CN115452572B - Test device and method for testing neutral axis position and longitudinal equivalent bending stiffness of shield tunnel - Google Patents
Test device and method for testing neutral axis position and longitudinal equivalent bending stiffness of shield tunnel Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B21/00—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant
- G01B21/32—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring the deformation in a solid
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/02—Details
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/20—Investigating strength properties of solid materials by application of mechanical stress by applying steady bending forces
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- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
- G01N2203/0023—Bending
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- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
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- G01N2203/067—Parameter measured for estimating the property
- G01N2203/0676—Force, weight, load, energy, speed or acceleration
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/067—Parameter measured for estimating the property
- G01N2203/0682—Spatial dimension, e.g. length, area, angle
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Abstract
A test device and method for testing neutral axis position and longitudinal equivalent bending stiffness of a shield tunnel comprises a test platform, a shield tunnel model, a loading device, a displacement acquisition device and a strain acquisition device; the test platform comprises a bottom plate, steel columns, steel beams, a displacement bracket and a shield tunnel model support; the shield tunnel model comprises segments and bolts, and is manufactured by reducing the segments of a real shield tunnel according to a certain proportion and adopting various practical assembly modes. The shield tunnel model is strictly manufactured according to a real shield tunnel assembling mode, and can simulate four types of shield tunnels with through slots without mortises, through slots with mortises, staggered slots without mortises, staggered slots with mortises; by measuring the vertical displacement of the shield tunnel model and the strain at the circumferential seam, the longitudinal mechanical properties of the shield tunnel with different structural characteristics and different assembly modes can be researched; and the neutral axis position and the longitudinal equivalent bending rigidity of the shield tunnel are better obtained.
Description
Technical Field
The invention relates to the field of longitudinal deformation research of shield tunnels, in particular to a test device and a test method for testing neutral axis positions and longitudinal equivalent bending stiffness of shield tunnels.
Background
Due to the continuous development of urban construction, the shield tunnel is often influenced by construction activities such as foundation pit excavation, surface loading or tunnel crossing, and the like, so that the shield tunnel is often greatly deformed in the longitudinal direction. Deformation of the shield tunnel in the longitudinal direction often causes segment damage, bolt breakage and water seepage of the shield tunnel, and the subway safety operation is seriously affected.
Therefore, the longitudinal bending resistance of the shield tunnel is required to be developed and researched, and a plurality of scholars at home and abroad mainly develop and research the longitudinal bending resistance of the shield tunnel through theoretical analysis and model tests. In the field of theoretical analysis, a longitudinal equivalent continuous model is the most common theoretical model for simulating a shield tunnel, and the longitudinal equivalent bending stiffness and the neutral axis position of the shield tunnel are two key parameters for determining the mechanical characteristics of the model. The theoretical analysis method often ignores the influence of the shield tunnel assembly mode and the segment microstructure characteristics on the longitudinal bending resistance of the shield tunnel, so that the theoretical analysis method is difficult to reasonably research the shield tunnel expansion aiming at different assembly modes and different segment microstructure characteristics. Considering the limitation of theoretical analysis, a plurality of students study the longitudinal bending resistance of the shield tunnel through model tests. However, in the existing model test research, the shield tunnel model has the problem of excessive simplification, and accurate reduction of the segment lining detail of the shield tunnel is difficult. Firstly, the shield tunnel models mostly adopt a mode of grooving on a shield tunnel model lining ring to simulate the assembly characteristics of a shield tunnel in the ring direction, but a real shield tunnel lining ring is assembled by duct pieces and bolts, so that the assembly mode of the shield tunnel models is insufficient in the existing model test. Secondly, the segments of the existing shield tunnel model are all flat end surfaces, and a true shield tunnel is often provided with concave-convex mortises on the end surfaces of the segments to increase the connection rigidity between the segments, so that the existing shield tunnel model has the defects in the aspect of simulating the microstructure characteristics of the segments. Finally, the conventional model test research focuses on the longitudinal equivalent bending stiffness of the shield tunnel, and the neutral axis position of the shield tunnel is not yet researched by the model test.
In summary, the existing theoretical analysis and model test have some defects, and the longitudinal bending resistance of the shield tunnel cannot be comprehensively and carefully studied.
Disclosure of Invention
The invention aims to solve the technical problems that the defects of the prior shield tunnel in solving the longitudinal bending resistance can be overcome, and provides a test device and a test method for testing the neutral axis position and the longitudinal equivalent bending stiffness of the shield tunnel, which can be used for researching four types of shield tunnel models, namely, through-slit mortises, staggered-slit mortises and staggered-slit mortises, and have great advantages in researching the longitudinal equivalent bending stiffness and the neutral axis position of the shield tunnel.
The invention adopts the technical scheme for solving the technical problems that:
a test device for testing the neutral axis position and the longitudinal equivalent bending stiffness of a shield tunnel comprises a test platform, a shield tunnel model, a loading device, a displacement acquisition device and a strain acquisition device;
the test platform comprises a bottom plate, steel columns, steel beams, displacement brackets and shield tunnel model supports, wherein the number of the steel columns is four, the steel columns are installed on the bottom plate, the number of the steel beams is correspondingly four, the steel columns are respectively connected to the upper parts between every two steel columns, the bottom plate, the steel columns and the steel beams are connected to form a steel frame, and the steel frame is used for fixing the displacement brackets and the shield tunnel model supports and providing counter force by means of self gravity; the displacement bracket is arranged on the steel column; the shield tunnel model support comprises support legs and support cylinders, wherein the support legs are welded on the bottom plate, and the support cylinders are arranged above the support legs and used for fixing the shield tunnel model and providing counter force for the shield tunnel model;
the shield tunnel model comprises a duct piece and a bolt, wherein the duct piece comprises a top sealing block, an adjacent block, a standard block, a longitudinal bolt hole and a circumferential bolt hole, and the duct piece is reduced by a real shield tunnel duct piece according to a certain proportion; the bolts are also reduced according to the same proportion according to the real shield tunnel bolts and are used for connecting and assembling the duct pieces into the shield tunnel model;
the loading device comprises a loading rope loop, a hook and a weight, wherein the loading rope loop is sleeved at the loading position of the shield tunnel model and is used for transmitting the gravity of the hook and the weight to the shield tunnel model; the hook is hung at the bottom of the loading rope loop and is used for placing the weight; the weight is arranged on the hook, and the weight self gravity is utilized to apply load to the shield tunnel model;
the displacement acquisition device comprises a displacement rod, a displacement meter and a displacement data acquisition instrument, wherein the displacement rod is arranged on the displacement bracket; the displacement meter is arranged on the displacement rod and is used for measuring the vertical displacement of the shield tunnel model; the displacement data acquisition instrument is connected with each displacement meter through a displacement acquisition device wire and is used for acquiring the vertical displacement of the shield tunnel model obtained by measurement of the displacement meters;
the strain acquisition device comprises a strain gauge and a strain data acquisition instrument, wherein the strain gauge is uniformly adhered to the circumferential seam of the shield tunnel model and is used for monitoring circumferential seam strain data of the shield tunnel model; the strain data acquisition instrument is connected with each strain gauge through a strain acquisition device wire and is used for acquiring circumferential seam strain data obtained by monitoring each strain gauge.
Further, triangle-shaped steel plates are welded at the joint of the bottom plate and the steel column and the joint of the steel column and the steel beam, and are used for enhancing the overall rigidity of the test platform.
Further, the middle part of each steel column is provided with two displacement support holes, two displacement supports are respectively arranged between the two steel columns at two sides, and two ends of each displacement support are arranged at the positions of the displacement support holes of the two steel columns at the corresponding sides; and the middle positions of the two displacement brackets are provided with displacement holes, and the displacement holes are used for installing the displacement rods.
Further, the displacement bracket holes and the displacement bracket are rectangular; the displacement hole and the displacement rod are both circular.
Further, the inner diameter of the support cylinder is the same as the outer diameter of the shield tunnel model so as to ensure that the support cylinder is in close contact with the shield tunnel model.
Further, the segment is reduced by the real shield tunnel segment according to the proportion of 30:1-40:1, and is manufactured by adopting a 3D printing technology (ensuring that the shield tunnel model segment is similar to the real shield tunnel segment).
Further, the duct piece is divided into a mortise-equipped duct piece and a mortice-free duct piece; the shield tunnel model assembling mode is divided into two modes of through seam assembling and staggered seam assembling; the shield tunnel model is provided with four types of through seam mortises, staggered seam mortises and staggered seam mortises.
Further, each lining ring of the shield tunnel model is provided with 16 longitudinal bolt holes and 18 circumferential bolt holes.
Further, the displacement rod is a rod with a circular section, and the displacement rod is provided with distance scales so as to facilitate the installation and positioning of the displacement meter.
The invention also provides a test method of the test device for testing the neutral axis position and the longitudinal equivalent bending stiffness of the shield tunnel, which comprises the following steps:
step 1, assembling and connecting the bottom plate, the steel column and the steel beam to form a steel frame;
step 2, welding a shield tunnel model support onto the bottom plate;
step 3, splicing the mortice-free segments manufactured by 3D printing into a lining ring by using bolts, and respectively connecting a plurality of lining rings by using bolts according to a through seam splicing mode and a staggered seam splicing mode to form a through seam mortice-free shield tunnel model and a staggered seam mortice-free model; assembling the 3D printed mortised pipe pieces into a lining ring by using bolts, and then respectively connecting a plurality of lining rings by using bolts according to a through seam assembling and staggered seam assembling mode to form a through seam mortised shield tunnel model and a staggered seam mortised tunnel model;
step 4, pasting a plurality of strain gauges at the circumferential seam of the shield tunnel model, smearing a layer of emulsion on the surface of the circumferential seam before pasting the strain gauges, and uniformly pasting the strain gauges at the circumferential seam after the emulsion is completely dried;
step 5, arranging the shield tunnel model on a shield tunnel model support, adjusting the position of the shield tunnel model, and ensuring that the contact length of the shield tunnel model and the left and right shield tunnel model supports is the same;
step 6, sleeving a loading rope loop at a preset loading position of the shield tunnel model, and ensuring that the distances between the loading rope loop and a nearest shield tunnel model support are equal to form a pure bending section between loading points of the shield tunnel model;
step 7, installing a displacement meter on a displacement rod according to set scales, and enabling the displacement rod to penetrate through the inside of the shield tunnel model; the displacement bracket passes through a rectangular displacement bracket hole reserved on the steel column; respectively inserting the left end and the right end of the displacement rod into the reserved displacement holes on the displacement bracket; the position of the displacement rod is adjusted, so that the displacement meter is ensured to prop against the arch bottom of the shield tunnel model;
step 8, respectively connecting the displacement meter and the strain gauge to a displacement data acquisition instrument and a strain data acquisition instrument;
step 9, hanging the hook at the bottom of the loading rope loop;
step 10, after the hook is stable, opening a displacement data acquisition instrument and a strain data acquisition instrument, and starting to acquire a data initial value;
step 11, hanging weights on the hooks, starting loading, and keeping the number of the weights on the two hooks consistent; the shield tunnel model is loaded to be obviously damaged, and the loading is stopped;
step 12, replacing different shield tunnel models, and repeating the steps 4-11 to obtain the vertical displacement and circumferential strain data of the different shield tunnel models;
step 13, result analysis: processing the vertical displacement data obtained by the displacement acquisition device to obtain the longitudinal equivalent bending stiffness of the shield tunnel model; and processing the strain data obtained by the measurement of the strain acquisition device to obtain the neutral axis position of the shield tunnel model.
Compared with the prior art, the invention has the following beneficial effects:
1. the shield tunnel model is more similar to a real shield tunnel, has four types of shield tunnel models, namely a through seam without a mortice, a through seam with a mortice, a staggered seam without a mortice, a staggered seam with a mortice, and can study the longitudinal mechanical characteristics of the shield tunnel with different structural characteristics and different splicing modes;
2. the neutral axis position and the longitudinal equivalent bending stiffness of the shield tunnel can be better studied.
Drawings
FIG. 1 is a front view of a test apparatus for testing neutral axis position and longitudinal equivalent bending stiffness of a shield tunnel according to the present invention;
FIG. 2 is a side view of the test apparatus of the present invention for testing the neutral axis position and longitudinal equivalent bending stiffness of a shield tunnel;
FIG. 3 is a top view of the test apparatus of the present invention for testing the neutral axis position and longitudinal equivalent bending stiffness of a shield tunnel;
FIG. 4 is a cross-sectional view of a slotted shield tunnel model of the present invention;
FIG. 5 is a cross-sectional view of a mortarless shield tunnel model of the invention;
FIG. 6 is a schematic diagram of a bolt structure of a mortarless shield tunnel model of the present invention;
FIG. 7 is a schematic diagram of a bolt structure of a mortice shield tunnel model of the invention;
FIG. 8 is a schematic view of a split shield tunnel model of the present invention;
FIG. 9 is a schematic diagram of a split joint assembly shield tunnel model of the present invention;
FIG. 10 is a graph showing the vertical displacement distribution of the arch bottom of the shield tunnel model of the present invention under different vertical loads;
FIG. 11 is a graph showing the change of the longitudinal bending stiffness effective rate of the shield tunnel model according to the invention;
FIG. 12 is a graph showing the change of neutral axis position of a shield tunnel model according to the present invention;
in the figure: 1. test platform, 2, shield tunnel model, 3, loading device, 4, displacement acquisition device, 5, strain acquisition device, 11, bottom plate, 12, steel column, 13, steel beam, 14, displacement bracket, 15, shield tunnel model support, 21, segment, 22, bolt, 31, loading rope loop, 32, hook, 33, weight, 41, displacement rod, 42, displacement meter, 43, displacement data acquisition instrument, 44, displacement acquisition device wire, 51, strain gage, 52, strain data acquisition instrument, 53, strain acquisition device wire, 151, support leg, 152, support cylinder, 211, jacking block, 212, abutting block, 213, standard block, 214, longitudinal bolt hole, 215, annular bolt hole, 216, mortice.
Detailed Description
The invention is further illustrated below in conjunction with specific embodiments and the accompanying drawings. These examples are only for illustrating the present invention and are not intended to limit the scope of the present invention.
The device for testing the neutral axis position and the longitudinal equivalent bending stiffness of the shield tunnel comprises a test platform 1, a shield tunnel model 2, a loading device 3, a displacement acquisition device 4 and a strain acquisition device 5.
As shown in fig. 1 to 3, the test platform 1 comprises a bottom plate 11, steel columns 12, steel beams 13, displacement brackets 14 and shield tunnel model supports 15, wherein four steel columns 12 are arranged and are installed on the bottom plate 11, the steel beams 13 are correspondingly arranged and are respectively connected to the upper parts of every two steel columns 12, the bottom plate 11, the steel columns 12 and the steel beams 13 are connected to form a steel frame, and the steel frame is used for fixing the displacement brackets 14 and the shield tunnel model supports 15 and providing counter force by means of self gravity; triangular steel plates are welded at the joint of the bottom plate 11 and the steel column 12 and the joint of the steel column 12 and the steel beam 13 for enhancing the overall rigidity of the test platform 1; the middle part of each steel column 12 is provided with rectangular displacement support holes, two displacement supports 14 are arranged between the two steel columns 12 at two sides respectively, two ends of each displacement support 14 are arranged at the rectangular displacement support holes of the two steel columns 12 at the corresponding sides, and the middle positions of the two displacement supports 14 are provided with circular displacement holes for installing the displacement rods 41 of the displacement acquisition device 4; the shield tunnel model support 15 comprises support legs 151 and support cylinders 152, the support legs 151 are welded on the bottom plate 11, and the support cylinders 152 are arranged above the support legs 151 and are used for fixing the shield tunnel model 2 and providing counterforces for the shield tunnel model; the inner diameter of the support cylinder 152 is the same as the outer diameter of the shield tunnel model 2 to ensure that the support cylinder 152 is in close contact with the shield tunnel model 2.
As shown in fig. 4 to 7, the shield tunnel model 2 comprises two parts of a segment 21 and a bolt 22, the segment 21 comprises a capping block 211, an abutting block 212, a standard block 213, a longitudinal bolt hole 214 and a circumferential bolt hole 215, and the segment 21 is formed by a real shield tunnel segment according to 35:1, and adopting a 3D printing technology to manufacture so as to ensure that the segment 21 of the shield tunnel model 2 is similar to a real shield tunnel segment; bolt 22 is also according to true shield tunnel bolt 35:1 is used for connecting and assembling the duct piece 21 into a shield tunnel model 2; segment 21 is divided into two types, namely, a mortise 216 and a mortice-free segment; the assembly mode of the shield tunnel model 2 is divided into two modes of through seam assembly and staggered seam assembly, as shown in figures 8-9; each lining ring of the shield tunnel model 2 has 16 longitudinal bolt holes 214 and 18 circumferential bolt holes 215.
As shown in fig. 2, the loading device 3 comprises a loading rope loop 31, a hook 32 and a weight 33, wherein the loading rope loop 31 is sleeved at the loading position of the shield tunnel model 2 and is used for transmitting the gravity of the hook 32 and the weight 33 to the shield tunnel model 2; the hook 32 is hung at the bottom of the loading rope ring 31 and is used for placing the weight 33; the weight 33 is placed on the hook 32, and the weight 33 itself is used to apply a load to the shield tunnel model 2.
As shown in fig. 1, the displacement acquisition device 4 comprises a displacement rod 41, a displacement meter 42 and a displacement data acquisition instrument 43, wherein the displacement rod 41 is arranged at a circular displacement hole on the displacement bracket 14, the displacement rod 41 is a rod with a circular section, and the displacement rod 41 is provided with distance scales so as to be convenient for the installation and positioning of the displacement meter 42; the displacement meter 42 is mounted on the displacement rod 41 and is used for measuring the vertical displacement of the shield tunnel model 2; the displacement data acquisition instrument 43 is connected with each displacement meter 42 through a displacement acquisition device lead 44 and is used for acquiring the vertical displacement of the shield tunnel model 2 measured by the displacement meter 42.
As shown in fig. 1, the strain acquisition device 5 comprises a strain gauge 51, a strain data acquisition instrument 52 and a strain acquisition device lead 53, wherein the strain gauge 51 is adhered to a circumferential seam of the shield tunnel model 2 and is used for monitoring circumferential seam strain data (tensile and compression state) of the shield tunnel model 2; the strain data acquisition instrument 52 is connected with each strain gauge 51 through a strain acquisition device lead 53 and is used for acquiring circumferential seam strain data obtained by monitoring each strain gauge 51.
The invention relates to a test method of a test device for testing the neutral axis position and the longitudinal equivalent bending stiffness of a shield tunnel, which comprises the following steps:
step 1, assembling and connecting a bottom plate 11, a steel column 12 and a steel beam 13 to form a steel frame (a mode of matching and connecting bolts and nuts can be adopted);
step 2, welding a shield tunnel model support 15 onto the bottom plate 11;
step 3, splicing the mortice-free segments manufactured by 3D printing into a lining ring by using bolts 22, and respectively connecting a plurality of lining rings by using bolts 22 according to a through seam splicing mode and a staggered seam splicing mode to form a through seam mortice-free shield tunnel model and a staggered seam mortice-free model; assembling the 3D printed mortised pipe pieces into a lining ring by using bolts 22, and then respectively connecting a plurality of lining rings by using bolts according to a through seam assembling and staggered seam assembling mode to form a through seam mortised shield tunnel model and a staggered seam mortised tunnel model;
step 4, pasting a plurality of strain gauges 51 at the circumferential seam of the shield tunnel model 2, and smearing a layer of emulsion on the surface of the circumferential seam before pasting the strain gauges 51 so as to prevent glue from penetrating into the circumferential seam when pasting the strain gauges, and uniformly pasting the strain gauges 51 at the circumferential seam after the emulsion is completely dried;
step 5, arranging the shield tunnel model 2 on a shield tunnel model support 15, adjusting the position of the shield tunnel model 2, and ensuring that the contact length of the shield tunnel model 2 and the left and right shield tunnel model supports 15 is the same;
step 6, sleeving a loading rope ring 31 at a preset loading position of the shield tunnel model 2, wherein the distance between the loading rope ring 31 and the nearest shield tunnel model support 15 is ensured to be equal, so that a pure bending section is formed between loading points of the shield tunnel model 2;
step 7, installing a displacement meter 42 on a displacement rod 41 according to set scales, and then penetrating the displacement rod 41 into the shield tunnel model 2; passing the displacement bracket 14 through a rectangular displacement bracket hole reserved on the steel column 12; the left and right ends of the displacement rod 41 are respectively inserted into circular displacement holes reserved on the displacement bracket 14; adjusting the position of the displacement rod to ensure that the displacement meter 42 is propped against the arch bottom of the shield tunnel model 2;
step 8, connecting the displacement meter 42 and the strain gauge 51 to the displacement data acquisition instrument 43 and the strain data acquisition instrument 52 respectively;
step 9, hanging a hook 32 to the bottom of the loading rope loop 31;
step 10, after the hook 32 is stable, the displacement data acquisition instrument 43 and the stress data acquisition instrument 52 are opened, and the initial value of the data is started to be acquired;
step 11, hanging weights 33 on the hooks 32, starting loading, and keeping the number of the weights 33 on the two hooks 32 consistent; obvious damage occurs when the shield tunnel model 2 is loaded, and loading is stopped;
step 12, replacing different shield tunnel models 2, and repeating the steps 4-10 to obtain the vertical displacement and circumferential strain data of the different shield tunnel models 2;
step 13, result analysis: processing the vertical displacement data obtained by the displacement acquisition device 4 to obtain the longitudinal equivalent bending stiffness of the shield tunnel model 2; and processing the strain data measured by the strain acquisition device 5 to obtain the neutral axis position of the shield tunnel model 2. The specific analysis method is as follows:
because the shield tunnel model 2 is formed by splicing the duct pieces 21 and the bolts 22, a large number of joints exist, and the existence of the joints weakens the longitudinal bending rigidity of the shield tunnel model 2, so that the longitudinal bending rigidity of the shield tunnel needs to be reduced and corrected. The longitudinal equivalent bending stiffness of the shield tunnel is calculated by adopting a formula (1)
EI eq ＝ηEI (1)
Wherein: EI (electronic equipment) eq For the longitudinal equivalent bending rigidity of the shield tunnel, eta is the effective rate of the longitudinal bending rigidity of the shield tunnel, and EI is the longitudinal bending rigidity of the homogeneous shield tunnel.
EI is calculated as (2)
Wherein: e is the elastic modulus of the segment 21, D is the outer diameter of the shield tunnel model 2, and t is the thickness of the segment 21.
The effective rate eta of the longitudinal bending rigidity is obtained by a formula (3)
Wherein: omega is the maximum vertical displacement of the homogeneous shield tunnel under the same loading condition as that of the test, omega m Is the maximum vertical displacement of the shield tunnel model 2.
Omega is calculated by the formula (4)
Wherein: f is a single-point vertical load, a is the distance between the loading point and the support, and l is the length of the shield tunnel model 2.
Omega is obtained by experiment m And combining the formulas to obtain the longitudinal equivalent bending stiffness of the shield tunnel model 2.
According to the principle of material mechanics, the upper part of the shield tunnel model 2 is in a compressed state, the lower part is in a tension state, and the numerical values of the strain gauges 51 at corresponding positions are respectively negative and positive. And according to the strain data obtained by the test, a strain gauge with a strain value at positive and negative boundary points is found, and two strain zero points are found by an interpolation method. The connecting line of the two strain zero points is the neutral axis of the shield tunnel model 2.
Referring to fig. 10-12, the salient effects and significant advances of the present invention were verified with a specific test case verification, specifically:
the shield tunnel model 2 adopted in the test is assembled by using the segment without mortises 216 according to the through seam mode, and the number of lining rings is 23. Strain gauges 51 are arranged at circumferential seams on two sides of the middle ring of the shield tunnel model 2 to monitor strain at the circumferential seams. And 9 displacement meters 42 are arranged in the shield tunnel model and are used for monitoring the vertical displacement of the 2-type arch bottom of the shield tunnel model. Vertical loads are respectively applied to 8 lining rings and 13 lining rings which are away from the left shield tunnel model support, each level of load is 1kg, and 16kg of load is applied in total.
Fig. 10 is a graph showing the vertical displacement distribution of the arch bottom of the shield tunnel model under the vertical load. As can be seen from fig. 10, the deformation of the shield tunnel model 2 is substantially symmetrical, with the maximum displacement occurring at the intermediate ring. By using the method described in step 13, the effective longitudinal bending stiffness of the shield tunnel model 2 can be obtained. FIG. 11 is a graph showing the change of the longitudinal bending stiffness effective rate of the shield tunnel model. As can be seen from fig. 11, the effective longitudinal bending stiffness of the shield tunnel model 2 is not a constant value, and the effective efficiency decreases from 0.192 to 0.011 as the load increases. This decrease is also not linear, but rather exhibits a trend of going fast and then slow, and gradually approaches a steady value.
And according to the strain data obtained by the test, a strain gauge with a strain value at positive and negative boundary points is found, and two strain zero points are found by an interpolation method. The connecting line of the two strain zero points is the neutral axis of the shield tunnel model 2. Fig. 12 is a graph showing the change of the neutral axis position of the shield tunnel model. As can be seen from fig. 12, as the load increases, the position of the neutral axis of the shield tunnel model rises from below the arch to above the arch, and this change is not linear, but rather exhibits a tendency to slow down first.
The test results show that the test device and the test method have strong practicability in the aspect of testing the neutral axis position and the longitudinal equivalent bending stiffness of the shield tunnel, and can well achieve the set test aim.
The foregoing description of the preferred embodiments of the invention is not intended to limit the invention to the precise form disclosed, and any such modifications, equivalents, and alternatives falling within the spirit and scope of the invention are intended to be included within the scope of the invention.
Claims (10)
1. The test device for testing the neutral axis position and the longitudinal equivalent bending stiffness of the shield tunnel is characterized by comprising a test platform, a shield tunnel model, a loading device, a displacement acquisition device and a strain acquisition device;
the test platform comprises a bottom plate, steel columns, steel beams, displacement brackets and shield tunnel model supports, wherein the number of the steel columns is four, the steel columns are installed on the bottom plate, the number of the steel beams is correspondingly four, the steel columns are respectively connected to the upper parts between every two steel columns, the bottom plate, the steel columns and the steel beams are connected to form a steel frame, and the steel frame is used for fixing the displacement brackets and the shield tunnel model supports and providing counter force by means of self gravity; the displacement bracket is arranged on the steel column; the shield tunnel model support comprises support legs and support cylinders, wherein the support legs are welded on the bottom plate, and the support cylinders are arranged above the support legs and used for fixing the shield tunnel model and providing counter force for the shield tunnel model;
the shield tunnel model comprises a duct piece and a bolt, wherein the duct piece comprises a top sealing block, an adjacent block, a standard block, a longitudinal bolt hole and a circumferential bolt hole, and the duct piece is reduced by a real shield tunnel duct piece according to a certain proportion; the bolts are also reduced according to the same proportion according to the real shield tunnel bolts and are used for connecting and assembling the duct pieces into the shield tunnel model;
the loading device comprises a loading rope loop, a hook and a weight, wherein the loading rope loop is sleeved at the loading position of the shield tunnel model and is used for transmitting the gravity of the hook and the weight to the shield tunnel model; the hook is hung at the bottom of the loading rope loop and is used for placing the weight; the weight is arranged on the hook, and the weight self gravity is utilized to apply load to the shield tunnel model;
the displacement acquisition device comprises a displacement rod, a displacement meter and a displacement data acquisition instrument, wherein the displacement rod is arranged on the displacement bracket; the displacement meter is arranged on the displacement rod and is used for measuring the vertical displacement of the shield tunnel model; the displacement data acquisition instrument is connected with each displacement meter through a displacement acquisition device wire and is used for acquiring the vertical displacement of the shield tunnel model obtained by measurement of the displacement meters;
the strain acquisition device comprises a strain gauge and a strain data acquisition instrument, wherein the strain gauge is uniformly adhered to the circumferential seam of the shield tunnel model and is used for monitoring circumferential seam strain data of the shield tunnel model; the strain data acquisition instrument is connected with each strain gauge through a strain acquisition device wire and is used for acquiring circumferential seam strain data obtained by monitoring each strain gauge.
2. The test device for testing the neutral axis position and the longitudinal equivalent bending stiffness of the shield tunnel according to claim 1, wherein triangular steel plates are welded at the joint of the bottom plate and the steel column and the joint of the steel column and the steel beam for enhancing the overall stiffness of the test platform.
3. The test device for testing the neutral axis position and the longitudinal equivalent bending stiffness of the shield tunnel according to claim 1, wherein two displacement brackets are arranged in the middle of each steel column and are respectively arranged between the two steel columns at two sides, and two ends of each displacement bracket are arranged at the positions of the displacement bracket holes of the two steel columns at the corresponding sides; and the middle positions of the two displacement brackets are provided with displacement holes, and the displacement holes are used for installing the displacement rods.
4. A test device for testing the neutral axis position and the longitudinal equivalent bending stiffness of a shield tunnel according to claim 3, wherein the displacement bracket holes and the displacement bracket are rectangular; the displacement hole and the displacement rod are both circular.
5. The test device for testing the neutral axis position and the longitudinal equivalent bending stiffness of the shield tunnel according to claim 1, wherein the inner diameter of the support cylinder is the same as the outer diameter of the shield tunnel model so as to ensure that the support cylinder is in close contact with the shield tunnel model.
6. The test device for testing the neutral axis position and the longitudinal equivalent bending stiffness of the shield tunnel according to claim 1, wherein the segment is reduced by a real shield tunnel segment according to a ratio of 30:1-40:1 and is manufactured by adopting a 3D printing technology.
7. The test device for testing the neutral axis position and the longitudinal equivalent bending stiffness of the shield tunnel according to claim 1, wherein the duct pieces are divided into two types, namely a mortice type and a mortice-free type; the shield tunnel model assembling mode is divided into two modes of through seam assembling and staggered seam assembling; the shield tunnel model is provided with four types of through seam mortises, staggered seam mortises and staggered seam mortises.
8. A test device for testing the neutral axis position and the longitudinal equivalent bending stiffness of a shield tunnel according to claim 1, wherein each lining ring of the shield tunnel model is provided with 16 longitudinal bolt holes and 18 circumferential bolt holes.
9. The test device for testing the neutral axis position and the longitudinal equivalent bending stiffness of the shield tunnel according to claim 1, wherein the displacement rod is a circular section rod, and distance scales are arranged on the displacement rod so as to facilitate the installation and positioning of the displacement meter.
10. A test method by the test device for testing neutral axis position and longitudinal equivalent bending stiffness of a shield tunnel according to any one of claims 1 to 9, comprising the steps of:
step 1, assembling and connecting the bottom plate, the steel column and the steel beam to form a steel frame;
step 2, welding a shield tunnel model support onto the bottom plate;
step 3, splicing the mortice-free segments manufactured by 3D printing into a lining ring by using bolts, and respectively connecting a plurality of lining rings by using bolts according to a through seam splicing mode and a staggered seam splicing mode to form a through seam mortice-free shield tunnel model and a staggered seam mortice-free model; assembling the 3D printed mortised pipe pieces into a lining ring by using bolts, and then respectively connecting a plurality of lining rings by using bolts according to a through seam assembling and staggered seam assembling mode to form a through seam mortised shield tunnel model and a staggered seam mortised tunnel model;
step 4, pasting a plurality of strain gauges at the circumferential seam of the shield tunnel model, smearing a layer of emulsion on the surface of the circumferential seam before pasting the strain gauges, and uniformly pasting the strain gauges at the circumferential seam after the emulsion is completely dried;
step 5, arranging the shield tunnel model on a shield tunnel model support, adjusting the position of the shield tunnel model, and ensuring that the contact length of the shield tunnel model and the left and right shield tunnel model supports is the same;
step 6, sleeving a loading rope loop at a preset loading position of the shield tunnel model, and ensuring that the distances between the loading rope loop and a nearest shield tunnel model support are equal to form a pure bending section between loading points of the shield tunnel model;
step 7, installing a displacement meter on a displacement rod according to set scales, and enabling the displacement rod to penetrate through the inside of the shield tunnel model; the displacement bracket passes through a rectangular displacement bracket hole reserved on the steel column; respectively inserting the left end and the right end of the displacement rod into the reserved displacement holes on the displacement bracket; the position of the displacement rod is adjusted, so that the displacement meter is ensured to prop against the arch bottom of the shield tunnel model;
step 8, respectively connecting the displacement meter and the strain gauge to a displacement data acquisition instrument and a strain data acquisition instrument;
step 9, hanging the hook at the bottom of the loading rope loop;
step 10, after the hook is stable, opening a displacement data acquisition instrument and a strain data acquisition instrument, and starting to acquire a data initial value;
step 11, hanging weights on the hooks, starting loading, and keeping the number of the weights on the two hooks consistent; the shield tunnel model is loaded to be obviously damaged, and the loading is stopped;
step 12, replacing different shield tunnel models, and repeating the steps 4-11 to obtain the vertical displacement and circumferential strain data of the different shield tunnel models;
step 13, result analysis: processing the vertical displacement data obtained by the displacement acquisition device to obtain the longitudinal equivalent bending stiffness of the shield tunnel model; and processing the strain data obtained by the measurement of the strain acquisition device to obtain the neutral axis position of the shield tunnel model.
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| JPH03148037A (en) * | 1989-11-04 | 1991-06-24 | Kubota Corp | Method for analyzing stress in segment ring for shield tunnel |
| CN209843057U (en) * | 2019-01-31 | 2019-12-24 | 安徽省建筑科学研究设计院 | Tunnel longitudinal bending rigidity calibration experiment demonstration device |
| CN113959856A (en) * | 2021-10-25 | 2022-01-21 | 福州大学 | Test device for simulating longitudinal bending resistance of shield tunnel |
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| JPH03148037A (en) * | 1989-11-04 | 1991-06-24 | Kubota Corp | Method for analyzing stress in segment ring for shield tunnel |
| CN209843057U (en) * | 2019-01-31 | 2019-12-24 | 安徽省建筑科学研究设计院 | Tunnel longitudinal bending rigidity calibration experiment demonstration device |
| CN113959856A (en) * | 2021-10-25 | 2022-01-21 | 福州大学 | Test device for simulating longitudinal bending resistance of shield tunnel |
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