A device and method for preparing undisturbed soil samples for triaxial compression test

Abstract

A device and method for preparing an original soil sample for a triaxial compression test, comprising a vertical screw, a fixed crossbeam, a movable crossbeam, a vertical bracket, an L-shaped connecting rod, a hoop, an adapter, a ring cutting tube, a sampling tube, a magnetic seat, a round table, and a base. Two vertical brackets are fixedly installed on both sides of the base, the two ends of the fixed crossbeam are respectively fixed on the two vertical brackets, and the two ends of the movable crossbeam are respectively assembled with the two vertical brackets and can move up and down along the vertical brackets. The vertical screw passes through the fixed crossbeam and the movable crossbeam in sequence and is assembled with the fixed crossbeam and the movable crossbeam. An adapter is provided at the bottom of the vertical screw, and the adapter is connected to the ring cutting tube. The movable crossbeam is installed with an L-shaped connecting rod, and the L-shaped connecting rod is connected with a hoop, and the hoop is provided with a sampling tube. A magnetic seat is provided on the base. The invention relates to an original soil sample preparation device and preparation method for triaxial compression test, so as to solve the problems of large disturbance to soil sample, irregular sample size, difficulty in sample formation, inconvenience of film covering, etc. in the cutting process using wire saw or soil cutter in the traditional method.

Description

Technical Field

[0001] The invention belongs to the field of geotechnical testing instrument development, and in particular relates to an original soil sample preparation device and a preparation method for a triaxial compression test. Background Art

[0002] The triaxial compression test is one of the test methods for determining the shear strength parameters of soil in civil engineering and water conservancy engineering. In order to accurately reflect the physical and mechanical properties of the soil, the test should try to use undisturbed soil samples with less disturbance. However, for a long time, the method used to prepare the undisturbed samples for triaxial compression tests is mostly to first take the soil sample out of the sampling tube, then carefully cut it to the specified size with a wire saw or a soil cutter, and finally cover it with a geotextile latex film. However, during the entire sample preparation process, the release of the surrounding pressure when the soil sample is taken out of the sampling tube, the disturbance of the soil sample by cutting and covering the film, will lead to irregular sample size, and sometimes even the situation where the sample cannot be formed. Therefore, how to prepare triaxial undisturbed samples with less disturbance and standard size without releasing the surrounding pressure has always been a problem to be solved. Summary of the invention

[0003] The present invention provides an original soil sample preparation device and preparation method for triaxial compression test, so as to solve the problems of large disturbance to soil sample, irregular sample size, difficulty in sample formation, inconvenience of covering film, etc. in the cutting process using wire saw or soil cutter in the traditional method.

[0004] The technical solution adopted by the present invention is:

[0005] An original soil sample preparation device for triaxial compression test, comprising a vertical screw, a fixed crossbeam, a movable crossbeam, a vertical bracket, an L-shaped connecting rod, a hoop, an adapter, a ring cutting cylinder, a sampling cylinder, a magnetic seat, a round table, and a base;

[0006] Two vertical brackets are fixedly installed on both sides of the base, two ends of the fixed crossbeam are respectively fixed on the two vertical brackets, and two ends of the movable crossbeam are respectively assembled with the two vertical brackets and can move up and down along the vertical brackets.

[0007] The vertical screw rod passes through the fixed cross beam and the movable cross beam in sequence and is assembled with the fixed cross beam and the movable cross beam. A conversion joint is arranged at the bottom of the vertical screw rod, and the conversion joint is connected with the annular cutting cylinder.

[0008] The movable crossbeam is equipped with an L-shaped connecting rod, the L-shaped connecting rod is connected with a hoop, and the hoop is provided with a sampling tube.

[0009] A round table is arranged on the base, and the magnetic seat is adsorbed on the round table and is located just below the sampling tube.

[0010] The top of the vertical screw rod is provided with a cross handle for easy rotation; the vertical screw rod is divided into three sections: the upper longer threaded section is threadedly connected to the middle threaded hole of the fixed crossbeam; the middle smooth section is assembled with the bearing on the movable crossbeam; the lower shorter threaded section is connected to the adapter.

[0011] The fixed crossbeam has holes at both ends, and its two ends are respectively connected to two vertical brackets through second butterfly nuts to form a frame structure that constrains the vertical screw and the movable crossbeam; the longer threaded section on the upper part of the vertical screw is threadedly connected to the middle threaded hole, and the vertical screw rotates through the middle threaded hole to rise or fall.

[0012] The movable crossbeam has circular holes at both ends with a diameter larger than that of the vertical bracket, so that the movable crossbeam can move up and down along the vertical bracket; a bearing is provided in the middle of the movable crossbeam, so that the vertical screw can rotate freely on the movable crossbeam without affecting the up and down movement of the movable crossbeam; the movable crossbeam is provided with two sections of sliding grooves symmetrical about the bearing, which are used to adjust the relative distance between the left and right L-shaped connecting rods.

[0013] The L-shaped connecting rod is fixed on the movable crossbeam through a first butterfly nut and can move up and down with the movable crossbeam; a threaded hole is provided at the lower end of the L-shaped connecting rod, and it is fixed to the two ends of the hoop through bolts.

[0014] The top of the adapter is provided with a threaded hole, which is tightly connected with the shorter threaded section at the lower part of the vertical screw and rotates therewith, and the lower part of the adapter is threadedly connected with the annular cutting cylinder.

[0015] The lower end of the ring cutting cylinder is provided with saw teeth evenly distributed along the circumference to reduce the annular resistance during the cutting process and reduce the disturbance to the soil sample.

[0016] The two ends of the hoop are provided with threaded holes, which can be adjusted by bolts; the hoop tightens the sampling tube and is connected to the L-shaped connecting rod by bolts to ensure that the sampling tube and the L-shaped connecting rod move together.

[0017] The upper end of the sampling tube is connected to the L-shaped connecting rod through a hoop, and the lower end of the sampling tube is provided with a cutting edge to reduce the downward cutting resistance during on-site sampling.

[0018] Two layers of removable circular iron pads are provided at the upper end of the magnetic base. The upper layer is a first pad with a thickness of 2 cm and a diameter the same as the inner diameter of the sampling tube; the lower layer is a second pad with a thickness of 2 cm and a diameter the same as the inner diameter of the ring cutting tube; the two layers of pads are fixed together by the attraction of the magnetic base.

[0019] The vertical support is provided with a scale to facilitate reading the descending distance of the movable crossbeam and to accurately control the cut height of the sample.

[0020] The present invention provides an original soil sample preparation device and preparation method for triaxial compression test, and the technical effects are as follows:

[0021] 1: The size of the sampling tube is slightly larger than the sample size, while the size of the ring cutting tube is the same as the standard sample. During the sample preparation process, the soil sample is cut by the ring cutting tube while being pushed into the ring cutting tube from the top of the sampling tube by the upper pad on the magnetic seat. In this process, the pressure around the soil is not further released, which greatly reduces the disturbance of the soil by cutting with wire saws or soil cutters in traditional sample preparation methods.

[0022] 2: The cut soil sample is pushed out of the toothed thin cylinder through the lower pad on the magnetic seat, and the geotextile latex membrane is put on at the same time as the soil sample comes out, which greatly facilitates the process of membrane covering and avoids the disturbance of soil sample and the rupture of latex membrane caused by artificial membrane covering. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the overall structure of the present invention when cutting samples.

[0024] Figure 2 It is a schematic diagram of the front view structure of the vertical screw of the present invention.

[0025] Figure 3 It is a schematic diagram of the top view structure of the fixed crossbeam of the present invention.

[0026] Figure 4 It is a schematic diagram of the top view structure of the movable crossbeam of the present invention.

[0027] Figure 5 It is a schematic diagram of the front view structure of the L-shaped connecting rod of the present invention.

[0028] Figure 6 It is a schematic diagram of the hoop structure viewed from above of the present invention.

[0029] Figure 7 It is a schematic diagram of the front view structure of the adapter and the ring cutting tube of the present invention.

[0030] Figure 8 It is a schematic diagram of the front view structure of the magnetic base and the round table of the present invention.

[0031] Fig. 9 It is a schematic diagram of the overall structure of the film cover of the present invention. DETAILED DESCRIPTION

[0032] See also Figure 1As shown, an original soil sample preparation device for triaxial compression test includes a vertical screw 1, a fixed beam 2, a movable beam 3, a vertical bracket 12, an L-shaped connecting rod 4, a hoop 7, an adapter 5, a ring cutting tube 6, a sampling tube 8, a magnetic seat 9, a round table 20, and a base 13. The vertical bracket 12 is fixed at both ends of the base 13 to support the entire structure; the fixed beam 2 is fixed on the vertical bracket 12; the movable beam 3 is horizontally limited by the vertical bracket 12, but can move up and down along the vertical bracket 12; the vertical screw 1 connects the fixed beam 2, the movable beam 3 and the adapter 5; the L-shaped connecting rod 4 is used to connect the movable beam 3 and the hoop 7; the magnetic seat 9 is adsorbed on the round table 20 fixed in the center of the base 13.

[0033] See also Figure 2 As shown, a cross handle 19 is provided on the top of the vertical screw rod 1 for easy rotation; the vertical screw rod 1 is divided into three sections:

[0034] The upper longer threaded section is threadedly connected to the middle threaded hole 18 of the fixed beam 2; the middle smooth section is assembled with the bearing 15 on the movable beam 3; and the lower shorter threaded section is connected to the adapter 5.

[0035] See also Figure 3 As shown, holes are opened at both ends of the fixed beam 2, and the two ends are connected to the vertical bracket 12 fixed on the base 13 by the second butterfly nut 17, so as to form a frame structure for constraining the vertical screw 1 and the movable beam 3; a threaded hole 18 is provided in the middle of the fixed beam 2, and the long section of thread on the upper part of the vertical screw 1 is tightly connected with the threaded hole 18 on the fixed beam 2, and can be rotated up and down through the threaded hole 18.

[0036] See also Figure 4 As shown, circular holes with a diameter slightly larger than that of the vertical bracket 12 are opened at both ends of the movable beam 3 to ensure that the movable beam 3 can move up and down along the vertical bracket 12; a bearing 15 is provided in the middle of the movable beam 3 to ensure that the vertical screw 1 can rotate freely on the movable beam 3 without affecting the up and down movement of the movable beam 3; the movable beam 3 is provided with two sections of sliding grooves 14 symmetrical about the bearing 15 to facilitate the adjustment of the relative distance between the left and right L-shaped connecting rods 4.

[0037] The vertical support 12 is provided with a scale to facilitate reading the descending distance of the movable crossbeam 3 and to accurately control the cut height of the sample.

[0038] See also Figure 5 As shown, the upper end of the L-shaped connecting rod 4 is fixed in the slide groove on the movable crossbeam 3 by a first butterfly nut 16, and can move up and down with the movable crossbeam 3. The relative distance between the left and right L-shaped connecting rods can be adjusted by the slide groove 14; the lower end of the L-shaped connecting rod 4 is provided with a threaded hole, which is fixed together with the two ends of the hoop 7 by bolts.

[0039] See also Figure 6 As shown, the two ends of the hoop 7 are provided with threaded holes, and the tightness can be adjusted by bolts. The inner diameter of the hoop 7 is 20cm and 15cm, see Figure 1 As shown, the large hoop serves to connect the sampling tube 8 and the L-shaped connecting rod 4 during the sample cutting process; see Fig. 9 As shown, the small hoop plays a role in connecting the ring cutting cylinder 6 and the L-shaped connecting rod 4 during the film covering process.

[0040] See also Figure 7 As shown, the top of the adapter 5 is provided with a threaded hole, which is tightly connected to the bottom thread of the vertical screw 1 and rotates therewith, and the lower part is connected to the ring cutting cylinder 6 by thread.

[0041] See also Figure 7 As shown, the lower end of the ring cutting cylinder 6 is provided with saw teeth evenly distributed along the circumference to reduce the annular resistance during the cutting process and reduce the disturbance to the soil sample.

[0042] The upper end of the sampling tube 8 is connected to the L-shaped connecting rod 4 through a hoop 7, and the lower end is provided with a cutting edge to reduce the downward cutting resistance when taking rough samples on site.

[0043] See also Figure 8 As shown, the magnetic seat 9 is adsorbed on the round table 20, and the round table 20 is fixed to the base 13 by screws. Two layers of removable circular iron pads are arranged on the upper end of the magnetic seat 9, the upper layer is a first pad 10 with a thickness of 2 cm and a diameter the same as the inner diameter of the sampling tube 7; the lower layer is a second pad 11 with a thickness of 2 cm and a diameter the same as the inner diameter of the ring cutting tube 5, and the two layers of pads are fixed together by the attraction of the magnetic seat 9.

[0044] A device for preparing an original soil sample for a triaxial compression test, the operating method of the device comprising the following steps:

[0045] Sampling steps, such as Figure 1 As shown:

[0046] Step 1: Use a cutter to cut off the disturbed parts of the soil sample at both ends of the sampling tube 8, so that the height of the remaining soil sample in the tube is not less than twice the diameter, and ensure that both ends are flat.

[0047] Step 2: Press the first cushion block 10 and the second cushion block 11 Figure 1 The first pad 10 and the second pad 11 are stacked in the middle in sequence, and the magnetic base 9 is opened to fix the first pad 10 and the second pad 11. The sampling tube 8 containing the original soil is placed horizontally and centered on the first pad 10, and the height of the ring cutting tube 6 is adjusted by rotating the cross handle 19 at the top of the vertical screw 1 so that the serrations at its lower end just contact the upper surface of the soil sample.

[0048] Step 3: Put the large hoop 7 with a diameter of 20 cm on the sampling tube 8, adjust the relative positions of the left and right L-shaped connecting rods 4 through the slide grooves 14 on the movable crossbeam 3, so that the threaded holes at the lower ends coincide with the threaded holes at both ends of the large hoop 7, and then tighten the first butterfly nut 16 at the upper end of the L-shaped connecting rod 4 to fix it, and tighten the bolts at both ends of the large hoop with a wrench to ensure that the L-shaped connecting rod 4 and the sampling tube 8 are firmly connected.

[0049] Step 4: Rotate the cross handle 19 at the top of the vertical screw 1 at a uniform speed to drive the cutting tube 6 to cut the soil sample. During this process, the soil sample is cut in the sampling tube 8, and the surrounding pressure is not released, thereby reducing the disturbance to the soil sample and ensuring the regularity of the soil sample size. Observe the descending distance of the cutting tube 6 through the scale on the vertical bracket 12 to avoid friction between the saw teeth at the lower end of the cutting tube 6 and the pad 10 caused by excessive cutting.

[0050] Step 5: After the cutting is completed, unscrew the butterfly nut 16 on the upper end of the L-shaped connecting rod 4 and loosen the large hoop 7 with a wrench, and remove the L-shaped connecting rod 4 and the large hoop 7. Reversely rotate the cross handle 19 of the vertical screw rod 1 to remove the adapter 5 from the ring cutting cylinder 6, and then screw the adapter 5 off the vertical screw rod 1.

[0051] Encapsulation steps, such as Fig. 9 As shown:

[0052] S1: Insert the small hoop 7 with a diameter of 15 cm into the ring cutting tube 6. Adjust the position of the L-shaped connecting rod 4 in the movable crossbeam slide groove 14 so that the threaded hole at its lower end is aligned with the threaded holes at both ends of the small hoop 7, then tighten the first butterfly nut 16 to fix the position of the L-shaped connecting rod 4, and tighten the bolts at both ends of the small hoop 7 with a wrench to ensure that the L-shaped connecting rod 4, the small hoop 7 and the ring cutting tube 6 are firmly connected.

[0053] S2: Close the magnetic base 9, and pull out the first cushion block 10 whose upper diameter is close to the inner diameter of the sampling tube 8. Use the second cushion block 21 whose diameter is close to the inner diameter of the ring cutting tube 6 and thickness is 2 cm to open one end of the geotextile latex membrane 22, and tighten it with a small hoop 23, and put the remaining part of the geotextile latex membrane 22 into the upper end of the ring cutting tube 6.

[0054] S3: Slowly rotate the cross handle 19 on the vertical screw 1 to separate the ring cutting tube 6 from the soil sample, and the geotextile latex membrane 22 is also slowly put on. In this process, the geotextile latex membrane 22 is smoothly transferred from the ring cutting tube 6 to the soil sample, which not only ensures that the geotextile latex membrane 22 will not break, but also reduces the friction disturbance to the soil sample. Remove the small hoop 23 and the second pad 21, and you can get the standard sample with the geotextile latex membrane.

Claims

1. An undisturbed soil sample preparation device for triaxial compression test, comprising a vertical screw (1), a fixed crossbeam (2), a movable crossbeam (3), a vertical bracket (12), an L-shaped connecting rod (4), a hoop (7), an adapter (5), a ring cutting cylinder (6), a sampling cylinder (8), a magnetic base (9), a round table (20), and a base (13); characterized in that: Two vertical brackets (12) are fixedly mounted on both sides of the base (13); two ends of the fixed crossbeam (2) are respectively fixed on the two vertical brackets (12); two ends of the movable crossbeam (3) are respectively assembled with the two vertical brackets (12) and can move up and down along the vertical brackets (12); The vertical screw rod (1) passes through the fixed cross beam (2) and the movable cross beam (3) in sequence and is assembled with the fixed cross beam (2) and the movable cross beam (3). A conversion joint (5) is provided at the bottom of the vertical screw rod (1), and the conversion joint (5) is connected to the ring cutting cylinder (6); The movable crossbeam (3) is installed with an L-shaped connecting rod (4), the L-shaped connecting rod (4) is connected with a hoop (7), and the hoop (7) is provided with a sampling tube (8); A truncated platform (20) is provided on the base (13), and the magnetic base (9) is adsorbed on the truncated platform (20) and is located below the sampling tube (8); The top of the vertical screw rod (1) is provided with a cross handle (19), and the vertical screw rod (1) is divided into three sections: The upper longer threaded section is threadedly connected to the middle threaded hole (18) of the fixed crossbeam (2); A middle smooth section assembled with a bearing (15) on the movable crossbeam (3); A shorter threaded section at the bottom connected to the adapter (5); The movable crossbeam (3) has circular holes at both ends thereof, the diameter of which is larger than that of the vertical bracket (12), so that the movable crossbeam (3) can move up and down along the vertical bracket (12); A bearing (15) is provided in the middle of the movable crossbeam (3), so that the vertical screw (1) can rotate freely on the movable crossbeam (3) without affecting the up and down movement of the movable crossbeam (3); The movable crossbeam (3) is provided with two sections of slide grooves (14) symmetrical about the bearing (15) for adjusting the relative distance between the left and right L-shaped connecting rods; The vertical support (12) is provided with a scale to facilitate reading the descending distance of the movable crossbeam (3), so as to accurately control the cutting height of the sample.

2. The undisturbed soil sample preparation device for triaxial compression test according to claim 1, characterized in that: The fixed crossbeam (2) has holes at both ends, and its two ends are respectively connected to two vertical brackets (12) via second butterfly nuts (17), forming a frame structure that constrains the vertical screw rod (1) and the movable crossbeam (3); the upper longer threaded section of the vertical screw rod (1) is threadedly connected to the middle threaded hole (18), and the vertical screw rod (1) is rotated through the middle threaded hole (18) to rise or fall.

3. The undisturbed soil sample preparation device for triaxial compression test according to claim 1, characterized in that: The top of the adapter (5) is provided with a threaded hole, which is tightly connected to the shorter threaded section at the bottom of the vertical screw (1) and rotates therewith, and the bottom of the adapter (5) is threadedly connected to the annular cutting cylinder (6).

4. The undisturbed soil sample preparation device for triaxial compression test according to claim 1, characterized in that: The upper end of the sampling tube (8) is connected to the L-shaped connecting rod (4) via a hoop (7), and the lower end of the sampling tube (8) is provided with a cutting edge to reduce the downward cutting resistance during on-site sampling.

5. The undisturbed soil sample preparation device for triaxial compression test according to claim 1, characterized in that: The upper end of the magnetic seat (9) is provided with two layers of removable circular iron pads, the upper layer being a first pad (10); and the lower layer being a second pad (11); the two layers of pads are fixed together by the attraction force of the magnetic seat (9).

6. A method for preparing an undisturbed soil sample using the undisturbed soil sample preparation device according to any one of claims 1 to 5, characterized in that: Including cutting steps: Step 1: Cut off the disturbed parts of the soil sample at both ends of the sampling tube (8) so that the height of the remaining soil sample in the tube is not less than twice the diameter, and ensure that both ends are flat; Step 2: stack the first cushion block (10) and the second cushion block (11) on the magnetic base (9), open the magnetic base (9) to fix the two cushion blocks, place the sampling tube (8) containing the original soil horizontally and centrally on the first cushion block (10), and adjust the height of the ring cutting tube (6) by rotating the cross handle (19) at the top of the vertical screw (1) so that the saw teeth at its lower end just contact the upper surface of the soil sample; Step 3: Put the large hoop on the sampling tube (8), adjust the relative positions of the left and right L-shaped connecting rods (4) through the slide grooves (14) on the movable crossbeam (3), so that the threaded holes at the lower ends thereof coincide with the threaded holes at both ends of the large hoop, then tighten the first butterfly nut (16) at the upper end of the L-shaped connecting rod (4) to fix it, and tighten the bolts at both ends of the large hoop so that the L-shaped connecting rod (4) and the sampling tube (8) are firmly connected; Step 4: The cross handle (19) at the top of the vertical screw (1) is rotated at a constant speed to drive the cutting tube (6) to cut the soil sample. During this process, the soil sample is cut in the sampling tube (8) and the surrounding pressure is not released. The descending distance of the cutting tube (6) is observed through the scale on the vertical support (12) to avoid friction between the saw teeth at the lower end of the cutting tube (6) and the first pad (10) caused by excessive cutting. Step 5: After the cutting is completed, unscrew the first butterfly nut (16) at the upper end of the L-shaped connecting rod (4), and loosen the hoop (7) with a larger diameter, remove the L-shaped connecting rod (4) and the large hoop, rotate the cross handle (19) of the vertical screw rod (1) in the opposite direction, remove the adapter (5) from the ring cutting cylinder (6), and then remove the adapter (5) from the vertical screw rod (1).

7. A method for preparing an undisturbed soil sample using the undisturbed soil sample preparation device according to any one of claims 1 to 5, characterized in that: Including the steps of covering: S1: insert the small hoop into the ring cutting tube (6), adjust the position of the L-shaped connecting rod (4) in the slide groove (14) of the movable crossbeam (3) so that the threaded hole at the lower end thereof is aligned with the threaded holes at both ends of the small hoop, then tighten the first butterfly nut (16) to fix the position of the L-shaped connecting rod (4), and tighten the bolts at both ends of the small hoop so that the L-shaped connecting rod (4), the small hoop and the ring cutting tube (6) are firmly connected; S2: close the magnetic base (9), extract the first cushion block (10) whose diameter at the upper end of the magnetic base (9) is close to the inner diameter of the sampling tube (8), use the second cushion block (11) to open one end of the geotextile latex membrane (22), and tighten it with a small hoop, and put the remaining part of the geotextile latex membrane (22) into the upper end of the ring cutting tube (6); S3: Slowly rotate the cross handle (19) on the vertical screw (1) to separate the ring cutting cylinder (6) from the soil sample, and at the same time, slowly put on the geolatex membrane (22). During this process, the geolatex membrane (22) is smoothly transferred from the ring cutting cylinder (6) to the soil sample. Remove the small hoop and the second pad (11) to obtain a standard sample covered with the geolatex membrane.

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