A method for removing columns left in diaphragm walls

Abstract

This application provides a method for removing columns left in diaphragm walls, including: calculating the safe range of the diaphragm wall to be removed; preparing for construction; marking out the column area and removal location; drilling hoisting holes and wire saw holes, and then cutting the diaphragm wall with a wire saw; hoisting and transporting the cut diaphragm wall after the crane is safely positioned; peeling off the concrete at the connection between the column and the slab, welding a waterstop steel plate, and constructing a post-cast strip; curing the post-cast strip concrete; and removing the left column. This method, by first removing the middle part of the diaphragm wall at the interface to ensure the stability of the load-bearing structural system during the transition, then removing the diaphragm walls at both ends of the interface, results in less vibration and disturbance to the structural system, as well as less noise, less dust, and lower cost.

Description

Technical Field

[0001] This application relates to the field of architecture, and more particularly to a method for removing columns left in diaphragm walls. Background Technology

[0002] Diaphragm walls, also known as underground continuous walls, are continuous underground walls formed by excavating narrow and deep trenches in the designed ground surface using various trenching machines and with the help of slurry wall protection. Appropriate materials are then poured into these trenches to create a continuous underground wall with functions of seepage prevention, soil retention, and load-bearing. Diaphragm walls were first applied in water conservancy and hydropower projects in my country, and subsequently widely used in various foundation engineering projects. Due to their high rigidity, high load-bearing capacity, good seepage prevention performance, ability to be constructed using reverse methods, suitability for various foundation conditions, small construction scope, and high investment efficiency, diaphragm walls have replaced many traditional construction methods and are used in many aspects of various foundation engineering projects. In the initial stages of their introduction to my country, diaphragm walls were mainly used as seepage prevention walls or temporary retaining walls. Through the development in recent years, with the application of many new technologies, methods, equipment, and materials, diaphragm walls are now increasingly used as part of the structure or as the main structure. In recent years, due to economic development and social progress, urban buildings have become increasingly taller and deeper, leading to the emergence of various deep foundations. As a result, diaphragm walls are now widely used in various deep foundation projects.

[0003] In subway station design, diaphragm walls are increasingly used as enclosure structures. However, during the second phase of station ancillary structure construction after the completion of the main station structure, the structural system conversion in the junction area necessitates the removal of the diaphragm walls at the interface. The removal of diaphragm walls at the interface between subway station ancillary structures and the main station structure is usually carried out in stages, first cutting off the outer layer of steel reinforcement, then using an excavator to break the concrete, or using a method of vertically erecting steel pipe supports immediately after the diaphragm wall is removed. This type of treatment is ineffective, slow, noisy, dusty, and poses safety risks such as numerous construction joints and potential water leakage. It also significantly delays the construction period, causes significant construction safety hazards, wastes materials, and leads to economic and time losses. Summary of the Invention

[0004] This application provides a method for removing columns left in diaphragm walls, aiming to solve the problem of poor construction results in the removal of diaphragm walls in existing underground space engineering.

[0005] The technical solution of this application is:

[0006] A method for removing columns left in diaphragm walls includes the following steps:

[0007] S1, calculate the safe range for the diaphragm wall that needs to be demolished;

[0008] S2, to carry out pre-construction preparations;

[0009] S3, Laying out and positioning the column area and demolition location;

[0010] S4. After drilling the hoisting holes and wire saw holes, use the wire saw to cut the diaphragm wall.

[0011] S5. After the crane is safely positioned, the cut diaphragm wall is lifted and transported out.

[0012] S6, peel off the concrete at the connection between the H-shaped steel concrete column and the slab, weld the waterstop steel plate, and construct the post-pouring strip;

[0013] S7, Curing of post-cast strip concrete;

[0014] S8, Remove the remaining H-shaped steel-concrete column.

[0015] As a technical solution of this application, in step S1, the range of the diaphragm wall that needs to be demolished at the middle part of the interface in the first construction stage, accounting for one-third of the total wall width to be removed, is determined by safety calculation. The range of the remaining diaphragm wall that needs to be demolished at other locations on the interface in the second construction stage, accounting for two-thirds of the total wall width to be removed, is also determined. The 1.2m thick diaphragm wall is left with a column according to a cross section of 1200mm×600mm, and the 0.8m thick diaphragm wall is left with a column according to a cross section of 800mm×600mm.

[0016] As one technical solution of this application, in step S3, the arrangement of the cutting lines and measurement lines of the diaphragm wall is carried out, which includes, in sequence, designing the diaphragm wall to be cut into sections, breaking the upper and lower boundaries of the diaphragm wall respectively, and performing measurement and layout:

[0017] The segmented design of the diaphragm wall includes: before construction, the diaphragm wall is segmented, using the edges of the reserved openings in the auxiliary structures of the building structure as the starting and ending points of the horizontal and vertical cutting lines, respectively. The intermediate vertical cutting lines are located at the edge protective layer of the H-shaped steel-concrete column or at the structural corner of the diaphragm wall. The diaphragm wall is then segmented into multiple blocks, each with a length of 1.5m to 3m, a width of 1m, and an area of ​​1.5m². 2 ~3m 2 The weight is 4.5 to 5 tons;

[0018] The removal of the upper and lower boundaries of the diaphragm wall includes setting the upper boundary of the area to be removed at an elevation of 400mm above the top surface of the top plate of the auxiliary main structure in the building structure, and setting the lower boundary of the area to be removed at an elevation of 200mm below the bottom surface of the bottom plate of the auxiliary main structure in the building structure.

[0019] The surveying and setting out process includes: based on the elevation data of the design drawings, laying out the upper edge line of the cutting area of ​​the diaphragm wall, marking the elevation line when the earthwork is excavated to the corresponding elevation, and spraying markings on the diaphragm wall.

[0020] As one technical solution of this application, in step S4, the drilling process in the process of drilling the hoisting hole and the wire saw hole includes the following steps:

[0021] S411: Erecting a manned gantry;

[0022] S412: Drill bolt holes according to the layout and positioning;

[0023] S413: Install water drill;

[0024] S414: Drilling and cutting, and controlling the cutting time during the drilling and cutting process, wherein, when the diaphragm wall that needs to be removed at the middle part of the interface and accounts for one-third of the total number of wall sections to be removed is cut off, the H-shaped steel-concrete column is removed when the excavation of the building structure's attached earthwork reaches the lower part while retaining the H-shaped steel-concrete column; when the strength of the side walls, middle plate, bottom plate, plate bracing, beam bracing of the attached structure in the building structure and the retained H-shaped steel-concrete column reaches the design requirements, the remaining two-thirds of the diaphragm wall is removed; when water drilling is performed, a 100mm diameter drill bit is used to water drill the diaphragm wall according to the released cutting line.

[0025] As one technical solution of this application, in step S4, the wire saw cutting process includes:

[0026] S421: Install guide wheels, secure and connect the wire saw;

[0027] S422: When using the wire saw machine for wire sawing, first make horizontal cuts according to the cutting block size lines arranged on the diaphragm wall, and then make vertical cuts; excavate and cut the diaphragm wall and the attached earthwork in the building structure within one-third of the middle part of the interface as they are excavated; after the strength of the slab support and the strength of the beam support in the attached middle plate of the building structure have reached the design requirements, cut off the remaining two-thirds of the diaphragm wall on the interface from top to bottom within the range from the top plate to the bottom plate of the building structure.

[0028] As one technical solution of this application, in step S422, the wire saw cutting process includes: winding a diamond wire around the drive wheel and the auxiliary wheel of the cutting equipment respectively; adjusting the cutting equipment, starting the electric motor, and adjusting the drive wheel through the control panel to make the diamond wire taut; supplying circulating cooling water in the chain cutting area, and then starting another electric motor to drive the drive wheel to drive the diamond wire to perform rotary cutting on the diaphragm wall.

[0029] As one technical solution of this application, in step S5, the crane hoisting and transportation includes the following steps:

[0030] S51: First, lift out the uppermost cutting blocks on the ground wall in order of increasing size, and then use steel wire ropes to tie each cutting block in sequence through the lifting holes;

[0031] S52: Starting from the side closest to the crane, lift each of the cutting blocks in sequence from the outside to the inside and from top to bottom; when the cutting blocks begin to leave the wall of the diaphragm wall, if the cutting blocks become eccentric, stop lifting, adjust the cutting blocks to a balanced state, and then lift again. When the bottom of the cutting block is 50cm above the ground, rotate the cutting block to the ground and then lower it along the direction of the sleepers and support it. After loading the cutting blocks onto the truck, transport them out.

[0032] As a technical solution of this application, in step S6, the top and bottom surfaces of the diaphragm wall are removed by pneumatic picks. The top and bottom surfaces of the interface between the auxiliary structure and the main structure in the building structure are removed manually by hand-held pneumatic picks. First, the protective layer of concrete on the outside of the main reinforcement of the diaphragm wall is removed, and then the outer layer of reinforcement on the diaphragm wall is cut off using oxyacetylene welding. Then, the remaining concrete on the diaphragm wall is removed inward, and the reinforcement on the inner side of the diaphragm wall is cut off. Then, the building structure is waterproofed. First, the concrete at the post-cast strip on the H-shaped steel-concrete column in the building structure is peeled off. Water-stop steel plates are welded around the H-shaped steel-concrete column on the bottom and top plates of the building structure, and micro-expansion concrete is poured at the post-cast strip.

[0033] As one technical solution of this application, in step S7, the post-pouring strip concrete is cured. After the post-pouring strip micro-expansion concrete is poured, the micro-expansion concrete is then kept warm and moist for curing, and the curing time is ≥28 days.

[0034] As a technical solution of this application, in step S8, the H-shaped steel-concrete column is demolished. After the concrete of the top slab of the building structure reaches the design requirements, the remaining H-shaped steel-concrete column is demolished and the H-shaped steel-concrete column is lifted out from the soil outlet or hoisting hole on the main part of the building structure.

[0035] The beneficial effects of this application are:

[0036] This application provides a method for removing columns left in diaphragm walls. It involves first removing the middle section of the diaphragm wall at the interface, ensuring the structural system remains stable during the transition, and then removing the diaphragm walls at both ends of the interface. This method minimizes vibration and disturbance to the structural system, resulting in less noise, dust, and lower costs. The concrete blocks are not immediately removed after cutting; instead, they are gradually removed after the remaining retaining structure has slowly released stress and stabilized during the cutting process, thus minimizing safety risks. It also reduces the consumption of steel supports and other peripheral materials, lowering construction costs. Multiple machines can be used in different areas, allowing for large-scale, safe, efficient, and aesthetically pleasing removal of the diaphragm wall concrete. This ensures the quality of subsequent construction steps (waterstop steel plates are welded around the exposed H-shaped steel-concrete columns before the construction of the post-pouring strip). The method can be carried out in stages simultaneously with the excavation of the station's auxiliary foundation pit and the erection of floor formwork supports. The rapid removal of the diaphragm wall concrete avoids prolonged exposure of the post-pouring strip, maintaining the stability of the foundation pit. After safety calculations, columns were left within the diaphragm wall, allowing the H-shaped steel-concrete columns to bear the loads of the upper diaphragm wall and capping beam. Then, a large quantity of diaphragm wall concrete was efficiently cut from the first to the second basement level using a wire saw, forming a complete construction method. This method utilizes safety calculations to determine reasonable cutting times and spatial nodes, ensuring both construction safety and quality. Furthermore, it produces less dust and noise, is economical, environmentally friendly, and low-risk, possessing significant value for widespread application. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show...

[0038] Some embodiments of the application should not be considered as limiting the scope. For those skilled in the art, other related drawings can be obtained from these drawings without any inventive effort.

[0039] Figure 1 This is a schematic diagram of the process for removing columns left in diaphragm walls according to the first embodiment of this application;

[0040] Figure 2 This is a schematic diagram of the process for removing columns left in diaphragm walls according to the first embodiment of this application;

[0041] Figure 3 This is a schematic elevation view of the process for removing columns left in the diaphragm wall, as provided in the first embodiment of this application.

[0042] Figure 4 This is a schematic diagram of the segmented demolition of the diaphragm wall in the conventional demolition method provided in the second embodiment of this application;

[0043] Figure 5 A step-by-step cross-sectional view of the conventional demolition method supported by H-beam concrete columns, as provided in the second embodiment of this application;

[0044] Figure 6 This is a schematic diagram of the structural cross-section after the H-shaped steel-concrete column has been cut with a wire saw in the conventional demolition method provided in the second embodiment of this application. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can typically be arranged and designed in various different configurations.

[0046] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0047] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0048] In the description of this application, it should be noted that the terms "upper" and "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use. They are only used to facilitate the description of this application and to simplify the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0049] Furthermore, in this application, unless otherwise expressly specified and limited, "above or below" the first feature may include direct contact between the first and second features, or contact between the first and second features through another feature between them. Moreover, "above," "over," and "on" the first feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the first feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0050] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0051] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0052] First embodiment:

[0053] Please refer to Figure 1 (Refer to) Figure 2 and Figure 3 This application provides a method for removing columns left in diaphragm walls, which includes the following steps:

[0054] S1: Perform safety calculations for the diaphragm walls that need to be demolished;

[0055] S2: Carry out preparatory work before construction;

[0056] S3: Laying out and positioning the column area and demolition location;

[0057] S4. After drilling the hoisting holes and wire saw holes, use the wire saw to cut the diaphragm wall.

[0058] S5, After the crane is safely positioned, the cut diaphragm wall is lifted and transported out.

[0059] S6, peel off the concrete at the connection between the H-shaped steel concrete column and the slab, weld the waterstop steel plate, and construct the post-pouring strip;

[0060] S7, Curing of post-cast strip concrete;

[0061] S8, Remove the remaining H-shaped steel-concrete columns.

[0062] Further, in step S1, the demolition range of the diaphragm wall, which accounts for 1 / 3 of the total number of wall sections to be removed, at the middle part of the interface to be demolished in the first construction stage is first determined by safety calculation. Then, the remaining diaphragm wall range, which accounts for two-thirds of the total number of wall sections to be removed, at other locations of the interface to be demolished in the second construction stage is determined. Among them, the 1.2m thick diaphragm wall is left as a column with a cross section of 1200mm×600mm, and the 0.8m thick diaphragm wall is left as a column with a cross section of 800mm×600mm. If it is a diaphragm wall connecting section, the concrete on the connecting section edge of the H-shaped steel concrete column is completely stripped after cutting.

[0063] Meanwhile, in step S2, by setting up a cordon around the demolition site to prevent people from passing through at will, the upper and lower levels of the construction area are sealed off, and non-construction personnel are not allowed to enter. In addition, machinery and equipment are prepared, and water and electricity are ensured, thereby completing the preparatory work before construction.

[0064] Further, in step S3, the cutting lines and measurement layout of the diaphragm wall are arranged, which includes, in sequence, designing the diaphragm wall into blocks, breaking the upper and lower boundaries of the diaphragm wall, and performing measurement layout:

[0065] The segmented design of the diaphragm wall includes: before construction, the diaphragm wall is segmented, using the edge of the reserved opening in the station's ancillary structure as the starting and ending points of the horizontal and vertical cutting lines. The intermediate vertical cutting line is located at the edge protective layer of the H-shaped steel-concrete column of the diaphragm wall or at the structural corner. This process divides the diaphragm wall into multiple segments, each with a length of 1.5m to 3m, a width of 1m, and an area of ​​1.5m². 2 ~3m 2 The weight is 4.5 to 5 tons;

[0066] The upper and lower boundaries of the diaphragm wall are to be broken, including: cutting thin concrete blocks of 100mm thickness at the top of the diaphragm wall so that other large diaphragm wall blocks are not squeezed out by the vertical movement after being pushed out manually; the upper boundary of the diaphragm wall breaking area is set at an elevation of 400mm above the top slab of the station's auxiliary main structure to ensure sufficient working surface during the construction of the auxiliary structure's top slab, while the lower boundary should be 200mm below the bottom surface of the auxiliary main structure's bottom slab, which is also flush with the bottom surface of the waterproof layer;

[0067] The surveying and setting out process includes: based on the elevation data on the drawings, mainly setting out the upper edge line of the cutting area. The elevation line can be marked when the earthwork is excavated to the corresponding elevation, or marked by personnel using steel ladders or gantry frames, and the marking is painted on the diaphragm wall with red spray paint.

[0068] Furthermore, in step S4, the drilling process for drilling the hoisting hole and the wire saw hole includes the following steps:

[0069] S411: Erecting a manned gantry;

[0070] S412: Drill bolt holes according to the layout and positioning;

[0071] S413: Install water drill;

[0072] S414: Drilling and cutting, and controlling the cutting time during the drilling and cutting process; when cutting the diaphragm wall that needs to be removed in the middle part of the interface and accounts for one-third of the total number of wall panels to be removed, it should be removed as the earthwork of the station ancillary structure is excavated to a suitable depth while retaining the H-shaped steel concrete columns; when the concrete strength of the side walls, middle plate or bottom plate of the station ancillary structure has reached the design requirements, and when the plate supports and beam supports are sufficient to resist the compression deformation outside the enclosure structure, and when the retained H-shaped steel concrete columns are sufficient to bear the upper load, the remaining two-thirds of the diaphragm wall panels can be removed; when performing water drilling and cutting, use a 100mm diameter drill bit to perform water drilling and cutting according to the cut line, and the cutting depth is the thickness of the diaphragm wall concrete block.

[0073] Meanwhile, in step S4, the wire saw cutting process includes:

[0074] S421: Install guide wheels, secure and connect the wire saw;

[0075] S422: Wire saw cutting. When using wire saw cutting, cut horizontally first and then vertically according to the arranged cutting block size lines. The diaphragm wall in the middle third of the interface can be cut as the station's auxiliary earthwork is excavated. After the strength of the slab support and beam support of the station's auxiliary middle plate reaches the design requirements, the remaining two-thirds of the diaphragm wall of the interface is cut from top to bottom from the top plate to the middle plate to the bottom plate.

[0076] Specifically, in step S422, the wire saw cutting process includes: winding the diamond wire rope around the drive wheel and auxiliary wheel of the cutting equipment, with the driving direction of the diamond wire rope being consistent with the driving direction of the drive wheel; connecting the relevant lines for water, electricity, and mechanical equipment, and installing safety guardrails; debugging the cutting equipment, starting the electric motor, adjusting the drive wheel to increase tension via the control panel to ensure proper tension of the diamond wire rope, supplying circulating cooling water to the chain cutting area, and then starting another electric motor to drive the drive wheel to rotate and cut the diamond wire rope. During the cutting process, the stability of the machine base must be closely observed, and the guide wheel must be adjusted at any time to ensure that the cutting rope is in the same plane. During cutting, the stability of the machine base must be observed and the guide wheel offset adjusted in time to ensure that the saw rope is in the same vertical plane. The cutting parameters are adjusted by operating the control panel to keep the saw rope's linear speed at approximately 20 m / s. During the cutting process, sufficient cooling water is ensured to cool the wire and remove cutting debris.

[0077] Meanwhile, in step S5, a crane is selected. The concrete blocks on the diaphragm wall are lifted using a combination of a crane and wire rope. The equipment and materials are selected based on the maximum weight of the concrete block cutting unit and the lifting position. According to the previously calculated unit division, the weight of the concrete block is controlled below 5t. After the cutting is completed and the stress of the remaining retaining structure is fully released and deformed, a steel ladder or manned gantry is erected, and personnel wear lifting wire ropes. Based on the site conditions and working radius, by checking the parameter table of truck cranes, if a 55t truck crane is used, its working radius is within 16m, the boom length is 19.82m, and the rated lifting weight is 6.6t, which can meet the lifting requirement of the maximum weight of the wall cutting unit of 5t. Therefore, a 55t truck crane is selected. When the specific working environment changes, the appropriate crane is selected according to the basic selection principle based on the specific conditions.

[0078] When lifting concrete blocks, the following steps should be taken:

[0079] S51: First, forcefully push out the top layer of small thin blocks and lift them out, then lift the large concrete blocks. Use steel wire ropes to tie the concrete body through the lifting holes. The tying position is 0.5 to 1.0m away from the end of the concrete block. Add rubber pads at the lifting holes to prevent wear.

[0080] S52: No one is allowed to stand within the turning radius of the crane. After the safety measures are completed, start from the side closest to the hoisting equipment and lift the concrete block away in the order from the outside to the inside and from the top to the bottom. Before lifting, make sure the wire rope is properly threaded, lift the hook to a taut state and slowly lift it. Stop lifting when the wire rope is just under tension, check the center of the hook and the condition of each lifting point, and lift slowly after confirming that there are no abnormalities.

[0081] S53: When the concrete begins to separate from the wall, stop lifting if there is any eccentricity. Manually adjust the concrete until it is balanced and separated before lifting again. When the bottom of the entire concrete block is 50cm above the ground, rotate it to an open space on the ground and lower it along the direction of the sleepers and support it to prevent it from tipping over. After the concrete block is loaded onto the truck, transport it to a suitable location for dismantling or reuse.

[0082] In addition, in step S6, the top and bottom surfaces are chiseled with pneumatic picks. In the building structure, the top and bottom surfaces of the interface between the auxiliary structure and the main structure are difficult to cut. Specialized chiseling workers use handheld pneumatic picks to chisel the parts. First, the protective layer of concrete outside the main reinforcement of the diaphragm wall is chiseled away. The outer layer of reinforcement of the diaphragm wall is cut away with oxyacetylene welding. Then, the remaining concrete of the diaphragm wall is chiseled away inward. The inner reinforcement is then cut away. Waterproofing is then carried out. First, the concrete at the post-cast strip on the H-shaped steel concrete column is peeled off. Water-stop steel plates are welded around the H-shaped steel concrete columns on the bottom and top slabs. Micro-expansion concrete is then poured at the post-cast strip.

[0083] Furthermore, in step S7, the post-cast strip concrete is cured. After the micro-expansion concrete of the post-cast strip is poured, it is then subjected to heat preservation and moisture retention curing for ≥28 days.

[0084] Meanwhile, in step S8, the H-shaped steel concrete columns are dismantled. After the concrete of the top slab post-cast strip reaches the design requirements, the remaining H-shaped steel concrete columns are removed and lifted out from the station's main structure's excavation hole or hoisting hole.

[0085] Therefore, the working principle of this method is as follows:

[0086] After safety calculations, the H-beams, the space between the steel flanges, and their protective concrete layers at the diaphragm wall joints are retained as H-beam concrete columns to bear the upper load. Their compressive, bending, shear, and deformation resistance, i.e., strength, stiffness, and stability, all meet the specifications. The H-beams at the diaphragm wall joints serve as the core load-bearing carriers of the H-beam concrete columns. The H-beams, their space between the flanges, and their protective concrete layers (for 1.2m thick diaphragm walls, columns are retained with a 1200mm×600mm cross-section) together bear the load of the upper diaphragm wall and the capping beam. The diaphragm wall concrete in the middle of the joint, which accounts for 1 / 3 of the total wall width, is cut into blocks using a wire saw. The blocks are removed as they are excavated. The remaining diaphragm wall blocks are removed after they can withstand the compression deformation from outside the enclosure structure, thanks to the support plates or beams in the auxiliary structure (bottom). The cut concrete blocks are then lifted out using a crane with appropriate safety performance.

[0087] Furthermore, this method was applied to a civil engineering pre-embedded project at an intersection. The station is a three-level underground island platform station with an effective platform width of 14m. The average depth of the entrance and exit pits is 17.6m, with a local depth of 19.3m, classifying it as an ultra-deep pit with a high safety risk factor due to long-term exposure. The diaphragm wall to be demolished is 43 meters long, and the first-floor attached wall to be demolished is 2 × 17.9 meters long, with an equivalent wall height of 14.1 meters, for a total equivalent wall length of 60 meters and a thickness of 1.2 meters. The amount of concrete required for demolition is 14.1 × 60 × 1.2 = 1015 cubic meters. 3 Using conventional intervals to break down the material would take at least 3 months, while this method only took 1 month in total.

[0088] The results of this application demonstrate that this method can comprehensively, quickly, safely, and over large areas remove the diaphragm wall concrete at the interface between the main body and auxiliary structures of subway stations, avoiding the risk of prolonged exposure of ultra-deep station auxiliary foundation pits. Furthermore, it ensures the construction quality of the post-cast strip at the interface between the station auxiliary structures and the main body while saving time and effort and ensuring the project schedule. If this method can be widely promoted and applied, underground space projects such as subway stations and phased underground parking lots can be completed and put into use sooner, which will undoubtedly yield good economic and social benefits.

[0089] In summary, this application provides a method for removing diaphragm wall columns. It involves first removing the middle section of the diaphragm wall at the interface, ensuring the structural system remains stable during the transition, and then removing the diaphragm walls at both ends of the interface. This method minimizes vibration and disturbance to the structural system, resulting in low noise, minimal dust, and low cost. The concrete blocks are not immediately removed after cutting; instead, they are gradually removed after the remaining retaining structure has released stress and stabilized during the cutting process. This reduces safety risks, decreases the consumption of steel supports and other peripheral materials, lowers construction costs, allows for multi-unit operation in different areas, and enables large-scale, safe, efficient, and aesthetically pleasing removal of the diaphragm wall concrete. It also ensures the quality of subsequent construction steps (waterstop steel plates are welded around the exposed H-shaped steel-concrete columns before the post-pouring strip is constructed). The method can be carried out in stages simultaneously with the excavation of the station's auxiliary foundation pit and the erection of floor formwork supports. The rapid removal of the diaphragm wall concrete avoids prolonged exposure of the post-pouring strip, thus maintaining the stability of the foundation pit. After safety calculations, columns were left in the diaphragm wall, allowing the H-shaped steel-concrete columns in the diaphragm wall to bear the load of the upper diaphragm wall and the capping beam. Then, a large number of diaphragm wall concrete were efficiently cut from the first basement level to the second basement level using a wire saw, forming a complete construction method. This method uses safety calculations to determine reasonable cutting time and spatial nodes, ensuring both construction safety and quality. It also produces less dust and noise, is economical, environmentally friendly, and low-risk, and has significant value for widespread application.

[0090] Second embodiment:

[0091] It should be noted that traditional demolition methods, such as Figures 4 to 6As shown below, according to Figure 5 and Figure 6 A quantitative economic benefit comparison analysis was conducted: If steel columns were used for support during the demolition of diaphragm walls or structural walls in accordance with design requirements, the amount of steel column material required for demolishing a station wall would be:

[0092] 60m (length) × 3 × 14.1m (height) / 7.1m = 357.5m, (Equation 1);

[0093] According to the project tender list:

[0094] 357.5 × 0.84 × 2384 / 10000 = 715,900 yuan (Equation 2);

[0095] In the formula: the length of the structure to be demolished is 60m (see the application example in the first embodiment), and the height of the two-story structural wall is 14.1m (see the application example in the first embodiment);

[0096] It should be noted that the weight of a 1m φ800δ20 steel support is 0.84t, and the list price for 1t of steel support material is 2384 yuan.

[0097] Therefore, the economic benefits of the construction method in the first embodiment are compared and analyzed with those of the traditional construction method. The comparison and analysis table is shown in Table 1:

[0098] Table 1. Comparative Analysis of Economic Benefits of Different Construction Methods

[0099]

[0100] Therefore, by removing diaphragm walls or structural walls, a subway station can save 715,900 yuan in steel column materials. In addition, the saved construction time, reduced vibration disturbance to the station structure, and low noise and low risk characteristics result in considerable overall benefits.

[0101] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for removing columns left in diaphragm walls, characterized in that, The following steps are involved: S1, calculate the safe range for the diaphragm wall that needs to be demolished; S2, to carry out pre-construction preparations; S3, Laying out and positioning the column area and demolition location; S4. After drilling the hoisting holes and wire saw holes, use the wire saw to cut the diaphragm wall. S5. After the crane is safely positioned, the cut diaphragm wall is lifted and transported out. S6. Remove the concrete at the connection between the H-shaped steel-concrete columns and the slab in the building structure, weld water-stop steel plates, and construct the post-pouring strip: Remove the top and bottom surfaces of the diaphragm wall using a pneumatic pick. Remove the top and bottom surfaces of the interface between the auxiliary structure and the main structure using a handheld pneumatic pick. First, remove the protective layer of concrete outside the main reinforcement of the diaphragm wall, then use oxyacetylene welding to cut off the outer layer of reinforcement on the diaphragm wall. Then, remove the remaining concrete on the diaphragm wall inwards, and cut off the reinforcement on the inner side of the diaphragm wall. Waterproof the building structure by first removing the concrete at the post-pouring strip on the H-shaped steel-concrete columns in the building structure, welding water-stop steel plates around the H-shaped steel-concrete columns on the bottom and top slabs of the building structure, and pouring micro-expansion concrete at the post-pouring strip. S7, Curing of post-cast strip concrete; S8, Remove the remaining H-shaped steel-concrete column.

2. The method for removing columns left in diaphragm walls according to claim 1, characterized in that, In step S1, the scope of the diaphragm wall that needs to be demolished at the middle part of the interface in the first construction stage, accounting for one-third of the total wall width to be removed, is determined through safety calculation. The scope of the remaining diaphragm wall that needs to be demolished at other locations on the interface in the second construction stage, accounting for two-thirds of the total wall width to be removed, is also determined. The 1.2m thick diaphragm wall is left with a column according to a cross section of 1200mm×600mm, and the 0.8m thick diaphragm wall is left with a column according to a cross section of 800mm×600mm.

3. The method for removing columns left in diaphragm walls according to claim 1, characterized in that, In step S3, the cutting lines and measurement layout of the diaphragm wall are arranged, which includes, in sequence, designing the diaphragm wall into sections, breaking the upper and lower boundaries of the diaphragm wall, and performing measurement layout. The segmented design of the diaphragm wall includes: before construction, the diaphragm wall is segmented, using the edges of the reserved openings in the auxiliary structures of the building structure as the starting and ending points of the horizontal and vertical cutting lines, respectively. The intermediate vertical cutting lines are located at the edge protective layer of the H-shaped steel-concrete column or at the structural corner of the diaphragm wall. The diaphragm wall is then segmented into multiple blocks, each with a length of 1.5m to 3m, a width of 1m, and an area of ​​1.5m². 2 ~3m 2 The weight is 4.5 to 5 tons; The removal of the upper and lower boundaries of the diaphragm wall includes setting the upper boundary of the area to be removed at an elevation of 400mm above the top surface of the top plate of the auxiliary main structure in the building structure, and setting the lower boundary of the area to be removed at an elevation of 200mm below the bottom surface of the bottom plate of the auxiliary main structure in the building structure. The surveying and setting out process includes: based on the elevation data of the design drawings, laying out the upper edge line of the cutting area of ​​the diaphragm wall, marking the elevation line when the earthwork is excavated to the corresponding elevation, and spraying markings on the diaphragm wall.

4. The method for removing columns left in diaphragm walls according to claim 1, characterized in that, In step S4, the drilling process for drilling the hoisting hole and the wire saw hole includes the following steps: S411: Erecting a manned gantry; S412: Drill bolt holes according to the layout and positioning; S413: Install water drill; S414: Drilling and cutting, and controlling the cutting time during the drilling and cutting process, wherein, when the diaphragm wall that needs to be removed at the middle part of the interface and accounts for one-third of the total number of wall sections to be removed is cut off, the H-shaped steel-concrete column is removed when the excavation of the building structure's attached earthwork reaches the lower part while retaining the H-shaped steel-concrete column; when the strength of the side walls, middle plate, bottom plate, plate support, beam support and the retained H-shaped steel-concrete column of the attached structure in the building structure reaches the design requirements, the remaining two-thirds of the diaphragm wall is removed; when water drilling is performed, a 100mm diameter drill bit is used to water drill the diaphragm wall according to the released cutting line.

5. The method for removing columns left in diaphragm walls according to claim 1, characterized in that, In step S4, the wire saw cutting process includes: S421: Install guide wheels, secure and connect the wire saw; S422: When using the wire saw machine for wire sawing, first make horizontal cuts according to the cutting block size lines arranged on the diaphragm wall, and then make vertical cuts; excavate and cut the diaphragm wall and the attached earthwork in the building structure within one-third of the middle part of the interface as they are excavated; after the strength of the slab support and the strength of the beam support in the attached middle plate of the building structure have reached the design requirements, cut off the remaining two-thirds of the diaphragm wall on the interface from top to bottom within the range from the top plate to the bottom plate of the building structure.

6. The method for removing columns left in diaphragm walls according to claim 5, characterized in that, In step S422, the wire saw cutting process includes: winding a diamond wire around the drive wheel and the auxiliary wheel of the cutting equipment; adjusting the cutting equipment, starting the electric motor, and adjusting the drive wheel through the control panel to make the diamond wire taut; supplying circulating cooling water to the chain cutting area, and then starting another electric motor to drive the drive wheel to rotate and cut the diaphragm wall with the diamond wire.

7. The method for removing columns left in diaphragm walls according to claim 1, characterized in that, In step S5, the crane lifting and transporting includes the following steps: S51: First, lift out the uppermost cutting blocks on the ground wall in order of increasing size, and then use steel wire ropes to tie each cutting block in sequence through the lifting holes; S52: Starting from the side closest to the crane, lift each of the cutting blocks in sequence from the outside to the inside and from top to bottom; when the cutting blocks begin to leave the wall of the diaphragm wall, if the cutting blocks become eccentric, stop lifting, adjust the cutting blocks to a balanced state, and then lift again. When the bottom of the cutting block is 50cm above the ground, rotate the cutting block to the ground and then lower it along the direction of the sleepers and support it. After loading the cutting blocks onto the truck, transport them out.

8. The method for removing columns left in diaphragm walls according to claim 1, characterized in that, In step S7, the post-cast strip concrete is cured. After the post-cast strip micro-expansion concrete is poured, the micro-expansion concrete is then kept warm and moist for curing, and the curing time is ≥28 days.

9. The method for removing columns left in diaphragm walls according to claim 1, characterized in that, In step S8, the H-shaped steel-concrete columns are demolished. After the concrete of the top slab of the building structure reaches the design requirements, the remaining H-shaped steel-concrete columns are demolished and lifted out from the soil outlet or hoisting hole on the main part of the building structure.

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