A test method suitable for simulating loading of a water tunnel

Abstract

The application discloses a kind of test methods suitable for simulating loading of underpass water conveyance tunnel, including step 1. Design model parameters;Step 2: fill the model;Step 3: build water conveying device;Step 4: carry out simulation test. Can effectively simulate the influence of water level change on tunnel structure. According to the similarity relationship between the corresponding quantities of model test and actual engineering and its similarity ratio, the selection and proportioning of similar materials;Model box and structure model, including the size of model box, pouring of tunnel model, production of water conveyance tunnel model, and modification and installation of water tank and manual gate valve of water level control device;According to the research points, reasonably select the test section and test sensor, design four loading conditions combined with the actual engineering, and determine the loading water level and sequence;Layered ramming filling of model box and embedding of model and sensor.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of tunnel model test, and particularly relates to a test method suitable for simulating loading of a tunnel underpassing a water conveying tunnel. BACKGROUND

[0002] With the rapid development of railway construction, there are many tunnel projects that are close to each other in space and underpass or overpass existing structures. For a new tunnel underpassing an unlined water conveying tunnel, in construction and later operation, water in the water conveying tunnel will infiltrate into surrounding rock and the tunnel, resulting in a change in the stress state of the tunnel structure. The underpassing tunnel section may become a weak section, and when the water level rises, serious consequences may occur, such as the formation of a leakage channel or cracking of the tunnel lining. In addition, the tunnel underpassing the water conveying tunnel is surrounded by water, and once the water level rise in the water conveying tunnel causes cracks in the tunnel, the seepage will be affected under this action, thereby exacerbating the deformation and damage of the tunnel. Therefore, the water level change as a direct factor will cause deformation and damage of the tunnel, and the existence of the indirect factor of the crack caused by the water level rise will exacerbate the development of the deformation and damage.

[0003] Due to the restriction of various factors and objective conditions, the model test research on the tunnel structure under the water level change load has not made substantial breakthroughs, and the research on the mechanical response characteristics of the railway tunnel underpassing the water conveying tunnel is almost blank. The similar material simulation test can study the mechanical response characteristics of the tunnel structure under the water level change of the water conveying tunnel according to the actual geological data on site, artificially change the test conditions, select a spatial intersection section to carry out a model test of the mechanical response characteristics of the tunnel under the water level change, and analyze the change law of the tunnel monitoring surface strain, soil pressure, pore water pressure and water content with the water level rise. Therefore, an easy-to-operate, reliable-precision and reasonably-designed model test device is particularly important to achieve the above-mentioned goals. SUMMARY

[0004] The present application provides a test method suitable for simulating loading of a tunnel underpassing a water conveying tunnel, and aims to study the influence of the water level change on the water conveying tunnel through simulation test.

[0005] To this end, the present application adopts the following technical scheme:

[0006] A test method suitable for simulating loading of a tunnel underpassing a water conveying tunnel, comprising the following steps:

[0007] Step 1. Designing model parameters

[0008] According to the size and geological data of the actual water conveying tunnel, the model box size, geometric similarity scale, size of the tunnel model, surrounding rock material, buried depth of the tunnel model and elastic modulus similarity ratio of the model test are determined according to the principles of geometric similarity ratio, density similarity ratio and elastic modulus similarity ratio.

[0009] According to the determined parameters, the tunnel model is made, and the tunnel model includes three sections, namely, a center section, a head section and a tail section;

[0010] Step 2: filling the model

[0011] Holes are opened on the left and right side plates of the model box, and the hole positions are the installation positions of the tunnel model. The size of the hole 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 each layer is tamped. When the filling height reaches the hole position, the three sections of the tunnel model are spliced and installed at the hole position. At least three monitoring sections are provided on the center section of the tunnel model. Sensors are installed at the monitoring section positions while filling. The sensors include strain gauge sensors, soil pressure sensors, pore water pressure and soil moisture content sensors, acceleration sensors and dynamic strain gauge sensors.

[0012] After the model is filled, the head section and the tail section of the tunnel model are pulled out through the hole position of the model box, and the center section is left in the model box.

[0013] Step 3: building a water conveying device

[0014] The water conveying device includes a water tank. The front end of the water tank is provided with a water outlet. A plug valve is connected to the water outlet. The plug valve is used to control the water outlet height. A guide cylinder with the same size as the tunnel model is connected to the front section of the plug valve. The guide cylinder adjusts the shape of the water outlet end of the plug valve to the shape of the tunnel model, which facilitates the control of the water level in the tunnel model. The water tank is placed at the water inlet end. The front end of the guide cylinder is horizontally fixed to the water inlet end position of the model box. The water in the water tank enters the tunnel model through the plug valve and the guide cylinder. A water receiving bucket is provided at the water outlet end of the simulated tunnel.

[0015] Step 4: performing simulation test

[0016] During the test, the influence of the water level rise in the simulated water conveying tunnel on the mechanical response characteristics of the tunnel structure is simulated. The water level starts from 0 cm and rises by 1 cm each time, a total of 3 cm, i.e. a total of 4 working conditions are set. At this time, the data collection interface is observed at all times, and the test records are well kept.

[0017] Step 5: data processing

[0018] According to the data measured in the test, strain time history curves are drawn, including the original strain curves and the smoothed strain curves of each measuring point, and then the strain change characteristics of each section measuring point under each working condition are analyzed. The strain maximum value and the tension and compression conditions of each point are included. The positive strain is defined as the tensile strain, which makes the elongation. The negative strain is defined as the compressive strain, which makes the shortening. The positive and negative of the strain do not represent the size, and the curve fitting of the relationship between the strain and the time is carried out to illustrate the variation law of the strain with the time.

[0019] Further, the front and back sides of the model box are provided with tempered glass, and the left and right sides of the model box are provided with wood plates, and the wood plates are provided with holes.

[0020] Further, the inverted arch of the tunnel model is rectangular, and the arch top is semicircular.

[0021] The beneficial effects of the present application are:

[0022] 1. The influence of water level change on the tunnel structure can be effectively simulated. According to the similarity relationship and similarity ratio between the corresponding quantities of the model test and the actual engineering designed according to the geometric similarity ratio, the selection and proportioning of the similar materials; the model box and the structure model, including the size of the model box, the pouring of the tunnel model, the manufacturing of the water conveying tunnel model, and the modification and installation of the water tank and the manual plug valve of the water level control device;

[0023] 2. According to the research points, the test section and the test sensor are reasonably selected, 4 loading conditions are designed according to the actual engineering, the loading water level and the sequence are determined; the model box is layered and tamped, and the model and the sensor are buried. The design of the model test scheme is the basis of the test, and the rationality of the scheme is related to the accuracy and effectiveness of the test results;

[0024] 3. By digging out the hole of the straight wall structure on the water inlet wood plate, finally sticking the other side of the plug valve to the wood plate where the water inlet is located, the water tank opening, the plug valve opening and the wood plate water inlet are completely matched and stuck together. During the test, water flows out of the water tank, the water level is controlled by the plug valve, and then flows into the model box through the water inlet on the wood plate;

[0025] 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 conveying tunnel at any time. The device can be connected with a deformation and stress monitoring system, which can realize the real continuous deformation and stress state monitoring of the railway tunnel under the water conveying tunnel under the water level change factor condition, and provide reliable device and method for the large deformation mechanism problem research of the tunnel structure. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a layout schematic diagram of the model box of the present application;

[0027] Figure 2 is a schematic diagram of the tunnel model of the present application;

[0028] Figure 3 is a model filling assembly flowchart of the embodiment;

[0029] Figure 4 is a working condition loading flowchart of the embodiment;

[0030] Figure 5 is the original strain curve and the smoothed strain curve corresponding to each measuring point on the outside of section I under working condition 1;

[0031] Figure 6 is the original strain curve and the smoothed strain curve corresponding to each measuring point on the inside of section I under working condition 1;

[0032] Figure 7 is the original strain curve and the smoothed strain curve corresponding to each measuring point on the outside of section II under working condition 1;

[0033] Figure 8 is the original strain curve and the smoothed strain curve corresponding to each measuring point on the inside of section II under working condition 1;

[0034] Figure 9 is the original strain curve and the smoothed strain curve corresponding to each measuring point on the outside of section III under working condition 1;

[0035] Figure 10 is the original strain curve and the smoothed strain curve corresponding to each measuring point on the inside of section III under working condition 1;

[0036] In the figure: 1 - model box, 2 - tunnel model, 201 - center section, 202 - head section, 203 - tail section, 204 - water inlet end, 205 - water outlet end, 3 - water guide channel, 4 - water tank, 5 - plug valve. DETAILED DESCRIPTION

[0037] A test method suitable for simulating loading under a water conveying tunnel is provided, and the specific steps are as follows:

[0038] Step 1. Design model parameters

[0039] 1) Prototype engineering generalization

[0040] Tunnel prototype engineering refers to the process of creating prototypes or models during tunnel construction and design to simulate and test the design, structure, and construction methods of tunnels. By creating physical or digital models, non-essential factors that are not essential or have little relevance to the research purpose are excluded, and a model scheme with test operability and real objectivity is abstracted, and a reasonable conceptual model is established, and quantitative research is carried out through indoor test means. The geometry, structural strength and construction method of the tunnel can be evaluated to identify problems and optimize the design of the experiment. 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 appropriate response strategies to reduce construction risks.

[0041] 2) Test parameter determination

[0042] According to the generalization model obtained in 1), it is generally impossible for model test to be completely consistent with the engineering prototype due to the limitations of laboratory site, model box 1 size and load applied, so the general model test is basically a scale test. When designing the test, the first thing to determine is the similarity relationship between the engineering prototype and the test model. Today, many scholars use dimensional analysis method to determine the similarity ratio, but in the derivation process, all quantities must satisfy the same characteristic equation, which makes it impossible to achieve similar design for soil and structure. In addition, the remaining similarity ratios derived also need to meet the model similarity design, which is difficult to achieve in model test. In model test, three quantities that are relatively easy to determine are usually selected as control parameters, and other parameters that are not easy to determine are derived according to the relationship. According to the existing research, only important parameters are considered in the similarity design of this scheme, and some secondary parameters are ignored. In order to meet the test purpose, the geometric similarity ratio, density similarity ratio and elastic modulus similarity ratio are taken as the three basic similarity ratios. Considering that the model box 1 with a height of 2m is selected in the test, and the test section tunnel has a burial depth of 58.7m, the geometric similarity scale of this test is determined to be 1:50 according to the height of the model box 1 and the actual burial depth of the tunnel. Through the comparison of the existing materials in the test site and the materials of the tunnel surrounding rock and lining, the density similarity ratio is determined to be 1:1, and the elastic modulus similarity ratio is determined to be 1:50. Then, the similarity ratios of other quantities are determined by using dimensional analysis method and three similarity theorems. After calculation, the similarity ratios of various physical and mechanical parameters between the prototype and the model can be obtained.

[0043] 3) Similar material selection

[0044] According to the on-site engineering geological investigation report, the surrounding rock grade of the test section tunnel is grade IV. When selecting the surrounding rock material, the research on the similarity material ratio of grade IV surrounding rock by scholars is referred to, and the practicability and economy of the material are considered. Finally, the grade IV surrounding rock material ratio obtained through orthogonal ratio test is adopted, which includes soil, sand, heavy spar powder, gypsum, water, etc. Among them, the soil-sand ratio is 2:4, and the proportions of heavy spar powder, gypsum and water are 40%, 7% and 10% respectively. Since gypsum is used in the ratio of the material, 0.5% borax needs to be added to the water as a retarder.

[0045] 4) Sensor layout

[0046] According to the test purpose, strain gauges are used to monitor the deformation of the inside and outside of the tunnel model, soil pressure sensors are used to monitor the soil pressure on the lining, pore water pressure sensors are used to test the pore water pressure in the tunnel and surrounding rock, and moisture content sensors are used to test the moisture content in the surrounding rock of the tunnel.

[0047] a. Strain gage sensor

[0048] The strain gage used in the test was a resistance strain gauge, model BX120-20AA-P150-D, with a resistance of 120.0 ± 0.2 Ω and a sensitivity coefficient of 2.08 ± 1%. In the test, after the strain gage was pasted at the monitoring point with glue, a layer of silicone was applied for fixing and waterproofing. In addition, since the strain gage sensor has a certain temperature coefficient, in order to prevent the temperature change and the length of the wire from affecting the output of the strain signal, the strain gage was temperature compensated to reduce the error.

[0049] b. Soil pressure sensor

[0050] The soil pressure sensor used in the test was model JTM-Y2000, with a specification of 0.5, and an average sensitivity of 17.6, with the advantages of high precision, stable working performance, small size, light weight, waterproof and moisture-proof. In the test, the soil pressure sensor was placed at the specified monitoring point of the tunnel and fixed on the tunnel model with transparent tape.

[0051] c. Pore water pressure and soil moisture content sensor

[0052] The pore water pressure sensor used in the test was 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 content sensor mainly tests the moisture content in the surrounding rock of the tunnel.

[0053] Step 2: Filling the model

[0054] 1) Water conveyance tunnel model

[0055] The field water conveyance tunnel has a width of 2m and a height of 3m with a straight wall structure on the arch, with a buried depth of 39m. According to the geometric similarity ratio calculation, the tunnel model 2 has a width of 4cm and a height of 6cm. In the test, an aluminum alloy pipe with a rectangular cross-section of 4cm in width and 4cm in height was used as the lower half structure of the tunnel model 2, and a semi-circular PVC pipe with a cross-sectional diameter of 4cm was used as the upper half structure of the tunnel model 2. Then the two structures were tightly spliced together, and finally the upper and lower structures were firmly bonded together with strong glue and adhesive tape. The tunnel model 2 is 155cm long, and plastic real compaction is inserted into the inner cavity to enhance the hardness and bending resistance of the tunnel model 2. The tunnel model 2 includes three sections, namely the center section 201, the head section 202 and the tail section 203.

[0056] 2) Model box 1

[0057] According to the geometric similarity ratio, the size of the model box 1 is 1.5m x 1m x 2m (length x width x height) which matches the model test. The boundary of the model box 1 and the middle of the left and right vertical glass surfaces are limited by angle steel to prevent 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 conveying tunnel inlet and outlet are made of 2cm thick wood instead of glass, so as to open the water conveying tunnel inlet and outlet on the wood board. The upper and lower surfaces of the model box 1 are not installed with glass or wood board, especially the bottom surface, in order to prevent the water infiltrated into the bottom of the model box 1 from continuing to infiltrate in the opposite direction and interfering with the test. A hole with the same shape and size as the tunnel model 2 is drilled at a specified position of the 1.5m x 2m box surface, so that one end of the tunnel model is lapped on the wood board hole during 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 wood board, in terms of up and down, the hole is 19cm high, the hole arch distance from the box bottom is 40cm, and the hole arch top distance from the box top surface is 141cm.

[0058] Step 3: Build water conveying device

[0059] 1) Water tank 4 device

[0060] The water level control device mainly includes a water tank 4 and a manual plug valve 5. The size of the water tank 4 is 55cm x 35cm x 24cm, and a hole with the same structure as the cross section of the tunnel model 2 is drilled on the 35cm x 24cm surface, the distance from the hole bottom to the water tank 4 bottom is consistent with the distance from the plug valve 5 water inlet bottom edge to the plug valve 5 bottom. A round hole is drilled on the upper edge of the other 35cm x 24cm surface and a water faucet is installed to prevent the water in the water tank 4 from overflowing due to excessive water during the test, and it can also 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.

[0061] 2) Manual plug valve 5 device

[0062] The manual plug valve 5 has a width of 24 cm and a height of 55 cm, and the gate hole is a square hole with a size of 15 cm x 15 cm. The water flows out of the water tank 4 and then flows into the model tank 1 through the plug valve 5 to control the water level. Since the water inlet of the plug valve 5 is square, and the actual tunnel is a vault straight wall structure, the gate hole is modified. On a 15 cm x 15 cm plastic foam board, the same vault straight wall structure as the cross section of the tunnel model 2 is excavated, and then the remaining part is clamped in the clamping groove of the water inlet of the plug valve 5 gate hole. The foam board is firmly glued to the side wall of the plug valve 5 with strong glue. Then the perforated water tank 4 surface is glued to the plug valve 5 using strong waterproof glue, so that the hole on the water tank 4 and the water inlet of the plug valve 5 are completely matched and glued together. The foam board is the guide cylinder. In addition, the hole with the vault straight wall structure needs to be excavated on the water inlet wooden board. Finally, the other side of the plug valve 5 is glued to the wooden board of the water inlet, so that the water tank 4 hole, the plug valve 5 hole, and the wooden board water inlet are completely matched and glued together. During the test, the water flows out of the water tank 4, the water level is controlled by the plug valve 5, and then the water flows into the model tank 1 through the water inlet on the wooden board.

[0063] Step 4: Perform simulation test

[0064] 1) Measurement point layout

[0065] Three cross sections were selected as research surfaces in the 90 cm long center section 201 of the tunnel model 2. Cross section I is located directly below the intersection of the tunnel and the tunnel space. Cross sections II and III are 30 cm away from cross section I and are distributed on both sides of cross section I. Cross section II is close to the water inlet end 204, and cross section III is close to the water outlet end 205. The side of the tunnel model 2 close to the water inlet end 204 is the left side, and the side close to the water outlet end 205 is the right side. Sensors are arranged at key positions such as the vault, left and right haunches, left and right springers, and inverted arches in each cross section for monitoring. Among them, strain gauges and soil pressure sensors are arranged at the outside of each cross section, and strain gauges are also arranged at the inside of each cross section in the tunnel model 2. Pore water pressure and moisture content sensors are arranged at the outside of cross section I. In addition, pore water pressure and moisture content sensors are arranged at the center of the intersection of the tunnel and the tunnel, and a pore water pressure sensor is arranged at the inverted arch of the tunnel.

[0066] 2) Model filling

[0067] The material ratio of the tunnel surrounding rock material is prepared according to the similar ratio. First, the soil, sand, barite powder, gypsum, water and other materials are weighed according to the ratio, and then they are poured into the mixer and stirred with water. Since the mixed material has many large particles and uneven thickness, manual screening is performed again. Before filling the soil, the tunnel model opening is sealed with foam board to prevent the surrounding rock from entering the tunnel model. Then, the filling is performed by layer compaction, and the compaction is performed every 10 cm or so during the filling process to ensure that the density of each layer of surrounding rock is the same, thereby ensuring the same density. In addition, to avoid layering during each filling process, the next layer is filled after the first layer is compacted and then shaved. When the filling height reaches the tunnel invert position, the tunnel model is placed in the designated position, and the corresponding sensors are buried at each cross-section measurement point. After the burial is completed, the sensor line is combed. Then, continue to fill to the height of the water conveying tunnel, and the tunnel model 2 is connected to the wooden inlet and outlet of the water tunnel. Then, fill and compact until the design height is reached. The head section 202 and tail section 203 of the tunnel model 2 are slowly pulled out from the inlet 204 and outlet 205, and at this time, the surrounding rock presents a tunnel with an unlined arch straight wall structure;

[0068] 3) Experimental condition loading

[0069] During the test, the influence of water level rise in the water conveying tunnel on the mechanical response characteristics of the tunnel structure is simulated. The water level is raised by 1 cm each time from 0 cm, and a total of 3 cm, i.e. a total of 4 working conditions. At this time, the data collection interface is observed at all times, and the test record is completed.

[0070] Step 5: Data processing

[0071] According to the data measured in the test, the strain time history curve is drawn, including the original strain curve and the smoothed strain curve of each measurement point, and then the strain change characteristics of each cross-section measurement point under each working condition are analyzed, mainly the maximum strain and the tension and compression of each point. Here, 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, i.e. the positive and negative of the strain do not represent the size, and the relationship between strain and time is curve fitted to illustrate the variation law of strain with time.

[0072] Taking the strain response of the tunnel of working condition 1 as an example

[0073] 1) Analysis of strain response of each measurement point on the outside of cross-section I of working condition 1

[0074] As Figure 5 , the original strain curve and the smoothed strain curve of each measurement point on the outside of cross-section I of working condition 1

[0075] When the water level in the water diversion tunnel is 0, the strains at all locations outside the tunnel section I except the right arch foot are 0 and remain unchanged, while the strain at the right arch foot increases rapidly from the beginning. At about 10s, it begins to fluctuate slightly, then slowly rises and gradually stabilizes. The right arch foot is under tension during the whole process.

[0076] 2) Strain response analysis of each measuring point inside section I in working condition 1

[0077] like Figure 6 , the original strain curve and smoothed strain curve corresponding to each measuring point on the inner side of section I of working condition 1

[0078] When the water level in the water conveyance tunnel is zero, the strains at all locations inside the tunnel section I except the left arch foot are zero and remain unchanged. However, the initial strain at the left arch foot is zero. From the 12th second, compressive strain begins to occur and gradually increases. The overall growth rate gradually slows down and fluctuates within a local range.

[0079] 3) Strain response analysis of each measuring point on the outside of Section II under working condition 1

[0080] 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

[0081] When the water level in the water diversion tunnel is 0, the strains at all locations outside the tunnel section II except the left arch foot are 0 and remain unchanged. The initial strain at the left arch foot is also 0 until a tensile strain of 1.01 appears at 236 seconds and lasts until 292 seconds. From 293 seconds to the end, the strain at the left arch foot fluctuates between 1.01 and 2.01.

[0082] 4) Strain response analysis of each measuring point inside section II of working condition 1

[0083] like Figure 8 , the original strain curve and smoothed strain curve corresponding to each measuring point on the inner side of section II of working condition 1

[0084] At zero water level in the water diversion tunnel, the strains at the inner dome and left waist of tunnel section II remain zero. Compressive strains occur successively at the right arch foot, right arch waist, left arch foot, and inverted arch. The strain at the inverted arch is large and fluctuates within a small range after its onset. After the strains at the right arch foot, right arch waist, and left arch foot occur, the increasing trend gradually slows down. The strain at the right arch foot is higher than that at the right arch waist and then higher than that at the left arch foot.

[0085] 5) Strain response analysis of each measuring point on the outside of Section III under working condition 1

[0086] like Figure 9, the original strain curve and smoothed strain curve corresponding to each measuring point on the outside of section III of working condition 1

[0087] At zero water level in the water conveyance tunnel, strains at all locations outside tunnel section III, except the right haunch and invert, remained zero and stable. Compressive strain began to develop at the right haunch at 8 seconds and then began to increase, with the rate of increase gradually slowing until it stabilized. Compressive stress appeared at the invert at 257 seconds, fluctuated briefly, and then stabilized at -1.01.

[0088] 6) Strain response analysis of each measuring point on the inner side of Section III under working condition 1

[0089] like Figure 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

[0090] When the water level in the water conveyance tunnel is 0, the strains at all locations inside the tunnel section III except the right arch foot are 0. Compressive strain begins to appear 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 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 opened with holes, and the opening positions are the installation positions of the tunnel model (2). The opening size is the same as that of the tunnel model (2), and the opening at one end 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. 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), a front end of the water tank (4) is provided with a water outlet, a plug valve (5) connected to the water outlet, and the plug valve (5) is used to control the water outlet height; the front end of the plug valve (5) is connected to a guide cylinder of the same size as the tunnel model (2), and the guide cylinder adjusts the shape of the water outlet end (205) of the plug 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) is placed at the water inlet end (204), and the front end of the guide cylinder is horizontally fixedly connected to the water inlet end (204) of the model box (1), and the water in the water tank (4) enters the tunnel model (2) after passing through the plug valve (5) and the guide cylinder; a water receiving bucket is provided at the water outlet end (205) of the simulated tunnel; Step 4: Conduct a simulation test The test simulated the effect of rising water levels in the water conveyance tunnel on the mechanical response characteristics of the tunnel structure. The water level started at 0 cm and rose by 1 cm at a time, for a total of 3 cm, i.e., four different operating conditions were set. During this time, the data acquisition interface was constantly monitored and 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 smoothed 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. Positive strain is defined as tensile strain, which causes elongation, and negative strain as compressive strain, which causes shortening. That is, the positive or negative value of strain does not indicate its magnitude. Curve fitting is performed on the relationship between strain and time to illustrate the law of strain change over time.

2. The test method for simulating loading under a water tunnel according to claim 1, characterized in that: Tempered glass is installed on the front and back 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 tunnel according to claim 1, characterized in that: The inverted arch of the tunnel model (2) is rectangular, and the dome is semi-dome-shaped.

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