Centrifugal test device for simulating the interaction between tunnel and buried strip foundation structure

Abstract

The present invention relates to the field of geotechnical engineering physical simulation, and in particular to a centrifugal test device for simulating the interaction between a tunnel and an embedded strip foundation structure; the device comprises a centrifugal model box and a top-opening centrifugal model container composed of a transparent front side panel; a sand sample is filled therein, and a model tunnel and an embedded strip foundation structure are embedded in the sand sample; in a first state, external baffles are provided between the left and right foundation columns and the side panels, and internal baffles are provided between adjacent foundation columns; in a second state, an upper support block is provided on the upper portion of the upper horizontal layer; and the internal baffle is suspended between the lower horizontal layer and the sand sample. The centrifugal test device and preparation method of the present invention can accurately reproduce the soil properties surrounding the embedded strip foundation structure, avoid the disturbance of the soil layer by the traditional insertion method, and thus accurately simulate the deformation response of the embedded strip foundation structure caused by tunnel construction.

Description

Technical Field

[0001] The present invention relates to the field of geotechnical engineering physical simulation, in particular to a centrifugal test device for simulating the interaction between a tunnel and an embedded strip foundation structure and a test preparation method. Background Art

[0002] With the rapid advancement of urbanization, available surface space in cities is becoming increasingly limited, leading to the large-scale development and utilization of underground space, particularly tunnels. Shield tunneling machines (TBMs) are widely used in urban areas with densely populated surface buildings and extensive underground structures and infrastructure. Despite rapid advances in shield tunneling technology, large-scale ground subsidence and even collapses occur frequently when encountering unusual geological conditions or due to operational errors, significantly impacting public safety and social stability. Therefore, studying the impact of tunnel construction on adjacent structures and predicting and assessing building deformation has important engineering value and social development implications.

[0003] Assessing the deformation impact of tunnel construction on adjacent structures is a critical task throughout the design and construction phases of tunnel projects. During the design phase, evaluating the impact of tunnel construction on surrounding structures can help optimize tunnel alignment, thereby avoiding adverse environmental impacts during tunnel construction. During shield tunnel construction, unusual geological conditions or operational errors can easily cause deformation and damage to surrounding structures. Assessing the extent of building deformation in these situations is crucial for subsequent repair and reinforcement. However, accurately predicting the impact of tunnel construction on surrounding buildings still faces numerous challenges, including complex soil properties, highly nonlinear soil-structure interaction mechanisms, and a wide variety of building foundation types and materials.

[0004] Currently, there are three main methods for studying the impact of tunnel construction on surrounding structures. The first is numerical simulation or simplified theoretical calculations. While these methods offer low research costs, the reliability of the results is relatively low. The second is field measurements or full-scale testing. These methods can account for complex factors and obtain accurate results, but the associated research costs are high and they cannot be used for large-scale predictive assessments. Physical model testing provides a more reliable research tool, enabling a more accurate study of the impact of tunnel construction on surrounding structures. To further improve the accuracy of model testing, centrifuge model testing, which utilizes a hypergravity environment to simulate realistic soil stresses, has gained widespread acceptance. Because the gravitational acceleration of the entire model chamber must be increased to tens or even hundreds of times that of conventional Earth gravity, centrifuge model test chambers are generally small, and the various models within them are also small in size. This poses significant challenges to model fabrication and test preparation.

[0005] Centrifuge model tests investigating the impact of tunnel construction on surrounding structures generally use a two-dimensional plane strain model. Particle image velocimetry is then used to collect test data through a transparent window on one side. To simulate uniform soil properties, researchers prepare sand samples using a sand-sprinkling method, where sand is dropped at a constant velocity from a certain height into a model box. Therefore, in a two-dimensional plane strain model, the model box must be tilted to ensure that the plane strain tunnel or building model is parallel to the direction of sand drop (i.e., vertically downward). Furthermore, a partition is temporarily supported on one side of the model box, where the top of the sand sample is located when the model box is placed vertically. For surface-mounted raft foundation building models, the building model can be placed directly on top of the soil layer after the sand sample is prepared and the model box is placed vertically. However, for embedded structures such as buried strip foundation buildings (buried strip foundation structures), effective centrifuge model test equipment and preparation methods are currently lacking. Existing studies generally place the embedded foundation simply on the surface or press the structure into a specified depth above a prepared sand sample. Both methods are unable to simulate the uniform soil properties around the buried foundation, thus affecting the accuracy of the model test results. Summary of the Invention

[0006] To address the above technical issues, the present invention proposes a centrifugal test device and test preparation method for simulating the interaction between a tunnel and an embedded strip foundation structure. The test device includes a centrifugal model box and a transparent side panel. The centrifugal model box is a rectangular box with four faces, including a bottom plate and a left side panel, a rear side panel, and a right side panel connected to the bottom plate. The transparent side panel serves as a front side panel and is detachably connected to the front opening of the centrifugal model box.

[0007] It also includes a sand sample, which is filled in a centrifugal model container assembled from a centrifugal model box and a transparent side panel, and a model tunnel arranged in a front-to-back direction is buried in the sand sample; a plurality of strip foundations are buried at intervals along the left-right direction at a certain depth in the surface layer of the sand sample, and each strip foundation is fixedly provided with a foundation column, the bottom of the foundation column is buried in the sand sample, a horizontal layer is fixedly provided on the top of the foundation column, which is the lower horizontal layer, and an interlayer column is fixedly provided on the upper part of the lower horizontal layer corresponding to each foundation column directly above, and another horizontal layer is fixedly provided on the top of the interlayer column, which is the upper horizontal layer;

[0008] In the first state, the second state is a state in which the test device is being prepared, an external baffle is set between the leftmost foundation column and the left side plate, an external baffle is set between the rightmost foundation column and the right side plate; and internal baffles are set between adjacent foundation columns;

[0009] In the second state, which is the state when the test device is fully prepared, it also includes an upper support block and a rubber block. A rubber block is arranged on the upper part of the upper horizontal layer plate corresponding to each interlayer column, and the left and right widths of the rubber blocks are smaller than the width of the interlayer columns; an upper support block is arranged between adjacent rubber blocks and is tightly attached to the rubber blocks; the internal baffle is suspended between the lower horizontal layer plate and the surface layer of the sand sample.

[0010] Preferably, the front end of the model tunnel abuts against the transparent side panel, and the rear end abuts against the rear side panel; the front ends of the strip foundation, foundation columns, horizontal layer panels, and interlayer columns leave a small gap with the transparent side panel, and the rear ends leave a small gap with the rear side panel.

[0011] Preferably, a circular protrusion with an outer diameter consistent with the inner diameter of the model tunnel is provided on the rear side plate, or a circular groove with an inner diameter consistent with the outer diameter of the model tunnel is provided on the rear side plate.

[0012] Preferably, in the first state, the outer baffle, the inner baffle and the structures on the left and right sides thereof are sealed and fixed by foam tape.

[0013] Preferably, in the first state, it also includes a top baffle, which is detachably fixed to the inner side of the left panel and the inner side of the right panel respectively; the outer baffle is fixed to the top baffle by a threaded screw, and the inner baffle is fixed to the top baffle by a threaded screw, and the threaded screw connected to the internal baffle passes through the horizontal layer plate.

[0014] Preferably, in the first state, the front ends of the outer baffle and the inner baffle abut against the transparent side panel, and the rear ends abut against the rear side panel.

[0015] Preferably, in the second state, a small gap is left between the front ends of the upper support block and the rubber block and the transparent side panel, and a small gap is left between the rear ends and the rear side panel.

[0016] Preferably, in the second state, a threaded screw is fixedly connected to the top of the internal baffle, and the upper part of the threaded screw passes through the horizontal layer plate and the upper support block and is positioned by a nut.

[0017] Based on the above-mentioned centrifugal test device for simulating the interaction between a tunnel and an embedded strip-shaped foundation structure, the present invention further provides a centrifugal test preparation method for simulating the interaction between a tunnel and an embedded strip-shaped foundation structure, comprising the following steps:

[0018] Step 1: First, push the centrifugal model box backward so that the rear side panels are flat on the ground. Place the model tunnel at the set position and mark the desired position of the sand sample. Place the embedded strip foundation structure including horizontal layer panels, interlayer columns, foundation columns and strip foundation at the designated position. Fix the inner and outer baffles at the desired position of the sand sample. The outer and inner baffles act as top and side panels.

[0019] Step 2: Dry sand is dropped from a certain height at a constant speed using the sand spreading method, with the direction of the drop parallel to the tunnel model axis. After the sand sample is filled, the transparent side panels are fixed;

[0020] Step 3: Place the centrifugal test device upright, that is, place the bottom plate flat on the ground; remove the external baffle and its fixing device, and suspend the internal baffle between the lower horizontal layer and the surface of the sand sample.

[0021] Preferably, in the third step, the upper support block is placed on the upper horizontal layer, and the nut is screwed into the upper part of the upper support block from above the threaded screw, and the rotation is continued to gradually lift the inner baffle.

[0022] The present invention has the following innovative features:

[0023] 1. This invention breaks through the technical bottleneck of existing centrifuge model testing technology that cannot achieve uniform soil layer layout of the buried strip foundation structure model. It can accurately reproduce the soil properties around the buried strip foundation structure, avoid the disturbance of the soil layer by traditional insertion methods, and thus achieve accurate simulation of the deformation response of the buried strip foundation structure caused by tunnel construction.

[0024] 2. The centrifugal test device of the present invention not only achieves uniform soil layer arrangement, but also ensures that the overall design is reasonable, simple and easy to operate. Moreover, the slender threaded screw running through it has no influence on the stability and strength of the embedded strip foundation structure due to its small size and light weight.

[0025] 3. The present invention lifts the internal baffle by means of a slender screw that penetrates the interior, and the entire weight is supported by the upper support block, thereby achieving the purpose of not changing the rigidity of the embedded strip foundation structure itself, and the two ends of the upper support block are placed on the horizontal layer plate directly above the interlayer column, and the adjacent support blocks are flexibly connected by rubber blocks with good compressibility, ensuring that the upper support block can dynamically adjust its orientation as the embedded strip foundation structure deforms, ensuring that the upper support block constantly and stably suspends the internal baffle.

[0026] 4. The internal baffles designed in the present invention are provided with sufficient clearance from the foundation columns when in the hoisted state, which can ensure that the horizontal displacement of the foundation columns during the centrifugal test is not affected by the internal baffles, and can more accurately achieve the test purpose of simulating the interaction between the tunnel and the buried strip foundation structure.

[0027] 5. The upper support block designed in the present invention can be used as a platform for adjusting the self-weight load of the embedded strip foundation structure. The loading of the embedded strip foundation structure can be achieved by placing additional fixed weights or other heavy objects on the upper support block without changing the stiffness of the embedded strip foundation structure itself or affecting the stress state of its horizontal layer plates. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 1 is a schematic diagram of the overall structure of the centrifugal test device of the present invention in the first state (front view);

[0029] Figure 2 1 is a schematic diagram of the overall structure of the centrifugal test device of the present invention in the first state (front view);

[0030] Figure 3 Schematic diagram of the operation process of the centrifugal test preparation method of the present invention (side view);

[0031] In the figure: 1. Interlayer columns; 2. Transparent side panels; 3. Centrifugal model box; 4. Model tunnel; 5. Sand sample; 6. Horizontal layer; 7. Foundation columns; 8. Strip foundation; 9. Internal baffle; 10. External baffle; 11. Foam tape; 12. Top baffle; 13. Threaded screw; 14. L-shaped angle aluminum; 15. Upper support block; 16. Nut; 17. Rubber block; 18. Screw; 19. Bolt. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and specific working methods.

[0033] like Figure 1-3 As shown, the present invention proposes a centrifugal test device for simulating the interaction between a tunnel and an embedded strip foundation structure, wherein the embedded strip foundation structure is an embedded strip foundation building. The centrifugal test device includes a centrifugal model box 3 and a transparent side panel 2. The centrifugal model box 3 is a rectangular box with four faces, including a bottom plate and a left side panel, a rear side panel, and a right side panel connected to the bottom plate. The left side panel, the rear side panel, and the right side panel are connected in sequence. The transparent side panel 2 serves as a front side panel and is detachably connected to the front opening of the centrifugal model box 3.

[0034] It also includes a sand sample 5, which is filled in a centrifugal model container assembled from a centrifugal model box 3 and a transparent side panel 2, and is filled to a certain height but does not reach the top surface; a model tunnel 4 arranged in the front-to-back direction is buried in the middle or lower middle part of the sand sample 5, and a sand sample 5 is arranged inside the model tunnel 4; a plurality of strip foundations 8 are buried at intervals along the left-right direction at a certain depth on the surface of the sand sample 5, and the spacing between adjacent strip foundations 8 can be the same, and a foundation column 7 is fixedly provided on each strip foundation 8, the bottom of the foundation column 7 is buried in the sand sample 5, and the upper part leaks out of the sand sample 5, and a horizontal layer plate 6 is fixed on the top of the foundation column 7, which is the lower horizontal layer plate. An interlayer column 1 is fixedly arranged on the upper part of the horizontal layer plate 6 corresponding to each foundation column 7, and a horizontal layer plate 6 is fixed on the top of the interlayer column 1, which is the upper horizontal layer plate 6. The upper horizontal layer plate 6 is parallel to the lower horizontal layer plate 6; wherein, the front end of the model tunnel 4 abuts against the transparent side plate 2, and the rear end abuts against the rear side plate, and the model tunnel 4 is preferably plugged into the rear side plate, such as providing a circular protrusion with an outer diameter consistent with the inner diameter of the model tunnel 4 on the rear side plate, or providing a circular groove with an inner diameter consistent with the outer diameter of the model tunnel 4 on the rear side plate; a small gap is left between the front end of the strip foundation 8, the foundation column 7, the horizontal layer plate 6, and the interlayer column 1 and the transparent side plate 2, and a small gap is left between the rear end and the rear side plate;

[0035] like Figure 1 As shown, in the first state, which is the state before the top baffle 12 is removed, an external baffle 10 is connected between the leftmost foundation column 7 and the left side plate by a foam tape 11, and an external baffle 10 is connected between the rightmost foundation column 7 and the right side plate by a foam tape 11, and one side of the foam tape 11 is pasted on the side of the external baffle 10; an internal baffle 9 is connected between adjacent foundation columns 7 by a foam tape 11, and the foam tape 11 is pasted on the side of the foundation column 7; and a top baffle 12 is also included, and the left and right ends of the top baffle 12 are fixedly connected by L-shaped angle aluminum 14 respectively On the inner side of the left and right panels, each L-shaped angle aluminum 14 is connected to the top baffle 12 and the centrifugal model box side panel respectively by screws 18; the lower end of a threaded screw 13 (cylindrical rod, the same below) is fixedly connected to the top of the outer baffle 10, and the other end is fixedly connected to the top baffle 12; the lower end of the threaded screw 13 is fixedly connected to the top of the inner baffle 9, and then passes through the horizontal layer 6 and rests on the bottom surface of the top baffle 12; at least two threaded screws 13 are arranged at intervals along the front-to-back direction; wherein, the front ends of the outer baffle 10 and the inner baffle 9 abut against the transparent side panel 2, and the rear ends abut against the rear side panel;

[0036] like Figure 2As shown, in the second state, which is the state when the test device is ready, the top baffle 12, L-shaped angle aluminum 14, and screws 18 are removed; the external baffle 10 between the leftmost foundation column 7 and the left side plate and the threaded screw 13 and foam tape 11 on the external baffle are removed, and the external baffle 10 between the rightmost foundation column 7 and the right side plate and the threaded screw 13 and foam tape 11 on the external baffle are removed; in the second state, it also includes upper support blocks 15 and rubber blocks 17, and an upper support block 15 is arranged on the upper part of the upper horizontal layer plate 6 corresponding to each internal baffle 9, and an upper support block 15 is arranged on the upper part of the upper horizontal layer plate 6 corresponding to the interlayer column 1 and A rubber block 17 is respectively arranged between adjacent upper support blocks 15, and the left and right widths of the rubber blocks 17 are smaller than the width of the interlayer column 1; the upper support blocks 15 are tightly attached to the rubber blocks 17, and the rubber blocks 17 are placed between adjacent upper support blocks 15 to flexibly fill the gaps between the adjacent upper support blocks 15; the upper part of the threaded screw 13 fixedly connected to the top of the internal baffle 9 passes through the horizontal layer 6 and the upper support block 15 and is positioned by the nut 16. At this time, the internal baffle 9 is suspended between the lower horizontal layer 6 and the surface of the sand sample 5; a small gap is left between the front end of the upper support block 15 and the rubber block 17 and the transparent side panel 2, and a small gap is left between the rear end and the rear side panel.

[0037] Based on the centrifugal test device for simulating the interaction between a tunnel and an embedded strip-shaped foundation structure, the present invention further proposes a centrifugal test preparation method for simulating the interaction between a tunnel and an embedded strip-shaped foundation structure, such as Figure 3 As shown, the following steps are included:

[0038] Step 1: If Figure 3 As shown in the side view (a), first push the centrifugal model box 3 backward so that the rear side plate is flat on the ground, place the model tunnel 4 at the set position, and mark the position where the sand sample 5 needs to reach; place the embedded strip foundation structure including the horizontal layer plate 6, the interlayer column 1, the foundation column 7 and the strip foundation 8, and the internal baffle 9 connected with the threaded screw 13 at the specified position, and the threaded screw 13 passes through the horizontal layer plate 6; fix the external baffle 10 and the top baffle 12 together through the threaded screw 13, and then The top baffle 12 is fixed to the side panels of the centrifugal model box 3 by L-shaped angle aluminum 14 and screws 18; the positions of the inner baffle 9 and the outer baffle 10 are the positions required for the sand sample 5 to reach; the outer baffle 10 and the inner baffle 9 are connected by foam tape 11; at this time, the threaded screw 13 connected to the inner baffle 9 abuts against the top baffle 12; at this time, the foam tape 11, the outer baffle 10 and the inner baffle 9 together form a temporary lateral support for the sand sample 5, which is equivalent to the top side panel;

[0039] Step 2: If Figure 3(b) As shown in the side view, dry sand is dropped from a certain height at a constant speed by spreading sand, with the direction of the drop parallel to the tunnel model axis to avoid interference during the sand drop. After the sand sample 5 is filled, the surface of the sand sample 5 is scraped and leveled using a tool, and then the transparent side panel 2 is installed and fixed to the model box 3 using bolts 19.

[0040] Step 3: If Figure 3 (c) As shown in the side view, the centrifuge test device is placed upright, that is, the bottom plate is placed flat on the ground; Figure 3 (d) As shown in the side view, the top baffle 12, L-shaped angle aluminum 14, and screws 18 are removed; the external baffle 10 and the threaded screw 13 and foam tape 11 on the external baffle are removed and taken out; the upper support block 15 is placed on the upper horizontal layer 6, and the nut 16 is screwed from above the threaded screw 13 to above the upper support block 15, and the rotation is continued to gradually lift the internal baffle 9 to a distance of at least 2 cm from the upper surface of the sand sample 5. After the internal baffle 9 is lifted, it is separated from the foam tape 11 pasted on the side of the foundation column 7, thereby forming a certain gap with the foundation column 7, so that the internal baffle 9 has no contact with the embedded strip foundation structure and the sand sample 5.

[0041] Subsequently, the centrifuge test device was placed on the centrifuge to carry out centrifuge model tests to study the impact of tunnel construction on the embedded strip foundation structure.

[0042] While the present invention has been described above with reference to preferred embodiments, this is not intended to limit the present invention. Persons skilled in the art will readily appreciate that various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A centrifugal test device for simulating the interaction between a tunnel and an embedded strip foundation structure, characterized in that: The test device includes a centrifugal model box and a transparent side panel. The centrifugal model box is a rectangular box with four faces, including a bottom plate and a left side plate, a rear side plate and a right side plate connected to the bottom plate. The transparent side panel serves as a front side panel and is detachably connected to the front opening of the centrifugal model box. It also includes a sand sample, which is filled in a centrifugal model container assembled from a centrifugal model box and a transparent side panel, and a model tunnel arranged in a front-to-back direction is buried in the sand sample; a plurality of strip foundations are buried at intervals along the left-right direction at a certain depth in the surface layer of the sand sample, and each strip foundation is fixedly provided with a foundation column, the bottom of the foundation column is buried in the sand sample, a horizontal layer is fixedly provided on the top of the foundation column, which is the lower horizontal layer, and an interlayer column is fixedly provided on the upper part of the lower horizontal layer corresponding to each foundation column directly above, and another horizontal layer is fixedly provided on the top of the interlayer column, which is the upper horizontal layer; In the first state, an external baffle is provided between the leftmost foundation column and the left side plate, and an external baffle is provided between the rightmost foundation column and the right side plate; and internal baffles are provided between adjacent foundation columns; In the second state, which is the state when the test device is fully prepared, it also includes an upper support block and a rubber block. A rubber block is arranged on the upper part of the upper horizontal layer plate corresponding to each interlayer column, and the left and right widths of the rubber blocks are smaller than the width of the interlayer columns; an upper support block is arranged between adjacent rubber blocks and is tightly attached to the rubber blocks; the internal baffle is suspended between the lower horizontal layer plate and the surface layer of the sand sample.

2. The centrifugal test device according to claim 1, characterized in that The front end of the model tunnel abuts against the transparent side panel, and the rear end abuts against the rear side panel; the front ends of the strip foundation, foundation columns, horizontal layer panels, and interlayer columns leave a small gap with the transparent side panel, and the rear ends leave a small gap with the rear side panel; the front ends of the upper support blocks and rubber blocks leave a small gap with the transparent side panel, and the rear ends leave a small gap with the rear side panel.

3. The centrifugal test device according to claim 1, wherein A circular protrusion with an outer diameter consistent with the inner diameter of the model tunnel is provided on the rear side plate, or a circular groove with an inner diameter consistent with the outer diameter of the model tunnel is provided on the rear side plate.

4. The centrifugal test device according to claim 1, wherein In the first state, the outer baffle, the inner baffle and the structures on the left and right sides thereof are fixed by foam tape.

5. The centrifugal test device according to claim 1, wherein: In the first state, it also includes a top baffle, which is detachably fixed to the inner side of the left panel and the inner side of the right panel respectively; the outer baffle is fixed to the top baffle by a threaded screw, and the inner baffle is fixed to the top baffle by a threaded screw, and the threaded screw connected to the inner baffle passes through the horizontal layer plate.

6. The centrifugal test device according to claim 1, wherein: In the first state, the front ends of the outer baffle and the inner baffle abut against the transparent side plate, and the rear ends abut against the rear side plate.

7. The centrifugal test device according to claim 1, wherein: In the second state, a threaded screw is fixedly connected to the top of the internal baffle, and the upper part of the threaded screw passes through the horizontal layer plate and the upper support block and is positioned by a nut.

8. A method for preparing a centrifuge test for simulating the interaction between a tunnel and an embedded strip-shaped infrastructure, based on the centrifuge test apparatus according to any one of claims 1 to 7, comprising the following steps: Step 1: First, push the centrifugal model box backward so that the rear side plate is flat on the ground, place the model tunnel at the set position, and mark the position where the sand sample needs to be placed; place the embedded strip foundation structure including horizontal layer plates, interlayer columns, foundation columns and strip foundation at the designated position; fix the inner and outer baffles at the position where the sand sample needs to be placed, and the outer and inner baffles act as top and side plates; Step 2: Dry sand is dropped from a certain height at a constant speed using the sand spreading method, with the direction of the drop parallel to the tunnel model axis. After the sand sample is filled, the transparent side panels are fixed; Step 3: Place the centrifugal test device upright, that is, place the bottom plate flat on the ground; remove the external baffle and its fixing device, and suspend the internal baffle between the lower horizontal layer and the surface of the sand sample.

9. The centrifuge test preparation method according to claim 8, wherein in the third step, the upper support block is placed on a horizontal shelf, a nut is screwed into the upper portion of the upper support block from above the threaded screw, and the nut is continued to be rotated to gradually lift the inner baffle.

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