In-situ test method for soil particle invasion condition of drainage channel of plastic drainage plate

Abstract

The invention discloses an in-situ test method for soil particle invasion condition of a drainage channel of a plastic drainage plate, which comprises the following steps: preparing a test container, arranging a vertical degradable plastic drainage plate sample to be tested in the test container, and filling the test container with a soil sample; scanning the test container in the degradation culture process by adopting a CT (Computed Tomography) scanning imaging unit to obtain RAW projection data; rebuilding the RAW projection data into three-dimensional grayscale image data, cutting off the test container and the plastic drainage plate positioning bracket from the three-dimensional grayscale image data, and reserving a degradable plastic drainage plate sample area; and then cutting a series of two-dimensional section slices along the length direction of the degradable plastic drainage plate sample, identifying and calculating a gap region enclosed by a core plate and a filter membrane in each section slice, calculating the area of the gap region, if a soil sample is found to invade the gap region, recording as drainage channel loss, and further calculating the channel loss rate.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering and materials engineering testing technology, and specifically relates to an in-situ testing method for soil particle intrusion in drainage channels of plastic drainage boards. Background Technology

[0002] Plastic drainage boards, also known as plastic drainage strips, are materials used in drainage projects for soft soil foundations. They consist of an internal core board skeleton and a filter membrane wrapped around the core board skeleton. In use, they are vertically inserted into the soft soil foundation, acting as an efficient vertical drainage channel. Together with a horizontal sand cushion layer, they form a drainage system. Under load (such as pre-loaded soil or vacuum preloading), they accelerate the drainage and consolidation of the soft soil foundation, thereby improving the strength and stability of the foundation.

[0003] Biodegradable plastic drainage boards are widely used in soft soil foundation treatment projects. However, the gradual degradation of their filter membranes in the soil can lead to soil particles intruding into the drainage channels between the core board and the filter membrane, causing blockage and resulting in decreased drainage performance, which affects the long-term stability of the project. Currently, the performance evaluation of this type of drainage board mainly relies on destructive sampling and laboratory physicochemical tests. This traditional testing method requires removing the drainage board from the soil, disrupting its contact with the surrounding soil, making continuous, in-situ observation impossible, and it is difficult to quantify the soil particle intrusion into the drainage channels between the core board and the filter membrane. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide an in-situ testing method for soil particle intrusion in drainage channels of plastic drainage boards. This method enables a visual and quantitative evaluation of soil particle intrusion in drainage channels between the core board and filter membrane of a biodegradable drainage board without disturbing the sample and maintaining a realistic soil environment.

[0005] This invention is achieved through the following technical solution: An in-situ testing method for soil particle intrusion in drainage channels of plastic drainage boards includes the following steps: Step 1: Prepare a test container, place the vertical plastic drainage board sample to be tested in the test container, and fill the test container with soil sample so that the plastic drainage board sample is completely buried by the soil sample; set a pressure plate in the test container to apply pressure load to the soil sample. Step 2: Place the test container containing the soil sample and the plastic drainage board sample in a constant temperature and humidity environment for degradation culture; during the culture process, apply a pressure load to the soil sample in the test container to simulate the service status of the plastic drainage board in the construction scenario of drainage reinforcement of soft soil foundation. Step 3: At the predetermined time point, place the entire test container on the rotating stage of the CT scanning imaging unit and perform a 360-degree rotation scan to obtain RAW projection data. Step 4: Reconstruct the RAW projection data into 3D grayscale image data; Step 5: Cut out the test container and plastic drainage board positioning bracket from the 3D grayscale image data, retaining the plastic drainage board sample area; Step 6: Cut a series of two-dimensional cross-sectional slices along the length of the plastic drainage board sample, identify and calculate the void region enclosed by the core board and filter membrane in each cross-sectional slice, and calculate the area S of the void region. flow If soil samples are found to have intruded into the void area, it is recorded as a drainage channel loss, and the channel loss rate is further calculated.

[0006] In the above technical solution, the test container shall be made of a non-metallic material that has low attenuation of X-rays, high light transmittance, and mechanical strength that meets the requirements of earth pressure.

[0007] In the above technical solution, the test container is a cylindrical container with a removable top cover.

[0008] In the above technical solution, the top cover is connected to the top of the test container by bolts, and a sealing ring is set between the top of the test container and the top cover to ensure the airtightness of the test container.

[0009] In the above technical solution, a plastic drainage board positioning bracket is set at the bottom center of the test container. The plastic drainage board positioning bracket is a long strip structure with a slot. The bottom end of the plastic drainage board sample to be tested is inserted into the slot of the plastic drainage board positioning bracket, so that the sample is vertically positioned in the center of the test container.

[0010] In the above technical solution, a pressure plate is movably installed inside the test container. The pressure plate is equipped with a vertical connecting rod, which is installed through the through hole in the top cover. During the test, a pressure application device applies downward pressure to the vertical connecting rod, thereby driving the pressure plate to apply a pressure load to the soil sample inside the test container.

[0011] In the above technical solution, the structure of the pressure application device is as follows: it includes a drive rod mechanism, which is vertically mounted on a reaction frame, and the reaction frame is mounted on a bottom platform.

[0012] In the above technical solution, the pressure plate and the vertical connecting rod are an integral structure, and their material is the same as that of the test container.

[0013] In the above technical solution, the test container, pressure plate, and vertical connecting rod are all made of PMMA (polymethyl methacrylate).

[0014] In the above technical solution, the positioning bracket for the plastic drainage board is made of PMMA (polymethyl methacrylate).

[0015] The advantages and beneficial effects of this invention are as follows: This invention enables a visual and quantitative evaluation of soil particle intrusion in the drainage channels between the core board and filter membrane of a biodegradable drainage board without disturbing the sample and maintaining the real soil environment. Attached Figure Description

[0016] Figure 1 This is a flowchart of the in-situ testing method for soil particle intrusion in the drainage channel of the plastic drainage board according to the present invention.

[0017] Figure 2 This is a schematic diagram of the overall structure of the test container used in this invention.

[0018] Figure 3 This is a schematic diagram of the pressure plate in the test container used in this invention.

[0019] Figure 4 This is a schematic diagram of the pressure application device used in this invention.

[0020] For those skilled in the art, other related figures can be obtained from the above figures without any creative effort. Detailed Implementation

[0021] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be further described below with reference to specific embodiments.

[0022] This invention provides an in-situ testing method for soil particle intrusion in drainage channels of plastic drainage boards, see appendix. Figure 1 This includes the following steps: Step 1: Prepare a test container, place the biodegradable plastic drainage board sample to be tested vertically in the test container, and fill the test container with soil sample so that the biodegradable plastic drainage board sample is completely buried by the soil sample.

[0023] The test container shall be made of a non-metallic material (such as PMMA polymethyl methacrylate) that has low attenuation to X-rays, high light transmittance, and mechanical strength that meets the requirements of soil pressure. The test container shall be a sealed structure that can maintain a high moisture content soil environment inside for a long time.

[0024] For example, see Appendix Figure 2 and attached Figure 3 The test container 1 is a cylindrical container with an inner diameter of 130mm, a height of 200mm, and a wall thickness of 5mm. It is equipped with a removable top cover 2, which is connected to the flange 101 on the top of the test container 1 by bolts 3 (bolts 3 are made of nylon). A sealing ring 6 is provided between the flange 101 and the top cover 2 to ensure the airtightness of the test container 1.

[0025] A plastic drainage board positioning bracket 4 is set at the bottom center of the test container 1. The plastic drainage board positioning bracket 4 is a long strip structure with a slot. The bottom end of the biodegradable plastic drainage board sample 5 to be tested is inserted into the slot of the plastic drainage board positioning bracket 4, so that the sample is vertically positioned in the middle of the test container (ensuring that the sample does not contact the inner wall of the test container so that the sample is completely buried by the soil sample).

[0026] A movable pressure plate 7 is also installed inside the test container 1. A vertical connecting rod 71 is mounted on the pressure plate 7, and this connecting rod 71 passes through the through hole 21 in the upper cover 2 (a sealing rubber ring can be installed between the through hole 21 and the vertical connecting rod 71). During testing, a downward pressure is applied to the vertical connecting rod 71 by a pressure application device, thereby driving the pressure plate 7 to apply a pressure load to the soil sample inside the test container 1, thus simulating the service state of the plastic drainage board in the soft soil foundation drainage reinforcement construction scenario (typically a foundation drainage reinforcement construction method of vacuum preloading, surcharge preloading, or a combination of vacuum and surcharge preloading). Furthermore, the pressure plate 7 and the vertical connecting rod 71 are an integral structure, and their material is the same as that of the test container 1.

[0027] Furthermore, a covered drainage hole 22 is provided on the upper cover 2 of the test container 1. During the test, when the pressure plate 7 applies a pressure load to the soil sample in the test container 1, the water in the soil sample rises. At this time, the cover of the drainage hole 22 is opened, and the water that has risen is sucked out through the suction tube. Then the cover of the drainage hole 22 is closed.

[0028] For example, see Appendix Figure 4 The pressure application device can be structured as follows: it includes a drive rod mechanism 81 (which can be a hydraulic cylinder or a hand-cranked pressure rod mechanism), which is vertically mounted on a reaction frame 82, and the reaction frame 82 is mounted on a bottom platform 83. During testing, the test container 1 is placed on the bottom platform 83, and the drive rod mechanism 81 applies downward pressure to the vertical connecting rod 71 of the pressure plate 7 of the test container 1, thereby driving the pressure plate 7 to apply a pressure load to the soil sample inside the test container 1.

[0029] For example, the soil sample is a high moisture content soil sample, with the moisture content controlled between 80% and 100%, to simulate actual soft soil conditions; the soil sample is filled in layers and lightly vibrated to remove large air bubbles, ensuring that the soil sample is in close contact with the biodegradable plastic drainage board sample.

[0030] For example, the biodegradable plastic drainage board sample is 4mm×100mm×200mm in size, and the sample is vertically fixed in the center of the test container using a plastic drainage board positioning bracket.

[0031] Step 2: Place the test container containing the soil sample and the biodegradable plastic drainage board sample in a constant temperature and humidity environment for degradation cultivation. During the cultivation process, apply a pressure load to the soil sample in test container 1 according to the test requirements to simulate the service condition of the plastic drainage board in the soft soil foundation drainage reinforcement construction scenario. Specifically, when the pressure plate 7 applies a pressure load to the soil sample in test container 1, water in the soil sample rises. At this time, open the cover of the drainage hole 22 of test container 1, suck out the precipitated water using a suction tube, and then close the cover of the drainage hole 22.

[0032] Step 3: At predetermined time points (e.g., 0, 30, 60, 90 days), place the entire test container on the rotating stage of the CT scanning imaging unit and set the scanning parameters: voltage recommended 120kV-140kV (to penetrate the soil sample), current 200-300μA, integration time 500ms (adjust according to the equipment), and perform a 360-degree rotating scan to obtain RAW projection data.

[0033] Step 4: Use the FDK algorithm to reconstruct the RAW projection data into three-dimensional grayscale image data.

[0034] Step 5: Based on the differences in CT values ​​of different substances, different phases such as soil, water, the test container body, the plastic drainage board positioning bracket, and the core board and filter membrane of the biodegradable plastic drainage board sample can be distinguished; the test container and the plastic drainage board positioning bracket are cropped from the three-dimensional grayscale image data, and the biodegradable plastic drainage board sample area is retained.

[0035] Step 6: Cut a series of two-dimensional cross-sectional slices along the length of the biodegradable plastic drainage board sample, identify and calculate the void region enclosed by the core board and filter membrane in each cross-sectional slice, and calculate the area S of the void region. flow If soil samples are found to have intruded into the void area, it is recorded as a drainage channel loss, and the channel loss rate is further calculated (the channel loss rate is equal to the area of ​​the intruded soil sample divided by the original area of ​​the void area).

[0036] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A method of in situ testing of the ingress of soil particles into a drainage passage of a plastic drainage board, characterized in that: The method comprises the following steps: Step 1, preparing a test container, arranging a vertical plastic drainage board sample to be tested in the test container, and filling the test container with soil samples so that the plastic drainage board sample is completely filled with the soil samples; a pressure plate for applying pressure load to the soil samples is arranged in the test container; Step 2, placing the test container filled with the soil samples and the plastic drainage board sample to be tested in a constant temperature and humidity environment for degradation culture; during the culture process, pressure load is applied to the soil samples in the test container to simulate the service state of the plastic drainage board in the soft soil foundation drainage reinforcement construction scene; Step 3, at a predetermined time point, placing the entire test container on a rotating table of a CT scanning imaging unit for 360-degree rotation scanning to obtain RAW projection data; Step 4, reconstructing the RAW projection data into three-dimensional gray scale image data; Step 5, cutting off the test container and the plastic drainage board positioning support from the three-dimensional gray scale image data, and retaining the plastic drainage board sample area; Step 6, a series of two-dimensional cross-section slices are cut along the length direction of the plastic drainage plate sample, the void region surrounded by the core plate and filter membrane in each cross-section slice is identified and calculated, and the area S of the void region is calculated flow If the soil sample invades the void region, it is recorded as drainage channel loss, and the channel loss rate is further calculated.

2. The method of in-situ testing for soil intrusion into a drainage passage of a plastic drainage board according to claim 1, characterized in that: The test container is made of non-metallic material.

3. The method of in-situ testing for soil intrusion into a drainage passage of a plastic drainage board according to claim 1, wherein: The test container is a cylindrical container, and the top of the test container is provided with a detachable upper cover.

4. The method of in-situ testing for soil intrusion into a drainage passage of a plastic drainage board according to claim 3, wherein: The upper cover is connected to the top of the test container through bolts, and a sealing ring is arranged between the top of the test container and the upper cover.

5. The method of in-situ testing for soil intrusion into a drainage passage of a plastic drainage board according to claim 1, wherein: A plastic drainage board positioning support is arranged at the middle position of the bottom of the test container, and the plastic drainage board positioning support is a long strip structure with a slot, the bottom end of the plastic drainage board sample to be tested is inserted into the slot of the plastic drainage board positioning support, so that the sample is vertically arranged at the middle position of the test container.

6. The method of in-situ testing for soil intrusion into a drainage passage of a plastic drainage board according to claim 1, wherein: The pressure plate is movably installed in the test container, and a vertical connecting rod is arranged on the pressure plate and penetrates through a through hole in the upper cover of the test container; during testing, a pressure applying device is used to apply downward pressure to the vertical connecting rod, thereby driving the pressure plate to apply pressure load to the soil samples in the test container.

7. The method of in-situ testing for soil intrusion into a drainage passage of a plastic drainage board according to claim 6, wherein: The pressure applying device comprises a driving rod mechanism, and the driving rod mechanism is vertically installed on a counterforce frame, and the counterforce frame is installed on a bottom platform.

8. The method of in-situ testing for soil intrusion into a drainage passage of a plastic drainage board according to claim 6, wherein: The pressure plate and the vertical connecting rod are an integral structure, and the material thereof is the same as that of the test container.

9. The method of in-situ testing for soil intrusion into a drainage passage of a plastic drainage board according to claim 6, wherein: The material of the test container, the pressure plate and the vertical connecting rod is polymethyl methacrylate.

10. The method of in-situ testing for soil intrusion into the drainage passage of a plastic drainage board according to claim 5, wherein: The plastic drainage board positioning support is made of polymethyl methacrylate.

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