CN108225904B - The fixture that rocks in direct tension is tested and the test method based on the fixture - Google Patents
The fixture that rocks in direct tension is tested and the test method based on the fixture Download PDFInfo
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- CN108225904B CN108225904B CN201810322299.0A CN201810322299A CN108225904B CN 108225904 B CN108225904 B CN 108225904B CN 201810322299 A CN201810322299 A CN 201810322299A CN 108225904 B CN108225904 B CN 108225904B
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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
- 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
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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
- G01N2203/04—Chucks, fixtures, jaws, holders or anvils
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Abstract
The fixture of test and test method based on the fixture, belong to rock mechanics testing field.The fixture can be directly used for rock three-axis force testing machine, including seaming chuck and push-down head, hollow sliding groove is provided at the top of push-down head, sliding groove includes the mobile side of two pulleys disposed in parallel, it further include two groups of dumbbell shaped wheel shafts and two stretching chain bars, dumbbell shaped wheel shaft includes two sliding wheel shafts being connected by tensile axis, the two sliding wheel shafts are able to slide on the mobile side of two pulleys, one end that every tensile axis respectively stretches chain bar with one is connected, the other end of two stretching chain bars is connected with the both ends of test specimen respectively, it further include the wedge clamp being set between two tensile axis, the top length of wedge clamp is greater than bottom length, under the action of seaming chuck, wedge clamp can be gradually reduced, with the decline of wedge clamp, two stretching distance between axles increase, two stretching chain bars are stretched, with tensile test specimen；Suitable for carrying out the test of rock tensile strength.
Description
Technical field
The invention belongs to rock-soil mechanics testing fields, and rock can be realized on conventional rock mechanics machine by being related to one kind
The fixture of direct tensile test and the test method that the test of rock tensile strength is carried out based on the fixture.
Background technique
The failure mode of rock can be divided into following three classes: brittle break, ductile fracture and plane of weakness failure by shear mostly.And rock
Stone occurs to destroy mainly as caused by one of shearing, pressure, pulling force or many factors, therefore the tension of study of rocks is strong
Degree has considerable meaning to the failure mode and failure criteria of study of rocks.
Since the tensile strength of rock is smaller, it is relatively difficult that direct tensile test is carried out to rock, therefore indoor survey at present
The tensile strength of amount rock is mainly carried out by indirect drawing process.Wherein, most widely used method be split the law (bar
Western split the law) measurement rock tensile strength.Split the law is to concentrate pressure by applying to its diametrical direction using cylindrical type test specimen
What power was realized, step is simple, easily operated, it is only necessary to which a rock pressure machine can carry out.However, determined by this method
There are certain errors for the tensile strength that tensile strength and direct tensile test measure, and are difficult to obtain and stretch resultant stress strain song
Line.
It is the device that rocks in direct tension test is selected in the prior art as shown in Figure 1, is set respectively in about 6 two sides of test specimen
It is equipped with upper end cap 12 and lower endcaps 13, upper end cap 12, which is connected with, stretches chain 15, and 13 bottom of lower endcaps is connect with backing plate 11, test specimen
Fixing groove 14 is connect with backing plate 11, is had the support of rigid sleeve 16 below backing plate 11, is stretched the bolt of chain 15 and test specimen fixing groove
14 connections, due to there is certain interval between backing plate 11 and the test specimen fixing groove 14 of lower endcaps 13, rigid sleeve 16 cannot be entire
Effective supporting role is played to the weight of test specimen and lower endcaps during test.After test specimen institute tension stress reaches peak value,
Under the action of gravity suffered by failure mechanics test specimen below, lower endcaps 13 and the stretching chain 15 of lower part, test specimen occurs to destroy suddenly,
Leading to the rock tensile strength measured at present, there are further errors, and mechanics effect test is also more tired after carrying out peak stress
Difficulty, falling there is also the sample after destruction causes the sensors such as extensometer or its interface etc. to be risk of damage to.Although at present
Generation when thering are some researchs to improve for rock tensile test specimen and fixture, but not being avoided that gravity to rock tensile failure
Influence.On the other hand, axially loaded rate need to be reduced in order to test to obtain ess-strain result behind rock peak, tradition is directly drawn
Stretching experiment is controlled by reducing linear variable difference transformer LVDT rate, is difficult to reality for the equipment that LVDT is not configured
It is tested behind existing peak, and the minimum loading speed of equipment is limited, the loading speed cannot be reduced without limitation.Therefore, one is needed
It kind can be effectively reduced gravity and influence, improve result precision and can use conventional rock press machine and can be in conventional rock
What the rocks in direct tension intensity and destruction that loading speed is further decreased on the basis of the minimum loading speed of press machine were tested
Rock straightway testing system and method.
Meanwhile it is more for the research of compressive strength of rock in the prior art, interior utilizes conventional rock mechanics machine
The technology comparative maturity of compressive strength of rock is measured, and a variety of auxiliary such as acoustic emission test, optical strain measurement occurs
Measuring technique, with reflect rock sample when destroying the germinating of crackle, nucleation, extension, perforation until gross fracture process.For
The subsidiary function of conventional rock mechanics machine is made full use of, reducing gravity influences, improves result precision and can be with
Using conventional rock press machine and loading speed can be further decreased on the basis of conventional rock press machine minimum loading speed
Rocks in direct tension intensity and destruction test, rock can be realized on conventional rock mechanics machine by needing to invent one kind
The fixture and test method of direct tensile test measure destructive process of the rock sample in direct tensile test, and can draw
The curve in post-peak area of rock tensile failure is produced, to draw rock tensile failure whole English teaching, acquisition more can reaction engineering
Actual Tensile Strength of Rock.
Summary of the invention
The technical problem to be solved by the present invention is in order to overcome in the prior art rocks in direct tension test by gravity shadow
Pilot causes result accuracy rate low, and it is straight cannot to provide a kind of rock directly the shortcomings that being tested on conventional rock press machine
The fixture of tension test and the test method based on the fixture are connect, which can be real directly on conventional rock mechanics machine
Existing rocks in direct tension test, as a result accuracy rate is high, and can realize that loading speed reduction obtains by changing the radian of fixture
Obtain Complete Stress-Strain Curve.
The technical solution adopted by the present invention to solve the technical problems is: the fixture of rocks in direct tension test, the fixture
It can be directly used for rock three-axis force testing machine, including seaming chuck and push-down head, be provided with hollow sliding at the top of push-down head
Slot, sliding groove include the mobile side of two pulleys disposed in parallel, further include two groups of dumbbell shaped wheel shafts and two stretching chain bars, dumbbell
Shape wheel shaft includes two sliding wheel shafts being connected by tensile axis, the two sliding wheel shafts are able to mobile in two pulleys
Slided on side, every tensile axis respectively with one stretch chain bar one end be connected, two stretch chain bar the other end respectively with test specimen
Both ends be connected, further include the wedge clamp being set between two tensile axis, it is long that the top length of wedge clamp is greater than bottom end
Degree, under the action of seaming chuck, wedge clamp can be gradually reduced, and with the decline of wedge clamp, two stretching distance between axles increase
Greatly, two stretching chain bars are stretched, to realize the stretching of test specimen.
Specifically, test specimen is dog-bone, including cylinder body, cylinder body both ends are respectively provided with a discoid test specimen
Pull head, the diameter of test specimen pull head are greater than the diameter of cylinder body.
Specifically, sliding groove is rectangular-shape grid structure, it is welded to each other by 12 solid steel tubes, in sliding groove top
A solid fixed block is respectively arranged at portion's four points of connection.
Further, it is equipped with test specimen collet on the outside of test specimen pull head, is provided with latch groove on test specimen collet, is also set on tensile axis
Have a latch groove, stretch the steel rod piece that chain bar is high tensile, the both ends for stretching chain bar are both provided with latch groove, by with insert
The bolt that cotter way matches is connected with test specimen pull head and tensile axis respectively by chain bar is stretched.
Further, guide rail is provided at the top of sliding groove, sliding wheel shaft can be free to slide on guide rail.
Specifically, wedge clamp is two identical change radian pressing plates, thickness of compressive plate is 4~6mm, wedge clamp bottom
End length is slightly less than the total length that test specimen adds both ends to stretch chain bar, and wedge clamp top length adds both ends drawing chain slightly larger than test specimen
The total length of bar, the side of wedge clamp from bottom end to top as radius of curvature is gradually increased, tangent line with it is vertical to angle by
It is decrescence small.
Specifically, being provided with connecting plate between at the top of two wedge clamps, seaming chuck is acted on connecting plate, passes through company
The effect of power is passed to two pieces of wedge clamps by fishplate bar.
Preferably, seaming chuck is cylindric or rectangular-shape single solid steel briquetting, the size and shape and seaming chuck of push-down head
It is identical.
Another technical solution adopted by the present invention to solve the technical problem thereof is that: rock stretching test method, based on above-mentioned
The fixture of test specimen tension test, comprising the following steps:
A. the rock sample for selecting meet the requirements size and quality, records the master data of test specimen, and at the both ends of test specimen
Test specimen collet is pasted, master data includes test specimen internal diameter D2；
B. suitably upper push-down head is selected, and records the quality m of seaming chuck0, push-down head is placed on test motor spindle pressure
On head, and sliding groove is placed on push-down head, so that testing machine bottom ram, push-down head bottom center and test motor spindle pressure
Test specimen is fixed on the tensile axis of movable pulley between centers of sliding groove by the alignment of head center by stretching chain bar；
C. wedge clamp is vertically filled among sliding wheel shaft, squeezes wedge clamp from top to down, makes wedge clamp and cunning
Driving wheel axis two sides fit closely, and assemble seaming chuck, are aligned seaming chuck top center with testing machine upper pressure head center；
D. the axially mounted Axial extensometer in the middle part of test specimen, circumferential direction install circumferential extensometer, and slightly elevated machine displacement is straight
It closely compresses to seaming chuck and machine seaming chuck, is loaded with constant axial displacement loading speed, until experiment terminates, recorded
Related data, can measure and obtain rock sample complete stress-strain diagram during stretching, and record Complete Stress-Strain Relationship of Rock is bent
The inclination angle value of wedge clamp and tensile axis point of intersection when the stress of line reaches peak value, and it is recorded as peak value inclination value θ,
The peak value P of test specimen axial stresscr；
E. rock tensile strength σ is calculated according to the data of recordt=2* (Pcr+m0g)*tanθ/(πD2 2), wherein PcrFor axis
To the peak value of stress, m0For seaming chuck quality, D2For test specimen diameter, θ is peak value inclination value.
Specifically, test specimen is fixed on the tensile axis of movable pulley between centers of sliding groove by stretching chain bar in step B, have
Body be stretching chain bar is separately connected on the outside of two test specimen collets, and will stretch the other end of chain bar respectively with a tensile axis phase
Even, stretch and be reserved with latch groove on the both ends of chain bar, using the bolt to match with latch groove will stretch chain bar and test specimen collet,
Tensile axis is connected.
The beneficial effects of the present invention are: structure is simple, and it is easily operated, it converts draw direction to by traditional vertical direction
Horizontal direction keeps gravity orthogonal with axle power is stretched, and avoids influence of the gravity to axle power is stretched, while resitting an exam certainly by seaming chuck
Consider within test influence factor, further reduces experimental error, meanwhile, it is loaded by becoming radian wedge shape clamping plate,
When test specimen reaches destruction, test specimen axial rate reaches minimum, can be enterprising on the minimum loading speed basis of conventional rock press machine
One step reduces loading speed, is conducive to Complete Stress-Strain Curve in complete picture rock drawing process, and it is accurate to improve test result
Property；Further, since it directly can realize the direct tensile test of rock in conventional rock mechanics machine, tradition is made full use of
The function of Rock Mechanics Test machine, extends the purposes of conventional rock mechanics machine, and can combine conventional rock mechanical test
The loaded type CT scan of machine, acoustic emission monitor(ing) subsidiary means, monitor the destructive process of rock through a variety of ways, favorably
In further explore rock during stretching crackle generation, extension and perforation process.The present invention is suitable for carrying out rock and draws
Stretch strength test.
Detailed description of the invention
Fig. 1 is the structural schematic diagram for the device that existing direct tensile test is selected；
Fig. 2 is the structural schematic diagram of fixture in the present invention；
Fig. 3 is the structural schematic diagram A-A section plan view of fixture in the present invention；
Fig. 4 is the structural schematic diagram of wedge clamp in the present invention；
Fig. 5 is the structural schematic diagram for implementing rock tension test in the present invention on testing machine；
Fig. 6 is the structural schematic diagram of dog-bone sample in the present invention；
Wherein, 11 be backing plate, and 12 be upper end cap, and 13 be lower endcaps, and 14 be test specimen fixing groove, and 15 is stretch chain, and 16 are
Rigid sleeve, 1 is seaming chuck, and 2 be wedge clamp, and 3 be sliding wheel shaft, and 4 be sliding groove, and 5 be push-down head, and 6 be test specimen, and 7 be drawing
Chain bar is stretched, 8 be tensile axis, and 61 be cylinder body, and 62 be test specimen pull head.
Specific embodiment
With reference to the accompanying drawing, the technical schemes of the invention are described in detail.Conventional rock press machine described in text, that is, common rock
Stone press machine.
The fixture of rocks in direct tension test as shown in figures 2-3, including seaming chuck 1 and push-down head 5,5 top of push-down head
It is provided with hollow sliding groove 4, it further includes two groups of dumbbell shaped wheel shafts that sliding groove 4, which includes the mobile side of two pulleys disposed in parallel,
And two stretching chain bars 7, dumbbell shaped wheel shaft include two sliding wheel shafts 3 being connected by tensile axis 8, it is preferred that movable pulley
It is connected between axis 3 and tensile axis 8 with bolt, distance should be slightly bigger than sliding groove between two sliding wheel shafts of every group of dumbbell shaped wheel shaft
The distance on the mobile side of two pulleys makes the two sliding wheel shafts be able to slide on the mobile side of two pulleys, every stretching
One end that axis 8 respectively stretches chain bar 7 with one is connected, and the other end of two stretching chain bars 7 is connected with the both ends of test specimen respectively, also wraps
The wedge clamp 2 being set between two tensile axis 8 is included, the top length of wedge clamp 2 is greater than bottom length, in seaming chuck 1
Under the action of, wedge clamp 2 can be gradually reduced, and with the decline of wedge clamp 2, two 8 spacing of tensile axis increase, two drawings
It stretches chain bar 7 to be stretched, to realize the stretching of test specimen.
Seaming chuck is cylindric or rectangular-shape single solid steel briquetting, and when installation makes seaming chuck center and rock mechanics experiment
The alignment of machine seaming chuck center.As long as in test seaming chuck can press against wedge clamp and walk downward, push-down head can cushion sliding groove
Just meet condition.The size and shape of push-down head are identical as seaming chuck, in order to purchase and process.
Sliding groove 4 can choose rectangular-shape grid structure formula, is welded to each other by 12 solid steel tubes.Cuboid tool
There are 12 sides, therefore make sliding groove using 12 steel pipes, other connection types can be used, but in view of being connected and fixed effect
It is good, preferably with welding.The length of sliding groove should be greater than test specimen and both ends added to stretch the total length of chain bar, and need to reserve certain distance
For sliding wheel shaft sliding.The width of push-down head is greater than the width of sliding groove, may be implemented for sliding groove to be erected on push-down head,
It is respectively arranged with a solid fixed block at 4 top four points of connection of sliding groove, it is such as solid in four pieces of sliding groove apex welding
Bloom slides from sliding groove to avoid sliding wheel shaft.In order to control the slide-and-guide of sliding wheel shaft, it is arranged at the top of sliding groove
There is guide rail, sliding wheel shaft can be free to slide on guide rail.
Based on pulling force consider, stretch chain bar 7 be high tensile steel rod piece, stretch chain bar both ends be both provided with it is slotting
Cotter way is connected with test specimen pull head and tensile axis by the bolt to match with latch groove by chain bar is stretched respectively.Rod piece two sides with
Bolt is separately connected test specimen collet and stretches steel shaft, preferably compression helical spring, and it is straight to substitute tradition using compression helical spring
Connect the rigid sleeve of cupping machine use.There is a pin clamp in the middle part of tensile axis and stretching chain bar, insertion bolt keeps the two solid
It is fixed.
As shown in figure 4, wedge clamp 2 be two identical change radian pressing plates, thickness of compressive plate be not easy it is blocked up, preferably 4
~6mm, wedge clamp bottom length should be slightly less than the total length that test specimen adds both ends to stretch chain bar, preferably 290mm, and top length is answered
Slightly larger than the total length that test specimen plus both ends stretch chain bar, preferably 310mm, the side of wedge clamp is from bottom end to top with curvature
Radius is gradually increased, and tangent line is gradually reduced with vertical to angle.In front of test specimen and one piece of wedge clamp is filled at rear respectively.On
Pressure head bottom surface size is slightly larger than two pieces of wedge clamp spacing, it can be achieved that giving two pieces of wedge clamps to apply pressure simultaneously using seaming chuck
So that wedge clamp declines, in addition it is also possible to be provided with connecting plate between at the top of two wedge clamps, seaming chuck acts on company
On fishplate bar, connecting plate is parallel with seaming chuck bottom surface, and the effect of power is passed to two pieces of wedge clamps by connecting plate.
As shown in figure 5, the fixture of rocks in direct tension test can be directly used for rock three-axis force testing machine, by test specimen
Test can be carried out by being fixed in three-axis force experimental machine by components such as wedge-shaped clamping plate and sliding grooves.Pass through the fixture energy
The load conversion for the vertical direction that testing machine is applied is the load of horizontal direction, eliminates as much as gravity in rocks in direct tension
The influence generated during test.In addition, by using the wedge clamp of radian is become to control loading speed, with test into
The loading velocity of row horizontal direction is slower and slower, to reach load maximum value when rock tensile test specimen is up to destruction.
As shown in fig. 6, test specimen is dog-bone, including cylinder body 61,61 both ends of cylinder body are respectively provided with a disk
The characteristics of test specimen pull head 62 of shape, circular cross-section, is uniform force, is able to bear bigger active force, comes from force analysis
It says, circular stress is more reasonable than other shapes uniformly, is not in the phenomenon that stress is concentrated, improves result accuracy.Test specimen
The diameter of pull head 62 is greater than the diameter of cylinder body 61, and the universality based on test toolss selects following parameter: cylinder body 61
Height be 90~110mm, a diameter of 28~32mm, test specimen pull head 62 be discoid, a diameter of 48~54mm.It can be used
It is bonded or welded mode to connect test specimen pull head 62 at 61 both ends of cylinder body, based on the deformation small consideration of small and error in length, preferably
Bonding way.
Rocks in direct tension test method, including following step are carried out on conventional rock mechanics machine based on above-mentioned fixture
It is rapid:
(1) it samples.
In this example, sampling work is unfolded in the underground power house of Sichuan Province's Pubugou Hydropower Station, chooses 1# tailwater tunnel
Granite, be named as biotite monzonitic granite, hereinafter referred to as Pubugou Project granite.Rock sample visually observes as in canescence
Coarse grain inequigranular structure, massive structure, rock constituents are mainly quartzy (grey), and potassium feldspar (flesh pink), plagioclase is (greyish white
Color) and less dark minerals, the distribution of mineral constituent it is less uniform.Microscopically observation is middle coarse grain seriate hypidiomorphic granular
Structure, massive structure.Rock constituents are mainly made of two kinds of feldspars, quartz and a small amount of biotite.Part has stronger fragmentation.
(2) test specimen is prepared.
The Pubugou Project granite core or sillar chosen from scene are machined into directly in use for laboratory drilling machine or lathe etc.
Diameter is 50mm, is highly the standard specimen of 100mm, and ratio of height to diameter is (2 ± 0.2), in the middle part of test specimen of polishing later, until being in the middle part of test specimen
Diameter 30mm, the cylinder body of height 90mm, test specimen pull head are the prolate test specimen of diameter 60mm, height 5mm, form dog-bone
Test specimen.It is designed to that dog-bone test specimen in order to stretch, provides tensile stress.Sample preparation standard is referring to " GB50266-2013 engineering rock
Body test method standard " etc. relevant regulations carry out, with grinding machine process surface of test piece, be less than test specimen two ends face nonparallelism
0.05mm；Test specimen upper and lower side diameter difference is less than 0.3mm；Surface of test piece is answered smooth, and avoids what is generated by irregular surface from answering
Power concentration phenomenon.
(3) process is tested.
1) sample preparation: being 227.87g, height of specimen 105.21mm, test specimen outer diameter with electronic balance measurement test specimen quality
48.68mm, test specimen diameter D2For 30.09mm, calculating and obtaining Sample density is 2.64g/cm3Test specimen complies with standard, and records above-mentioned
Data.Test specimen collet is bonded on the outside of test specimen pull head with epoxy resin AB glue and is put into constant temperature oven in test specimen two ends later
In be heated to colloid solidification.Test specimen collet is a kind of existing plastic clamp, also be will use in traditional tension test, collet
On have latch groove, for stretch chain connection.After test specimen is cooling, examination is connected with the stretching chain bar side of the reserved latch groove in both ends
Part collet, side connection sliding wheel shaft, insertion bolt connect and check whether bolt connection is close.
2) placing component: selecting two diameters is 120mm, the pressure head of height 30mm, respectively as seaming chuck and push-down head,
It is 2.663kg that weighing, which obtains monolithic pressure head quality, and push-down head bottom center is aligned with testing machine bottom ram center；It selects real
The rectangular-shape grid structure sliding groove of heart steel pipe building, sliding groove overall dimensions are length 350mm, width 200mm, height
Sliding groove is placed on push-down head by 200mm, is aligned sliding groove bottom rectangular centre with push-down head bottom ram center.
3) it places rock sample: the test specimen that step 1) obtains is being slided together with stretching chain bar and sliding wheel shaft device
On slot, moderate lubrication oil is smeared on sliding groove, pushes sliding wheel shaft, checks whether test specimen entirety can be on solid sliding groove
It is free to slide.Bottom 290mm, top 310mm are selected, wedge clamp is vertically filled in sliding wheel shaft by the wedge clamp of thickness 5mm
Centre, in front of rock sample and one piece of wedge clamp is respectively filled at rear.Wedge clamp is suitably squeezed from top to down, makes wedge pressure
Plate is fitted closely with sliding wheel shaft two sides, is assembled seaming chuck, is aligned seaming chuck top center with testing machine upper pressure head center.
4) test: the axially mounted Axial extensometer in the middle part of rock sample, circumferential direction install circumferential extensometer.Slightly elevated machine
Device displacement is closely compressed until seaming chuck and machine seaming chuck, is displaced loading speed later with the constant axial of 0.005mm/min
It is loaded, until breaking test, which occurs, to be terminated, records related data, related data herein includes using on paper when destroying
Ruler draws tangential angle, and with the tilt angle of the protractor wedge clamp measured and tensile axis point of intersection, can
Measurement obtains rock sample complete stress-strain diagram during stretching.Record the axial stress of Complete Stress-Strain Relationship of Rock curve
Reaching the tilt angle that peak value is wedge clamp and tensile axis point of intersection is 15 °, and is recorded as peak value inclination value θ, such as Fig. 2
Shown in middle B point, the peak value P of axial stresscrFor 13.137kN, above-mentioned stress all refers to the axial stress that rock sample is subject to.
(5) calculated result.Rock tensile strength is calculated according to the data of record
σt=2* (Pcr+m0g)*tanθ/(πD2 2)=2* (13.137+2.663*9.8/1000) * 1000*tan (15 °)/
(π*30.092)=48MPa wherein, PcrFor the peak value of axial stress, m0For seaming chuck quality, D2For test specimen diameter, θ inclines for peak value
Angle value.
In order to improve result precision, it can repeatedly measure and average.
Claims (10)
1. the fixture of rocks in direct tension test, which is characterized in that including seaming chuck (1) and push-down head (5), push-down head (5) top
Portion is provided with hollow sliding groove (4), and it further includes two groups of dumbbells that sliding groove (4), which includes the mobile side of two pulleys disposed in parallel,
Shape wheel shaft and two stretching chain bars (7), dumbbell shaped wheel shaft include two sliding wheel shafts (3) being connected by tensile axis (8), this
Two sliding wheel shafts are able to slide on the mobile side of two pulleys, and every tensile axis (8) respectively stretches chain bar (7) with one
One end is connected, and it further includes being set to two tensile axis that two other ends for stretching chain bar (7) are connected with the both ends of test specimen respectively
(8) wedge clamp (2) between, wedge clamp (2) are two identical change radian pressing plates, and the side of wedge clamp is the bottom of from
It holds to top as radius of curvature is gradually increased, tangent line is gradually reduced with vertical to angle；The top length of wedge clamp (2) is big
In bottom length, in front of test specimen and one piece of wedge clamp is filled at rear respectively, under the action of seaming chuck (1), wedge clamp
(2) it can be gradually reduced, with the decline of wedge clamp (2), two tensile axis (8) spacing increase, two stretching chain bar (7) quilts
It stretches, to realize the stretching of test specimen.
2. fixture as described in claim 1, which is characterized in that test specimen is dog-bone, including cylinder body (61), cylinder master
Body (61) both ends are respectively provided with a discoid test specimen pull head (62), and the diameter of test specimen pull head (62) is greater than cylinder body (61)
Diameter.
3. fixture as described in claim 1, which is characterized in that sliding groove (4) is rectangular-shape grid structure, solid by 12
Steel pipe is welded to each other, and is respectively arranged with a solid fixed block at the four points of connection of sliding groove (4) top.
4. fixture as claimed in claim 2, which is characterized in that be equipped with test specimen collet on the outside of test specimen pull head, set on test specimen collet
It is equipped with latch groove, latch groove also is provided on tensile axis, the steel rod piece that chain bar is high tensile is stretched, stretches the both ends of chain bar
It is both provided with latch groove, is connected respectively with test specimen collet and tensile axis by the bolt to match with latch groove by chain bar is stretched.
5. fixture as described in claim 1, which is characterized in that be provided with guide rail at the top of sliding groove, sliding wheel shaft can led
It is free to slide on rail.
6. fixture as described in claim 1, which is characterized in that for wedge clamp (2) with a thickness of 4~6mm, wedge clamp bottom end is long
Degree is slightly less than the total length that test specimen adds both ends to stretch chain bar, and wedge clamp top length adds both ends to stretch chain bar slightly larger than test specimen
Total length.
7. fixture as claimed in claim 6, which is characterized in that it is provided with connecting plate between at the top of two wedge clamps, on
Pressure head acts on connecting plate, and the effect of power is passed to two pieces of wedge clamps by connecting plate.
8. fixture as described in claim 1, which is characterized in that seaming chuck is cylindric or rectangular-shape single solid steel briquetting, under
The size and shape of pressure head are identical as seaming chuck.
9. rocks in direct tension test method, which is characterized in that based on as described in any claim in claim 1~8
The fixture of rocks in direct tension test, comprising the following steps:
A. the rock sample for selecting meet the requirements size and quality, records the master data of test specimen, and paste at the both ends of test specimen
Test specimen collet, master data include test specimen internal diameter D2；
B. suitably upper push-down head is selected, and records the quality m of seaming chuck0, push-down head is placed in testing machine bottom ram,
And sliding groove is placed on push-down head, so that in testing machine bottom ram, push-down head bottom center and testing machine bottom ram
Test specimen is fixed on the tensile axis of movable pulley between centers of sliding groove by heart alignment by stretching chain bar；
C. wedge clamp is vertically filled among sliding wheel shaft, squeezes wedge clamp from top to down, makes wedge clamp and movable pulley
Axis two sides fit closely, and assemble seaming chuck, are aligned seaming chuck top center with testing machine upper pressure head center；
D. the axially mounted Axial extensometer in the middle part of test specimen, circumferential direction install circumferential extensometer, and slightly elevated machine displacement is until upper
Pressure head is closely compressed with machine seaming chuck, is loaded with constant axial displacement loading speed, until experiment terminates, record is related
Data can measure and obtain rock sample complete stress-strain diagram during stretching, record Complete Stress-Strain Relationship of Rock curve
The inclination angle value of wedge clamp and tensile axis point of intersection when stress reaches peak value, and it is recorded as peak value inclination value θ, test specimen
The peak value P of axial stresscr；
E. rock tensile strength σ is calculated according to the data of recordt=2* (Pcr+m0g)*tanθ/(πD2 2), wherein PcrIt is answered to be axial
The peak value of power, m0For seaming chuck quality, D2For test specimen diameter, θ is peak value inclination value.
10. method as claimed in claim 9, which is characterized in that test specimen is fixed on sliding groove by stretching chain bar in step B
Movable pulley between centers tensile axis on, specifically, being separately connected stretching chain bar on the outside of two test specimen collets, and chain bar will be stretched
The other end be respectively connected with a tensile axis, stretch and be reserved with latch groove on the both ends of chain bar, utilize what is matched with latch groove
Bolt will stretch chain bar and be connected with test specimen collet, tensile axis.
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