CN109163975B - Rock biaxial tension experimental device and application method thereof - Google Patents

Abstract

The invention discloses a rock biaxial tensile experiment device and an application method thereof. The device comprises a base, a vertical fixed frame and a movable frame, and a horizontal telescopic assembly. The base is arranged horizontally, the fixed frame is connected to the center of the base, and the movable frame is sleeved on the fixed frame which can move up and down. The upper end of the fixed frame is connected with an upper stretch pad, and the lower end of the movable frame is connected with a lower stretch pad. The telescopic assembly includes a lateral loading plate and its connected force transmission member. The force transmission member is symmetrically connected to the base and is separated On both sides of the fixed frame, the upper end of the movable frame is linked with the force transmission member. The top surface and bottom surface of the sample are respectively bonded to the two tensile pads, and a pair of side surfaces are respectively bonded to the lateral loading plate. A downward vertical load is applied to the upper end of the movable frame, and the movable frame moves downwards while driving the transmission. The force member moves laterally, and the sample is stretched vertically and horizontally biaxially at the same time, and the experimental data is true and reliable.

Description

A kind of rock biaxial tensile test device and its application method

technical field

The invention relates to a rock mechanical parameter testing device, in particular to a rock biaxial tensile test device and an application method thereof.

Background technique

Rock, as a heterogeneous material, has undergone hundreds of millions of years of geological action, and its mechanical properties are also affected by its internal mineral composition and micro-cracks. Therefore, the mechanical properties of rock materials are important for evaluating the stability of underground engineering structures. index. Traditional rock mechanical property tests include uniaxial compression, uniaxial tension and shear tests, etc. The mechanical parameters obtained through these experimental testing methods can provide important references for general rock mass engineering design and support. However, the traditional mechanical performance test parameters cannot reflect the real stress state of the rock mass in all projects, such as the rock thin plate. The uniaxial tensile test has been unable to accurately describe the mechanical properties of the rock sheet.

At present, general rock testing machines are unable to perform biaxial tensile tests, and large-scale testing machines cannot further study the microscopic cracking behavior and mechanism of rocks under biaxial tension.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a biaxial tensile test device and an application method thereof which can test accurately and reliably and can effectively solve the problem that the current experimental system cannot perform the biaxial tensile test of rocks.

In the rock biaxial tensile test device provided by the present invention, the rock sample is a rectangular parallelepiped sample. The device includes a base, a vertical fixed frame, a movable frame, and a horizontal telescopic assembly. The base is arranged horizontally, the fixed frame is connected to the center of the base, and the movable frame is connected to the fixed frame through a sleeve that can move up and down. The upper end of the movable frame is located between the upper and lower ends of the movable frame, the upper end of the fixed frame is connected with an upper stretch pad, the lower end of the movable frame is connected with a lower stretch pad, and the telescopic assembly includes a transverse loading plate and its connected force transmission member , the force transmission member is symmetrically connected to the base and placed on both sides of the fixed frame. The upper end of the movable frame and the force transmission member are linked together. The top and bottom surfaces of the sample are respectively bonded to two tensile pads, a pair of The sides are respectively bonded to the lateral loading plate, and when a downward vertical load is applied to the upper end of the movable frame, the movable frame moves downward and drives the force transmission member to move laterally, and the sample is stretched vertically and laterally biaxially at the same time. .

In an embodiment of the above technical solution, the upper surface of the base is a horizontal plane, the fixed frame includes a horizontal top plate and a support member connected to the lower side of the horizontal top plate, and the lower end of the support member is connected to the upper surface of the base.

In an embodiment of the above technical solution, the movable frame includes a rectangular top plate, a rectangular bottom plate and a connecting column, the plane size of the rectangular top plate is larger than that of the rectangular bottom plate, and both are arranged horizontally, and the four corners of the rectangular bottom plate are respectively A connecting column is fixed, and the upper end of the connecting column passes through the horizontal top plate of the fixed frame and is fixed on the rectangular top plate.

In an embodiment of the above technical solution, a linear bearing is installed on the horizontal top plate of the fixed frame corresponding to the position of the connecting column, the upper end of the connecting column passes through the linear bearing, and the linear bearing guides the up and down movement of the connecting column. .

In an embodiment of the above technical solution, a rectangular groove is formed on the upper surface of the base corresponding to the rectangular bottom plate of the movable frame, and the rectangular bottom plate is located in the rectangular groove.

In an embodiment of the above technical solution, the force transmission member of the telescopic assembly is a transverse stretching rod, and the transverse stretching rod is equipped with a sliding rail, one end of the transverse stretching rod is connected to the transverse loading plate, and the other end passes through the sliding groove. The sliding rail is connected to the sliding rail symmetrically about the fixed frame, and the upper surface of the base corresponds to the longitudinal center plane of the rectangular top plate of the movable frame.

In an embodiment of the above technical solution, two ends of the rectangular top plate of the movable frame are respectively hinged with retractable linkage rods with the transverse stretching rods, and both ends of the linkage rod can rotate around the hinged joints.

In an embodiment of the above technical solution, a T-shaped groove is formed on the rectangular bottom plate of the movable frame, the cross-sectional shape of the lower stretch pad is an I-shaped, and the lower wing plate of the lower stretch pad is inserted. Connected to the T-slot.

In an embodiment of the above technical solution, the upper tensile pad is a rectangular plate, and a screw rod is connected at the central position thereof, and the screw rod is locked by a nut after passing through the horizontal top plate of the fixed frame.

The method for carrying out biaxial tensile experiments on rocks using the above technical solution provided by the present invention includes the following steps:

(1) Bond the lateral loading plate to a pair of side walls of the sample, and bond the sample to the upper surface of the lower tensile pad;

(2) Connect the lower tensile pad to the rectangular bottom plate of the movable frame;

(3) Lift the inner frame upward, and connect the lateral loading plate with the force transmission assembly;

(4) Bond the sample to the upper tensile pad;

(5) Use a rock shear rheometer to apply a downward vertical load to the upper end of the movable frame until the sample breaks and fail; during the loading process, a front camera is used to photograph the crack propagation process inside the sample, and record real-time Load, displacement and observation and photographing of the failure surface;

(6) Analyze the recorded data after the experiment;

(7) Replace the sample and repeat the above steps to apply different vertical loads to the sample.

The working principle of the present invention is as follows: the top surface of the sample is connected to the horizontal top plate of the fixed frame through the upper tensile pad and the screw nut, the bottom surface of the sample is connected to the rectangular bottom plate of the movable frame through the lower tensile pad, and the A pair of side walls are respectively connected with the symmetrically arranged retractable components. The upper end of the movable frame and the retractable components are connected together by linkage rods, so when a vertical downward load is applied to the movable top plate of the movable frame, the movable frame moves downward, and its rectangular bottom plate is pulled down by the lower tension pad. The specimen is pulled down, while the upper tensile pad pulls the specimen up. When the movable frame moves downward, the transverse stretching rod of the telescopic assembly slides out along the slide rail through the linkage rod, and at the same time, the transverse stretching is applied to the sample. That is to say, by applying a vertical load to the rectangular top plate of the movable frame, the vertical and lateral biaxial stretching of the specimen can be achieved at the same time.

With the linkage between the vertical movable frame and the horizontal telescopic assembly of the present invention, the sample can be simultaneously stretched vertically and laterally biaxially only by applying a vertical load, and the lateral stretching of the movable frame and the telescopic assembly The movement of the rod is stable and reliable, so it has the advantages of simple structure and convenient operation. At the same time, the load is applied by the rock axial loading instrument, so the experimental data obtained by the simultaneous biaxial stretching of the sample by this device is true and reliable, which can provide scientific experimental conditions for the excavation and design of underground engineering.

Description of drawings

FIG. 1 is a schematic front view of an embodiment of the present invention.

FIG. 2 is a schematic top view of FIG. 1 .

FIG. 3 is a schematic side view of FIG. 1 .

FIG. 4 is a schematic diagram of the assembly of the base, the fixed frame, the movable frame and the upper backing plate in FIG. 1 .

FIG. 5 is an assembly schematic diagram of the telescopic assembly, the telescopic linkage rod and the movable frame in FIG. 1 .

Detailed ways

As shown in FIG. 1 , in the rock biaxial tensile test device disclosed in this embodiment, the rock sample is a rectangular parallelepiped. The experimental device mainly includes a base 1 , a fixed frame 2 , a movable frame 3 , a telescopic assembly 4 , a linkage rod 5 , an upward pulling pad 6 , and a lower stretching pad 7 .

1 and 2 , the base 1 of the present embodiment is a rectangular seat, and a rectangular groove 11 is formed at the middle position of the upper surface in the length direction. The width of the rectangular groove is the same as the width of the base 1 .

1, 3 and 4, the fixed frame 2 of this embodiment is composed of a horizontal top plate 21 and four supporting plates at the lower corners, and the shape of the horizontal top plate is a rectangle.

1 , 3 and 4 , the lower ends of the four support plates of the fixed frame 2 are fixed on the base 1 , and the longitudinal center plane of the horizontal top plate 21 is coplanar with the longitudinal center plane of the rectangular groove 11 .

In order to ensure the overall performance of the base and the fixed frame, it can be considered that the base and the fixed frame are cut and formed with a convex-shaped integral steel.

1, 2 and 4, the movable frame 3 includes a rectangular top plate 31, a rectangular bottom plate 32 and a connecting column 33. The plane size of the rectangular top plate is larger than that of the rectangular bottom plate, and the two are arranged along the horizontal plane. The rectangular bottom plate 32 is located in the rectangular groove on the base 1, and its size is slightly smaller than that of the rectangular groove. The rectangular top plate 31 is located above the horizontal top plate 21 of the fixed frame 2 , the lower ends of the four connecting columns 33 are respectively fixed to the four corners of the rectangular bottom plate 32 , and the upper ends pass through the horizontal top plate 21 respectively and are connected and fixed to the rectangular top plate 31 . A linear bearing is installed on the horizontal top plate at the position corresponding to the connecting column, and the connecting column passes through the linear bearing 22 . When the connecting column moves up and down, the linear bearing not only has low friction but also plays a guiding role.

1, 2 and 5, it can be seen that the telescopic assembly 4 includes a transverse stretching rod 41, a rectangular loading plate 42 and a slide rail 43, and one end of the transverse stretching rod 41 is detachably connected vertically to the rectangular loading plate 42. At the central position, the other end is connected to the slide rail 43 through the chute, and the slide rail 43 is symmetrically connected to the upper surface of the base 1 with respect to the center plane in the longitudinal direction of the base 1 . The connection position of the sliding rail on the base corresponds to the longitudinal center plane of the rectangular top plate of the movable frame.

The slide rail 43 in this embodiment adopts a cylinder with an axial plane, and the circular arc angle of the cylinder is about 3/4 of the circumference angle. The sliding groove on the transverse stretching rod 41 wraps the sliding rail 43 as much as possible to ensure that the transverse stretching rod 41 is partially derailed during the sliding process.

1 , 3 and 5 , the two ends of the linkage rod 5 are hinged to the rectangular top plate 31 of the movable frame 3 and the transverse stretch rod 41 of the telescopic assembly 4 respectively through pins. The two ends of the central plane in the length direction of the rectangular top plate are respectively provided with hinged lugs, and the outer ends of the transverse stretch rods are provided with hinged grooves. The length of the linkage rod 5 is adjustable.

As shown in Figure 1, the upper tensile pad 6 is a rectangular plate, its plane size is the same as that of the top surface of the sample, and a screw 8 is connected at the center position, and the upper end of the screw rod passes through the center position of the horizontal top plate of the fixed frame After the installation hole, it is locked by the wing nut. The height position of the upper stretch pad can be adjusted by the screw.

As shown in FIG. 1 , a T-shaped groove is formed on the longitudinal center surface of the upper surface of the rectangular bottom plate of the movable frame 3 . The cross-sectional shape of the lower tensile pad 7 is I-shaped, and the lower wing plate is inserted into the T-shaped groove.

The working principle of this device is as follows: the top surface of the sample is connected to the horizontal top plate of the fixed frame through the upper tension plate and the screw nut, the bottom surface of the sample is connected to the rectangular bottom plate of the movable frame through the lower tension plate, and the bottom of the sample is connected to the rectangular bottom plate of the movable frame through the lower tension plate. A pair of side walls are respectively connected with the symmetrically arranged retractable components. The upper end of the movable frame and the retractable components are connected together by linkage rods, so when a vertical downward load is applied to the movable top plate of the movable frame, the movable frame moves downward, and its rectangular bottom plate is pulled down by the lower tension pad. The specimen is pulled down, while the upper tensile pad pulls the specimen up. When the movable frame moves downward, the transverse stretching rod of the telescopic assembly slides out along the slide rail through the linkage rod, and at the same time, the transverse stretching is applied to the sample. That is to say, by applying a vertical load to the rectangular top plate of the movable frame, the vertical and horizontal biaxial stretching of the sample can be realized at the same time, the structure is simple, and the operation is convenient and reliable.

The movement of the movable frame and the transverse tension rod is stable and reliable, and the load is applied by the rock axial loading instrument, so the experimental data obtained by the simultaneous biaxial tension of the sample by this device is true and reliable.

When the device performs biaxial tensile test on the sample, the whole device is placed on the rock axial loading machine, and the vertical load is applied through the axial loading table. The specific steps of the experiment are as follows:

(1) Apply strong glue to a pair of side walls of the sample, bond the lateral loading plate to the pair of side walls, then apply strong glue to the bottom surface of the sample, and bond the sample to the lower tensile pad on the upper wing.

(2) Insert the lower wing plate of the lower stretch pad into the T-slot on the rectangular bottom plate of the movable frame.

(3) Lift the inner frame upwards, and connect the transverse loading plate and the transverse tension rod with bolts.

(4) Apply strong glue on the top surface of the sample, and adjust the height position of the upper tensile pad through the screw connected to the upper tensile pad, so that the upper tensile pad is bonded to the top surface of the sample.

(5) Use the rock axial loading instrument to apply a downward vertical load to the rectangular top plate of the movable frame, and the loading rate is 0.1mm/min until the sample breaks and fails; during the loading process, a camera is used to monitor the crack propagation process inside the sample. Take pictures, record real-time load, displacement, and observe and take pictures of the failure surface. The setting of the camera corresponds to the front of the other pair of side walls of the specimen.

(6) After the experiment, parameters such as load and displacement can be saved and exported through Excel, and researchers can use these data to analyze the mechanical properties of rocks under biaxial tension.

(7) Replace the sample, apply different vertical loads to the sample, and repeat the experiment to obtain the corresponding data. The invention can not only realize the biaxial tensile test of the rock, but also facilitates the observation of the crack initiation and propagation process of the internal crack of the rock under the biaxial tensile test.

Claims (10)

1. The utility model provides a tensile experimental apparatus of rock biax, rock sample is cuboid shape appearance body, its characterized in that: the device comprises a base, a vertical fixed frame, a movable frame and a transverse telescopic component, wherein the base is transversely arranged, the fixed frame is connected at the central position of the base, the movable frame can be penetrated and connected on the fixed frame in an up-and-down motion way, the upper end of the fixed frame is positioned between the upper end and the lower end of the movable frame, the upper end of the fixed frame is connected with an upper stretching base plate, the lower end of the movable frame is connected with a lower stretching base plate, the telescopic component comprises a transverse loading plate and a force transmission piece connected with the transverse loading plate, the force transmission piece is symmetrically connected on the base and is respectively arranged at two sides of the fixed frame, the upper end of the movable frame is linked with the force transmission piece, the top surface and the bottom surface of a sample are respectively bonded with the two stretching base plates, a pair of side surfaces are respectively bonded with the transverse loading plate, when, the specimens were simultaneously biaxially stretched vertically and transversely.

2. The rock biaxial tension test device of claim 1, wherein: the upper surface of base is the horizontal plane, fixed frame includes horizontal roof and connects the support piece of horizontal roof downside, and the lower extreme of support piece is connected in the upper surface of base.

3. The rock biaxial tension test device of claim 2, wherein: the movable frame comprises a rectangular top plate, a rectangular bottom plate and connecting columns, the plane size of the rectangular top plate is larger than that of the rectangular bottom plate, the rectangular top plate and the rectangular bottom plate are both horizontally arranged, the connecting columns are respectively fixed at four corners of the rectangular bottom plate, and the upper ends of the connecting columns penetrate through the horizontal top plate of the fixed frame and then are fixed on the rectangular top plate.

4. The rock biaxial tension test device of claim 3, wherein: the upper end of the connecting column penetrates through the linear bearing, and the linear bearing guides the vertical movement of the connecting column.

5. The rock biaxial tension test device of claim 3, wherein: the upper surface of the base is provided with a rectangular groove at the position corresponding to the rectangular bottom plate of the movable frame, and the rectangular bottom plate is positioned in the rectangular groove.

6. The rock biaxial tension test device of claim 3, wherein: the force transmission piece of the telescopic assembly is a transverse stretching rod, the transverse stretching rod is matched with a sliding rail, one end of the transverse stretching rod is connected with the transverse loading plate, the other end of the transverse stretching rod is connected onto the sliding rail through a sliding groove, and the sliding rail is symmetrically connected to the upper surface of the base corresponding to the central surface of the movable frame rectangular top plate in the length direction.

7. The rock biaxial tension test device of claim 6, wherein: linkage rods are hinged between the two ends of the rectangular top plate of the movable frame and the transverse stretching rods respectively, and the two ends of each linkage rod can rotate around the hinged position.

8. The rock biaxial tension test device of claim 3, wherein: a T-shaped groove is formed in the rectangular bottom plate of the movable frame, the cross section of the lower stretching base plate is I-shaped, and the lower wing plate of the lower stretching base plate is inserted into the T-shaped groove.

9. The rock biaxial tension test device of claim 2, wherein: the upper stretching base plate is a rectangular plate, a screw rod is connected to the center of the upper stretching base plate, and the screw rod penetrates through the horizontal top plate of the fixed frame and then is locked through a nut.

10. A method of using the apparatus of claim 1 to perform biaxial stretching experiments on rock comprising the steps of:

(1) bonding a transverse loading plate to a pair of side walls of a sample, and bonding the sample to the upper surface of a lower tensile base plate;

(2) connecting the lower stretching base plate to the rectangular bottom plate of the movable frame;

(3) lifting the inner frame upwards, and connecting the transverse loading plate with the force transmission assembly;

(4) bonding the sample with the upper stretching base plate;

(5) applying a downward vertical load to the upper end of the movable frame by using a rock shear rheometer until the test sample is broken and destroyed; shooting a crack propagation process in the sample by adopting a front-mounted camera in the loading process, recording real-time load and displacement, and observing and shooting a damaged surface;

(6) analyzing the recorded data after the experiment is finished;

(7) and replacing the sample, repeating the steps and applying different vertical loads to the sample.

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