Unsaturated soil column permeation device capable of simulating different rainfall intensities and test method

Abstract

The invention relates to an unsaturated soil column permeation device capable of simulating different rainfall intensities and a test method. The unsaturated soil column permeation device comprises a water pumping adjustment module and a water flow scattering module which are connected, a rainfall simulation area, a soil sample filling area, a screen partition plate assembly and a funnel are sequentially arranged below the water flow scattering module; the soil sample filling area is of a columnar structure, and a plurality of moisture meters and a plurality of tensiometers are arranged along the soil sample filling area; the lower end of the funnel is connected with the first water tank, and a first balance scale is arranged below the first water tank; the end, away from the funnel, of the first water tank is connected with a transfer pool, a second balance scale is arranged below the transfer pool, and a multi-layer filter screen is arranged on one side of the transfer pool. One side of the transfer water tank provided with the filter screen is connected with the water storage tank through a second water tank. The device has the beneficial effects that through the synergistic effect of the water pumping adjusting module and the water flow scattering module, the water flow speed and the water yield of the rainfall opening can be accurately controlled, and different rainfall environments from low intensity to high intensity are simulated.

Description

Technical Field

[0001] The invention relates to the field of geotechnical engineering, and more specifically, to an unsaturated soil column penetration device and a test method capable of simulating different rainfall intensities. Background Art

[0002] With the acceleration of urbanization and the increase in infrastructure construction projects, many projects such as roads, bridges, tunnels, etc. need to be constructed under various geological conditions. Unsaturated soil is common in the natural environment, especially in arid and semi-arid areas, so the study of its permeability characteristics is crucial to ensure the quality of the project.

[0003] In addition, the permeability characteristics of unsaturated soil have an important impact on the spread and control of groundwater pollution. For example, near potential pollution sources such as landfills and chemical plants, understanding the permeability characteristics of unsaturated soil can help design effective anti-seepage measures to prevent pollutants from penetrating into groundwater. In general, traditional soil mechanics research mainly focuses on saturated soil, but unsaturated soil is more common in actual engineering. Therefore, the study of unsaturated soil mechanics has become a hot topic in the field of soil mechanics in recent years.

[0004] In the field of unsaturated soil mechanics, existing technologies mainly rely on a series of experimental equipment and techniques to measure and analyze the physical and mechanical properties of soil under different moisture content conditions. These technologies include but are not limited to traditional penetration tests, suction control devices, and stress-strain relationship analysis. However, current unsaturated soil sample penetration devices have some defects, such as the difficulty in accurately simulating the complex environment in the natural environment, restrictions on sample size, and instability in maintaining constant suction, which may cause the experimental results to deviate from the actual situation. In addition, traditional devices are often complex in structure and cumbersome in operation, which makes the experimental preparation time long and inefficient, and cannot stably monitor the precipitated particles. Summary of the invention

[0005] The purpose of the present invention is to address the deficiencies of the prior art and to propose an unsaturated soil column penetration device and a test method that can simulate different rainfall intensities.

[0006] In a first aspect, an unsaturated soil column infiltration device capable of simulating different rainfall intensities is provided, comprising: a pump water regulating module and a water flow scattering module connected to each other; a simulated rainfall area, a soil sample filling area, a screen partition assembly and a funnel are sequentially arranged below the water flow scattering module; the soil sample filling area is a columnar structure, and a plurality of moisture meters and a plurality of tensiometers are arranged along the soil sample filling area; the lower end of the funnel is connected to a first water trough, and a first level scale is arranged below the first water trough; the end of the first water trough away from the funnel is connected to a transfer water tank, a second level scale is arranged below the transfer water tank, and a multi-layer filter screen is arranged on one side of the transfer water tank; the side of the transfer water tank provided with the filter screen is connected to a water storage tank through a second water trough.

[0007] Preferably, the water flow scattering module comprises a flow rate regulating nozzle, a water delivery area and a water drop outlet;

[0008] Among them, the flow rate regulating nozzle is arranged on the upper surface of the water delivery area, and the water droplet is arranged on the lower surface of the water delivery area; the flow rate regulating nozzle is connected to the water pump regulating module; the flow rate regulating nozzle is used to control the water volume of the water flow in the water delivery area.

[0009] Preferably, the rainoutlets are evenly distributed in a scattered pattern.

[0010] Preferably, a pressure stabilizing port is further included, and the pressure stabilizing port is used to maintain the pressure in the simulated rainfall area without changing with rainfall intensity.

[0011] Preferably, the screen partition assembly consists of a partition and a screen, a circular notch is provided at the center of the partition, and the screen is arranged at the position of the circular notch.

[0012] In a second aspect, there is also provided an unsaturated soil column penetration test method capable of simulating different rainfall intensities, which is performed by any device described in the first aspect, and comprises:

[0013] Step 1: Place the dried sample in multiple layers into the soil sample filling area, and compact each layer with a vibrator to achieve a compaction close to that of the in-situ soil;

[0014] Step 2: Simulate rainfall environments of different intensities through the water pumping and regulating module and the water flow scattering module;

[0015] Step 3, observe whether the weight of the sample changes by using the first balance scale. When the weight of the sample remains unchanged, obtain the instantaneous volumetric moisture content of samples at different depths by using multiple moisture meters, measure the matrix suction value of the sample with the instantaneous volumetric moisture content by using multiple tensiometers, and calculate the unsaturated permeability coefficient of the sample.

[0016] Preferably, in step 2, the closing degree of the nozzle and the power of the water pump regulating module are adjusted by controlling the flow rate, and the water flow rate and water output of the precipitation outlet are adjusted to simulate rainfall environments of different intensities.

[0017] As a preference, it also includes:

[0018] Step 4: intercept the fine particles brought out by water flowing through the sample through multiple layers of filters, calculate the particle loss content after drying, and analyze the change pattern of particle loss over time.

[0019] The beneficial effects of the present invention are:

[0020] 1. The present invention can accurately control the water flow velocity and water output of the precipitation outlet through the synergistic effect of the pump water regulation module and the water flow scattering module, and simulate different rainfall environments from low intensity to high intensity.

[0021] 2. The present invention is equipped with multiple moisture meters and tensiometers, which can monitor the volumetric moisture content and matrix suction value of the sample at different depths in real time. Combined with the monitoring of the sample weight by an electronic balance, the unsaturated permeability coefficient can be accurately calculated. In addition, the device can also intercept fine particles through multi-layer filter screens, calculate the particle loss content after drying, and analyze the change law of particle loss over time, providing comprehensive data support for studying the permeability characteristics of unsaturated soil.

[0022] 3. The setting of the pressure stabilizing port of the present invention ensures the stability of the pressure in the simulated rainfall area, avoids the experimental error caused by the change of rainfall intensity, and thus improves the accuracy and reliability of the experimental data. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of the structure of an unsaturated soil column infiltration device capable of simulating different rainfall intensities provided by an embodiment of the present invention;

[0024] Figure 2 A schematic diagram of the structure of a water flow scattering module provided in an embodiment of the present invention;

[0025] Figure 3 A schematic diagram of a sample installation area provided in an embodiment of the present invention;

[0026] Figure 4 A local schematic diagram of sample penetration provided by an embodiment of the present invention;

[0027] Figure 5 A schematic diagram of a particle filtration area provided by an embodiment of the present invention;

[0028] Explanation of the reference numerals: water pump regulating module 1, water flow scattering module 2, flow rate regulating nozzle 201, water delivery area 202, precipitation outlet 203, simulated rainfall area 3, soil sample filling area 4, screen partition assembly 5, partition 501, screen 502, funnel 6, moisture meter 7, tensiometer 8, first water tank 9, first level scale 10, transfer water tank 11, second level scale 12, filter 13, second water tank 14, water storage tank 15, pressure stabilizing port 16. DETAILED DESCRIPTION

[0029] 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.

[0030] Embodiment 1:

[0031] Embodiment 1 of the present application provides an unsaturated soil column infiltration device that can simulate different rainfall intensities, including: a pump water regulating module 1 and a water flow scattering module 2 that are connected; a simulated rainfall area 3, a soil sample filling area 4, a screen partition assembly 5 and a funnel 6 are sequentially arranged below the water flow scattering module 2; the soil sample filling area 4 is a columnar structure, and a plurality of moisture meters 7 and a plurality of tensiometers 8 are arranged along the soil sample filling area 4; the lower end of the funnel 6 is connected to a first water trough 9, and a first leveling scale 10 is arranged below the first water trough 9; the end of the first water trough 9 away from the funnel 6 is connected to a transfer water tank 11, a second leveling scale 12 is arranged below the transfer water tank 11, and a multi-layer filter screen 13 is arranged on one side of the transfer water tank 12; the side of the transfer water tank 12 provided with the filter screen 13 is connected to a water storage tank 15 through a second water trough 14.

[0032] Embodiment 2:

[0033] Based on Example 1, Example 2 of the present application provides a more specific unsaturated soil column infiltration device that can simulate different rainfall intensities, including: a pump water regulation module 1, a water flow scattering module 2, a simulated rainfall area 3, a soil sample filling area 4, a screen partition assembly 5, a funnel 6, a moisture meter 7, a tensiometer 8, a first water tank 9, a first level scale 10, a transfer water tank 11, a second level scale 12, a filter 13, a second water tank 14, a water storage tank 15 and a pressure regulating port 16.

[0034] Specifically, the water flow scattering module 2 includes a flow rate regulating nozzle 201, a water delivery area 202 and a water drop outlet 203;

[0035] Among them, the flow rate regulating nozzle 201 is arranged on the upper surface of the water delivery area 202, and the water droplet 203 is arranged on the lower surface of the water delivery area 202; the flow rate regulating nozzle 201 is connected to the water pump regulating module 1; the flow rate regulating nozzle 201 is used to control the water volume of the water flow in the water delivery area 202.

[0036] The water pump regulating module 1 is used together with the water flow scattering module 2. By controlling the closing degree of the flow rate regulating nozzle 201 and the power of the water pump regulating module 1, the water volume of the water flow in the water delivery area 202 can be directly affected, thereby controlling the water flow speed and water output of the precipitation outlet 203; wherein the precipitation outlet 203 presents a uniform scattered point shape, so the water flow scattering module 2 can simulate rainfall environments of different intensities, and the water flow passes through the simulated rainfall area 3 to act on the surface of the sample in the soil sample filling area 4.

[0037] In addition, the pressure stabilizing port 16 is used to maintain the pressure of the simulated rainfall area 3 without changing with the rainfall intensity. The pressure stabilizing port is located at the lower surface edge of the transition area between the simulated rainfall area 3 and the water flow scattering module 2 .

[0038] The screen partition assembly 5 is composed of a partition 501 and a screen 502. A circular notch is provided at the center of the partition 501, and the screen 502 is arranged at the position of the circular notch.

[0039] It should be noted that the parts in this embodiment that are the same or similar to those in Embodiment 1 can be referenced to each other and will not be described in detail in this application.

[0040] Embodiment 3:

[0041] Based on Example 2, Example 3 of the present application provides an unsaturated soil column permeability test method that can simulate different rainfall intensities, including:

[0042] Step 1: Place the dried sample in multiple layers (such as three layers) into the soil sample filling area 4, and compact each layer with a vibrator to achieve a compaction close to that of the original soil.

[0043] Step 2: Simulate rainfall environments of different intensities through the water pumping regulation module 1 and the water flow scattering module 2.

[0044] In step 2, the closing degree of the nozzle 201 and the power of the water pump regulating module 1 are adjusted by controlling the flow rate, and the water flow rate and water output of the precipitation outlet 203 are adjusted to simulate rainfall environments of different intensities.

[0045] Step 3, observe whether the weight of the sample changes by the first balance scale 10. When the weight of the sample remains unchanged, obtain the instantaneous volumetric moisture content of the samples at different depths by multiple moisture meters 7, measure the matrix suction value of the sample with the instantaneous volumetric moisture content by multiple tensiometers 8, and calculate the unsaturated permeability coefficient of the sample.

[0046] The specific formula for calculating the unsaturated permeability coefficient may vary depending on the theoretical model used. A commonly used model is based on the Van Genuchten equation to describe the soil moisture characteristic curve, and combined with the Mualem function to estimate the relative permeability under unsaturated conditions. The permeability coefficient obtained can be expressed as:

[0047]

[0048] Where k(θ) is the permeability coefficient at a given water content θ, k s is the permeability coefficient at saturation, θ r is the residual moisture content (i.e. the moisture content under very dry conditions), θ s is the saturated water content, m is a shape parameter related to the soil type, usually m = 1-1 / n, and n is another shape parameter in the Van Genuchten equation.

[0049] For example, the present application arranges three moisture meters 7 and three tensiometers 8 equidistantly along the soil column.

[0050] Step 4: intercept the fine particles brought out by the water flow through the sample through the multi-layer filter screen 13, calculate the particle loss content after drying, and analyze the change pattern of particle loss over time.

[0051] Specifically, before the water flow is turned off, the change in the amount of particle loss over time during the infiltration test can be observed and counted; after the water flow is turned off, the lost particles are collected and dried to calculate the particle loss content of the sample, and the law of how the particle loss changes over time during the infiltration test can be obtained.

[0052] It should be noted that the method provided in this embodiment is the test method corresponding to the device provided in Example 2. Therefore, the parts in this embodiment that are the same or similar to those in Example 2 can be referenced to each other and will not be repeated in this application.

Claims

1. An unsaturated soil column infiltration device that can simulate different rainfall intensities, characterized in that: include: A pump water regulating module (1) and a water flow scattering module (2) are connected to each other; a simulated rainfall area (3), a soil sample filling area (4), a screen partition assembly (5) and a funnel (6) are arranged in sequence below the water flow scattering module (2); the soil sample filling area (4) is a columnar structure, and a plurality of moisture meters (7) and a plurality of tensiometers (8) are arranged along the soil sample filling area (4); the lower end of the funnel (6) is connected to a first water trough (9), and a first leveling scale (10) is arranged below the first water trough (9); the end of the first water trough (9) away from the funnel (6) is connected to a transfer water tank (11), a second leveling scale (12) is arranged below the transfer water tank (11), and a multi-layer filter screen (13) is arranged on one side of the transfer water tank (12); the side of the transfer water tank (12) provided with the filter screen (13) is connected to a water storage tank (15) through a second water trough (14).

2. The unsaturated soil column infiltration device capable of simulating different rainfall intensities according to claim 1 is characterized in that: The water flow scattering module (2) comprises a flow rate regulating nozzle (201), a water delivery area (202) and a water drop outlet (203); The flow rate regulating nozzle (201) is arranged on the upper surface of the water delivery area (202), and the water drop outlet (203) is arranged on the lower surface of the water delivery area (202); the flow rate regulating nozzle (201) is connected to the water pump regulating module (1); and the flow rate regulating nozzle (201) is used to control the water volume of the water flow in the water delivery area (202).

3. The unsaturated soil column infiltration device capable of simulating different rainfall intensities according to claim 2 is characterized in that: The rainoutlets (203) are evenly distributed in a scattered pattern.

4. The unsaturated soil column infiltration device capable of simulating different rainfall intensities according to claim 3 is characterized in that: It also comprises a pressure stabilizing port (16), wherein the pressure stabilizing port (16) is used to maintain the pressure of the simulated rainfall area (3) so as not to change with rainfall intensity.

5. The unsaturated soil column infiltration device capable of simulating different rainfall intensities according to claim 4 is characterized in that: The screen partition assembly (5) is composed of a partition (501) and a screen (502); a circular notch is provided at the center of the partition (501), and the screen (502) is arranged at the position of the circular notch.

6. A method for testing the permeability of unsaturated soil columns that can simulate different rainfall intensities, characterized in that: Executed by the device according to any one of claims 1 to 5, comprising: Step 1: Place the dried sample in multiple layers into the soil sample filling area (4), and compact each layer with a vibrator to achieve a compaction close to that of the original soil; Step 2, simulating rainfall environments of different intensities through the water pumping and regulating module (1) and the water flow scattering module (2); Step 3, using the first balance scale (10) to observe whether the weight of the sample changes. When the weight of the sample remains unchanged, the instantaneous volumetric moisture content of the samples at different depths is obtained using multiple moisture meters (7), and the matrix suction value of the sample with the instantaneous volumetric moisture content is measured using multiple tensiometers (8), and the unsaturated permeability coefficient of the sample is calculated.

7. The unsaturated soil column permeability test method capable of simulating different rainfall intensities according to claim 6 is characterized in that: In step 2, the closing degree of the nozzle (201) and the power of the water pump regulating module (1) are adjusted by controlling the flow rate, and the water flow rate and water output of the precipitation outlet (203) are adjusted to simulate rainfall environments of different intensities.

8. The unsaturated soil column permeability test method capable of simulating different rainfall intensities according to claim 7 is characterized in that: Also includes: Step 4: intercept fine particles brought out by water flowing through the sample through a multi-layer filter (13), calculate the particle loss content after drying, and analyze the change pattern of particle loss over time.

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