Freeze-thaw simulation tunnel gushing mud test method

Abstract

The application discloses a kind of freeze-thaw simulation tunnel gushing mud test methods, temperature control device, tunnel model device and karst water pressure device are equipped in model box, tunnel model device includes the tunnel model in surrounding rock model and the rock mass model of preventing outburst, rock mass model of preventing outburst adopts the water-sand-stone-mud solidification block of design mix proportion, karst water pressure device includes open box, open box can be filled with medium, filling medium can exert pressure on rock mass model of preventing outburst, test method includes making surrounding rock model in model box, and in the process of forming surrounding rock model, rock mass model of preventing outburst, karst water pressure device and pressure measuring device for measuring karst water pressure are inserted, fill filling medium to karst water pressure device to adjust water pressure load that it acts on rock mass model of preventing outburst, adjust temperature in tank to make rock mass model of preventing outburst gradually melt, simulate gushing mud process and record.Model box structure is simple, easy to make, convenient to operate, test method is simple, economical, repeatable.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of test methods for simulating tunnel gushing mud. BACKGROUND

[0002] With the development of engineering technology, the ratio of bridge and tunnel in highway and railway engineering is higher and higher, and "building road when meeting mountain, building bridge when meeting water" has become the norm of infrastructure construction. Gushing mud occurs most frequently in karst tunnel disasters, accounting for 74.5% of the statistics of tunnels. Tunnel gushing mud disaster is very harmful, which may cause delay of construction period and economic loss, or even cause serious casualties. In addition, tunnel gushing mud destroys the underground water circulation system, causing a series of problems such as groundwater depletion, surface water seepage and vegetation ecological destruction, which cannot be ignored. Therefore, in the construction of tunnel engineering, attention should be paid to the disaster-causing mechanism of gushing mud. Whether in the pre-construction survey or in the implementation stage of the project, the changes in the disaster-causing environment and their influence need to be clarified. Tunnel gushing mud disaster has strong suddenness, and it is very difficult to study due to limited visual angle, insufficient preparation time and large gushing water volume in the outdoor environment of the project. Indoor simulation test is more conducive to the study of the mechanism and rules of the occurrence process of tunnel gushing mud under complex variable conditions.

[0003] In recent years, some researches on test models for simulating tunnel gushing mud have been carried out in China. For example, CN104807960A. In the design of the above test model, the strength of the simulation material of gushing mud does not change during the test, and the flow of the material is controlled by high-pressure water flow and a partition. In fact, it cannot completely simulate the process that the strength of the local material changes during the actual occurrence of gushing mud disaster. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a freeze-thaw simulation tunnel gushing mud test method that can more realistically simulate tunnel gushing mud.

[0005] The technical solution adopted by the present application to solve the technical problem is: a freeze-thaw simulation tunnel gushing mud test method, which employs a model box including a model box body, a tunnel model device and a karst water pressure device arranged in the model box body, the tunnel model device including a tunnel model in a surrounding rock model and a gushing rock model, the surrounding rock model being formed by pouring foam lightweight concrete, the reserved tunnel opening of the tunnel model being located on the wall of the model box body, the gushing rock model being made of water-sand-stone-mud solidification blocks with a designed mix ratio, the karst water pressure device including an open box, the opening of the open box being adjacent to the gushing rock model, the open box being filled with a medium, the medium being capable of applying pressure to the gushing rock model, a temperature control device being arranged in the model box body to control the strength of the gushing rock model, and the test method including the following steps:

[0006] a, make a model box, install temperature control device in the model box, prefabricate the model of the burst-proof rock mass, make the karst water pressure device;

[0007] b, make the surrounding rock model in the model box, and put the burst-proof rock mass model, the karst water pressure device and the pressure measuring device for measuring the karst water pressure in the process of forming the surrounding rock model, and keep the burst-proof rock mass model from melting in this process;

[0008] c, fill the filling medium into the karst water pressure device to adjust the water pressure load of the burst-proof rock mass model, adjust the temperature in the model box, and make the burst-proof rock mass model melt gradually to simulate the water gushing and mud bursting process and record.

[0009] In the above method, the cross-sectional shape and size of the tunnel model can be changed according to the experimental design, the shape of the burst-proof rock mass model is adapted to the cross-sectional shape of the tunnel model, and the thickness of the burst-proof rock mass model can also be changed in a large range according to the experimental design and the corresponding production is completed. Most importantly, the burst-proof rock mass model uses water-sand-stone-mud solidified blocks with a designed mix ratio, and with the help of the temperature control device, the strength change of the burst-proof rock mass model can be controlled. The burst-proof rock mass model is made in a low temperature state by using the condensation temperature of water, and gradually warms up in the test, the water melts gradually, the strength of the solidified block is weakened, and the filling medium in the opening box can break through the burst-proof rock mass model to the tunnel model, which more realistically simulates the change of the burst-proof rock mass in the water gushing and mud bursting process, so that more accurate experimental conclusions can be obtained.

[0010] Further, the filling medium is water, the opening box is connected with an external water source box located outside the model box through a water pipe, the external water source box is located on a liftable base, and the pressure of the filling medium acting on the burst-proof rock mass model is changed by adjusting the volume of the filling medium in the opening box or the height of the external water source box, so that stepless adjustment of the pressure of the burst-proof rock mass model is realized at a lower cost.

[0011] In order to facilitate observation of the pressure change of the burst-proof rock mass model, the opening box is connected with a hydraulic pipe, a filter screen is arranged at the pipe end in the opening box, the pressure parameter can be directly fed back to the tester, and the filter screen can prevent the pipe opening from being blocked to affect the hydraulic transmission.

[0012] The temperature control device comprises a temperature raising device and a temperature lowering device. In order to facilitate temperature control in the model box, the model box is arranged in layers, a water storage tank with water inlet and outlet is arranged at the bottom, a lower support plate is arranged at the top of the water storage tank, a tunnel model device and a karst water pressure device are arranged on the lower support plate, an upper support plate is arranged at the top of the surrounding rock model, a space above the upper support plate is used as an installation space of the temperature lowering device, and the temperature lowering device and the water storage tank are used as the temperature control device. After the anti-burst rock mass model is placed, before the surrounding rock model is formed, the temperature lowering device is used to make the temperature in the model box lower than zero, so that the solidification state of the anti-burst rock mass model is maintained. After the surrounding rock model is formed and the anti-burst rock mass model is loaded with a set pressure, flowable liquid water is supplied to the water storage tank, so that the temperature in the model box rises, and the water inrush and mud burst process is simulated. The temperature lowering device is used to maintain a low temperature during model making, so that the anti-burst rock mass model is prevented from softening due to water melting. By supplying ice water or hot water with different temperatures to the water storage tank, slow temperature regulation and control are realized. The above design facilitates model making and control, and has low cost.

[0013] Since it is not necessary to accurately control the temperature below zero, a suspension beam is installed in the installation space of the temperature lowering device, a serpentine condensing pipe in communication with a self-pressurized liquid nitrogen tank is installed on the suspension beam, the flow of the liquid nitrogen is used to control the temperature in the box, which is convenient and easy to realize, and the cost is not high. The suspension beam can be fixed on the model box, so that the temperature lowering device can be quickly installed.

[0014] A temperature sensor is installed in the water storage tank, and the temperature sensor is connected with a control terminal, so that data recording is facilitated.

[0015] The model box has the advantages of simple overall structure, easy manufacturing, convenient operation, simple, economical and repeatable test method. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is the overall structure schematic diagram of the freeze-thaw simulation tunnel water inrush and mud burst test model box adopted in the present application.

[0017] Figure 2 is Figure 1 the installation schematic diagram of the serpentine condensing pipe.

[0018] Marked in the figure: 1- from the booster nitrogen tank, 2- first stop valve, 3- pressure gauge, 4- pressure relief valve, 5- heat insulation plate, 6- suspension beam, 7- serpentine condenser tube, 8- upper support plate, 9- second stop valve, 10- vacuum pump, 11- buffer bottle, 12- external water source tank inlet, 13- external water source tank, 14- external water source tank outlet, 15- gate valve, 16- liftable base, 17- water pipe, 18- model box, 19- reserved tunnel port of tunnel model, 20- steel pipe, 21- burst rock mass model, 22- open box, 23- filling medium, 24- filter screen, 25- hydraulic pipe, 26- water storage tank inlet, 27- stand, 28- temperature sensor, 29- lower support plate, 30- water storage tank outlet, 31- control terminal, 32- bolt, 33- surrounding rock model, 34 water storage tank. DETAILED DESCRIPTION

[0019] The application will be further described below in combination with the drawings and examples.

[0020] As shown in Figure 1 , Figure 2 , the model box used in the freeze-thaw simulation tunnel gushing mud test in the application includes a transparent model box 18, the model box 18 is provided with a temperature control device, a tunnel model device and a karst water pressure device, the tunnel model device includes a tunnel model in a surrounding rock model 33 and a burst rock mass model 21, the surrounding rock model 33 is formed by pouring foamed lightweight concrete, a reserved tunnel port 19 of the tunnel model is located on the wall of the model box 18, the simulated gushing mud is discharged outward from the tunnel port 19, which is convenient for observation and cleaning, the burst rock mass model 21 uses water-sand-stone-mud solidification blocks with a designed mixing ratio, and in combination with the temperature control of the model box, the simulation of the local material strength change in the gushing mud process can be realized, the actual disaster occurrence condition can be more truly simulated, the karst water pressure device is also located in the surrounding rock model 33, the karst water pressure device includes an open box 22, the open box 22 is connected with an external water source tank 13 through a water pipe 17, the external water source tank 13 is located on a liftable base 16, an opening of the open box 22 is adjacent to the burst rock mass model 21, the open box 22 can be filled with a filling medium, since the open box 22 and the tunnel model are both surrounded by the surrounding rock model 33, the filling medium 23 can apply pressure to the burst rock mass model 21, which is convenient for adjusting the applied pressure.

[0021] The temperature control device in combination with water-sand-stone-mud solidification blocks with different sizes and shapes and a designed mixing ratio better simulates the condition that the burst rock mass will change in strength under the actual gushing mud disaster occurrence condition, the gushing mud condition of the tunnel under various thickness and strength burst rock mass conditions can be simulated, the model is easy to make, the test process is easy to control, and observation is convenient.

[0022] Example:

[0023] As Figure 1 、 Figure 2 shown, freeze-thaw simulation tunnel gushing mud test model box, model box 18 is made of transparent acrylic plate visible box, the transparent test model box is provided with heat preservation layer on each inner side, and has a hole at the required position; temperature control device, tunnel model device and karst water pressure device are arranged in the model box 18, the tunnel model device includes the tunnel model in the surrounding rock model 33 and the rock burst prevention rock mass model 21, the tunnel model is divided into two parts, the excavation section and the unexcavated section, wherein the excavation section adopts steel pipe 20 as lining support upper load, the unexcavated section, namely the rock burst prevention rock mass model 21, adopts water-sand-stone-mud solidification block with designed mixing ratio, the surrounding rock model 33 is poured and formed by foamed lightweight concrete, the reserved tunnel portal 19 of the tunnel model is located on the wall of the model box 18, the karst water pressure device includes the open box 22, the opening of the open box 22 faces the rock burst prevention rock mass model 21, the outer contour of the opening is consistent with the end face contour of the one end of the open box 22 adjacent to the rock burst prevention rock mass model 21, after the open box 18 is filled with medium, the pressure of the filling medium can act on the rock burst prevention rock mass model 21.

[0024] The temperature control device is composed of the water storage tank 34 reserved below the transparent test model box and the cooling device in the space reserved above, the temperature of the upper structure is indirectly controlled by controlling the water temperature in the water storage tank 34, the bottom plate of the water storage tank 34 is the bottom plate of the model box 18, which is formed by placing a steel plate as the lower support plate 29 to support the weight of the upper tunnel model, the water storage tank 34 is provided with a water inlet 26 and a water outlet 30, the column 27 is arranged around the rock burst prevention rock mass model 21 below, the temperature sensor 28 is installed on the column 27, and the multiple temperature sensors 28 are uniformly arranged around the rock burst prevention rock mass model 21 below and are signal connected with the control terminal 31. The cooling device includes the self-pressurized liquid nitrogen tank 1, the control valve, the serpentine condenser pipe 7, the buffer bottle 11 and the vacuum pump 10, which are connected with each other, for reducing the temperature in the test model box, a plurality of pressure gauges 3 are arranged on the liquid nitrogen pipeline, for observing the nitrogen pressure in the self-pressurized liquid nitrogen tank 1 and the serpentine condenser pipe 7 respectively, so as to adjust the liquid nitrogen control valve, namely the first stop valve 2 and the second stop valve 9. The serpentine condenser pipe 7 is arranged in the arrangement plane in axis symmetry, which is beneficial to uniform cooling.

[0025] The karst water pressure device comprises an external water source tank 13, a water stop valve 15, a water pipe 17 and an opening tank 22 connected in sequence, and is used for injecting a certain amount of water into the opening tank 22 to provide a set pressure for the outburst prevention rock mass model 21. The external water source tank 13 is supported by a liftable base 16, the water pressure provided by the external water source tank 13 can be controlled, and the external water source tank 13 is provided with a water inlet and a water outlet. A hydraulic pipe 25 is connected with the bottom of the opening tank 22 to form a pressure measuring device, the water pressure at the bottom of the opening tank can be measured by reading the height of the hydraulic pipe, and a filter screen 24 is arranged at the port where the hydraulic pipe 25 is connected with the opening tank 22 to prevent the filling medium from entering the hydraulic pipe 25 and blocking the hydraulic pipe 25.

[0026] The outburst prevention rock mass model 21 is a water-sand-stone-mud prefabricated columnar ice block which can have different mixing ratios. By changing the shape and size of the prefabricated columnar ice block, the change of the tunnel with different cross-sectional shapes and sizes which may be affected by gushing water and mud can be studied. The surrounding rock model 33 is formed by pouring foam lightweight concrete, simulating the rock mass around the outburst prevention rock mass, and at the same time playing a heat preservation and insulation role for the columnar ice block.

[0027] The steps of applying the model box to carry out the test are as follows.

[0028] Step 1: a transparent test model box 18 is made, a heat insulation plate 5 is installed on the inner side, and a prefabricated outburst prevention rock mass model 21 is prepared.

[0029] Step 2: a cooling device is installed, and a self-pressurized liquid nitrogen tank 1, a pressure gauge 3, a first stop valve 2, a pressure gauge 3, a coiled condenser tube 7, another pressure gauge 3, a buffer bottle 11, a second stop valve 9 and a vacuum pump 10 are connected.

[0030] Step 3: a karst water pressure device is assembled, and an external water source tank 13, a water stop valve 15, a water pipe 17 and an opening tank 22 are connected. An external water source tank water inlet 12 and an external water source tank water outlet 14 are installed on the external water source tank 13 at the same time, and the external water source tank 13 is placed on a liftable base 16 to facilitate the adjustment of the water pressure.

[0031] Step 4: a pressure measuring device is installed, that is, a filter screen 24 and a hydraulic pipe 25 are installed at the bottom of the opening tank 22.

[0032] Step 5: a stand 27 and a steel plate as a lower supporting plate 29 are installed to form a water storage tank 34. After pouring foam lightweight concrete to the reserved tunnel opening 19, the outburst prevention rock mass model 21, the steel pipe 20 and the assembled karst water pressure device are placed in the corresponding positions, the foam lightweight concrete is quickly poured to form the surrounding rock model 33, and a plurality of temperature sensors 28 are placed in advance at the preset positions inside the surrounding rock model 33 and connected with an external terminal 31.

[0033] Step 6: After the pouring is completed, the upper support plate 8 is placed on the foam light concrete, the cooling device is installed on the top plate of the transparent test model box through the suspension beam 6, then the top plate is fixed, the cooling device is immediately started to prevent the anti-burst rock mass model 21 from melting. At the same time, cold water is filled into the water storage tank 34 at the bottom of the model box 18 through the water inlet 26 of the water storage tank to reduce the temperature in the transparent test model box.

[0034] Step 7: After the concrete is solidified, the water gushing and mud bursting simulation test can be carried out.

[0035] Step 8: The temperature in the transparent test model box is controlled through the cooling device and the water storage tank, and the strength of the anti-burst rock mass model 21 is indirectly controlled. The strength of the anti-burst rock mass model 21 is controlled by filling hot water into the water storage tank 34 through the water inlet 26 of the water storage tank, and when the strength of the anti-burst rock mass model 21 is reduced to a certain extent, water gushing and mud bursting occur, and the change of the filling medium 23 can be observed and recorded by a high-speed camera. The filling medium 23 can be ice blocks pre-inserted into the open box 22 during the model manufacturing process or water added into the open box 22 through the external water source tank 13.

[0036] As can be seen from the above, the model box used in the application adopts a layered structure arrangement, the bottom layer water storage tank 34 is mainly used for temperature control, the top layer serpentine condenser pipe 7 is used for temperature control, and the middle layer is used for model arrangement. The rapid cooling and heating of the model box can be realized by using liquid nitrogen vaporization heat absorption and filling ice water or hot water into the water storage tank 34. The liquid nitrogen is cheap, easy to obtain and fast in cooling. The low-temperature water and high-temperature water are efficient and simple to obtain, belong to clean energy, can be recycled, have no pollution, will not produce harmful gases during the test process, the overall structure of the box body is simple, easy to manufacture and convenient to operate, and the test method is simple, economical and repeatable.

Claims

1. A method for simulating water inrush and mudslide in tunnels using freeze-thaw simulation, characterized by: The model box used includes a model box body (18), which is equipped with a temperature control device, a tunnel model device and a karst water pressure device. The tunnel model device includes a tunnel model in the surrounding rock model (33) and an anti-outburst rock mass model (21). The surrounding rock model (33) is formed by casting foamed lightweight concrete. The reserved tunnel opening (19) of the tunnel model is located on the wall of the model box body (18). The anti-outburst rock mass model (21) is made of water-sand-stone-mud solidified blocks with a designed mix ratio. The karst water pressure device includes an open box (22). The opening of the open box (22) is adjacent to the anti-outburst rock mass model (21). The open box (22) can be filled with a medium, which can apply pressure to the anti-outburst rock mass model (21). The test method includes the following steps: a. Make model box (18), prefabricate anti-burst rock mass model (21), and make karst water pressure device; b. Make a surrounding rock model (33) inside the model box (18), and place an anti-burst rock mass model (21), a karst water pressure device and a pressure measuring device for measuring karst water pressure in the process of forming the surrounding rock model (33), and keep the anti-burst rock mass model (21) from melting during this process; c. Fill the karst water pressure device with filling medium to adjust the load it applies to the anti-burst rock mass model (21), adjust the temperature inside the model box (18) so that the anti-burst rock mass model (21) gradually melts, simulates the process of water inrush and mud inrush and records it.

2. The method for simulating tunnel water inrush and mudslide testing as described in claim 1, characterized in that: The filling medium is water. The open box (22) is connected to the external water source box (13) located outside the model box (18) through the water pipe (17). The external water source box (13) is located on the liftable base (16). The pressure applied by the filling medium to the anti-outburst rock mass model (21) can be changed by adjusting the volume of the filling medium in the open box (22) or the height of the external water source box (13).

3. The method for simulating tunnel water inrush and mudslide testing as described in claim 1, characterized in that: The open box (22) is connected to the hydraulic pipe (25), and the end of the hydraulic pipe (25) inside the open box (22) is equipped with a filter screen (24).

4. The method for simulating tunnel water inrush and mudslide testing as described in claim 1, 2, or 3, characterized in that: The model box (18) is arranged in layers. A water storage tank (34) with inlet and outlet is set at the bottom. A lower support plate (29) is set on the top of the water storage tank (34). A tunnel model device and a karst water pressure device are set on the lower support plate (29). An upper support plate (8) is set on the top of the surrounding rock model (33). The space above the upper support plate (8) is used as the installation space for the cooling device. The cooling device and the water storage tank are used as temperature control devices. After the anti-outburst rock mass model (21) is placed in and before the surrounding rock model (33) is formed, the temperature inside the model box (18) is kept below zero degrees to keep the anti-outburst rock mass model (21) in a solidified state. After the surrounding rock model (33) is formed and a set pressure is applied to the anti-outburst rock mass model (21), flowing liquid water is introduced into the water storage tank (34) to raise the temperature inside the model box (18) and simulate the process of water inrush and mud inrush.

5. The method for simulating tunnel water inrush and mudslide testing as described in claim 4, characterized in that: The cooling device is installed in the installation space of a suspension beam (6), and a serpentine condenser (7) connected to the self-pressurized liquid nitrogen tank (1) is installed on the suspension beam (6), with the serpentine condenser (7) serving as the cooling device.

6. The method for simulating tunnel water inrush and mudslide testing as described in claim 4, characterized in that: A temperature sensor (28) is installed inside the water storage tank (34), and the temperature sensor (28) is connected to the control terminal (31).

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