Simple support structure post-tensioning prestress duct grouting construction method

Abstract

The present application relates to the technical field of civil engineering construction, and particularly relates to a simple support structure post-tensioned prestress duct grouting construction method. The present application analyzes the formation mechanism of the cavity after the prestress duct grouting, and correspondingly improves the process of the whole grouting construction. The bleeding and air bubbles in the grout are discharged from the end of the steel strand, the problem of the non-dense anchoring after the post-tensioned prestress duct grouting is solved, the density of the grouting is greatly improved, the effect of the dense and full duct grouting is achieved at one time, the construction process is reduced, the labor cost is saved, and the dense and full requirement of the grouting inlet and outlet and the anchoring pad is achieved.

Description

Technical Field

[0001] This invention relates to the field of civil engineering construction technology, and in particular to a method for grouting construction of post-tensioned prestressed ducts in simply supported structures. Background Technology

[0002] Since post-tensioned prestressed duct grouting is a concealed project, on-site construction inspections, tests, physical inspections, and dissections have revealed that existing post-tensioned prestressed duct grouting in simply supported beam structures where the anchorage is located high in the duct generally suffers from problems such as incomplete grouting after anchorage, exposed and corroded steel strands, and loosening of anchor clips under micro-vibration due to the large exposed length of steel strands, threatening structural safety and posing significant safety hazards.

[0003] However, the quality of post-tensioned prestressed duct grouting construction is not easy to guarantee, and it is not easy to expose problems in the early stages of use. As a result, many projects have been found to have major structural safety hazards such as mid-span deflection and cracking 20 to 30 years after construction, and have had to be demolished and rebuilt. To this day, the problem of non-compactness of post-tensioned prestressed duct grouting anchor has not been solved. Table 1 below is a statistical data on the distribution range of void volume in simply supported beams up to 2019.

[0004] Table 1. Distribution range of void volume in simply supported beams; Therefore, this invention proposes a method for grouting construction of post-tensioned prestressed ducts in simply supported structures. Summary of the Invention

[0005] The technical objective of this invention is to propose a grouting construction method for post-tensioned prestressed ducts in simply supported structures, thereby solving the problem of insufficient compaction after grouting anchors in post-tensioned prestressed ducts and greatly improving the compactness of the grouting.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A method for grouting construction of post-tensioned prestressed ducts in a simply supported structure, comprising the following steps: Grouting preparation: S1: Prestressed steel strands are produced by mechanical cutting; S2: Remove impurities from inside the channel using compressed air; S3: Use a cleaning agent that does not corrode the prestressed steel strands and ducts to rinse off the oil stains. After rinsing, use oil-free high-pressure air to remove the water accumulated in the ducts. S4: Seal the anchor clamps, anchor plates, anchor pads, and other gaps where grout leakage may occur; Start grouting: S5: Use slurry with a deposition flow ratio and deposition density ratio of over 96%; S6: Before the grout is injected into the duct, the water and thin grout in the grouting pipeline are drained. When the fluidity of the drained grout is the same as that of the grout in the storage device, the grout is injected into the duct. S7: During grouting, maintain the pressure at the grouting port between 0.5 and 0.7 MPa; S8: When the slurry discharged from the outlet has no obvious bubbles or foam, and the slurry flowability is the same as that of the slurry at the inlet, close the stop valve at the outlet. S9: Close the grout outlet, continue to inject grout, maintain the pressure inside the duct until the oozing water at the steel strand end changes from turbid to clear water, then close the grout stop valve at the grouting end. S10: After 24 hours, remove the grout stop valve and check the grout compaction at the grout inlet and outlet. S11: If voids or even exposed steel strands are found, secondary grouting shall be carried out.

[0007] As a preferred embodiment of the grouting construction method for post-tensioned prestressed ducts in a simply supported structure according to the present invention, in step S1, the exposed length of the prestressed steel strand after cutting is not less than 30mm and not less than 1.5 times the diameter of the prestressed steel strand.

[0008] As a preferred embodiment of the grouting construction method for post-tensioned prestressed ducts in a simply supported structure as described in this invention, in step S4, in order to ensure that the gaps in the steel strands can also be filled with the original grout, the ends of the steel strands, which serve as channels for air and water drainage, cannot be blocked.

[0009] As a preferred embodiment of the grouting construction method for post-tensioned prestressed ducts in a simply supported structure according to the present invention, in step S9, the internal pressure of the duct is stable and not less than 0.5 MPa.

[0010] As a preferred embodiment of the grouting construction method for post-tensioned prestressed ducts in a simply supported structure according to the present invention, in step S9, the pressure stabilization time inside the duct is greater than 5 minutes.

[0011] As a preferred embodiment of the grouting construction method for post-tensioned prestressed ducts in a simply supported structure according to the present invention, in step S10, an endoscope is used to check the grouting density in the grout inlet and outlet.

[0012] As a preferred embodiment of the grouting construction method for post-tensioned prestressed ducts in a simply supported structure according to the present invention, in step S11, the secondary grouting is vacuum grouting, and the vacuum degree is 0.1 MPa negative pressure.

[0013] As a preferred embodiment of the grouting construction method for post-tensioned prestressed ducts in a simply supported structure according to the present invention, in step S11, the gaps at the ends of the steel strands should be sealed or anchoring should be carried out before grouting.

[0014] As a preferred embodiment of the grouting construction method for post-tensioned prestressed ducts in a simply supported structure according to the present invention, the grout inlet and outlet are both located above the center of the anchor plate, and the inner diameter of the grout inlet and outlet is not less than 20mm.

[0015] As a preferred embodiment of the grouting construction method for post-tensioned prestressed ducts in a simply supported structure as described in this invention, the entire grouting process employs a screw-type grouting pump.

[0016] The beneficial effects of this invention are: This invention increases the detection of grout deposition rate, controlling the grout deposition flowability ratio and deposition density ratio to above 96%, thereby reducing the grout bleeding rate. Combined with grouting construction, grout is continuously injected into the duct, maintaining the grout pressure within a certain range. After a period of pressure stabilization, the bleeding water and air bubbles in the grout are discharged from the ends of the steel strands, significantly improving the grout density. This achieves a dense and full grouting effect in one go, reducing construction steps, saving labor costs, and ensuring that the grout inlet and outlet of the post-tensioned prestressed duct and the area under the anchor plate meet the requirements for density and fullness. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the internal structure of the anchor in an embodiment of this disclosure.

[0018] Figure 2 This is a schematic diagram of the end of the anchor in an embodiment of this disclosure.

[0019] Reference numerals: 1. Steel strand; 2. Anchor clamp; 3. Anchor plate; 4. Anchor pad; 5. Duct; 6. Grout stop valve. Detailed Implementation

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0021] like Figures 1 to 2 As shown, a method for grouting post-tensioned prestressed ducts in a simply supported structure includes the following steps: Grouting preparation: S1: Prestressed steel strand 1 after mechanical cutting; S2: Remove impurities from inside channel 5 using compressed air; Remove any substances from the duct 5 that affect the compactness and performance of the grout. Check and confirm that there is no water accumulation, debris, or blockages that hinder grouting in the duct 5. Debris or water in the duct 5 can be removed with compressed air.

[0022] S3: Use a cleaning agent that does not corrode the prestressed steel strand 1 and the duct 5 to rinse off the oil stains. After rinsing, use oil-free high-pressure air to remove the water accumulated in the duct 5. The cleaning agent needs to be diluted with water before rinsing. Check if there is any damage to the duct 5. If there is damage that may affect the compactness of the grouting, it needs to be treated.

[0023] S4: Seal the anchor wedge 2, anchor plate 3, anchor pad 4 and other gaps where grout leakage may occur; Inspect the slurry inlet and outlet to ensure unobstructed flow and tight connections within the pipes.

[0024] Start grouting: S5: Use slurry with a deposition flow ratio and deposition density ratio of over 96%; thereby reducing the bleeding rate of the slurry; To ensure that the sedimentation flow ratio and sedimentation density ratio of the slurry are above 96%, the slurry needs to be tested in advance. The prepared slurry is filled into a 5-liter capacity cylinder. After the excess slurry is discharged through the limit overflow hole, the overflow hole is sealed. After standing for 1 hour, the valve of the outflow hole in the middle of the cylinder is opened to separate the upper half of the slurry.

[0025] Flowability ratio determination: The flowability of the upper slurry and the lower slurry are measured separately using a flowability meter. The flowability value of the clean slurry is in seconds, and the measurement result is accurate to 0.2 seconds.

[0026] Density ratio determination: The density of the upper slurry and the lower slurry were measured separately using a 2-liter volumetric cylinder. The net slurry density value was expressed in kg / m³. 3 Units, measurement results accurate to 1 kg / m³ 3 .

[0027] The test results need to ensure that: Slurry deposition flow ratio = upper flowability / lower flowability × 100%; pass rate ≥ 96%.

[0028] Slurry deposition density ratio = upper density / lower density × 100%; pass rate ≥ 96%.

[0029] S6: Before the grout is injected into the duct 5, the water and thin grout in the grouting pipeline are discharged. When the flowability of the discharged grout is the same as that of the grout in the storage device, the grout is injected into the duct 5. It should be noted that a stop valve 6 is installed at both the slurry inlet and the slurry outlet. The slurry inlet should be located at the lower end, and the slurry outlet should be located at the higher end.

[0030] Throughout the grouting process, grouting should be carried out smoothly. Grouting of the same duct 5 should be carried out continuously and completed in one go. For ducts 5 that are set up in upper and lower layers in the structure or component, grouting should be carried out in the order of lower layer first and upper layer last.

[0031] S7: During grouting, maintain the pressure at the grouting port between 0.5 and 0.7 MPa; The pressure at the grouting port is between 0.5 and 0.7 MPa. This is to enable the grout to overcome resistance and reach the outlet and overflow. Secondly, it allows the grout to withstand a certain pressure to improve the density of the grout.

[0032] The test results show that, under certain grout properties and a certain duct length, increasing the grouting pressure can improve the grout density. However, when the pressure continues to increase beyond approximately 0.80 MPa, this improvement effect is minimal, and further grouting pressure is unnecessary. Furthermore, considering construction and structural safety, the grouting pressure should not be excessive.

[0033] S8: When the slurry discharged from the outlet has no obvious bubbles or foam, and the slurry flowability is the same as that of the slurry at the inlet, close the stop valve 6 at the outlet. S9: Close the grout outlet, continue to inject grout, maintain the internal pressure of the channel 5 until the oozing water at the end of the steel strand 1 changes from turbid to clear water, and close the grout stop valve 6 at the grouting end. During the grout stabilization period, air and oozing water flow towards the anchor plate 4 and are discharged from the end of the steel strand 1 through the gap in the middle of the steel strand 1.

[0034] S10: After 24 hours, remove the grout stop valve 6 and check the grout compaction at the grout inlet and outlet. If there is a slight lack of density, gravity filling can be performed.

[0035] S11: If voids or even exposed steel strand 1 are found, secondary grouting shall be carried out.

[0036] From the start of grouting until the initial setting of the grout, the air bubbles and oozing water flowing from the channel 5 to the anchor plate 4 are discharged from the end of the steel strand 1 through the gap in the middle of the steel strand 1 under pressure.

[0037] Within 48 hours after the grout has set, the quality of the grouting behind the anchor should be checked. After the grout is fully compacted, the ends should be sealed.

[0038] In step S1, the exposed length of the prestressed steel strand 1 after cutting shall not be less than 30 mm and not less than 1.5 times the diameter of the prestressed steel strand 1.

[0039] In step S4, in order to ensure that the gaps in the steel strand 1 can also be filled with the original slurry, the end of the steel strand 1, which serves as a channel for air and water leakage, cannot be blocked.

[0040] In step S9, the internal pressure of the channel 5 is stable and not less than 0.5 MPa.

[0041] It should be noted that, since a moderate pressure is maintained inside the duct 5, the pressure is released through tiny air bubbles in the slurry before the slurry initially sets, thus compensating for or reducing the slurry shrinkage caused by micro-shrinkage.

[0042] After the grout stop valve 6 is closed, it forms a sealed state. The continuous pressure replenishment provided by the micro-expansion of the grout provides continuous power for the air bubbles and oozing water to be expelled from the gaps in the steel strand 1 after the pressure stabilization period until the initial setting of the grout.

[0043] In step S9, the pressure stabilization time inside channel 5 is greater than 5 minutes.

[0044] After the pressure stabilization period, the continuous micro-expansion provided by the compressed air bubbles can effectively reduce the micro-shrinkage of the slurry before initial setting, without causing obvious voids.

[0045] During the voltage stabilization period, it is necessary to ensure that the seepage water at the end of the steel strand 1 changes from turbid water to clear water.

[0046] Grouting during the stabilization period allows grout to enter the interior of the steel strand 1, effectively improving the situation where there is no grout inside the steel strand 1. Furthermore, the grout can be discharged through the gas and water seepage in the grout, thereby improving the compactness of the grout.

[0047] In step S10, an endoscope is used to check the compaction of the grout inlet and outlet.

[0048] After removing the grout stop valve 6 at the grout inlet and outlet, the grouting quality should be inspected using an endoscope through the grout inlet and outlet to determine whether the grout inside is dense. If it is not dense, secondary grouting is required.

[0049] In step S11, the secondary grouting is vacuum grouting, and the vacuum degree is 0.1 MPa negative pressure.

[0050] It should be noted that the secondary grouting is vacuum grouting, which uses existing technology, such as the invention patent with publication number CN111733707A. The grouting construction is carried out according to the requirements of the patent, and the voids and exposed steel strands 1 are treated with grouting.

[0051] If there is grout on the surface, the grouting material should be replaced according to the grouting raw materials specified in the invention patent with announcement number CN104876496B.

[0052] In step S11, before grouting, the gaps at the ends of the steel strand 1 should be sealed or anchoring should be carried out.

[0053] This is to ensure the effectiveness of the grouting and prevent the grout from leaking through the gaps.

[0054] The grout inlet and outlet are both located directly above the center of the anchor plate 4, and the inner diameter of the grout inlet and outlet is not less than 20 mm.

[0055] like Figure 2 As shown, in the actual construction process, the grout inlet and outlet of the simply supported structure are located at the high point of the duct 5, and are located directly above the center of the anchor plate 4 in the vertical direction.

[0056] Both the grout inlet and outlet are equipped with grout stop valves 6 to control the flow of grout. If grouting cannot be continuous due to blockage of the grout channel 5, cross-hole failure, or interruption due to malfunction, the grout channel 5 should be flushed with pressurized water and dried with oil-free high-pressure air in a timely manner, or other measures should be taken before grouting can be resumed.

[0057] Furthermore, samples should be taken from the grout storage device at any time during the grouting process to test the fluidity of the grout.

[0058] The entire grouting process uses a screw-type grouting pump. The screw-type grouting pump can operate continuously.

[0059] After the entire grouting process is completed, the grout stop valves 6 installed at the grout inlet and outlet should only be removed after the grout has set. After the grouting pipe is removed, the fullness and density of the grout in the grouting hole and outlet should be checked in a timely manner.

[0060] Grouting equipment and pipelines should be cleaned promptly after construction. In addition to running automatic cleaning programs, automated and information-based grouting equipment should also be cleaned manually.

[0061] Finally, complete grouting records should be kept, including the grouting date, raw materials, mix proportions, grouting and stabilization pressure, stabilization period duration and grout flowability, details of failures and accidents, and other necessary information for each duct 5.

[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for grouting construction of post-tensioned prestressed ducts in a simply supported structure, characterized in that, The construction method includes the following steps: Grouting preparation: S1: Prestressed steel strands are mechanically cut (1); S2: Remove impurities inside the channel (5) by compressed air; S3: Use a cleaning agent that does not corrode the prestressed steel strand (1) and the duct (5) to rinse off the oil stains. After rinsing, use oil-free high-pressure air to remove the water in the duct (5). S4: Seal the anchor clamps (2), anchor plates (3), anchor pads (4) and other gaps where grout leakage may occur; Start grouting: S5: Use slurry with a deposition flow ratio and deposition density ratio of over 96%; S6: Before the grout is injected into the duct (5), the water and thin grout in the grouting pipeline are discharged. When the fluidity of the discharged grout is the same as that of the grout in the storage device, the grout is injected into the duct (5). S7: During grouting, maintain the pressure at the grouting port between 0.5 and 0.7 MPa; S8: When the slurry discharged from the outlet has no obvious bubbles and foam, and the slurry flowability is the same as that of the slurry at the inlet, close the stop valve at the outlet (6). S9: Close the grout outlet, continue to inject grout, maintain the internal pressure of the channel (5) until the oozing water at the end of the steel strand (1) changes from turbid to clear water, and close the grout stop valve (6) at the grouting end. S10: After 24 hours, remove the grout stop valve (6) and check the grout compaction at the grout inlet and outlet. S11: If voids or even exposed steel strands (1) are found, secondary grouting shall be carried out.

2. The method for grouting construction of post-tensioned prestressed ducts in a simply supported structure as described in claim 1, characterized in that: In step S1, the exposed length of the prestressed steel strand (1) after cutting shall not be less than 30 mm and not less than 1.5 times the diameter of the prestressed steel strand (1).

3. The method for grouting construction of post-tensioned prestressed ducts in a simply supported structure as described in claim 1, characterized in that: In step S4, in order to fill the gaps in the steel strand (1) with the original slurry, the ends of the steel strand (1) serve as channels for air and water discharge and should not be blocked.

4. The method for grouting construction of post-tensioned prestressed ducts in a simply supported structure as described in claim 1, characterized in that: In step S9, the internal pressure of the channel (5) is stable and not less than 0.5 MPa.

5. The method for grouting construction of post-tensioned prestressed ducts in a simply supported structure as described in claim 1, characterized in that: In step S9, the internal pressure stabilization time of the channel (5) is greater than 5 minutes.

6. The method for grouting construction of post-tensioned prestressed ducts in a simply supported structure as described in claim 1, characterized in that: In step S10, an endoscope is used to check the compaction of the grout inlet and outlet.

7. The method for grouting construction of post-tensioned prestressed ducts in a simply supported structure as described in claim 1, characterized in that: In step S11, the secondary grouting is vacuum grouting, and the vacuum degree is 0.1 MPa negative pressure.

8. The method for grouting construction of post-tensioned prestressed ducts in a simply supported structure as described in claim 1, characterized in that: In step S11, before grouting, the gaps at the ends of the steel strand (1) should be sealed or the anchoring work should be carried out.

9. The method for grouting construction of post-tensioned prestressed ducts in a simply supported structure as described in claim 1, characterized in that: The grout inlet and outlet are both located above the center of the anchor plate (4), and the inner diameter of the grout inlet and outlet is not less than 20 mm.

10. The method for grouting construction of post-tensioned prestressed ducts in a simply supported structure as described in claim 1, characterized in that: The entire grouting process uses a screw-type grouting pump.

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