In-situ ring shearing device and method

Abstract

The invention belongs to the technical field of engineering geological exploration, and discloses an in-situ ring shearing device and method.The device comprises a force application assembly and a ring shearing assembly arranged in a drill hole and coaxial with the drill hole; the force application assembly is connected with the ring shear assembly and used for driving the ring shear assembly to rotate in the circumferential direction. The ring shearing assembly comprises a rotating shaft, a shearing cylinder and a ring shearing unit; one end of the rotating shaft is connected with the force application assembly, and the other end of the rotating shaft extends into the shearing cylinder and is fixedly connected with the shearing cylinder; the ring shearing unit is arranged on the outer side of the bottom plate of the shearing cylinder, is inserted into the soil body at the bottom of the drill hole and is used for annularly shearing the soil body; the ring shearing unit comprises an outer circular ring, an inner circular ring and a plurality of shearing needles which are equal in height; the diameter of the outer ring is the same as the outer diameter of the shearing cylinder; the diameter of the inner ring is equal to the outer diameter of the rotating shaft; the multiple shearing needles are arranged in an annular area formed by the outer circular ring and the inner circular ring. Due to the adoption of the ring shear mode, the overall shear parameters of the soil body can be obtained, and the shear parameters are more accurate.

Description

Technical Field

[0001] The invention belongs to the technical field of engineering geological exploration and relates to an in-situ soil ring shear device and method. Background Art

[0002] During the construction process, soil shear strength is an important parameter in the engineering geological survey stage, which affects the selection and design of the later foundation treatment plan. At present, there are two main methods for determining soil shear strength parameters: indoor shear test and in-situ shear test. Indoor shear tests often use direct shear test and triaxial test. Direct shear test has the advantages of simple equipment, convenient soil sample preparation and test operation, but it cannot strictly control the drainage conditions, resulting in inaccurate data results when measuring collapsible soil; triaxial test can better simulate the stress condition of soil in the stratum, and can accurately measure the change of pore water pressure during shear process, but the sample preparation is complicated and the operation is difficult, and the common pseudo triaxial test is also difficult to imitate the stratum conditions well.

[0003] Compared with indoor shear tests, in-situ shear tests have the advantages of strong representativeness, low disturbance, and the ability to truly and accurately reflect the actual situation of the project, which can greatly meet the needs of engineering design and disaster management. At present, the in-situ shear tests for determining the shear strength parameters of soil mainly include two methods: soil column shear and in-hole pull-out. The soil column shear method requires digging a test pit and leaving a soil column for shear testing, which is time-consuming and labor-intensive, and can only be used to test the surface soil, and cannot perform shear strength tests on collapsible soils at different depths; the in-hole pull-out method is to place the shear device close to the inner wall of the borehole, use the corresponding pressure device to apply normal stress to the hole wall, and then pull the entire shear device to obtain the interface parameters. Although the in-hole pull-out method makes up for the deficiency of the soil column shear method that it is difficult to obtain the shear strength parameters of deep soil, the parameters obtained are the interface shear strength parameters between the shear device and the soil, which have a certain gap with the actual shear strength parameters of the soil; and the in-hole pull-out method generates huge pressure on the base outside the hole, which is not conducive to the stability of the device, and the shear rate is also difficult to guarantee.

[0004] During the above-mentioned indoor and in-situ shear tests, the shear surface of the soil has changed, making it difficult to obtain multiple shear parameters of the current soil layer, resulting in the inability to accurately reflect the shear strength of the soil. Summary of the invention

[0005] The object of the present invention is to provide an in-situ ring shear device and method to solve the technical problem that the in-situ shear test in the prior art can only obtain the interface shear strength parameters between the shear device and the soil, and because the current soil layer will be destroyed after shearing, it is difficult to obtain multiple shear parameters of the current soil layer, resulting in the inability to accurately reflect the shear strength of the soil.

[0006] The first aspect of the present invention provides an in-situ ring shear device, comprising a force-applying component and a ring shearing component arranged in a borehole and coaxial with the borehole; the force-applying component is connected to the ring shearing component to drive the ring shearing component to rotate circumferentially; the ring shearing component comprises a rotating shaft, a shearing cylinder and a ring shearing unit; one end of the rotating shaft is connected to the force-applying component, and the other end extends into the shearing cylinder and is fixedly connected to the shearing cylinder; the ring shearing unit is arranged on the outer side of the bottom plate of the shearing cylinder and inserted into the soil at the bottom of the borehole, for performing annular shearing on the soil; the ring shearing unit comprises an outer ring, an inner ring and a plurality of shearing pins of equal height; the diameter of the outer ring is the same as the outer diameter of the shearing cylinder; the diameter of the inner ring is the same as the outer diameter of the rotating shaft; the plurality of shearing pins are arranged in the annular area formed by the outer ring and the inner ring.

[0007] Preferably, the ring shear assembly further includes a load applying unit; the load applying unit is arranged in the shear cylinder and is used to apply a vertical load to the ring shear unit.

[0008] Preferably, the load applying unit comprises a force applying member; the force applying member comprises a plurality of arc-shaped weights, and the plurality of arc-shaped weights are connected end to end to form a circular ring.

[0009] Preferably, there are multiple groups of force-applying members, and the multiple groups of force-applying members are stacked along the axial direction of the shearing cylinder.

[0010] Preferably, it further comprises a data acquisition unit; the data acquisition unit is connected to the force-applying component and is used to obtain the torque of the force-applying component and the rotation angle of the rotating shaft connected to the force-applying component.

[0011] Preferably, it also includes a data processing unit connected to the data acquisition unit.

[0012] Preferably, the ring shear assembly also includes a plurality of fixing bolts; a plurality of parallel sliding rails are provided on the outer wall of the rotating shaft; each of the sliding rails extends axially along the rotating shaft; a groove matching the sliding rail is provided in the shearing cylinder, and the groove is connected to the corresponding sliding rail; the plurality of fixing bolts respectively pass through the connected sliding rails and the grooves.

[0013] Preferably, it also includes a supporting assembly and a telescopic assembly; the supporting assembly is arranged on the ground where the borehole is located, and the center of gravity of the supporting assembly is located on the axis of the borehole; one end of the telescopic assembly is connected to the force-applying assembly, and the other end is connected to the supporting assembly; the telescopic end of the telescopic assembly moves along the axial direction of the borehole.

[0014] A second aspect of the present invention provides an in-situ ring cutting method, comprising:

[0015] Step 1: Assemble the above-mentioned in-situ ring shear device.

[0016] Step 2: Lower the ring shear unit in the assembled in-situ ring shear device into the soil at the bottom of the borehole.

[0017] Step 3: Use a force-applying component to apply torque to the ring shear unit for shearing, and stop shearing when the torque remains unchanged.

[0018] Preferably, after step 3, the method further includes:

[0019] Step 4: determining the shear stress of the soil according to the torque of the force-applying assembly when shearing is completed, the radii of the inner and outer rings of the ring shear unit, and the radius of the inner ring.

[0020] Step 5: determining the shear strain of the soil according to the rotation angle of the rotation axis, the radii of the inner and outer rings of the ring shear unit, the radius of the inner ring, and the height of the ring shear unit.

[0021] Compared with the prior art, the in-situ ring shearing device and method of the present invention have the following beneficial effects:

[0022] The in-situ ring shearing device and method of the present invention can obtain the shearing parameters of the whole soil body more accurately because the ring shearing method is adopted. Furthermore, the present invention adopts a rotating method to perform ring shearing, and the impact on the surrounding soil body after the shearing is completed is small. Therefore, the soil body of the same soil layer in the borehole can be sheared multiple times from the outside to the inside or from the inside to the outside, and more comprehensive and accurate shearing parameters can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic structural diagram of an in-situ ring shear device according to an embodiment of the present invention.

[0024] Figure 2 It is a top view of the assembled rotating shaft and shearing cylinder in the ring shearing assembly in the in-situ ring shearing device according to an embodiment of the present invention.

[0025] Figure 3 It is an exploded view of the rotating shaft and the shearing cylinder in the ring shear assembly in the in-situ ring shear device according to an embodiment of the present invention.

[0026] Figure 4 It is a schematic diagram of the bottom structure of the shearing cylinder in the ring shearing assembly in the in-situ ring shearing device according to an embodiment of the present invention.

[0027] Figure 5 It is a schematic diagram of the structure of the weights in the in-situ ring shear device according to an embodiment of the present invention.

[0028] In the figure: 1 is a data acquisition unit; 2 is a telescopic component; 3 is a support rod; 4 is a force-applying component; 5 is a connecting rod; 6 is a rotating shaft; 6-1 is a slide rail; 6-2 is a first threaded hole; 7 is a shear cylinder; 7-1 is an outer wall; 7-2 is a groove; 7-3 is a second threaded hole; 7-4 is a bottom plate; 7-5 is an inner ring; 7-6 is an outer ring; 8 is a shear pin; 9 is soil; 10 is a weight; 11 is a fixing bolt. DETAILED DESCRIPTION

[0029] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0030] A first aspect of an embodiment of the present invention provides an in-situ ring shearing device, such as Figures 1 to 5 As shown, it includes a force-applying component 4 and a ring shear component arranged in the borehole and coaxial with the borehole.

[0031] The force-applying assembly 4 is connected to the ring shear assembly, and the force-applying assembly 4 is used to drive the ring shear assembly to rotate circumferentially in the borehole; the ring shear assembly includes a rotating shaft 6, a shearing cylinder 7 and a ring shear unit; one end of the rotating shaft 6 is connected to the force-applying assembly 4 through a connecting rod 5, and the other end extends into the shearing cylinder 7 and is fixedly connected to the shearing cylinder 7; the ring shear unit is arranged outside the bottom plate 7-4 of the shearing cylinder 7, and is inserted into the soil 9 at the bottom of the borehole, and is used to perform annular shearing on the soil 9. The force-applying assembly 4 of the embodiment of the present invention can be specifically a motor for applying torque.

[0032] The present invention uses a force-applying component 4 to drive the ring shear unit to rotate circumferentially in the borehole via the rotating shaft 6 in the ring shear component, thereby performing annular shearing on the soil 9. Due to the ring shearing method, the shearing part is a ring-shaped whole piece of soil, not just a single interface of the soil 9. Therefore, the shearing parameters determined after shearing in the present invention are closer to the real shearing parameters of the soil 9. Furthermore, the present invention adopts a rotating method to perform ring shearing. After the shearing is completed, the impact on the surrounding soil 9 is small and there is no need to make the outer wall 7-1 of the shearing cylinder in the ring shear component close to the inner wall of the borehole like the in-hole pulling method. Therefore, the soil 9 of the same soil layer in the borehole can be sheared multiple times from the outside to the inside or from the inside to the outside using ring shear components of different outer diameters to obtain multiple sets of shearing parameters of the same soil layer 9. The final shearing parameters of the layer of soil 9 are determined by averaging or selecting the median for the multiple sets of shearing parameters, and the obtained shearing parameters are more comprehensive and accurate.

[0033] It is necessary to apply vertical load to the ring shear assembly when performing ring shearing. Therefore, the ring shear assembly of the embodiment of the present invention also includes a load applying unit; wherein the load applying unit is arranged in the shearing cylinder 7 and is arranged around the rotating shaft 6 arranged in the shearing cylinder 7, for applying vertical load to the ring shear unit.

[0034] The present invention arranges the load applying unit in the shearing cylinder 7, which has a simple structure, occupies a small space, has a stable structure, and can apply a more stable vertical load to the ring shearing unit.

[0035] The load applying unit includes a force applying member; the force applying member may be a weight 10, such as a ring-shaped weight or a Figure 5 The multiple arc-shaped weights shown are connected end to end to form a ring. Since using multiple arc-shaped weights is easy to operate, the embodiment of the present invention preferably uses multiple arc-shaped weights as force applying members.

[0036] The number of force-applying members in the embodiment of the present invention is multiple groups; the multiple groups of force-applying members are stacked along the axial direction of the shear cylinder 7. For example, the number of force-applying members in the embodiment of the present invention is 6 groups, each group of force-applying members includes 4 arc-shaped weights, and the vertical load applied by each group of force-applying members is 100 kPa, so the 6 groups of force-applying members can apply a maximum vertical load of 600 kPa.

[0037] To achieve ring shear, Figure 4 As shown, the ring shear unit of the embodiment of the present invention comprises an outer ring 7-6, an inner ring 7-5 and a plurality of shearing needles 8 of equal height; wherein the diameter of the outer ring 7-6 is the same as the outer diameter of the shearing cylinder 7; the diameter of the inner ring 7-5 is the same as the outer diameter of the rotating shaft 6; the plurality of shearing needles 8 are arranged in the annular area formed by the outer ring 7-6 and the inner ring 7-5, and each shearing needle 8 is a conical structure with a conical tip at the bottom. Exemplarily, the number of shearing needles 8 in the embodiment of the present invention is 60.

[0038] The embodiment of the present invention uses an outer ring 7-6 and an inner ring 7-5 to define a shearing area, and uses a plurality of shearing needles 8 for shearing, thereby achieving shearing of the entire soil body in the annular area and obtaining shearing parameters that are closer to the actual soil body 9.

[0039] In order to intuitively and quickly obtain the intermediate parameters required for the subsequent determination of shearing parameters during the ring cutting process, the in-situ ring cutting device of the embodiment of the present invention further includes a data acquisition unit 1; wherein the data acquisition unit 1 is connected to the force-applying component 4, and is used to obtain the torque of the force-applying component 4 and the rotation angle of the rotating shaft 6 connected to the force-applying component. The above-mentioned data acquisition unit 1 may specifically include a torque sensor and an angle sensor, wherein the torque sensor and the angle sensor are both connected to the controller of the motor constituting the force-applying component 4, so as to obtain the torque of the force-applying component 4 and the rotation angle value of the rotating shaft 6 connected to the force-applying component.

[0040] After obtaining the above intermediate parameters, the shear parameters can be calculated manually or by computer according to the above intermediate parameters. In order to realize computer calculation, the embodiment of the present invention also includes a data processing unit (not shown in the figure) that is connected to the data acquisition unit 1 in communication; the data processing unit is used to determine the shear stress of the soil body 9 according to the torque, the radius of the outer ring 7-6 and the radius of the inner ring 7-5. Exemplarily, the shear stress of the soil body 9 is determined according to the following formula (1):

[0041] (1)

[0042] In the formula, is the shear stress of soil 9, in kPa; is the torque, unit is KN·m; is the radius of the inner ring, is the radius of the outer ring, in meters.

[0043] The data processing unit of the embodiment of the present invention is also used to determine the shear strain of the soil 9 according to the rotation angle, the radius of the outer ring 7-6, the radius of the inner ring 7-5 and the height of the ring shear unit. Exemplarily, the shear strain of the soil 9 is determined according to the following formula (2):

[0044] (2)

[0045] In the formula, is the shear strain of soil 9, in degrees; is the rotation angle, in degrees; is the radius of the inner ring, is the radius of the outer ring, in m; is the height of the ring shear unit, which is equal to the height of the outer ring 7-6 and is expressed in m.

[0046] In order to ensure the stability of the fixed connection between the rotating shaft 6 and the shearing cylinder 7 in the ring shear assembly, the ring shear assembly of the embodiment of the present invention further includes a plurality of fixing bolts 11 .

[0047] The outer wall of the rotating shaft 6 of the embodiment of the present invention is provided with a plurality of parallel slide rails 6-1; each slide rail 6-1 extends along the axial direction of the rotating shaft 6; a groove 7-2 matching the slide rail 6-1 is provided in the shear cylinder 7, and the groove 7-2 is connected to the corresponding slide rail 6-1; a plurality of fixing bolts 11 pass through the connected slide rails 6-1 and the groove 7-2 respectively. For example, Figure 2 and Figure 3As shown, there are four parallel T-shaped slide rails 6-1 on the outer wall of the rotating shaft 6, and the T-shaped slide rails 6-1 are at the same height as the shearing cylinder 7; correspondingly, four grooves 7-2 matching the slide rails 6-1 are arranged in the shearing cylinder 7; each T-shaped slide rail 6-1 is provided with four first threaded holes 6-2 evenly opened from top to bottom, and a second threaded hole 7-3 is opened at the corresponding position of each groove 7-2, and the fixing bolt 11 passes through the second threaded hole 7-3 and the first threaded hole 6-2 in sequence to fix the rotating shaft 6 and the shearing cylinder 7 to prevent the two from detaching.

[0048] In order to achieve stable support for the in-situ ring shear device of the present invention and enable it to be applied to ring shearing of soil bodies 9 at different depths, the embodiment of the present invention further includes a support assembly and a telescopic assembly 2; the support assembly is arranged on the ground where the borehole is located, and the center of gravity of the support assembly is located on the axis of the borehole; one end of the telescopic assembly 2 is connected to the force-applying assembly 4, and the other end is connected to the support assembly; the telescopic end of the telescopic assembly 2 moves along the axial direction of the borehole. Exemplarily, the support assembly of the embodiment of the present invention is composed of three support rods 3 arranged around the telescopic assembly 2.

[0049] A second aspect of the present invention provides an in-situ ring cutting method, comprising:

[0050] Step 1: assemble the above-mentioned in-situ ring shear device, specifically:

[0051] Step 1.1, after connecting the support assembly and the telescopic assembly 2, erect the support assembly above the drilled hole.

[0052] Step 1.2, assemble the ring shear assembly, specifically insert the T-shaped slide rail 6-1 of the rotating shaft 6 into the T-shaped groove 7-2 inside the shear cylinder 7, and pass the fixing bolt 11 through the second threaded hole 7-3 and the first threaded hole 6-2 in sequence. The ring shear unit is a structure integrally connected to the outer side of the bottom plate of the shear cylinder.

[0053] Step 1.3, load a force-applying member corresponding to the required positive pressure in the shear cylinder 7 and connect the upper part of the rotating shaft 6 with the lower part of the force-applying assembly 4, and connect the upper part of the force-applying assembly 4 with the telescopic assembly 2.

[0054] Step 2: lower the ring shear unit in the above-mentioned in-situ ring shear device into the soil 9 at the bottom of the borehole, and ensure that the shear needle 8 in the ring shear unit is completely inserted into the soil 9.

[0055] Step 3, keep the device stable, then use the force component 4 to apply torque to the ring shear unit for shearing, stop shearing when the torque is stable, and calculate the shear parameters of the original soil 9 based on the obtained torque of the force component 4 and the rotation angle of the rotating shaft 6.

[0056] The shear parameters shear stress and shear strain are determined by using the above formula (1) and formula (2) respectively, and will not be described here.

[0057] The in-situ ring shear device of the present invention has a circular shear surface, so the shear stress distribution is relatively uniform, and the shear surface does not change during the shearing process, which can more comprehensively reflect the shear resistance of the soil 9; the present invention does not need to fit the outer wall of the device to the wall of the drilled hole, is less affected by the hole diameter, and reduces the cost of the device; the present invention uses weights 10 for vertical loading, and does not require the support assembly to provide a reaction force, which greatly reduces the burden of the support assembly, saves the time for device construction, reduces the site use requirements and the layout process of the support assembly, and can be used under more working conditions; the shear surface does not change during the shearing process of the present invention, and the data is more accurate; the present invention integrates data collection, processing, and output, and can quickly obtain accurate shear parameters of the soil 9.

[0058] The above are only several embodiments of the present invention and are not intended to limit the present invention in any form. Although the present invention is disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with the profession, without departing from the scope of the technical solution of the present invention, using the above disclosed technical content to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. An in-situ ring shearing device, characterized in that: It includes a force-applying component and a ring shear component disposed in a borehole and coaxial with the borehole; The force-applying assembly is connected to the ring shear assembly and is used to drive the ring shear assembly to rotate circumferentially; The ring shear assembly comprises a rotating shaft, a shearing cylinder and a ring shear unit; One end of the rotating shaft is connected to the force-applying assembly, and the other end extends into the shearing cylinder and is fixedly connected to the shearing cylinder; The ring shear unit is arranged outside the bottom plate of the shear cylinder and inserted into the soil at the bottom of the borehole to perform ring shearing on the soil; The ring shear unit includes an outer ring, an inner ring and a plurality of shearing needles of equal height; the diameter of the outer ring is the same as the outer diameter of the shearing cylinder; the diameter of the inner ring is the same as the outer diameter of the rotating shaft; the plurality of shearing needles are arranged in the annular area formed by the outer ring and the inner ring.

2. The in-situ ring shearing device according to claim 1, characterized in that: The ring shear assembly also includes a load applying unit; The load applying unit is arranged in the shearing cylinder and is used for applying a vertical load to the ring shearing unit.

3. The in-situ ring shearing device according to claim 2, characterized in that: The load applying unit includes a force applying member; The force applying member comprises a plurality of arc-shaped weights, and the plurality of arc-shaped weights are connected end to end to form a circular ring.

4. The in-situ ring shearing device according to claim 3, characterized in that: The number of the force applying members is multiple groups; A plurality of groups of force applying members are stacked along the axial direction of the shearing cylinder.

5. The in-situ ring shearing device according to claim 1, characterized in that: Also includes a data acquisition unit; The data acquisition unit is connected to the force-applying component and is used to obtain the torque of the force-applying component and the rotation angle of the rotating shaft connected to the force-applying component.

6. The in-situ ring shearing device according to claim 5, characterized in that: It also includes a data processing unit connected to the data acquisition unit.

7. The in-situ ring shearing device according to claim 1, characterized in that: The ring shear assembly also includes a plurality of fixing bolts; The outer wall of the rotating shaft is provided with a plurality of parallel slide rails; each of the slide rails extends along the axial direction of the rotating shaft; A groove matching the slide rail is provided in the shearing cylinder, and the groove is connected to the corresponding slide rail; The plurality of fixing bolts pass through the connected slide rails and the grooves respectively.

8. The in-situ ring shearing device according to any one of claims 1 to 7, characterized in that: Also includes a support assembly and a telescopic assembly; The support assembly is arranged on the ground where the borehole is located, and the center of gravity of the support assembly is located on the axis of the borehole; One end of the telescopic component is connected to the force-applying component, and the other end is connected to the supporting component; the telescopic end of the telescopic component moves along the axial direction of the borehole.

9. An in-situ ring shearing method, characterized in that: include: Step 1, assembling the in-situ ring shearing device according to any one of claims 1 to 8; Step 2: lowering the ring shear unit in the assembled in-situ ring shear device into the soil at the bottom of the borehole; Step 3: Use a force-applying component to apply torque to the ring shear unit for shearing, and stop shearing when the torque remains unchanged.

10. The in-situ ring shearing method according to claim 9, characterized in that: After step 3, the method further includes: Step 4, determining the shear stress of the soil according to the torque of the force-applying assembly when shearing is completed, the radii of the inner and outer rings of the ring shear unit, and the radius of the inner ring; Step 5: determining the shear strain of the soil according to the rotation angle of the rotation axis, the radii of the inner and outer rings of the ring shear unit, the radius of the inner ring, and the height of the ring shear unit.

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