Prestressed pipe grouting structure and grouting technology based on string theory

Abstract

The present invention relates to a prestressed pipe grouting structure and grouting process based on the chord theory, the structure comprises three grouting pipes arranged on the prestressed pipe and extending upward to the upper surface of the beam body, the three grouting pipes are all pre-placed in the beam body, thereby forming a chord structure with the grouting pipe as a support rod, the prestressed pipe as an upper chord, and the beam body as a lower chord; the process firstly injects slurry from the top of the middle grouting pipe, the slurry flows from top to bottom, grouting the middle part of the prestressed pipe, and then injects grouting from the ends of both sides of the prestressed pipe respectively, until the top of the grouting pipes on both sides flows out the thick slurry and then stops grouting. The present invention can make the grouting in the prestressed pipe more dense, improve the bearing capacity of the structure, and extend the life of the structure.

Description

Technical Field

[0001] The invention relates to a prestressed pipe grouting structure and a grouting process based on the tension-string theory, and belongs to the technical field of bridge building construction. Background Art

[0002] Post-tensioning prestressed pipe grouting construction is a key process in prestressed bridge construction. Prestressed pipes are also called corrugated pipes. The steel strands in the prestressed pipes must give full play to the design effect to offset the pressure of vehicles and pedestrians on the bridge deck. The grouting quality of prestressed pipes is one of the most important factors, which is related to the safety and durability of the bridge structure.

[0003] The occurrence of a large number of prestressed bridge collapse accidents is often related to loose grouting. The loose grouting of the prestressed pipe makes the steel strands in the pipe not wrapped by cement slurry, which is easy to rust prematurely. There have been many bridge collapse incidents at home and abroad due to the loss of bearing section caused by the corrosion of prestressed steel bars; on the other hand, the prestressed steel strands cannot form an integral force with the concrete structure, which reduces the bearing capacity of the structure and shortens the service life of the bridge.

[0004] The traditional prestressed pipe grouting process is to use a single-cylinder piston pump to pressurize the slurry from the slurry inlet, and the thick slurry flows out from the slurry outlet. The grouting is completed once the slurry flows through the pipeline. There is no control over the slurry flow and pressure in the pipeline, and the air in the pipeline cannot be effectively removed, resulting in air chambers in the pipeline after the grouting is completed, forming voids. In addition, the use of a piston single-cylinder pump for pressure relief pressurization cannot control the grouting pressure by adjusting the slurry flow rate, and insufficient pressure will inevitably lead to the slurry in the pipeline cannot be filled up, forming voids. Therefore, how to improve the density of grouting in prestressed pipelines has become an urgent problem to be solved. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a grouting structure and a grouting process which can make the grouting in the prestressed pipe more compact, improve the bearing capacity and extend the service life of the structure.

[0006] In order to solve the above technical problems, one of the technical solutions proposed in the present invention is: a prestressed pipe grouting structure based on the tension-chord theory, the prestressed pipe is pre-placed in the beam body, and a steel strand is arranged in the prestressed pipe; the prestressed pipe is provided with three grouting pipes extending upward to the upper surface of the beam body, and the three grouting pipes are all pre-placed in the beam body, thereby forming a tension-chord structure with the grouting pipe as the support rod, the prestressed pipe as the upper chord, and the beam body as the lower chord.

[0007] In order to solve the above technical problems, the second technical solution proposed in the present invention is: a grouting process using the grouting structure of one of the technical solutions, first, grouting the slurry from the top of the middle grouting pipe, the slurry flows from top to bottom, and grouting is performed on the middle part of the prestressed pipe, and the grouting range does not exceed the connection between the grouting pipes on both sides and the prestressed pipe; secondly, grouting is performed from the ends of both sides of the prestressed pipe respectively, and the grouting is stopped after the thick slurry flows out from the top of the grouting pipes on both sides.

[0008] The principle of the cable-stayed structure can be traced back to the cast iron bridge in the early 19th century, as well as the later appearance of the tension arch, King Post truss, self-anchored suspension bridge, etc. The cable-stayed structure is a rigid-flexible hybrid structure composed of a rigid member of the upper chord and a high-strength tension cable connected by a number of support rods. It uses form resistance and pre-tension to resist external loads and is an efficient large-span spatial structure system.

[0009] In the present invention, the beam body is a rigid member as the lower chord, and the prestressed pipe is the upper chord, thereby forming a special tensioned structure in the opposite direction to the traditional tensioned structure. In this way, the lateral thrust exerted on the prestressed pipe can be balanced by the slurry guide pipe, making it difficult for the prestressed steel strand to directly contact the prestressed pipe. Therefore, not only the bearing pressure is greatly improved, but also the prestressed steel strand can form an integral force with the concrete structure in the prestressed pipe, thereby improving the bearing capacity of the structure.

[0010] At the same time, the present invention improves the grouting process, firstly grouting the middle part of the prestressed pipe from top to bottom through the middle grouting pipe, which is equivalent to high-pressure grouting, and increases the grouting pressure. At the same time, the grouting pipes on both sides act as exhaust holes, which can effectively discharge the air in the prestressed pipe, so the grouting is dense and not easy to form voids. Then, grouting is performed from the ends of both sides of the prestressed pipe. At this time, the grouting pipes at the corresponding positions act as exhaust holes, which can effectively discharge the air in the prestressed pipe. Moreover, the slurry needs to flow into the grouting pipe, which is equivalent to grouting from bottom to top. Therefore, the slurry in the grouting pipe forms a secondary pressurization of the slurry in the prestressed pipe, which improves the grouting density of the prestressed pipe and improves the bearing capacity of the structure. In addition, the present invention divides the prestressed pipe into three parts and grouts them separately, which is equivalent to shortening the length of a single grouting, and is also conducive to improving the grouting density of the pipe. It is worth mentioning that after the slurry is injected into the three grouting pipes and solidified, the strength of the grouting pipes is also improved, further improving the bearing capacity of the structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present invention will be further described below in conjunction with the accompanying drawings.

[0012] Figure 1 It is a cross-sectional schematic diagram of the prestressed pipe grouting structure in the first embodiment of the present invention.

[0013] Figure 2 It is a structural schematic diagram of the prestressed pipe grouting structure after grouting in Example 1 of the present invention.

[0014] Figure 3 It is a schematic diagram of the grouting process in the first embodiment of the present invention.

[0015] Figure 4 It is a structural schematic diagram of the prestressed pipe grouting structure after grouting in the second embodiment of the present invention.

[0016] Figure numerals: box body 1, steel strand 2, middle slurry guide pipe 3, right slurry guide pipe 4, left slurry guide pipe 5, prestressed pipe 6. DETAILED DESCRIPTION

[0017] Embodiment 1

[0018] This embodiment relates to a prestressed pipe grouting structure based on the string theory, such as Figure 1 and Figure 2 As shown, the prestressed pipe 6 is pre-placed in the beam body 1, and a steel strand 2 is arranged in the prestressed pipe 6; the prestressed pipe 6 is provided with three slurry guide pipes (i.e., the middle slurry guide pipe 3, the right slurry guide pipe 4, and the left slurry guide pipe 5) extending upward to the upper surface of the beam body 1, and the three slurry guide pipes are pre-placed in the beam body 1, thereby forming a string structure with the slurry guide pipe as a support rod, the prestressed pipe 6 as an upper chord, and the beam body 1 as a lower chord. Although the string structure is opposite to the commonly used string structure in direction, the principle is the same, that is, the bearing capacity of the prestressed pipe 6 is increased by the support rod, and the lateral thrust on the prestressed pipe can be balanced, so that the prestressed steel strand is not easy to directly contact the prestressed pipe, thereby increasing the life of the steel strand, and thus increasing the service life of the entire beam body.

[0019] The grouting structure can also be improved as follows: the middle grouting pipe 3 is vertically arranged, and the three grouting pipes are perpendicular to the tangent line of the intersection of the prestressed pipe 6. In this way, the tension or pressure from the grouting pipe will not cause the prestressed pipe 6 to generate a tangential force component, which is conducive to improving the pressure bearing capacity of the prestressed pipe 6.

[0020] This embodiment also relates to a grouting process using the above grouting structure, such as Figure 3As shown in the figure (the arrow in the figure is the grouting direction), the process firstly injects the slurry from the top of the middle grouting pipe 3, and the slurry flows from top to bottom, which is equivalent to high-pressure grouting, increasing the grouting pressure, and grouting the middle part of the prestressed pipe 6. The grouting range does not exceed the connection between the grouting pipes on both sides and the prestressed pipe. The grouting range can be controlled by calculating the required slurry. At this time, the grouting pipes on both sides act as exhaust holes, which can effectively discharge the air in the prestressed pipe, so the grouting is dense and it is not easy to form voids. Secondly, grouting is performed from the ends of both sides of the prestressed pipe 6 respectively until the thick slurry flows out from the top of the grouting pipes (4, 5) on both sides, and then the grouting is stopped. The grouting pipes at the corresponding positions act as exhaust holes, which can effectively discharge the air in the prestressed pipe, and the slurry needs to flow into the grouting pipe, which is equivalent to grouting from bottom to top. Therefore, the slurry in the grouting pipe forms a secondary pressurization of the slurry in the prestressed pipe, which also improves the grouting density of the prestressed pipe.

[0021] As a preferred solution, after the slurry poured in the middle of the prestressed pipe solidifies, grouting is performed on both sides of the prestressed pipe.

[0022] In this embodiment, the prestressed pipe is divided into three parts and grouting is performed separately, which is equivalent to shortening the length of a single grouting and is also beneficial to improving the grouting density of the pipe.

[0023] Embodiment 2

[0024] This embodiment is an improvement on the grouting structure and grouting process of the first embodiment, wherein the improvement on the grouting structure is as follows: Figure 1-3 As shown, the prestressed pipe 6 is divided into three sections along the length direction, and the connection points between the three slurry guide pipes and the prestressed pipe 6 are respectively located in different sections, wherein the lengths of the two sections near the ends of the prestressed pipe are greater than 1 / 4 of the length of the prestressed pipe. Figure 1-2 As shown, the three segments are AB segment, BC segment and CD segment, and the two segments near the end of the prestressed pipe are AB segment and CD segment. Assuming that the length of the prestressed pipe is L, the lengths of AB segment and CD segment are both greater than L / 4. Because the weakest part of the prestressed pipe 6 is located at 1 / 4 of the length from the end, it is preferred that the three segments have the same length, which is 1 / 3 of the length of the prestressed pipe 6. The junction of the middle slurry guide pipe and the prestressed pipe 6 is located in the middle of the BC segment, and the slurry guide pipes on both sides are located at L / 4 from the two ends of the prestressed pipe.

[0025] Accordingly, if Figure 3 As shown, the improvement of the grouting structure is: when grouting the middle of the prestressed pipe, the grouting range is the middle segment BC of the prestressed pipe 6; when grouting the two sides of the prestressed pipe, the grouting range is the two side segments (i.e., the AB segment and the CD segment).

[0026] The slurry is preferably made of UHPC. UHPC has ultra-high performance. It not only has high strength, but also contains fiber segments to prevent cracking.

[0027] Embodiment 3

[0028] The difference between this embodiment and the first and second embodiments is that: Figure 4 As shown, the three slurry guide pipes are all arranged vertically. The vertically arranged slurry guide pipes have better supporting capacity, which is beneficial to improving the bearing capacity of the overall structure.

[0029] The present invention is not limited to the specific technical solutions described in the above embodiments. In addition to the above embodiments, the present invention may also have other implementation modes. For those skilled in the art, any technical solutions formed by any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A grouting process using a prestressed pipe grouting structure based on the tension-chord theory, wherein the prestressed pipe is pre-placed in a beam body, and a steel strand is arranged in the prestressed pipe; the prestressed pipe is provided with three grouting pipes extending upward to the upper surface of the beam body, and the three grouting pipes are pre-placed in the beam body, thereby forming a tension-chord structure with the grouting pipe as a support rod, the prestressed pipe as an upper chord, and the beam body as a lower chord; characterized in that: The grouting process comprises the following steps: first, grouting the slurry from the top of the middle slurry guide pipe, the slurry flows from top to bottom, and grouting is performed on the middle part of the prestressed pipe, and the grouting range does not exceed the connection between the slurry guide pipes on both sides and the prestressed pipe; secondly, grouting is performed from the ends of both sides of the prestressed pipe respectively, and the grouting is stopped after the thick slurry flows out from the top of the slurry guide pipes on both sides.

2. The grouting process according to claim 1, characterized in that: After the slurry poured in the middle of the prestressed pipe solidifies, grouting is performed on both sides of the prestressed pipe.

3. The grouting process according to claim 1 or 2, characterized in that: The slurry is made of UHPC.

4. The grouting process according to claim 1 or 2, characterized in that: The middle slurry guide pipe is vertically arranged, and each slurry guide pipe is perpendicular to the tangent line of the intersection of the prestressed pipe.

5. The grouting process according to claim 1 or 2, characterized in that: The three slurry guide pipes are all arranged vertically.

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