vertical enclosure structure, so that the steel can be recycled and have high economic benefits.

6) Compared with traditional construction methods, less construction waste and noise are generated during the construction process. The steel supports can be recycled after being dismantled, avoiding waste of resources, meeting the green construction concept advocated by the country, and having good economic and social benefits. benefit

Description of the drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without exerting creative efforts.

Figure 1 is a process flow chart of the construction method for dismantling the inner support of the deep foundation pit steel-concrete combination according to the present invention.

Figure 2 is a plan layout diagram of the dismantling sequence of the foundation pit steel combined support in the present invention.

Figure 3 is a schematic diagram of the connection relationship between the reinforced concrete support and the steel support in a preferred embodiment of the present invention.

Figure 4 is a cross-sectional view of the force-transmitting component of the back-cast belt of the mid-sole plate of the present invention.

The corresponding relationship between the numbers in the attached drawing is as follows:

1C1, 1C2, 1C3, 1C4, 1C5, 1C6 - first-floor foundation pit corner braces; 1C7, 1C8, 1C9 - first-floor foundation pit corner braces; 2C1, 2C2, 2C3, 2C4, 2C5, 2C6 - second-floor foundation pit corner braces ; 2C7, 2C8, 2C9-Second-story foundation pit supporting; 3-Demolition sequence; 4-Bottom plate; 5-Head plate; 6-Waterproof steel plate; 7-I-beam; 8-Reinforced concrete support; 91-No. One section steel support; 92 - the second section steel support; 101 - the first purlin; 102 - the second purlin; 11 - trestle bridge; 12 - trestle board; 13 - top beam; 14 - lattice column.

Detailed ways

The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted here that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

The technical problem to be solved by this invention is that the currently commonly used foundation pit support removal technology mainly consists of two methods: blasting demolition and hydraulic hammer demolition. Blasting demolition has hazards such as flying rocks, shock waves and vibrations, and is easy to cause damage to the project body and the surrounding environment. It has a large impact and requires the erection of safety protection frames. The cost of manpower and material resources is high. The technology is highly professional and needs to be approved by relevant departments, and the approval procedures are cumbersome. Hydraulic hammer demolition technology has a long construction period and is prone to continuous noise during the construction process, which has a great impact on surrounding residential areas. At the same time, the mechanical power is large, the vibration is strong, and the mechanical broken pieces are large, which will affect the reserved steel bars on the floor. Therefore, a construction method for the removal of steel-concrete composite internal supports in deep foundation pits is provided, which reduces the construction cost and avoids the need for demolition. The bracing caused excessive deformation of the enclosure structure, ensuring construction safety. At the same time, static cutting was used to remove the concrete supports, crown beams, pit-to-ground connecting walls and middle partition walls, reducing the impact of vibration on the surrounding environment.

Referring to Figures 1 to 3, the present invention provides a construction method for dismantling the steel-concrete composite internal support of a deep foundation pit, which is used to dismantle the steel-concrete composite internal support system of a deep foundation pit. The internal support system includes horizontal supports on The horizontal support structure and the vertical support in the deep foundation pit are combined with the intermediate partition wall structure in the deep foundation pit. The horizontal support structure includes a reinforced concrete support connected to the enclosure structure of the deep foundation pit and a steel support fixedly connected to the reinforced concrete support.

Further, as shown in Figure 4, it is a preferred embodiment of the connection relationship between the reinforced concrete support and the profile steel support in the present invention. This embodiment includes multiple prestressed profile steel supports, respectively the first profile steel support 91 and a second profile steel support 92. The second profile steel support 92 is fixedly connected to the steel frame concrete support 8 through the first purlin 101, and the steel frame concrete support 8 is fixedly connected to the foundation pit enclosure structure through the second purlin 102. Furthermore, in this embodiment, the first steel frame concrete support is replaced by a trestle bridge 11 in the foundation pit. A trestle bridge 11 is poured with a trestle plate 12, and both the trestle bridge 11 and the trestle plate 12 are connected to the foundation pit enclosure through the top beam 13. The protective structure is fixedly connected. Preferably, the first steel support 91 in the foundation pit is fixedly connected to one end of the trestle bridge 11 and the trestle plate 12 relative to the foundation pit protective structure. The first purlin 101 passes through vertical lattice columns. 14 Carry out temporary support.

The present invention's deep foundation pit steel-concrete combination internal support removal construction method includes the following construction steps:

S1 construction preparation

According to the drawings and specification requirements, combined with the actual situation of the project site, review and confirm the support removal conditions, submit a removal application to the supervision unit in a timely manner, and issue a removal instruction to the professional subcontracting unit after approval;

Determine the temporary storage site for the support parts, plan the loading and lifting points of the support parts (to meet the requirements for parking and lifting of the 50-ton truck crane) and the traffic routes on the site. The support dismantling parts on the day shall not be stacked in a concentrated manner on the upper part of the floor, and at the same time, it shall be 5m close to the foundation pit. Long-term stacking is not allowed within the scope and should be loaded and transported in time;

Agree on the cross-working conditions for support demolition and underground structure construction, clarify the working surface handover requirements, and hand over the working surface as soon as possible for the subsequent construction of the underground structure at the demolition site;

Implement the investment in personnel and equipment required for dismantling. When multiple supports are eligible for dismantling at the same time, the investment in personnel and equipment should be increased according to the progress requirements, and ensure that each support has the necessary safe operating space to avoid safety hazards caused by crowding;

Combined with the amount of demolition work, arrange transportation vehicles in advance to ensure that the dismantled supports are loaded and transported out of the site as soon as possible (the temporary stacking time on site should not exceed 24 hours);

Implement precipitation outside the pit (to reduce pressure outside the pit), increase the frequency of foundation pit monitoring during support dismantling, and strengthen collaboration with foundation pit monitoring units during the dismantling process to achieve timely sharing of information.

S2 reinforced concrete support removal

Set up temporary supports under the reinforced concrete supports in the foundation pit, use static cutting to remove the reinforced concrete supports and hoist them to the temporary stacking position, including the following operating points:

① Cutting wire rope and placing cutting line

According to the static cutting construction technology adopted, before cutting, a steel wire rope is first stretched on the upper part of the support as a lifeline for the support dismantling workers, and then the steel pipe protection on the upper part of the reinforced concrete support is removed. When placing the cutting line, the support should be accurately marked according to the actual construction plan requirements. Cut the line and notify the supervisor of the delay.

② Set up temporary support

After passing the acceptance check, I-beam brackets are used to set up temporary supports. In this embodiment, the temporary supports use horse stool support brackets, and the horse stool support bracket columns are made of No. 12 I-beam steel, and the cross-section specifications of the cross beams are 120mm× A 60mm×5mm (length*width*thick) square tube. A single custom-made horse stool support bracket is made of steel frames. Two brackets are placed under each section of reinforced concrete support. The distance between the horse stool support bracket and the supporting column is controlled. The distance between the horse stool support bracket and the concrete cutting line should be controlled at 300mm to 600mm. The distance between the support bracket and the concrete cutting line should be controlled at 300mm to 500mm. After the support section cutting line is marked, a joint inspection by the three parties should be carried out. There should be a gap between the horse stool support bracket and the concrete support. The gap There is a filler inside, and in this embodiment, square wooden plugs are used to cushion it firmly. It should be noted that square wooden blocks are used as fillers to ensure that the connection between the support bracket and the concrete support is firm. This provides better stability and support and prevents the support bracket from loosening or shifting during use. Square cork pads can fill in gaps and provide additional support, making the entire structure stronger and more reliable.

③Cut reinforced concrete inner supports

Use a diamond chain saw with a drilling machine for cutting. The pure cutting speed of the chain saw is: 40 minutes/section to 60 minutes/section. The installation time is: 20 minutes/time to 40 minutes/time. The pure cutting speed of the drilling machine is: 12 hours/time. Section, installation time: 5 minutes/time, connect water and electricity for cutting. Use a chain saw to cut from bottom to top, leaving about 100mm to 150mm of support on the upper part (the main ribs on the upper part of the beam are not broken).

④Drill floor pin size

Thread the chain and use hydraulic pliers to connect the joints and open them. Open the water pipe, adjust the water flow, and tighten the chain through the controller. The size of the pin that fixes the drill floor, the distance from the cutting line to the center of the pin is 42cm.

⑤ Cut the steel bars on both sides and transport and stack the concrete blocks

Use a 20-ton forklift to insert into the gap between the I-beam bracket and the support and tighten it upward. Then use a gas cutting gun to cut the steel bars on both sides of the support. Then the forklift slowly lowers the concrete block to the floor height, and then removes the concrete block. Transport to the designated stacking location, and lay 1cm thick steel plates through the floor reinforcement area at the forklift location to avoid damaging the steel bars.

⑥ Hoisting and transporting concrete blocks

A 70-ton to 100-ton truck crane is used to lift and load the concrete blocks for outbound transportation. The concrete support blocks and purlins are stacked and laid flat on the structural floor. Stacking is strictly prohibited and should be stacked on beams to avoid concentrated loads.

S3 steel support removal

After the reinforced concrete supports are removed, the pre-loaded axial force of the steel supports is unloaded step by step, and the brackets and force transmission parts welded between the steel supports and the vertical enclosure structure are cut off using gas cutting to dismantle the steel supports. It should be noted that when dismantling the bracket connected to the steel column, it is necessary to loosen the high-strength bolts first, use a manual hoist to lift the bracket, then take out the high-strength bolts, use the hoist to place it on the floor surface, and transport it to the temporary storage area. Use gas cutting to cut off the brackets and force transmission parts welded to the vertical enclosure structure to meet the requirements for section steel recycling. The removal of section steel supports specifically includes the following operating points:

①Support and pressure relief

After completing the support removal order, the steel supports will be removed. Release the mechanical lock before removal. During dismantling, in order to avoid excessive instantaneous pre-stress release and causing local deformation and cracking of the structure, a step-by-step unloading method is adopted. The unloading is performed in three levels of 80%, 50%, and 0% of the pre-loaded axial force. When the pressure is relieved to 0, the jack piston is retracted.

②Remove the oil pipe and sensor

Next, remove the oil pipe and sensor wiring and remove the ultrasonic sensor (the ultrasonic must be removed in advance, and it is strictly prohibited to hoist the support head assembly when there is an ultrasonic sensor). The displacement line plug should be tightly wrapped with electrical tape, and the oil pipe joint and jack joint should be tightened with plugs to prevent hydraulic oil leakage. Observe the dipstick of the oil pump mailbox at any time during unloading. If the hydraulic oil is full, pump the hydraulic oil into the oil barrel in time.

③ Hoisting and outsourcing parts

The steel supports are then lifted out and disassembled on the ground. The disassembled parts should be sorted and stored in designated areas in an orderly manner for centralized loading and transportation.

As shown in Figure 2, it is a plan layout diagram of the demolition sequence of the foundation pit steel composite support according to one embodiment of the present invention. The one-layer steel support is composed of six foundation pit corner braces and three foundation pit opposite braces. The six-layer one-layer corner braces They are named 1C1, 1C2, 1C3, 1C4, 1C5, and 1C6. The three first-floor foundation pit braces are named 1C7, 1C8, and 1C9. The second-floor steel supports are also composed of six foundation pit corner braces and three foundation pit braces. , the six second-story corner braces are named 2C1, 2C2, 2C3, 2C4, 2C5, and 2C6, and the three second-story foundation pit braces are named 2C7, 2C8, and 2C9. They are to be removed in the order of first the second floor and then the first floor. The removal sequence 3 of the corner braces of the first-floor foundation pit is ①2C1→2C2→2C3; ②2C4→2C5→2C6. The removal sequence 3 of the corner braces of the first-floor foundation pit is ①1C1→1C2→1C3; ②1C4→1C5→1C6, the opposite braces of the second-floor foundation pit. The dismantling sequence 3 is 2C9→2C8→2C7 (adjusted according to the working conditions); the dismantling sequence 3 of the first-floor foundation pit support is 1C9→1C8→2C7 (adjusted according to the working conditions). Removal of partition wall in S4

The middle partition wall structure will be dismantled layer by layer in a top-down order using a demolition method mainly based on static cutting and supplemented by mechanical demolition. Specifically, it includes the following steps:

Set bracing columns between both sides of the central partition wall structure and the frame columns of the main structure;

Remove the vertical support racks from the middle partition wall structure to the frame columns of the main structure on both sides;

Use the vaulting method to cut off the middle partition wall structure and the main structural floors on both sides in the order of first moving from the two sides to the middle, and then from the middle to both sides;

The connecting floors are constructed in sections to connect the main structural floors on both sides of the central partition wall structure, and the supporting columns are removed and replaced layer by layer.

Furthermore, the demolition of the middle partition wall structure also includes the following operating points:

①Remove the middle partition wall from the middle to both sides

The middle partition wall will be removed after the structures on both sides of the middle partition wall reach the design strength. The middle partition wall will be dismantled in 2m sections, and will be dismantled section by section using the warehouse jumping method. It is dismantled from both sides to the middle, and the floor slabs are connected in sections, and then dismantled from the middle to both sides, and the floor slabs are connected. After completion, it is dismantled layer by layer from top to bottom, and the post-casting tape is closed, as shown in Figure 3. When the post-casting tape is closed, the sealing plates 5 on both sides of the I-beam 7 are connected to the floor slabs on both sides. Number 4 in the figure is Bottom plate, number 6 is a water-proof steel plate.

②Remove the middle partition wall from top to bottom

In addition to playing the role of dividing pit excavation, the middle partition wall structure is also an important horizontal force transmission structure in the deep foundation pit support structure. Therefore, when dismantling the middle partition wall structure, it must be ensured that the main structure does not move horizontally. The force is unbalanced. The construction method is mainly static cutting and demolition, supplemented by mechanical demolition, and the middle partition wall structure is demolished layer by layer from top to bottom.

During the construction of the main structure, the vertical support racks on each floor within the range from both sides of the central partition wall structure to the frame columns will not be dismantled before preparations for the demolition and construction of the central partition wall structure. In order to free up the construction work surface before demolition, After installing the replacement support columns, remove the support racks. After the cutting is completed, a forklift is used to clear and transport the middle partition wall structure at the construction floor, and then the construction floors are connected. As the structure is constructed, the supporting columns are removed layer by layer.

S4 hoisting and outbound transportation of dismantled objects

After all supports are removed, a crane is used to hoist the dismantled objects and transport them off-site.

The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and modifications can be made to these embodiments without departing from the principle and spirit of the invention, and they still fall within the protection scope of the invention.

Claims (6)

1. The construction method for dismantling the steel-concrete combined inner support of the deep foundation pit is used for dismantling the steel-concrete combined inner support system of the deep foundation pit, the inner support system comprises a horizontal support structure and a vertical support structure, wherein the horizontal support structure is arranged in the deep foundation pit and comprises a reinforced concrete support connected with an enclosure structure of the deep foundation pit and a section steel support fixedly connected with the reinforced concrete support, and the construction method is characterized by comprising the following steps of:

placing a temporary support under the reinforced concrete support in the foundation pit, dismantling the reinforced concrete support in a static cutting mode, and hoisting to a temporary stacking position;

unloading the pre-applied axial force of the section steel support step by step, cutting off the section steel support from the vertical enclosure structure, and hoisting to a temporary stacking position;

and adopting a dismantling method taking static cutting dismantling as a main part and mechanical breaking dismantling as an auxiliary part to dismantle the intermediate wall structure layer by layer according to the sequence from top to bottom.

2. The deep foundation pit steel-concrete combined inner support dismantling construction method is characterized by comprising the following steps of: and when the reinforced concrete support is dismantled, the gas cutting gun is used for cutting off the steel bars at the two sides of the reinforced concrete support.

3. The deep foundation pit steel-concrete combined inner support dismantling construction method is characterized by comprising the following steps of: and the reinforced concrete support is pulled to be provided with a steel wire rope at the upper part of the reinforced concrete support before the reinforced concrete support is removed, the upper steel tube is removed for protection, and a cutting line is placed.

4. The deep foundation pit steel-concrete combined inner support dismantling construction method is characterized by comprising the following steps of: the temporary support is a split heads support bracket, two split heads support brackets are arranged below each section of reinforced concrete support, a gap is reserved between each split heads support bracket and each reinforced concrete support, and a filler is arranged in each gap.

5. The deep foundation pit steel-concrete combined inner support dismantling construction method is characterized by comprising the following steps of: and when the section steel support is dismantled, a gas cutting mode is adopted to cut off the support and the force transmission piece, which are connected with the vertical enclosure structure, of the section steel support.

6. The deep foundation pit steel-concrete combined inner support dismantling construction method as claimed in claim 1, wherein the intermediate wall structure comprises the following steps when dismantling:

a replacement supporting column is arranged between two sides of the intermediate wall structure and the frame column of the main body structure;

removing the intermediate wall structure to the vertical support bent within the range of the frame columns of the main body structures at the two sides;

the middle partition wall structure and the main structure floors at the two sides are cut off by adopting a bin jump method according to the sequence from the two sides to the middle and then from the middle to the two sides;

and successively constructing connection floors in sections to connect main structure floors on two sides of the intermediate wall structure, and removing support-changing upright posts layer by layer.