A method for detecting the effect of post-grouting of the bottom of a bridge cast-in-place pile

Abstract

The application discloses a kind of bridge bored pile pile bottom post grouting effect detection methods, it is related to bridge pile foundation engineering technical field, including steps: acoustic reflection enhancement treatment is carried out to the bladder skin of pile bottom post grouting device;Vertical extension detection tube is laid in the inside of post grouting device, and the bottom end of detection tube extends to the bottom position of bladder skin;Water is filled in detection tube;After pile body concrete molding reaches standard, ultrasonic probe is lowered to the bottom end of detection tube;From bottom to top, ultrasonic probe is sequentially lifted according to preset layer spacing, and every lifting is detected layer position, controls ultrasonic probe to complete 360 ° circumferential ultrasonic pulse emission and echo signal reception;Cross section ultrasonic detection data of all detection layer positions is spliced according to corresponding depth coordinates, and three-dimensional point cloud model of pile end bladder skin area is constructed.The present application detection method, easy to operate, without additional drilling detection hole and can intuitively feedback pile end post grouting effect.

Description

Technical Field

[0001] This invention relates to the field of bridge pile foundation engineering technology, and in particular to a method for detecting the effect of post-grouting at the bottom of bridge cast-in-place piles. Background Technology

[0002] In bridge construction, cast-in-place pile foundations have become the mainstream foundation type for long-span and high-pier bridges of highways and railways due to their advantages such as strong geological adaptability, high single-pile bearing capacity, and mature construction technology. Their bearing capacity and settlement characteristics directly determine the operational safety and long-term durability of the overall bridge structure. With the development of transportation construction towards heavy loads and long spans, the requirements for the bearing capacity and deformation control of cast-in-place piles are continuously increasing. Post-grouting technology at the pile bottom, as a core process for reinforcing pile foundation performance, has been widely applied in engineering projects. This technology involves pre-embedding grouting pipelines during the pile formation stage. After the pile concrete reaches its design strength, cement-based grout is injected under high pressure into the pile tip to fill the gaps in the pile bottom sediment and compact the bearing layer at the pile tip, thereby significantly improving the pile tip resistance and reducing pile foundation settlement.

[0003] To address the issues of uncontrollable grout diffusion and highly variable reinforcement effects associated with traditional open-type grouting, composite bladder-type post-grouting technology has been gradually promoted. This technology lowers a ring-shaped grouting device with a bladder to the bottom of the pile. Grouting is carried out after the pile is completed and passes quality inspection. After injection, the grout expands directionally under the constraint of the bladder, forming a regular enlarged head at the pile end. Simultaneously, it diffuses into the surrounding bearing layer through pre-set permeation channels, achieving both enlarged head reinforcement and soil consolidation, significantly improving the stability of grouting quality. However, post-grouting at the pile bottom is a typical underground concealed project. The entire grouting operation is completed within the enclosed space at the pile end. Key indicators directly reflecting the grouting effect, such as the bladder expansion morphology, the size of the enlarged head at the pile end, and the grout saturation, cannot be directly observed. Accurate detection and quantitative evaluation of the grouting effect remain the core challenge restricting the quality control of this technology.

[0004] Currently, the engineering field mainly employs two indirect detection methods for assessing the effectiveness of post-grouting at the pile bottom: cross-hole elastic wave CT and side-hole detection. Cross-hole elastic wave CT involves drilling paired detection holes around the pile, emitting and receiving high-frequency elastic waves within these holes, and inferring the medium wave velocity distribution in the pile tip region based on the difference in sound wave propagation speed in different media, thereby inferring the extent and strength of the grouting reinforcement. Side-hole detection involves drilling holes along the pile side and embedding sensing equipment, collecting stress wave signals generated by pile top vibration, and analyzing the amplitude and travel time characteristics of the reflected waves at the pile tip to indirectly evaluate the reinforcement effect of the pile tip grouting.

[0005] The aforementioned existing testing technologies have several insurmountable drawbacks in practical engineering applications: First, the testing procedures are complex and costly. Both methods require drilling dedicated testing holes around the pile, adding extra drilling and equipment installation steps, which not only increases engineering testing costs but also prolongs the overall construction period. Furthermore, drilling operations can easily cause secondary disturbance to the soil around the pile, affecting the original stress state of the pile foundation. Second, the testing results lack intuitiveness. Existing technologies can only output indirect data such as wave velocity cloud maps and time-domain waveform curves, failing to intuitively reproduce the three-dimensional contour of the swell and the true shape of the enlarged head at the pile end. The evaluation of grouting effect is highly dependent on the engineering experience of the testing personnel, resulting in significant limitations in the objectivity and accuracy of the evaluation results. Third, the testing efficiency is low. Single-pile testing is cumbersome and time-consuming, making it difficult to adapt to the large-scale, batch testing needs of large bridge pile foundations and unable to support efficient quality control for large-scale projects.

[0006] In summary, there is an urgent need for a technical solution that is easy to operate, requires no additional drilling of inspection holes, and can provide intuitive feedback on the post-grouting effect at the pile end. Summary of the Invention

[0007] The purpose of this invention is to provide a method for detecting the post-grouting effect at the bottom of bridge cast-in-place piles, so as to solve the problems existing in the prior art. The method is simple to operate, does not require additional drilling of detection holes, and can intuitively provide feedback on the post-grouting effect at the pile end.

[0008] To achieve the above objectives, the present invention provides the following solution: This invention provides a method for detecting the post-grouting effect at the bottom of a bridge cast-in-place pile, comprising the following steps: Step 1, subjecting the outer shell of the post-grouting device at the bottom of the pile to acoustic reflection enhancement treatment, wherein the acoustic reflection enhancement treatment involves adding high reflectivity filler to the raw materials for preparing the outer shell, or coating the outer surface of the outer shell with an acoustic reflection coating; Step 2, arranging a vertically extending probe tube inside the post-grouting device, wherein the bottom end of the probe tube extends to the bottom of the outer shell, and the probe tube is tied and fixed to the longitudinal main reinforcement of the cast-in-place pile reinforcement cage; filling the probe tube with water to balance the pressure difference inside and outside the probe tube wall during the pile formation process; Step 3: After the pile concrete has reached the required standard, lower the ultrasonic probe to the bottom of the detection tube; raise the ultrasonic probe from bottom to top according to the preset layer spacing, and control the ultrasonic probe to complete 360° circumferential ultrasonic pulse transmission and echo signal reception at each detection layer, collect the cross-sectional ultrasonic test data of that layer, and simultaneously record the depth information corresponding to each detection layer; Step 4: stitch together the cross-sectional ultrasonic test data of all detection layers according to the corresponding depth coordinates to construct a three-dimensional point cloud model of the pile end skin area; generate a three-dimensional mesh model or three-dimensional cloud map of the pile end enlarged head.

[0009] This invention utilizes the difference in propagation speed of ultrasound in different media and the principle of reflection to detect the enlarged head structure at the bottom of piles. A trace amount of high-reflectivity filler is incorporated into the shell formulation or an acoustic reflective coating is applied to the shell surface to enhance the reflected signal of the enlarged head. When ultrasound encounters the shell, part of it penetrates and part is reflected, and the ultrasonic probe receives the echo signal. Starting from the bottom, the ultrasonic probe is raised sequentially according to a preset layer spacing, transmitting and receiving signals at each layer in a 360° pattern. A cross-sectional point cloud is generated for each layer, recording the corresponding depth. The point clouds scanned from all layers are stitched together according to depth coordinates to form a complete three-dimensional model. Triangulation is performed using specialized software to generate a three-dimensional mesh model or a three-dimensional cloud map. The detection results are presented intuitively in image form. The operation is simple, requires no additional drilling of detection holes, and provides direct feedback on the post-grouting effect at the pile end. This has practical guiding significance for the overall quality control of post-grouting construction and the real-time adjustment of grouting parameters.

[0010] In one embodiment, in step two, the spare open grouting pipe of the post-grouting device is used as the detection pipe, and the inner diameter of the spare open grouting pipe is larger than the maximum outer diameter of the ultrasonic probe.

[0011] In one embodiment, the high reflectivity filler is one or more of barite powder, iron ore powder, steel grit, and magnetic powder.

[0012] In one embodiment, the acoustic reflective coating is epoxy resin-based and / or hollow glass microspheres.

[0013] In one embodiment, the high-frequency acoustic pulse emitted by the ultrasonic probe has a frequency of 1~2.25MHz.

[0014] In one embodiment, the preset interlayer spacing ranges from 1cm to 10cm.

[0015] In one embodiment, in step three, the lowering and raising of the ultrasonic probe is controlled by a cable winch set on the ground, and the depth information of the ultrasonic probe is collected by the ranging module of the cable winch.

[0016] In one embodiment, the ultrasonic probe is an ultrasonic transceiver integrated probe. The ultrasonic probe is connected to a ground-based data acquisition and processing system via a communication cable, and works with a cable winch to complete signal acquisition, data transmission, and imaging processing.

[0017] In one embodiment, in step three, the distance between the ultrasonic probe and the capsule is calculated based on the time difference between the ultrasonic pulse emission and the received echo.

[0018] In one embodiment, the detection processes in steps three and four can be carried out during grouting, after grouting is completed, and after the grout has solidified.

[0019] The present invention achieves the following technical effects compared to the prior art: This invention utilizes the difference in propagation speed of ultrasound in different media and the principle of reflection to detect the enlarged head structure at the bottom of piles. A trace amount of high-reflectivity filler is incorporated into the shell formulation or an acoustic reflective coating is applied to the shell surface to enhance the reflected signal of the enlarged head. When ultrasound encounters the shell, part of it penetrates and part is reflected, and the ultrasonic probe receives the echo signal. Starting from the bottom, the ultrasonic probe is raised sequentially according to a preset layer spacing, transmitting and receiving signals at each layer in a 360° pattern. A cross-sectional point cloud is generated for each layer, recording the corresponding depth. The point clouds scanned from all layers are stitched together according to depth coordinates to form a complete three-dimensional model. Triangulation is performed using specialized software to generate a three-dimensional mesh model or a three-dimensional cloud map. This allows for real-time monitoring of the entire post-grouting process, including during grouting, after grouting, and after grout solidification. The detection results are presented intuitively in image form. The operation is simple, requires no additional drilling of detection holes, and provides direct feedback on the post-grouting effect at the pile end. It has practical guiding significance for the overall quality control of post-grouting construction and the real-time adjustment of grouting parameters. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram illustrating the principle of a method for detecting the post-grouting effect at the bottom of a bridge cast-in-place pile in one or more embodiments of the present invention. Figure 2 This is a schematic diagram illustrating the principle of a method for detecting the grouting effect at the bottom of a bridge cast-in-place pile when an open grouting pipe is used as a probe in one or more embodiments of the present invention.

[0022] In the diagram: 1-Ultrasonic probe; 2-Communication cable; 3-Cable winch; 4-Data acquisition and processing system; 5-Detection tube; 6-Pile body; 7-Closed grouting pipe; 8-Open grouting pipe; 9-Sheath; 10-Pile end enlargement head. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] The purpose of this invention is to provide a method for detecting the post-grouting effect at the bottom of bridge cast-in-place piles, so as to solve the problems existing in the prior art. The method is simple to operate, does not require additional drilling of detection holes, and can intuitively provide feedback on the post-grouting effect at the pile end.

[0025] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] This invention provides a method for detecting the grouting effect at the bottom of bridge cast-in-place piles, with reference to... Figure 1 and Figure 2 It includes the following steps: Step 1: The outer shell 9 of the pile bottom grouting device is subjected to acoustic reflection enhancement treatment. The acoustic reflection enhancement treatment is to add high reflectivity filler to the raw materials for preparing the outer shell 9, or to coat the outer surface of the outer shell 9 with an acoustic reflection coating. The high reflectivity filler is one or more of barite powder, iron ore powder, steel grit, and magnetic powder. The acoustic reflection coating is epoxy resin-based and / or hollow glass microspheres. Step 2: Install vertically extending probes 5 inside the post-grouting device. The bottom end of probes 5 extends to the bottom of the bladder 9. Probes 5 are tied and fixed to the longitudinal main bars of the cast-in-place pile reinforcement cage. Fill probes 5 with water and maintain this state of full water by external pressure maintenance or sealing the top of probes 5 to balance the pressure difference inside and outside the probes 5 during the pile formation process. Step 3: After the concrete of pile body 6 has reached the required standard, lower the ultrasonic probe 1 to the bottom of the detection tube 5. Before lowering, drain the water from the detection tube 5 to provide space for the ultrasonic probe 1. Raise the ultrasonic probe 1 sequentially from bottom to top according to the preset layer spacing. Control the lowering and raising of the ultrasonic probe 1 using a cable winch 3 on the ground. Simultaneously, collect the depth information of the ultrasonic probe 1 using the ranging module of the cable winch 3. The ultrasonic probe 1 is an integrated ultrasonic transceiver probe. It is connected to the ground data acquisition and processing system 4 via a communication cable 2, working with the cable winch 3 to complete signal acquisition, data transmission, and imaging processing. The preset layer spacing is 1cm to 10cm. Each time the probe is raised to a detection layer, control the ultrasonic probe 1 to complete 360° circumferential ultrasonic pulse emission and echo signal reception, collect the cross-sectional ultrasonic detection data of that layer, and simultaneously record the depth information corresponding to each detection layer. Calculate the span from the ultrasonic probe 1 to the bladder 9 based on the time difference between ultrasonic pulse emission and echo reception. The high-frequency acoustic pulse emitted by the ultrasonic probe 1 has a frequency of 1 to 2.25MHz. Step 4: stitch together the point clouds from all layers of scanning into a complete 3D model according to depth coordinates, use existing professional software to perform triangulation, construct a 3D point cloud model of the 9th region of the pile end skin, and generate a 3D mesh model or 3D cloud map.

[0027] The above detection method enables real-time monitoring of the entire post-grouting process, including three stages: during grouting, after grouting, and after grout solidification. The detection results are presented intuitively in image form, providing practical guidance for overall quality control and real-time adjustment of grouting parameters in post-grouting construction. This invention's detection method is simple and easy to implement, requires no additional probe holes, and provides intuitive image feedback on the post-grouting effect at the pile end.

[0028] The post-grouting device for the pile bottom involved in this invention is installed at the bottom of the pile body 6, including an annular steel plate and a bladder 9 coaxially installed at the bottom of the annular steel plate. The bladder 9 can be made of high-strength rubber or other elastic materials, and the overall structure is similar to a swimming ring. Its internal space can be used for grouting. The space formed by the annular holes on the inner side of the annular steel plate is reserved for cleaning the sediment at the bottom of the hole and for subsequent open grouting. Multiple grouting holes are opened on the annular steel plate, and the space on the inner side of the annular steel plate is connected to an open grouting pipe 8. The top of the open grouting pipe 8 is connected to the ground grouting equipment through a pipeline for injecting open grouting into the space at a set pressure. The upper part of the grouting shell 9 has multiple closed grouting ports that communicate with the internal cavity of the grouting shell 9. Each closed grouting port corresponds to a grouting hole and is fixed to a ring-shaped steel plate. A closed grouting pipe 7 is connected to the top of each closed grouting port. The top of the closed grouting pipe 7 is connected to ground-based grouting equipment via a pipeline for closed grouting into the grouting shell 9. After grouting and fixing inside the grouting shell 9, it forms the pile end enlarged head 10. The grouting equipment is existing technology and will not be described in detail. Each closed grouting pipe 7 is equipped with a one-way valve. During the concrete pouring of the pile body 6, the one-way valve's check valve function prevents concrete or slurry from entering the closed grouting pipe 7, avoiding pipe blockage and grouting failure. In the post-grouting stage, it prevents high-pressure grout from flowing back along the pipe and forces the grout from the outlet into the soil at the pile bottom, ensuring grouting pressure and reinforcement effect. Using one-way valves significantly reduces the risk of pipe blockage and improves the success rate of post-grouting construction. The grouting sleeve 9 is located at the lower part of the annular steel plate and is fixed by corresponding grouting holes in the annular steel plate through its closed grouting port. The closed grouting port, in addition to injecting grout into the grouting sleeve 9, also serves to fix the sleeve 9. Additional hoops and rivets can be installed to further secure the sleeve 9. The sleeve 9 exhibits good consistency and integrity, and is not prone to tearing, detachment, or grout leakage, resulting in a high overall sealing degree. A vertically extending protective steel ring is fixedly connected to the inner ring of the annular steel plate, with its outer wall abutting against the sleeve 9. A vertically arranged reinforcing cage is provided on the inner ring of the protective steel ring. The pile bottom grouting device is equipped with two open grouting pipes 8, one of which serves as a backup open grouting pipe. When the other open grouting pipe 8 can complete the grouting, the backup open grouting pipe can be used for grouting without being activated. The open grouting pipe 8 is used to grout the space inside the annular steel plate. The open grouting pipe 8 is located in the inner ring of the annular steel plate and is fixed to the inner side wall of the protective steel ring. The bottom of the open grouting pipe 8 is flush with the bottom of the reinforcing cage.

[0029] In one embodiment, the detection tube 5 is tied and fixed to the longitudinal main reinforcement of the steel cage. If the spare open grouting pipe of the post-grouting device meets the detection requirements, it can also be used as the detection tube 5. The inner diameter of the spare open grouting pipe is larger than the maximum outer diameter of the ultrasonic probe 1, which facilitates the up and down movement of the ultrasonic probe 1.

[0030] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for detecting the grouting effect at the bottom of a bridge cast-in-place pile, characterized in that: Includes the following steps: Step 1: Perform acoustic reflection enhancement treatment on the bladder of the post-grouting device at the pile bottom. The acoustic reflection enhancement treatment is to add high reflectivity filler to the raw materials for preparing the bladder, or to coat the outer surface of the bladder with an acoustic reflection coating. Step 2: Install vertically extending probes inside the post-grouting device. The bottom end of the probes extends to the bottom of the bladder. The probes are tied and fixed to the longitudinal main bars of the cast-in-place pile reinforcement cage. Fill the probes with water to balance the pressure difference between the inside and outside of the probe wall during the pile formation process. Step 3: After the pile concrete has reached the required standard, lower the ultrasonic probe to the bottom of the detection tube; raise the ultrasonic probe from bottom to top according to the preset layer spacing. Each time it is raised to a detection layer, control the ultrasonic probe to complete the 360° circumferential ultrasonic pulse emission and echo signal reception, collect the cross-sectional ultrasonic detection data of that layer, and simultaneously record the depth information corresponding to each detection layer. Step 4: The cross-sectional ultrasonic test data of all test layers are stitched together according to the corresponding depth coordinates to construct a three-dimensional point cloud model of the pile end skin area; and a three-dimensional mesh model or three-dimensional cloud map of the pile end enlarged head is generated.

2. The method for detecting the grouting effect at the bottom of bridge cast-in-place piles according to claim 1, characterized in that: In step two, the spare open grouting pipe of the post-grouting device is used as the detection pipe, and the inner diameter of the spare open grouting pipe is larger than the maximum outer diameter of the ultrasonic probe.

3. The method for detecting the grouting effect at the bottom of bridge cast-in-place piles according to claim 1, characterized in that: The high reflectivity filler is one or more of barite powder, iron ore powder, steel grit, and magnetic powder.

4. The method for detecting the grouting effect at the bottom of bridge cast-in-place piles according to claim 1, characterized in that: The acoustic reflective coating is epoxy resin-based and / or hollow glass microspheres.

5. The method for detecting the grouting effect at the bottom of bridge cast-in-place piles according to claim 1, characterized in that: The ultrasonic probe emits high-frequency acoustic pulses with a frequency of 1~2.25MHz.

6. The method for detecting the grouting effect at the bottom of bridge cast-in-place piles according to claim 1, characterized in that: The preset interlayer spacing ranges from 1cm to 10cm.

7. The method for detecting the grouting effect at the bottom of bridge cast-in-place piles according to claim 1, characterized in that: In step three, the lowering and raising of the ultrasonic probe is controlled by a cable winch set up on the ground, and the depth information of the ultrasonic probe is collected by the ranging module of the cable winch.

8. The method for detecting the grouting effect at the bottom of bridge cast-in-place piles according to claim 1, characterized in that: The ultrasonic probe is an integrated ultrasonic transceiver probe. The ultrasonic probe is connected to the ground data acquisition and processing system via a communication cable, and works with a cable winch to complete signal acquisition, data transmission and imaging processing.

9. The method for detecting the grouting effect at the bottom of bridge cast-in-place piles according to claim 1, characterized in that: In step three, the distance between the ultrasonic probe and the capsule is calculated based on the time difference between the ultrasonic pulse transmission and the received echo.

10. The method for detecting the grouting effect at the bottom of bridge cast-in-place piles according to claim 1, characterized in that: The testing processes in steps three and four can be carried out during grouting, after grouting is completed, and after the grout has solidified.

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