CN106932558B

CN106932558B - Closed refrigerating and heating device for testing salt expansion amount of salinized soil

Info

Publication number: CN106932558B
Application number: CN201710257294.XA
Authority: CN
Inventors: 张莎莎; 常春普; 杨晓华
Original assignee: Changan University
Current assignee: Changan University
Priority date: 2017-04-19
Filing date: 2017-04-19
Publication date: 2023-02-24
Anticipated expiration: 2037-04-19
Also published as: CN106932558A

Abstract

A closed refrigerating and heating device for testing saline soil salt expansion amount comprises a box body, wherein a spiral groove for installing a liquid circulation pipe is formed in a bottom plate of the box body, the liquid circulation pipe is communicated with a low-temperature constant-temperature groove, at least one sample box is placed on a convex edge, a closed steel plate is arranged at the top of the sample box, a probe connected with a digital display sensor is embedded in a sample of the sample box, a displacement and force transmission device which penetrates through the closed steel plate and a top cover and is connected with a dial indicator and an annular rubber ring with an inflation tube are placed at the top of the sample in the sample box, a strain gauge is arranged between the displacement and force transmission device and the annular rubber ring, a top cover is arranged at the top of the box body, a spiral groove is formed in the inner wall of the top cover, a liquid circulation pipe is arranged in the spiral groove, and heat insulation layers are arranged on the outer walls of the box body and the top cover; the invention has the advantages of large closed space, convenient reading, accurate test data, low cost, energy saving and environmental protection.

Description

Closed refrigerating and heating device for testing salt expansion amount of salinized soil

Technical Field

The invention belongs to the technical field of salinized soil salt swelling capacity test experimental equipment or devices, and particularly relates to a closed refrigeration heating device for testing salinized soil salt swelling capacity, which can perform a salinized soil salt swelling capacity test and a freeze-thaw cycle test in a closed space with an automatically adjustable temperature and test the swelling capacity of salinized soil and the swelling force of the salinized soil during salinized soil salt swelling.

Background

The saline soil refers to soil with salt content exceeding a certain amount. Salt content is generally expressed as the ratio of the weight (or mass) of salt in a given body of soil to the weight (or mass) of its dry soil, expressed as a percentage. The distribution of saline soils is wide throughout the world, and a lot of countries in asia, the middle east and europe cause huge economic losses each year due to the harm of saline soils. With the promotion and development of the 'one-by-one-way' advocate, high-grade roads and railways need to be constructed in more and more saline soil areas, and the research on the engineering properties of the saline soil is particularly important. The salinized soil is a special soil, and has the most remarkable characteristic that the soil contains a certain amount of easily soluble salts, when the salts can be fully dissolved in water of a soil body, the volume of liquid cannot be increased, but the specific gravity of the liquid can be increased; when these salts are not sufficiently soluble in the water of the soil body, the insoluble salts exist in the form of crystalline solids between the soil particles, and act as a framework together with the soil particles. Among these lyotropic salts are mainly sodium sulfate, magnesium sulfate, sodium chloride, sodium carbonate, etc., wherein the temperature has the greatest influence on the solubility of sodium sulfate. Sodium sulfate, also known as thenardite, is easily dissolved and is particularly sensitive to temperature variation. At the temperature of 32.4 ℃, the solubility of the sodium sulfate reaches a peak value and can reach 40.8g, and the solubility is reduced when the temperature rises or falls; the solubility of sodium sulphate was only 4.9g at a temperature of 0 ℃. In a saline soil area with large seasonal temperature change, in winter, the temperature of a roadbed is reduced along with the natural temperature, 10 water molecules absorbed by sodium sulfate in roadbed soil under the influence of the temperature reduction are changed into mirabilite crystals, the volume of the mirabilite crystals is 3.1 times of that of anhydrous mirabilite, and the crystals push soil particles to increase the volume of a roadbed soil body to form salt expansion; in spring and summer, the temperature of the roadbed soil body gradually rises, sodium sulfate among soil particles is dissolved in water again, the pore increasing density in the soil body becomes small, and under the action of the traveling load, the uneven deformation of the roadbed, pavement waves, bulges, cracks and the like are generated. The rainwater can infiltrate the road bed through the crack on the road surface, and the undissolved crystal salt is completely dissolved in the soil body of the road bed, so that the structure of the soil body is further destroyed, the strength is reduced, and particularly, under the action of the driving load, the soil particles are rearranged, the pores are reduced, and the dissolution is generated. Under the effect of alternate season freeze-thaw cycles, the subsidence can gradually increase, and the running capacity of the road is seriously reduced. The solubility of the chloride salt is high, but the solubility is slightly influenced by temperature change; the chloride has obvious hygroscopicity, moisture absorbed by the chloride is not easy to evaporate, and the volume of the chloride does not change obviously when the chloride is crystallized and separated out from the solution. When chloride salt crystals exist in the soil body, the shear strength of the soil body is increased along with the increase of the salt content, and the compression coefficient is reduced along with the increase of the salt content. The sodium chloride is doped into the sulfate saline soil, and the solubility of the sodium sulfate is reduced due to the homoionic effect of the sodium chloride on the sodium sulfate, so that the crystallization precipitation amount is reduced; meanwhile, the temperature of the transformation point of Miscanthus nitens and Anhydrous Miscanthus nites can be reduced by adding sodium chloride, which has an inhibiting effect on the salt expansion characteristic of the sulfate saline soil. However, the excessive addition of sodium chloride does not inhibit salt expansion, but increases the salt expansion: the addition of the sodium chloride reduces the freezing point of water, water in the soil becomes unfrozen water in the cooling process, a water source is provided for the occurrence of salt expansion, and under the condition of negative temperature, the excessive sodium chloride can absorb two other water molecules to synthesize ice salt, so that the expansion of a soil body is aggravated. The solubility of sodium chloride is high and is not influenced by temperature, so that after a large amount of sodium chloride is mixed, the dissolution amount of the roadbed is increased once the roadbed is infiltrated by rainwater. Therefore, the saline swelling characteristic of the saline soil after the sodium chloride is doped into the saline soil needs to be researched, the limit value of the content of the sodium chloride for inhibiting the saline swelling of the saline soil, the influence weight of the sodium chloride, the water content, the compaction degree and the additional load on the saline swelling and the influence of the sodium chloride on the dissolution and sinking characteristics of the saline soil doped with the sodium chloride need to be researched. In the past, the research on the salt expansion characteristic of saline soil is mainly completed by a high-low temperature test box, but the high-low temperature test box also has many disadvantages: (1) for the salt expansion test of coarse-grain saline soil, in order to avoid the size effect of particles, the manufactured test is generally large, the box body space of a high-low temperature test box is small, the volume and the loading size of a sample are limited, and the requirements of the test conditions cannot be met; (2) the dial indicator or the displacement sensor for measuring the salt expansion amount is arranged in the high-low temperature test box body, when the temperature is reduced to reach a certain temperature reading, the box must be opened for reading, and under the effect of cold and hot air flow exchange, a pointer of the dial indicator is unstable, so that the reading is inaccurate. The door reading is opened, the temperature in the box body is influenced, and temperature fluctuation is caused. (3) When the high-low temperature test box works, the noise is large; the refrigerant leaks to pollute the air; expensive and very expensive to maintain.

Disclosure of Invention

The invention aims to overcome the defects of a test device and provide the sealed refrigerating and heating device for testing the saline soil salt expansion amount, which has the advantages of reasonable design, simple structure, large sealed space, convenient reading, accurate test data, low cost, energy conservation and environmental protection.

The technical scheme for solving the technical problems is as follows: the intelligent liquid storage box comprises a box body, the box bottom plate on be provided with spiral groove, spiral groove edge be provided with the bead, spiral groove in be provided with the liquid circulation pipe, liquid circulation pipe one end run through the liquid outlet that box lateral wall and low temperature constant temperature groove are linked together, the other end along box lateral wall spiral coil and run through the inlet that box lateral wall and low temperature constant temperature groove are linked together, the liquid circulation pipe that box lateral wall coiled be fixed in on the box lateral wall through the fixed plate, the bead on placed at least one sample case, sample case top be provided with the sealed steel sheet, sample case sample in bury and to have the probe that is connected with digital display sensor, sample case in place and run through displacement and the power transmission device that sealed steel sheet and top cap and be connected with the percentage table, the annular rubber circle that has the gas tube, displacement and power transmission device and annular rubber circle between be provided with the foil gage, the foil gage be connected with outside computer through the wire, box top be provided with the top cap, the top cap inner wall be provided with spiral groove, the spiral groove in be provided with the liquid heat preservation that the one end runs through the liquid outlet and the low temperature constant temperature groove.

The bottom plate of the box body is provided with a plurality of concentric annular grooves, the bottom plate of the box body is also provided with a radial groove of which the central line is coincident with the diameter of the bottom plate, the liquid circulation pipe is firstly arranged on the bottom plate of the upper half part along the annular groove disc, the liquid circulation pipe is upwards bent into a U-shaped structure at the central position of the bottom plate, and then the liquid circulation pipe is arranged on the bottom plate of the lower half part along the annular groove disc.

The displacement and force transmission device comprises an extension bar, one end of the extension bar is fixed on a round steel plate, air holes are formed in the round steel plate, and external threads matched with internal threads of a measuring bar of a dial indicator are processed at the free end of the extension bar.

The invention is characterized in that a cover plate is arranged on a convex edge of a bottom plate of a box body, a sample box is placed on the cover plate, and the cover plate is an annular plate uniformly provided with vent holes; the top cover is internally provided with a supporting plate, and the supporting plate is an annular plate which is uniformly provided with air holes.

The cover plate and the support plate are made of aluminum materials.

The liquid circulating pipe of the invention is a copper pipe.

The liquid outlet of the low-temperature constant-temperature groove is provided with a pressure pump.

The coiling height of the liquid circulating pipe spirally coiled along the side wall of the box body is higher than that of the sample box.

The height of the liquid circulation tube bent into a U-shaped structure of the invention is higher than that of the sample box.

The invention has the following beneficial effects:

1. utilize displacement and power transmission device to be as for the percentage table outside the box, can make things convenient for the reading, avoid unstable air current to influence the percentage table and stabilize and cause the reading inaccurate, avoid simultaneously freezing at cooling in-process percentage table and lead to experimental failure.

2. The probe line of the digital display sensor can penetrate out of the box body through the hole of the top cover, and the temperature, the water content, the strain value and the like of the sample soil body in the cooling process can be directly tested.

3. The swelling force of the saline soil during salt swelling can be tested while the salt swelling amount is tested.

4. The test box is large in size, can meet the requirement that coarse grain saline soil is designed into a large-size sample by avoiding the particle size effect, can meet the loading space requirement, can be used for placing a plurality of samples during the experiment, and can increase the parallel test and the comparison sample.

5. The temperature reduction is realized by reducing the temperature of the antifreeze through the low-temperature thermostatic bath, and the antifreeze can be reused, volatilizes, does not pollute air, and is economical, safe and environment-friendly.

6. The cost is low.

Drawings

Fig. 1 is a schematic structural diagram of an embodiment of the present invention.

Fig. 2 is a schematic view of the displacement and force transmission means 17 of fig. 1.

Fig. 3 is a top view of fig. 2.

Fig. 4 is a schematic structural view of a bottom plate of the case 7 in another embodiment of the present invention.

Fig. 5 is a schematic structural view of the cover plate 8 in fig. 1.

In the figure: 1. a low-temperature constant-temperature tank; 2. a computer; 3. a dial indicator; 4. a digital display sensor; 5. a top cover; 6. a support plate; 7. a box body; 8. a cover plate; 9. a liquid circulation pipe; 10. a sample box; 11. a probe; 12. a strain gauge; 13. an annular rubber ring; 14. a fixing plate; 15. a heat-insulating layer; 16. sealing the steel plate; 17. displacement and force transmission means; 18. a pressure pump; a. an annular groove; b. a radial groove; 17-1, round steel plates; 17-2, lengthening the rod.

Detailed Description

The present invention will be described in further detail with reference to the following drawings and examples, but the present invention is not limited to these examples.

Example 1

In fig. 1, 2, 3, 4, and 5, the invention relates to a closed refrigeration heating device for testing saline soil salt expansion amount, which comprises a box body 7, wherein a spiral groove is processed on a bottom plate of the box body 7, a convex edge is processed on the edge of the spiral groove, a liquid circulation pipe 9 is coiled in the spiral groove, one end of the liquid circulation pipe 9 penetrates through the side wall of the box body 7 and is communicated with a liquid outlet of a low-temperature constant temperature tank 1, and the other end of the liquid circulation pipe 9 spirally coils along the side wall of the box body 7 and is communicated with a liquid inlet of the low-temperature constant temperature tank 1 through the side wall of the box body 7. The liquid circulation pipe 9 coiled on the side wall of the box body 7 is fixed on the side wall of the box body 7 through a fixing plate 14 by a screw fastening connector, and in order to ensure the cooling or heating effect, the coiling height of the liquid circulation pipe 9 spirally coiled along the side wall of the box body is higher than that of the sample box 10. At least one sample box 10 is placed on a convex edge of a bottom plate of a box body 7, the number of the sample boxes 10 is specifically determined according to experimental needs, the test boxes 10 are placed on the convex edge to avoid being in contact with a liquid circulation pipe 9 to press the liquid circulation pipe 9, so that flowing of refrigerating fluid is influenced, furthermore, in order to ensure that the sample boxes 10 are not in contact with the liquid circulation pipe 9, cover plates 8 can be installed on the convex edge, the cover plates 8 are annular plates processed with air holes, the cover plates 8 are made of aluminum materials and have good heat transfer effects, the air holes processed on the cover plates are more beneficial to heat transfer, a closed steel plate 16 is arranged at the top of the sample boxes 10, probes 11 connected with a digital display sensor 4 are embedded in samples of the sample boxes 10, the digital display sensor 4 is arranged outside the box body 7 to directly test temperature, water content and the like of sample soil bodies in a cooling process, a displacement and force transfer device 17 which penetrates through the closed steel plate 16 and a top cover 5 and is connected with a dial indicator 3 and an annular rubber ring 13 with the annular steel plate 17, the displacement and the annular rubber ring 13 is arranged on an extension bar 2-17, the extension bar which is integrated with a circular steel plate 17, the extension bar 2-17, the extension bar which is installed on a circular extension bar 2-17, and a water meter which is integrated with an extension bar capable of processing rod capable of preventing freezing. The strain gauge 12 is arranged between the displacement and force transfer device 17 and the annular rubber ring 13, the strain gauge 12 is connected with an external computer 2 through a wire, the computer 2 displays and processes transferred data, the strain gauge 12 is completely attached to the bottom of the annular rubber ring 13, the annular rubber ring 13 is filled with air, the sealed steel plate 16 is tightly pressed and fixed at the top of the sample box 10 in the cooling process, the saline soil in the sample box 10 is subjected to a salt expansion phenomenon in the cooling process, the surface layer of a soil body is bulged to jack up the round steel plate 17-1, the dial indicator 3 rotates to obtain a salt expansion amount at the moment, the round steel plate 17-1 extrudes the annular rubber ring 13 to deform, the strain gauge 12 also deforms, the strain amount of the annular rubber ring 13 is the strain amount of the saline soil when the saline soil is subjected to the salt expansion, and the expansion force of the saline soil can be obtained through conversion of the elastic modulus of the soil body. Top cap 8 is installed with screw thread fastening connection spare fixed connection at the top of

box

7, 8 inner walls of top cap are processed there is spiral groove, spiral groove inner disc has one end to run through top cap 8 and is linked together with 1 liquid outlet of low temperature constant temperature bath, the other end runs through the liquid circulation pipe 9 that top cap 8 and low temperature constant temperature bath 1's inlet are linked together, the refrigerated liquid that flows through liquid circulation pipe 9 inner loop is cooled down or is heated up to the upper portion in the box, 8 inside backup pad 6 of installing with screw thread fastening connection spare fixed connection of top cap, backup pad 6 is the annular slab that has the bleeder vent of processing, backup pad 6 prevents that 8 inner disc of top cap from putting's liquid circulation pipe 9 from droing, backup pad 6 is made by aluminium system material, the heat transfer is respond well, the bleeder vent of processing on it more does benefit to heat transfer,

box

7 and 8 lid outer walls all wrap up heat preservation 15, prevent the inside and outside heat exchange of box 7, the temperature transfer.

Example 2

In embodiment 1, a bottom plate of a box body 7 of this embodiment is provided with a plurality of concentric annular grooves a, the bottom plate of the box body 7 is further provided with a radial groove b, a center line of the radial groove b is coincident with the diameter of the bottom plate, a liquid circulation pipe 9 is firstly arranged on the upper half part of the bottom plate along a disc of the annular groove a, the liquid circulation pipe is bent upwards to form a U-shaped structure at the center position of the bottom plate, the liquid circulation pipe is then arranged on the lower half part of the bottom plate along the disc of the annular groove a, in order to ensure the effect of temperature reduction or temperature rise, the height of the liquid circulation pipe 9 bent to form the U-shaped structure is higher than that of a sample box 10, and the connection relationship between the rest parts and parts is completely the same as that in embodiment 1.

The test steps of the saline soil expansive force test and the single cooling salt expansion test by using the devices of the embodiments 1 and 2 of the invention are as follows:

laying heat insulation materials around a box body 7 to prevent heat exchange between the interior of the box body and ambient air, compacting a soil sample with set gradation according to certain salt content and water content, sealing the material for 24 hours, compacting the compacted soil sample in layers and filling the compacted soil sample into a sample box 10 to a certain height, wherein the compacting times are determined according to the degree of compaction and the compacting thickness, placing the sample box 10 filled with the saline soil into the box body 7, placing a displacement and force transmission device 17 on the surface of the soil sample, flatly attaching a strain gauge 12 to the bottom of an annular rubber ring 13, placing the annular rubber ring 13 on a circular steel plate 17-1 through an extension rod 17-2 of the displacement and force transmission device 17, placing a sealed steel plate 16 on the top of the sample box 10, penetrating a lead of the strain gauge 12 and an inflation tube of the annular rubber ball out of a hole punched in the sealed steel plate 16, and fastening and fixing the sealed steel plate 16 on the top of the sample box 10 by using a thread connecting piece to enable the sealed steel plate 16 to be in close contact. The top cover 5 of the box body 7 is well covered, the heat insulation material covers the top cover 5, and meanwhile, the extension bar 17-2, the lead of the strain gauge 12 and the inflation tube of the annular rubber ring 13 penetrate out of the top cover 5 and the heat insulation layer 15. The strain gauge wire is connected with a computer 2, a probe 11 is connected with a digital display sensor 4 through a wire, an annular rubber ring 13 is inflated, when the computer 2 displays a strain value, the inflation pipe is immediately stopped to be sealed, a dial indicator 3 is installed on an extension rod 17-2, a liquid outlet and a liquid inlet of a low-temperature constant temperature tank 1 are connected with a liquid circulation pipe 9 through rubber hoses, a pressure pump 18 can be installed on the rubber hose of the liquid outlet of the low-temperature constant temperature tank 1 according to the liquid flowing condition, the low-temperature constant temperature tank 1 is opened after tight connection is ensured, the control temperature of the low-temperature constant temperature tank 1 is changed, the strain value of each cooling stage and the final soil body can be measured, and the expansion force of the saline soil can be obtained through conversion of the elastic modulus of the soil body.

The working principle of the invention is as follows:

the antifreeze solution is added into the low-temperature constant-temperature tank 1, the low-temperature constant-temperature tank 1 is opened to cool the antifreeze solution, the antifreeze solution enters the liquid circulation pipe 9 from the liquid outlet of the low-temperature constant-temperature tank 1 to circularly flow to cool the interior of the box body 7, and finally returns to the low-temperature constant-temperature tank 1 from the liquid inlet of the low-temperature constant-temperature tank 1, so that the cyclic utilization of the refrigerating solution is realized, and the resources are saved. The temperature of the antifreeze is controlled by the cryostat tank 1 to adjust the temperature in the box body 7, and a pressure pump 18 is mounted on a pipeline at the liquid outlet of the cryostat tank 1 in order to ensure that the refrigerant has sufficient pressure and can rapidly flow circularly.

Claims

1. The utility model provides a test saline soil salt swelling capacity's airtight refrigeration heating device, includes the box, its characterized in that: the test box is characterized in that a spiral groove is formed in the bottom plate of the box body, a convex edge is arranged at the edge of the spiral groove, a liquid circulating pipe is arranged in the spiral groove, one end of the liquid circulating pipe penetrates through the side wall of the box body and is communicated with a liquid outlet of the low-temperature constant temperature groove, the other end of the liquid circulating pipe is spirally wound along the side wall of the box body and penetrates through the side wall of the box body and is communicated with a liquid inlet of the low-temperature constant temperature groove, the liquid circulating pipe wound on the side wall of the box body is fixed on the side wall of the box body through a fixing plate, at least one test sample box is placed on the convex edge, a sealed steel plate is arranged at the top of the test sample box, and a probe connected with a digital display sensor is embedded in a test sample of the test sample box, the top of a sample in the sample box is provided with a displacement and force transmission device which penetrates through a sealed steel plate and a top cover and is connected with a dial indicator, and an annular rubber ring with an inflation tube, wherein a strain gauge is arranged between the displacement and force transmission device and the annular rubber ring, the strain gauge is connected with an external computer through a wire, the top of the box body is provided with the top cover, the inner wall of the top cover is provided with a spiral groove, a liquid circulation tube with one end penetrating through the top cover and communicated with a liquid outlet of a low-temperature constant temperature groove and the other end penetrating through the top cover and communicated with a liquid inlet of the low-temperature constant temperature groove is arranged in the spiral groove, and the outer walls of the box body and the top cover are provided with heat insulation layers;

the bottom plate of the box body is provided with a plurality of concentric annular grooves, the bottom plate of the box body is also provided with a radial groove, the central line of the radial groove is coincident with the diameter of the bottom plate, the liquid circulation pipe is firstly arranged on the bottom plate of the upper half part along the annular groove disc, the liquid circulation pipe is bent upwards to form a U-shaped structure at the central position of the bottom plate, and then the liquid circulation pipe is arranged on the bottom plate of the lower half part along the annular groove disc;

the displacement and force transmission device comprises an extension bar, one end of the extension bar is fixed on a circular steel plate, air holes are formed in the circular steel plate, and external threads matched with the internal threads of the measuring bar of the dial indicator are processed at the free end of the extension bar;

the cover plate is arranged on the convex edge of the bottom plate of the box body, the sample box is placed on the cover plate, and the cover plate is an annular plate uniformly provided with air holes; the top cover is internally provided with a supporting plate, and the supporting plate is an annular plate which is uniformly provided with air holes.

2. The closed refrigerating and heating device for testing the salt swelling capacity of the saline soil as claimed in claim 1, wherein: the cover plate and the support plate are made of aluminum materials.

3. The closed refrigerating and heating device for testing the salt swelling capacity of the saline soil as claimed in claim 1, wherein: the liquid circulating pipe is a copper pipe.

4. The closed refrigerating and heating device for testing the salt swelling capacity of the saline soil as claimed in claim 1, wherein: and a pressure pump is arranged at the liquid outlet of the low-temperature constant-temperature groove.

5. The closed refrigerating and heating device for testing the salt swelling capacity of the saline soil as claimed in claim 1, wherein: the coiling height of the liquid circulating pipe spirally coiled along the side wall of the box body is higher than that of the sample box.

6. The closed refrigerating and heating device for testing the salt swelling capacity of the saline soil as claimed in claim 1, wherein: the height of the liquid circulating pipe bent into the U-shaped structure is higher than that of the sample box.