CN113552006B - Deep sea soft clay thixotropy combined determination system and method - Google Patents
Deep sea soft clay thixotropy combined determination system and method Download PDFInfo
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/24—Investigating strength properties of solid materials by application of mechanical stress by applying steady shearing forces
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
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- G01N3/066—Special adaptations of indicating or recording means with electrical indicating or recording means
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0058—Kind of property studied
- G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
- G01N2203/0075—Strain-stress relations or elastic constants
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/022—Environment of the test
- G01N2203/0222—Temperature
- G01N2203/0228—Low temperature; Cooling means
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/022—Environment of the test
- G01N2203/023—Pressure
- G01N2203/0232—High pressure
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
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- G01N2203/0617—Electrical or magnetic indicating, recording or sensing means
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/0658—Indicating or recording means; Sensing means using acoustic or ultrasonic detectors
Abstract
The invention discloses a deep sea soft clay thixotropy joint determination system and a deep sea soft clay thixotropy joint determination method, and belongs to the field of ocean geotechnical engineering. The system comprises a micro shear rheometer, a loading platform, a temperature control autoclave, a water depth simulation system, a resistivity test system, a temperature control system and a shear modulus test system. The method utilizes the hydraulic source and the temperature controller to simulate the deep-sea low-temperature high-pressure environment, utilizes the micro shear rheometer, the bending element wafer and the electrode element to jointly measure the changes of the shear strength, the shear modulus and the resistivity along with time in the thixotropic process of the soil body, and has the advantages of complete evaluation indexes, high precision, quantitative analysis, good comprehensiveness and the like.
Description
Technical Field
The invention belongs to the field of ocean geotechnical engineering, and relates to a system for measuring thixotropy of deep sea soft clay and a clay thixotropy combined measuring method capable of simulating deep sea temperature and pressure environment.
Background
With the progress of technology, the development of ocean oil and gas resources is moving from the 'shallow sea' to the 'deep open sea' with richer reserves, and the severe temperature and pressure environment, complex geology and hydraulic conditions of the deep sea also present new challenges. For most marine structures, seabed soft clay is the 'root base' of the foundation structure, and the stability of seabed foundation and foundation is crucial to the safety and stability of the marine structure. Unlike general land source and offshore soft clay, deep sea soft clay is mostly composed of soft soil or ultra-soft soil rich in biomass debris, has very low strength (generally less than 20kPa), has high sensitivity, and is very easy to soften under the action of earthquake load and various dynamic loads indirectly transmitted by structures. On the other hand, the deep-sea soft clay often has a strong thixotropic recovery characteristic, and after the external unfavorable vibration load disappears, the internal structure and the strength of the soil body gradually recover along with the increase of time. For the marine structure foundation in a bad stratum, the strength recovery characteristic of softened marine soil is accurately mastered, and the method has great significance for the optimal design of the marine anchoring foundation and the safety assessment in the operation process. Therefore, by utilizing an effective test means, the research on the thixotropy of the deep-sea soft clay is developed, the physical and mechanical property recovery characteristics of the disturbed soil body are accurately evaluated, and the method has important practical application value for deep-sea engineering.
However, at present, the research on the thixotropy of the soft clay is limited to methods such as a falling cone test, a shear rheological test and an unconfined compression test, and the test and the evaluation are carried out only by starting from a single index of shear strength recovery, and the change of the shear modulus and the resistivity in the thixotropic process cannot be fully considered. On the other hand, the existing testing method is mostly carried out under the indoor normal temperature and normal pressure conditions, and the influence of the low-temperature and high-water pressure environmental conditions in deep sea on the thixotropy of the soft clay cannot be fully considered. Therefore, it is difficult to provide accurate reference and effective guidance for deep sea engineering design. In order to solve the problems, the invention provides a combined measuring system and method for thixotropy of deep sea soft clay from the viewpoints of reducing deep sea environment, improving test precision, reducing adverse disturbance and the like. Compared with the existing method, the method has the advantages of complete evaluation indexes, high precision, quantitative analysis, good comprehensiveness and the like, and has important referential significance for the comprehensive evaluation and in-depth research of the thixotropic property of the deep-sea soft clay.
Disclosure of Invention
In order to overcome the defects of the existing measuring means, the invention provides a deep sea soft clay thixotropy joint determination system and a deep sea soft clay thixotropy joint determination method. The method utilizes the hydraulic source and the temperature controller to simulate the deep-sea low-temperature high-pressure environment, and utilizes the micro shear rheometer, the bending element wafer and the electrode element to jointly determine the changes of the shear strength, the shear modulus and the resistivity of the soil body along with the time in the thixotropic process. The invention has the advantages of complete evaluation index, high precision, quantitative analysis, good comprehensiveness and the like.
In order to realize the purpose, the technical scheme of the invention is as follows:
a combined measuring system for thixotropy of deep sea soft clay comprises a micro shear rheometer 1, a loading platform 2, a temperature control autoclave 3, a water depth simulation system, a resistivity test system, a temperature control system and a shear modulus test system.
The loading platform 2 comprises a cross beam 2-1, a supporting upright 2-2 and a platform base 2-3. Wherein, the center of the platform base 2-3 is provided with a limit groove 2-5 for installing a temperature control high-pressure kettle. Two sides of the limiting groove 2-5 are symmetrically fixed with two supporting upright posts 2-2, and the top ends of the two supporting upright posts 2-2 are connected through a cross beam 2-1.
The temperature control autoclave 3 comprises an upper top cover 3-1, a lower top cover 3-2 and a middle cylinder 3-3. Wherein, two ends of the middle cylinder 3-3 are respectively arranged on the circular grooves of the upper top cover 3-1 and the lower top cover 3-2, and the upper top cover 3-1 and the lower top cover 3-2 are connected through a limiting bolt 3-4. The lower top cover 3-2 is arranged in a limiting groove 2-5 of the platform base 2-3, and a bending element wafer 8, a pore pressure sensor 9 and an electrode element 10 are arranged on a circular groove of the lower top cover 3-2. The circular groove of the upper top cover 3-1 is provided with a bending element wafer 8, an electrode element 10 and a temperature sensor 11. The middle cylinder 3-3 is of a cylindrical structure, the side wall of the middle cylinder is provided with a water inlet 3-3-2 and a water outlet 3-3-1 respectively, and the water inlet 3-3-2 and the water outlet 3-3-1 are communicated through a spiral pipeline arranged on the side wall of the middle cylinder 3-3.
The micro shear rheometer 1 is used for testing the shear strength S of a soil body in the thixotropic processuTThe change of the generator comprises an excitation motor 1-1, a connecting rod 1-2 and a cross shearing blade 1-3; the excitation motor 1-1 is installed in the middle of a cross beam 2-1 of the loading platform, one end of a connecting rod 1-2 is connected with the excitation motor 1-1, and the other end of the connecting rod sequentially penetrates through the cross beam 2-1 and an upper top cover 3-1 to be connected with a cross shearing blade 1-3. Wherein, the cross shearing blades 1-3 can be selected and replaced according to the intensity of soil mass.
The water depth simulation system comprises a hydraulic source 4, a high-pressure pipeline 4-1 and a pore pressure sensor 9 which are sequentially connected, and is used for providing hydrostatic pressure to simulate water depth.
The resistivity testing system comprises electrode elements 10 and an impedance analyzer 5, wherein the electrode elements 10 on the upper top cover and the lower top cover are connected with the impedance analyzer 5 and used for testing the resistivity change in the thixotropic process of a soil body.
The temperature control system comprises a cooling circulator 6 and a temperature sensor 11, the temperature sensor 11 on the upper top cover 3-1 is connected with the cooling circulator 6, and the cooling circulator 6 is connected with a water inlet 3-3-2 and a water outlet 3-3-1 on the middle cylinder 3-3 through a heat insulation pipeline 6-1 and is used for simulating a deep sea low-temperature environment and ensuring the constant temperature of the soil sample in the test process.
The shear modulus testing system comprises an oscilloscope 7 and a bending element wafer 8, wherein the bending element wafers 8 on the upper top cover and the lower top cover are both connected with the oscilloscope 7 and used for testing the change of the shear modulus in the thixotropic process of the soil body.
A combined testing method for thixotropy of deep sea soft clay comprises the following steps:
step 1: installation test soil sample
Firstly, a lower top cover 3-2 of a temperature control high-pressure kettle 3 is arranged on a loading platform 2, and a bending element wafer 8, a pore pressure sensor 9 and an electrode element 10 are arranged on the lower top cover 3-2; further installing a temperature-controlled autoclave middle cylinder 3-3, placing a test soil sample in the middle cylinder 3-3, and inserting the cross-shaped shearing blades 1-3.
Then, the upper top cover 3-1 of the temperature-controlled autoclave is provided with a bending element wafer 8, an electrode element 10 and a temperature sensor 11, and the temperature-controlled autoclave 3 is assembled through a limit screw to check the tightness.
Then connecting the cooling circulator 6 with a water inlet 3-3-2 and a water outlet 3-3-1 of a cylinder 3-3 in the temperature control high-pressure autoclave through a heat insulation pipeline 6-1, and connecting a temperature sensor 11 with the cooling circulator 6; connecting a pore pressure sensor 9 with a hydraulic source 4 through a high-pressure pipeline 4-1; connecting the bending element wafer 8 with an oscilloscope 7, and connecting an electrode element 10 with an impedance analyzer 5; and testing the effect of switching on after the connection of each system is finished.
And finally, installing the excitation motor 1-1 on the cross beam 2-1 and connecting the cross shearing blades 1-3 through the connecting rods 1-2.
And 2, step: the water depth simulation system and the temperature control system are matched to simulate the specific temperature and pressure environment of the deep sea.
Simulating a high hydrostatic pressure environment of deep sea by using a water depth simulation system: the hydraulic pressure of the high-pressure pipeline 4-1 is controlled by the hydraulic source 4 to simulate the set water depth pressure, the water pressure is applied to the soil body, and the pore pressure value in the soil body is monitored in real time through the pore pressure sensor 9.
Further cooperate and use temperature control system, the specific temperature environment in simulation deep sea: setting a preset temperature, refrigerating the cooling liquid by using a cooling circulator 6, wherein the cooling liquid enters from a water inlet 3-3-2 on a middle cylinder 3-2 and flows out from a water outlet 3-3-1, and the temperature of the soil body is monitored by a temperature sensor 11.
And carrying out the next test after the pressure and temperature environment of the soil body reach set values.
And step 3: in the thixotropic test process, the resistivity and the change of the shear modulus of the soil body are continuously tested in real time by using the resistivity test system and the shear modulus test system. The method specifically comprises the following steps:
applying voltage to the soil body by using the electrode element 10, obtaining the resistance of the soil body by using the impedance analyzer 5, and monitoring the change of the resistivity in real time in the thixotropic process of the soil body; the shear modulus was calculated using the waveform displayed on the oscilloscope 7 by emitting and receiving ultrasonic waves from the flexor crystal 8.
And 4, step 4: the soil body strength at a specific moment is tested by using the micro shear rheometer 1, and the thixotropic strength ratio N is calculatedT：
Wherein S isu0The shear strength of undisturbed soil can be obtained by a triaxial shear test; suTFor shear strength, the calculation formula is as follows:
wherein M is the cross shear plate test torque, and D and H are the width and height of the cross shear plate respectively.
And 5: and 3, establishing a dimensionless thixotropic strength ratio and a functional relation between the normalized shear modulus and the normalized resistivity by utilizing the resistivity and the shear modulus obtained in the step 3 through a normalization method:
wherein the content of the first and second substances,
in order to be a normalized shear modulus,
to normalize resistivity.
The invention has the beneficial effects that: the invention provides a combined determination system and method for thixotropy of deep sea soft clay on the basis of reducing the actual high-pressure and low-temperature environment of deep sea, overcomes the defects of the existing measurement means, and has the advantages of complete evaluation indexes, high precision, quantitative analysis, good comprehensiveness and the like.
Drawings
FIG. 1 is a schematic view showing the overall configuration of the measurement system of the present invention.
Fig. 2 is a schematic structural diagram of the loading platform.
FIG. 3 is a schematic diagram of the structure of the upper head of the temperature-controlled autoclave.
FIG. 4 is a schematic diagram of the construction of the middle cylinder of the temperature controlled autoclave.
FIG. 5 is a schematic view of the construction of the lower head of a temperature controlled autoclave.
Fig. 6 is a schematic view of a micro shear rheometer arrangement.
In the figure: 1, a miniature shear rheometer, 1-1 of an excitation motor, 1-2 of connecting rods and 1-3 of cross shear blades; 2, a loading platform, 2-1 cross beams, 2-2 supporting upright columns, 2-3 platform bases, 2-4 wiring channels and 2-5 limiting grooves; 3, controlling the temperature of the autoclave, 3-1, installing a top cover, 3-1-1 limiting bolt holes A, 3-1-2 connecting rod limiting holes, 3-1-3 sensor installing holes A, 3-2 lower top covers and 3-2-1 limiting bolt holes B; 3-2-2 sensor mounting holes B; 3-2-3 wiring channel, 3-3 middle cylinder, 3-3-1 water outlet, 3-3-2 water inlet and 3-4 limit bolt; 4 hydraulic source, 4-1 high pressure pipeline; 5 an impedance analyzer; 6 cooling circulator, 6-1 heat preservation pipeline; 7, an oscilloscope; 8 bending the element wafer; a 9-hole pressure sensor; 10 an electrode element; 11 temperature sensor.
Detailed Description
The following examples and drawings are included to further illustrate the embodiments of the present invention and are not intended to limit the invention thereto.
As shown in fig. 1, a combined determination system for thixotropy of deep sea soft clay comprises a micro shear rheometer 1, a loading platform 2, a temperature control autoclave 3, a water depth simulation system, a resistivity test system, a temperature control system and a shear modulus test system.
The loading platform 2 comprises a cross beam 2-1, a supporting upright 2-2 and a platform base 2-3. Wherein, the center of the platform base 2-3 is provided with a limit groove 2-5 for installing a temperature control autoclave. Two sides of the limiting groove 2-5 are symmetrically fixed with two supporting columns 2-2, and the top ends of the two supporting columns 2-2 are connected through a cross beam 2-1.
The temperature control autoclave 3 comprises an upper top cover 3-1, a lower top cover 3-2 and a middle cylinder 3-3. Wherein, two ends of the middle cylinder 3-3 are respectively arranged on the circular grooves of the upper top cover 3-1 and the lower top cover 3-2, and the upper top cover 3-1 is connected with the lower top cover 3-2 through a limit bolt 3-4. The lower top cover 3-2 is arranged in a limiting groove 2-5 of the platform base 2-3, and a bending element wafer 8, a pore pressure sensor 9 and an electrode element 10 are arranged on a circular groove of the lower top cover 3-2. The upper top cover 3-1 is provided with a bending element wafer 8, an electrode element 10 and a temperature sensor 11 on a circular groove. The middle cylinder 3-3 is of a cylindrical structure, the side wall of the middle cylinder is provided with a water inlet 3-3-2 and a water outlet 3-3-1 respectively, and the water inlet 3-3-2 and the water outlet 3-3-1 are communicated through a spiral pipeline arranged on the side wall of the middle cylinder 3-3.
The micro shear rheometer 1 comprises an excitation motor 1-1, a connecting rod 1-2 and cross shear blades 1-3; the excitation motor 1-1 is installed in the middle of a cross beam 2-1 of the loading platform, one end of a connecting rod 1-2 is connected with the excitation motor 1-1, and the other end of the connecting rod sequentially penetrates through the cross beam 2-1 and an upper top cover 3-1 to be connected with a cross shearing blade 1-3.
The water depth simulation system comprises a hydraulic source 4, a high-pressure pipeline 4-1 and a pore pressure sensor 9 which are connected in sequence.
The resistivity test system comprises electrode elements 10 and an impedance analyzer 5, wherein the electrode elements 10 on the upper top cover and the lower top cover are connected with the impedance analyzer 5 and used for testing the resistivity change in the thixotropic process of a soil body.
The temperature control system comprises a cooling circulator 6 and a temperature sensor 11, the temperature sensor 11 on the upper top cover 3-1 is connected with the cooling circulator 6, and the cooling circulator 6 is connected with a water inlet 3-3-2 and a water outlet 3-3-1 on the middle cylinder 3-3 through a heat preservation pipeline 6-1.
The shear modulus test system comprises an oscilloscope 7 and a bending element wafer 8, wherein the bending element wafers 8 on the upper top cover and the lower top cover are connected with the oscilloscope 7 and are used for testing the change of the shear modulus in the thixotropic process of a soil body.
The method for performing the deep sea soft clay thixotropy combined test by adopting the measuring system comprises the following steps:
step 1: installation test soil sample
Firstly, a lower top cover 3-2 of a temperature control high-pressure kettle 3 is arranged on a loading platform 2, and a bending element wafer 8, a hole pressure sensor 9 and an electrode element 10 are arranged on the lower top cover 3-2; and further installing a temperature-controlled autoclave middle cylinder 3-3, placing a test soil sample in the middle cylinder 3-3, and inserting the cross shearing blades 1-3. .
Then, the bending element wafer 8, the temperature sensor 11 and the electrode element 10 are mounted on the upper top cover 3-1 of the temperature-controlled autoclave, and the temperature-controlled autoclave is assembled by a limit screw to check the tightness.
Then connecting the cooling circulator 6 to a temperature control autoclave middle cylinder 3-3 by using a heat insulation pipeline 6-1, and connecting a temperature sensor 11 with the cooling circulator 6; connecting a hydraulic source 4 with a pore pressure sensor 9 through a high-pressure pipeline 4-1; connecting the bending element wafer 8 with an oscilloscope 7, and connecting an electrode element 10 with an impedance analyzer 5; and testing the effect of switching on after the connection of each system is finished.
And finally, installing the excitation motor 1-1 on the cross beam 2-1 and connecting the cross shearing blades through the connecting rod 1-2.
And 2, step: and controlling the temperature of the soil body to 4 ℃ by using a temperature control system, applying hydrostatic pressure to the soil body by using a water depth simulation system, and simulating a preset water depth environment.
And carrying out the next thixotropic test after the temperature and pore pressure of the soil body are stable.
And step 3: in the thixotropic test process, the shear modulus G is continuously monitored by a shear modulus test system and a resistivity test systemTAnd resistivity ρTChange over time.
And 4, step 4: starting the micro shear rheometer 1 after the preset time is reached, and testing the shear strength S of the soil body uT：
Wherein M is the test torque of the cross shear plate, and D and H are the width and height of the cross shear plate respectively.
Further calculating the thixotropic strength ratio N of the soil bodyT：
And 5: further utilizing the obtained resistivity, and establishing a dimensionless thixotropic strength ratio N by a normalization methodTAnd normalized shear modulus
And normalized resistivity
The functional relationship of (a) is used for guiding engineering practice:
Claims (3)
1. the combined determination system for the thixotropy of the deep sea soft clay is characterized by comprising a micro shear rheometer (1), a loading platform (2), a temperature control high-pressure kettle (3), a water depth simulation system, a resistivity test system, a temperature control system and a shear modulus test system;
the loading platform (2) comprises a cross beam (2-1), a supporting upright post (2-2) and a platform base (2-3); wherein, the center of the platform base (2-3) is provided with a limiting groove (2-5), two sides of the limiting groove (2-5) are symmetrically fixed with two supporting upright posts (2-2), and the top ends of the two supporting upright posts (2-2) are connected through a cross beam (2-1);
the temperature control high-pressure kettle (3) comprises an upper top cover (3-1), a lower top cover (3-2) and a middle cylinder (3-3); wherein, two ends of the middle cylinder (3-3) are respectively arranged on the circular grooves of the upper top cover (3-1) and the lower top cover (3-2), and the upper top cover (3-1) is connected with the lower top cover (3-2) through a limit bolt (3-4);
The lower top cover (3-2) is arranged in a limiting groove (2-5) of the platform base (2-3), and a bending element wafer (8), a hole pressure sensor (9) and an electrode element (10) are arranged on a circular groove of the lower top cover (3-2); a bending element wafer (8), an electrode element (10) and a temperature sensor (11) are arranged on the circular groove of the upper top cover (3-1); the middle cylinder (3-3) is of a cylindrical structure, and the side wall of the middle cylinder is provided with a water inlet (3-3-2) and a water outlet (3-3-1) which are communicated through a spiral pipeline arranged on the side wall of the middle cylinder;
the miniature shear rheometer (1) comprises an excitation motor (1-1), a connecting rod (1-2) and a cross shear blade (1-3); the device comprises an excitation motor (1-1), a connecting rod (1-2), a cross shear blade (1-3), an upper top cover (3-1) and a cross shear blade, wherein the excitation motor (1-1) is arranged in the middle of a cross beam (2-1) of a loading platform, one end of the connecting rod (1-2) is connected with the excitation motor (1-1), and the other end of the connecting rod sequentially penetrates through the cross beam (2-1) and the upper top cover (3-1) to be connected with the cross shear blade (1-3);
the water depth simulation system is used for providing hydrostatic pressure to simulate water depth and comprises a hydraulic source (4), a high-pressure pipeline (4-1) and a pore pressure sensor (9) which are connected in sequence;
the resistivity testing system is used for testing the resistivity change in the thixotropic process of a soil body and comprises electrode elements (10) and an impedance analyzer (5), wherein the electrode elements (10) on the upper top cover and the lower top cover are connected with the impedance analyzer (5);
The temperature control system comprises a cooling circulator (6) and a temperature sensor (11); a temperature sensor (11) on the upper top cover (3-1) is connected with a cooling circulator (6), and the cooling circulator (6) is connected with a water inlet (3-3-2) and a water outlet (3-3-1) on the middle cylinder through a heat-insulating pipeline (6-1);
the shear modulus testing system is used for testing the change of the shear modulus in the thixotropic process of a soil body and comprises an oscilloscope (7) and a bending element wafer (8); the bending element wafers (8) on the upper and lower top covers are connected with an oscilloscope (7).
2. The testing method of the deep sea soft clay thixotropy combined determination system according to claim 1, characterized in that the testing method comprises the following steps:
step 1: installing a test soil sample;
and 2, step: the cooperation is used depth of water analog system and temperature control system, and the specific temperature in simulation deep sea and pressure environment specifically are:
simulating a high hydrostatic pressure environment of the deep sea by using a water depth simulation system: the hydraulic pressure of the high-pressure pipeline (4-1) is controlled by the hydraulic source (4) to simulate the set water depth pressure, the water pressure is applied to the soil body, and the internal pore pressure value of the soil body is monitored in real time by the pore pressure sensor (9);
further cooperate and use temperature control system, the specific temperature environment in simulation deep sea: setting a preset temperature, refrigerating cooling liquid by using a cooling circulator (6), wherein the cooling liquid enters from a water inlet (3-3-2) on the middle cylinder and flows out from a water outlet (3-3-1), and monitoring the temperature of a soil body by using a temperature sensor (11);
Carrying out the next test after the pressure and temperature environment of the soil body reach set values;
and step 3: in the thixotropic test process, the resistivity and the change of the shear modulus of the soil body are continuously tested in real time by using a resistivity test system and a shear modulus test system, and the method specifically comprises the following steps:
applying voltage to the soil body by using the electrode element (10), obtaining the resistance of the soil body by using the impedance analyzer (5), and monitoring the change of the resistivity in real time in the thixotropic process of the soil body; transmitting and receiving ultrasonic waves by using the bent element crystal (8), and calculating the shear modulus by using a waveform displayed by an oscilloscope (7);
and 4, step 4: testing the soil strength at a specific moment by using a micro shear rheometer, and calculating the thixotropic strength ratio NT：
Wherein S isu0The shear strength of undisturbed soil is obtained by a triaxial shear test; suTFor shear strength, the calculation formula is as follows:
wherein M is the testing torque of the cross shear plate, and D and H are the width and height of the cross shear plate respectively;
and 5: and 3, establishing a dimensionless thixotropic strength ratio and a functional relation between the normalized shear modulus and the normalized resistivity by utilizing the resistivity and the shear modulus obtained in the step 3 through a normalization method:
wherein the content of the first and second substances,
in order to be a normalized shear modulus, 
To normalize the resistivity.
3. The test method according to claim 2, wherein the specific process of step 1 is:
firstly, a lower top cover (3-2) of a temperature control autoclave is arranged on a loading platform (2), and a bending element wafer (8), a pore pressure sensor (9) and an electrode element (10) are arranged on the lower top cover (3-2); further installing a temperature control autoclave middle cylinder (3-3), placing a test soil sample in the middle cylinder (3-3), and inserting a cross shearing blade (1-3);
then, a bending element wafer (8), an electrode element (10) and a temperature sensor (11) are arranged on an upper top cover (3-1) of the temperature control high-pressure autoclave, the temperature control high-pressure autoclave is assembled through a limiting screw rod, and the tightness is checked;
then connecting the cooling circulator (6) with a water inlet (3-3-2) and a water outlet (3-3-1) of a cylinder in the temperature control high-pressure kettle, and connecting a temperature sensor (11) with the cooling circulator (6); connecting a pore pressure sensor (9) with a hydraulic source (4) through a high-pressure pipeline (4-1); connecting the bending element wafer (8) with an oscilloscope (7), and connecting the electrode element (10) with an impedance analyzer (5); testing the effect of switching on after the connection of each system is finished;
and finally, mounting the excitation motor (1-1) on the cross beam (2-1) and connecting the cross shearing blade (1-3) through the connecting rod (1-2).
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| CN202110798189.3A CN113552006B (en) | 2021-07-15 | 2021-07-15 | Deep sea soft clay thixotropy combined determination system and method |
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