CN107560960B - A device and method for measuring the splash corrosion resistance of fine-grained soil - Google Patents

Abstract

The invention discloses a device for measuring the splash corrosion resistance of fine-grained soil, which includes a water supply system, a main pipe structure, a raindrop control system and a measurement system. It also discloses a method for measuring the splash corrosion resistance of fine-grained soil. It includes three steps: sample preparation, device debugging, and testing. It can quantitatively test and evaluate the splash erosion resistance of different fine-grained soils (sand, silt, silty clay, clay, red clay, expansive soil, etc.) under the action of raindrops, which is important for the anti-scouring design of roadbed slopes. Reference and guidance significance.

Description

A device and method for measuring the splash corrosion resistance of fine-grained soil

Technical field

The invention belongs to the technical field of geotechnical engineering, and specifically relates to a device for measuring the splash corrosion resistance of fine-grained soil, and also relates to a method for measuring the splash corrosion resistance of fine-grained soil.

Background technique

Soil splash erosion is an important form and component of soil erosion. It refers to an erosion process in which soil particles are dispersed and migrated due to rainfall and raindrops hitting the soil surface. It is the early stage and key link in the soil erosion process and affects slope stability.

The process of raindrop splash erosion is also an energy conversion process: when there is no runoff on the surface, raindrops with kinetic energy hit the surface, and part of the energy is absorbed by the soil particles and converted into heat energy. The "excess" energy that has not been absorbed destroys the soil structure and is even converted into potential energy of soil particles, causing some soil particles to jump. Due to the effect of gravity, these splashed soil particles fall back to the surface and become "isolated" soil particles. As the raindrops continue to hit, this process of splashing soil particles continues. When runoff occurs on the surface, the direct impact of raindrops changes from the soil to the "water layer". That is, the raindrops first collide with the water layer, part of the energy is absorbed by the water layer to generate heat, and the "remaining" energy collides with the soil again. Part of the remaining energy is absorbed by the soil particles, and the other part is used to destroy the soil structure. But at this time, this "secondary residual" energy is smaller, and the resulting sputter erosion is smaller.

Although the diameter of raindrops generally does not exceed 6mm, the energy accumulated by long-term concentrated heavy rain cannot be underestimated, so its intensity is significantly affected by rainfall. At present, the amount of splash erosion of raindrops is generally measured using the splash plate or splash cup method. Factors affecting the amount of splash erosion can be roughly divided into two categories: one is kinetic energy factors, which are related to the size of raindrops and falling speed; the other is surface factors, which are related to soil type, soil surface density, vegetation conditions, etc. Scholars at home and abroad have done a lot of experiments on the above influencing factors, but most of them only studied the changes in the amount of splash erosion, and did not further study the splash erosion damage of soil. Therefore, studying the surface damage of soil during the splash erosion process is of great significance to the research on the splash corrosion resistance of fine-grained soil.

Contents of the invention

In order to determine the damage of fine-grained soil under the action of rainwater and evaluate the splash corrosion resistance of fine-grained soil, the present invention proposes a device for measuring the splash corrosion resistance of fine-grained soil. A method for measuring the splash corrosion resistance of fine-grained soils.

In order to achieve the above objects, the present invention adopts the following technical solutions:

A device for measuring the splash corrosion resistance of fine-grained soil, including a water supply system, a main pipe structure, a raindrop control system and a measurement system,

The water supply system includes a water container. The water container is connected to the upper end of the main pipe structure through a rubber hose. A water stop clamp is provided on the rubber hose.

An overflow pipe is provided at the upper end of the main pipe structure, and an overflow receiving bottle is provided below the overflow pipe.

The raindrop control system includes a regulating valve installed on the main pipe structure, a dripper installed at the lower end of the main pipe structure, and a water stop sleeve installed at the drip port of the dripper.

The measurement system includes a camera installed on the top inner wall of the test environment box and a laser rangefinder located above the test soil sample in the test environment box.

The main pipe structure as described above includes a first vertical pipe section, a horizontal pipe section and a second vertical pipe section. The bottom end of the first vertical pipe section is connected with one end of the horizontal pipe section, and the other end of the horizontal pipe end is connected with the top end of the second vertical pipe section. The top of a vertical pipe section is connected to the water container through a rubber hose, the overflow pipe is set at the upper part of the first vertical pipe section, the regulating valve is set on the horizontal pipe section, and the dripper is set at the bottom of the second vertical pipe section.

As mentioned above, the first vertical pipe section, the horizontal pipe section and the second vertical pipe section are all PVC pipes with a pipe diameter of 25mm. The volume of the water container is 4L, the dripping diameter of the dripper is 10ml, and the test environment box is a transparent plate with a thickness of 3mm. Acrylic board, the height × width × length of the test environment box are 1200cm × 40cm × 40cm.

The main pipe structure is mainly to ensure that the water pressure of the pipeline remains stable during the test. The raindrop control system is mainly to control the number of water droplets falling per unit time. The measurement system is mainly to measure the amount of splash pits produced on the surface of fine-grained soil under the action of water droplets. Depth and area, the test environment box is mainly to eliminate the interference caused by environmental factors on the test.

When the water flows over the overflow pipe, water will flow out of the overflow pipe to maintain stable water pressure in the pipe.

A method for measuring the splash corrosion resistance of fine-grained soil, including the following steps:

Step 1. Prepare the test soil sample. The test soil sample is undisturbed soil or compacted soil. The shape of the test soil sample is cylindrical soil sample;

Step 2. Control the number of water droplets from the drip port of the dripper per unit time;

Step 3. First, place the test soil sample into the test environment box, and use a laser rangefinder to collect the surface height data H1 of the test soil sample. Then open the water-stop sleeve and set the time to conduct the test experiment on the test soil sample. Test After the test is completed, the regulating valve is closed, and the depth and area of the splash pit of the test soil sample are measured using a laser rangefinder and a camera respectively.

The preparation of compacted soil as described above involves the following steps:

Step 1.1: First, screen out the particles with a particle size greater than 40mm in the sample, and then use the quartering method to divide the sieved sample into 8 parts, and add 6 of the samples to the setting. Different amounts of water, mix well and stuff it overnight for later use.

Step 1.2. Take out the 6 samples after stuffing and conduct the heavy-duty II-2 compaction test. In the heavy-duty II-2 compaction test, each sample is divided into 3 small parts and compacted in 3 layers to obtain the test result. Then measure the mass of each sample, calculate the corresponding dry density, take the central soil sample of the sample, and measure the moisture content of the central soil sample. Take the dry density as the ordinate and the moisture content as the abscissa. Mark each sample point in to draw the relationship curve between the dry density and moisture content of the sample, and obtain the maximum dry density of the sample. The optimal moisture content of the sample can also be obtained. Use the interpolation method to calculate the dry density of the sample. The moisture content corresponding to 93% of the maximum dry density is obtained from the relationship curve with moisture content.

Step 1.3. Finally, add an appropriate amount of water to the remaining 2 samples in step 1.1, so that the moisture content reaches the moisture content corresponding to the maximum dry density of 93%, and then perform heavy-duty II-2 compaction. Heavy-duty II-2 compaction Carry out in three layers to prepare compacted soil samples.

Step 2 as described above includes the following steps:

Open the water stop clamp, and the water will flow from the rubber hose into the main pipe structure and flow out from the overflow pipe. Ensure that the main pipe structure is filled with water and keep the overflow pipe with a uniform flow rate of water flowing out. Open the water stop sleeve, adjust the regulating valve, and use Stopwatch counts, and finally controls the amount of water droplets within 60 seconds to the set number of drops, and finally closes the water-stop sleeve.

As mentioned above, using a laser rangefinder and a camera to measure the depth and area of the splash pit in the test soil sample in step 3 includes the following steps:

First, a laser rangefinder is used to measure the surface height data H1 of the soil sample before the distance between the laser rangefinder and the water droplet causing a splash pit. After the water stop sleeve is opened and the test soil sample is tested for a set time, the laser rangefinder is used again to measure the laser range. The height data of the rangefinder from the bottom of the splash pit is H2, then the depth of the splash pit is D=H2-H1, and then a square sheet with a set size of 10mm×10mm is placed in the soil sample splash pit as a ruler. Next, a camera is used to take pictures of the square sheet and the sputter pit at the same time to obtain the measurement image. According to the measurement image, the average length L1 of the three sides of the square sheet is calculated. Based on the measurement image, the three diameters of the sputter pit are calculated. The average value Φ1, the true aperture diameter of the sputter pit Φ = , and then obtain the sputter pit area.

Compared with the prior art, the present invention has the following beneficial effects:

It is innovatively proposed to evaluate the splash corrosion resistance of fine-grained soil based on the damage condition of the soil surface, which makes up for the current situation that the existing soil splash corrosion test only evaluates the changes in the amount of splash corrosion. Not only the changing trend of the depth of the splash pit with time during the water droplet splash erosion of fine-grained soil is considered, but also the change of the pore size of the splash pit with time is also considered. The damage to the surface morphology of fine-grained soil during the dripping process of water droplets was evaluated from many aspects, providing a practical and effective evaluation device and method for evaluating its rainfall erosion resistance.

Description of the drawings

Figure 1 is a schematic structural diagram of the device of the present invention;

Figure 2 is a schematic diagram of the internal structure of the test environment box.

In the picture: 1-water supply system; 1a-water container; 1b-water stop clamp; 1c-rubber hose; 2-main pipe structure; 2a-overflow pipe; 3-raindrop control system; 3a-regulating valve; 3b-stop Water jacket; 3c-water dripper; 4a-laser range finder; 4b-camera; 5-test environment box; 6-test soil sample; 7-overflow receiving bottle.

Detailed ways

In order to clearly explain the purpose, technical solution and advantages of the present invention, the present invention will be introduced in further detail below in conjunction with the embodiments. The specific embodiments described here are only used to explain the present invention and are not intended to limit the present invention.

Example 1

As shown in Figures 1 to 2, a device for measuring the splash corrosion resistance of fine-grained soil includes a water supply system 1, a main pipe structure 2, a raindrop control system 3 and a measurement system.

The water supply system 1 includes a water container 1a. The water container 1a is connected to the upper end of the main pipe structure 2 through a rubber hose 1c. The rubber hose 1c is provided with a water stop clamp 1b.

An overflow pipe 2a is provided at the upper end of the main pipe structure 2, and an overflow receiving bottle 7 is provided below the overflow pipe 2a.

The raindrop control system 3 includes a regulating valve 3a provided on the main pipe structure 2, a dripper 3c provided at the lower end of the main pipe structure 2, and a water stop sleeve 3b provided at the drip port of the dripper 3c.

The measurement system includes a camera 4b installed on the top inner wall of the test environment box 5 and a laser rangefinder 4a located above the test soil sample 6 in the test environment box 5 .

The main pipe structure 2 includes a first vertical pipe section, a horizontal pipe section and a second vertical pipe section. The bottom end of the first vertical pipe section is connected to one end of the horizontal pipe section, and the other end of the horizontal pipe end is connected to the top of the second vertical pipe section. The first vertical pipe section The top end is connected to the water container 1a through the rubber hose 1c, the overflow pipe 2a is set at the upper part of the first vertical pipe section, the regulating valve 3a is set at the horizontal pipe section, and the dripper 3c is set at the bottom end of the second vertical pipe section.

As mentioned above, the first vertical pipe section, the horizontal pipe section and the second vertical pipe section are all PVC pipes with a pipe diameter of 25mm. The volume of the water container 1a is 4L, the dripping diameter of the dripper 3c is 10ml, and the test environment box 5 is plate thickness 3mm transparent acrylic board, the height × width × length of the test environment box 5 is 1200cm × 40cm × 40cm.

The main pipe structure is mainly to ensure that the water pressure of the pipeline remains stable during the test. The raindrop control system is mainly to control the number of water droplets falling per unit time. The measurement system is mainly to measure the amount of splash pits produced on the surface of fine-grained soil under the action of water droplets. Depth and area, the test environment box is mainly to eliminate the interference caused by environmental factors on the test.

When the water flows over the overflow pipe, water will flow out of the overflow pipe to maintain stable water pressure in the pipe.

As shown in Figures 1 to 2, a test method for testing the splash corrosion resistance of fine-grained soil has the following test steps: The entire test process includes three steps: sample preparation, device debugging, and test testing. Specifically:

Step 1. Prepare the test soil sample. The test soil sample is undisturbed soil or compacted soil. The shape of the test soil sample is cylindrical soil sample;

Step 2. Control the number of water droplets falling from the drip port of the dripper 3c per unit time;

Step 3. First, place the test soil sample into the test environment box 5, and use the laser rangefinder 4a to collect the surface height data H1 of the test soil sample, and then open the water stop 3b to set the time to test the test soil sample. After the experiment, the test test is completed, the regulating valve 3a is closed, and the laser rangefinder 4a and the camera 4b are used to measure the depth and area of the splash pit of the test soil sample respectively.

This set of testing devices and methods is easy to operate and can quantitatively test and evaluate the splash corrosion resistance of different fine-grained soils (sand, silt, silty clay, clay, red clay, expansive soil, etc.) under the action of raindrops. It has important reference and guiding significance for the anti-scouring design of roadbed slopes.

The preparation of the undisturbed soil includes the following steps: Sampling of the undisturbed soil, the sampling method should comply with the requirements for undisturbed soil sampling in the national standard "Code for Geotechnical Engineering Investigation" (GB 50021), and it is appropriate to use Level I soil testing. To carry out this experiment, the outer diameter of the soil collector should be ≥75mm, and the cylindrical soil sample should be taken with a height of not less than 10cm.

The preparation of the compacted soil includes the following steps:

Step 1.1: First, screen out the particles with a particle size greater than 40mm in the sample, and then use the quartering method to divide the sieved sample into 8 parts, and add 6 of the samples to the setting. Different amounts of water, mix well and stuff it overnight for later use.

Step 1.2. Take out the 6 samples after stuffing and conduct the heavy-duty II-2 compaction test. In the heavy-duty II-2 compaction test, each sample is divided into 3 small parts and compacted in 3 layers to obtain the test result. Then measure the mass of each sample, calculate the corresponding dry density, take the central soil sample of the sample, and measure the moisture content of the central soil sample. Take the dry density as the ordinate and the moisture content as the abscissa. Mark each sample point in to draw the relationship curve between the dry density and moisture content of the sample, and obtain the maximum dry density of the sample. The optimal moisture content of the sample can also be obtained. Use the interpolation method to calculate the dry density of the sample. The moisture content corresponding to 93% of the maximum dry density is obtained from the relationship curve with moisture content.

Step 1.3. Finally, add an appropriate amount of water to the remaining 2 samples in step 1.1, so that the moisture content reaches the moisture content corresponding to the maximum dry density of 93%, and then perform heavy-duty II-2 compaction. Heavy-duty II-2 compaction Carry out in three layers to prepare compacted soil samples.

The described step 2 includes the following steps:

Open the water stop clamp 1b, water flows into the main pipe structure 2 from the rubber hose 1c and flows out from the overflow pipe 2a. Ensure that the main pipe structure 2 is filled with water and maintain a uniform flow rate of water flowing out of the overflow pipe 2a. Open the water stop sleeve. 3b, adjust the regulating valve 3a, use a stopwatch to time, and finally control the amount of water droplets within 60 seconds to the set number of drops, and finally close the water stop sleeve 3b.

The use of the laser rangefinder 4a and the camera 4b to measure the depth and area of the splash pit of the test soil sample in step 3 includes the following steps:

First, the laser rangefinder 4a is used to measure the surface height data H1 of the soil sample before the distance between the laser rangefinder 4a and the water droplet causing the splash pit. After opening the water stop 3b and setting the time to test the soil sample, the laser rangefinder is used again. The instrument 4a measures the height data H2 of the distance between the laser rangefinder 4a and the bottom of the sputter pit, then the depth of the sputter pit is D=H2-H1, and then a square sheet with a set size of 10mm×10mm is placed as a ruler. Next to the splash pit of the soil sample, the camera 4b is used to take pictures of the square sheet and the splash pit at the same time to obtain a measurement image. The average length L1 of the three sides of the square sheet is calculated based on the measurement image, and the splash erosion is calculated based on the measurement image. The average of the three diameters of the pit Φ1, the true aperture diameter of the sputter pit Φ = , and then obtain the sputter pit area.

Example 2

The soil sample in step 1 is undisturbed soil. It is prepared on site in accordance with the sampling requirements of undisturbed soil in the national standard "Geotechnical Engineering Survey Specifications" (GB 50021). It is suitable for testing the splash corrosion resistance of natural soil on the surface. Steps The amount of water droplets in step 2 is 30 drops per minute, and the set time for testing the soil sample in step 3 is 120 minutes. Others are consistent with Example 1. The test results are shown in Table 1.

Table 1 Sputter pit depth and aperture test data

Example 3

The soil sample in step 1 is compacted soil. It is suitable for testing the splash corrosion resistance of compacted subgrade soil. The amount of water droplets in step 2 is 30 drops/minute. The set time for testing the soil sample in step 3 is 120 minutes. Others are consistent with Example 1. The test results are shown in Table 2.

Table 2 Sputter pit depth and aperture test data

The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which the present invention belongs can make various modifications or additions to the described specific embodiments or substitute them in similar ways, but this will not deviate from the spirit of the present invention or exceed the definition of the appended claims. range.

Claims (4)

1. A method for measuring the splash erosion resistance of fine-grained soil, which utilizes a device for measuring the splash erosion resistance of fine-grained soil, the device comprises a water supply system (1), a main body pipe structure (2), a raindrop control system (3) and a measuring system,

the water supply system (1) comprises a water container (1 a), the water container (1 a) is communicated with the upper end of the main body pipe structure (2) through a rubber hose (1 c), a water stop clamp (1 b) is arranged on the rubber hose (1 c),

an overflow pipe (2 a) is arranged at the upper end of the main body pipe structure (2), an overflow receiving bottle (7) is arranged below the overflow pipe (2 a),

the raindrop control system (3) comprises a regulating valve (3 a) arranged on the main body pipe structure (2), a water dropper (3 c) arranged at the lower end of the main body pipe structure (2) and a water stopping sleeve (3 b) arranged at the water dropping opening of the water dropper (3 c),

the measuring system comprises a camera (4 b) arranged on the top inner wall of the test environment box (5) and a laser range finder (4 a) positioned above a test soil sample (6) in the test environment box (5),

the main body pipe structure (2) comprises a first vertical pipe section, a horizontal pipe section and a second vertical pipe section, wherein the bottom end of the first vertical pipe section is communicated with one end of the horizontal pipe section, the other end of the horizontal pipe section is communicated with the top end of the second vertical pipe section, the top end of the first vertical pipe section is communicated with a water container (1 a) through a rubber hose (1 c), an overflow pipe (2 a) is arranged on the upper part of the first vertical pipe section, a regulating valve (3 a) is arranged on the horizontal pipe section, a water dropper (3 c) is arranged at the bottom end of the second vertical pipe section,

the method is characterized by comprising the following steps:

step 1, preparing a test soil sample, wherein the test soil sample is undisturbed soil or compacted soil, and the test soil sample is cylindrical;

step 2, controlling the drop number of water drops of a water drop outlet of the water dropper (3 c) in unit time;

and 3, firstly placing a test soil sample into a test environment box (5), collecting surface height data H1 of the test soil sample by adopting a laser range finder (4 a), then opening a water stop sleeve (3 b) for a set time to test the test soil sample, closing a regulating valve (3 a) after the test is completed, and measuring the depth and the area of a splash pit of the test soil sample by adopting the laser range finder (4 a) and a camera (4 b) respectively.

2. A method for measuring the splash and etch resistance of fine earth according to claim 1,

the preparation of the compacted soil comprises the following steps:

step 1.1, firstly screening out particles with the particle size larger than 40mm in a sample, then dividing the screened sample into 8 parts by a quarter method sequentially by adopting a quarter method sample, respectively adding 6 parts of the sample into different amounts of water, uniformly stirring, and then filling for one night for later use,

step 1.2, taking out 6 samples subjected to the choke plug, carrying out a heavy type II-2 compaction test, dividing each sample in the heavy type II-2 compaction test into 3 small parts and carrying out compaction in 3 layers to obtain samples, measuring the mass of each sample, calculating the corresponding dry density, taking a central soil sample of the sample, measuring the water content of the central soil sample, marking each sample point in the coordinates by taking the dry density as an ordinate and the water content as an abscissa, drawing a relation curve of the dry density and the water content of the sample to obtain the maximum dry density of the sample, obtaining the water content corresponding to 93% of the maximum dry density on the relation curve of the dry density and the water content of the sample by an interpolation method,

and step 1.3, adding a proper amount of water into the rest 2 samples in the step 1.1 to ensure that the water content reaches 93% of the water content corresponding to the maximum dry density, and then carrying out heavy type II-2 compaction, wherein the heavy type II-2 compaction is carried out in 3 layers to prepare the compacted soil sample.

3. A method for measuring the splash and etch resistance of fine earth according to claim 2, wherein said step 2 comprises the steps of:

opening a water stop clamp (1 b), enabling water to flow into a main body pipe structure (2) through a rubber hose (1 c) and flow out of an overflow pipe (2 a), ensuring that the main body pipe structure (2) is filled with water and water with uniform flow rate flows out of the overflow pipe (2 a), opening a water stop sleeve (3 b), adjusting a regulating valve (3 a), adopting a stopwatch to time, finally controlling the water drop amount in 60 seconds to be a set drop number, and finally closing the water stop sleeve (3 b).

4. A method for measuring the splash and erosion resistance of fine soil according to claim 3, wherein the step 3 of measuring the splash and erosion pit depth and area of the test soil sample by using a laser range finder (4 a) and a camera (4 b) respectively comprises the following steps:

firstly, measuring soil sample surface height data H1 before a splash pit is caused by a laser range finder (4 a) from water drops, opening a water stop sleeve (3 b) to perform a test experiment on a test soil sample after a set time is set, measuring the height data H2 of the laser range finder (4 a) from the pit bottom of the splash pit by the laser range finder (4 a), measuring the splash pit depth D=H2-H1, then placing a square sheet with the set size of 10mm multiplied by 10mm as a scale object beside the splash pit of the soil sample, photographing the square sheet and the splash pit at the same time by adopting a camera (4 b), and obtaining a measurement image according to the measurementThe average value L1 of the side lengths of three sides of the square sheet is obtained by the quantitative image, the average value phi 1 of the three diameters of the sputtering pit is obtained according to the measured image, and the real aperture of the sputtering pit is obtainedFurther, the area of the sputtering pit is obtained.