Simulation device and test method for chloride ion transmission under action of circumferential water and soil pressure of PHC (prestressed high-strength concrete) pipe pile

Abstract

The invention discloses a device for simulating chloride ion transmission under the action of circumferential water and soil pressure of a PHC tubular pile, which comprises a loading device and an environmental simulation test box, and is characterized in that the environmental simulation test box comprises an oil source system and an environmental test box, the oil source system sets the pressure of a soil pressure box in the test box according to the actual engineering condition, and the environmental test box is connected with the loading device; the closed-loop control of the soil pressure is realized, and the soil pressure value, the oil cylinder oil pressure and the test time are displayed in real time; the loading device comprises an oil cylinder and a pressure plate, the chlorine salt-containing water and soil mixture in the environmental test box is loaded through the loading device, and the circumferential water and soil pressure borne by the PHC pipe pile in the actual chlorine salt-containing service environment in the coastal region is simulated through the acting force of the mixed soil body on the pipe pile under the action of the load and the box body constraining force; the invention relates to a test method for solving the transmission performance of chloride ions in a PHC pipe pile in an actual service environment. The device is simple in structure, low in manufacturing cost, convenient to operate and practical.

Description

Technical Field

[0001] The invention belongs to the technical field related to civil engineering, and in particular relates to a chloride ion transmission simulation device and a test method for a PHC pipe pile under annular water and soil pressure. Background Art

[0002] The durability of pile foundation structure is an important factor affecting the safety of upper concrete structure. Compared with above-ground building structures, coastal or offshore PHC pipe piles work in closed and humid environments, permanent immersion or alternating dry and wet environments. In these underground geotechnical environments, the durability of concrete pile foundations is affected by multiple factors such as geotechnical media, annular pressure of water and soil on the pile side, and the corrosion of corrosive ions in groundwater. Its service environment is far more complex than that of above-ground structures. The Ministry of Transport’s survey on the status of concrete structures in my country’s port projects showed that more than 80% of the pile foundation structures of docks had suffered serious or relatively serious steel corrosion damage, and some had steel rust damage after only 5-10 years of service.

[0003] The existing chloride ion transmission test methods are basically steady-state and non-steady-state diffusion test methods conducted in the laboratory. The research conditions are far from the actual service environment conditions of the pile foundation, and it is impossible to accurately explain the chloride ion transmission behavior and the durability degradation mechanism of the pile during the actual service process.

[0004] Previous studies have shown that load has a significant impact on the transport behavior of chloride ions in concrete.

[0005] Therefore, how to simulate the actual service environment of PHC piles under annular water and soil pressure and conduct research on the transmission performance of chloride ions based on this is a key technical problem in the field of concrete durability research. Summary of the invention

[0006] The purpose of the present invention is to provide a simulation device for chloride ion transmission under annular water and soil pressure of a PHC pipe pile, so as to solve the problem of evaluating and characterizing the chloride ion transmission performance of the PHC pipe pile under the actual service environment proposed in the above background technology.

[0007] Another object of the present invention is to provide a test method using the above-mentioned PHC pipe pile annular water and soil pressure simulation device to simulate the annular water and soil pressure borne by the PHC pipe pile in the actual chloride-containing salt service environment in coastal areas, and to solve the test method for the transmission performance of chloride ions in PHC pipe piles in the actual service environment.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A chloride ion transmission simulation device under the annular water and soil pressure of a PHC pile, comprising a loading device and an environmental simulation test box, wherein the environmental simulation test box comprises an oil source system and an environmental test box, wherein the oil source system sets the pressure of a soil pressure box in the test box according to the actual engineering situation, realizes closed-loop control of the soil pressure, and displays the soil pressure value, the oil pressure of the oil cylinder, and the test time in real time;

[0010] The loading device comprises an oil cylinder and a pressure plate, through which an annular load is applied to a pipe pile specimen placed in a chloride-salt mixed soil environment test box to simulate the annular water and soil pressure borne by the PHC pipe pile in an actual chloride-salt service environment in coastal areas.

[0011] Preferably, the oil source system is divided into a four-branch system, and the four branches work independently of each other, realizing multi-channel and multi-station, and each branch test is independent of each other, which is convenient for operation and maintenance.

[0012] Preferably, the branch line of the oil source system is provided with a main line accumulator, a safety valve, a manual valve, a branch line accumulator, a pressure transmitter, a pressure-compensating solenoid valve and a pressure-releasing solenoid valve, and the main line accumulator, the safety valve, the branch line accumulator, the pressure transmitter, the pressure-compensating solenoid valve and the pressure-releasing solenoid valve are all electrically connected to the PLC controller.

[0013] Preferably, the environmental test chamber includes a test chamber, a rock-soil-water mixture, a crossbeam, columns and a base plate, wherein the test chamber is provided in the middle of the upper surface of the base plate, and longitudinal columns are provided on both sides of the upper surface of the base plate close to the test chamber, and a crossbeam is provided on the upper side of the two columns, and the crossbeam is fixed to the two columns by two nuts.

[0014] Preferably, a pipe pile sample is provided at the inner center of the test box, the pipe pile sample and the test box are filled with water-soil mixture, and a plurality of earth pressure boxes with equal intervals are provided inside the water-soil mixture.

[0015] Preferably, the oil cylinder is installed in the middle of the upper surface of the beam, and the telescopic rod of the oil cylinder passes through the beam and extends toward the test box. A pressure plate is installed at the bottom of the telescopic rod of the oil cylinder, and through the extension and retraction of the telescopic rod of the oil cylinder, the pressure plate presses against the water-soil mixture to generate annular water-soil pressure, and transmits it to the pipe pile sample buried in the soil.

[0016] In addition, the present invention also provides a test method using the above-mentioned chloride ion transmission simulation device under the annular water and soil pressure of the PHC pile, comprising the following steps:

[0017] Step 1: Cut a 50cm long pipe pile with cracks and smooth both ends of the pipe pile specimen with cement mortar;

[0018] Step 2: Prepare a sodium chloride solution with the same concentration according to the chloride ion concentration in the actual engineering environment; mix the sodium chloride solution and the actual sand and soil in the engineering in proportion;

[0019] Step 3: Place the pipe pile specimen in the environmental test chamber, fill the mixed water-soil mixture into the environmental test chamber, and compact it to ensure that the water-soil mixture fills the entire chamber;

[0020] Step 4: Start the oil source system of the test device and load the soil in the environmental test chamber through the oil cylinder to control the pressure plate;

[0021] Step 5: Take out the PHC pile specimen, collect concrete samples by core drilling method, and conduct chloride ion concentration distribution test.

[0022] Compared with the prior art, the device and method for simulating chloride ion transmission under the annular water and soil pressure of the PHC pile of the present invention have the following beneficial effects:

[0023] 1. The present invention loads the chloride-salt soil mixture in the environmental test box by a loading device, and simulates the annular water-soil pressure borne by the PHC piles in the actual chloride-salt service environment in the coastal area by the force of the mixed soil on the piles under the action of the load and the box constraint force, so as to solve the test method for the transmission performance of chloride ions in the PHC piles in the actual service environment; 2. The present invention has a simple structure, low manufacturing cost, convenient operation, and is practical. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0025] Figure 1 It is a schematic diagram of a chloride ion transmission simulation device under the annular water and soil pressure of a PHC pipe pile proposed in the present invention;

[0026] Figure 2 for Figure 1 A schematic diagram of a semi-sectioned three-dimensional structure;

[0027] Figure 3 for Figure 2 A schematic diagram of the front view structure of

[0028] Figure 4 for Figure 1 Schematic diagram of the principle structure;

[0029] Figure 5 for Figure 1 Test method control flow chart;

[0030] Figure 6 for Figure 1Flow chart of the method steps;

[0031] Figure 7 This is a graph showing the change in chloride ion content in concrete.

[0032] In the figure: 1. beam; 2. column; 3. bottom plate; 4. test box; 5. pressure plate; 6. nut; 7. oil cylinder; 8. soil pressure box; 9. pipe pile sample; 10. water-soil mixed soil; 11. main circuit accumulator; 12. manual valve; 13. pressure sensor; 14. pressure relief solenoid valve; 15. branch accumulator; 16. pressure supplement solenoid valve; 17. safety valve; 18. touch screen; 19. PLC controller. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0034] Example 1

[0035] See also Figure 1-6 As shown, the present invention discloses a chloride ion transmission simulation device for a PHC pipe pile under annular water and soil pressure, comprising a loading device and an environmental simulation test box, wherein the environmental simulation test box comprises an oil source system and an environmental test box. The oil source system sets the pressure of a soil pressure box 8 in the test box according to actual engineering conditions, implements closed-loop control of the soil pressure, and displays the soil pressure value, the oil pressure of the oil cylinder 7, and the test time in real time.

[0036] The loading device comprises an oil cylinder 7 and a pressure plate 5, through which an annular load is applied to a pipe pile specimen placed in an environmental test box of chloride-salt mixed soil to simulate the annular water and soil pressure borne by the PHC pipe pile in the actual chloride-salt service environment in coastal areas.

[0037] The oil source system is divided into a four-way branch system, and the four-way branches work independently of each other, realizing multi-way and multi-station, and each test is independent of each other, which is convenient for operation and maintenance. Tests can be carried out simultaneously without affecting each other. When a certain sample is damaged, the solenoid valve of the road can be automatically closed, and the experiments of other roads are not affected as usual; the branch roads of the oil source system are provided with a main road accumulator 11, a safety valve 17, a manual valve 12, a branch road accumulator 15, a pressure transmitter, a pressure-replenishing solenoid valve 16 and a pressure-relief solenoid valve 14, and the main road accumulator 11, the safety valve 17, the branch road accumulator 15, the pressure transmitter, the pressure-replenishing solenoid valve 16 and the pressure-relief solenoid valve 14 are all electrically connected to a PLC controller 19, and the PLC controller 19 is electrically connected to a touch screen 18;

[0038] The system pressure is 16MPa, the area of ​​the oil cylinder 7 is 125cm, and the diameter of the oil cylinder 7 is 13cm. It can apply a continuous pressure to the soil in the box. The annular water and soil pressure generated in the soil is transmitted to the pipe pile specimen buried in the soil. The data is monitored by the soil pressure box pre-buried in the soil, so as to simulate the annular water and soil pressure that the pipe pile is subjected to in the actual service environment.

[0039] The environmental test box includes a test box body 4, a rock-soil-water mixture, a crossbeam 1, a column 2 and a bottom plate 3, wherein the test box body 4 is provided in the middle of the upper surface of the bottom plate 3. The upper surface of the bottom plate 3 is provided with longitudinal columns 2 near the two sides of the test box body 4, and the upper sides of the two columns 2 are provided with a crossbeam 1, and the crossbeam 1 is fixed to the two columns 2 by two nuts 6. A pipe pile sample 9 is provided at the inner center of the test box body 4, and the pipe pile sample 9 and the test box body 4 are filled with water-soil mixed soil 10, and a plurality of soil pressure boxes 8 with equal spacing are provided inside the water-soil mixed soil 10. The test box body 4 is made of corrosion-resistant carbon steel pipe, and the inner surface is lined with a 1mm thick 304 stainless steel plate.

[0040] The oil cylinder 7 is installed in the middle of the upper surface of the beam 1, and the telescopic rod of the oil cylinder 7 passes through the beam 1 and extends to the test box 4. A pressure plate 5 is installed at the bottom of the telescopic rod of the oil cylinder 7, and through the extension and retraction of the telescopic rod of the oil cylinder 7, the pressure plate 5 presses on the water-soil mixed soil 10 to generate annular water-soil pressure, and transmits it to the pipe pile sample 9 buried in the soil.

[0041] Example 2

[0042] The test method of the chloride ion transmission simulation device under the annular water and soil pressure of the PHC pile comprises the following steps:

[0043] Step 1: Cut a 50cm long pipe pile with cracks and smooth both ends of the pipe pile specimen with cement mortar;

[0044] Step 2: Prepare a sodium chloride solution (2.5%) of the same concentration according to the chloride ion concentration in the actual engineering environment; refer to the actual engineering environment, mix the sodium chloride solution and the actual engineering sand in proportion (mass ratio 1:60);

[0045] Step 3: Place the pipe pile specimen in the environmental test chamber, fill the mixed water-soil mixture into the environmental test chamber, and compact it to ensure that the water-soil mixture fills the entire chamber;

[0046] Step 4: Start the oil source system of the test device, and control the pressure plate 5 to load the soil in the environmental test box through the oil cylinder 7, and set the loads to 25KPa, 50KPa, and 100KPa respectively;

[0047] When the pressure in the environmental test chamber reaches the set pressure, the pressure sensor 13 feeds back the pressure signal to the oil source system, and the oil source system issues a command to close the pressure-compensating solenoid valve 16, so that the environmental test chamber maintains a constant pressure;

[0048] The oil source system monitors the soil pressure in real time through the soil pressure box. If the soil pressure drops, the oil source system will control the pressure replenishing solenoid valve 16 to replenish the pressure of the oil cylinder 7;

[0049] When the soil pressure increases, the oil source system issues a command to open the pressure relief solenoid valve 14 to relieve the pressure. After the soil reaches the set pressure, the pressure relief solenoid valve 14 closes, forming a closed-loop control system to keep the sample at a constant pressure for a long time and keep the pressure in the sample within the control accuracy range (1KPa).

[0050] When the test reaches a predetermined age, the load is unloaded through the oil source system and the pressure plate 5 is removed;

[0051] Step 5: Take out the PHC pile specimen, collect concrete samples by core drilling method, and conduct chloride ion concentration distribution test.

[0052] Step 6: According to the chloride ion test method for hardened concrete, the concrete core sample is crushed, screened, and ground. The chloride ions in the concrete are extracted by acid dissolution method, and the chloride ion content is tested by titration method. Figure 7 As shown, the chloride ion content in the figure is the mass percentage of chloride ions in the core sample concrete.

[0053] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A chloride ion transmission simulation device for a PHC pile under annular water and soil pressure, comprising a loading device and an environmental simulation test chamber, characterized in that: The environmental simulation test box includes an oil source system and an environmental test box. The oil source system sets the pressure of the soil pressure box in the test box according to the actual engineering situation, realizes closed-loop control of the soil pressure, and displays the soil pressure value, cylinder oil pressure, and test time in real time. The loading device comprises an oil cylinder and a pressure plate, through which an annular load is applied to a pipe pile specimen placed in an environmental test box of chloride-salt mixed soil, so as to simulate the annular water and soil pressure borne by the PHC pipe pile in the actual chloride-salt service environment in coastal areas.

2. The device for simulating chloride ion transmission under annular water and soil pressure of a PHC pile as claimed in claim 1, characterized in that: The oil source system is divided into a four-branch system, and the four branches work independently of each other, realizing multi-channel and multi-station, and each branch test is independent of each other, which is convenient for operation and maintenance.

3. The device for simulating chloride ion transmission under annular water and soil pressure of a PHC pile as claimed in claim 2, characterized in that: The branch line of the oil source system is provided with a main line accumulator, a safety valve, a manual valve, a branch line accumulator, a pressure transmitter, a pressure replenishing solenoid valve and a pressure relief solenoid valve, and the main line accumulator, the safety valve, the branch line accumulator, the pressure transmitter, the pressure replenishing solenoid valve and the pressure relief solenoid valve are all electrically connected to the PLC controller.

4. The device for simulating chloride ion transmission under annular water and soil pressure of a PHC pile as claimed in claim 3, characterized in that: The environmental test box includes a test box body, a rock-soil-water mixture, a crossbeam, a column and a bottom plate. The test box body is provided in the middle of the upper surface of the bottom plate, and longitudinal columns are provided on both sides of the upper surface of the bottom plate close to the test box body. The upper sides of the two columns are provided with a crossbeam, and the crossbeam is fixed to the two columns by two nuts.

5. The device for simulating chloride ion transmission under annular water and soil pressure of a PHC pile as claimed in claim 4, characterized in that: A pipe pile sample is arranged at the inner center of the test box, the pipe pile sample and the test box are filled with water-soil mixture, and a plurality of earth pressure boxes with equal spacing are arranged inside the water-soil mixture.

6. The device for simulating chloride ion transmission under annular water and soil pressure of a PHC pile as claimed in claim 5, characterized in that: The oil cylinder is installed in the middle of the upper surface of the beam, and the telescopic rod of the oil cylinder passes through the beam and extends to the test box. A pressure plate is installed at the bottom of the telescopic rod of the oil cylinder, and through the extension and retraction of the telescopic rod of the oil cylinder, the pressure plate presses the water-soil mixed soil to generate annular water-soil pressure, and transmits it to the pipe pile sample buried in the soil.

7. A test method using the chloride ion transmission environment simulation device under the annular water and soil pressure of the PHC pile according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1: Cut a 50cm long pipe pile with cracks and smooth both ends of the pipe pile specimen with cement mortar; Step 2: Prepare a sodium chloride solution with the same concentration according to the chloride ion concentration in the actual engineering environment; mix the sodium chloride solution and the actual sand and soil in the engineering in proportion; Step 3: Place the pipe pile specimen in the environmental test chamber, fill the mixed water-soil mixture into the environmental test chamber, and compact it to ensure that the water-soil mixture fills the entire chamber; Step 4: Start the oil source system of the test device and load the soil in the environmental test chamber through the oil cylinder to control the pressure plate; Step 5: Take out the PHC pile specimen, collect concrete samples by core drilling method, and conduct chloride ion concentration distribution test.

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