阅读说明：本技术 一种多孔沥青混合料冻胀应力及其释放特征测试装置及方法 (Device and method for testing frost heaving stress and release characteristic of porous asphalt mixture ) 是由 吴胜坤 朱文兵 周俊 臧小双 桂佳佳 周大松 刘野 陈雷 冯浩 于 2019-08-02 设计创作，主要内容包括：本发明是测量多孔沥青混合料车辙板冻胀应力及其释放特征的测试装置及方法。装置包括车辙板固定装置、电阻式土压力盒、静态应变测试仪。本装置的使用包含以下步骤：成型多孔沥青混合料车辙板试件并控制其孔隙水饱和度,模拟多孔沥青混合料车辙板的冻融过程,通过静态应变测试仪输出应变并通过公式计算应力。通过对比不同方向应力变化,分析冻胀应力及释放特征的方向差异性。通过观察融化时车辙板的应力变化,分析融化时的应力释放特征。通过对比有无车辙情况下的车辙板的冻胀应力和释放特征,判断车辙对冻融耐久性的影响。(The invention relates to a testing device and a method for measuring frost heaving stress and release characteristics of a porous asphalt mixture track plate. The device comprises a rut plate fixing device, a resistance type soil pressure cell and a static strain tester. The use of the device comprises the following steps: and forming a porous asphalt mixture track plate test piece, controlling the pore water saturation of the test piece, simulating the freeze-thaw process of the porous asphalt mixture track plate, outputting strain through a static strain tester and calculating the stress through a formula. By comparing stress changes in different directions, the directional differences of frost heaving stress and release characteristics are analyzed. Stress relief characteristics during melting were analyzed by observing stress changes in the rut plate during melting. And judging the influence of the ruts on the freeze-thaw durability by comparing the frost heaving stress and the release characteristics of the rut plates under the condition of the ruts.)

1. Device of test porous bituminous mixture rut board frost heaving stress, its characterized in that: the device comprises a track plate fixing device main body, a resistance type soil pressure cell and a static strain tester.

2. The apparatus of claim 1, wherein: the main body of the rut plate fixing device is formed by splicing an L-shaped steel plate and two rectangular steel plates, and is fixed through 8 pull rods in two directions, and the pull rods are arranged in a vertically staggered mode.

3. The apparatus of claim 2, wherein: two U-shaped grooves for fixing the soil pressure box are welded in the middle of the rectangular steel plate.

4. The apparatus of claim 1, wherein: the soil pressure cell selects a resistance-type soil pressure cell, is connected with a static strain tester to output strain, and calculates the stress through a formula.

5. The method for testing frost heaving stress of the porous asphalt mixture rut plate is characterized by comprising the following steps of: (1) a porous asphalt mixture track plate test piece (2) with required pore water saturation is obtained by a pore water saturation control method, the test piece is placed in a cubic structure formed by three steel plates and a lower pull rod, an upper pull rod is installed, an earth pressure box is placed in a U-shaped groove, the pull rod is adjusted to enable a stress surface of the earth pressure box to be tightly attached to the test piece, an unstressed surface of the earth pressure box is tightly attached to the steel plates, a connecting line of the earth pressure box is connected with a static strain tester (3) test piece and the whole device is placed in a refrigerator, the temperature is adjusted to 5 degrees, the earth pressure box is kept still for 10 to 20 minutes, the temperature is adjusted to-20 degrees, the frost heaving process of the porous asphalt mixture track plate is simulated, the frost heaving strain is recorded once every 15 minutes, the frost heaving stress (4) is calculated by a formula P ═ mu ∈ K, the frost heaving process is stopped when the reading of the static strain tester is stable, and (3) simulating the melting process of the porous mixture track plate, recording the released strain amount once every 15min, calculating the stress, and stopping the test when the reading of the static strain tester is not changed any more.

6. The method of claim 5, further comprising: in the step (2), the stress surface of the soil pressure cell needs to be strictly contacted with the surface of the test piece, and the non-stress surface is tightly attached to the rectangular steel plate.

Technical Field

The invention belongs to the field of stress test of porous mixtures, and particularly relates to a test for frost heaving stress change and release characteristics of a rut plate of a porous mixture.

Background

Porous asphalt pavements have become an important form of pavement because of their advantages of skid resistance, noise reduction, safe driving in rainy days, effective supplement of underground water resources, etc. However, the problem of insufficient freeze-thaw durability caused by freeze-thaw damage influences the wide application of the porous asphalt pavement. Therefore, in order to promote the popularization and application of the porous asphalt pavement, research on freeze-thaw damage caused by frost heaving and residual stress should be deeply developed.

The particularity of the internal pore structure of the porous asphalt mixture makes the freeze-thaw process and the damage condition of the porous asphalt mixture obviously different from those of the common asphalt mixture. Because the porous water containing the large number of communicated pores is contained, when the pore water saturation is large, the volume expansion generated by freezing the pore water is restrained by the pore wall, so that the frost heaving pressure stress is generated on the pore wall, and the frost heaving stress is generated on the mixture under the condition that the stress is not effectively released, so that the frost heaving damage is caused. In addition, during the melting process, frost heaving pressure stress on the pore wall can be gradually attenuated, but even if ice is completely melted into water, residual deformation still exists in the mixture, and the freeze-thaw resistance of the mixture is affected. It follows that the process of freeze-thaw damage can be studied by observing the changes in stress during the freeze-thaw process.

For the research on the freeze-thaw damage of the porous asphalt mixture, the influence of freeze thawing on the relative dynamic elastic modulus, the mass change rate, the water absorption rate, the bending and pulling strength, the compressive strength and the compression-fracture ratio of the porous asphalt mixture is analyzed through tests at home and abroad, and then the attenuation rule of the pavement performance of the porous asphalt mixture under the freeze thawing action is summarized. And for the test of frost heaving stress and the analysis of release characteristics, each country has no uniform standard and specific method. Therefore, the simple and rapid testing method for the frost heaving stress and the release characteristic of the porous asphalt mixture is provided, and has important value for deeply analyzing and understanding the essence of the freeze-thaw process of the porous asphalt mixture and promoting the application of the porous asphalt mixture in the frozen region.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to comprehensively and accurately analyze and evaluate the frost heaving stress change of the porous asphalt mixture rut plate.

The invention aims to solve the technical problem of providing a testing device which is simple in structure and simple and convenient to operate, overcomes the inconvenience of stress testing during freeze thawing of outdoor pavements, and provides test conditions for accurately testing the frost heaving stress and the release characteristics of a porous asphalt mixture track plate.

The technical scheme is as follows:

1. porous asphalt rut plate frost heaving stress testing device

The utility model provides a test porous bituminous mixture rut board frost heaving stress's device which characterized in that: the device comprises a track plate fixing device main body, a resistance type soil pressure cell and a static strain tester.

The rut plate fixing device main body is formed by splicing an L-shaped steel plate and two rectangular steel plates, and the L-shaped steel plate and the rectangular steel plates are fixed through 8 pull rods in two directions after being spliced.

And U-shaped grooves of the two soil fixing pressure boxes are welded in the middle of the rectangular steel plate.

The soil pressure cell selects a resistance-type soil pressure cell, is connected with a static strain tester to output strain, and calculates the stress through a formula.

The method for testing frost heaving stress of the porous asphalt mixture rut plate is characterized by comprising the following steps of:

the method comprises the following steps: forming a porous asphalt mixture track plate test piece, and obtaining the porous asphalt mixture track plate test piece with the required pore water saturation through a pore water saturation control method;

step two: placing a test piece into a cubic structure formed by combining three steel plates and a lower pull rod, and installing an upper pull rod; placing the soil pressure cell into a U-shaped groove, adjusting a pull rod to enable a stressed surface of the soil pressure cell to be tightly attached to a test piece, enabling an unstressed surface of the soil pressure cell to be tightly attached to a steel plate, and connecting a soil pressure cell connecting line with a static strain tester;

step three: placing the test piece and the whole device into a refrigerator, adjusting the temperature to 5 ℃, and standing for 10-20 min; adjusting the temperature to-20 degrees, simulating the frost heaving process of the porous asphalt mixture track plate, recording frost heaving strain every 15min, and calculating the frost heaving stress through a formula P which is mu epsilon multiplied by K;

step four: stopping the frost heaving process when the reading of the static strain tester is stable; the temperature was adjusted to 15 ° to simulate the melting process of the porous mix rut plate. The amount of released strain was recorded every 15min and the stress was calculated. And stopping the test when the reading of the static strain tester is not changed any more.

When the soil pressure cell is installed, the stress surface must strictly contact the surface of the test piece, and the non-stress surface is tightly attached to the rectangular steel plate.

The calculation formula P ═ μ ∈ × K where K is the calibration coefficient and the basic coefficient of the soil pressure cell.

In the frost heaving experiment, before the temperature is adjusted to-20 ℃, the sample is kept stand for 10-15 min in an environment of 5 ℃ so as to eliminate the influence possibly caused by the difference of the initial test temperature.

The method for controlling the saturation of the pore water comprises the following specific steps:

the method comprises the following steps: forming a porous mixture rut plate test piece, measuring the volume V, wrapping the bottom surface and the side surface of the porous mixture with a plastic soft film and an adhesive tape, and weighing the mass m of the porous asphalt mixture rut plate₀g, immersing the porous asphalt mixture rut plate in water, standing for 15min under the vacuum degree of-97.5 kPa, recovering the normal pressure, standing the test piece in the water for 30min, and weighing the mass m of the porous asphalt mixture rut plate completely saturated with water₁g, calculating the void volume content as (m)₁-m₀)cm³；

Step two: drying the porous asphalt mixture rut plate test piece obtained in the step one to constant weight, and injecting mass m into the porous asphalt mixture rut plate test piece₂g of water to give a void saturation ofThe upper surface of the porous asphalt mixture track plate test piece is sealed by a plastic soft filmAnd obtaining the porous asphalt mixture rut plate test piece with the porosity saturation degree of C.

Compared with the prior art, the invention has the beneficial effects that: (1) the frost heaving stress change and release characteristics of the porous asphalt mixture rut plate can be accurately tested, and the device is simple in structure, convenient to disassemble and assemble, safe, reliable, and simple and convenient to test and operate. (2) And adjusting the water content of the test piece through actually measuring the void ratio so as to test the test pieces with different saturation degrees. (3) By testing the test piece after the rutting test, the influence of the existence of the rutting on the frost heaving stress and the release characteristic of the frost heaving stress can be compared.

The foregoing is only an overview of the technical solutions of the present invention, and in order to more clearly understand the technical solutions of the present invention, the present invention is further described below with reference to the accompanying drawings.

Drawings

FIG. 1 is a schematic view of the main body of the apparatus;

FIG. 2 is a detailed top view of the apparatus;

FIG. 3 is a detail view of the soil pressure cell inside the rectangular steel plate;

FIG. 4 is a front view of the apparatus;

fig. 5 is a left side view of the device.

(1. porous mixture rut plate to be measured, 2. soil pressure cell connecting line, 3. soil pressure cell, 4. high-strength pull rod, 5. L-shaped steel plate, 6. rectangular steel plate, 7. U-shaped groove)

FIG. 6 is a graph showing the frost heaving stress and the release characteristic curve of a 40% saturation rut plate

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

Forming a porous asphalt mixture track plate according to the mixing proportion of the required void ratio, measuring the volume V, wrapping the bottom surface and the side surface of a test piece with a plastic soft film and an adhesive tape, and weighing the mass m of the porous asphalt mixture track plate₀g; immersing the porous asphalt mixture track plate in water, putting the porous asphalt mixture track plate into a vacuum drying oven, standing for 15min under the condition of vacuum degree of-97.5 kPa, then opening a valve, recovering normal pressure, standing the test piece in water for 30min, and thenWeighing the mass m of a porous asphalt mixture rut plate completely saturated with water₁g, calculating the void volume content as (m)₁-m₀)cm³。

Drying the porous asphalt mixture rut plate test piece obtained in the step to constant weight, and injecting mass m into the porous asphalt mixture rut plate test piece₂g of water to give a void saturation ofThe upper surface of the porous asphalt mixture rut plate test piece is sealed by a plastic soft film to obtain the porous asphalt mixture rut plate test piece with the pore water saturation of C.

And splicing the L-shaped steel plate and the two rectangular steel plates, fixing by four pull rods at the lower part, putting a porous asphalt mixture rut plate test piece after water saturation into the device, and installing an upper pull rod to complete the rut plate fixing device shown in the figure 1. The soil pressure cell is fixed in a U-shaped groove as shown in figure 2, the stress surface of the soil pressure cell is tightly attached to the surface of a test piece by adjusting the pull rod, the non-stress surface of the soil pressure cell is tightly attached to the surface of a steel plate, and the soil pressure cell is connected to the static strain tester through a connecting wire to complete the assembly of the device.

Placing the test piece and the whole device into a refrigerator, adjusting the temperature to 5 ℃, and standing for 10-20 min; adjusting the temperature to-20 degrees, simulating the frost heaving process of the porous asphalt mixture track plate, recording data every 15min, and stopping the frost heaving process when the reading of the static strain tester is stable; and adjusting the temperature to 15 degrees, simulating the melting process of the porous mixture track plate, recording the release strain amount once every 15min, and calculating the stress. And stopping the test when the reading of the static strain tester is not changed any more.

The data obtained by the static strain tester are strain quantities μ ∈, and the stress is calculated by the formula P ═ μ ∈ × K.

The method is characterized in that a plurality of groups of porous asphalt rut plates with different saturation degrees are tested, frost heaving stress and release characteristic curves with different saturation degrees are drawn in the same graph, and the changes of the stress in frost heaving and release under different saturation degrees are contrastively analyzed.

And carrying out a rutting test on the test piece through a rutting tester, carrying out a freeze thawing test on a rutting plate with ruts in the same environment, and comparing the influence of the rutting on the change of frost heaving stress.