Anti-floating reinforcement construction method for existing underground structure in narrow space

Abstract

The invention belongs to the technical field of anti-floating anchor rod construction, discloses an anti-floating reinforcement construction method for an existing underground structure in a narrow space, and aims to solve the problem of poor anti-floating capacity caused by the fact that common steel bar anti-floating anchor rods are used for anti-floating reinforcement in the prior art. The anchor hole comprises the first expanded head section, the equal-diameter section and the second expanded head section which are sequentially arranged from top to bottom, the finish-rolled twisted steel is directly used as the anchor rod and implanted into the anchor hole, and the reinforced anti-floating anchor rod is formed after grouting. The anti-floating capacity of a single anti-floating anchor rod can be improved, the reinforcing number of the anti-floating anchor rods can be reduced, and the purpose of reducing the anti-floating reinforcing cost is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of anti-floating anchor construction, and particularly relates to a construction method for anti-floating reinforcement of existing underground structures in narrow spaces. Background Art

[0002] As an anti-floating measure for building structures, anti-floating anchor rods are connected to the foundation slab of the building to resist the buoyancy generated by groundwater on the underground structure of the building and prevent the underground structure from being damaged due to the buoyancy of groundwater.

[0003] During the construction of a building, anti-floating anchor rods will be arranged according to the groundwater conditions to achieve the purpose of anti-floating. However, after long-term use, when the groundwater changes rapidly in a short period of time, and after long-term use of the anti-floating anchor rods, along with the gradual loss of prestress and the reduction of the anti-floating capacity of the anti-floating anchor rods themselves, it will cause the underground structure to be damaged due to excessive groundwater buoyancy, and even affect the structural safety of the entire building.

[0004] Currently, for the anti-floating reinforcement of underground structures, ordinary anchor bar steel anti-floating anchor rods and steel wire anti-floating anchor rods are used. Limited by the height and space of the underground structure, ordinary anchor bar steel can only be implanted in segments and then welded to form a whole. This welding method is prone to stress concentration problems, resulting in poor anti-floating capacity of a single anti-floating anchor rod for reinforcement construction. Therefore, it is necessary to increase the number of anti-floating anchor rods to make up for it, which in turn leads to high construction costs.

[0005] If the anti-floating reinforcement uses strand anti-floating anchor rods, since the strand anti-floating anchor rods themselves have the defect of insufficient bearing capacity compared with ordinary steel bar anti-anchor rods, and the external waterproof construction is also more troublesome, therefore, strand anti-floating anchor rods are rarely used for the anti-floating reinforcement of existing buildings. Summary of the Invention

[0006] The present invention provides a construction method for anti-floating reinforcement of existing underground structures in narrow spaces in order to solve the problem of poor anti-floating capacity of ordinary steel bar anti-floating anchor rods used in existing anti-floating reinforcement, which can improve the anti-floating capacity of a single anti-floating anchor rod, and thus can reduce the number of anti-floating anchor rods for reinforcement, and further achieve the purpose of reducing the cost of anti-floating reinforcement.

[0007] In order to solve the technical problems, the technical solution adopted by the present invention is: A construction method for anti-floating reinforcement of existing underground structures in narrow spaces, characterized by including: (1) Measuring and laying out lines on the existing underground structure to determine the anchor hole positions of the anti-floating anchor rods for reinforcement.

[0008] (2) The drilling machine is positioned and drilled to form a preliminary anchor hole, and the preliminary anchor hole includes a constant-diameter section and a first enlarged head section located at the upper end of the constant-diameter section. The diameter of the first enlarged head section is larger than that of the constant-diameter section.

[0009] (3) The formed preliminary anchor hole is used to carry out dewatering operation on groundwater so that the groundwater level reaches the required level for construction.

[0010] (4) The drilling machine reams the constant-diameter section at the lower part of the preliminary anchor hole to form a second enlarged head section, thereby obtaining a complete anchor hole. A spacing is formed between the first enlarged section and the second enlarged section by the constant-diameter section. That is to say, the anchor hole successively includes a first enlarged head section, a constant-diameter section and a second enlarged head section from top to bottom.

[0011] (5) Carry out hole cleaning operation on the anchor hole obtained in step (4).

[0012] (6) Segmentally implant the rolled and threaded steel bar anchor into the anchor hole and connect each section of the rolled and threaded steel bar into a whole as the anchor rod, and then carry out grouting.

[0013] (7) When the grout for grouting and pouring solidifies to reach the design strength, prestress is applied to and anchored on the rolled and threaded steel bar to complete the reinforcement construction of the anti-floating anchor rod for the underground structure.

[0014] In some embodiments, a plurality of bearing plates are arranged at intervals on the periphery of the section of the rolled and threaded steel bar corresponding to the second enlarged head section of the anchor hole.

[0015] In some embodiments, the drilling machine is positioned and drilled to form a preliminary anchor hole specifically includes: (1) Use an anchor rod drilling machine to drill on the anti-floating bottom plate of the existing underground structure and form a through hole on the anti-floating bottom plate, and then continue to drill into the soil until the depth of the hole in the soil matches the depth of the designed first enlarged head section; (2) Replace the drill bit with a larger size and use the anchor rod drilling machine or a reaming drill to ream the through hole of the anti-floating bottom plate of the existing underground structure to form an enlarged through hole. The diameter of the enlarged through hole is larger than the size of the through hole and smaller than the diameter of the first enlarged head section; (3) Use a high-pressure jet grouting drilling machine to ream the hole formed in step (1) to form the first enlarged head section; (4) Use the drill bit in step (1) to continue drilling downward so that the depth of the preliminary anchor hole reaches the design requirements.

[0016] In some embodiments, the depth of the first enlarged head section is less than half of the depth of the preliminary anchor hole. Preferably, the depth of the first enlarged head section is between one-third and one-half of the depth of the preliminary anchor hole.

[0017] In some embodiments, the diameters of the first enlarged head section and the second enlarged head section are the same, so that it is not necessary to make excessive adjustments to the parameters of the jet grouting rig, improving the convenience of operation.

[0018] Compared with the prior art, the present invention has the following beneficial effects: In the present invention, a first enlarged head section is formed by machining at the upper end of the equal-diameter section of the preliminary anchor hole. After the grouting solidifies, a first enlarged head is formed at the upper end of the equal-diameter section. The function of the first enlarged head can not only reinforce the formation under the underground structure of the existing building. Especially when the rapidly changing groundwater level affects the bearing capacity of the formation, the present invention utilizes the first enlarged head formed after grouting and pouring of the first enlarged head section to achieve the purpose of improving the bearing capacity of the foundation. On the other hand, when prestressing the anchor rod made of precision rolled threaded steel and when the anti-floating anchor rod plays an anti-floating role in the later stage, the first enlarged head can be used to increase the contact area with the anti-floating floor of the underground structure (i.e., the existing underground structure) of the existing building, avoiding the risk of damage to the original anti-floating floor.

[0019] In addition, the first enlarged head formed by grouting and pouring of the first enlarged section can shorten the distance from the grouting body of the anchorage section of the anti-floating anchor rod (i.e., the second enlarged head formed after grouting and pouring of the second enlarged section), thereby reducing the thickness of the formation above the anchorage section. That is to say, it increases the stiffness of the formation, and further reduces the degree of compression of the formation, and finally reduces the disturbance to the original formation (or called the original soil body).

[0020] The present invention directly uses an anchor rod drilling rig to drill on the anti-floating floor of the underground structure of the existing building. Compared with the prior art that uses the method of smashing and damaging the anti-floating floor, it can reduce the impact on the original anti-floating floor, and further reduce the impact on the existing underground structure, ensuring the safety of the existing building.

[0021] The present invention uses an anchor rod drilling rig to pre-drill a through hole on the anti-floating floor of the existing underground structure, and then ream the hole to form an enlarged through hole. When the anchor hole is poured, by using the method of grouting and bonding between the first enlarged head hole and the existing anti-floating floor, the contact area between the reinforced anti-floating anchor rod and the existing anti-floating floor can be increased; and due to the setting of the first enlarged head section, when grouting into the anchor hole, the grout will also penetrate more into the gap between the existing anti-floating floor and the top surface of the soil body, thereby further increasing the bonding strength between the reinforced anti-floating anchor rod and the existing anti-floating floor. At the same time, since the pores in the area under the existing anti-floating floor are strengthened, the risk of damage to the existing anti-floating floor during the later prestressing and the anti-floating anchor rod playing an anti-floating role is avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic structural diagram of an embodiment of the present invention; Figure 2 This is a schematic structural diagram of the present invention when initially drilling an anchor hole; Figure 3 This is a schematic structural diagram of the present invention when forming a complete anchor hole; Figure 4 This is a schematic front view structural diagram of the bearing plate of the present invention; Figure 5 This is a schematic bottom view structural diagram of the bearing plate of the present invention.

[0023] Markings in the figure: 1, precision rolled threaded steel bar; 2, connecting sleeve; 3, bearing plate; 4, spiral steel bar; 5, anchoring tool; 6, existing anti - floating bottom slab; 61, enlarged through - hole; 7, anchor hole; 71, equal - diameter section; 72, first enlarged - head section; 73, second enlarged - head section. Detailed implementation manners

[0024] The following further describes the present invention in combination with embodiments. The described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, other embodiments obtained by those of ordinary skill in the art without creative efforts all fall within the protection scope of the present invention.

[0025] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the present invention; the terms "first", "second", "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance; in addition, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0026] Combined with the drawings, the construction method for anti - floating reinforcement of existing underground structures in a narrow space of the present invention includes: (1) Measuring and laying out lines on the existing underground structure to determine the positions of the anchor holes of the anti - floating anchor rods for reinforcement.

[0027] (2)The drilling machine is positioned and drilled to form a preliminary anchor hole. The preliminary anchor hole includes an equal-diameter section and a first enlarged head section located at the upper end of the equal-diameter section. The diameter of the first enlarged head section is larger than that of the equal-diameter section. Among them, the depth of the preliminary anchor hole should meet the design requirements (that is, the depth of the preliminary anchor hole is drilled to the design depth). According to the characteristics of the anti-floating anchor rod, the anti-floating anchor rod includes a free section and an anchoring section. Since the first enlarged head section is located at the upper end of the equal-diameter section, the first enlarged head section is located in the free section of the anti-floating anchor rod. In the present invention, by processing the upper end of the equal-diameter section of the preliminary anchor hole to form the first enlarged head section, a first enlarged head is formed at the upper end of the equal-diameter section after the grout solidifies. The function of the first enlarged head can not only reinforce the formation under the underground structure of the existing building. Especially, the rapidly changing groundwater level will affect the bearing capacity of the formation. The present invention uses the first enlarged head formed after the grout pouring of the first enlarged head section to achieve the purpose of improving the bearing capacity of the foundation. On the other hand, when prestressing the anchor rod made of fine-threaded steel bars and during the later anti-floating effect of the anti-floating anchor rod, the first enlarged head can be used to increase the contact area with the anti-floating floor of the underground structure of the existing building (that is, the existing underground structure), avoiding the risk of damage to the original anti-floating floor.

[0028] In addition, the first enlarged head formed by grout pouring of the first enlarged section can shorten the distance between the grout body of the anchoring section of the anti-floating anchor rod (that is, the second enlarged head formed after the grout pouring of the second enlarged section). Those skilled in the art can understand that for the enlarged head anti-floating anchor rod, when prestressing is applied, it mainly relies on the extrusion between the anchoring section and the upper rock and soil mass to resist (that is, mainly relies on the rock and soil mass above the second enlarged head to resist the second enlarged head). In this process, the formation above the anchoring section (that is, above the second enlarged head) will be more or less compressed and disturbed to a certain extent. The present invention reduces the thickness of the formation above the anchoring section by grout pouring the first enlarged head section formed by the first enlarged head, that is, increases the stiffness of the formation, thereby reducing the degree of compression of the formation and finally reducing the disturbance to the original formation.

[0029] (3)Use the formed preliminary anchor hole to carry out groundwater dewatering operation to make the groundwater level reach the required level for construction; in the specific implementation process, since groundwater will affect the construction of the anti-floating anchor rod (mainly greatly reducing the forming quality of the grout), it is necessary to carry out groundwater dewatering operation. For the underground structure of the existing building, basically none of the dewatering wells during the previous foundation pit construction can be used. The present invention uses the preliminary anchor hole of the anti-floating anchor rod to carry out groundwater dewatering, so that the anchor hole can achieve the purpose of dual use, without the need to construct a new dewatering well to achieve the dewatering operation purpose, and thus reduce the construction cost due to reducing the construction operation of the dewatering well.

[0030] In the prior art, before constructing the underground structure of a building, by setting dewatering wells, due to the large number of dewatering wells, the large size of a single dewatering well, the great depth of a single dewatering well, and the long dewatering time, after dewatering by the dewatering wells, the groundwater levels in various areas below the entire underground structure of the building are basically in the same state, that is, the pores in the original soil mass are all in a hollow state. Therefore, when prestressing the anti-floating anchor rod, the influence on the surrounding rock and soil mass will transition smoothly, and finally the disturbance to the original soil mass is small.

[0031] When constructing and strengthening the anti-floating anchor rod, limited by the small size of the anchor hole and the short dewatering time, even if the groundwater around the initial anchor hole is excluded, the groundwater level in the remaining areas of the entire underground structure does not decrease or decreases less. Especially when the groundwater level in the formation around the initial anchor hole is drained, the pores between the soil particles in the formation around the anchor hole are in a hollow state, resulting in a greatly increased compressibility of the soil. This will lead to a large difference in the compressibility of the soil around the anchor hole and the soil in other areas of the underground structure. When prestressing the anti-floating anchor rod, it is very likely that the influence on the surrounding soil will show a fault situation, and thus the disturbance to the soil is large. Therefore, the present invention uses the first enlarged head formed after grouting and pouring the first enlarged head section to reduce the thickness of the original soil mass above the anchoring section (i.e., the second enlarged head formed after grouting and pouring the second enlarged head section) and increase the stiffness of the original soil mass above, reduce the amount of compression of the original soil mass above, and further reduce the probability of faults, and finally achieve the purpose of reducing the disturbance to the original soil mass.

[0032] That is to say, when prestressing the anti-floating anchor rod, it will cause a large disturbance to the original soil mass, and the first enlarged head formed by grouting the first enlarged head section can reduce the disturbance to the original soil mass when prestressing.

[0033] (4) The drilling machine reams the equal-diameter section of the lower part of the initial anchor hole to form a second enlarged head section, so as to obtain a complete anchor hole. A spacing is formed between the first enlarged section and the second enlarged section by using the equal-diameter section. The position of the second enlarged head section corresponds to the anchoring section of the anti-floating anchor rod, that is to say, the second enlarged head section is located in the bearing stratum in the formation. In the specific implementation process, according to the geological structure, the depth of the second enlarged head section entering the bearing stratum will also be different. For example, for the rock anchoring section, the length of the enlarged head section should not be less than 3m; for the soil layer (such as the strongly weathered soil layer) anchoring section, the length of the enlarged head section should not be less than 6m. The length of the anchoring section (i.e., the length of the second enlarged head section) can also be calculated by those skilled in the art using formulas. For the design of the length of the anchoring section, it is not an improvement point of the present invention, and those skilled in the art can all understand and comprehend, so it will not be elaborated here.

[0034] (5) Carry out hole cleaning operation on the anchor hole obtained in step (4).

[0035] (6) Segmentally implant the rolled and threaded steel bar anchor into the anchor hole and connect each segment of the rolled and threaded steel bar into a whole as the anchor, and then grout. After the grout solidifies, a first enlarged head is formed in the first enlarged head section, and a second enlarged head is formed in the second enlarged head section after the grout solidifies; between the first enlarged head and the second enlarged head is an equal-diameter section, and the diameters of the first enlarged head and the second enlarged head are both larger than the diameter of the equal-diameter section.

[0036] (7) Apply prestress and anchor to complete the reinforcement construction of the anti-floating anchor of the underground structure. Among them, the application of prestress and anchoring of the anti-floating anchor both belong to the prior art. Generally, an anchoring tool composed of a prestressed anchor plate (or called a prestressed anchor backing plate) and a prestressed anchor head is used for anchoring. Those skilled in the art can understand and comprehend, and will not be elaborated here.

[0037] In the specific implementation process, a protection pipe is sleeved on the outer periphery of the section of the rolled and threaded steel bar anchor corresponding to the first enlarged section of the anchor hole and the equal-diameter section of the anchor hole, and an anti-corrosion grease is applied between the protection pipe and the rolled and threaded steel bar.

[0038] The present invention uses the rolled and threaded steel bar as the anchor for reinforcing the anti-floating anchor. Compared with the prior art that uses ordinary steel bars as the anchor, the rolled and threaded steel bar has higher yield strength and tensile strength, and can significantly improve the pull-out bearing capacity of the reinforced anti-floating anchor. And compared with the ordinary steel bar anti-floating anchor, it has the advantages of convenient anchoring and construction, etc., achieving the purpose of reducing costs.

[0039] At the same time, the rolled and threaded steel bars can be directly connected by means of fastening nuts, connecting sleeves, etc., that is, the adjacent section of the rolled and threaded steel bars are spliced by means of fastening nuts, connecting sleeves, etc. Compared with the connection method of welding used for ordinary steel bar anchors, the problem of stress concentration is avoided, and the anti-floating capacity of the reinforced anti-floating anchor is further improved.

[0040] In some embodiments, a plurality of bearing plates are spaced apart on the outer periphery of the section of the rolled and threaded steel bar corresponding to the second enlarged head section of the anchor hole. The bearing plates are used to improve the bonding force after the grout solidifies, thereby achieving the purpose of improving the anti-floating capacity.

[0041] In some embodiments, the drilling machine is in place and drills to form a preliminary anchor hole, which specifically includes: (1) Use an anchor drill to drill on the anti-floating bottom plate of the existing underground structure and form a through hole on the anti-floating bottom plate, and then continuously drill into the soil until the depth of the hole in the soil matches the depth of the designed first enlarged head section; (2) Replace the drill bit with a larger-sized drill bit. Use an anchor drill or a reamer to ream the through-hole of the anti-floating floor slab of the existing underground structure to form a reamed through-hole. The diameter of the reamed through-hole is larger than the size of the through-hole and smaller than the diameter of the first enlarged head section. (3) Use a high-pressure jet grouting rig to ream the hole formed in step (1) to form the first enlarged head section. (4) Use the drill bit in step (1) to continue drilling downward so that the depth of the preliminary anchor hole reaches the design requirements.

[0042] That is to say, in the specific implementation process, when forming the preliminary anchor hole, an anchor drill, a high-pressure jet grouting rig or a combination of an anchor drill and a high-pressure jet grouting rig can be used to drill to form the preliminary anchor hole.

[0043] The present invention directly uses an anchor drill to drill on the anti-floating floor slab of the underground structure of an existing building. Compared with the prior art method of smashing and damaging the anti-floating floor slab, it can reduce the impact on the original anti-floating floor slab, and further reduce the impact on the existing underground structure, ensuring the safety of the existing building.

[0044] The present invention uses an anchor drill to pre-drill a through-hole on the anti-floating floor slab of the existing underground structure, and then reams it to form an enlarged through-hole. When the anchor hole is poured, by means of grouting and bonding between the first enlarged head hole and the existing anti-floating floor slab, the contact area between the reinforced anti-floating anchor and the existing anti-floating floor slab can be increased; and due to the setting of the first enlarged head section, when grouting into the anchor hole, the grout will also penetrate more into the gap between the existing anti-floating floor slab and the top surface of the soil body, thereby further increasing the bonding strength between the reinforced anti-floating anchor and the existing anti-floating floor slab. At the same time, since the pores in the area below the existing anti-floating floor slab are strengthened, the risk of damage to the existing anti-floating floor slab during the later application of prestress and the anti-floating action of the anti-floating anchor is avoided.

[0045] After long-term use of a concrete structure, especially for the anti-floating floor slab, problems such as a reduction in the strength of the anti-floating floor slab due to aging and subsequent cracking will more or less occur under the corrosion of groundwater vapor and the like. When constructing and reinforcing the anti-floating anchor, the present invention can play a certain role in strengthening and reinforcing the periphery of the existing anti-floating floor slab corresponding to the anti-floating anchor, and improve the service life of the existing anti-floating floor slab.

[0046] In the prior art, since there is no first enlarged head section in the anchor hole and the diameter of the anchor hole is relatively small, the contact area between the reinforced ordinary steel bar anti-floating anchor and the anti-floating floor slab is small. On the one hand, this leads to a low bonding strength between the reinforced ordinary steel bar anti-floating anchor and the existing anti-floating floor slab. On the other hand, the strengthening and reinforcing effect on the existing anti-floating anchor is almost negligible.

[0047] In addition, in the prior art, there is also an implementation method of using steel pipes (such as grouting perforated pipes) as anchor rods for anti-floating anchor rods. However, the size of the steel pipes used for anchor rods is generally larger than that of ordinary steel bar anchor rods and high-strength deformed steel bar anchor rods. Therefore, the size of the anchor holes for the steel pipes has to be increased. In this case, it will lead to an increase in the hole-forming cost of the anchor holes and an increase in the grouting volume, resulting in an increase in the cost of strengthening the anti-floating anchor rods. In addition, it is also necessary to fixedly install a bearing plate around the steel pipe and connect adjacent sections of the steel pipe. These steps will, on the one hand, lead to an increase in cost, and on the other hand, make it difficult to control the quality of the anti-floating anchor rods. More importantly, due to the relatively smooth outer periphery of the steel pipe, the bonding force between the steel pipe and the injected slurry will be reduced, thus affecting the anti-floating ability; and if the anti-floating ability is to be ensured, it is necessary to further process the circumferential wall of the steel pipe, ultimately resulting in high costs.

[0048] The present invention directly uses high-strength deformed steel bars as anchor rods. In addition to having higher yield strength and tensile strength, the splicing between each section can be realized by convenient and fast methods such as fastening nuts and connecting sleeves, and the bearing plate can also be directly sleeved on the high-strength deformed steel bar through threads, so as to achieve the purpose of reducing costs and improving construction efficiency.

[0049] In some embodiments, the depth of the first enlarged head section is less than half of the preliminary anchor hole depth. Preferably, the depth of the first enlarged head section is between one-third and one-half of the preliminary anchor hole depth. If the depth of the first enlarged head section is too long (i.e., greater than half of the preliminary anchor hole), since the diameter of the first enlarged head section is larger than that of the equal-diameter section, the processing of the too-long first enlarged head section will increase the construction difficulty and construction cost; while if the depth of the first enlarged head section is too short (i.e., less than one-third of the preliminary anchor hole), it will lead to an insignificant reinforcement effect of the first enlarged head section on the soil body and cannot improve the bearing capacity of the foundation.

[0050] In the specific implementation process, those skilled in the art can adjust the depth of the first enlarged head section according to the weight of the existing building and the bearing capacity of the foundation. Those skilled in the art can understand and comprehend this, and will not be elaborated here.

[0051] In some embodiments, the diameter of the first enlarged head section is the same as that of the second enlarged head section, so that it is not necessary to make excessive adjustments to the parameters of the jet grouting rig, improving the convenience of operation.

[0052] In some embodiments, when grouting and pouring the anchor holes, the grout should overflow the enlarged through holes of the existing anti-floating floor slab. In the specific implementation process, the thickness of the anti-floating floor slab is generally between 0.4m and 0.5m, so as to use the thickness of the existing anti-floating floor slab to guide the height of the grout, thereby improving the pouring quality of the anti-floating anchor. Those skilled in the art can understand that after the grout solidifies, the immersion of the grout into the rock and soil will cause the liquid level of the grout to drop, and at the same time, the segregation and stratification of the top grout will lead to a reduction in the strength of the top area of the anti-floating anchor. The existing technology has to additionally set up pipes to limit the highest position of the grout because the anti-floating floor slab is broken. This method makes the grouting process cumbersome (one is the implantation, centering and fixation of the pipes, and the other is the removal of the pipes). The present invention directly utilizes the enlarged through holes of the existing anti-floating floor slab, makes full use of the existing conditions, and improves the convenience of construction.

[0053] In some embodiments, after the grouting in step (6) is completed, spiral steel bars are implanted into the grout, and the lower ends of the spiral steel bars penetrate into the first enlarged head section. Thus, the upper area of the anti-floating anchor is processed by using the spiral steel bars to improve the structural strength.

Claims

1. A construction method for anti - floating reinforcement of existing underground structures in narrow spaces, characterized in that, Including: (1) Measuring and setting out on the existing underground structure to determine the anchor hole positions of the anti - floating anchor rods for reinforcement; (2) The drilling machine is in place and drills to form a preliminary anchor hole. The preliminary anchor hole includes an equal - diameter section and a first enlarged - head section located at the upper end of the equal - diameter section. The diameter of the first enlarged - head section is larger than that of the equal - diameter section; (3) Using the formed preliminary anchor hole to conduct dewatering operation on the groundwater to make the groundwater level reach the required level for construction; (4) The drilling machine reams the equal - diameter section at the lower part of the preliminary anchor hole to form a second enlarged - head section, thereby obtaining a complete anchor hole. There is a spacing formed by the equal - diameter section between the first enlarged section and the second enlarged section; (5) Conducting hole - cleaning operation on the anchor hole obtained in step (4); (6) Segmentally implanting high - strength deformed steel bar anchor rods into the anchor hole and connecting each segment of the high - strength deformed steel bars into a whole as the anchor rod, and then grouting; (7) When the grout for grouting and pouring solidifies and reaches the design strength, prestress is applied to and anchored on the high - strength deformed steel bars to complete the reinforcement construction of the anti - floating anchor rods of the underground structure.

2. The construction method for anti-floating reinforcement of existing underground structures in narrow spaces according to claim 1, characterized in that The specific process of the drilling machine being in place and drilling to form a preliminary anchor hole includes: (1) Using an anchor rod drilling machine to drill on the anti - floating bottom plate of the existing underground structure and form a through - hole on the anti - floating bottom plate, and then continuously drill into the soil until the hole depth in the soil matches the depth of the designed first enlarged - head section; (2) Replacing the drill bit with a larger - sized one and using the anchor rod drilling machine or a reaming drill to ream the through - hole on the anti - floating bottom plate of the existing underground structure to form an enlarged - type through - hole. The diameter of the enlarged - type through - hole is larger than the size of the through - hole and smaller than the diameter of the first enlarged - head section; (3) Using a high - pressure jet grouting drilling machine to ream the hole formed in step (1) to form the first enlarged - head section; (4) Using the drill bit in step (1) to continue drilling downward so that the depth of the preliminary anchor hole reaches the design requirements.

3. The anti-floating reinforcement construction method for existing underground structures in narrow spaces according to claim 2, characterized in that, When grouting and pouring the anchor hole, the grout for grouting should overflow the enlarged - type through - hole of the existing anti - floating bottom plate.

4. The anti - floating reinforcement construction method for existing underground structures in narrow spaces according to claim 1, characterized in that, The depth of the first enlarged - head section is less than half of the depth of the preliminary anchor hole.

5. The anti-floating reinforcement construction method for existing underground structures in narrow spaces according to claim 4, characterized in that, The depth of the first enlarged - head section is between one - third and one - half of the depth of the preliminary anchor hole.

6. The construction method for anti - floating reinforcement of existing underground structures in narrow spaces according to claim 1, wherein, The diameter of the first enlarged - head section is the same as that of the second enlarged - head section.

7. The construction method for anti - floating reinforcement of existing underground structures in narrow spaces according to any one of claims 1 - 6, characterized in that, Multiple bearing plates are arranged at intervals on the periphery of the section of the high - strength deformed steel bar corresponding to the second enlarged - head section of the anchor hole.

8. According to the construction method for anti - floating reinforcement of an existing underground structure in a narrow space according to any one of claims 1 - 6, after completing the grouting in step (6), spiral steel bars are implanted into the grout, and the lower end of the spiral steel bars extends into the first enlarged - head section.

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