Experimental device for controlling upward floating of duct piece in water-rich hard rock stratum and optimization method of experimental device

Abstract

The invention discloses an experimental device for controlling duct piece floating in a water-rich hard rock stratum, which comprises a model test box, a tunnel model and a data acquisition system, a rock-soil body is arranged in the model test box, the tunnel model is surrounded by the rock-soil body, and an outer pipe of the tunnel model simulates a boundary interface between a hard rock stratum in the rock-soil body and the outer edge of a gap. The inner pipe simulates a shield segment, an air bag or slurry is arranged in a gap between the outer pipe and the inner pipe, and the data acquisition system is connected with the model test box. When the air bags are arranged in the gaps, the size of air pressure in the air bags at different positions is adjusted to simulate dilution of the slurry influenced by underground water and injection of the high-elasticity-modulus slurry; when no air bag exists in the gap, common grout is injected, and the real grouting condition is simulated. According to the optimization method, multiple experiments are carried out through the experimental device to simulate different conditions such as increase of the elasticity modulus of slurry, influence parameters for controlling floating of the duct piece are confirmed, mutual verification can be carried out according to theoretical data, and the influence parameters are optimized.

Description

Technical Field

[0001] The invention belongs to the technical field of underground engineering construction, and in particular relates to an experimental device for controlling the floating of a pipe segment in a water-rich hard rock formation and an optimization method thereof. Background Art

[0002] In the past decade, in order to ease traffic pressure and expand the habitable area of ​​the city, rail transit has become the best solution for urban transportation due to its advantages of large capacity, low pollution and fast pace. my country's geology is complex and changeable, and there are significant differences between different regions. The floating phenomenon of the shield segment during the construction process under different geological conditions frequently occurs. The existing research on the floating problem of the segment is mainly focused on the construction environment of soft soil layers. Due to its weak self-stabilizing ability, after the segment is separated from the shield tail, the soil will immediately move to the segment until the gap at the shield tail is eliminated. The rock properties of hard rock formations are relatively hard. When the shield is excavated in this type of formation, after the segment is separated from the shield tail, the surrounding rock mass can remain self-stabilized for a certain period of time, and the gap between the segment and the surrounding rock mass can be in a stable state. At this time, if the synchronous grouting can completely fill the gap, the deadweight load of the overlying stratum can be considered not to act directly on the segment, and there is space for the segment to float. The main type of groundwater in this stratum is bedrock fissure water, which is generally connected with surface water and stratum pore water, and they replenish each other. There will be large amounts of groundwater gushing out from the excavation surface and surrounding rock.

[0003] The factors affecting the flotation of pipe segments in water-rich hard rock formations are particular. Therefore, there are relatively few studies on the law of slurry buoyancy changes and the flotation mechanism of pipe segments in water-rich hard rock, and there is a lack of theoretical basis, which restricts the proposal of flotation control methods and is a scientific problem that needs to be solved urgently. The research on flotation control methods for pipe segments in water-rich hard rock formations is in the exploratory stage, and the mechanism of action of the control method has not been accurately revealed, so that the flotation of pipe segments cannot be effectively prevented and controlled, which is a problem that needs to be solved urgently in engineering. Summary of the invention

[0004] The present invention is an experimental device and optimization method for segment flotation designed for water-rich hard rock formations. It can not only effectively simulate and monitor the flotation of the segment in the formation, derive the flotation law based on the theoretical flotation value, but also further verify the effect of the designed segment control method.

[0005] The invention discloses an experimental device for controlling the floating of a pipe segment in a water-rich hard rock stratum, comprising a model test box, a tunnel model and a data acquisition system. The inner walls on both sides of the model test box are provided with mounting holes which are arranged opposite to and penetrate through the inner walls. The tunnel model is installed in the mounting holes. A rock and soil body is arranged in the model test box, and the rock and soil body surrounds the tunnel model. The tunnel model comprises an outer tube and an inner tube. The outer tube simulates the boundary interface between the hard rock stratum in the rock and soil body and the outer edge of the gap. The inner tube simulates the pipe segment. An air bag or slurry is arranged in the gap between the outer tube and the inner tube. The data acquisition system is connected to the model test box.

[0006] The experimental device is designed based on the characteristics of hard rock being impermeable and having a certain degree of self-stability after excavation. The outer tube and the inner tube are both impermeable materials with a certain strength. The outer tube forms a stable outer edge of the gap, and a stable gap can be formed between the outer tube and the inner tube to simulate the gap between the pipe segment and the hard rock formation. The combination of the outer tube and the soil simulates hard rock. When the gap is equipped with air bags, the air pressure in the air bags at different positions is adjusted to simulate the dilution of the slurry affected by groundwater and the injection of high elastic modulus slurry; when there is no air bag in the gap, ordinary slurry is injected to simulate the real grouting situation.

[0007] Furthermore, longitudinal and transverse grooves are made on the surface of the inner tube. The longitudinal grooves divide the inner tube into several inner tube rings. Every two adjacent inner tube rings are surrounded by an air bag. A single air bag includes an upper air bag and a lower air bag. The upper air bag and the lower air bag wrap the inner tube. The air bags are marked as the first, second, ..., nth in the reverse direction of tunnel excavation.

[0008] The grooves on the inner tube surface simulate the longitudinal and transverse seams of the segment joints. The airbag is composed of an upper airbag and a lower airbag, and the air pressure of the upper airbag and the lower airbag can be adjusted to simulate the floating of the segment. The airbag is composed of multiple airbags, and different situations such as slurry dilution and changing the grouting elastic modulus can be simulated by adjusting the air pressure of different airbags or injecting high elastic modulus slurry into the airbag.

[0009] The outer tube can be a metal tube, preferably steel, and the inner tube can be a plastic tube, preferably a PE tube.

[0010] Furthermore, the inner tube is provided with an inner tube reserved hole, the air pipe is connected to the air bag through the inner tube reserved hole, the air pipe is connected to the air pressure control device, the air pressure control device includes a pressure gauge, a valve and an air compressor, and the water pipe is connected to the water tank through the inner tube reserved hole to make the gap.

[0011] The reserved hole in the inner tube can not only be connected to the air pressure control device, but also to the water tank, and different things can be injected according to different simulation situations. The air compressor and the valve are opened, and the air compressor presses high-pressure air into the air bag, and the air pressure gauge monitors the air bag pressure in real time. The air pressure gauge, valve, air pipe and air compressor can be common models on the market.

[0012] Furthermore, the outer tube is provided with an outer tube reserved hole, and the data acquisition system includes a pore pressure gauge, a laser displacement meter and a data acquisition instrument. The data acquisition instrument is located outside the model test box, the pore pressure gauge is installed in the outer tube reserved hole, a long rod is provided in the inner tube, the laser displacement meter is fixed on the long rod, and the pore pressure gauge and the laser displacement meter are connected to the data acquisition instrument.

[0013] The pore pressure gauge detects the pressure change in the gap between the outer tube and the inner tube, the laser displacement meter detects the displacement data of the inner tube, and the data acquisition instrument collects the data of the pore pressure gauge and the laser displacement meter. The pore pressure gauge, the laser displacement meter and the data acquisition instrument can be common models on the market.

[0014] An optimization method for controlling the flotation of a pipe segment in a water-rich hard rock formation comprises the following steps:

[0015] 1 Assemble the experimental device, surround the tunnel model with the air bag and put it into the model experimental box;

[0016] 2. Use the experimental device to simulate the displacement of the pipe segments after real grouting, slurry dilution and the set control pipe segment floating method, and record the experimental data of the inner pipe floating;

[0017] 3. Make assumptions about the tunnel environment and calculate the theoretical data of the segment floating after using the set control segment floating method;

[0018] 4. Compare the experimental data obtained in step 2 with the theoretical data obtained in step 3, determine the influencing parameters of the control method and optimize them, and repeat step 2 and / or step 3 until the optimal influencing parameters are obtained.

[0019] The experimental device is used to simulate the inner tube floating situation under different conditions and verify the theoretical data, determine the influencing parameters of the segment floating and optimize them, and obtain the optimal method to control the segment floating.

[0020] Preferably, in step 2, a method for controlling the floating of the pipe segment based on changing the elastic modulus of grouting is set, and the specific experimental steps are as follows:

[0021] 2.1 Control the air pressure of all airbags to be the same, so that the inner tube is in a uniform air pressure wrapped state, and keep the inner tube in a horizontal state, simulating the buoyancy force on the actual tube segment, and the laser displacement meter reads the initial value of the inner tube position;

[0022] 2.2 Keep the air pressure of the first airbag unchanged, select and increase the elastic modulus of one or more airbags from the second to the nth airbags, and make the air pressure of the other airbags consistent with that of the first ring airbag. Determine the value of the inner tube position at this time by using a laser displacement meter;

[0023] 2.3 Adjust the air pressure of other airbags except the airbag with increased elastic modulus to simulate the phenomenon of slurry being diluted by groundwater, record the reading of the laser displacement meter at this time, monitor the displacement of the inner tube at this time, and compare it with the initial value to obtain the floating amount at this time;

[0024] 2.4 Except for the first airbag and the airbag with increased elastic modulus, adjust the pressure difference of other airbags, record the reading of the laser displacement meter, and monitor the displacement of the inner tube at this time.

[0025] The method is based on changing the elastic modulus of grouting. By increasing the elastic modulus of the selected airbag to simulate increasing the elastic modulus of grouting at a certain point of the pipe segment, the buoyancy of the experimental inner pipe is obtained.

[0026] Preferably, in step 2.2, increasing the elastic modulus of one or more airbags from the second to the nth airbags includes the following two methods:

[0027] a. Using an air pressure control device, inject air into the selected airbag to increase the elastic modulus by increasing the air pressure of the airbag;

[0028] b. By injecting quick-setting, high-strength slurry including water glass slurry, cement slurry, and cement-water glass slurry into the air bag, the elastic modulus of the air bag is rapidly increased.

[0029] Preferably, in step 3, a method for controlling the floating of the pipe segment based on changing the elastic modulus of grouting is set, and the specific theoretical calculation steps are as follows:

[0030] 3.1 Assuming that the tunnel is equivalent to a homogeneous ring, the ring stiffness takes into account the effects of longitudinal joint bolts and annular gaps, and the elastic foundation beam model is used to simulate the interaction between the tunnel and the slurry and surrounding rock formations;

[0031] 3.2 Theoretically, the buoyancy formula is:

[0032]

[0033] where Y i is the buoyancy, i is the beam segment number, α i is the elastic characteristic coefficient of the inner tube, x is the position where the buoyancy acts on the inner tube, A i is the general solution coefficient, q i (x) is the floating load, k i is the vertical foundation coefficient, b is the length of the tunnel cross section under the foundation reaction force, and EI is the bending strength of the inner tube;

[0034] 3.3 Substitute the experimental parameters in step 2 into the buoyancy formula and calculate the theoretical buoyancy.

[0035] An optimization method for controlling the flotation of a pipe segment in a water-rich hard rock formation comprises the following steps:

[0036] 1 Assemble the experimental device, surround the tunnel model with the air bag and put it into the model experimental box;

[0037] 2. Control the air pressure of all airbags to be the same, so that the inner tube is in a uniform air pressure wrapped state, and keep the inner tube in a horizontal state, and the laser displacement meter reads the initial value of the inner tube position;

[0038] 3. The pressure in the airbag is controlled by the air pressure control device, and the pressure of one of the second to nth airbags until the last airbag is adjusted to simulate the distance between the diluted synchronous grouting and the shield machine casing just separated in the actual project, and the displacement of the inner tube under different conditions is measured by the laser displacement meter;

[0039] 4. Select different ways of reducing the airbag pressure to simulate the law of slurry dilution in actual engineering, and measure the displacement of the inner tube under different conditions by using a laser displacement meter;

[0040] 5. Change the pressure difference between the upper and lower airbags in the airbag to simulate the buoyancy of the actual tube segment, and measure the displacement of the inner tube under different conditions by a laser displacement meter;

[0041] 6. Analyze the inner tube displacement data obtained in the above steps, determine the influencing parameters of the control method and optimize them, and repeat steps 2 to 5 until the optimal influencing parameters are obtained.

[0042] The air pressure values ​​of the second to the nth airbags are controlled to be equal to the last one to simulate the stable state from the ring to the last ring of the segment. By controlling the distance between the ring and the segment just separated from the shield machine shell, the length of the air pressure airbag is reduced, thereby simulating the length of slurry dilution.

[0043] The airbag pressure reduction modes include uniform reduction and linear reduction.

[0044] By adjusting the air pressure of the airbags at different positions, the following three possible influencing parameters are simulated:

[0045] 1. The air pressure reduces the length of the airbag to simulate the length of the diluted slurry;

[0046] 2. The degree of reduction in air pressure simulates the degree of dilution of the slurry;

[0047] 3. What function does the way in which air pressure is reduced conform to? What is the impact of the dilution function of the diluted slurry in the horizontal direction on the buoyancy of the pipe segment?

[0048] The experiment was repeated several times to determine the parameters that affect the buoyancy of the segment.

[0049] An optimization method for controlling the flotation of a pipe segment in a water-rich hard rock formation, simulating real grouting, comprises the following steps:

[0050] 1 Assemble the experimental device, surround the tunnel model with the air bag and put it into the model experimental box;

[0051] 2. Do not install the airbag in the gap between the outer tube and the inner tube, and seal the holes on the outer tube and the inner tube with plugging bolts;

[0052] 3. Install a pore pressure gauge and connect it to the data acquisition equipment to monitor the air pressure changes in the gap between the outer tube and the inner tube to determine the injection status of the slurry and the changes in the pore pressure in the slurry after the slurry is injected;

[0053] 4 Two water tanks are set up on both sides of the tunnel model. The water tanks are connected to the gap between the outer pipe and the inner pipe through pipes and water pumps. The interface on the inner pipe connected to the water tank is selected according to the proposed slurry dilution position. The change of the water head difference is achieved by adjusting the height of the water tank on one side;

[0054] 5. Install the grouting pipe in the reserved hole of the inner tube, connect the grouting pipe to the grouting equipment for grouting, and monitor the grouting situation through the changes of the pore pressure gauge. After the grouting is completed, turn on the water pump, and water enters the gap from the water tank to dilute the slurry. During this process, monitor the changes in the readings of the pore pressure gauge and laser displacement meter;

[0055] 6. Analyze the inner tube displacement data obtained in the above steps, determine the influencing parameters of the control method and optimize them, and repeat steps 2 to 5 until the optimal influencing parameters are obtained.

[0056] By injecting slurry and water into the gaps, the injection of shield synchronous grouting in actual engineering is simulated, that is, the engineering situation when the shield synchronous grouting is injected behind the segment under a certain flow rate and water pressure is simulated, so that the dilution effect of water pressure and water flow on the synchronous grouting and the influence law on the buoyancy of the segment can be clarified.

[0057] Due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0058] The experimental device simulates hard rock through a combination of an outer tube and soil, and uses the diameter difference between the inner and outer tubes to simulate the gap between the pipe segment and the surrounding rock. When an air bag is provided in the gap, the air pressure in the air bag at different positions is adjusted to simulate the dilution of the slurry due to the influence of groundwater and the injection of high elastic modulus slurry. When there is no air bag in the gap, ordinary slurry is injected to simulate the real grouting situation.

[0059] The airbag is composed of an upper airbag and a lower airbag, and the air pressure of the upper airbag and the lower airbag can be adjusted respectively to simulate the floating of the pipe segment. The airbag is composed of multiple airbags, and the air pressure of different airbags can be adjusted to simulate different situations, such as increasing the elastic modulus of the slurry.

[0060] The experimental device can be used to determine and optimize the parameters that influence the buoyancy of the pipe segments through various optimization methods:

[0061] 1. Through the experimental device, the inner tube floating conditions under different conditions are simulated and verified with the theoretical data, the influencing parameters of the segment floating are determined and optimized, and the optimal method for controlling the segment floating is obtained.

[0062] 2. Conduct multiple experiments using the experimental device to determine and optimize the parameters that affect the floating of the pipe segments, and obtain the best method to control the floating of the pipe segments. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The present invention will be further described below by means of the accompanying drawings.

[0064] Figure 1 This is a schematic structural diagram of an experimental device for controlling the flotation of a pipe segment in a water-rich hard rock formation in Example 1.

[0065] Figure 2 This is a schematic structural diagram of an experimental device for controlling the flotation of a pipe segment in a water-rich hard rock formation in Example 2.

[0066] Figure 3 This is a schematic structural diagram of an experimental device for controlling the flotation of a pipe segment in a water-rich hard rock formation in Example 3.

[0067] Figure 4 This is a schematic diagram of the tunnel model.

[0068] Figure 5 Schematic diagram of the structure of the airbag.

[0069] Figure 6 This is an analysis diagram of the tunnel model in Example 1. DETAILED DESCRIPTION

[0070] like Figure 1 and Figure 2 The experimental device for controlling the floating of pipe segments in water-rich hard rock formations shown in the figure comprises a model test box 1, a tunnel model and a data acquisition system. The inner wall of the model test box 1 is provided with mounting holes 2 which are arranged opposite to each other and penetrate the inner wall, the tunnel model is installed in the mounting holes 2, and a rock and soil body 3 is provided in the model test box 1, and the rock and soil body 3 surrounds the tunnel model.

[0071] The model test box 1 is a cube, made of steel frame and acrylic board. The tunnel model includes a steel outer tube 4 and a PE inner tube 5. The inner tube 5 simulates the pipe segment, which is intended to be set as 16 rings. The longitudinal and transverse grooves 6 are cut on the surface to simulate the joints of the pipe segment. Figure 4 shown.

[0072] It is assumed that an air bag 7 is installed on every two rings of the inner tube 5, and an air bag 7 includes an upper air bag 71 and a lower air bag 72. Figure 5As shown. The upper airbag 71 and the lower airbag 72 wrap the inner tube 5, and each two adjacent inner tubes 5 are surrounded by an airbag 7. The inner tubes 5 are marked as the first ring, the second ring, ... the eighth ring in the reverse direction of tunnel excavation, and a total of 8 groups of airbags 7 are provided. The inner tube 5 has 16 inner tube reserved holes reserved for the airbag inflation work during the test, and the outer tube has 3 outer tube reserved holes 14 reserved for the later installation of the borehole pressure gauge 8. The inner tube 5 and the outer tube 4 are sealed at both ends by a sealing ring 18.

[0073] The data acquisition system includes a pore pressure gauge 8, a laser displacement meter 9 and a data acquisition instrument 10. The data acquisition instrument 10 is located outside the model test box 1. The pore pressure gauge 8 is installed in the reserved hole 14 of the outer tube. A long rod 11 is provided in the inner tube 5. The laser displacement meter 9 is fixed to the long rod 11. The pore pressure gauge 8 and the laser displacement meter 9 are connected to the data acquisition instrument 10.

[0074] In the following embodiments, there are a total of 16 inner tube rings and 8 air bags are used.

[0075] Example 1

[0076] An optimization method for controlling the flotation of a pipe segment in a water-rich hard rock formation, simulating the change of the elastic modulus of grouting, comprises the following steps:

[0077] 1Assemble as Figure 1 The experimental device shown is a tunnel model surrounded by an air bag and placed in a model test box.

[0078] 2 Use the experimental device to simulate the displacement of the pipe segment after using the set control pipe segment floating method, and record the experimental data of the inner pipe floating. The specific steps are as follows:

[0079] 2.1 Use an air pressure control device, which includes a pressure gauge 15, a valve 23, an air pipe 16 and an air compressor 17, to control the air pressure of all air bags 7 to be at the same air pressure of 50 kPa, so that the inner tube 5 is in a uniform air pressure wrapping state and keeps the inner tube 5 in a horizontal state, simulating the buoyancy of the actual segment, and the laser displacement meter 9 reads the initial value of the position of the inner tube 5.

[0080] 2.2 Keep the air pressure of the first airbag 7 unchanged, select the third airbag 7A, open the valve 23 corresponding to the airbag 7A, and inject air into the selected airbag 7A through the trachea 16. By increasing the air pressure of the airbag 7A, its elastic modulus increases from 1 kPa to 20 kPa. The air pressure of other airbags 7 is consistent with that of the first airbag 7. The value of the position of the inner tube 5 at this time is determined by the laser displacement meter 9.

[0081] 2.3 Adjust the air pressure of the other airbags 7 except the third airbag 7A to reduce by 5 kPa, simulate the phenomenon of slurry being diluted by groundwater, record the reading of the laser displacement meter 9 at this time, monitor the floating condition of the inner tube 5 at this time, and compare it with the initial value to obtain the floating amount Y at this time i .

[0082] 2.4 Except for the first airbag 7 and the fourth airbag 7, adjust the pressure difference between the upper airbag 71 and the lower airbag 72 of other airbags 7 to 10 kPa, record the reading of the laser displacement meter 9, and monitor the floating condition of the inner tube 5 at this time.

[0083] 3. Assume the tunnel environment and calculate the theoretical data of the segment floating after using the set control segment floating method. The specific calculation method is as follows:

[0084] 3.1 Assuming that the tunnel is equivalent to a homogeneous ring, the ring stiffness takes into account the effects of longitudinal joint bolts and annular gaps, and the elastic foundation beam model is used to simulate the interaction between the tunnel and the slurry and surrounding rock formations;

[0085] 3.2 Theoretically, the buoyancy formula is:

[0086]

[0087] where Y i is the buoyancy, i is the beam segment number, α i is the elastic characteristic coefficient of the inner tube, x is the position where the buoyancy acts on the inner tube, A i1 , A i2 , A i3 , A i4 are general solution coefficients, q i (x) is the floating load, k i is the vertical base coefficient of the foundation, b is the length of the tunnel cross section caused by the foundation reaction force, and EI is the bending strength of the inner tube.

[0088] 3.3 Set the parameters i, α of the experimental device in step 2 i ,x,A i1 , A i2 , A i3 , A i4 ,q i (x), k i , b, EI actual value is substituted into the floating amount formula to obtain the theoretical floating amount Y i .

[0089] like Figure 6 As shown in the figure, when the deflection of the beam is known, the rotation angle θ of any interface of the beam is i , bending moment M i , shear force Q i It can be calculated according to the material mechanics formula, namely:

[0090]

[0091] The third airbag 7A increases the air pressure to simulate the actual injection of water glass outside the third segment, and the remaining segments are not grouted. It is assumed that the floating load is a uniformly distributed load.

[0092] q i (x) = d (6)

[0093] i is the beam segment number; when i = 1, d = p; when i = 2, d = 0. p is the buoyancy per unit width of the segment.

[0094] The boundary conditions on the left side of the model are

[0095] Q 1,x＝0 =Q0=0 (7)

[0096] At x = l1, the coordination equations of the deformation y, rotation angle θ, bending moment M, and shear force Q of the elastic foundation beam should be satisfied, that is,

[0097]

[0098] At x = l1 + l2 = l a The coordination equations of deformation, rotation, bending moment and shear force of the elastic foundation beam should be satisfied at

[0099]

[0100] The boundary conditions on the right side of the model are

[0101] y 4,x→+∞ =0 (14)

[0102] Model Solution

[0103] Calculate the 1st, 2nd, and 3rd order derivatives of formula (1) respectively:

[0104]

[0105] Where C = cos(α i x)-sin(α i x), D = cos(α i x)+sin(α i x).

[0106] Substituting equation (14) into equation (1), we can obtain the two coefficients A in the general solution: 41 =A 42 = 0, then combine equations (3) to (6) and (7) to (17) to obtain the remaining 14 coefficients A in the general solution. 11 , A 12 , A 13 , A 14, A 21 , A 22 , A 23 , A 24 , A 31 , A 32 , A 33 , A 34 , A 43 , A 44 .

[0107] Substituting the 16 coefficients into (1) and equations (15) to (17), we can obtain the floating load q i (x) is the floating amount Y of the beam in the tunnel i under the model state. i .

[0108] 4 Compare the experimental data obtained in step 2 with the theoretical data obtained in step 3, change the parameters and repeat steps 2 and 3 again, determine the elastic modulus of grouting as the influencing parameter, change the elastic modulus of cement slurry and repeat steps 2 and 3 until the floating amount is 0, and confirm the optimal elastic modulus.

[0109] Example 2

[0110] An optimization method for controlling the flotation of segments in water-rich hard rock formations, simulating slurry dilution, the specific steps are as follows:

[0111] 1 Modify the experimental apparatus in Example 1 as follows Figure 2 .

[0112] The air pressure of all airbags 7 is controlled to be the same at 50 kPa, so that the inner tube 5 is in a uniform air pressure wrapped state and the inner tube 5 is kept in a horizontal state. The laser displacement meter 9 reads the initial value of the position of the inner tube 5.

[0113] The pressure in the airbag is controlled by the air pressure control device, which includes a pressure gauge 15, a valve 23, an air pipe 16 and an air compressor 17. The pressure of the second to the eighth of the airbags 7 is adjusted to 30 kPa to simulate the distance between the diluted synchronous grouting and the shield machine casing just separated in the actual project. Then, the pressure of all the airbags 7 is uniformly reduced to simulate the law of slurry dilution in the actual project. The reduction speed is 1 kPa / min. At the same time, the displacement of the inner tube under different conditions is measured by the laser displacement meter 9.

[0114] The pressure difference between the upper airbag 71 and the lower airbag 72 of the second to eighth airbags 7 is adjusted to 10 kPa to simulate the buoyancy force on the actual tube segment, and the buoyancy of the inner tube 5 is measured by the laser displacement meter 9.

[0115] Change the following parameters and repeat the experiment to confirm and optimize the influencing parameters during slurry dilution.

[0116] 1. Air pressure reduces the length of the airbag to simulate the length of the diluted slurry.

[0117] 2. The degree of reduction in air pressure simulates the degree of dilution of the slurry.

[0118] 3. What function does the way in which air pressure is reduced conform to? What is the impact of the dilution function of the diluted slurry in the horizontal direction on the buoyancy of the pipe segment?

[0119] Example 3

[0120] An optimization method for controlling the flotation of a pipe segment in a water-rich hard rock formation, simulating real grouting, comprises the following steps:

[0121] 1 Modify the experimental apparatus in Example 1 as follows Figure 3 .

[0122] The gap 19 between the outer tube 4 and the inner tube 5 is not provided with an air bag, and the reserved hole of the inner tube is sealed with a plugging bolt 21.

[0123] A pore pressure gauge 8 is installed in the reserved hole 14 of the outer tube and connected to a data acquisition device to monitor the air pressure change in the gap between the outer tube 4 and the inner tube 5, so as to determine the injection status of the slurry and the change of the pore pressure in the slurry after the slurry is injected.

[0124] Two water tanks 12 are arranged on both sides of the tunnel model. The water tanks 12 are connected to the gap 19 between the outer tube 4 and the inner tube 5 through the pipeline 24 and the water pump 25. The interface on the inner tube 5 connected to the water tank 12 is selected according to the proposed slurry dilution position. The water head difference can be changed from 5 cm to 20 cm by adjusting the height of the water tank 12 on the right side.

[0125] The reserved hole of the inner tube is used to install the grouting pipe 13, which is connected to the grouting equipment 22 for grouting. The grouting condition is monitored by the change of the pore pressure gauge 8. After the grouting is completed, the water pump 25 is turned on, and water enters the gap 19 from the water tank 12 to dilute the slurry. During this process, the reading changes of the pore pressure gauge 8 and the laser displacement meter 9 are monitored.

[0126] 6. Analyze the inner tube displacement data obtained in the above steps, change the water pressure and water flow, determine the water pressure and water flow as influencing parameters and optimize them, and repeat steps 2 to 5 until the optimal influencing parameters are obtained.

[0127] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent replacements or modifications made based on the present invention to solve basically the same technical problems and achieve basically the same technical effects are all included in the protection scope of the present invention.

Claims

1. An experimental device for controlling the flotation of a pipe segment in a water-rich hard rock formation, characterized in that: The invention comprises a model test box, a tunnel model and a data acquisition system. The inner walls on both sides of the model test box are provided with mounting holes which are arranged opposite to each other and penetrate through the model test box. The tunnel model is installed in the mounting holes. A rock and soil body is arranged in the model test box. The rock and soil body surrounds the tunnel model. The tunnel model comprises an outer tube and an inner tube. The outer tube simulates the boundary interface between the hard rock layer in the rock and soil body and the outer edge of the gap. The inner tube simulates the pipe segment. An air bag or slurry is arranged in the gap between the outer tube and the inner tube. The data acquisition system is connected to the model test box.

2. The experimental device for controlling the floating of pipe segments in water-rich hard rock formations according to claim 2, characterized in that: The inner tube surface is grooved longitudinally and transversely, the longitudinal grooves divide the inner tube into a plurality of inner tube rings, every two adjacent inner tube rings are surrounded by an airbag, a single airbag comprises an upper airbag and a lower airbag, the upper airbag and the lower airbag wrap the inner tube, and the airbags are sequentially recorded as the first, second, ..., nth in the direction opposite to the tunnel excavation direction.

3. The experimental device for controlling the floating of pipe segments in water-rich hard rock formations according to claim 1, characterized in that: The inner tube is provided with an inner tube reserved hole, the air pipe is connected to the air bag through the inner tube reserved hole, the air pipe is connected to the air pressure control device, the air pressure control device includes a pressure gauge, a valve and an air compressor, and the water pipe passes through the inner tube reserved hole to connect the gap with the water tank.

4. The experimental device for controlling the floating of pipe segments in water-rich hard rock formations according to claim 1, characterized in that: The outer tube is provided with an outer tube reserved hole, and the data acquisition system includes a pore pressure gauge, a laser displacement meter and a data acquisition instrument. The data acquisition instrument is located outside the model test box, the pore pressure gauge is installed in the outer tube reserved hole, a long rod is provided in the inner tube, the laser displacement meter is fixed to the long rod, and the pore pressure gauge and the laser displacement meter are connected to the data acquisition instrument.

5. An optimization method for controlling the flotation of a pipe segment in a water-rich hard rock formation using the experimental device according to any one of claims 1 to 4, characterized in that: The steps include: 1 Assemble the experimental device, surround the tunnel model with the air bag and put it into the model experimental box; 2. Use the experimental device to simulate the displacement of the pipe segment after using the set control pipe segment floating method, and record the experimental data of the inner pipe floating; 3. Make assumptions about the tunnel environment and calculate the theoretical data of the segment floating after using the set control segment floating method; 4. Compare the experimental data obtained in step 2 with the theoretical data obtained in step 3, determine the influencing parameters of the control method and optimize them, and repeat step 2 and / or step 3 until the optimal influencing parameters are obtained.

6. The optimization method for controlling the flotation of a pipe segment in a water-rich hard rock formation according to claim 5, characterized in that: In step 2, a method for controlling the floating of the segment based on changing the elastic modulus of grouting is set. The specific experimental steps are as follows: 2.1 Control the air pressure of all airbags to be the same, so that the inner tube is in a uniform air pressure wrapped state, and keep the inner tube in a horizontal state, simulating the buoyancy force on the actual tube segment, and the laser displacement meter reads the initial value of the inner tube position; 2.2 Keep the air pressure of the first airbag unchanged, select and increase the elastic modulus of one or more airbags from the second to the nth airbags, and make the air pressure of the other airbags consistent with that of the first ring airbag. Determine the value of the inner tube position at this time by using a laser displacement meter; 2.3 Adjust the air pressure of other airbags except the airbag with increased elastic modulus to simulate the phenomenon of slurry being diluted by groundwater, record the reading of the laser displacement meter at this time, monitor the displacement of the inner tube at this time, and compare it with the initial value to obtain the floating amount at this time; 2.4 Except for the first airbag and the airbag with increased elastic modulus, adjust the pressure difference of other airbags, record the reading of the laser displacement meter, and monitor the displacement of the inner tube at this time.

7. The experimental method for controlling the flotation of a pipe segment in a water-rich hard rock formation according to claim 6, characterized in that: In step 2.2, increasing the elastic modulus of one or more airbags from the second to the nth airbags includes the following two methods: a. Using an air pressure control device, inject air into the selected airbag to increase the elastic modulus by increasing the air pressure of the airbag; b. By injecting quick-setting, high-strength slurry including water glass slurry, cement slurry, and cement-water glass slurry into the air bag, the elastic modulus of the air bag is rapidly increased.

8. The optimization method for controlling the flotation of a pipe segment in a water-rich hard rock formation according to claim 5, characterized in that: In step 3, a method for controlling the floating of the segment based on changing the elastic modulus of grouting is set. The specific theoretical calculation steps are as follows: 3.1 Assuming that the tunnel is equivalent to a homogeneous ring, the ring stiffness takes into account the effects of longitudinal joint bolts and annular gaps, and the elastic foundation beam model is used to simulate the interaction between the tunnel and the slurry and surrounding rock formations; 3.2 Theoretically, the buoyancy formula is: where Y i is the buoyancy, i is the beam segment number, α i is the elastic characteristic coefficient of the inner tube, x is the position where the buoyancy acts on the inner tube, A i is the general solution coefficient, q i (x) is the floating load, k i is the vertical foundation coefficient, b is the length of the tunnel cross section under the foundation reaction force, and EI is the bending strength of the inner tube; 3.3 Substitute the experimental parameters in step 2 into the buoyancy formula and calculate the theoretical buoyancy.

9. An optimization method for controlling the flotation of a pipe segment in a water-rich hard rock formation using the experimental device according to any one of claims 1 to 4, characterized in that: Simulating slurry dilution, including the following steps: 1 Assemble the experimental device, surround the tunnel model with the air bag and put it into the model experimental box; 2. Control the air pressure of all airbags to be the same, so that the inner tube is in a uniform air pressure wrapped state, and keep the inner tube in a horizontal state, and the laser displacement meter reads the initial value of the inner tube position; 3. The pressure in the airbag is controlled by the air pressure control device, and the pressure of one of the second to nth airbags until the last airbag is adjusted to simulate the distance between the diluted synchronous grouting and the shield machine casing just separated in the actual project, and the displacement of the inner tube under different conditions is measured by the laser displacement meter; 4. Select different ways of reducing the airbag pressure to simulate the law of slurry dilution in actual engineering, and measure the displacement of the inner tube under different conditions by using a laser displacement meter; 5. Change the pressure difference between the upper and lower airbags in the airbag to simulate the buoyancy of the actual tube segment, and measure the displacement of the inner tube under different conditions by a laser displacement meter; 6. Analyze the inner tube displacement data obtained in the above steps, determine the influencing parameters of the control method and optimize them, and repeat steps 2 to 5 until the optimal influencing parameters are obtained.

10. An optimization method for controlling the flotation of a pipe segment in a water-rich hard rock formation using the experimental device according to any one of claims 1 to 4, characterized in that: Simulating real grouting includes the following steps: 1 Assemble the experimental device, surround the tunnel model with the air bag and put it into the model experimental box; 2. Do not install the airbag in the gap between the outer tube and the inner tube, and seal the holes on the outer tube and the inner tube with plugging bolts; 3. Install a pore pressure gauge and connect it to the data acquisition equipment to monitor the air pressure changes in the gap between the outer tube and the inner tube to determine the injection status of the slurry and the changes in the pore pressure in the slurry after the slurry is injected; 4 Two water tanks are set up on both sides of the tunnel model. The water tanks are connected to the gap between the outer pipe and the inner pipe through pipes and water pumps. The interface on the inner pipe connected to the water tank is selected according to the proposed slurry dilution position. The change of the water head difference is achieved by adjusting the height of the water tank on one side; 5. Install the grouting pipe in the reserved hole of the inner tube, connect the grouting pipe to the grouting equipment for grouting, and monitor the grouting situation through the changes of the pore pressure gauge. After the grouting is completed, turn on the water pump, and water enters the gap from the water tank to dilute the slurry. During this process, monitor the changes in the readings of the pore pressure gauge and laser displacement meter; 6. Analyze the inner tube displacement data obtained in the above steps, determine the influencing parameters of the control method and optimize them, and repeat steps 2 to 5 until the optimal influencing parameters are obtained.

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