Test method suitable for simulation loading of underpass water conveyance tunnel

Abstract

The invention discloses a test method suitable for simulation loading of an underpass water conveyance tunnel. The test method comprises the steps that 1, model parameters are designed; 2, filling a model; 3, a water conveying device is built; and 4, carrying out a simulation test. The influence of water level change on the tunnel structure can be effectively simulated. According to a geometric similarity ratio, designing a similarity relationship between corresponding quantities of a model test and an actual project and selection and proportion of a similarity ratio and a similar material; the model box and the structure model comprise the size of the model box, pouring of a tunnel model and manufacturing of a water delivery tunnel model, and a water tank and a manual gate valve of a water level control device are modified and installed; according to research key points, a test section and a test sensor are reasonably selected, four loading working conditions are designed in combination with actual engineering, and the loading water level and sequence are determined; and layered tamping and filling of the model box and burying of the model and the sensor.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel model tests, and in particular relates to a test method suitable for simulating loading of an underpass water conveyance tunnel. Background Art

[0002] With the rapid development of railway construction in my country, many tunnel projects that are close to existing structures have emerged. For newly built tunnels that pass under unlined water tunnels, during construction and later operation, the water in the water tunnel will infiltrate into the surrounding rock and the tunnel, causing the stress state of the tunnel structure to change. The section under the tunnel may become a weak section. When the water level rises, it will cause serious consequences, which may form a leakage channel or crack the tunnel lining. In addition, the tunnel under the water tunnel is rich in water. Once the water level rises in the water tunnel and causes cracks in the tunnel, it will affect the seepage under this effect, thereby aggravating the damage and deformation of the tunnel. Therefore, water level changes as a direct factor will cause tunnel damage and deformation. In addition, the existence of indirect factors such as cracks caused by water level rise will aggravate the development of such damage and deformation.

[0003] Limited by various factors and objective conditions, the current model test research on tunnel structures under the action of water level change loads has not made substantial breakthroughs, and the research on the mechanical response characteristics of railway tunnels under water tunnels is almost blank. The use of similar material simulation tests can be based on the actual geological data on site, artificially changing the test conditions to study the mechanical response characteristics of the tunnel structure when the water level of the water tunnel changes, selecting spatial intersection sections to carry out model tests on the mechanical response characteristics of the tunnel under water level changes, and analyzing the changes in the tunnel monitoring surface strain, soil pressure, pore water pressure, and water content as the water level rises. Therefore, a model test device that is easy to operate, reliable in accuracy, and reasonably designed is particularly important to achieve the above goals. Summary of the invention

[0004] The invention provides a test method suitable for simulating loading of an underpass water conveyance tunnel, aiming at studying the influence of water level change on the water conveyance tunnel through a simulation test.

[0005] To this end, the present invention adopts the following technical solutions: A test method suitable for simulating loading of a water conveyance tunnel, comprising the following steps: Step 1. Design model parameters According to the actual size of the water conveyance tunnel and geological data, and based on the principles of geometric similarity ratio, density similarity ratio and elastic modulus similarity ratio, the model box size, geometric similarity scale, tunnel model size, surrounding rock material, tunnel model burial depth and elastic modulus similarity ratio of the model test are determined; A tunnel model is made according to the determined parameters. The tunnel model includes three sections, namely a central section, a head section and a tail section; Step 2: Fill the Model Holes are respectively opened on the left and right side plates of the model box. The positions of the holes are the installation positions of the tunnel model. The size of the holes is the same as that of the tunnel model. One end of the hole is the water inlet end and the other end is the water outlet end. The surrounding rock is filled in the model box, and the filling and compaction are carried out layer by layer. When the filling height reaches the opening position, the three sections of the tunnel model are spliced ​​and installed at the opening position. At least three monitoring sections are set on the central section of the tunnel model. While filling, sensors are installed at the monitoring section positions. The sensors include strain gauge sensors, soil pressure sensors, pore water pressure and soil moisture sensors, acceleration sensors, and dynamic strain gauge sensors. After the model is filled, the head and tail sections of the tunnel model are pulled out through the opening of the model box, and the center section remains in the model box; Step 3: Build the water delivery device The water delivery device includes a water tank, a water outlet is provided at the front end of the water tank, and a gate valve is connected to the water outlet, and the gate valve is used to control the water outlet height; the front end of the gate valve is connected to a guide cylinder of the same size as the tunnel model, and the guide cylinder adjusts the shape of the water outlet end of the gate valve to the shape of the tunnel model, so as to facilitate the control of the water level height in the tunnel model; the water tank is placed at the water inlet end, and the front end of the guide cylinder is horizontally fixedly connected to the water inlet end position of the model box, and the water in the water tank enters the tunnel model after passing through the gate valve and the guide cylinder; a water receiving bucket is provided at the water outlet end of the simulated tunnel; Step 4: Conduct a simulation test During the test, the influence of the rising water level in the water conveyance tunnel on the mechanical response characteristics of the tunnel structure was simulated. The water level rose by 1 cm each time from 0 cm, and rose by 3 cm in total, that is, 4 working conditions were set in total. At this time, the data acquisition interface was always observed, and the test records were kept; Step 5: Data Processing According to the data measured in the test, the strain time history curve is drawn, including the original strain curve and smooth strain curve corresponding to each measuring point, and then the strain change characteristics at each cross-section measuring point under each working condition are analyzed; including the maximum strain value and the tension and compression conditions of each point, and the positive strain is defined as the tensile strain, which makes it elongate, and the negative strain is defined as the compressive strain, which makes it shorten, that is, the positive and negative of the strain does not indicate the size, and the relationship between the strain and time is curve fitted to illustrate the law of strain change over time.

[0006] Furthermore, tempered glass is installed on the front and back sides of the model box, and wooden boards are installed on the left and right sides of the model box, and holes are opened on the wooden boards; the bottom of the model box is not blocked to facilitate water seepage.

[0007] Furthermore, the invert of the tunnel model is rectangular and the dome is semi-dome-shaped.

[0008] The beneficial effects of the present invention are: 1. It can effectively simulate the impact of water level changes on tunnel structures. According to the geometric similarity ratio, the similarity relationship and similarity ratio between the model test and the corresponding quantities of the actual project, the selection and proportion of similar materials; model box and structural model, including the size of the model box, the casting of the tunnel model, the production of the water conveyance tunnel model, and the modification and installation of the water tank and manual gate valve of the water level control device; 2. According to the research points, rationally select the test section and test sensor, combine the actual engineering design of 4 loading conditions, clarify the loading water level and sequence; layered compaction filling of the model box and the burial of the model and sensor. The design of the model test plan is the basis for the test, and the rationality of the plan is related to the accuracy and effectiveness of the test results; 3. Make a hole in the arched straight wall structure on the water inlet wooden board, and finally stick the other side of the gate valve to the wooden board where the water inlet is located, so that the water tank hole, gate valve hole, and wooden board water inlet are completely matched and stuck together. During the test, water flows out of the water tank, controls the water level through the gate valve, and then flows into the model box through the water inlet on the wooden board; 4. The side wall of the model box can be made of organic glass, which is convenient for test personnel to observe and record the deformation and damage of the railway tunnel under the water tunnel at any time. The device of the present invention can be connected to the deformation and stress monitoring system, which can realize the real continuous deformation and stress state monitoring of the railway tunnel under the water tunnel when the water level changes, and provide a reliable device and method for the study of the large deformation mechanism of the tunnel structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a schematic diagram of the layout of the model box of the present invention; Figure 2 is a schematic diagram of a tunnel model of the present invention; Figure 3 is a flow chart of model filling and assembly of an embodiment; Figure 4 is a working condition loading flow chart of an embodiment; Figure 5 are the original strain curve and smoothed strain curve corresponding to each measuring point on the outside of section I in working condition 1; Figure 6 are the original strain curve and smoothed strain curve corresponding to each measuring point on the inner side of section I in working condition 1; Figure 7 It is the original strain curve and smoothed strain curve corresponding to each measuring point on the outside of section II of working condition 1; Figure 8 are the original strain curves and smoothed strain curves corresponding to each measuring point on the inner side of section II of working condition 1; Fig. 9are the original strain curves and smoothed strain curves corresponding to each measuring point on the outside of section III of working condition 1; Fig.10 are the original strain curves and smoothed strain curves corresponding to each measuring point on the inner side of section III of working condition 1; In the figure: 1-model box, 2-tunnel model, 201-central section, 202-head section, 203-tail section, 204-water inlet end, 205-water outlet end, 3-water guide channel, 4-water tank, 5-gate valve. DETAILED DESCRIPTION

[0010] A test method suitable for simulating loading under a water diversion tunnel, the specific steps are as follows: Step 1. Design model parameters 1) Prototype engineering generalization Tunnel Prototype Engineering refers to the process of creating prototypes or models to simulate and test the design, structure and construction methods of tunnels during the construction and design of tunnels. By creating physical or digital models, non-essential factors that are essentially irrelevant or have little relevance to the research purpose are excluded, and a model scheme with experimental operability and true objectivity is abstracted, and then a reasonable conceptual model is established, and quantitative research is carried out through indoor experimental means. The geometry, structural strength and construction methods of the tunnel can be evaluated, so that problems can be found and optimized when designing experiments. Tunnel construction involves complex geological and environmental conditions, and prototype engineering can help identify potential risks and challenges. By simulating different construction scenarios and geological conditions, engineers can develop corresponding response strategies to reduce construction risks.

[0011] 2) Determination of test parameters According to the generalized model obtained in 1), the experimental parameters are determined. Generally speaking, due to the limitations of the laboratory site, the size of the model box 1 and the applied load, it is almost impossible to make the model test completely consistent with the engineering prototype, so general model tests are basically scaled tests. When designing the test, the first thing to determine is the similarity relationship between the engineering prototype and the test model. Nowadays, many scholars use dimensional analysis to determine the similarity ratio. However, in the process of derivation, all quantities must satisfy the same characteristic equation, which makes it impossible to achieve the similarity design of soil and structure one by one. In addition, the other similarity ratios derived must also satisfy the model similarity design, which is difficult to achieve in model tests. In model tests, three relatively easy-to-determine quantities are generally selected as control parameters, and other parameters that are difficult to determine are derived according to the relationship. According to the importance of each parameter to the test, it can be divided into control parameters, key parameters, related parameters and irrelevant parameters. According to existing relevant research, the similarity design in this scheme only considers important parameters, while ignoring some minor parameters. In order to meet the purpose of the test, the geometric similarity ratio, density similarity ratio and elastic modulus similarity ratio are used as the three basic similarity ratios. Considering that the model box 1 with a height of 2m was selected in the test, and the buried depth of the test section tunnel was 58.7m, the geometric similarity scale of this test was determined to be 1:50 based on the height of the model box 1 and the actual buried depth of the tunnel. By comparing the existing materials in the test site with the surrounding rock and lining materials of the tunnel, the density similarity ratio was determined to be 1:1 and the elastic modulus similarity ratio was 1:50. Then, the dimensional analysis method and the three similarity theorems were used to determine the similarity ratios of other quantities. After calculation, the similarity ratios of various physical and mechanical parameters between the prototype and the model can be obtained.

[0012] 3) Selection of similar materials According to the on-site engineering geological survey report, the surrounding rock grade of the test section tunnel is Grade IV. When selecting the surrounding rock materials, we refer to scholars' research on the proportion of similar materials for Grade IV surrounding rocks, and consider the practicality and economy of the materials. Finally, we adopt the proportion of Grade IV surrounding rock materials obtained through orthogonal proportioning test. The proportioning materials include soil, sand, barite powder, gypsum, water, etc. Among them, the soil-sand ratio is 2:4, and the proportions of barite powder, gypsum, and water are 40%, 7%, and 10% respectively. Since gypsum is used in the proportioning materials, 0.5% borax needs to be added to the water as a retarder.

[0013] 4) Sensor layout According to the test purpose, strain gauges are selected to monitor the deformation inside and outside the tunnel model, and soil pressure sensors are used to monitor the magnitude of the soil pressure on the lining. The pore water pressure sensor is used to test the magnitude of the pore water pressure in the tunnel and the surrounding rock. The moisture content sensor is used to test the moisture content around the tunnel and its surrounding rock.

[0014] a. Strain gauge sensor The strain gauge used in the test is a resistance strain gauge, model BX120-20AA-P150-D, with a resistance value of 120.0±0.2Ω and a sensitivity coefficient of 2.08±1%. In the test, after the strain gauge is glued at the monitoring point, a layer of silicone is applied to fix and waterproof it. In addition, since the strain gauge sensor has a certain temperature coefficient, in order to prevent temperature changes and the length of the wire from affecting the output strain signal, the strain gauge is temperature compensated to reduce the error.

[0015] b. Soil pressure sensor The soil pressure sensor used in the test is JTM-Y2000, with a specification of 0.5 and an average sensitivity of 17.6. It has the advantages of high accuracy, stable working performance, small size, light weight, waterproof and moisture-proof. In the test, the soil pressure sensor was placed at a specific monitoring point in the tunnel and fixed to the tunnel model with transparent tape.

[0016] c. Pore water pressure and soil moisture sensor The pore water pressure sensor used in the test is model DY 1200, with a measurement range of (0~20) kPa, an accuracy level of ±0.25%FS, and a sensitivity and zero temperature coefficient of ≤ 1.0 × 10−4 / ℃ ∙ F ∙ S. The soil moisture sensor mainly tests the moisture content in the surrounding rock around the tunnel.

[0017] Step 2: Fill the Model 1) Water diversion tunnel model The on-site water delivery tunnel is a 2m wide and 3m high arched straight wall structure, with an arch buried depth of 39m. According to the geometric similarity ratio calculation, the tunnel model 2 is 4cm wide and 6cm high. In the experiment, a rectangular cross-section aluminum alloy tube with a width of 4cm and a height of 4cm is used as the lower structure of the tunnel model 2, and a semicircular PVC tube with a cross-sectional diameter of 4cm is used as the upper structure of the tunnel model 2. The two structures are then compactly spliced ​​together, and finally the upper and lower structures are firmly bonded together with strong glue and tape. The tunnel model 2 is 155cm long, and plastic objects are stuffed into the inner cavity for compaction to enhance the hardness and bending and compression resistance of the tunnel model 2. The tunnel model 2 includes three sections, namely the central section 201, the head section 202 and the tail section 203.

[0018] 2) Model box 1 According to the geometric similarity ratio, the model box 1 matching the model test is selected with a size of 1.5m×1m×2m (length×width×height). Angle steel is used in the boundary of the model box 1 and the middle of the left and right vertical glass surfaces to limit its deformation. In order to better observe the test phenomenon, the left and right surfaces of the model box 1 are made of 2cm thick transparent hard glass, and the front and rear surfaces of the water tunnel inlet and outlet are made of 2cm thick wooden boards instead of glass, so that the inlet and outlet of the tunnel can be cut out on the wooden board. Glass or wooden boards are not placed on the upper and lower surfaces of the model box 1, especially on the bottom surface, in order to prevent the water that has penetrated into the bottom of the model box 1 from continuing to infiltrate in the reverse direction due to the inability to be discharged, thereby interfering with the test. A hole with the same shape and size as the tunnel model 2 is chiseled at a specified position on a 1.5m×2m box surface, so that one end of the tunnel model can be overlapped at the wooden board hole in the test, so as to adjust the exciter in the tunnel and observe the phenomenon. In terms of left and right, the hole is in the middle of the wooden board, and in terms of top and bottom, the hole is 19 cm high, the arch of the hole is 40 cm away from the bottom of the box, and the top of the hole arch is 141 cm away from the top of the box.

[0019] Step 3: Build the water delivery device 1) Water tank 4 device The water level control device mainly includes a water tank 4 and a manual gate valve 5. The water tank 4 has a length, width and height of 55cm×35cm×24cm. A hole with an arched straight wall structure identical to the cross section of the tunnel model 2 is punched on its 35cm×24cm surface. The distance between the bottom of the hole and the bottom surface of the water tank 4 is consistent with the distance from the bottom edge of the gate valve 5 water inlet to the bottom of the gate valve 5. A round hole is punched at the upper edge of another 35cm×24cm surface and a faucet is installed to prevent the water in the water tank 4 from overflowing due to excessive water during the test. At the same time, it can be used to adjust the water level in the water tank 4 to be constant, reducing the impact of unstable water level on the test.

[0020] 2) Manual gate valve 5 device The width and height of the manual gate valve 5 are 24cm and 55cm, and the gate hole is a square hole of 15cm×15cm. After the water flows out of the water tank 4, the water level flowing into the model box 1 is controlled by the gate valve 5. Since the water inlet of the gate valve 5 is square, and the tunnel in the actual project is a vaulted straight wall structure, the gate hole is modified. On a 15cm×15cm plastic foam board, take out the vaulted straight wall structure with the same cross-section as the tunnel model 2, and then clamp the remaining part in the card slot of the gate hole water inlet of the gate valve 5, and use strong glue to firmly stick the foam board to the side wall of the gate valve 5. Then use strong waterproof glue to bond the perforated water tank 4 surface with the gate valve 5, so that the hole on the water tank 4 and the water inlet of the gate valve 5 are completely matched and fit together, and the foam board is the guide cylinder. In addition, a hole of the arched straight wall structure needs to be dug out on the water inlet wooden board, and finally the other side of the gate valve 5 is pasted to the wooden board where the water inlet is located, so that the hole of the water tank 4, the hole of the gate valve 5, and the water inlet of the wooden board are completely matched and pasted together. During the test, water flows out of the water tank 4, controls the water level through the gate valve 5, and then flows into the model box 1 through the water inlet on the wooden board.

[0021] Step 4: Conduct a simulation test 1) Measurement point layout Three sections were selected as the research surface in the 90cm long central section 201 tunnel model 2. Section I was located directly below the intersection of the tunnel and the tunnel space. Sections II and III were 30cm away from section I and were respectively distributed on both sides of section I. Section II was close to the water inlet 204, and section III was close to the water outlet 205. The side of the tunnel model 2 close to the water inlet 204 was the left side, and the side close to the water outlet 205 was the right side. Sensors were arranged at the key parts of each section, including the arch crown, left and right arch waists, left and right arch feet, and inverted arches for monitoring. Strain gauges and earth pressure sensors were arranged at the monitoring points on the outside of each section, and strain gauge sensors were also arranged at the monitoring points on each section on the inside of the tunnel model 2. Pore water pressure and water content sensors were arranged at the measuring points on the outside of section I. In addition, pore water pressure sensors and water content sensors were arranged in the middle of the intersection of the tunnel and the tunnel, and a pore water pressure sensor was arranged at the tunnel inverted arch.

[0022] 2) Model filling The tunnel surrounding rock materials are prepared according to the material ratio obtained by the similarity ratio. First, weigh the soil, sand, barite powder, gypsum, water and other materials in proportion, pour them into the mixer and add water to stir. Since there are many large particles and uneven coarseness after mixing, they are screened manually again. Before filling, the tunnel model hole is blocked with foam board to prevent the surrounding rock from entering the tunnel model. Then, the layered compaction method is used for filling. During the filling process, it is compacted every 10 cm to ensure that the density of each layer of surrounding rock is the same, so as to ensure the same density. In addition, in order to avoid stratification during each filling process, the hair is scraped after compaction before the next layer is filled. When the filling height reaches the tunnel invert arch, the tunnel model is placed at the specified position, and the corresponding sensors are buried at each cross-section measuring point. After the burial is completed, the sensor lines are combed. Then continue to fill to the height of the water diversion tunnel, overlap one end of the pre-made tunnel model 2 at the wooden board water inlet and the other end at the wooden board water outlet, and then fill and tamp until the design height is reached. Slowly pull out the head section 202 and the tail section 203 of the tunnel model 2 from the water inlet end 204 and the water outlet end 205. At this time, an unlined arched straight wall structure tunnel appears in the surrounding rock; 3) Experimental loading During the test, the influence of the rising water level in the water conveyance tunnel on the mechanical response characteristics of the tunnel structure was simulated. The water level rose by 1 cm each time from 0 cm, and rose by 3 cm in total, that is, 4 working conditions were set. At this time, the data acquisition interface was always observed, and the test records were kept.

[0023] Step 5: Data Processing According to the data measured in the test, the strain time history curve is drawn, including the original strain curve and smooth strain curve corresponding to each measuring point, and then the strain change characteristics at each cross-section measuring point under each working condition are analyzed, mainly the maximum strain value and the tension and compression conditions of each point. Here, positive strain is defined as tensile strain, which makes it elongate, and negative strain is defined as compressive strain, which makes it shorten. That is, the positive and negative of strain does not indicate the size, and the relationship between strain and time is fitted by curve fitting to illustrate the law of strain change over time.

[0024] Take the strain response of each section of tunnel in working condition 1 as an example 1) Strain response analysis of each measuring point on the outside of section I under working condition 1 like Figure 5 , the original strain curve and smoothed strain curve corresponding to each measuring point on the outside of section I under working condition 1 When the water level in the water diversion tunnel is 0, the strains at other locations on the outside of tunnel section I except the right arch foot are all 0 and remain unchanged, while the strain at the right arch foot increases rapidly from the beginning, and at about 10s, it begins to fluctuate slightly, then slowly rises and gradually stabilizes. During the whole process, the right arch foot is under tension.

[0025] 2) Strain response analysis of each measuring point inside section I under working condition 1 like Figure 6 , the original strain curve and smoothed strain curve corresponding to each measuring point on the inner side of section I under working condition 1 When the water level in the water conveyance tunnel is 0, the strains at other locations on the inner side of the tunnel section I except the left arch foot are all 0 and remain unchanged, while the initial strain at the left arch foot is 0. From the 12th second, compressive strain begins to occur and gradually increases, and the overall growth rate gradually slows down, fluctuating up and down in the local range.

[0026] 3) Strain response analysis of each measuring point on the outer side of section II under working condition 1 like Figure 7 , the original strain curve and smoothed strain curve corresponding to each measuring point on the outside of section II of working condition 1 When the water level in the water diversion tunnel is 0, the strains at all positions on the outside of tunnel section II except the left arch foot are 0 and remain unchanged, and the initial strain at the left arch foot is also 0, until the tensile strain of 1.01 appears from the 236th second and lasts until the 292nd second. From the 293rd second to the end, the strain at the left arch foot fluctuates between 1.01 and 2.01.

[0027] 4) Strain response analysis of each measuring point on the inner side of section II under working condition 1 like Figure 8 , the original strain curve and smooth strain curve corresponding to each measuring point on the inner side of section II of working condition 1 When the water level in the water conveyance tunnel is 0, the strain at the inner arch crown and left arch waist of tunnel section II is always 0, and compressive strains are generated in the right arch foot, right arch waist, left arch foot, and inverted arch successively. The strain at the inverted arch is larger and fluctuates within a small range after it occurs. After the strain at the right arch foot, right arch waist, and left arch foot occurs, the increasing trend slowly slows down, and the strain at the right arch foot is higher than the right arch waist and then higher than the left arch foot.

[0028] 5) Strain response analysis of each measuring point on the outside of section III under working condition 1 like Fig. 9 , the original strain curve and smoothed strain curve corresponding to each measuring point on the outside of section III of working condition 1 When the water level in the water conveyance tunnel is 0, the strains of the locations outside the tunnel section III except the right arch waist and the invert are all 0 and remain unchanged. The right arch waist begins to produce compressive strain from the 8th second and begins to increase. The rate of increase gradually slows down until it becomes stable. After the compressive stress appears at the invert from the 257th second, it fluctuates and then stabilizes at -1.01.

[0029] 6) Strain response analysis of each measuring point on the inner side of section III under working condition 1 like Fig.10 , the original strain curve and smoothed strain curve corresponding to each measuring point on the inner side of section III of working condition 1 When the water level in the water conveyance tunnel is 0, the strains at other locations on the inner side of tunnel section III except the right arch foot are all 0. Compressive strain begins to occur at the right arch foot from the 7th second, and the rate of increase gradually decreases until it tends to be a gentle fluctuation.

Claims

1. A test method suitable for simulating loading under a water diversion tunnel, characterized in that: The following steps are involved: Step 1. Design model parameters According to the size of the actual water conveyance tunnel and geological data, and based on the principles of geometric similarity ratio, density similarity ratio and elastic modulus similarity ratio, the size of the model box (1), geometric similarity scale, size of the tunnel model (2), surrounding rock material, burial depth of the tunnel model (2) and elastic modulus similarity ratio of the model test are determined; A tunnel model (2) is produced according to the determined parameters, wherein the tunnel model (2) includes three sections, namely a central section (201), a head section (202) and a tail section (203); Step 2: Fill the Model The left and right side plates of the model box (1) are respectively provided with holes, the positions of the holes are the installation positions of the tunnel model (2), the size of the holes is the same as the size of the tunnel model (2), one end of the hole is the water inlet end (204), and the other end is the water outlet end (205); the surrounding rock is filled in the model box (1), and the filling and compaction are carried out layer by layer; when the filling height reaches the opening position, the three sections of the tunnel model (2) are spliced ​​and installed at the opening position; at least three monitoring sections are set on the central section (201) of the tunnel model (2), and sensors are installed at the monitoring section positions while filling, and the sensors include strain gauge sensors, soil pressure sensors, pore water pressure and soil moisture sensors; after the model filling is completed, the head section (202) and the tail section (203) of the tunnel model (2) are extracted through the opening position of the model box (1), and the central section (201) is left in the model box (1); Step 3: Build the water delivery device The water delivery device comprises a water tank (4), the front end of the water tank (4) being provided with a water outlet, a gate valve (5) connected to the water outlet, the gate valve (5) being used to control the water outlet height; the front end of the gate valve (5) being connected with a guide cylinder of the same size as the tunnel model (2), the guide cylinder adjusting the shape of the water outlet end (205) of the gate valve (5) to the shape of the tunnel model (2), so as to facilitate the control of the water level height in the tunnel model (2); the water tank (4) being placed at the water inlet end (204), the front end of the guide cylinder being horizontally fixedly connected to the water inlet end (204) of the model box (1), the water in the water tank (4) passing through the gate valve (5) and the guide cylinder enters the tunnel model (2); a water receiving bucket is provided at the water outlet end (205) of the simulated tunnel; Step 4: Conduct a simulation test During the test, the influence of the rising water level in the water conveyance tunnel on the mechanical response characteristics of the tunnel structure was simulated. The water level rose by 1 cm each time from 0 cm, and rose by 3 cm in total, that is, 4 working conditions were set in total. At this time, the data acquisition interface was always observed, and the test records were kept; Step 5: Data Processing According to the data measured in the test, the strain time history curve is drawn, including the original strain curve and smooth strain curve corresponding to each measuring point, and then the strain change characteristics at each cross-section measuring point under each working condition are analyzed; It includes the maximum strain value and the tension and compression conditions of each point. The positive strain is defined as the tensile strain, which causes it to stretch, and the negative strain is defined as the compressive strain, which causes it to shorten. That is, the positive or negative value of the strain does not indicate its size. The relationship between strain and time is then curve-fitted to illustrate the law of strain change over time.

2. The test method for simulating loading under a water diversion tunnel according to claim 1 is characterized in that: Tempered glass is installed on the front and rear sides of the model box (1), and wooden boards are installed on the left and right sides of the model box (1), and holes are opened on the wooden boards; the bottom of the model box (1) is not blocked to facilitate water seepage.

3. The test method for simulating loading under a water diversion tunnel according to claim 1 is characterized in that: The invert of the tunnel model (2) is rectangular, and the dome is semi-dome-shaped.

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