Device and method for measuring permeability coefficient of waste mud vacuum preloading siltation layer

Abstract

The present invention relates to a device and method for measuring the permeability coefficient of a waste mud vacuum preloading clogging layer, comprising: a mud tank is connected to a suction bottle and a vacuum pump in sequence through a drainage pipe; the top and bottom of the mud tank are respectively combined with the mud tank top cover and the mud tank bottom cover, and a displacement measuring hole is opened in the center of the mud tank top cover; between the mud liquid surface floating plate and the bottom of the mud tank, it is divided into waste mud and a clogging layer in sequence according to the gravity direction; the tank body of the mud tank is opened with two detection holes; the lower part of the mud tank is arranged with two layers of stainless steel filter screens, and a drainage filter membrane is sandwiched between the two layers of stainless steel filter screens. The beneficial effects of the present invention are: the present invention uses the basic theory of filtration and makes improvements on the basis of Darcy's law. The permeability coefficient of the clogging layer in the range near the drainage plate of the waste mud during vacuum solidification is calculated by formula, and the thickness of the clogging layer can be further calculated on this basis, and the accuracy of the calculation result is relatively high.

Description

Technical Field

[0001] The invention relates to the technical field of engineering waste mud treatment, and more specifically, to a device and method for measuring the permeability coefficient of a waste mud vacuum pre-pressing siltation layer. Background Art

[0002] With the rapid development of my country's infrastructure, a large amount of waste mud will be generated on construction sites. These waste muds have high water content and strong fluidity, and are often difficult to transport. Random discharge will pollute the environment. How to quickly deal with waste mud from construction projects has become a difficult problem that needs to be urgently solved in the engineering community.

[0003] Since Kjellman proposed the vacuum preloading method, a large number of researchers have studied it. With the continuous development of material technology in recent years and the large-scale application of PVCD drainage boards, vacuum preloading technology has been widely used in China. From soft soil foundation to blown silt to engineering waste mud, the advantages of vacuum preloading technology in treating high-water content mud-water mixtures have gradually been reflected. The vacuum preloading treatment time is usually predicted by the sand well consolidation theory. The permeability coefficient used in the sand well consolidation theory refers to the permeability coefficient of the soil around the vertical drainage body. The permeability coefficient can be obtained by taking soil samples for permeability tests before vacuum preloading treatment. However, when vacuum preloading is used to dehydrate the waste mud, the mud, as a mud-water mixture, is completely different from the soil body, and the permeability coefficient cannot be directly sampled and measured. In addition, during the vacuum preloading drainage process, the soil particles in the mud will gradually be blocked by the filter cloth and other soil particles around the vertical drainage body to form a dense soil layer that is completely different from the state of the surrounding mud. We call it a siltation layer. The permeability of the siltation layer is the key factor in determining the vacuum preloading treatment time. Therefore, a reasonable method is needed to determine the permeability coefficient of the siltation layer. However, since the clogging layer is formed during the vacuum preloading drainage process, it cannot be directly determined by the traditional permeability tester, and a new method is needed for determination. However, in actual application, due to the special properties of mud-water mixture, the traditional sand well consolidation theory cannot be fully applied, and the vacuum preloading duration prediction is more difficult. From the on-site construction results, a layer of dense soil with a permeability coefficient significantly different from the surrounding will be formed near the drainage board. The thickness and permeability of this dense soil layer cannot be accurately predicted using the traditional sand well theory.

[0004] In order to improve the efficiency of waste mud treatment and accurately predict the effect of vacuum preloading treatment, it is necessary to invent a permeability measurement device and calculation method for waste mud treatment with vacuum preloading to obtain vacuum preloading related parameters through simple experiments. Accurately measuring the permeability coefficient of the waste mud blockage layer can solve the problem that the effect of vacuum preloading treatment of waste mud is difficult to predict, provide scientific measurement methods and calculation methods for on-site construction personnel, shorten the project cycle, reduce mud discharge, and reduce environmental pollution. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a device and method for measuring the permeability coefficient of a waste mud vacuum preloading siltation layer.

[0006] In the first aspect, a device for measuring the permeability coefficient of a silted layer by vacuum preloading of waste mud is provided, wherein the mud tank is connected to a suction filter bottle and a vacuum pump in sequence through a drainage pipe;

[0007] Among them, the top and bottom of the mud tank are respectively combined with the mud tank top cover and the mud tank bottom cover; a displacement measuring hole is opened in the center of the mud tank top cover, and the probe of the displacement sensor passes through the displacement measuring hole to touch the mud liquid surface floating plate; between the mud liquid surface floating plate and the bottom of the mud tank, it is divided into waste mud and siltation layer in sequence according to the gravity direction; the tank body of the mud tank is opened with two detection holes, and two vacuum sensors respectively pass through the two detection holes to probe into the mud and the lower cavity of the stainless steel filter; two layers of stainless steel filter are arranged at the bottom of the mud tank, and a drainage filter membrane is sandwiched between the two layers of stainless steel filter; a drainage joint is arranged on the bottom cover of the mud tank, and the drainage joint is connected to the drain pipe; the bottle plug of the suction bottle is connected with a vacuum gauge.

[0008] Preferably, the mud tank top cover is compressed by a sealing screw to tighten a rubber sealing ring inside the cover and the top of the mud tank; the mud tank bottom cover is sealed and connected to the bottom of the mud tank by a sealing screw to tighten a rubber sealing ring inside the cover.

[0009] Preferably, the detection hole is provided with a rubber gasket and a lead screw, the lead of the vacuum sensor passes through the hollow channel of the screw, the nut is sealed with glue, and the lead screw is screwed into the detection hole to press the rubber gasket.

[0010] Preferably, the mud tank is made of a transparent material, a first liquid level scale line is provided on the body of the mud tank, and a second liquid level scale line is provided on the body of the suction filtration bottle.

[0011] Preferably, two pairs of rectangular protrusions are arranged at the lower part of the mud tank in the direction of gravity, the gap distance between the two pairs of rectangular protrusions is greater than the thickness of two layers of stainless steel filter screens, and the stainless steel filter screen is symmetrically provided with two rectangular notches along the diameter, and the rectangular notches are larger than the rectangular protrusions.

[0012] In a second aspect, a method for measuring the permeability coefficient of a waste mud vacuum preloading blockage layer is provided, which is performed by any device for measuring the permeability coefficient of a waste mud vacuum preloading blockage layer described in the first aspect, comprising:

[0013] S1. Determine the basic physical properties of the mud and weigh the stainless steel filter screen and the drainage board filter membrane;

[0014] S2, assembling a device for measuring the permeability coefficient of the waste mud vacuum preloading siltation layer, and injecting mud into the mud tank;

[0015] S3. Check the air tightness of the device, start the vacuum pump, and after the water output is stable, record the liquid level reading V, pumping time M and vacuum reading P0 of the filter bottle;

[0016] S4. When no filtrate flows out, turn off the vacuum pump, unscrew the sealing screws on the bottom cover of the mud tank, remove the bottom cover of the mud tank, keep the mud tank in a fixed position, rotate the two layers of stainless steel filter mesh to the rectangular protrusion, and vertically remove the stainless steel filter mesh 7 and the clogging layer downward;

[0017] S5. Weigh the weight of the stainless steel filter and the clogging layer in S4, and calculate the permeability coefficient k of the clogging layer. c And the thickness of the clogging layer L.

[0018] Preferably, S1 comprises:

[0019] S101, determination of solid particle mass percentage w s , the total mass of mud M and the density of mud solid particles ρ d ;

[0020] S102. Clamp the wet drainage board filter membrane with two stainless steel filter screens and weigh its weight M1.

[0021] Preferably, S2 comprises:

[0022] S201, clamp two stainless steel filter screens and the drainage plate filter membrane into the rectangular protrusion and rotate to clamp;

[0023] S202, install the bottom cover of the mud tank, tighten the sealing screws symmetrically, and use a drain pipe to connect the drain joint at the bottom of the mud tank to the filter bottle and the vacuum pump in sequence;

[0024] S203, install the vacuum sensor, insert it into the detection hole and fix it;

[0025] S204, slowly and evenly inject a certain amount of engineering waste mud into the mud tank, record the scale reading on the side of the tank, and calculate the volume V1 of the waste mud;

[0026] S205, slowly and horizontally place the mud liquid surface floating plate on the top surface of the waste mud layer, cover the mud tank top cover, symmetrically tighten the sealing screws, and press the rubber sealing ring inside the cover;

[0027] S206. Insert the probe of the displacement sensor vertically into the displacement measuring hole until it touches the mud liquid surface float.

[0028] Preferably, S6 includes:

[0029] S501, weigh the mass M2 of the stainless steel filter and the clogging layer, put the weighed stainless steel filter and the clogging layer into an oven, dry them to constant weight, calculate their moisture content according to the mass difference ΔM before and after drying, and calculate the porosity e of the clogging layer soil according to the moisture content;

[0030] S502, according to the liquid level reading V of the filter bottle and the pumping time t, draw Scatter plot, the horizontal axis of the scatter plot is the liquid level reading V of the filtration bottle, and the vertical axis is Fitting a straight line in Excel based on scattered data picture;

[0031] S503, based on the known parameters solid particle mass percentage w s , total mass of mud M, density of water ρ W , mud solid particle density ρ s , the porosity ratio e of the soil in the siltation layer is substituted into the following formula to obtain the parameter λ:

[0032]

[0033] S504, according to The slope of the straight line is obtained by substituting the known parameters of filtration area A, parameter λ and water density γ into w , we can get the permeability coefficient k of the silted layer c , the calculation formula is as follows:

[0034]

[0035] S505, according to the permeability coefficient k of the siltation layer c , pumping time t, vacuum reading P0, parameter λ and water density γ w , the thickness of the clogging layer L can be obtained, and the calculation formula is as follows:

[0036]

[0037] The beneficial effects of the present invention are:

[0038] (1) The present invention uses the basic theory of filtration and makes improvements based on Darcy's law. The permeability coefficient of the clogging layer in the vicinity of the drainage board during the vacuum solidification process of the waste mud is calculated through a formula. On this basis, the thickness of the clogging layer can be further calculated, and the calculation result has a high accuracy rate.

[0039] (2) The stainless steel filter screen of the present invention is inserted into the rectangular protrusions of the mud tank through the notch for fixation. The drainage filter membrane sandwiched by the two stainless steel filter screens can be replaced according to the filter membrane used for the vacuum preloading drainage board at the engineering site, and the use flexibility is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A schematic diagram of the structure of the device for measuring the permeability of a waste mud vacuum preloading plugging layer provided in this application;

[0041] Figure 2 A top view of a device for measuring the permeability of a waste mud vacuum preloading plugging layer provided in the present application;

[0042] Figure 3 A top view of the mud tank top cover and the mud tank bottom cover provided in this application;

[0043] Figure 4 A top view of the stainless steel filter and rectangular protrusion provided in this application;

[0044] Figure 5 Schematic diagram of sensor lead sealing provided for this application;

[0045] Figure 6 A schematic diagram of the data fitting provided for this application;

[0046] Explanation of the reference numerals in the accompanying drawings: displacement sensor 1, rubber sealing ring 2, first liquid level mark 3, mud liquid level float 4, waste mud 5, clogging layer 6, stainless steel filter screen 7, drainage filter membrane 8, lead screw 9, sealing screw 10, mud tank top cover 11, vacuum sensor 12, rectangular protrusion 13, mud tank bottom cover 14, drain pipe 15, drain joint 16, vacuum gauge 17, suction bottle 18, vacuum pump 19, displacement measuring hole 20, mud tank 21, second liquid level mark 22, rubber gasket 23. DETAILED DESCRIPTION

[0047] The present invention is further described below in conjunction with embodiments. The description of the following embodiments is only used to help understand the present invention. It should be noted that for ordinary persons in the art, without departing from the principle of the present invention, the present invention can also be modified in some ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0048] Embodiment 1:

[0049] In order to solve the problem that it is difficult to obtain the permeability coefficient of the siltation layer in the prior art, the present application provides a device for measuring the permeability coefficient of the siltation layer by vacuum preloading of waste mud, such as Figures 1 to 5 As shown, the mud tank 21 is connected to the suction bottle 18 and the vacuum pump 19 in sequence through the drain pipe 15;

[0050] Among them, the top and bottom of the mud tank 21 are respectively combined with the mud tank top cover 11 and the mud tank bottom cover 14. The mud tank top cover 11 is pressed against the top of the mud tank 21 by the sealing screws 10 with the rubber sealing ring 2 inside the cover, and the mud tank bottom cover 14 is sealed and connected to the bottom of the mud tank 21 by pressing the rubber sealing ring 2 inside the cover with the sealing screws 10. For example, the mud tank top cover 11 and the mud tank bottom cover 14 are each combined with the mud tank 21 by pressing the rubber sealing ring 2 with four sealing screws 10. A displacement measuring hole 20 is provided in the center of the mud tank top cover 11, and the probe of the displacement sensor 1 passes through the displacement measuring hole 20 and touches the mud liquid surface floating plate 4; between the mud liquid surface floating plate 4 and the bottom of the mud tank 21, it is divided into waste mud 5 and clogging layer 6 in sequence according to the direction of gravity; the tank body of the mud tank 21 is provided with two detection holes, and two vacuum sensors 12 respectively pass through the two detection holes to probe into the mud and the lower cavity of the stainless steel filter; two layers of stainless steel filter screens 7 are arranged at the lower part of the mud tank 21, and a drainage filter membrane 8 is sandwiched between the two layers of stainless steel filter screens 7; a drainage joint 16 is provided on the mud tank bottom cover 14, and the drainage joint 16 is connected to the drainage pipe 15; the bottle stopper of the suction filter bottle 18 is connected to a vacuum gauge 17.

[0051] A rubber gasket 23 and a lead screw 9 are provided on the detection hole. The lead of the vacuum sensor 12 passes through the hollow channel of the screw. The nut is sealed with glue. The lead screw 9 is screwed into the detection hole to press the rubber gasket 23 tightly.

[0052] The mud tank 21 is made of a transparent material. A first liquid level scale line 3 is formed on the body of the mud tank 21 , and a second liquid level scale line 22 is formed on the body of the suction filtration bottle 18 .

[0053] Two pairs of rectangular protrusions 13 are arranged at the bottom of the mud tank 21 in the direction of gravity. The gap between the two pairs of rectangular protrusions 13 is greater than the thickness of the two layers of stainless steel filter screens 7. The stainless steel filter screen 7 is symmetrically provided with two rectangular notches along the diameter, and the rectangular notches are larger than the rectangular protrusions 13.

[0054] Embodiment 2:

[0055] First, the following assumptions are made: the mud achieves solid-liquid separation through the filter membrane, and forms a clogging layer 6 behind the filter screen; the mud solid particles cannot be compressed; the liquid flow conforms to Darcy's law; the liquid flow rate in the clogging layer 6 is equal to the permeate flow rate. On this basis, the method for determining the permeability coefficient of the waste mud vacuum preloading clogging layer provided in this application includes:

[0056] S1. Determine the basic physical property parameters of the mud and weigh the weight of the stainless steel filter screen 7 and the drainage plate filter membrane 8;

[0057] S2, assembling a device for measuring the permeability coefficient of the waste mud vacuum preloading siltation layer, and injecting mud into the mud tank 21;

[0058] S3. Check the air tightness of the device, start the vacuum pump 19, and after the water output is stable, record the liquid level reading V, the pumping time t and the vacuum reading P0 of the filter bottle 19; for example, the vacuum degree is 70 kPa.

[0059] S4. When no filtrate flows out, turn off the vacuum pump 19, unscrew the sealing screw 10 on the bottom cover 14 of the mud tank, remove the bottom cover 14 of the mud tank, keep the direction of the mud tank, rotate the two layers of stainless steel filter screen 7 to the rectangular protrusion 13, and vertically remove the stainless steel filter screen 7 and the clogging layer 6 downward;

[0060] S5. Weigh the weight of the stainless steel filter 7 and the clogging layer 6 in S4, and calculate the permeability coefficient k of the clogging layer. c And the thickness of the clogging layer L.

[0061] S1 includes:

[0062] S101. Determination of solid particle mass percentage w s , the total mass of mud M and the density of mud solid particles ρ d ;

[0063] S102. Clamp the wet drainage board filter membrane 8 with two stainless steel filter screens 7 and weigh its weight M1.

[0064] S2 includes:

[0065] S201, clamp two stainless steel filter screens 7 and drainage plate filter membrane 8 into the rectangular protrusion 13 and rotate to clamp;

[0066] S202, install the mud tank bottom cover 14, tighten the sealing screws 10 symmetrically, and connect the drainage joint 16 at the bottom of the mud tank 21 to the suction bottle 18 and the vacuum pump 19 in sequence through the drainage pipe 15;

[0067] S203, installing the vacuum sensor 12, inserting it into the detection hole and fixing it;

[0068] S204, slowly and evenly inject a certain amount of engineering waste mud into the mud tank 21, record the scale reading on the side of the tank, and calculate the volume V of the waste mud; for example, the volume V of the mud is 350 ml.

[0069] S205, slowly and horizontally place the mud surface float 4 on the top surface of the waste mud layer 5, cover the mud tank top cover 11, symmetrically tighten the sealing screws 10, and press the rubber sealing ring 2 in the cover;

[0070] S206 , vertically insert the probe of the displacement sensor 1 into the displacement measuring hole 20 until it touches the mud liquid surface floating plate 4 .

[0071] S5 includes:

[0072] S501, weigh the mass M2 of the stainless steel filter 7 and the clogging layer 8, put the weighed stainless steel filter 7 and the clogging layer 8 into an oven, maintain 105°C and dry them to constant weight, calculate the moisture content according to the mass difference ΔM before and after drying, and calculate the porosity e of the clogging layer soil according to the moisture content, for example, the porosity e of the clogging layer soil is 2.5;

[0073] S502, according to the liquid level reading V of the suction filter bottle 19 and the pumping time t, draw Scatter plot, the horizontal axis of the scatter plot is the liquid level reading V of the suction filtration bottle 19, and the vertical axis is Fitting a straight line in Excel based on scattered data Figure, for example, Figure 6 The linear fitting results were used for the measured data of this application;

[0074] S503, based on the known parameters solid particle mass percentage w s , total mass of mud M, density of mud solid particles ρ d , the porosity ratio e of the soil in the siltation layer is substituted into the following formula to obtain the parameter λ:

[0075]

[0076] S504, according to The slope of the straight line is obtained by substituting the known parameters of filtration area A, parameter λ and water density γ into w , we can get the permeability coefficient k of the silted layer c , for example, the permeability coefficient of the blocking layer k c 2.2×10 -9 cm / s, calculated as follows:

[0077]

[0078] S505, according to the permeability coefficient k of the siltation layer c , pumping time t, vacuum reading P0, parameter λ and water density γ w , we can get the thickness of the clogging layer L. For example, the thickness of the clogging layer L is 4.7 cm, and the calculation formula is as follows:

[0079]

[0080] Embodiment 3:

[0081] The present application also provides a derivation process of the theory of measuring the permeability coefficient of the waste mud vacuum preloading plugging layer, wherein Darcy's law can be expressed as:

[0082]

[0083] Where V is the volume of filtrate, A is the filtration area, t is the filtration time, μ is the viscosity of the liquid, L is the thickness of the clogging layer, Δh is the head difference, and k c Represents the permeability coefficient of the silted layer. Δh can be calculated by the following formula:

[0084]

[0085] Furthermore, the above Darcy's law can also be expressed as:

[0086]

[0087] Among them, P0 represents the external total pressure, γ w Indicates the weight of water.

[0088] Assuming that the thickness of the clogging layer increases linearly under constant vacuum pressure, the parameter λ is introduced, which is expressed as:

[0089]

[0090] The solution of λ can be considered from the perspective of mass balance. The mass of the mud solid and liquid at the microscopic level is equal to the mass of the mud solid and liquid at the macroscopic level.

[0091] From a microscopic perspective, the mass of solid particles in the clogging layer is: (1-n c )ALρ S

[0092] The mass of liquid particles in the clogging layer is: n c ALρ w

[0093] The mass percentage of solid particles in the mud is known to be w S , the total mass of the mud is M, and the solid mass from a macroscopic perspective is:

[0094] w S M

[0095] The mass of the liquid is:

[0096] (1-w S )M

[0097] Considering from the perspective of mud liquid mass balance, the following formula can be obtained:

[0098] (1-w s )M=Vρ w +n c ρ w LA

[0099] Considering from the perspective of mud solid mass balance, the following formula can be obtained:

[0100] w s M=(1-n c )ρ s LA

[0101] This application takes the consideration from different angles under macroscopic conditions as an example, and substitutes the above calculation formula of L into it, eliminating M and V, and we can get:

[0102]

[0103] Furthermore, the calculation formula of L can be expressed as:

[0104]

[0105] Substituting this into Darcy's law above, we get:

[0106]

[0107] Furthermore, dt can be expressed as:

[0108]

[0109] Integrating the equation from 0 to t with respect to t, we can easily obtain:

[0110]

[0111] We can get:

[0112]

[0113] Furthermore, the permeability coefficient of the siltation layer k c The calculation formula is:

[0114]

[0115] It can be seen from this that k c Can be seen as A proportional coefficient between and V. If V is taken as the independent variable, then As the dependent variable, we can get:

[0116]

[0117] Then, substituting the calculation formula of L into the equation, we can get:

[0118]

[0119] In summary, the present application can calculate the permeability coefficient of the silt layer in the vicinity of the drainage board during vacuum solidification of the waste mud through a formula, and on this basis, the thickness of the silt layer can be further calculated, and the calculation result has a high accuracy rate.

Claims

1. A device for measuring the permeability coefficient of waste mud vacuum preloading siltation layer, characterized in that: The mud tank (21) is connected to the suction filter bottle (18) and the vacuum pump (19) in sequence through the drainage pipe (15); The top and bottom of the mud tank (21) are respectively combined with the mud tank top cover (11) and the mud tank bottom cover (14); a displacement measuring hole (20) is opened in the center of the mud tank top cover (11); a probe of the displacement sensor (1) passes through the displacement measuring hole (20) and touches the mud liquid surface floating plate (4); between the mud liquid surface floating plate (4) and the bottom of the mud tank (21), waste mud (5) and a clogging layer (6) are sequentially divided according to the gravity direction; the mud tank (21) ) is provided with two detection holes on its tank body, and two vacuum sensors (12) respectively penetrate through the two detection holes and probe into the cavity below the mud and the stainless steel filter; two layers of stainless steel filter (7) are arranged at the bottom of the mud tank (21), and a drainage filter membrane (8) is sandwiched between the two layers of stainless steel filter (7); a drainage joint (16) is provided on the bottom cover (14) of the mud tank, and the drainage joint (16) is connected to the drainage pipe (15); and a vacuum gauge (17) is connected to the bottle stopper of the suction filter bottle (18).

2. The device for measuring the permeability coefficient of waste mud vacuum preloading siltation layer according to claim 1 is characterized in that: The mud tank top cover (11) is pressed against the rubber sealing ring (2) inside the cover by means of a sealing screw (10) and is combined with the top of the mud tank (21); the mud tank bottom cover (14) is pressed against the rubber sealing ring (2) inside the cover by means of a sealing screw (10) and is sealed and connected with the bottom of the mud tank (21).

3. The device for measuring the permeability coefficient of waste mud vacuum preloading blockage layer according to claim 1 is characterized in that: The detection hole is provided with a rubber gasket (23) and a lead screw (9), the lead of the vacuum sensor (12) passes through the hollow channel of the screw, the nut is sealed with glue, and the lead screw (9) is screwed into the detection hole to press the rubber gasket (23).

4. The device for measuring the permeability coefficient of waste mud vacuum preloading blockage layer according to claim 1 is characterized in that: The mud tank (21) is made of a transparent material. The body of the mud tank (21) has a first liquid level scale line (3), and the body of the suction filtration bottle (18) has a second liquid level scale line (22).

5. The device for measuring the permeability coefficient of waste mud vacuum preloading blockage layer according to claim 1 is characterized in that: The lower part of the mud tank (21) is provided with two pairs of rectangular protrusions (13) in the direction of gravity, the gap distance between the two pairs of rectangular protrusions (13) is greater than the thickness of two layers of stainless steel filter screens (7), and the stainless steel filter screen (7) is symmetrically provided with two rectangular notches along the diameter, and the rectangular notches are larger than the rectangular protrusions (13).

6. A method for determining the permeability coefficient of a silted layer by vacuum preloading of waste mud, characterized in that: The method is performed by the device for measuring the permeability coefficient of the waste mud vacuum preloading plugging layer according to any one of claims 1 to 5, comprising: S1. Determine the basic physical property parameters of the mud and weigh the stainless steel filter (7) and the drainage filter membrane (8); S2, assembling a device for measuring the permeability coefficient of a waste mud vacuum preloading siltation layer, and injecting mud into a mud tank (21); S3, check the air tightness of the device, start the vacuum pump (19), and after the water output is stable, record the liquid level reading V, the water extraction time t and the vacuum reading P0 of the suction filter bottle (18); S4. When no filtrate flows out, turn off the vacuum pump (19), unscrew the sealing screw (10) on the bottom cover (14) of the mud tank, remove the bottom cover (14) of the mud tank, keep the mud tank (21) in a fixed position, rotate the two layers of stainless steel filter (7) to the rectangular protrusion (13), and vertically remove the stainless steel filter (7) and the clogging layer (6) downward; S5. Weigh the weight of the stainless steel filter (7) and the clogging layer (6) in S4, and calculate the permeability coefficient k of the clogging layer. c and the thickness of the clogging layer L; S5 includes: S501, weighing the mass M2 of the stainless steel filter (7) and the clogging layer (6), placing the weighed stainless steel filter (7) and the clogging layer (6) together in an oven, drying them to constant weight, calculating their moisture content based on the mass difference ΔM before and after drying, and calculating the porosity e of the clogging layer soil based on the moisture content; S502, according to the liquid level reading V of the suction filter bottle (18) and the pumping time t, draw Scatter plot, the horizontal axis of the scatter plot is the liquid level reading V of the suction filtration bottle (18), and the vertical axis is Fitting a straight line in Excel based on scattered data picture; S503, based on the known parameters solid particle mass percentage w s , total mass of mud M, density of water ρ W Mud solid particle density ρ S , the porosity ratio e of the soil in the siltation layer is substituted into the following formula to obtain the parameter λ: S504, according to The slope of the straight line is obtained by substituting the known parameters of filtration area A, parameter λ and water density γ into w , the permeability coefficient k of the siltation layer can be obtained c , the calculation formula is as follows: S505, according to the permeability coefficient k of the siltation layer c , pumping time t, vacuum reading P0, parameter λ and water density γ w , the thickness of the clogging layer L can be obtained, and the calculation formula is as follows:

7. The method for determining the permeability coefficient of the waste mud vacuum preloading blockage layer according to claim 6 is characterized in that: S1 includes: S101, determination of solid particle mass percentage w s , the total mass of mud M and the density of mud solid particles ρ d ; S102. Clamp the wet drainage filter membrane (8) with two stainless steel filter screens (7), and weigh its weight M1.

8. The method for determining the permeability coefficient of the waste mud vacuum preloading blockage layer according to claim 7, characterized in that S2 include: S201, clamp two stainless steel filter screens (7) and drainage filter membrane (8) into the rectangular protrusion (13) and rotate to clamp; S202, install the bottom cover (14) of the mud tank, tighten the sealing screws (10) symmetrically, and connect the drainage joint (16) at the bottom of the mud tank (21) to the suction filtration bottle (18) and the vacuum pump (19) in sequence through the drainage pipe (15); S203, installing the vacuum sensor (12), inserting it into the detection hole and fixing it; S204, slowly and evenly injecting a certain amount of engineering waste mud into the mud tank (21), recording the scale reading on the side of the tank, and calculating the volume V1 of the waste mud; S205, slowly and horizontally place the mud surface float (4) on the top surface of the waste mud (5), cover the mud tank top cover (11), symmetrically tighten the sealing screws (10), and press the rubber sealing ring (2) in the cover; S206, vertically insert the probe of the displacement sensor (1) from the displacement measuring hole (20) until it touches the mud liquid surface floating plate (4).

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