A ring-shaped rock specimen longitudinal tensile cracking test device and test method

Abstract

The present invention discloses a longitudinal tensile cracking test device and test method for an annular rock specimen, comprising a base, a top seat, a pressure bag and a barrier, wherein the inner cavity of the pressure bag is integrally formed with a bulge, the bulge divides the inner cavity of the pressure bag into two left and right separation cavities, and the bulge is filled with a barrier; the base and the top seat are both annular structures, and are both sleeved on the outer periphery of the pressure bag, the top seat is fixedly mounted on the upper part of the base through a support frame, and an annular test space surrounding the pressure bag is formed between the base and the top seat. The present invention applies pressure to the rock sample, and the rock is broken at the reserved fracture interface to obtain the tensile strength of the rock.

Description

Technical Field

[0001] The invention relates to rock testing equipment, and more specifically to a longitudinal tensile cracking testing device for an annular rock specimen, and also to a longitudinal tensile cracking testing method for an annular rock specimen. Background Art

[0002] The tensile strength of rock refers to the maximum stress that rock can withstand when subjected to tensile force. Unlike compressive strength, tensile strength describes the resistance of rock under tension. There are two ways to measure the tensile strength of rock: direct tensile test and indirect tensile test. Direct test usually uses cement slurry or other forms of bonding to connect the end of the cylindrical sample with the pull head of the tensile machine until the specimen is damaged or reaches its limit. However, due to the influence of various factors during bonding, the bonding effect is not good, the success rate of the test is low, and it is not conducive to promotion. Indirect test methods include Brazilian splitting test, three-point bending test and four-point bending test. The above indirect test methods can all realize the tensile strength test of rock. However, the indirect test method is not a direct rock breaking in the strict sense, but a rock sample breaking. There is a large deviation in the force direction inside the rock sample, and then it is indirectly converted into tensile strength. The accuracy of the tensile strength obtained is low.

[0003] Therefore, a new solution needs to be proposed to solve this problem. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a ring-shaped rock specimen longitudinal tensile cracking test device capable of performing a tensile strength test on a rock sample.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A device for testing longitudinal tensile cracking of an annular rock specimen comprises a base, a top seat, a pressure bag and a barrier. The inner cavity of the pressure bag is integrally formed with a raised portion, the raised portion divides the inner cavity of the pressure bag into two left and right separation chambers, and the raised portion is filled with a barrier. The base and the top seat are both annular in structure and are both sleeved on the outer circumference of the pressure bag. The top seat is fixedly mounted on the upper part of the base by a support frame, and an annular test space surrounding the pressure bag is formed between the base and the top seat.

[0007] The present invention is further configured such that an inner cavity is provided in the base, the bottom of the inner cavity is closed, the top is open, the upper and lower ends of the top seat are connected, the outer periphery of the base is fixedly connected to a support ring, and the support ring is fixedly connected to the base through a support frame.

[0008] The present invention is further configured such that the support frame includes a screw and a support rod, the upper and lower ends of the support rod are respectively against the upper end surfaces of the support ring and the base, and the screw passes through the support ring and the support rod in sequence and is threadedly connected to the base.

[0009] The present invention is further configured such that the inner cavity of the pressure bag is pressurized and can be elastically deformed toward the periphery; the outer peripheral contour of the pressure bag is mutually adapted to the inner peripheral contours of the base and the top seat.

[0010] The present invention is further configured such that the raised portion extends toward the periphery of the pressure bag and is connected to the inner peripheral walls on both sides of the pressure bag; the raised portion is a hollow structure and forms an opening that passes through both sides of the periphery of the pressure bag.

[0011] The present invention is further configured such that the lower side of the pressure bag abuts against the bottom surface of the inner cavity 2 of the base; the raised portion extends toward the bottom of the pressure bag and is connected to the bottom of the pressure bag, and an opening penetrating downward is formed at the raised portion of the pressure bag.

[0012] The present invention is further configured such that an opening is formed at the upper portion of the pressure bag, and a flange is formed at the outer periphery of the opening; and further includes an end cover, which is arranged at the upper side of the opening and can close the opening, and the flange at the outer periphery of the opening is embedded between the top seat and the end cover to achieve sealing.

[0013] The present invention is further configured such that the top seat and the end cover are connected and fixed by bolts, a plurality of connection holes 2 are opened at the flange, and the bolts pass through the connection holes 2.

[0014] The present invention is further configured such that the end cover is provided with a through hole, a joint is installed at the through hole, and the through hole is used to connect to an external pressure source.

[0015] The present invention also provides a method for testing the longitudinal tensile cracking of an annular rock specimen, which uses the longitudinal tensile cracking testing device for annular rock specimens as described above. During the test, the annular rock specimen is installed in the test space, and the annular rock specimen is sleeved on the outer periphery of a pressure bag. By increasing the pressure inside the pressure bag, the outer peripheral wall of the pressure bag will elastically expand outward, applying pressure to the inner periphery of the annular rock specimen until the annular rock specimen cracks.

[0016] In summary, the present invention has the following beneficial effects:

[0017] By adopting a pressure bag with elastic deformation ability, pressure is applied to the inward part of the annular rock specimen; and a bulge is formed in the pressure bag to separate the pressure bag into two left and right chambers, and a reserved stress concentration point is formed on the periphery of the pressure bag to form a reserved fracture interface; by applying pressure inside the pressure bag through hydraulic oil, the annular rock specimen will be broken at the reserved fracture interface, and the tensile strength of the rock can be obtained according to the internal pressure of the pressure bag at the time of fracture. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic structural diagram of a ring-shaped rock specimen longitudinal tensile cracking test device in this embodiment;

[0019] Figure 2 This is an exploded view of a longitudinal tensile cracking test device for a ring-shaped rock specimen in this embodiment;

[0020] Figure 3 A cross-sectional view of a ring-shaped rock specimen longitudinal tensile cracking test device in this embodiment Figure 1 ;

[0021] Figure 4 A cross-sectional view of a ring-shaped rock specimen longitudinal tensile cracking test device in this embodiment Figure 2 ;

[0022] Figure 5 It is a schematic diagram of the structure of the pressure bag and the barrier 10 in this embodiment;

[0023] Figure 6 The cross-section diagram of the pressure bag, the barrier and the annular rock specimen in this embodiment is shown in FIG. Figure 1 ;

[0024] Figure 7 The cross-section diagram of the pressure bag, the barrier and the annular rock specimen in this embodiment is shown in FIG. Figure 2 .

[0025] Figure numerals: base 1; inner cavity 11; screw hole 12; top seat 2; inner cavity 21; support ring 22; connection hole 1 23; screw hole 24; pressure bag 3; opening 31; flange 32; connection hole 2 33; raised portion 34; partition cavity 35; end cover 4; connection hole 3 41; through hole 42; screw rod 5; support rod 6; bolt 7; annular rock specimen 8; test space 800; joint 9; barrier 10; splicing piece 101. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] The present embodiment discloses a longitudinal tensile cracking test device for an annular rock specimen, which serves to perform a cracking test on an annular rock specimen 8. During the test, pressure is applied to the inner circumference of the annular rock specimen 8, and the inner circumference of the annular rock specimen 8 is subjected to pressure, and the rock will be broken, thereby realizing a tensile cracking test of the rock specimen.

[0028] Reference Figure 1-Figure 7 As shown, the annular rock specimen longitudinal tensile cracking test device comprises a base 1, a top seat 2, a pressure bag 3 and a barrier 10. The base 1 and the top seat 2 are both annular structures and are sleeved on the outer periphery of the pressure bag 3. The top seat 2 is fixedly mounted on the upper part of the base 1 through a support frame, and an annular test space 800 surrounding the pressure bag 3 is formed between the base 1 and the top seat 2. During the test, the annular rock specimen 8 is installed in the annular test space 800 and sleeved outside the pressure bag 3. The outer circumference size of the pressure bag 3 is matched with the inner circumference size of the annular rock specimen 8. The internal pressure of the pressure bag 3 applies pressure to the annular rock specimen 8, thereby realizing the rock tensile cracking test.

[0029] An inner cavity 11 is provided in the base 1, the bottom of the inner cavity 11 is closed and the top is open. The top seat 2 is connected at both ends, and the inner cavity contours of the base 1 and the top seat 2 are adapted. A support ring 22 is fixedly connected to the outer periphery of the base 1, and the support ring 22 is fixedly connected to the base 1 through a support frame.

[0030] The support frame includes a plurality of screw rods 5 and support rods 6, forming a plurality of evenly distributed support structures between the base 1 and the top seat 2. The upper and lower ends of the support rod 6 are respectively against the support ring 22 and the upper end surface of the base 1, and a hole is provided in the support rod 6 that passes through the upper and lower parts, and a plurality of connection holes 23 are provided in the support ring 22, and a plurality of screw holes 12 are provided in the upper end surface of the base 1. During installation, the screw rod 5 passes through the support ring 22 and the support rod 6 in sequence and is threadedly connected to the base 1, thereby connecting and fixing the base 1 and the top seat 2. Due to the support of the support rod 6, an annular test space 800 can be formed between the base 1 and the top seat 2.

[0031] The pressure bag 3 may be an elastic rubber bag structure, and the inner cavity of the pressure bag 3 can be elastically deformed toward the periphery after being pressurized. Specifically, the circumferential contour of the pressure bag 3 is roughly a circular structure, the pressure bag 3 is installed in the inner cavity 21 of the top seat 2, and the lower part of the pressure bag 3 extends into the inner cavity 11 of the base 1, and the lower side of the pressure bag 3 is against the bottom surface of the inner cavity 21 of the base 1.

[0032] Reference Figure 5 As shown, a bulge 34 is integrally formed in the inner cavity of the pressure bag 3, and the bulge 34 divides the inner cavity of the pressure bag 3 into two left and right separation cavities 35. The bulge 34 is filled with a barrier 10, which is a plate-like structure and can form a separation structure between the two separation cavities 35, and can separate the pressure in the middle of the pressure bag 3.

[0033] The raised portion 34 extends toward the periphery of the pressure bladder 3 and is connected to the inner circumferential walls on both sides of the pressure bladder 3. The raised portion 34 is hollow and forms an opening that passes through both sides of the periphery of the pressure bladder 3, forming two notches on both sides of the periphery of the pressure bladder 3. Moreover, the raised portion 34 extends toward the bottom of the pressure bladder 3 and is connected to the bottom of the pressure bladder 3, and a downwardly penetrating opening is formed at the raised portion 34 of the pressure bladder 3.

[0034] The two sides of the barrier 10 are arc-shaped structures. When the barrier 10 is embedded in the pressure bag 3, the pressure bag 3 and the barrier 10 can be combined to form a complete circular structure, so that the circular structure can fit with the inner periphery of the base 1 and the top seat 2, and a loading gap can be formed at the barrier 10, so that the positions of concentrated force can be formed at the two sides of the barrier 10. The tensile fracture of the annular rock specimen 8 also corresponds to the position of the barrier 10.

[0035] The outer contour of the pressure bag 3 is mutually adapted to the inner contour of the base 1 and the top seat 2. The outer peripheral part of the pressure bag 3 can be mutually fitted with the inner wall of the base 1 and the top seat 2 to form a support and limit for the pressure bag 3.

[0036] An opening 31 is formed at the upper part of the pressure bag 3, and a flange 32 is formed at the outer periphery of the opening 31. The upper side of the opening 31 is covered with an end cap 4 to close the opening 31. In addition, since the flange 32 and the main body of the pressure bag 3 are made of the same material, they are elastic and can act as a sealing ring. After the flange 32 at the outer periphery of the opening 31 is embedded between the top seat 2 and the end cap 4, the sealing can be achieved by mutual compression of the two.

[0037] Specifically, the top seat 2 and the end cover 4 are connected and fixed by a plurality of bolts 7, a plurality of second connection holes 33 are provided at the flange 32, a plurality of third connection holes 41 are provided at corresponding positions of the end cover 4, and a plurality of second screw holes 24 are provided at corresponding positions on the upper side of the support ring 22. During installation, the bolts 7 pass through the third connection hole 41 and the second connection hole 33 in sequence, and are threadedly connected to the second screw hole 24. Through thread locking, a clamping load can be applied between the top seat 2 and the end cover 4 to form a sealed connection structure.

[0038] In addition, a through hole 42 is provided in the end cover 4, and the through hole 42 can be connected to the inner cavity of the pressure bag 3, and at the same time, the two separation cavities 35 of the pressure bag 3 are connected. A joint 9 can be installed at the through hole 42, and the through hole 42 can be blocked by the joint 9, and an external pressure source can also be connected. During the test, a high-pressure liquid is introduced into the pressure bag 3 through the through hole 42.

[0039] Generally, two through holes 42 are provided, wherein one through hole 42 is used to convey pressurized liquid, and the other through hole 42 is used to exhaust gas, which can basically exhaust the gas in the pressure bag 3 and keep the internal pressure of the pressure bag 3 stable.

[0040] Since the pressure bag 3 is a special-shaped structure, during the pressure process, due to the boundary effect, the deformation and stress of the special-shaped pressure bag 3 at the upper and lower ends are not uniform, and the deformation in the middle of the special-shaped pressure bag 3 is relatively uniform. Therefore, after the annular rock specimen 8 is installed, the position of the annular rock specimen 8 corresponds to the middle section of the special-shaped pressure bag 3, and the middle section of the special-shaped pressure bag 3 applies pressure to the inner periphery of the annular rock specimen 8.

[0041] In addition, the barrier 10 may adopt a splicing structure, which is formed by splicing a plurality of splicing pieces 101 up and down, so that it can be used to separate pressure bags 3 of different heights and sizes.

[0042] This embodiment also discloses a method for testing longitudinal tensile cracking of annular rock specimens, using the aforementioned apparatus for testing longitudinal tensile cracking of annular rock specimens.

[0043] Before the test, the rock sample is processed into a circular ring structure of appropriate size to form a ring-shaped rock specimen 8.

[0044] During installation, the annular rock specimen 8 is installed in the test space 800 between the base 1 and the top seat 2, and the base 1 and the top seat 2 are locked and fixed by the support rod 6 and the screw 5; then, the barrier 10 is inserted into the raised portion 34 of the pressure bag 3, and the barrier 10 and the pressure bag 3 are combined to form a roughly cylindrical structure; then, the barrier 10 is connected to the barrier 10 and inserted into the chamber surrounded by the base 1, the annular rock specimen 8, and the top seat 2, at which time the bottom of the pressure bag 3 and the bottom of the top seat 2 fit each other, and the outer periphery of the pressure bag 3 and the inner circumferential wall of the chamber fit each other; then, the end cover 4 is installed on the upper part of the opening 31 of the pressure bag 3, and the flange 32 on the outer periphery of the opening 31 is embedded between the end cover 4 and the support ring 22, and the end cover 4 is fixed and locked by the bolt 7, and the opening of the pressure bag 3 is sealed and closed at the same time; then, the through hole 42 of the end cover 4 is connected to the external hydraulic source through the joint.

[0045] During the test, hydraulic oil is injected into the pressure bag 3 through an external hydraulic source to gradually increase the pressure in the pressure bag 3. At the same time, the pressure in the pressure bag 3 is detected by a pressure detector; Figure 7 As shown, during the pressure process inside the pressure bag 3, the outer peripheral wall of the pressure bag 3 will elastically expand outward, exerting pressure on the inner periphery of the annular rock specimen 8 until the annular rock specimen 8 cracks.

[0046] Since there is a bulge 34 in the middle of the pressure bag 3 and a barrier 10 is embedded therein, the two separation chambers 35 exert forces on the opposite sides on the sides close to the outer circumference, and the hydraulic pressure on the side close to the bulge 34 will act on the barrier 10, and the forces in the two separation chambers 35 will cancel each other out, and the pressure of the pressure bag 3 on the annular rock specimen 8 will be concentrated on both sides of the bulge 34. As the pressure inside the pressure bag 3 increases, the annular rock specimen 8 will crack, as shown in FIG. Figure 7 As shown, the rock at the reserved fracture interface is broken so that the tensile strength of the rock can be obtained.

[0047] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A ring-shaped rock specimen longitudinal tensile cracking test device, characterized in that: The device comprises a base (1), a top seat (2), a pressure bag (3) and a barrier (10); the inner cavity of the pressure bag (3) is integrally formed with a raised portion (34); the raised portion (34) divides the inner cavity of the pressure bag (3) into two left and right separation chambers (35); the raised portion (34) is filled with the barrier (10); the base (1) and the top seat (2) are both annular in structure and are sleeved on the outer circumference of the pressure bag (3); the top seat (2) is fixedly mounted on the upper part of the base (1) by a support frame; an annular test space (800) surrounding the pressure bag (3) is formed between the base (1) and the top seat (2); The inner cavity of the pressure bag (3) is capable of elastically deforming toward the periphery when under pressure; the outer peripheral contour of the pressure bag (3) is mutually compatible with the inner peripheral contours of the base (1) and the top seat (2); The bulge (34) extends toward the periphery of the pressure bag (3) and is connected to the inner peripheral walls on both sides of the pressure bag (3); the bulge (34) is a hollow structure and forms an opening that passes through both sides of the periphery of the pressure bag (3), forming two notches on both sides of the periphery of the pressure bag (3); The lower side of the pressure bag (3) abuts against the bottom surface of the second inner cavity (21) of the base (1); the raised portion (34) extends toward the bottom of the pressure bag (3) and is in communication with the bottom of the pressure bag (3); the raised portion (34) of the pressure bag (3) forms an opening that passes downward; The barrier (10) is a plate-shaped structure, which can separate between the two separation chambers (35) and can separate the pressure in the middle of the pressure bag (3); the two sides of the barrier (10) are arc-shaped structures. When the barrier (10) is embedded in the inner side of the raised portion (34) of the pressure bag (3), the pressure bag (3) and the barrier (10) can be combined to form a complete circular structure, which can fit with the inner periphery of the base (1) and the top seat (2), and can form a pressure loading gap at the barrier (10), thereby forming a position where the force is concentrated at the two sides of the barrier (10), and the tensile fracture position of the annular rock specimen (8) corresponds to the position of the barrier (10); The annular test space (800) is used to install an annular rock specimen (8). After the annular rock specimen (8) is installed, the position of the annular rock specimen (8) corresponds to the middle section of the pressure bag (3), and the middle section of the pressure bag (3) applies pressure to the inner periphery of the annular rock specimen (8). A bulge (34) is provided in the middle position of the pressure bag (3) and a barrier (10) is embedded therein. The two separation chambers (35) exert forces on opposite sides on the side close to the outer peripheral direction, respectively, and on the side close to the bulge (34), hydraulic pressure acts on the barrier (10), and the forces of the two separation chambers (35) toward the barrier (10) offset each other. The pressure of the pressure bag (3) on the annular rock specimen (8) is concentrated at the open positions on both sides of the bulge (34).

2. The ring-shaped rock specimen longitudinal tensile cracking test device according to claim 1 is characterized in that: The base (1) is provided with an inner cavity (11), the bottom of the inner cavity (11) is closed and the top is open, the upper and lower ends of the top seat (2) are connected, and the outer periphery of the base (1) is fixedly connected with a support ring (22), and the support ring (22) is fixedly connected to the base (1) through a support frame.

3. The ring-shaped rock specimen longitudinal tensile cracking test device according to claim 2 is characterized in that: The support frame comprises a screw rod (5) and a support rod (6); the upper and lower ends of the support rod (6) respectively abut against the support ring (22) and the upper end surface of the base (1); the screw rod (5) sequentially penetrates the support ring (22) and the support rod (6) and is threadedly connected to the base (1).

4. The ring-shaped rock specimen longitudinal tensile cracking test device according to claim 1, characterized in that: The pressure bag (3) is formed with an opening (31) at the top, and a flange (32) is formed on the outer periphery of the opening (31); and an end cover (4) is also included. The end cover (4) is arranged on the upper side of the opening (31) and can close the opening (31). The flange (32) on the outer periphery of the opening (31) is embedded between the top seat (2) and the end cover (4) to achieve sealing.

5. The ring-shaped rock specimen longitudinal tensile cracking test device according to claim 4, characterized in that: The top seat (2) and the end cover (4) are connected and fixed by bolts (7); a plurality of second connection holes (33) are provided at the flange (32); and the bolts (7) pass through the second connection holes (33).

6. The ring-shaped rock specimen longitudinal tensile cracking test device according to claim 4, characterized in that: The end cover (4) is provided with a through hole (42), a joint (9) is installed at the through hole (42), and the through hole (42) is used to connect to an external pressure source.

7. A method for testing longitudinal tensile cracking of annular rock specimens, characterized in that: A longitudinal tensile cracking test device for an annular rock specimen as described in any one of claims 1 to 6 is used. During the test, the annular rock specimen (8) is installed in the test space (800), and the annular rock specimen (8) is sleeved on the outer periphery of the pressure bag (3). By increasing the pressure inside the pressure bag (3), the outer peripheral wall of the pressure bag (3) will elastically expand outward, applying pressure to the inner periphery of the annular rock specimen (8) until the annular rock specimen (8) cracks.

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