An in-situ soil permeability test device based on a thin-walled sampling bucket

Abstract

This invention relates to an undisturbed soil permeability testing device based on a thin-walled sampling barrel, comprising: a base, a top cover, a thin-walled sampling barrel, and a fixing screw; the base is fixed below the thin-walled sampling barrel, and the outer wall of the base is provided with, from bottom to top, an annular step, a sealing groove, and a trapezoidal corner, with the radial dimensions decreasing sequentially; the outer wall of the top cover is provided with, from top to bottom, an annular step, a sealing groove, and a trapezoidal corner, with the radial dimensions decreasing sequentially; the thin-walled sampling barrel is a hollow cylindrical body with a rolled edge at the lower end and a sampling cutting edge at the upper end; the lower end of the thin-walled sampling barrel abuts against the annular step of the base, and the upper end abuts against the top cover; a second O-ring is provided in the sealing groove of the base, and a first O-ring is provided in the sealing groove of the top cover. Compared with the prior art, this invention minimizes soil sample disturbance and ensures data authenticity; it has excellent structural sealing performance, high and uniform saturation efficiency; and it has high testing efficiency and strong versatility.

Description

Technical Field

[0001] This invention relates to the field of geotechnical testing technology, and in particular to an undisturbed soil permeability testing device based on a thin-walled sampling bucket. Background Technology

[0002] In the field of geotechnical engineering investigation and design, soil permeability coefficient is a key physical parameter for evaluating the seepage prevention performance of foundations, judging the stability of foundation pits and slopes, and guiding site waterproofing treatment. Its testing accuracy directly affects project safety and economic benefits. Currently, permeability coefficient determination is mainly divided into two methods: in-situ testing and laboratory testing. While in-situ testing can reflect the actual working conditions of the site, it suffers from drawbacks such as high cost, long cycle time, bulky equipment, and significant limitations imposed by geological and environmental conditions, making it difficult to apply in large quantities in conventional engineering projects. Therefore, laboratory permeability testing remains the mainstream technical means for obtaining soil permeability parameters.

[0003] Indoor permeability tests can be divided into undisturbed soil tests and remolded soil tests based on soil sample type. Remolded soil samples are prepared manually and compacted in layers. Sample preparation is convenient and homogeneous, and the ring sampler method is often used for molding. However, the sample structure, density, and stress state differ significantly from natural strata, leading to test results that often deviate considerably from actual engineering conditions and fail to accurately reflect the permeability characteristics of the soil in the field. In contrast, undisturbed soil samples retain the structure, density, and stratification characteristics of natural soil, resulting in more representative test data. Therefore, they are preferred in engineering practice.

[0004] Currently, the ring sampler method is commonly used for indoor undisturbed soil permeability testing. This involves first obtaining a soil sample from the field using a thin-walled sampler, then pushing the sample out of the sampling tube, cutting it, and pressing it into the ring sampler. This process has several insurmountable technical shortcomings: First, the multiple operations of removing, cutting, and pressing the sample disturb the undisturbed soil, damaging its original structure and leading to distorted test results. Second, for soils with high density, high hardness, or strong structure, the ring sampler is difficult to press in, easily resulting in problems such as chipped corners, cracks, and edge damage, leading to a low pass rate. Third, there is an assembly gap between the ring sampler and the testing device, which allows water to easily seep through during the test, resulting in an overestimation of the measured permeability coefficient, poor data repeatability, and seriously affecting the reliability of the test.

[0005] CN201120427016.2 discloses a novel permeameter, including a base with two vent pipes, one inlet pipe, a circular groove, and an annular groove. The vent pipes connect to the wall of the circular groove, and the vent outlet is equipped with an vent valve. The inlet pipe connects to the bottom of the circular groove. A first permeable stone is placed on the circular groove, a ring cutter is placed on the first permeable stone, and a second permeable stone is placed on the ring cutter. A first rubber ring, a sleeve, and a second rubber ring are sequentially placed on the annular groove. A top cover is placed on the second permeable stone and the second rubber ring, and the top cover has an outlet pipe. Both the base and the top cover have three lugs. The base and the top cover are connected and fixed by three bolts through their respective lugs. However, this method requires secondary sample preparation, carries a high risk of disturbance, and only allows venting and water inlet on one side of the bottom.

[0006] In summary, existing indoor undisturbed soil permeability tests have significant shortcomings in the sampling, sample loading, sealing, and assembly processes. There is an urgent need for an undisturbed soil permeability test device and method that can reduce soil sample disturbance, simplify the sample loading process, improve the sealing effect, and enhance the test accuracy. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the existing technology by providing an undisturbed soil permeability testing device based on a thin-walled sampling bucket, which minimizes soil sample disturbance and ensures data authenticity; has excellent structural sealing performance to prevent bypass leakage; features bidirectional water inlet and air outlet, resulting in high and uniform saturation efficiency; is convenient for sample loading and has high testing efficiency; and is applicable to a wide range of soil types with strong versatility.

[0008] The objective of this invention can be achieved through the following technical solutions: This invention provides an undisturbed soil permeability testing device based on a thin-walled sampling bucket, comprising: a base, a top cover, a thin-walled sampling bucket, and a fixing screw; The base is fixed below the thin-walled sampling barrel. The outer wall of the base is provided with an annular step, a sealing groove, and a trapezoidal corner from bottom to top. The radial dimensions of the annular step, the trapezoidal corner, and the sealing groove decrease in sequence. The outer wall of the top cover is provided with a top cover annular step, a top cover sealing groove and a top cover trapezoidal corner from top to bottom, and the radial dimensions of the top cover annular step, the top cover trapezoidal corner and the top cover sealing groove decrease in sequence. The thin-walled sampling barrel is a hollow cylindrical body with a rolled edge at the lower end and a sampling blade at the upper end; the lower end of the thin-walled sampling barrel abuts against the annular step of the base, and the upper end abuts against the top cover; The base sealing groove is provided with a second O-ring rubber ring, and the top cover sealing groove is provided with a first O-ring rubber ring. The base and top cover are evenly fixed circumferentially by the fixing screws to achieve axial clamping of the thin-walled sampling barrel.

[0009] Furthermore, the inner radial width of the second O-ring is smaller than the radial width of the base sealing groove, and the outer radial width of the second O-ring is larger than the wall thickness of the thin-walled sampling barrel; the inner radial width of the first O-ring is smaller than the radial width of the top cover sealing groove, and the outer radial width of the first O-ring is larger than the wall thickness of the thin-walled sampling barrel.

[0010] Furthermore, it also includes a base-side permeable stone, a top-side permeable stone, a base-side filter paper, and a top-side filter paper. The base-side permeable stone is horizontally arranged at the upper end of the trapezoidal corner of the base, and the upper surface of the base-side permeable stone is attached to the lower surface of the base-side filter paper.

[0011] Furthermore, the outer diameter of the trapezoidal corner of the base, the diameter of the permeable stone on the side of the base, the diameter of the filter paper on the side of the base, and the inner diameter of the thin-walled sampling bucket are all the same; the outer diameter of the trapezoidal corner of the top cover, the diameter of the permeable stone on the side of the top cover, the diameter of the filter paper on the side of the top cover, and the inner diameter of the thin-walled sampling bucket are all the same.

[0012] Furthermore, the base is provided with a base water inlet and a base vent, both of which are connected to the permeable stone on the side of the base; the top cover is provided with a top cover water inlet and a top cover vent, both of which are connected to the permeable stone on the side of the top cover.

[0013] Furthermore, the base inlet is connected to a second ball valve switch, and the base vent is connected to a second vent valve; the top cover inlet is connected to a first ball valve switch, and the top cover vent is connected to a first vent valve; the first ball valve switch is sealed to the top cover via a first sealing gasket, and the second ball valve switch is sealed to the base via a second sealing gasket.

[0014] Furthermore, it also includes undisturbed soil samples, which are directly contained in the thin-walled sampling bucket. The lower surface of the undisturbed soil sample contacts the base in sequence through the filter paper on the base side and the permeable stone on the base side, and the upper surface contacts the top cover in sequence through the filter paper on the top cover side and the permeable stone on the top cover side.

[0015] Furthermore, the undisturbed soil sample is obtained by drilling and using a thin-walled sampling bucket to directly cut and shape it in a preset area.

[0016] Furthermore, the base has a ring-shaped step with threaded holes evenly distributed along the circumference at 120°; the top cover has a ring-shaped step with threaded holes evenly distributed along the circumference at 120°; the lower end of the fixing screw has a lower threaded section, and the upper end has an upper threaded section. The fixing screw passes through the threaded holes in the base and the threaded holes in the top cover and is locked by a cap nut.

[0017] Furthermore, the fixing screw has a clamping groove near its lower end.

[0018] The undisturbed soil permeability test method based on thin-walled sampling buckets includes the following steps: Install the undisturbed soil sample from the thin-walled sampling bucket between the base and the top cover; Water is injected into the device by switching on and off the ball valve and the vent valve. Open the exhaust valve to release the gas inside the device until the original soil sample reaches water saturation. After closing the air vent valve, the permeability coefficient of the undisturbed soil sample was calculated by monitoring the inflow and outflow rates.

[0019] Compared with the prior art, the present invention has the following advantages: (1) Minimize soil sample disturbance and ensure data authenticity. This invention directly uses a thin-walled sampling bucket and the undisturbed soil sample inside for testing, eliminating the multiple secondary operation steps of "pushing the soil sample out of the sampling tube, cutting, and then pressing it into the ring cutter" in traditional methods. This avoids damage to the original structure of the soil during the sample preparation process. This is especially important for undisturbed soft soil with low strength and cohesive soil with complex structure, and can significantly improve the reliability and representativeness of undisturbed soil permeability coefficient testing.

[0020] (2) Excellent structural sealing performance, eliminating bypass leakage. The base and top cover of the device are designed with annular steps, sealing grooves and trapezoidal corners, and are equipped with O-rings of specific dimensions (their outer radial width is greater than the wall thickness of the thin-walled sampling barrel). When the fixing screw is tightened, the O-ring is deformed under pressure, which can tightly fill the tiny gap between the thin-walled sampling barrel and the device, forming multiple sealing barriers. This solves the common sidewall "bypass leakage" problem in traditional tests, ensuring that all water flow passes through the soil sample body, thereby improving the accuracy of the test.

[0021] (3) Two-way water inlet and air outlet, resulting in high and uniform saturation efficiency. The device is equipped with a water inlet (ball valve switch) and an air outlet on the base and top cover, respectively. By adopting a two-way water inlet and air outlet method, water can be supplied to the soil sample from both ends simultaneously and air can be discharged, allowing the undisturbed soil sample to quickly and uniformly reach saturation. Compared with the traditional one-way water inlet method, this greatly shortens the test preparation time and ensures the stability of the test boundary conditions.

[0022] (4) Convenient sample loading and high testing efficiency. The device uses three circumferentially evenly arranged fixing screws in conjunction with a base and top cover with trapezoidal corners to fix the thin-walled sampling bucket. The structural design is simple and reasonable. The operator only needs to place the sampling bucket in place and tighten the nut to complete the assembly. There is no need for complicated leveling or centering operations, which reduces the labor intensity and technical threshold of the test personnel and facilitates batch testing.

[0023] (5) It has a wide range of applicable soil types and strong versatility. Because it uses a large-diameter thin-walled sampling bucket for direct testing, it is not only suitable for conventional cohesive soils, but also solves the problem of obtaining qualified samples in indoor tests for soils that are difficult to cut and shape and have strong structure, thus expanding the scope of application of indoor permeability tests. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of an undisturbed soil permeability testing device based on a thin-walled sampling bucket. Figure 2 This is a cross-sectional view of an undisturbed soil permeability test apparatus based on a thin-walled sampling bucket.

[0025] Reference numerals: 1-Base; 2-Fixing screw; 3-Thin-walled sampling bucket; 4-Cap nut; 5-Top cover; 6-Spring washer; 7-Flat washer; 8-Original soil sample; 11-Base threaded hole; 12-Base annular step; 13-Base sealing groove; 14-Base trapezoidal corner; 15-Base water inlet; 16-Base vent; 21-Clamping rod groove; 22-Lower threaded section; 23-Upper threaded section; 31-End flange; 32-Sampling cutting edge; 41-First ball valve switch; 4 2-Second ball valve switch; 51-Top cover threaded hole; 52-Top cover annular step; 53-Top cover sealing groove; 54-Top cover trapezoidal corner; 55-Top cover water inlet; 56-Top cover vent; 61-First sealing gasket; 62-Second sealing gasket; 71-First vent valve; 72-Second vent valve; 81-First O-ring; 82-Second O-ring; 91-Top cover side permeable stone; 92-Base side permeable stone; 101-Top cover side filter paper; 102-Base side filter paper. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Component models, material names, connection structures, control methods, algorithms, and other features not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0027] Example 1 This embodiment provides an undisturbed soil permeability testing device based on a thin-walled sampling bucket, such as... Figure 1 , 2 As shown, it includes: base 1, top cover 5, thin-walled sampling bucket 3 and fixing screw 2; The base 1 is fixed below the thin-walled sampling barrel 3. The outer wall of the base 1 is provided with a base annular step 12, a base sealing groove 13 and a base trapezoidal corner 14 from bottom to top. The radial dimensions of the base annular step 12, the base trapezoidal corner 14 and the base sealing groove 13 decrease in sequence. The outer wall of the top cover 5 is provided with a top cover annular step 52, a top cover sealing groove 53 and a top cover trapezoidal corner 54 from top to bottom, and the radial dimensions of the top cover annular step 52, the top cover trapezoidal corner 54 and the top cover sealing groove 53 decrease in sequence. The thin-walled sampling barrel 3 is a hollow cylindrical body with a rolled edge 31 at the lower end and a sampling blade 32 at the upper end; the lower end of the thin-walled sampling barrel 3 abuts against the annular step 12 of the base and the upper end abuts against the top cover 5. The base sealing groove 13 is provided with a second O-ring rubber ring 82, and the top cover sealing groove 53 is provided with a first O-ring rubber ring 81. The base 1 and the top cover 5 are evenly fixed in the circumferential direction by the fixing screw 2, so as to achieve axial clamping of the thin-walled sampling barrel 3.

[0028] Example 2 This embodiment provides an undisturbed soil permeability testing device based on a thin-walled sampling bucket, such as... Figure 1 , 2 As shown, it includes: a base 1, a top cover 5, a thin-walled sampling bucket 3, and three fixing screws 2; The base 1 is fixed below the thin-walled sampling barrel 3. The outer wall of the base 1 is provided with a base annular step 12, a base sealing groove 13 and a base trapezoidal corner 14 from bottom to top. The radial dimensions of the base annular step 12, the base trapezoidal corner 14 and the base sealing groove 13 decrease in sequence. The outer wall of the top cover 5 is provided with a top cover annular step 52, a top cover sealing groove 53 and a top cover trapezoidal corner 54 from top to bottom, and the radial dimensions of the top cover annular step 52, the top cover trapezoidal corner 54 and the top cover sealing groove 53 decrease in sequence. The thin-walled sampling barrel 3 is a hollow cylindrical body with a rolled edge 31 at the lower end and a sampling blade 32 at the upper end; the lower end of the thin-walled sampling barrel 3 abuts against the annular step 12 of the base and the upper end abuts against the top cover 5. The base sealing groove 13 is provided with a second O-ring rubber ring 82, and the top cover sealing groove 53 is provided with a first O-ring rubber ring 81. The base 1 and the top cover 5 are evenly fixed in the circumferential direction by three fixing screws 2, so as to achieve axial clamping of the thin-walled sampling barrel 3.

[0029] In a specific embodiment, the inner radial width of the second O-ring 82 is less than the radial width of the base sealing groove 13, and the outer radial width of the second O-ring 82 is greater than the wall thickness of the thin-walled sampling barrel 3; the inner radial width of the first O-ring 81 is less than the radial width of the top cover sealing groove 53, and the outer radial width of the first O-ring 81 is greater than the wall thickness of the thin-walled sampling barrel 3.

[0030] In a specific embodiment, it also includes a base-side permeable stone 92, a top-side permeable stone 91, a base-side filter paper 102, and a top-side filter paper 101. The base-side permeable stone 92 is horizontally arranged at the upper end of the trapezoidal corner 14 of the base, and the upper surface of the base-side permeable stone 92 is in contact with the lower surface of the base-side filter paper 102.

[0031] In a specific embodiment, the outer diameter of the trapezoidal corner 14 of the base, the diameter of the permeable stone 92 on the base side, the diameter of the filter paper 102 on the base side, and the inner diameter of the thin-walled sampling barrel 3 are all the same; the outer diameter of the trapezoidal corner 54 of the top cover, the diameter of the permeable stone 91 on the top cover side, the diameter of the filter paper 101 on the top cover side, and the inner diameter of the thin-walled sampling barrel 3 are all the same.

[0032] In a specific embodiment, the base 1 is provided with a base water inlet 15 and a base exhaust outlet 16, both of which are connected to the base side permeable stone 92; the top cover 5 is provided with a top cover water inlet 55 and a top cover exhaust outlet 56, both of which are connected to the top cover side permeable stone 91.

[0033] In a specific embodiment, the base inlet 15 is connected to a second ball valve switch 42, and the base vent 16 is connected to a second vent valve 72; the top cover inlet 55 is connected to a first ball valve switch 41, and the top cover vent 56 is connected to a first vent valve 71; the first ball valve switch 41 is sealed to the top cover 5 through a first sealing gasket 61, and the second ball valve switch 42 is sealed to the base 1 through a second sealing gasket 62.

[0034] In a specific embodiment, it also includes an undisturbed soil sample 8, which is directly contained in the thin-walled sampling bucket 3. The lower surface of the undisturbed soil sample 8 contacts the base 1 in sequence through the base-side filter paper 102 and the base-side permeable stone 92, and the upper surface contacts the top cover 5 in sequence through the top cover-side filter paper 101 and the top cover-side permeable stone 91.

[0035] In a specific implementation, the undisturbed soil sample 8 is obtained by drilling and using a thin-walled sampling bucket 3 to directly cut and shape it in a preset area.

[0036] In a specific embodiment, the base annular step 12 is provided with base threaded holes 11 evenly distributed along the circumference at 120°; the top cover annular step 52 is provided with top cover threaded holes 51 evenly distributed along the circumference at 120°; the lower end of the fixing screw 2 is provided with a lower threaded section 22, and the upper end is provided with an upper threaded section 23. The fixing screw 2 passes through the base threaded holes 11 and the top cover threaded holes 51 and is locked by a cap nut 4.

[0037] In a specific embodiment, the fixing screw 2 has a clamping groove 21 at a position about one-fifth of its length near the lower end.

[0038] Components not described in detail in this embodiment are all existing components that can be purchased through public channels.

[0039] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A undisturbed soil permeability testing device based on a thin-walled sampling bucket, characterized in that, include: Base (1), top cover (5), thin-walled sampling bucket (3) and fixing screw (2); The base (1) is fixed below the thin-walled sampling barrel (3). The outer wall of the base (1) is provided with a base annular step (12), a base sealing groove (13) and a base trapezoidal corner (14) from bottom to top. The radial dimensions of the base annular step (12), the base trapezoidal corner (14) and the base sealing groove (13) decrease in sequence. The outer wall of the top cover (5) is provided with a top cover annular step (52), a top cover sealing groove (53) and a top cover trapezoidal corner (54) from top to bottom. The radial dimensions of the top cover annular step (52), the top cover trapezoidal corner (54) and the top cover sealing groove (53) decrease sequentially. The thin-walled sampling barrel (3) is a hollow cylindrical body with a rolled edge (31) at the lower end and a sampling blade (32) at the upper end; the lower end of the thin-walled sampling barrel (3) abuts against the annular step (12) of the base and the upper end abuts against the top cover (5). The base sealing groove (13) is provided with a second O-ring (82), and the top cover sealing groove (53) is provided with a first O-ring (81). The base (1) and the top cover (5) are fixed circumferentially by the fixing screw (2) to achieve axial clamping of the thin-walled sampling bucket (3).

2. The undisturbed soil permeability testing device based on a thin-walled sampling bucket according to claim 1, characterized in that, The inner radial width of the second O-ring (82) is less than the radial width of the base sealing groove (13), and the outer radial width of the second O-ring (82) is greater than the wall thickness of the thin-walled sampling barrel (3); the inner radial width of the first O-ring (81) is less than the radial width of the top cover sealing groove (53), and the outer radial width of the first O-ring (81) is greater than the wall thickness of the thin-walled sampling barrel (3).

3. The undisturbed soil permeability testing device based on a thin-walled sampling bucket according to claim 1, characterized in that, It also includes a base-side permeable stone (92), a top-side permeable stone (91), a base-side filter paper (102), and a top-side filter paper (101). The base-side permeable stone (92) is horizontally arranged at the upper end of the trapezoidal corner (14) of the base, and the upper surface of the base-side permeable stone (92) is in contact with the lower surface of the base-side filter paper (102).

4. The undisturbed soil permeability testing device based on a thin-walled sampling bucket according to claim 3, characterized in that, The outer diameter of the trapezoidal corner (14) of the base, the diameter of the permeable stone (92) on the side of the base, the diameter of the filter paper (102) on the side of the base, and the inner diameter of the thin-walled sampling bucket (3) are all the same; the outer diameter of the trapezoidal corner (54) of the top cover, the diameter of the permeable stone (91) on the side of the top cover, the diameter of the filter paper (101) on the side of the top cover, and the inner diameter of the thin-walled sampling bucket (3) are all the same.

5. The undisturbed soil permeability testing device based on a thin-walled sampling bucket according to claim 3, characterized in that, The base (1) is provided with a base water inlet (15) and a base exhaust port (16), both of which are connected to the base side permeable stone (92); the top cover (5) is provided with a top cover water inlet (55) and a top cover exhaust port (56), both of which are connected to the top cover side permeable stone (91).

6. The undisturbed soil permeability testing device based on a thin-walled sampling bucket according to claim 5, characterized in that, The base inlet (15) is connected to a second ball valve switch (42), and the base vent (16) is connected to a second vent valve (72); the top cover inlet (55) is connected to a first ball valve switch (41), and the top cover vent (56) is connected to a first vent valve (71); the first ball valve switch (41) is sealed to the top cover (5) through a first sealing gasket (61), and the second ball valve switch (42) is sealed to the base (1) through a second sealing gasket (62).

7. The undisturbed soil permeability testing device based on a thin-walled sampling bucket according to claim 3, characterized in that, It also includes an undisturbed soil sample (8), which is directly contained in the thin-walled sampling bucket (3). The lower surface of the undisturbed soil sample (8) contacts the base (1) in sequence through the base-side filter paper (102) and the base-side permeable stone (92), and the upper surface contacts the top cover (5) in sequence through the top cover-side filter paper (101) and the top cover-side permeable stone (91).

8. The undisturbed soil permeability testing device based on a thin-walled sampling bucket according to claim 7, characterized in that, The original soil sample (8) is formed by drilling and using a thin-walled sampling bucket (3) to directly cut and shape it in a preset area.

9. The undisturbed soil permeability testing device based on a thin-walled sampling bucket according to claim 1, characterized in that, The base ring step (12) is provided with a base threaded hole (11) evenly distributed along the circumference at 120°; the top cover ring step (52) is provided with a top cover threaded hole (51) evenly distributed along the circumference at 120°; the lower end of the fixing screw (2) is provided with a lower threaded section (22), and the upper end is provided with an upper threaded section (23). The fixing screw (2) passes through the base threaded hole (11) and the top cover threaded hole (51) and is locked by a cap nut (4).

10. The undisturbed soil permeability testing device based on a thin-walled sampling bucket according to claim 1, characterized in that, The fixing screw (2) has a clamping groove (21) near its lower end.

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