Open caisson duct piece bending resistance test method for sinking type vertical shaft tunneling construction method

Abstract

The invention discloses an open caisson segment bending resistance testing method for a sinking type vertical shaft tunneling construction method. The open caisson segment bending resistance testing method comprises the steps that S1, multi-dimensional parameters of an open caisson segment to be tested and a vertical shaft body are obtained; s2, selecting a proper soil pressure coefficient; s3, calculating a load condition acting on the to-be-tested open caisson segment; s4, defining boundary conditions of the to-be-detected open caisson duct piece; s5, the maximum bending moment borne by the open caisson segment to be measured is obtained; s6, the state of the single segment placed on the bending resistance test loading platform is simulated, and boundary conditions of four corner points of the single segment are set according to the open caisson segment state of the sinking type vertical shaft tunneling construction method; s7, determining the application area of the uniformly distributed load; and S8, adjusting the size of the uniformly distributed load until the maximum bending moment of the current single segment is the same as the maximum bending moment of the to-be-tested open caisson segment under the double service condition, and obtaining the design load and the maximum load. The research on the service characteristics of the VSM construction method open caisson segment is more scientific and accurate.

Description

Technical Field

[0001] The invention relates to the technical field of civil engineering and underground engineering, and in particular to a method for testing the bending resistance of caisson segments used in a sinking shaft excavation method. Background Art

[0002] The Vertical Sinking Machine (VSM) is a highly intensive shaft construction method based on the concept of prefabricated shaft excavation and settlement. In the VSM method, the shaft is excavated underwater using a submersible machine. After the prefabricated segments are assembled on the surface, the shaft wall is lowered by the structure's own weight. The VSM method offers advantages such as high construction efficiency, a small footprint, and wide geological adaptability. It is particularly suitable for large-diameter and deep shaft projects, such as vertical underground parking garages and power tunnel working shafts.

[0003] In the process of constructing the working shaft of a power tunnel using the VSM method, the working shaft wall is usually assembled from prefabricated wedge-shaped segments. According to the current design specifications and standards, prefabricated reinforced concrete components need to complete the bending performance acceptance to ensure the safety and stability of the segments during hoisting, sinking and service. In the existing technology, the commonly used segment bending performance test instrument is only applicable to horizontal shield tunnel segments, and can only perform bending performance acceptance on shield segments whose segment supports can slide horizontally and bear vertical downward loads. In the VSM method, the service conditions and boundary conditions of the caisson segments are completely different from those of conventional shield tunnel segments. The existing shield tunnel segment bending performance test instrument cannot be directly applied to the VSM method caisson segments. Therefore, it is particularly important to develop a caisson segment bending performance test method suitable for the sinking vertical shaft excavation method. Summary of the Invention

[0004] The present invention provides a more targeted, scientifically and accurately studied method for testing the bending resistance of caisson segments for a sinking shaft excavation method, which can solve at least one of the above-mentioned technical problems.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] The method for testing the bending resistance of caisson segments used in the sinking shaft excavation method comprises the following steps:

[0007] S1. Obtain multi-dimensional parameters of the caisson segment and the vertical shaft body to be tested;

[0008] S2. Obtaining the earth pressure coefficient of each soil layer based on the multidimensional parameters and selecting an appropriate earth pressure coefficient according to the construction status of the sunken shaft excavation method;

[0009] S3. Calculate the load conditions acting on the caisson segment to be tested by combining the multi-dimensional parameters obtained in S1 and the earth pressure coefficient selected in S2. The load conditions include the magnitude of the lateral earth pressure, the magnitude of the lateral water pressure, and the top vertical pressure.

[0010] S4. Considering the linear distribution of pressure in the height direction and the self-weight stress of the caisson segment, the boundary conditions of the caisson segment to be tested are defined according to the connection conditions of the top and bottom of the caisson segment to be tested;

[0011] S5. Based on the load conditions calculated in S3 and the boundary conditions defined in S4, combined with the multi-dimensional parameters obtained in S1, the finite element unit algorithm is used to calculate the bending moment distribution inside the caisson segment to be tested, and the stress conditions of each ring of the caisson segment are compared to obtain the maximum bending moment M of the caisson segment to be tested. max ;

[0012] S6. Consider the loading conditions of the caisson segments during the bending test, simulate the state of a single segment placed on the bending test loading platform, and set the boundary conditions of the four corner points of the single segment based on the state of the caisson segments during the sinking shaft excavation method;

[0013] S7. According to the load application setting of the bending performance test loading platform, the uniformly distributed load p applied to the 1 / 3 and 2 / 3 spans of the long side of the single segment is obtained. m , determine the application area A of the uniformly distributed load;

[0014] S8. When calculating the maximum bending moment M' inside a single segment using the finite element algorithm to simulate the bending performance test, max , adjust the uniformly distributed load p m The maximum bending moment of the current single segment is twice the maximum bending moment of the caisson segment to be tested under the service condition 2*M max The same as above, and the design load F of the single segment in the bending performance test is obtained de and the maximum load F max .

[0015] Furthermore, in said S1, the multi-dimensional parameters of the caisson segment include at least: elastic modulus E, Poisson's ratio ν, bulk density γ, segment height h, segment depth z and segment thickness d;

[0016] The multi-dimensional parameters of the vertical shaft include at least: the shaft excavation diameter R, the height z of the liquid level inside the shaft from the top of the shaft during construction, and the w , the thickness of each soil layer outside the well body h i , severe γ i , internal friction angle Cohesion c i And the foundation reaction coefficient P on the pipe segment, the water density γ w ;

[0017] Where i is the number of the soil layer being calculated.

[0018] Furthermore, in said S2, based on the internal friction angle of each soil layer outside the well body Obtain the earth pressure coefficient of each soil layer, which includes the active earth pressure coefficient K ai and static earth pressure coefficient K 0i , respectively:

[0019]

[0020] Furthermore, in S2, if there is no obvious relative displacement between the soil layer and the shaft body, the static earth pressure coefficient K is selected. 0i Calculate the lateral earth pressure. If active displacement between the soil layer and the shaft is considered, the active earth pressure coefficient K is selected. ai Calculate the lateral earth pressure.

[0021] Furthermore, in S3, the lateral earth pressure acting on the caisson segments includes the outer top lateral earth pressure p st and the outer bottom lateral earth pressure p sb ;

[0022] Based on the weight of each soil layer outside the shaft body γ i , thickness h i , cohesion c i And the selected earth pressure coefficient K ai or K 0i , the lateral earth pressure p acting on the outer top of the caisson segment is calculated st ;

[0023] Based on the weight of each soil layer outside the shaft body γ i , thickness h i , cohesion c i , the segment height h of the caisson segment and the selected earth pressure coefficient K ai or K 0i , the lateral earth pressure p acting on the outer bottom of the caisson segment is calculated sb ;

[0024] If the earth pressure coefficient is selected as the static earth pressure coefficient K 0i , then the lateral earth pressure p acting on the outer top of the caisson segment st and the outer bottom lateral earth pressure p sb They are:

[0025] p st =∑γ i h i K 0i

[0026] p sb =∑γ i h i K 0i +γ i+1 hK 0i+1

[0027] If the earth pressure coefficient is selected as the active earth pressure coefficient K ai , then the lateral earth pressure p acting on the outer top of the caisson segment st and the outer bottom lateral earth pressure p sb They are:

[0028]

[0029] Furthermore, in S3, the lateral water pressure acting on the caisson segments includes the inner top lateral water pressure p wt and the inner bottom lateral water pressure p wb ;

[0030] Based on the construction process of the vertical shaft body, the height z of the liquid level inside the shaft body from the top of the shaft body w , water density γ w As well as the segment depth z of the caisson segment, the lateral water pressure p acting on the inner top of the caisson segment is calculated. wt ;

[0031] Based on the construction process of the vertical shaft body, the height z of the liquid level inside the shaft body from the top of the shaft body w , water density γ w As well as the segment depth z and segment height h of the caisson segment, the lateral water pressure p acting on the inner bottom of the caisson segment is calculated. wb ;

[0032] p wt =γ w (zz w )

[0033] p wb =γ w (z+hz w ).

[0034] Furthermore, in step S3, the vertical pressure p acting on the top of the caisson segment is calculated based on the segment bulk density γ and segment depth z of the caisson segment. v :

[0035] p v =γz.

[0036] Furthermore, in S4, if the boundary of the caisson segment is the connection between the segments, the boundary condition of the caisson segment to be tested is defined as a simple hinged boundary condition; if the boundary of the caisson segment is the connection between the segment and the concrete bottom seal of the entire caisson, the boundary condition of the caisson segment to be tested is defined as a completely fixed boundary condition.

[0037] Furthermore, in S6, in the bending performance simulation test of the single segment in the sunken shaft excavation method, the boundary conditions of the four corner points are all set to be completely fixed boundary conditions.

[0038] Furthermore, in said S8, when M' max =2*M max When the uniform load p m and the application area A of the uniformly distributed load to determine the design load F of the single segment in the bending performance test de and the maximum load F max They are:

[0039] F de =p m A

[0040] F max =1.2p m A.

[0041] The beneficial effects of the present invention are embodied in:

[0042] 1. The present invention overcomes the limitation that the existing shield tunnel segment bending performance test instrument cannot be directly applied to the VSM method caisson segments, and provides a caisson segment bending performance test method for the sunken vertical shaft excavation method. According to the characteristics of the caisson segments, the bending performance test loading platform is creatively combined with the finite element load structure method, so as to simulate the load conditions of the caisson segments under service conditions in the bending performance test, and explore the bending performance issues of the caisson segments that are closer to the actual engineering situation.

[0043] 2. The test device of the present invention has a simple structure and is easy to operate. It can be widely used in the bending performance test of wedge-shaped caisson segments of various sizes. The test process is concise and the functions are complete. Through the finite element load structure method, the load condition of the VSM caisson segment can be accurately determined, and the load size setting of the test loading platform can be guided, which is helpful to more scientifically and accurately study the service characteristics and quality control of the VSM caisson segment. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The drawings described herein are used to provide further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0045] Figure 1 It is a schematic diagram of the overall process of the bending performance test method according to an embodiment of the present invention.

[0046] Figure 2 Schematic diagram of the change of the maximum bending moment of the pipe segment with the cumulative loading value / design load value in an embodiment of the present invention.

[0047] Figure 3 It is a schematic diagram of the change of the vertical displacement of the pipe segment with the cumulative loading value / design load value in an embodiment of the present invention.

[0048] Figure 4 Schematic diagram of the change of shear stress at the maximum bending moment with cumulative loading value / design load value in an embodiment of the present invention.

[0049] Figure 5 It is a schematic diagram of the overall structure of the bending performance test loading platform of an embodiment of the present invention.

[0050] Figure 6 It is a side view of the segment corner support platform according to an embodiment of the present invention.

[0051] Figure 7 It is a schematic diagram of the use process of the bending performance test loading platform according to an embodiment of the present invention.

[0052] Figure 8 It is a schematic diagram of actual load simulation using the finite element load structure method according to an embodiment of the present invention.

[0053] Figure 9 3. It is a schematic diagram of a finite element load structure method test simulation according to an embodiment of the present invention.

[0054] Figure 10 It is a structural block diagram of a computer device according to an embodiment of the present invention.

[0055] The components in the accompanying drawings are marked as follows: 1. Load application unit; 2. Adaptive segment support unit; 3. Data monitoring unit; 4. Loading reaction frame; 5. Loading beam; 6. Servo telescopic pressure rod; 7. Load distribution beam; 8. Pressure rod; 9. Base; 10. Guide rail; 11. Segment corner support platform; 1101. Braking module; 1102. Hydraulic lifting module; 12. Pressure gauge; 13. Displacement meter; 14. Strain gauge; 15. Visualization camera. DETAILED DESCRIPTION

[0056] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. In the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0057] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly. In addition, the meaning of "and / or" appearing in the full text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or schemes in which A and B are satisfied at the same time. In addition, "multiple" refers to more than two. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0058] See also Figure 1 The embodiment of the present invention provides a method for testing the bending resistance of caisson segments used in a sinking shaft excavation method, comprising the following steps:

[0059] S1. Obtain multi-dimensional parameters of the caisson segment and the vertical shaft body to be tested;

[0060] S2. Obtaining the earth pressure coefficient of each soil layer based on the multidimensional parameters and selecting an appropriate earth pressure coefficient according to the construction status of the sunken shaft excavation method;

[0061] S3. Calculate the load conditions acting on the caisson segment to be tested by combining the multi-dimensional parameters obtained in S1 and the earth pressure coefficient selected in S2. The load conditions include the magnitude of the lateral earth pressure, the magnitude of the lateral water pressure, and the top vertical pressure.

[0062] S4. Considering the linear distribution of pressure in the height direction and the self-weight stress of the caisson segment, the boundary conditions of the caisson segment to be tested are defined according to the connection conditions of the top and bottom of the caisson segment to be tested;

[0063] S5. Based on the load conditions calculated in S3 and the boundary conditions defined in S4, combined with the multi-dimensional parameters obtained in S1, the finite element unit algorithm is used to calculate the bending moment distribution inside the caisson segment to be tested, and the stress conditions of each ring of the caisson segment are compared to obtain the maximum bending moment M of the caisson segment to be tested. max ;

[0064] S6. Consider the loading conditions of the caisson segments during the bending test, simulate the state of a single segment placed on the bending test loading platform, and set the boundary conditions of the four corner points of the single segment based on the state of the caisson segments during the sinking shaft excavation method;

[0065] S7. According to the load application setting of the bending performance test loading platform, the uniformly distributed load p applied to the 1 / 3 and 2 / 3 spans of the long side of the single segment is obtained. m , determine the application area A of the uniformly distributed load;

[0066] S8. When calculating the maximum bending moment M' inside a single segment using the finite element algorithm to simulate the bending performance test, max , adjust the uniformly distributed load p m The maximum bending moment of the current single segment is twice the maximum bending moment of the caisson segment to be tested under the service condition 2*M max The same as above, and the design load F of the single segment in the bending performance test is obtained de and the maximum load F max .

[0067] In this embodiment, in S1, the multi-dimensional parameters of the caisson segment include at least: elastic modulus E, Poisson's ratio ν, bulk density γ, segment height h, segment depth z, and segment thickness d;

[0068] The multi-dimensional parameters of the vertical shaft include at least: the shaft excavation diameter R, the height z of the liquid level inside the shaft from the top of the shaft during construction, and the w , the thickness of each soil layer outside the well body h i , severe γ i , internal friction angle Cohesion c i And the foundation reaction coefficient P on the pipe segment, the water density γ w ;

[0069] Where i is the number of the soil layer being calculated.

[0070] In this embodiment, in S2, based on the internal friction angle of each soil layer outside the well body, Obtain the earth pressure coefficient of each soil layer, which includes the active earth pressure coefficient K ai and static earth pressure coefficient K 0i , respectively:

[0071]

[0072] In this embodiment, in S2, if there is no obvious relative displacement between the soil layer and the shaft body, the static earth pressure coefficient K is selected. 0i Calculate the lateral earth pressure. If active displacement between the soil layer and the shaft is considered, the active earth pressure coefficient K is selected. ai Calculate the lateral earth pressure.

[0073] In this embodiment, in S3, the lateral earth pressure acting on the caisson segments includes the outer top lateral earth pressure p st and the outer bottom lateral earth pressure p sb ;

[0074] Based on the weight of each soil layer outside the shaft body γ i , thickness h i , cohesion c i And the selected earth pressure coefficient K ai or K 0i , the lateral earth pressure p acting on the outer top of the caisson segment is calculated st ;

[0075] Based on the weight of each soil layer outside the shaft body γ i , thickness h i , cohesion c i , the segment height h of the caisson segment and the selected earth pressure coefficient K ai or K 0i , the lateral earth pressure p acting on the outer bottom of the caisson segment is calculated sb ;

[0076] If the earth pressure coefficient is selected as the static earth pressure coefficient K 0i , then the lateral earth pressure p acting on the outer top of the caisson segment st and the outer bottom lateral earth pressure p sb They are:

[0077] p st =∑γ i h i K 0i

[0078] p sb =∑γ i h i K 0i +γ i+1 hK 0i+1

[0079] If the earth pressure coefficient is selected as the active earth pressure coefficient K ai, then the lateral earth pressure p acting on the outer top of the caisson segment st and the outer bottom lateral earth pressure p sb They are:

[0080]

[0081] In this embodiment, in S3, the lateral water pressure acting on the caisson segment includes the inner top lateral water pressure p wt and the inner bottom lateral water pressure p wb ;

[0082] Based on the construction process of the vertical shaft body, the height z of the liquid level inside the shaft body from the top of the shaft body w , water density γ w As well as the segment depth z of the caisson segment, the lateral water pressure p acting on the inner top of the caisson segment is calculated. wt ;

[0083] Based on the construction process of the vertical shaft body, the height z of the liquid level inside the shaft body from the top of the shaft body w , water density γ w As well as the segment depth z and segment height h of the caisson segment, the lateral water pressure p acting on the inner bottom of the caisson segment is calculated. wb ;

[0084] p wt =γ w (zz w )

[0085] p wb =γ w (z+hz w ).

[0086] In this embodiment, in S3, based on the bulk density γ and the depth z of the caisson segment, the vertical pressure p acting on the top of the caisson segment is calculated. v :

[0087] p v =γz.

[0088] In this embodiment, in S4, if the boundary of the caisson segment is the connection between the segments, the boundary condition of the caisson segment to be tested is defined as a simple hinged boundary condition; if the boundary of the caisson segment is the connection between the segment and the concrete bottom seal of the entire caisson, the boundary condition of the caisson segment to be tested is defined as a completely fixed boundary condition.

[0089] In this embodiment, in S6, in the bending performance simulation test of the single segment in the sunken shaft excavation method, the boundary conditions of the four corner points are all set to be completely fixed boundary conditions.

[0090] The boundary conditions of the four corner points of the segment in the bending performance simulation test should be set according to the status of the segment in the sunken shaft excavation method. Unlike the shield segment, in the sunken shaft excavation method, the single segment is not allowed to move. Therefore, the four corner points need to be set to fully fixed boundary conditions.

[0091] In this embodiment, in S8, when M' max =2*M max When the uniform load p m and the application area A of the uniformly distributed load to determine the design load F of the single segment in the bending performance test de and the maximum load F max They are:

[0092] F de =p m A

[0093] F max =1.2p m A.

[0094] In a certain actual bending performance test, the maximum bending moment of the segment changes with the cumulative load value / design load value, the vertical displacement of the segment changes with the cumulative load value / design load value, and the shear stress at the maximum bending moment changes with the cumulative load value / design load value, respectively. Figure 2 、 Figure 3 and Figure 4 shown.

[0095] See also Figure 5 The embodiment of the present invention further provides a loading platform for testing the bending resistance of caisson segments for a sinking shaft excavation method, comprising:

[0096] The load application unit 1 is used to apply a set load to a single segment simulating a sinking shaft excavation method. It includes a load distribution beam 7 and a pressure rod 8. The load distribution beam 7 is placed horizontally above the single segment and has a range of movement to move up and down to apply different loads to the single segment. There are multiple pressure rods 8, each of which can be detachably mounted on the bottom of the load distribution beam 7 to accommodate single segments of different sizes.

[0097] The adaptive segment support unit 2 is used to simulate the boundary conditions of the connection between a single segment and the other segments in the service state, and includes a base 9 and a segment corner support platform 11. The segment corner support platform 11 has four segments and can be slidably assembled on the base 9 to support the four corner points of the single segment that are not in the same position or level.

[0098] The data monitoring unit 3 is used to collect and record the changes in multiple parameters of the single segment during the test, including pressure gauges 12, displacement gauges 13, strain gauges 14 and visualization cameras 15 distributed at different points.

[0099] See also Figure 5 In this embodiment, the plurality of pressure rods 8 have different length specifications and can be replaceably assembled along the length direction of the load distribution beam 7 to adapt to the length or width dimensions of different single-piece segments.

[0100] See also Figure 5 In this embodiment, the load applying unit 1 further includes a loading reaction frame 4, a loading beam 5 and a servo telescopic pressure rod 6. The loading reaction frame 4 has two pairs, which are vertically spaced apart. The loading beam 5 is horizontally mounted on the two loading reaction frames 4. The servo telescopic pressure rod 6 is centrally mounted on the loading beam 5 and can extend downward and pass through the loading beam 5 to be connected to the load distribution beam 7. The servo telescopic pressure rod 6 is connected to an external electro-hydraulic servo system for adjusting the load applied to the load distribution beam 7 and the single pipe segment.

[0101] See also Figure 5 and Figure 6 In this embodiment, the segment corner support platform 11 is an L-shaped structure, including a vertical plate and a horizontal plate that are vertically connected and integrally formed. The corner of a single segment can slide against the horizontal plate until it is tightly pressed against the vertical plate, and a hydraulic lifting module 1102 is installed on the horizontal plate. The hydraulic lifting module 1102 can be controlled to adjust its own height to meet the needs of a single segment whose corners are not at the same horizontal height.

[0102] See also Figure 5 In this embodiment, the adaptive segment support unit 2 also includes a guide rail 10, and the guide rail 10 has multiple sections, which are arranged in parallel along the length direction or width direction of the base 9. The bottom of the horizontal plate of the segment corner support platform 11 is provided with a roller, and the roller is slidably matched with the guide rail 10. The positions of the multiple segment corner support platforms 11 in different guide rails 10 can be adjusted according to the length or width size of a single segment.

[0103] See also Figure 5 and Figure 6 In this embodiment, the segment corner support platform 11 further includes a braking module 1101 , which is installed at the bottom of the horizontal plate to limit and fix the position of the segment corner support platform 11 in the guide rail 10 .

[0104] See also Figure 5In this embodiment, there are multiple pressure gauges 12, which are respectively installed on each of the pressure rods 8 to measure the pressure size and pressure change at different pressure points during the test. The displacement meter 13 is installed on the servo telescopic pressure rod 6 to measure the vertical displacement size and vertical displacement change of the load distribution beam 7 and the pressure rod 8 during the test. There are multiple strain gauges 14, which are distributed at different points on the single pipe segment to measure the stress and strain state of the single pipe segment during the test. The visualization camera 15 is built into the load distribution beam 7 to record the change state of cracks on the single pipe segment during the test.

[0105] See also Figure 5 In this embodiment, each device in the data monitoring unit 3 establishes a wireless or wired communication connection with the remote device, so as to upload the collected or recorded parameter data to the remote device.

[0106] See also Figure 7 The steps for using the loading platform for the caisson segment bending performance test of the sinking shaft excavation method are as follows:

[0107] Step 1: Install the strain gauge 14 on the VSM caisson segments used in the test, and adjust the position and spacing of the support platforms 11 at each segment corner according to the size of the segments.

[0108] Step 2: Place the caisson segments on the segment corner support platform 11 by using a crane, and adjust the segment curved surface sections to the same height by using the self-adaptive height-adjusting hydraulic lifting module 1102;

[0109] Step 3: Turn on the brake module 1101 of the segment corner support platform 11 to fix the position of the segment corner support platform 11;

[0110] Step 4. Replace the appropriate pressure rods 8 according to the size of the segment, ensuring that the length of the pressure rods 8 is the same as the width of the segment, and adjust the position and spacing of the pressure rods 8 on the load distribution beam 7 to ensure that the pressure rods 8 are pressed at 1 / 3 and 2 / 3 of the segment length respectively;

[0111] Step 5: Install and start each data acquisition device in the data monitoring unit 3;

[0112] Step 6. Apply loads step by step according to Table 1. The constant load time for each level should not be less than 5 minutes. Record the displacement and strain of each measuring point under each level of load. When cracks appear on the segment, continue to apply the load of that level for 10 minutes to observe the development of the cracks in the segment. Take the load value of that level as the measured value of the cracking load. When the load reaches the design load, maintain it for 30 minutes, observe the development of the cracks and the strain changes in the segment, and record the maximum crack width.

[0113] Step 7. Uninstall and end the test.

[0114] Table 1 Loading value table for bending performance test

[0115]

[0116] It should be noted that the present invention combines the finite element load structure method to determine the load conditions of the VSM caisson segments under service conditions, and obtains the load design value of the load application unit when the segments are in the same load state by simulating the segment bending performance test.

[0117] See also Figure 8 The present invention investigates the critical load conditions of single-ring segments in the sunken shaft excavation method through the finite element load structure method. During the service process, the shaft is mainly affected by the lateral earth pressure and water pressure outside the shaft, the deadweight of the upper segments, and the lateral pressure of the bottom seal concrete at the bottom of the shaft. The lowest single-ring segment in a critical state is selected as the analysis object of the finite element load structure method. The earth pressure, water pressure and deadweight load of the segment are applied to the segment model according to the actual situation. Considering the service characteristics of the shaft, the connection between the analyzed single-ring segment and the upper structure is set as an ordinary hinged connection. Due to the limiting effect of the bottom seal concrete, the connection between the analyzed single-ring segment and the lower structure is set as a rigid contact. In addition, the contact between the segment and the surrounding soil is simulated by a curved spring that can only withstand pressure.

[0118] In this embodiment, the maximum bending moment in the segment is 170 kN·m / m. It is worth noting that for caissons constructed using the sunken shaft excavation method, the stress on the segments will vary depending on the external conditions. However, the finite element load structure method can be used to obtain the maximum bending moment value under service conditions.

[0119] See also Figure 9 The finite element load structure method was used to examine the loading conditions of the caisson segments during the bending performance test. Considering that lateral deformation of the segments is difficult during the sinking shaft excavation method, fixed constraints were set at the four corners of the segment. Uniformly distributed loads of a certain width were applied at the 1 / 3 and 2 / 3 positions of the segment to simulate the effect of pressure rods 8 during the actual bending performance test. In this example, to examine the full service performance of the segment, the design load was set at twice the standard value, i.e., the maximum bending moment in the test was 340 kN·m / m.

[0120] Based on the area of the uniformly distributed load, the vertical pressure is 1650 kN, which corresponds to the design load value of 1650 kN in Table 1. It should be noted that the maximum load that the bending test loading platform can provide must not be less than 1.2 times the design load value, or 1980 kN, to ensure safety during the bending test.

[0121] An embodiment of the present invention also provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the processor executes the steps of the above-mentioned method for testing the bending resistance of caisson segments for the sunken vertical shaft excavation method.

[0122] See also Figure 10 An embodiment of the present invention further provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the above-mentioned method for testing the bending resistance of caisson segments for the sunken vertical shaft excavation method.

[0123] An embodiment of the present invention further provides a computer program product comprising instructions, which, when executed on a computer, enables the computer to execute the steps of the above-mentioned method for testing the bending resistance of caisson segments for a sunken shaft excavation method.

[0124] It is understandable that the system, equipment and storage medium provided in the embodiments of the present invention correspond to the method provided in the embodiments of the present invention. The explanation, examples and beneficial effects of the relevant contents can refer to the corresponding parts of the above-mentioned test method for the bending resistance of caisson segments for the sunken vertical shaft excavation method.

[0125] It should be noted that those skilled in the art will understand that all or part of the steps implemented in the embodiments of the present invention can be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented using hardware, it can be implemented in whole or in part in the form of purchased standard parts or modified parts. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the process or function described in the embodiments of the present application is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via a wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) method. The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server or data center that includes one or more available media integrated therein. The available medium may be a magnetic medium (eg, a floppy disk, a hard disk, a magnetic tape), an optical medium (eg, a DVD), or a semiconductor medium (eg, a solid state disk (SSD)).

[0126] In summary, in order to overcome the limitation that the existing shield tunnel segment bending performance test instruments cannot be directly applied to VSM method caisson segments, the present invention provides a bending performance test method and a test loading platform for caisson segments used in the sunken vertical shaft excavation method. According to the characteristics of the caisson segments and combined with the finite element load structure method, the load conditions of the VSM method caisson segments are accurately determined, and the load size setting of the test loading platform is guided, which significantly improves the accuracy and practicality of the test and helps to more scientifically and accurately study the service characteristics and quality control of the VSM method caisson segments.

[0127] It should be understood that the examples and implementation methods described herein are for illustrative purposes only and are not intended to limit the present invention. Those skilled in the art may make various modifications or changes based on them. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A test method for the bending resistance of caisson segments used in a sinking shaft excavation method, characterized in that: The following steps are involved: S1. Obtain multi-dimensional parameters of the caisson segment and the shaft body to be tested; S2. Obtaining the earth pressure coefficient of each soil layer based on the multidimensional parameters and selecting an appropriate earth pressure coefficient according to the construction status of the sunken shaft excavation method; S3. Calculate the load conditions acting on the caisson segment to be tested by combining the multi-dimensional parameters obtained in S1 and the earth pressure coefficient selected in S2. The load conditions include the magnitude of the lateral earth pressure, the magnitude of the lateral water pressure, and the top vertical pressure. S4. Considering the linear distribution of pressure in the height direction and the self-weight stress of the caisson segment, the boundary conditions of the caisson segment to be tested are defined according to the connection conditions of the top and bottom of the caisson segment to be tested; S5. Based on the load conditions calculated in S3 and the boundary conditions defined in S4, combined with the multi-dimensional parameters obtained in S1, the finite element unit algorithm is used to calculate the bending moment distribution inside the caisson segment to be tested, and the stress conditions of each ring of the caisson segment are compared to obtain the maximum bending moment M of the caisson segment to be tested. max ; S6. Consider the loading conditions of the caisson segments during the bending test, simulate the state of a single segment placed on the bending test loading platform, and set the boundary conditions of the four corner points of the single segment based on the state of the caisson segments during the sinking shaft excavation method; S7. According to the load application setting of the bending performance test loading platform, the uniformly distributed load p applied to the 1 / 3 and 2 / 3 spans of the long side of the single segment is obtained. m , determine the application area A of the uniformly distributed load; S8. When calculating the maximum bending moment M' inside a single segment using the finite element algorithm to simulate the bending performance test, max , adjust the uniformly distributed load p m The maximum bending moment of the current single segment is twice the maximum bending moment of the caisson segment to be tested under the service condition 2*M max The same as above, and the design load F of the single segment in the bending performance test is obtained de and the maximum load F max .

2. The method for testing the bending resistance of caisson segments for a sinking shaft excavation method according to claim 1, wherein: In said S1, the multi-dimensional parameters of the caisson segment include at least: elastic modulus E, Poisson's ratio ν, bulk density γ, segment height h, segment depth z and segment thickness d; The multi-dimensional parameters of the vertical shaft include at least: the shaft excavation diameter R, the height z of the liquid level inside the shaft from the top of the shaft during construction, and the w , the thickness of each soil layer outside the well body h i , severe γ i , internal friction angle Cohesion c i And the foundation reaction coefficient P of the pipe segment, the water density γ w ; Where i is the number of the soil layer being calculated.

3. The method for testing the bending resistance of caisson segments for a sinking shaft excavation method according to claim 1, wherein: In S2, based on the internal friction angle of each soil layer outside the well body, Obtain the earth pressure coefficient of each soil layer, which includes the active earth pressure coefficient K ai and static earth pressure coefficient K 0i , respectively:

4. The method for testing the bending resistance of caisson segments for a sinking shaft excavation method according to claim 3, wherein: In S2, if there is no obvious relative displacement between the soil layer and the shaft body, the static earth pressure coefficient K is selected. 0i Calculate the lateral earth pressure. If active displacement between the soil layer and the shaft is considered, the active earth pressure coefficient K is selected. ai Calculate the lateral earth pressure.

5. The method for testing the bending resistance of caisson segments for a sinking shaft excavation method according to claim 1, wherein: In S3, the lateral earth pressure acting on the caisson segment includes the outer top lateral earth pressure p st and the outer bottom lateral earth pressure p sb ; Based on the weight of each soil layer outside the shaft body γ i , thickness h i , cohesion c i And the selected earth pressure coefficient K ai or K 0i , the lateral earth pressure p acting on the outer top of the caisson segment is calculated st ; Based on the weight of each soil layer outside the shaft body γ i , thickness h i , cohesion c i , the segment height h of the caisson segment and the selected earth pressure coefficient K ai or K 0i , the lateral earth pressure p acting on the outer bottom of the caisson segment is calculated sb ; If the earth pressure coefficient is selected as the static earth pressure coefficient K 0i , then the lateral earth pressure p acting on the outer top of the caisson segment st and the outer bottom lateral earth pressure p sb They are: p st =∑γ i h i K 0i p sb =∑γ i h i K 0i +γ i+1 hK 0i+1 If the earth pressure coefficient is selected as the active earth pressure coefficient K ai , then the lateral earth pressure p acting on the outer top of the caisson segment st and the outer bottom lateral earth pressure p sb They are:

6. The method for testing the bending resistance of caisson segments for a sinking shaft excavation method according to claim 1, wherein: In S3, the lateral water pressure acting on the caisson segments includes the inner top lateral water pressure p wt and the inner bottom lateral water pressure p wb ; Based on the construction process of the vertical shaft body, the height z of the liquid level inside the shaft body from the top of the shaft body w , water density γ w As well as the segment depth z of the caisson segment, the lateral water pressure p acting on the inner top of the caisson segment is calculated. wt ; Based on the construction process of the vertical shaft body, the height z of the liquid level inside the shaft body from the top of the shaft body w , water density γ w As well as the segment depth z and segment height h of the caisson segment, the lateral water pressure p acting on the inner bottom of the caisson segment is calculated. wb ; p wt =γ w (zz w ) p wb =γ w (z+hz w )。 7. The method for testing the bending resistance of caisson segments in a sinking shaft excavation method according to claim 1, wherein: In S3, the vertical pressure p acting on the top of the caisson segment is calculated based on the segment bulk density γ and segment depth z of the caisson segment. v : p v =γz。 8. The method for testing the bending resistance of caisson segments for a sinking shaft excavation method according to claim 1, wherein: In S4, if the boundary of the caisson segment is the connection between the segments, the boundary condition of the caisson segment to be tested is defined as a simple hinged boundary condition; if the boundary of the caisson segment is the connection between the segment and the concrete bottom seal of the entire caisson, the boundary condition of the caisson segment to be tested is defined as a completely fixed boundary condition.

9. The method for testing the bending resistance of caisson segments for a sinking shaft excavation method according to claim 8, wherein: In S6, in the simulation test of the bending performance of the single segment in the sunken shaft excavation method, the boundary conditions of the four corner points are all set to be completely fixed boundary conditions.

10. The method for testing the bending resistance of caisson segments for a sinking shaft excavation method according to claim 1, wherein: In S8, when M' max =2*M max When the uniform load p m and the application area A of the uniformly distributed load to determine the design load F of the single segment in the bending performance test de and the maximum load F max They are: F de =p m A F max =1.2p m A。

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