Experimental device and method for pipe jacking curve tunneling research in cavity stratum

Abstract

The invention belongs to the field of rectangular pipe-jacking tunnel construction, and discloses an experimental device and method for pipe-jacking curve tunneling research in a cavity stratum.According to the device, soil is contained in a model test box to simulate the stratum environment, and cavity defects are preset in cooperation with a built-in cavity forming device; the advancing direction of the model pipe jacking machine is precisely restrained through a bottom rail device, controllable tunneling power is provided by a jacking system, and meanwhile a monitoring device is arranged on the surface of a soil body to collect earth surface deformation data. The device constructs an integrated physical test environment, effectively solves the problem that the traditional method is difficult to accurately control the cooperative influence of cavity parameters and a tunneling path, can directly reveal the internal mechanism of surface deformation induced by pipe jacking construction in a cavity stratum, provides a reliable experimental basis for evaluating stratum stability and optimizing a construction process, and has a wide application prospect. The system has the comprehensive advantages of high structure integration degree, real working condition simulation, accurate variable control and efficient data acquisition.

Description

Technical Field

[0001] This invention belongs to the field of rectangular pipe jacking tunnel construction technology, specifically relating to an experimental device and method for studying curved pipe jacking excavation in cavitary strata. Background Technology

[0002] With the continuous development and utilization of urban underground space, the demand for underground engineering construction continues to rise. Pipe jacking, as a trenchless construction technology, has gained widespread popularity due to its significant advantages, including minimal impact on the surrounding environment, flexible construction, and high efficiency. Rectangular pipe jacking, in particular, offers higher space utilization compared to circular pipe jacking. Currently, pipe jacking tunnels are developing towards longer distances, larger cross-sections, and curved designs. In scenarios with dense underground pipelines and complex underground construction environments, the application of curved pipe jacking tunnel projects is increasing.

[0003] However, curved rectangular pipe jacking construction faces several challenging problems. Cavity strata, formed by factors such as groundwater level changes and soil erosion, are characterized by their concealment and high construction risks. During the excavation of curved rectangular pipe jacking, the inherent characteristics of the pipe jacking method inevitably lead to a backsoil effect. Construction in cavity strata can easily trigger surface subsidence, potentially causing uneven settlement, cracks, or even collapse—serious engineering problems. It can also damage underground pipelines, causing inconvenience and safety hazards to people's lives and livelihoods. Furthermore, existing research struggles to accurately predict surface deformation theoretically. On-site monitoring points are constrained by the surrounding environment, often only monitoring a single indicator, and it's impossible to change conditions for repeated monitoring. The resulting data cannot comprehensively reflect the surface deformation patterns caused by actual pipe jacking tunnel construction.

[0004] It is evident that existing experimental research methods for excavating curved rectangular pipes in cavitary strata are insufficient to accurately grasp and fully reflect the surface deformation patterns. Summary of the Invention

[0005] This invention provides an experimental device and method for studying curved pipe jacking in cavitary strata. The experimental device can accurately grasp and comprehensively reflect the surface deformation law during the tunneling process of curved rectangular pipes in cavitary strata.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: An experimental apparatus for studying curved tunneling in cavitary strata includes: The model test chamber is used to hold soil to simulate the geological environment during pipe jacking. A cavity forming device is installed in the soil within a model test chamber to create cavities in the soil. The track device is interspersed at the bottom of the model test box to constrain the direction of the pipe jacking curve excavation; Model pipe jacking machine, connected to the track device; The jacking system, connected to the jacking end of the model pipe jacking machine, is used to provide tunneling power for the pipe jacking machine; The monitoring device is installed on the soil surface to collect surface deformation data.

[0007] Furthermore, the cavity forming device includes an airbag, a high-pressure inflation pipe, and an air pump connected in sequence; a ball valve switch is provided on the high-pressure inflation pipe; the airbag is placed in the cavity position reserved in the soil; after the soil is filled, the gas in the airbag is discharged to form a cavity in the cavity position reserved in the soil.

[0008] Furthermore, the model test chamber includes a chamber body; the chamber body adopts a topless design, and the inlet and outlet of the chamber body are provided with through holes for the model pipe jacking machine to pass through; each through hole is provided with an openable door panel; the chamber body is divided into multiple spaces by partitions to realize the filling of soil at different depths in the chamber body; the partitions are provided with holes for the model pipe jacking machine to pass through.

[0009] Furthermore, the track device includes two tracks, which enter the model test chamber from the inlet and exit from the outlet after passing through the test chamber. Several sleepers are laid along the track path. The tracks are fixed to the sleepers. A slider is slidably connected to the inner side of the two tracks, and the top of the slider is flush with the top surface of the track. One end of the slider is connected to the excavation end of the model pipe jacking machine. The track as a whole is a curved track.

[0010] Furthermore, the model pipe jacking machine is connected to multiple pipe sections; the pipe sections are connected to the model pipe jacking machine and the multiple pipe sections using joint assemblies.

[0011] Furthermore, the joint assembly includes a ball joint connection structure, a highly elastic rubber pad, a water-swellable sealing strip, a highly elastic sealing ring, and a stainless steel hose ring; The top and bottom ends of the pipe section are connected in sequence to a water-swellable sealing strip, a stainless steel flexible hose ring, a high-elasticity sealing ring, and a high-elasticity rubber pad; the high-elasticity rubber pad is connected to a ball joint structure.

[0012] Furthermore, both the pipe section and the bottom of the model pipe jacking machine are equipped with wheels; each wheel includes a frustum and a disc; multiple ball bearings are arranged in the groove of the disc, and the two wheels are connected by bearings.

[0013] Furthermore, the jacking system includes diagonal braces, vertical braces, and a rear wall connected in sequence; Servo jacks are connected to the rear wall, and the servo jacks are evenly distributed and connected to the last pipe section connected to the tail of the model pipe jacking machine.

[0014] Furthermore, the experimental apparatus also includes a support system; the support system includes base plates disposed on both sides of the model test chamber; The base plate is equipped with a frame for fixing the track device.

[0015] A working method for an experimental apparatus used in research on pipe jacking curve tunneling in cavitary strata, based on the aforementioned experimental apparatus for research on pipe jacking curve tunneling in cavitary strata, comprising: The model test chamber was filled with soil to simulate the geological environment of pipe jacking. Multiple cavities are created in the soil using a cavity forming device; A jacking system is used to provide tunneling power to the pipe jacking machine, so that the pipe jacking machine can tunnel into the soil in the model test box along the direction constrained by the track device. Throughout the tunneling process, surface deformation data was collected using monitoring devices.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention provides an experimental device for studying curved tunneling with pipe jacking in cavitary strata. The device uses a model test chamber to simulate the geological environment by containing soil. A built-in cavity forming device pre-determines cavities, and a bottom track device precisely constrains the direction of travel of the model pipe jacking machine. The jacking system provides controllable tunneling power, while monitoring devices are deployed on the soil surface to collect surface deformation data. This device systematically integrates three key elements: cavity defect simulation, controllable jacking path, and surface response monitoring. The cavity forming device can generate cavities of specific shapes at set locations, realistically reproducing geological defects; the track device physically restricts the pipe jacking trajectory, eliminating directional deviation interference and ensuring that experimental variables focus on the influence of cavities; and the monitoring devices capture real-time changes in the surface displacement field as the jacking system drives the pipe jacking machine through cavitary strata. This device constructs an integrated physical testing environment, effectively solving the problem of the difficulty in accurately controlling the synergistic effects of cavity parameters and tunneling path using traditional methods. It can directly reveal the intrinsic mechanism of surface deformation induced by pipe jacking construction in cavity strata, providing reliable experimental basis for assessing stratum stability and optimizing construction technology. It has comprehensive advantages such as high structural integration, realistic working condition simulation, precise variable control, and efficient data acquisition.

[0017] Preferably, in this invention, the cavity forming device comprises an airbag, a high-pressure inflation pipe, and an air pump, forming a cavity through exhaust. This design enables controllable cavity generation and precise positioning, avoiding the problem of unstable cavity morphology in traditional methods. The removable nature of the airbag allows for repeated experiments, while the ball valve switch ensures ease of operation and safety. This significantly improves the accuracy and repeatability of cavity simulation, enabling researchers to systematically study the impact of different cavity parameters on pipe jacking, thereby enhancing the reliability and application value of experimental results.

[0018] Preferably, in this invention, the model test chamber includes a topless structure, inlet and outlet openings, and space divided by doors and partitions. This layout provides a highly flexible experimental environment; the doors facilitate the entry and exit of the pipe jacking machine, while the topless design simplifies soil filling and observation operations. The partitions allow for the simulation of soil layers at different depths, enabling the reproduction of diverse geological scenarios. This greatly enhances the adaptability and scalability of the experiment, allowing researchers to specifically test various geological conditions, improve experimental efficiency, and reduce human error.

[0019] Preferably, in this invention, the track device includes a track, sleepers, and a slider connecting the model pipe jacking machine. The design of the slider slidingly connected to the inner side of the track ensures strict constraints on the tunneling direction and smooth movement, while the sleepers provide stable support to eliminate vibration interference. The flush arrangement of the slider top with the track further reduces frictional resistance. This effectively prevents directional deviations during tunneling, focusing experimental variables on the effects of voids, thereby improving the accuracy of data acquisition and the controllability of the experiment, providing a reliable basis for analyzing the mechanical behavior of pipe jacking.

[0020] Preferably, in this invention, the model pipe jacking machine connects multiple pipe sections via a joint assembly. The joint assembly offers high flexibility, better adapting to curved tracks; this modular design allows for easy expansion and disassembly of pipe sections, simulating the continuous advancement process of real pipe jacking. The use of the joint assembly enhances the structural flexibility and assemblability, enabling experiments to adapt to different tunneling lengths and conditions. This simplifies experimental setup and maintenance, while improving system consistency and repeatability, facilitating in-depth analysis of the dynamic behavior of the pipe jacking machine in cavitary formations.

[0021] Preferably, in this invention, the joint assembly includes a ball joint connection structure, a highly elastic rubber gasket, a water-swellable sealing strip, a highly elastic sealing ring, and a stainless steel flexible hose ring. These components together provide excellent sealing and flexibility; the water-swellable sealing strip automatically adapts to the water environment to prevent leakage; the highly elastic material absorbs tunneling impacts; and the ball joint connection allows for a certain angular offset. This ensures the reliability and durability of the pipe section connection, reduces the risk of leakage or deformation during experiments, thereby improving data accuracy and simulating joint performance under real-world working conditions.

[0022] Preferably, in this invention, the wheel structure is located at the bottom of the pipe section and the model pipe jacking machine, comprising a frustum and a disc, connected by built-in ball bearings and bearings. This wheel mechanism significantly reduces tunneling resistance, while the ball bearings and bearings ensure smooth rolling and low-friction movement, and the frustum shape adapts to changes in the track. This improves the movement efficiency and stability of the pipe jacking machine, making the tunneling process closer to real mechanical behavior, thereby optimizing experimental performance and reducing energy consumption.

[0023] Preferably, in this invention, the jacking system includes diagonal braces, vertical braces, a rear support wall, and servo jack connecting pipe sections. The servo jacks provide precise and controllable jacking power, while the rear support wall and supporting structure ensure uniform thrust distribution and system stability. This enables fine adjustment and reliable transmission of tunneling force, avoiding local overload or deviation, thereby improving the controllability of the experiment and data consistency, and providing a solid foundation for studying the dynamic response of pipe jacking.

[0024] Preferably, in this invention, the support system includes a base plate and a platform for fixing the track. The base plate is positioned on both sides of the model test chamber, and the platform provides additional support to anchor the track. This enhances the overall stability and vibration resistance of the device, prevents displacement or tilting during the experiment, and ensures the accuracy of track constraints and the tunneling direction. This improves the reliability and repeatability of the experimental results and reduces interference from external factors. This invention provides a working method for an experimental device used in the study of curved tunneling with pipe jacking in cavitary strata. Based on this experimental device, the method simulates the geological environment by filling a model test chamber with soil. Multiple controllable cavities are pre-set using a cavity forming device. The jacking system drives the model pipe jacking machine to excavate at a constant speed along the direction constrained by the track device. Simultaneously, a monitoring device collects real-time surface deformation data throughout the entire process. This method achieves a closed-loop experimental logic of "defect pre-fabrication - directional tunneling - dynamic monitoring" through a standardized process: pre-set cavities accurately reproduce the spatial distribution characteristics of geological defects; the physical constraints of the track device eliminate deviations in the pipe jacking trajectory, ensuring that tunneling variables focus on the influence of cavities; and synchronous monitoring fully captures the dynamic evolution of the surface displacement field when the pipe jacks through cavities. This design establishes a highly controllable quantitative research method, effectively solving the problem that traditional experiments struggle to separate the coupling effect of cavity parameters and tunneling disturbances. It can directly reveal the spatiotemporal evolution mechanism of surface deformation induced by pipe jacking in cavitary strata, providing a universal experimental paradigm for assessing stratum instability risk and optimizing tunneling parameters. It has comprehensive advantages such as strong reproducibility of working conditions, precise variable control, complete data chain, and intuitive mechanism revelation. Attached Figure Description Figure 1 This is a schematic diagram of the structure of an experimental device for studying curved tunneling in cavitary strata, provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the track device within the box area provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the pipe section provided in an embodiment of the present invention; Figure 4 A front view of a pipe section provided in an embodiment of the present invention; Figure 5 A detailed schematic diagram of a pipe section provided in an embodiment of the present invention; Figure 6This is a detailed structural diagram of the track device within the box area provided in an embodiment of the present invention; Figure 7 This is a schematic diagram of the guide rail device provided in an embodiment of the present invention; Figure 8 The image shows the bottom assembly diagram of the model pipe jacking machine and pipe section provided in the embodiment of the present invention, wherein the left image is the overall assembly diagram; and the right image shows the specific structure of the wheel. Figure 9 A bottom view of the model pipe jacking machine and pipe section provided in an embodiment of the present invention; Figure 10 This is a schematic diagram of the inlet and outlet of the model test chamber provided in an embodiment of the present invention; Figure 11 This is a schematic diagram of the void forming device provided in an embodiment of the present invention.

[0025] Figure label: 1. Model test chamber; 2. Multi-point displacement gauge; 3. Track; 4. Base plate; 5. Steel pipe; 6. Model pipe jacking machine; 7. Platform; 8. Servo jack; 9. Diagonal brace; 10. Vertical brace; 11. Rear wall support; 12. Top iron; 13. Pipe section; 14. Door panel; 15. Sleeper; 16. Sliding block; 17. Hole; 18. Partition plate; 19. Joint assembly; 20. Raised structure; 21. Groove; 22. Wheel; 23. Ball joint 24. Connecting structure; 25. Steel frame; 26. Water-swellable sealing strip; 27. High-elasticity sealing ring; 28. High-elasticity rubber pad; 29. ​​Stainless steel flexible hose ring; 30. Steel ball; 31. Spherical groove; 32. Bolt; 33. Opening; 34. Buckle plate; 35. Bearing; 36. Ball bearing; 37. Door bolt; 38. Hinge; 39. Slot; 40. Ball valve switch; 41. High-pressure air inflator; 42. Air pump; 43. Airbag. Detailed Implementation

[0026] To further understand the content of this invention, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments are merely illustrative and not limiting of the invention.

[0027] As described in the background section, during the excavation of curved rectangular pipe jacking tunnels, the backsoil effect is unavoidable due to the characteristics of pipe jacking construction. This is especially true when constructing in cavitary strata, which can easily cause surface subsidence. This can lead to serious engineering problems such as uneven surface subsidence, cracks, and even collapse. It can also damage underground pipelines, causing inconvenience and safety hazards to people's lives and production. Existing research struggles to accurately predict this theoretically, and on-site monitoring points are constrained by the surrounding environment, often monitoring only a single indicator without the ability to monitor repeatedly under different conditions. The data obtained is insufficient to comprehensively reflect the surface deformation patterns caused by actual pipe jacking tunnel construction. Therefore, it is necessary to conduct research on the surface deformation patterns caused by curved rectangular pipe jacking tunnels in cavitary strata.

[0028] To address the aforementioned issues, this embodiment provides an experimental apparatus for studying curved pipe jacking tunneling in cavitary strata. This apparatus can reveal the deformation patterns of the strata caused by the actual construction process of curved rectangular pipe jacking, even when the strata are cavitary or the burial depth of the cavities is altered. This provides a reference for related research on curved pipe jacking tunnels.

[0029] This embodiment provides an experimental apparatus for studying curved pipe jacking in cavitary strata, comprising: a model test chamber 1 for holding soil to simulate the geological environment of pipe jacking; a cavity forming device, set in the soil within the model test chamber 1, for forming cavities 17 in the soil; a track device, interposed at the bottom of the model test chamber 1, for constraining the curved pipe jacking direction; a model pipe jacking machine 6, connected to the track device; a jacking system, connected to the jacking end of the model pipe jacking machine 6, for providing jacking power to the pipe jacking machine 6; and a monitoring device, set on the soil surface, for collecting surface deformation data.

[0030] The experimental apparatus for studying pipe jacking curve tunneling in cavitary strata provided in this embodiment will be described in detail below with reference to the accompanying drawings: This embodiment relates to an experimental apparatus and method for studying curved tunneling with pipe jacking in cavitary strata, mainly including a model test box 1, a model pipe jacking machine 6, prefabricated pipe sections 13, a jacking system, a support system, an initial reaction frame, and a cavity forming device. The specific structure and experimental method include: like Figure 1 , Figure 2 , Figure 6 , Figure 7 , Figure 10 and Figure 11As shown, the model test chamber 1 has no top cover, and is constructed from welded steel plates on the front, back, left, right, and bottom, reinforced with steel pipes 5 on the outside. Rectangular pipe jacking machine entry and exit holes are provided on the left and right sides of the chamber, larger than the excavation cross-section of the rectangular pipe jacking machine 6, to meet the construction requirements of the rectangular pipe jacking machine. Door panels 14 are provided for the entry and exit points. One side of the door panel 14 is connected to the chamber via a hinge 37, which is welded to both the chamber and the door panel 14. The other side is connected to a latch 36 via a door bolt 36, which is rotatable. The latch 38 is L-shaped and welded to the chamber. Grooves are provided on the inner sides of the steel plates on the front and back sides of the chamber for placing partitions 18. The partitions 18 are placed inside the chamber through these grooves, dividing the chamber into three different parts, each filled with soil at a different depth, to simulate the effects of excavation at different depths in soil containing cavities 17. The partitions 18 have openings to accommodate the simulation requirements of the model pipe jacking machine and the construction process. The model test box 1 is filled with soil. The soil must be filled in layers, starting with the portion below the inlet and outlet. When filling to the inlet and outlet positions, the sleepers 15 of the box are placed, and a track 3 is fixed to the sleepers 15. The track 3 is a curved track with a certain curvature. A slider 16 is used to block the upper soil, preventing it from falling into the track 3 and facilitating the passage of the model pipe jacking machine 6. After the guide rail device is installed, the inlet and outlet doors 14 are closed. According to the predetermined soil depth, soil is filled sequentially to the three sections of the box above the inlet and outlet. The filling depth for each section is different. When reaching the corresponding position of the cavity 17, an inflated airbag 42 is buried in the soil at the cavity 17 position. Soil is then filled, and the airbag 42 is deflated to form the cavity 17. Finally, multiple displacement gauges 2 are installed on the soil surface to monitor surface deformation data. The remaining two sections are filled using the same method.

[0031] like Figure 1 , Figure 2 , Figure 6 , Figure 7 As shown, the support device is divided into two parts: a front support and a rear support, which are respectively the support at the starting point and the support at the receiving point. The support structures of the two parts are identical. To ensure even stress distribution on the support platform, the support platform 7 is integrally made in an arc shape, with a base plate 4 at the bottom. The support platform 7 is mounted on the base plate using bolts 31. The support platform 7 is welded from steel pipes 5, and a steel panel is welded to the top surface of the platform 7. The track 3 is connected to the sleeper 15 via bolts 31. The track 3 has an "I"-shaped cross-section and is placed on the support platform 7. The support structure includes the track 3, sleeper 15, and slider 16. The base plate 4, track 3, platform 7, and support platform 7 are all designed in an arc shape, with a radius of curvature similar to that of a curved tunnel.

[0032] like Figure 1 , Figure 2 , Figure 3 , Figure 6 , Figure 7 As shown, the slider 16 is filled between the two tracks 3 to prevent the upper soil from falling into the interior of the tracks 3 and hindering the normal forward movement of the model pipe jacking machine 6 and the pipe section 13. The bottom of the middle slider 16 contacts the bottom surface of the groove in the middle of the track 3, and the top surface is flush with the track 3. A spherical groove 30 is provided on the slider 16, in which steel balls 29 are placed. Part of the steel balls 29 are embedded in the slider 16, and part of them are in contact with the track 3, thereby reducing the frictional resistance between the slider 16 and the track 3 and not restricting the free movement of the slider 16. The slider 16 moves forward together with the pipe jacking construction process, relying on the push of the steel frame 24 at the bottom of the pipe jacking machine.

[0033] like Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 7 , Figure 9 As shown, the connectors at both ends of pipe section 13 have the same structure, both being plug-in type components. The connector assembly 19 of pipe section 13 includes a ball joint connection structure 23, a high-elasticity rubber pad 27, a water-swellable sealing strip 25, a high-elasticity sealing ring 26, and a stainless steel flexible hose ring 28. The end of pipe section 13 is provided with a protruding structure 20, on which a serrated groove 21 is provided for accommodating the ball joint connection structure 23. Bolt holes are pre-embedded in the groove 21 of the pipe section, and the ball joint connection structure 23 is connected to pipe section 13 by bolts. The ball joint connection structure 23 is a steel cylinder with one end welded to a steel ball and the other end welded to a rectangular steel plate. The other half is a steel cylinder with one end connected to the steel plate and the other end connected to a device with a spherical groove. Four ball joints 23 are used to connect the two pipe sections. A certain gap is left between the pipe sections 13 connected by the ball joints 23 to facilitate pipe bending. The gap is filled with a high-elasticity rubber pad 27. When the pipe section 13 bends, the high-elasticity rubber pad 27 will deform, and the ball joints 23 will rotate accordingly to meet the requirement of free deflection of the pipe section. A water-swellable sealing strip 25 is installed on the protruding spigot of each pipe section, and a high-elasticity sealing ring 26 is wrapped around it. The outermost layer is a stainless steel flexible hose ring 28 to achieve a flexible connection between the pipe sections 13, which can adapt to the bending requirements of the curved section of the tunnel and reduce stress concentration between the pipe sections 13. At the same time, the track 3 and the ball joints 23 constrain the two pipe sections 13 so that they will not separate or undergo arbitrary uncontrollable deflection during jacking.

[0034] like Figure 11 As shown, the cavity forming device consists of a high-pressure inflation pipe 40, an air bladder 42, an air pump 41, and a ball valve switch 39. The air bladder 42 is inflated by the air pump 41, and the ball valve switch 39 has the function of inflating and deflating the air bladder 42.

[0035] like Figure 1 , Figure 3 , Figure 4 , Figure 5 and Figure 9 As shown, the model pipe jacking machine 6 and pipe section 13 need to be scaled down proportionally. The model pipe jacking machine 6 can perform functions such as cutting soil and grouting behind pipe section 13. The bottom of the model pipe jacking machine 6 and pipe section 13 is equipped with wheels 22, which enables the model pipe jacking machine 6 to advance along curved tunnels. Figure 8 As shown, the wheels 22 at the bottom of the model pipe jacking machine 6 and pipe section 13 are composed of a frustum, a disc, ball bearings 35 and a crossbeam welded together. The bearings and steel frame are then welded together and connected to the upper model pipe jacking machine 6 or pipe section 13 as a whole by bolts 31. Multiple ball bearings 35 are provided in the groove of the disc, and the two wheels 22 are connected by bearings 34.

[0036] like Figure 1-11 As shown in the diagram, the starting and receiving platforms of the model test box 1 are set up. The rear wall 11 is welded to the base plate 4. The rear wall 11 is reinforced by vertical supports 10 and diagonal supports 9. According to the actual experimental research requirements, the soil depth of each part is filled in the model test box 1 and the voids 17 are made. The multi-point displacement gauge 2 for monitoring surface settlement is installed. The door of the model test box is opened. The guide rail device is placed on the front support platform. The model pipe jacking machine 6, pipe section 13 and jacking iron are placed on the track 3. The wheels 22 of pipe section 13 and model pipe jacking machine 6 are placed in the grooves inside the track 3. The model pipe jacking machine 6 is powered by twelve servo jacks 8. One end of the servo jacks 8 is installed on the rear wall 11, and the other end is evenly distributed on the pipe section 13. When the rectangular pipe jacking machine and pipe section are pushed forward by the servo jacks 8, the movement of the slider 16 is supported by the steel frame 24 at the bottom of the pipe jacking model machine, so that the slider 16 moves forward. Simultaneously, the rear support device was installed. The tunneling control system was started to begin the tunneling test. Displacement gauge data was recorded after each tunnel segment was excavated, and synchronous grouting was performed in a timely manner until the tunneling was completed. The model pipe jacking machine 6 was then docked on the receiving end platform 7, and the experiment was completed. Finally, the soil deformation graph was plotted based on the experimental data.

[0037] In summary, this invention provides an experimental apparatus for studying curved tunneling in cavitary strata, which has the following advantages compared to existing technologies: This experimental setup improves the rectangular pipe jacking machine, pipe sections, and guide rail device, solving the problem of difficulty in correcting deviations during the simulation of curved rectangular pipe jacking. Traditional rigid pipe joints cause stress concentration at the connection points, leading to higher stress levels on the inner side of the curve during jacking, potentially even damaging the joints. This makes it unsuitable for curved tunnels. By changing to flexible joints, it not only meets the bending requirements of curved rectangular pipe jacking but also prevents stress concentration. The constraint of the curved rails cleverly simulates the construction process of rectangular pipe jacking in cavitary strata. Dividing the model test box allows for obtaining surface settlement data for curved rectangular pipe jacking construction under three different burial depths in cavitary conditions, achieving twice the result with half the effort. The setup is simple to operate and easy to implement. It provides an effective and reliable method for simulating the construction process of curved pipe jacking tunnels, revealing the surface deformation patterns caused by curved rectangular pipe jacking in cavitary strata, and providing guidance for the construction and design of practical projects.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. An experimental apparatus for studying curved tunneling with pipe jacking in cavitary strata, characterized in that, include: Model test chamber (1) is used to hold soil to simulate the geological environment of pipe jacking; A cavity forming device is set in the soil in the model test box (1) to form cavities (17) in the soil. The track device is interspersed at the bottom of the model test box (1) to constrain the direction of the jacking curve tunneling; The model pipe jacking machine (6) is connected to the track device; The jacking system is connected to the jacking end of the model pipe jacking machine (6) and is used to provide tunneling power for the pipe jacking machine (6); The monitoring device is installed on the soil surface to collect surface deformation data.

2. The experimental apparatus for studying curved tunneling in cavitary strata according to claim 1, characterized in that, The cavity forming device includes an airbag (42), a high-pressure inflation pipe (40), and an air pump (41) connected in sequence; a ball valve switch (39) is provided on the high-pressure inflation pipe (40); the airbag (42) is placed in the reserved cavity (17) position in the soil; after the soil is filled, the gas in the airbag (42) is discharged to form a cavity (17) in the reserved cavity (17) position in the soil.

3. The experimental apparatus for studying curved tunneling in cavitary strata according to claim 1, characterized in that, The model test chamber (1) includes a chamber body; the chamber body adopts a topless design, and the inlet and outlet of the chamber body are provided with through holes for the model pipe jacking machine (6) to pass through; each through hole is provided with a door panel (14) that can be opened and closed; the chamber body is divided into multiple spaces by a partition (18) to realize the filling of soil at different depths in the chamber body; the partition (18) is provided with holes for the model pipe jacking machine (6) to pass through.

4. The experimental apparatus for studying curved tunneling in cavitary strata according to claim 1, characterized in that, The track device includes two tracks (3), which are inserted into the model test box (1) from the inlet and exit from the outlet of the model test box (1) after passing through the model test box (1); several sleepers (15) are laid along the path of the track (3); the track (3) is fixed on the sleepers (15); sliders (16) are slidably connected to the inner sides of the two tracks (3), and the top of the sliders (16) is flush with the top surface of the track (3); one end of the sliders (16) is connected to the tunneling end of the model pipe jacking machine (6); the track (3) is a curved track as a whole.

5. The experimental apparatus for studying curved tunneling in cavitary strata according to claim 1, characterized in that, The model pipe jacking machine (6) is connected to multiple pipe sections (13); the pipe sections (13) are connected to the model pipe jacking machine (6) and the multiple pipe sections (13) by a joint assembly (19).

6. The experimental apparatus for studying curved tunneling in cavitary strata according to claim 5, characterized in that, The joint assembly (19) includes a ball joint connection structure (23), a high-elasticity rubber pad (27), a water-swellable sealing strip (25), a high-elasticity sealing ring (26), and a stainless steel hose ring (28). The top and bottom ends of the pipe section (13) are connected in sequence to a water-swellable sealing strip (25), a stainless steel flexible hose ring (28), a high-elasticity sealing ring (26), and a high-elasticity rubber pad (27); the high-elasticity rubber pad (27) is connected to a ball joint connection structure (23).

7. The experimental apparatus for studying curved tunneling in cavitary strata according to claim 5, characterized in that, Both the pipe section (13) and the model pipe jacking machine (6) are equipped with wheels (22) at their bottoms; each wheel (22) includes a frustum and a disc; a plurality of balls (35) are provided in the groove of the disc, and the two wheels (22) are connected by bearings (34).

8. The experimental apparatus for studying curved tunneling in cavitary strata according to claim 1, characterized in that, The jacking system includes a diagonal brace (9), a vertical brace (10), and a rear wall (11) connected in sequence. A servo jack (8) is connected to the rear wall (11), and the servo jack (8) is evenly connected to the end pipe section (13) connected to the tail of the model pipe jacking machine (6).

9. The experimental apparatus for studying curved tunneling in cavitary strata according to claim 1, characterized in that, The experimental apparatus also includes a support system; the support system includes a base plate (4) disposed on both sides of the model test chamber (1); The base plate (4) is provided with a platform (7) for fixing the track device.

10. A working method for an experimental apparatus used in the study of curved tunneling with pipe jacking in cavitary strata, characterized in that, The experimental apparatus for studying pipe jacking curve tunneling in cavitary strata according to any one of claims 1-9 includes: Soil was filled into the model test box (1) to simulate the geological environment of pipe jacking; Multiple cavities are formed in the soil using a cavity forming device (17). A jacking system is used to provide tunneling power to the pipe jacking machine (6) so that the pipe jacking machine (6) can tunnel into the soil in the model test box (1) along the direction constrained by the track device; Throughout the tunneling process, surface deformation data was collected using monitoring devices.

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