Device and method for testing thermal conductivity of granular materials

Abstract

The application provides a device and method for testing the heat conduction characteristics of granular materials, and relates to the field of geotechnical engineering, which comprises a probe body, a cylinder, a lower support platform, an upper support platform and a tamping device; the lower support platform and the upper support platform are respectively threadedly connected with the cylinder; a reserved hole column is installed at the top center of the lower support platform; the tamping device comprises a vertical pipe, a pressure plate, a plug and a lower tamping hammer; the outer diameter of the pressure plate is smaller than the inner diameter of the cylinder; a connecting hole with a wide top and a narrow bottom is formed at the center of the pressure plate; the top end of the connecting hole is threadedly connected with the bottom end of the vertical pipe; the plug is a T-shaped column structure, the outer diameter of the horizontal part of the plug is larger than the outer diameter of the reserved hole column and smaller than the inner diameter of the top end of the connecting hole; the outer diameter of the vertical part of the plug, the inner diameter of the bottom end of the connecting hole and the outer diameter of the reserved hole column are the same and are not larger than the inner diameter of the vertical pipe; the lower tamping hammer is sleeved on the vertical pipe; the application can effectively avoid the defects existing in the heat conduction characteristic test of the sample by using the drilling method.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering, and specifically to an apparatus and method for testing the thermal conductivity of granular materials. Background Technology

[0002] In the field of geotechnical engineering, when using the thermal probe method to measure the thermal conductivity of materials such as cohesive soil (e.g., powdered objects such as soil, sand, and cement), the sample must first be molded in a mold, then the sample is demolded and drilled, and then the probe is inserted into the drilled hole to measure the thermal conductivity of the sample.

[0003] For example, Section 2.3.2 on page 17 of the TEMPOS thermal property analyzer user manual discloses that "a hole of appropriate size can be created using a drill bit or a guide pin," while Section 3.3.2 on page 22 discloses that "b) insert the guide pin into the wet cement, c) ensure that there are enough pins for fixation, and d) ensure that the guide pin is inserted deep enough so that the needle can be fully inserted after the concrete has hardened."

[0004] However, in the above methods, when drilling is used to measure the thermal conductivity of the sample, on the one hand, the obtained drill hole is affected by the operator's proficiency in drilling, and defects such as tilting and difficulty in accurately controlling the hole depth are prone to occur during the drilling process. This results in defects such as difficulty in inserting the probe into the sample and the hole depth not matching the required probe insertion depth, which is not conducive to testing, and the probe is easily damaged when inserted into the hole. On the other hand, the size of the drill hole is difficult to control, which affects the test accuracy.

[0005] Therefore, it is urgent to provide a testing device that can avoid damaging the probe and ensure testing accuracy. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] To address the shortcomings of existing technologies, this invention provides an apparatus and method for testing the thermal conductivity of granular materials, thereby solving the technical problems in existing technologies where drilling of samples easily results in defects such as tilted pores and difficulty in controlling the pore inner diameter, which damage the probe and affect the testing accuracy.

[0008] (II) Technical Solution

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] In a first aspect, the present invention provides an apparatus for testing the thermal conductivity of granular materials, comprising a probe body, a transparent cylinder, a lower support, an upper support, and a compaction device;

[0011] The top of the lower support is located inside the bottom end of the cylinder and is threadedly connected.

[0012] The bottom end of the upper support is located inside the top end of the cylinder and is threadedly connected.

[0013] A pre-drilled column is installed at the top center of the lower support platform;

[0014] The outer diameter and height of the reserved hole column are the same as the outer diameter and height of the probe body; and the height of the reserved hole column is less than the distance between the top of the lower support and the bottom of the upper support.

[0015] The compaction device comprises a vertical tube, a pressure plate, a plug, and a lower compaction hammer;

[0016] The outer diameter of the pressure plate is smaller than the inner diameter of the cylinder;

[0017] A connecting hole with a coarser upper section and a finer lower section is provided at the center of the pressure plate;

[0018] The top end of the connecting hole is threaded to the bottom end of the vertical pipe;

[0019] The plug is specifically a T-shaped columnar structure, the outer diameter of its horizontal part is larger than the outer diameter of the reserved hole column and smaller than the inner diameter of the top of the connecting hole;

[0020] The outer diameter of the vertical part of the plug, the inner diameter of the bottom end of the connecting hole, and the outer diameter of the reserved hole column are all the same and are not greater than the inner diameter of the vertical pipe.

[0021] The impact hammer is mounted on the vertical tube.

[0022] Furthermore, the compaction device also includes an upper compaction hammer sleeved on the vertical tube and positioned above the lower compaction hammer;

[0023] The upper and lower hammers are movably connected by a first connector; the height of the upper and lower hammers as a whole is greater than the distance between the top of the lower support and the top of the cylinder.

[0024] Furthermore, the first connector comprises a guide sleeve, a limiting post, a guide hole, a limiting space, and a limiting notch;

[0025] The guide sleeve is fitted onto the vertical tube and is fixedly connected to the bottom of the hammer.

[0026] A limiting post is vertically connected to the outer wall of the guide sleeve;

[0027] The guide hole is opened on the top of the hammer and is coaxially distributed with the vertical tube. The inner diameter of the guide hole is the same as the outer diameter of the guide sleeve, and the length of the guide hole is not less than the length of the guide sleeve.

[0028] The limiting space is opened inside the top of the hammer and communicates with the guide hole. The inner diameter of the limiting space is not less than the vertical distance between the axis of the guide sleeve and the outer end of the limiting post.

[0029] The limiting notch is located at the top of the hammer and is connected to the limiting space, allowing the limiting post to enter and exit the limiting space in the vertical direction.

[0030] Furthermore, a spring is provided inside the bottom end of the guide hole and sleeved outside the vertical tube. The bottom of the spring is connected to the bottom of the guide hole, and the height of the guide hole is greater than the height of the guide sleeve. During the process of the spring being compressed to the limit, the bottom of the upper hammer and the top of the lower hammer are in contact.

[0031] Furthermore, a balance hole is provided in the reserved hole column, the top end of the balance hole penetrates the top end of the reserved hole column, and the bottom end of the balance hole penetrates the reserved hole column and the lower support in sequence; a balance needle with the same outer diameter is provided in the balance hole, the bottom end of the balance needle is connected to the bottom of the lower support through a second connector, and the top end of the balance needle closes the top end of the balance hole.

[0032] Furthermore, a columnar lower embedding groove is provided on the top of the lower support platform, and lower permeable holes are evenly provided on the portion of the lower support platform below the lower embedding groove; the reserved hole column is fixedly installed at the bottom center of the lower embedding groove; a lower permeable layer and a lower sealing layer are also provided, and the dimensions of the lower permeable layer, the lower sealing layer and the lower embedding groove are all the same; and a through hole for the reserved hole column to pass through is provided at the center of both the lower permeable layer and the lower sealing layer.

[0033] The bottom of the upper support platform is provided with an upper embedding groove, and the portion of the upper support platform above the upper embedding groove is provided with upper permeable holes evenly distributed; an upper permeable layer and an upper sealing layer are also provided, and the upper permeable layer, the upper sealing layer and the upper embedding groove are all the same size.

[0034] Furthermore, the cylinder, lower support platform, upper support platform, lower sealing layer, and upper sealing layer are all made of transparent material with low thermal conductivity.

[0035] Furthermore, the lower sealed layer, the lower permeable layer, the upper sealed layer, and the upper permeable layer are all the same size; and sealing rings are embedded in the vertical walls of the lower sealed layer, the lower permeable layer, the upper sealed layer, and the upper permeable layer, and annular sealing grooves are provided on the inner walls of the lower embedded groove and the upper embedded groove.

[0036] A second aspect of the present invention also provides a method for testing the thermal conductivity of granular materials using the above-described apparatus for testing the thermal conductivity of granular materials, the method comprising the following steps:

[0037] The resulting sample is divided into j compacted layers from bottom to top, with each compacted layer having a thickness of h. e And h e ·k=l,h e ·j=H; where l is the height of the reserved hole column above the upper bearing platform, k is the number of compacted layers corresponding to the reserved hole column, H is the distance between the top of the lower bearing platform and the bottom of the upper bearing platform when both the lower and upper bearing platforms are connected to the cylinder, and k and j are both integers;

[0038] Each compacted layer is numbered from bottom to top; where the αth compacted layer corresponds to the filler mass m. α =m t •θ α ;m t θ is the total mass of the obtained sample. α The filler coefficient for the compacted layer α;

[0039] V 总 =πR 2 H, V 柱 =πr 2 l, R is the radius of the inner wall of the cylinder, r is the radius of the outer wall of the pre-drilled hole, V S =V 总 -V 柱 ;in,

[0040] The lower support platform with the pre-drilled column is connected to the cylinder, and the lower sealing layer is embedded in the lower embedding groove; wherein, the second connecting piece is connected to the lower support platform, and the balance pin is located in the balance hole;

[0041] Compaction step: Add the αth compacted layer with a corresponding mass of m into the cylinder. α The packing material is compacted by placing a vertical pipe connected to a pressure plate onto the pre-drilled column, with the pressure plate covering the top of the packing material, until the thickness of the added packing material becomes h. e Remove the compaction device and roughen the top of the packing material; initially, α = 1;

[0042] Let α+1 be the new α. If the new α ≥ k, then install the plug between the vertical pipe and the pressure plate, and repeat the compaction step until the new α > j. Then proceed to the testing step. When the new α = j, remove the compaction device and do not treat the top of the packing. If the new α < k, then repeat the compaction step.

[0043] Test procedure: Perform thermal conductivity test on unsaturated samples;

[0044] The thermal conductivity test of the unsaturated sample includes:

[0045] Install the upper support with the upper sealing layer on the cylinder, invert the cylinder so that the lower support is above the upper support; remove the balance needle, and then screw the lower support back and forth several times before screwing it off. Insert the probe body into the obtained sample, cover the top of the cylinder with an insulation layer, and then perform a thermal conductivity test.

[0046] Furthermore, the testing steps also include: conducting a thermal conductivity test on the saturated sample; the thermal conductivity test of the saturated sample includes:

[0047] Install the upper bearing platform with the upper permeable layer on the cylinder, invert the cylinder so that the lower bearing platform is above the upper bearing platform; remove the balance pin, and then screw the lower bearing platform back and forth several times before screwing it off. Then replace the lower sealing layer with the lower permeable layer, and then connect the lower bearing platform to the cylinder.

[0048] Place the cylinder into a vacuum cylinder, evacuate it, and then inject degassing water.

[0049] After the obtained sample is saturated, the cylinder is erected and the lower support is placed below the upper support. The upper support is unscrewed, and the upper permeable layer is replaced with the upper sealed layer. Then, the upper support is connected to the cylinder, and the cylinder is inverted. After repeatedly screwing the lower support several times, the lower support is screwed off and the probe body is inserted into the obtained sample. A heat insulation and moisture-retaining layer is covered on the top of the cylinder, and then the thermal conductivity characteristics are tested.

[0050] (III) Beneficial Effects

[0051] This invention provides an apparatus and method for testing the thermal conductivity of granular materials. Compared with the prior art, it has the following advantages:

[0052] By setting up pre-drilled columns, pre-drilled holes can be effectively formed in the obtained sample for the insertion of the probe body, and the size of the pre-drilled holes is consistent with the size required for the insertion of the probe body, thereby effectively ensuring the accurate insertion of the probe in the later stage.

[0053] Secondly, the pre-reserved holes eliminate the need for drilling tests on the resulting samples, thus avoiding the defects associated with drilling tests on the samples. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1 A three-dimensional structural schematic diagram of the apparatus for testing the thermal conductivity properties of granular materials provided in the embodiment;

[0056] Figure 2 This is a cross-sectional view of the compaction device in the embodiment;

[0057] Figure 3 This is a sectional view of the upper bearing platform;

[0058] Figure 4 This is a sectional view of the lower bearing platform.

[0059] In the diagram: 1. Cylinder; 2. Lower support platform; 3. Upper support platform; 4. Compacting device; 5. Pre-drilled hole column; 4-1. Vertical pipe; 4-2. Pressure plate; 4-3. Plug; 4-4. Lower compacting hammer; 4-2-1. Connecting hole; 4-5. Upper compacting hammer; 4-6-1. Guide sleeve; 4-6-2. Guide hole; 4-6-3. Limiting post; 4-6-4. Limiting space; 4-6-5. Limiting notch; 4-7. Spring; 5-1. Balance hole; 5-2. Balance pin; 5-3. Second connecting piece; 2-1. Lower embedding groove; 2-2. Lower water permeable hole; 2-3. Lower sealing layer; 2-4. Through hole; 3-1. Upper embedding groove; 3-2. Upper water permeable hole; 3-3. Upper sealing layer. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0061] In existing technologies, to address the drawbacks of using the thermal probe method to measure the thermal conductivity of cohesive soils, such as the tendency of the obtained borehole to tilt or the difficulty in controlling the borehole diameter, which leads to problems during subsequent thermal conductivity testing, including easy damage to the probe during insertion into the borehole, large gaps between the probe and the borehole wall, and difficulty in inserting the probe into the borehole, the solutions are mostly to select drill bits of specific sizes, fix the drilling equipment on a vertically adjustable device, or improve drilling accuracy by increasing drilling proficiency.

[0062] The main idea of ​​this application to solve the above-mentioned technical problems is as follows:

[0063] A device for testing the thermal conductivity of granular materials is provided. It mainly involves setting a pre-drilled column 5 in the device so that the obtained sample has a pre-drilled hole for probe insertion, avoiding the defects caused by drilling with a drill bit later. This provides a new technical approach that can effectively test the thermal conductivity of the sample while avoiding the defects existing in the prior art.

[0064] To better understand the technical solution of this application, the technical solution of this application will be described in detail below with reference to specific embodiments and accompanying drawings.

[0065] Example 1

[0066] Combined with appendix Figure 1-4 This embodiment provides an apparatus for testing the thermal conductivity of granular materials, including a probe body for testing the thermal conductivity of a sample (since the probe body is a conventional device, it is not shown in the accompanying drawings); secondly, in order to prepare the sample, the testing apparatus further includes:

[0067] 1. Transparent cylindrical tube; 2. Lower support platform; 3. Upper support platform; and 4. Compacting device.

[0068] Among them, the cylinder 1 is made of transparent materials with low thermal conductivity such as plastic and resin. On the one hand, it avoids the obtained sample from being affected by external temperature changes. On the other hand, the transparent setting helps to observe the preparation of the sample from the outside to the inside.

[0069] The upper support platform 3 and the lower support platform 2 are made of the same material as the cylinder 1, thus achieving a consistent effect.

[0070] The connection relationships between the above structures are as follows:

[0071] The top of the lower support 2 is located inside the bottom of the cylinder 1, and the two are threaded together; that is, the lower support 2 is an inverted T-shaped columnar structure, the vertical part of which is located inside the cylinder 1 and threadedly connected to the inner wall of the bottom of the cylinder 1; the top of the lower support 2 is a horizontal plane to ensure that the surface corresponding to the obtained sample is horizontal.

[0072] The top of the upper support 3 is located inside the top of the cylinder 1, and the two are threaded together; that is, the upper support 3 is a T-shaped columnar structure, the vertical part of which is located inside the cylinder 1 and threadedly connected to the inner wall of the top of the cylinder 1; the bottom of the upper support 3 is a horizontal surface to ensure that the surface corresponding to the obtained sample is horizontal.

[0073] When the upper support platform 3 and the lower support platform 2 are connected to the cylinder 1 respectively, the space enclosed by the upper support platform 3, the lower support platform 2 and the cylinder 1 is the sample preparation space.

[0074] In order to reserve a hole for the probe body to be inserted into the prepared sample, in this embodiment, a reserved hole column 5 is installed at the top center of the lower support 2 (the reserved hole column 5 and the lower support 2 can be fixedly connected or threadedly connected. When threadedly connected, the thread connection direction between the reserved hole column 5 and the lower support 2 is opposite to the thread connection direction between the lower support 2 and the cylinder 1). The height and outer diameter of the reserved hole column 5 above the lower support 2 are the same as the height and outer diameter of the part of the probe body that needs to be inside the sample (that is, the shape of the reserved hole formed by the reserved hole column 5 later is the same as the shape of the part of the probe body that needs to be inserted into the sample), so that the reserved hole obtained later can match the probe body. The height of the sample preparation space is greater than the height of the reserved hole column 5 above the lower support 2, and the higher part meets the requirements of the obtained sample completely covering the probe body and the test, for example, it is 15mm higher.

[0075] In order to prepare the sample, in this embodiment, reference is made to... Figure 2 The compaction device 4 consists of a vertical tube 4-1, a pressure plate 4-2, a plug 4-3, and a lower compaction hammer 4-4;

[0076] The inner diameter of the pressure plate 4-2 is smaller than that of the cylinder 1 (the difference between the two is in the range of 1-2 mm), which facilitates the compaction of the material inside the cylinder 1 and helps to expel the gas inside the material. In order to facilitate the preparation of the part of the sample surrounding the reserved hole column 5, a connecting hole 4-2-1 with a thicker upper part and a thinner lower part is opened at the center of the pressure plate 4-2, and the top of the connecting hole 4-2-1 is threaded to the bottom of the vertical tube 4-1.

[0077] The inner diameter of the vertical pipe 4-1, the inner diameter of the bottom end of the connecting hole 4-2-1, and the outer diameter of the reserved hole column 5 are the same. That is, the reserved hole column 5 is inserted into the vertical pipe 4-1 through the connecting hole 4-2-1, so that the pressure plate 4-2 can compact and cover the filler around the reserved hole column 5.

[0078] In order to ensure that all the filler can be compacted after it exceeds the pre-reserved hole column 5, the plug 4-3 in this embodiment is specifically a T-shaped column structure. The outer diameter of its horizontal part is larger than the outer diameter of the pre-reserved hole column 5 but not larger than the inner diameter of the top of the connecting hole 4-2-1, and the thickness of this part is less than the height of the thicker part of the connecting hole 4-2-1; that is, this part can be placed inside the top of the connecting hole 4-2-1. Secondly, the outer diameter of the vertical part of the plug 4-3 is the same as the inner diameter of the bottom of the connecting hole 4-2-1, and the two are the same height; that is, the vertical part of the plug 4-3 can fill the thinner part of the connecting hole 4-2-1.

[0079] In use, first insert the plug 4-3 into the connecting hole 4-2-1 from top to bottom, so that its horizontal part is positioned inside the connecting hole 4-2-1, while its vertical part fills the bottom of the connecting hole 4-2-1. At this time, the bottom of the plug 4-3 is coplanar with the bottom of the pressure plate 4-2, and the top of the plug 4-3 is below the top of the pressure plate 4-2. Then, screw the bottom end of the vertical tube 4-1 into the top of the connecting hole 4-2-1 and thread it to connect with it, and press the top of the plug 4-3 tightly. Then, the filling material above the reserved hole column 5 can be compacted.

[0080] In order to carry out the compaction operation, the impact hammer 4-4 is fitted on the vertical tube 4-1 and positioned above the pressure plate 4-2.

[0081] The working principle of the above equipment:

[0082] During sample preparation, firstly, the top of the lower support 2 is screwed into the cylinder 1 (the pre-drilled column 5 is connected to the lower support 2). Then, the target amount of filler is filled into the cylinder 1. Next, the entire assembly consisting of the vertical tube 4-1 and the pressure plate 4-2 is placed into the cylinder 1, with the pressure plate 4-2 pressing down on the top of the filler. The vertical tube 4-1 is fitted over the pre-drilled column 5. Then, the lower hammer 4-4 is lifted to the target height and allowed to fall freely, thus hammering the pressure plate 4-2. After being hammered, the pressure plate 4-2 compacts the filler below it. The above operation is repeated until the filler in the cylinder 1 reaches the target thickness, forming the current compacted layer. Then, the top of the compacted filler is roughened with a sharp object (to facilitate the transition between this compacted layer and subsequent compacted layers).

[0083] Fill the cylinder 1 with filler again, then insert the vertical tube 4-1 and the pressure plate 4-2 into the cylinder 1. Repeat the above operation to form a new compacted layer, and repeat the above operation again until the total thickness of all compacted layers in the cylinder 1 is close to the height of the pre-drilled column 5 above the upper support 3. Then, unscrew the pressure plate 4-2, insert the plug 4-3 into the connecting hole 4-2-1 from top to bottom, screw the vertical tube 4-1 into the top of the connecting hole 4-2-1, and compact the plug 4-3. Fill the cylinder 1 with the target amount of filler again, cover the top of the filler with the pressure plate 4-2, set the hammer 4-4 on the vertical pipe 4-1, lift it to the target height, and let it fall freely to hammer the pressure plate 4-2. After being hammered, the pressure plate 4-2 compacts the filler below it. Repeat the above compaction operation until the top of the new filler in the cylinder 1 reaches the target height (i.e., it is level with the top of the reserved hole column). Then use a sharp object to scrape the top of the compacted filler to form a new compacted layer.

[0084] Repeat the above operation until the total thickness of the packing inside cylinder 1 reaches the target requirement, then stop the operation, and the top layer of packing does not need to be scraped.

[0085] After processing, screw the bottom of the upper bearing platform 3 into the cylinder 1, and make the bottom of the upper bearing platform 3 fit against the top of the packing.

[0086] At this point, all the fillers inside cylinder 1 constitute the obtained sample.

[0087] In the above process, the thickness h of each compacted layer e It can be set based on experience values, and it meets the requirements. It is an integer. Where l is the height of the reserved hole column 5 above the lower foundation (i.e. the height of the reserved hole required later), and k is the number of compaction layers corresponding to the reserved hole column 5.

[0088] Total number of compacted layers corresponding to the sample H is the distance between the bottom of the upper bearing platform 3 and the top of the lower bearing platform 2 inside the cylinder 1.

[0089] The total mass of the sample required inside the cylinder is m t Then the mass m of the packing material in the αth compacted layer α =m t ·θ α .

[0090] Wherein, the filler coefficient of the αth compacted layer and Then the mass m of the packing material in the αth compacted layer α =m t ·θ α Among them, V 总 =πR 2 H, V 柱 =πr 2 l, R is the radius of the inner wall of cylinder 1, r is the radius of the outer wall of the pre-drilled hole column, V S =V 总 -V 柱 .

[0091] Using the above-mentioned device, the thermal conductivity characteristics of the sample can be effectively tested, and the drawbacks of the existing technology of using drilling to test thermal conductivity characteristics are avoided, thereby improving the test accuracy and the service life of the thermal probe.

[0092] In this embodiment, combined with Figure 2To ensure the compacted layer accurately reaches the target thickness and to reduce the operational difficulties of a single-hammer 4-4 during compaction, the following drawbacks exist: For example, when using a single-hammer 4-4, its height must be such that its top is outside the cylinder 1 when its bottom is in contact with the top of the lower support 2. Otherwise, repeatedly lifting the hammer 4-4 from inside the cylinder 1 is difficult. Furthermore, this design results in a relatively high hammer height, leading to excessive weight and hindering operation. Additionally, the excessive weight makes it difficult to achieve or operate with lower hammering forces. Therefore, the single-hammer 4-4 design has certain drawbacks.

[0093] To overcome the above-mentioned shortcomings, combined with the appendix Figure 2 In some embodiments, the compaction device 4 also includes an upper compaction hammer 4-5 sleeved on the vertical tube 4-1 and positioned above the lower compaction hammer 4-4. The weight of the upper compaction hammer 4-5 is not greater than that of the lower compaction hammer 4-4. In some embodiments, the weight of the upper compaction hammer 4-5 is less than that of the lower compaction hammer 4-4.

[0094] The lower hammer 4-4 and the upper hammer 4-5 are movably connected by the first connector. When they are not connected by the first connector, they can be separated to allow for selection of the striking force as needed. The lower hammer 4-4 and the upper hammer 4-5, when connected by the first connector, form a whole A, and the height of the whole A is greater than the height between the top of the lower support 2 and the top of the cylinder 1.

[0095] That is, when using integral A to impact the packing, the top of integral A can be freely grasped from outside the cylinder to lift integral A, avoiding the defects of single impact hammer 4-4; when a smaller impact force is required, the lower impact hammer 4-4 is disconnected from the upper impact hammer 4-5, and the lower impact hammer 4-4 is kept on top of the pressure plate 4-2 without participating in free fall, while only the upper impact hammer 4-5 is operated to perform free fall. This effectively reduces the impact force compared to integral A, and facilitates precise control of the impact process, so as to make precise thickness adjustment of the compacted layer.

[0096] Combined with appendix Figure 2 In some embodiments, the first connector comprises a guide sleeve 4-6-1, a guide hole 4-6-2, a limiting post 4-6-3, a limiting space 4-6-4, and a limiting notch 4-6-5.

[0097] The guide sleeve 4-6-1 is fitted onto the vertical tube 4-1 and fixedly connected to the bottom of the upper impact hammer 4-5 (or can be manufactured as a single piece). To guide the guide sleeve 4-6-1, a guide hole 4-6-2 is formed at the top of the lower impact hammer 4-4 and coaxially distributed with the vertical tube 4-1. The inner diameter of the guide hole 4-6-2 is the same as the outer diameter of the guide sleeve 4-6-1, and the height of the guide hole 4-6-2 is greater than the height of the guide sleeve 4-6-1; that is, the upper impact hammer... When the hammer 4-5 and the hammer 4-4 are not connected by the first connector, when the hammer 4-5 is lifted, the guide sleeve 4-6-1 moves upward synchronously. When the hammer 4-5 falls freely, the guide sleeve 4-6-1 moves downward synchronously and inserts into the guide hole 4-6-2 without colliding with the bottom of the guide hole 4-6-2. The force transmission between the hammer 4-5 and the hammer 4-4 is achieved through the contact between the top and bottom of the hammer 4-5.

[0098] To facilitate the connection between the upper hammer 4-5 and the lower hammer 4-4, the limiting post 4-6-3 is horizontally positioned and vertically connected to the outer wall of the guide sleeve 4-6-1. Furthermore, the limiting space 4-6-4 is located within the top of the lower hammer 4-4 and communicates with the guide hole 4-6-2. The limiting space 4-6-4 is a cylindrical cavity with an inner diameter not less than the vertical distance between the axis of the guide sleeve 4-6-1 and the outer end of the limiting post 4-6-3. To allow the limiting post 4-6-3 to enter the limiting space 4-6-4, a limiting notch 4-6-5 communicating with the limiting space 4-6-4 is provided at the top of the hammer 4-4. The size of the limiting notch 4-6-5 is such that the limiting post 4-6-3, located directly above it, can pass through the limiting space 4-6-4 from top to bottom. After rotating a certain angle, the top of the limiting post 4-6-3 is blocked by the top of the hammer 4-4, thus... When the limiting post 4-6-3 cannot pass through the limiting space 4-6-4 from bottom to top, the upper hammer 4-5 and the lower hammer 4-4 are effectively connected. However, when the limiting post 4-6-3 is within the projection range of the limiting notch 4-6-5, the limiting post 4-6-3 can detach from the limiting space 4-6-4 from bottom to top, allowing the upper hammer 4-5 and the lower hammer 4-4 to separate. Specifically, when the limiting post 4-6-3 passes through the limiting notch 4-6... -5 enters the limiting space 4-6-4, and when the bottom of the upper hammer 4-5 is in contact with the top of the lower hammer 4-4, rotate the upper hammer 4-5 so that the limiting post 4-6-3 is outside the projection range of the limiting notch 4-6-5 and above the top of the upper hammer 4-5. At this time, the top of the limiting post 4-6-3 is in contact with the top of the limiting space 4-6-4, which facilitates a stable connection between the upper hammer 4-5 and the lower hammer 4-4.

[0099] Based on the above embodiments, in order to make the internal filler distribution of the obtained sample more uniform and dense, in some embodiments, a spring 4-7 is provided inside the bottom end of the guide hole 4-6-2 and sleeved outside the vertical tube 4-1. The bottom end of the spring 4-7 is fixedly connected to the bottom of the guide hole 4-6-2, while the top end of the spring 4-7 is not connected to the upper hammer.

[0100] When the upper hammer 4-5 is not connected to the lower hammer 4-4 and is used alone for hammering (with the limiting post 4-6-3 directly above the limiting notch 4-6-5), the free-falling hammer first contacts the spring 4-7 through the guide sleeve 4-6-1 and compresses the spring 4-7. On the one hand, this reduces the impact force brought by the free fall of the upper hammer 4-5. On the other hand, the spring 4-7 releases its stored energy after compression, allowing the upper hammer 4-5 to reciprocate for a period of time. This allows the lower hammer 4-4 to be subjected to high-frequency and small-force impact and vibration, making the packing under the pressure plate 4-2 more uniform and dense after vibration. This helps to improve the quality of the obtained sample and improve the accuracy of the thermal conductivity test results.

[0101] Secondly, when the upper hammer 4-5 and the lower hammer 4-4 are connected, the spring 4-7 will be compressed, so that there is a certain friction between the limiting post 4-6-3 and the top of the limiting space 4-6-4, which makes it easier to maintain the connection stability of the upper hammer 4-5 and the lower hammer 4-4.

[0102] In some embodiments, the top of the limiting space 4-6-4 may be an upwardly convex curved surface, and the top of the corresponding limiting post 4-6-3 may be a curved surface that can fit with it, thereby facilitating further increase in the stability of the connection between the upper impact hammer 4-5 and the lower impact hammer 4-4.

[0103] In this embodiment, combined with Figure 4 To avoid difficulties in the extraction process and the risk of inward collapse of the pre-reserved hole column 5 due to its being surrounded by filler during sample extraction, a balance hole 5-1 is also provided in the pre-reserved hole column 5. The two ends of the balance hole 5-1 pass through the top of the pre-reserved hole column 5 and the lower support 2, respectively. At the same time, a balance needle 5-2 with the same outer diameter as its inner diameter is provided in the balance hole 5-1. The top of the balance needle 5-2 seals the top of the balance hole 5-1 (to prevent filler from entering the balance hole 5-1 during sample preparation), while the bottom of the balance needle 5-2 passes through the lower support 2 and connects to the second connecting piece 5-3. The second connecting piece 5-3 is movably connected to the lower support 2.

[0104] That is, when the reserved hole column 5 is fixedly connected to the lower support 2, the balance hole 5-1 penetrates the lower support 2, and the bottom end of the balance pin 5-2 is connected to the bottom of the lower support 2 through the second connector 5-3 (in this embodiment, the reserved hole column 5 is fixedly connected to the lower support 2).

[0105] In some embodiments, when the bottom end of the reserved hole column 5 is threadedly connected to the lower support 2, the bottom end of the balance hole 5-1 still penetrates the lower support 2. That is, the lower support 2 is provided with a balance channel that communicates with the balance hole 5-1 in the reserved hole column 5, and the bottom end of the balance needle 5-2 passes through the balance hole 5-1 and the balance channel to connect with the second connector 5-3.

[0106] The second connecting piece 5-3 can be a knob with threads on its outer wall, and the knob is threadedly connected to the bottom of the lower support 2.

[0107] In this embodiment, when preparing the sample using the balance pin 5-2, the balance hole 5-1 and the reserved hole column 5, the second connector 5-3 is initially tightly connected to the lower support 2, so that the top of the balance pin 5-2 seals the top of the balance hole 5-1, and then the sample is prepared as described above.

[0108] After the sample preparation is completed, the lower support 2 is positioned above the upper support 3. Then, the second connecting piece 5-3 is operated to disengage it from the lower support 2, and the balance pin 5-2 is removed to connect the balance hole 5-1 with the space outside the cylinder 1. After that, the lower support 2 is slowly screwed on and rotated repeatedly to unscrew the reserved hole column 5, forming the reserved hole.

[0109] During this process, as the balance needle 5-2 is removed, the external pressure and the pressure around the pre-reserved hole column 5 approach equilibrium, making it easier to remove the pre-reserved hole column 5. Secondly, after the balance needle 5-2 is pulled out, a certain amount of dry air can be blown into the balance hole 5-1, which helps to reduce the friction between the outer wall of the pre-reserved hole column 5 and the surrounding packing, making it easier to remove the pre-reserved hole column 5 and helping to maintain the integrity of the obtained pre-reserved hole.

[0110] In this embodiment, combined with Figure 3 and 4 In order to enable the device to prepare both unsaturated and saturated samples, a columnar lower embedding groove 2-1 is provided on the top of the lower support 2, and lower permeable holes 2-2 are evenly provided on the part of the lower support 2 below the lower embedding groove 2-1 (for water to flow through the lower permeable holes 2-2 into the sample). At this time, the reserved hole column 5 is fixedly installed at the bottom center of the lower embedding groove 2-1. At the same time, a lower permeable layer (not shown in the figure) and a lower sealing layer 2-3 are also provided. The dimensions of the lower permeable layer, the lower sealing layer 2-3 and the lower embedding groove 2-1 are the same. And a through hole 2-4 for the reserved hole column 5 to pass through is provided at the center of both the lower permeable layer and the lower sealing layer 2-3.

[0111] Secondly, an upper embedding groove 3-1 is provided at the bottom of the upper support platform 3, and upper permeable holes 3-2 are evenly provided on the part of the upper support platform 3 above the upper embedding groove 3-1 (for water to flow through the upper permeable holes into the sample); an upper permeable layer (not shown in the figure) and an upper sealing layer 3-3 are also provided, and the upper permeable layer, the upper sealing layer 3-3 and the upper embedding groove 3-1 are all the same size.

[0112] That is, when the above-mentioned device is used, if it is necessary to prepare an unsaturated sample, it can be done by using the lower sealing layer 2-3 and the upper sealing layer 3-3 in combination.

[0113] When it is necessary to prepare a saturated sample, the lower sealing layer 2-3, the lower permeable layer and the upper permeable layer can be used in combination during the venting and water injection process.

[0114] In some embodiments, to avoid the defect of the vertical tube swinging during the compaction operation when the pressure plate 4-2 is smaller than the inner diameter of the cylinder 1 (because the vertical tube is controlled by the operator during the compaction operation), the outer diameter of the pressure plate 4-2 is made the same as the inner diameter of the cylinder 1, and pressure relief grooves are uniformly opened on the vertical wall of the pressure plate 4-2 (its bottom outer edge can be set as an annular inclined surface, and the outer edge of the inclined surface is above its inner source). At this time, the outer diameter of the pressure plate 4-2 is equal to the inner diameter of the cylinder 1, and the pressure relief grooves connect the space below and above the pressure plate 4-2, thereby facilitating the preparation of the sample. The pressure plate 4-2 itself has a certain thickness, so the vertical tube 4-1 can be limited by the contact between the pressure plate 4-2 and the cylinder 1, thereby helping to maintain the stability of the vertical tube during the compaction process.

[0115] In this embodiment, the materials of the lower sealing layer 2-3 and the upper sealing layer 3-3 are consistent with the material of the cylinder 1, so as to avoid the defects that exist when different materials are used. The lower permeable layer and the upper permeable layer can be made of porous permeable stone.

[0116] In order to facilitate the stable connection between the lower sealing layer 2-3 and the lower permeable layer and the lower embedded groove 2-1, and between the upper sealing layer 3-3 and the upper permeable layer 3-2 and the upper embedded groove 3-1, sealing rings are embedded in the lower sealing layer 2-3, the lower permeable layer, the upper sealing layer 3-3 and the upper permeable layer 3-2, and annular sealing grooves are provided on the inner walls of the lower embedded groove 2-1 and the upper embedded groove 3-1, so as to tightly connect the relevant structures through the sealing cavity and the sealing groove;

[0117] In some embodiments, a scale is provided on the outer wall of the cylinder 1 to facilitate precise control of the thickness of each compacted layer.

[0118] Based on the above setup, the resulting device can effectively prepare samples.

[0119] Example 2

[0120] A second aspect of this application also provides a method for testing the thermal conductivity of granular materials using the aforementioned apparatus, the method comprising the following steps:

[0121] First, the sample to be obtained is divided into j compacted layers from bottom to top, where the thickness of each compacted layer is h. e And h e ·k=l,h e ·j=H; where l is the height of the reserved hole column above the upper bearing platform, k is the number of compacted layers corresponding to the reserved hole column, and H is the distance between the top of the lower bearing platform and the bottom of the upper bearing platform when both the lower and upper bearing platforms are connected to the cylinder; k and j are both integers.

[0122] Each compacted layer is numbered from bottom to top; where the αth compacted layer corresponds to the filler mass m. α =m t ·θ α m t θ is the total mass of the obtained sample. α The filler coefficient for the compacted layer α;

[0123] V 总 =πR 2 H, V 柱 =πr 2 l, R is the radius of the inner wall of the cylinder, r is the radius of the outer wall of the pre-drilled hole, V S =V 总 -V 柱 ;in,

[0124] The lower support platform with the pre-drilled column is connected to the cylinder, and the lower sealing layer is embedded in the lower embedding groove; wherein, the second connecting piece is connected to the lower support platform, and the balance pin is located in the balance hole;

[0125] Compaction step: Add the αth compacted layer with a corresponding mass of m into the cylinder. α The packing material is compacted by placing a vertical pipe connected to a pressure plate onto the pre-drilled column, with the pressure plate covering the top of the packing material, until the thickness of the added packing material becomes h. e Remove the compaction device and roughen the top of the packing material; initially, α = 1;

[0126] Let α+1 be the new α. If the new α ≥ k, then install the plug between the vertical pipe and the pressure plate, and repeat the compaction step until the new α > j. Then proceed to the test step. When the new α = j and the compaction step is repeated, after removing the compaction device, do not treat the top of the packing. If the new α < k, then repeat the compaction step.

[0127] Test procedure: Perform thermal conductivity tests on unsaturated samples or on saturated samples; wherein:

[0128] The thermal conductivity test of unsaturated samples includes:

[0129] Install the upper bearing platform with the upper sealing layer on the cylinder, invert the cylinder so that the lower bearing platform is above the upper bearing platform; remove the balance needle, and then screw the lower bearing platform back and forth several times before screwing it off. At this time, all the fillers in the cylinder constitute the obtained sample.

[0130] Insert the probe body into the obtained sample, cover the top of the cylinder with an insulation layer, and then conduct a thermal conductivity test. The insulation layer consists of a plastic wrap, i.e., after the probe body is inserted into the pre-drilled hole in the sample, the plastic wrap is placed over the top of the cylinder and sealed. At this time, the probe body is also under the plastic wrap. Then, a material with the same density as the obtained sample components is covered on the plastic wrap. This material can be prepared during the sample material preparation period (i.e., the total amount of prepared sample material is greater than the amount required for the sample, and the excess sample is compacted to the same degree and then used to cover the plastic wrap).

[0131] The thermal conductivity test of the saturated sample includes:

[0132] Install the upper bearing platform with the upper permeable layer on the cylinder, invert the cylinder so that the lower bearing platform is above the upper bearing platform; remove the balance pin, and then screw the lower bearing platform back and forth several times before screwing it off. Then replace the lower sealing layer with the lower permeable layer, and then connect the lower bearing platform to the cylinder.

[0133] Place the cylinder into the vacuum cylinder and evacuate it to a pressure close to 100 kPa. After 0.5 to 1 hour, open the connecting pipe on the vacuum cylinder and slowly inject degaussed water. This process keeps the vacuum gauge reading basically unchanged until the cylinder and the sample inside are completely submerged. Then stop evacuating and place the sample in a negative pressure environment of 100 kPa for more than 24 hours. The sample is considered saturated. The vacuum saturation process follows the "Standard for Geotechnical Testing Methods GB / T50123-2019".

[0134] After the obtained sample is saturated, the cylinder is stood up and the lower support is placed below the upper support. The upper support is unscrewed, and the upper permeable layer is replaced with the upper sealed layer. Then, the upper support is connected to the cylinder, and the cylinder is inverted. After repeatedly screwing the lower support several times, the lower support is screwed off. At this time, all the fillers in the cylinder constitute the obtained sample.

[0135] Insert the probe body into the obtained sample, then cover the top of the cylinder with an insulation layer, and then conduct a thermal conductivity test. The insulation layer consists of a plastic wrap. After the probe body is inserted into the pre-drilled hole in the sample, the plastic wrap is placed over the top of the cylinder and sealed. At this time, the probe body is also under the plastic wrap. Then, a material with the same composition as the obtained sample is placed on the plastic wrap (as described above).

[0136] The above method can be used to test the thermal conductivity of various granular materials and viscous materials, whether saturated or unsaturated. Especially for non-cohesive soil samples, the vacuum saturation method is incorporated, which can effectively test their thermal conductivity when fully water-saturated.

[0137] Example 3

[0138] This embodiment uses the method provided in Embodiment 2 and the testing device provided in Embodiment 1 to test the thermal conductivity of the sample.

[0139] In this embodiment, the inner diameter of the cylinder 1 is 40 mm, the height of the sample to be formed is 80 mm, the diameter of the pre-drilled column 5 is 1.3 mm, and the height of the pre-drilled hole to be formed is 60 mm. The thermal conductivity and its error of the mixture of calcareous sand cs, quartz sand s, and kaolin c under unsaturated state are verified by using the TEMPOS thermal property analyzer manufactured by Meter and the KS-3 probe in accordance with the method shown in Example 2.

[0140] Given: m i G represents the total mass corresponding to phase i in the granular mass of the sample. si e0 is the specific gravity of phase i in the granular material that makes up the sample, and e0 is the initial porosity of the sample.

[0141] In this embodiment, the phases used to prepare the sample are calcareous sand (cs), silt (s), and kaolin (c), then:

[0142]

[0143] Where, m cs m s m c The masses of calcareous sand (cs), silt (s), and kaolin (c) in the obtained samples are respectively, and G is the mass of the calcareous sand (cs), silt (s), and kaolin (c). scs G ss G sc Let cs be the specific gravity of calcareous sand, ssilt be the specific gravity of kaolinite, and e0 be the initial void ratio of the sample. The specific gravity of calcareous sand is known to be G. scs =2.77, the specific gravity of quartz sand is G ss =2.63, the specific gravity of kaolin is G sc =2.60.

[0144] In this embodiment, nine sets of experiments were conducted (as shown in Table 1), and the amount of each phase in each set of samples is shown in Table 1; among them, sets 1-6 were for thermal conductivity testing of unsaturated samples, and sets 7-9 were for thermal conductivity testing of fully water-saturated samples.

[0145] As shown in Table 1, the initial void ratio e0 of groups 1-6 was 0.682, and the amounts of calcareous sand, quartz sand and kaolin in the samples obtained from groups 1-6 were different. The amount of water was configured according to the needs, and each phase was fully mixed after preparation before sample preparation.

[0146] Groups 7, 8, and 9 were thermal conductivity tests conducted on fully water-saturated samples of pure calcareous sand, pure quartz sand, and pure kaolin, respectively.

[0147] After the sample preparation was completed, the results of the thermal conductivity test are shown in Table 2.

[0148] Table 1. Composition of the corresponding samples and initial porosity ratio in each group of experiments

[0149]

[0150] Table 2. Test Results and Errors

[0151]

[0152] Four measurements of thermal conductivity were performed on groups 1-9 respectively, and the results (thermal conductivity λ) are shown in Table 2. Table 2 shows that, regardless of whether it is a single / multiple group of dispersed granular materials or saturated / unsaturated granular materials, the error obtained when testing the thermal conductivity of the samples using the method provided in Example 2 and the testing apparatus provided in Example 1 is very small. This proves the feasibility of the apparatus and method while ensuring the accuracy of sample preparation.

[0153] In summary, the apparatus and method for testing the thermal conductivity of granular materials provided in this application have the following beneficial effects:

[0154] 1. With the help of the pre-drilled column, the obtained sample can form a pre-drilled hole, which is convenient for inserting the probe body and can effectively avoid the defects of drilling holes in the sample to test the thermal conductivity.

[0155] 2. By utilizing two sealed layers, two permeable layers, and two embedding grooves, saturated and unsaturated samples can be prepared effectively.

[0156] 3. The use of pre-drilled columns ensures high accuracy in the thermal conductivity test results of the obtained samples;

[0157] 4. The integrity and accuracy of the obtained reserved holes can be effectively improved by using balancing holes and balancing pins, which facilitates the improvement of testing accuracy;

[0158] 5. The preparation efficiency of saturated samples can be improved by using balance holes, and the uniformity of the obtained samples is better.

[0159] 6. In order to prepare the test samples, the calculation method of the filler mass of the existing layered compaction method was improved. During the hammering test sample preparation process, a plug was selected to improve the pressure plate so that it could be used to compact layers of different heights, thereby improving the accuracy of the obtained test samples.

[0160] 7. For non-sticky granular samples, the above-mentioned apparatus can be used to prepare saturated samples using the vacuum saturation method.

[0161] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0162] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for testing the thermal conductivity of granular materials, comprising a probe body, characterized in that, It also includes a transparent cylinder, a lower support platform, an upper support platform, and a compaction device; The top of the lower support is located inside the bottom end of the cylinder and is threadedly connected. The bottom end of the upper support is located inside the top end of the cylinder and is threadedly connected. A pre-drilled column is installed at the top center of the lower support platform; The outer diameter and height of the reserved hole column are the same as the outer diameter and height of the probe body; and the height of the reserved hole column is less than the distance between the top of the lower support and the bottom of the upper support. A balance hole is provided in the reserved hole column. The top end of the balance hole passes through the top end of the reserved hole column, and the bottom end of the balance hole passes through the reserved hole column and the lower support in sequence. A balance needle with the same outer diameter is provided in the balance hole. The bottom end of the balance needle is connected to the bottom of the lower support through a second connector, and the top end of the balance needle closes the top end of the balance hole. The compaction device comprises a vertical tube, a pressure plate, a plug, and a lower compaction hammer; The outer diameter of the pressure plate is smaller than the inner diameter of the cylinder; A connecting hole with a coarser upper section and a finer lower section is provided at the center of the pressure plate; The top end of the connecting hole is threaded to the bottom end of the vertical pipe; The plug is specifically a T-shaped columnar structure, the outer diameter of its horizontal part is larger than the outer diameter of the reserved hole column and smaller than the inner diameter of the top of the connecting hole; The outer diameter of the vertical part of the plug, the inner diameter of the bottom end of the connecting hole, and the outer diameter of the reserved hole column are all the same and are not greater than the inner diameter of the vertical pipe. The impact hammer is mounted on the vertical tube.

2. The apparatus for testing the thermal conductivity of granular materials according to claim 1, characterized in that, The compaction device also includes an upper compaction hammer that is sleeved on the vertical tube and located above the lower compaction hammer. The upper and lower hammers are movably connected by a first connector; the height of the upper and lower hammers as a whole is greater than the distance between the top of the lower support and the top of the cylinder.

3. The apparatus for testing the thermal conductivity of granular materials according to claim 2, characterized in that, The first connector comprises a guide sleeve, a limiting post, a guide hole, a limiting space, and a limiting notch; The guide sleeve is fitted onto the vertical tube and is fixedly connected to the bottom of the hammer. A limiting post is vertically connected to the outer wall of the guide sleeve; The guide hole is opened on the top of the hammer and is coaxially distributed with the vertical tube. The inner diameter of the guide hole is the same as the outer diameter of the guide sleeve, and the length of the guide hole is not less than the length of the guide sleeve. The limiting space is opened inside the top of the hammer and communicates with the guide hole. The inner diameter of the limiting space is not less than the vertical distance between the axis of the guide sleeve and the outer end of the limiting post. The limiting notch is located at the top of the hammer and is connected to the limiting space, allowing the limiting post to enter and exit the limiting space in the vertical direction.

4. The apparatus for testing the thermal conductivity of granular materials according to claim 3, characterized in that, A spring is provided inside the bottom of the guide hole and sleeved outside the vertical tube. The bottom of the spring is connected to the bottom of the guide hole, and the height of the guide hole is greater than the height of the guide sleeve. When the spring is compressed to its limit, the bottom of the upper hammer and the top of the lower hammer are in contact.

5. The apparatus for testing the thermal conductivity of granular materials according to claim 4, characterized in that, The lower support platform has a columnar lower embedding groove at its top, and the portion of the lower support platform below the lower embedding groove has evenly spaced lower permeable holes; the reserved hole column is fixedly installed at the bottom center of the lower embedding groove; a lower permeable layer and a lower sealing layer are also provided, and the dimensions of the lower permeable layer, the lower sealing layer, and the lower embedding groove are all the same; and a through hole for the reserved hole column to pass through is provided at the center of both the lower permeable layer and the lower sealing layer; The bottom of the upper support platform is provided with an upper embedding groove, and the portion of the upper support platform above the upper embedding groove is provided with upper permeable holes evenly distributed; an upper permeable layer and an upper sealing layer are also provided, and the upper permeable layer, the upper sealing layer and the upper embedding groove are all the same size.

6. The apparatus for testing the thermal conductivity of granular materials according to claim 5, characterized in that, The cylinder, lower support, upper support, lower sealing layer, and upper sealing layer are all made of a transparent material with low thermal conductivity.

7. The apparatus for testing the thermal conductivity of granular materials according to claim 6, characterized in that, The lower sealed layer, lower permeable layer, upper sealed layer, and upper permeable layer are all the same size; and sealing rings are embedded in the vertical walls of the lower sealed layer, lower permeable layer, upper sealed layer, and upper permeable layer, and annular sealing grooves are provided on the inner walls of the lower and upper embedded grooves.

8. A method for testing the thermal conductivity of granular materials using the apparatus for testing the thermal conductivity of granular materials according to any one of claims 5-7, characterized in that, The method includes the following steps: The sample to be prepared is divided into sections from bottom to top. Each compacted layer has a thickness of [missing information]. ;and , ;in, To reserve the height of the pre-drilled column above the upper bearing platform, To determine the number of compaction layers corresponding to the reserved borehole column, This refers to the distance between the top of the lower bearing platform and the bottom of the upper bearing platform when both the lower and upper bearing platforms are connected to the cylinder. and All are integers; Each compacted layer is numbered from bottom to top; among them, the first... The mass of the compacted layer corresponding to the filler material ; The total mass of the obtained sample, To compact the layer The packing coefficient; , , , Let be the radius of the inner wall of the cylinder. , ;in, ; The lower support platform with the pre-drilled column is connected to the cylinder, and the lower sealing layer is embedded in the lower embedding groove; wherein, the second connecting piece is connected to the lower support platform, and the balance pin is located in the balance hole; Compaction step: Add the first step into the cylinder The mass corresponding to each compacted layer is The packing material is compacted by placing a vertical pipe connected to a pressure plate onto the pre-drilled column, with the pressure plate covering the top of the packing material, until the added packing material reaches a certain thickness. Remove the compaction device and roughen the top of the packing material; initially... ; make As a new If new Then install the plug between the vertical pipe and the pressure plate, and repeat the compaction steps until a new one is installed. Proceed to the testing phase, where the new... When the compaction device is removed, no treatment is done on the top of the packing material; if a new one is used... Then repeat the compaction step; Test procedure: Perform thermal conductivity test on unsaturated samples; The thermal conductivity test of the unsaturated sample includes: Install the upper support with the upper sealing layer on the cylinder, invert the cylinder so that the lower support is above the upper support; remove the balance needle, and then screw the lower support back and forth several times before screwing it off. Insert the probe body into the obtained sample, cover the top of the cylinder with a heat insulation and moisture-retaining layer, and then perform a thermal conductivity test.

9. The method according to claim 8, characterized in that, The testing steps also include: conducting a thermal conductivity test on the saturated sample; the thermal conductivity test of the saturated sample includes: Install the upper bearing platform with the upper permeable layer on the cylinder, invert the cylinder so that the lower bearing platform is above the upper bearing platform; remove the balance pin, and then screw the lower bearing platform back and forth several times before screwing it off. Then replace the lower sealing layer with the lower permeable layer, and then connect the lower bearing platform to the cylinder. Place the cylinder into a vacuum cylinder, evacuate it, and then inject degassing water. After the obtained sample is saturated, the cylinder is erected and the lower support is placed below the upper support. The upper support is unscrewed, and the upper permeable layer is replaced with the upper sealed layer. Then, the upper support is connected to the cylinder, and the cylinder is inverted. After repeatedly screwing the lower support several times, the lower support is screwed off and the probe body is inserted into the obtained sample. A heat insulation and moisture-retaining layer is covered on the top of the cylinder, and then the thermal conductivity characteristics are tested.

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