CN-122016508-A - Device and method for testing mechanical properties and shear modulus of soil body by combining bending element and true triaxial

Abstract

The invention relates to the technical field of geotechnical tests, in particular to a device and a method for testing the mechanical properties and shear modulus of soil bodies by combining bending elements and true triaxial. The device comprises a true triaxial test system and a bending element test system, wherein the true triaxial test system has independent three-way loading capacity, and the bending element system is integrated in a loading cap. During the test, the cube sample is loaded in a true triaxial system according to a set path, after each stage of load is stable, a bending element system is started to test shear wave speed, and deformation, load and pore pressure data of the sample are synchronously collected. The stress-strain relation and the maximum shear modulus of the soil body under different stress states can be synchronously obtained through one-time test, and the static and dynamic parameter integrated test is realized. The invention avoids errors caused by the difference between the duplicate sample and the test conditions, and remarkably improves the test efficiency and the data consistency.

Inventors

• WANG YANLI
• DING SHAOLIN
• WANG LEI
• ZHANG TING
• Zhen Yunyan
• DAI XIANREN
• LIU CHUNPENG
• PAN JIAJUN
• ZUO YONGZHEN
• LU YIWEI
• XU HAN
• Luo Zequan
• YI SHUN

Assignees

• 长江水利委员会长江科学院

Dates

Publication Date

20260512

Application Date

20260129

Claims (10)

1. 1. A device for testing the mechanical properties and the shear modulus of a soil body by combining a bending element and a true triaxial, which is characterized by comprising: The true triaxial test system comprises a pressure chamber (4), a cavity arranged in the pressure chamber (4) and used for accommodating a cube sample (12), a loading mechanism for independently applying load to the cube sample (12) in three orthogonal directions, a servo control module for controlling the loading mechanism, and a measurement and data acquisition module for acquiring test data; The bending element testing system comprises at least two pairs of bending elements (10), wherein one pair of the bending elements (10) are respectively embedded into loading caps (8) positioned at the vertical two ends of a cube sample (12), and the other pair of the bending elements (10) are respectively embedded into the loading caps (8) positioned at the horizontal two ends of the cube sample (12); The loading cap (8) is connected with the loading mechanism, and the bending element (10) is electrically connected with the measuring and data acquisition module.
2. 2. The apparatus according to claim 1, wherein: the bottom of the pressure chamber (4) is provided with a bottom water inlet (11) for water injection saturation and back pressure supply, and the top of the pressure chamber is provided with an air source interface (6) for applying confining pressure.
3. 3. The apparatus according to claim 2, wherein: The loading cap (8) or the base at the bottom of the cube sample (12) is provided with a Kong Yajin water gap (24) and a saturated water inlet (22) which are mutually independent, the Kong Yajin water gap (24) is connected with the pore pressure sensor (18) through a pipeline, and the saturated water inlet (22) is connected with an external water source control valve through a pipeline.
4. 4. A device according to claim 3, characterized in that: the loading cap (8) at the top of the cube sample (12) is provided with a back pressure water inlet and outlet (20) for draining water or applying back pressure during sample saturation and test.
5. 5. The apparatus according to claim 1, wherein: Square permeable stones are arranged between the top and the bottom of the cube sample (12) and the loading cap (8), and a latex film is wrapped outside the cube sample (12).
6. 6. The apparatus according to claim 1, wherein: The loading mechanism comprises a vertical loading rod and a horizontal loading rod, the vertical loading rod (1) is connected with a loading cap (8) at the top through a load sensor (7), the horizontal loading rod (1) is connected with the horizontal loading cap (8) through the load sensor (7), and a compressible force transmission plate (9) is arranged between the horizontal loading cap (8) and a cube sample (12).
7. 7. A method of testing the mechanical properties and shear modulus of a soil body using the apparatus of any one of claims 1 to 6, comprising the steps of: S1, sample preparation and system assembly Preparing a cube sample (12), wrapping a latex film outside the cube sample, placing the cube sample on a base of an inner cavity of the pressure chamber (4), installing a top and a horizontal loading cap (8), and tightly sealing the latex film between the cube sample (12) and the loading cap (8); s2, pressure chamber sealing and system initialization The pressure chamber (4) is closed, air is injected into the pressure chamber (4) through a water inlet (11) at the bottom, and air is discharged, and after the pressure chamber is filled with the air, the set confining pressure is applied through an air source interface (6) at the top; s3, combined loading and data acquisition After the sample is deformed stably under each stage of load, a bending element testing system is started, a bending element (10) is excited to generate shear waves and receive signals, and meanwhile, displacement, load and pore pressure data of the sample are collected through a measuring module; s4, parameter calculation and analysis Calculating the stress-strain relation of the cube sample (12) in different stress states based on the displacement and load data acquired in the step S3 to acquire a soil body mechanical characteristic parameter; S5, continuously testing until the sample is destroyed Repeating the steps S3 and S4 until the cube sample (12) reaches the damage standard or the preset loading path is completed, and ending the test.
8. 8. The method according to claim 7, wherein: In the step S2, the sample is saturated by adopting a water head saturation or back pressure saturation method, and the saturation completion standard is that the B value measured by the pore pressure sensor (18) is not lower than 0.95.
9. 9. The method according to claim 7, wherein: In the step S3, the judging standard of the deformation stability of the sample to be tested under each stage of load is that the axial deformation increment of the sample is smaller than 0.001 mm in 10 minutes.
10. 10. The method according to claim 7, wherein: in step S4, the maximum shear modulus G max is calculated by the formula gmax=ρv s 2 , where ρ is the sample density and V s is the shear wave velocity calculated based on the bending element signal head wave arrival time difference and propagation distance.

Description

Device and method for testing mechanical properties and shear modulus of soil body by combining bending element and true triaxial Technical Field The invention relates to the technical field of geotechnical tests, in particular to a device and a method for testing the mechanical properties and shear modulus of soil bodies by combining bending elements and true triaxial. Background At present, the geotechnical triaxial apparatus is a geotechnical test apparatus for truly simulating a three-way stress state of a soil body, the geotechnical triaxial apparatus adopts a cube sample and is independently loaded from 3 main stress directions, so that uniform stress and strain are generated in the soil body, and compared with a conventional triaxial test, the geotechnical triaxial test can more comprehensively and truly reflect the deformation rule of a soil body unit in the three-way stress state, and can be used for researching the stress-strain characteristics of the soil body, verifying and developing a soil body constitutive model and the like. The bending element is an indoor test method capable of simply and rapidly determining the shear wave speed of the soil body, and the shear modulus of the soil body can be calculated through the shear wave speed, and the bending element is simple in principle and convenient to test and is frequently installed on geotechnical test instruments such as a consolidation instrument, a dynamic triaxial apparatus and a resonance column in recent years. The inventor of the application finds that the true triaxial test can obtain the mechanical property of the soil body, the bending element system can obtain the shear modulus of the soil body, and the static and dynamic parameters of the soil body can be obtained simultaneously in a group of test processes by combining the true triaxial test and the shear modulus of the soil body. Disclosure of Invention Aiming at the defects existing in the prior art, the invention aims to provide a device for testing the mechanical properties and the shear modulus of a soil body by combining a bending element and a true triaxial, which can simultaneously meet the requirements of testing the mechanical properties and the shear modulus of the soil body. The aim of the invention is achieved by the following technical scheme: a device for testing the mechanical properties and the shear modulus of a soil body by combining a bending element and a true triaxial, which is characterized by comprising: The true triaxial test system comprises a pressure chamber, a cavity arranged in the pressure chamber and used for accommodating a cubic sample, a loading mechanism for independently applying load to the cubic sample in three orthogonal directions, a servo control module used for controlling the loading mechanism, and a measurement and data acquisition module used for acquiring test data; The bending element testing system comprises at least two pairs of bending elements, wherein one pair of bending elements are respectively embedded into loading caps positioned at the two vertical ends of the cube sample, and the other pair of bending elements are respectively embedded into loading caps positioned at the two horizontal ends of the cube sample; the loading cap is connected with the loading mechanism, and the bending element is electrically connected with the measuring and data acquisition module. Further, the bottom of the pressure chamber is provided with a bottom water inlet for water injection saturation and back pressure supply, and the top of the pressure chamber is provided with an air source interface for applying confining pressure. Further, a Kong Yajin water gap and a saturated water inlet which are mutually independent are arranged on the loading cap or the base which is positioned at the bottom of the cube sample, the Kong Yajin water gap is connected with the pore pressure sensor through a pipeline, and the saturated water inlet is connected with an external water source control valve through a pipeline. Further, a back pressure water inlet and outlet is arranged on a loading cap positioned at the top of the cube sample and is used for draining water or applying back pressure in the saturation and test process of the sample. Further, square permeable stones are arranged between the top and the bottom of the cube sample and the loading cap, and the outside of the cube sample is wrapped with a latex film. Further, the loading mechanism comprises a vertical loading rod and a horizontal loading rod, the vertical loading rod is connected with a loading cap at the top through a load sensor, the horizontal loading rod is connected with the horizontal loading cap through the load sensor, and a compressible force transmission plate is arranged between the horizontal loading cap and the cube sample. A method for testing the mechanical properties and shear modulus of a soil body using the apparatus as described above, comprising the steps of: S1, sample p