CN113281190B - Hydraulic asphalt concrete direct tensile test device and application method thereof - Google Patents
Hydraulic asphalt concrete direct tensile test device and application method thereof Download PDFInfo
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- CN113281190B CN113281190B CN202110400382.7A CN202110400382A CN113281190B CN 113281190 B CN113281190 B CN 113281190B CN 202110400382 A CN202110400382 A CN 202110400382A CN 113281190 B CN113281190 B CN 113281190B
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
- G01N3/18—Performing tests at high or low temperatures
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/02—Details
- G01N3/04—Chucks
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
- G01N2203/0016—Tensile or compressive
- G01N2203/0017—Tensile
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/022—Environment of the test
- G01N2203/0222—Temperature
- G01N2203/0228—Low temperature; Cooling means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/04—Chucks, fixtures, jaws, holders or anvils
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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
Technical Field
The invention belongs to the technical field of civil engineering experiments, and relates to a hydraulic asphalt concrete direct tensile test device.
The invention also relates to an application method of the hydraulic asphalt concrete direct tensile test device.
Background
The hydraulic asphalt concrete is a composite material formed by mixing coarse aggregate, fine aggregate, asphalt, filler and other materials according to a certain proportion, has the advantages of good deformation performance, strong seepage-proofing performance and the like, and is mainly applied to hydraulic seepage-proofing body structures, such as earth-rock dam seepage-proofing core walls or panels. A great deal of research shows that when the dam foundation of the earth-rock dam is unevenly settled, the asphalt concrete panel is inevitably subjected to the action of tensile stress; when the earth-rock dam is slip deformed along a steep bank slope toward the center of the valley, the asphalt concrete core wall shoulder is inevitably subjected to tensile stress, and the tensile stress increases as the core wall dam height increases. In practical engineering, the tensile strength and tensile deformation of asphalt concrete are far lower than the compressive strength and compressive deformation, so that the size and the damage degree of the damage area of the anti-seepage body structure are greatly dependent on the tensile mechanical property of asphalt concrete materials, and when the asphalt concrete is structurally cracked and damaged, the damage area and the damage degree of the anti-seepage body structure have great damage to the safety of a dam.
The common methods for testing the tensile mechanical property index of the asphalt concrete material comprise a direct tensile test, a splitting test and a bending test, and the axial direct tensile test is the most suitable and accurate test method for obtaining the tensile mechanical property of the material. However, there are several problems associated with currently developed axial direct tensile tests for bituminous concrete materials: firstly, the axle center stretching state of the test piece is difficult to ensure in the mounting and loading processes, so that the stretching mechanical index of the test has larger error. Secondly, according to the characteristics of the hydraulic asphalt concrete raw material and molding, a proper tensile test piece size is selected. The current test piece size of carrying out hydraulic asphalt concrete direct tensile test is 40mm x 220 mm's prism, to this kind of small-size prism test piece, if directly carry out shaping preparation, can't guarantee closely knit, can't reach hydraulic asphalt concrete's impermeable performance requirement, so under the general circumstances, this kind of prism test piece is through laboratory shaping (marshall compaction shaping, hydrostatic forming etc.) or on-the-spot core drilling sampling earlier, and the cutting preparation is again made, and the re-cutting processing can inevitably cause initial damage to the test piece. In addition, the maximum aggregate size of the hydraulic asphalt concrete is 19mm, and the influence of the aggregate size effect is also considered when a test piece with the section size of 40mm multiplied by 40mm is adopted for carrying out a tensile test. Thirdly, the accuracy of the test result is affected by the connection mode of the test piece and the clamp. As a non-uniform phase change material, the temperature or the loading rate has obvious influence on mechanical properties such as tensile strength, rigidity and the like, and as the temperature is reduced or the loading rate is increased, the rigidity of the asphalt concrete is increased, and further, the connection rigidity of a test piece and a clamp is required to be larger. In addition, when a tensile test is performed by using a test piece with a larger cross-sectional size, higher requirements are put on the connection rigidity and stability of the test piece and the clamp. Fourthly, when the material cracks, the crack rapidly expands, the stress drops sharply, and the acquisition precision of the existing sensor is difficult to accurately measure the stress-strain curve of the test piece after reaching the peak stress.
Therefore, aiming at the characteristics of hydraulic asphalt concrete materials, the research of the hydraulic asphalt concrete axial tensile test device and the application method thereof is developed, and the hydraulic asphalt concrete axial tensile test device has very important theoretical significance and engineering application value.
Disclosure of Invention
The invention aims to provide a hydraulic asphalt concrete direct tensile test device, which solves the problems of difficult centering, small test piece size, unstable connection between the test piece and a clamp, complicated installation process and low test precision in the existing hydraulic asphalt concrete tensile test.
Another object of the invention is to provide a method for applying the hydraulic asphalt concrete direct tensile test apparatus.
The hydraulic asphalt concrete direct tensile test device comprises a support frame body, wherein a horizontal cross beam is arranged at the top of the support frame body, a loading table surface parallel to the cross beam is arranged at the bottom of the support frame body, an MTS actuator is connected to the bottom of the cross beam, a first sliding T-shaped connecting piece is connected to the bottom of the MTS actuator, and the first sliding T-shaped connecting piece is connected with a first tensile clamp through a first floating spherical hinge; a tension sensor is also arranged between the first sliding T-shaped connecting piece and the first floating spherical hinge;
the top of the loading table top is connected with a loading platform base, one end of the loading platform base, which is far away from the loading table top, is connected with a second sliding T-shaped connecting piece, the second sliding T-shaped connecting piece is connected with a second stretching clamp through a second floating spherical hinge, the first stretching clamp is opposite to the second stretching clamp, and the parts are all positioned on the central axes of the cross beam and the loading table top; still include the test piece, the test piece presss from both sides and locates between first tensile anchor clamps and the tensile anchor clamps of second, still be provided with grating displacement sensor on the test piece, still include high low temperature environment case, the test piece is located high low temperature environment case.
The first technical scheme of the invention is characterized in that:
the support frame body further comprises two steel columns which are arranged in parallel, the two steel columns are positioned between the cross beam and the loading table top, and the steel columns are perpendicular to the cross beam;
the first sliding T-shaped connecting piece comprises a first sliding groove and a first clamping groove, the first sliding groove is fixedly connected with the MTS actuator, the first sliding T-shaped connecting piece further comprises a first T-shaped connecting piece, the horizontal end of the first T-shaped connecting piece is embedded into the first clamping groove, a plurality of steel rollers are arranged on the inner side of the first clamping groove, and the first T-shaped connecting piece is movably connected with the first clamping groove through the steel rollers; the end part of the vertical end of the first T-shaped connecting piece is provided with a screw hole, a screw is embedded in the screw hole, the first T-shaped connecting piece is fixedly connected with the first floating spherical hinge through the screw, and the tension sensor is positioned at the vertical end of the first T-shaped connecting piece;
the two sides of the outer part of the first clamping groove are respectively provided with a fastening bolt, and the fastening bolts extend into the first clamping groove to be connected with the first T-shaped connecting piece;
the second sliding T-shaped connecting piece and the first sliding T-shaped connecting piece are identical in structure, a sliding groove of the second sliding T-shaped connecting piece extends into the loading platform base and is fixedly connected with the loading platform base, and the T-shaped connecting piece of the second sliding T-shaped connecting piece is connected with the second floating spherical hinge;
the first stretching clamp comprises a C-shaped clamp and side plates positioned on two sides of the C-shaped clamp, the side plates are connected with the C-shaped clamp through bolts, screw holes are further formed in the bottoms of the C-shaped clamp, screw rods are embedded in the screw holes, and one end, far away from the first sliding T-shaped connecting piece, of the first floating spherical hinge is fixedly connected with the first stretching clamp through the screw rods;
the second stretching clamp and the first stretching clamp are identical in structure, the bottom of the second stretching clamp is connected with a Y-shaped joint through a screw hole, an opening end of the Y-shaped joint is embedded with an I-shaped joint, the second stretching clamp further comprises a cylindrical pin, the cylindrical pin sequentially penetrates through the Y-shaped joint and the I-shaped joint to fix the Y-shaped joint and the I-shaped joint, and one end of the I-shaped joint far away from the Y-shaped joint is connected with one end of the second floating spherical hinge far away from the second sliding T-shaped connecting piece;
the test piece 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 is positioned between the first stretching clamp and the second stretching clamp, one end of the test piece is embedded into the C-shaped clamp of the clamp, the test piece is fixedly connected with the C-shaped clamp through the strong adhesive layer, and a rubber pad is arranged between the side plate and the test piece;
the lifting frames are fixed on the loading table top and positioned on two sides of the loading platform base, wheels are connected on two sides of the bottom of the high-low temperature environment box, guide rails are arranged at the end parts of the joints of the lifting frames and the high-low temperature environment box, clamping grooves are embedded in the guide rails, and the wheels are positioned in the guide rails and matched with the guide rails.
The second technical scheme of the invention is that an application method of the hydraulic asphalt concrete direct tensile test device is implemented by adopting the hydraulic asphalt concrete direct tensile test device, and the method comprises the following steps of:
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 the sample; 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, two end plates and a bottom plate, the two end plates and the bottom plate are connected through bolts, a bulge matched with a test piece is arranged at the center of each forming side plate, the forming process is single-layer double-sided compaction forming, and the concrete steps are as follows: firstly mixing asphalt mixture, wherein the temperature range of the asphalt mixture is 145-155 ℃, heating a forming die to 100-110 ℃, coating 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, mounting a bottom plate in the forming die on the upper part, overturning the test piece, carrying out 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, removing the mold after the test piece is naturally cooled, polishing the end connection area of the test piece, polishing the upper and lower end surfaces of the test piece to be flat, and polishing the side surfaces and the inclined surfaces of the test piece to form honeycomb pitted surfaces;
step 3, connecting a test piece with the clamp; connecting two ends of a test piece with a first stretching clamp and a second stretching clamp respectively through a strong adhesive and a rubber pad, then defining a test area, measuring and recording the section size of the test area by using vernier calipers at the two ends and the middle part of the test area, and installing grating displacement sensors in the test area, wherein the grating displacement sensors are symmetrically distributed around the test piece and are arranged in a flush manner;
step 4, installing a test piece; the first sliding T-shaped connecting piece and the second sliding T-shaped connecting piece are vertically arranged, sliding grooves of the two connecting pieces are respectively connected and fixed with the MTS actuator and the loading table top, 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 instrument, and then the fixing clamping groove is screwed to fix the T-shaped connecting pieces; sequentially connecting a tension sensor, a first floating spherical hinge, a first stretching clamp and a test piece with a first sliding T-shaped connecting piece, connecting a second floating spherical hinge with a second sliding T-shaped connecting piece to enable the test piece to be in a free plumb state, respectively connecting a Y-shaped joint and an I-shaped joint with the second stretching clamp and the second floating spherical hinge, inserting a cylindrical pin, and completing connection and installation of the test piece and loading equipment; adjusting the initial stretching state by adjusting the screw spacing between the second floating spherical hinge and the Y-shaped joint as well as between the second floating spherical hinge and the I-shaped joint;
step 5, test preloading; the method comprises the steps of accessing a tension sensor and a grating displacement sensor into an acquisition system, checking each test device, debugging an MTS actuator, 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 when the readings of the displacement sensor change uniformly, the next step can be carried out, 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 through a fixing clamping groove, setting a test temperature, and keeping the test piece constant temperature 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.
The beneficial effects of the invention are as follows:
according to the hydraulic asphalt concrete direct tensile test device and the application method thereof, the eccentric problem of asphalt concrete in the installation and tensile process is reduced to the greatest extent by the sliding T-shaped connecting piece and the floating spherical hinge; the Y-shaped joint and the I-shaped joint of the test piece connecting system can be quickly installed; the shape of the test piece and the connection mode of the test piece and the tensile clamp break through the problem that the asphalt concrete tensile test is limited by the size of the test piece, and the high probability of the tensile fracture surface occurring in the middle section of the test piece can be realized; the high-precision and high-sensitivity tension sensor and the displacement sensor are arranged in the test piece connecting system, so that not only can the mechanical data of the test piece before the tensile strength is achieved, but also the indexes such as load and deformation after the tensile strength is achieved can be accurately tested; in a word, a hydraulic asphalt concrete direct tensile test device and an application method thereof can not only carry out direct tensile test of hydraulic asphalt concrete in a unidirectional loading state, but also test tensile mechanical properties under reciprocating loading conditions such as pulling-pulling circulation, loading and unloading and the like; the method is not only suitable for developing static and dynamic tensile mechanical tests of the asphalt concrete under normal temperature conditions, but also can test the tensile mechanical properties under low temperature conditions.
Drawings
FIG. 1 is a schematic diagram of a hydraulic asphalt concrete test piece direct tensile test apparatus of the present invention;
FIG. 2a is a schematic illustration of the dimensions of a hydraulic asphalt concrete test piece in a direct tensile test apparatus according to the present invention;
FIG. 2b is a schematic illustration of the dimensions of an end of a test piece in a hydraulic asphalt concrete test piece direct tensile test apparatus according to the present invention;
FIG. 2c is a schematic view of the dimensions of the other end of the test piece in the hydraulic asphalt concrete test piece direct tensile test apparatus according to the present invention;
FIG. 3a is a schematic side view of a sliding T-piece in a hydraulic asphalt concrete test piece direct tensile test apparatus according to the present invention;
FIG. 3b is a schematic diagram of the front structure of a sliding T-shaped part in a hydraulic asphalt concrete test piece direct tensile test apparatus according to the present invention;
FIG. 4 is a schematic drawing of a tensile fixture in a hydraulic asphalt concrete test piece direct tensile test apparatus of the present invention;
FIG. 5a is a front view of a test piece connected to a tensile fixture in a hydraulic asphalt concrete test piece direct tensile test apparatus of the present invention;
FIG. 5b is a side view of a test piece connected to a tensile fixture in a hydraulic asphalt concrete test piece direct tensile test apparatus of the present invention;
FIG. 6 is a schematic view of a Y-joint in a hydraulic asphalt concrete test piece direct tensile test apparatus according to the present invention;
FIG. 7 is a schematic illustration of a type I joint in a hydraulic asphalt concrete test piece direct tensile test apparatus of the present invention;
fig. 8 is a schematic diagram of a forming die in a hydraulic asphalt concrete test piece direct tensile test apparatus according to the present invention.
In the drawings, 1 a first sliding T-shaped connector, 2a second sliding T-shaped connector, 3a first tension clamp, 4 a first floating ball joint, 5a second floating ball joint, 6 a test piece, 7 a tension sensor, 8 a grating displacement sensor, 9 a cylindrical pin, 10 a high and low temperature environment box, 11 a MTS actuator, 12 a loading platform base, 13 a loading table top, 14 a steel column, 15 a cross beam, 16 a first sliding chute, 17 a first clamping groove, 18 a steel roller, 19 a screw hole, 20 a first T-shaped connector, 21 a side plate, 22 a C-shaped clamp, 23 a fastening bolt, 24 a strong adhesive layer, 25 a rubber pad, 26 a Y-shaped joint, 27 a I-shaped joint, 28 a guide rail, 29 a wheel, 30 a lifting frame, 31 a end plate, 32 a forming side plate, 33 a bottom plate, 34 a second tension clamp and 35 a bolt.
Detailed Description
The invention will be described in detail below with reference to the drawings and the detailed description.
The invention provides a hydraulic asphalt concrete direct tensile test device, as shown in fig. 1, which comprises a support frame body, wherein the top of the support frame body is provided with a horizontal cross beam 15, the bottom of the support frame body is provided with a loading table top 13 parallel to the cross beam 15, the support frame body also comprises two steel columns 14 which are arranged in parallel, the two steel columns 14 are positioned between the cross beam 15 and the loading table top 13, and the steel columns 14 are vertical to the cross beam 15; the bottom of the cross beam 15 is connected with an MTS actuator 11, the bottom of the MTS actuator 11 is connected with a first sliding T-shaped connecting piece 1, and the first sliding T-shaped connecting piece 1 is connected with a first stretching 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 measuring range of the tension sensor 7 is 0-10 kN and 0-40 kN respectively, and the measuring precision is 0.05N-0.1N;
the top of the loading table top 13 is connected with a loading platform base 12, one end of the loading platform base 12, which is far away from the loading table top 13, 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 further comprises a test piece 6, wherein the test piece 6 is clamped between the first stretching clamp 3 and the second stretching clamp 34, the test piece 6 is further provided with a grating displacement sensor 8, the measuring range of the grating displacement sensor 8 is 0-5 mm, the measuring precision is 0.001-0.005 mm, the working temperature range is-40-50 ℃, and the acquisition frequency of the data acquisition system is not less than 10000; the device also comprises a high-low temperature environment box 10, the temperature change range is-50 ℃, the control precision is 0.1-0.5 ℃, the clearance height dimension is 700-900 mm, and the clearance length and width dimension is 400-500 mm; the test piece 6 is positioned in the high-low temperature environment box 10; the two ends of the bottom of the high-low temperature environment box 10 are respectively connected with a lifting frame 30, the lifting frames 30 are fixed on the loading table top 13 and positioned at two sides of the loading platform base 12, the two sides of the bottom of the high-low temperature environment box 10 are also connected with wheels 29, the end part of the joint of the lifting frames 30 and the high-low temperature environment box 10 is provided with a guide rail 28, the guide rail 28 is embedded with a clamping groove, and the wheels 29 are positioned in the guide rail 28 and matched with the guide rail; the high-low temperature environment box 10 can move on the loading table 13 through the guide rail 28, moves up and down through the lifting frame 30 and is fixed in a test area through the clamping groove;
the first floating spherical hinge 4 and the second floating spherical hinge 5 freely rotate within the range of-10 degrees to 10 degrees;
as shown in fig. 3a and 3b, the first sliding T-shaped connector 1 includes a first chute 16 and a first clamping groove 17, where the first chute 16 is fixedly connected with the MTS actuator 11, and further includes a first T-shaped connector 20, the horizontal end of the first T-shaped connector 20 is embedded into the first clamping groove 17, and a plurality of steel rollers 18 are disposed inside the first clamping groove 17, and the first T-shaped connector 20 is movably connected with the first clamping groove 17 through the steel rollers 18; screw holes 19 are formed in the end parts of the vertical ends of the first T-shaped connecting pieces 20, screw rods are embedded in the screw holes 19, the first T-shaped connecting pieces 20 are fixedly connected with the first floating spherical hinges 4 through the screw rods, the tension sensor 7 is located at the vertical ends of the first T-shaped connecting pieces 20, fastening bolts 23 are respectively arranged on two sides of the outer portion of the first clamping groove 17, and extend into the first clamping groove 17 to be connected with the first T-shaped connecting pieces 20;
the second sliding T-shaped connecting piece 2 has the same structure as the first sliding T-shaped connecting piece 2, a chute of the second sliding T-shaped connecting piece 2 extends into the loading platform base 12 and is fixedly connected with the loading platform base 12, and a T-shaped connecting piece of the second sliding T-shaped connecting piece 2 is connected with the second floating spherical hinge 5;
as shown in fig. 4, the first stretching clamp 3 includes a C-shaped clamp 22 and side plates 21 located at 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 bottom of the C-shaped clamp 22, screws are embedded in the screw holes, and one end, far away from the first sliding T-shaped connecting piece 2, of the first floating ball hinge (4) is fixedly connected with the first stretching clamp 3 through the screws;
as shown in fig. 6 and 7, the second stretching clamp 34 has the same structure as the first stretching clamp 3, the bottom of the second stretching clamp 34 is connected with a Y-shaped joint 26 through a screw hole, the opening end of the Y-shaped joint 26 is embedded with an I-shaped joint 27, 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 of the I-shaped joint 27, which is far away from the Y-shaped joint 26, is connected with one end of the second floating spherical hinge 5, which is far away from the second sliding T-shaped connecting piece 2; the diameters of screw rods of the Y-shaped joint 26 and the I-shaped joint 27 are not smaller than 20mm;
as shown in fig. 2a, 2B, 2c, 5a and 5B, the test piece 6 is a dumbbell-shaped test piece, the height-width dimension B of the test area of the test piece is 3-5 times that of the largest 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 positioned 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 with the thickness of 1 mm-2 mm is also arranged between the side plate 21 and the test piece 6;
the invention also provides an application method of the hydraulic asphalt concrete direct tensile test device, which is implemented by adopting the hydraulic asphalt concrete direct tensile test device and specifically comprises the following steps of:
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;
if the molding is performed in a laboratory, a molding die matched with the method is required to be processed, and the concrete process of the laboratory molding is as follows: as shown in fig. 8, the forming mold is first assembled, the forming mold includes two forming side plates 32, two end plates 31 and a bottom plate 33, the two end plates are all connected by bolts, a protrusion matched with the test piece 6 is arranged at the center of the forming side plate 32, the forming process is single-layer double-sided compaction forming, and the specific steps are as follows: preparing asphalt mixture according to the mixing ratio required by hydraulic asphalt concrete standard, wherein the temperature range of the asphalt mixture is 145-155 ℃, heating a forming die to 100-110 ℃, coating a release agent, feeding the prepared asphalt mixture into the forming die, placing a flat plate on the upper part after the asphalt mixture is paved, adjusting the flatness of the asphalt mixture by observing a leveling bead, pulling a compaction hammer to a preset height to freely fall, 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; the 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 the MTS actuator 11 and the 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 instrument, and then the fixing clamping groove is screwed to fix the T-shaped connecting pieces; the tension sensor 7, the first floating spherical hinge 4, the first stretching clamp 3 and the test piece 6 are sequentially connected with the first sliding T-shaped connecting piece 1, the second floating spherical hinge 5 is connected with the second sliding T-shaped connecting piece 2, the test piece 6 is in a free plumb state, the Y-shaped connector 26 and the I-shaped connector 27 are respectively connected with the second stretching clamp 34 and the second floating spherical hinge 5, and the cylindrical pin 9 is inserted to complete the connection and installation of the test piece 6 and the 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 the I-shaped joint 27;
step 5, test preloading; the tension sensor 7 and the grating displacement sensor 8 are connected into an acquisition system, each test device is checked, the MTS actuator 11 is debugged, a loading system is set, the preloading is carried out under the room temperature condition, the preloading range is 20% -40% of the tensile strength of hydraulic asphalt concrete, when the readings of the displacement sensors are uniformly changed, the next step can be carried out, and otherwise, the test piece connection system is debugged 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.
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.
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