CN110823717B - Semi-flexible pavement shear strength testing device and testing method - Google Patents

Abstract

The invention relates to a semi-flexible pavement shear strength testing device and a testing method. It includes the following steps: S1: processing the inner core of the specimen, and wrapping the outer surface of the inner core with asphalt to make the asphalt specimen; S2: fixing the asphalt specimen at the fixing hole of the box cover; S3: fixing the asphalt specimen The asphalt specimen on the box cover is inserted into the box, and then the test material is injected into the box through the injection hole on the box cover; S4: After the test material is solidified, the asphalt specimen is pulled out from the test material by the tensile equipment; S5: Measurement And calculate the shear contact area between each asphalt specimen and the test material, and then calculate the total shear contact area by summing up; S6: Read the force load of the tensile equipment, and use the force load to contact the total shear contact The ratio of the areas determines the shear stress. The invention provides equipment and method support for the test of the shear strength of the semi-flexible pavement, and greatly facilitates the research on the shear resistance of the semi-flexible pavement.

Description

A kind of semi-flexible pavement shear strength testing device and testing method

technical field

The invention relates to the technical field of semi-flexible pavement shear strength testing, in particular to a semi-flexible pavement shear strength testing device and a testing method.

Background technique

In road engineering, the failure forms of asphalt pavement are various and the reasons are not the same. One of the important reasons is the strength and stability of asphalt mixture. In the process of pavement damage caused by the destruction of mixture, shear failure is its main form of destruction. The shear failure of the mixture is mainly the shear failure of the asphalt itself and the shear failure of the contact surface between the asphalt and the aggregate.

In the past, due to various reasons such as test technology and test equipment, there were no clear requirements for the test of the shear performance of the pavement structure, and there was no suitable test equipment for the shear test of asphalt mixture and pavement. The test is of great significance to the study of road damage, and can provide important data and theoretical basis for the on-site construction of asphalt pavement. In view of this, providing a test device and test method specially used to measure the shear strength of asphalt pavement has become a Urgent problem to be solved.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for testing the shear strength of semi-flexible pavement, which is used to solve the technical problem of lack of a corresponding test method for the shear strength test of semi-flexible pavement such as asphalt in the prior art. Another object of the present invention is to provide a semi-flexible pavement shear strength testing device applied to the testing method.

In order to achieve the above purpose, the present invention provides a semi-flexible pavement shear strength testing device, which adopts the following technical solutions:

A semi-flexible pavement shear strength testing device comprises a box body and a box cover which are arranged separately, the box body is provided with an opening for the box cover to be buckled; the box cover is provided with a fixing hole, an injection hole and a handle structure , the fixing hole is used to fix the asphalt sample, the injection hole is used to inject the test material into the box, and the handle structure is used to connect with the tensile device to pull the asphalt sample out of the injected test material.

Further, the handle structure is threadedly assembled on the box cover, and the box cover is provided with a threaded through hole for fixing the handle structure, and the threaded through hole constitutes the injection hole.

Further, the injection holes are arranged in the middle position, and the fixing holes are plural and arranged at intervals along the circumferential direction of the injection holes.

Further, the circumferential edge of the box cover is provided with a blocking structure, and the blocking structure is used to block each other with the opening edge of the box body, so as to stop and limit the box cover to the opening of the box body. location.

The present invention also provides a method for testing the shear strength of semi-flexible pavement, which adopts the following technical solutions:

A method for testing shear strength of semi-flexible pavement comprises the following steps:

S1: Process the inner core of the specimen, and wrap the outer surface of the inner core of the specimen with asphalt to make an asphalt specimen;

S2: Fix the asphalt specimen at the fixing hole of the box cover;

S3: Insert the asphalt specimen on the box cover into the box, and then inject the test material into the box through the injection hole on the box cover;

S4: After the test material is solidified, the asphalt specimen is pulled out from the test material by tensile equipment;

S5: Measure and calculate the shear contact area between each asphalt specimen and the test material, and then calculate the total shear contact area by summing;

S6: Read the applied load of the tensile device, and determine the shear stress by the ratio of the applied load to the total shear contact area.

Further, the following steps are further included: S7: Repeat the above steps and measure multiple sets of shear stress data, and average the measured shear stress data.

Further, in step S1, the inner core of the test piece is processed and ground into a cylinder.

Further, in step S2, the asphalt sample is pasted and fixed at the corresponding fixing hole by an adhesive.

Further, in step S5, the shear contact area is calculated by the product of the perimeter of the bottom surface of the asphalt specimen and the height of the shear contact surface.

Further, in step S4, it also includes fixing a pressure sensor on the bottom peripheral side of the asphalt test piece, and the pressure sensor is used to monitor whether the asphalt test piece has been completely pulled out from the test material.

Compared with the prior art, a device for testing the shear strength of a semi-flexible pavement and a method for testing the shear strength of a semi-flexible pavement according to the embodiments of the present invention have the following beneficial effects: The test device and test method for testing the shear strength provide equipment and method support for the test of the shear strength of the semi-flexible pavement, which greatly facilitates the study of the shear effect of the semi-flexible pavement. In addition, the testing device of the present invention has simple structure and low cost, and can fully meet the requirements of limited testing funds.

Description of drawings

FIG. 1 is a side plan view of a semi-flexible pavement shear strength testing device according to Embodiment 1 of the present invention;

2 is a schematic bottom view of the semi-flexible pavement shear strength testing device according to Embodiment 1 of the present invention;

3 is a side plan view of the semi-flexible pavement shear strength testing device according to Embodiment 2 of the present invention;

FIG. 4 is a schematic bottom side view of the device for testing the shear strength of the semi-flexible pavement according to Embodiment 2 of the present invention.

In the figure, 1-box body, 2-box cover, 201-handle structure, 202-fixing hole, 203-injection hole, 204-stop structure.

Detailed ways

The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and embodiments. The following examples are intended to illustrate the present invention, but not to limit the scope of the present invention.

Embodiment 1 of the semi-flexible pavement shear strength testing device of the present invention

As shown in FIG. 1 and FIG. 2 , a semi-flexible pavement shear strength test device (hereinafter referred to as a test device) is a preferred embodiment of the embodiment of the present invention. The test device includes a box body 1 and a box cover 2 that are arranged separately. The box body 1 is provided with an opening for the box cover 2 to be buckled; the box cover 2 is provided with a fixing hole 202, an injection hole 203 and a handle structure 201. , the fixing hole 202 is used to fix the asphalt sample, the injection hole 203 is used to inject the test material into the box 1, and the handle structure 201 is used to connect with the tensile equipment to inject the asphalt sample from the injection test material is pulled out.

Specifically, the box body 1 of the testing device in this embodiment is cylindrical, the box body 1 includes a bottom cover and a curved side wall, and the top of the box body 1 is open. In accordance with the shape of the opening of the box body 1 , in this embodiment, the box cover 2 is in the shape of a circular plate, and the box cover 2 is provided with a fixing hole 202 , an injection hole 203 and a handle structure 201 . In this embodiment, the handle structure 201 is in a stepped shape as a whole. The handle structure 201 includes a round cake portion and a cylindrical portion. The round cake portion is a circular plate, and the cylindrical portion is a cylinder. In this embodiment, the handle structure 201 is threadedly assembled on the box cover 2. Specifically, the center of the box cover 2 is provided with a threaded through hole for the handle structure 201 to be threadedly assembled, and the outer peripheral side of the cylindrical portion is correspondingly provided with an external thread. When fixing the handle structure 201, the cylindrical portion can be screwed into the threaded through hole.

It should be noted that in this embodiment, the radial dimension of the box cover 2 is slightly smaller than the opening size of the box body 1, so that the box cover 2 can be inserted into the opening during the test, and the box cover 2 and the inner wall of the opening can be blocked by the box cover 2. The limiting effect can make the asphalt specimen fixed at each fixing hole 202 be inserted vertically into the box body 1, so as to avoid the direction of the pulling force applied to the box cover 2 when the asphalt specimen is inserted into the opening obliquely. The specimen is in a non-parallel condition. When this happens, the test material will have a certain blocking effect on the asphalt specimen, which will increase the force of pulling out the asphalt specimen and affect the accuracy of the test measurement.

In this embodiment, the injection hole 203 is used to inject the test material into the box body 1 when the box cover 2 is fastened at the opening of the box body 1. In order to simplify the arrangement of the injection hole 203 on the box cover 2, in this embodiment The injection hole 203 and the threaded through hole on the box cover 2 for fixing the handle structure 201 are designed as a whole. In other embodiments, the injection hole 203 can also be provided separately from the threaded through hole, and in this case, the threaded through hole for fixing the handle can be a blind hole. Since the handle structure 201 needs to bear the force during the test, in order to ensure the balanced distribution of the applied force, the threaded through hole is arranged at the center position of the box cover 2 in this embodiment.

In this embodiment, there are multiple fixing holes 202 , and the fixing holes 202 are all round holes. In other embodiments, they may also be square holes, pentagonal holes, hexagonal holes, semi-circular holes, special-shaped holes, and the like. These fixing holes 202 are arranged at equal intervals along the circumferential direction of the threaded through holes (ie, the injection holes 203 ). Specifically as shown in Figure 2. In this embodiment, the fixing holes 202 are used to fix the asphalt samples. During the test, a plurality of asphalt samples can be fixed on the box cover 2 at the same time. By testing multiple asphalt samples at the same time, the number of asphalt samples can be reduced to a certain extent. Reduce the experimental error caused by a small amount of time and improve the accuracy of the test results.

Embodiment 2 of the semi-flexible pavement shear strength testing device of the present invention

As shown in FIG. 3 and FIG. 4 , the technical feature of the difference between Embodiment 2 and Embodiment 1 is that in this embodiment, a stop structure 204 is provided at the circumferential edge position of the box cover 2 . The stop structure 204 is a circle of protrusions arranged on the periphery of the box cover 2. When the box cover 2 is buckled at the opening of the box body 1, the box cover 2 is partially inserted into the opening, and the stop structure 204 is connected to the opening. The positions of the mouth edges of the mouth block each other, thereby preventing the box cover 2 from being completely inserted into the box body 1 or falling into the box body 1 . The setting of the blocking structure 204 makes the amount of the box cover 2 inserted into the box body 1 to be fixed, which can avoid the test error caused by the difference of each insertion depth, improve the consistency of each test, and further eliminate the test error .

In addition, each fixing hole 202 in this embodiment is a through hole provided on the box cover 2. Since the asphalt sample in this embodiment is pasted and fixed in the corresponding fixing hole 202 by an adhesive, the adhesive is specific. For epoxy resin, the design of each fixing hole 202 as a through hole facilitates the removal of residual epoxy resin in the later stage.

The third embodiment of the semi-flexible pavement shear strength testing device of the present invention

The technical feature of the difference between Example 3 and Example 1 is that: in order to facilitate the observation of the injection of the test material in the box body 1, in this embodiment, an observation window is provided on the box body 1, and the observation window is fixed on the side of the box body 1. A transparent panel on the wall. The transparent plate is strip-shaped and extends along the depth direction of the box body 1 , and a scale is also provided on the transparent plate.

Embodiment 1 of the test method for shear strength of semi-flexible pavement (hereinafter referred to as the test method) of the present invention

The test method of the present embodiment comprises the following steps:

S1: Process the inner core of the specimen, and wrap the outer surface of the inner core of the specimen with asphalt to make an asphalt specimen

Specifically, in this embodiment, multiple inner cores of the test pieces need to be processed first, and the inner cores are cylindrical, and in other embodiments, they may also be prismatic, semi-cylindrical, or the like. In this example, the material of the inner core of the test piece is natural stone, and the inner core of each test piece needs to be processed into a uniform specification with a diameter of 20 mm and a height of 100 mm. It should be noted that the specification parameters of the introspection of the test piece in this embodiment are It is selected according to the diameter of the fixing hole 202 and the depth of the box body 1 . When the diameter of the fixing hole 202 and the depth of the box body 1 are adjusted, the corresponding processing specification can be selected. After the inner core of the test piece is processed, put the inner core of the test piece into the mixer for mixing with the asphalt, so as to realize the coating of the asphalt on the outer surface of the inner core of the test piece. It should be noted that, in other embodiments, it is also possible to The surface of the inner core of the specimen was coated with asphalt by smearing. Asphalt specimens were made after the inner core of each specimen was wrapped.

S2: Fix the asphalt sample at the fixing hole 202 of the box cover 2

Specifically, in this embodiment, each asphalt sample is fixed in each fixing hole 202 by means of pasting, and in this embodiment, the asphalt sample is pasted in each fixing hole 202 by an adhesive, and the adhesive is specifically: Epoxy resin, the adhesive can be smeared on the corresponding end of the asphalt sample during the pasting process, or the adhesive can be poured into the fixing hole 202 first.

S3: Insert the asphalt sample on the box cover 2 into the box body 1, and then inject the test material into the box body 1 through the injection hole 203 on the box cover 2

Specifically, after each asphalt test piece is uniformly pasted and fixed in the corresponding fixing hole 202 , each asphalt test piece can be inserted into the box body 1 . It should be noted that, in this embodiment, the box cover 2 is not provided with the stop structure 204 . After each asphalt sample is inserted, the bottom of each asphalt sample is in contact with the bottom of the box 1 . Then, unscrew the handle structure 201, and inject the test material into the box body 1 through the threaded through hole (ie, the injection hole 203). After the injection is completed, the handle structure 201 is screwed on again. In this example, the test material is concrete mortar.

S4: After the test material is solidified, the asphalt specimen is pulled out from the test material by the tensile device

Specifically, after the injection of the test material is completed, let it stand for a period of time to make the mortar solidify, and then the test device can be prevented from pulling out each asphalt test piece from the test material at the special tensile device. It should be noted that, in this embodiment, the tension device is a universal tester. Before starting the tension device for pulling, the round cake portion of the handle structure 201 and the tension head of the tension device need to be pasted and fixed together with an adhesive. In order to ensure the accuracy of the test results, the direction of the tension applied by the tension head in this embodiment should be as parallel as possible to the extension direction of each asphalt specimen.

In addition, this embodiment also includes the step of fixing the pressure sensor on the bottom peripheral side (non-stick end) of the asphalt specimen. In this embodiment, the pressure sensor is specifically a pressure strain gauge, and the pressure sensor is connected to the data acquisition device through a wire. In the embodiment, the data acquisition device is a notebook computer. The setting of the pressure sensor is convenient to observe whether the asphalt specimen is completely pulled out. When the asphalt specimen is completely separated from the test material, the pressure sensor will be in a non-stressed state, and the pressure data on the laptop will no longer be displayed. Thereby, it can be judged that the asphalt specimen has been completely pulled out from the test material, and the end of the tensile test can be judged. In other embodiments, it is also possible to judge whether the asphalt test piece is completely separated from the test material by means of human eye observation, and the pressure sensor may not be provided in this case.

It should be noted that, in order to ensure the stability of the pulling force application process, in this embodiment, the pulling speed of the pulling force device is selected as 2 mm/min. In other embodiments, the corresponding pulling speed may be selected according to the actual situation.

S5: Measure and calculate the shear contact area between each asphalt specimen and the test material, and then calculate the total shear contact area by summing

Specifically, after the asphalt sample is completely pulled out of the test material, the testing device is removed, and then the shear contact area of each asphalt sample on the tank cover 2 is measured. In this example, since the shear stress between the asphalt specimen and the test material is measured, part of the outer peripheral surface of each asphalt specimen is the shear contact area. The product of the height of the shear contact area is calculated. When measuring, it is necessary to first measure the perimeter of the bottom surface of the corresponding asphalt sample. Specifically, the perimeter of the bottom surface can be obtained by first measuring the diameter of the bottom surface of the asphalt sample, and then calculating the perimeter of the bottom surface from the diameter, or by winding the asphalt test piece with a soft rope. Pieces one week, and then measure the corresponding length of the cord to obtain.

In this embodiment, the height of the shear contact area is obtained by direct measurement. Since the surface of the asphalt specimen sheared and separated from the test material will leave an imprint of the test material, the shear can be measured by measuring the height of the imprint. The height of the contact area.

Finally, the shear contact area of a single asphalt specimen can be calculated by multiplying the height of the shear contact area by the measured bottom perimeter of the asphalt specimen, and then the total shear contact area can be obtained by summing the calculated shear contact areas. Cut contact area.

S6: Read the applied load of the tensile device, and determine the shear stress by the ratio of the applied load to the total shear contact area

Specifically, in this embodiment, since each asphalt test piece is pulled out from the test material is a process, the applied load of the tension device read in this embodiment is actually the average value of the tension in this process. Through the force analysis, the read force load of the tensile equipment can be regarded as the shear force required when the asphalt and the test material are damaged. Since the total shear contact surface can be known in step S5, by reading The corresponding shear stress can be obtained by dividing the applied load of the tensile equipment by the total shear contact area, and the shear stress is the shear strength to be measured in this embodiment.

S7: Repeat the above steps and measure multiple sets of shear stress data, and average the measured shear stress data

Specifically, in order to further eliminate the test error, multiple groups of tests are designed in this embodiment, and the above steps S4 to S6 are repeated for each group of tests, so as to obtain the shear stress data measured in each group, and finally The average value of each shear stress data can be obtained, and the obtained average value can be regarded as the shear strength value of the asphalt pavement measured in the final test.

To sum up, the embodiments of the present invention provide a semi-flexible pavement shear strength test device and a corresponding semi-flexible pavement shear strength test method, which provide equipment and method support for the semi-flexible pavement shear strength test, greatly It is convenient to study the shear effect of semi-flexible pavement. In addition, the testing device of the present invention has simple structure and low cost, and can fully meet the requirements of limited testing funds.

The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the technical principle of the present invention, several improvements and replacements can be made. These improvements and replacements It should also be regarded as the protection scope of the present invention.

Claims (9)

1. A semi-flexible pavement shear strength testing device, characterized in that: it comprises a box body (1) and a box cover (2) that are arranged separately, and the box body (1) is provided with a supply box cover (2) A buckled opening; the box cover (2) is provided with a fixing hole (202), an injection hole (203) and a handle structure (201), the fixing hole (202) is used for fixing the asphalt sample, and the injection hole (203) is used for injecting test material into the box (1), and the handle structure (201) is used for connecting with a tensile device to pull out the asphalt test piece from the injected test material; the handle structure (201) ) is screwed on the box cover (2), the box cover (2) is provided with a threaded through hole for fixing the handle structure (201), and the threaded through hole constitutes the injection hole (203). 2. The device for testing the shear strength of semi-flexible pavement according to claim 1, characterized in that: the injection hole (203) is arranged in the middle position, and the fixing holes (202) are multiple along the injection hole (203). 203) are arranged at intervals in the circumferential direction. 3. The semi-flexible pavement shear strength testing device according to claim 1, characterized in that: a stop structure (204) is provided on the circumferential edge of the box cover (2), and the stop structure (204) The opening edge of the box body (1) is used to block each other, so as to stop and limit the box cover (2) at the opening position of the box body (1). 4. a semi-flexible pavement shear strength testing method, is characterized in that comprising the following steps: S1: Process the inner core of the specimen, and wrap the outer surface of the inner core of the specimen with asphalt to make an asphalt specimen; S2: Fix the asphalt test piece at the fixing hole (202) of the box cover (2); S3: Insert the asphalt test piece on the box cover (2) into the box body (1), and then inject the test material into the box body (1) through the injection hole (203) on the box cover (2); S4: After the test material is solidified, the asphalt specimen is pulled out from the test material by tensile equipment; S5: Measure and calculate the shear contact area between each asphalt specimen and the test material, and then calculate the total shear contact area by summing; S6: Read the applied load of the tensile device, and determine the shear stress by the ratio of the applied load to the total shear contact area. 5. The method for testing the shear strength of semi-flexible pavement according to claim 4, further comprising the following steps: S7: Repeat the above steps and measure multiple groups of shear stress data, and average the measured shear stress data value. 6 . The method for testing the shear strength of semi-flexible pavement according to claim 5 , wherein in step S1 , the inner core of the test piece is processed and ground into a cylinder. 7 . 7 . The method for testing the shear strength of semi-flexible pavement according to claim 5 , wherein in step S2 , the asphalt sample is pasted and fixed at the corresponding fixing hole ( 202 ) by an adhesive. 8 . 8. The method for testing the shear strength of semi-flexible pavement according to claim 5, wherein in step S5, the shear contact area is the product of the bottom surface perimeter of the asphalt test piece and the height of the shear contact surface Calculated. 9 . The method for testing the shear strength of semi-flexible pavement according to claim 5 , wherein in step S4 , the method further comprises fixing a pressure sensor on the bottom peripheral side of the asphalt test piece, and the pressure sensor is used for monitoring the asphalt test piece. 10 . whether the piece has been completely pulled out of the test material.

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