A soil freezing and thawing device with multi-dimensional dynamic sensing function

Abstract

The present invention relates to the field of road engineering, and in particular to a soil freezing and thawing device with a multi-dimensional dynamic sensing function. The soil freezing and thawing device provided by the present invention comprises a soil holding device, the soil holding device comprises a cylindrical soil holding cavity, the soil holding cavity holds the soil to be measured, and the soil holding cavity is also provided with an optical fiber measuring device and a point sensor, the optical fiber measuring device comprises an optical fiber load member whose extension direction matches the soil holding cavity and a heatable optical fiber loaded on the optical fiber load member, the point sensor is evenly distributed in the soil holding cavity, the bottom of the soil holding cavity is provided with a permeable layer and a gravel layer, the permeable layer is located between the soil to be measured and the gravel layer, the soil holding cavity is also provided with a load member, the load member acts on the soil to be measured by gravity, and a displacement monitoring device is also provided on the load member. The device provided by the present application has the advantages of modular installation, precise simulation, multi-dimensional dynamic monitoring, multi-purpose expansion, and easy modification.

Description

Technical Field

[0001] The invention relates to the field of road engineering, and in particular to a soil freezing and thawing device with a multi-dimensional dynamic sensing function. Background Art

[0002] Seasonally frozen areas account for 53.5% of my country's land area. Infrastructure foundations in such areas generally experience freeze-thaw cycles, which leads to the attenuation of soil strength, uneven deformation of the foundation, and further causes slope instability, building cracks and other diseases. When the soil freezes at low temperatures, a temperature gradient is generated in the frozen soil, causing a large amount of free water to move to the surface of the foundation, forming ice crystals after freezing, aggravating the frost heave of the soil; when the soil melts at high temperatures, the frost heave ice crystals disappear in the soil, resulting in a decrease in soil compaction and strength, weakening the stability of infrastructure.

[0003] Studying the laws of water-heat changes in the freeze-thaw cycle inside the soil is of great significance to ensuring the safety of infrastructure in seasonally frozen areas. Soil freeze-thaw is a coupling effect of water-heat-force multi-physical fields, and the soil physical field has temporal and spatial gradient changes. At present, comprehensive tests on the water-heat deformation field of foundations in seasonally frozen areas are not yet mature, and the monitoring methods used often have disadvantages such as low efficiency, low coverage, and high deployment cost. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a soil freeze-thaw device with a multi-dimensional dynamic sensing function, so as to solve the problems in the prior art.

[0005] To achieve the above-mentioned purpose and other related purposes, the present invention provides, on the one hand, a soil freezing and thawing device with a multi-dimensional dynamic sensing function, including a soil holding device, the soil holding device including a cylindrical soil holding cavity, the soil holding cavity containing a soil to be measured, and the soil holding cavity is also provided with an optical fiber measuring device and a point sensor, the optical fiber measuring device includes an optical fiber load member whose extension direction matches the soil holding cavity and a heatable optical fiber loaded on the optical fiber load member, the point sensor is evenly distributed in the soil holding cavity, a permeable layer and a gravel layer are provided at the bottom of the soil holding cavity, the permeable layer is located between the soil to be measured and the gravel layer, a load member is also provided in the soil holding cavity, the load member acts on the soil to be measured by gravity, and a displacement monitoring device is also provided on the load member.

[0006] In some embodiments of the present invention, a cold supply device is further included, wherein the cold supply device is in contact with the fluid in the soil receiving cavity above the load element.

[0007] In some embodiments of the present invention, a water body providing device is further included, wherein the water body providing device is in fluid communication with the gravel layer, and the water body providing device is a constant pressure water body providing device.

[0008] In some embodiments of the present invention, a flow metering device is provided on the connecting pipe between the water supply device and the gravel layer.

[0009] In some embodiments of the present invention, a plurality of point sensors are included, and the monitoring distance between each point sensor is ≥10 cm.

[0010] In some embodiments of the present invention, the thickness of the permeable layer is ≤0.1 cm, and the maximum passing particle size is ≤0.075 mm.

[0011] In some embodiments of the present invention, a thermal insulation layer is further provided on the outer wall of the soil containing device.

[0012] In some embodiments of the present invention, an optical fiber demodulation device and a heating device are also included, and the optical fiber demodulation device and the heating device are electrically connected to the heatable optical fiber respectively;

[0013] And / or, further comprising a displacement information acquisition device, wherein the displacement information acquisition device is electrically connected to the displacement monitoring device;

[0014] And / or, it also includes a point information collection device, and the point information collection device is electrically connected to each point sensor respectively.

[0015] Another aspect of the present invention provides a soil freezing and thawing simulation method, which uses the soil freezing and thawing device with multi-dimensional dynamic sensing function, and comprises:

[0016] S1) Introducing an appropriate amount of water into the gravel layer;

[0017] S2) introducing cold energy into the soil holding cavity above the load element;

[0018] S3) collecting monitoring data of the heatable optical fiber and / or point sensor and / or displacement sensor;

[0019] S4) Providing soil information based on the monitoring data provided in step S3).

[0020] In some embodiments of the present invention, in step S4), the soil information includes one or more combinations of soil moisture content, soil temperature, and soil deformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Shown is a schematic diagram of the overall structure of the soil freezing and thawing device with multi-dimensional dynamic sensing function provided by the present invention.

[0022] Figure 2 Shown is a schematic diagram of the partial structure of the optical fiber measuring device in the soil freezing and thawing device with multi-dimensional dynamic sensing function provided by the present invention.

[0023] Figure 3 Shown is a schematic diagram of the experimental steps in Example 1 of the present invention.

[0024] Figure 4 Shown is a schematic diagram of soil temperature field changes measured by distributed optical fiber in Example 1 of the present invention.

[0025] Figure 5 It shows a schematic diagram of the temperature changes at various points in the soil measured by the point sensor in Example 1 of the present invention.

[0026] Figure 6 Shown is a schematic diagram of soil moisture field changes measured by distributed optical fiber in Example 1 of the present invention.

[0027] Figure 7 It shows a schematic diagram of the change in moisture content at each point of the soil measured by the point sensor in Example 1 of the present invention.

[0028] Figure 8 It shows a schematic diagram of the soil water inflow measured by a Marsh flask in Example 1 of the present invention.

[0029] Fig. 9 It shows a schematic diagram of the displacement change measured by the LVDT at the top of the soil body in Example 1 of the present invention.

[0030] Component number description

[0031] 1 Soil containment device

[0032] 101 Soil holding cavity

[0033] 2 Soil to be tested

[0034] 3 Fiber Optic Measurement Device

[0035] 301 Fiber Optic Load

[0036] 302 Heatable Fiber

[0037] 303 Fiber Optic Demodulation Device

[0038] 304 Heating device

[0039] 4-point sensor

[0040] 401 Point Information Collection Device

[0041] 5. Permeation layer

[0042] 6 Gravel layer

[0043] 7 Loading parts

[0044] 8 Displacement monitoring device

[0045] 801 Displacement Information Acquisition Device

[0046] 9 Cooling device

[0047] 901 Temperature control device bracket

[0048] 902 Temperature control device insulation layer

[0049] 903 Compressor

[0050] 903 Condenser

[0051] 905 Radiator

[0052] 906 Temperature Controller

[0053] 10 Water supply device

[0054] 11 Insulation layer DETAILED DESCRIPTION

[0055] In order to make the invention objectives, technical solutions and beneficial technical effects of the present invention clearer, the present invention is further described in detail below in conjunction with embodiments. People familiar with this technology can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0056] A first aspect of the present invention provides a soil freezing and thawing device with a multi-dimensional dynamic sensing function, comprising a soil holding device 1, wherein the soil holding device 1 comprises a cylindrical soil holding cavity 101, wherein the soil holding cavity 101 holds a soil body 2 to be measured, wherein the soil holding cavity 101 is further provided with an optical fiber measuring device 3 and a point sensor 4, wherein the optical fiber measuring device 3 comprises an optical fiber load member 301 whose extension direction matches the soil holding cavity 101 and a heatable optical fiber 302 loaded on the optical fiber load member 301, wherein the point sensor 4 is evenly distributed in the soil holding cavity 101, wherein a permeable layer 5 and a gravel layer 6 are provided at the bottom of the soil holding cavity 101, wherein the permeable layer 5 is located between the soil body 2 to be measured and the gravel layer 6, wherein a load member 7 is further provided in the soil holding cavity 101, wherein the load member 7 acts on the soil body 2 to be measured by gravity, and wherein a displacement monitoring device 8 is further provided on the load member 7. When the above-mentioned soil freeze-thaw device with multi-dimensional dynamic sensing function is used, an appropriate amount of water can be introduced into the gravel layer, and the cold can be (continuously) introduced into the soil holding cavity above the load member. After the load member 7 of appropriate weight acts on the soil 2 to be tested by gravity, the monitoring data provided by the heatable optical fiber and / or point sensor can be collected, and soil information (for example, the moisture content of the soil, the temperature of the soil, etc.) can be further provided based on the monitoring data provided.

[0057] In the soil freezing and thawing device with multi-dimensional dynamic sensing function provided by the present invention, the soil holding device 1 can generally include a soil holding chamber 101. Since the experiment usually requires the load member 7 to apply a load to the soil body 2 to be tested by gravity, the soil holding chamber 101 is generally a cylindrical structure extending in a straight line, and the shape and size of the load member 7 are generally matched with the cross-section of the soil holding chamber 101. Generally speaking, the load member 7 can move up and down in the soil holding chamber 101 with appropriate degrees of freedom, but can basically close the upper space of the soil body 2 to be tested and fully contact the soil body 2 to be tested, and its mass generally depends on the load that needs to be applied to the soil body 2 to be tested, for example, it can be determined according to the stress level of the corresponding roadbed, which can be about 10 kPa to 10 kPa. The specific shape, size and material of the soil holding device 1 and the soil holding chamber 101 included therein can generally be adjusted according to the experimental needs. For example, the cross-sectional shape of the soil holding chamber 101 can generally be rectangular, circular, elliptical, etc., and the cross-sectional area can be 1600 cm 2 ~3600cm 2 The height of the soil holding cavity 101 can be 100 cm to 200 cm. For another example, the material of the soil holding device 1 can be metal (for example, steel), organic glass, etc. The outer wall of the soil holding device 1 can also be additionally provided with a heat-insulating layer 11 and other components, so as to further ensure the stability of the temperature environment in the soil 2 to be tested. A suitable heat-insulating layer usually has a low thermal conductivity, for example, the thermal conductivity can be no greater than 0.025 W·m -1 ·K -1 The material of the thermal insulation layer 11 can be polyurethane, vacuum insulation board, polystyrene foam and other materials.

[0058] The soil freezing and thawing device with multi-dimensional dynamic sensing function provided by the present invention may also include a cold supply device 9, and the cold supply device 9 is in fluid communication with the soil containing cavity 101 above the load member 7. The cold supply device 9 can generally be used to provide a cold source, and the cold supply device 9 can generally contact the fluid in the soil containing cavity 101 above the load member 7, thereby forming a heat exchange, so as to achieve the effect of controlling the top temperature of the soil during the freezing and thawing process of the soil. Those skilled in the art can select a suitable cold supply device 9 for use in the above-mentioned soil freezing and thawing device. For example, the cold supply device 9 can generally include a compressor, a condenser, an evaporator and other devices.

[0059] In the soil freezing and thawing device with multi-dimensional dynamic sensing function provided by the present invention, a permeable layer 5 and a gravel layer 6 may be provided at the bottom of the soil holding cavity 101, and the presence of the permeable layer 5 and the gravel layer 6 is mainly to simulate the state of groundwater holding water. The gravel in the gravel layer 6 usually has larger particles, so that it can provide a certain support effect for the soil body 2 to be tested, and it can also ensure that water can flow fully in the gravel layer 6. For example, the particle size of the gravel particles in the gravel layer 6 can usually be ≥9.5mm, and the height can be ≤5cm. The gravel used in the gravel layer 6 can be pebbles, permeable stones, etc. The permeable layer 5 is mainly used to prevent the upper soil from falling into the gravel layer 6. At the same time, the water body can usually pass through the permeable layer 5 relatively freely, so as to ensure that the water body in the gravel layer 6 can be fully in contact with the soil body 2 to be tested. For example, the thickness of the permeable layer 5 can be ≤0.1cm, and the maximum passing particle size can be ≤0.075mm.

[0060] The soil freezing and thawing device with multi-dimensional dynamic sensing function provided by the present invention may also include a water supply device 10, which can usually be connected to the gravel layer 6 fluid. The water supply device 10 can usually be a suitable container that can hold fluid (for example, water, etc.), preferably a constant pressure water supply device (for example, a Malchow flask, etc., which can keep the water supply head height in the device unchanged). The water supply level of the water supply device should not be less than the height of the gravel layer 6. The connecting pipe between the water supply device 10 and the gravel layer 6 can also be usually provided with a flow metering device and / or a flow regulating device, so that an appropriate amount of water can be introduced into the gravel layer 6 at an appropriate time.

[0061] In the soil freezing and thawing device with multi-dimensional dynamic sensing function provided by the present invention, the point sensor 4 can generally be used to monitor parameters such as soil temperature, volumetric water content, matrix suction, thermal conductivity, etc. The number of point sensors 4 distributed in the soil holding cavity 101 can be one or more. Generally speaking, a plurality of point sensors 4 can be distributed in the soil holding cavity 101, and the distribution state thereof can generally be uniformly distributed, so that the soil information of each part of the soil body 2 to be tested can be effectively collected. For example, the monitoring spacing between each point sensor 4 can be ≥10cm. Those skilled in the art can select suitable point sensors 4 for use in the above-mentioned soil freezing and thawing device, for example, it can be a point hydrothermal sensor or other device. Generally speaking, the soil freezing and thawing device can also include a point information collection device 401 (for example, a low-power data collector, etc.), and the point information collection device 401 can be electrically connected to each point sensor 4 respectively, so that the information monitored by each point sensor 4 can be collected.

[0062] In the soil freezing and thawing device with multi-dimensional dynamic sensing function provided by the present invention, the optical fiber measuring device 3 can generally be used to monitor parameters such as soil temperature and soil moisture content. The optical fiber measuring device 3 can generally include an optical fiber load 301 whose extension direction matches the soil holding cavity 101 and a heatable optical fiber 302 loaded on the optical fiber load 301, so that the heatable optical fiber 302 can be evenly distributed in the soil 2 to be measured, so as to effectively collect soil information of each part of the soil 2 to be measured. Generally speaking, the optical fiber load 301 can be a substrate with a certain rigidity, for example, it can be a PVC pipe. The extension direction of the optical fiber load 301 is generally matched with the soil holding cavity 101, and the heatable optical fiber 302 can be tightly wound on the optical fiber load 301. For example, according to the extension direction of the optical fiber load 301, within the unit length range, the length of the heatable optical fiber 302 can be 15 cm to 15 cm, and the length can be adjusted by adjusting the diameter of the cross section of the optical fiber load 301. The heatable optical fiber 302 generally includes an internal optical cable portion and a heatable layer wrapped around the outside of the optical cable. Those skilled in the art can select a suitable heatable optical fiber 302 for use in the above-mentioned soil freeze-thaw device, for example, it can be a (carbon fiber) internal heating optical cable, etc. Generally speaking, the soil freeze-thaw device can also include an optical fiber demodulation device 303 (for example, a DTS demodulator, etc.) and / or a heating device 304 (for example, a heating transformer, etc.), and the optical fiber demodulation device 303 and the heating device 304 are electrically connected to the heatable optical fiber 302, respectively. Specifically, the optical cable portion in the heatable optical fiber 302 and the heatable layer wrapped around the outside of the optical cable can be electrically connected to the optical fiber demodulation device 303 and the heating device 304, respectively, and the optical fiber demodulation device 303 can collect the information obtained by monitoring the optical cable portion, and the heating device 304 can heat the heatable layer.

[0063] In the soil freeze-thaw device with multi-dimensional dynamic sensing function provided by the present invention, the displacement monitoring device 8 is mainly used to detect the displacement change of the load member 7, which may be in direct contact with the load member or may not be in direct contact. Those skilled in the art can select a suitable displacement monitoring device 8 for use in the above-mentioned soil freeze-thaw device, for example, it can be a linear variable differential transformer, etc. Generally speaking, the soil freeze-thaw device can also include a displacement information acquisition device 801 (for example, a digital acquisition instrument, etc.), and the displacement information acquisition device 801 is electrically connected to the displacement monitoring device 8, so that the information monitored by the displacement monitoring device 8 can be collected.

[0064] The second aspect of the present invention provides a soil freezing and thawing simulation method, which uses the soil freezing and thawing device with multi-dimensional dynamic sensing function provided by the first aspect of the present invention, comprising:

[0065] S1) Introducing an appropriate amount of water into the gravel layer;

[0066] S2) introducing cold energy into the soil holding cavity above the load element;

[0067] S3) collecting monitoring data of the heatable optical fiber and / or point sensor and / or displacement sensor;

[0068] S4) Providing soil information based on the monitoring data provided in step S3.

[0069] As mentioned above, when simulating soil freezing and thawing, it is usually necessary to introduce an appropriate amount of water into the gravel layer to simulate the state of groundwater holding water, and to perform heat exchange with the soil holding cavity above the load part through the cold supply device (continuously) to achieve the effect of controlling the top temperature of the soil during the freezing and thawing process. At the same time, the monitoring data of the heatable optical fiber and / or point sensor and / or displacement sensor can be collected, and the soil information can be calculated through the monitoring data, for example, one or more information of the moisture content of the soil, the temperature of the soil, the deformation of the soil, etc. Among them, the method of calculating the soil temperature and moisture content through the heatable optical fiber data can refer to the relevant content disclosed in CN201310398355.6 "A Distributed Measurement Method and System for Soil Moisture Content".

[0070] Compared with the prior art, the soil freezing and thawing device with multi-dimensional dynamic sensing function provided by the present invention has the following significant features:

[0071] 1. Modular installation: The test device is modularized, the installation process is simple and the cost is controllable.

[0072] 2. Accurate simulation: The test device can be set to different working conditions to accurately simulate the engineering environment. The compaction degree of the soil to be tested can be selected according to the actual working conditions; different sizes of mass blocks can be selected to simulate different levels of upper loads; the sides of the soil to be tested are covered with insulation materials to reduce the impact of air temperature, and the bottom is grounded to simulate constant ground temperature conditions; the top surface temperature of the soil to be tested can be set to a constant negative temperature or temperature cycle and other conditions. Preferably, a Martens flask water replenishment device with a metering function can be optionally equipped, and the water head height in the water replenishment device can be adjusted.

[0073] 3. Multi-dimensional dynamic monitoring: The test device can carry out multi-dimensional dynamic monitoring of the soil physical field during the freezing and thawing process based on fully distributed sensing for multiple indicators such as moisture content, temperature, and deformation. The entire system can monitor the moisture field and temperature field of the soil to be tested from a spatial dimension, and realize high-precision fully distributed monitoring of the physical field of the soil to be tested; the displacement monitoring device can carry out continuous monitoring of the macroscopic deformation of the soil to be tested, and effectively evaluate the frost heave and thaw settlement effect of the soil to be tested during the freezing and thawing process. Preferably, the point sensor can continuously monitor the changes in the water and heat data of the soil to be tested over time, and calibrate the heatable optical fiber, and form a complete and accurate spatiotemporal change law of the water and heat data in combination with the heatable optical fiber sensing system, and the optional water supply device with metering function can record the overall flow of the soil to be tested, and further calibrate the aforementioned sensors.

[0074] 4. Multi-purpose expansion: The temperature control device is set to a constant temperature, and the water replenishment device maintains a constant water replenishment to simulate the groundwater rising process behind the new fill body; the water replenishment device can be used to replenish or add water from the top to construct different moisture content fields, combined with different working temperatures, to achieve the calibration of heatable optical fiber parameters under different working conditions.

[0075] 5. Easy to modify: Earth pressure gauges, displacement monitoring optical cables and other sensors can be installed in the soil to be tested to expand the monitoring indicators during the freezing and thawing process; insulation materials such as insulation layers can be installed in the soil to be tested to simulate the implementation effect of engineering insulation measures in frozen soil areas.

[0076] The present application is further described below by way of examples, but the scope of the present application is not limited thereby.

[0077] Example 1

[0078] The structure of the soil freezing and thawing device used in the embodiment is described as follows:

[0079] The test box is equipped with a heat preservation test box containing the soil to be tested. The size of the open test box is a steel rectangular open test box with an inner diameter of 40cm×40cm×100cm, a wall thickness of 3mm, and a test box insulation layer of 5cm thick polyurethane insulation board with a thermal conductivity of 0.025W·m-1·K-1. The permeable layer set in the test box is a composite structure of geotextile and steel wire mesh, and the gravel layer 14 is composed of pebbles with a nominal particle size of more than 9.5mm, and the height of the gravel layer is 5cm.

[0080] The temperature control device for regulating the top surface temperature of the soil to be tested includes a temperature control device bracket 901 (a steel rectangular open box with an inner diameter of 42 cm × 42 cm × 20 cm and a wall thickness of 3 mm), a temperature control device insulation layer 902 (a 5 cm thick polyurethane insulation board with a thermal conductivity of 0.025 W·m-1·K-1), a compressor 903 (the compressor model is SCOPE SC18L, the power is 496 W, and the cooling capacity is 920 W at an evaporation temperature of -20 °C), and a condenser 904 (a heat exchange area of ​​8 m2 ) Radiator 905 (heat exchange area is 6m 2 ) and temperature controller 906, which is installed on the top of the insulation test box and can adjust the temperature to control the top temperature of the soil during the freezing and thawing process. The working principle of this device is similar to that of a refrigerator. The refrigerant in the radiator 905 partially exchanges heat in the air to take away heat.

[0081] The mass block simulating the load on the upper part of the soil to be tested is located on the upper part of the test soil, and the upper and lower surfaces are perpendicular to the outer wall of the thermal insulation test box. Specifically, it is a 5 cm thick steel plate. The outer size of the mass block is consistent with the inner diameter of the open test box. A circular hole with a diameter of 6 cm is set in the middle of the mass block 3, which is slightly larger than the outer diameter of the heatable optical fiber measuring tube.

[0082] Heatable distributed optical fiber (NZS DTS C09 carbon fiber internal heating optical cable of Nanzhi Sensing Technology Co., Ltd.) is wrapped with epoxy resin and glued to the surface of PVC tube. Each circle of optical fiber is tightly glued. The outer diameter of PVC tube is 5cm. Both ends of PVC tube should be sealed with plugs. Fine sand can be filled in the tube and compacted. The winding method of heatable distributed optical fiber can refer to Figure 2 Both ends are set on the top of the PVC tube. The distributed optical fiber head that can be heated needs to be connected in groups. The internal core of the optical fiber is fused with the optical fiber jumper and connected to the DTS demodulator (DTS-ROTDR optical fiber temperature demodulator of Nanzhi Sensing Technology Co., Ltd.), and the external carbon fiber heating layer is connected to the heating transformer (Chint TDGC2-0.5KVA).

[0083] The point water and heat sensing system includes multiple point water and heat sensors (SWR-00W from Hebei Leishen Electronics) and a signal acquisition instrument (LPDL low-power data acquisition device from Hebei Leishen Electronics) that can measure the water content and temperature of the soil to be tested. The point water and heat sensors are buried in layers in the soil to be tested, and all point water and heat sensors should be connected to the signal acquisition instrument. There are 6 point water and heat sensors, which are laid in the soil to be tested at a depth interval of 10 cm. The communication cable of the water and heat sensor should be surface-mounted along the inner wall of the open test box and led out through the wiring hole.

[0084] The displacement monitoring system includes a linear variable differential transformer (LVDT, KTR-10 type, Shanghai Mansheng Electronic Technology Co., Ltd.) for monitoring soil deformation, with a monitoring accuracy higher than 0.1 mm, a linear variable differential transformer fixture and a displacement acquisition computer (Altai Technology DAM3204D digital acquisition instrument). The linear variable differential transformer must be placed perpendicular to the mass block and above it. All linear variable differential transformers are connected to the displacement acquisition computer. During installation, the variable differential transformer fixture should be installed on the top of the open test box and fixed by the bracket fixing screws and bracket fixing nuts. The linear variable differential transformer should be installed in the fixed slot and fixed by the clamping screws.

[0085] The water replenishing device is a Martens flask with a water level scale, a control valve and a flow meter, and the device is connected to the bottom of the thermal insulation test box through a water pipe.

[0086] When using a soil freeze-thaw device to carry out soil freeze-thaw tests, the test process used is as follows: Figure 3 As shown, it mainly includes the following steps:

[0087] 1) Soil sample acquisition: obtain soil samples for soil freeze-thaw test;

[0088] 2) Filling of soil to be tested and installation of sensors: Temporarily fix the optical fiber measuring tube to the middle of the open test box, and pay attention to adjusting the position of the optical fiber measuring tube at any time in the subsequent steps to avoid large deviations.

[0089] The bottom of the open test is filled with crushed stone, and then a permeable layer is installed on top of the crushed stone layer.

[0090] The soil samples used for soil freeze-thaw test shall be filled in layers. The filling height of each layer and the required soil sample mass shall be calculated according to the designed compaction degree, and the moisture content of the filled soil shall be determined according to the actual situation. After the single layer of soil is filled, a scraper shall be used to roughen it.

[0091] During the layered filling of soil samples, a single-point water and heat sensor is installed according to the designed height, and the distance between the sensor probe and the optical fiber measuring tube should not be greater than 2 cm.

[0092] After the soil to be tested is filled to the designed elevation, the mass block is placed, and the mass block is closely connected to the soil to be tested through leveling and compaction.

[0093] After the mass block is installed, the LVDT fixture 52 is installed, and then the LVDT is installed into the fixture and locked.

[0094] Install temperature control device.

[0095] 3) Install the data acquisition instrument and debug the equipment: connect the point-type water heat sensor and the signal acquisition instrument; connect the heatable optical fiber measuring tube, optical fiber jumper and optical fiber demodulator, connect the heatable optical fiber measuring tube wire and the heating transformer; connect the linear variable differential transformer and the displacement acquisition computer. Turn on the temperature control device and the above-mentioned acquisition sensor equipment in turn, and debug to ensure the availability of the equipment.

[0096] 4) Complete the freeze-thaw or related tests of the soil to be tested: turn on the relevant equipment, set the temperature control parameters of the temperature control device, set the sensor acquisition frequency, complete the capillary water rise, soil freeze-thaw (cycle), etc. according to the test plan and collect process data. Using the above equipment, when the temperature control temperature is set to -15℃, the soil temperature field measured by the distributed optical fiber changes as follows Figure 4 As shown in the figure, the temperature changes of each point in the soil measured by the point sensor are as follows: Figure 5As shown in Figure 2, the soil moisture field changes measured by distributed optical fiber are as follows: Figure 6 As shown in the figure, the moisture content of each point in the soil measured by the point sensor changes as shown in the figure Figure 7 As shown in the figure, the soil water inflow measured by the Martens flask is Figure 8 As shown in the figure, the displacement change measured by the LVDT at the top of the soil is as follows Fig. 9 shown.

[0097] 5) Test data collation: Analyze the moisture field, temperature field, and deformation field data based on the data collected by each sensor in step 4). The method of using distributed optical fiber to test soil temperature and soil moisture content can refer to the relevant content disclosed in CN201310398355.6 "A distributed measurement method and system for soil moisture content".

[0098] In summary, the present invention effectively overcomes various shortcomings of the prior art and has high industrial utilization value.

[0099] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A soil freezing and thawing device with multi-dimensional dynamic sensing function, It is characterized in that The invention comprises a soil containing device (1), wherein the soil containing device (1) comprises a columnar soil containing cavity (101), wherein the soil containing cavity (101) contains a soil to be measured (2), wherein the soil containing cavity (101) is further provided with an optical fiber measuring device (3) and a point sensor (4), wherein the optical fiber measuring device (3) comprises an optical fiber load member (301) whose extension direction matches the soil containing cavity (101) and a heatable optical fiber (302) loaded on the optical fiber load member (301), wherein the point sensor (4) is evenly distributed in the soil containing cavity (101), and wherein a permeable layer is provided at the bottom of the soil containing cavity (101). The invention relates to a method for measuring a soil body (2) to be measured and a crushed stone layer (6), wherein the permeable layer (5) is located between the soil body (2) to be measured and the crushed stone layer (6), wherein a load member (7) is also provided in the soil body receiving cavity (101), wherein the load member (7) acts on the soil body (2) to be measured by gravity, and wherein a displacement monitoring device (8) is also provided on the load member (7); further comprising a cold supply device (9), wherein the cold supply device (9) is in contact with the fluid in the soil body receiving cavity (101) above the load member (7); and further comprising a water supply device (10), wherein the water supply device (10) is in fluid communication with the crushed stone layer (6), and wherein the water supply device (10) is a constant pressure water supply device.

2. The soil freezing and thawing device with multi-dimensional dynamic sensing function as claimed in claim 1, It is characterized in that A flow metering device is provided on the connecting pipe between the water supply device (10) and the gravel layer (6).

3. The soil freezing and thawing device with multi-dimensional dynamic sensing function as claimed in claim 1, It is characterized in that It comprises a plurality of point sensors (4), wherein the monitoring distance between the point sensors (4) is ≥10 cm.

4. The soil freezing and thawing device with multi-dimensional dynamic sensing function as claimed in claim 1, It is characterized in that The thickness of the permeable layer (5) is ≤0.1 cm, and the maximum passing particle size is ≤0.075 mm.

5. The soil freezing and thawing device with multi-dimensional dynamic sensing function as claimed in claim 1, It is characterized in that A heat-insulating layer (11) is also provided on the outer wall of the soil containing device (1).

6. The soil freezing and thawing device with multi-dimensional dynamic sensing function as claimed in claim 1, It is characterized in that It also includes an optical fiber demodulation device (303) and a heating device (304), wherein the optical fiber demodulation device (303) and the heating device (304) are electrically connected to the heatable optical fiber (302) respectively; And / or, further comprising a displacement information acquisition device (801), wherein the displacement information acquisition device (801) is electrically connected to the displacement monitoring device (8); And / or, it further comprises a point-type information collection device (401), wherein the point-type information collection device (401) is electrically connected to each point-type sensor (4) respectively.

7. A soil freezing and thawing simulation method, using the soil freezing and thawing device with multi-dimensional dynamic sensing function as claimed in any one of claims 1 to 6, include: S1) Introducing an appropriate amount of water into the gravel layer; S2) introducing cold energy into the soil holding cavity above the load element; S3) collecting monitoring data of the heatable optical fiber and / or point sensor and / or displacement sensor; S4) Providing soil information based on the monitoring data provided in step S3).

8. The soil freezing and thawing simulation method according to claim 7, It is characterized in that In the step S4), the soil information includes one or more combinations of soil moisture content, soil temperature, and soil deformation.

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