Device and method for testing limited deformation of soil body in dehumidification process

Abstract

The invention relates to the technical field of soil deformation testing, in particular to a device and method for testing limited deformation of a soil body in the dehumidification process, and the device comprises data acquisition and processing equipment, a strain measurement module and a sealed environment chamber; a weighing device, a loading and unloading device, an air pressure loading system, a relative temperature and humidity sensor and a relative humidity controller are arranged in the environment chamber; the air pressure loading system is used for automatically unloading a sample placed in loading and unloading equipment through the loading and unloading equipment; a wave test device is configured on the loading and unloading device; the loading and unloading equipment is also provided with a pressure sensor; and the data acquisition and processing equipment is in sampling connection with the weighing equipment, the relative humidity controller, the pressure sensor, the relative temperature and humidity sensor and the strain measurement module. The method can accurately test the change condition of the bulk modulus of the soil body along with the water content.

Description

Technical Field

[0001] This invention relates to the field of soil deformation testing technology, specifically to a testing device and method for testing limited deformation of soil during dehydration. Background Technology

[0002] Clayey soils contain a large number of highly hydrophilic minerals, making them particularly sensitive to climate change. Their mechanical properties change significantly after wet-dry cycles, leading to engineering disasters. In recent years, the impact of the shrinkage behavior of clayey soils during drying on their mechanical and hydraulic properties has attracted widespread attention. However, the intergranular stress during drying and its evolution with water content remains unexperimentally understood. Current research on unsaturated soil mechanics typically neglects the changes in elastic parameters during the soil's self-shrinkage and self-consolidation process. However, the swelling and shrinkage characteristics of clayey soils are closely related to their bulk modulus, a crucial parameter for measuring the soil's resistance to elastic deformation and key to calculating intergranular stress during swelling and shrinkage. Currently, the analysis of intergranular stress relies primarily on theoretical calculations, lacking direct experimental data. The rationality and accuracy of these calculations are verified through indirect comparison and analysis with experimental data. Therefore, to more accurately describe the mechanical behavior of unsaturated clayey soils, obtaining the evolution of elastic parameters with water content during the soil's drying shrinkage process is crucial and helps reveal the intrinsic mechanism of soil swelling and shrinkage behavior.

[0003] There are many test devices for testing the elastic parameters of soil, but current testing methods cannot obtain the finite deformation bulk modulus of cohesive soil during the drying shrinkage process. Furthermore, when calculating the bulk modulus according to elastic theory, Poisson's ratio is usually taken as a constant of 0.25, but the Poisson's ratio of soil is not constant during the drying process and changes with the moisture content. Therefore, the law of change of bulk modulus with moisture content during the calculation process is currently unknown. Patent document CN 111008457 B discloses a method for predicting the water-cement ratio, strength, and stiffness of cement-reinforced expansive soil, and proposes an optimized selection model for the water-cement ratio of cement-reinforced expansive soil; patent document CN 112284899 B discloses a device and method for measuring the Poisson's ratio of bulk materials in a spoil heap; patent application CN 119322163 A discloses a test device for measuring the characteristic curve and shear modulus of unsaturated soil; patent document CN 113075027 B discloses a test device and method for determining the dynamic elastic modulus of a soil model, realizing the simultaneous measurement of the dynamic shear modulus and dynamic elastic modulus of soil; patent document CN 114673205... Patent document B discloses an experimental device and method for measuring the stiffness characteristics of soil around piles under cyclic loading. This device can achieve high-pressure self-balancing preloading consolidation of clay in a large-scale model box, and can perform long-term, stable, and variable-amplitude cyclic loading on piles of different lengths. Patent application document CN 118917189 A discloses a rapid estimation method, system, storage medium, and terminal for the elastic modulus of glacial till in indoor environments. It mainly corrects the concept of calculating the elastic modulus of glacial till through the analysis of a large amount of indoor test data, and uses filtering, baseline leveling, and peak inflection point identification to evaluate the elastic modulus values ​​of glacial till in batches. All of the above patents have focused on the elastic parameters of soil or building materials and have conducted fruitful research. However, foundation pit engineering, slope engineering, and roadbed engineering exposed to the atmosphere are in a state of long-term large changes in soil moisture content, making their stability during design, construction, and operation closely related to the finite deformation modulus and moisture content of the soil. The finite deformation modulus is a key parameter for analyzing the deformation stability of unsaturated cohesive soil and its stress state during the drying process. Generally, elastic parameters such as the soil bulk modulus are considered constants. However, the evolution of the elastic parameters of the soil with changes in water content and the amplitude of their fluctuations during the dehydration process have not been clearly determined by experiments. Therefore, it is urgent to develop an experimental device and method that can test the variation law of the finite deformation modulus with water content during the drying process of soil. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a testing device and method for testing the limited deformation of soil during the dehydration process. The specific technical solution adopted is as follows: In a first aspect, the present invention provides a soil finite deformation testing device during dehumidification. The device includes a data acquisition and processing device, a strain measurement module, and a sealed environmental chamber. The environmental chamber is equipped with a weighing device, a loading and unloading device, a pneumatic loading system, a relative temperature and humidity sensor, and a relative humidity controller. The pneumatic loading system automatically unloads the sample placed within the loading and unloading device. The loading and unloading device is equipped with a wave testing device for testing the waveform of the sample during automatic loading and unloading. The loading and unloading device is also equipped with a pressure sensor for measuring the pressure value experienced by the sample during automatic unloading. The strain measurement module is used to collect vertical deformation data of the sample during loading and unloading, and then calculate the vertical strain. The weighing device is used to test the weight of the sample. The relative humidity controller is used to control the relative humidity of the environmental chamber, and the relative temperature and humidity sensor is used to test the relative temperature and humidity of the environmental chamber. The data acquisition and processing device is connected to the weighing device, the relative humidity controller, the pressure sensor, the relative temperature and humidity sensor, and the strain measurement module.

[0005] In conjunction with the first aspect above, in some possible implementations, the weighing device includes a sample holder and an electronic balance. The upper part of the sample holder is used to place the sample, and a loading top plate is provided above the sample holder. The sample holder is located above the electronic balance for measuring the weight of the sample.

[0006] In conjunction with the first aspect above, in some possible implementations, the loading and unloading device includes a loading top plate and a loading bottom plate, the upper part of the loading bottom plate is used to place the sample, and the loading top plate is disposed above the loading bottom plate.

[0007] In conjunction with the first aspect above, in some possible implementations, the wave testing equipment includes a wave elastic velocity sensor, a waveform generator, and an oscilloscope. The elastic velocity sensor includes an excitation end and a receiving end. The excitation end is disposed on a loading base plate, and the receiving end is disposed on a loading top plate. The excitation end is connected to the waveform generator, and the receiving end is connected to the oscilloscope. The waveform generator is connected to the oscilloscope through a power amplifier.

[0008] In conjunction with the first aspect above, in some possible implementations, the pneumatic loading system includes an automatically controlled air compressor, a pressure gauge, a pressure chamber, and a rubber mold. The automatically controlled air compressor is connected to the pressure chamber via the pressure gauge and is used to introduce compressed air into the pressure chamber. The pressure chamber is used to transmit pressure to the rubber mold, and the rubber mold expands and deforms to compress the loading top plate.

[0009] In conjunction with the first aspect above, in some possible implementations, the strain measurement module is an industrial camera, and the data acquisition and processing equipment includes a computer and a data acquisition instrument.

[0010] Secondly, the present invention also provides a method for testing the finite deformation of soil during the dehydration process, applicable to a soil finite deformation testing device for the dehydration process described in any of the above claims, the method comprising: Acquire relevant test data of the sample during the automatic unloading process. The relevant test data shall include at least: the pressure value data of the sample, the weight data of the sample, the vertical deformation data, the waveform data, and the relative temperature and humidity data of the environmental chamber. Based on the relevant test data, the elastic modulus and Poisson's ratio of the sample at each moisture content were determined; Based on the elastic modulus and the Poisson's ratio, the bulk modulus of the sample at each moisture content is determined.

[0011] In conjunction with the second aspect above, in some possible implementations, determining the elastic modulus of the sample at each moisture content includes: Based on the sample weight data, the moisture content of the sample is determined; Based on the pressure data and vertical deformation data, and in conjunction with the moisture content, the stress increment and vertical strain increment of the specimen at each moisture content are determined. The ratio of the stress increment to the vertical strain increment is determined as the elastic modulus of the specimen at each moisture content.

[0012] In conjunction with the second aspect above, in some possible implementations, determining the Poisson's ratio of the sample at each moisture content includes: Based on the waveform data and the relative temperature and humidity data of the environmental chamber, and in combination with the vertical deformation data and the moisture content, the shear wave velocity and compression wave velocity at each moisture content are determined. Based on the shear wave velocity and compression wave velocity, the Poisson's ratio of the sample at each moisture content is determined using the following formula:

[0013] In the formula, Indicates the Poisson's ratio of the sample. and These represent the shear wave velocity and the compression wave velocity, respectively.

[0014] In conjunction with the second aspect above, in some possible implementation methods, the bulk modulus of the sample at each moisture content is determined, and the corresponding calculation formula is as follows:

[0015] In the formula, This represents the bulk modulus of the sample at each moisture content. Indicates the Poisson's ratio of the sample. This indicates the elastic modulus of the sample.

[0016] This invention offers the following advantages: It incorporates a data acquisition and processing device, a strain measurement module, and a sealed environmental chamber. The environmental chamber houses a weighing device, a loading and unloading device, a pneumatic loading system, a relative temperature and humidity sensor, and a relative humidity controller. The pneumatic loading system automatically unloads the sample placed within the loading and unloading device. The loading and unloading device is equipped with a wave testing device and a pressure sensor. The data acquisition and processing device is connected to the weighing device, relative humidity controller, pressure sensor, relative temperature and humidity sensor, and strain measurement module. This invention utilizes a pneumatic loading system and controlled relative humidity in the environmental chamber to conduct loading and unloading tests during the soil drying process. By controlling the loading and unloading process with pneumatic pressure, it avoids the uneven stress that may occur with rigid loading of the sample, and can accurately obtain the variation law of the bulk modulus of finite deformation with moisture content. Attached Figure Description

[0017] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of a soil finite deformation testing device for a desiccation process according to an embodiment of the present invention; Figure 2 The loading and unloading stress-strain curves are from an embodiment of the present invention. Figure 3 The curve showing the change of bulk modulus with moisture content when the Poisson's ratio is a constant of 0.25, according to an embodiment of the present invention; Figure 4 This illustrates the variation of Poisson's ratio with moisture content in an embodiment of the present invention. Figure 5 This is a curve showing the change of bulk modulus with water content, where Poisson's ratio is a variable, according to an embodiment of the present invention. Figure 6 This is a flowchart illustrating the steps of a soil finite deformation test method during dehydration, according to an embodiment of the present invention. Among them: 1-computer, 2-data acquisition instrument, 3-industrial camera, 4-clay sample, 5-sample holder, 6-electronic balance, 7-pressure sensor, 8-elastic wave velocity sensor, 9-loading top plate, 10-rubber mold, 11-pressure chamber, 12-pressure gauge, 13-automatic control air compressor, 14-oscilloscope, 15-power amplifier, 16-waveform generator, 17-relative humidity controller, 18-valve, 19-relative temperature and humidity sensor, 20-environmental chamber, 21-loading base plate. Detailed Implementation

[0019] To clearly illustrate the technical features of this solution, the invention will be described in detail below through specific embodiments and in conjunction with the accompanying drawings.

[0020] Embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. While some embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the invention. It should be understood that the accompanying drawings and embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the invention.

[0021] It should be understood that the various steps described in the method embodiments of the present invention may be performed in different orders and / or in parallel. Furthermore, the method embodiments may include additional steps and / or omit the steps shown. The scope of the present invention is not limited in this respect.

[0022] The term "comprising" and its variations as used herein are open-ended inclusions, meaning "including but not limited to". The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". Definitions of other terms will be given in the description below.

[0023] It should be noted that the concepts of "first" and "second" mentioned in this invention are only used to distinguish different devices, modules or units, and are not used to limit the order of functions performed by these devices, modules or units or their interdependencies.

[0024] Although operations or steps are described in a specific order in the accompanying drawings in the embodiments of the present invention, this should not be construed as requiring these operations or steps to be performed in the specific order or serial order shown, or requiring all of the shown operations or steps to be performed to obtain the desired result. In the embodiments of the present invention, these operations or steps may be performed serially; they may be performed in parallel; or a portion of these operations or steps may be performed.

[0025] Furthermore, it is understood that the data involved in the technical solutions of this invention (including but not limited to the data itself, the acquisition or use of the data) shall comply with the requirements of relevant laws, regulations and related provisions. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains, and all parameters or indicators in the formulas involved in this invention are normalized values ​​that have eliminated the influence of dimensions.

[0026] The following will describe in detail, with reference to the accompanying drawings, a soil finite deformation testing device and testing method provided by an embodiment of the present invention.

[0027] Device Example: This invention provides a soil finite deformation testing device for a dehumidification process. The device includes a data acquisition and processing unit, a strain measurement module, and an environmental chamber. The environmental chamber is equipped with a weighing device, a loading and unloading device, a pneumatic loading system, a relative temperature and humidity sensor, and a relative humidity controller. The pneumatic loading system automatically unloads the sample placed within the loading and unloading device. A wave testing device is installed on the loading and unloading device to test the waveform of the sample during the automatic loading and unloading process. The loading and unloading device also includes a pressure sensor to measure the pressure value experienced by the sample during automatic unloading. The strain measurement module collects vertical deformation data of the sample during loading and unloading and calculates the vertical strain. The weighing device tests the weight of the sample. The relative humidity controller controls the relative humidity of the environmental chamber. The relative temperature and humidity sensor tests the relative temperature and humidity of the environmental chamber. The data acquisition and processing unit samples and connects to the weighing device, relative humidity controller, pressure sensor, and relative temperature and humidity sensor to test the relative temperature and humidity sensor and strain measurement module of the environmental chamber.

[0028] In one possible implementation, the weighing device includes a sample holder and an electronic balance. The upper part of the sample holder is used to place the sample, and a loading top plate is provided above the sample holder. The sample holder is positioned above the electronic balance for measuring the weight of the sample.

[0029] In one possible implementation, the loading and unloading device includes a loading top plate and a loading bottom plate, the upper part of which is used to place the sample, and the loading top plate is positioned above the loading bottom plate.

[0030] In one possible implementation, the wave testing equipment includes a wave elastic velocity sensor, a waveform generator, and an oscilloscope. The elastic velocity sensor includes an excitation end and a receiving end. The excitation end is mounted on a loading base plate, and the receiving end is mounted on a loading top plate. The excitation end is connected to the waveform generator, and the receiving end is connected to the oscilloscope. The waveform generator is connected to the oscilloscope through a power amplifier.

[0031] In one possible implementation, the pneumatic loading system includes an automatically controlled air compressor, a pressure gauge, a pressure chamber, and a rubber mold. The automatically controlled air compressor is connected to the pressure chamber via the pressure gauge and is used to introduce compressed air into the pressure chamber. The pressure chamber is used to transmit pressure to the rubber mold, which expands and deforms to compress the loading top plate.

[0032] In one possible implementation, the strain measurement module is an industrial camera, and the data acquisition and processing equipment includes a computer and a data acquisition instrument.

[0033] In a specific example, an embodiment of the present invention provides a soil finite deformation testing device for the desiccation process, such as... Figure 1 As shown, it comprises: a computer 1, a data acquisition instrument 2, an industrial camera 3, a clay sample 4, a sample holder 5, an electronic balance 6, a pressure sensor 7, an elastic wave velocity sensor 8, a loading top plate 9, a rubber mold 10, a pressure chamber 11, a pressure gauge 12, an automatic control air compressor 13, an oscilloscope 14, a power amplifier 15, a waveform generator 16, a relative humidity controller 17, a valve 18, a relative temperature and humidity sensor 19, an environmental chamber 20, and a loading base plate 21.

[0034] The following is combined Figure 1 The following is a detailed explanation of each piece of equipment and its function in the soil finite deformation testing device for the above-mentioned desiccation process: The environmental chamber 20 is used to conduct loading and unloading tests under different relative humidity conditions.

[0035] The electronic balance 6, relative humidity controller 17, and pressure sensor 7 are connected to the data acquisition instrument 2. The data acquisition instrument 2 acquires the sample mass change, relative temperature and humidity in the environmental chamber 20, and the pressure on the sample. The computer 1 can also acquire the mass of the clay sample 4, the relative temperature and humidity in the environmental chamber 20, and the pressure in real time.

[0036] The industrial camera 3 can capture changes in the height of the sample, that is, capture the vertical deformation of the sample during loading and unloading, and then calculate the axial strain of the sample during loading and unloading.

[0037] After clay sample 4 is prepared, it is placed in a vacuum cylinder for saturation. Two parallel saturated samples are then placed on the sample holder 5 and the loading base plate 21 in the environmental chamber 20, respectively. One sample is used to monitor changes in moisture content, and the other is used to conduct loading and unloading tests.

[0038] The sample holder 5 is mainly placed on the electronic balance 6 to support the clay sample with varying moisture content. That is, the clay sample 4 and the sample holder 5 are placed on the electronic balance 6 to record the changes in sample mass during the drying process, and then calculate the sample moisture content.

[0039] The upper and lower sets of elastic wave velocity sensors 8 test the shear wave and compression wave of the sample, respectively. The lower sensor of the elastic wave velocity sensor 8 is the excitation end, which is connected to the waveform generator 16, and the upper end is the receiving end, which is connected to the oscilloscope 14. The waveform generator 16 is connected to the power amplifier 15 for filtering and noise reduction. At the same time, the power amplifier 15 is connected to the oscilloscope 14, and the processed signal and the excitation pulse of the waveform generator 16 are displayed on the oscilloscope 14.

[0040] The oscilloscope 14 is used to display and record waveform data from the transmitting and receiving ends of the wave velocity sensor to determine the wave velocity arrival time, and then calculate the shear wave and compression wave velocities. The power amplifier 15 is used to amplify the waveform data amplitude and reduce noise. The waveform generator 16 applies a waveform, such as a sine wave or square wave, to the sensor excitation end with a given frequency and other parameters.

[0041] The loading top plate 9 and loading bottom plate 21 are used for loading and unloading the sample. They can be embedded 2 mm into the sample, and the loading top plate 9 and loading bottom plate 21 have a threaded hole in the middle for mounting a wave velocity sensor. Preloading moves the loading top plate 9 to embed the elastic wave velocity sensor 8 2 mm into the sample, stops the preloading, and records the pressure.

[0042] The automatic control air compressor 13 can automatically control the gas pressure according to the set loading and unloading path to complete the loading and unloading test. The automatic control air compressor 13 is connected to the pressure chamber 11 via a pressure gauge 12. By introducing compressed air into the pressure chamber 11, the pressure is transmitted to the rubber mold 10. The rubber mold 10 expands and deforms, compressing and loading the sample through the loading top plate 9. After reaching the preset load target, it automatically unloads. The pressure chamber 11 is a gas-sealed loading chamber, where air is introduced to perform the loading and unloading test on the sample. The pressure gauge 12 is used to monitor the gas pressure in the pressure chamber 11. The rubber mold 10 is a high-strength elastic membrane with a bearing capacity of up to 1 MPa.

[0043] The relative humidity controller 17 is used to control the relative humidity of the environmental chamber 20 and can be adjusted according to the set relative humidity. The valve 18 is used to maintain the environmental chamber 20 at normal pressure. The relative humidity controller 17 mixes dry air and water vapor according to the set relative humidity and introduces the mixed gas into the environmental chamber 20, while simultaneously opening the valve 18 to ensure that the environmental chamber 20 is at normal pressure.

[0044] The relative temperature and humidity sensor 19 is used to monitor the temperature and relative humidity data inside the environmental chamber 20. The pressure sensor 7 has an accuracy of 0.037% and can monitor and collect the pressure on the soil sample in real time.

[0045] The aforementioned soil finite deformation testing device during the desiccation process is suitable for testing the finite deformation bulk modulus of cohesive soil during the drying process. The sample is saturated by vacuuming, requiring five pre-prepared saturated parallel samples. After saturation, the samples are loaded for testing. The specific test procedure is as follows: Step 1: Place the saturated clay sample 4 above the loading base plate 21, and use the automatic control air compressor 13 to load until the sample is destroyed, and read the failure load of the sample.

[0046] Step 2: Remove the damaged specimen and repeat Step 1 using another saturated specimen, but only load it to 50% of the failure load. After confirming that the specimen has not undergone plastic failure, record the load value at this time as the target elastic load for the loading process, and then remove the specimen.

[0047] Step 3: Take two parallel saturated samples and place them on the loading base plate 21 and the sample holder 5 respectively. Use the automatic control air compressor 1313 to preload the samples so that the upper and lower pairs of elastic wave velocity sensors 8 are embedded 2 mm into the samples and the loading stops. Place the loading top plate 9 on top of the other sample for monitoring the mass to ensure that the drainage channels of the other parallel sample are consistent.

[0048] Step 4: Seal the environment chamber 20 and set the relative humidity of the relative temperature and humidity sensor 19 to decrease step by step from 100%, 98%, 96%, 94%, 92%, 90%, 85%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10%, and 5%.

[0049] Step 5: During the loading process, pressure chamber 11 is introduced at a constant rate of 0.1 kPa / min, and then transmitted to clay sample 4 through rubber mold 10. Below clay sample 4 is a high-precision pressure sensor 7 (accuracy 0.037%), which can monitor and collect the pressure on clay sample 4 in real time. Elastic waves are transmitted through the soil from the excitation end to the receiving end, and the receiving end converts the received mechanical vibration into an electrical signal displayed on oscilloscope 14. After loading is completed, the soil sample is completely unloaded.

[0050] Step 6: Based on the pressure data, weight data, vertical deformation data, waveform data, and relative temperature and humidity data of the environmental chamber during the automatic unloading process, determine the bulk modulus of the soil sample. The specific implementation process includes: First, the sample weight data is used to calculate the evaporation of moisture from the sample, and then the moisture content of the sample is calculated.

[0051] Secondly, based on the pressure data and vertical deformation data, and in conjunction with the moisture content, the elastic modulus of the sample at each moisture content is determined using the following formula: E = ΔP / Δε (1) In the formula: E represents the elastic modulus of the sample at each moisture content; ΔP represents the stress increment of the sample, which can be obtained from the slope of the linear portion of the stress-strain curve obtained by fitting the pressure data; Δε represents the vertical strain increment of the sample, which can be obtained from the attached formula. Figure 2The loading and unloading stress-strain curves are obtained from vertical deformation data and pressure value data.

[0052] Next, based on the waveform data and the relative temperature and humidity data of the environmental chamber, the propagation time of shear waves and compression waves inside the specimen under different relative humidities was determined. Then, the shear wave velocity was calculated from the vertical height of the specimen in the vertical deformation data. With compression wave speed That is, shear wave velocity and compressed wave speed The Poisson's ratio can be obtained by dividing the sensor spacing by the elastic wave propagation time, and then calculated using wave velocity and elasticity theory. The calculation formula is as follows: (2) In the formula: ν represents Poisson's ratio at each moisture content. Figure 4 The curve showing the change of Poisson's ratio with water content is shown.

[0053] Finally, based on the elastic modulus and Poisson's ratio, and in conjunction with the moisture content of the sample, the bulk modulus of the sample at each moisture content is determined using the following formula: (3) In the formula: K represents the bulk modulus of the sample at each moisture content, E represents the elastic modulus of the sample, and ν represents the Poisson's ratio of the sample.

[0054] Considering that Poisson's ratio is not constant, the bulk modulus changes significantly with decreasing moisture content. The bulk modulus corresponding to the lowest moisture content is 5 times that when Poisson's ratio is 0.25. (See [reference needed]). Figure 3 and Figure 5 .

[0055] In the soil finite deformation testing device provided above, the elastic modulus of finite deformation under different moisture contents can be obtained by changing the relative humidity of the ambient chamber; the flexible loading and unloading is controlled by air pressure to avoid the uneven stress that may be generated by rigid loading of the specimen; the axial deformation of the specimen is obtained by using digital image method, which reduces the local error caused by the displacement sensor measuring the strain; and the variation law of the bulk modulus of finite deformation of the specimen with moisture content is obtained by considering the change of Poisson's ratio with moisture content.

[0056] Method Implementation Examples: Based on the same inventive concept and the aforementioned soil finite deformation testing device for the dehydration process, this embodiment of the invention also provides a method for testing soil finite deformation during the dehydration process, such as... Figure 6 As shown, the method includes: Acquire relevant test data of the sample during the automatic unloading process. The relevant test data shall include at least: the pressure value data of the sample, the weight data of the sample, the vertical deformation data, the waveform data, and the relative temperature and humidity data of the environmental chamber. Based on the relevant test data, the elastic modulus and Poisson's ratio of the sample at each moisture content were determined; Based on the elastic modulus and the Poisson's ratio, the bulk modulus of the sample at each moisture content is determined.

[0057] Since the specific implementation methods of each step in the above-mentioned soil finite deformation test method for dehumidification process have been described in detail in the above-mentioned device embodiment, they will not be repeated here.

[0058] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A soil finite deformation testing device during desiccation process, characterized in that, The device includes a data acquisition and processing unit, a strain measurement module, and a sealed environmental chamber. The environmental chamber is equipped with a weighing device, a loading and unloading device, a pneumatic loading system, a relative temperature and humidity sensor, and a relative humidity controller. The pneumatic loading system automatically unloads the sample placed within the loading and unloading device. The loading and unloading device is equipped with a wave testing device to test the waveform of the sample during automatic loading and unloading. The loading and unloading device is also equipped with a pressure sensor to measure the pressure value experienced by the sample during automatic unloading. The strain measurement module collects vertical deformation data of the sample during loading and unloading, and then calculates the vertical strain. The weighing device is used to test the weight of the sample. The relative humidity controller controls the relative humidity of the environmental chamber, and the relative temperature and humidity sensor tests the relative temperature and humidity of the environmental chamber. The data acquisition and processing unit is connected to the weighing device, the relative humidity controller, the pressure sensor, the relative temperature and humidity sensor, and the strain measurement module.

2. The soil finite deformation testing device during dehydration process according to claim 1, characterized in that, The weighing device includes a sample holder and an electronic balance. The upper part of the sample holder is used to place the sample, and a loading top plate is provided above the sample holder. The sample holder is located on the upper part of the electronic balance for measuring the weight of the sample.

3. The soil finite deformation testing device during desiccation process according to claim 1, characterized in that, The loading and unloading device includes a loading top plate and a loading bottom plate. The upper part of the loading bottom plate is used to place the sample, and the loading top plate is located above the loading bottom plate.

4. The soil finite deformation testing device during desiccation process according to claim 3, characterized in that, The wave testing equipment includes a wave elastic velocity sensor, a waveform generator, and an oscilloscope. The elastic velocity sensor includes an excitation end and a receiving end. The excitation end is disposed on the loading base plate, and the receiving end is disposed on the loading top plate. The excitation end is connected to the waveform generator, and the receiving end is connected to the oscilloscope. The waveform generator is connected to the oscilloscope through a power amplifier.

5. The soil finite deformation testing device during desiccation process according to claim 3, characterized in that, The pneumatic loading system includes an automatic control air compressor, a pressure gauge, a pressure chamber, and a rubber mold. The automatic control air compressor is connected to the pressure chamber through the pressure gauge and is used to introduce compressed air into the pressure chamber. The pressure chamber is used to transmit pressure to the rubber mold, and the rubber mold expands and deforms to squeeze the loading top plate.

6. The soil finite deformation testing device during desiccation process according to claim 1, characterized in that, The strain measurement module is an industrial camera, and the data acquisition and processing equipment includes a computer and a data acquisition instrument.

7. A method for testing the finite deformation of soil during the dehydration process, applied to the soil finite deformation testing device according to any one of claims 1-6, characterized in that, The method includes: Acquire relevant test data of the sample during the automatic unloading process. The relevant test data shall include at least: the pressure value data of the sample, the weight data of the sample, the vertical deformation data, the waveform data, and the relative temperature and humidity data of the environmental chamber. Based on the relevant test data, the elastic modulus and Poisson's ratio of the sample at each moisture content were determined; Based on the elastic modulus and the Poisson's ratio, the bulk modulus of the sample at each moisture content is determined.

8. The method for testing finite deformation of soil during desiccation process according to claim 7, characterized in that, Determine the elastic modulus of the sample at each moisture content, including: Based on the sample weight data, the moisture content of the sample is determined; Based on the pressure data and vertical deformation data, and in conjunction with the moisture content, the stress increment and vertical strain increment of the specimen at each moisture content are determined. The ratio of the stress increment to the vertical strain increment is determined as the elastic modulus of the specimen at each moisture content.

9. The soil finite deformation testing device during desiccation process according to claim 8, characterized in that, Determining the Poisson's ratio of the sample at each moisture content includes: Based on the waveform data and the relative temperature and humidity data of the environmental chamber, and in combination with the vertical deformation data and the moisture content, the shear wave velocity and compression wave velocity at each moisture content are determined. Based on the shear wave velocity and compression wave velocity, the Poisson's ratio of the sample at each moisture content is determined using the following formula: In the formula, Indicates the Poisson's ratio of the sample. and These represent the shear wave velocity and the compression wave velocity, respectively.

10. The soil finite deformation testing device during dehydration process according to claim 7, characterized in that, The bulk modulus of the sample at each moisture content is determined by the following formula: In the formula, This represents the bulk modulus of the sample at each moisture content. Indicates the Poisson's ratio of the sample. This indicates the elastic modulus of the sample.

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