Isothermal Adsorption Test Apparatus and Test Method for Weighing Clay-Bound Water

Abstract

This invention provides an isothermal adsorption test device and method for weighing clay bound water, relating to the field of high-speed railway subgrade engineering technology. The device includes a test chamber, a constant temperature and humidity structure, a sampling structure, and a weighing structure. Multiple sets of the constant temperature and humidity structure are arranged, each set containing multiple structures. All structures are housed within the test chamber, with identical spacing between adjacent structures within the same set. The sampling structure is located at the top of the test chamber, above the constant temperature and humidity chamber. The weighing structure is located directly below the sampling module. This invention achieves fully controlled and enclosed operation of temperature, humidity, and weighing during the clay isothermal adsorption process, significantly reducing mass disturbance errors caused by sample exposure to the external environment in traditional adsorption tests, and greatly improving the stability and reliability of test data.

Description

Technical Field

[0001] This invention relates to the field of high-speed railway subgrade engineering technology, and more specifically, to an isothermal adsorption test apparatus and test method for weighing clay-bound water. Background Technology

[0002] Existing isothermal adsorption testing methods (such as the traditional desiccator method) rely on a saturated salt solution providing the corresponding relative humidity in a fixed, stable environment. Soil samples are placed in a desiccator to adsorb moisture, and the mass change is manually weighed and recorded. However, this method suffers from problems such as difficulty in precisely controlling the ambient temperature, poor sealing, the need for repeated exposure of the sample to room temperature during weighing, and long testing cycles, making it difficult to obtain high-precision clay adsorption data. Furthermore, methods for determining bound water based on adsorption curves typically require manual judgment of the inflection point of the isothermal adsorption line, which is highly subjective and prone to misjudgment. While commercial gas adsorption instruments possess precise temperature and humidity control capabilities, they are designed for powder materials, have small chamber volumes, and limited sample volumes, making them unsuitable for testing the macroscopic properties of engineering clays. Moreover, their high cost makes them unsuitable for widespread use in railway geotechnical laboratories.

[0003] Therefore, there is an urgent need for a test device and system that can achieve automatic sampling and weighing in a constant temperature environment, independent humidity control of multiple chambers, batch testing, and automatic identification of bound water. Summary of the Invention

[0004] The purpose of this invention is to provide an isothermal adsorption test apparatus and method for weighing clay-bound water, thereby improving the aforementioned problems. To achieve the above objective, the technical solution adopted by this invention is as follows:

[0005] In a first aspect, this application provides an isothermal adsorption test device for weighing clay-bound water, comprising: a test chamber, a constant temperature and humidity structure, a sampling structure, and a weighing structure. The constant temperature and humidity structure is provided in multiple groups, each group having multiple constant temperature and humidity structures. All constant temperature and humidity structures are located inside the test chamber, and the interval between two adjacent constant temperature and humidity structures in the same group is the same. The sampling structure is located on the top of the test chamber, above the constant temperature and humidity chamber. The weighing structure is located directly below the sampling module.

[0006] Secondly, this application also provides an isothermal adsorption test method for weighing clay-bound water, comprising:

[0007] Obtain the preset constant temperature and humidity structure number, preset sample number, and preset relative humidity;

[0008] Based on the preset constant temperature and humidity structure number, preset sample number and preset relative humidity, place the corresponding saturated salt solution at the bottom of each constant temperature and humidity structure.

[0009] Place the dry clay sample in the sample box and record the dry mass of the sample.

[0010] The overall system temperature was adjusted and stabilized to the target temperature, and the sample box carrying the sample was placed in a constant temperature and humidity structure with corresponding humidity and temperature to carry out the adsorption test.

[0011] The sampling structure automatically removes the sample box from the constant temperature and humidity structure after the adsorption test and transports it to the weighing structure for weighing to obtain the sample mass data.

[0012] The sample box is automatically returned to the original cavity, and the test and weighing steps are repeated until the sample mass reaches adsorption equilibrium, and the equilibrium adsorption amount data under the preset relative humidity is obtained.

[0013] An adsorption isotherm is generated based on the equilibrium adsorption data, and the bound water content is calculated based on the curvature change of the adsorption isotherm.

[0014] The beneficial effects of this invention are as follows:

[0015] This invention achieves fully controlled and enclosed operation of temperature, humidity and weighing processes during the clay isothermal adsorption process through the collaborative design of a multi-cavity constant temperature and humidity module and an automatic sampling high-precision weighing module. This significantly reduces the mass disturbance error caused by the sample being exposed to the external environment in traditional adsorption experiments, and greatly improves the stability and reliability of test data.

[0016] The automated sampling robotic arm can complete sample grabbing and weighing operations in a constant temperature environment. This not only ensures that the weighing process is not affected by temperature changes, but also enables multiple humidity chambers and multiple parallel samples to be tested automatically in a cycle according to the program, realizing true batch testing and high-throughput operation, and significantly improving testing efficiency.

[0017] This invention utilizes an independent humidity chamber structure constructed with a saturated salt solution, which does not rely on a complex humidity generator. The chamber's sealing door automatically opens or closes upon command, ensuring the stability of the humidity environment while facilitating the free entry and exit of the robotic arm, thus improving the overall reliability and maintainability of the structure.

[0018] This invention automatically records the mass change of the sample under different humidity conditions and calculates the adsorption isotherm. Combined with the curvature change method or the two-component fitting method, it automatically identifies the bound water content, avoiding the subjective error caused by manual point selection, and making the determination of bound water more objective, accurate and repeatable.

[0019] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing embodiments of the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the isothermal adsorption test method for weighing clay-bound water as described in an embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of the isothermal adsorption test device for weighing clay-bound water as described in an embodiment of the present invention.

[0023] Figure 3 This is a schematic diagram of the isothermal adsorption test equipment for weighing clay-bound water as described in an embodiment of the present invention.

[0024] In the diagram: 1. Constant temperature and humidity chamber; 2. Automatic opening and closing sealing door; 3. Elastic sealing strip; 4. Robotic arm; 5. Electronic balance; 6. First slide rail; 7. Sampling gripper; 8. Position encoder; 9. Porous partition; 10. Temperature and humidity sensor; 11. Saturated salt solution; 12. Sample box; 13. Wind shield; 14. Vibration isolation base; 15. Limiter; 16. Second slide rail. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0026] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0027] Example 1:

[0028] See Figure 1 and Figure 2 This embodiment provides an isothermal adsorption test apparatus for weighing clay-bound water, comprising:

[0029] Test chamber;

[0030] The constant temperature and humidity structure is provided in multiple groups, and each group is provided with multiple constant temperature and humidity structures. All constant temperature and humidity structures are set in the test chamber, and the interval between two adjacent constant temperature and humidity structures in the same group is the same.

[0031] A sampling structure is provided on the top of the test chamber, and the sampling structure is positioned above the constant temperature and humidity structure.

[0032] A weighing structure is provided, which is positioned directly below the sampling module.

[0033] It is understood that this invention defines the core architecture of the device. By integrating multiple sets of constant temperature and humidity structures, each with multiple components, into a single test chamber and controlling them uniformly via a top sampling structure, while a weighing structure is located below, a highly integrated and fully automated testing environment is constructed. This enables batch and automated testing: multiple independent constant temperature and humidity structures allow for parallel tests under different humidity conditions simultaneously; the equidistant arrangement within each set facilitates programmed positioning of the robotic arm, significantly improving testing efficiency; it ensures the consistency of the testing environment: all structures are placed within the same test chamber, ensuring a highly uniform and stable temperature field and avoiding environmental disturbances caused by sample transfer between different devices; and it forms a closed-loop testing process: the integrated design of sampling, transfer, and weighing allows the sample to complete the "adsorption-weighing" cycle under conditions of near-isolation from external interference, fundamentally eliminating the errors introduced by manual sampling exposed to room temperature in traditional methods, and providing a hardware foundation for obtaining high-precision adsorption data.

[0034] The constant temperature and humidity structure includes a constant temperature and humidity chamber 1, a porous partition 9, a temperature and humidity sensor 10, a saturated salt solution 11, and a sample box 12. The constant temperature and humidity chamber 1 is placed inside the test chamber. The saturated salt solution 11 is placed at the bottom of the constant temperature and humidity chamber 1. The porous partition 9 is placed directly above the saturated salt solution 11. The temperature and humidity sensor 10 is placed on the bottom surface of the porous partition 9. The sample box 12 is placed on the upper surface of the porous partition 9.

[0035] It is understood that this invention establishes a stable, stratified humidity environment: the saturated salt solution 11 provides a precise and stable source of relative humidity; the porous partition 9 above prevents solution splashing and contamination of the sample, while ensuring natural convection and uniform distribution of humid air within the cavity. In-situ monitoring and sample protection are achieved: the temperature and humidity sensor 10, located on the bottom surface of the partition, can directly monitor the real environmental parameters near the sample area, providing more accurate feedback; the sample box 12, placed on the partition, maintains a safe distance from the solution, ensuring experimental safety and sample purity. This structure, through a simple and reliable physical method, achieves high-precision, long-term constant temperature and humidity control of the local microenvironment of a single sample.

[0036] The saturated salt solution 11 is selected from one or more of LiBr, LiCl, CH3COOK, MgCl2, K2CO3, NaBr, KI, NaCl, KCl, Na2SO3, Na2SO4, and K2SO4.

[0037] It is understood that this invention provides a broad and precise coverage of relative humidity ranges. The listed salt solutions (such as LiBr to K2SO4) provide a range of defined and stable relative humidity values ​​from approximately 6.6% to 97.6% at standard temperatures. This allows the device to accurately simulate the entire moisture absorption process of clay from extremely dry to near saturation, providing a crucial and reliable environmental condition benchmark for plotting complete isothermal adsorption curves and studying the characteristics of bound water at different humidity stages.

[0038] Humidity control is achieved using the saturated salt solution method 11. Commonly used saturated salts and their equilibrium humidity at 20 degrees Celsius are shown in Table 1.

[0039] Table 1. Saturated salt solutions and corresponding relative humidity

[0040]

[0041] The constant temperature and humidity chamber 1 is equipped with an automatic opening and closing sealing door 2 on its top, and an elastic sealing strip 3 is provided between the automatic opening and closing sealing door 2 and the constant temperature and humidity chamber 1.

[0042] It is understood that this invention minimizes humidity fluctuations during sampling or return operations. The sealing door can be opened and closed quickly, greatly shortening the air exchange time between the inside of the chamber and the external chamber environment, effectively maintaining the stability of the target humidity within the chamber. It also ensures reliable sealing: the design of the elastic sealing strip 3 guarantees tightness after the door is closed, preventing humidity drift caused by minor leaks during non-operational periods, thereby ensuring the continuous purity and stability of each independent humidity environment during long-term testing.

[0043] The sampling structure includes a first slide rail 6, a second slide rail 16, a robotic arm 4, a sampling gripper 7, and a position encoder 8. Two first slide rails 6 are provided, and the two first slide rails 6 are respectively provided on two opposite side walls of the test chamber. The second slide rail 16 is provided between the two first slide rails 6. The robotic arm 4 and the position encoder 8 are provided on the second slide rail 16, and the sampling gripper 7 is provided on the robotic arm 4.

[0044] It is understood that this invention achieves high-precision, high-degree-of-freedom three-dimensional spatial positioning. The dual first slide rails 6 and the second slide rail 16 form a robust planar moving frame. Combined with the movement of the robotic arm 4 itself, this allows the sampling gripper 7 to accurately reach the upper opening position of any constant temperature and humidity structure within the test chamber, as well as the upper part of the weighing structure, with flexible movement paths. 2) Ensuring the repeatability and accuracy of the operation: The application of the position encoder 8 enables every movement position of the robotic arm 4 and the gripper to be accurately recorded and reproduced, avoiding random positional errors caused by manual operation, and providing core control assurance for the reliable execution of the fully automated process.

[0045] The sampling structure further includes a limiter 15, which is disposed on the second slide rail 16 and directly above the weighing structure.

[0046] It is understood that this invention provides physical calibration and safety assurance for critical operating points. By positioning the limiter 15 directly above the weighing structure, the robotic arm 4 can use the limiter 15 as a precise mechanical reference point each time it places the sample box 12 onto the electronic balance 5, ensuring that the sample box 12 is always placed in the same centered position on the weighing pan. This eliminates weighing errors caused by deviations in repeatability accuracy and also serves as a rigid safety limit for the motion system, preventing the robotic arm 4 from excessively descending and damaging the precision electronic balance 5.

[0047] The weighing structure includes a vibration isolation base 14, an electronic balance 5, and a wind shield 13. The vibration isolation base 14 is located directly below the sampling structure, the electronic balance 5 is mounted on the vibration isolation base 14, and the wind shield 13 covers the electronic balance 5.

[0048] It is understood that this invention significantly improves the stability and accuracy of weighing results: the vibration isolation base 14 effectively isolates minor vibrations that may be generated from the test chamber and mechanical movement, ensuring stable readings of the electronic balance 5; the wind shield 13 shields the interference of the weak airflow generated by air circulation within the chamber on the weighing process. This creates an ideal high-precision weighing microenvironment: the combination of these two elements creates a static, undisturbed weighing space for the electronic balance 5 within the relatively dynamic test chamber, enabling reliable detection of microgram-level mass changes in the sample during adsorption. This is the final key step in achieving high-precision bound water measurement.

[0049] Example 2:

[0050] like Figure 3 As shown, this embodiment provides an isothermal adsorption test method for weighing clay-bound water, the steps of which include steps S1, S2, S3, S4, S5, S6 and S7.

[0051] Step S1: Obtain the preset constant temperature and humidity structure number, preset sample number, and preset relative humidity;

[0052] Understandably, this step enables automatic scheduling of the experimental process and standardized parameter input, avoiding errors from manual settings and improving the consistency and repeatability of the experiment.

[0053] Step S2: Based on the preset constant temperature and humidity structure number, preset sample number and preset relative humidity, place the corresponding saturated salt solution at the bottom of each constant temperature and humidity structure;

[0054] It is understandable that this step, by pre-setting the humidity environment and temperature stability control, ensures uniform initial experimental conditions, reduces the impact of temperature fluctuations on the adsorption process, and improves data accuracy.

[0055] Step S3: Place the dried clay sample in the sample box and record the dry mass of the sample.

[0056] Understandably, this step involves thoroughly drying the clay sample and then placing it in a sample box made of inert, stable materials such as stainless steel. Before placing the sample box in a temperature and humidity controlled environment to begin the adsorption test, the total mass of the sample and sample box at this point must be accurately weighed and recorded, i.e., the "dry mass." This data serves as the absolute baseline for subsequent calculations of all adsorption amounts.

[0057] Step S4: Adjust and stabilize the overall system temperature to the target temperature, and place the sample box carrying the sample into a constant temperature and humidity structure with corresponding humidity and temperature for adsorption test.

[0058] Understandably, this step begins by activating the device's temperature control system (such as thermoelectric cooling / heating components and circulating air ducts) to adjust and stabilize the entire internal space of the test chamber at the target temperature (e.g., 20°C), with a control accuracy of ±0.1°C. Subsequently, the sample box, containing the recorded dry mass of the sample, is placed in a constant temperature and humidity chamber pre-prepared with the corresponding saturated salt solution. Each chamber maintains a fixed relative humidity environment through a specific saturated salt solution at its bottom. The sample begins to absorb moisture in this sealed, constant temperature and humidity environment.

[0059] Step S5: The sample box is automatically removed from the constant temperature and humidity structure after the adsorption test by the sampling structure and transported to the weighing structure for weighing to obtain the sample mass data.

[0060] Understandably, in this step, the robotic arm moves along the slide rail to the top of the target temperature and humidity chamber, automatically opens its sealed door, grabs the sample box with its sampling grippers, and then transports and stably places it onto a high-precision electronic balance located inside the chamber, protected by a vibration-damping base and a windproof cover. Under constant temperature conditions, the balance stabilizes and automatically reads the current mass of the sample (denoted as meq(RH)). This process ensures that the sample remains in a constant temperature environment during weighing, avoiding errors introduced by exposure to varying external temperature and humidity conditions.

[0061] Step S6: Automatically return the sample box to the original cavity and repeat the test and weighing steps until the sample mass reaches adsorption equilibrium, and obtain the equilibrium adsorption amount data under the preset relative humidity.

[0062] Understandably, this step constitutes a dynamic monitoring cycle. After weighing, the robotic arm automatically returns the sample box to the original temperature and humidity chamber and closes the sealed door, allowing the adsorption process to continue. The system then periodically repeats the steps (i.e., take out - weigh - put back). The adsorption equilibrium criterion is: when the sample mass changes by less than 0.01g within one week, it is considered to have reached equilibrium.

[0063] Step S7: Generate an adsorption isotherm based on the equilibrium adsorption data, and calculate the bound water content based on the curvature change of the adsorption isotherm.

[0064] Understandably, this step begins by plotting an adsorption isotherm with relative humidity on the x-axis and equilibrium adsorption amount on the y-axis. Then, bound water is automatically identified based on the curvature change of the isotherm adsorption line.

[0065] Step S5 includes steps S51, S52 and S53.

[0066] Step S51: Perform sampling decision processing based on the preset sample number and preset relative humidity. By calling the pre-trained recurrent neural network model, analyze the historical adsorption kinetic curve segment of the current sample under the target relative humidity, predict the time window when its mass change tends to stabilize, and obtain the optimal sampling trigger command.

[0067] Understandably, this step uses a pre-trained LSTM neural network model to perform sampling decision processing based on the preset sample number and relative humidity parameters. This model learns and predicts the time window when the adsorption kinetic curve approaches the equilibrium plateau by analyzing historical data of the mass change of the current sample under a specific humidity environment. This generates an optimal sampling trigger time instruction that can capture effective mass changes without disturbing the adsorption process too frequently. This solves the problem that traditional fixed time interval sampling may miss rapid changes if it is too sparse in the early stage of adsorption, and is inefficient if it is too dense in the later stage.

[0068] The model uses a normalized sequence of mass change rates calculated from historical sampling times and corresponding sample masses as input features. Supervised training is conducted using a large amount of historical adsorption experimental data, covering complete adsorption kinetic curves of different clay types under varying humidity conditions. The training process uses mean squared error as the loss function and employs the Adam optimization algorithm to adjust model parameters, aiming to teach the model the mapping from historical mass change rate segments to future short-term mass change trends. During model deployment and online application, the latest mass change rates at several time steps are input into the trained model, which then outputs a predicted value for the mass change rate at the next time step. When the absolute value of this predicted value is continuously lower than a preset threshold multiple times, the system determines that the sample's mass change has entered a stable phase and generates an optimal sampling trigger command containing the sample number, target humidity, and planned execution timestamp. The number of consecutive determinations is typically set to five, while the specific value of the threshold is determined based on the measurement accuracy of the electronic balance used and the physical definition of adsorption equilibrium.

[0069] Step S52: Perform motion planning processing according to the optimal sampling trigger command. Through a deep deterministic strategy gradient network, fuse the encoder position signal and the opening and closing state of the automatic opening and closing sealing door to generate a collision-free, anti-oscillation smooth motion trajectory of the robotic arm online, and obtain the grasping and placement path point sequence.

[0070] Understandably, upon receiving the trigger command, the system initiates motion planning processing, utilizing a deep deterministic policy gradient network. This is a reinforcement learning method specifically designed to learn optimal policies in a continuous motion space. It receives precise position feedback from the encoders of each joint of the robotic arm in real time, as well as real-time status signals from the automatic opening and closing of the sealing door on the target temperature and humidity control structure. Based on these multi-source real-time status inputs, the network calculates and outputs the optimal motion trajectory of the robotic arm's end effector as it moves among the densely arranged temperature and humidity control structures. This trajectory not only ensures no collisions but also optimizes the acceleration curve to minimize mechanical vibrations and prevent them from being transmitted to the precision weighing area of ​​the balance, generating a smooth sequence of gripping and placement path points.

[0071] The policy network is responsible for directly outputting deterministic actions (i.e., the expected joint motion increments) based on the current state, while the value network is responsible for evaluating the value of state-action pairs. The state space includes the target position, the current 3D coordinates of the robotic arm's end effector, and the normalized velocity command vectors for each joint. The action space consists of the normalized velocity command vectors for each joint. The design of the reward function is central to this scenario, guiding the network to learn and generate collision-free, oscillation-resistant smooth trajectories.

[0072] The reward function is as follows:

[0073]

[0074] in, For the sum of reward functions, , , and These are the weighting coefficients for each reward. , , and These are the internal coefficients of each item. The current three-dimensional coordinates of the robotic arm's end effector. The three-dimensional coordinates represent the position of the balance or the target constant temperature and humidity chamber. for Action vector at time step, for Action vector at time step, The distance from the current point to the nearest obstacle. As a preset safe distance, This is a reward for synchronizing with the gate state.

[0075] Step S53: Perform grabbing and placement operations based on the grabbing and placement path point sequence until the operation is completed.

[0076] Understandably, the motion control system in this step strictly follows this path sequence, driving the robotic arm and sampling gripper to complete the entire sequence of operations from opening the sealed door of the specific constant temperature and humidity chamber, grabbing the sample box, smoothly transferring it to the electronic balance inside the windshield, waiting for stable weighing, taking it out and putting it back into the original chamber and closing the sealed door. Thus, without human intervention, the instantaneous mass data of the sample in the constant temperature environment can be obtained efficiently, smoothly and with high precision.

[0077] Step S7 includes steps S71, S72 and S73.

[0078] Step S71: Calculate the first and second derivatives of the adsorption isotherm based on the adsorption isotherm.

[0079] It is understandable that this step employs overall isothermal control, with a target temperature accuracy of ±0.1℃. The high-precision weighing area is located at the end of the robotic arm's slide rail. The balance base features a vibration-isolation design, and a wind shield is installed around the balance placement platform to block reading noise caused by micro-flow. The high-precision weighing area undergoes automatic stabilization before actual weighing: after the robotic arm places the sample box, the system waits for three consecutive balance readings to show a difference of <0.3 mg.

[0080] The equilibrium adsorption capacity of the sample under different relative humidities is calculated using the following formula:

[0081]

[0082] In the formula: Relative humidity (%) For the sample in The equilibrium mass (g / g) is below. For the sample in The equilibrium mass (g) at the bottom; The sample drying mass (g) is given. Equilibrium is considered reached when the sample mass changes by less than 0.01 g within one week.

[0083] The device's built-in bound water identification module automatically identifies the bound water adsorption range based on the curvature change of the isothermal adsorption line. First, it measures the adsorption specific water absorption capacity. First and second derivatives are calculated, with the second derivative calculated using the central difference scheme to improve the numerical stability and accuracy of curvature recognition.

[0084]

[0085]

[0086] In the formula: The first derivative of the isothermal adsorption line This reflects the change in adsorption rate; The second derivative of the isothermal adsorption line This reflects changes in adsorption acceleration or curvature. The relative humidity at the current observation point; and For the next and previous adjacent temperature measurement points.

[0087] Step S72: Determine the relative humidity corresponding to the peak point of the second derivative of the adsorption isotherm as the critical relative humidity corresponding to the adsorption of bound water.

[0088] It is understandable that this step involves the critical relative humidity (RH) corresponding to water adsorption. b The peak point of the second derivative of the adsorption curve:

[0089]

[0090] In the formula: The critical relative humidity (%) corresponding to bound water; Indicates that the function The relative humidity value corresponding to the maximum value.

[0091] Step S73: Calculate the bound water content of the sample at the critical relative humidity based on the adsorption amount at the critical relative humidity and the preset formula for calculating the bound water content.

[0092] It is understandable that this step involves the following formula for calculating water content:

[0093]

[0094] In the formula: The percentage of bound water (g / g) represents the mass of bound water per unit mass of dry soil. The adsorption amount (g / g) is the amount of water adsorbed at the critical humidity.

[0095] Step S74: Decompose the bound water content of the sample under critical relative humidity according to the preset decomposition formula to obtain the bound water adsorption content and the free water adsorption content.

[0096] It is understandable that this step uses a two-component adsorption fitting model, which decomposes the total adsorption amount into two parts: bound water adsorption and free water adsorption. The calculation formula is shown below:

[0097]

[0098] In the formula: The free water adsorption coefficient (g / g); The adsorption growth function (dimensionless) can be expressed as an exponential function, logarithmic function, or empirical adsorption function. These are the fitting parameters.

[0099] It should be noted that the specific manner in which each module performs its operation in the apparatus described in the above embodiments has been described in detail in the embodiments of the method, and will not be elaborated here.

[0100] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0101] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An isothermal adsorption test device for clay-bound water weighing, characterized by, include: Test chamber; The constant temperature and humidity structure is provided in multiple groups, and each group is provided with multiple constant temperature and humidity structures. All constant temperature and humidity structures are set in the test chamber, and the interval between two adjacent constant temperature and humidity structures in the same group is the same. A sampling structure is provided on the top of the test chamber, and the sampling structure is positioned above the constant temperature and humidity structure. A weighing structure is provided, which is positioned directly below the sampling module.

2. The isothermal adsorption test apparatus for weighing clay-bound water according to claim 1, characterized in that... The constant temperature and humidity structure includes a constant temperature and humidity chamber (1), a porous partition (9), a temperature and humidity sensor (10), a saturated salt solution (11), and a sample box (12). The constant temperature and humidity chamber (1) is set inside the test chamber. The bottom of the constant temperature and humidity chamber (1) is provided with a saturated salt solution (11). The porous partition (9) is set directly above the saturated salt solution (11). The temperature and humidity sensor (10) is set on the bottom surface of the porous partition (9). The sample box (12) is set on the upper surface of the porous partition (9).

3. The isothermal adsorption test apparatus for weighing clay-bound water according to claim 1, characterized in that... The saturated salt solution (11) is selected from one or more of LiBr, LiCl, CH3COOK, MgCl2, K2CO3, NaBr, KI, NaCl, KCl, Na2SO3, Na2SO4, and K2SO4.

4. The isothermal adsorption test apparatus for weighing clay-bound water according to claim 1, characterized in that... The top of the constant temperature and humidity chamber (1) is provided with an automatic opening and closing sealing door (2), and an elastic sealing strip (3) is provided between the automatic opening and closing sealing door (2) and the constant temperature and humidity chamber (1).

5. The isothermal adsorption test apparatus for weighing clay-bound water according to claim 1, characterized in that... The sampling structure includes a first slide rail (6), a second slide rail (16), a robotic arm (4), a sampling gripper (7), and a position encoder (8). There are two first slide rails (6), which are respectively set on two opposite side walls of the test chamber. The second slide rail (16) is set between the two first slide rails (6). The robotic arm (4) and the position encoder (8) are set on the second slide rail (16). The sampling gripper (7) is set on the robotic arm (4).

6. The isothermal adsorption test apparatus for weighing clay-bound water according to claim 1, characterized in that... The sampling structure also includes a limiter (15), which is disposed on the second slide rail (16) and is located directly above the weighing structure.

7. The isothermal adsorption test apparatus for weighing clay-bound water according to claim 1, characterized in that... The weighing structure includes a vibration isolation base (14), an electronic balance (5), and a wind shield (13). The vibration isolation base (14) is located directly below the sampling structure. The electronic balance (5) is installed on the vibration isolation base (14), and the wind shield (13) covers the electronic balance (5).

8. An isothermal adsorption test method for weighing bound water in clay, characterized in that, include: Obtain the preset constant temperature and humidity structure number, preset sample number, and preset relative humidity; Based on the preset constant temperature and humidity structure number, preset sample number and preset relative humidity, place the corresponding saturated salt solution at the bottom of each constant temperature and humidity structure. Place the dry clay sample in the sample box and record the dry mass of the sample. The overall system temperature was adjusted and stabilized to the target temperature, and the sample box carrying the sample was placed in a constant temperature and humidity structure with corresponding humidity and temperature to carry out the adsorption test. The sampling structure automatically removes the sample box from the constant temperature and humidity structure after the adsorption test and transports it to the weighing structure for weighing to obtain the sample mass data. The sample box is automatically returned to the original cavity, and the test and weighing steps are repeated until the sample mass reaches adsorption equilibrium, and the equilibrium adsorption amount data under the preset relative humidity is obtained. An adsorption isotherm is generated based on the equilibrium adsorption data, and the bound water content is calculated based on the curvature change of the adsorption isotherm.

9. The isothermal adsorption test method for weighing clay-bound water according to claim 8, characterized in that, The step of generating an adsorption isotherm based on the equilibrium adsorption data and calculating the bound water content based on the curvature change of the adsorption isotherm includes: The first and second derivatives of the adsorption isotherm are calculated based on the adsorption isotherm. The relative humidity corresponding to the peak point of the second derivative of the adsorption isotherm is determined as the critical relative humidity corresponding to the adsorption of bound water. The bound water content of the sample at the critical relative humidity is calculated based on the adsorption amount at the critical relative humidity and the preset formula for calculating the bound water content. The bound water content of the sample under critical relative humidity is decomposed according to a preset decomposition formula to obtain the bound water adsorption content and the free water adsorption content.

10. The isothermal adsorption test method for weighing clay-bound water according to claim 8, characterized in that, The sampling structure automatically removes the sample box from the constant temperature and humidity structure after the adsorption test and transports it to the weighing structure for weighing, obtaining sample mass data, including: Based on the preset sample number and preset relative humidity, a sampling decision is made. By calling a pre-trained recurrent neural network model, the historical adsorption kinetic curve segment of the current sample under the target relative humidity is analyzed, the time window when its mass change tends to stabilize is predicted, and the optimal sampling trigger command is obtained. Motion planning is performed based on the optimal sampling trigger command. Through a deep deterministic strategy gradient network, the encoder position signal and the opening and closing state of the automatic opening and closing sealing door are fused to generate a collision-free, anti-oscillation smooth motion trajectory of the robotic arm online, and obtain the grasping and placement path point sequence. The grabbing and placement operations are performed based on the grabbing and placement path point sequence until the operation is completed.

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