Testing device and method for non-Darcy seepage in ultra-soft soil

Abstract

The present invention discloses a testing device and method for non-Darcy seepage in supersoft soil, comprising a water supply tank, a pressure tank, a compressor, a pipeline mechanism, a detection unit, and an intelligent monitoring system, wherein the compressor is connected to the inlet of the pressure tank, and the water supply tank is connected to the pressure tank via a three-way switch; the detection unit comprises a permeator, a water collector, and an electronic scale, wherein the inlet of the permeator is connected to the three-way switch via a pipeline mechanism, the outlet of the permeator is connected to the water collector, and the water collector is placed on an electronic scale, the intelligent monitoring system is used to monitor the numerical changes of the electronic scale during the test, and the intelligent monitoring system is connected to the pipeline mechanism. The present invention has a high degree of automation, can improve the accuracy of the test results, avoid misjudgment, and can also avoid human factors and improve reliability.

Description

Technical Field

[0001] The invention relates to the field of permeability technology, and in particular to a testing device and method for non-Darcy seepage of ultra-soft soil. Background Art

[0002] Over the past decade, my country has made significant progress in the field of ultra-soft foundation reinforcement technology. It's well known that seepage is a necessary condition for consolidation. However, due to its high moisture content, high compressibility, and high porosity, the flow characteristics of water in ultra-soft soil differ from those of ordinary saturated soft soil. In the early and even mid-stage of the reinforcement process using the sandless vacuum preloading method, the water flow in the soil exhibits a nonlinear relationship between the flow velocity v and the hydraulic gradient i under the influence of high hydraulic gradients, resulting in complex non-Darcy seepage characteristics.

[0003] Constant head permeability test devices and variable head permeability test devices are often used to explore the permeability characteristics of soil. The traditional constant head permeability test device is suitable for measuring the permeability coefficient of coarse-grained soil, and the variable head permeability test device is suitable for measuring the permeability coefficient of fine-grained soil. However, the measurement accuracy of the above two methods is difficult to capture the slight changes in the water seepage characteristics of supersoft soil. In addition, the hydraulic gradient of supersoft soil is large in the early and middle stages of vacuum preloading consolidation. Due to size limitations, these two traditional permeability test devices can provide a small hydraulic gradient and cannot accurately measure the seepage characteristics of supersoft soil.

[0004] In addition, Figure 1 The most important characteristic of the seepage rate-hydraulic head gradient relationship for non-Darcy flow is the curve 0ac, which represents the actual seepage rate-hydraulic head gradient relationship. The seepage velocity in segment 0a is very low (but not zero), making it difficult to accurately measure the true value using current experimental techniques. The seepage rate-hydraulic head gradient relationship is often simplified to consist of segments 0b and bd, where the velocity in segment 0b is zero and segments bd vary linearly, with point b representing the initial hydraulic head gradient, I0. Alternatively, more rigorously, point a is defined as the initial hydraulic head gradient, which then varies according to the curve AB, ignoring the slight difference between points a and b. However, this simplified representation of non-Darcy flow does not correspond to actual non-Darcy flow.

[0005] In summary, the flow characteristics of water in ultrasoft soil are different from those of conventional saturated soft soil, and its seepage characteristics cannot be tested by conventional means. Therefore, it is necessary to develop a test device and method with high test accuracy and suitable for testing the non-Darcy seepage of ultrasoft soil. Summary of the Invention

[0006] The present invention aims to overcome the deficiencies of the above-mentioned prior art and provides a device for testing non-Darcy seepage in ultra-soft soil. The device has high testing accuracy and reduces errors caused by human factors.

[0007] Another object of the present invention is to provide a method for testing non-Darcy seepage of supersoft soil.

[0008] The object of the present invention is achieved through the following technical solution: The testing device for non-Darcy seepage of ultra-soft soil includes a water supply tank, a pressure tank, a compressor, a pipeline mechanism, a detection unit and an intelligent monitoring system, wherein the compressor is connected to the inlet of the pressure tank, and the water supply tank is connected to the pressure tank through a three-way switch;

[0009] The detection unit includes a permeator, a water collector and an electronic scale. The inlet of the permeator is connected to a three-way switch through a pipeline mechanism, and the outlet of the permeator is connected to the water collector. The water collector is placed on the electronic scale. The intelligent monitoring system is used to monitor the numerical changes of the electronic scale during the test, and the intelligent monitoring system is connected to the pipeline mechanism.

[0010] Preferably, the pipeline mechanism includes a main pipeline and multiple branch pipelines, the number of the branch pipelines is equal to the number of detection units, one end of the main pipeline is connected to the branch pipeline through a water distributor, and the other end of the main pipeline is connected to the water supply tank and the pressure tank at the same time, and a flow meter and a first automatic exhaust valve are sequentially provided in the main pipeline along the direction of water flow, and an automatic pressure regulating valve and a second automatic exhaust valve are sequentially provided in the branch pipeline along the direction of water flow, and the automatic exhaust valve and the automatic pressure regulating valve are both connected to the intelligent monitoring system.

[0011] Preferably, the branch pipe is provided with a digital thermometer, and the digital thermometer is located between the automatic pressure regulating valve and the second automatic exhaust valve.

[0012] Preferably, the branch pipeline is provided with a precision electronic water pressure gauge.

[0013] Preferably, the water collector comprises a conical flask and a rubber stopper, the rubber stopper seals the opening of the conical flask, and the outlet of the permeator is connected to the inner cavity of the conical flask through a connecting tube.

[0014] Preferably, the intelligent monitoring system includes an intelligent monitor for monitoring changes in the electronic scale reading and a controller for controlling the opening and closing of the pipeline mechanism and the water pressure.

[0015] The method for testing the non-Darcy seepage of ultra-soft soil, using the above-mentioned testing device for the non-Darcy seepage of ultra-soft soil, comprises the following steps:

[0016] S1. Prepare the sample and place the prepared sample in the permeator, and then vacuum treat the permeator;

[0017] S2. Connect the inlet and outlet of the permeator to the pipeline mechanism and the water collector respectively, open the first automatic exhaust valve, the second automatic exhaust valve and the automatic pressure regulating valve to exhaust the gas in the pipeline, and then close the first automatic exhaust valve, the second automatic exhaust valve and the automatic pressure regulating valve;

[0018] S3. Open the first automatic exhaust valve, the second automatic exhaust valve, and the automatic pressure regulating valve to increase the water pressure. When the first drop of water falls into the water collector, the intelligent monitoring system detects a change in the reading of the electronic scale to determine the initial water head gradient I0.

[0019] S4, set the water pressure p through the automatic pressure regulating valve i , where i is a natural number, and the water pressure p i Next, measure the corresponding time period T i The amount of water flowing into the water collector Q i , then:

[0020] and I i =p i / h,

[0021] where v i is the water velocity, ρ i is the gravity density of water, A is the cross-sectional area of ​​the sample, and h is the height of the sample in the permeator;

[0022] S5, where the data obtained in S4 is used according to the formula:

[0023]

[0024] Determine the soil permeability of the sample.

[0025] Preferably, the process of determining the initial water head gradient I0 in step S3 is as follows:

[0026] When the first drop of water falls into the water collector, the intelligent monitoring system detects a change in the reading on the electronic scale, controls the automatic pressure regulating valve to keep the water pressure constant, and records the water pressure value as p0;

[0027] If within 120 minutes, the intelligent monitoring system detects that the reading of the electronic scale changes again, that is, when the second drop of water falls, let I0 = p0 / h, where h is the height of the sample in the permeator;

[0028] If the reading on the electric scale does not change within 120 minutes, the automatic pressure regulating valve will be controlled to adjust the water pressure.

[0029] Preferably, if the reading on the electric scale does not change within 120 minutes, the automatic pressure regulating valve controls the water pressure in the branch pipeline to increase at a uniform rate of 0.5 kPa / min.

[0030] The present invention has the following advantages over the prior art:

[0031] 1. The ultrasoft soil non-Darcy seepage test device of the present invention adopts a high water pressure system consisting of a water supply tank, a pressure tank and a compressor to provide a water pressure of 1.5 MPa to ensure the effective implementation of the ultrasoft soil non-Darcy seepage test.

[0032] 2. The testing device for non-Darcy seepage in ultra-soft soil of the present invention is mainly composed of a water supply tank, a pressure tank, a compressor, a piping mechanism, a detection unit and an intelligent monitoring system. The high water pressure system composed of the water supply tank, the pressure tank and the compressor is used to realize automatic water supply. The detection unit is mainly composed of a permeabilizer, a water collector and an electronic scale. The intelligent monitoring system can not only accurately determine the water pressure at the beginning of seepage in a timely manner to avoid misjudgment, but also avoid human factors, improve reliability, and at the same time improve the accuracy of the test results.

[0033] 3. The pipeline mechanism in the ultra-soft soil non-Darcy seepage test device of the present invention is provided with multiple branch pipelines, so multiple groups of the same sample or different samples can be tested simultaneously, comparative experiments can be realized, and the accuracy of the test results can be further ensured.

[0034] 4. The present invention can obtain a true non-Darcy seepage relationship curve, accurately measure the permeability characteristics of super-soft soil, and provide a basis for the seepage and consolidation of super-soft soil in coastal areas. It has high theoretical significance and important engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the non-Darcy seepage relationship curve.

[0036] Figure 2 It is a structural schematic diagram of a testing device for non-Darcy seepage in supersoft soil according to the present invention.

[0037] Figure 3 It is a structural diagram of the intelligent monitoring system of the present invention.

[0038] Figure 4 It is a schematic diagram of the non-Darcy seepage relationship curve of super soft soil.

[0039] Among them, 1 is a water supply tank, 2 is a pressure tank, 3 is a compressor, 4 is a pipeline mechanism, 5 is a detection unit, 6 is an intelligent monitoring system, 7 is a three-way switch, 8 is a permeator, 9 is a water collector, 10 is an electronic scale, 11 is a main pipeline, 12 is a branch pipeline, 13 is a water distributor, 14 is a flow meter, 15 is a first automatic exhaust valve, 16 is an automatic pressure regulating valve, 17 is a second automatic exhaust valve, 18 is a digital hygrometer, 19 is a precision electronic water pressure gauge, 20 is a conical flask, 21 is a rubber stopper, 22 is a control valve, 23 is an intelligent monitor, and 24 is a controller. DETAILED DESCRIPTION

[0040] The present invention will be further described below with reference to the accompanying drawings and examples.

[0041] like Figure 2 The ultra-soft soil non-Darcy seepage test device shown includes a water supply tank, a pressure tank, a compressor, a pipeline mechanism, a detection unit and an intelligent monitoring system. The compressor is connected to the inlet of the pressure tank, and the water supply tank is connected to the pressure tank through a three-way switch.

[0042] The detection unit includes a permeator, a water collector and an electronic scale. The inlet of the permeator is connected to a three-way switch through a pipeline mechanism, and the outlet of the permeator is connected to the water collector. The water collector is placed on the electronic scale. The intelligent monitoring system is used to monitor the numerical changes of the electronic scale during the test, and the intelligent monitoring system is connected to the pipeline mechanism.

[0043] Specifically, the compressor adopts a ZP-W65 single-phase air compressor, which is connected in series with a large-volume pressure tank so that air pressure can be applied accurately. In this embodiment, the volume of the pressure tank is 100L to ensure the stability of the water pressure during the test; the volume of the water supply tank is 120L. The permeameter adopts a TST-55 permeameter to ensure the accuracy of the test. The water collector includes a conical flask and a rubber stopper, and the rubber stopper seals the opening of the conical flask. The outlet of the permeameter is connected to the inner cavity of the conical flask through a connecting tube. The water collector of this structure has a better sealing performance to prevent water evaporation. The electronic scale is used to measure the weight of water flowing out of the outlet of the permeameter with an accuracy of 0.001g.

[0044] The pipeline mechanism includes a main pipeline and multiple branch pipelines. The number of the branch pipelines is equal to the number of detection units. One end of the main pipeline is connected to the branch pipeline through a water distributor, and the other end of the main pipeline is connected to the water supply tank and the pressure tank at the same time. A flow meter and a first automatic exhaust valve are sequentially provided in the main pipeline along the direction of water flow, and an automatic pressure regulating valve and a second automatic exhaust valve are sequentially provided in the branch pipeline along the direction of water flow. The automatic exhaust valve and the automatic pressure regulating valve are both connected to the intelligent monitoring system. The main pipeline and the branch pipeline both use transparent plastic water pipes with a diameter of 10 mm to ensure water flow and diversion. The automatic pressure regulating valve is used to adjust the water pressure, and the adjustment pressure range is 0 to 1.5 MPa. In order to further ensure precise control, a control valve is provided in the main pipeline.

[0045] The branch pipeline is provided with a digital thermometer, which is located between the automatic pressure regulating valve and the second automatic exhaust valve.

[0046] The branch pipe is equipped with a precision electronic water pressure gauge, which detects the water pressure in the branch pipe in real time, provides a basis for control instructions for the intelligent monitoring system, and ensures that the test is carried out effectively.

[0047] like Figure 3As shown, the intelligent monitoring system includes an intelligent monitor for monitoring the change of the electronic scale reading and a controller for controlling the opening and closing of the pipeline mechanism and the water pressure. The controller in this embodiment is a computer.

[0048] The method for testing the non-Darcy seepage of ultra-soft soil, using the above-mentioned testing device for the non-Darcy seepage of ultra-soft soil, comprises the following steps:

[0049] S1. Prepare the sample and place it in the infiltrator, then vacuum-treat the infiltrator. Specifically, use a circular cutter to cut the original sample or disturbed soil at a vertical or parallel level to prepare a sample of a given density, then place the sample in the infiltrator. After the infiltrator is installed, vacuum saturate it. For specific operations, refer to Section 4.6.3 of the "Standard for Geotechnical Test Methods" GBT 50123-2019.

[0050] S2. Connect the inlet and outlet of the permeator to the pipeline mechanism and the water collector respectively, open the first automatic exhaust valve, the second automatic exhaust valve and the automatic pressure regulating valve to exhaust the gas in the pipeline, and then close the first automatic exhaust valve, the second automatic exhaust valve and the automatic pressure regulating valve;

[0051] S3. Open the first automatic exhaust valve, the second automatic exhaust valve, and the automatic pressure regulating valve to increase the water pressure. When the first drop of water falls into the water collector, the intelligent monitoring system detects a change in the reading of the electronic scale to determine the initial water head gradient I0.

[0052] The process of determining the initial water head gradient I0 in step S3 is as follows:

[0053] When the first drop of water falls into the water collector, the intelligent monitoring system detects a change in the reading on the electronic scale, controls the automatic pressure regulating valve to keep the water pressure constant, and records the water pressure value as p0;

[0054] If within 120 minutes, the intelligent monitoring system detects that the reading of the electronic scale changes again, that is, when the second drop of water falls, let I0 = p0 / h, where h is the height of the sample in the permeator;

[0055] If the reading on the electric scale does not change within 120 minutes, the automatic pressure regulating valve is controlled to adjust the water pressure. Specifically, the automatic pressure regulating valve is controlled to adjust the water pressure to increase at a uniform rate of 0.5kPa / min. When water drops are detected again, the automatic pressure regulating valve controls the water pressure to remain unchanged. If the water pressure increases to 100kPa at this time, if water drops again within 120 minutes, it will be recorded as 100kPa. If no water drops fall within 120 minutes, it can be considered that the first water drop after the pressure adjustment is not generated by the seepage of the sample, and the automatic pressure regulating valve needs to control the water pressure again to increase by 0.5kPa / min and repeat the above operation.

[0056] S4, set the water pressure p through the automatic pressure regulating valve i , where i is a natural number, and the water pressure p i Next, measure the corresponding time period T i The amount of water flowing into the water collector Q i , then:

[0057] and I i =p i / h,

[0058] Among them, v i is the water velocity, ρ i is the gravity density of water, A is the cross-sectional area of ​​the sample, and h is the height of the sample in the permeator;

[0059] Specifically, based on the measured data and combined with the above formula, the v-I0 relationship test point data is obtained, and the super-soft soil non-Darcy seepage relationship curve is obtained, as shown in Figure 4 shown.

[0060] S5, where the data obtained in S4 is used according to the formula:

[0061]

[0062] Determine the soil permeability of the sample.

[0063] The above method can accurately determine the water pressure at the beginning of seepage in a timely manner to avoid misjudgment; it can avoid human factors and improve reliability; it can accurately test the non-Darcy seepage characteristics of ultra-soft soil and provide a basis for the seepage and consolidation of ultra-soft soil in coastal areas.

[0064] The above specific implementation manner is a preferred embodiment of the present invention and does not limit the present invention. Any other changes or other equivalent replacement methods that do not deviate from the technical solution of the present invention are included in the protection scope of the present invention.

Claims

1. Testing device for non-Darcy seepage in ultra-soft soil, characterized by: It includes a water supply tank, a pressure tank, a compressor, a pipeline mechanism, a detection unit and an intelligent monitoring system. The compressor is connected to the inlet of the pressure tank, and the water supply tank is connected to the pressure tank through a three-way switch. The detection unit includes a permeator, a water collector, and an electronic scale. The inlet of the permeator is connected to a three-way switch through a pipeline mechanism, and the outlet of the permeator is connected to the water collector. The water collector is placed on the electronic scale. The intelligent monitoring system is used to monitor the value changes of the electronic scale during the test, and the intelligent monitoring system is connected to the pipeline mechanism. The pipeline mechanism includes a main pipeline and multiple branch pipelines, the number of the branch pipelines is equal to the number of detection units, one end of the main pipeline is connected to the branch pipeline through a water distributor, and the other end of the main pipeline is connected to the water supply tank and the pressure tank at the same time. A flow meter and a first automatic exhaust valve are sequentially provided in the main pipeline along the direction of water flow, and an automatic pressure regulating valve and a second automatic exhaust valve are sequentially provided in the branch pipeline along the direction of water flow. The automatic exhaust valve and the automatic pressure regulating valve are both connected to the intelligent monitoring system.

2. The device for testing non-Darcy seepage in ultrasoft soil according to claim 1, characterized in that: The branch pipeline is provided with a digital thermometer, which is located between the automatic pressure regulating valve and the second automatic exhaust valve.

3. The device for testing non-Darcy seepage in ultrasoft soil according to claim 1, characterized in that: The branch pipeline is provided with a precision electronic water pressure gauge.

4. The device for testing non-Darcy seepage in ultrasoft soil according to claim 1, characterized in that: The water collector comprises a conical flask and a rubber stopper, wherein the rubber stopper seals the opening of the conical flask, and the outlet of the permeator is connected to the inner cavity of the conical flask through a connecting tube.

5. The device for testing non-Darcy seepage in ultrasoft soil according to claim 1, characterized in that: The intelligent monitoring system includes an intelligent monitor for monitoring changes in the electronic scale reading and a controller for controlling the opening and closing of a pipeline mechanism and the size of water pressure.

6. The test method for non-Darcy seepage of ultra-soft soil is characterized by: The device for testing non-Darcy seepage of ultrasoft soil according to any one of claims 1 to 5 comprises the following steps: S1. Prepare the sample and place the prepared sample in the permeator, and then vacuum treat the permeator; S2. Connect the inlet and outlet of the permeator to the pipeline mechanism and the water collector respectively, open the first automatic exhaust valve, the second automatic exhaust valve and the automatic pressure regulating valve to exhaust the gas in the pipeline, and then close the first automatic exhaust valve, the second automatic exhaust valve and the automatic pressure regulating valve; S3. Open the first automatic exhaust valve, the second automatic exhaust valve, and the automatic pressure regulating valve to increase the water pressure. When the first drop of water falls into the water collector, the intelligent monitoring system detects a change in the reading of the electronic scale to determine the initial water head gradient I0. The process of determining the initial water head gradient I0 in step S3 is as follows: When the first drop of water falls into the water collector, the intelligent monitoring system detects a change in the reading on the electronic scale, controls the automatic pressure regulating valve to keep the water pressure constant, and records the water pressure value as p0; If within 120 minutes, the intelligent monitoring system detects that the reading of the electronic scale changes again, that is, when the second drop of water falls, let I0 = p0 / h, where h is the height of the sample in the permeator; If the reading on the electric scale does not change within 120 minutes, the automatic pressure regulating valve will be controlled to adjust the water pressure; S4, set the water pressure p through the automatic pressure regulating valve i , where i is a natural number, and the water pressure p i Next, measure the corresponding time period T i The amount of water flowing into the water collector Q i , then: and I i =p i / h, Among them, v i is the seepage velocity, ρ i is the gravity density of water, A is the cross-sectional area of ​​the sample, and h is the height of the sample in the permeator; S5, where the data obtained in S4 is used according to the formula: Determine the soil permeability of the sample.

7. The method for testing non-Darcy seepage in ultrasoft soil according to claim 6, wherein: If the reading on the electric scale does not change within 120 minutes, the automatic pressure regulating valve controls the water pressure in the branch pipeline to increase at a uniform rate of 0.5 kPa / min.

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