CN115629096A - Foundation concrete freeze-thaw cycle test method influenced by underground water - Google Patents
Foundation concrete freeze-thaw cycle test method influenced by underground water Download PDFInfo
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- CN115629096A CN115629096A CN202211270480.4A CN202211270480A CN115629096A CN 115629096 A CN115629096 A CN 115629096A CN 202211270480 A CN202211270480 A CN 202211270480A CN 115629096 A CN115629096 A CN 115629096A
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 324
- 238000010998 test method Methods 0.000 title claims abstract description 23
- 238000012360 testing method Methods 0.000 claims abstract description 210
- 238000004088 simulation Methods 0.000 claims abstract description 203
- 239000002689 soil Substances 0.000 claims abstract description 60
- 230000008595 infiltration Effects 0.000 claims abstract description 33
- 238000001764 infiltration Methods 0.000 claims abstract description 33
- 239000000463 material Substances 0.000 claims abstract description 30
- 230000008859 change Effects 0.000 claims abstract description 17
- 238000003825 pressing Methods 0.000 claims abstract description 13
- 238000000034 method Methods 0.000 claims abstract description 11
- 230000005855 radiation Effects 0.000 claims abstract description 10
- 238000002360 preparation method Methods 0.000 claims abstract description 4
- 239000003673 groundwater Substances 0.000 claims description 50
- 230000007246 mechanism Effects 0.000 claims description 25
- 238000005057 refrigeration Methods 0.000 claims description 20
- 238000001514 detection method Methods 0.000 claims description 11
- 238000005485 electric heating Methods 0.000 claims description 9
- 238000003860 storage Methods 0.000 claims description 7
- 238000012669 compression test Methods 0.000 claims description 6
- 238000010276 construction Methods 0.000 claims description 5
- 238000010438 heat treatment Methods 0.000 claims description 4
- 230000015556 catabolic process Effects 0.000 claims description 3
- 239000004927 clay Substances 0.000 claims description 3
- 238000006731 degradation reaction Methods 0.000 claims description 3
- 239000012780 transparent material Substances 0.000 claims description 3
- 238000010257 thawing Methods 0.000 description 21
- 238000007710 freezing Methods 0.000 description 17
- 230000008014 freezing Effects 0.000 description 17
- 230000000694 effects Effects 0.000 description 15
- 238000007789 sealing Methods 0.000 description 10
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- 238000004364 calculation method Methods 0.000 description 4
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D33/00—Testing foundations or foundation structures
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0001—Type of application of the stress
- G01N2203/0003—Steady
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
- G01N2203/0016—Tensile or compressive
- G01N2203/0019—Compressive
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0058—Kind of property studied
- G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
- G01N2203/0075—Strain-stress relations or elastic constants
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/025—Geometry of the test
- G01N2203/0252—Monoaxial, i.e. the forces being applied along a single axis of the specimen
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/025—Geometry of the test
- G01N2203/0256—Triaxial, i.e. the forces being applied along three normal axes of the specimen
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/067—Parameter measured for estimating the property
- G01N2203/0676—Force, weight, load, energy, speed or acceleration
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Abstract
The invention discloses a freeze-thaw cycle test method of foundation concrete influenced by underground water, which is characterized in that a concrete test piece is fixed in a simulation box and is buried in a simulated soil body material; simulating the infiltration condition of the underground water by means of the infiltration water at the lower part of the simulation box; applying pressure to the concrete test piece according to the pressure bearing size of the foundation concrete of the building to finish preparation work; during the test, cold air is introduced and cooled until the infiltrated water body is frozen, after the test is maintained for a period of time, the test piece is heated by applying electrothermal radiation on the concrete test piece until the frozen water body is defrosted, so that freeze-thaw cycle is repeatedly formed until the test time is over, and the performance change of the foundation concrete of the building, which is influenced by freeze-thaw, is obtained. The invention can simulate the freeze-thaw soil environment more truly and reliably, and obtain the freeze-thaw durability of the foundation concrete structure under the condition of infiltration of underground water; the method can be better used for safety assessment guidance of building foundations, and the building safety performance in the freeze-thaw environment is improved.
Description
Technical Field
The invention relates to the technical field of concrete freezing and thawing performance research, in particular to a freeze-thawing cycle test method for foundation concrete influenced by underground water.
Background
Land freeze-thaw refers to a physical geological role and phenomenon in which soil layers freeze and thaw due to temperature falling below zero and rising above zero. In cold regions of east and west of China, earth surface soil bodies are usually in freeze-thawing environments in stages due to seasons, large day-night temperature difference and the like. The underground concrete foundation part of the building in the freeze-thaw area is subjected to cyclic freeze-thaw damage at all times, so that the safety problem of the building is caused. Specifically, during the freezing process of soil, water in the soil is frozen into ice, and a plurality of ice interlayers and ice mirror bodies are generated, so that relative displacement of soil particles is caused, and soil body expansion is generated, which is called frost heaving. The appearance phenomenon of frost heaving is uniform or non-uniform swelling, bulging, cracking and the like of the soil layer; after melting, the alloy obviously sinks, so that the structure is greatly damaged. Generally, when water freezes in soil, the volume increases by about 9%, causing the foundation soil to expand around. For the foundation containing underground water, the water content in the foundation is determined by the depth of the underground water, when the foundation is under the underground water level, the water content is higher, frost heaving damage is more likely to occur, and the formed cracks can cause foundation cracking, so that the strength and deformation of the foundation are influenced. Therefore, research on the freezing, melting and deterioration of foundation soil structures under different underground water level depths is necessary.
Generally, the maximum influence depth of surface temperature change on the temperature of rock-soil mass is about 2.5 m, the influence from the surface to the bottom can be changed, namely, the temperature can be gradually increased from top to bottom, and the effect of freeze-thaw cycle on the soil mass structure can be influenced; meanwhile, the contact between the underground water and the soil body in the stratum can influence the effect of freeze-thaw cycle on the soil body, namely the contact surface of the soil body and the water can be subjected to the frost heaving effect under the condition of freezing, but the phenomenon of the non-water-soil contact surface is avoided. Most of the existing freeze-thaw test methods do not take the influence of these factors into consideration. For example, CN114486512A discloses a device for testing durability of concrete under the coupling effect of load and multiple environmental factors; the device can truly simulate various different environmental conditions, realize the concrete durability test under the coupling action of load and multi-environmental factors, and provide basic equipment for systematic and comprehensive research on the durability test of the concrete under the coupling action of load and multi-environmental factors. But the device still can not simulate the freeze-thaw durability performance of the soil body under the condition of infiltration of underground water.
Therefore, how to provide a test method capable of better simulating a freeze-thaw soil environment and obtaining the freeze-thaw durability of a foundation concrete structure under the infiltration action of underground water becomes a problem to be further considered and solved by technical personnel in the field.
Disclosure of Invention
Aiming at the defects of the prior art, the technical problems to be solved by the invention are as follows: how to provide a freeze-thaw cycle test method of foundation concrete, which can better simulate the freeze-thaw soil environment and obtain the freeze-thaw durability of the foundation concrete structure under the condition of infiltration of underground water and is affected by the underground water; the method is used for safety assessment guidance of building foundations and improves building safety performance in freeze-thaw environments.
In order to solve the technical problems, the invention adopts the following technical scheme:
a freeze-thaw cycle test method for foundation concrete influenced by underground water is characterized in that a corresponding concrete test piece is prepared according to the performance requirement of the foundation concrete of a building to be tested, and the concrete test piece is fixed in a simulation box; simulating the soil condition of the construction environment of the foundation concrete of the building, and embedding the concrete test piece into a simulated soil material; simulating the actual infiltration condition of the foundation concrete of the building by using the infiltration water at the lower part of the simulation box; applying pressure to the concrete sample according to the pressure bearing size (which can be obtained by calculation) of the foundation concrete of the building to finish the preparation work; during the test, cold air is introduced and cooled until the infiltrated water body is frozen, after the test is maintained for a period of time, the frozen water body is heated by applying electric heating radiation on the concrete test piece to finish unfreezing, and the operation is repeated after the operation is continued for a period of time to form freeze-thaw cycle, until the freeze-thaw test time is over, the concrete test piece is taken out and the performance of the concrete test piece is tested, and compared with the same concrete test piece which is not tested, the performance change parameters of the foundation concrete of the building, which are influenced by the freeze-thaw environment, are obtained.
The test method of the invention better simulates the condition that the concrete structure of the building foundation is buried by the soil body and infiltrated by the underground water. Meanwhile, the test is carried out by simulating the freezing and thawing condition that the thawing is actually completed by cold air blowing at night and by solar illumination radiation in the daytime. The actual freezing and thawing situation of the foundation concrete of the building can be better simulated. The performance parameter change obtained by testing after the test can better reflect the influence of the actual freeze-thaw situation on the performance. The method can be better used for safety monitoring of concrete foundations of actual buildings or pre-construction safety performance evaluation. The safety of the building is improved.
Furthermore, the test environment temperature cooled by introducing cold air is determined by the lowest temperature of the foundation concrete of the building in spring, autumn and night.
In this way, the simulation is performed with extreme environmental parameters, allowing the test results to be better used for safety assessment.
Further, the temperature of the electric heating radiation heating mode during the test is determined by the highest temperature of the foundation concrete of the building in spring and autumn in the daytime.
In this way, the simulation is carried out by using the limit environmental parameters, so that the test result can be better used for building safety assessment.
Further, when the concrete test piece is prepared, the building foundation concrete to be tested is poured according to the same concrete formula to obtain the cylindrical test piece.
Therefore, the test result of the concrete test piece can better reflect the performance change condition of the actual freezing and melting influence of the foundation concrete of the building. The test reliability is improved.
Furthermore, the simulated soil body material is prepared by adopting broken stones, silt and clay materials and simulating the actual soil body condition around the foundation concrete of the building. Preferably, the actual soil body around the foundation concrete of the building is directly excavated to obtain a simulated soil body material, and the material contains corresponding microorganisms, so that the influence effect of the microorganisms on the concrete of the rock mass can be kept consistent.
Therefore, the actual situation can be better simulated, and the test reliability is improved.
Further, when the depth of the simulation box (which refers to the depth capable of being used for the test) is greater than the infiltration depth of the foundation concrete of the building to be tested under the groundwater, the infiltration depth of the lower part of the simulation box is consistent with the actual infiltration depth of the groundwater; when the depth of the simulation box (which refers to the depth capable of being used for testing) is less than the infiltration depth of the foundation concrete of the building to be tested by the underground water, the simulation box is closed, gas is introduced for pressurizing, and the water pressure at the bottom of the simulation box is detected to ensure that the water pressure is consistent with the actual water pressure (the actual water pressure value can be obtained through actual detection or calculation) at the lowest part of the foundation concrete of the building to be tested.
Therefore, when the underground water infiltration depth of the foundation concrete of the building to be tested is larger, a deeper underground water infiltration condition can be simulated by adopting a smaller simulation box, and the application range of the test is greatly improved. When a pressure applying mode is adopted for simulation test, the height of the concrete test piece can be set to be consistent with the testable depth of the simulation box, then the simulation soil body material is covered until the simulation soil body material is consistent with the height of the concrete test piece, then the lower part of the simulation box is infiltrated to a depth of 5-10cm of the non-infiltrated soil body material above the simulation box, and therefore the actual condition that the concrete test piece is infiltrated by underground water can be better simulated.
Further, one freezing-thawing cycle time is 24 hours, including 12 hours of freezing and 12 hours of thawing; the number of freeze-thaw cycles was set to 7, 15, 30, 60 or 90 times according to the study, corresponding to a period of 7, 15, 30, 60 or 90 days.
This is because it is generally difficult to react to a change for less than seven days. And if the time is more than 90 days, the time is too long, and the significance of the test is difficult to play. After the freeze-thaw test is completed within a limited time, the performance change condition of the concrete test piece can be obtained by detecting the performance parameters of the concrete test piece, and the performance change condition caused by more time of freeze-thaw action can be reasonably calculated so as to guide actual safety monitoring.
Further, after the freeze-thaw test time is finished, taking out the concrete test piece, performing a uniaxial compression test or a triaxial compression test on the concrete test piece, testing the mechanical properties of the concrete test piece after the freeze-thaw cycle, including compressive strength and elastic modulus parameters, and comparing the mechanical property parameters of the concrete test piece which is not subjected to freeze-thaw to obtain the degradation degree of the mechanical properties of the foundation concrete of the building, which is influenced by the freeze-thaw environment.
The test method is realized by depending on a foundation concrete freeze-thaw cycle test system, the foundation concrete freeze-thaw cycle test system comprises a simulation box, an openable top cover is arranged at the upper end of the simulation box, a test piece positioning device is arranged at the middle lower part in the simulation box, and a pressure device is also arranged over the positioning device; one side of the middle lower part of the side surface of one end of the simulation box is communicated with a water pipeline with a switch valve, the other end of the water pipeline is connected with the water storage box, and the bottom surface of the other end of the simulation box is downwards communicated with a drainage pipeline with a switch valve; the refrigeration evaporator is internally provided with a built-in fan and an air inlet and an air outlet which form internal circulation in the simulation box chamber, and the refrigeration evaporator is connected with a compressor which is externally arranged outside the simulation box to form a refrigeration circulation system; the electric heating tube is fixed on the inner surface of the top cover of the simulation box; the simulation box also comprises a groundwater depth regulation simulation device for realizing groundwater depth regulation simulation in the simulation box.
Like this, among the above-mentioned device, the concrete test piece is conveniently fixed a position temporarily in order to do benefit to the simulation soil body and bury the setting by the dependence with test piece positioner, relies on the pressure device can exert pressure to the concrete test piece and simulate its actual pressurized condition, relies on water storage box water injection and drainage pipe drainage can conveniently pour into and discharge the groundwater of simulation, then relies on groundwater degree of depth to adjust analogue means control and adjust groundwater degree of depth and actual conditions unanimity. The simulation box is used for realizing the cooling and freezing of the interior of the simulation box by virtue of a refrigeration cycle system, and the electrothermal radiation thawing of the frozen and thawed soil is realized by virtue of the electrothermal tube, so that the actual working frozen and thawed conditions of the concrete foundation of the building can be better simulated. Therefore, the test system can be well used for the simulation test method, is simple, reliable and effective to operate, can better improve the test convenience degree and the simulation effect, and better improves the test result accuracy.
Furthermore, the test piece positioning device comprises a positioning ring positioned in the middle, the inner diameter of the positioning ring is 1-10mm larger than the outer diameter of the test piece, and the periphery of the positioning ring is fixed on the inner side wall of the simulation box through a horizontally arranged fixing rod. Therefore, the structure is simple, and the test piece can be conveniently placed and positioned.
Further, pressure device, including just setting up the pressure head in the top to the holding ring, the pressure head top links to each other through telescopic depression bar and hydraulic pressure case, and hydraulic pressure case side passes through support arm fixed mounting on the simulation incasement lateral wall, and the hydraulic pressure case passes through the hydraulic pressure pipeline and links to each other with the outer control oil tank of simulation case.
Like this, conveniently through control oil tank control hydraulic tank for the pressure head stretches out downwards and applys pressure to the concrete test piece of location in the retaining ring, simulates its actual work atress condition.
Further, the lower surface of the pressure head is provided with a test piece pressure detection sensor. The size of applying pressure to the concrete test piece is conveniently detected.
Furthermore, the upper surface of the drainage pipeline is provided with a gauze. Thus, the silt can be prevented from leaking along with the water during drainage.
Further, the number of the refrigeration evaporators was 4 and arranged at four corner positions of the top of the simulation tank. This results in a more rapid and uniform cooling.
Furthermore, the simulation box is made of transparent materials. Like this, conveniently observe the simulation case internal test condition.
Further, at least one side of the simulation box is provided with a vertical graduated scale. Therefore, the underground water level condition is convenient to observe.
Further, analogue means is adjusted to groundwater degree of depth, including being located the inboard water catch bowl that sets up in the simulation case side at water pipe place, the water catch bowl sets up along the whole length direction of the simulation case lateral wall at water pipe place, and water catch bowl upper surface height is not less than test piece positioner place height, and the water catch bowl sets up to removing the barricade towards the barricade of one side of test piece positioner is whole, removes the barricade both sides and can slide ground joint cooperation in the barricade spout from top to bottom, removes the barricade and links to each other with a barricade vertical movement control mechanism.
Therefore, when water is input into the water conveying pipeline to simulate underground water, the water can be conveyed into the water collecting tank firstly, and then the movable retaining wall is controlled to be integrally lifted to the preset underground water depth position, so that the water in the water collecting tank flows out from the position with the fixed height below the movable retaining wall to form the underground water. The groundwater simulation that realizes like this is convenient more reliable, and groundwater depth of water precision can control the accuracy better.
Furthermore, the side, facing the test piece positioning device, of the movable retaining wall is sequentially and outwards fixedly provided with a support grid and sponge materials fixed on the support grid. Therefore, the effect that the sand and soil are isolated from entering the water collecting tank to influence the lifting control of the movable retaining wall but not to obstruct the water in the water collecting tank from flowing outwards can be achieved. Meanwhile, the impact of the direct outflow water flow in the water collecting tank on the sandy soil can be avoided to influence the test.
Further, barricade vertical movement control mechanism, including vertical fixing the barricade rack in removal barricade one side both ends position department, two barricade racks respectively with one be located same level for the control gear engagement of barricade, two for the control gear fixation of barricade are in the barricade for the control pivot that same level set up, both ends of barricade for the control pivot are rotationally installed on the simulation case and one end is worn out the simulation case and is provided with a barricade for the control rotatory handle.
Like this, can conveniently through rotating barricade control and with rotatory handle, through the meshing of barricade control with gear and barricade rack, drive and remove the barricade and reciprocate along the barricade spout. Simple structure and reliable and stable.
Furthermore, a graduated scale arranged on the side face of the simulation box is located at the position of the movable retaining wall. Therefore, the numerical value of the height of the movable retaining wall lifted upwards can be visually seen, so that the underground water discharge depth can be conveniently and accurately controlled.
Furtherly, groundwater degree of depth regulation analogue means keeps away from conduit direction one side and a breakwater that sets up with the parallel interval of this side including being located the simulation incasement, but in the breakwater spout of breakwater inside wall was cooperated in the joint of breakwater both ends gliding ground joint from top to bottom, the simulation bottom of the case portion of breakwater below was provided with a breakwater heavy groove downwards, and breakwater and a breakwater vertical movement control mechanism link to each other, breakwater vertical movement control mechanism can control the breakwater upwards to stretch out or retract the breakwater heavy groove downwards, and the breakwater upwards stretches out the back and forms a drainage chamber in one side that deviates from the conduit direction, and drainage pipe sets up in the drainage chamber bottom surface.
Therefore, when the groundwater is simulated, the water baffle can be controlled to extend upwards to the depth position of the groundwater to be simulated (or slightly lower than the depth of the groundwater to be simulated by 1-5cm so as to offset the water level height of the part of the water baffle overflowing out of the test area). When the water inlet in the simulation box reaches the height of the water baffle, the water inlet can cross the water baffle to flow into the drainage cavity and be discharged out of the drainage pipeline. Therefore, the underground water depth in the test area can be better ensured to meet the simulation requirement. In addition, the process shows that when the water baffle and the water baffle are combined, the outflow depth of water in the water collecting tank is controlled by the water baffle, water is retained by the water baffle, the infiltration depth of the test area by water flow can meet the requirement, and therefore accurate simulation of the underground water depth can be better achieved. More specifically, in the process of the freeze-thaw cycle test, when the underground water is in a frozen state, the operation is simple, and only the water pipeline needs to be closed. However, when groundwater is in a thawing state, because a freezing and thawing area is usually a mountain land environment, groundwater is usually in a slow flowing undercurrent state after being thawed, when the water baffle and the water baffle wall are used together, the underground water slow flowing undercurrent state can be better simulated under the condition that enough groundwater depth is ensured to be maintained by controlling the upper end of the water baffle to extend out to be lower than the lower end of the water baffle wall to reserve a spacing height (namely the groundwater depth to be simulated) for a distance (usually 1-5 cm), and simultaneously opening the water conveying pipeline to supply water according to the flow speed and flow of the actual undercurrent of the groundwater to be simulated. Particularly, when the underground water simulation depth of the simulation box is not enough and the air pressure needs to be increased in the simulation box to increase the underground water simulation depth, the combination of the water retaining wall and the water retaining plate can better ensure that the water can still maintain the sufficient underground water depth and simulate a good undercurrent state under the condition of increasing the air pressure (water flow cannot be pressed away by high pressure); and meanwhile, the increased air pressure can better press the underground water in the area between the water baffle and the water baffle wall, so that a stronger water pressure effect can be better formed at the bottom of the test area, and the effect of increasing the simulated water depth by means of the air pressure is better realized. And when increasing atmospheric pressure in order to strengthen the simulation, can also close drainage pipe in order to avoid atmospheric pressure to produce when great and lose heart, also can rely on the drainage cavity regional retaining that the breakwater formed this moment, satisfy the undercurrent simulation demand in test area.
Furthermore, one side of the water baffle, which faces the water pipeline, is sequentially and outwards fixedly provided with a support grid and sponge materials fixed on the support grid.
Therefore, the effect of preventing sand from entering to influence the lifting control of the water baffle plate can be achieved, and the flowing of water is not hindered. Meanwhile, the influence of the sand for the test on the test due to the washing away of the water flow can be avoided.
Further, the up-and-down movement control mechanism for the water baffles comprises water baffle racks vertically fixed at two end positions on one side of the water baffles, the two water baffle racks are respectively meshed with a gear for controlling the water baffles located at the same horizontal level, the gears for controlling the two water baffles are fixed on a rotating shaft for controlling the water baffles arranged at the same level, two ends of the rotating shaft for controlling the water baffles are rotatably installed on the simulation box, and one end of the rotating shaft penetrates out of the simulation box to be provided with a rotating handle for controlling the water baffles.
Therefore, the rotating handle for controlling the water baffle can be conveniently rotated, and the water baffle is driven to move up and down along the water baffle sliding groove through the meshing of the gear for controlling the water baffle and the water baffle rack. Simple structure and reliable and stable.
Furthermore, a graduated scale is arranged on the side surface of the simulation box at the position of the water baffle. Therefore, the numerical value of the height of the water baffle lifted upwards can be visually seen, so that the depth of underground water can be conveniently and accurately controlled.
Furthermore, the groundwater depth adjustment simulation device further comprises a sealing strip and a top cover pressing and sealing mechanism which are arranged between the top cover and the box body of the simulation box, and further comprises a water pressure detection sensor positioned at the bottom of the simulation box and an air pressure conveying pipeline communicated with the simulation box, wherein the air pressure conveying pipeline is connected with an air compressor outside the simulation box.
Like this, when the simulation case can simulate groundwater degree of depth not enough, can rely on sealing strip and top cap to compress tightly sealing mechanism and compress tightly the top cap, realize the sealed of simulation case, then input atmospheric pressure to the simulation incasement through aerostatic press and pneumatic conveying pipeline, under atmospheric pressure and hydraulic combined action, rely on the water pressure detection sensor of simulation bottom of the case portion to detect this place water pressure, make its and the building foundation concrete bottom of waiting to test actually receive groundwater water pressure unanimously, make it maintain and accomplish freeze-thaw cycle test under the water pressure condition unanimous with actual conditions, accomplish the simulation to deeper groundwater infiltration condition. The application range of the test is better expanded. Wherein top cap compresses tightly sealing mechanism can be for bolt fastening or connect existing mechanism realization such as buckle is fixed soon, and concrete structure does not detail here.
More specifically, when the test system is used for a concrete test (taking the case that the depth of underground water meets the simulation depth of the simulation box as an example), the top cover of the simulation box is opened firstly, then the prepared concrete test piece is positioned and erected in the simulation box by virtue of the test piece positioning device, the vertical positioning of the concrete test piece is kept, and a pressure head is controlled to extend downwards and is pressed at the upper end of the concrete test piece until the detection pressure reaches the test pressure; and then, the simulated soil body material is poured into the simulation box until the periphery of the concrete test piece is buried. Then adjusting the water baffle to extend upwards from the water baffle sink tank to a depth 0-5cm lower than the preset water depth; and then opening a switch valve on the water conveying pipeline to inject water in the water storage tank into the water collection tank, controlling the movable retaining wall of the water collection tank to be lifted upwards until the lower end of the movable retaining wall is exposed to a preset water depth position, enabling the water in the water collection tank to flow out from the lower end of the movable retaining wall until the water flows over the water baffle and flows to the water conveying pipeline, closing the water conveying pipeline until the water level in the water collection tank drops to the height position of the lower port of the movable retaining wall, and then closing the water conveying pipeline. Controlling a refrigeration cycle system to start to refrigerate the inside of the simulation box, so that frozen soil is formed by the simulation soil body materials, and then maintaining the environment temperature in the simulation box to be the lowest temperature of the foundation concrete of the building in spring and autumn at night until the freezing time is finished (usually 12 hours); then closing the refrigeration cycle system, starting the electric heating tube for heating, so that the temperature in the simulation box rises for thawing, and maintaining the highest temperature of the temperature in the simulation box in the local spring and autumn of the foundation concrete of the building until the thawing time is finished (usually 12 hours); then repeating the freeze-thaw cycle until the test days are over; the top cover of the simulation box can be opened, the concrete sample is taken out, the performance of the concrete sample is tested, and the performance change parameter characteristic is obtained.
In conclusion, the invention can simulate the freeze-thaw soil environment more truly and reliably, and the freeze-thaw durability of the foundation concrete structure under the condition of infiltration of underground water is obtained; the method can be better used for safety assessment guidance of building foundations and can improve the building safety performance in freeze-thaw environments.
Drawings
Fig. 1 is a schematic structural diagram of a rock mass freeze-thaw cycle test system adopted in the implementation of the invention.
Fig. 2 is a schematic structural view of the single underground water depth adjusting simulation apparatus in fig. 1.
Fig. 3 is a schematic structural view of the retaining wall up-and-down movement control mechanism in the side view of fig. 1.
Fig. 4 is a schematic structural view of the water deflector up-down movement control mechanism in the side view of fig. 1.
Fig. 5 is a schematic view of the structure of the single pressing device in fig. 1.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments.
The specific implementation mode is as follows: a freeze-thaw cycle test method for foundation concrete influenced by underground water is disclosed, wherein a corresponding concrete test piece is prepared according to the performance requirement of the foundation concrete of a building to be tested, and the concrete test piece is fixed in a simulation box; simulating the soil condition of the building foundation concrete construction environment, and embedding the concrete test piece into a simulated soil material; simulating the actual infiltration condition of the foundation concrete of the building by using the infiltration water at the lower part of the simulation box; applying pressure to the concrete sample according to the pressure bearing size (which can be obtained by calculation) of the foundation concrete of the building to finish the preparation work; during the test, cold air is introduced and cooled until the infiltrated water body is frozen, after the test is maintained for a period of time, the test piece is heated by applying electrothermal radiation on the concrete test piece until the frozen water body is defrozen, and the operation is repeated after the test is continued for a period of time to form freeze-thaw cycle, until the freeze-thaw test is finished, the concrete test piece is taken out and the performance of the concrete test piece is tested, and compared with the same concrete test piece which is not tested, the performance change parameters of the foundation concrete of the building, which are influenced by the freeze-thaw environment, are obtained.
The test method of the invention better simulates the condition that the concrete structure of the building foundation is buried by the soil body and is infiltrated by the underground water. Meanwhile, the freeze-thaw condition that the freezing is actually formed by blowing cold air at night and the thawing is completed by irradiation of solar light at daytime is simulated for testing. The actual freezing and thawing situation of the foundation concrete of the building can be better simulated. The performance parameter change obtained by the test after the test can better reflect the influence of the actual freeze-thaw situation on the performance. The method can be better used for safety monitoring of concrete foundations of actual buildings or pre-construction safety performance evaluation. The safety of the building is improved.
During the test, the temperature of the test environment cooled by introducing cold air is determined by the lowest temperature of the foundation concrete of the building in spring and autumn.
In this way, the simulation is performed with the extreme environmental parameters, so that the test results can be better used for safety evaluation.
During the test, the temperature heated by adopting an electric heating radiation mode is determined according to the highest temperature of the foundation concrete of the building in local spring and autumn in the daytime.
In this way, the simulation is performed with the extreme environmental parameters, so that the test results can be better used for building safety assessment.
When the concrete test piece is prepared, the building foundation concrete to be tested is poured according to the same concrete formula to obtain the cylindrical test piece.
Therefore, the test result of the concrete test piece can better reflect the performance change condition of the actual freezing and melting influence of the foundation concrete of the building. The test reliability is improved.
During the experiment, the simulated soil body material is prepared by adopting broken stones, silt and clay materials and simulating the actual soil body condition around the foundation concrete of the building. Preferably, the actual soil around the foundation concrete of the building is directly excavated to obtain a simulated soil material, and the simulated soil material contains corresponding microorganisms, so that the influence effect of the rock mass microorganisms on the concrete can be kept consistent.
Therefore, the actual situation can be better simulated, and the test reliability is improved.
When the depth of the simulation box (which refers to the depth capable of being used for the test) is larger than the infiltration depth of the underground water of the foundation concrete of the building to be tested, the infiltration depth of the lower part of the simulation box is consistent with the actual underground water infiltration depth; when the depth of the simulation box (which refers to the depth capable of being used for testing) is less than the infiltration depth of the foundation concrete of the building to be tested by the underground water, the simulation box is closed, gas is introduced for pressurizing, and the water pressure at the bottom of the simulation box is detected to ensure that the water pressure is consistent with the actual water pressure (the actual water pressure value can be obtained through actual detection or calculation) at the lowest part of the foundation concrete of the building to be tested.
Therefore, when the infiltration depth of the foundation concrete of the building to be tested by the underground water is larger, the deeper underground water infiltration condition can be simulated by adopting a smaller simulation box, and the application range of the test is greatly improved. When a pressure applying mode is adopted for simulation test, the height of the concrete test piece can be set to be consistent with the testable depth of the simulation box, then the simulation soil body material is covered until the simulation soil body material is consistent with the height of the concrete test piece, then the lower part of the simulation box is infiltrated to a depth of 5-10cm of the non-infiltrated soil body material above the simulation box, and therefore the actual condition that the concrete test piece is infiltrated by underground water can be better simulated.
Specifically, the one-time freeze-thaw cycle time is 24 hours, including 12 hours of freezing and 12 hours of thawing; the number of freeze-thaw cycles was set to 7, 15, 30, 60 or 90 times according to the study, with the corresponding time being 7, 15, 30, 60 or 90 days.
This is because it is generally difficult to react to a change for less than seven days. And if the time is more than 90 days, the time is too long, and the significance of the test is difficult to play. After the freeze-thaw test is completed within a limited time, the performance change condition of the concrete test piece can be obtained by detecting the performance parameters of the concrete test piece, and the performance change condition caused by more time of freeze-thaw action can be reasonably calculated so as to guide actual safety monitoring.
After the freeze-thaw test time is finished, taking out the concrete test piece, carrying out a uniaxial compression test or a triaxial compression test on the concrete test piece, testing the mechanical properties of the concrete test piece after the freeze-thaw cycle, including compressive strength and elastic modulus parameters, and comparing the mechanical property parameters of the concrete test piece which is not subjected to freeze-thaw to obtain the degradation degree of the mechanical properties of the foundation concrete of the building, which is influenced by the freeze-thaw environment.
In specific implementation, the test method is realized by the aid of the ground concrete freeze-thaw cycle test system shown in the figures 1-5, the ground concrete freeze-thaw cycle test system comprises a simulation box 1, an openable top cover 2 is arranged at the upper end of the simulation box 1, a test piece positioning device is arranged at the middle lower part in the simulation box 1, and a pressure device is arranged above the positioning device in a facing manner; one side of the middle lower part of the side surface of one end of the simulation box is communicated with a water conveying pipeline 4 with a switch valve, the other end of the water conveying pipeline 4 is connected with a water storage box 5, and the bottom surface of the other end of the simulation box 1 is communicated downwards with a drainage pipeline 6 with a switch valve; the simulation box is characterized by further comprising a refrigeration evaporator 7 arranged at the upper part of the simulation box, wherein a built-in fan is arranged in the refrigeration evaporator 7, an air inlet and an air outlet which form internal circulation in the simulation box chamber are formed in the refrigeration evaporator 7, and the refrigeration evaporator 7 is connected with a compressor 8 which is externally arranged outside the simulation box to form a refrigeration circulation system; the electric heating tube 9 is fixed on the inner surface of the top cover of the simulation box; the simulation box also comprises a groundwater depth regulation simulation device for realizing groundwater depth regulation simulation in the simulation box.
Like this, among the above-mentioned device, the concrete test piece is conveniently fixed a position temporarily in order to do benefit to the simulation soil body and bury the setting by the dependence with test piece positioner, relies on the pressure device can exert pressure to the concrete test piece and simulate its actual pressurized condition, relies on water storage box water injection and drainage pipe drainage can conveniently pour into and discharge the groundwater of simulation, then relies on groundwater degree of depth to adjust analogue means control and adjust groundwater degree of depth and actual conditions unanimity. The simulation box is cooled and frozen by the aid of the refrigeration cycle system, and the frozen and thawed soil is thawed by the aid of electrothermal radiation of the electrothermal tubes, so that actual working frozen and thawed conditions of a concrete foundation of a building can be better simulated. Therefore, the test system can be well used for the simulation test method, is simple, reliable and effective to operate, can better improve the test convenience degree and the simulation effect, and better improves the test result accuracy.
The test piece positioning device comprises a positioning ring 10 positioned in the middle, the inner diameter of the positioning ring 10 is larger than the outer diameter of the test piece by 1-10mm, and the periphery of the positioning ring is fixed on the inner side wall of the simulation box through a horizontally arranged fixing rod. Therefore, the structure is simple, and the test piece can be conveniently placed into the positioning device.
Wherein, pressure device, including just setting up the pressure head 11 above the holding ring, pressure head 11 top links to each other through telescopic depression bar and hydraulic pressure case 12, and hydraulic pressure case 12 side is through support arm 13 fixed mounting on simulation case 1 inside wall, and hydraulic pressure case 12 links to each other through hydraulic pressure pipeline and the outer control oil tank 3 of simulation case.
Like this, conveniently control the hydraulic tank through the control oil tank for the pressure head stretches out downwards and applys pressure to the concrete test piece of location in the locating ring, simulates its actual work atress condition.
Wherein, the lower surface of the pressure head 11 is provided with a test piece pressure detection sensor 14. The size of applying pressure to the concrete test piece is conveniently detected.
Wherein, the upper surface of the drainage pipeline is provided with a gauze. Thus, the silt can be prevented from leaking along with the water during the drainage.
Wherein, 4 refrigeration evaporators are arranged at four corner positions at the top of the simulation box. This results in a more rapid and uniform cooling.
Wherein, the simulation box 1 is made of transparent materials. Thus, the test condition inside the simulation box can be conveniently observed.
Wherein, simulation case 1 at least one side is provided with vertical scale 15. Therefore, the underground water level condition is convenient to observe.
The underground water depth adjusting simulation device comprises a water collection tank 16 which is arranged on the inner side of the side face of a simulation box where a water pipeline is located, the water collection tank 16 is arranged along the whole length direction of the side wall of the simulation box where the water pipeline is located, the height of the upper surface of the water collection tank is not lower than that of a test piece positioning device, the whole retaining wall of one side, facing the test piece positioning device, of the water collection tank is arranged to be a movable retaining wall 17, the two sides of the movable retaining wall can be clamped and matched in a retaining wall sliding groove 18 in a vertically sliding mode, and the movable retaining wall 17 is connected with a retaining wall vertical movement control mechanism.
Therefore, when water is input into the water conveying pipeline to simulate underground water, the water can be conveyed into the water collecting tank firstly, and then the movable retaining wall is controlled to be integrally lifted to the preset underground water depth position, so that the water in the water collecting tank flows out from the position with the fixed height below the movable retaining wall to form the underground water. The underground water simulation realized in this way is more convenient and reliable, and the depth precision of the underground water can be better controlled and accurate.
Wherein, the side of the movable retaining wall 17 facing the test piece positioning device is also sequentially and outwardly fixedly provided with a support grid 19 and sponge materials fixed on the support grid. Therefore, the effect that the sand and soil are isolated from entering the water collecting tank to influence the lifting control of the movable retaining wall but not to obstruct the water in the water collecting tank from flowing outwards can be achieved. Meanwhile, the impact of the direct outflow water flow in the water collecting tank on the sand can be avoided to influence the test.
Wherein, barricade vertical movement control mechanism, including vertical fixing at the barricade rack 20 that removes barricade one side both ends position department, two barricade racks 20 respectively with one be located same level for the control gear 21 meshing of barricade, two for the control gear 21 fix on the barricade for the control pivot 22 that same level set up, barricade for the control pivot 22 both ends rotationally install on the simulation case and one end is worn out the simulation case and is provided with a barricade for the control rotatory handle 23.
Like this, can conveniently through rotating barricade control and with rotatory handle, through the meshing of barricade control with gear and barricade rack, drive and remove the barricade and reciprocate along the barricade spout. Simple structure and reliable and stable.
Wherein, the scale that the simulation case side set up is located the position that removes the barricade. Therefore, the numerical value of the height of the movable retaining wall lifted upwards can be visually seen, so that the underground water discharge depth can be conveniently and accurately controlled.
Wherein, groundwater depth control analogue means, including being located the simulation incasement keep away from conduit direction one side and with a breakwater 25 that this side parallel interval set up, the cooperation of joint is in the breakwater spout 26 of simulation incasement lateral wall about the breakwater 25 both ends can slide, and the simulation bottom of the case portion of breakwater 25 below is provided with a breakwater heavy groove 27 downwards, and breakwater 26 and a breakwater vertical movement control mechanism link to each other, breakwater vertical movement control mechanism can control the breakwater upwards to stretch out or retract breakwater heavy groove 27 downwards, and the breakwater upwards stretches out the back and forms a drainage chamber in the one side that deviates from the conduit direction, and drainage pipe sets up in drainage chamber bottom surface.
Therefore, when the underground water is simulated, the water baffle can be controlled to extend upwards to the depth position of the underground water to be simulated (or slightly lower than the depth of the underground water to be simulated by 1-5cm so as to offset the height of the water level of the part, which overflows from the water baffle, in the test area). When the water inlet in the simulation box reaches the height of the water baffle, the water inlet can cross the water baffle to flow into the drainage cavity and be discharged out of the drainage pipeline. Therefore, the underground water depth in the test area can be better ensured to meet the simulation requirement. In addition, the process shows that when the water baffle and the water baffle are used together, the outflow depth of water in the water collecting tank is controlled by the water baffle, the water is retained by the water baffle, the infiltration depth of the water in the test area can meet the requirement, and therefore accurate simulation of the depth of underground water can be better achieved. More specifically, in the process of the freeze-thaw cycle test, when the underground water is in a frozen state, the operation is simple, and only the water pipeline needs to be closed. However, when groundwater is in a thawing state, because a freezing and thawing area is usually in a mountain environment, groundwater is usually in a slow flowing underflow state after being thawed, when the water baffle and the water baffle wall are used together, the water baffle plate and the water baffle wall are controlled to extend out of the upper end of the water baffle plate to a certain distance (usually 1-5 cm) lower than the reserved spacing height (namely the depth of groundwater to be simulated) of the lower end of the water baffle wall, and meanwhile, water is supplied by opening a water pipeline according to the flow speed and the flow of actual underflow of groundwater to be simulated, so that the slow flowing underflow state of groundwater can be better simulated under the condition of ensuring that enough groundwater depth is maintained. Particularly, when the underground water simulation depth of the simulation box is not enough and the air pressure needs to be increased in the simulation box to increase the underground water simulation depth, the combination of the water retaining wall and the water retaining plate can better ensure that the water can still maintain the sufficient underground water depth and simulate a good undercurrent state under the condition of increasing the air pressure (water flow cannot be pressed away by high pressure); and meanwhile, the increased air pressure can better press the underground water in the area between the water baffle and the water baffle wall, so that a stronger water pressure effect can be better formed at the bottom of the test area, and the effect of increasing the simulated water depth by means of the air pressure is better realized. And when increasing atmospheric pressure in order to strengthen the simulation, can also close drainage pipe in order to avoid atmospheric pressure to produce when great and lose heart, also can rely on the drainage cavity regional retaining that the breakwater formed this moment, satisfy the undercurrent simulation demand in test area.
Wherein, one side of the water baffle 25 facing to the water pipeline is also sequentially and outwards fixedly provided with a support grid 28 and sponge materials fixed on the support grid.
Therefore, the effect of preventing sand from entering to influence the lifting control of the water baffle plate can be achieved, and the flowing of water is not hindered. Meanwhile, the influence of the sand for the test, which is washed away by water flow, on the test can be avoided.
The up-and-down movement control mechanism for the water baffle comprises water baffle racks 29 which are vertically fixed at two ends of one side of the water baffle, the two water baffle racks 29 are respectively meshed with a gear 30 for controlling the water baffle at the same horizontal height, the two gears 30 for controlling the water baffle are fixed on a rotating shaft 31 for controlling the water baffle arranged at the same horizontal level, two ends of the rotating shaft 31 for controlling the water baffle are rotatably installed on a simulation box, and one end of the rotating shaft 31 penetrates out of the simulation box to be provided with a rotating handle 32 for controlling the water baffle.
Therefore, the rotating handle for controlling the water baffle can be conveniently rotated, and the water baffle is driven to move up and down along the water baffle sliding groove through the meshing of the gear for controlling the water baffle and the water baffle rack. Simple structure and reliable and stable.
Wherein, the simulation case side is located the breakwater position and is provided with the scale. Therefore, the numerical value of the height of the water baffle lifted upwards can be visually seen, so that the depth of underground water can be conveniently and accurately controlled.
The groundwater depth adjusting and simulating device further comprises a sealing strip and a top cover pressing and sealing mechanism 35 which are installed between the top cover 2 and the box body 1 of the simulation box, a water pressure detection sensor (not shown in the figure) which is positioned at the bottom of the simulation box and an air pressure conveying pipeline 36 which is communicated with the simulation box, wherein the air pressure conveying pipeline is connected with an air compressor (not shown in the figure) outside the simulation box.
Like this, when the simulation case can simulate groundwater degree of depth not enough, can rely on sealing strip and top cap to compress tightly sealing mechanism and compress tightly the top cap, realize the sealed of simulation case, then input atmospheric pressure to the simulation incasement through aerostatic press and pneumatic conveying pipeline, under atmospheric pressure and hydraulic combined action, rely on the water pressure detection sensor of simulation bottom of the case portion to detect this place water pressure, make its and the building foundation concrete bottom of waiting to test actually receive groundwater water pressure unanimously, make it maintain and accomplish freeze-thaw cycle test under the water pressure condition unanimous with actual conditions, accomplish the simulation to deeper groundwater infiltration condition. The application range of the test is better expanded. Wherein top cap compresses tightly sealing mechanism can be for bolt fastening or connect existing mechanism realization such as buckle is fixed soon, and concrete structure does not detail here.
More specifically, when the test system is used for a specific test (taking the example that the depth of underground water meets the simulation depth of the simulation box), firstly, the top cover of the simulation box is opened, then, the prepared concrete test piece is positioned and erected in the simulation box by virtue of the test piece positioning device, the vertical positioning of the concrete test piece is maintained, and the pressure head is controlled to extend downwards and is pressed at the upper end of the concrete test piece until the detection pressure reaches the test pressure; and then, the simulated soil body material is poured into the simulation box until the periphery of the concrete test piece is buried. Then adjusting the water baffle to extend upwards from the water baffle sink tank to a depth 0-5cm lower than the preset water depth; and then, opening a switch valve on the water pipe to inject water in the water storage tank into the water collection tank, controlling the movable retaining wall of the water collection tank to lift upwards to enable the lower end to be exposed to a preset water depth position, enabling the water in the water collection tank to flow out from the lower end until the water flows over the water baffle and flows to the water discharge pipe, closing the water pipe, and then closing the water discharge pipe when the water level in the water collection tank drops to the height position of the lower port of the movable retaining wall. Controlling a refrigeration cycle system to start refrigeration in the simulation box to enable the simulation soil mass material to form frozen soil, and then maintaining the environment temperature in the simulation box to be the lowest temperature of the foundation concrete of the building in spring and autumn at night until the freezing time is finished (generally 12 hours); then closing the refrigeration cycle system, starting the electric heating tube for heating, so that the temperature in the simulation box rises for thawing, and maintaining the highest temperature of the temperature in the simulation box in the local spring and autumn of the foundation concrete of the building until the thawing time is finished (usually 12 hours); then repeating the freeze thawing cycle until the test days are over; the top cover of the simulation box can be opened, the concrete sample is taken out, the performance of the concrete sample is tested, and the performance change parameter characteristic is obtained.
Claims (10)
1. A freeze-thaw cycle test method of foundation concrete influenced by underground water is characterized in that a corresponding concrete test piece is prepared according to the performance requirement of the foundation concrete of a building to be tested, and the concrete test piece is fixed in a simulation box; simulating the soil condition of the building foundation concrete construction environment, and embedding the concrete test piece into a simulated soil material; simulating the actual infiltration condition of the foundation concrete of the building by using the infiltration water at the lower part of the simulation box; applying pressure to the concrete test piece according to the pressure bearing size of the foundation concrete of the building to finish the preparation work; during the test, cold air is introduced and cooled until the infiltrated water body is frozen, after the test is maintained for a period of time, the test piece is heated by applying electrothermal radiation on the concrete test piece until the frozen water body is defrozen, and the operation is repeated after the test is continued for a period of time to form freeze-thaw cycle, until the freeze-thaw test is finished, the concrete test piece is taken out and the performance of the concrete test piece is tested, and compared with the same concrete test piece which is not tested, the performance change parameters of the foundation concrete of the building, which are influenced by the freeze-thaw environment, are obtained.
2. The groundwater-influenced freeze-thaw cycle test method for ground-based concrete according to claim 1, wherein the test environment temperature cooled by introducing cold wind is determined according to the local spring, autumn and night minimum temperature of the ground-based concrete of the building during the test;
the temperature of the heating in the mode of electric heating radiation is determined by the highest temperature of the foundation concrete of the building in spring and autumn in the day and the local.
3. The groundwater-affected ground concrete freeze-thaw cycle test method according to claim 1, wherein the concrete test piece is prepared by pouring a cylindrical test piece obtained by pouring the ground concrete of the building to be tested according to the same concrete formula;
the simulated soil body material is prepared by adopting broken stones, silt and clay materials and simulating the actual soil body condition around the foundation concrete of the building.
4. The groundwater affected ground concrete freeze-thaw cycle testing method according to claim 1, wherein when the simulated box depth (which is the depth available for testing) is greater than the groundwater infiltration depth of the ground concrete of the building to be tested, the infiltration depth of the lower part of the simulated box is the same as the actual groundwater infiltration depth; and when the depth of the simulation box is less than the infiltration depth of the foundation concrete of the building to be tested under the underground water, closing the simulation box, introducing gas for pressurizing, and detecting the position water pressure of the bottom of the simulation box to enable the position water pressure to be consistent with the actual water pressure of the lowest position of the foundation concrete of the building to be tested.
5. The groundwater-affected ground-based concrete freeze-thaw cycle test method of claim 1, wherein a freeze-thaw cycle time is 24 hours including 12 hours frozen and 12 hours thawed; the number of freeze-thaw cycles is set to 7, 15, 30, 60 or 90 times according to the study, and the corresponding time is 7, 15, 30, 60 or 90 days;
and after the freeze-thaw test time is over, taking out the concrete test piece, carrying out a uniaxial compression test or a triaxial compression test on the concrete test piece, testing the mechanical properties of the concrete test piece after freeze-thaw cycle, including the parameters of compressive strength and elastic modulus, and comparing the parameters of the mechanical properties of the concrete test piece which is not subjected to freeze-thaw, thereby obtaining the degradation degree of the mechanical properties of the foundation concrete of the building, which is influenced by the freeze-thaw environment.
6. The method for testing the freeze-thaw cycle of the foundation concrete affected by the groundwater as claimed in claim 1, wherein the test method is implemented by means of a test system for the freeze-thaw cycle of the foundation concrete, the test system for the freeze-thaw cycle of the foundation concrete comprises a simulation box, an openable top cover is arranged at the upper end of the simulation box, a test piece positioning device is arranged at the middle lower part in the simulation box, and a pressure applying device is arranged over the positioning device; one side of the middle lower part of the side surface of one end of the simulation box is communicated with a water pipeline with a switch valve, the other end of the water pipeline is connected with the water storage box, and the bottom surface of the other end of the simulation box is downwards communicated with a drainage pipeline with a switch valve; the simulation box is internally provided with a fan, an air inlet and an air outlet which form internal circulation in the simulation box chamber, and the refrigeration evaporator is connected with a compressor externally arranged outside the simulation box to form a refrigeration circulation system; the electric heating tube is fixed on the inner surface of the top cover of the simulation box; the simulation box also comprises a groundwater depth regulation simulation device for realizing groundwater depth regulation simulation in the simulation box.
7. The freeze-thaw cycle test method for ground-based concrete affected by groundwater as claimed in claim 6, wherein the test piece positioning device comprises a positioning ring located in the middle part, the inner diameter of the positioning ring is 1-10mm larger than the outer diameter of the test piece, and the periphery of the positioning ring is fixed on the inner side wall of the simulation box through a horizontally arranged fixing rod;
the pressing device comprises a pressing head which is arranged over the positioning ring in a right-facing mode, the upper portion of the pressing head is connected with a hydraulic box through a telescopic pressing rod, the side face of the hydraulic box is fixedly installed on the inner side wall of the simulation box through a supporting arm, and the hydraulic box is connected with a control oil tank outside the simulation box through a hydraulic pipeline;
and a test piece pressure detection sensor is arranged on the lower surface of the pressure head. .
8. The groundwater affected ground concrete freeze-thaw cycle test method of claim 6, wherein a gauze is provided on an upper surface of the drainage pipeline;
4 refrigeration evaporators are arranged at four corner positions at the top of the simulation box;
the simulation box is made of transparent materials;
at least one side of the simulation box is provided with a vertical graduated scale.
9. The groundwater-influenced foundation concrete freeze-thaw cycle testing method according to claim 6, wherein the groundwater depth adjustment simulating device comprises a water collecting tank arranged on the inner side of the side surface of the simulation box where the water pipeline is located, the water collecting tank is arranged along the length direction of the whole side wall of the simulation box where the water pipeline is located, the height of the upper surface of the water collecting tank is not lower than the height of the test piece positioning device, the whole retaining wall on the side of the water collecting tank facing the test piece positioning device is arranged as a movable retaining wall, the two sides of the movable retaining wall can be clamped and matched in the retaining wall sliding grooves in an up-and-down sliding manner, and the movable retaining wall is connected with a retaining wall up-and-down movement control mechanism;
the side, facing the test piece positioning device, of the movable retaining wall is also sequentially and outwards fixedly provided with a support grid and sponge materials fixed on the support grid;
the retaining wall vertical movement control mechanism comprises retaining wall racks which are vertically fixed at two end positions on one side of the movable retaining wall, the two retaining wall racks are respectively meshed with a retaining wall control gear located at the same level, the two retaining wall control gears are fixed on a retaining wall control rotating shaft arranged at the same level, two ends of the retaining wall control rotating shaft are rotatably installed on the simulation box, and one end of the retaining wall control rotating shaft penetrates through the simulation box to be provided with a retaining wall control rotating handle.
10. The freeze-thaw cycle test method for foundation concrete affected by groundwater according to claim 6, wherein the groundwater depth adjustment simulation device comprises a water baffle plate located at one side of the simulation tank far away from the direction of the water pipeline and spaced from the side in parallel, two ends of the water baffle plate are vertically slidably clamped and fitted in a water baffle plate chute on the inner side wall of the simulation tank, a water baffle plate sink is downwardly arranged at the bottom of the simulation tank below the water baffle plate, the water baffle plate is connected with a water baffle plate up-and-down movement control mechanism, the water baffle plate up-and-down movement control mechanism can control the water baffle plate to upwardly extend out or downwardly retract into the water baffle plate sink, a drainage cavity is formed at one side far away from the direction of the water pipeline after the water baffle plate extends out upwardly, and a drainage pipeline is arranged at the bottom of the drainage cavity;
the side of the water baffle, which faces the water pipeline, is sequentially and externally fixedly provided with a support grid and sponge materials fixed on the support grid;
the up-and-down movement control mechanism comprises water baffle racks vertically fixed at two ends of one side of the water baffle, the two water baffle racks are respectively meshed with a gear located at the same level for water baffle control, the gear for the two water baffle control is fixed on a rotating shaft for water baffle control arranged at the same level, two ends of the rotating shaft for the water baffle control are rotatably installed on the simulation box, and one end of the rotating shaft penetrates out of the simulation box to be provided with a rotating handle for water baffle control.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN202211270480.4A CN115629096A (en) | 2022-10-18 | 2022-10-18 | Foundation concrete freeze-thaw cycle test method influenced by underground water |
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