CN114397200A - Device and method for testing static and dynamic direct tensile strength of annular rock core - Google Patents
Device and method for testing static and dynamic direct tensile strength of annular rock core Download PDFInfo
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- CN114397200A CN114397200A CN202111482907.2A CN202111482907A CN114397200A CN 114397200 A CN114397200 A CN 114397200A CN 202111482907 A CN202111482907 A CN 202111482907A CN 114397200 A CN114397200 A CN 114397200A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/30—Investigating strength properties of solid materials by application of mechanical stress by applying a single impulsive force, e.g. by falling weight
- G01N3/303—Investigating strength properties of solid materials by application of mechanical stress by applying a single impulsive force, e.g. by falling weight generated only by free-falling weight
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/02—Details
- G01N3/04—Chucks
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/067—Parameter measured for estimating the property
- G01N2203/0676—Force, weight, load, energy, speed or acceleration
Abstract
A testing device and a testing method for static and dynamic direct tensile strength of an annular rock core are disclosed, and the device comprises: two fixed bearing platforms with fixed guide rails are fixedly connected to the left part and the right part at the upper end of the bottom supporting seat at intervals left and right; the pressure-pull transshipment mechanism consists of a sliding bearing platform, a transshipment block and a loading unit; the lower end of the sliding bearing platform is provided with a sliding chute; a guide inclined plane is arranged at the inner end of the transfer block; the loading unit consists of a strip-shaped connecting block and a semicircular loading head; the left side and the right side of the lower end of the wedge-shaped loading block are provided with loading inclined planes, and the lower end of the wedge-shaped loading block is arranged between the upper ends of the two transfer blocks. The method comprises the following steps: processing the obtained core into an annular core; fixing the testing device; and applying a load to carry out a test, and recording data. The device is rational in infrastructure, and convenient operation, the tensile strength of reaction rock that can be true can effectively improve measuring result's accuracy nature. The method has simple steps and simple operation, and can effectively test the direct tensile strength in the horizontal direction of the rock sample.
Description
Technical Field
The invention relates to the technical field of rock mechanics, in particular to a device and a method for testing static and dynamic direct tensile strength of an annular rock core.
Background
Determination of rock strength under various loading conditions (compression, tension and shear) is one of the major problems in rock mechanics. Most rocks and even rock-like materials tend to be more susceptible to tensile failure because the tensile strength of the rock material is very low compared to the compressive strength. Therefore, the tensile strength of the rock is an important parameter in engineering such as stability evaluation of rock engineering, design of tunnel boring machines, hydraulic fracturing construction and the like. The evaluation of tensile strength of rock requires a suitable sample and test procedure. Currently, the existing methods for testing tensile strength can be classified into indirect testing methods and direct testing methods.
The indirect test method mainly comprises a Brazilian splitting method, a ring compression splitting method, a three-point bending method and a four-point bending method, and the used test rock sample is generally processed into a disc shape, a ring shape and a strip shape. The Brazilian splitting method is recommended by the international rock mechanics society, is a tensile strength testing method which is most widely applied at present, and in the testing process, a processed disc-shaped test piece is horizontally placed between two strip-shaped or arc-shaped loading plates, and then load is applied to enable the test piece to be pressed to generate splitting damage along the center, so that the tensile strength of the test piece is obtained. The three-point or four-point bending tensile test is that a strip-shaped test sample with a rectangular cross section is placed on a bending device, and loading is carried out after the span is adjusted, so that the test sample is stretched and broken at the lower edge of the beam. No matter which indirect tensile strength test is adopted, the tensile strength value of the rock is indirectly obtained through the splitting fracture load obtained through the test, because the applied compressive load generates the tensile stress in some areas of the sample, the sample is generally split along the area with the maximum induced tensile stress instead of being damaged along the part with the minimum bearing capacity, and therefore, a certain deviation exists between the obtained tensile strength value and the actual tensile strength.
Different from the indirect test method, the direct tensile test is a method for directly measuring the tensile strength of the rock, a tested sample is under the action of pure tensile stress in the tensile process, and the test piece can be guaranteed to be broken along the weakest part of the bearing capacity, so that the tensile strength of the rock can be truly reflected in the test process, and the obtained measurement result is more accurate than that of an indirect test method. The common direct test method mainly comprises a bonding method and a clamping method, wherein a cylindrical or dumbbell-shaped test piece made of rock is required, two ends of the test piece are fixed with a clamp in a bonding or clamping mode during testing, and then the test piece is broken through stretching the clamp to determine a corresponding tensile strength value. However, the bonding method or the clamping method has difficulties in actual testing, debonding easily occurs at the bonding position or clamping failure occurs at the clamping position due to stress concentration, and meanwhile, the influence of eccentric loading needs to be eliminated in the testing process, so that the practical application and popularization of the direct testing method are greatly limited.
To sum up, at present, a direct tensile testing device which is simple in structure and convenient to operate and can be suitable for a conventional rock mechanical testing machine is needed to obtain tensile strength parameters of rocks more accurately in a direct tensile mode.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides the device and the method for testing the static and dynamic direct tensile strength of the annular rock core, the device has reasonable structure and convenient operation, can more accurately obtain the tensile strength parameter of the rock in a direct tensile mode, can truly reflect the tensile strength of the rock, and can effectively improve the accuracy of a measuring result; the method has simple steps and simple operation, can effectively and directly test the tensile strength of the rock sample in the horizontal direction, and can more accurately obtain the tensile strength parameter of the rock.
In order to achieve the aim, the invention provides a device for testing the static and dynamic direct tensile strength of an annular rock core, which comprises a bottom supporting seat, a fixed bearing platform, a pressing and pulling transfer mechanism and a wedge-shaped loading block, wherein the bottom supporting seat is provided with a support base; the length direction of the bottom support seat extends along the left-right direction;
the fixed bearing table is horizontally arranged, and the upper end of the fixed bearing table is fixedly connected with a fixed guide rail extending in the left-right direction; the two fixed bearing tables are fixedly connected to the left part and the right part at the upper end of the bottom supporting seat at intervals left and right;
the number of the pressure-pull transshipment mechanisms is two, and each pressure-pull transshipment mechanism consists of a sliding bearing platform, a transshipment block and a loading unit; the sliding bearing table is horizontally arranged, and the lower end of the sliding bearing table is provided with a sliding chute extending in the left-right direction; the transfer block is fixedly connected to the upper part of the inner end of the sliding bearing table, and a guide inclined plane with a high outer part and a low inner part is arranged at the inner end of the transfer block; the loading unit consists of a strip-shaped connecting block and a semicircular loading head; the front end of the strip-shaped connecting block is fixedly connected to the rear end face of the inner end of the transfer block; the inner end of the loading head is fixedly connected with the rear end of the strip-shaped connecting block; the two pressing-pulling transferring mechanisms are arranged above the two fixed bearing tables in a left-right opposite mode, and the sliding bearing tables are sleeved on the fixed guide rails in a sliding mode through the sliding grooves so as to realize sliding fit of the pressing-pulling transferring mechanisms and the fixed bearing tables in the left-right direction; when the two pressure-pull transfer mechanisms slide to a contact state, the two loading heads form a circular loading ring;
the upper end of the wedge-shaped loading block is of a plane structure, and the left side and the right side of the lower end of the wedge-shaped loading block are symmetrically provided with two loading inclined planes which are high outside and low inside; the lower end of the wedge-shaped loading block is arranged between the upper ends of the two transfer blocks, and the loading inclined planes on the two sides are respectively in sliding fit with the guide inclined planes of the two transfer blocks.
Preferably, the bottom support seat consists of a support bottom plate, two support top plates and two vertical supports, wherein the two support top plates are arranged on the left part and the right part above the support bottom plate in a left-right opposite mode; the two vertical supports are correspondingly arranged below the two supporting top plates, the upper ends of the vertical supports are fixedly connected with the lower end faces of the supporting top plates, and the lower ends of the vertical supports are fixedly connected with the upper end faces of the supporting bottom plates; the middle part of the upper end of the supporting bottom plate is fixedly connected with a limiting block between the two vertical supports, and the height of the limiting block is lower than that of the vertical supports.
Furthermore, in order to facilitate assembly and separation, a first bolt hole matched with the pressure testing machine platform is formed in the periphery of the supporting bottom plate; a plurality of bolt holes II are formed in the supporting top plate; a plurality of bolt holes III are formed in the fixed bearing platform, and the fixed bearing platform is fixedly connected with the bottom supporting seat through first connecting bolts penetrating through the bolt holes III and the bolt holes II.
Furthermore, in order to facilitate assembly and separation, a plurality of bolts IV are arranged on the sliding bearing table; and a plurality of bolt holes five are formed in the transfer block, and the transfer block is fixedly connected with the sliding bearing platform through connecting bolts two penetrating through the bolt holes four and the bolt holes five.
Furthermore, in order to ensure the stability and reliability of the sliding fit between the pressing-pulling transferring mechanism and the fixed bearing platform, the sections of the fixed guide rail and the chute are both in a dovetail shape.
Further, in order to guarantee reliable connection strength, the rear end of the strip-shaped connecting block extends to the rear end of the inner arc surface of the loading head, and the rear end of the strip-shaped connecting block is fixedly connected to the middle of the inner arc surface of the loading head.
Preferably, the strip-shaped connecting block and the loading head are of an integrated structure.
Further, in order to smoothly apply a vertical load during the test, the inclination angles of the guide slope and the loading slope are consistent.
According to the invention, the arrangement of the bottom supporting seat can provide stable and reliable support for the testing device; the upper end of the bottom supporting seat is fixedly connected with a fixed bearing platform with a fixed guide rail, and the bottom of a sliding bearing platform in the pressing-pulling transferring mechanism is provided with a sliding chute matched with the fixed guide rail, so that the pressing-pulling transferring mechanism and the fixed bearing platform can transversely slide in the left-right direction; the inner end of the transfer platform of the pressure-pull transfer mechanism is provided with the guide inclined plane, so that a wedge-shaped groove can be formed between the two pressure-pull transfer mechanisms, meanwhile, the two sides of the lower end of the wedge-shaped loading block are provided with the loading inclined planes, the vertical load applied to the top of the wedge-shaped loading block can be converted into the transverse load transversely acting on the two pressure-pull transfer mechanisms, and thus, the compression load acting on the top of the wedge-shaped loading block can be converted into a pair of tensile loads acting on the inner surface of the annular rock core, so that the pure tensile load can be applied to the rock sample without adopting a bonding or clamping mode, the condition that the test fails due to bonding damage at the bonding part or clamping damage at the clamping part due to stress concentration in the existing direct tensile test method is avoided, and meanwhile, the tensile load is applied through the annular loading head matched with the inner surface of the annular rock core to be tested, the problem of eccentric tension in a direct tension test by a bonding or clamping method is avoided. In addition, the testing machine only needs to provide compression load, so that the testing equipment is low in requirement, the testing machine does not need to have a stretching function, and the testing machine can be widely applied to universal testing machines with various specifications and can realize static direct tensile strength testing of rocks. Meanwhile, the invention can also be arranged in a drop hammer testing machine, and can convert the impact force formed by the drop hammer falling into dynamic tensile force, thereby obtaining the dynamic direct tensile strength of the rock. The invention provides a device for testing static and dynamic direct tensile strength of an annular rock core loaded by using compression-tension conversion, which has the advantages of simple structure, convenient operation, convenient popularization and application in various conventional rock mechanical testing machines, realization of rock tensile strength testing under direct tensile conditions, real reaction on the tensile strength of rocks, and effective improvement on the accuracy of tensile strength parameter testing.
The invention provides a static and dynamic direct tensile strength testing method for an annular rock core, which comprises the following steps:
the method comprises the following steps: processing the obtained core into an annular core;
step two: firstly, fixing a support bottom plate on a rock mechanical pressure tester platform through a fastening bolt so as to fix a bottom support seat; the two fixed bearing tables are respectively and fixedly connected to the upper ends of the two supporting top plates through a first connecting bolt; then the two pressure-pull transfer mechanisms are assembled on the two fixed bearing tables in a sliding manner, and the inner ends of the two pressure-pull transfer mechanisms are in the initial positions of mutual abutting;
step three: sleeving the prepared annular rock core outside a circular loading ring formed by enclosing of loading heads on the two pressing and pulling transferring mechanisms, ensuring that the annular rock core is coaxial with the circular loading ring, then placing a wedge-shaped loading block in a wedge-shaped groove formed between the transferring blocks on the two pressing and pulling transferring mechanisms, and ensuring that the upper end of the wedge-shaped loading block is in a horizontal position;
step four: starting a compression testing machine to apply a compression load on the top of a wedge-shaped loading block, converting the compression load P into a pair of symmetrical tensile loads T acting on the inner surface of the annular rock core by the wedge-shaped loading block through a compression-tension transfer mechanism, recording vertical pressure and vertical displacement applied by the compression testing machine to obtain horizontal tension and horizontal tensile displacement applied to the annular rock core, and calculating the tensile strength sigma of the rock through a formula (1)t；
In the formula: p is the maximum compression load when the annular core is broken by tension, and the unit is N; t is the thickness of the annular core in m; doIs the outer circular radius of the circular core, in m; diIs the inner circular radius of the circular core in m.
The method has simple steps, can convert vertical pressure into two horizontal pulling forces acting on the inner surface of the annular rock core, so that the annular rock core is directly stretched and damaged, and can effectively and directly test the tensile strength of the rock sample in the horizontal direction, overcome the technical problems of bonding failure, stress concentration and eccentric stretching in the conventional direct tensile test, and more accurately obtain the tensile strength parameters of the rock; meanwhile, the invention is convenient to operate, can be suitable for various conventional rock mechanical testing machines, and has great popularization and application values.
Drawings
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is a schematic view of the assembly of the present invention in connection with an annular core;
FIG. 3 is a schematic structural view of the present invention with the wedge loading block and the right side of the compression-pull transfer mechanism removed;
FIG. 4 is a schematic structural view of a press-pull transfer mechanism according to the present invention;
FIG. 5 is a schematic view of the bottom bracket of the present invention;
FIG. 6 is a schematic view of the assembly of the bottom support base and two fixed carriers of the present invention;
FIG. 7 is a schematic structural diagram of a wedge loading block according to the present invention;
fig. 8 is a schematic structural diagram of the transfer block of the present invention.
In the figure: 1. bottom sprag seat, 2, supporting baseplate, 3, wedge loading piece, 4, fixed plummer, 5, roof support, 6, vertical support, 7, fixed guide rail, 8, pressure and pull reprint mechanism, 9, slip plummer, 10, spout, 11, reprint piece, 12, loading unit, 13, direction inclined plane, 14, bar connecting block, 15, loading head, 16, loading inclined plane, 17, annular core, 18, bolt hole one, 19, bolt hole two, 20, bolt hole three, 21, stopper, 22, vertical plane, 23, reprint backup pad, 24, loading piece.
Detailed Description
The invention will be further explained with reference to the drawings.
As shown in fig. 1 to 8, the invention provides a device for testing static and dynamic direct tensile strength of an annular rock core, which comprises a bottom supporting seat 1, a fixed bearing platform 4, a pressure-pull transfer mechanism 8 and a wedge-shaped loading block 3; the length direction of the bottom support seat 1 extends along the left-right direction;
the fixed bearing table 4 is horizontally arranged, the upper end of the fixed bearing table 4 is fixedly connected with a fixed guide rail 7 extending in the left-right direction, the left end and the right end of the fixed guide rail 7 are arranged in parallel with the left end and the right end of the fixed bearing table 4, and the fixed guide rail 7 is positioned in the center of the fixed bearing table 4 in the width direction; the two fixed bearing platforms 4 are fixedly connected to the left part and the right part of the upper end of the bottom supporting seat 1 at intervals left and right;
the number of the pressing and pulling transfer mechanisms 8 is two, and each pressing and pulling transfer mechanism 8 consists of a sliding bearing platform 9, a transfer block 11 and a loading unit 12; the sliding bearing table 9 is horizontally arranged, and the lower end of the sliding bearing table is provided with a sliding chute 10 extending in the left-right direction; the transshipment block 11 is fixedly connected to the upper part of the inner end of the sliding bearing table 9, the inner end of the transshipment block is provided with a guide inclined plane 13 with a high outer part and a low inner part, as a priority, the transshipment block 11 consists of a transshipment supporting plate 23 positioned at the bottom and a loading block 24 fixedly connected to the upper end of the transshipment supporting plate 23, and the guide inclined plane 13 is formed at the inner end of the loading block 24; preferably, the transfer support plate 23 and the loading block 24 are of an integral structure; the loading unit 12 consists of a strip-shaped connecting block 14 and a semicircular loading head 15; the front end of the strip-shaped connecting block 14 is fixedly connected to the rear end face of the inner end of the transfer block 11; the inner end of the loading head 15 is fixedly connected with the rear end of the strip-shaped connecting block 14; the two pressing-pulling transferring mechanisms 8 are oppositely arranged above the two fixed bearing tables 4 from left to right, and the sliding bearing tables 9 are slidably sleeved on the fixed guide rails 7 through the sliding chutes 10, so that the pressing-pulling transferring mechanisms 8 are in sliding fit with the fixed bearing tables 4 in the left-right direction; when the two pressure-pull transfer mechanisms 8 slide to a contact state, the two loading heads 15 form a circular loading ring; preferably, in order to enable the loading head 15 to be suitable for annular rock cores 17 with different inner diameters, semicircular annular cushion plates can be further arranged, the inner diameters of the semicircular annular cushion plates are matched with the outer diameter of the loading head 15 and are arranged on the outer surface of the loading head 15 in an attached mode, the number of the semicircular annular cushion plates is two, and the semicircular annular cushion plates are arranged on the outer surfaces of the two loading heads 15 in a left-right opposite mode.
The upper end of the wedge-shaped loading block 3 is of a plane structure, the left side and the right side of the lower end of the wedge-shaped loading block are symmetrically provided with two loading inclined planes 16 with high outside and low inside, and the bottom ends of the two loading inclined planes 16 are intersected to form a V-shaped structure; the lower end of the wedge-shaped loading block 3 is arranged between the upper ends of the two transfer blocks 11, and the loading inclined planes 16 on the two sides are respectively in sliding fit with the guide inclined planes 13 of the two transfer blocks 11. Preferably, the upper parts of the left end and the right end of the wedge-shaped loading block 3 are both provided with vertical planes 22, and the lower ends of the vertical planes 22 are connected with the upper ends of the loading inclined planes 16.
Preferably, the bottom support seat 1 consists of a support bottom plate 2, two support top plates 5 and two vertical supports 6, wherein the two support top plates 5 are arranged at the left part and the right part above the support bottom plate 2 in a left-right opposite mode; the two vertical supports 6 are correspondingly arranged below the two supporting top plates 5, the upper ends of the vertical supports 6 are fixedly connected with the lower end faces of the supporting top plates 5, and the lower ends of the vertical supports 6 are fixedly connected with the upper end faces of the supporting bottom plates 2; the middle part of the upper end of the supporting bottom plate 2 is fixedly connected with a limiting block 21 between the two vertical supports 6, and the height of the limiting block 21 is lower than that of the vertical supports 6.
In order to facilitate assembly and separation, a first bolt hole 18 matched with the pressure testing machine platform is formed in the periphery of the supporting base plate 2; a plurality of bolt holes II 19 are formed in the supporting top plate 5; the fixed bearing platform 4 is provided with a plurality of bolt holes three 20, and is fixedly connected with the bottom support seat 1 through connecting bolts one penetrating through the bolt holes three 20 and the bolt holes two 19.
In order to facilitate assembly and separation, a plurality of bolts IV are arranged on the sliding bearing table 9; and a plurality of bolt holes five are formed in the transfer block 11, and the transfer block is fixedly connected with the sliding bearing platform 9 through connecting bolts two penetrating through the bolt holes four and the bolt holes five.
In order to ensure the stability and reliability of the sliding fit between the pressure-pull transfer mechanism and the fixed bearing platform, the sections of the fixed guide rail 7 and the chute 10 are both in a dovetail shape.
In order to ensure reliable connection strength, the rear end of the bar-shaped connecting block 14 extends to the rear end of the intrados of the loading head 15, and the rear end of the bar-shaped connecting block 14 is fixedly connected to the middle of the intrados of the loading head 15.
Preferably, the strip-shaped connecting block 14 and the loading head 15 are of a one-piece structure.
In order to smoothly apply the vertical load during the test, the inclination angles of the guide slope 13 and the loading slope 16 are consistent.
According to the invention, the arrangement of the bottom supporting seat can provide stable and reliable support for the testing device; the upper end of the bottom supporting seat is fixedly connected with a fixed bearing platform with a fixed guide rail, and the bottom of a sliding bearing platform in the pressing-pulling transferring mechanism is provided with a sliding chute matched with the fixed guide rail, so that the pressing-pulling transferring mechanism and the fixed bearing platform can transversely slide in the left-right direction; the inner end of the transfer platform of the pressure-pull transfer mechanism is provided with the guide inclined plane, so that a wedge-shaped groove can be formed between the two pressure-pull transfer mechanisms, meanwhile, the two sides of the lower end of the wedge-shaped loading block are provided with the loading inclined planes, the vertical load applied to the top of the wedge-shaped loading block can be converted into the transverse load transversely acting on the two pressure-pull transfer mechanisms, and thus, the compression load applied to the top of the wedge-shaped loading block can be converted into a pair of tensile loads acting on the inner surface of the annular rock core, so that the pure tensile load can be applied to the rock sample without adopting a bonding or clamping mode, the condition that the test fails due to bonding damage at the bonding part or clamping damage at the clamping part due to stress concentration in the existing direct tensile test method is avoided, and meanwhile, the tensile load is applied through the annular loading head matched with the inner surface of the annular rock core to be tested, the problem of eccentric tension in a direct tension test by a bonding or clamping method is avoided. In addition, the testing machine only needs to provide compression load, so that the testing equipment is low in requirement, the testing machine does not need to have a stretching function, and the testing machine can be widely applied to universal testing machines with various specifications and can realize static direct tensile strength testing of rocks. Meanwhile, the invention can also be arranged in a drop hammer testing machine, and can convert the impact force formed by the drop hammer falling into dynamic tensile force, thereby obtaining the dynamic direct tensile strength of the rock. The invention provides a device for testing static and dynamic direct tensile strength of an annular rock core loaded by using compression-tension conversion, which has the advantages of simple structure, convenient operation, convenient popularization and application in various conventional rock mechanical testing machines, realization of rock tensile strength testing under direct tensile conditions, real reaction on the tensile strength of rocks, and effective improvement on the accuracy of tensile strength parameter testing.
The invention also provides a method for testing static and dynamic direct tensile strength of the annular rock core, which comprises the following steps:
the method comprises the following steps: processing the obtained rock core into an annular rock core 17 with the thickness of 40-50 mm and the inner and outer diameters of 50-70 mm and 70-140 mm respectively;
step two: firstly, fixing a support base plate 2 on a rock mechanical compression testing machine platform through a fastening bolt so as to fix a bottom support seat 1; the two fixed bearing tables 4 are respectively and fixedly connected to the upper ends of the two supporting top plates 5 through first connecting bolts; then, the two pressing-pulling transferring mechanisms 8 are assembled on the two fixed bearing tables 4 in a sliding manner, and the inner ends of the two pressing-pulling transferring mechanisms 8 are in the initial positions of mutual abutting;
step three: sleeving a prepared annular rock core 17 outside a circular loading ring formed by enclosing of loading heads 15 on two pressure-pull transshipment mechanisms 8, ensuring that the annular rock core 17 is coaxial with the circular loading ring, then placing a wedge-shaped loading block 3 in a wedge-shaped groove formed between the transshipment blocks 11 on the two pressure-pull transshipment mechanisms 8, and ensuring that the upper end of the wedge-shaped loading block 3 is in a horizontal position;
step four: the compression testing machine is started to apply compression load on the top of the wedge-shaped loading block 3, the wedge-shaped loading block 3 converts the compression load P into a pair of symmetrical tensile loads T acting on the inner surface of the annular rock core 17 through the compression-tension transfer mechanism 8, the horizontal tension and the horizontal tensile displacement borne by the annular rock core 17 can be obtained by recording the vertical pressure and the vertical displacement applied by the compression testing machine, and the tensile strength sigma of the rock is obtained through calculation of a formula 1t；
In the formula: p is the maximum compressive load of the annular core 17 at the time of tensile failure, and the unit is N; t is the thickness of the annular core 17 in m; doIs the outer circular radius of the annular core 17 in m; diIs the inner circular radius of the circular core 17 in m.
The method has simple steps, can convert vertical pressure into two horizontal pulling forces acting on the inner surface of the annular rock core, so that the annular rock core is directly stretched and damaged, and can effectively and directly test the tensile strength of the rock sample in the horizontal direction, overcome the technical problems of bonding failure, stress concentration and eccentric stretching in the conventional direct tensile test, and more accurately obtain the tensile strength parameters of the rock; meanwhile, the invention is convenient to operate, can be suitable for various conventional rock mechanical testing machines, and has great popularization and application values.
Claims (9)
1. The device for testing the static and dynamic direct tensile strength of the annular rock core comprises a bottom supporting seat (1), wherein the length direction of the bottom supporting seat (1) extends along the left-right direction; the device is characterized by also comprising a fixed bearing table (4), a pressing-pulling transferring mechanism (8) and a wedge-shaped loading block (3);
the fixed bearing table (4) is horizontally arranged, and the upper end of the fixed bearing table is fixedly connected with a fixed guide rail (7) extending in the left-right direction; the two fixed bearing tables (4) are fixedly connected to the left part and the right part of the upper end of the bottom supporting seat (1) at intervals left and right;
the number of the pressing-pulling transshipment mechanisms (8) is two, and each pressing-pulling transshipment mechanism (8) consists of a sliding bearing platform (9), a transshipment block (11) and a loading unit (12); the sliding bearing table (9) is horizontally arranged, and the lower end of the sliding bearing table is provided with a sliding chute (10) extending in the left-right direction; the transfer block (11) is fixedly connected to the upper part of the inner end of the sliding bearing table (9), and a guide inclined plane (13) with a high outer part and a low inner part is arranged at the inner end of the transfer block; the loading unit (12) consists of a strip-shaped connecting block (14) and a semicircular loading head (15); the front end of the strip-shaped connecting block (14) is fixedly connected to the rear end face of the inner end of the transfer block (11); the inner end of the loading head (15) is fixedly connected with the rear end of the strip-shaped connecting block (14); the two pressing-pulling transferring mechanisms (8) are arranged above the two fixed bearing tables (4) in a left-right opposite mode, and the sliding bearing tables (9) are sleeved on the fixed guide rails (7) in a sliding mode through sliding grooves (10) so that the pressing-pulling transferring mechanisms (8) are in sliding fit with the fixed bearing tables (4) in the left-right direction; when the two pressure-pull transfer mechanisms (8) slide to a contact state, the two loading heads (15) form a circular loading ring;
the upper end of the wedge-shaped loading block (3) is of a plane structure, and the left side and the right side of the lower end of the wedge-shaped loading block are symmetrically provided with two loading inclined planes (16) which are high outside and low inside; the lower end of the wedge-shaped loading block (3) is arranged between the upper ends of the two transfer blocks (11), and the loading inclined planes (16) on the two sides are respectively in sliding fit with the guide inclined planes (13) of the two transfer blocks (11).
2. The device for testing the static and dynamic direct tensile strength of the annular rock core according to claim 1, wherein the bottom supporting seat (1) is composed of a supporting bottom plate (2), two supporting top plates (5) and two vertical supports (6), and the two supporting top plates (5) are arranged on the left part and the right part above the supporting bottom plate (2) in a left-right opposite mode; the two vertical supports (6) are correspondingly arranged below the two supporting top plates (5), the upper ends of the vertical supports (6) are fixedly connected with the lower end faces of the supporting top plates (5), and the lower ends of the vertical supports (6) are fixedly connected with the upper end faces of the supporting bottom plates (2); the middle part of the upper end of the supporting bottom plate (2) is fixedly connected with a limiting block (21) between the two vertical supports (6), and the height of the limiting block (21) is lower than that of the vertical supports (6).
3. The device for testing the static and dynamic direct tensile strength of the annular rock core according to claim 1 or 2, wherein a first bolt hole (18) matched with a platform of a pressure tester is formed in the periphery of the supporting bottom plate (2); a plurality of second bolt holes (19) are formed in the supporting top plate (5); a plurality of bolt holes III (20) are formed in the fixed bearing platform (4), and the fixed bearing platform is fixedly connected with the bottom supporting seat (1) through first connecting bolts penetrating through the bolt holes III (20) and the bolt holes II (19).
4. The device for testing the static and dynamic direct tensile strength of the annular rock core according to claim 3, wherein a plurality of bolts IV are arranged on the sliding bearing table (9); and a plurality of bolt holes five are formed in the transfer block (11), and the transfer block is fixedly connected with the sliding bearing platform (9) through connecting bolts two penetrating through the bolt holes four and the bolt holes five.
5. The device for testing the static and dynamic direct tensile strength of the annular rock core according to claim 4, wherein the sections of the fixed guide rail (7) and the sliding chute (10) are both in a dovetail shape.
6. The device for testing the static and dynamic direct tensile strength of the annular rock core as claimed in claim 5, wherein the rear end of the strip-shaped connecting block (14) extends to the rear end of the intrados of the loading head (15), and the rear end of the strip-shaped connecting block (14) is fixedly connected to the middle of the intrados of the loading head (15).
7. The annular rock core static and dynamic direct tensile strength testing device is characterized in that the strip-shaped connecting block (14) and the loading head (15) are of an integrated structure.
8. The annular core static and dynamic direct tensile strength testing device according to claim 7, wherein the inclination angles of the guide slope (13) and the loading slope (16) are consistent.
9. The method for testing the static and dynamic direct tensile strength of the annular rock core is characterized by comprising the following steps of:
the method comprises the following steps: processing the obtained core into an annular core (17);
step two: firstly, fixing a support base plate (2) on a rock mechanical compression testing machine platform through a fastening bolt so as to fix a bottom support seat (1); the two fixed bearing tables (4) are respectively and fixedly connected to the upper ends of the two supporting top plates (5) through a first connecting bolt; then the two pressing-pulling transferring mechanisms (8) are assembled on the two fixed bearing tables (4) in a sliding manner, and the inner ends of the two pressing-pulling transferring mechanisms (8) are in initial positions in mutual abutting joint;
step three: sleeving a prepared annular rock core (17) outside a circular loading ring formed by enclosing of loading heads (15) on two pressing and pulling transferring mechanisms (8), ensuring that the annular rock core (17) is coaxial with the circular loading ring, then placing a wedge-shaped loading block (3) in a wedge-shaped groove formed between the transferring blocks (11) on the two pressing and pulling transferring mechanisms (8), and ensuring that the upper end of the wedge-shaped loading block (3) is in a horizontal position;
step four: starting a compression testing machine to apply a compression load on the top of a wedge-shaped loading block (3), converting the compression load P into a pair of symmetrical tensile loads T acting on the inner surface of an annular rock core (17) through a compression-tension transfer mechanism (8) by the wedge-shaped loading block (3), and recording the vertical pressure and the vertical displacement applied by the compression testing machine to obtain the annular rock core (17)The tensile strength sigma of the rock is obtained by calculating the formula (1)t；
In the formula: p is the maximum compression load of the annular rock core (17) during tensile fracture, and the unit is N; t is the thickness of the annular core (17) in m; doIs the radius of the outer circular ring of the annular core (17) and the unit is m; diIs the inner circular radius of the circular core (17) in m.
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| CN115219366A (en) * | 2022-09-20 | 2022-10-21 | 徐州矿安新材料研究院有限公司 | Aluminum alloy plate detection device and detection method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115219366A (en) * | 2022-09-20 | 2022-10-21 | 徐州矿安新材料研究院有限公司 | Aluminum alloy plate detection device and detection method thereof |
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