A high-precision device and method for determining the saturation of model soil

Abstract

This invention discloses a high-precision device and method for determining the saturation of a model soil. A soil model is placed inside a saturation chamber, a target is placed on the soil model, and a monitoring component is installed on top of the saturation chamber to collect liquid level information of the soil model and pressure within the saturation chamber, thereby determining the saturation of the soil model within the chamber. The method includes placing the model in the saturation chamber and placing the target on the model surface, with a laser displacement meter installed above the target; subsequently, the saturation chamber is sealed to allow the model to saturate under vacuum; after saturation, the vacuum is gradually released, and a portable data acquisition instrument automatically records the pressure and the liquid level height changes measured by the laser displacement meter; finally, the saturation of the model is calculated based on the recorded liquid level height changes and pressure changes. Compared with methods such as compression wave measurement, the saturation determination device and method of this invention have advantages such as system simplicity, high precision, high automation, and low cost.

Description

Technical Field

[0001] This invention belongs to the field of physical model test monitoring technology, specifically involving a high-precision model soil saturation measurement device and method. Background Technology

[0002] Soil saturation is a key physical parameter in soil mechanics and engineering. The degree of saturation directly reflects the extent of water saturation in the soil, significantly influencing various soil properties and engineering behaviors. Saturation has a significant impact on the shear strength of soil. Soil saturation is a crucial parameter connecting soil mechanics, hydraulics, geological engineering, and environmental engineering; its changes affect the mechanical properties, permeability, and environmental behavior of soil. In engineering practice, accurate assessment and control of soil saturation not only helps improve the scientific validity and safety of designs but also reduces potential risks and ensures the long-term stability of projects. Geotechnical model testing is a research method that simulates the actual working conditions of soil and rock masses and engineering structures on a scale. Through model tests, theoretical calculation results can be verified, engineering design schemes optimized, the complex mechanical mechanisms within soil and rock masses revealed, and reliable evidence provided for engineering practice. Simultaneously, this technique also provides important calibration parameters and verification data for numerical simulations, making it an indispensable method in geotechnical engineering research. Since soil saturation is a crucial indicator, accurately determining the saturation of the model before conducting experiments is essential.

[0003] In geotechnical engineering, the most commonly used method for determining saturation is the B-value test. However, for low-saturation soils, gas dissolution and bubble compression can introduce complex nonlinear responses, affecting the accuracy of the test. Secondly, it can only indirectly infer saturation and cannot obtain specific information on water distribution. Most importantly, in model tests, it is difficult to monitor changes in pore water pressure inside the model after pressurization. Therefore, it is mostly used in unit volume tests and is difficult to extend to model tests.

[0004] Currently, model saturation is commonly determined in model tests using theoretical calculations, electrical conductivity, and compressive wave velocity measurements. The accuracy of theoretical calculations depends on the accurate measurement of void volume and the volume of saturated fluid entering the model. However, the calculation or measurement of saturated fluid volume often involves uncertainty, especially in complex soils or heterogeneous materials, where errors can be significant. Electrical conductivity methods are highly dependent on electrolytes, have complex calibration processes, and the non-uniformity of electrical conductivity distribution within the soil (such as cracks and air bubbles) can lead to measurement errors. Compressive wave velocity measurements of model saturation can result in large errors, are based on complex principles, involve complex measurement systems, have low system reliability, and are costly. Summary of the Invention

[0005] In order to solve the problems existing in the background technology, the purpose of this invention is to provide a high-precision model soil saturation measurement device and method to solve the technical difficulties in model saturation measurement in existing physical model tests.

[0006] I. A high-precision device for measuring the saturation of model soil:

[0007] It includes a saturation chamber, a target, a soil model, and a monitoring component. The soil model to be tested is placed inside the saturation chamber, the target is placed on the upper surface of the soil model, and the monitoring component is installed on the top of the saturation chamber. The monitoring component is used to collect the liquid level information in the soil model and the pressure inside the saturation chamber, thereby determining the saturation of the soil model to be tested inside the saturation chamber.

[0008] The monitoring components include a laser displacement meter, a portable data acquisition device, and a vacuum pressure gauge. Both the laser displacement meter and the vacuum pressure gauge are electrically connected to the portable data acquisition device, which is located outside the saturation chamber. Both the laser displacement meter and the vacuum pressure gauge are mounted on the top of the saturation chamber, with the laser displacement meter positioned directly above the target. The laser emitted by the laser displacement meter illuminates the center of the target. The laser displacement meter is used to collect the vertical distance change of the target and send the target's position information to the portable data acquisition device. The vacuum pressure gauge is used to collect the pressure inside the saturation chamber and send the pressure information of the saturation chamber to the portable data acquisition device.

[0009] The laser displacement meter has a measurement resolution greater than 10 μm.

[0010] The target is a flat plate that can float on the surface of the liquid in the soil model, and the target floats up and down as the liquid level rises and falls.

[0011] II. A high-precision method for determining the soil saturation of a model, comprising the following steps:

[0012] Step S1: First, prepare a soil model and place the prepared soil model horizontally in a saturation chamber;

[0013] Step S2: Next, fix the laser displacement gauge and vacuum pressure gauge, and then place the target on the surface of the soil model so that the center of the target is directly below the laser displacement gauge.

[0014] Step S3: Saturate the soil model, measure the pressure and liquid level data of the soil model after saturation, and use the pressure and liquid level data to obtain the saturation degree of the soil model.

[0015] The specific steps of step S3 are as follows:

[0016] Step S3.1: Saturate the soil model. After the soil model is saturated, connect both the laser displacement gauge and the vacuum pressure gauge to the portable data acquisition instrument.

[0017] Step S3.2: Start the portable data acquisition instrument, gradually reduce the vacuum level in the saturation tank, and record the pressure data in the saturation tank and the height data of the liquid level in the soil model.

[0018] Step S3.3: Obtain the saturation of the soil model using the pressure data of the saturation tank and the height data of the liquid level in the soil model.

[0019] In step S3.3, the saturation of the soil model is obtained according to the following formula:

[0020]

[0021] Among them, S r p1 represents the saturation degree of the soil model; p1 represents the real-time pressure inside the saturation tank recorded by the portable data acquisition instrument; Δh represents the height difference of the liquid level in the soil model under pressure p1 compared to the initial pressure p0 of the saturation tank; A represents the bottom area of ​​the soil model; p a V represents standard atmospheric pressure; v This represents the volume of voids in the soil model.

[0022] The measurement accuracy of this invention can reach 0.1% or higher. Since the measurement accuracy is only related to gas pressure and vertical displacement, and the accuracy of digital pressure gauges for measuring gas pressure is typically around 0.1%, while the accuracy of laser displacement gauges can reach the micrometer or even nanometer level, the measurement error is negligible. In contrast, the accuracy of traditional theoretical calculation methods and wave velocity methods is typically only 1%-5%, and may be even lower in some special cases. This invention significantly improves the testing accuracy, achieving an improvement of two orders of magnitude compared to existing technologies.

[0023] This invention only requires adding a laser displacement meter to the existing model saturation system to measure changes in liquid level and a portable data acquisition instrument for recording and storing data, thus achieving high-precision saturation measurement with low system modification costs. In contrast, the compression wave velocity method requires complex and expensive equipment such as oscilloscopes, function generators, charge amplifiers, and piezoelectric elements. This invention not only significantly simplifies the measurement system and reduces measurement costs but also effectively improves the system's stability and reliability.

[0024] This invention is based on a simple principle and does not rely on complex theoretical foundations or cumbersome preliminary calibration experiments, significantly reducing the technical threshold and operational difficulty of saturation measurement. Its high efficiency and convenience enable users to quickly obtain accurate results, while avoiding the accuracy degradation that may occur in traditional methods due to model complexity or experimental errors, thus significantly improving the practicality and widespread value of measurement work.

[0025] This invention is highly applicable and has a wide range of applications. Its core principle is based on the ideal gas equation, directly measuring the gas volume in the model. Compared with traditional methods, the measurement results of this invention are not affected by complex factors such as ion concentration, mineral composition, or saturation in the soil. It can maintain high measurement accuracy even under high saturation conditions, exhibiting stronger stability and reliability, and is suitable for the precise testing needs of model saturation in various complex environments.

[0026] The data post-processing process of this invention is simple and efficient. It only requires linear fitting of the measured data to directly calculate the final saturation of the model. In contrast, the compressed wave velocity method requires complex signal processing principles and precise determination of wave propagation time, typically demanding professional signal processing knowledge from the operator. Similarly, the conductivity method also requires tedious post-processing to obtain results. These complex processes undoubtedly increase the operational difficulty and professional threshold. In comparison, this invention significantly simplifies the data processing process, making saturation measurement more convenient and practical.

[0027] The beneficial effects of this invention are:

[0028] 1. This invention uses a high-precision laser displacement meter, and the measurement accuracy of saturation can reach 0.1% or higher. This invention significantly improves the testing accuracy, achieving an improvement of two orders of magnitude over the prior art.

[0029] 2. This invention not only greatly simplifies the measurement system and reduces measurement costs, but also effectively improves the stability and reliability of the system, is easy to operate, and significantly enhances the practicality and promotional value of measurement work.

[0030] 3. This invention has strong applicability and a wide range of applications. The measurement results are not affected by complex factors such as ion concentration, mineral composition or saturation in the soil. It can still maintain high measurement accuracy under high saturation conditions and has stronger stability and reliability.

[0031] 4. This invention significantly simplifies the data processing process, making saturation measurement more convenient and practical. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the overall composition of the device of the present invention;

[0033] Figure 2 This refers to the data collected and processed in the embodiments of the present invention.

[0034] In the diagram: 1-Saturation box; 2-Laser displacement gauge; 3-Target; 4-Portable data acquisition instrument; 5-Vacuum pressure gauge; 6-Soil model. Detailed Implementation

[0035] The apparatus of the present invention will be further described below with reference to the accompanying drawings and embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0036] like Figure 1 As shown, the device includes a saturation chamber 1, a target 3, a soil model 6, and a monitoring component. The soil model 6 to be tested is placed inside the saturation chamber 1, the target 3 is placed on the upper surface of the soil model 6, and the monitoring component is installed on the top of the saturation chamber 1. The monitoring component is used to collect the position information of the soil model 6 and the pressure inside the saturation chamber 1, and then to measure the saturation of the soil model 6 to be tested inside the saturation chamber 1.

[0037] The monitoring components include a laser displacement meter 2, a portable data acquisition instrument 4, and a vacuum pressure gauge 5. Both the laser displacement meter 2 and the vacuum pressure gauge 5 are electrically connected to the portable data acquisition instrument 4, which is located outside the saturation tank 1. Both the laser displacement meter 2 and the vacuum pressure gauge 5 are installed on the top of the saturation tank 1, with the laser displacement meter 2 positioned directly above the target 3. The laser emitted by the laser displacement meter 2 illuminates the center of the target 3. The laser displacement meter 2 is used to collect the vertical distance change of the target 3, thereby obtaining the height data of the liquid level in the soil model 6, and sending the position information of the target 3 to the portable data acquisition instrument 4. The vacuum pressure gauge 5 is used to collect the pressure inside the saturation tank 1 and send the pressure information of the saturation tank 1 to the portable data acquisition instrument 4.

[0038] The signal line of the laser displacement gauge 2 is connected to the portable data acquisition instrument 4 located outside the saturation box 1 through an opening in the saturation box 1. A vacuum pressure gauge 5 is used to monitor pressure changes inside the saturation box 1. The laser displacement gauge 2 is an instrument made based on the principle of laser reflection, used to measure changes in the vertical distance of the target 3, with a measurement resolution of 10 μm or higher. The portable data acquisition instrument 4 uses a device capable of recording the signal from the laser displacement gauge 2.

[0039] The laser displacement meter 2 has a measurement resolution greater than 10 μm.

[0040] The target 3 is a flat plate that can float on the surface of the liquid in the soil model 6. The target 3 can float up and down with the rise and fall of the liquid level. It cannot be fixed on the surface of the soil in the soil model 6. The target 3 needs to have strong reflectivity so that the laser displacement meter 2 can measure it. The target 3 is placed on the surface of the soil model 6 below the laser displacement meter 2.

[0041] Embodiments of the present invention include the following steps:

[0042] Step S1: First, prepare the soil model 6 and place the prepared soil model 6 horizontally in the saturation box 1;

[0043] Step S2: Next, fix the laser displacement gauge 2 and the vacuum pressure gauge 5, and then place the target 3 on the surface of the soil model 6 so that the center of the target 3 is directly below the laser displacement gauge 2.

[0044] Step S3: Saturate the soil model 6, measure the pressure and liquid level height data of the soil model 6 after saturation, and use the pressure and liquid level height data to obtain the saturation degree of the soil model 6.

[0045] Specifically, step S3 is as follows:

[0046] Step S3.1: Saturate the soil model 6. After the soil model 6 is saturated, connect both the laser displacement gauge 2 and the vacuum pressure gauge 5 to the portable data acquisition instrument 4.

[0047] Step S3.2: Start the portable data acquisition instrument 4, gradually reduce the vacuum level in the saturation tank 1, and record the pressure change data in the saturation tank 1 and the liquid level height change data in the soil model 6.

[0048] Step S3.3: Obtain the saturation of soil model 6 using the pressure data of saturation tank 1 and the height data of liquid level in soil model 6.

[0049] The principle of step S3.3 is to determine the gas volume of soil model 6 using the ideal gas law, and then calculate the gas volume and saturation of soil model 6.

[0050] In step S3.3, the saturation of soil model 6 is obtained according to the following formula:

[0051]

[0052] Among them, S rp1 represents the saturation degree of soil model 6; p1 represents the real-time pressure in saturation tank 1 recorded by portable data acquisition instrument 4 (i.e., the pressure data collected by vacuum pressure gauge 5); Δh represents the height difference of the liquid level in soil model 6 under pressure p1 compared to the initial pressure p0 of saturation tank 1. In specific implementation, the initial pressure p0 = -90 kPa. A represents the bottom area of ​​soil model 6. a V represents standard atmospheric pressure; v This represents the volume of voids in soil model 6.

[0053] In step S3.3, a pressure-liquid level curve can be plotted based on the pressure-liquid level data collected at different times: the abscissa of the pressure-liquid level curve is (p a -p1), with the ordinate being (p1Δh), for each time point (p a By fitting the data points from -p1) to (p1Δh), the pressure-liquid level height curve can be obtained. Then, the saturation S of soil model 6 can be obtained using this curve. r :

[0054]

[0055] Where k is the slope of the pressure-liquid level curve;

[0056] like Figure 1 As shown, in the model test, the soil model was 74cm long, 34cm wide, and 40cm high. Therefore, the base area of ​​the soil model can be obtained as A = 2516cm². 2 The volume is V = 100640 cm³ 3 Model dry density ρ d =1570kg / m 3 The specific gravity of the soil is G s =2.65. The model uses degassed water for saturation, and the density of water ρ is... w =1570kg / m 3 According to the following soil mechanics formula, the void ratio of the soil is e = 0.688:

[0057]

[0058] The void ratio of the soil is calculated. Based on the definition of void ratio, the void volume V in the soil can be obtained using the following formula. v =41019cm 3 :

[0059]

[0060] The model is first placed in saturation box 1, then laser displacement meter 2 is installed on the top cover of saturation box 1, then target 3 is placed below laser displacement meter 2, and finally saturation box 1 is sealed.

[0061] Upon saturation, the saturation chamber 1 was first evacuated to a vacuum of -90 kPa using a vacuum pump. Then, silicone oil was used for saturation under vacuum. The model saturation was completed after 72 hours. After saturation, the laser displacement gauge 2 and vacuum pressure gauge 5 were connected to the portable data acquisition instrument 4. The portable data acquisition instrument 4 was turned on, and data acquisition was ensured to be normal. It is assumed that the gas contained in the model conforms to the ideal gas assumption and satisfies the following equation of state:

[0062] pV g =nRT

[0063] In the formula, n is the amount of substance of the gas; T is the temperature; p is the real-time pressure of the gas; V g Let R be the gas volume; R be the universal gas constant; during the test, the temperature can be assumed to be constant, therefore the gas volume is inversely proportional to the current pressure. If the vacuum equipment is slowly controlled to gradually increase the pressure in the saturation tank 1 from the initial p0 = -90 kPa, then if the model contains gas, it will contract, causing the liquid level to drop. Moreover, the lower the model saturation and the more gas there is, the greater the drop in liquid level. The drop in liquid level can be obtained by monitoring the vertical displacement change of the target 3 using a laser displacement gauge 2. The laser displacement gauge 2 typically has a measurement accuracy of micrometers or even nanometers, possessing extremely high resolution and accuracy. It can capture minute displacements or deformations and is insensitive to environmental factors (such as temperature, humidity, and vibration), making it particularly suitable for monitoring minute parameters such as liquid level changes, displacement, and deformation. After obtaining the sedimentation Δh at a certain pressure p1 using the laser displacement gauge 2, the following formula can be used to obtain:

[0064]

[0065] In the formula, p a The standard atmospheric pressure is equal to 101 kPa. p1 represents the real-time pressure inside the saturation chamber (1) recorded by the portable data acquisition instrument 4; V1 represents the volume of gas at pressure p1; the gas volume V can be solved using the following formula. g The expression is:

[0066]

[0067] Combining this with the definition of saturation, we can finally obtain the expression S for saturation. r for:

[0068]

[0069] Among them, V wV represents the volume of the saturated fluid in the model; v This represents the volume of voids in the model;

[0070] Therefore, the real-time pressure p1 and sedimentation Δh collected by the portable data acquisition instrument 4 are in the range of (p1Δh)-(p a The model will approximate as a straight line under the -p1) coordinate system. The greater the slope of the line, the lower the saturation of the model. The higher the saturation, the smaller the slope. Figure 2 The measured data in the examples show a similarity to the theoretical derivation; the experimentally measured data points are located at (p1Δh)-(p a -p1) Under the coordinate system, it appears as a straight line with a slope of k = 0.2025. Substituting this slope into the above equation, we get:

[0071]

[0072] Given a base area A = 2516 cm² 2 Substituting the values, the final measured model saturation was 98.76%.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-precision method for determining the saturation of model soil, characterized in that, The measurement method employs a high-precision model soil saturation measuring device, which includes a saturation chamber (1), a target (3), a soil model (6), and a monitoring component. The soil model (6) to be measured is placed inside the saturation chamber (1), the target (3) is placed on the upper surface of the soil model (6), and the monitoring component is installed on the top of the saturation chamber (1). The monitoring component is used to collect the liquid level information in the soil model (6) and the pressure inside the saturation chamber (1), thereby measuring the saturation of the soil model (6) to be measured inside the saturation chamber (1). The monitoring components include a laser displacement meter (2), a portable data acquisition instrument (4), and a vacuum pressure gauge (5); the laser displacement meter (2) and the vacuum pressure gauge (5) are electrically connected to the portable data acquisition instrument (4), and the portable data acquisition instrument (4) is located outside the saturation box (1). The laser displacement meter (2) and the vacuum pressure gauge (5) are both installed on the top of the saturation box (1), and the laser displacement meter (2) is located directly above the target (3). The laser emitted by the laser displacement meter (2) illuminates the middle part of the target (3). The laser displacement meter (2) is used to collect the distance change of the target (3) in the vertical direction and send the position information of the target (3) to the portable data acquisition instrument (4); the vacuum pressure gauge (5) is used to collect the pressure inside the saturation box (1) and send the pressure information of the saturation box (1) to the portable data acquisition instrument (4); The determination method includes the following steps: Step S1: First, prepare a soil model (6) and place the prepared soil model (6) horizontally in a saturation box (1); Step S2: Next, fix the laser displacement meter (2) and the vacuum pressure gauge (5), and then place the target (3) on the surface of the soil model (6) so that the center of the target (3) is directly below the laser displacement meter (2); Step S3: Saturate the soil model (6), measure the pressure and liquid level height data of the soil model (6) after saturation, and use the pressure and liquid level height data to obtain the saturation degree of the soil model (6); The specific steps of step S3 are as follows: Step S3.1: Saturate the soil model (6). After the soil model (6) is saturated, connect the laser displacement gauge (2) and the vacuum pressure gauge (5) to the portable data acquisition instrument (4). Step S3.2: Start the portable data acquisition instrument (4), gradually reduce the vacuum level in the saturation tank (1), and record the pressure data in the saturation tank (1) and the height data of the liquid level in the soil model (6); Step S3.3: Obtain the saturation of the soil model (6) using the pressure data of the saturation tank (1) and the height data of the liquid level in the soil model (6); In step S3.3, the saturation of the soil model (6) is obtained according to the following formula: Among them, S r The saturation of the soil model (6) is represented by p0; the initial pressure in the saturation tank (1) is represented by p0; the real-time pressure in the saturation tank (1) recorded by the portable data acquisition instrument (4) is represented by p1; Δh represents the height difference of the liquid level in the soil model (6) under pressure p1 compared to the initial pressure p0 of the saturation tank (1); A represents the bottom area of ​​the soil model (6); V v This represents the volume of voids in the soil model (6).

2. The method for determining the saturation of a high-precision model soil according to claim 1, characterized in that, The laser displacement meter (2) has a measurement resolution greater than 10 μm.

3. The method for determining the saturation of a high-precision model soil according to claim 1, characterized in that, The target (3) is a flat plate that can float on the surface of the liquid in the soil model (6), and the target (3) floats up and down as the liquid level rises and falls.

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