CN105865925A - Device for utilizing real triaxial testing machine to realize rock biaxial tension test - Google Patents

Abstract

A device that utilizes a true triaxial testing machine to realize a rock biaxial tension and compression test, including a sample bonding assembly, a tensile assembly and a support assembly, the specimen bonding assembly includes an upper groove plate and a lower groove plate, and the center of the upper groove plate is Screw holes are provided, and the tensile assembly includes a first top plate, a first bottom plate and connecting rods, the connecting rods are located on the groove walls on both sides of the groove of the first bottom plate, and there are also groove walls on both sides of the groove of the first bottom plate. A first through hole is opened, and the support assembly includes screws, a second top plate, a second bottom plate and a pillar, and a screw installation hole is opened in the center of the second top plate, and the pillar is installed in the first through hole of the tension assembly, and the second top plate There is also a second through hole on the top, the connecting rod of the tension assembly is installed in the second through hole, and the screw is installed in the screw installation hole and the screw hole. The device can accurately measure the strength and deformation of rock materials under biaxial tension and compression conditions by means of a true triaxial pressure testing machine.

Description

A device for rock biaxial tension and compression test using a true triaxial testing machine

technical field

The invention relates to a rock biaxial tension-compression test device realized by a true triaxial testing machine, which is suitable for research on deformation and failure characteristics of rock under tension-compression stress conditions, and belongs to the technical field of rock mechanics and engineering.

Background technique

Rockburst is a geological disaster phenomenon caused by the catapult rupture of the surrounding rock caused by the excavation and unloading of underground engineering in areas with high ground stress. The occurrence of rockburst usually leads to casualties of personnel, destruction of equipment and delay of construction period, resulting in significant economic losses. The mechanism of rockbursts is extremely complex, and there is no unified and clear theory to explain the phenomenon of rockbursts. Therefore, it is of great significance to carry out the indoor rockburst test, reproduce the rockburst phenomenon, and analyze the occurrence process of the rockburst in detail to promote the research on the damage mechanism of the rockburst. At present, existing studies have shown that the incubation process of rockbursts can be summarized into four stages: splitting into slabs, shearing into blocks, slab bending and breaking, and overall ejection. After the excavation of deep hard rock tunnels in high geostress areas, the stress state of the rock mass around the tunnel is: the circumferential compressive stress gradually increases. When the circumferential compressive stress exceeds the bearing capacity of the rock mass, it will cause the Tension splitting damage occurs in the surrounding rock. Under the action of the circumferential compressive stress of the tunnel and the radial deformation in the tunnel, the rock mass on the surface of the free face appears tension splitting damage to form a thin plate, and the thin plate appears under the circumferential pressure. Bending phenomenon, when the thin plate is bent to a certain extent, the thin plate will break, resulting in the ejection of the broken thin plate and the internal rock blocks at a certain initial velocity, thus forming a rockburst. Therefore, after the excavation of a deep-buried hard rock tunnel with high geostress, the cracked rock mass on the boundary of the free face will be subjected to tension in the radial direction of the tunnel and pressure in the tangential direction around the tunnel. are closely related to the special stress state. In addition, in the powerhouse of an underground hydropower station, rock masses such as surrounding rocks in contact with rock anchor beams and rock walls between hydroelectric generating units are often in a state of tension in one direction and compression in the other vertical direction. Therefore, it is of great theoretical value and engineering significance for the safety of deep underground tunnel engineering to study the mechanical properties of rock under the condition of biaxial tension and compression through laboratory experiments at the same time.

At present, the biaxial tension and compression test can be realized by a special spring tension and compression testing machine. The development of the spring tension and compression testing machine is relatively mature, and it has the characteristics of high measurement accuracy and high centering accuracy. However, this type of test equipment is relatively expensive, and the maintenance and use costs are high, and professional staff are required for use. In addition, the spring tension-compression testing machine is mainly used for testing the tensile-compression mechanical properties of small-sized specimens, which can provide low tensile-compressive stress, and is not suitable for high-stress tensile-compressive performance tests of large-sized rock specimens.

In addition to spring tension testing machines, there are many other devices for tension and compression testing of materials. For example: "Rock and Soil Mechanics" No. 11, 2007 introduced a dynamic direct tensile test device for rock materials with lateral pressure; the invention patent with the application publication number: CN101881716A introduced a quantitative tension-compression test device; authorized publication The patent No. CN201955268U introduces a loading test device for biaxial tension and compression of concrete. The physical structure of the above-mentioned tensile and compressive testing equipment is different, and the measurement methods used in the tensile and compressive testing of materials are also very different, and there is no unified evaluation standard for the obtained results.

The biaxial tension and compression test can also be realized by using a true triaxial compression testing machine combined with a special device. The true triaxial compression testing machine is a commonly used rock mechanics test equipment, which has the function of three-dimensional independent compression, and is used for the mechanical performance test of the three-dimensional stress complex state of the rock test. The true triaxial compression testing machine cannot directly perform biaxial tension and compression tests, but can be realized by special supporting devices.

The invention patent with application publication number CN102735542A describes a concrete multiaxial tension and compression method. Before the test, the tensile surface of the specimen was directly bonded to the compression plate. During the test, the specimen with the pressure plate attached is placed on the triaxial testing machine, the pressure plate and the loading push head are connected by bolts, and the loading push head is far away from each other to realize the tension of the rock sample. At the same time, the compressive stress is directly applied to the specimen through the compressive loading plate. During the test, the operation process is more complicated, it is not easy to center, and it is difficult to ensure that the test piece is evenly stressed by preloading.

The invention patent with the application publication number CN102323157A discloses a method for combining tensile and compressive stresses of concrete. Firstly, the plastic brush is bonded to the test piece with glue, and the tooth surface of the plastic brush is placed on the tensile surface of the test piece and compacted. Then stick the bonded steel plate and the base surface of the brush with an adhesive. During the test, the bonded steel plate and the force-transmitting steel plate are bonded together by bolts with spherical hinges, and the force-transmitting steel plate is far away from each other to realize the tension of the rock sample. At the same time, the pressure is directly applied to the rock sample through the pressure loading plate. Using this device for tension and compression test requires complicated sample preparation. The brush and the bonded steel plate, the bonded steel plate and the force-transmitting steel plate are pasted together by adhesive glue, which may easily cause uneven stress on the rock sample during the test process, resulting in large errors.

The patent for invention with the application publication number CN103487317A introduces a design method of pusher head under tension and compression loading under concrete multiaxial test. The device does not need to use structural glue to connect the cubic specimen and the pressure plate, but connects the tensile loading plate through the embedded components inside the specimen. The pull loading plate and the loading push head are connected by a tie rod with a semicircular ball hinge, which ensures the precise alignment of the loading push head and the pull loading plate. The loading pushers are far away from each other to realize the tension of the rock sample. While applying tension, the pressure-loaded plate is fixed on the test piece by electromagnetic lock, and the pressure is directly applied to the test piece through the pressure-loaded plate. This device has special requirements for the test piece and is not suitable for the research on the tensile and compressive deformation and failure of rock materials.

The tension-compression devices introduced in the above documents are mainly used for tension-compression tests of concrete, and less for rocks.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention provides a device for realizing a rock biaxial tension-compression test by using a true triaxial testing machine, which makes it possible to carry out a biaxial tension-compression test in combination with a true triaxial testing machine.

In order to achieve the above object, the present invention adopts the following technical solutions:

A device that utilizes a true triaxial testing machine to realize rock biaxial tension and compression tests, including a sample bonding assembly, a tensile assembly and a support assembly,

The test piece bonding assembly includes an upper slot plate and a lower slot plate, and the center of the upper slot plate is provided with a screw hole,

The tensile assembly includes a first top plate, a first bottom plate and a connecting rod, the first bottom plate is provided with a groove with an inverted T-shaped cross section, and the connecting rods are located on the groove walls on both sides of the first bottom plate groove, connecting The upper end of the rod is fixed on the first top plate, the lower end of the connecting rod is fixed on the first bottom plate, the groove walls on both sides of the groove of the first bottom plate are also provided with first through holes,

The support assembly includes screws, a second top plate, a second bottom plate and a pillar, the center of the second top plate is provided with a screw installation hole, the pillar is installed in the first through hole of the tension assembly, and the upper end of the pillar is fixed on the second top plate, The lower end of the pillar is fixed on the second bottom plate, and the second top plate is also provided with a second through hole, the connecting rod of the tension assembly is installed in the second through hole, and the screw is installed in the screw mounting hole and the screw hole.

It also includes a compression assembly, the compression assembly includes two pressure bearing plates and two pressure plate connectors, the two pressure bearing plates are respectively installed on two opposite sides of the rock sample, and the two pressure plate connectors are respectively installed on the rock On the other two opposite sides of the sample, the two ends of the pressure bearing plate are respectively provided with screw holes, and the connecting parts of the pressure plate are respectively provided with long strip-shaped through holes near the two ends, and the limit screws are installed through the long strip through holes. in the screw hole.

The screw is a ball head screw, and the shape of the screw mounting hole matches the ball head screw.

The connecting rods are installed at the four corners between the first top board and the first bottom board to form a cube frame, and the pillars are installed at the four corners of the second top board and the second bottom board to form a cube frame.

An operation through hole is arranged on the first top plate.

During the test, the sample is also included. The upper end of the sample is bonded in the groove of the upper groove plate, and the lower end of the sample is bonded in the groove of the lower groove plate. The lower groove plate is closely fitted and installed in the horizontal part of the inverted T-shaped groove. , the sample is installed in the vertical part of the inverted T-shaped groove.

The sample is in the shape of a cube, and the grooves of the lower slot plate and the upper slot plate are in the form of square grooves that closely match the top and bottom surfaces of the sample.

Compared with the prior art, the present invention has the beneficial effects:

(1) Research on the tensile and compressive characteristics of large-scale rock specimens: this device can be used for tensile and compressive tests on rock specimens with a size of 200mm×200mm×200mm (length×width×height).

(2) Ensure that the test piece bears force on the axis of force and is not eccentric: the upper and lower ends of the test piece are fixed in the groove of the bonding plate by adhesive glue to ensure that the center of the test piece and the center of the cemented plate are accurately aligned. The ball screw is used to pass through the center screw holes of the upper pressure plate of the B frame and the upper bonding plate to ensure that the centers of the upper frame pressure plate and the bonding plate are accurately aligned.

(3) Simple operation: install the cube specimen into the device, and apply the load to the device according to the loading method of ordinary mechanical experiments, and then the tension and compression test of the specimen can be realized.

(4) It is beneficial to the centering of the sample and can ensure uniform force. With the help of a true triaxial pressure testing machine, the strength and deformation of rock materials under biaxial tension and compression conditions can be accurately measured. The installation and disassembly of the fixture is convenient, and the test process is easy to operate. Therefore, compared with the existing rock tension-compression test equipment, the tension-compression test device is simpler and more practical.

(5) Realize the mechanical test of the tension-compression rock sample under the tension-compression condition, which provides an effective research method for analyzing the deformation and failure characteristics of the rock mass under the tension-compression stress state.

Description of drawings

Fig. 1 is a schematic diagram of the structure when the tensile component and the support component are assembled together.

Figure 2 is a schematic cross-sectional view of the bonded assembly structure of the specimen.

Fig. 3 is a schematic diagram of the structure of the stretching assembly.

Fig. 4 is a structural schematic diagram of the support assembly.

Figure 5 is a schematic diagram of the installation of the compression assembly.

Fig. 6 is a planar cross-sectional schematic diagram 1 of the overall structure of the biaxial tension-compression device.

Fig. 7 is a second schematic plan view of the overall structure of the biaxial tension-compression device.

detailed description

The technical solution of the present invention will be further elaborated below through examples.

Example 1

A device that utilizes a true triaxial testing machine to realize rock biaxial tension and compression tests, including a sample bonding assembly, a tensile assembly and a support assembly,

The test piece bonding assembly includes an upper slot plate 10 and a lower slot plate 8, and the center of the upper slot plate 10 is provided with a screw hole 13,

The tensile assembly includes a first top plate 1, a first bottom plate 4, and a connecting rod 2. The first bottom plate 4 is provided with a groove with an inverted T-shaped cross section, and the connecting rods 2 are located on both sides of the groove of the first bottom plate 4. On the groove wall, the upper end of the connecting rod 2 is fixed on the first top plate 1, the lower end of the connecting rod 2 is fixed on the first bottom plate 4, and the first through hole 15 is also opened on the groove walls on both sides of the groove of the first bottom plate 4 ,

The support assembly includes screws 14, a second top plate 3, a second bottom plate 6 and a pillar 5, the center of the second top plate 3 is provided with a screw mounting hole 17, the pillar 5 is installed in the first through hole 15 of the tension assembly, and the pillar 5, the upper end is fixed on the second top plate 3, the lower end of the pillar 5 is fixed on the second bottom plate 6, and the second top plate 3 is also provided with a second through hole 16, and the connecting rod 2 of the tensile assembly is installed in the second through hole, Screws 14 are installed in screw mounting holes 17 and screw holes 13 .

It also includes a compression assembly, which includes two pressure bearing plates 12 and two pressure plate connectors 9, the two pressure bearing plates 12 are respectively installed on two opposite sides of the rock sample 7, and the two pressure plate connectors 9 are respectively installed on the other two opposite sides of the rock sample 7, the two ends of the pressure bearing plate 12 are respectively provided with screw holes, the pressure plate connector 9 is respectively provided with strip-shaped through holes near the two ends, and the limit screw Installed in the screw hole through the strip through hole.

The screw 14 is a ball head screw, and the shape of the screw mounting hole 17 is matched with the ball head screw.

The connecting rods 2 are installed at the four corners between the first top board 1 and the first bottom board 4 to form a cube frame, and the pillars are installed at the four corners of the second top board 3 and the second bottom board 6 to form a cube frame.

An operation through hole 18 is provided on the first top plate. The through hole 18 is operated for the convenience of installing or removing the screw 14 .

During the test, sample 7 is also included. The upper end of sample 7 is bonded in the groove of the upper slot plate 10, the lower end of sample 7 is bonded in the groove of the lower slot plate 8, and the lower slot plate 8 is closely fitted and installed on the inverted T. The horizontal part of the T-shaped groove, and the sample 7 is installed in the vertical part of the inverted T-shaped groove.

The sample 7 is in the shape of a cube, and the grooves of the lower slot plate 8 and the upper slot plate 10 are in the form of square grooves that closely match the top and bottom surfaces of the sample 7 .

The steps of using the device of the present invention are as follows:

(1) Take a cube-shaped rock sample 7, spread the adhesive glue with higher viscous strength evenly on the groove bottom of the upper groove plate 10 and the lower groove plate 8, the inner wall around the groove and the upper and lower sides of the rock sample 7 At both ends, put the rock sample 7 into the square groove of the lower groove plate 8, and buckle the upper groove plate 10 on the upper end of the rock sample to ensure that the upper and lower end surfaces and the left and right end surfaces are closely attached to the groove surface and the inner wall of the groove. There are no cracks, and the contact area between the test piece and the bonding plate is increased. After placing it for 24 hours, the bonding glue solidifies, and the viscosity between the rock sample 7 and the upper groove plate 10 and the lower groove plate 8 reaches a certain strength.

(2) Install the assembled test piece bonding assembly into the tensile assembly, the lower groove plate 8 is installed in the horizontal part of the inverted T-shaped groove closely, and the rock sample 7 is installed in the vertical part of the inverted T-shaped groove. part. The cross-section is an inverted T-shaped groove, which means that the width of the bottom horizontal part of the groove is greater than the width of the vertical part at the opening, so the lower groove plate 8 is stuck in the horizontal part of the groove.

(4) Lift up the first bottom plate 4, screw the screw 14 into the screw mounting hole 17 and the screw hole 13, so that the upper slot plate 10 and the second top plate 3 are fixed together, and at the same time, it is necessary to ensure that the test piece can be accurately aligned. , no eccentricity when the vertical force is applied.

(5) Install two pressure bearing plates 12 and two pressure plate connectors 9. Since the pressure plate connectors 9 are provided with elongated through holes near both ends, the two pressure bearing plates 12 can move toward the center to apply force , the external load can be uniformly applied to the surface of the rock sample 7 through the pressure bearing plate 12 .

(6) Place the above-mentioned assembled test device in the pressure chamber of a true triaxial press, and gradually apply vertical axial pressure to the first top plate 1, the entire tensile assembly moves downward, and the first bottom plate 1 moves downward, Since the lower groove plate 8 is buckled in the first bottom plate 4, the vertical axial pressure drives the rock sample 7 to move downward together. While the support assembly is fixed, the upper end surface of the rock sample 7 is fixed together with the second top plate 3 through the upper groove plate 10, the upper end of the rock sample 7 is fixed, and the lower end moves downward, so that the rock sample 7 is vertically vertical. The purpose of the direction of the pull.

(7) While being tensioned in the vertical direction, the horizontal push head 11 of the true triaxial pressure testing machine is used to apply pressure to the rock specimen 7 through two pressure bearing plates 12, thereby realizing the pulling of the rock specimen 7 in the room. Stress test.

(4) During the tension and compression test of the rock specimen 7, the stress and strain signals can be collected through the force sensor and the external LVDT differential deformation sensor, and transmitted to the computer. Record the stress-strain relationship curves in the direction of tensile stress and compressive stress in detail, and finally obtain the tensile and compressive strength of the rock when the rock is damaged, as well as the tensile deformation and compression deformation of the rock.

The working principle of this device is: use the two sets of frame structures of the device to convert the vertical pressure into vertical tension, so that the upper and lower ends of the test piece are pulled. In addition, the pressure is directly applied to one horizontal axis of the specimen through the pressure bearing plate. In this way, the biaxial tension and compression loading of the rock specimen is realized. The function of the specimen bonding assembly is to fix the rock specimen. The function of the tension component is to convert the pressure into tension and apply it to both ends of the rock specimen. The upper and lower ends of the test piece are fixed in the grooves of the upper slot plate 10 and the lower slot plate 8 by adhesive glue, to ensure that the center of the test piece is accurately aligned with the center of the upper slot plate 10 and the lower slot plate 8, and to ensure that the first top plate 1 and the lower slot plate 8 are accurately aligned. The center of the upper groove plate 10 is accurately aligned to ensure that when the pressure is applied, the axis of the test piece is pulled without eccentricity.

Claims (7)

1. A device utilizing a true triaxial testing machine to realize a rock biaxial tension-compression test is characterized in that it comprises a sample bonding assembly, a tensile assembly and a support assembly, The test piece bonding assembly includes an upper slot plate and a lower slot plate, and the center of the upper slot plate is provided with a screw hole, The tensile assembly includes a first top plate, a first bottom plate and a connecting rod, the first bottom plate is provided with a groove with an inverted T-shaped cross section, and the connecting rods are located on the groove walls on both sides of the first bottom plate groove, connecting The upper end of the rod is fixed on the first top plate, the lower end of the connecting rod is fixed on the first bottom plate, the groove walls on both sides of the groove of the first bottom plate are also provided with first through holes, The support assembly includes screws, a second top plate, a second bottom plate and a pillar, the center of the second top plate is provided with a screw installation hole, the pillar is installed in the first through hole of the tension assembly, and the upper end of the pillar is fixed on the second top plate, The lower end of the pillar is fixed on the second bottom plate, and the second top plate is also provided with a second through hole, the connecting rod of the tension assembly is installed in the second through hole, and the screw is installed in the screw mounting hole and the screw hole. 2. The device for utilizing a true triaxial testing machine to realize a rock biaxial tension-compression test as claimed in claim 1, further comprising a compression assembly comprising two pressure bearing plates and two pressure plates connected The two pressure bearing plates are respectively installed on two opposite sides of the rock sample, and the two pressure plate connectors are respectively installed on the other two opposite sides of the rock sample. The two ends of the connecting piece of the pressure plate are respectively provided with strip-shaped through holes, and the limit screws pass through the strip through holes and are installed in the screw holes. 3. The device for realizing rock biaxial tension-compression testing by using a true triaxial testing machine as claimed in claim 1, wherein the screw is a ball-head screw, and the shape of the screw mounting hole matches the ball-head screw. 4. The device of utilizing a true triaxial testing machine to realize a rock biaxial tension and compression test as claimed in claim 1, wherein the connecting rods are installed at four corners between the first top plate and the first bottom plate to form a cube frame , the pillars are installed at the four corners of the second top plate and the second bottom plate to form a cube frame. 5. The device for realizing the rock biaxial tension and compression test by using a true triaxial testing machine as claimed in claim 1, characterized in that, the first top plate is provided with an operation through hole. 6. the device utilizing true triaxial testing machine to realize rock biaxial tension-compression test as claimed in claim 1, is characterized in that, during test, also comprises sample, and the upper end of sample is bonded in the groove of upper groove plate , the lower end of the sample is bonded in the groove of the lower slot plate, the lower slot plate is closely fitted and installed in the horizontal part of the inverted T-shaped groove, and the sample is installed in the vertical part of the inverted T-shaped groove. 7. utilize true triaxial testing machine to realize the device of rock biaxial tension-compression test as claimed in claim 6, it is characterized in that, described sample is cube shape, the groove of described lower groove plate and the groove of upper groove plate The shape of the groove is a square groove that closely fits the top and bottom surfaces of the sample.