Device and method for measuring resistance reduction effect of slurry on side wall of fabricated open caisson

Abstract

The invention discloses a device and method for measuring the resistance reduction effect of slurry on the side wall of an assembled open caisson, and particularly relates to the field of open caisson construction.The device comprises a base, and an experiment loading device, a slurry pumping device, a transparent soil body supporting device and a transparent acrylic barrel are arranged at the top of the base; the transparent soil body supporting device is arranged on the inner side of the transparent acrylic barrel, the transparent acrylic barrel is arranged at the bottom of the experiment loading device, the experiment loading device is composed of a telescopic column, a loading cross beam, a clamp and a jack, the telescopic column is fixedly connected to the top of the base, the loading cross beam is fixedly connected to the top end of the telescopic column, and the clamp is fixedly connected to the top end of the telescopic column. The number of the clamps and the number of the jacks are both two, the clamps and the jacks are symmetrically distributed, and the two jacks are fixedly connected to the bottoms of the two clamps respectively. The device is designed according to the vertical stress characteristic of a novel prefabricated open caisson construction method, and the actual working condition can be reflected more truly, so that the reliability of an experimental result is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of caisson construction technology, and more specifically, to an apparatus and method for measuring the drag reduction effect of mud slurry on the sidewalls of prefabricated caissons. Background Technology

[0002] During the construction of caissons, in order to reduce the resistance of the caisson descent and ensure that the caisson sinks smoothly to the predetermined depth, additional resistance reduction measures need to be taken. The commonly used resistance reduction measure is grouting, which involves injecting a specific grout around the caisson to change the physical properties of the surrounding soil, thereby reducing the resistance of the caisson. To ensure that the grouting resistance reduction effect meets expectations, it is necessary to measure it in advance to ensure the smooth progress of grouting resistance reduction.

[0003] A grouting drag reduction model test device for ultra-large diameter and ultra-deep caisson construction, disclosed in Chinese Publication No. CN118913919A, includes a test loading device, a soil box, caisson segments, a caisson segment control device, a data acquisition system, a grouting device, and a control system. The soil box is located above the test loading device. The test soil box of this invention can simulate the caisson construction process under different soil layers (sand layer, clay layer, sand-clay composite stratum) and different water content conditions in different test groups according to test requirements.

[0004] The aforementioned device is only suitable for traditional caisson sinking grouting drag reduction model tests. However, the new prefabricated assembled caisson construction method differs significantly from traditional caissons in terms of vertical stress, especially with the added lifting force. Furthermore, this device simulates a drained sinking condition, while current new prefabricated assembled caissons are actually excavated without drainage, resulting in inconsistencies between the two conditions. The device lacks pressure-maintaining measures, which can easily lead to slurry overflow during grouting. In actual engineering, maintaining stable slurry pressure is required; the lack of a pressure-maintaining device directly affects the slurry's friction-reducing effect—insufficient slurry pressure reduces its support capacity for the sidewall soil and may even cause surrounding soil collapse, leading to distorted test results. On the other hand, excessive slurry pressure during grouting may also cause soil collapse, resulting in soil contact with the caisson wall and blockage of the slurry channels, preventing the formation of a uniform slurry film and causing uneven distribution of the friction-reducing effect, further affecting the accuracy of the test. Regarding earth pressure application, the device lacks a uniform pressure application mechanism, which can easily lead to uneven stress on the soil, affecting the reliability of the test results. In addition, the soil extraction process relies on manual operation, which has low precision. It is difficult to accurately control the soil extraction depth and amount, which will also introduce significant experimental errors. Therefore, in order to address this problem, this application provides a device for measuring the drag reduction effect of mud slurry on the sidewall of prefabricated caissons to meet the requirements. Summary of the Invention

[0005] To overcome the aforementioned deficiencies of the prior art, embodiments of the present invention provide a device for measuring the drag reduction effect of mud slurry on the sidewall of a prefabricated caisson. Designed specifically for the vertical stress characteristics of the novel prefabricated caisson construction method, it can more realistically reflect the actual working conditions, thereby ensuring the reliability of the experimental results and solving the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A device for determining the drag reduction effect of mud slurry on the sidewall of a prefabricated caisson includes a base. The top of the base is equipped with an experimental loading device, a mud pumping device, a transparent soil support device, and a transparent acrylic cylinder. The transparent soil support device is located inside the transparent acrylic cylinder, which is located at the bottom of the experimental loading device. The experimental loading device consists of a telescopic column, a loading beam, clamps, and jacks. The telescopic column is fixedly connected to the top of the base, and the loading beam is fixedly connected to the top of the telescopic column. Two clamps and two jacks are symmetrically distributed. The two jacks are fixedly connected to the bottom of the two clamps, and both jacks are inserted into the inside of the transparent acrylic cylinder.

[0007] In a preferred embodiment, the mud pumping device includes a mud pump disposed on the top of the base, and a mud pipe disposed on the top of the mud pump, the mud pipe being connected to the transparent soil support device.

[0008] In a preferred embodiment, an air compressor is provided on the top of the base, and an air pipe is provided on the top of the air compressor. The air pipe is connected to the transparent soil support device, and switches are provided on the outside of both the mud pipe and the air pipe.

[0009] In a preferred embodiment, a winch is provided at the bottom of the loading beam, the winch is fixedly connected to the top of the transparent soil support device, a mud pressure gauge is provided at the top of the transparent soil support device, and a tension gauge is provided inside the transparent soil support device.

[0010] In a preferred embodiment, soil is provided on the inner side of the transparent acrylic cylinder, the soil is located on the outer side of the transparent soil support device, and multiple soil pressure gauges are provided inside the soil.

[0011] In a preferred embodiment, a well segment is provided on the inner side of the transparent acrylic cylinder, the well segment is located at the bottom end of the transparent soil support device, and the well segment is fixedly connected to the bottom of the tension gauge.

[0012] In a preferred embodiment, a sealing ring is slidably connected to the outer side of the transparent soil support device, the sealing ring is slidably connected to the inner side of the transparent acrylic cylinder, and a rubber ring is provided on the outer side of the sealing ring.

[0013] The present invention also provides a method for determining the drag reduction effect of mud slurry on the sidewall of a prefabricated caisson, comprising the following steps: S1. Experimental Preparation: a. Prepare friction-reducing mud and determine its proportions according to the experimental design; b. Prepare soil samples taken from the construction site and control their moisture content and density to simulate actual geological conditions; c. Prefabricated caisson segments 18 that conform to the experimental design dimensions; d. Inspect all components of the test apparatus, including the transparent acrylic cylinder 10, the transparent soil support device 11, the sealing ring 13, the mud pump 5, the air pressure device, the tension gauge 16, the earth pressure gauge 6, and related pipelines and connectors; S2. Device assembly and soil sample filling: The caisson segment 18 is positioned in the center of the transparent acrylic cylinder 10. The transparent soil support device 11 is fitted on the outside of the segment and connected to the tension gauge 16 and the lifting system. Then, the soil sample is filled in layers and compacted to the set density. During the process, the soil pressure gauge 6 is placed in the soil to monitor the change of soil pressure. S3. Sealing and Soil Loading: The sealing ring 13 is placed on the outside of the transparent soil support device 11, so that its bottom surface contacts the soil surface. A vertical load is applied to the sealing ring 13 by jack until the soil reaches the preset test pressure value. Then, the pressurization is stopped and the load is kept stable. S4. Mud Injection and Pressure Building: Connect the mud delivery pipeline, start the mud pump 5, open the grouting switch 3 to inject mud into the wellbore, and after the mud level reaches the set height, turn off the mud pump 5, then turn on the air pressure device, adjust and maintain the mud pressure to the value required for the test. S5. Improve testing and data collection: Start the lifting system and slowly lift the transparent soil support device 11. When the device rises to a certain height, the tension gauge 16 begins to bear force and drives the well wall to move upward. At this time, the reading of the tension gauge 16 gradually changes. Continue to lift at a constant speed. After the reading of the tension gauge 16 stabilizes, record the value. This stable tension value can be used to evaluate the drag reduction effect of the mud and then analyze the changes in side friction resistance under different mud mix ratios.

[0014] The technical effects and advantages of this invention are as follows: This invention significantly improves the accuracy of the sinking process control by using a reverse lifting mechanism to replace traditional manual soil removal, and better simulates the vertical stress state in actual construction, making it more consistent with actual stress conditions; by filling the well shaft with drag-reducing mud, it accurately simulates the actual construction conditions of non-drainage excavation, thus improving the environmental realism of the test. A circular pressure plate matching the cross-sectional dimensions of the soil is installed on the upper part of the soil to ensure that the load transmitted by the jack is evenly distributed, avoiding test deviations caused by uneven stress on the soil. Rubber sealing sleeves are installed on the inner and outer sides of the circular ring to keep the soil in a sealed state, providing the necessary conditions for establishing and maintaining the side wall mud pressure. A pre-supported structure is used to provide support on the outside of the well wall to prevent soil collapse and reduce operational errors caused by manual soil removal. The reserved mud channels ensure that the mud can be evenly distributed around the well wall, avoiding soil collapse and grout blockage caused by improper grouting pressure, thus ensuring the effectiveness and consistency of the friction reduction effect. The sealing effect of the rubber ring can achieve stable mud pressure, effectively supporting the surrounding soil and further simulating the mud wall protection effect in actual engineering. This device is easy to manufacture, economical and practical, and has important engineering significance and theoretical reference value for guiding the selection and construction of actual projects. Attached Figure Description

[0015] Figure 1 A front structural schematic diagram of the device used to measure the drag reduction effect of mud slurry on the sidewall of a prefabricated caisson construction method. Figure 2 for Figure 1 Enlarged view of the A-section structure; Figure 3 for Figure 2 Enlarged view of the structure of part B.

[0016] The attached diagram is labeled as follows: 1. Clamp; 2. Loading beam; 3. Switch; 4. Mud pipe; 5. Mud pump; 6. Earth pressure gauge; 7. Winch; 8. Jack; 9. Air pipe; 10. Transparent acrylic cylinder; 11. Transparent soil support device; 12. Rubber ring; 13. Sealing ring; 14. Mud pressure gauge; 15. Soil; 16. Tension gauge; 17. Air compressor; 18. Caisson segment; 19. Telescopic column; 20. Base. Detailed Implementation

[0017] 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.

[0018] Refer to the instruction manual appendix Figures 1-3 As shown, an embodiment of the present invention provides a device for measuring the drag reduction effect of mud slurry on the sidewall of a prefabricated caisson. The device includes a base 20, with an experimental loading device, a mud pumping device, a transparent soil support device 11, and a transparent acrylic cylinder 10 mounted on the top of the base 20. If simulating a larger pressure, a metal cylinder can be used instead of an acrylic cylinder to avoid structural damage. The transparent soil support device 11 is located inside the transparent acrylic cylinder 10, which is located at the bottom of the experimental loading device. The experimental loading device applies a vertical load to the soil. The experimental loading device consists of a telescopic column 19, a loading beam 2, clamps 1, and jacks 8. The telescopic column 19 is fixedly connected to the top of the base 20, and the loading beam 2 is fixedly connected to the top of the telescopic column 19. The clamps 1 and jacks 8 are both set to two and are symmetrically distributed. The two jacks 8 are respectively fixedly connected to the bottom of the two clamps 1, and both jacks 8 are inserted into the inside of the transparent acrylic cylinder 10.

[0019] The mud pumping device includes a mud pump 5 mounted on top of the base 20, a mud pipe 4 mounted on top of the mud pump 5, which is connected to the transparent soil support device 11. An air compressor 17 is mounted on top of the base 20 to maintain stable mud pressure. An air pipe 9 is mounted on top of the air compressor 17 and is connected to the transparent soil support device 11. Switches 3 are mounted on the outer sides of both the mud pipe 4 and the air pipe 9. A winch 7 is mounted at the bottom of the loading beam 2 and is fixedly connected to the top of the transparent soil support device 11. A mud pressure gauge 14 is mounted on top of the transparent soil support device 11. A tension gauge 16 is mounted inside the transparent soil support device 11. Soil 15 is mounted inside the transparent acrylic cylinder 10. Multiple earth pressure gauges 6 are installed on the outside of the soil support device 11 and inside the soil 15. A well segment 18 is installed on the inside of the transparent acrylic cylinder 10. The well segment 18 is made of water, sand and concrete in a certain proportion, and its outer surface roughness is consistent with that of the actual segment. The well segment 18 is set at the bottom of the transparent soil support device 11 and is fixedly connected to the bottom of the tension gauge 16. A sealing ring 13 is slidably connected to the outside of the transparent soil support device 11 and is slidably connected to the inside of the transparent acrylic cylinder 10. A rubber ring 12 is installed on the outside of the sealing ring 13. The inner diameter of the sealing ring 13 is adapted to the outer diameter of the transparent soil support device 11 and the outer diameter of the sealing ring 13 is adapted to the inner diameter of the transparent acrylic cylinder 10. The sealing and loading of the soil 15 are achieved by applying pressure through the jack 8.

[0020] It should be noted that, in this process, the caisson segments 18 are prefabricated according to the actual engineering design and positioned within the transparent acrylic cylinder 10. A transparent soil support device 11 is fitted over the outside of the caisson segments 18 and connected to the tension gauge 16 and the lifting rope of the winch 7. Subsequently, the site soil sample is compacted in layers inside the cylinder, controlling the moisture content and compaction to match the actual working conditions. Simultaneously, a soil pressure gauge 6 is placed in the soil. A sealing ring 13 is fitted onto the transparent soil support device 11, ensuring its bottom surface contacts the soil. A load is applied to the sealing ring 13 using a jack 8 to compress the soil. The pressure is brought to the predetermined value, and the seal is achieved by the rubber ring 12. The switch 3 on the mud pipe 4 is turned on to transport the mud and inject it into the well to the set height. Then the mud pump 5 is turned off, the switch 3 on the outside of the air pipe 9 is turned on, the mud pressure is adjusted and maintained at the value required for the test, the winch 7 is started, and the transparent soil support device 11 is slowly lifted. After the device rises to a certain height, the tension gauge 16 begins to show a change in value, and the well wall moves up slowly. The lifting continues until the tension gauge reading stabilizes. The tension value at this time is recorded for analysis of the mud drag reduction effect.

[0021] This method, employing a reverse lifting mechanism to replace traditional manual soil removal, significantly improves the precision of the sinking process control, better simulates the vertical stress state during actual construction, and makes it more closely resembles actual stress conditions. By filling the shaft with drag-reducing mud, the actual construction conditions of non-drainage excavation are accurately simulated, enhancing the environmental realism of the experiment. A circular pressure plate matching the cross-sectional dimensions of the soil is installed on the upper part of the soil to ensure uniform load distribution transmitted by the jacks, avoiding experimental deviations caused by uneven soil stress. Rubber sealing sleeves are installed on the inner and outer sides of the circular ring to keep the soil in a sealed state, providing the necessary conditions for establishing and maintaining sidewall mud pressure. Requirements: A pre-supported structure is used to provide support on the outside of the well wall, preventing soil collapse and reducing operational errors caused by manual soil removal; pre-reserved mud channels ensure that mud is evenly distributed around the well wall, preventing soil collapse and grout blockage due to improper grouting pressure, thus guaranteeing the effectiveness and consistency of the friction reduction effect; relying on the sealing effect of the rubber ring, the mud pressure can be stably maintained, effectively supporting the surrounding soil and further simulating the mud wall protection effect in actual engineering; this device is easy to manufacture, economical and practical, and has significant engineering significance and theoretical reference value for guiding the selection and construction of actual projects.

[0022] This invention also discloses a method for determining the drag reduction effect of mud slurry on the sidewall of a prefabricated caisson, comprising the following steps: Experimental preparation a. Prepare friction-reducing mud and determine its proportions according to the experimental design; b. Prepare soil samples taken from the construction site and control their moisture content and density to simulate actual geological conditions; c. Prefabricated caisson segments 18 that conform to the experimental design dimensions; d. Inspect all components of the test apparatus, including the transparent acrylic cylinder 10, the transparent soil support device 11, the sealing ring 13, the mud pump 5, the air pressure device, the tension gauge 16, the soil pressure gauge 6, and related pipelines and connectors.

[0023] Device assembly and soil sample filling: The caisson segment 18 is positioned at the center of the transparent acrylic cylinder 10. The transparent soil support device 11 is fitted onto the outside of the segment and connected to the tension gauge 16 and the lifting system. Then, the soil sample is filled in layers and compacted to the set density. During the process, the soil pressure gauge 6 is placed in the soil to monitor the changes in soil pressure.

[0024] Sealing and soil loading: The sealing ring 13 is placed on the outside of the transparent soil support device 11, so that its bottom surface contacts the soil surface. A vertical load is applied to the sealing ring 13 by a jack until the soil reaches the preset test pressure value. Then, the pressurization is stopped and the load is kept stable.

[0025] Mud injection and pressure build-up: Connect the mud delivery pipeline, start the mud pump 5, open the grouting switch 3 to inject mud into the wellbore, and after the mud level reaches the set height, turn off the mud pump 5. Then turn on the air pressure device to adjust and maintain the mud pressure to the value required for the test.

[0026] Improve testing and data collection: Start the lifting system and slowly lift the transparent soil support device 11. When the device rises to a certain height, the tension gauge 16 begins to bear force and drives the well wall to move upward. At this time, the reading of the tension gauge 16 gradually changes. Continue to lift at a constant speed. After the reading of the tension gauge 16 stabilizes, record the value. This stable tension value can be used to evaluate the drag reduction effect of the mud and then analyze the changes in side friction resistance under different mud mix ratios.

[0027] Finally, the following points should be noted: First, in the description of this application, it should be noted that, unless otherwise specified and limited, the terms "installation", "connection", and "linkage" should be interpreted broadly, and can be mechanical or electrical connections, or internal connections between two components, or direct connections. "Up", "down", "left", "right", etc. are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may change. Secondly: The accompanying drawings of the embodiments disclosed in this invention only involve the structures involved in the embodiments disclosed in this invention. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other. In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A device for measuring the drag reduction effect of mud slurry on the sidewall of a prefabricated caisson, comprising a base (20), characterized in that: The top of the base (20) is provided with an experimental loading device, a mud pumping device, a transparent soil support device (11) and a transparent acrylic cylinder (10). The transparent soil support device (11) is located inside the transparent acrylic cylinder (10). The transparent acrylic cylinder (10) is located at the bottom of the experimental loading device. The experimental loading device consists of a telescopic column (19), a loading beam (2), a clamp (1), and a jack (8). The telescopic column (19) is fixedly connected to the top of the base (20). The loading beam (2) is fixedly connected to the top of the telescopic column (19). The clamp (1) and the jack (8) are both set to two and are symmetrically distributed. The two jacks (8) are fixedly connected to the bottom of the two clamps (1) respectively. The two jacks (8) are inserted into the inside of the transparent acrylic cylinder (10).

2. The device for measuring the drag reduction effect of mud slurry on the sidewall of a prefabricated caisson according to claim 1, characterized in that: The mud pumping device includes a mud pump (5) installed on the top of the base (20), and a mud pipe (4) is installed on the top of the mud pump (5). The mud pipe (4) is connected to the transparent soil support device (11).

3. The device for measuring the drag reduction effect of mud slurry on the sidewall of a prefabricated caisson according to claim 2, characterized in that: An air compressor (17) is provided on the top of the base (20), and an air pipe (9) is provided on the top of the air compressor (17). The air pipe (9) is connected to the transparent soil support device (11). Switches (3) are provided on the outside of both the mud pipe (4) and the air pipe (9).

4. The device for measuring the drag reduction effect of mud slurry on the sidewall of a prefabricated caisson according to claim 1, characterized in that: The bottom of the loading beam (2) is provided with a winch device (7), which is fixedly connected to the top of the transparent soil support device (11). The top of the transparent soil support device (11) is provided with a mud pressure gauge (14), and the inside of the transparent soil support device (11) is provided with a tension gauge (16).

5. The device for measuring the drag reduction effect of mud slurry on the sidewall of a prefabricated caisson according to claim 1, characterized in that: The transparent acrylic cylinder (10) has a soil body (15) on its inner side. The soil body (15) is located on the outside of the transparent soil support device (11). Multiple soil pressure gauges (6) are installed inside the soil body (15).

6. The device for measuring the drag reduction effect of mud slurry on the sidewall of a prefabricated caisson according to claim 4, characterized in that: The inner side of the transparent acrylic cylinder (10) is provided with a well segment (18), which is located at the bottom of the transparent soil support device (11) and is fixedly connected to the bottom of the tension gauge (16).

7. The device for measuring the drag reduction effect of mud slurry on the sidewall of a prefabricated caisson according to claim 4, characterized in that: A sealing ring (13) is slidably connected to the outside of the transparent soil support device (11). The sealing ring (13) is slidably connected to the inside of the transparent acrylic cylinder (10). A rubber ring (12) is provided on the outside of the sealing ring (13).

8. A method for determining the drag reduction effect of mud slurry on the sidewall of a prefabricated caisson, based on the apparatus for determining the drag reduction effect of mud slurry on the sidewall of a prefabricated caisson as described in any one of claims 1-7, comprising the following steps: S1. Experimental Preparation: a. Prepare friction-reducing mud and determine its proportions according to the experimental design; b. Prepare soil samples taken from the construction site and control their moisture content and density to simulate actual geological conditions; c. Prefabricated caisson segments 18 that conform to the experimental design dimensions; d. Inspect all components of the test apparatus, including the transparent acrylic cylinder 10, the transparent soil support device 11, the sealing ring 13, the mud pump 5, the air pressure device, the tension gauge 16, the earth pressure gauge 6, and related pipelines and connectors; S2. Device assembly and soil sample filling: The caisson segment 18 is positioned in the center of the transparent acrylic cylinder 10. The transparent soil support device 11 is fitted on the outside of the segment and connected to the tension gauge 16 and the lifting system. Then, the soil sample is filled in layers and compacted to the set density. During the process, the soil pressure gauge 6 is placed in the soil to monitor the change of soil pressure. S3. Sealing and Soil Loading: The sealing ring 13 is placed on the outside of the transparent soil support device 11, so that its bottom surface contacts the soil surface. A vertical load is applied to the sealing ring 13 by jack until the soil reaches the preset test pressure value. Then, the pressurization is stopped and the load is kept stable. S4. Mud Injection and Pressure Building: Connect the mud delivery pipeline, start the mud pump 5, open the grouting switch 3 to inject mud into the wellbore, and after the mud level reaches the set height, turn off the mud pump 5, then turn on the air pressure device, adjust and maintain the mud pressure to the value required for the test. S5. Improve testing and data collection: Start the lifting system and slowly lift the transparent soil support device 11. When the device rises to a certain height, the tension gauge 16 begins to bear force and drives the well wall to move upward. At this time, the reading of the tension gauge 16 gradually changes. Continue to lift at a constant speed. After the reading of the tension gauge 16 stabilizes, record the value. This stable tension value can be used to evaluate the drag reduction effect of the mud and then analyze the changes in side friction resistance under different mud mix ratios.

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