CN104316416A - Semicircle loading direct shear test device and method for bituminous mixture - Google Patents
Semicircle loading direct shear test device and method for bituminous mixture Download PDFInfo
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- 238000012360 testing method Methods 0.000 title claims abstract description 244
- 239000000203 mixture Substances 0.000 title claims abstract description 23
- 238000000034 method Methods 0.000 title claims description 20
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 50
- 239000010959 steel Substances 0.000 claims abstract description 50
- 238000010998 test method Methods 0.000 claims abstract description 22
- 239000010426 asphalt Substances 0.000 claims description 63
- 238000003825 pressing Methods 0.000 claims description 40
- 238000010008 shearing Methods 0.000 claims description 28
- 238000012937 correction Methods 0.000 claims description 15
- 238000009413 insulation Methods 0.000 claims description 9
- 238000013461 design Methods 0.000 claims description 8
- 230000008569 process Effects 0.000 claims description 7
- 238000005070 sampling Methods 0.000 claims description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 6
- 238000002360 preparation method Methods 0.000 claims description 3
- JLQUFIHWVLZVTJ-UHFFFAOYSA-N carbosulfan Chemical compound CCCCN(CCCC)SN(C)C(=O)OC1=CC=CC2=C1OC(C)(C)C2 JLQUFIHWVLZVTJ-UHFFFAOYSA-N 0.000 description 12
- 238000012669 compression test Methods 0.000 description 8
- 238000011156 evaluation Methods 0.000 description 8
- 239000000463 material Substances 0.000 description 7
- 238000010276 construction Methods 0.000 description 5
- 238000006073 displacement reaction Methods 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 238000007493 shaping process Methods 0.000 description 3
- 238000007660 shear property test Methods 0.000 description 3
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Abstract
The invention discloses a semicircle loading direct shear test device for a bituminous mixture. The semicircle loading direct shear test device comprises a cylindrical test piece, a press plate, a top cover, a bottom cover, a steel sleeve and a base. The sectional area of the press plate, the sectional area of the top cover and the sectional area of the bottom cover are equal, and the diameter of the test piece and the diameter of the top cover are each equal to the inner diameter of the steel sleeve; the steel sleeve is fixedly connected to the base, the top cover and the bottom cover are located in an inner cavity of the steel sleeve, the bottom cover is fixedly connected to the wall face at the bottom of the steel sleeve, the top cover is fixedly connected to the wall face on the upper portion of the steel sleeve, the test piece is located in the steel sleeve, the press plate is located on the test piece and embedded between the top cover and the wall face of the steel sleeve, and the bottom, opposite to the press plate, of the test piece is suspended. The test device is simple in structure and convenient to operate, when the test device is used for testing, the stress distribution state of the test piece is simple, and the failure surface of the test piece is clear. The invention further provides a test method for the test device, the test method is simple and easy to operate, and an indoor formed Marshall test piece and a core sample drilled from an actual road surface can be detected.
Description
Technical field
The invention belongs to highway engineering performance of asphalt mixture detection field, specifically, relate to a kind of asphalt semicircle and load direct shear test device and test method thereof.
Background technology
Ended for the end of the year 2013, the highway of China has broken through 100,000 kilometers, and total kilometrage leaps to the first in the world.From last century the nineties, China enters the period of highway construction fast development, and especially since implementation of China pro-active fiscal policy in 1998, more than highway construction on-stream item, investment quantity is big highly visible.In expressway construction, because bituminous pavement has good comfortableness and excellent usability, construction speed is fast, easy to maintenance, and the parent receiving people looks at.
But along with the surge of the volume of traffic, the increasing substantially and the formation of canalized traffic of overrun and overload vehicle ratio, the disease of bituminous pavement is also on the rise.Among China's most area 1 year, have tens of sky and even more than 100 day summer road table temperature higher than 40 ~ 50 DEG C, this temperature has has met or exceeded road asphalt softening point.Under the high temperature conditions, bituminous concrete pavement bears the repeated action that wheel rolls, and the shear stress that load produces exceedes the shearing strength of asphalt, makes flow deformation constantly accumulate formation rut.Temperature is higher, and pitch is softer, and surface deformation is larger.In addition, wheel load effect belongs to non-uniform distributed pressure, produces larger shear stress, if stability at high temperature of asphalt mixture is not enough, will produce larger detrusion by asphalt road surface local region.
At present, the shear resistance evaluating asphalt is not required in the middle of the Asphalt Mixture Design code of China, wherein mainly contain two reasons: one is not yet reach common understanding to suitable compound shear behavior evaluation method in the industry, equipment test method cheap, simple to operate is not subject to extensive accreditation, even and if the test method of apparatus expensive, complicated operation is approved, but be difficult to promote on a large scale in engineering; Two is in Asphalt Mixture Design process, have employed this empirical index of dynamic stability at present to evaluate rutting resistance, has partly filled up the blank that Anti-Shear Characteristics of Asphalt Mixtures is evaluated.
In fact, China is in the Ministry of Construction's " urban road Flexible Pavement Design method and index study " achievement of Ministry of Communications's " highway flexible pavement bending resistance is drawn, anti-shearing index study " of nineteen eighty-two and 1986, establish shear index, occur in the case of a high temperature to prevent bituminous pavement gathering around bag, pushing and shear fracture.But on the one hand because highway is not at that time developed, so there is no cause pay abundant attention, Road Design specification is not given and being listed in; On the other hand, because triaxial test mensuration shearing strength is cumbersome, is difficult to popularity, does not thus consider formally to adopt shear index always.
By extensively investigating the test method of domestic and international shear strength of asphalt mixture, find that the research about pitch and Anti-Shear Characteristics of Asphalt Mixtures receives extensive concern.Wherein, some evaluation methods need to introduce expensive set of equipments, and test operation is complicated and cost that is each test is higher, comprises Superpave simple shear test, triaxial compression test, direct shear test and rotational shear test etc.; Other test methods, testing equipment is relatively simple and easy, but has special requirement to the shape of bitumen mixture specimen and size, is unsuitable for the common cylinder body core that road pavement scene drills through and evaluates, as oblique scissor test and coaxial shear test etc.; The test method also had, as uniaxial penetration test, test specimen bears multidirectional complex stress condition, though the macro-stress distribution of simulated roadway structure under tyre load as much as possible, but the non-homogeneous load of tire and the load assignment of rigid pressure head differ greatly after all, are still subject to a lot of restriction in actual applications.
To sum up, for overcoming many defects that existing test method exists, this invention exploits a kind of novel asphalt compound shear behavior method of testing---semicircle loads direct shear test (as shown in Figure 1, Figure 2), this shear test has that testing equipment is simple, convenient operation, test specimen stress distribution is clear and definite, can shaping marshal piece and actual road surface drill through in sensing chamber simultaneously core.
Summary of the invention
Technical matters: technical matters to be solved by this invention is: provide a kind of asphalt semicircle to load direct shear test device, this test unit structure is simple, convenient operation, during the test of this test unit, test specimen stress distribution is simple, test specimen failure mechanics is clear and definite; Also provide the test method of this test unit, this test method is simple to operation simultaneously, can core that simultaneously shaping marshal piece and actual road surface drill through in sensing chamber.
Technical scheme: for solving the problems of the technologies described above, the technical solution used in the present invention is:
A kind of asphalt semicircle loads direct shear test device, this device comprises the right cylinder test specimen be made up of asphalt, semicircle pressing plate, semi-circular rounded top, semicircle bottom, steel bushing and base, the area of section of the area of section of pressing plate, the area of section of top cover and bottom is all equal, and the diameter of test specimen, the diameter of top cover are equal with the internal diameter of steel bushing respectively; Steel bushing is fixedly connected on base, and top cover and bottom are arranged in steel bushing inner chamber, and bottom is fixedly connected in steel bushing bottom wall, and top cover is fixedly connected on the wall of steel bushing top; Top cover and bottom are oppositely arranged; Test specimen is arranged in steel bushing, and test specimen is between top cover and bottom; Pressing plate is positioned at above test specimen, and is embedded between top cover and steel bushing wall, and pressing plate and top cover symmetry are laid; The arc surface of the arc surface of bottom, the arc surface of pressing plate, top cover is fitted with steel bushing inside surface respectively; Be in unsettled bottom the test specimen relative with pressing plate.
Further, described base top surface is provided with annular groove, and the bottom of steel bushing is embedded in the annular groove of base.
Further, described bottom is bolted to connection in steel bushing bottom wall, and top cover is bolted to connection on the wall of steel bushing top.
Further, the end face of described pressing plate is provided with groove, and this groove is positioned at the middle part of pressing plate.
Above-mentioned asphalt semicircle loads a test method for direct shear test device, and the method comprises the following steps:
Step 10) prepare test specimen: utilize and newly mix asphalt, adopt compacting process to make right cylinder test specimen; Or by bituminous pavement core boring sampling, will the bitumen mixture specimen of core acquisition be bored as right cylinder test specimen;
Step 20) test specimen insulation: the Water Tank with Temp.-controlled that right cylinder test specimen and test mould are placed in design temperature is respectively incubated, insulation test specimen 45min ~ 60min, the below of right cylinder test specimen is provided with cushion block, and the bottom of right cylinder test specimen and the distance of bottom of gullet are more than or equal to 5cm;
Step 30) test preparation: first right cylinder test specimen is placed on the bottom of test mould, again top cover is installed, then pressing plate is placed on above right cylinder test specimen, and top cover and pressing plate are in same plane, then be placed on by test mould in environment insulation can, temperature control is at-0.5 DEG C ~ 0.5 DEG C;
Step 40) start-up loading: start universal testing machine, the pressure head of universal testing machine acts on pressing plate, with the loading speed uniform load of 1mm/min, until right cylinder test specimen destroys; The load obtained by universal testing machine data acquisition system (DAS) and test piece deformation curve, read the load peak value P in loading procedure, load peak value P is multiplied by correction factor g (h), obtains the load correction of peak value value of corresponding differing heights right cylinder test specimen; G (h)=79.45h
-0.95, wherein h represents the height of right cylinder test specimen;
Step 50) measuring and calculating shearing strength: by step 40) the load correction of peak value value that obtains is multiplied by maximum shear intensive parameter 0.783, obtains the shearing strength of right cylinder test specimen.
Further, described step 10) in, make n right cylinder test specimen as parallel test specimen; Described step 20) in, the distance in Water Tank with Temp.-controlled between n right cylinder test specimen is more than or equal to 10mm; Respectively step 30 is performed to each right cylinder test specimen) to step 50), obtain the shearing strength of n right cylinder test specimen, get the mean value of the shearing strength of n right cylinder test specimen, as the shearing strength of right cylinder test specimen.
Beneficial effect: compared with prior art, technical scheme of the present invention has following beneficial effect: asphalt semicircle of the present invention loads direct shear test device, comprises right cylinder test specimen, semicircle pressing plate, semi-circular rounded top, semicircle bottom, steel bushing and base.Top cover and bottom are oppositely arranged, and pressing plate and top cover symmetry are laid, and the half of test specimen bottom surface is in unsettled, and half is positioned at above bottom.The structure of whole test unit is simple.This test unit is utilized effectively to test the shear behavior of test specimen.Semicircle of the present invention loads direct shear test method, direct shear test device is loaded by large cylinder bitumen mixture specimen is put into semicircle by assigned position, universal testing machine is utilized at the uniform velocity to load the semicircle pressure head in test unit, the change of the vertical position of displacement transducer double spherical head is coordinated to monitor in real time, measure the development of maximum shear strength obtaining asphalt, coordinate the uniaxial compression test of asphalt simultaneously, measuring and calculating obtains cohesion and the angle of internal friction of asphalt mixture material, reach accurate, the object of effective evaluation asphalt anti-shear performance.The method has several large advantage compared with the Anti-Shear Characteristics of Asphalt Mixtures evaluation method of other types: first, obvious failure mechanics is had below the diametrical position of semicircle pressure head, the stress distribution of asphalt is simple and clear, and shear stress presents antisymmetry distribution relative to failure mechanics; Second, this test method is evaluated field at material shear behavior and is belonged to direct shear test category, compare direct shear test method traditional in soil mechanics, this method is without the need to the complete direct shear test equipment by costliness, only need to adopt semicircle to load direct shear test device, coordinate and utilize universal testing machine and displacement transducer just can complete shearing strength test; 3rd, this test method can coordinate asphalt uniaxial compression test and reduction formula, calculates crucial shear behavior evaluation index, cohesion and angle of internal friction in mole strength theory
serve the effect replacing triaxial compression test, compare triaxial compression test, the method is without the need to its set of equipments, and test operation is simple, with low cost.
Accompanying drawing explanation
Fig. 1 is the cut-open view of test unit of the present invention.
Fig. 2 is the vertical view of test unit of the present invention.
Fig. 3 is during the present invention tests, the stress distribution cloud atlas of large cylinder test specimen.
Fig. 4 is during the present invention tests, right cylinder test specimen axle center maximum shear distribution plan under different load.
Fig. 5 is during the present invention tests, differing heights right cylinder test specimen axle center maximum shear distribution plan.
Fig. 6 is during the present invention tests, large and small marshal piece surface diameter direction maximum shear distribution plan.
Have in figure: test specimen 1, pressing plate 2, top cover 3, bottom 4, steel bushing 5, base 6, bolt 7.
Embodiment
Below in conjunction with accompanying drawing, technical scheme of the present invention is described in further details.
As depicted in figs. 1 and 2, a kind of asphalt semicircle of the present invention loads direct shear test device, comprises right cylinder test specimen 1, semicircle pressing plate 2, semi-circular rounded top 3, semicircle bottom 4, steel bushing 5 and the base 6 be made up of asphalt.The area of section of the area of section of pressing plate 2, the area of section of top cover 3 and bottom 4 is all equal.The diameter of test specimen 1, the diameter of top cover 3 are equal with the internal diameter of steel bushing 5 respectively.Steel bushing 5 is fixedly connected on base 6, and top cover 3 and bottom 4 are arranged in steel bushing 5 inner chamber, and bottom 4 is fixedly connected in steel bushing 5 bottom wall, and top cover 3 is fixedly connected on the wall of steel bushing 5 top.Top cover 3 and bottom 4 are oppositely arranged.Test specimen 1 is arranged in steel bushing 5, and test specimen 1 is between top cover 3 and bottom 4.Pressing plate 2 is positioned at above test specimen 1, and is embedded between top cover 3 and steel bushing 5 wall, and pressing plate 2 and top cover 3 symmetry are laid.The arc surface of the arc surface of bottom 4, the arc surface of pressing plate 2, top cover 3 is fitted with steel bushing 5 inside surface respectively.Be in unsettled bottom the test specimen 1 relative with pressing plate 2.Like this, test specimen 1 bottom surface, half area is positioned on bottom 4, and half area is in unsettled.
Further, described base 6 end face is provided with annular groove, and the bottom of steel bushing 5 is embedded in the annular groove of base 6.Steel bushing 5 has multiple with the connected mode of base 6.As a kind of preferred version, between the steel bushing 5 in the present invention and base 6, adopt on-fixed connected mode.Adopt this kind of connected mode after each shear test terminates, steel bushing 5 can be separated with base 6, the asphalt chip remained in device is removed clean.
Further, described bottom 4 is fixedly connected in steel bushing 5 bottom wall by bolt 7, and top cover 3 is fixedly connected on the wall of steel bushing 5 top by bolt 7.Top cover 3 is fixedly connected on the wall of steel bushing 5 top by bolt 7.When the height of test specimen 1 is different, can assembling-disassembling bolt 7 be passed through, come again top cover 3 to be fixed in place.The standard so just not needing the height of test specimen 1 all to keep unified, is conducive to producing of test specimen 1, especially to existing bituminous pavement core boring sampling.Connect top cover 3 by bolt 7, be convenient to regulate the distance between bottom 4 and top cover 3.
Further, the end face of described pressing plate 2 is provided with groove, and this groove is positioned at the middle part of pressing plate 2.Groove is set at the middle part of pressing plate 2, the loading position of universal testing machine pressure head can be fixed, facilitate it to apply uniform pressure to pressing plate 2.
Above-mentioned asphalt semicircle loads the test method of direct shear test device, comprises the following steps:
Step 10) prepare test specimen: utilize and newly mix asphalt, adopt compacting process to make right cylinder test specimen 1; Or by bituminous pavement core boring sampling, will the bitumen mixture specimen of core acquisition be bored as right cylinder test specimen 1.The effective object of test unit in this patent, both can be utilize the right cylinder test specimen 1 newly mixed asphalt and make in laboratory, can be again to existing bituminous pavement core boring sampling.
In step 10) in, as preferably, the diameter of test specimen 1 is 152.4mm, and the height of test specimen 1 is between 40mm ~ 95.3mm.The altitude datum of test specimen 1 is 95.3mm.Compacting process can according to Bitumen Mix Design, and the method for operating specified according to the T0702-2011 in " highway engineering pitch and Asphalt Mixture Experiment code " JTG E20-2011 is carried out.
Step 20) test specimen insulation: the Water Tank with Temp.-controlled that right cylinder test specimen 1 and test mould are placed in design temperature is respectively incubated, insulation test specimen 45min ~ 60min, the below of right cylinder test specimen 1 is provided with cushion block, and the bottom of right cylinder test specimen 1 and the distance of bottom of gullet are more than or equal to 5cm.
Step 30) test preparation: first right cylinder test specimen 1 is placed on the bottom 4 of test mould, top cover 3 is installed again, then pressing plate 2 is placed on above right cylinder test specimen 1, and top cover 3 and pressing plate 2 are in same plane, then be placed on by test mould in environment insulation can, temperature control is at-0.5 DEG C ~ 0.5 DEG C.
Step 40) start-up loading: start universal testing machine, the pressure head of universal testing machine acts on pressing plate 2, with the loading speed uniform load of 1mm/min, until right cylinder test specimen 1 destroys; The load obtained by universal testing machine data acquisition system (DAS) and test piece deformation curve, read the load peak value P in loading procedure, load peak value P is multiplied by correction factor g (h), obtains the load correction of peak value value of corresponding differing heights right cylinder test specimen 1; G (h)=79.45h
-0.95, wherein h represents the height of right cylinder test specimen 1.Semicircle loads direct shear test only can the load application ground surface material testing equipment that also test is out of shape need carry out at universal testing machine or other, by test piece deformation determinator displacement transducer LVDT, (LVDT full name is linear variable difference transformer, for a kind of linear displacement transducer) and data acquisition system (DAS), can the electromotive signal of pick-up transducers automatically, store in data acquisition system (DAS) and draw load and test piece deformation curve.
Step 50) measuring and calculating shearing strength: by step 40) the load correction of peak value value that obtains is multiplied by maximum shear intensive parameter 0.783, obtains the shearing strength of right cylinder test specimen 1.
In addition, in step 10) in, make n right cylinder test specimen 1 as parallel test specimen; Described step 20) in, the distance in Water Tank with Temp.-controlled between n right cylinder test specimen 1 is more than or equal to 10mm; Respectively step 30 is performed to each right cylinder test specimen 1) to step 50), obtain the shearing strength of n right cylinder test specimen 1, get the mean value of the shearing strength of n right cylinder test specimen 1, as the shearing strength of right cylinder test specimen 1.Like this, by arranging parallel test specimen, getting the shearing strength of mean value as right cylinder test specimen 1 of shearing strength, being conducive to improving measuring accuracy.
Asphalt semicircle of the present invention loads direct shear test method, semicircle pressing plate is adopted asphalt right cylinder test specimen at the uniform velocity to be loaded to the shearing strength measuring material, this test has made test unit of the present invention, conventional universal testing machine is coordinated to load, by test piece deformation determinator LVDT and data acquisition system (DAS), the electromotive signal of automatic pick-up transducers, stores and draws load and test piece deformation curve in data acquisition system (DAS).By revising read load peak value, calculate the shearing strength of asphalt, and by the intensive parameter that institute's apply-official formula and l-G simulation test are established calculate asphalt shear behavior parameter c and
this test method has that testing equipment is simple, the stress distribution of convenient operation, test specimen and failure mechanics clear and definite, be suitable for the shearing strength of marshal piece shaping in sensing chamber and actual road surface core boring sampling, there is important promotional value.
Load the feasibility of direct shear test in order to prove semicircle, and the size of test specimen is optimized, have employed ABAQUS Finite Element Method and set up 3D model, to simulate the loading destructive process that semicircle loads direct shear test, and the stress distribution of calculation testing piece inside.In test, asphalt modulus gets E=1200Mpa, Poisson ratio μ=0.35, and cell type is three-dimensional hexahedron structure unit.In simulation process, when to have calculated semicircle pressing plate well-distributed pressure be respectively 0.2Mpa ~ 1Mpa (step-length 0.2Mpa), the maximum shear distribution of right cylinder test specimen, structure is as shown in table 1.
Table 1 large marshal piece axle center maximum shear distribution (MPa)
As shown in Table 1, along test specimen axle center (highly) direction, maximum shear is not equally distributed, there is certain stress within the scope of the upper and lower surface 20mm of test specimen to concentrate, the maximum position of shear stress is in distance upper and lower surface height 12mm position, and shear stress minimum point is at 1/2 At The Height, both differ 32%.No matter external loads applies much, the overall rule along axle center distribution of right cylinder test specimen shear stress is consistent, as shown in Figure 4.
For the large marshal piece of φ 152.4mm × 95.3mm, it is under well-distributed pressure 0.2Mpa ~ 1Mpa condition, the maximum shear τ at shaft core position place
mdistribute as shown in table 1, Fig. 3 is shown in by stress distribution cloud atlas.As can be seen from Figure 3: under the condition that semicircle pressure head loads, the upper and lower surface diametrical position of large marshal piece can produce very large shear stress, along with the Slow loading of pressure head, will test specimen be cut as two halves, to produce shear breakage in the midsection of test specimen, the stress state of test specimen presents antisymmetry distribution relative to midsection.
Further, by reducing the height of right cylinder test specimen 1, test test specimen 1 height is for the impact of stress distribution situation.The situation that the maximum shear comparing the test specimen being highly 95.3mm and 40mm in Fig. 5 distributes along height of specimen.In Fig. 5, with differing heights place, axle center shear stress τ
mwith axle center maximum shear (τ
m)
maxratio τ
m/ (τ
m)
maxas ordinate, the ratio h of shear stress place shaft core position height h ' and height of specimen is as horizontal ordinate.As can be seen from Figure 5: the height of right cylinder test specimen 1 is for the not impact of the overall rule of maximum shear distribution vertically.As can be seen here, load direct shear test for semicircle, the unfixing specification of height of right cylinder test specimen, only needs the variability from the test of material composition Angle ambiguity.The upper layer majority of usual bituminous pavement adopts AC13, SMA13, minority also adopts the asphalt of OGFC13, for the asphalt of nominal maximum particle diameter 13mm, height of specimen is adopted to be greater than 40mm (being namely three times in nominal maximum particle diameter), be conducive to reducing semicircle and load direct shear test variability, also meet the actual conditions of most bituminous pavement upper layer thickness simultaneously.With standard large marshal piece φ 152.4mm × 95.3mm for benchmark, altitude correction factor is multiplied by the large cylinder test specimen shearing strength of differing heights and carries out intensity correction, as shown in table 2.
Table 2 semicircle loads the altitude correction factor of direct shear test
| Height of specimen (mm) | Correction factor |
| 95.3 | 1.000 |
| 90 | 1.065 |
| 80 | 1.195 |
| 70 | 1.331 |
| 60 | 1.562 |
| 50 | 1.869 |
| 40 | 2.308 |
Except the coefficient of shear strength that above height of specimen is corresponding, coefficient of shear strength can also calculate by being multiplied by altitude correction factor, and in formula, h is the height (mm) of large cylinder test specimen:
G (h)=79.45h
-0.95formula (1)
In order to study marshal piece in the diametric stress distribution situation of semicircle pressure head surface of contact, respectively the large marshal piece being of a size of φ 152.4mm × 95.3mm and the little marshal piece that is of a size of φ 101.6mm × 63.5mm are applied with to the well-distributed pressure of 1MPa, calculated stress concentrates situation, and result as shown in Figure 6.Can see by Fig. 6, diameter edges at two ends position 1.2cm among a small circle in, there will be stress concentration phenomenon to a certain degree.Little owing to there is the regional extent that stress is concentrated, and at the marginal position of pressure head, little on the impact of shearing strength.In process of the test, notice that pressure head two ends being avoided as far as possible coarse aggregate just can reduce this impact further.Meanwhile, consider that large Marshall's cross-sectional area is large, the impact being therefore subject to edge stress concentrated is much smaller.In addition, this experiment is not only applicable to the less asphalt mat of nominal maximum particle diameter, is applicable to the flexbile base that nominal maximum particle diameter is greater than 25mm yet, therefore the large cylinder test specimen that diameter is 152.4mm is optimal selection.
Except shearing strength, the anti-shear performance of evaluating material also has two large important parameters, i.e. cohesion c and angle of internal friction
at present, in view of the loading mode of soil mechanics, only have triaxial compression test can according to mole strength theoretical directly calculate asphalt c and
by taking semicircle to load direct shear test device, coordinate asphalt uniaxial compression test, just can derive based on semicircle loading direct shear test device c,
measure formula.
formula (2)
formula (3)
Wherein, σ
1for the first principal stress of mechanics of materials mole strength theory, computing formula is such as formula (4).σ
3for the third principal stress of mechanics of materials mole strength theory, computing formula is such as formula (5).σ
ufor the asphalt unconfined compressive strength (MPa) that uniaxial compression test records.
σ
1=C
1g (h) P formula (4)
σ
3=C
3g (h) P formula (5)
Wherein, P is the load peak value (MPa) adopting semicircle loading direct shear test device to record, and g (h) is the height correction formula of right cylinder test specimen shearing strength, C
1for first principal stress σ
1intensive parameter, C3 is third principal stress σ
3intensive parameter.Load direct shear test for semicircle, fundamental strength parameter is as shown in table 3.
Table 3
| Stress | First principal stress σ 1 | Third principal stress σ 3 | Maximum shear τ m |
| Intensive parameter | 1.835 | 0.268 | 0.783 |
To sum up, semicircle of the present invention loads direct shear test device and test method can the anti-shear performance of effective evaluation asphalt, and test specimen is stressed clearly, equipment is cheap, simple to operate, the shear behavior evaluation requirements of right cylinder core in indoor marshal piece and Practical Project can be met, contribute to the evaluation instructing the remaining performance of Bitumen Mix Design and rebuilding old road medium pitch road surface, have important using value at highway engineering detection field.
The above is only the preferred embodiment of the present invention; be noted that for those skilled in the art; under the premise without departing from the principles of the invention; some improvement and equivalent replacement can also be made; these improve the claims in the present invention and are equal to the technical scheme after replacing, and all fall into protection scope of the present invention.
Claims (8)
1. an asphalt semicircle loads direct shear test device, it is characterized in that, this device comprises the right cylinder test specimen (1) be made up of asphalt, semicircle pressing plate (2), semi-circular rounded top (3), semicircle bottom (4), steel bushing (5) and base (6), the area of section of the area of section of pressing plate (2), the area of section of top cover (3) and bottom (4) is all equal, and the diameter of test specimen (1), the diameter of top cover (3) are equal with the internal diameter of steel bushing (5) respectively; Steel bushing (5) is fixedly connected on base (6), top cover (3) and bottom (4) are arranged in steel bushing (5) inner chamber, and bottom (4) is fixedly connected in steel bushing (5) bottom wall, top cover (3) is fixedly connected on the wall of steel bushing (5) top; Top cover (3) and bottom (4) are oppositely arranged; Test specimen (1) is arranged in steel bushing (5), and test specimen (1) is positioned between top cover (3) and bottom (4); Pressing plate (2) is positioned at test specimen (1) top, and is embedded between top cover (3) and steel bushing (5) wall, and pressing plate (2) and top cover (3) symmetry are laid; The arc surface of the arc surface of bottom (4), the arc surface of pressing plate (2), top cover (3) is fitted with steel bushing (5) inside surface respectively; Test specimen (1) bottom relative with pressing plate (2) is in unsettled.
2. asphalt semicircle according to claim 1 loads direct shear test device, it is characterized in that, described base (6) end face is provided with annular groove, and the bottom of steel bushing (5) is embedded in the annular groove of base (6).
3. asphalt semicircle according to claim 1 loads direct shear test device, it is characterized in that, described bottom (4) is fixedly connected in steel bushing (5) bottom wall by bolt (7), and top cover (3) is fixedly connected on the wall of steel bushing (5) top by bolt (7).
4. asphalt semicircle according to claim 1 loads direct shear test device, and it is characterized in that, the end face of described pressing plate (2) is provided with groove, and this groove is positioned at the middle part of pressing plate (2).
5. asphalt semicircle according to claim 1 loads a test method for direct shear test device, and it is characterized in that, the method comprises the following steps:
Step 10) prepare test specimen: utilize and newly mix asphalt, adopt compacting process to make right cylinder test specimen (1); Or by bituminous pavement core boring sampling, will the bitumen mixture specimen of core acquisition be bored as right cylinder test specimen (1);
Step 20) test specimen insulation: the Water Tank with Temp.-controlled that right cylinder test specimen (1) and test mould are placed in design temperature is respectively incubated, insulation test specimen 45min ~ 60min, the below of right cylinder test specimen (1) is provided with cushion block, and the bottom of right cylinder test specimen (1) and the distance of bottom of gullet are more than or equal to 5cm;
Step 30) test preparation: first right cylinder test specimen (1) is placed on the bottom (4) of test mould, top cover (3) is installed again, then pressing plate (2) is placed on right cylinder test specimen (1) top, and top cover (3) and pressing plate (2) are in same plane, then be placed on by test mould in environment insulation can, temperature control is at-0.5 DEG C ~ 0.5 DEG C;
Step 40) start-up loading: start universal testing machine, the pressure head of universal testing machine acts on pressing plate (2), with the loading speed uniform load of 1mm/min, until right cylinder test specimen (1) destroys; The load obtained by universal testing machine data acquisition system (DAS) and test piece deformation curve, read the load peak value P in loading procedure, load peak value P is multiplied by correction factor g (h), obtains the load correction of peak value value of corresponding differing heights right cylinder test specimen (1); G (h)=79.45h
-0.95, wherein h represents the height of right cylinder test specimen (1);
Step 50) measuring and calculating shearing strength: by step 40) the load correction of peak value value that obtains is multiplied by maximum shear intensive parameter 0.783, obtains the shearing strength of right cylinder test specimen (1).
6. the test method of direct shear test device is loaded according to asphalt semicircle according to claim 5, it is characterized in that, described step 10) in, the diameter of test specimen (1) is 152.4mm, and the height of test specimen (1) is between 40mm ~ 95.3mm.
7. load the test method of direct shear test device according to asphalt semicircle according to claim 5, it is characterized in that, described altitude datum is 95.3mm.
8. load the test method of direct shear test device according to asphalt semicircle according to claim 5, it is characterized in that, described step 10) in, make n right cylinder test specimen (1) as parallel test specimen; Described step 20) in, the distance in Water Tank with Temp.-controlled between n right cylinder test specimen (1) is more than or equal to 10mm; Respectively step 30 is performed to each right cylinder test specimen (1)) to step 50), obtain the shearing strength of n right cylinder test specimen (1), get the mean value of the shearing strength of n right cylinder test specimen (1), as the shearing strength of right cylinder test specimen (1).
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