Horizontal freezing simulation device and test method for urban underground engineering

Abstract

The present invention relates to a horizontal freezing simulation device and a test method for an urban underground engineering, comprising a frost heave chamber, wherein the lower bottom plate of the frost heave chamber is a detachable permeable plate, a water pool is provided below the frost heave chamber, a No. 1 temperature sensor and a water temperature regulating device are provided in the water pool, and a water pump is connected to the right side of the water pool; a vertically placed hydraulic cylinder is fixedly installed on the upper end surface of the frost heave chamber, a push rod of the hydraulic cylinder passes through the top plate of the frost heave chamber and extends into the frost heave chamber, and is fixedly connected with a pressing plate. The present invention adopts a method in which the water pool is used to pressurize and penetrate the frost heave chamber through the permeable plate, so as to simulate the process of groundwater infiltration into the model of the target tunnel, so that the experimental data is more reliable; an air bag filled in a ceramic spacer is used to simulate the unexcavated land space, and then the support for the upper soil is gradually released by unloading the air bag and removing the ceramic spacer, so as to simulate the excavation process, so as to obtain more realistic experimental data of the internal pressure, temperature and moisture changes of the frozen soil body during the excavation process.

Description

Technical Field

[0001] The invention relates to the technical field of soil frost heave test equipment, in particular to a horizontal freezing simulation device and a test method for an urban underground engineering. Background Art

[0002] The large-scale freezing model testing machine is mainly used to make large frozen soil samples and measure the physical phenomena of the frost heave process of the hollow cylindrical model of multiple frost heave tubes. The functions of the machine in the whole test process are as follows:

[0003] 1. It can measure the vertical frost heave force, and under vertical constraint conditions, it can measure the internal stress of the model and the radial displacement of the hollow cylinder model.

[0004] 2. According to engineering requirements, the radial temperature distribution in the middle of the model height and the interface temperature of the upper and lower models can be measured symmetrically.

[0005] 3. When the model is subject to longitudinal constraints, the radial deformation of the vertical cylindrical model under constant pressure can be measured and controlled, and the internal stress under constant radial deformation can be measured and controlled.

[0006] 4. According to the needs of the project, the low-temperature constant temperature circulation, measurement and control of multiple freezing pipes can be completed.

[0007] In the prior art, the measurement of frost heave experimental data usually uses pressure sensors, displacement sensors, precision motor servo systems and other devices, and cooperates with a full digital controller to transmit the processed information to a PC to complete the display of various engineering quantities, and to display the pressure, deformation and temperature and their relationship curves in real time. Through the measurement and control of the expansion module, the frost heave coefficient can be calculated. However, in the process of simulating the freezing of urban underground horizontal, there is no systematic device, and it is difficult to ensure the accuracy of each measurement item when multiple measurement items are carried out simultaneously. Summary of the invention

[0008] In view of the defects of the above-mentioned technology, the present invention proposes a simulation device and test method for horizontal freezing of urban underground engineering.

[0009] The invention discloses a horizontal freezing simulation device for urban underground engineering, comprising a freezing system, a loading system, a testing system and a water replenishing system. The loading system is installed on the upper part of the freezing system and is used to pressurize the freezing system. The testing system is distributed in the freezing system and is used to test the internal environment of the freezing system. The water replenishing system is connected to the freezing system and is used to replenish water into the freezing system.

[0010] The freezing system includes a frost heave chamber, the lower bottom plate of the frost heave chamber is a detachable permeable plate, four card frames are fixed longitudinally in the middle of the frost heave chamber, the card frames are respectively located at the four corners of the quadrilateral, and an arc-shaped ceramic spacer is respectively embedded between the card frames. The ceramic spacer is in a circular ring shape, and four partitions are interspersed inside the ceramic spacer. The partitions divide the circle surrounded by the ceramic spacers into five subspaces, and an air bag is placed in each subspace, and the air bag completely fills the corresponding subspace.

[0011] A plurality of frost heave tubes are longitudinally fixed in the frost heave chamber. The frost heave tubes are evenly distributed on the periphery of the ceramic spacer. The frost heave tubes are all double-layer tubes. The inner tube of the frost heave tube is a water inlet pipe, and the outer tube of the frost heave tube is a return pipe. A clamping strip for fixing the relative position of the inner tube and the outer tube is provided between the inner tube and the outer tube. The rear ends of the frost heave tubes pass through the frost heave chamber and are connected to a refrigeration system.

[0012] The water replenishment system includes a water pool located below the frost heave chamber, a temperature sensor No. 1 and a water temperature regulating device are arranged in the water pool, a water pump is connected to the right side of the water pool, and the water pool and the frost heave chamber are sealed.

[0013] The loading system includes a longitudinal pressure hydraulic cylinder and a transverse pressure hydraulic cylinder. The longitudinal pressure hydraulic cylinder is fixedly installed on the upper part of the frost heave chamber. The push rod of the hydraulic cylinder vertically passes through the top plate of the frost heave chamber and is connected to a vertical loading plate. The vertical loading plate is located above the frost heave chamber and is used to apply force downward into the frost heave chamber. The transverse pressure hydraulic cylinder is installed on the right side of the frost heave chamber. The push rod of the transverse pressure hydraulic cylinder passes through the right side wall of the frost heave chamber and is connected to a transverse loading plate located on the right side of the interior of the frost heave chamber.

[0014] The test system comprises: a plurality of humidity sensors, a second temperature sensor and a pressure sensor are evenly distributed from the upper left corner to the lower right corner in the frost heave chamber; and a plurality of borehole cameras are evenly distributed from the lower left corner to the upper right corner in the frost heave chamber.

[0015] The airbag is a rubber airbag with a ventilation port.

[0016] The frost heave pipe is made of stainless steel.

[0017] The second humidity sensor is an integrated humidity sensor.

[0018] The implementation method of the present invention specifically comprises the following steps:

[0019] (1) Installation of model filling and test system; (2) Installation of loading system and freezing system; (3) Start the longitudinal pressure hydraulic cylinder and the transverse pressure hydraulic cylinder to load the soil; (4) Quickly freeze the soil on one side of the ceramic spacer 8 and release the airbags on this side in turn to simulate the excavation on this side. At the same time, the supporting structure can be added to simulate the construction activities in the tunnel; (5) Freeze the soil near the ceramic spacer 8 on the other side and release the airbags on this side; (6) Stop all freezing activities, carry out a natural thawing process to delay the thawing process, and then carry out a forced thawing, that is, increase the thawing rate. During the two thawing processes, use various sensors to record the environmental changes of the soil during the tunnel excavation process.

[0020] The beneficial effects of the present invention are:

[0021] 1. The present invention adopts a systematic measurement method to unify the determination of urban groundwater changes, pressure distribution, land deformation, and groundwater temperature in the same experimental model.

[0022] 2. The present invention uses a water pool to pressurize water into the frost heave chamber through a permeable plate to simulate the process of groundwater infiltration into the model of the target tunnel, making the experimental data more reliable; a hydraulic cylinder is used to pressurize the model of the target tunnel from above, which can simulate the pressure on the target tunnel at different stratum depths.

[0023] 3. The present invention uses air bags filled in ceramic spacers to simulate unexcavated land space, and then gradually releases the support for the upper soil by unloading the air bags and removing the ceramic spacers to simulate the excavation process, thereby more realistically obtaining experimental data on the changes in the frozen soil body during the excavation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0025] Figure 1 is a stereogram of the present invention;

[0026] Figure 2 It is a schematic diagram of the use of the frost heave pipe of the present invention;

[0027] Figure 3 It is a connection relationship diagram between the frost expansion pipe of the present invention and a refrigeration system. DETAILED DESCRIPTION

[0028] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below.

[0029] like Figures 1 to 3As shown, the horizontal freezing simulation device for urban underground engineering includes a freezing system, a loading system, a testing system and a moisture replenishing system. The loading system is installed on the upper part of the freezing system and is used to pressurize the freezing system. The testing system is distributed in the freezing system and is used to test the internal environment of the freezing system. The moisture replenishing system is connected to the freezing system and is used to replenish moisture into the freezing system.

[0030] The freezing system includes a frost heave chamber 1, the lower bottom plate of the frost heave chamber 1 is a detachable permeable plate 2, four brackets 7 are longitudinally fixed in the middle of the frost heave chamber 1, the brackets 7 are respectively located at the four corners of the quadrilateral, and an arc-shaped ceramic spacer 8 is respectively embedded between the brackets 7. The ceramic spacer 8 is in a circular ring shape, and four partitions 9 are interspersed inside the ceramic spacer 8. The partitions 9 divide the circle surrounded by the ceramic spacer 8 into five subspaces, and a rubber airbag with a ventilation port is placed in each subspace, and the airbag completely fills the corresponding subspace.

[0031] A plurality of frost heave tubes 10 made of stainless steel are longitudinally fixed in the frost heave chamber 1. The frost heave tubes 10 are evenly distributed around the ceramic spacer 8. Stainless steel has low cost, good thermal conductivity, good corrosion resistance, and can timely control the temperature change of the soil. The frost heave tubes 10 are all double-layer tubes. The inner tube 11 of the frost heave tube 10 is a water inlet pipe, and the outer tube 12 of the frost heave tube 10 is a return pipe. A clamping strip 13 for fixing the relative position of the inner tube 11 and the outer tube 12 is provided between the inner tube 11 and the outer tube 12; the inner tube 11 is connected to an evaporator 14, and the end of the evaporator 14 connected to the inner tube 11 is connected to a condenser 15, and a throttle valve is installed between the evaporator 14 and the condenser 15. The condenser 15 is connected to a compressor 16, and the compressor 16 is connected to the other end of the evaporator 14. The end of the evaporator 14 connected to the compressor 16 is connected to the outer tube 12, and is also connected to a brine supply pipeline 17.

[0032] The water replenishment system includes a water pool 4 located below the frost heave chamber 1, wherein the water pool 4 is provided with a temperature sensor No. 1 for detecting the water temperature and a water temperature regulating device for heating or cooling the water temperature, and a water pump is connected to the right side of the water pool 4. The water pool 4 and the frost heave chamber 1 are sealed and the water pool 4 replenishes water for the frost heave chamber 1 under the pressurized action of the water pump.

[0033] The loading system includes a longitudinal pressure hydraulic cylinder 5 and a transverse pressure hydraulic cylinder. The longitudinal pressure hydraulic cylinder is fixedly installed on the upper part of the frost heave chamber 1. The push rod of the hydraulic cylinder vertically passes through the top plate of the frost heave chamber 1 downward and is connected to a vertical loading plate 6. The vertical loading plate 6 is located above the frost heave chamber 1 and is used to apply force downward into the frost heave chamber 1. The transverse pressure hydraulic cylinder is installed on the right side of the frost heave chamber 1. The push rod of the transverse pressure hydraulic cylinder passes through the right side wall of the frost heave chamber 1 and is connected to a transverse loading plate located on the right side inside the frost heave chamber 1.

[0034] The test system includes: a number of humidity sensors for measuring soil moisture content, a second temperature sensor for measuring soil temperature changes, and a pressure sensor for measuring soil pressure changes are evenly distributed from the upper left corner to the lower right corner in the frost heave chamber 1; a number of borehole cameras for measuring soil deformation are evenly distributed from the lower left corner to the upper right corner in the frost heave chamber 1. The humidity sensor, the second temperature sensor, the pressure sensor, and the borehole camera are fixed in the frozen soil in an evenly distributed manner to detect the change process of multi-dimensional information data in various areas of the frozen soil. The second humidity sensor is an integrated humidity sensor, which is generally affected as little as possible by the expansion and contraction of the frozen soil while detecting the freezing environment.

[0035] The method of using the urban underground horizontal freezing simulation device and the implementation method thereof of the present invention is as follows:

[0036] When in use, the air bag is first used to fill the internal space of the ceramic spacer 8, and then the soil of the simulated stratum is filled in the frost heave chamber 1, and the signals of the sensing elements such as the humidity sensor, the No. 1 temperature sensor, the No. 2 temperature sensor, the pressure sensor, and the borehole camera are detected by an external controller. The water pool 4 is pressurized by a water pump, and the water pool 4 and the frost heave chamber 1 are sealed environments, so the water in the water pool 4 will penetrate from the permeable plate 2 to the frost heave chamber 1 under pressure. The brine supply pipeline 17 is connected to the brine pump, and under the action of the brine pump, the brine treated by the refrigeration system is driven to circulate between the inner tube 11 and the outer tube 12 to simulate the changes of the soil in winter and summer. The brine can be a calcium chloride solution.

[0037] By reducing the air pressure of the airbags one by one from top to bottom and withdrawing the ceramic spacer 88 on the corresponding side, the action of excavating the soil is simulated. During this process, the changes in temperature, moisture content, pressure and deformation of each soil point are monitored using an external controller and display device.

[0038] In order to more comprehensively simulate the changes in frozen soil during freezing construction, the two methods of natural thawing and forced thawing are implemented. The specific implementation is as follows:

[0039] (1) Installation of model filling and test system; (2) Installation of loading system and freezing system; (3) Start the longitudinal pressure hydraulic cylinder 5 and the transverse pressure hydraulic cylinder to load the soil; (4) Quickly freeze the soil on one side of the ceramic spacer 8 and release the airbags on this side in turn to simulate the excavation on this side. At the same time, the supporting structure can be added to simulate the construction activities in the tunnel; (5) Freeze the soil near the ceramic spacer 8 on the other side and release the airbags on this side; (6) Stop all freezing activities, carry out a natural thawing process to delay the thawing process, and then carry out a forced thawing, that is, increase the thawing rate. During the two thawing processes, use various sensors to record the environmental changes of the soil during the tunnel excavation process.

[0040] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A horizontal freezing simulation device for urban underground engineering, including a freezing system, a loading system, a testing system and a water replenishing system, characterized in that: The loading system is installed on the upper part of the freezing system and is used to pressurize the freezing system. The testing system is distributed in the freezing system and is used to test the internal environment of the freezing system. The water replenishing system is connected to the freezing system and is used to replenish water into the freezing system. The freezing system comprises a frost heave chamber, wherein the lower bottom plate of the frost heave chamber is a detachable water-permeable plate, and four brackets are longitudinally fixed in the middle of the frost heave chamber, wherein the brackets are respectively located at the four corners of the quadrilateral, and an arc-shaped ceramic spacer is respectively embedded between the brackets, wherein the ceramic spacer is in a circular ring shape, and four partitions are interspersed inside the ceramic spacer, wherein the partition divides the circle formed by the ceramic spacer into five subspaces, and an air bag is placed in each subspace, and the air bag completely fills the corresponding subspace; A plurality of frost heave tubes are longitudinally fixed in the frost heave chamber, and the frost heave tubes are evenly distributed on the periphery of the ceramic spacer. The frost heave tubes are all double-layer tubes, the inner tube of the frost heave tube is the water inlet tube, and the outer tube of the frost heave tube is the return tube. A clamping strip for fixing the relative position of the inner tube and the outer tube is provided between the inner tube and the outer tube; the inner tubes are all connected to an evaporator, and the end of the evaporator connected to the inner tube is connected to a condenser, a throttle valve is installed between the evaporator and the condenser, the condenser is connected to a compressor, the compressor is connected to the other end of the evaporator, and the end of the evaporator connected to the compressor is connected to the outer tube, and is also connected to a brine supply pipeline; water replenishment The charging system includes a water pool located below the frost heave chamber, wherein the water pool is provided with a No. 1 temperature sensor and a water temperature regulating device, a water pump is connected to the right side of the water pool, and the water pool and the frost heave chamber are sealed; the loading system includes a longitudinal pressure hydraulic cylinder and a transverse pressure hydraulic cylinder, the longitudinal pressure hydraulic cylinder is fixedly installed on the upper part of the frost heave chamber, a push rod of the hydraulic cylinder vertically downward passes through the top plate of the frost heave chamber and is connected to a vertical loading plate, the vertical loading plate is located above the frost heave chamber and is used to apply force downward into the frost heave chamber, the transverse pressure hydraulic cylinder is installed on the right side of the frost heave chamber, and a push rod of the transverse pressure hydraulic cylinder passes through the right side wall of the frost heave chamber and is connected to a transverse loading plate located on the right side of the interior of the frost heave chamber.

2. The urban underground engineering horizontal freezing simulation device according to claim 1 is characterized in that: The test system comprises: a plurality of humidity sensors, a second temperature sensor and a pressure sensor are evenly distributed from the upper left corner to the lower right corner in the frost heave chamber; and a plurality of borehole cameras are evenly distributed from the lower left corner to the upper right corner in the frost heave chamber.

3. The urban underground engineering horizontal freezing simulation device according to claim 1 is characterized in that: The airbag is a rubber airbag with a ventilation port.

4. The urban underground engineering horizontal freezing simulation device according to claim 1 is characterized in that: The frost heave pipe is made of stainless steel.

5. The urban underground engineering horizontal freezing simulation device according to claim 2 is characterized in that: The humidity sensor is an integrated humidity sensor.

6. The test method of the urban underground engineering horizontal freezing simulation device according to any one of claims 1 to 5, characterized in that: The specific steps include: (1) Installation of model filling and test system; (2) Installation of loading system and freezing system; (3) Starting the longitudinal hydraulic cylinder and the transverse hydraulic cylinder to load the soil; (4) Quickly freezing the soil on one side of the ceramic spacer and releasing the airbags on that side in turn to simulate excavation on that side, while adding support structures to simulate construction activities in the tunnel; (5) Freezing the soil near the ceramic spacer on the other side and releasing the airbags on that side; (6) Stopping all freezing activities, carrying out a natural thawing process to delay the thawing process, and then carrying out a forced thawing process to increase the thawing rate. During the two thawing processes, various sensors are used to record the environmental changes of the soil during the tunnel excavation process.

Images