Constant head water seepage testing device based on Marshall test piece

Abstract

The utility model discloses a constant head water seepage testing device based on a Marshall test piece, belongs to the technical field of pavement water seepage coefficient testing, and is mainly used for testing the water seepage coefficient of the Marshall test piece. The utility model provides a constant head water seepage testing device based on a Marshall test piece. A water storage assembly comprises a water inlet bucket and a water outlet bucket, wherein a first water outlet pipe and a second water inlet pipe are respectively arranged below the water inlet bucket and the water outlet bucket; the Marshall test piece clamp comprises an upper clamp and a lower clamp, wherein the middle of the upper clamp and the middle of the lower clamp clamp an undemolded Marshall test piece. The upper clamp and the lower clamp comprise a first hollow cylinder and a second hollow cylinder. A third water inlet pipe is arranged on the first cylinder, a third water outlet pipe is arranged on the second cylinder, a flowmeter is arranged at one end, close to the water inlet bucket, of the first water conveying pipe, and a U-shaped pressure gauge is arranged between the third water inlet pipe and the third water outlet pipe. The testing device can be used for testing the permeability coefficient of the undemoulded Marshall test piece, is simple in structure and simple and convenient to operate, is high in reliability of obtained data, and ensures the authenticity and accuracy of the data.

Description

Technical Field

[0001] The utility model relates to the technical field of pavement seepage coefficient testing, in particular to a constant head seepage testing device based on Marshall specimens. Background Technique

[0002] At present, more than 90% of the expressways built in China are asphalt concrete pavements. In the traditional asphalt pavement structure form, the void ratio of the structural layer is generally controlled within 5%. The small void ratio design ensures the mechanical performance requirements of the pavement, while also preventing the damage of the base layer caused by rainwater penetration. However, due to the non-drainage characteristics of the traditional asphalt pavement, in rainy and snowy days, the anti-skid ability of the pavement decreases rapidly, and vehicles are prone to produce water mist and hydroplaning. The reflection caused by the accumulated water on the road surface at night also seriously affects the safety of drivers and passengers. To solve these problems that occur in existing roads, porous asphalt pavement has emerged. The drainage capacity of porous asphalt pavement is determined by the permeability coefficient of the porous asphalt mixture. The permeability coefficient K, also known as the hydraulic conductivity coefficient, is an important index reflecting the penetration ability of porous media. The correct determination of its value is of great significance for penetration calculation. Therefore, testing and obtaining the permeability coefficient of the porous asphalt mixture that is close to the actual application in pavement construction is related to the drainage capacity of the porous asphalt pavement and plays a key guiding role in the design of the porous asphalt mixture.

[0003] The determination of the permeability coefficient K at home and abroad is mainly divided into two methods: the "falling head method" and the "constant head method". In the "constant head method", the head difference between the two sides is controlled to be a constant value during the test, while in the "falling head method", the head height changes continuously during the test. However, the theoretical basis of both methods is Darcy's law.

[0004] At present, the "falling head" principle is adopted in China to determine the seepage coefficient of asphalt concrete pavement. Specifically, reference can be made to the "Code for Field Testing of Highway Subgrade and Pavement" JTGE60-2008 or the "Code for Tests of Bitumen and Bituminous Mixtures for Highway Engineering" JTG E20-2011, the asphalt mixture seepage test T0730-2011. The testing device used is as Figure 1The water permeability tester used in domestic specifications shown in the figure. This test device is divided into an upper structure and a lower structure. The upper part is a graduated water storage cylinder made of transparent organic glass with a volume of 600 ml, and there are thick markings at 100 ml and 500 ml. It is connected to the base through a 10-mm thin tube below, and there is a switch in the middle. During the test, the instrument is placed on the rutting plate specimen to be tested, and it can only be tested after sealing the bottom with sealant. The whole process of this test device requires manual operation. When visually judging the water level drop, the stopwatch is manually started at the same time, resulting in a time difference between reception and reaction, causing deviations in the measurement of water permeability and water permeability time, inaccurate calculation of the water permeability coefficient, and a relatively complex operation process, often requiring multiple people to cooperate. Japan uses the on-site water permeability test in the "Pavement Test Method Handbook" of the Road Association. The on-site water permeability tester in Japan is based on the law of conservation of mass. The pavement water permeability tester in Japan is generally similar to that in China, but the difference is that the height of the water storage cylinder in Japan is 324 mm, and the height of the lower structure is 263 mm. That is, when measuring, the water head difference of the water permeability tester in Japan is larger. It has the same disadvantages as the domestic water permeability tester. The United States uses single-ring or double-ring infiltration tests, and its test basis is also based on the principle of variable water head. There is an obvious "size effect" in the single-ring test. It is difficult to ensure the parallelism and accuracy of the test data. The double-ring test has certain requirements for the test object, the operation is relatively complex, and the interference of human factors is also relatively large.

[0005] However, due to the large porosity and large permeability coefficient of the porous asphalt pavement, but relevant research shows that: the variable water head method is applicable to materials with weak permeability ability and whose permeability coefficient is not easy to be measured, and its permeability coefficient is generally less than 10 -3 cm / s, while the constant water head method is applicable to materials with strong permeability ability, and the permeability coefficient is generally greater than 10 -2 cm / s. Therefore, for the special requirements of the porous asphalt pavement, there is an urgent need for a water permeability tester based on the "constant water head method"; considering the problems such as large test errors of the "variable water head" instrument, inapplicability to the drainage pavement, and lack of standardization and unification of the "constant water head" water permeability tester. Through the improvement of the traditional water permeability tester, an apparatus is invented based on the "constant water head" principle for testing the permeability coefficient of cylindrical Marshall specimens made of porous asphalt mixture, with convenient operation and strong universality for indoor use. Utility Model Content

[0006] The technical problem to be solved by the present utility model is to provide a constant water head water permeability test device based on Marshall specimens, which is mainly used for testing the water permeability coefficient of Marshall specimens, so as to achieve the purpose of measuring the permeability coefficient of Marshall specimens by using the "constant water head" test method, and then obtaining the water permeability coefficient of the porous asphalt pavement, and ensuring the authenticity and accuracy of the test data.

[0007] A constant-head water permeability test device based on Marshall specimens disclosed by the utility model includes a water storage assembly and a Marshall specimen fixture. The water storage assembly includes a water inlet bucket and a water outlet bucket both having openings at the top. A first water outlet pipe is provided below the water inlet bucket, and a water inlet bucket control valve is provided on the first water outlet pipe. A second water inlet pipe is provided below the water outlet bucket, and a water outlet bucket control valve is provided on the second water inlet pipe. The Marshall specimen fixture includes an upper fixture and a lower fixture. An undemolded Marshall specimen is clamped between the upper fixture and the lower fixture. The upper fixture includes a first cylinder which is hollow inside and has a first opening at the bottom for clamping with the undemolded Marshall specimen. A third water inlet pipe which is higher than the first opening and communicates with the first cylinder is provided on the side wall of the first cylinder. The lower fixture includes a second cylinder which is hollow inside and has a second opening at the top for clamping with the undemolded Marshall specimen. A third water outlet pipe which is higher than the second opening and communicates with the first cylinder is provided on the side wall of the second cylinder. A first water delivery pipe communicating with the first water outlet pipe is provided on the third water inlet pipe, and a second water delivery pipe communicating with the second water inlet pipe is provided on the third water outlet pipe. A flow meter for monitoring water flow is provided at one end of the first water delivery pipe close to the first water outlet pipe. A U-shaped manometer is communicated with the third water inlet pipe, and the other end of the U-shaped manometer is communicated with the third water outlet pipe.

[0008] Further, a first flange is provided below the first cylinder and aligned with the first opening, and the third water inlet pipe is higher than the first flange. A second flange is provided above the second cylinder and aligned with the second opening, and the third water outlet pipe is higher than the second flange. A third flange is provided at the upper end of the undemolded Marshall specimen, and a fourth flange is provided at the lower end of the undemolded Marshall specimen. The first flange is bolted to the third flange, and the second flange is bolted to the fourth flange.

[0009] Further, waterproof silicone gasket is provided at the joint of the inner sides of the first opening and the second opening and the undemolded Marshall specimen.

[0010] As a preferred mode, a first water inlet pipe is further provided on the water inlet bucket. The first water inlet pipe is above the first water outlet pipe and on the same straight line. A second water outlet pipe is further provided on the water outlet bucket. The second water outlet pipe is above the second water inlet pipe and on the same straight line.

[0011] As a preferred mode, the first water outlet pipe is 30 mm higher than the bottom of the water inlet bucket, and the first water inlet pipe is 30 mm lower than the top of the water inlet bucket. The second water inlet pipe is 30 mm higher than the bottom of the water outlet bucket, and the second water outlet pipe is 30 mm lower than the top of the water outlet bucket.

[0012] Furthermore, the outer side of the unmolded Marshall specimen is wrapped with a transparent mold.

[0013] The beneficial effects of the present utility model are as follows: By adopting a split-type designed Marshall specimen fixture, the unmolded Marshall specimen can be directly clamped between the upper fixture and the lower fixture. The mold of the Marshall specimen is used to seal the periphery of the Marshall specimen, reducing the operation steps of the operator for demolding the Marshall specimen. Moreover, it is ensured that the first opening and the second opening can be engaged with the unmolded Marshall specimen, and through holes are opened at the upper and lower ends of the Marshall specimen, which is convenient for installation and operation. The structure of this Marshall specimen fixture is simple, easy to manufacture and has a low cost. The upper fixture adopts a first hollow cylinder, and the lower fixture adopts a second hollow cylinder, so that the upper end of the unmolded Marshall specimen clamped inside the first cylinder and the lower end clamped inside the second cylinder respectively form sealed chambers with the first cylinder and the second cylinder. When the water inlet bucket conveys water to the Marshall specimen fixture, it can ensure that the water located inside the first cylinder can completely cover the top of the unmolded Marshall specimen, so that the water can only flow downward from the top of the unmolded Marshall specimen into the second cylinder below, in order to monitor the water flow rate and pressure difference passing through the unmolded Marshall specimen by the set flowmeter and U-shaped manometer. The monitoring has high accuracy, good parallelism, few human interference factors, and the obtained experimental data has a high reliability. The accuracy of the permeability coefficient of the unmolded Marshall specimen calculated using such data is high and more real, and it can be directly involved in the design guidance process, truly and objectively reflecting the real water permeability performance of the material, thus being more conducive to the mix design of drainage asphalt mixture. Description of the Drawings

[0014] Figure 1 : Structural schematic diagram of a domestic water permeameter;

[0015] Figure 2 : Testing device provided by the present utility model for testing the permeability coefficient of an unmolded Marshall specimen;

[0016] Figure 3 : Structural schematic diagram of a Marshall specimen fixture;

[0017] Figure 4 : Cross-sectional view of the upper fixture;

[0018] Reference numerals: 1 - water storage assembly; 11 - water inlet bucket; 111 - first water inlet pipe; 112 - first water outlet pipe; 113 - water inlet bucket valve; 12 - water outlet bucket; 121 - second water inlet pipe; 122 - second water outlet pipe; 123 - water outlet bucket valve; 13 - first water delivery pipe; 14 - second water delivery pipe; 2 - Marshall specimen fixture; 21 - upper fixture; 211 - first cylinder; 212 - first opening; 213 - third water inlet pipe; 214 - first flange; 22 - lower fixture; 221 - second cylinder; 222 - second opening; 223 - third water outlet pipe; 224 - second flange; 23 - waterproof silicone gasket; 3 - non - demolded Marshall specimen; 31 - third flange; 32 - fourth flange; 4 - flowmeter; 5 - U - type manometer. Detailed implementation manners

[0019] The present utility model will be further described below.

[0020] The present utility model provides a constant - head water - seepage test device based on Marshall specimens, which is mainly used for testing the water - seepage coefficient of Marshall specimens. It includes a water storage assembly 1 and a Marshall specimen fixture 2. The water storage assembly 1 includes a water inlet bucket 11 and a water outlet bucket 12 both having openings at the top. A first water outlet pipe 112 is provided below the water inlet bucket 11, and a water inlet bucket control valve 113 is provided on the first water outlet pipe 112. A second water inlet pipe 121 is provided below the water outlet bucket 12, and a water outlet bucket control valve 123 is provided on the second water inlet pipe 121. The Marshall specimen fixture 2 includes an upper fixture 21 and a lower fixture 22. An undemolded Marshall specimen 3 is clamped between the upper fixture 21 and the lower fixture 22. The upper fixture 21 includes a first cylinder 211 with a hollow interior and a first opening 212 provided below for clamping with the undemolded Marshall specimen 3. A third water inlet pipe 213 which is higher than the first opening 212 and communicates with the first cylinder 211 is provided on the side wall of the first cylinder 211. The lower fixture 22 includes a second cylinder 221 with a hollow interior and a second opening 222 provided above for clamping with the undemolded Marshall specimen 3. A third water outlet pipe 223 which is higher than the second opening 222 and communicates with the first cylinder 211 is provided on the side wall of the second cylinder 221. A first water delivery pipe 13 which communicates with the first water outlet pipe 112 is provided on the third water inlet pipe 213, and a second water delivery pipe 14 which communicates with the second water inlet pipe 121 is provided on the third water outlet pipe 223. A flowmeter 4 for monitoring the water flow rate is provided at one end of the first water delivery pipe 13 close to the first water outlet pipe 112. A U - type manometer 5 is communicated with the third water inlet pipe 213, and the other end of the U - type manometer 5 is communicated with the third water outlet pipe 223.

[0021] As Figures 2 - 4As shown in the figure, the first water outlet pipe 112 of the water inlet bucket 11 is connected to the third water inlet pipe 213 of the first cylinder 211 through the first water delivery pipe 13. The third water outlet pipe 223 of the second cylinder 221 is connected to the second water inlet pipe 121 of the water outlet bucket 12 through the second water delivery pipe 14. The first water outlet pipe 112 is arranged below the water inlet bucket 11 to ensure the stability of the water inlet flow rate and the sufficiency of the water source. The second water inlet pipe 121 is arranged below the water outlet bucket 12 to ensure that the water output from the third water outlet pipe 223 will not cause a change in water pressure due to the height difference, thereby affecting the normal water delivery of the third water outlet pipe 223 to the water outlet bucket 12. The top of the water inlet bucket 11 is open to ensure that the water pressure inside the water inlet bucket 11 is always the same as the atmospheric pressure, avoiding the change in water pressure caused by the change in the water volume inside the water inlet bucket 11, which may lead to the change in the water flow rate output from the first water delivery pipe 13. At the same time, the external faucet can directly deliver water to the water inlet bucket 11 from the top opening of the water inlet bucket 11 to continuously provide a water source. The top of the water outlet bucket 12 is open to ensure that the water pressure inside the water outlet bucket 12 is always the same as the atmospheric pressure, so that the water flow rate output from the second water inlet pipe 121 to the water outlet bucket 12 is always the same as the water flow rate output from the third water outlet pipe 223 on the second cylinder 221, and the third water outlet pipe 223 will not be unable to discharge water normally due to the change in the internal water pressure of the water outlet bucket 12. A water inlet bucket control valve 113 is arranged on the first water outlet pipe 112, and a water outlet bucket control valve 123 is arranged on the second water inlet pipe 121 to control the water outlet of the water inlet bucket 11 and the water inlet of the water outlet bucket 12. During the test, the relative height between the water inlet bucket 11 and the water outlet bucket 12 can be adjusted to regulate the head pressure. The Marshall specimen fixture 2 is designed as a split upper fixture 21 and lower fixture 22. The permeability coefficient measurement test can be directly carried out using the non-demolded Marshall specimen 3, as long as through holes are opened at the upper and lower ends of the Marshall specimen. This reduces the operation steps for the operator to demold the Marshall specimen, and there is no need to seal the perimeter of the Marshall specimen after it is installed, so as to seal the flow path around the Marshall specimen, thereby ensuring that only vertical seepage occurs inside the Marshall specimen. Moreover, the split upper fixture 21 and lower fixture 22 are convenient for installing the non-demolded Marshall specimen 3, as long as the first opening 212 and the second opening 222 can be engaged with the non-demolded Marshall specimen 3. The upper fixture 21 is the first cylinder 211, and the lower fixture 22 is the second cylinder 221, so that they can be adapted to the non-demolded Marshall specimen 3 in the shape of a cylinder. The first cylinder 211 and the second cylinder 221 are hollow structures inside, so that when water is delivered from the water inlet bucket 11 to the Marshall specimen fixture 2, the water can be stored in the first cylinder 211 and the second cylinder 221. And when the first water outlet pipe 112 fills the upper fixture 21 with water, the water in the first cylinder 211 can completely cover the top of the non-demolded Marshall specimen 3. And because the non-demolded Marshall specimen 3 is used, the water can only flow downward from the top of the non-demolded Marshall specimen 3 into the second cylinder 221;On the side wall of the first cylinder 211, there is a third water inlet pipe 213 communicating with the first cylinder 211. The water in the water inlet bucket 11 is injected into the first cylinder 211 through the third water inlet pipe 213. On the side wall of the second cylinder 221, there is a third water outlet pipe 223 communicating with the second cylinder 221. The third water outlet pipe 223 outputs the water that has penetrated from the inside of the non-demolded Marshall specimen 3 into the water outlet bucket 12. A flow meter 4 is provided at one end of the first water pipe 13 close to the first water outlet pipe 112. This flow meter 4 is a digital display flow meter, which can display the flow rate and the cumulative flow. During actual use, according to the different sizes of the non-demolded Marshall specimens 3 to be tested, a flow meter 4 with a corresponding range can be selected for monitoring. During the test, after the water flow of the test device is stable, the value can be directly read and calculated. Between the first water pipe 13 and the second water pipe 14, there is a U-shaped pressure gauge 5 communicating with both of them. Specifically, one end of the U-shaped pressure gauge 5 is communicated with the input port of the third water inlet pipe 213, and the other end is communicated with the output port of the third water outlet pipe 223. During the test, first connect the two ends of the pressure gauge to the third water inlet pipe 213 and the third water outlet pipe 223 respectively through hoses. When the water penetrates through the specimen, the pressure difference can be directly read.

[0022] When using this constant head water permeability test device based on Marshall specimens, first clamp the upper end of the non-demolded Marshall specimen 3 in the first opening 212 of the first cylinder 211, and clamp the lower end of the non-demolded Marshall specimen 3 in the second opening 222 of the second cylinder 221. Then connect the first water outlet pipe 112 of the water inlet bucket 11 and the third water inlet pipe 213 of the first cylinder 211 through the first water pipe 13, and connect the second water inlet pipe 121 of the water outlet bucket 12 and the third water outlet pipe 223 of the second cylinder 221 through the second water pipe 14. At this time, open the water inlet bucket control valve 113 and close the water outlet bucket control valve 123, and then inject water from an external faucet into the water inlet bucket 11. The water flow flows along the first water pipe 13 to the Marshall specimen fixture 2. After the first cylinder 211 and the second cylinder 221 are filled with water, open the water outlet bucket control valve 123. Since both ends of the U-shaped pressure gauge 5 are connected to the third water inlet pipe 213 and the third water outlet pipe 223 through hoses, when waiting for the water to penetrate the non-demolded Marshall specimen 3, the value difference on the U-shaped pressure gauge can be directly read, that is, the water level height difference between the first water outlet pipe and the second water inlet pipe. After the water head is stable, start observing the flow meter 4. Select a time period, that is, the test start time t1 and the test end time t2, observe and record the cumulative flow monitored on the flow meter 4, and calculate the difference to obtain the total flow Q flowing through the non-demolded Marshall specimen 3 during this time period. Calculate according to the formula for the constant head test of the permeability coefficient to obtain the permeability coefficient of the Marshall specimen. The formula for the constant head test of the permeability coefficient is as follows:

[0023]

[0024] Where: K: permeability coefficient, cm / s; L: height of the Marshall specimen without demolding, cm; h: water level difference (water level difference between the first water outlet pipe and the second water inlet pipe), cm; Q: total flow rate, cm 3 ; P: value of the pressure difference; A: cross-sectional area of the Marshall specimen without demolding, cm 2 ; t1: start time of the test; t2: end time of the test.

[0025] When using this constant head water permeability test device based on the Marshall specimen to test the permeability coefficient, since the Marshall specimen fixture 2 is designed as a split upper fixture 21 and lower fixture 22, the permeability coefficient determination test can be directly carried out using the Marshall specimen 3 without demolding. It only needs to ensure that the first opening 212 and the second opening 222 can be clamped with the Marshall specimen 3 without demolding, and through holes are opened at the upper and lower ends of the Marshall specimen, that is, the mold of the Marshall specimen is used to seal the periphery of the Marshall specimen, reducing the operation steps of the operator for demolding the Marshall specimen, which is convenient for operation. The structure of the Marshall specimen fixture 2 is simple, easy to manufacture and has a low cost; and the upper fixture 21 uses a first hollow cylinder 211, and the lower fixture 22 uses a second hollow cylinder 221, so that the Marshall specimen 3 without demolding is clamped at the upper end inside the first cylinder 211 and the lower end inside the second cylinder 221 to form a sealed chamber with the first cylinder 211 and the second cylinder 221 respectively. When the water inlet bucket 11 conveys water to the Marshall specimen fixture 2, it can ensure that the water in the first cylinder 211 can completely cover the top of the Marshall specimen 3 without demolding, so that the water can only flow downward from the top of the Marshall specimen 3 without demolding into the second cylinder 221 below, so as to monitor the water flow rate and pressure difference passing through the Marshall specimen 3 without demolding by the set flow meter 4 and U-shaped manometer 5. And the accuracy is relatively high, the parallelism is good, the human interference factors are less, and the reliability of the obtained experimental data is high. The accuracy of the permeability coefficient of the Marshall specimen 3 without demolding calculated using such data is high and more real, and it can be directly involved in the design guidance process, truly and objectively reflecting the real water permeability performance of the material, thus being more conducive to the mix design of porous asphalt mixture.

[0026] To ensure the tight connection between the first cylinder 211, the second cylinder 221 and the Marshall specimen 3 without demolding, and to avoid the detachment of the Marshall specimen 3 without demolding due to excessive water pressure in the first cylinder 211 during the test; such as Figure 2 、 Figure 3As shown in the figure, a first flange 214 aligned with the first opening 212 is provided below the first cylinder 211, and the third water inlet pipe 213 is higher than the first flange 214; a second flange 224 aligned with the second opening 222 is provided above the second cylinder 221, and the third water outlet pipe 223 is higher than the second flange 224; a third flange 31 is provided at the upper end of the non-demolded Marshall specimen 3, and a fourth flange 32 is provided at the lower end of the non-demolded Marshall specimen 3. The first flange 214 is bolted to the third flange 31, and the second flange 224 is bolted to the fourth flange 32; the first cylinder 211, the second cylinder 221 and the non-demolded Marshall specimen 3 are detachably connected by means of flange connection. Specifically, a first flange 214 with an opening aligned with the first opening 212 is provided below the first cylinder 211, and the first flange 214 is bolted to the third flange 31 provided at the upper end of the non-demolded Marshall specimen 3. A second flange 224 with an opening aligned with the second opening 222 is provided above the second cylinder 221, and the second flange 224 is bolted to the fourth flange 32 provided at the lower end of the non-demolded Marshall specimen 3. The flange connection makes the connection between the first cylinder 211, the second cylinder 221 and the non-demolded Marshall specimen 3 tighter, and the non-demolded Marshall specimen 3 will not fall off due to excessive water pressure.

[0027] To avoid gaps at the connection between the Marshall specimen fixture 2 and the non-demolded Marshall specimen 3, causing water to flow out from the gaps and affecting the authenticity of the data measured by the flowmeter 4 and the U-shaped manometer 5, as Figure 3 shown in the figure, waterproof silicone gaskets 23 are provided at the joints where the inner sides of the first opening 212 and the second opening 222 are in contact with the non-demolded Marshall specimen 3; the waterproof silicone gaskets 23 are added to seal the gaps in the clamping contact between the first cylinder 211, the second cylinder 221 and the non-demolded Marshall specimen 3; when using flanges for connection, the waterproof silicone gaskets 23 should extend between the first flange 214 and the third flange 31, and extend between the second flange 224 and the fourth flange 32 to achieve the airtightness of the non-demolded Marshall specimen 3 and reduce the data monitoring error caused by water overflowing from the gap between the Marshall specimen fixture 2 and the non-demolded Marshall specimen 3.

[0028] To facilitate the control of the water flow input of the water inlet bucket 11 and the water flow output of the water outlet bucket 12, as Figure 2As shown, a first water inlet pipe 111 is further provided on the water inlet bucket 11. The first water inlet pipe 111 is arranged above the water inlet bucket 11 and is on the same straight line as the first water outlet pipe 112. A second water outlet pipe 122 is further provided on the water outlet bucket 12. The second water outlet pipe 122 is arranged above the water outlet bucket 12 and is on the same straight line as the second water inlet pipe 121. By adding the first water inlet pipe 111 to the water inlet bucket 11, it is convenient to connect an external faucet through a hose, and it can ensure a stable water supply, ensure the water pressure in the water inlet bucket 11, and avoid the change of the water delivery rate of the first water outlet pipe 112 caused by the change of water pressure, resulting in errors in the water flow monitored by the flowmeter 4. And the fact that the first water inlet pipe 111 and the first water outlet pipe 112 are on the same straight line can ensure the head difference in the water inlet bucket 11. By adding the second water outlet pipe 122 to the water outlet bucket 12, it is convenient to lead out the water overflowing from the water outlet bucket 12 through the second water outlet pipe 122, avoiding the water from overflowing everywhere and affecting the experimental environment. And the water led out from the second water outlet pipe 122 can also be connected to a measuring cylinder to check the water flow monitored by the flowmeter 4, ensuring the accuracy of the monitored data. And the fact that the second water outlet pipe 122 and the second water inlet pipe 121 are on the same straight line can ensure the head difference in the water outlet bucket 12. Specifically, the water inlet bucket 11 and the water outlet bucket 12 have the same size specifications, with an internal net height of 300 mm and a diameter of 200 mm. As a preferred method, to ensure the normal water inlet and outlet of the water inlet bucket 11 and the water outlet bucket 12, the first water outlet pipe 112 is 30 mm higher than the bottom of the water inlet bucket 11, and the first water inlet pipe 111 is 30 mm lower than the top of the water inlet bucket 11. The second water inlet pipe 121 is 30 mm higher than the bottom of the water outlet bucket 12, and the second water outlet pipe 122 is 30 mm lower than the top of the water outlet bucket 12. Setting the first water outlet pipe 112 at a position 30 mm away from the bottom of the water inlet bucket 11 can not only ensure the water outlet stability but also avoid the phenomenon of no water outlet due to too low water level. Setting the first water inlet pipe 111 at a position 30 mm away from the top of the water inlet bucket 11 can not only serve as a water level line to ensure that the water does not overflow from the water inlet bucket 11 but also be connected to an external faucet to provide stable water supply, while increasing the water storage capacity of the water inlet bucket 11. Setting the second water inlet pipe 121 at a position 30 mm away from the bottom of the water outlet bucket 12 can ensure that the water flowing out from the Marshall specimen fixture 2 can continuously flow into the water outlet bucket 12 and will not be affected by the change of the water volume in the water outlet bucket 12, resulting in the phenomenon of no drainage towards the water outlet bucket 12. Setting the second water outlet pipe 122 at a position 30 mm away from the bottom of the water outlet bucket 12 can serve as an outlet to ensure that the water in the water outlet bucket 12 only drains out through the second water outlet pipe 122, without affecting the surrounding test environment, while increasing the water storage capacity of the water outlet bucket 12. The above-mentioned first water inlet pipe 111, first water outlet pipe 112, second water inlet pipe 121, and second water outlet pipe 122 are all made of stainless steel pipes with an inner diameter of 20 mm.

[0029] For facilitating the observation of the flow direction of water within the Marshall specimen, the outer side of the non-demolded Marshall specimen 3 is covered with a transparent mold. Specifically, a mold for fabricating the Marshall specimen can be made of transparent acrylic board.

Claims

1. A constant head water seepage test device based on a Marshall specimen, characterized in that: The invention comprises a water storage component (1) and a Marshall specimen fixture (2), wherein the water storage component (1) comprises a water inlet bucket (11) and a water outlet bucket (12) both of which are provided with openings at the tops, a first water outlet pipe (112) is provided below the water inlet bucket (11), a water inlet bucket control valve (113) is provided on the first water outlet pipe (112), a second water inlet pipe (121) is provided below the water outlet bucket (12), and a water outlet bucket control valve (123) is provided on the second water inlet pipe (121); The Marshall specimen fixture (2) comprises an upper fixture (21) and a lower fixture (22), wherein an un-demolded Marshall specimen (3) is clamped between the upper fixture (21) and the lower fixture (22), wherein the upper fixture (21) comprises a first cylinder (211), wherein the first cylinder (211) is hollow inside and has a first opening (212) at the bottom thereof for clamping with the un-demolded Marshall specimen (3), wherein the side wall of the first cylinder (211) is provided with a The lower fixture (22) comprises a second cylinder (221), the second cylinder (221) is hollow inside and has a second opening (222) on the top for clamping with the un-demolded Marshall specimen (3), and a third water outlet pipe (223) is provided on the side wall of the second cylinder (221) and is higher than the second opening (222) and is connected to the first cylinder (211); the third water inlet pipe (213) is provided with a A first water pipe (13) is provided which is connected to a first water outlet pipe (112); a second water pipe (14) which is connected to a second water inlet pipe (121) is provided on the third water outlet pipe (223); a flow meter (4) for monitoring water flow is provided at one end of the first water pipe (13) close to the first water outlet pipe (112); a U-shaped pressure gauge (5) is connected to the third water inlet pipe (213); and the other end of the U-shaped pressure gauge (5) is connected to the third water outlet pipe (223).

2. A constant head water seepage test device based on a Marshall specimen as claimed in claim 1, characterized in that: A first flange (214) aligned with the first opening (212) is provided below the first cylinder (211), and the third water inlet pipe (213) is higher than the first flange (214); a second flange (224) aligned with the second opening (222) is provided above the second cylinder (221), and the third water outlet pipe (223) is higher than the second flange (224); a third flange (31) is provided at the upper end of the un-demolded Marshall specimen (3), and a fourth flange (32) is provided at the lower end of the un-demolded Marshall specimen (3); the first flange (214) is bolted to the third flange (31), and the second flange (224) is bolted to the fourth flange (32).

3. A constant head water seepage test device based on a Marshall specimen as claimed in claim 1 or 2, characterized in that: Waterproof silicone gaskets (23) are provided at the locations where the inner sides of the first opening (212) and the second opening (222) meet the un-demolded Marshall test piece (3).

4. A constant head water seepage test device based on a Marshall specimen as claimed in claim 3, characterized in that: The water inlet bucket (11) is also provided with a first water inlet pipe (111), the first water inlet pipe (111) is located above the first water outlet pipe (112) and is located in the same straight line; the water outlet bucket (12) is also provided with a second water outlet pipe (122), the second water outlet pipe (122) is located above the second water inlet pipe (121) and is located in the same straight line.

5. A constant head water seepage test device based on a Marshall specimen as claimed in claim 4, characterized in that: The first water outlet pipe (112) is 30 mm higher than the bottom of the water inlet bucket (11), and the first water inlet pipe (111) is 30 mm lower than the top of the water inlet bucket (11); the second water inlet pipe (121) is 30 mm higher than the bottom of the water outlet bucket (12), and the second water outlet pipe (122) is 30 mm lower than the top of the water outlet bucket (12).

6. A constant head water seepage test device based on a Marshall specimen as claimed in claim 1, characterized in that: The outer side of the un-demolded Marshall test piece (3) is covered with a transparent mold.

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