CN113281190B - Hydraulic asphalt concrete direct tensile test device and application method thereof - Google Patents

Abstract

The invention discloses a hydraulic asphalt concrete direct tensile test device, which comprises a test piece connecting system, a sensor system, an acquisition system, a loading system and a temperature control system; the test piece connecting system comprises a sliding T-shaped connecting piece, a floating spherical hinge, a stretching clamp, a test piece, a Y-shaped connector and an I-shaped connector, wherein the floating spherical hinge is connected with the T-shaped connecting piece, the stretching clamp and the Y-shaped connector and the I-shaped connector; the sensor comprises a force sensor and a grating displacement sensor, and the force sensor is respectively connected with the T-shaped connecting piece and the floating spherical hinge; the loading system is an MTS static power actuator fixed on the loading table top, dynamic loading modes such as static and sine can be provided, the temperature control system is a high-low temperature environment box, and the application method of the device is also provided, so that the problems that centering is difficult in the installation and loading process in the hydraulic asphalt concrete tensile test, the size of a test piece is small, the connection between the test piece and a clamp is unstable, the installation process is complex, and the test precision is low are solved.

Description

A hydraulic asphalt concrete direct tension test device and its application method

technical field

The invention belongs to the technical field of civil engineering experiments, and relates to a direct tension test device for hydraulic asphalt concrete.

The invention also relates to an application method of a hydraulic asphalt concrete direct tension test device.

Background technique

Hydraulic asphalt concrete is a composite material mixed with coarse aggregate, fine aggregate, asphalt, filler and other materials in a certain proportion. It has the advantages of good deformation performance and strong anti-seepage performance. It is mainly used in hydraulic anti-seepage In solid structures, such as anti-seepage core walls or panels of earth-rock dams. A large number of studies have shown that when the dam foundation of an earth-rock dam has uneven settlement, the asphalt concrete face will inevitably be subjected to tensile stress; Avoid being affected by the tensile stress, and the tensile stress increases with the increase of the height of the core wall dam. In actual engineering, the tensile strength and tensile deformation of asphalt concrete are much lower than the compressive strength and compression deformation, so the size and degree of damage of the anti-seepage body structure largely depend on the tensile mechanical properties of the asphalt concrete material. When the asphalt concrete is structurally cracked and damaged, it is bound to cause great harm to the safety of the dam.

The common methods for testing the tensile mechanical properties of asphalt concrete materials include direct tensile test, split test and bending test, and the axial direct tensile test is the most suitable and accurate test method to obtain the tensile mechanical properties of materials. However, there are several major problems in the current axial direct tensile test of asphalt concrete materials: First, it is difficult to ensure the axial tensile state of the specimen during the installation and loading process, resulting in large errors in the tensile mechanical indicators of the test. Second, according to the characteristics of raw materials and molding of hydraulic asphalt concrete, an appropriate tensile test piece size should be selected. Existing specimens for hydraulic asphalt concrete direct tension tests are prisms with a size of 40mm×40mm×220mm. For such small-sized prism specimens, if they are directly molded and prepared, the compactness cannot be guaranteed, and the water quality cannot be achieved. The anti-seepage performance requirements of asphalt concrete, so usually, this kind of prism specimens are formed by laboratory molding (Marshall compaction molding, static pressure molding, etc.) or on-site core sampling, and then made by cutting , and re-cutting will inevitably cause initial damage to the specimen. In addition, the maximum aggregate size of hydraulic asphalt concrete is 19mm, and the influence of aggregate size effect needs to be considered when carrying out tensile tests with specimens with a cross-sectional size of 40mm×40mm. The third is that the connection mode between the specimen and the fixture affects the accuracy of the test results. Asphalt concrete is a kind of heterogeneous phase change material. Temperature or loading rate has a significant impact on its mechanical properties such as tensile strength and stiffness. The rigidity of the connection between the parts and the fixture is greater. In addition, when a larger cross-sectional size specimen is used for tensile testing, higher requirements are placed on the stiffness and stability of the connection between the specimen and the fixture. Fourth, when the material cracks, the crack expands rapidly and the stress drops sharply. The acquisition accuracy of existing sensors is difficult to accurately measure the stress-strain curve of the specimen after reaching the peak stress.

Therefore, according to the material characteristics of hydraulic asphalt concrete, it is of great theoretical significance and engineering application value to carry out research on the axial tensile test device and its application method of hydraulic asphalt concrete.

Contents of the invention

The purpose of the present invention is to provide a hydraulic asphalt concrete direct tensile test device, which solves the difficulties in the installation and loading process in the existing hydraulic asphalt concrete tensile test, the small size of the test piece, the difficulty of the test piece and the fixture The connection is not firm, the installation process is cumbersome, and the test accuracy is low.

Another object of the present invention is to provide an application method of a hydraulic asphalt concrete direct tensile test device.

The first technical solution adopted by the present invention is a hydraulic asphalt concrete direct tensile test device, which includes a support frame body, a horizontal beam is installed on the top of the support frame body, and a horizontal beam parallel to the beam is installed on the bottom of the support frame body. Loading the table top, the bottom of the crossbeam is connected with an MTS actuator, the bottom of the MTS actuator is connected with a first sliding T-row connector, and the first sliding T-row connector is connected to the first tensile fixture through a first floating ball hinge; A tension sensor is also arranged between the first sliding T-line connector and the first floating ball joint;

The top of the loading table is connected with a loading platform base, and the end of the loading platform base away from the loading table is connected with a second sliding T-row connector, and the second sliding T-row connector is connected with a second tensioning fixture through a second floating ball hinge, The first tensile fixture and the second tensile fixture are opposite, and the above-mentioned components are all located on the central axis of the crossbeam and the loading table; a test piece is also included, and the test piece is clamped between the first tensile fixture and the second tensile fixture. Between the clamps, a grating displacement sensor is arranged on the test piece, and a high and low temperature environment box is included, and the test piece is located in the high and low temperature environment box.

The first technical solution of the present invention is characterized in that:

The supporting frame body also includes two steel columns arranged in parallel, the two steel columns are located between the beam and the loading platform, and the steel column is perpendicular to the beam;

Wherein the first sliding T-row connecting piece includes a first chute and a first card slot, the first chute is fixedly connected with the MTS actuator, and also includes a first T-shaped connecting piece, the level of the first T-shaped connecting piece The end is embedded in the first card slot, and a plurality of steel rollers are arranged inside the first card slot, and the first T-shaped connector is movably connected with the first card slot through the steel rollers; the vertical end of the first T-shaped connector A screw hole is opened on the top, a screw is embedded in the screw hole, the first T-shaped connector is fixedly connected with the first floating ball hinge through the screw, and the tension sensor is located at the vertical end of the first T-shaped connector;

Wherein, fastening bolts are respectively arranged on both sides outside the first card slot, and the fastening bolts extend into the first card slot and connect with the first T-shaped connector;

Wherein the second sliding T row connector has the same structure as the first sliding T row connector, the chute of the second sliding T row connector extends into the loading platform base and is fixedly connected with the loading platform base, the T of the second sliding T row connector The type connector is connected with the second floating ball joint;

Wherein the first tensile fixture includes a C-shaped fixture and side plates located on both sides of the C-shaped fixture, the side plates and the C-shaped fixture are connected by bolts, and a screw hole is provided at the bottom of the C-shaped fixture, and a screw is embedded in the screw hole , one end of the first floating ball joint away from the first sliding T row connector is fixedly connected to the first tensioning fixture through a screw;

Wherein the structure of the second stretching fixture is the same as that of the first stretching fixture, the bottom of the second stretching fixture is connected with a Y-shaped joint through a screw hole, the open end of the Y-shaped joint is embedded with an I-shaped joint, and also includes a cylindrical pin, The cylindrical pin passes through the Y-shaped joint and the I-shaped joint in sequence to fix the Y-shaped joint and the I-shaped joint, and the end of the I-shaped joint away from the Y-shaped joint is connected with the end of the second floating ball joint away from the second sliding T-row connector;

Among them, the specimen is a dumbbell-shaped specimen, the height and width dimension b of the test area of the specimen is 3 to 5 times that of the largest aggregate, the aspect ratio l/b of the test area is 1.2 to 1.5, and the total length L of the specimen and the test The ratio of the width b in the middle of the area is 3.5 to 4.5, the ratio of the total length L to the width B of the end of the specimen is 2.5 to 3, and the side slope n is 2.5 to 4; the specimen is located between the first tensile fixture and the second tensile Between the fixtures, one end of the test piece is embedded in the C-shaped fixture of the fixture, and the test piece is fixedly connected to the C-shaped fixture through a strong adhesive layer, and a rubber pad is also arranged between the side plate and the test piece;

The two ends of the bottom of the high and low temperature environment box are respectively connected with lifting frames, and the lifting frames are fixed on the loading table and located on both sides of the loading platform base. A guide rail is arranged at the end of the joint, and a card slot is embedded in the guide rail, and the wheels are located in the guide rail and cooperate with the guide rail.

The second technical scheme of the present invention is, a kind of application method of hydraulic asphalt concrete direct tensile test device, adopts above-mentioned a kind of hydraulic asphalt concrete direct tensile test device, specifically implements according to the following steps:

Step 1, test piece molding: laboratory molding or on-site molding;

The specific process of on-site forming is as follows: through on-site core drilling and sampling preparation, first drill a sample with a length of not less than 320mm with a drill with an inner diameter of not less than 150mm, and then cut it according to the shape of the test piece; the test piece obtained in this way is long, Width and height deviations are ±2mm, ±1mm and ±1mm respectively;

The specific process of laboratory molding is as follows: first, the forming mold is assembled, and the forming mold includes two forming side plates, two end plates and a bottom plate, and the joint plates are connected by bolts, and the center of the forming side plate is provided with a test piece. The matching protrusions, the molding process is single-layer double-sided compaction molding, the specific steps are: first mix the asphalt mixture, the temperature range of the asphalt mixture is 145 ° C ~ 155 ° C, heat the forming mold to 100 ° C ~ 110 ° C, apply Brush the release agent, put the prepared asphalt mixture into the forming mold, after the asphalt mixture is paved, place a flat plate on the upper part, adjust the flatness of the asphalt mixture by observing the level bead, and pull the compaction hammer to the predetermined height Free fall, compact the test piece evenly, then install the bottom plate in the forming mold to the upper part, turn over the test piece, take the same steps to compact the test piece twice, the number of times of compaction reaches the Marshall standard with the density of the test piece The density of the compacted test piece is ±1%, and the height dimension deviation is ±1mm;

Step 2, polish the test piece, remove the mold after the test piece is naturally cooled, polish the connection area at the end of the test piece, polish the upper and lower end surfaces of the test piece flat, and polish the side and inclined surface into a honeycomb pitted surface;

Step 3, connect the test piece and the fixture; connect the two ends of the test piece to the first tensile fixture and the second tensile fixture respectively through strong adhesive and rubber pad, and then delineate the test area, the length of the test area is not less than 100mm, Use a vernier caliper to measure and record the cross-sectional size at both ends and the middle of the test area, install a grating displacement sensor in the test area, and the grating displacement sensor is symmetrically distributed around the test piece and arranged flush;

Step 4, install the test piece; arrange the first sliding T-shaped connector and the second sliding T-shaped connector vertically, connect and fix the chutes of the two connecting parts with the MTS actuator and the loading table respectively, and pass the steel roller Adjust the position of the T-shaped connector, and use the infrared vertical instrument to ensure that the centerlines of the upper and lower T-shaped connectors coincide, and then tighten the fixing slot to fix the T-shaped connector; put the tension sensor, the first floating ball joint, and the first tensile fixture Connect the test piece with the first sliding T-shaped joint in turn, connect the second floating ball joint with the second sliding T-shaped joint, let the test piece be in a free plumb state, and connect the Y-shaped joint and the I-shaped joint with the first sliding T-shaped joint respectively. The second tensile fixture is connected with the second floating ball joint, and the cylindrical pin is inserted to complete the connection and installation of the test piece and the loading equipment; by adjusting the screw spacing between the second floating ball joint and the Y-type joint and the I-type joint, the initial tension is adjusted. Stretch state;

Step 5, test preloading; connect the tension sensor and grating displacement sensor to the acquisition system, check each test equipment, debug the MTS actuator, set the loading system, and perform preloading at room temperature. The preloading range is hydraulic When the tensile strength of the asphalt concrete is 20% to 40%, the reading of the displacement sensor changes evenly, then proceed to the next step, otherwise, adjust the connection system of the specimen again until the preloading condition is met;

Step 6, constant temperature test piece; fix the high and low temperature environment through the fixed card slot, set the test temperature, and keep the temperature constant for the test piece. The constant temperature time is not less than 6 hours; if there is no special regulation on the test temperature, the annual average temperature of the project location can be used or 20°C and 5°C;

Step 7, the test is formally loaded; after the above steps are prepared, carry out the tensile test according to the set loading system, record the data of the tension sensor and displacement sensor during the test, until the specimen is loaded and destroyed, and calculate the tensile strength, deformation and other information , draw the tensile stress-strain curve.

The beneficial effects of the present invention are:

A hydraulic asphalt concrete direct tension test device and its application method according to the present invention, the sliding T-shaped connector and the floating spherical joint greatly reduce the eccentricity of the asphalt concrete in the process of installation and tension; The Y-type joint and I-type joint of the system can be quickly installed; the shape of the specimen and the connection method between the specimen and the tensile fixture have broken through the problem that the tensile test of asphalt concrete is limited by the size of the specimen, and can achieve a large tensile fracture surface. The probability occurs in the middle section of the specimen; the specimen connection system is equipped with a high-precision, high-sensitivity tension sensor and a displacement sensor, which can not only accurately collect the mechanical data before the specimen reaches the tensile strength, but also accurately test the specimen to reach the tensile strength. In short, a hydraulic asphalt concrete direct tensile test device and its application method can not only carry out direct tensile test of hydraulic asphalt concrete under unidirectional loading state, but also can test tensile strength of hydraulic asphalt concrete. - Tensile mechanical properties under reciprocating loading conditions such as pulling cycle and loading and unloading; it is not only suitable for static and dynamic tensile mechanical tests of asphalt concrete under normal temperature conditions, but also for testing tensile mechanical properties under low temperature conditions.

Description of drawings

Fig. 1 is a kind of hydraulic asphalt concrete sample direct tensile test device schematic diagram of the present invention;

Fig. 2 a is a schematic diagram of the size of the test piece in a hydraulic asphalt concrete test piece direct tensile test device of the present invention;

Fig. 2 b is a schematic diagram of the size of one end of the test piece in a hydraulic asphalt concrete test piece direct tensile test device of the present invention;

Fig. 2c is a schematic diagram of the size of the other end of the test piece in a hydraulic asphalt concrete test piece direct tensile test device of the present invention;

Fig. 3 a is a schematic diagram of the side structure of a sliding T-shaped piece in a hydraulic asphalt concrete specimen direct tension test device of the present invention;

Fig. 3 b is a schematic diagram of the front structure of a sliding T-shaped piece in a hydraulic asphalt concrete specimen direct tensile test device of the present invention;

Fig. 4 is a schematic drawing of the tensile fixture in the direct tension test device of a hydraulic asphalt concrete specimen of the present invention;

Fig. 5 a is the front view of the connection between the test piece and the tensile fixture in the direct tension test device of a hydraulic asphalt concrete test piece of the present invention;

Fig. 5 b is a side view of the connection between the test piece and the tensile fixture in the direct tension test device of a hydraulic asphalt concrete test piece of the present invention;

Fig. 6 is a Y-shaped joint schematic diagram in a kind of hydraulic asphalt concrete specimen direct tensile test device of the present invention;

Fig. 7 is the I-type joint schematic diagram in a kind of hydraulic asphalt concrete specimen direct tension test device of the present invention;

Fig. 8 is a schematic diagram of a forming mold in a direct tensile test device for a hydraulic asphalt concrete specimen of the present invention.

In the figure, 1. The first sliding T-shaped connector, 2. The second sliding T-shaped connector, 3. The first tensile fixture, 4. The first floating ball joint, 5. The second floating ball joint, 6. Test Components, 7. Tension sensor, 8. Grating displacement sensor, 9. Cylindrical pin, 10. High and low temperature environment box, 11. MTS actuator, 12. Loading platform base, 13. Loading table, 14. Steel column, 15. Beam, 16. The first chute, 17. The first clamping groove, 18. Steel roller, 19. Screw hole, 20. The first T-shaped connector, 21. Side plate, 22. C-shaped clamp, 23. Fastening bolts, 24. Strong adhesive layer, 25. Rubber pad, 26. Y-type joint, 27. I-type joint, 28. Guide rail, 29. Wheel, 30. Lifting frame, 31. End plate, 32. Forming Side plate, 33. Bottom plate, 34. Second tensile clamp, 35. Bolt.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

The invention provides a hydraulic asphalt concrete direct tensile test device, as shown in Figure 1, comprising a support frame body, the top of the support frame body is equipped with a horizontal beam 15, and the bottom of the support frame body is provided with a horizontal beam 15 parallel Loading table 13, the support frame body also includes two steel columns 14 arranged in parallel, two steel columns 14 are located between crossbeam 15 and loading table 13, and steel column 14 is perpendicular to crossbeam 15; The bottom of described crossbeam 15 is connected with MTS actuator 11, the bottom of MTS actuator 11 is connected with the first sliding T-line connector 1, the first sliding T-row connector 1 is connected to the first tensile fixture 3 through the first floating ball joint 4; the first sliding T A tension sensor 7 is also arranged between the row connector 1 and the first floating ball joint 4; the measurement ranges of the tension sensor 7 are 0-10kN and 0-40kN respectively, and the measurement accuracy is 0.05N-0.1N;

The top of the loading platform 13 is connected with a loading platform base 12, and the end of the loading platform base 12 far away from the loading platform 13 is connected with a second sliding T-row connector 2, and the second sliding T-row connecting member 2 is connected by a second floating ball hinge 5 There is a second tensile fixture 34, the first tensile fixture 3 and the second tensile fixture 34 are opposite, and the above-mentioned components are all located on the central axis of the crossbeam 15 and the loading table 13; also include the test piece 6, the test piece 6 is clamped between the first tensile fixture 3 and the second tensile fixture 34, and the test piece 6 is also provided with a grating displacement sensor 8, the measurement range of the grating displacement sensor 8 is 0-5mm, and the measurement accuracy is 0.001mm ～0.005mm, the working temperature range is -40℃～50℃, the acquisition frequency of the data acquisition system is not less than 10000; it also includes high and low temperature environmental chamber 10, the temperature range is -50℃～50℃, and the control accuracy is 0.1℃～ 0.5°C, the height of the headroom is 700mm-900mm, and the length and width of the headroom are 400mm-500mm; the test piece 6 is located in the high and low temperature environment chamber 10; The lifting frame 30 is fixed on the loading platform 13 and located on both sides of the loading platform base 12, and the two sides of the bottom of the high and low temperature environment box 10 are also connected with wheels 29, and the end of the connection between the lifting frame 30 and the high and low temperature environment box 10 is provided with a guide rail 28, The guide rail 28 is embedded with a card slot, and the wheels 29 are located in the guide rail 28 to cooperate with the guide rail; the high and low temperature environment chamber 10 can move on the loading table 13 through the guide rail 28, move up and down through the lifting frame 30, and be fixed in the test area through the card slot ;

The first floating ball joint 4 and the second floating ball joint 5 are free to rotate within the range of -10° to 10°;

As shown in Fig. 3a and Fig. 3b, the first sliding T row connector 1 includes a first chute 16 and a first card slot 17, the first chute 16 is fixedly connected with the MTS actuator 11, and also includes a first T-shaped connector 20, the horizontal end of the first T-shaped connector 20 is embedded in the first card slot 17, and a plurality of steel rollers 18 are also arranged inside the first card slot 17, and the first T-shaped connector 20 is made of steel The roller 18 is movably connected with the first draw-in groove 17; the vertical end of the first T-shaped connector 20 is provided with a screw hole 19, and a screw is embedded in the screw hole 19, and the first T-shaped connector 20 connects with the first floating through the screw. The ball hinge 4 is fixedly connected, and the tension sensor 7 is located at the vertical end of the first T-shaped connector 20. Fastening bolts 23 are respectively arranged on both sides of the first slot 17, and the fastening bolts extend into the first slot 17. The inside is connected with the first T-shaped connector 20;

The second sliding T row connector 2 has the same structure as the first sliding T row connector 2. The chute of the second sliding T row connector 2 extends into the loading platform base 12 and is fixedly connected with the loading platform base 12. The second sliding T row The T-shaped connecting piece of the connecting piece 2 is connected with the second floating ball joint 5;

As shown in Figure 4, the first tensile clamp 3 comprises a C-shaped clamp 22 and side plates 21 positioned at both sides of the C-shaped clamp 22, the side plates 21 and the C-shaped clamp 22 are connected by bolts 35, and the C-shaped clamp 22 The bottom is also provided with a screw hole, and a screw is embedded in the screw hole, and the end of the first floating ball joint (4) away from the first sliding T-row connector 2 is fixedly connected with the first tensile fixture 3 through the screw;

As shown in Figures 6 and 7, the second stretching fixture 34 has the same structure as the first stretching fixture 3, and the bottom of the second stretching fixture 34 is connected with a Y-shaped joint 26 through a screw hole, and the opening of the Y-shaped joint 26 The end is embedded with an I-shaped joint 27, and also includes a cylindrical pin 9, and the cylindrical pin 9 passes through the Y-shaped joint 26 and the I-shaped joint 27 to fix the Y-shaped joint 26 and the I-shaped joint 27, and the I-shaped joint 27 is away from the Y-shaped joint. One end of the joint 26 is connected to the end of the second floating ball joint 5 away from the second sliding T-line connector 2; the diameter of the screw rods of the Y-shaped joint 26 and the I-shaped joint 27 is not less than 20mm;

As shown in Fig. 2a, Fig. 2b, Fig. 2c and Fig. 5a, Fig. 5b, the specimen 6 is a dumbbell-shaped specimen, the height and width b of the test area of the specimen is 3 to 5 times of the largest aggregate, and the length of the test area is The width ratio l/b is 1.2~1.5, the ratio of the total length L of the test piece to the width b in the middle of the test area is 3.5~4.5, the ratio of the total length L to the end width B of the test piece is 2.5~3, and the side slope n 2.5 to 4; the test piece 6 is located between the first tensile fixture 3 and the second tensile fixture 34, one end of the test piece 6 is embedded in the C-shaped clamp 22 of the fixture, and the test piece 6 is connected to the C-shaped clamp through the strong adhesive layer 24 The type fixture 22 is fixedly connected, and a rubber pad 25 with a thickness of 1 mm to 2 mm is also arranged between the side plate 21 and the test piece 6;

The present invention also provides an application method of a hydraulic asphalt concrete direct tensile test device, adopting the hydraulic asphalt concrete direct tensile test device, specifically implementing the following steps:

Step 1, test piece molding: laboratory molding or on-site molding;

The specific process of on-site forming is as follows: preparation by on-site core drilling, first use a drill with an inner diameter of not less than 150mm to drill a sample with a length of not less than 320mm, and then cut it according to the shape of the test piece 6; the length of the test piece obtained in this way is , width and height deviations are ±2mm, ±1mm and ±1mm respectively;

If it is molded by a laboratory, then it is necessary to process a molding die that is matched with the present invention. The specific process of the laboratory molding is as follows: as shown in Figure 8, the molding mold is first combined, and the molding mold includes two molding side plates 32, two The two end plates 31 and the bottom plate 33 are all connected by bolts, and the center of the formed side plate 32 is provided with a protrusion that matches the test piece 6. The forming process is single-layer double-sided compaction molding, and the specific steps are as follows: Prepare the asphalt mixture according to the mix ratio required by the "Hydraulic Asphalt Concrete Specification". Put the mixture into the forming mold. After the asphalt mixture is paved, place a flat plate on the top, adjust the flatness of the asphalt mixture by observing the level bead, pull the compaction hammer to the predetermined height and drop it freely, compact the test piece evenly, and then Install the bottom plate 33 in the forming mold to the upper part, turn over the test piece, and take the same steps to carry out secondary compaction on the test piece, and the number of times of compaction should reach ±1% of the density of the Marshall standard compacted test piece Standard, the height dimension deviation is ±1mm;

Step 2, polish the test piece 6, remove the mold after the test piece 6 is cooled naturally, polish the connection area at the end of the test piece 6, polish the upper and lower end surfaces of the test piece flat, and polish the side and inclined surfaces into a honeycomb pockmarked surface;

Step 3, connect the test piece and the fixture; connect the two ends of the test piece 6 with the first tensile fixture 3 and the second tensile fixture 34 respectively by a strong adhesive and a rubber pad 25, then delineate the test area, the length of the test area Not less than 100mm, measure and record the cross-sectional size with a vernier caliper at both ends and in the middle of the test area, install a grating displacement sensor 8 in the test area, and the grating displacement sensor 8 is symmetrically distributed around the test piece 6 and arranged flush;

Step 4, install the test piece; vertically arrange the first sliding T-shaped connector 1 and the second sliding T-shaped connector 2, connect and fix the chutes of the two connectors with the MTS actuator 11 and the loading table 13 respectively, Adjust the position of the T-shaped connector through the steel roller, ensure that the centerlines of the upper and lower T-shaped connectors coincide with each other through the infrared vertical instrument, and then tighten the fixing slot to fix the T-shaped connector; connect the tension sensor 7 and the first floating ball hinge 4 1. The first tensile fixture 3 and the test piece 6 are connected with the first sliding T-shaped connector 1 in turn, and the second floating ball joint 5 is connected with the second sliding T-shaped connector 2, so that the test piece 6 is in a free plumb state , the Y-shaped joint 26 and the I-shaped joint 27 are connected with the second tensile fixture 34 and the second floating ball joint 5 respectively, and the cylindrical pin 9 is inserted to complete the connection and installation of the test piece 6 and the loading device; by adjusting the second floating ball The screw spacing between the hinge 5 and the Y-shaped joint 26 and the I-shaped joint 27 is used to adjust the initial tension state;

Step 5, test preloading; connect the tension sensor 7 and the grating displacement sensor 8 to the acquisition system, check each test equipment, debug the MTS actuator 11, set the loading system, and perform preloading at room temperature, the preloading range The tensile strength of the hydraulic asphalt concrete is 20% to 40%, and the reading of the displacement sensor changes evenly before proceeding to the next step, otherwise, the connection system of the test piece is adjusted again until the preloading condition is met;

Step 6, constant temperature test piece; fix the high and low temperature environment 10 through the fixed card slot, set the test temperature, and carry out constant temperature on the test piece 6, and the constant temperature time is not less than 6h; Average temperature or 20°C and 5°C;

Step 7, the test is formally loaded; after the above steps are prepared, carry out the tensile test according to the set loading system, record the data of the tension sensor and displacement sensor during the test, until the specimen is loaded and destroyed, and calculate the tensile strength, deformation and other information , draw the tensile stress-strain curve.

Claims (6)

1. The hydraulic asphalt concrete direct tensile test device is characterized by comprising a support frame body, wherein a horizontal cross beam (15) is arranged at the top of the support frame body, a loading table board (13) parallel to the cross beam (15) is arranged at the bottom of the support frame body, an MTS actuator (11) is connected to the bottom of the cross beam (15), a first sliding T-shaped connecting piece (1) is connected to the bottom of the MTS actuator (11), and the first sliding T-shaped connecting piece (1) is connected with a first tensile clamp (3) through a first floating spherical hinge (4); a tension sensor (7) is also arranged between the first sliding T-shaped connecting piece (1) and the first floating spherical hinge (4);

the first sliding T-shaped connecting piece (1) comprises a first sliding groove (16) and a first clamping groove (17), the first sliding groove (16) is fixedly connected with the MTS actuator (11), the first sliding T-shaped connecting piece also comprises a first T-shaped connecting piece (20), the horizontal end of the first T-shaped connecting piece (20) is embedded into the first clamping groove (17), a plurality of steel rollers (18) are further arranged on the inner side of the first clamping groove (17), and the first T-shaped connecting piece (20) is movably connected with the first clamping groove (17) through the steel rollers (18); the end part of the vertical end of the first T-shaped connecting piece (20) is provided with a screw hole (19), a screw is embedded in the screw hole (19), the first T-shaped connecting piece (20) is fixedly connected with the first floating spherical hinge (4) through the screw, and the tension sensor (7) is positioned at the vertical end of the first T-shaped connecting piece (20);

the first stretching clamp (3) comprises a C-shaped clamp (22) and side plates (21) positioned on two sides of the C-shaped clamp (22), the side plates (21) are connected with the C-shaped clamp (22) through bolts (35), screw holes are further formed in the bottoms of the C-shaped clamp (22), screw rods are embedded in the screw holes, and one end, far away from the first sliding T-shaped connecting piece (2), of the first floating spherical hinge (4) is fixedly connected with the first stretching clamp (3) through the screw rods;

the top of the loading table top (13) is connected with a loading platform base (12), one end, far away from the loading table top (13), of the loading platform base (12) is connected with a second sliding T-shaped connecting piece (2), the second sliding T-shaped connecting piece (2) is connected with a second stretching clamp (34) through a second floating spherical hinge (5), the first stretching clamp (3) is opposite to the second stretching clamp (34), and the components are all positioned on the central axes of the cross beam (15) and the loading table top (13); the device comprises a first stretching clamp (3) and a second stretching clamp (34), and is characterized by further comprising a test piece (6), wherein the test piece (6) is clamped between the first stretching clamp (3) and the second stretching clamp (34), a grating displacement sensor (8) is further arranged on the test piece (6), the device also comprises a high-low temperature environment box (10), and the test piece (6) is positioned in the high-low temperature environment box (10);

the second stretching clamp (34) is identical to the first stretching clamp (3) in structure, a Y-shaped joint (26) is connected to the bottom of the second stretching clamp (34) through a screw hole, an I-shaped joint (27) is embedded into the opening end of the Y-shaped joint (26), the second stretching clamp further comprises a cylindrical pin (9), the cylindrical pin (9) sequentially penetrates through the Y-shaped joint (26) and the I-shaped joint (27) to fix the Y-shaped joint (26) and the I-shaped joint (27), and one end, far away from the Y-shaped joint (26), of the I-shaped joint (27) is connected with one end, far away from the second sliding T-shaped connecting piece (2), of the second floating spherical hinge (5);

the test piece (6) is a dumbbell-shaped test piece, the height-width dimension B of a test area of the test piece is 3-5 times of the maximum aggregate, the length-width ratio L/B of the test area is 1.2-1.5, the ratio of the total length L of the test piece to the width B of the middle part of the test area is 3.5-4.5, the ratio of the total length L to the width B of the end part of the test piece is 2.5-3, and the side slope n is 2.5-4; the test piece (6) is located between the first stretching clamp (3) and the second stretching clamp (34), one end of the test piece (6) is embedded into the C-shaped clamp (22) of the clamp, the test piece (6) is fixedly connected with the C-shaped clamp (22) through the strong adhesive layer (24), and a rubber pad (25) is further arranged between the side plate (21) and the test piece (6).

2. The hydraulic asphalt concrete direct tensile test apparatus according to claim 1, wherein said supporting frame body further comprises two steel columns (14) arranged in parallel, said two steel columns (14) are located between the cross beam (15) and the loading table (13), and said steel columns (14) are perpendicular to the cross beam (15).

3. The hydraulic asphalt concrete direct tensile test device according to claim 1, wherein fastening bolts (23) are respectively arranged at two sides of the outside of the first clamping groove (17), and extend into the first clamping groove (17) to be connected with the first T-shaped connecting piece (20).

4. The hydraulic asphalt concrete direct tensile test device according to claim 1, wherein the second sliding T-line connecting piece (2) has the same structure as the first sliding T-line connecting piece (2), a sliding groove of the second sliding T-line connecting piece (2) extends into the loading platform base (12) to be fixedly connected with the loading platform base (12), and a T-shaped connecting piece of the second sliding T-line connecting piece (2) is connected with the second floating spherical hinge (5).

5. The hydraulic asphalt concrete direct tensile test device according to claim 1, wherein two ends of the bottom of the high-low temperature environment box (10) are further connected with lifting frames (30) respectively, the lifting frames (30) are fixed on a loading table top (13) and located on two sides of a loading platform base (12), wheels (29) are further connected on two sides of the bottom of the high-low temperature environment box (10), guide rails (28) are arranged at the end parts of the connecting parts of the lifting frames (30) and the high-low temperature environment box (10), clamping grooves are embedded in the guide rails (28), and the wheels (29) are located in the guide rails (28) and matched with the guide rails.

6. An application method of a hydraulic asphalt concrete direct tensile test device is characterized in that the hydraulic asphalt concrete direct tensile test device is adopted according to the claims 1-5, and the method is implemented according to the following steps:

step 1, test piece molding: laboratory molding or field molding;

the specific process of the on-site forming is as follows: firstly, drilling a sample with the length of not less than 320mm by using a drill bit with the inner diameter of not less than 150mm, and then cutting according to the shape of a test piece (6); the length, width and height dimensional deviations of the test piece obtained by the method are +/-2 mm, +/-1 mm and +/-1 mm respectively;

the specific process of laboratory molding is as follows: firstly, a forming die is combined, the forming die comprises two forming side plates (32), two end plates (31) and a bottom plate (33), the two end plates are connected through bolts, a bulge matched with a test piece (6) is arranged at the center of each forming side plate (32), the forming process is single-layer double-sided compaction forming, and the specific steps are as follows: firstly mixing asphalt mixture, heating a forming die to 100-110 ℃ within the temperature range of 145-155 ℃, brushing a release agent, feeding the prepared asphalt mixture into the forming die, after the asphalt mixture is paved, placing a flat plate on the upper part, adjusting the flatness of the asphalt mixture by observing a leveling bead, drawing a compaction hammer to a preset height to freely fall down, uniformly compacting a test piece, then installing a bottom plate (33) in the forming die on the upper part, overturning the test piece, performing secondary compaction on the test piece by adopting the same steps, wherein the compaction times are based on that the density of the test piece reaches +/-1% of the density of a Marshall standard compaction test piece, and the height dimension deviation is +/-1 mm;

step 2, polishing the test piece (6), removing the mould after the test piece (6) is naturally cooled, polishing the end connection area of the test piece (6), polishing the upper and lower end surfaces of the test piece to be flat, and polishing the side surfaces and the inclined surfaces to be honeycomb pitted surfaces;

step 3, connecting a test piece with the clamp; two ends of a test piece (6) are respectively connected with a first stretching clamp (3) and a second stretching clamp (34) through a strong adhesive and a rubber pad (25), then a test area is defined, the length of the test area is not less than 100mm, the two ends and the middle of the test area are measured by vernier calipers and the section size is recorded, grating displacement sensors (8) are arranged in the test area, and the grating displacement sensors (8) are symmetrically distributed around the test piece (6) and are arranged in a flush manner;

step 4, installing a test piece; the first sliding T-shaped connecting piece (1) and the second sliding T-shaped connecting piece (2) are vertically arranged, sliding grooves of the two connecting pieces are respectively connected and fixed with an MTS actuator (11) and a loading table top (13), the positions of the T-shaped connecting pieces are adjusted through steel rollers, the central lines of the upper T-shaped connecting piece and the lower T-shaped connecting piece are ensured to coincide through an infrared perpendicularity meter, and then the fixing clamping groove is screwed to fix the T-shaped connecting pieces; sequentially connecting a tension sensor (7), a first floating spherical hinge (4), a first stretching clamp (3) and a test piece (6) with a first sliding T-shaped connecting piece (1), connecting a second floating spherical hinge (5) with a second sliding T-shaped connecting piece (2), enabling the test piece (6) to be in a free plumb state, respectively connecting a Y-shaped joint (26) and an I-shaped joint (27) with a second stretching clamp (34) and a second floating spherical hinge (5), inserting a cylindrical pin (9), and completing connection and installation of the test piece (6) and loading equipment; the initial stretching state is adjusted by adjusting the screw spacing between the second floating spherical hinge (5) and the Y-shaped joint (26) and between the second floating spherical hinge and the I-shaped joint (27);

step 5, test preloading; the method comprises the steps of accessing a tension sensor (7) and a grating displacement sensor (8) into an acquisition system, checking each test device, debugging an MTS actuator (11), setting a loading system, preloading under the condition of room temperature, wherein the preloading range is 20% -40% of the tensile strength of hydraulic asphalt concrete, and the next step can be carried out when the readings of the displacement sensors are uniformly changed, otherwise, debugging the test piece connection system again until the preloading condition is met;

step 6, a constant temperature test piece; fixing the high-low temperature environment (10) through a fixing clamping groove, setting a test temperature, and keeping the test piece (6) constant for at least 6 hours; if the test temperature is not specially specified, the annual average temperature of the engineering site or 20 ℃ and 5 ℃ can be adopted;

step 7, testing formal loading; and after the steps are prepared, carrying out a tensile test according to a set loading system, recording data of the tension sensor and the displacement sensor in the test process until the test piece is loaded and destroyed, calculating information such as tensile strength, deformation and the like, and drawing a tensile stress-strain curve.