A lateral confinement compression testing device

Abstract

The utility model discloses a kind of side limit compression test devices, including base, detachably connected with loading cylinder on base, inside of loading cylinder is through and through, the internal space of loading cylinder is divided into upper cylinder and lower cylinder, the inner diameter of upper cylinder is less than the inner diameter of lower cylinder;Mould cylinder is placed coaxially in lower cylinder, weakly cemented filling material sample can be placed in mould cylinder, loading plate is placed in upper cylinder, and pressure head is connected on loading plate;The inner diameter of lower cylinder is consistent with the outer diameter of mould cylinder, the inner diameter of mould cylinder, the inner diameter of upper cylinder, the diameter of sample, the diameter of loading plate are consistent.The device is convenient to assemble and operate, and can meet the test needs of multi-age sample, and can provide reliable test for weakly cemented filling body sample mechanical property research.

Description

Technical Field

[0001] This utility model specifically relates to a lateral compression test device, belonging to the technical field of geotechnical mechanics test equipment. Background Technology

[0002] In the backfilling coal mining technology system, the selection and performance control of backfilling materials directly determine the backfilling effect and mining safety. Among them, weakly cemented backfilling materials have become one of the most widely used material types in the current "three-under" (under buildings, railways, and water bodies) coal backfilling mining due to their advantages such as wide availability of raw materials (large amounts of tailings, aeolian sand, fly ash, etc. can be added, requiring only a small amount of cement as a binder), relatively low cost, and strong construction adaptability. These materials form weakly cemented, low-strength backfill bodies through cementation. After being filled in the goaf, they can effectively control the overburden migration pattern, limit the overburden subsidence, and thus significantly reduce surface subsidence, providing key support for the safe mining of coal in "three-under" areas. However, the mechanical properties of weakly cemented backfill bodies are significantly affected by a variety of factors, among which age (material curing time), moisture content (internal moisture content of the material), and loading method (external stress form) are the most critical influencing factors. From the perspective of practical engineering applications, the weakly cemented backfill in goaf areas, under the weight of the overlying strata and the load from the superstructure, is essentially in a state of laterally confined compression—that is, the backfill is constrained horizontally by the surrounding rock of the goaf or adjacent backfill, and can only undergo compressive deformation in the vertical direction. Therefore, accurately understanding the mechanical properties of weakly cemented backfill under laterally confined compression (such as compressive strength, elastic modulus, stress-strain relationship, etc.) is a prerequisite for scientifically designing backfill schemes, rationally determining backfill parameters, and ensuring the safety and efficiency of backfill mining. It has crucial guiding significance for the engineering application of backfill mining technology. Despite the urgent need for research on the lateral compression mechanical properties of weakly cemented backfill bodies, the current industry still has significant shortcomings in testing equipment and techniques for this field. On the one hand, existing compression testing devices are mostly general-purpose devices designed for high-strength materials such as ordinary concrete and rock. These devices cannot accurately simulate the lateral compression environment of weakly cemented backfill bodies in goaf areas, making it difficult to meet the special requirements of lateral compression testing of weakly cemented backfill bodies. On the other hand, a mature product and technical solution for a fully lateral compression testing device specifically designed for weakly cemented backfill bodies has not yet been developed, resulting in a lack of reliable testing platform support for related research. Summary of the Invention

[0003] Current research on the lateral compression mechanical properties of weakly cemented backfill materials faces challenges such as equipment shortages, mismatched test conditions, and insufficient reliability of test results. These issues have become bottlenecks restricting the further optimization and promotion of backfill mining technology. Against this backdrop, developing a lateral compression testing device and method for weakly cemented backfill materials that can accurately simulate the lateral compression environment, effectively protect the integrity of the sample, eliminate moisture interference, and adapt to testing requirements at different ages has become an urgent need in the industry. This has significant practical and engineering value for promoting research on the mechanical properties of weakly cemented backfill materials, improving the backfill mining technology system, and enhancing the level of underground coal mining.

[0004] The technical solution of this utility model is as follows: A confined compression testing device for weakly cemented filling materials includes a base, a loading cylinder detachably connected to the base, the loading cylinder having a through-hole design, and its internal space divided into an upper cylinder and a lower cylinder, the inner diameter of the upper cylinder being smaller than that of the lower cylinder; a mold cylinder is coaxially placed inside the lower cylinder, and a weakly cemented filling material sample to be tested can be placed inside the mold cylinder; a loading plate is placed inside the upper cylinder, and a pressure head is connected to the loading plate; the inner diameter of the lower cylinder is the same as the outer diameter of the mold cylinder, and the inner diameters of the mold cylinder, the upper cylinder, the sample, and the loading plate are all the same.

[0005] Furthermore, a mesh fabric is laid between the base and the loading cylinder.

[0006] Furthermore, multiple water-permeable holes are provided on the base.

[0007] Furthermore, a loading cover is detachably installed on the top of the loading cylinder, and the pressure head passes vertically through the loading cover.

[0008] Furthermore, a drain hole is provided on the loading cover.

[0009] Furthermore, the pressure head is connected to the loading plate via a ball joint.

[0010] Furthermore, a plurality of through holes are provided radially on the lower sidewall of the loading cylinder.

[0011] Furthermore, the lateral compression test apparatus also includes a mold assembly for preparing the sample, the mold assembly including the mold cylinder, the lower support ring, and the upper support ring.

[0012] Furthermore, the mold cylinder is divided into two semi-circular tube walls, and the mold cylinder formed by splicing the two semi-circular tube walls is a hollow cylinder.

[0013] Furthermore, a lower support ring can be inserted into the bottom of the mold cylinder, and an upper support ring can be fitted onto the top of the mold cylinder.

[0014] Beneficial effects: The lateral compression testing device for weakly cemented backfill materials described in this patent fills the gap in the industry for fully lateral compression testing equipment for weakly cemented backfill bodies. Through the integrated design of "mold-sample", it protects the integrity of the sample throughout the process. The multi-layer moisture drainage structure eliminates the interference of moisture on the test results. Moreover, the device is easy to assemble and operate, and adaptable to the testing needs of samples of various ages. It can provide reliable support for the study of the mechanical properties of weakly cemented backfill samples, thereby helping to optimize backfill mining technology, promoting the green and sustainable development of the coal industry, and possessing both scientific research value and economic and social benefits. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the three-dimensional structure of the lateral compression test device.

[0016] Figure 2 yes Figure 1 Front view.

[0017] Figure 3 yes Figure 2 AA section view in the image.

[0018] Figure 4 yes Figure 3 Enlarged view of area B in the middle.

[0019] Figure 5 This is a three-dimensional schematic diagram of the loading cylinder.

[0020] Figure 6 Yes, yes Figure 5 A sectional view.

[0021] Figure 7 This is a 3D schematic diagram of the mold components.

[0022] Figure 8 yes Figure 7 A sectional view.

[0023] Figure descriptions: 1. Base, 2. Loading cylinder, 3. Loading cover, 4. Pressure head, 5. Loading plate, 6. Ball joint, 7. Mesh cloth, 8. Mold assembly, 9. Sample, 11. Water-permeable hole, 21. Through hole, 22. Upper cylinder, 23. Lower cylinder, 24. Ring platform, 71. Drainage hole, 81. Mold cylinder, 82. Lower support ring, 83. Upper support ring. Detailed Implementation

[0024] The present invention will now be described in a clear and complete detail with reference to the accompanying drawings.

[0025] I. Structure of the Lateral Compression Test Apparatus for Weakly Cemented Filler Materials like Figure 1-6As shown, the lateral compression test device for weakly cemented filling materials mainly consists of a base 1, a loading cylinder 2, a loading cover 3, a pressure head 4, a loading plate 5, a mold cylinder 81, and other components. The components work together to achieve accurate lateral compression testing of weakly cemented filling materials. The specific structure is as follows.

[0026] (I) Core Carrier Loading cylinder 2 and base 1: The loading cylinder 2 is a cylindrical hollow structure made of high-strength metal material such as stainless steel. It is detachably and fixedly connected to the high-strength metal base 1 via bolts to ensure the stability of the loading cylinder during the test. A mesh fabric 7 is laid on top of the base 1. The mesh fabric 7 provides support for the filling sample 9 and has multiple drainage holes 71 to facilitate water drainage. Simultaneously, multiple permeable holes 11 are provided on the base 1 corresponding to the mesh fabric area. These drainage holes and permeable holes communicate with the outside, forming a water drainage channel. Multiple through holes 21 are provided radially on the lower side wall of the loading cylinder 2 for easy sample removal after the test.

[0027] Indenter 4 and loading plate 5: The indenter 4 is made of high-strength metal material, and its lower end is connected to the loading plate 5 via a ball joint 6. This connection method ensures that the loading plate 5 remains in contact with the surface of the filling sample 9 during loading, avoiding local damage to the sample due to uneven force. The loading plate is also made of high-strength metal material, and its diameter is exactly the same as the diameter of the filling sample to be tested (e.g., 100 mm), ensuring that the loading force can be evenly transmitted to the sample surface; in addition, several water-permeable holes are evenly distributed on the loading plate to drain the moisture generated by the filling sample during loading. Loading cover 3 and loading cavity: Loading cover 3 is a circular metal cover that matches the loading cylinder 2. The loading cover 3 is detachably connected to the loading cylinder 2 with bolts. During the test, it is closed at the top of the loading cylinder, which can provide a certain degree of protection for the internal structure of the loading cylinder and at the same time provide a guiding function for the indenter. The indenter 4 passes vertically through the loading cover 3. The cylindrical space formed inside the loading cylinder is the loading cavity. The loading cavity is provided with an annular platform 24, which divides the loading cylinder into an upper cylinder 22 and a lower cylinder 23. The inner diameter of the upper cylinder 22 is smaller than the inner diameter of the lower cylinder 23. A mold cylinder 81 is placed coaxially in the lower cylinder 23. The weak cemented filling material sample 9 to be tested can be placed in the mold cylinder 81. A loading plate 5 is placed in the upper cylinder 22, and the indenter 4 is connected to the loading plate 5. The inner diameter of the lower cylinder 23 is the same as the outer diameter of the mold cylinder 81. The inner diameter of the mold cylinder 81, the inner diameter of the upper cylinder 22, the diameter of the sample 9, and the diameter of the loading plate 5 are all the same. This configuration ensures that the mold cylinder 81 can be placed exactly inside the lower cylinder 23, and the mold cylinder 81 can just accommodate the sample 9. When the loading plate 5 presses down on the sample 9, the mold cylinder and the loading cylinder can play a lateral constraint role on the filling sample, simulating its lateral compression environment in the goaf.

[0028] (II) Sample preparation and fixation components Mold components such as Figure 7-8 As shown: The mold assembly is used to prepare standard filling body specimens 9. The mold assembly includes the mold cylinder 81, the lower support ring 82, and the upper support ring 83. The mold cylinder is divided into two semi-cylinders along the axial direction, and the mold cylinder formed by splicing the two semi-cylinders is a hollow cylinder. The mold cylinder 81 is made of metal tube, such as stainless steel tube, and is cylindrical in shape. Its dimensions are, for example, an inner diameter of 100 mm and a height of 200 mm, which perfectly match the dimensions of the specimen to be tested (diameter 100 mm, height 200 mm). The mold cylinder 81 consists of two symmetrical semi-circular tube walls. The edges of the semi-circular tube walls are provided with connecting structures that facilitate splicing. After splicing, a complete cylindrical mold cylinder can be formed, which facilitates demolding after specimen preparation and re-wrapping during subsequent tests.

[0029] Mold cylinder fixing ends: Both the lower support ring 82 and the upper support ring 83 are mold cylinder fixing ends, both being annular structures made of metal. Their inner diameter matches the outer diameter of the mold cylinder, and they are used to fix the assembled mold cylinder. After the two semi-circular tube walls are spliced ​​to form a complete mold cylinder, it is inserted into the lower support ring, and then the upper support ring is fitted onto the top of the mold cylinder to further tighten the mold tube wall. An annular platform is also provided inside the upper support ring 83 to ensure that the upper support ring will not slip down. The use of mold cylinder fixing ends can prevent the mold cylinder from loosening or deforming during sample preparation and transfer, ensuring the accuracy of the prepared sample dimensions.

[0030] II. Instructions for use of the confined compression test apparatus for weakly cemented filling materials Based on the above-mentioned test apparatus, this patent also provides a method for lateral compression testing of weakly cemented filling materials, the specific steps of which are as follows.

[0031] (I) Sample preparation stage First, the mold cylinder is pre-treated by evenly coating the inner walls of the two semi-circular tubes with oil. The oil reduces the adhesion between the filling slurry and the inner wall of the mold cylinder, making it easier to disassemble the mold later. Then, the two semi-circular tubes are spliced ​​together to form a complete cylindrical mold cylinder, which is then vertically placed into the lower support ring. An upper support ring is fitted on the upper part to achieve stable fixation of the mold. Prepare the weakly cemented filling slurry (components include tailings, aeolian sand, fly ash and a small amount of cement) according to the preset mixing ratio. After the slurry is evenly mixed, slowly pour it into the fixed mold cylinder. During the pouring process, avoid generating too many air bubbles in the slurry. After the slurry fills the mold, let it stand for 1 day to allow the slurry to initially solidify and form a cylindrical filling sample.

[0032] (II) Sample curing stage After standing for 1 day, the mold containing the preliminary molded sample is removed from the fixed end of the mold and placed in the tray of the curing chamber. The two halves of the mold cylinder are then removed. The temperature, humidity, and other parameters of the curing chamber are set according to the experimental requirements, and the sample is cured for different number of days (e.g., 3d, 7d, 28d, etc.) to fully simulate the curing environment of the weakly cemented filling material in actual engineering, ensuring that the mechanical properties of the cured sample are consistent with the actual engineering conditions.

[0033] (III) Lateral compression test stage After the sample has cured for the preset number of days, the sample is wrapped again using the two semi-circular walls of the mold cylinder, and the entire sample is removed from the curing chamber. Then, oil is evenly applied to the outer surface of the mold cylinder. The oil reduces friction between the mold cylinder and the inner wall of the loading cavity, facilitating the insertion of the mold cylinder into the loading cavity. Next, the mold cylinder, containing the sample, is placed centered on the base covered with mesh cloth, and then the loading cylinder is inserted from top to bottom, allowing the mold cylinder to enter the loading cavity. After the loading cylinder is in place, it is tightened again with bolts to ensure the overall stability of the device. Then, the loading plate and pressure head are installed sequentially at the top of the loading cylinder, ensuring the lower end face of the loading plate is in contact with the top face of the sample inside the mold cylinder. The loading cover is then placed on top, aligning the tip of the pressure head with the force application end of the servo press. Start the servo press and apply a vertically downward load to the indenter according to the preset loading rate (set according to the characteristics of the weak cemented filling material, such as 0.5-2kN / s). The indenter drives the loading plate through the ball joint to evenly transfer the load to the sample surface and perform a lateral compression test on the sample. During the test, the water generated by the sample seeps out through the water-permeable holes on the loading plate and / or is filtered by the mesh cloth on the base and discharged outside the device through the water-permeable holes on the base. During the test, the load, displacement and other data were recorded in real time through the data acquisition system of the servo press until the specimen reached the ultimate compressive strength and failed, at which point the loading was stopped. Based on the collected data, the stress-strain relationship, compressive strength, elastic modulus and other mechanical parameters of the weak cemented filling under lateral compression were analyzed to complete this lateral compression test.

[0034] After the test, remove the loading cover and pressure head, and remove the loading cylinder from the base. Due to the expansion of the sample under pressure, the mold cylinder and the sample may be difficult to remove from the loading cylinder. At this time, a top rod can be inserted into the through hole 21 on the side wall of the loading cylinder to hit the mold cylinder and help the mold cylinder and the sample to be removed from the loading cylinder.

[0035] This patent addresses the lack of key equipment and testing methods in current research on the lateral compression mechanical properties of weakly cemented backfill bodies. It provides a reliable testing device and scientific application method for accurately understanding the mechanical properties of weakly cemented backfill bodies under lateral compression, thereby providing strong support for the optimization and application of backfill mining technology. Specifically, this patent addresses at least three issues: First, weakly cemented fillings have low strength (especially early-age specimens), making them highly susceptible to damage during specimen preparation, transfer, curing, and loading due to manual operation and mold assembly / disassembly. This leads to distorted test data that fails to accurately reflect the mechanical properties. This patent utilizes a mold cylinder to effectively protect the specimens. Second, weakly cemented fillings contain a certain amount of moisture, which gradually overflows under pressure during lateral compression loading. If the testing device lacks an effective moisture drainage structure, the overflowing moisture accumulates on the specimen surface or within the test space, interfering with load transfer and stress distribution, directly affecting the accuracy of the test results. This patent incorporates multiple permeable and oozing holes to facilitate moisture drainage. Third, existing testing devices struggle to meet the testing needs of weakly cemented fillings at different ages, hindering convenient and efficient completion of lateral compression tests on specimens with varying curing days. This restricts in-depth research into the influence of age on the mechanical properties of weakly cemented fillings. This patent is adaptable to testing specimens at different ages. Thanks to the solution to the above problems and its advantages, the fully confined compression test device for weakly cemented backfill described in this patent can accurately test the mechanical properties of weakly cemented backfill materials, which are widely used in "three-under" coal backfilling mining. It can test the mechanical properties of samples at different ages, moisture contents, and loading methods, providing accurate data support for backfilling mining.

Claims

1. A lateral compression testing device, characterized in that, The device includes a base, on which a loading cylinder is detachably connected. The loading cylinder is internally continuous, divided into an upper cylinder and a lower cylinder, with the inner diameter of the upper cylinder being smaller than that of the lower cylinder. A mold cylinder is coaxially placed inside the lower cylinder, and a weakly cemented filling material sample to be tested can be placed inside the mold cylinder. A loading plate is placed inside the upper cylinder, and a pressure head is connected to the loading plate. The inner diameter of the lower cylinder is the same as the outer diameter of the mold cylinder, and the inner diameters of the mold cylinder, the upper cylinder, the sample, and the loading plate are all the same.

2. The confined compression testing apparatus according to claim 1, characterized in that, A mesh fabric is also laid between the base and the loading cylinder.

3. The confined compression testing device according to claim 1, characterized in that, The base is also provided with multiple water-permeable holes.

4. The confined compression testing device according to claim 1, characterized in that, A loading cover is detachably installed on the top of the loading cylinder, and the pressure head passes vertically through the loading cover.

5. The lateral compression testing apparatus according to claim 4, characterized in that, The loading cover is provided with a drainage hole.

6. The confined compression testing apparatus according to claim 1, characterized in that, The pressure head and the loading plate are connected by a ball joint.

7. The confined compression testing apparatus according to claim 1, characterized in that, Multiple through holes are provided radially on the lower side wall of the loading cylinder.

8. The confined compression testing apparatus according to claim 1, characterized in that, The lateral compression test apparatus further includes a mold assembly for preparing the sample, the mold assembly including the mold cylinder, the lower support ring, and the upper support ring.

9. A lateral compression testing apparatus according to claim 8, characterized in that, The mold cylinder is divided into two semi-circular tube walls, and the mold cylinder formed by splicing the two semi-circular tube walls is a hollow cylinder.

10. A lateral compression testing apparatus according to claim 8, characterized in that, The bottom of the mold cylinder can be fitted with a lower support ring, and the upper support ring can be fitted onto the top of the mold cylinder.

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