Reverse grouting repair construction method for upstream face of deep foundation pit underground structure

Abstract

The invention discloses a reverse grouting repair construction method for an upstream face of an underground structure of a deep foundation pit. The reverse grouting repair construction method comprises the following steps that firstly, drainage is conducted in the pit; the purpose of drainage in the pit is to facilitate the next grouting and drilling work, and water in the structure is drained through a submersible pump and a self-priming pump; step 2, drilling and pipe arrangement; the obvious water leakage position of the bottom plate is punched through a long-rod drill bit. And a long rod drill bit is used for drilling holes in the bottom plate according to the longitudinal and transverse distance of 1.5 meters. The length of the grouting pipe inserted into the foundation slab is calculated according to the thickness of the slab, and it is guaranteed that a grout outlet of the grouting pipe just extends out of the foundation slab structure. According to the reverse grouting repairing technology, the traditional grouting repairing technology is mainly adopted, meanwhile, specific equipment is adopted for changing the grouting position, the geological environment and the high water level pressure around the foundation pit are utilized, the effect that grouting is in place and grouting is effectively reserved is achieved, and the purposes of structure repairing and water stopping are achieved. Practice shows that the effect is good.

Description

Technical Field

[0001] The present invention belongs to the technical field of grouting construction, and particularly relates to a construction method for reverse grouting repair on the water-facing side of the underground structure of a deep foundation pit. Background Technique

[0002] Foundation pit engineering mainly includes the design and construction of the foundation pit support system and earth excavation, and is a comprehensive systematic project. It requires close cooperation between geotechnical engineering and structural engineering technicians. The foundation pit support system is a temporary structure and is no longer needed after the completion of the underground project construction.

[0003] When a rigid self-waterproof structure is adopted for a deep foundation pit with a high water level in a construction project, it is relatively easy to initially see leakage due to cracks in the foundation slab or external wall structure. When the geology around the deep foundation pit is clay, sand, etc., the method of grouting on the outside of the structure can be used for water-stop repair. However, when the geology around the deep foundation pit is cobblestones, etc., the grouting on the outside of the structure cannot be evenly distributed into each cobblestone gap. Especially when the underground water level is high, there is almost no water-stop effect.

[0004] When pouring the concrete of the deep foundation pit floor structure, there is a phenomenon of water gushing in the foundation pit. In order to rush the progress, the construction unit sometimes forcibly pours the concrete. Although, after core sampling later, the experimental results show that the concrete strength is qualified, but there are multiple water seepage and water gushing phenomena in the floor concrete.

[0005] Due to problems in the construction technology of the foundation pit floor structure resulting in leakage due to floor cracking, when the underground water level is high, the water head at the leakage part is large and there are many leakage parts. At this time, the process of repairing grouting inside the foundation pit cannot solve the problem of the large water head and water pressure at the leakage point. At the same time, when the geology around the foundation pit is a cobblestone layer and the traditional method of grouting outside the foundation pit is not applicable. A reverse grouting repair process needs to be adopted.

[0006] The reverse grouting repair process mainly adopts the traditional grouting repair process, and at the same time, uses specific equipment to change the grouting position, utilizes the geological environment and high water level pressure around the foundation pit to achieve the effect of grouting in place and effective retention of grout, so as to achieve the purpose of structural repair and water stop. Summary of the Invention

[0007] The present invention provides a reverse grouting repair construction method for deep foundation pit underground structures to solve the problems of water leakage caused by cracks in the bottom slab due to problems in the construction technology of the foundation pit floor structure at the current stage. When the groundwater level is high, there is a large water head and many water leakage points at the water leakage part. At this time, processes such as in-pit repair grouting cannot solve the problem of large water head and water pressure at the water leakage points; and the grout for grouting outside the structure cannot effectively fill the gaps between the pebbles; the method of repairing the concrete structure by inner repair and grouting with repair materials has many water leakage points, and at the same time, due to the large water pressure and large water flow at the water leakage points, the repair materials are washed away before they have time to react and harden, resulting in repair failure.

[0008] To achieve the above object, the present invention provides a reverse grouting repair construction method for the water-facing surface of deep foundation pit underground structures. The reverse grouting repair construction includes the following steps: Step 1, in-pit drainage; the purpose of in-pit drainage is to facilitate the subsequent grouting drilling work, and the water in the structure is drained through a submersible pump and a self-priming pump; Step 2, drilling and pipe laying; a. Punch holes through a long rod drill bit at the obvious water leakage points on the bottom slab.

[0009] b. Punch holes through a long rod drill bit at a spacing of 1.5 meters in the longitudinal and transverse directions on the bottom slab.

[0010] c. Conduct orifice treatment at the drilling positions to facilitate subsequent plugging.

[0011] d. Lay pipes through the holes that have been drilled through a long rod drill bit at a spacing of 1.5 meters on the bottom slab. Note that the length of the grouting pipe inserted into the foundation bottom slab is calculated according to the thickness of the bottom slab to ensure that the slurry outlet of the grouting pipe just protrudes from the foundation bottom slab structure.

[0012] Step 3, in-pit water filling; after the pipe laying is completed, evacuate the personnel and conduct in-pit water filling. It is sufficient to achieve the balance of water pressure inside and outside the pit.

[0013] Step 4, pressure grouting; Step 5, curing; according to the properties of the grouting material, keep the water level in the pit. Until the grouting material solidifies. The solidification time of the grouting material refers to the grouting volume instruction manual. Note: The purpose is to allow the slurry remaining on the water-facing surface of the structure to have time to react and harden. The density of the slurry is greater than that of water, and under the condition of consistent internal and external pressure and static water, the slurry can be effectively retained under the structure bottom slab. At the same time, since the slurry is on the water-facing surface of the structure, the external water pressure can allow the slurry to penetrate into the structure gaps from the outside.

[0014] Step 6, observe the effect by in-pit drainage; a. The purpose of in-pit drainage is to observe the grouting effect that has been completed, mark whether there is still water leakage and mark the water leakage points.

[0015] b. If water leakage is still found, drill holes at the leakage points and repeat Step 2, i.e., drill holes and lay pipes.

[0016] Step 7, plug the drill holes.

[0017] a. If the grouting effect is good and no new water leakage is found, plug the original drill holes.

[0018] b. After cleaning the slurry in the connecting casing, use a special plugging device - plug head to plug the original drill holes.

[0019] Adopt the cement grouting method; applicable to grouting of gravel layers and rock fissures.

[0020] Furthermore, in Step 1, the efficiency of the water pump should be greater than the water leakage speed inside the structure, and at least meet the requirement that people can stand on the floor for construction.

[0021] Furthermore, in Step 2, before drilling, first chisel the structural protective layer to the upper surface reinforcement according to the preset position to avoid the reinforcement position for drilling.

[0022] Furthermore, in Step 3, the height of the filled water is level with the groundwater level; to achieve the balance of water pressure inside and outside the structure, and let the water flow at the water leakage point of the structure be relatively static to give the grouting material time to react.

[0023] Furthermore, in Step 4, adopt the cement grouting method; applicable to grouting of gravel layers, pebble layers and rock fissures.

[0024] Furthermore, use ordinary portland cement, the water - cement ratio is 1:1, and 2% - 5% sodium silicate is added as a setting accelerator.

[0025] Furthermore, for grouting, use an ordinary extrusion mortar pump, and the grouting pressure is less than 1 MPa; for fine sand and cohesive soil with a permeability coefficient less than 10 - 4 cm / s, split grouting can be adopted.

[0026] Furthermore, conduct pressure grouting through professional equipment; Furthermore, judge through the technical grouting volume (calculate the grouting volume by calculating the area of the structural floor slab and the expected grouting thickness), and whether the grouting is evenly distributed to the bottom layer of the foundation.

[0027] Furthermore, the consistency of the cement slurry used for split grouting is relatively large, and the water - cement ratio is 0.45 - 0.60.

[0028] Furthermore, adopt the flower - tube method and the one - way valve tube method for grouting.

[0029] Furthermore, the grouting pressure is at least 4 MPa.

[0030] Furthermore, the connection structure includes the structural foundation floor slab and the grouting pipe units arranged at intervals; The grouting pipe unit includes an upper grouting pipe, a lower grouting pipe, a connecting sleeve, and a water stop ring; the upper grouting pipe and the lower grouting pipe are threadedly connected, the connecting sleeve is arranged outside the upper grouting pipe and the lower grouting pipe, and the water stop ring is abutted on the structural foundation floor; Further, the diameters of both the upper grouting pipe and the lower grouting pipe are 25 mm.

[0031] Further, a slurry outlet hole is provided at the bottom.

[0032] Further, the distance between the grouting pipe units is 1000 - 1500 mm.

[0033] Further, a round hole for passing through the connecting sleeve is provided in the middle of the water stop ring.

[0034] Further, a thread is also provided inside the water stop ring, which is convenient for plugging with a plug in the later stage.

[0035] Further, the distance between the grouting pipe units at both ends from the inner wall of the foundation of the foundation pit structure is at least 300 mm.

[0036] Further, after grouting is completed, a plug is inserted into the top of the upper grouting pipe.

[0037] The beneficial effects of the present invention are reflected in: 1. The reverse grouting repair construction method for the water-facing surface of the deep foundation pit underground structure provided by the present invention proposes a reverse grouting repair method of injecting the grouting liquid onto the water-facing surface of the structure. The reverse grouting repair process mainly adopts the traditional grouting repair process, and at the same time, specific equipment is used to change the grouting position, and the geological environment and high water level pressure around the foundation pit are utilized to make the grouting reach the position and be effectively retained, achieving the purpose of structural repair and water stop. The practical effect is good.

[0038] 2. The reverse grouting repair construction method for the water-facing surface of the deep foundation pit underground structure provided by the present invention solves the problems of water leakage caused by cracks in the bottom slab due to problems in the construction process of the foundation pit floor structure at the present stage, and presents the problems of large water head and many water leakage parts at the water leakage parts under the condition of high groundwater level.

[0039] 3. The reverse grouting repair construction method for the water-facing surface of the deep foundation pit underground structure provided by the present invention repairs the concrete structure by means of inner repair and grouting of the repair material, perfectly solving the problem that the repair material is washed away before it has time to react and harden due to many water leakage points, large water pressure, and large water flow, resulting in repair failure.

[0040] 4. The reverse grouting repair construction method for the water-facing surface of the deep foundation pit underground structure provided by the present invention well overcomes the technical prejudice. When constructing at the water leakage part of the structure, the operation of filling water in the pit is adopted, and the filling height is flush with the groundwater level. The internal and external water pressures of the structure are balanced, and the water flow at the water leakage part of the structure is relatively static, allowing the grouting material to have a reaction time.

[0041] Other features and advantages of the present invention will be set forth in the following description, and will become, in part, apparent from the description, or may be learned by practice of the present invention. The main object and other advantages of the present invention can be achieved and obtained by the solutions specifically pointed out in the description. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The present invention will be further described in detail below with reference to the accompanying drawings.

[0043] Figure 1 It is a schematic diagram for chiseling grouting holes.

[0044] Figure 2 It is a schematic diagram of the lower grouting pipe.

[0045] Figure 3 It is a schematic diagram of the grouting hole arrangement.

[0046] Figure 4 It is a schematic diagram of the grouting pipe installation.

[0047] Figure 5 It is a schematic diagram of the grouting flow direction of the floor slab.

[0048] Figure 6 It is a schematic diagram of the removal of the grouting pipe and the plugging of the drilling area.

[0049] Figure 7 It is a schematic diagram of the plugging of the drilling area.

[0050] Figure 8 It is a schematic diagram of the position of the water stop ring.

[0051] Figure 9 It is a cross-sectional view of the foundation pit.

[0052] Figure 10 It is a schematic diagram of the plug.

[0053] Figure 11 It is a schematic diagram of filling water in the pit.

[0054] Figure 12 It is a schematic diagram of the materials for the grouting method.

[0055] BRIEF DESCRIPTION OF THE DRAWINGS: 1 - Foundation pit, 2 - Floor slab, 3 - Upper grouting pipe, 4 - Lower grouting pipe, 5 - Connecting sleeve, 6 - Water stop ring, 7 - Grout outlet hole, 8 - Plug, 9 - Floor slab steel bars, 10 - Grouting pipe unit, 11 - External thread. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0056] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0057] Here, it should also be noted that in order to avoid obscuring the present invention due to unnecessary details, only the structures and / or processing steps closely related to the solution of the present invention are shown in the drawings, while other details less related to the present invention are omitted.

[0058] After inspecting the site, the applicant proposed a reverse grouting repair method of injecting the grouting liquid onto the water-facing side of the structure. The practical effect is good. The reverse grouting repair process is introduced in detail at each key point, and the principle is expounded.

[0059] This project is located about 0.5 km northeast of the center of a foreign city and beside a certain river. The structure of the deep foundation pit 1 is a water intake pump station with a water supply capacity of 12,760 m³ / d. The base depth is 21.1 m.

[0060] The buried depth of the groundwater level at the site is 1.01 m, and the water level elevation is 8.30 m. The current water surface elevation of the adjacent XX River is 6.18 m, and the category and situation of the groundwater are not clear.

[0061] The excavation of this foundation pit 1 adopted the method of steel sheet piles and concrete retaining walls.

[0062] The on-site situation is that the construction of the deep foundation pit 1 structure is completed, and there is no water seepage in the external wall of the underground structure, but there are many leakage points in the structural foundation slab 2. According to the investigation, the groundwater gushing was relatively large during the pouring of the structural foundation slab 2, resulting in irregular cracks in the structural slab 2.

[0063] See Figure 1-11 As shown, on the one hand, the present invention provides a grouting pipe grouting connection structure. The connection structure includes a structural foundation slab 2 and spaced grouting pipe units 10; The grouting pipe unit 10 includes an upper grouting pipe 3, a lower grouting pipe 4, a connecting sleeve 5, and a water stop ring 6; the upper grouting pipe 3 is threadedly connected to the lower grouting pipe 4, the connecting sleeve 5 is arranged outside the upper grouting pipe 3 and the lower grouting pipe 4, and the water stop ring 6 is abutted and arranged on the structural foundation slab 2; a round hole for passing through the connecting sleeve 5 is arranged in the middle of the water stop ring 6.

[0064] The diameters of both the upper grouting pipe 3 and the lower grouting pipe 4 are 25 mm. The bottom of the lower grouting pipe 4 is provided with a slurry outlet hole 7. The distance between the grouting pipe units 10 is 1000 - 1500 mm. The distance from the grouting pipe units 10 at both ends to the inner wall of the structural foundation is at least 300 mm.

[0065] After the grouting is completed, the top of the upper grouting pipe 3 is inserted into a plug 8 with an external thread 11.

[0066] See Figure 2-Figure 9 As shown, the reverse grouting process includes the following steps: Step 1, drain the water in the foundation pit 1; the purpose of draining the water in the foundation pit 1 is to facilitate the next grouting drilling work, and the water in the structure is drained through a submersible pump and a self-priming pump. Note that the efficiency of the pump should be greater than the water leakage rate in the structure, and at least ensure that people can stand and construct on the bottom plate 2.

[0067] Step 2, drill holes and lay pipes; a. Drill holes at the obvious water leakage points on the bottom plate 2 with a long rod drill bit. Note: Before drilling, first chisel the structural protective layer to the upper surface steel bar 9 according to the preset position, and avoid the position of the steel bar 9 for drilling. See Figure 2 as shown.

[0068] b. Drill holes on the bottom plate 2 at a vertical and horizontal interval of 1.5 m with a long rod drill bit. See Figure 5 as shown.

[0069] c. Treat the orifice at the drilling position to facilitate subsequent plugging.

[0070] d. Lay pipes through the holes that have been drilled on the bottom plate 2 at a 1.5 m interval with a long rod drill bit. Note that the length of the grouting pipe inserted into the foundation bottom plate 2 is calculated according to the thickness of the bottom plate 2 to ensure that the slurry outlet of the grouting pipe just protrudes from the structure of the foundation bottom plate 2.

[0071] Step 3, fill the foundation pit 1 with water; after laying the pipes, evacuate the personnel and fill the foundation pit 1 with water. It is sufficient to achieve the hydrostatic pressure balance inside and outside the foundation pit 1.

[0072] Step 4, pressure grouting; in this case project, the cement grouting method is adopted; it is applicable to grouting of gravel layers and rock fissures. Ordinary Portland cement is used, the water-cement ratio is 1:1, and 2% - 5% water glass is added as a setting accelerator. The grouting uses an ordinary extrusion mortar pump, and the maximum grouting pressure does not exceed 1 MPa. For fine sand and cohesive soil with a permeability coefficient less than 10-4 cm / s, split grouting can be used. The consistency of the cement slurry used for split grouting is relatively large, and the water-cement ratio is 0.45 - 0.60. The grouting adopts the flower pipe method and the one-way valve pipe method. The maximum grouting pressure is generally greater than 4 MPa.

[0073] a. Carry out pressure grouting through professional equipment; b. Judge whether the grouting is evenly distributed to the foundation bottom layer through the technical grouting volume. Note: The purpose is to let the slurry remain on the water-facing side of the structure.

[0074] Step 5, curing; according to the properties of the grouting material, keep the water level in the foundation pit 1. Until the grouting material solidifies. The solidification time of the grouting material refers to the grouting volume instruction manual. Note: The purpose is to let the slurry remaining on the water-facing side of the structure have time to react and harden. At the same time, because the slurry is on the water-facing side of the structure, the external water pressure can make the slurry seep into the structure cracks from the outside.

[0075] Step 6, drain the water in the foundation pit 1 and observe the effect; a. The purpose of draining water in the foundation pit 1 is to observe the grouting effect, mark whether there is still water leakage and mark the water leakage points.

[0076] b. If water leakage is still found, drill holes at the water leakage points and repeat step two, that is, drill holes and lay pipes.

[0077] Step seven, drill hole plugging.

[0078] a. If the grouting effect is good and no new water leakage is found, plug the original drill holes.

[0079] b. After cleaning the slurry in the connecting sleeve 5, use a special plugging device, the plug 8, to plug the original drill holes.

[0080] Adopt the cement grouting method; it is applicable to grouting of gravel layers and rock fissures. For details, see Figure 12 .

[0081] For different geological conditions and regions, the underground grouting treatment methods are different and need to be treated specifically according to the geological conditions and specific situations. This treatment process effectively solves the problem of water leakage at the foundation slab 2 under high water pressure in the pebble layer.

Claims

1. A reverse grouting repair construction method for the water-facing surface of a deep foundation pit underground structure, characterized in that: Reverse grouting repair construction includes the following steps: Step 1: draining the foundation pit (1); the purpose of draining the foundation pit (1) is to facilitate the grouting and drilling work in the next step, and the water in the structure is drained by a submersible pump and a self-priming pump; Step 2: drilling holes and laying pipes; Drill holes at obvious water leaking locations on the bottom plate (2) using a long-stem drill bit; Drill holes on the bottom plate (2) at intervals of 1.5 meters in both directions using a long-barrel drill bit; c. Perform hole treatment at the drilling location to facilitate subsequent plugging; d. Arrange pipes on the base plate (2) at intervals of 1.5 meters through holes drilled by a long-bar drill bit; the length of the grouting pipe inserted into the base plate (2) is calculated based on the thickness of the base plate (2) to ensure that the grouting pipe outlet just protrudes out of the base plate (2) structure; Step three, water is poured into the foundation pit (1); after the pipes are laid, personnel are evacuated and water is poured into the foundation pit (1) until the water pressure inside and outside the foundation pit (1) is balanced; Step 4: pressure grouting; Step 5: Maintenance: According to the properties of the grouting material, the water level in the foundation pit (1) is maintained until the grouting material solidifies; the solidification time of the grouting material refers to the grouting quantity instruction manual; Note: The purpose is to allow the slurry left on the water-facing surface of the structure to react and harden. The density of the slurry is greater than that of water. Under the condition of uniform internal and external pressures and static water, the slurry can be effectively retained under the structural bottom plate (2). At the same time, because the slurry is on the water-facing surface of the structure, the external water pressure can allow the slurry to penetrate into the structural gaps from the outside; Step 6: Observe the drainage effect in the foundation pit (1); a. The purpose of drainage in the foundation pit (1) is to observe the effect of the completed grouting, mark whether there is any leakage and mark the leakage point; b. If water leakage is still found, drill holes at the leaking point and repeat step 2, i.e. drilling holes and laying pipes; Step 7: Drilling and sealing; a. If the grouting effect is good and no new water leakage is found, the original drilling hole will be sealed; b. After cleaning the slurry in the connecting sleeve (5), a special plugging device-plugging head (8) is used to plug the original drilled hole; Use cement grouting method; Suitable for grouting in gravel layers and rock fissures.

2. The construction method according to claim 1, characterized in that: In step 1, the efficiency of the water pump is greater than the speed of water leakage in the structure, at least enough to allow people to stand on the bottom plate (2) for construction.

3. The construction method according to claim 1, characterized in that: In step 2, before drilling, the structural protection layer is chiseled to the upper surface steel bars (9) according to the preset position so as to avoid the position of the steel bars (9) for drilling.

4. The construction method according to claim 1, characterized in that: In step three, the water filling height is level with the groundwater level, achieving a water pressure balance inside and outside the structure, and the water flow at the leaking part of the structure is relatively still, giving the grouting material time to react.

5. The construction method according to claim 1, characterized in that: Step 4, using cement grouting method; Suitable for grouting in gravel layers, pebble layers and rock cracks.

6. The construction method according to claim 5, characterized in that: Ordinary Portland cement is used with a water-cement ratio of 1:1, and 2% to 5% water glass is added as an accelerating agent.

7. The construction method according to claim 5, characterized in that: Grouting uses an ordinary extrusion mortar pump with a grouting pressure of less than 1MPa; for fine sand and clay with a permeability coefficient less than 10-4cm / s, split grouting can be used.

8. The construction method according to claim 5, characterized in that: The cement slurry used for splitting grouting has a relatively high consistency, with a water-cement ratio of 0.45 to 0.

60.

9. The construction method according to claim 5, characterized in that: Grouting adopts the flower pipe method and the one-way valve pipe method.

10. The construction method according to claim 1, characterized in that: The connection structure comprises a structural foundation bottom plate (2) and grouting pipe units (10) arranged at intervals; The grouting pipe unit (10) comprises an upper grouting pipe (3), a lower grouting pipe (4), a connecting sleeve (5), and a water stop ring (6); the upper grouting pipe (3) and the lower grouting pipe (4) are threadedly connected, the connecting sleeve (5) is arranged outside the upper grouting pipe (3) and the lower grouting pipe (4), and the water stop ring (6) is arranged in contact with the structural foundation bottom plate (2).

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