Shearing assembly for exploratory well in-situ shearing instrument and test method

Abstract

The invention discloses a shearing assembly for an exploratory well in-situ shearing instrument and a test method, and belongs to the technical field of engineering investigation. The shearing assembly comprises a plurality of shearing blades, a power base, an operating rod, an air bag, a combined supporting rod and a cylinder. The plurality of shearing blades are averagely divided into two groups which are respectively arranged above and below the cylinder; each group of shearing sheets are spliced to form a closed structure after being unfolded; the upper operating rod and the lower operating rod drive the power bases to move oppositely or oppositely through the bidirectional driving mechanism, and in the moving process, the combined supporting rods open the shearing blades in each group to form the combined blades. The air bag is fixedly arranged on the outer wall of the cylinder and used for bringing normal pressure to the inner wall of the exploratory well after being inflated. The problem that the shearing blade of the shearing instrument cannot be directly placed in the exploratory well under the condition that the diameter of the shearing blade is larger than that of the exploratory well is solved, and the in-situ measurement precision is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of engineering survey, and in particular relates to a shearing component and a test method for an in-situ shearing instrument for well exploration. Background Art

[0002] The shear strength index of soil is an important parameter for studying the mechanical properties of soil and conducting engineering design. There are two commonly used methods for measuring the shear strength of soil: indoor test and field test.

[0003] The shear strength of soil is generally obtained by drilling and sampling, and then taking the soil samples indoors for direct shear, quick shear, and consolidation quick shear tests. This test method has problems such as large disturbance of soil samples and long time consumption, which affects the accuracy. The direct shear test on the exploration well site is to perform shearing in a natural state, avoid disturbance, save time, and provide strength indicators of the relevant soil. Its biggest advantage is that it is easy to operate and highly repeatable. Compared with the existing on-site direct shear test, it does not require large-scale excavation of earthwork and has higher efficiency. The traditional indoor direct shear test will inevitably cause disturbance from on-site sampling to laboratory soil sample preparation, which may change the original soil structure. In addition, when doing the direct shear test, as the shear box moves up and down, the shear surface of the soil sample decreases, resulting in the increase of the normal stress of the soil sample, which is not a fixed value, and the shear strength index obtained is not accurate enough. Some data show that the results of the borehole shear test are very close to the consolidated undrained shear parameters.

[0004] However, the existing measuring instruments apply normal stress and shear stress on the same component, and the existing shear probe has a small tooth spacing, which may cause inaccurate test measurements during the test because it cannot completely cut into the soil. If you want to overcome the problem of a smaller shear surface, you can increase the tooth spacing of the shear probe, that is, increase the diameter of the shear blade. However, if the diameter of the shear blade is larger than the diameter of the exploration well, the shear probe cannot be directly placed in the exploration well, and effective test operations cannot be performed. Summary of the invention

[0005] The present invention overcomes the deficiencies of the prior art and proposes a shearing assembly and a test method for an in-situ shearing instrument for an exploration well; it solves the problem of how to place a shearing blade having a diameter greater than the diameter of the exploration well into the exploration well and conduct the test smoothly, so as to improve the accuracy of in-situ measurement.

[0006] The present invention is achieved through the following technical solutions: A shearing assembly for an in-situ shearing instrument for an exploration well, comprising a plurality of shearing blades, a power seat, an operating rod, an air bag, a combined strut and a cylinder; the shearing blade is divided into a left and a right part, and the left and right parts form a hinged structure through a connecting shaft; a plurality of shearing blades are evenly divided into two groups and are respectively arranged above and below the cylinder; each group of shearing blades are sequentially spliced ​​together to form a combined blade with a closed structure after being unfolded; a power seat is arranged above and below the cylinder; the power seat is connected to a corresponding group of shearing blades and the cylinder through a combined strut; an operating rod is arranged above and below the cylinder; the power seat is connected to one end of an operating rod on the same side, and the cylinder is connected to the upper and lower operating rods through a two-way driving mechanism; the upper and lower operating rods drive the upper and lower power seats to move toward the middle or to the upper and lower ends through the two-way driving mechanism; during the movement, the combined struts open the shearing blades of each group to form a combined blade; the air bag is fixedly arranged on the outer wall of the cylinder, and the air bag brings normal pressure to the inner wall of the exploration well after being inflated; The combined support rod comprises a first support rod and a second support rod; the first support rod is connected to the hinge of the left and right parts of the shear blade, and one end of the first support rod away from the shear blade is hinged to the cylinder; the power seat is evenly provided with second support rods along the circumference; the number of the second support rods is equal to that of the first support rods; one end of the second support rod is hinged to the power seat, and the other end of the second support rod is hinged to the middle part of the first support rod; The bidirectional driving mechanism comprises a rack, a gear and a stepper motor; the gear and the stepper motor are arranged in the cylinder; the gear is rotatably connected to the cylinder, the gear is connected to the output shaft of the stepper motor, and a rack is arranged on the inner wall of one side of the operating rod away from the end of the power seat; the racks of the upper and lower operating rods are symmetrically arranged on both sides of the gear and are respectively meshed with the gears; the two racks and the two operating rods are driven by the rotation of the gear to move up and down to control the bidirectional extension and retraction of the two power seats, thereby controlling the expansion angle of the shear blade; Positioning holes are symmetrically arranged on two opposite side walls of the operating rod; telescopic clamps are arranged at both ends of the bottom of the rack, and the telescopic clamps are connected to the bottom of the rack through telescopic springs; when the two operating rods move relatively to each other under the drive of the stepper motor, the telescopic clamp at the bottom of the upper operating rod is clamped into the positioning clamp hole on the lower operating rod, and the telescopic clamp at the top of the lower operating rod is clamped into the positioning clamp hole on the upper operating rod, so that the upper and lower shear blades are positioned.

[0007] Furthermore, the left and right parts of the shear blade are connected by a hinge to form the hinged structure.

[0008] Furthermore, the left and right parts of the shear blades on both sides of the hinge are respectively connected to the two ends of the same spring through a connecting line, and a protective cover is arranged on the outside of the spring.

[0009] Furthermore, a fixing rod is fixedly connected inside the cylinder; the airbag is sleeved outside the cylinder, and the airbag is fixedly connected to both ends of the fixing rod.

[0010] Furthermore, each set of shear blades are sequentially spliced ​​together to form a complete combined blade with a circular ring structure after being unfolded.

[0011] A test method for a shear assembly of an in-situ shear instrument for well exploration comprises the following steps: The first step is to build a test well in the stratum to be tested, and then expand the hole at different corresponding depths in the test well to dig out two grooves with larger diameters. The diameter of the expanded groove is the same as the diameter of the combined blade formed by each set of shear blades. At the same time, the net distance between the two grooves is consistent with the height of the airbag; The second step is to set up the well exploration shearing instrument and put the shearing assembly into the well exploration so that the air bag is located between the two grooves; The third step is to start the bidirectional driving mechanism, so that the upper and lower operating rods are moved closer to the middle. The upper and lower operating rods are connected to the power seat, and the upper and lower power seats move toward the middle, and the upper and lower shear blades are unfolded and fixed through the support of the combined support rod; The fourth step is to deliver gas into the air bag to expand it and bring normal pressure to the inner wall of the exploration well; The fifth step is to apply normal pressure while pulling the shear assembly upward at a constant speed, so that the soil between the upper and lower sets of shear blades slides relative to each other, resulting in shear failure; Step 6: Repeat the above steps to obtain test data under different normal pressures.

[0012] The beneficial effects of the present invention compared with the prior art are as follows: The present invention divides an entire annular blade into multiple arc-shaped blades of the same size, and places a hinge in the middle of the arc blade to form an angle, thereby converting the originally horizontal blade structure into a vertical blade structure. When the blade is rotated to a certain angle, it can be placed in the exploration well, and then rotated back to its original position to form a complete annular blade, thereby solving the problem that the shear blade of the shearing instrument cannot be directly placed in the exploration well when the diameter of the shear blade is larger than the diameter of the exploration well.

[0013] The shear test method provided by the present invention is simple to operate, has little disturbance to the soil at the test point, does not require large excavation of earthwork compared to the existing on-site direct shear test, and has higher efficiency. Compared with the indoor direct shear test, the indoor direct shear test will reduce the shear surface, while this shear test method overcomes the disadvantage of the reduced shear surface, and the size of the shear area will not change during the upward pulling process, thereby improving the accuracy of in-situ measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the overall three-dimensional structure of the shearing assembly of the present invention; Figure 2 is a front view of the shear assembly of the present invention; Figure 3 It is a schematic diagram of the structure of the shear blade below the cylinder in the present invention; Figure 4 is a structural schematic diagram of the bidirectional driving mechanism of the present invention; Figure 5 It is a schematic diagram of the three-dimensional structure of the lower shear blade.

[0015] In the figure: 1 is a shear blade, 2 is a power seat, 3 is an operating rod, 4 is an airbag, 5 is a spring, 6 is a gear, 7 is a stepping motor, 8 is a positioning card hole, 9 is a telescopic card head, 10 is a cylinder, 11 is a rack, 12 is a first support rod, 13 is a second support rod, and 14 is a fixed rod. DETAILED DESCRIPTION

[0016] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention is further described in detail in conjunction with the embodiments and the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. The technical solutions of the present invention are described in detail below in conjunction with the embodiments and the accompanying drawings, but the scope of protection is not limited thereto.

[0017] See also Figures 1 to 5 This embodiment proposes a shearing assembly for an in-situ shearing instrument for well exploration and a soil shear strength test method; the shearing assembly includes a plurality of shearing blades 1, two power seats 2, an operating rod 3, an airbag 4 and a cylinder 10; in this embodiment, the shearing blades 1 have a total of 12 pieces, 6 of which are located above the cylinder 10, and the remaining 6 are located below the cylinder 10.

[0018] The shear blade 1 is divided into two parts, left and right parts, which form a hinged structure through a connecting shaft; a hinge is provided at the connecting shaft of each shear blade 1, and the shear blade 1 can be expanded or closed along the central axis through the setting of the hinge; wherein, the upper 6 shear blades 1 can be spliced ​​in sequence after being expanded to form a complete circular ring structure combined blade; similarly, the lower 6 shear blades 1 can be spliced ​​in sequence after being expanded to form a complete circular ring structure combined blade; this structure of the combined blade is conducive to forming a better shearing effect when shearing soil.

[0019] The hinge of the shear blade 1 is connected to a first support rod 12, and one end of the first support rod 12 away from the shear blade 1 is hinged to the cylinder 10; a circular power seat 2 is respectively arranged above and below the cylinder 10, and the power seat 2 is evenly distributed with 6 second support rods 13 along the circumferential direction; one end of the second support rod 13 is hinged to the power seat 2, and the other end of the second support rod 13 is hinged to the middle part of the first support rod 12.

[0020] A gear 6 and a stepper motor 7 are arranged inside the cylinder 10; the gear 6 is rotatably connected to the cylinder 10, and the gear 6 is connected to the output shaft of the stepper motor 7, and the gear 6 is driven to rotate by the stepper motor 7; an operating rod 3 is welded in the middle of the power seat 2, and a rack 11 is arranged on the inner wall of one side of the end of the operating rod 3 away from the power seat 2; the racks 11 of the upper and lower operating rods 3 are symmetrically arranged on both sides of the gear 6, and are respectively meshed with the gear 6; the two racks 11 and the two operating rods 3 are driven up and down by the rotation of the gear 6 to control the bidirectional extension and retraction of the two power seats 2, thereby controlling the deployment angle of the shear blade 1.

[0021] Positioning holes 8 are symmetrically arranged on two opposite side walls of the operating rod 3; telescopic clamps 9 are arranged at both ends of the bottom of the rack 11, and the telescopic clamps 9 are connected to the bottom of the rack 11 through telescopic springs; when the two operating rods 3 move relatively under the drive of the stepper motor 7, the telescopic clamp 9 at the bottom of the upper operating rod 3 will be clamped into the positioning clamp hole 8 on the lower operating rod 3, and the telescopic clamp 9 at the top of the lower operating rod 3 will be clamped into the positioning clamp hole 8 on the upper operating rod 3, so that the upper and lower groups of shear blades 1 are positioned. Specifically, the stepper motor 7 drives the gear 6 to rotate, so that the operating rod 3 moves toward the middle. When it moves to a certain distance, the telescopic clamp 9 in the operating rod 3 is squeezed on both sides and shrinks. When it moves a part, the telescopic clamp 9 encounters the positioning clamp hole 8 and extends into the positioning clamp hole 8. In this way, the telescopic range can be fixed and the two parts can be made into a whole, which is convenient for subsequent lifting operations.

[0022] In order to better unfold the shear blade 1 to form a circular ring structure, the left and right parts of the shear blade 1 on both sides of the hinge are connected to the two ends of the same spring 5 through a connecting line, and a protective cover is provided on the outside of the spring 5; the spring 5 forms an angle in the middle of the shear blade 1, wherein the left and right parts of the upper shear blade 1 are connected by a connecting line, so that they restrain each other during the unfolding process and expand the angle. The lower shear blade 1 can automatically flatten in the upward process due to gravity.

[0023] A fixing rod 14 is passed through and fixedly connected to the cylinder 10 ; the airbag 4 is sleeved on the outside of the cylinder 10 , and the airbag 4 is fixedly connected to both ends of the fixing rod 14 .

[0024] This embodiment proposes a soil shear strength test method based on the shear assembly, which specifically includes the following steps: The first step is to build a test well in the stratum to be tested to reduce the disturbance to the soil at the test point, and then expand the hole at different corresponding depths in the test well to dig out two grooves with larger diameters. The diameter of the expanded groove is the same as the diameter of the circular ring structure combined blade formed by the combination of the six shear blades 1, and the net distance between the two grooves is consistent with the height of the airbag 4; The second step is to set up the well exploration shearing instrument and put the shearing assembly into the well exploration so that the airbag 4 is located between the two grooves; The third step is to start the stepper motor 7. The stepper motor 7 rotates to drive the gear 6 to rotate. The gear 6 rotates between the rack 11 so that the upper and lower operating rods 3 are brought closer to the middle. The upper and lower operating rods 3 are connected to the power seat 2. The upper and lower power seats 2 move toward the middle. The shear blade 1 slides in the arc direction through the support of the first support rod 12 and the second support rod 13. Due to the obstruction of the soil in the middle part, the hinge in the middle of the shear blade 1 is unfolded. At this time, the shear blade 1 is unfolded and combined into two complete circular rings. When the rack 11 rotates to a certain position, the telescopic clamp 9 at the end of the rack 11 coincides with the positioning clamp hole 8, and the telescopic clamp 9 is clamped in the positioning clamp hole 8 to make it a whole. The fourth step is to deliver gas into the airbag 4 to expand it and bring normal pressure to the inner wall of the exploration well; according to the test design, the normal pressure applied is 100kPa, 200kPa, 300kPa, and 400kPa.

[0025] The fifth step is to apply normal pressure while pulling the shear assembly upward at a uniform speed, so that the soil between the upper and lower sets of shear blades 1 will slide relative to each other and shear failure will occur; the rate of pulling the shear assembly upward is 1.2 mm / min, so that the soil will be sheared within 3-5 minutes.

[0026] Step 6: Repeat the above steps by constant speed loading to obtain test data under different normal pressures; Step 7: retract the shear blade 1, and then lower the airbag 4 and the shear blade 1 into the middle of the grooves of different depths, repeat the above steps, and record the data; Step 8: Data collation and analysis, finally get the cohesion and internal friction angle of different depths at the same location. Based on the test data under different normal pressures, the Mohr Coulomb strength envelope is fitted and drawn to get the cohesion and internal friction angle of the test formation.

[0027] Design principle: Under the total value P of the normal pressure continuously applied by the airbag 4, the shear blades 1 are pulled upward at a constant speed, so that the soil between the two sets of shear blades 1 slides relative to each other, and the pulling force T causes shear failure of the soil.

[0028] The outer perimeter R of the shear blade 1 is taken as the length of the shearing surface, and the height H of the airbag 4 is taken as the width of the shearing surface. The area A acting on the soil is: A=πR×H.

[0029] The calculation formula is as follows: In the formula, is the normal pressure; is the peak intensity of the shear stress versus shear displacement curve; is the shear stress; c is the cohesion of the soil; Φ is the internal friction angle of the soil.

[0030] By measuring multiple groups (usually four groups) of shear stress under different normal pressures, the data is linearly regressed using the least squares method, and the regression equation is obtained to obtain the shear strength parameters of the soil at the test depth. For specific test methods, please refer to the national standard "Standard for Geotechnical Test Methods" (GB∕T 50123-2019).

[0031] The above content is a further detailed description of the present invention in combination with a specific preferred embodiment. It cannot be determined that the specific embodiments of the present invention are limited to this. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the present invention, which should be regarded as belonging to the present invention and the scope of patent protection determined by the submitted claims.

Claims

1. A shearing assembly for an in-situ shearing instrument for well exploration, characterized in that: The invention comprises a plurality of shear blades (1), a power seat (2), an operating rod (3), an air bag (4), a combined support rod and a cylinder (10); the shear blades (1) are divided into two parts, the left and right parts are connected by a connecting shaft to form a hinge structure; the plurality of shear blades (1) are evenly divided into two groups, which are respectively arranged above and below the cylinder (10); each group of shear blades (1) are sequentially spliced ​​together after being unfolded to form a combined blade with a closed structure; a power seat (2) is provided above and below the cylinder (10); the power seat (2) and the corresponding group of shear blades (1) and the cylinder (10) are connected by a combined support rod. The cylinder (10) is connected to the upper and lower parts of the wellbore by a two-way driving mechanism; an operating rod (3) is provided above and below the cylinder (10); the power seat (2) is connected to one end of an operating rod (3) on the same side, and the cylinder (10) is connected to the upper and lower operating rods (3) through a two-way driving mechanism; the upper and lower operating rods (3) drive the upper and lower power seats (2) to move toward the middle or to the upper and lower ends through the two-way driving mechanism; during the movement, the combined support rods open each group of shear blades (1) to form a combined blade; the airbag (4) is fixedly arranged on the outer wall of the cylinder (10), and the airbag (4) brings normal pressure to the inner wall of the exploration well after being inflated; The combined support rod comprises a first support rod (12) and a second support rod (13); the first support rod (12) is connected to the hinged joint of the left and right parts of the shear blade (1), and one end of the first support rod (12) away from the shear blade (1) is hinged to the cylinder (10); the power seat (2) is evenly provided with second support rods (13) along the circumference; the number of the second support rods (13) and the first support rod (12) is equal; one end of the second support rod (13) is hinged to the power seat (2), and the other end of the second support rod (13) is hinged to the middle part of the first support rod (12); The bidirectional driving mechanism comprises a rack (11), a gear (6) and a stepping motor (7); the gear (6) and the stepping motor (7) are arranged in the cylinder (10); the gear (6) is rotatably connected to the cylinder (10), the gear (6) is connected to the output shaft of the stepping motor (7), and a rack (11) is arranged on the inner wall of one side of the operating rod (3) away from the end of the power seat (2); the racks (11) of the upper and lower operating rods (3) are symmetrically arranged on both sides of the gear (6) and are respectively meshed with the gear (6); the gear (6) rotates to drive the two racks (11) and the two operating rods (3) to move up and down to control the bidirectional extension and retraction of the two power seats (2), thereby controlling the expansion angle of the shear blade (1); Positioning holes (8) are symmetrically arranged on two opposite side walls of the operating rod (3); telescopic clamps (9) are arranged at both ends of the bottom of the rack (11), and the telescopic clamps (9) are connected to the bottom of the rack (11) through telescopic springs; when the two operating rods (3) are relatively moved under the drive of the stepping motor (7), the telescopic clamp (9) at the bottom of the upper operating rod (3) is clamped into the positioning hole (8) on the lower operating rod (3), and the telescopic clamp (9) at the top of the lower operating rod (3) is clamped into the positioning hole (8) on the upper operating rod (3), so that the upper and lower shear blades (1) are positioned.

2. A shearing assembly for an in-situ shearing instrument for well exploration according to claim 1, characterized in that: The left and right parts of the shear blade (1) are connected by a hinge to form the hinged structure.

3. A shearing assembly for an in-situ shearing instrument for well exploration according to claim 2, characterized in that: The left and right parts of the shear blades (1) on both sides of the hinge are respectively connected to the two ends of the same spring (5) via a connecting line, and a protective cover is arranged outside the spring (5).

4. A shearing assembly for an in-situ shearing instrument for well exploration according to claim 1, characterized in that: A fixing rod (14) is fixedly connected inside the cylinder (10); the airbag (4) is sleeved outside the cylinder (10), and the airbag (4) is fixedly connected to the fixing rod (14) at both ends.

5. The shearing assembly for an in-situ shearing instrument for well exploration according to claim 1, characterized in that: Each set of shear blades (1) are sequentially spliced ​​together after being unfolded to form a complete combination of blades in a circular ring structure.

6. A test method for a shear assembly of an in-situ shear instrument for well exploration according to any one of claims 1 to 5, characterized in that: The following steps are involved: The first step is to build a test well in the stratum to be tested, and then expand the hole at different corresponding depths in the test well to dig out two grooves with larger diameters. The diameter of the expanded groove is the same as the diameter of the combined blade formed by each set of shear blades (1), and the net distance between the two grooves is consistent with the height of the air bag (4); The second step is to set up the well exploration shearing instrument and place the shearing assembly into the well exploration so that the air bag (4) is located between the two grooves; The third step is to start the bidirectional driving mechanism so that the upper and lower operating rods (3) are moved toward the middle. The upper and lower operating rods (3) are connected to the power seat (2), and the upper and lower power seats (2) move toward the middle. The upper and lower shear blades (1) are unfolded and fixed by the support of the combined support rod. The fourth step is to supply gas to the air bag (4) to expand it and thereby exert normal pressure on the inner wall of the exploration well; The fifth step is to apply normal pressure while pulling the shear assembly upward at a constant speed, so that the soil between the upper and lower sets of shear blades (1) slides relative to each other, causing shear failure; Step 6: Repeat the above steps to obtain test data under different normal pressures.

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