Lime salinized soil multi-parameter coupling no-load expansion rate test platform under unsaturated condition

Abstract

The invention belongs to the technical field of soil tests, and provides a lime salinized soil multi-parameter coupling no-load expansion rate test platform under unsaturated conditions, which comprises a soil dilatometer, a temperature maintaining system, a moisture content control system and a data acquisition and processing system, and the data acquisition and processing system is responsible for managing the moisture content control system and the temperature maintaining system, collecting data, analyzing and processing the data and providing human-computer interface support input and display output. According to the invention, complex environmental conditions of an actual site can be simulated more accurately, and the change conditions of soil resistivity, moisture content, temperature and expansion rate can be obtained; furthermore, a coupling relationship between the non-load expansion rate and multiple parameters is given by establishing a non-load expansion rate prediction model, and the non-load expansion rate of the lime salinized soil can be predicted under specific parameter conditions. According to the invention, the test precision of the soil expansion behavior is improved, and a more scientific basis is provided for the improvement, field monitoring and engineering design of expansive soil.

Description

Technical Field

[0001] The invention belongs to the technical field of geotechnical testing, and in particular relates to a multi-parameter coupling no-load expansion rate testing platform for lime-salt soil under unsaturated conditions. Background Art

[0002] The expansibility of soil is an important cause of engineering disasters, and soils with expansibility are collectively referred to as expansibility soils. As a typical expansibility soil (such as bentonite, kaolinite, etc.), the expansion mechanism of expansibility soil is mainly manifested as water absorption and expansion. The research on expansibility soil has been relatively in-depth, and the current specification "Standard for Geotechnical Test Methods" (GB / T 50123-2019) has clearly stipulated the test method for the expansibility of expansibility soil. The no-load expansion rate is an important indicator for evaluating the expansibility of expansibility soil. The severity of the expansibility of expansibility soil can be evaluated by the size of the no-load expansion rate, thereby providing guidance for engineering. According to the "Standard for Geotechnical Test Methods" (GB / T50123-2019), the standard test equipment for the no-load expansion rate is the soil expansion meter. The test method is to put the prepared soil sample into the soil expansion meter, inject pure water into the instrument and use the dial indicator to read the timed reading to calculate the no-load expansion rate of the soil sample.

[0003] Lime-salt soil is a special type of expansive soil. Its expansion mechanism is significantly different from that of expansive soil. Due to the coupling effect of multiple parameters such as water content, temperature, and salt ion concentration, its maximum expansion rate shows a more complex response mechanism. The traditional soil expansion meter and expansion rate test method proposed in the "Standard for Geotechnical Test Methods" are only applicable to soil sample testing under saturated conditions, and cannot effectively control parameters such as water content and temperature. Therefore, it is difficult to meet the needs of accurate testing of the expansion rate of lime-salt soil under unsaturated conditions, which limits the in-depth study of the expansion characteristics of lime-salt soil. In addition, the existing research on the expansion characteristics of lime-salt soil lacks consideration of resistivity, a key parameter. The resistivity of soil is closely related to temperature, water content, saturation, salt ion concentration, and pore structure, all of which play an important role in the expansion characteristics. Therefore, when studying the expansion characteristics of lime-salt soil under unsaturated conditions, it is necessary to introduce resistivity as a coupling variable and analyze it in coordination with other multiple parameters. Summary of the invention

[0004] Purpose of the invention: In view of the limitations of the traditional soil expansion rate test method, especially the problem that it is not applicable to lime-salted soil affected by multi-parameter coupling under unsaturated conditions, the present invention is based on the original no-load expansion rate test method and proposes a multi-parameter coupling no-load expansion rate test platform for lime-salted soil under unsaturated conditions. The platform can achieve precise control of parameters such as moisture content and temperature, thereby achieving high-precision measurement of soil resistivity and expansion rate, and can monitor the dynamic changes of multiple parameters during the expansion process in real time. In addition, the platform further develops a no-load expansion rate prediction model to characterize the coupling relationship between the no-load expansion rate and multiple parameters, providing strong technical support for the in-depth study of the expansion characteristics of lime-salted soil, and providing a new theoretical basis and method system for the early warning and prevention and control of expansive soil disasters.

[0005] In order to achieve the above object, the present invention adopts the following technical solution: The multi-parameter coupling no-load expansion rate test platform of lime-salt soil under unsaturated conditions includes a soil expansion meter 1, a temperature maintenance system, a moisture content control system, and a data acquisition and processing system, among which: The soil expansion meter 1 is a basic device for performing soil expansion test; The temperature maintenance system is used to maintain the temperature stability during the test; The moisture content control system is used to maintain the stability of the moisture content during the test. The data acquisition and processing system is responsible for controlling and managing the moisture content control system, the temperature maintenance system, collecting data, analyzing and processing the data, and providing a human-machine interface to support input and display output.

[0006] Furthermore, the data acquisition and processing system includes various sensor devices and a PC computer 2-1; The various types of sensing equipment include a resistance measuring instrument 2-2-1, a resistance measuring instrument supporting probe, a temperature sensor, a moisture sensor, and a displacement sensor 2-5. The resistance measuring instrument supporting probe, the temperature sensor, the moisture sensor, and the displacement sensor 2-5 are layered in the soil sample in the soil expansion instrument 1. The resistance measuring instrument 2-2-1, the temperature sensor, the moisture sensor, and the displacement sensor 2-5 are connected to the PC computer 2-1. The PC computer 2-1 includes a human-machine interface input and output module, a control algorithm module, a database, a calculation module, a modeling and prediction module; When performing the no-load expansion test, the human-machine interface accepts the test conditions and test execution instructions configured by the operator. The configured test conditions include the temperature index T 目标 and moisture content index w 目标 , Then, the temperature maintenance system and moisture content control system are controlled and managed through the control algorithm module. The database then collects and stores real-time data collected by various sensor devices, including the temperature T in the current state of the test process. i , moisture content w i , Then the current resistivity ρ is calculated in real time through the calculation module i , no-load expansion rate , and store the calculated value in the database. The temperature T in the current state during the test is then displayed in real time through the human-machine interface. i , moisture content w i , resistivity ρ i , no-load expansion rate ; The calculation module sets the target moisture content w according to the human-machine interface. 目标 , calculate the current required water volume, the calculation formula is m i =(w 目标 -w i )*m 0 , where m i is the water spray mass, w 目标 is the preset moisture content index, w i is the current moisture content, m 0 is the mass of the soil sample; the current required water volume m i , provided to the control algorithm module for controlling the moisture content control system; The calculation module calculates the current resistivity ρ i , the calculation formula is ρ i =(R*A) / H, where R is the resistance value measured by the resistance measuring instrument, A is the cross-sectional area of ​​the soil sample, and H is the height of the soil sample; The calculation module calculates the current no-load expansion rate , the calculation formula is , where h is the displacement measured by the displacement sensor, and H is the height of the soil sample; By conducting multiple groups of no-load expansion tests under different soil moisture content, temperature and initial salt ion concentration conditions, a database including temperature, moisture content, initial salt ion concentration, resistivity, no-load expansion rate and time is established and improved to provide data support for the modeling and prediction modules; The modeling and prediction module mathematically models the expansion process of lime-salted soil based on the coupling relationship between resistivity, moisture content, temperature and salt ion concentration parameters in combination with the improved Archie's law and chemical reaction kinetics to obtain a no-load expansion rate prediction model. The parameters of the no-load expansion rate prediction model are determined based on an established database, and the quantitative relationship between the no-load expansion rate and multiple parameters is characterized to achieve the prediction of the no-load expansion rate of lime-salted soil under specific parameter conditions.

[0007] Based on the above technical solution, the present invention has the following beneficial effects: The multi-parameter coupled no-load expansion rate test platform for lime-salt soil under unsaturated conditions proposed in the present invention includes two functions: no-load expansion test and no-load expansion rate prediction. When conducting a no-load expansion test, it is able to more accurately simulate the complex environmental conditions of the actual site, such as dynamic water sources, seasonal temperature fluctuations, and the migration and cumulative effects of salt, and obtain changes in soil resistivity, moisture content, temperature, and expansion rate; when conducting a no-load expansion rate prediction, the no-load expansion rate of lime-salt soil under specific parameter conditions is predicted through a no-load expansion rate prediction model. The present invention not only improves the test accuracy of soil expansion behavior, but also provides a method for predicting no-load expansion rate, providing a more scientific basis for the improvement of expansive soils, on-site monitoring, and engineering design. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 The figure is a schematic diagram of the composition and structure of the test platform according to the embodiment of the present invention.

[0009] Figure 2 It is a schematic diagram of the detailed arrangement of a part of the test platform according to an embodiment of the present invention.

[0010] Figure 3 The figure is a schematic diagram of the arrangement of various sensor measuring points in the test platform according to the embodiment of the present invention.

[0011] Figure 4 This is a working diagram of the temperature maintenance system of the test platform according to an embodiment of the present invention.

[0012] Figure 5 The present invention is a flowchart of the moisture content control system of the test platform according to the embodiment of the present invention.

[0013] Figure 6 The present invention is a flowchart of the process of performing a no-load expansion test on the test platform according to an embodiment of the present invention.

[0014] In the figure: 1 soil expansion meter, 1-1 ring knife, 1-2 clamp, 1-3 porous cover plate, 1-4 guide ring, 1-5 guard ring; 2-1 PC; 2-2-1 resistance measuring instrument, 2-2-2 first probe, 2-2-3 second probe; 2-3-1 first temperature sensor, 2-3-2 second temperature sensor, 2-3-3 third temperature sensor; 2-4-1 the first moisture content sensor, 2-4-2 the second moisture content sensor, 2-4-3 the third moisture content sensor; 2-5 displacement sensor; 3-1 water pump, 3-2 flow meter, 3-3 annular nozzle, 3-4 hose; 4-1 temperature control switch, 4-2 heating module, 4-2-1 heating module opening. DETAILED DESCRIPTION

[0015] The expansion mechanism of unsaturated lime-salted soil is mainly reflected in the reaction of sulfate and clay minerals in the soil under the alkaline environment of lime to form calcium vanadate crystals. The formation process of calcium vanadate will continuously consume sulfate ions in the soil, causing its concentration to gradually decrease, thereby reducing the soil resistivity. At the same time, the formation of calcium vanadate requires a large amount of water, and changes in moisture content will directly affect its generation rate and crystal morphology. The complex internal relationship between resistivity, moisture content, salt ion concentration, temperature and no-load expansion rate, these factors are actually closely coupled and mutually influenced in the expansion process of unsaturated lime-salted soil. Resistivity is not only an intuitive reflection of the change in salt ion concentration, but also affected by moisture content; moisture content directly regulates the migration rate and reaction conditions of salt ions; temperature has a significant regulatory effect on the formation rate of calcium vanadate, salt ion diffusion and crystal growth of calcium vanadate, and changes in moisture content and temperature will eventually be reflected in the size of the no-load expansion rate. At the same time, for unsaturated soil, the thickness of the water film on the soil surface has an impact on the resistivity.

[0016] The multi-parameter coupled no-load expansion rate test platform for lime-saline soil under unsaturated conditions proposed in the present invention can not only realize the accurate test of the resistivity and expansion rate of lime-saline soil, but also predict the no-load expansion rate of lime-saline soil under given moisture content and temperature parameters.

[0017] The technical solution provided by the present application will be further described below in conjunction with specific embodiments and accompanying drawings. The advantages and features of the present application will become more apparent with the following description.

[0018] The multi-parameter coupled no-load expansion rate test platform for lime-salt soil under unsaturated conditions is installed and worked in the laboratory. Figure 1 , Figure 2As shown, it includes a soil expansion meter 1, a temperature maintenance system, a moisture content control system, and a data acquisition and processing system. The soil expansion meter 1 is the main equipment for soil expansion testing; the temperature maintenance system is used to maintain the temperature stability during the test; the moisture content control system is used to maintain the moisture content stability during the test; the data acquisition and processing system is responsible for controlling and managing the moisture content control system, the temperature maintenance system, and collecting data, analyzing and processing the data, and providing a human-machine interface to support input and display output. Among them: The soil expansion meter 1 adopts a traditional soil expansion meter, including a ring cutter 1-1, a clamp 1-2, a porous cover plate 1-3, a guide ring 1-4, a protective ring 1-5, etc. The ring cutter 1-3 is fixed between the guide ring 1-4 and the protective ring 1-5.

[0019] Data acquisition and processing system, including various sensor devices, PC computer 2-1; The various types of sensing equipment include a resistance measuring instrument 2-2-1, a resistance measuring instrument supporting probe connected to the resistance measuring instrument, a temperature sensor, a moisture sensor, and a displacement sensor 2-5. The resistance measuring instrument supporting probe, temperature sensor, moisture sensor, and displacement sensor 2-5 are layered in the soil sample in the soil expansion meter 1. The resistance measuring instrument 2-2-1, temperature sensor, moisture sensor, and displacement sensor 2-5 are connected to a PC computer 2-1.

[0020] As an embodiment, the resistance measuring instrument 2-2-1 is a VC4090A LCR digital bridge; the resistance measuring instrument supporting probes are two probes supporting the VC4090A LCR digital bridge, namely a first probe 2-2-2 and a second probe 2-2-3.

[0021] As an embodiment, there are three temperature sensors, namely a first temperature sensor 2-3-1, a second temperature sensor 2-3-2, and a third temperature sensor 2-3-3. The temperature sensor adopts NST1001 micro temperature sensor with a measurement accuracy of ±0.2°C.

[0022] As an embodiment, there are three moisture content sensors, namely the first moisture content sensor 2-4-1, the second moisture content sensor 2-4-2, and the third moisture content sensor 2-4-3. The moisture content sensor adopts EC-5 small soil moisture sensor with a measurement accuracy of ±0.1%.

[0023] As an embodiment, the PC computer 2 - 1 is installed with data processing software, such as Excel.

[0024] The above-mentioned various sensors are arranged in layers in the unsaturated soil sample. Figure 3As shown in the figure, the sensors are arranged in three layers at predetermined positions inside the unsaturated soil sample. The three setting surfaces are: the upper setting surface, the distance from the upper surface of the soil sample in the height direction is H 1 ; The middle setting surface is at a height distance H from the upper setting surface 2 ; The lower setting surface is at a height distance H from the middle setting surface 3 ; The height of the soil sample is H, H>(H 1 + H 2 + H 3 ).

[0025] Furthermore, two resistance measuring instrument supporting probes (first probe 2-2-2, second probe 2-2-3) are installed on the upper setting surface and the lower setting surface in the unsaturated soil sample, and connected to the resistance measuring instrument 2-2-1, for real-time measurement of the resistance of the unsaturated soil sample; Three temperature sensors (a first temperature sensor 2-3-1, a second temperature sensor 2-3-2, and a third temperature sensor 2-3-3) are installed on three setting surfaces (an upper setting surface, a middle setting surface, and a lower setting surface) in the unsaturated soil sample to monitor the temperature of the unsaturated soil sample; Three moisture content sensors (a first moisture content sensor 2-4-1, a second moisture content sensor 2-4-2, and a third moisture content sensor 2-4-3) are installed on three setting surfaces (an upper setting surface, a middle setting surface, and a lower setting surface) in the unsaturated soil sample to monitor the moisture content of the unsaturated soil sample; The displacement sensor 2-5 is mounted on the fixture 1-2 of the soil expansion instrument, and the lower end of the displacement sensor is against the porous cover plate 1-3 of the soil expansion instrument, and is used to measure the expansion amount of the unsaturated soil sample in real time; The resistance measuring instrument 2-2-1, the temperature sensor, the moisture content sensor, and the displacement sensor 2-5 are connected to the PC computer 2-1 through transmission lines, and the PC computer 2-1 is responsible for managing and processing data.

[0026] The PC computer 2-1 includes a human-machine interface input and output module, a control algorithm module, a database, a calculation module, a modeling and prediction module; When performing the no-load expansion test, the human-machine interface accepts the test conditions and test execution instructions configured by the operator. The configured test conditions include the temperature index T 目标 and moisture content index w 目标 , Then, the temperature maintenance system and moisture content control system are controlled and managed through the control algorithm module. The database then collects and stores real-time data collected by various sensor devices, including the temperature T in the current state of the test process. i , moisture content w i , Then the current resistivity ρ is calculated in real time through the calculation module i , no-load expansion rate , and store the calculated value in the database. The temperature T in the current state during the test is then displayed in real time through the human-machine interface. i , moisture content w i , resistivity ρ i , no-load expansion rate ; The calculation module sets the target moisture content w according to the human-machine interface. 目标 , calculate the current required water volume, the calculation formula is m i =(w 目标 -w i )*m 0 , where m i is the water spray mass, w 目标 is the preset moisture content index, w i is the current moisture content, m 0 is the mass of the soil sample; the current required water volume m i , provided to the control algorithm module for controlling the moisture content control system; The calculation module calculates the current resistivity ρ i , the calculation formula is ρ i =(R*A) / H, where R is the resistance value measured by the resistance measuring instrument, A is the cross-sectional area of ​​the soil sample, and H is the height of the soil sample; The calculation module calculates the current no-load expansion rate , the calculation formula is , where h is the displacement measured by the displacement sensor, and H is the height of the soil sample; By conducting multiple groups of no-load expansion tests under different soil moisture content, temperature and initial salt ion concentration conditions, a database containing parameters such as temperature, moisture content, initial salt ion concentration, resistivity, no-load expansion rate, time, etc. is established and improved to provide data support for the modeling and prediction modules; The modeling and prediction module mathematically models the expansion process of lime-salted soil based on the coupling relationship between resistivity, moisture content, temperature and salt ion concentration parameters in combination with the improved Archie's law and chemical reaction kinetics to obtain a no-load expansion rate prediction model. The parameters of the no-load expansion rate prediction model are determined based on an established database, and the quantitative relationship between the no-load expansion rate and multiple parameters is characterized to achieve the prediction of the no-load expansion rate of lime-salted soil under specific parameter conditions.

[0027] Furthermore, when multiple temperature sensors are provided, the average temperature monitored by all temperature sensors in the current state is taken as the temperature T in the current state. iWhen there are multiple moisture content sensors, the average moisture content monitored by all moisture content sensors in the current state is taken as the moisture content w in the current state i .

[0028] The temperature maintenance system includes a temperature control switch 4-1 and a heating module 4-2; wherein the heating module 4-2 is connected to the temperature control switch 4-1 through an electric wire, and the temperature control switch 4-1 is connected to the PC computer 2-1 of the data acquisition and processing system through a transmission line, and the operation of the temperature control switch 4-1 is controlled by the PC computer 2-1.

[0029] Specifically, the heating module 4-2 is composed of two ring parts, which are arranged in the soil expansion meter 1 to provide and maintain the temperature required for the test for the soil sample in the soil expansion meter 1. Specifically, the two ring parts of the heating module 4-2 embrace the guide ring 1-4, the protective ring 1-5 of the soil expansion meter 1 and the periphery of the ring knife 1-3 fixed between the guide ring 1-4 and the protective ring 1-5.

[0030] Furthermore, the heating module 4-2 is provided with an opening 4-2-1 for providing a transmission line channel for each sensor.

[0031] Furthermore, the work of the temperature maintenance system is controlled and managed by the control algorithm module of the data acquisition and processing system, specifically: Step (1): Set the temperature index T required for the test through the human-machine interface 目标 ; Step (2): Start the temperature maintenance system through the human-machine interface; Step (3): Start the temperature sensor to obtain the current temperature T of the soil sample. i , if the temperature T i Lower than the preset temperature index T 目标 , then the temperature control switch 4-1 is controlled to start the heating module 4-2; when the temperature of the soil sample monitored by the temperature sensor reaches a predetermined temperature index, the temperature control switch 4-1 is controlled to stop the heating module 4-2; as an embodiment, three temperature sensors are arranged in the soil sample, and the average value of the temperatures monitored by the three temperature sensors is taken as the soil sample temperature; Step (4): Turn off the temperature maintenance system, and the temperature maintenance system stops working.

[0032] As an embodiment, the temperature control switch 4-1 is recommended to use the PCE-D9000 intelligent temperature controller, and the heating module 4-2 is recommended to use the electric heating mold barrel of Zhongrui Alloy.

[0033] The moisture content control system includes a water pump 3-1, a flow meter 3-2, and an annular nozzle 3-3. The annular nozzle 3-3 is connected to the water pump 3-1 through a hose 3-4. The flow meter 3-2 is arranged at the outlet of the water pump 3-1, and the flow meter 3-2 is connected to the PC computer 2-1 of the data acquisition and processing system, and the PC computer is responsible for managing its work.

[0034] Specifically, the upper end of the annular nozzle 3-3 is fixed on the clamp 1-2 of the soil expansion meter 1. The annular nozzle 3-3 is located 5 to 7 mm above the porous cover plate 1-3 of the soil expansion meter 1 by adjusting the height of the clamp 1-2. The water pump 3-1, the flow meter 3-2, and the annular nozzle 3-3 are connected in sequence with a hose 3-4 of matching diameter; the flow meter 3-2 is connected to the PC computer 2-1 through a transmission line, and the PC computer 2-1 is responsible for managing its work. Furthermore, the work of the moisture content control system is controlled and managed by the control algorithm module of the data acquisition and processing system, specifically: Step (1): Set the moisture content index w required for the test through the human-machine interface 目标 ; Step (2): Start the moisture content control system through the human-machine interface; Step (3): Start the moisture sensor to obtain the moisture content w of the soil sample in its current state i , the moisture content w i Compared with the preset moisture content index w 目标 Compare, if it is lower than the preset moisture content index w 目标 , then the required water volume m output by the calculation module is called i , and control the flow meter 3-2 to start, the water pump 3-1 starts to work, and water is sprayed out from the annular nozzle 3-3; the water volume reaches the calculated required water volume m i When the flow meter 3-2 is controlled to be closed, the water pump 3-1 stops working; as an embodiment, three moisture content sensors are arranged in the soil sample, and the average value of the moisture content monitored by the three moisture content sensors is taken as the moisture content of the soil sample; Step (4): Turn off the moisture content control system, and the moisture content control system stops working.

[0035] As an embodiment, it is recommended that the water pump 3-1 in the water content control system adopts a 12V automatic micro water pump and the flow meter 3-2 adopts a turbine flow meter.

[0036] The test platform of the present invention performs a no-load expansion test, and the operation process includes the following steps: Step 1: Add soil sample to the ring cutter 1-1 in the soil expansion meter 1, and arrange the matching probes of the resistance measuring instrument (the first probe 2-2-2, the second probe 2-2-3), temperature sensors (the first temperature sensor 2-3-1, the second temperature sensor 2-3-2, the third temperature sensor 2-3-3), and moisture sensors (the first moisture sensor 2-4-1, the second moisture sensor 2-4-2, the third moisture sensor 2-4-3) in layers, as shown in FIG. Figure 3 , compact the soil sample after the layout is completed; Step 2: Assemble the soil expansion meter 1, and assemble the moisture content control system, temperature maintenance system, and data acquisition and processing system in sequence to ensure that each system works normally; Step 3: Design the parameters required for the test, including temperature, moisture content, initial salt ion concentration, etc., input the moisture content and temperature index required for the test, i.e., preset values, through the human-machine interface of the PC computer 2-1, and start the moisture content control system and temperature maintenance system; Step 4: During the test, regularly check the temperature, moisture content, resistivity, and no-load expansion rate displayed on the human-machine interface of PC computer 2-1 in the current state to ensure that the data is reliable during the test; Step 5: End the test, turn off the moisture content control system, temperature maintenance system, data acquisition and processing system, and clean the soil expansion meter 1.

[0037] Since the determination of resistivity is closely related to the temperature and the change of moisture content of the object being tested, in order to ensure the accuracy of the resistivity test data, it is necessary to keep the moisture content and temperature of the sample constant during the test through the moisture control system and the temperature maintenance system, so as to accurately test the resistivity and no-load expansion rate under the change of a single factor. After completing the test of the resistivity and no-load expansion rate under a certain moisture content, temperature condition, and initial salt ion concentration, the resistivity and no-load expansion rate under different moisture contents, temperatures, and initial salt ion concentrations can be tested according to the above-mentioned no-load expansion test operation method to obtain a series of test data, and establish a database containing parameters such as temperature, moisture content, initial salt ion concentration, resistivity, no-load expansion rate, time, etc., to provide data support for the modeling and prediction modules of the data acquisition and processing system.

[0038] The test platform of the present invention predicts the no-load expansion rate based on the modeling and prediction module of the PC computer in the data acquisition and processing system. The modeling and prediction module establishes a no-load expansion rate prediction model, which characterizes the coupling relationship between the no-load expansion rate and multiple parameters, and the multiple parameters include resistivity, water content, temperature and salt ion concentration. Specifically, the modeling and prediction module includes: S1: Mathematically model the expansion process of lime-salinized soil and establish a no-load expansion rate prediction model.

[0039] S1-1: Combining basic laws and experiments, establish a resistivity model related to salt ion concentration.

[0040] According to Archie's law, the resistivity ρ It can be decomposed into the combined effect of liquid phase conductivity and soil geometric structure, and we can get: (1) Among them, F is the parameter that characterizes soil properties; is the porosity, which characterizes the pore structure characteristics; is the soil saturation, characterizing the influence of liquid phase mass transfer, and n is the saturation index; is the liquid phase resistivity.

[0041] Soil saturation and moisture content both reflect the soil moisture status, and there is a quantitative relationship between saturation and moisture content through the porosity and maximum moisture content of the soil. The quantitative relationship between and moisture content w is: w / w max , w is the actual moisture content of the soil, w max is the maximum moisture content of the soil, indicating the moisture content when it is fully saturated. This relationship shows that under given soil porosity and soil structure, the saturation and moisture content are proportional. Therefore, for the simplicity of derivation, saturation will be used instead of moisture content in subsequent analysis.

[0042] Liquid phase resistivity and salt ion concentration c The relationship between can be obtained from Kohlrausch's law: (2) Wherein, Λ is the molar conductivity, and the empirical value is taken as 160.0 S·cm²·mol⁻¹ as an example; c is the salt ion concentration.

[0043] S1-2: Considering the influence of soil water film thickness and particle surface area on conductivity (resistivity) under unsaturated conditions, the resistivity model related to salt ion concentration established in S1-1 is modified.

[0044] Under low saturation conditions, the liquid phase is mainly distributed in small pores, and the conductivity is affected by capillary action. The influence of water film thickness needs to be further considered. Introducing the resistivity correction factor affected by water film thickness E , the water film thickness is negatively correlated with the soil saturation and positively correlated with the surface area of ​​soil particles, and we can get: (3) in, Eis the resistivity correction coefficient affected by the water film thickness; a is the negative correlation coefficient of soil saturation; b is the positive correlation coefficient of soil particle area; d is the coupling coefficient.

[0045] Combining equations (1), (2) and (3), we get: (4) In the formula, g=n+d.

[0046] S1-3: Consider the effects of resistivity and temperature on the chemical reactions occurring during the expansion process and establish a salt ion concentration change equation.

[0047] The concentration change of salt ions is controlled by chemical reactions. Studies have shown that in unsaturated lime saline soil, the main reaction process is the formation of calcium vanadate crystals by sulfate ions and calcium ions in an alkaline environment. The change rate of salt ion concentration can be expressed as: (5) Among them, k is the reaction rate; A, B and C are the reaction orders, which characterize the types of ions that undergo chemical reactions; A is The reaction order of soil is one; B is The reaction order of is first in soil; C represents the effect of alkaline environment on the reaction rate, which is generally second.

[0048] The reaction rate is affected by the temperature field and the resistivity ρ The influence of is expressed as: (6) In the formula, is the temperature field influence function. The temperature field will significantly affect the chemical reaction rate. T is the temperature. is the resistivity influence function; is the benchmark reaction rate, i.e. the reaction rate under the conditions of a specific initial salt ion concentration, constant resistivity, and constant temperature. The temperature field will significantly affect the migration rate of the reactants, and the resistivity will affect the conductivity in the system, i.e., the electron transfer rate. The temperature field and resistivity have a significant effect on the reaction rate.

[0049] S1-4: Based on the mathematical expressions of the relationship between resistivity, soil saturation, and salt ion concentration in S1-1 to S1-3, and further combined with the complex intrinsic relationship between these parameters and the no-load expansion rate, a multi-parameter coupled no-load expansion rate prediction model for lime-saline soil under unsaturated conditions is constructed.

[0050] The change of the no-load expansion rate P is caused by water absorption and volume expansion of chemical products, which can be expressed by the equation: (7) Where D is the expansion coefficient caused by chemical reaction, and Q is the expansion coefficient caused by water absorption.

[0051] Combining equations (4), (5), (6) and (7) gives the no-load expansion rate prediction model: (8) in, .

[0052] S2: In the parameter calibration stage, the parameters of the no-load expansion rate prediction model established in S1 are determined to characterize the quantitative relationship between the no-load expansion rate and multiple parameters.

[0053] S2-1: characteristic numerical parameters G, Λ, , , F, Temperature field influence function And the resistivity influence function Calibration: Characteristic numerical parameters G, Λ, , , F, Temperature field influence function And the resistivity influence function It is independent of t in the expansion test and is obtained by microscopic inspection and data fitting method before starting the expansion test. Specifically: The parameter Λ takes the empirical value of 160.0 S·cm²·mol⁻¹; parameter , measured by low temperature nitrogen adsorption method (BET method) microscopic detection means, and the parameters Add to database; Calibration of parameters F and g: Under constant temperature such as 25 degrees Celsius, at a specific saturation Under the test conditions of initial salt ion concentration, the resistivity of the soil is measured using a resistivity tester. ρ ; By performing multiple groups of different saturation and initial salt ion concentration conditions, and obtained multiple groups of different saturation Soil resistivity under initial salt ion concentration test conditions ρ The test data can be used to obtain the parameters F and g through data fitting based on formula (4), and the parameters F and g are added to the database.

[0054] Temperature field influence function Calibration: According to the theory of chemical kinetics, the relationship between chemical reaction rate k and temperature usually conforms to the Arrhenius equation. Temperature field influence function It is expressed as formula (9): (9) In the formula is the activation energy; is the gas constant (8.314 J / mol·K); It's the temperature.

[0055] Under the condition of specific initial salt ion concentration, chemical experiments were carried out on the formation of calcium vanadate crystals by sulfate ions and calcium ions under different temperature T conditions in an alkaline environment, and multiple reaction rates k were measured. According to the formula Perform curve fitting and obtain The curve changes with temperature T, As the slope, the specific value of the slope can be obtained by Substituting into formula (9) we can get the temperature field influence function under this condition: Then, according to the above steps, multiple groups of chemical experiments on the formation of calcium vanadium crystals by sulfate ions and calcium ions under different initial salt ion concentrations and different temperature T conditions were carried out in an alkaline environment, and multiple groups of temperature field influence functions related to the initial salt ion concentration were obtained. , establish the relationship between the initial salt ion concentration and Data set and add it to the database.

[0056] Resistivity influence function Calibration is achieved through function fitting. Under the conditions of specific initial salt ion concentration and constant temperature such as 25 degrees Celsius, carry out chemical experiments on the formation of calcium vanadate crystals by sulfate ions and calcium ions under different resistivity conditions in an alkaline environment, measure multiple reaction rates k, and use exponential, power function or fractional function form to fit and determine the function Then, according to the above steps, multiple groups of chemical experiments on the formation of calcium vanadium crystals by sulfate ions and calcium ions under different initial salt ion concentrations and different resistivity conditions under the same constant temperature were carried out, and multiple resistivity influence functions related to the initial salt ion concentration were obtained. , establish the relationship between the initial salt ion concentration and Data set and add it to the database.

[0057] Calibration of parameter G: Conduct chemical experiments on the formation of calcium vanadium crystals by sulfate ions and calcium ions in an alkaline environment under conditions of multiple initial salt ion concentrations, constant resistivity values ​​at the initial salt ion concentrations, and constant temperatures such as 25 degrees Celsius, and measure multiple benchmark reaction rates , substitute , (A=1, B=1, C=2), multiple Gs related to the initial salt ion concentration can be obtained, a G value data set related to the initial salt ion concentration is established, and added to the database.

[0058] S2-2: Calibration of the expansion coefficient D caused by chemical reaction and the expansion coefficient Q caused by water absorption, specifically: First, a set of no-load expansion tests under specific saturation, temperature and initial salt ion concentration conditions were carried out based on the test platform of the present invention, and the resistivity and no-load expansion rate at multiple moments under the conditions were obtained. The resistivity-time curve and the no-load expansion rate-time curve under the conditions were plotted; then, the slope value of the resistivity-time curve at multiple moments under the conditions was calculated. and the slope of the no-load expansion rate versus time curve , based on the database established in S2-1, obtain the characteristic numerical parameters G, Λ, , , F, Temperature field influence function And the resistivity influence function The specific value of is obtained by data fitting method based on formula (8) at multiple moments of this working condition; Next, according to the above steps, multiple groups of no-load expansion tests under different soil saturation and temperature and initial salt ion concentration conditions were carried out to obtain the resistivity and no-load expansion rate at multiple moments under each group of conditions, and the resistivity-time curve and no-load expansion rate-time curve under each group of conditions were plotted. Finally, the slope values ​​of the resistivity-time curves under multiple groups of different soil saturation and temperature and initial salt ion concentration conditions at multiple moments were obtained. , D and Q, construct the resistivity related to four parameters: saturation, temperature, initial salt ion concentration and time , , D and Q data sets and added them to the database.

[0059] At this point, parameter calibration is completed.

[0060] S3: In the prediction stage, the no-load expansion rate prediction model after parameter calibration is used to realize the prediction of the no-load expansion rate.

[0061] After the parameter calibration of S2, the no-load expansion rate prediction model can be used to predict the no-load expansion rate under specific saturation, temperature and initial salt ion concentration conditions. The modeling and prediction module receives the specific water content, temperature, initial salt ion concentration and time t input on the human-machine interface of the PC computer, calculates the saturation according to the water content, and predicts the no-load expansion rate at time t. The process is: Based on the database data established in S2, the characteristic numerical parameters G, Λ, , , the value of F, Get the resistivity at a specific input saturation, temperature, initial salt ion concentration and time t The value of The function value of Calculated based on the input temperature The function value of Get the D, Q and The value of G, Λ, , 、F、 The function value of The function value of Substituting D, E into formula (8) we can obtain , and then obtain P= by numerical integration t, and then further substitute t to obtain the no-load expansion rate P, and transmit the predicted no-load expansion rate to the human-machine interface for display.

[0062] The above description is only a description of the preferred embodiments of the present application, and is not intended to limit the scope of the present application. Any changes or modifications made by any person skilled in the art based on the above disclosed technical contents shall be deemed as equivalent effective embodiments and shall fall within the scope of protection of the technical solution of the present application.

Claims

1. A multi-parameter coupled no-load expansion rate test platform for lime-salt soil under unsaturated conditions, characterized by: It comprises a soil expansion meter (1), a temperature maintenance system, a moisture content control system, and a data acquisition and processing system, wherein: The soil expansion meter (1) is a basic device for conducting soil expansion tests; The temperature maintenance system is used to maintain the temperature stability during the soil expansion test; The moisture content control system is used to maintain the stability of the moisture content during the soil expansion test; The data acquisition and processing system is responsible for controlling and managing the moisture content control system, the temperature maintenance system, collecting data, analyzing and processing the data, and providing a human-machine interface to support input and display output.

2. The multi-parameter coupled no-load expansion rate test platform for lime-salted soil under unsaturated conditions as claimed in claim 1, characterized in that: The data acquisition and processing system includes various sensor devices and a PC computer (2-1); The various types of sensing equipment include a resistance measuring instrument (2-2-1), a probe supporting the resistance measuring instrument, a temperature sensor, a moisture content sensor, and a displacement sensor (2-5). The probe supporting the resistance measuring instrument, the temperature sensor, the moisture content sensor, and the displacement sensor (2-5) are arranged in layers in the soil sample in the soil expansion instrument (1). The resistance measuring instrument (2-2-1), the temperature sensor, the moisture content sensor, and the displacement sensor (2-5) are connected to a PC computer (2-1); The PC computer (2-1) includes a human-machine interface input and output module, a control algorithm module, a database, a calculation module, a modeling and prediction module; When performing the no-load expansion test, the human-machine interface accepts the test conditions and test execution instructions configured by the operator. The configured test conditions include the temperature index T 目标 and moisture content index w 目标 , Then, the temperature maintenance system and moisture content control system are controlled and managed through the control algorithm module. The database then collects and stores real-time data collected by various sensor devices, including the temperature T in the current state of the test process. i , moisture content w i , Then the current resistivity ρ is calculated in real time through the calculation module i , no-load expansion rate , and store the calculated value in the database. The temperature T in the current state during the test is then displayed in real time through the human-machine interface. i , moisture content w i , resistivity ρ i , no-load expansion rate ; The calculation module sets the target moisture content w according to the human-machine interface. 目标 , calculate the current required water volume, the calculation formula is m i =(w 目标 -w i )*m0, where m i is the water spray mass, w 目标 is the preset moisture content index, w i is the current moisture content, m0 is the mass of the soil sample; the current required water volume m i , provided to the control algorithm module for controlling the moisture content control system; The calculation module calculates the current resistivity ρ i , the calculation formula is ρ i =(R*A) / H, where R is the resistance value measured by the resistance meter, A is the cross-sectional area of ​​the soil sample, and H is the height of the soil sample; The calculation module calculates the current no-load expansion rate , the calculation formula is , where h is the displacement measured by the displacement sensor, and H is the height of the soil sample; By conducting multiple groups of no-load expansion tests under different soil moisture content, temperature and initial salt ion concentration conditions, a database including temperature, moisture content, initial salt ion concentration, resistivity, no-load expansion rate and time is established and improved to provide data support for the modeling and prediction modules; The modeling and prediction module mathematically models the expansion process of lime-salted soil based on the coupling relationship between resistivity, moisture content, temperature and salt ion concentration parameters in combination with the improved Archie's law and chemical reaction kinetics to obtain a no-load expansion rate prediction model. The parameters of the no-load expansion rate prediction model are determined based on an established database, and the quantitative relationship between the no-load expansion rate and multiple parameters is characterized to achieve the prediction of the no-load expansion rate of lime-salted soil under specific parameter conditions.

3. The multi-parameter coupling no-load expansion rate test platform for lime-salted soil under unsaturated conditions as claimed in claim 2, characterized in that: The temperature maintenance system comprises a heating module (4-2) and a temperature control switch (4-1), wherein: The heating module (4-2) is arranged in the soil expansion instrument (1); The temperature control switch (4-1) is connected to the heating module (4-2) and is used to control the operation of the heating module (4-2); The temperature control switch (4-1) is connected to the PC computer (2-1) of the data acquisition and processing system.

4. The multi-parameter coupled no-load expansion rate test platform for lime-salted soil under unsaturated conditions as claimed in claim 2, characterized in that: The water content control system comprises a water pump (3-1), a flow meter (3-2), and an annular nozzle (3-3); the annular nozzle (3-3) is connected to the water pump (3-1) via a hose (3-4); the flow meter (3-2) is arranged at the outlet of the water pump (3-1), and the flow meter (3-2) is connected to a PC computer (2-1) of the data acquisition and processing system.

5. The multi-parameter coupling no-load expansion rate test platform for lime-salted soil under unsaturated conditions as claimed in claim 3, characterized in that: The control algorithm module controls and manages the work of the temperature maintenance system, specifically: Step (1): Set the temperature index T required for the test through the human-machine interface 目标 ; Step (2): Start the temperature maintenance system through the human-machine interface; Step (3): Start the temperature sensor to obtain the current temperature T of the soil sample. i ,, if the temperature T i Lower than the preset temperature index T 目标 , the temperature control switch (4-1) is controlled to start the heating module (4-2); when the temperature of the soil sample monitored by the temperature sensor reaches a predetermined temperature index, the temperature control switch (4-1) is controlled to stop the heating module (4-2); Step (4): Turn off the temperature maintenance system, and the temperature maintenance system stops working.

6. The multi-parameter coupling no-load expansion rate test platform for lime-salted soil under unsaturated conditions as claimed in claim 4, characterized in that: The control algorithm module controls and manages the work of the moisture content control system, specifically: Step (1): Set the moisture content index w required for the test through the human-machine interface 目标 ; Step (2): Start the moisture content control system through the human-machine interface; Step (3): Start the moisture content sensor to obtain the moisture content w of the soil sample in its current state i , the moisture content w i With the preset moisture content index w 目标 If the water content is lower than the preset water content index, the required water volume m output by the calculation module is called. i , and control the flow meter (3-2) to start, the water pump (3-1) starts to work, and water is sprayed out from the annular nozzle (3-3); when the water volume reaches the calculated required water volume m i When the flow meter (3-2) is controlled to be closed, the water pump (3-1) stops working; Step (4): Turn off the moisture content control system, and the moisture content control system stops working.

7. The multi-parameter coupling no-load expansion rate test platform for lime-salted soil under unsaturated conditions as claimed in claim 2, characterized in that: The modeling and prediction module comprises: S1: In the modeling stage, the expansion process of lime-salted soil is mathematically modeled in combination with basic laws, and a no-load expansion rate prediction model is established; the no-load expansion rate prediction model establishes a coupling relationship between the no-load expansion rate and multiple parameters, and the multiple parameters include resistivity, moisture content, temperature and salt ion concentration; S2: In the parameter calibration stage, the parameters of the no-load expansion rate prediction model established in S1 are determined to characterize the quantitative relationship between the no-load expansion rate and multiple parameters; S3: In the prediction stage, the modeling and prediction module receives the parameters inputted in the human-machine interface of the PC computer, calls the no-load expansion rate prediction model to predict the no-load expansion rate, and transmits the predicted no-load expansion rate to the human-machine interface for display.

8. The multi-parameter coupled no-load expansion rate test platform for lime-salted soil under unsaturated conditions as claimed in claim 7, characterized in that: The S1 specifically includes: S1-1: Combine basic laws and experiments to establish a resistivity model related to salt ion concentration; According to Archie's law, the resistivity ρ Decomposed into the combined effect of liquid phase conductivity and soil geometric structure, we get: (1) Among them, F is the parameter characterizing soil properties; is the porosity, which characterizes the pore structure characteristics; is the soil saturation, characterizing the influence of liquid phase mass transfer, and n is the saturation index; is the liquid phase resistivity; There is a quantitative relationship between saturation and moisture content through the porosity and maximum moisture content of the soil; the saturation of the soil The quantitative relationship between and moisture content w is: w / w max , w is the actual moisture content of the soil, w max is the maximum moisture content of the soil; Liquid phase resistivity and salt ion concentration c The relationship is obtained from Kohlrausch's law: (2) Where Λ is the molar conductivity; c is the salt ion concentration; S1-2: Considering the influence of soil water film thickness and particle surface area on resistivity under unsaturated conditions, the resistivity model related to salt ion concentration established in S1-1 is modified; Introducing the resistivity correction factor affected by water film thickness E , the water film thickness is negatively correlated with the soil saturation and positively correlated with the surface area of ​​soil particles, and we get: (3) in, E is the resistivity correction coefficient affected by the water film thickness; a is the negative correlation coefficient of soil saturation; b is the positive correlation coefficient of soil particle area; d is the coupling coefficient; Combining equations (1), (2) and (3), we get: (4) Where g = n + d; S1-3: Consider the influence of resistivity and temperature on the chemical reaction occurring during the expansion process and establish the salt ion concentration variation equation; The rate of change of salt ion concentration is expressed as: (5) Among them, k is the reaction rate constant; A, B and C are the reaction orders, which characterize the types of ions that undergo chemical reactions; A is The reaction order of The reaction order of C represents the effect of alkaline environment on the reaction rate; The reaction rate constant is affected by the temperature field and the resistivity ρ The influence of is expressed as: (6) In the formula, is the temperature field influence function, T is the temperature; is the resistivity influence function; is the baseline reaction rate; S1-4: Based on the mathematical expressions of the relationship between resistivity, soil saturation and salt ion concentration in S1-1 to S1-3, and further combining the complex intrinsic relationship between these parameters and the no-load expansion rate, a multi-parameter coupled no-load expansion rate prediction model for lime-salinized soil under unsaturated conditions is constructed; The change in the no-load expansion rate P is caused by water absorption and volume expansion of chemical products, which can be expressed as (7) Where D is the expansion coefficient caused by chemical reaction, and Q is the expansion coefficient caused by water absorption; Combining equations (4), (5), (6) and (7) gives the no-load expansion rate prediction model: (8) in, .

9. The multi-parameter coupling no-load expansion rate test platform for lime-salted soil under unsaturated conditions as claimed in claim 8, characterized in that: The S2 specifically includes: S2-1: characteristic numerical parameters G, Λ, , , F, Temperature field influence function And the resistivity influence function Calibration: Characteristic numerical parameters G, Λ, , , F, Temperature field influence function And the resistivity influence function It is independent of t in the expansion test and is obtained by microscopic inspection and data fitting method before starting the expansion test. Specifically, it is: Parameter Λ, take the empirical value; parameter , measured by low-temperature nitrogen adsorption microscopic detection, and the parameters Add to database; Calibration of parameters F and g: Under constant temperature conditions, in a set of saturation Under the test conditions of initial salt ion concentration, the resistivity of the soil is measured using a resistivity tester. ρ ; By performing multiple groups of different saturation and initial salt ion concentration conditions, and obtained multiple groups of different saturation Soil resistivity under initial salt ion concentration test conditions ρ Test data, and then obtain parameters F and g through data fitting method based on formula (4), and add parameters F and g into the database; Temperature field influence function Calibration: Temperature field influence function It is expressed as formula (9): (9) In the formula is the activation energy; is the gas constant; is the temperature; Under the condition of specific initial salt ion concentration, chemical experiments were carried out on the formation of calcium vanadate crystals by sulfate ions and calcium ions under different temperature T conditions in an alkaline environment, and multiple reaction rates k were measured. According to the formula Perform curve fitting and obtain The curve changes with temperature T, is the slope, and the specific value of the slope is obtained. Substituting into formula (9), we can get the temperature field influence function under this condition: ; Then, according to the above steps, multiple groups of chemical experiments on the formation of calcium vanadium crystals by sulfate ions and calcium ions under different initial salt ion concentrations and different temperature T conditions were carried out in an alkaline environment, and multiple groups of temperature field influence functions related to the initial salt ion concentration were obtained. , establish the relationship between the initial salt ion concentration and Data set and add it to the database; Resistivity influence function Calibration: Under the conditions of specific initial salt ion concentration and constant temperature, carry out chemical experiments on the formation of calcium vanadium crystals by sulfate ions and calcium ions under different resistivity conditions in an alkaline environment, measure multiple reaction rates k, and fit the determined function ; Then, according to the above steps, multiple groups of chemical experiments on the formation of calcium vanadium crystals by sulfate ions and calcium ions under different initial salt ion concentrations and different resistivity conditions under the same constant temperature were carried out, and multiple resistivity influence functions related to the initial salt ion concentration were obtained. , establish the relationship between the initial salt ion concentration and Data set and add it to the database; Calibration of parameter G: Conduct chemical experiments on the formation of calcium vanadium crystals by sulfate ions and calcium ions in an alkaline environment under conditions of multiple initial salt ion concentrations, constant resistivity values, and constant temperature, and measure multiple benchmark reaction rates. , substitute , obtain multiple G values ​​related to the initial salt ion concentration, establish a G value data set related to the initial salt ion concentration, and add it to the database; S2-2: Calibration of the expansion coefficient D caused by chemical reaction and the expansion coefficient Q caused by water absorption, specifically: First, a set of no-load expansion tests under specific saturation, temperature and initial salt ion concentration conditions are carried out based on the test platform to obtain the resistivity and no-load expansion rate at multiple moments under the condition, and the resistivity versus time curve and the no-load expansion rate versus time curve under the condition are plotted; then, the slope value of the resistivity versus time curve at multiple moments under the condition is calculated. and the slope of the no-load expansion rate versus time curve , based on the database established in S2-1, obtain the characteristic numerical parameters G, Λ, , , F, Temperature field influence function And the resistivity influence function The specific value of is obtained by data fitting method based on formula (8) at multiple moments of this working condition; Next, according to the above steps, multiple groups of no-load expansion tests under different soil saturation and temperature and initial salt ion concentration conditions were carried out to obtain the resistivity and no-load expansion rate at multiple moments under each group of conditions, and the resistivity-time curve and no-load expansion rate-time curve were plotted under each group of conditions; finally, the slope values ​​of the resistivity-time curves under multiple groups of different soil saturation and temperature and initial salt ion concentration conditions at multiple moments were obtained. , D and Q, construct the resistivity related to four parameters: saturation, temperature, initial salt ion concentration and time , , D and Q data sets and added them to the database.

10. The multi-parameter coupling no-load expansion rate test platform for lime-salted soil under unsaturated conditions as claimed in claim 9, characterized in that: The S3: The modeling and prediction module receives the specific water content, temperature, initial salt ion concentration and time t inputted in the human-machine interface of the PC computer, calculates the saturation according to the water content, and predicts the no-load expansion rate at time t. The process is as follows: Based on the database data established in S2, the characteristic numerical parameters G, Λ, , , the value of F, Get the resistivity at a specific input saturation, temperature, initial salt ion concentration and time t The value of The function value of Calculated based on the input temperature The function value of Get the D, Q and The value of G, Λ, , , F, The function value of The function value of Substituting D, E into formula (8) we can obtain , and then obtain P= by numerical integration t, and then further substitute t to obtain the no-load expansion rate P, and transmit the predicted no-load expansion rate to the human-machine interface for display.

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