NL2033396A

NL2033396A - Test device and method for measuring frictional resistance of thixotropic mud

Info

Publication number: NL2033396A
Application number: NL2033396A
Authority: NL
Inventors: Zhou Xionghao; Wang Yebin; Wang Yin; Yu Kun; Zhang Meng; An Gangjian; Zhang Kunyong; Fu Juye; Sun Bin; Yuan Qihu; Yuan Zhengpu
Original assignee: China Railway No 4 Group Co Ltd; The Fourth Eng Co Ltd Of Ctce Group
Priority date: 2021-11-05
Filing date: 2022-10-26
Publication date: 2023-06-05
Also published as: WO2022105840A1; NL2033396B1; CN114216595B; CN114216595A

Abstract

A. test apparatus and. method for measuring the frictional resistance of a thixotropic mud, the test apparatus comprising: a test platform. A. prefabricated concrete block is filled in a sliding box and is used for simulating an on—site reinforced concrete box culvert, and a thixotropic mud is spread on the surface of the concrete. A loading apparatus is loaded above the concrete along the longitudinal direction, and a soil sample is filled in the loading apparatus, in order to simulate an overlying soil mass on the box culvert in a jacking construction process, and. once loaded, the soil sample is in contact with. the thixotropic mud. A horizontal force gauge is horizontally fixed onto a side portion of the loading apparatus, and a baffle facing the horizontal force gauge is arranged on the test platform. The sliding box is driven to slide along the test platform towards the baffle, and the baffle blocks the horizontal force gauge, so as to produce sliding displacement between the loading apparatus and the sliding box, and the frictional resistance between the soil sample and the concrete is displayed by means of the horizontal force gauge, thereby simulating the interactions between a box culvert, mudJ and. overlying' soil in. the box culvert jacking process.

Description

No. P141537NL00

TEST DEVICE AND METHOD FOR MEASURING FRICTIONAL RESISTANCE

OF THIXOTROPIC MUD

BACKGROUND Field of the Invention

The present invention is in the field of thixotropic mud evaluation, and particularly relates to test device and method for measuring the frictional resistance of thixotropic mud.

Background Information

With the rapid development of urban modernization in China, Construction of Box Jacking with Pipe Roof is widely used in urban underground space development. As an indispensable material in Construction of Box Jacking with

Pipe Roof, thixotropic mud can not only play a role in reducing resistance lubrication, but also play a supporting role in reducing settlement. Therefore, it is very important to accurately determine the frictional resistance of thixotropic mud, effectively evaluate the drag reduction effect of thixotropic mud, and select the appropriate proportion of thixotropic mud for engineering. The existing test device for measuring the frictional resistance of thixotropic mud is complex and the operation process is complicated, so it is difficult to accurately measure the true frictional resistance.

Accordingly, it is necessary to provide an improved solution to the above-mentioned deficiencies of the prior art.

SUMMARY

In order to achieve the above object, the present invention provides the following technical solutions: a test device for measuring frictional resistance of thixotropic mud, the test device comprising: a test platform; a sliding box where a concrete is filled in and is used for simulating an on-site box culvert, and a thixotropic mud is spread on the surface of concrete; a loading apparatus is loaded above the concrete along longitudinal direction, and a soil sample is filled in the loading apparatus, in order to simulate an overlying soll mass on the box culvert in a Jacking construction process, the soil sample is in contact with the thixotropic mud; a horizontal force gauge is horizontally fixed onto a side portion of the loading apparatus, and a baffle facing the horizontal force gauge is arranged on the test platform, the sliding box is driven to slide along the test platform towards the baffle, and the baffle blocks the horizontal force gauge, so as to produce sliding displacement between the loading apparatus and the sliding box, and the frictional resistance between the soil sample and the concrete is displayed by means of the horizontal force gauge, thereby simulating the interactions between a box culvert and overlying soil in the box culvert jacking process.

Advantageous Effects:

By using the device and method for measuring the frictional resistance of thixotropic mud according to the present invention, the problem of loss of thixotropic mud during the test can be prevented, not only the overlying soil pressure of the on-site box culvert can be simulated, but also the jacking speed of the box culvert can be simulated, the magnitude of the frictional resistance of thixotropic mud can be accurately measured, and the drag reduction effect of thixotropic mud can be accurately evaluated, so that a suitable proportion of drag reduction mud is recommended for the on-site construction, and the volume is small, the weight is light, the operation is convenient and the portability is convenient.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a structure diagram of the test device according to the detailed embodiment of the present invention.

Fig. 2 is a installation diagram of the loading frame according to the detailed embodiment of the present invention.

In the figures, 1: test platform; 2: sliding box; 3: driving device; 4: loading box; 5: loading frame; 6: vertical deformation dial test indicator; 7: horizontal force gauge; 8: lever; 9: weight; 10: sand; 11: waterproof plate; 12: concrete; 13: thixotropic mud; 14: soil sample; 15: water permeable plate; 16: loading plate; 17: fixing plate; 18: baffle; 19: upright ; 20: hinge shaft; 21: roller; 22: balance block; 23: sliding rod.

DETAILED DESCRIPTION OF EMBODIMENTS

As shown in Figs. 1-2, a test device for measuring frictional resistance of thixotropic mud, the test device comprising: a test platform 1 having at least one smooth upper surface for placing a sliding box 2; the sliding box 2, which is used for simulating an on-site box culvert, placed on the upper surface of the test platform 1 and can slide along the upper surface of the test platform 1, and a concrete 12 is filled in the sliding box 2 and a thixotropic mud 13 is spread on the surface of concrete 12; a loading apparatus is loaded above the concrete 12 along longitudinal direction, and a soil sample 14,which is preferably obtained by sampling at the on-site construction, so as to ensure that the humidity and density of the soil sample 14 are consistent at the on-site construction to the maximum extent, is filled in the loading apparatus, and once loaded, in order to simulate an overlying soil mass on the box culvert in a Jacking construction process, the soil, the mud and the concrete block is contacted; a horizontal {force gauge 7 is horizontally fixed onto a side portion of the loading apparatus, and a baffle 18 facing the horizontal force gauge 7 is arranged on the test platform 1, the sliding box 2 is driven to slide along the test platform 1 towards the baffle 18, and the baffle 18 blocks the horizontal force gauge 7, so as to produce sliding displacement between the loading apparatus and the sliding box 2, and the frictional resistance between the soil sample 14 and the concrete 12 is displayed by means of the horizontal force gauge 7, thereby simulating the interactions between a box culvert and overlying soil in the box culvert jacking process after the thixotropic mud 13 is injected. Wherein, the data showed on the horizontal force gauge 7 is the frictional resistance between the soil sample 14 and the concrete 12 after being filled with the thixotropic mud 13, thereby simulating the interactions between a box culvert, mud, and overlying soil in the box culvert jacking process, and then the drag reduction effect of the thixotropic mud 13 is evaluated. Wherein, the concrete 1s a prefabricated concrete block.

In another alternative embodiment, the loading apparatus comprises a loading box 4 and a loading plate 16 which is slidably fitted inside the loading box 4 along the longitudinal direction, and the soil sample 14 is filled between the loading plate 14 and the thixotropic mud 13 in the loading box 4; the loading box 4 is placed above the concrete 12 and the thixotropic mud 13, and at least the length in the driving direction of the sliding box 2 is less than the length corresponding to the inner cavity of the sliding box 2, so that during the test, the loading box 4 can perform a sliding displacement at a certain distance relative to the sliding box 2. In addition, the loading 5 plate 16 is loaded with a counterweight, and the counterweight is increased or decreased on the loading box 4 to change the magnitude of loading pressure so as to simulate different overlying soil pressures during the box culvert jacking process.

Specifically, the sliding box 2 is a square box mass with an open upper end, the loading box 4 is a square cylinder mass, and the overall size of the loading box 4 is smaller than that of the sliding box 2.

In another alternative embodiment, a square loading frame 5 is sleeved on the outside of the test platform 1 and the sliding box 2, a lever is hinged on the bottom of the test platform 1, and the counterweight is provided on the lever so as to load loading frame 5 with a pressure via the lever, so that the loading frame 5 exerts the pressure on the loading plate along the longitudinal direction. Based on the viewpoint of convenience of operation, the loading plate is placed above the test platform 1, the loading frame 5 is sleeved with the test platform 1 and the sliding box 2, and the counterweight is placed below the test platform 1, so as to effectively reduce the gravity center of the counterweight, improve the stability of the loading device during the test, and facilitate the operation, without transporting the counterweight through the test platform 1, the working intensity of the operator is reduced.

In another alternative embodiment, a sliding seat located directly below the loading plate is provided below the test platform 1, a sliding groove extending along the sliding direction of the sliding box 2 is provided on the sliding seat, the lever 8 is slidably fitted in the sliding groove via a hinge shaft 20, and the loading frame 5 is located at one side of the lever 8 corresponding to the counterweight and close to the hinge shaft 20, correspondingly. During the test, the lever 8 can slide along the sliding groove to ensure the stable load of the loading device during the test. A plurality of counterweights are detachably connected, and the force arm of the loading frame 5 on the lever 8 is smaller than the force arm of the counterweights. According to the principle of the lever 8, the force arm corresponding to the weight is larger, so that the counterweights with smaller weight can be used to generate a larger loading pressure, and the operation is convenient. By increasing or decreasing the weights or adjusting the weights, the pressure of the overlying soil at different depths can be simulated.

In the present embodiment, the counterweight can be the weight 9, the force arm of the counterweight is more than five times of the force arm of the loading frame 5, and the specific loading pressure is obtained after calculation according to the lever 8 theoren.

In the present embodiment, the sliding seat comprises two L-shaped fixing plates 17 arranged opposite to each other, the sliding groove is formed between two fixing plates 17, the middle part of the lever 8 is provided with an ear plate extending between two fixing plates 17, and the hinge shaft 20 is provided on the ear plate,

Preferably, a contact point corresponding to the loading frame 5 is provided on the lever 8 to fix the force arm corresponding to the loading frame 5. the contact point may be an arc notch, and on the premise of ensuring that the loading frame 5 can rotate relative to the lever 8, the position of the loading frame 5 on the lever 8 is defined, alternatively, a hinge plate is provided on the loading frame 5, and the loading frame 5is hinged on the lever 8 by hinge plate.

In some embodiments, in order to reduce the frictional resistance between the hinge shaft 20 and the sliding groove, a roller 21 is provided on the hinge shaft

: 20, and the roller 21 slides along the sliding groove, wherein the roller 21 is provided corresponding to both sides of the lever 8, the roller 21 is correspondingly placed on the horizontal portions of the two L-shaped fixing plates 17, and the distance between the horizontal portions of the two fixing plates 17 is adapted with the width of the lever so that the lever has sufficient rotation space, and the roller 21 may also be a ball bearing.

In another alternative embodiment, the loading frame 5 is square structure formed by combining four support rods, wherein the middle part of the support rods corresponding to the upper part of the loading plate is connected to a upright via a bolt, the upright is directed to the loading plate along the longitudinal direction, and a placement groove corresponding to the upright is provided on the loading plate. The placement groove corresponding to the upright 19 is provided on the loading plate 16, so as to ensure that the loading position of the upright 19 is constant, thereby improving the accuracy of the test data, in addition, it can also ensure that the upright 19 does not displace relative to the sliding box 2 during the test, and the placement groove is provided at the center of the loading plate 16, so as to ensure that the force is balanced, and always keep the load applied to the center of the soil sample. Specifically, the upright is provided between the loading frame 5 and the loading plate, a longitudinal through hole is provided on the upright above the loading frame 5, and a bolt passes through the through hole and is threadedly connected to the upright so as to fix the upright and the loading frame 5 and ensure stable load.

In another alternative embodiment, a sliding rod is extended at the end of the lever away from the weight, and a balance block 22 is slidably fitted in the sliding rod, the balance block 22 has a certain weight, so that the lever can be kept horizontal in an unloaded state, and preferably, a scale is provided on the sliding rod 23, so as to calculate the actual loading weight. Preferably, the balance block 22 is threadedly connected to the sliding rod 23 so as to keep the position of the balance block 22 from being displaced as the lever rotates, alternatively, the balance block is designed beforehand to determine the mass and is fixed on the sliding rod so as to maintain the lever balance in the unloaded state.

In an alternative embodiment, the bolt is provided with the vertical deformation dial test indicator 6 to observe the compression deformation of the soil sample after loading.

In another embodiment, on the two struts on both sides of the loading {frame 5, at least the upper ends thereof protrude with studs and correspondingly pass through the struts on the upper side of the loading frame 5, the nuts are provided on the studs on the upper and lower sides of the struts on the upper side of the loading frame 5, so that adjustment of the longitudinal length of the loading frame 5 is performed by means of the nuts to accommodate different thicknesses of concrete or thixotropic mud test.

In an alternative embodiment, the shape of the loading plate 16 matches the loading box 4, and the water permeable plate 15 is provided between the loading plate 16 and the soil sample 14, so as to avoid direct contact between the loading plate and the soil sample, and water may be added on the loading plate to ensure the water content of the soil sample.

In another alternative embodiment, the bottom of the sliding box 2 is made flat by sand 10, and a waterproof plate 11 is placed above the sand 10, and the concrete 12 is filled above the waterproof plate 11. The waterproof plate 11 is set to simulate the waterproof layer of the on- site construction, more realistically simulate the on-site construction situation, so as to standardize the test and ensure the reliability of the test results.

In an alternative embodiment, a driving device 3 is provided on the test platform 1, and the driving device 3 acts on the side of the sliding box 2 away from the baffle 18 and simulates the dynamic construction process of box culvert jacking by controlling the pushing rate. The driving device 3 may be any one of an oil cylinder and an air cylinder, and the driving speed is controlled by a control valve, so as to completely simulate the speed of the box culvert pushing, thereby simulating the dynamic construction process of the box culvert jacking, so as to simulate the frictional resistance experienced by the box culvert.

In another alternative embodiment, the distance between the upper surface of the thixotropic mud 13 and the upper surface of the sliding box 2 is not less than twice the thickness of the thixotropic mud 13. Since the thixotropic mud 13 will be partially squeezed out under the action of longitudinal load, there should be a certain distance between the mud and the top of the sliding box 2 to prevent the loss of the thixotropic mud 13 during the experiment, the effective contact area of the concrete 12 - thixotropic mud 13 - soil is the cross-sectional area of the soil sample 14, the level of the contact surface should be strictly controlled during the coating process of the thixotropic mud 13.

In an alternative embodiment, the upright 19 is provided with the vertical deformation dial test indicator 6 to observe the compression deformation of the soil sample after loading.

In some embodiments, a ball groove is provided on the upper surface of the test platform 1, and a ball is provided in the ball groove, wherein at least two of the ball grooves respectively correspond to two sides of the sliding box 2 and are directed towards the baffle 18, so as to reduce the frictional resistance between the sliding box 2 and the test platform 1. In another embodiment, an idler may be provided above the test platform 1, by means of which the sliding box 2 is carried.

In another alternative embodiment, there is also provided a test method for measuring the frictional resistance of a thixotropic mud 13, comprising:

Step S1, placing a sliding box 2, where a concrete 12 is filled in and is used for simulating an on- site box culvert, on a test platform 1 for simulating an on-site box culvert, and spreading a thixotropic mud 13 on the surface of the concrete 12;

Step S2, loading the loading apparatus, where the soil sample 14 filled in, above the concrete 12 along longitudinal direction, in order to simulate an overlying soil mass on the box culvert in a jacking construction process, the soil sample 14 is in contact with the thixotropic mud 13;

Step S3, making a horizontal force gauge 7 face a baffle 18 arranged on the test platform 1;

Step 54, driving the sliding box 2 to slide along the test platform 1 towards the baffle 18, and the baffle 18 blocks the horizontal force gauge 7, so as to produce sliding displacement between the loading apparatus and the sliding box 2, and the frictional resistance between the soil sample l4and the concrete 12 is displayed by means of the horizontal force gauge 7, thereby simulating the interactions between a box culvert and overlying soil in the box culvert jacking process.

In an alternative embodiment, the following detailed procedure is used for testing: 1) Placing the test platform 1, and applying a proper amount of lubricating oil in the ball grooves in the test platform 1 for lubrication, and then evenly place six balls of a certain size in each ball grooves. 2) Placing the sliding box 2 on the balls, making flat the bottom of the sliding box 2 by sand, and placing the waterproof plate 11, so as to avoid the adverse effect of subsequent filling inside the sliding box 2 of making flat by sand, more realistically simulate on-site construction conditions, and ensure the reliability of the test results.

3) Filling the concrete 12 into the sliding box 2 ‚ and the strength and material thereof are the same as those of the box culvert, so as to simulate the state of the box culvert in actually construction.

4) Uniformly spreading the thixotropic mud 13 on the surface of the concrete 12, the level of the contact surface is strictly controlled, and the distance between the surface of the thixotropic mud 13 and the top of the sliding box 2 should not be less than twice the thickness of the thixotropic mud 13.

5) Pe-filling the soil sample 14 into the loading box 4, and the soil mass should be sampled from the soil mass overlying the actual box culvert, the density of the soil sample 14 is the same as the density of the soil mass overlying the actual box culvert, the soil mass actually contacting the box culvert is simulated, the water permeable plate 15 is placed on the upper part of the soil sample 14, and the loading box 4 is placed inside the sliding box 2, and then the loading plate 16 and the loading frame 5 are placed, wherein the upright 19 is placed in a placement groove above the loading plate 16.

6) Zero setting the force gauge reading.

7) Calculating the weight of the weight 3 according to the test parameters, and the weight 9 is correspondingly set on the lever 8 to simulate the overlying soil pressure of the on-site box culvert.

8) Starting the stopwatch, moving the driving device 3 at the speed of 0.8-1.2mm/min, controlling the time within 3-5min, and simulating the speed of box culvert jacking.

The test is terminated if the force gauge reading are stable or if there is significant back-off.

9) Reading the force gauge while the horizontal displacement of sliding box 2 reaches 4 mm, and if the reading of the force gauge continues to increase, reading the reading of the force gauge when the horizontal displacement of the sliding box 2 reaches 6 mm, namely, determining the frictional resistance when the thixotropic mud 13 is applied, namely, evaluating the drag reduction effect of the thixotropic mud 13. 10) At the end of the test, removing the weight © and the loading box 4 as soon as possible and removing the soil, the thixotropic mud 13 and the concrete 12 for the next test. 11) By repeating steps 1) - 10) with different proportions of thixotropic mud 13, the frictional resistance of different proportions of thixotropic mud 13 can be determined, and the drag reduction effect of different thixotropic mud 13 can be compared. It is to be understood that the above description is intended to be illustrative, and the embodiments of the present application do not limit this.

In summary, the invention relates to a test apparatus and method for measuring the frictional resistance of a thixotropic mud, the test apparatus comprising: a test platform (1). A prefabricated concrete block is filled in a sliding box (2) and is used for simulating an on-site reinforced concrete box culvert, and a thixotropic mud (13) is spread on the surface of the concrete (12). A loading apparatus is loaded above the concrete (12) along the longitudinal direction, and a soil sample (14) is filled in the loading apparatus, in order to simulate an overlying soil mass on the box culvert in a

Jacking construction process, and once loaded, the soil sample (14) is in contact with the thixotropic mud (13). A horizontal force gauge (7) is horizontally fixed onto a side portion of the loading apparatus, and a baffle (18) facing the horizontal force gauge (7) is arranged on the test platform (1). The sliding box (2) is driven to slide along the test platform (1) towards the baffle (18), and the baffle (18) blocks the horizontal force gauge (7), so as to produce sliding displacement between the loading apparatus and the sliding box (2), and the frictional resistance between the soil sample (14) and the concrete (12) is displayed by means of the horizontal force gauge (7), thereby simulating the interactions between a box culvert, mud, and overlying soil in the box culvert jacking process.

Claims

CONCLUSIONS

A test apparatus for measuring the frictional resistance of thixotropic mud, the test apparatus comprising: a test platform. a sliding box filled with concrete and used to simulate a box culvert on site, and thixotropic mud is spread over the surface of the concrete; a loading device is loaded longitudinally above the concrete and a soil sample is filled into the loading device to simulate an overlying soil mass on the box culvert in a jacking construction where the soil sample is in contact with the thixotropic mud; a horizontal force gauge is fixed horizontally on a side part of the loading device, and a baffle facing the horizontal force gauge is applied to the test platform, the slide box is driven to slide along the test platform to the bulkhead, and the baffle blocks the horizontal force gauge, so that a sliding displacement between the loader and the sliding box is created, and the frictional resistance between the soil sample and the concrete is displayed by means of the horizontal force gauge, simulating the interactions between a box culvert and overlying soil when jacking the box culvert.

The test apparatus for measuring the frictional resistance of thixotropic mud according to claim 1, characterized in that the loading apparatus consists of a loading box and a loading plate which is slid longitudinally into the loading box, and that the soil sample is filled between the loading plate and the thixotropic mud in the bucket, where the load plate is loaded with a counterweight and the counterweight is raised or lowered to simulate different overlying ground pressures during jacking of the box culvert.

The test apparatus for measuring the frictional resistance of thixotropic mud according to claim 2, characterized in that a square loading frame is enclosed on the outside of the test platform and the slide box, a lever pivots on the bottom of the test platform, and the counterweight on the lever is provided to load the loading frame with a pressure via the lever, so that the loading frame exerts the pressure on the loading plate in the longitudinal direction.

The test apparatus for measuring the frictional resistance of thixotropic mud according to claim 3, characterized in that a sliding seat located directly below the loading plate is provided under the testing platform, a sliding groove running along the sliding direction of the sliding box is arranged on the sliding seat, the lever is slidably mounted in the slide groove via a pivot shaft, and the loading frame is on a side of the lever that corresponds to the counterweight and is close to the pivot shaft.

The test apparatus for measuring the frictional resistance of thixotropic mud according to claim 4, characterized in that the slide seat includes two opposed L-shaped fixing plates, the sliding groove is formed between two fixing plates, the middle part of the lever is provided with an ear plate that extends between two mounting plates, and the pivot shaft is mounted on the ear plate.

The test apparatus for measuring the frictional resistance of thixotropic mud according to claim 3, characterized in that the loading frame is a square structure formed by combining four support rods, the middle part of the support rods corresponding to the upper part wof the loading plate is connected to an upright via a bolt, the upright is directed in the longitudinal direction towards the loading plate, and a positioning groove corresponding to the upright is provided on the loading plate.

The test apparatus for measuring the frictional resistance of thixotropic mud according to claim 1, characterized in that the bottom of the sliding box is made flat by sand, and a waterproof plate is placed above the sand, and the concrete is filled above the waterproof plate.

The test apparatus for measuring the frictional resistance of thixotropic mud according to claim 1, characterized in that a driving mechanism is provided on the test platform, and the driving mechanism on the side of the sliding box does not operate at the bulkhead, simulating the dynamic construction process of the jacking the culvert by controlling the speed of pushing.

The test apparatus for measuring the frictional resistance of thixotropic mud according to claim 1, characterized in that a distance between the upper surface of the thixotropic mud and the upper surface of the sliding box should be not less than twice the thickness of the thixotropic mud .

10. A test method for measuring the frictional resistance of a thixotropic mud, comprising: Step S1, placing a sliding box, filled with concrete and used to simulate an on-site culvert, on a test platform for simulating a culvert on site, and spreading thixotropic mud on the surface of the concrete;

Step $2, after filling a soil sample into a loading device, loading the device above the concrete in the longitudinal direction, to simulate an overlying soil mass on the box culvert in jacking construction, the soil sample comes into contact with the thixotropic mud;

Step 53, making a horizontal force gauge opposite a bulkhead mounted on the test platform;

Step 54, where the sliding box is pushed along the test platform towards the bulkhead and the bulkhead blocks the horizontal force gauge, creating a sliding displacement between the loading device and the sliding box, and the frictional resistance between the soil sample and the concrete is represented by of the horizontal force gauge, simulating the interactions between a box diver and overlying ground during jacking of the box diver.

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