A shield segment joint fire-explosion coupling mechanical property test system

Abstract

The utility model relates to a kind of shield segment joint fire-explosion coupling mechanics performance test system, belong to shield tunnel segment joint test device technical field, and the system includes fire heat environment simulation unit, explosion impact simulation unit, heat insulation protection unit, rotating unit, loading unit and data acquisition unit.This test system can better simulate the thermal-mechanical-steam multi-field coupling stress state of tunnel lining segment under fire high temperature and explosion impact;Can simulate the interaction between lining segment and the action situation of surrounding rock mass to lining segment;Can exert positive bending moment or negative bending moment to lining segment joint, exert a load or carry out multiple load combination loading.This test system is safe and reliable, easy to operate, and can meet the requirements of shield tunnel segment fire-explosion coupling mechanics performance test.

Description

Technical Field

[0001] This invention belongs to the technical field of shield tunnel segment joint testing devices, specifically relating to a test system for the mechanical properties of shield tunnel segment joints under fire-explosion coupling effects. Background Technology

[0002] In recent years, with the continuous development of the economy and the gradual development of underground space, the number of tunnels put into operation both domestically and internationally has increased rapidly. The types of disasters affecting tunnel structures mainly include two categories: progressive disasters—such as deformation, leakage, and cracking—and sudden disasters—such as fires, explosions, and earthquakes. Currently, domestic and international research on tunnel structures primarily focuses on the response of tunnel structures under single sudden disasters such as explosions, deformation, and fires, while research on the mechanical properties of tunnel structures under the coupled effects of multiple disasters is still insufficient. Due to the complex and variable geographical, climatic, and geological conditions of tunnels, as well as their spatial morphology and operational status, tunnels are prone to developing weak points during long-term operation or in the event of a preliminary disaster. These weak points are often located at joints, leading to a more complex mechanical response and failure mode of the tunnel lining structure in subsequent disasters.

[0003] Fire-explosion accidents within tunnels can have severe consequences and greatly threaten the safe operation of tunnels. Therefore, it is necessary to study the mechanical properties of tunnel lining structures under the coupled effects of fire and explosion.

[0004] Due to their long, narrow structure, confined space, poor ventilation, and high temperatures, tunnels are difficult to extinguish quickly after a fire, often resulting in extremely serious consequences. If a tunnel structure is subjected to fire again after being damaged by an explosion, the mechanical response of the structure under subsequent fire will be more complex due to the damage caused by the explosion. Furthermore, the structural damage from the explosion poses a significant threat to the lives of firefighters and nearby residents. Explosions also generate shock waves that can scatter flammable materials into the air and surrounding areas, and can damage the protective layer of the reinforcing steel in the tunnel lining, exposing the steel and leading to deterioration of the lining's mechanical properties. Fires and explosions within tunnels severely endanger the lives and property of people inside, cause significant damage to the tunnel's electromechanical facilities, and the high temperatures and impacts of the fire and explosion can cause localized damage and mechanical degradation of the concrete, greatly reducing the load-bearing capacity of the tunnel lining structure.

[0005] Shield tunneling has been widely used due to its advantages such as strong adaptability to construction environments, minimal environmental impact, and safe and rapid construction. However, the large diameter, numerous segmented sections and joints, and weak ground constraint of shield tunnels make their structural behavior extremely complex under multiple disasters, including fire and explosion. Most studies only consider the impact of a single extreme disaster like fire or explosion on the tunnel structure, failing to provide guidance for tunnel structural design under fire-explosion coupling. The mechanical response characteristics and failure modes of shield tunnels under fire-explosion coupling urgently need to be addressed. Therefore, research on the mechanical response and failure modes of shield tunnel lining structures under fire-explosion coupling, and a thorough understanding of the mechanical response, deformation characteristics, and failure modes of shield tunnel segment joints and lining structures under such conditions, is of great significance for ensuring the safety of people's lives and property and the normal operation of shield tunnels.

[0006] Currently, there is no simple and reliable experimental equipment for exploring the mechanical response characteristics and failure modes of shield tunnels under fire-explosion coupling. This experimental system can effectively simulate fire-explosion coupling scenarios, taking into account the effects of high temperature and explosive impact on the mechanical properties of shield tunnel segment joints. With the help of sophisticated control programs and data acquisition technology, it provides a feasible approach to explore the mechanical response characteristics and failure modes of shield tunnels under fire-explosion coupling, which has significant practical and academic value. Summary of the Invention

[0007] In view of the existing problems regarding the fire-explosion coupling effect inside tunnels, the purpose of this invention is to provide a mechanical performance testing system for the fire-explosion coupling effect of shield tunnel segment joints, so as to safely, reliably, simply and efficiently carry out mechanical performance tests on the fire-explosion coupling effect of shield tunnel segment joints.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A mechanical performance testing system for fire-explosion coupling effect of tunnel segment joints includes: a fire thermal environment simulation unit, an explosion impact simulation unit, a heat insulation protection unit, a rotation unit, a loading unit, and a data acquisition unit.

[0010] The loading unit includes a reaction frame fixed on a horizontal ground. A rotating frame is installed inside the reaction frame via a rotating unit. The rotating frame can rotate relative to the reaction frame. A fire thermal environment simulation unit is installed inside the rotating frame. Horizontal loading jacks and vertical loading jacks are installed on the sides and top of the rotating frame, respectively. The horizontal loading jacks rest against supports installed on the rotating frame. The component to be tested is placed on the supports. Vertical and horizontal loads are applied to the component to be tested through the vertical and horizontal loading jacks.

[0011] The fire thermal environment simulation unit includes a heating furnace and resistance wires installed on the side wall and bottom plate of the heating furnace. An impact rod sleeve is installed on the bottom plate of the heating furnace.

[0012] The explosion impact simulation unit is a top arch impact device or a bottom arch impact device. The top arch impact device is installed on a horizontal ground, and the bottom arch impact device is installed on a reaction frame. The top arch impact device or the bottom arch impact device is detachably connected to the impact rod sleeve.

[0013] The heat insulation protection unit includes a movable heat insulation block, heat insulation fiber, and heat insulation plate, and the movable heat insulation block, heat insulation fiber, and heat insulation plate are placed at the connection position between the component under test and the heating furnace;

[0014] The data acquisition unit includes a vertical force sensor and a horizontal force sensor installed on the loading unit, a temperature sensor installed on the heating furnace, a velocity sensor installed on the bottom arch impact rod and the top arch impact rod, a component parameter measurement sensor installed on the component to be measured, a pressure sensor installed on the top arch impact device, and a computer.

[0015] The reaction frame includes two parallel columns, a top beam installed on the top of the two columns, and a central suspension beam installed on the inner wall of one of the columns.

[0016] The rotating frame includes two parallel frame columns, a crossbeam installed on the top of the two frame columns, and four cantilever beams installed in the middle and bottom of the two frame columns.

[0017] The rotating unit includes a rotary lock and a rotating shaft. One end of the rotating shaft is rotatably installed with the reaction frame column, and the other end is fixedly connected to the rotating frame. Rotary locks are symmetrically installed on the upper and lower sides of the rotating shaft between the reaction frame and the rotating frame, and the rotating frame is locked by the rotary locks.

[0018] The top arch impact device includes a nitrogen storage chamber arranged on a horizontal ground. The top of the nitrogen storage chamber is threadedly connected to one end of the impact rod fall buffer device, and the other end of the impact rod fall buffer device is connected to the threaded end of the impact rod sleeve. The air inlet of the nitrogen storage chamber is connected to the gas outlet of the nitrogen cylinder through a pipeline.

[0019] The impact rod fall-back buffer device includes a tube body, with the inner threaded end of the tube body threadedly connected to the nitrogen storage chamber and the outer threaded end threadedly connected to the impact rod sleeve. A spring is installed inside the tube body, and a top arch impact rod is installed on the top of the spring.

[0020] The bottom arch impact device includes a lifting motor installed on the middle suspension beam. The wire rope on the lifting motor passes through the pulley at the bottom of the top beam and its end is connected to the bottom arch impact rod. The extended threaded end of the impact rod sleeve is connected to the internal threaded end of the impact rod sleeve.

[0021] The outer periphery of the impact rod sleeve, the outer periphery of the impact rod sleeve extension tube, and the outer periphery of the impact rod fall buffer device are provided with heat insulation layers.

[0022] The component parameter measurement sensor consists of strain gauges, displacement gauges, accelerometers, goniometers, and digital image analyzers.

[0023] A load-sharing beam is provided between the vertical loading jack and the component to be tested. The load-sharing beam includes two loading heads that are in contact with the component to be tested, and a load-bearing beam that is connected at one end to the vertical loading jack and at the other end to the loading heads.

[0024] The technical effects of this invention are as follows:

[0025] This experimental system can effectively simulate fire-explosion coupling scenarios. By changing the direction of the rotating shaft, it can perform two loading methods: positive bending moment loading on the joints of shield tunnel segments at the top arch and negative bending moment loading on the joints of shield tunnel segments at the bottom arch. For positive and negative bending moment loading of the shield tunnel segment joints, top arch impact devices and bottom arch impact devices are matched respectively to achieve accurate simulation of tunnel explosions. Since the same heating furnace is used to heat the inner side of the test component for both positive and negative bending moment loading to simulate fire environments, electric heating is employed to ensure the lightweight and simple design of the fire thermal environment simulation unit experimental device, facilitating the rotation of the rotating frame. The rationally arranged heat insulation devices not only reduce heat loss within the heating furnace but also prevent the external testing and loading devices from being affected by high temperatures, thus avoiding accuracy loss. Simultaneously, this experimental system can also independently simulate scenarios of high-temperature fire effects, scenarios of high-temperature fire effects followed by cooling and subsequent explosion impact, and scenarios of high-temperature fire effects following explosion impact. With sophisticated control programs and data acquisition technology, the system significantly improves work efficiency and the reliability of experimental data. This testing system is safe, reliable, simple, and efficient, and can meet the requirements for mechanical performance testing of shield tunnel segment joints under fire-explosion coupling. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the mechanical performance test system for fire-explosion coupling effect of shield tunnel segment joints according to Embodiment 1 of the present invention;

[0027] Figure 2 This is the present invention. Figure 1 A schematic diagram of direction AA;

[0028] Figure 3 This is a schematic diagram of the composition of the fire thermal environment simulation unit in Embodiment 1 of the present invention;

[0029] Figure 4 This is a schematic diagram of the top arch impact device under positive bending moment loading according to Embodiment 1 of the present invention;

[0030] Figure 5 This is a schematic diagram of positive bending moment loading in Embodiment 1 of the present invention;

[0031] Figure 6 This is a schematic diagram of the impact rod sleeve of the present invention;

[0032] Figure 7 This is a schematic diagram of the bottom arch impact device under negative bending moment loading according to Embodiment 2 of the present invention;

[0033] Figure 8 This is a schematic diagram of negative bending moment loading in Embodiment 2 of the present invention.

[0034] 1-Rotary motor, 2-Resistance wire, 3-Heating furnace, 4-Electromagnetic check valve, 5-Component under test, 6-Pressure sensor, 7-Nitrogen cylinder, 8-Nitrogen storage chamber, 9-Impact rod return buffer device, 10-Impact rod sleeve, 11-Top arch impact rod, 12-Impact rod sleeve extension tube, 13-Lifting motor, 14-Bottom arch impact rod, 15-Modible heat insulation block, 16-Heat insulation fiber, 17-Heat insulation board, 18-Loading platform, 19-Support, 21-Rotating shaft, 22-Rotary lock, 24-Vertical loading jack, 25-Horizontal loading jack, 26-Rotating frame, 27-Reaction frame, 28-Vertical force sensor, 29-Horizontal force sensor, 30-Temperature sensor, 31-Protrusion. Detailed Implementation

[0035] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0036] Example 1

[0037] Mechanical property test of segment joints in top-arch shield tunnel

[0038] like Figures 1 to 6 As shown, a mechanical performance testing system for fire-explosion coupling effect of tunnel segment joints includes: a fire thermal environment simulation unit, an explosion impact simulation unit, a heat insulation protection unit, a rotation unit, a loading unit, and a data acquisition unit.

[0039] The loading unit includes a reaction frame 27 fixed on a horizontal ground. In this embodiment, the reaction frame 27 includes two parallel columns, a top beam installed on the top of the two columns, and a middle suspension beam installed on the inner wall of one of the columns. The middle suspension beam is used to install the lifting motor 13 of the bottom arch impact device. In this embodiment, the rotating frame 26 includes two parallel frame columns, a crossbeam installed on the top of the two frame columns, and four cantilever beams installed in the middle and bottom of the two frame columns. The cantilever beam in the middle is a loading platform 18, and the length of the cantilever beam at the bottom is longer than the length of the cantilever beam in the middle. The bottom cantilever beam and the cantilever beam in the middle are equipped with... A heating furnace 3 is installed. A vertical loading jack 24, which applies a vertical load to the component 5 under test, is installed at the center of the lower surface of the top crossbeam. A vertical force sensor 28 is installed between the vertical loading jack 24 and the crossbeam. A horizontal loading jack 25 is installed on the inner wall of the frame column at the top of the two cantilever beams. A horizontal force sensor 29 is installed between the horizontal loading jack 25 and the column of the reaction frame 27. In this embodiment, there are two horizontal loading jacks 25. The loading end of the horizontal loading jack 25 rests on the support 19. The support 19 is composed of a right-angle plate with a flat plate welded to the bottom. The support 19 is connected to the cantilever beam of the rotating frame 26 through the flat plate on it. This arrangement The method provides a stable platform for the loading process of the component under test 5, while avoiding damage to the component under test 5 caused by minor lateral deformation during loading. The support 19 can simulate a movable hinge support, a semi-fixed hinge support, or a fixed hinge support. The component under test 5 is placed between two supports 19, with both ends of the component under test 5 abutting against the right-angle plates of the support 19. A filler is set at the right angle of the support 19 to ensure that the ends of the component under test 5 are in full contact with the support 19. The column of the reaction frame 27 is equipped with a rotating frame 26 via a rotating shaft 21. One end of the rotating shaft 21 is rotatably installed with the column, and the other end is fixed to the frame column of the rotating frame 26. The middle cantilever beam is set higher than the rotating frame 26. A rotary motor 1 is installed on the outside of the column 27. The output shafts of the two rotary motors 1 are connected to the corresponding rotating shaft 21 via couplings. Rotary locks 22 are installed between the two ends of the rotating frame 26 and the reaction frame 27. In this embodiment, the rotary locks 22 are electromagnets, and the electromagnets are energized and de-energized by a computer. A load-sharing beam is set between the vertical loading jack 24 and the component under test 5. The load-sharing beam includes two loading heads that contact the component under test 5 and a bearing beam connected to the vertical loading jack 24. The entire loading system can achieve four-point loading, eliminating the influence of shear force on the weak points of the shield tunnel segment joints and better simulating the actual stress condition of the component under test 5. The maximum test force that the vertical loading jack 24 and the horizontal loading jack 25 can apply is 1000kN, and the maximum stroke is 500mm. They are responsible for applying horizontal and vertical loads to the component under test 5 to simulate the actual stress condition of the component under test 5 during operation.

[0040] The fire thermal environment simulation unit includes a heating furnace 3 made of refractory concrete and resistance wires 2 installed on the side walls and bottom plate of the heating furnace 3. Temperature sensors 30 are installed on the inner wall of the heating furnace 3. An impact rod sleeve 10 is installed on the bottom plate of the heating furnace 3, and the impact rod sleeve 10 is an integral part of the heating furnace 3. One part of the impact rod sleeve 10 is located inside the heating furnace 3, corresponding to the component 5 under test, while the other part is located outside the heating furnace 3, with its bottom end passing between two cantilever beams located at the bottom of the rotating frame 26. The impact rod sleeve 10 is a hollow tube, with internal threads machined at one end and a protrusion 31 facing the center at the other end.

[0041] Before heating, a temperature sensor 30 is installed inside the heating furnace 3; strain gauges, displacement gauges, accelerometers, goniometers, and digital image analyzer measuring points are installed on the component to be tested 5. During heating, the computer automatically adjusts the power of the resistance wire 2 according to the set temperature and the temperature inside the heating furnace 3 detected by the temperature sensor 30, so that the temperature inside the heating furnace 3 can rise according to the ISO834 standard heating curve, HC heating curve, RWS heating curve, or RABT heating curve. The temperature sensor 30 inside the heating furnace 3 detects the real-time temperature inside the furnace and feeds it back to the computer. If the computer analyzes the temperature data fed back by the temperature sensor 30 and finds that the heating rate does not conform to the predetermined heating curve, the computer controls the resistance wire 2 to cut off the power to ensure the safety of the test personnel and test instruments.

[0042] The rotating shaft 21, the rotary motor 1, and the rotary lock 22 form a rotating unit. During the explosive impact test, the top arch impact device and the bottom arch impact device adjust their directions through the rotating unit. During the test, after the component to be tested 5 is fixed, the rotating shaft 21 is rotated by the rotary motor 1 to rotate the rotating frame 26 to the required position. The position of the rotating frame 26 is fixed during the test by locking the rotary lock 22. When the top arch impact load is applied, the heating furnace 3 opens upward to heat the inside of the component to be tested 5. When the bottom arch impact load is applied, the rotating frame 26 rotates 180°, and the heating furnace 3 opens downward to heat the inside of the component to be tested 5. Whether it is the top arch impact load or the bottom arch impact load, the heating furnace 3 always heats the inside of the component to be tested 5.

[0043] The explosion impact simulation unit is either a top-arch impact device installed on a horizontal surface or a bottom-arch impact device installed on the middle cantilever of the reaction frame 27. The top-arch impact device and the bottom-arch impact device share a single impact rod sleeve 10. In this embodiment, a top-arch impact device is used for the test. The top-arch impact device includes a nitrogen storage chamber 8, which is arranged on a horizontal surface. A pressure sensor 6 is installed on the side wall of the nitrogen storage chamber 8. The gas inlet of the nitrogen storage chamber 8 is connected to the gas outlet of the nitrogen cylinder 7 through a pipeline, and an electromagnetic one-way valve 4 is installed at the gas outlet of the nitrogen cylinder 7. The impact fall buffer device 9 includes a tube and a spring. One end of the tube body is machined with an internal thread, and a boss is provided on the inner wall of the tube body at the top of the internal thread. A spring is provided on the top of the boss. In this embodiment, the spring is a compression spring. The other end of the tube body is machined with an external thread that mates with the internal thread of the impact rod sleeve 10. The top of the nitrogen storage chamber 8 is threadedly connected to the bottom end of the tube body of the impact fall buffer device 9. A top arch impact rod 11 is placed on the top of the spring and located inside the tube body. The impact end of the top arch impact rod 11 is machined into a hemispherical surface, and the non-impact end is machined with a boss that mates with the protrusion 31 of the impact rod sleeve 10. A speed sensor is installed on the top arch impact rod 11. The top end of the tube body of the impact fall buffer device 9 is threadedly connected to the bottom end of the impact rod sleeve 10. The pressure sensor 6 in the nitrogen storage chamber 8 detects the real-time pressure value in the nitrogen storage chamber 8 and feeds it back to the computer. If the computer analyzes the increase rate based on the feedback pressure value and finds that it does not match the expected rate, the computer will control the electromagnetic one-way valve 4 to close and stop the nitrogen supply to ensure the safety of the test personnel and test instruments.

[0044] The heat insulation protection unit includes a movable heat insulation block 15, heat insulation fiber 16, and heat insulation plate 17 located at the connection between the component under test 5 and the heating furnace 3. Specifically, as shown below... Figure 5 and Figure 7 As shown, the heat insulation plate 17 is located at the connection between the front and rear ends of the component under test 5 and the heating furnace 3. Heat insulation fiber 16 and movable heat insulation block 15 are sequentially arranged on the inner sides of both ends of the component under test 5 and the connection with the heating furnace 3.

[0045] The outer periphery of the impact rod sleeve 10, the outer periphery of the impact rod sleeve extension tube 12, and the outer periphery of the impact rod fall buffer device 9 are provided with heat insulation layers to reduce heat loss and at the same time avoid the impact of high temperature inside the furnace on external test equipment, loading equipment, test personnel, and the surrounding environment.

[0046] The data acquisition unit includes a vertical force sensor 28 connected to the vertical loading jack 24, a horizontal force sensor 29 connected to the horizontal loading jack 25, a temperature sensor 30 inside the heating furnace 3, velocity sensors on the top arch impact rod 11 and the bottom arch impact rod 14, a pressure sensor 6 installed on the side wall of the nitrogen storage chamber 8, and strain gauges, displacement gauges, accelerometers, goniometers, and digital image analyzers on the component under test 5. The output terminals of the vertical force sensor 28, horizontal force sensor 29, temperature sensor 30, velocity sensor, pressure sensor 6, strain gauges, displacement gauges, accelerometers, goniometers, and digital image analyzers are respectively connected to the input terminals of a computer. The output terminals of the computer are respectively connected to the input terminals of the lifting motor 13, the rotary motor 1, the resistance wire 2, and the electromagnetic one-way valve 4. The data is transmitted to the computer in real time for analysis to obtain the strain, displacement, acceleration, joint angle, and crack development of the component under test 5. In case of abnormality, the alarm device is activated to guide the control devices to handle the situation safely.

[0047] A test system for the mechanical properties of shield tunnel segment joints under fire-explosion coupling effects, comprising the following steps, using a top-arch impact device to test the mechanical properties of shield tunnel segment joints:

[0048] In the experiment, the rotating frame 26 was first locked by the rotary lock 22; a speed sensor was installed on the top arch impact rod 11 and placed in the impact rod fall buffer device 9; the nitrogen storage chamber 8, the impact rod fall buffer device 9, and the impact rod sleeve 10 were connected by threads; when the top arch impact test was carried out, the opening of the heating furnace 3 faced upwards, and the component under test 5 was continuously heated to simulate the continuous high temperature during a fire; the test gas pressure was set by the computer, and combined with the actual gas pressure fed back by the pressure sensor 6 on the nitrogen storage chamber 8, the electromagnetic one-way valve 4 on the nitrogen cylinder 7 was opened by the computer to supply nitrogen into the nitrogen storage chamber 8. When the pressure sensor 6 on the nitrogen storage chamber 8 fed back the detected actual gas pressure to the computer, when the computer determined that the actual gas pressure value was equal to the set test gas pressure value, the computer controlled the electromagnetic one-way valve 4 to close and stop the supply of nitrogen; the nitrogen released through the nitrogen storage chamber 8 pushed the top arch impact rod 11 through the impact rod sleeve 10 to impact the component under test 5, and the strain rate of the impact on the component under test 5 could reach 10. -1 -10 2 s -1 The end of the impact rod sleeve 10 is provided with a protrusion 31 to prevent the top arch impact rod 11 from being thrown out of the impact rod sleeve 10 after impact and causing danger. After the impact, the top arch impact rod 11 falls back to the impact rod return buffer device 9 by its own weight through the impact rod sleeve 10. The impact rod return buffer device 9 is provided with a spring to absorb the remaining energy of the top arch impact rod 11 when it falls back, so as to avoid damage to the test instrument.

[0049] Example 2

[0050] Mechanical property test of segment joints in bottom arch shield tunnels

[0051] like Figure 7 and Figure 8 As shown, the difference between Embodiment 2 and Embodiment 1 is that a bottom arch impact device is used. The specific bottom arch impact device includes a lifting motor 13 installed on the middle suspension beam. The installation position of the lifting motor 13 does not affect the loading path of the bottom arch impact rod 14. The wire rope on the lifting motor 13 passes through the pulley at the bottom of the top beam and its end is connected to the bottom arch impact rod 14. The impact end of the bottom arch impact rod 14 is processed into a hemispherical surface, and the non-impact end is processed with a boss that matches the protrusion 31 of the impact rod sleeve 10. A speed sensor is installed on the bottom arch impact rod 14, and the threaded end of the impact rod sleeve extension tube 12 is connected to the internal threaded end of the impact rod sleeve 10.

[0052] Currently, in the common heating methods used for high-temperature fire tests of components, when conducting mechanical property tests on the joints of shield tunnel segments under fire-explosion coupling under negative bending moment loading, the heating furnace 3, which rotates with the loading unit, is located below the component 5 under test, with the opening of the heating furnace 3 facing downwards. The existing methods do not meet the conditions required for heating using coke combustion, oil heating, and gas heating, and are extremely dangerous. The present invention uses electric heating, which is not affected by direction, and the test device is lighter and simpler. The resistance wire 2 is controlled by a computer to heat according to a predetermined curve, reaching 1400℃ with uniform temperature distribution. The operation is simple and convenient, and the test results are accurate and reliable.

[0053] A test system for the mechanical properties of shield tunnel segment joints under fire-explosion coupling effects, comprising the following steps, using a bottom arch impact device to test the mechanical properties of shield tunnel segment joints:

[0054] After the top arch impact test is completed, when conducting the bottom arch impact test, first disassemble the nitrogen storage chamber 8 and the impact rod return buffer device 9; start the rotary motor 1 to drive the rotating frame 26 to rotate 180° through the rotating shaft 21, so that the impact rod sleeve 10 rotates from the lower end to the upper end as the bottom arch impact rod sleeve, and turn off the rotary motor 1 while simultaneously locking the rotating frame 26 with the rotary lock 22; screw the impact rod sleeve extension tube 12 onto the threaded end of the impact rod sleeve 10; start the lifting motor 13 to lift the bottom arch impact rod 14 to the test height, and then release the bottom arch impact rod 14 into the impact rod sleeve extension tube 12 and the impact rod sleeve 10 and quickly slide down along both to impact the component 5 under test; after the impact is completed, the lifting motor 13 lifts the bottom arch impact rod 14.

Claims

1. A test system for the mechanical properties of shield tunnel segment joints under fire-explosion coupling effects, characterized in that, include: Fire thermal environment simulation unit, explosion impact simulation unit, heat insulation protection unit, rotation unit, loading unit and data acquisition unit; The loading unit includes a reaction frame fixed on a horizontal ground. A rotating frame is installed inside the reaction frame via a rotating unit. The rotating frame can rotate relative to the reaction frame. A fire thermal environment simulation unit is installed inside the rotating frame. Horizontal loading jacks and vertical loading jacks are installed on the sides and top of the rotating frame, respectively. The horizontal loading jacks rest against supports installed on the rotating frame. The component to be tested is placed on the supports. Vertical and horizontal loads are applied to the component to be tested through the vertical and horizontal loading jacks. The fire thermal environment simulation unit includes a heating furnace and resistance wires installed on the side wall and bottom plate of the heating furnace. An impact rod sleeve is installed on the bottom plate of the heating furnace. The impact rod sleeve is a hollow tube. One part of the impact rod sleeve is located inside the heating furnace and corresponds to the component to be tested. The other part is located outside the heating furnace and its bottom end passes through the two cantilever beams located at the bottom of the rotating frame. The explosion impact simulation unit is a top arch impact device or a bottom arch impact device. The top arch impact device is installed on a horizontal ground, and the bottom arch impact device is installed on a reaction frame. The top arch impact device or the bottom arch impact device is detachably connected to the impact rod sleeve. The heat insulation protection unit includes a movable heat insulation block, heat insulation fiber, and heat insulation plate, and the movable heat insulation block, heat insulation fiber, and heat insulation plate are placed at the connection position between the component under test and the heating furnace; The data acquisition unit includes a vertical force sensor and a horizontal force sensor installed on the loading unit, a temperature sensor installed on the heating furnace, a velocity sensor installed on the bottom arch impact rod and the top arch impact rod, a component parameter measurement sensor installed on the component to be measured, a pressure sensor installed on the top arch impact device, and a computer.

2. The mechanical performance testing system for fire-explosion coupling effect of shield tunnel segment joints according to claim 1, characterized in that: The reaction frame includes two parallel columns, a top beam installed on the top of the two columns, and a central suspension beam installed on the inner wall of one of the columns.

3. The mechanical performance testing system for fire-explosion coupling effect of shield tunnel segment joints according to claim 1, characterized in that: The rotating frame includes two parallel frame columns, a crossbeam installed on the top of the two frame columns, and cantilever beams installed in the middle and bottom of the two frame columns.

4. The mechanical performance testing system for fire-explosion coupling effect of shield tunnel segment joints according to claim 1, characterized in that: The rotating unit includes a rotary lock and a rotating shaft. One end of the rotating shaft is rotatably installed with the reaction frame column, and the other end is fixedly connected to the rotating frame. Rotary locks are symmetrically installed on the upper and lower sides of the rotating shaft between the reaction frame and the rotating frame, and the rotating frame is locked by the rotary locks.

5. The mechanical performance testing system for fire-explosion coupling effect of shield tunnel segment joints according to claim 1, characterized in that: The top arch impact device includes a nitrogen storage chamber arranged on a horizontal ground. The top of the nitrogen storage chamber is threadedly connected to one end of the impact rod fall buffer device, and the other end of the impact rod fall buffer device is connected to the threaded end of the impact rod sleeve. The air inlet of the nitrogen storage chamber is connected to the gas outlet of the nitrogen cylinder through a pipeline.

6. The mechanical performance testing system for fire-explosion coupling effect of shield tunnel segment joints according to claim 5, characterized in that: The impact rod fall-back buffer device includes a tube body, with the inner threaded end of the tube body threadedly connected to the nitrogen storage chamber and the outer threaded end threadedly connected to the impact rod sleeve. A spring is installed inside the tube body, and a top arch impact rod is installed on the top of the spring.

7. The mechanical performance testing system for fire-explosion coupling effect of shield tunnel segment joints according to claim 6, characterized in that: The bottom arch impact device includes a lifting motor installed on the middle suspension beam. The wire rope on the lifting motor passes through the pulley at the bottom of the top beam and its end is connected to the bottom arch impact rod. The extended threaded end of the impact rod sleeve is connected to the internal threaded end of the impact rod sleeve.

8. The mechanical performance testing system for fire-explosion coupling effect of shield tunnel segment joints according to claim 7, characterized in that: The outer periphery of the impact rod sleeve, the outer periphery of the impact rod sleeve extension tube, and the outer periphery of the impact rod fall buffer device are provided with heat insulation layers.

9. The mechanical performance testing system for fire-explosion coupling effect of shield tunnel segment joints according to claim 1, characterized in that: The component parameter measurement sensor consists of strain gauges, displacement gauges, accelerometers, goniometers, and digital image analyzers.

10. The mechanical performance testing system for fire-explosion coupling effect of shield tunnel segment joints according to claim 1, characterized in that: A load-sharing beam is provided between the vertical loading jack and the component to be tested. The load-sharing beam includes two loading heads that are in contact with the component to be tested, and a load-bearing beam that is connected at one end to the vertical loading jack and at the other end to the loading heads.

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