Apparatus and method for determining the consolidation coefficient of a foam-soil particle mixture

Abstract

The present application relates to the test device and method for determining the consolidation coefficient of foam-soil particle mixture, comprising a first container, the first container comprises a container body, the top of the container body is open and is provided with a top cover, the inner wall bottom surface of the container body is provided with an annular boss, the corresponding container inner space of the annular boss is connected with one end of a flexible drain pipe, the flexible drain pipe is provided with a valve, and the top cover is provided with an exhaust valve;It also includes a water-permeable stone, which is used to be placed on the top surface of the annular boss;It also includes a filter element for laying on the surface of the water-permeable stone, which allows water to pass through but foam-soil particles cannot pass through;It also includes a weighing element and a second container for placing on the weighing element, the second container is used to receive the water discharged by the flexible drain pipe, and the device and method of the present application realize the measurement of the consolidation coefficient of foam-soil particle mixture.

Description

Technical Field

[0001] This invention relates to the field of geotechnical testing technology, specifically to a test apparatus and method for determining the consolidation coefficient of foam-soil particle mixtures. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] The successful application of earth pressure balance (EPB) tunnel boring machines (TBMs) under various geological conditions is attributed to the support provided by soil improvement technology. The excavated soil from the excavation face enters the mixing chamber and is mixed with injected foam, bentonite, and other amendments. The resulting foam-soil mixture is in a low-permeability, homogeneous, and plastic state, effectively supporting the tunnel excavation face. This mixture is then discharged via a rotating screw conveyor located below the rear of the soil chamber. During TBM tunneling, the support pressure is controlled by adjusting the cutterhead excavation speed, the screw conveyor speed, and the amount of foam injected.

[0004] Because the pressure of the mixture in the mixing chamber is greater than the hydrostatic pressure at the excavation face, the ultra-clean pore water pressure in the mixture will cause seepage from the mixing chamber to the soil in front of the excavation face, which will further lead to the dissipation of the pressure of the mixture in the mixing chamber. This process will cause the consolidation of the foam-soil particle mixture, and the consolidation process will cause the change of the permeability coefficient of the mixture, thus affecting the pressure dissipation process of the mixture in reverse. Clarifying the consolidation coefficient of the foam-soil particle mixture is of great significance for revealing the support mechanism of the support pressure in the mixing chamber.

[0005] Due to the presence of a large amount of foam, the mixture is in a fluid state, making traditional consolidation apparatus unsuitable for its consolidation tests. Furthermore, conventional consolidation apparatus cannot observe pore water pressure and drainage during the consolidation process. Therefore, how to measure the consolidation coefficient of foam-soil particles is a pressing technical problem to be solved in this field. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a test device and method for determining the consolidation coefficient of foam-soil particle mixtures, which not only satisfies the requirement of measuring the consolidation coefficient of foam-soil particles, but also enables the measurement of pore water pressure and drainage volume.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, embodiments of the present invention provide a test apparatus for determining the consolidation coefficient of a foam-soil particle mixture, comprising a first container, the first container comprising a container body, a top cover provided on the open side of the top of the container body, an annular boss provided on the bottom surface of the inner wall of the container body, the container space corresponding to the annular boss being connected to one end of a flexible drainage pipe, the flexible drainage pipe being provided with a valve, and the top cover being provided with an exhaust valve. It also includes permeable stones, which are used to place on the top surface of the annular boss; It also includes filter elements for laying on the surface of permeable stone, which allow water to pass through while preventing foam-soil particles from passing through; It also includes a weighing element and a second container for placing the weighing element, the second container being used to receive water discharged from the flexible drain pipe.

[0008] Optionally, it also includes multiple pore pressure sensors connected to the container body, with the multiple pore pressure sensors spaced apart along the axial direction of the container body. The pore pressure sensors are used to detect the pore water pressure of the foam-soil particle test material.

[0009] Optionally, the bottom pore pressure sensor is located at a set height above the upper surface of the annular boss, and the set height is greater than the sum of the thicknesses of the permeable stone and the filter element.

[0010] Optionally, the container body can be made of a transparent material.

[0011] Optionally, the top cover is an arc-shaped cover that bulges away from the container body, and has an exhaust valve at its center.

[0012] Optionally, a sealing ring is provided between the top cap and the top of the container body.

[0013] Optionally, the filter element is a geomembrane, and the diameter of the geomembrane is larger than the diameter of the permeable stone.

[0014] Optionally, a water supply tank may also be included, which can be connected to a flexible drain pipe for injecting water into the first container through the drain pipe.

[0015] Optionally, it also includes a base, on which the first container is placed, and on which the base is placed on the test platform.

[0016] Secondly, embodiments of the present invention provide a test method for the test apparatus described in the first aspect for determining the consolidation coefficient of a foam-soil particle mixture, comprising the following steps: Place the permeable stone that has been soaked in water for a set time on the upper surface of the annular protrusion of the container body, connect the free end of the flexible drain pipe to the water supply tank, open the valve of the flexible drain pipe and the exhaust valve of the top cover, and inject water into the first container until the water level reaches the set position above the permeable stone. Place the filter element inside the first container so that the filter element fits against the upper surface of the permeable stone; Adjust the free end of the flexible drain pipe to be flush with the upper surface of the permeable stone and fix the flexible drain pipe. Place the second container below the free end of the flexible drain pipe, open the valve, and the water in the first container will be discharged through the flexible drain pipe until the flexible drain pipe stops discharging. At this time, the water level in the first container is flush with the upper surface of the filter element. Pour out the water from the second container, and then place a weighing element under the second container; The first container was filled with a foam-soil particle mixture, and the mass of the foam-soil particle mixture was recorded. Keep the exhaust valve on the top cover open, open the valve, turn on the weighing element, start measuring the drainage of the foam-soil particle mixture, continue for the second set time, and obtain the consolidation coefficient of the foam-soil particle mixture based on the drainage and the mass of the foam-soil particle mixture.

[0017] The beneficial effects of this invention are as follows: 1. The experimental apparatus and method of the present invention, through the arrangement of permeable stones and filter elements, enables the container body to contain a foam-soil particle mixture in a fluid state. Moreover, the use of permeable stones combined with filter elements results in a uniform flow distribution and does not cause significant interference to the flow field. When the free end of the flexible drainage pipe is adjusted to be flush with the upper surface of the permeable stone, a communicating vessel structure is formed between the space below the permeable stone and the flexible drainage pipe. Thus, the water generated during the consolidation process of the foam-soil particle mixture is the water discharged by the flexible drainage pipe, thereby realizing the measurement of the drainage volume of the foam-soil particle mixture and, consequently, the measurement of the consolidation coefficient of the foam-soil particle mixture.

[0018] 2. The experimental apparatus and method of the present invention are provided with multiple pore pressure sensors in the container body, which realizes the function of collecting the consolidation speed of the foam-soil particle mixture at different locations and the pore pressure change law during the consolidation process.

[0019] 3. The method of the test apparatus of the present invention firstly uses a water supply tank to inject water into the first container to a set height above the filter element, which can discharge the gas below the permeable stone in the first container, avoid the influence of gas on the drainage collection, and ensure the accuracy of the measurement results. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0021] Figure 1 This is a schematic diagram of the overall structure of Embodiment 1 of the present invention; Among them, 1. Container body, 2. Electronic balance, 3. Permeable stone, 4. Geotextile filter membrane, 5. Foam-soil particle mixture, 6. Valve, 7. Pore pressure sensor, 8. Flexible drainage pipe, 9. Top cover, 10. Base, 11. Glass beaker. Detailed Implementation

[0022] Example 1 This embodiment provides a test apparatus for determining the consolidation coefficient of foam-soil particle mixtures, such as... Figure 1 As shown, the system includes a base 10, a first container, a permeable stone 3, a filter element, a second container, a weighing element, multiple pore pressure sensors 7, and a water supply tank. The first container includes a container body 1 with an open top. A top cover 9 is detachably provided on the open top side of the container body 1. The top cover 9 is equipped with an exhaust valve. An annular protrusion is provided on the bottom of the inner side of the container body 1. The permeable stone 3 is placed on the upper surface of the annular protrusion, so that the container body 1 has a certain space below the permeable stone 3. This space is connected to one end of a flexible drain pipe 8, and the other end of the flexible drain pipe 8 is a free end.

[0023] The filter element is laid on the surface of the permeable stone 3 to filter the foam-soil particle mixture, so that the filter element only allows water to pass through and does not allow the foam-soil particle mixture to pass through.

[0024] The water supply tank can be detachably connected to the free end of the flexible drain pipe 8 for injecting water into the first container.

[0025] The second container is placed below the free end of the flexible drain pipe 8 to receive water discharged from the first container through the flexible drain pipe 8.

[0026] The weighing element is used to place the second container, thereby weighing the amount of water drained from the second container.

[0027] In this embodiment, the container body 1 adopts a cylindrical structure and is made of transparent material. Preferably, the container body is made of plexiglass. The container body is transparent and can observe the entire process of consolidation and change of the foam-soil particle mixture.

[0028] In this embodiment, the container body 1 has a wall thickness of 10mm, an inner diameter of 60mm, an outer diameter of 80mm, and a total height of 200mm. An annular boss is provided at a height of 45mm from the bottom surface of the container body 1, and the inner diameter of the annular boss is 58mm.

[0029] A flange is provided on the outer edge of the top open side of the container body 1. Correspondingly, a flange is also provided on the edge of the top cover 9. The container body and the top cover can be detachably and fixedly connected by the flange and bolts.

[0030] Furthermore, both the flange of the top cover and the flange of the container body are provided with corresponding sealing ring grooves. A sealing ring is provided in the sealing ring groove of the flange of the container body 1. After the top cover 9 and the container body 1 are fixed by the flange and bolts, the sealing ring can seal the space between the top cover 9 and the container body 1.

[0031] Preferably, the sealing ring is a rubber sealing ring.

[0032] Furthermore, the outer surface of the rubber sealing ring is coated with petroleum jelly to further enhance the sealing effect.

[0033] In this embodiment, the top cover 9 is also made of plexiglass. Preferably, the top cover 9 is an arc-shaped cover that protrudes away from the container body 1, and an exhaust pipe is provided at its center, with an exhaust valve installed on the exhaust pipe.

[0034] The side wall of the container body 1 is provided with multiple pore pressure sensors 7. The pore pressure sensors 7 can be existing sensors, such as the pore pressure sensor disclosed in patent application CN120685297A. Its specific structure will not be described in detail here.

[0035] The bottommost pore pressure sensor 7 is located at a set height on the upper surface of the annular boss, and this height is greater than the sum of the thicknesses of the permeable stone 3 and the filter element.

[0036] In this embodiment, the distance between the bottommost pore pressure sensor 7 and the bottom surface of the container body 1 is 50mm. Preferably, a total of four pore pressure sensors 7 are provided, namely pore pressure sensor K1, pore pressure sensor K2, pore pressure sensor K3 and pore pressure sensor K4 from bottom to top.

[0037] It is understood that those skilled in the art can set the number of pore pressure sensors according to actual needs, which will not be described in detail here.

[0038] In this embodiment, four pore pressure sensors 7 are distributed at equal intervals along the axial direction of the container body 1. Preferably, the interval between adjacent pore pressure sensors 7 is 40mm.

[0039] The permeable stone has a thickness of 5 mm and its diameter is smaller than the inner diameter of the annular boss. Preferably, the diameter of the permeable stone is 59.8 mm.

[0040] The filter element is a geomembrane 4, preferably a 120-mesh geomembrane 4. It is understood that those skilled in the art can select the mesh size of the geomembrane 4 according to the actual situation of the foam-soil particle mixture, which will not be described in detail here.

[0041] The diameter of the geomembrane 4 is larger than the diameter of the permeable stone 3, so that the geomembrane 4 can completely cover the upper surface of the permeable stone 3. Preferably, the diameter of the geomembrane 4 is 60 mm.

[0042] The flexible drainage pipe 8 can be made of plastic or rubber, etc., and can be set according to actual needs by those skilled in the art.

[0043] A valve 6 is installed on the flexible drain pipe 8 to control the opening and closing of the flexible drain pipe 8.

[0044] The second container is a glass beaker 11, used to receive water discharged from the flexible drain pipe 8. Preferably, the glass beaker 11 is a 500ml glass beaker.

[0045] The weighing element can be an existing electronic balance 2, and its specific structure will not be described in detail here.

[0046] The water supply tank is used to hold water, and its bottom is equipped with a water outlet pipe that can be plugged into the free end of the flexible drainage pipe 6. The water outlet pipe is equipped with a valve to control its opening and closing.

[0047] It also includes a base 10, which, in use, is used to place the first container on the base 10, which is used to place the container on the test platform.

[0048] Example 2 This embodiment provides a test method for determining the consolidation coefficient of foam-soil particle mixtures using the test apparatus described in Embodiment 1, comprising the following steps: Step 1: Slowly place the permeable stone 3, which has been soaked in water for a first set time, onto the upper surface of the annular protrusion inside the container body 1. Connect the free end of the flexible drain pipe 8 to the water supply tank. The height of the water supply tank is higher than the height of the bottom pore pressure sensor 7. Connect multiple pore pressure sensors 7 to the paperless recorder.

[0049] Preferably, the first set time is 24 hours.

[0050] Step 2: Open valve 6 of the water supply tank and flexible drain pipe 8, and open the vent valve of the top cover 9. Water is poured into the first container from the water supply tank through the flexible drain pipe. At the same time, the bottom of the first container is slowly shaken to expel air bubbles from the first container below the permeable stone 3. Continue until the water level in the first container reaches the set position, which must be higher than the height of the bottom pore pressure sensor 7. After the water level in the first container reaches the set position, close the valves of the water supply tank and flexible drain pipe 8.

[0051] Step 2 allows the gas below the permeable stone 3 in the first container to be discharged, ensuring the accuracy of the measurement results.

[0052] Step 3: Open the top cover 9 and put the geomembrane 4 into the container body 1. When the geomembrane 4 sinks into the upper surface of the permeable stone 3, use the plastic rod to slowly adjust the position of the geomembrane 4 so that the geomembrane 4 can adhere to the permeable stone 3 and completely cover the upper surface of the permeable stone 3.

[0053] Step 4: Separate the free end of the flexible drain pipe 8 from the water supply tank, adjust the height of the free end of the flexible drain pipe 8 until it is flush with the upper surface of the permeable stone 3, and fix the flexible drain pipe 8 with a clamp. The clamp can be any existing technology and will not be described in detail here. Place a glass beaker 11 below the free end of the flexible drain pipe 8.

[0054] Step 5: Open valve 6 on the flexible drainage pipe 8 to slowly drain the water in the first container. When the flexible drainage pipe stops draining, close the valve on the flexible drainage pipe. At this time, the water level in the first container is flush with the upper surface of the geomembrane 4.

[0055] Step 6: Pour out the water from glass beaker 11 and place electronic balance 2 below glass beaker 11.

[0056] Step 7: Turn on the paperless recorder and observe whether the readings of each pore pressure sensor 7 are within the standard range. If they are within the standard range, fill the top of the geomembrane 4 in the first container with foam-soil particle mixture 5 until it is full, and remove the excess mixture with a scraper. At the same time, record the mass of the foam-soil particle mixture 5 that has been filled.

[0057] Step 8: Secure the top cover 9 to the top of the container body 1, keeping the exhaust valve open.

[0058] Step 9: Turn on the electronic balance and start automatic recording. Open valve 6 of flexible drain pipe 8. The drainage during the consolidation process of foam-soil particle mixture 5 enters glass beaker 11 through flexible drain pipe 8. Use electronic balance 2 to obtain the drainage volume during the consolidation process of foam-soil particle mixture 5. Use pore pressure sensor 7 to collect the consolidation speed of foam-soil particle mixture 5 at the same location and the pore pressure change law during the consolidation process.

[0059] The above process continues for the second set time.

[0060] Preferably, the second set time is 60 minutes.

[0061] Step 10: After the test, close valve 6 of the flexible drainage pipe 8, stop the test recording, calculate the deformation during the consolidation process of the mixture based on the drainage volume and the mass of the foam-soil particle mixture 5, and obtain the consolidation coefficient of the foam-soil particle mixture 5 using Terzaghi's one-dimensional consolidation calculation formula. The method for obtaining the consolidation coefficient can use existing technology and will not be described in detail here.

[0062] The experimental apparatus and method of this embodiment, through the arrangement of permeable stone 3 and geomembrane 4, enable the container body 1 to contain a fluid-state foam-soil particle mixture. Moreover, the use of permeable stone 3 in combination with geomembrane 4 results in a uniform streamline distribution, which does not cause significant interference to the flow field. When the free end of flexible drainage pipe 8 is adjusted to be flush with the upper surface of permeable stone 3, a communicating vessel structure is formed between the space below permeable stone 3 and flexible drainage pipe 8. Thus, the water generated during the consolidation process of foam-soil particle mixture 5 is the water discharged by flexible drainage pipe 8, thereby realizing the measurement of the drainage volume of foam-soil particle mixture 5, and further realizing the measurement of the consolidation coefficient of foam-soil particle mixture 5.

[0063] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A test apparatus for determining the consolidation coefficient of a foam-soil particle mixture, characterized in that, The container includes a first container, which includes a container body. The container body has a top cover on the open side at the top. The container body has an annular protrusion on the bottom surface of the inner wall. The container space corresponding to the annular protrusion is connected to one end of a flexible drain pipe. The flexible drain pipe is equipped with a valve. The top cover is equipped with an exhaust valve. It also includes permeable stones, which are used to place on the top surface of the annular boss; It also includes filter elements for laying on the surface of permeable stone, which allow water to pass through while preventing foam-soil particles from passing through; It also includes a weighing element and a second container for placing the weighing element, the second container being used to receive water discharged from the flexible drain pipe.

2. The test apparatus for determining the consolidation coefficient of foam-soil particle mixtures as described in claim 1, characterized in that, It also includes multiple pore pressure sensors connected to the container body. The multiple pore pressure sensors are spaced apart along the axial direction of the container body. The pore pressure sensors are used to detect the pore water pressure of the foam-soil particle test material.

3. The test apparatus for determining the consolidation coefficient of foam-soil particle mixtures as described in claim 1, characterized in that, The bottom pore pressure sensor is located at a set height above the upper surface of the annular boss, and the set height is greater than the sum of the thicknesses of the permeable stone and the filter element.

4. The test apparatus for determining the consolidation coefficient of foam-soil particle mixtures as described in claim 1, characterized in that, The container body is made of transparent material.

5. The test apparatus for determining the consolidation coefficient of foam-soil particle mixtures as described in claim 1, characterized in that, The top cover is an arc-shaped cover that bulges away from the container body, and an exhaust valve is located in the center.

6. The test apparatus for determining the consolidation coefficient of foam-soil particle mixtures as described in claim 1, characterized in that, A sealing ring is provided between the top cover and the top of the container body.

7. The test apparatus for determining the consolidation coefficient of foam-soil particle mixtures as described in claim 1, characterized in that, The filter element is a geomembrane, and the diameter of the geomembrane is larger than the diameter of the permeable stone.

8. The test apparatus for determining the consolidation coefficient of foam-soil particle mixtures as described in claim 1, characterized in that, It also includes a water supply tank that can be connected to a flexible drain pipe for injecting water into the first container through the drain pipe.

9. The test apparatus for determining the consolidation coefficient of foam-soil particle mixtures as described in claim 1, characterized in that, It also includes a base, a first container for placement on the base, and the base for placement on the test platform.

10. A test method for a test apparatus for determining the consolidation coefficient of a foam-soil particle mixture according to any one of claims 1-9, characterized in that, Includes the following steps: Place the permeable stone that has been soaked in water for a set time on the upper surface of the annular protrusion of the container body, connect the free end of the flexible drain pipe to the water supply tank, open the valve of the flexible drain pipe and the exhaust valve of the top cover, and inject water into the first container until the water level reaches the set position above the permeable stone. Place the filter element inside the first container so that the filter element fits against the upper surface of the permeable stone; Adjust the free end of the flexible drain pipe to be flush with the upper surface of the permeable stone and fix the flexible drain pipe. Place the second container below the free end of the flexible drain pipe, open the valve, and the water in the first container will be discharged through the flexible drain pipe until the flexible drain pipe stops discharging. At this time, the water level in the first container is flush with the upper surface of the filter element. Pour out the water from the second container, and then place a weighing element under the second container; The first container was filled with a foam-soil particle mixture, and the mass of the foam-soil particle mixture was recorded. Keep the exhaust valve on the top cover open, open the valve, turn on the weighing element, start measuring the drainage of the foam-soil particle mixture, continue for the second set time, and obtain the consolidation coefficient of the foam-soil particle mixture based on the drainage and the mass of the foam-soil particle mixture.

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