Multi-functional oedometer for accurately measuring structural parameters of soil

Abstract

The application discloses a multifunctional consolidation instrument for precisely measuring soil structure parameters. A pressure spout is arranged above a base, a rigid guard ring is arranged between the pressure spout and the base to support the pressure spout and the base, and a soil sample cavity is formed, a pair of piezoelectric bending elements are arranged on the circular bosses of the pressure spout and the base; a lower annular water-permeable stone is arranged on the top surface of the base in the soil sample cavity, and an upper annular water-permeable stone is arranged on the bottom surface of the pressure spout in the soil sample cavity, wherein the upper annular water-permeable stone is located directly above the lower annular water-permeable stone; a pair of piezoelectric bending elements are arranged on the inner walls of one side of the rigid guard ring, and two diaphragm pressure gauges are respectively arranged on the inner walls of the other two sides of the rigid guard ring. The shear wave velocity and the lateral earth pressure of the soil sample are directly measured, and the precise determination of the soil structure parameters is realized.

Description

Technical Field

[0001] This invention relates to an instrument for measuring geotechnical parameters in the field of geotechnical testing, and in particular to a multifunctional consolidation instrument for accurately measuring the structural parameters of soil, especially for measuring shear wave velocity and lateral earth pressure in horizontal and vertical soil planes. Background Technology

[0002] Natural soil is a complex product of rocks formed through physical, chemical, and biological weathering, followed by transportation and deposition. It is characterized by its fragmentation and multiphase nature, and possesses structural properties. Specifically, soil structure refers to the comprehensive characteristics of soil particles or aggregates, as well as the size, shape, arrangement, and connections between them and their pores. Structure is a crucial feature of soil and significantly influences its mechanical behavior. Extensive research by scholars both domestically and internationally aims to identify parameters that directly reflect the essence of structure and to establish a link between structure and soil deformation-strength dynamics. To study soil structure, scholars use certain macroscopic mechanical properties of soil to characterize its structural level; for example, the shear modulus G of soil is closely related to its structure.

[0003] When the soil strain is less than 10 -5 When the strain is less than 10, the soil particle skeleton only undergoes elastic deformation, and the shear modulus remains essentially unchanged. However, when the strain is greater than 10... -5 At this time, the soil particle skeleton begins to undergo plastic deformation, and the shear modulus decreases with increasing strain. Therefore, strains less than 10... -5 The shear modulus at which the strain is small is called the small strain shear modulus G. max The low-strain shear modulus can characterize the structural level of soil to some extent. According to the elastic wave theory, the shear modulus G is related to the shear wave velocity V. S The relationship between them is: Where ρ is the mass density of the soil. Therefore, elastic wave velocity testing methods, represented by shear wave velocity, have become one of the important methods for evaluating the structural level of soil in the field and in the laboratory.

[0004] Currently, shear wave velocity is mainly measured using piezoelectric bending elements. The main structure of a piezoelectric bending element consists of two square piezoelectric ceramic sheets stacked together with a metal reinforcing layer in between, enabling the exchange of mechanical energy and electrical energy. During testing, a pair of piezoelectric bending elements are embedded in the soil, facing each other. The excitation voltage causes the piezoelectric bending element to bend and deform, transmitting shear waves to the surrounding area. The receiving piezoelectric bending element receives the transmitted shear wave signal, and the propagation time is obtained from the time difference t between the excitation and reception signals. Combined with the embedment distance L between the piezoelectric bending elements, the velocity is calculated using the formula V. S The shear wave velocity is calculated using the formula L / t.

[0005] Foreign scholars, represented by Hardin, have studied the small-strain shear modulus G of soil. max The relationship between porosity e, effective stress σ′, and overconsolidation ratio (OCR) was studied and quantitatively expressed as: Among them, A ij Let F(e) be a dimensionless structural parameter, and P be a void ratio function. a For reference stress, σ′ i and σ′ j Let n be the effective stress in the measurement plane, n be the stress exponent, and k be the overconsolidation ratio exponent. This is the famous Hardin formula. Generally, we only study the small-strain shear modulus in the horizontal and vertical planes. The small-strain shear modulus in the horizontal plane is expressed as: σ′ h The effective stress is horizontal (lateral earth pressure), at which point the vibration direction of the particles and the propagation direction of the wave are both horizontal; the small strain shear modulus in the vertical plane is expressed as: σ′ v This represents the effective vertical stress, where the particle vibration direction is horizontal while the wave propagation direction is vertical. The small-strain shear modulus measured in the horizontal and vertical planes is often different.

[0006] Currently, scholars both domestically and internationally commonly use the small strain shear modulus G. max It is used to characterize the structural level of soil, but this index comprehensively reflects the soil's structure, pore state, and stress level, making it a coupled index. The dimensionless structural parameter A... hh Or A vh This allows for the decoupling of soil structure from pore state and stress level, and is a normalized index. Compared to the small-strain shear modulus, dimensionless structural parameters can eliminate interference from other factors and more accurately characterize the soil's structural level. According to the Hardin formula described above, obtaining accurate soil structural parameters requires accurate measurement of the small-strain shear modulus G in both the horizontal and vertical planes. max And the effective horizontal stress (lateral earth pressure) σ′ h and vertical effective stress σ′ v .

[0007] Currently, soil structural parameter A hh Or A vh The effective vertical stress σ′ is usually obtained through approximate calculation. v In reality, the stress applied in the experimental design can be directly obtained using the loading instrument; it is a precise value. However, the effective horizontal stress σ′ is not the same. h σ′ is usually obtained through estimation. h =K0σ′ vK0 is the coefficient of earth pressure at rest, which is generally determined according to an empirical formula to ensure that the calculated σ′ h There is a significant error between the actual value and the measured value. Furthermore, existing consolidation apparatuses lack the capability to simultaneously measure shear wave velocities in both the horizontal and vertical planes of the soil sample. Therefore, based on current testing equipment and methods, accurate structural parameter A cannot be directly obtained. hh Or A vh . Summary of the Invention

[0008] This invention addresses the shortcomings of existing geotechnical testing instruments by providing a multifunctional consolidation apparatus equipped with a piezoelectric bending element and a thin-film pressure gauge. The piezoelectric bending element and the thin-film pressure gauge measure the shear wave velocity and lateral earth pressure of the soil sample, respectively, thereby achieving accurate determination of the structural parameter A of the soil. ij .

[0009] The present invention achieves the above objectives through the following technical solutions:

[0010] This invention includes a base, a rigid retaining ring, a pressure cap, an annular permeable stone, a piezoelectric bending element, and a thin-film pressure gauge. The pressure cap is located above the base, and the pressure cap and the base are supported by the rigid retaining ring. The pressure cap, the base, and the rigid retaining ring form a relatively closed inner cavity as a soil sample chamber, which is filled with soil sample. A circular boss is provided in the middle of the top surface of the base and the bottom surface of the pressure cap within the soil sample chamber. A first piezoelectric bending element exciter is installed in the middle of the circular boss of the pressure cap, and a first piezoelectric bending element receiver is installed in the middle of the circular boss of the base. The first piezoelectric bending element receiver is located at the first piezoelectric bending element exciter. Directly below; the top surface of the base located around the circular boss in the soil sample cavity is equipped with a lower annular permeable stone, and the bottom surface of the pressure cap located around the circular boss in the soil sample cavity is equipped with an upper annular permeable stone, with the upper annular permeable stone located directly above the lower annular permeable stone; the inner walls on both sides of the rigid retaining ring in one radial direction are respectively equipped with a second piezoelectric bending element exciter and a second piezoelectric bending element receiver, which are symmetrically arranged on both sides of the central axis of the rigid retaining ring; two thin-film pressure gauges are respectively installed on the inner walls on both sides of the rigid retaining ring in another radial direction.

[0011] The base of the first piezoelectric bending element receiver is embedded in the mounting groove at the center of the circular boss of the base, and the cantilever end of the first piezoelectric bending element receiver is inserted into the soil sample in the soil sample cavity with the cantilever end facing upward; the base of the first piezoelectric bending element exciter is embedded in the mounting groove at the center of the circular boss of the pressure cap, and the cantilever end of the first piezoelectric bending element exciter is inserted into the soil sample in the soil sample cavity with the cantilever end facing downward.

[0012] The first piezoelectric bending element receiver is electrically connected to an external testing system. The bottom of the mounting slot of the first piezoelectric bending element receiver on the base has a wiring hole for accessing the outside. The wire between the first piezoelectric bending element receiver and the testing system passes through the wiring hole. The first piezoelectric bending element exciter is also electrically connected to an external testing system. The bottom of the mounting slot of the first piezoelectric bending element exciter on the pressure cap has a wiring hole for accessing the outside. The wire between the first piezoelectric bending element exciter and the testing system passes through the wiring hole.

[0013] The bases of the second piezoelectric bending element exciter and the second piezoelectric bending element receiver are embedded in the mounting groove on the inner wall of the rigid protective ring, and the cantilever ends of the second piezoelectric bending element exciter and the second piezoelectric bending element receiver are horizontally inserted into the soil sample in the soil sample cavity.

[0014] The second piezoelectric bending element exciter is electrically connected to an external test system. The rigid retaining ring has a wiring hole for accessing the outside in the mounting groove of the second piezoelectric bending element exciter. The wire between the second piezoelectric bending element exciter and the test system passes through the wiring hole.

[0015] The second piezoelectric bending element receiver is electrically connected to an external testing system. The rigid retaining ring has a wiring hole for connecting to the outside in the mounting groove where the second piezoelectric bending element receiver is installed. The wire between the second piezoelectric bending element receiver and the testing system passes through the wiring hole.

[0016] The aforementioned diaphragm pressure gauge includes a sensing element and a terminal block. The sensing element is attached to the inner wall of a rigid retaining ring, and the terminal block is inserted into a pre-drilled hole in the base and leads out from the pre-drilled hole in the base to be electrically connected to an external measurement system.

[0017] The pressure cap bottom surface and the base top surface are provided with drainage channels that communicate with the outside, and the drainage channels are connected to the surface of the annular permeable stone.

[0018] The base of the first piezoelectric bending element receiver is provided with a shock-absorbing rubber sleeve between the walls of the mounting groove, and the first piezoelectric bending element receiver is wrapped by the shock-absorbing rubber sleeve; the base of the second piezoelectric bending element receiver is provided with a shock-absorbing rubber sleeve between the walls of the mounting groove, and the second piezoelectric bending element receiver is wrapped by the shock-absorbing rubber sleeve.

[0019] The long axis of the cantilever end of the first piezoelectric bending element exciter and the long axis of the cantilever end of the first piezoelectric bending element receiver are in the same plane.

[0020] The second piezoelectric bending element exciter and the second piezoelectric bending element receiver are arranged opposite each other along the diameter, and the long axis of the cantilever end of the second piezoelectric bending element exciter and the second piezoelectric bending element receiver are both in the vertical direction.

[0021] The beneficial effects of this invention are:

[0022] (1) The installation and waterproofing problems of the piezoelectric bending element on the inner wall of the consolidation apparatus were solved, ensuring the working performance of the piezoelectric bending element in high pressure and high humidity environments.

[0023] (2) It solves the problem of interference caused by shear waves propagating through non-soil media to wave velocity determination, and ensures the accuracy of shear wave velocity measurement.

[0024] (3) It solves the problem of measuring lateral earth pressure in the consolidation apparatus. The thickness of the thin film pressure gauge sensor is only 0.2 mm. It has the advantages of simple operation, high measurement accuracy and reliability, small impact on soil samples, and convenient installation and disassembly. Attached Figure Description

[0025] Figure 1 This is a front sectional view of the testing device;

[0026] Figure 2 This is a side sectional view of the testing device;

[0027] Figure 3 This is a top view of the base;

[0028] Figure 4 This is a bottom view of the pressure cap;

[0029] Figure 5 This is a top view of the rigid retaining ring;

[0030] Figure 6 This is a schematic diagram of a diaphragm pressure gauge;

[0031] Figure 7 This is a schematic diagram of a piezoelectric bending element.

[0032] In the diagram: 1-base; 2, 11-ring permeable stone; 3-soil sample chamber; 4, 8, 14, 19-wiring holes; 5, 12-piezoelectric bending element exciter; 6-thin film pressure gauge; 7-rigid retaining ring; 9-pressure cap; 10, 18-drainage channel; 13, 16-piezoelectric bending element receiver; 15, 17-shock-absorbing rubber sleeve; 20-reserved hole; 21, 22, 23, 24-mounting groove; 25-sensing plate; 26-wiring terminal; 27-cantilever end; 28-base. Detailed Implementation

[0033] The present invention will now be further described with reference to the accompanying drawings. The drawings are only schematic illustrations of the basic structure of the invention, and therefore only show the components relevant to the invention.

[0034] like Figure 1 and Figure 2As shown, the specific implementation includes a base 1, a rigid retaining ring 7, a pressure cap 9, an annular permeable stone 11, piezoelectric bending elements 5, 12, 13, 16, and a thin-film pressure gauge 6; the pressure cap 9 is located above the base 1, and the pressure cap 9 and the base 1 are connected and supported by the rigid retaining ring 7. The pressure cap 9, the base 1, and the rigid retaining ring 7 form a relatively closed inner cavity as a soil sample cavity 3, which is filled with soil sample; the lower end of the rigid retaining ring 7 can be embedded in the annular groove of the base 1.

[0035] A circular protrusion is provided in the middle of the top surface of the base 1 and the bottom surface of the pressure cap 9 inside the soil sample chamber 3. A first piezoelectric bending element exciter 12 is installed in the middle of the circular protrusion of the pressure cap 9, and a first piezoelectric bending element receiver 16 is installed in the middle of the circular protrusion of the base 1. The first piezoelectric bending element receiver 16 is located directly below the first piezoelectric bending element exciter 12, forming a first pair of piezoelectric bending elements.

[0036] like Figure 3 As shown, the base 28 of the first piezoelectric bending element receiver 16 is embedded in the mounting groove 21 at the center of the circular boss of the base 1, and the cantilever end 27 of the first piezoelectric bending element receiver 16 is inserted upward into the soil sample in the soil sample chamber 3; as Figure 4 As shown, the base 28 of the first piezoelectric bending element exciter 12 is embedded in the mounting groove 22 at the center of the circular boss of the pressure cap 9, and the cantilever end 27 of the first piezoelectric bending element exciter 12 is inserted downward into the soil sample in the soil sample cavity 3.

[0037] The first piezoelectric bending element receiver 16 is electrically connected to an external test system. The mounting groove 21 of the base 1 for mounting the first piezoelectric bending element receiver 16 has a wiring hole 19 at the bottom for accessing the outside. The wire between the first piezoelectric bending element receiver 16 and the test system passes through the wiring hole 19.

[0038] The first piezoelectric bending element exciter 12 is electrically connected to the external test system. The pressure cap 9 has a mounting slot 22 for mounting the first piezoelectric bending element exciter 12 with a wiring hole 8 at the bottom for accessing the outside. The wire between the first piezoelectric bending element exciter 12 and the test system passes through the wiring hole 8.

[0039] The top surface of the base 1, which is located inside the soil sample cavity 3 and around the circular protrusion, is provided with a lower annular permeable stone 2. The bottom surface of the pressure cap 9, which is located inside the soil sample cavity 3 and around the circular protrusion, is provided with an upper annular permeable stone 11. The upper annular permeable stone 11 is located directly above the lower annular permeable stone 2. The annular permeable stones are all encircled on the outside of the cylindrical protrusion.

[0040] A second piezoelectric bending element exciter 5 and a second piezoelectric bending element receiver 13 are respectively installed on the inner walls of the two sides in a radial direction inside the rigid retaining ring 7. The second piezoelectric bending element exciter 5 and the second piezoelectric bending element receiver 13 are arranged symmetrically on both sides of the central axis of the rigid retaining ring 7 to form a second pair of piezoelectric bending elements. In this way, the second pair of piezoelectric bending elements are installed opposite each other on the inner wall of the rigid retaining ring.

[0041] like Figure 5 As shown, the base 28 of the second piezoelectric bending element exciter 5 and the second piezoelectric bending element receiver 13 is embedded in the mounting grooves 23 and 24 on the inner wall of the rigid retaining ring 7, and the cantilever end 27 of the second piezoelectric bending element exciter 5 and the second piezoelectric bending element receiver 13 is horizontally inserted into the soil sample in the soil sample cavity 3.

[0042] The second piezoelectric bending element exciter 5 is electrically connected to the external test system. The rigid retaining ring 7 has a wiring hole 4 for connecting to the outside in the mounting groove 23 where the second piezoelectric bending element exciter 5 is installed. The wire between the second piezoelectric bending element exciter 5 and the test system passes through the wiring hole 4.

[0043] The second piezoelectric bending element receiver 13 is electrically connected to an external test system. The rigid retaining ring 7 has a wiring hole 14 for connecting to the outside in the mounting groove 24 where the second piezoelectric bending element receiver 13 is installed. The wire between the second piezoelectric bending element receiver 13 and the test system passes through the wiring hole 14.

[0044] Two diaphragm pressure gauges 6 are installed on the inner walls of the two sides in the other radial direction inside the rigid retaining ring 7.

[0045] like Figure 6 As shown, the diaphragm pressure gauge 6 includes a sensing element 25 and a terminal block 26. The sensing element 25 is attached to the inner wall of the rigid retaining ring 7, and the terminal block 26 is inserted into the reserved channel 20 of the base 1 and leads out from the reserved channel of the base 1 to connect electrically to an external measurement system. The reserved channel of the base is L-shaped, used for leading the diaphragm pressure gauge out from the soil sample chamber and for connecting the terminal block to the measurement system.

[0046] The bottom surface of the pressure cap 9 and the top surface of the base 1 are provided with drainage channels 10 and 18 that communicate with the outside. The drainage channels 10 and 18 are connected to the surface of the annular permeable stone.

[0047] The upper end face of the upper annular permeable stone 11 contacts the drainage channel 10 on the bottom surface of the pressure cap 9, and the lower end face contacts the soil sample in the soil sample chamber 3; the lower end face of the lower annular permeable stone 2 contacts the drainage channel 18 on the top surface of the base 1, and the upper end face contacts the soil sample in the soil sample chamber 3.

[0048] Piezoelectric bending elements all include a base 28 and a cantilever end 27, such as Figure 7 As shown.

[0049] The base 28 of the first piezoelectric bending element receiver 16 is provided with a shock-absorbing rubber sleeve 17 between the groove walls of the mounting groove 21, which wraps around the first piezoelectric bending element receiver 16. The base 28 of the second piezoelectric bending element receiver 13 is provided with a shock-absorbing rubber sleeve 15 between the groove walls of the mounting groove 24, which wraps around the second piezoelectric bending element receiver 13. By wrapping the base of the piezoelectric bending element receiver with shock-absorbing rubber sleeves 15 and 17, shear waves propagating through non-soil media are shielded.

[0050] The long axis of the cantilever end of the first piezoelectric bending element exciter 12 and the long axis of the cantilever end of the first piezoelectric bending element receiver 16 are in the same plane.

[0051] The second piezoelectric bending element exciter 5 and the second piezoelectric bending element receiver 13 are arranged opposite each other along the diameter, and the long axis of the cantilever end of the second piezoelectric bending element exciter 5 and the second piezoelectric bending element receiver 13 are both in the vertical direction.

[0052] The piezoelectric bending element exciter and receiver of the present invention are coated with epoxy resin of appropriate thickness for waterproof sealing.

[0053] The present invention specifically implements testing of the structural parameters of soil according to the following steps:

[0054] The first step is to place the lower ring permeable stone 2 onto the base 1 and install the rigid protective ring 7, and install the piezoelectric bending element excitation element 12 on the top surface of the base 1;

[0055] The second step is to evenly fill the soil sample cavity 3 above the base 1 with the test soil sample in layers, insert the cantilever end of the piezoelectric bending element exciter 12 into the soil sample, and flatten the top surface of the soil sample.

[0056] The third step is to place the upper ring permeable stone 11 on the top surface of the soil sample, and cover the top with a pressure cap 9. The bottom surface of the pressure cap 9 has been equipped with a piezoelectric bending element receiver 16, so that the cantilever end of the piezoelectric bending element receiver 16 on the pressure cap 9 is inserted into the soil sample.

[0057] Then install two thin-film pressure gauges 6 and piezoelectric bending element exciter 5 and piezoelectric bending element receiver 13 on the inner walls of both sides of the rigid retaining ring 7;

[0058] The fourth step involves applying a vertical effective stress σ′ to the soil sample in the soil sample chamber 3 according to the stress self-pressure cap 9 in the experimental design. v The effective horizontal stress (lateral earth pressure) σ′ was measured using a diaphragm pressure gauge 6. h ;

[0059] Fifth, after consolidation and stabilization, the shear wave velocity in the vertical and horizontal planes is measured using a piezoelectric bending element, and the small strain shear modulus G is calculated respectively. max,vh With Gmax,hh ;

[0060] The sixth step is to calculate the void ratio e based on the soil sample's compression, and finally, based on the small strain shear modulus G... max,vh With G max,hh Vertical effective stress σ′ v and horizontal effective stress σ′ h The structural parameter A of the soil is calculated using the following formula. vh With A hh :

[0061]

[0062]

[0063] F(e) = 1 / (0.3 + 0.7e) 2 )

[0064] Where F(e) is a function of the porosity e; P a This is the reference stress, let P be the value. a =100kPa; OCR is the overconsolidation ratio, and the OCR of normally consolidated soil is 1; n is the stress exponent, and the same soil type has the same n value, with n = 0.5 for sandy soil; k is the overconsolidation ratio exponent, and the same soil type has the same k value, while the k value of normally consolidated soil can be ignored; A vh A represents the structural parameters of the soil in the vertical plane. hh These represent the structural parameters of the soil at the horizontal plane.

[0065] As can be seen from this implementation, the present invention achieves accurate determination of soil structural parameters by directly measuring the shear wave velocity and lateral earth pressure of soil samples.

Claims

1. A method for accurate measurement of soil structural parameters based on a multi-function consolidometer, characterized in that: The method adopts a multifunctional consolidation instrument, which comprises a base (1), a rigid ring (7), a pressure cap (9), ring-shaped permeable stones (11), piezoelectric bending elements (5, 12, 13, 16) and thin film pressure gauges (6); the pressure cap (9) is located above the base (1), and the pressure cap (9) and the base (1) are connected and supported by the rigid ring (7); the pressure cap (9), the base (1) and the rigid ring (7) enclose a relatively closed inner cavity as a soil sample cavity (3), and the soil sample cavity (3) is filled with soil samples; a circular boss is arranged in the middle of the top surface of the base (1) and the bottom surface of the pressure cap (9) in the soil sample cavity (3); a first piezoelectric bending element exciting element (12) is arranged in the middle of the circular boss of the pressure cap (9), and a first piezoelectric bending element receiving element (16) is arranged in the middle of the circular boss of the base (1); the first piezoelectric bending element receiving element (16) is located directly below the first piezoelectric bending element exciting element (12); the top surface of the base (1) in the soil sample cavity (3) and around the circular boss is uniformly arranged with lower ring-shaped permeable stones (2), and the bottom surface of the pressure cap (9) in the soil sample cavity (3) and around the circular boss is uniformly arranged with upper ring-shaped permeable stones (11); the upper ring-shaped permeable stones (11) are located directly above the lower ring-shaped permeable stones (2); the second piezoelectric bending element exciting element (5) and the second piezoelectric bending element receiving element (13) are respectively arranged on the inner walls of the two sides of the rigid ring (7) in a radial direction; the second piezoelectric bending element exciting element (5) and the second piezoelectric bending element receiving element (13) are symmetrically arranged on both sides of the central axis of the rigid ring (7); two thin film pressure gauges (6) are respectively arranged on the inner walls of the two sides of the rigid ring (7) in another radial direction. The method comprises the following steps: In the first step, the lower ring-shaped permeable stones (2) are sleeved on the base (1), and the rigid ring (7) is installed, and the piezoelectric bending element exciting element (12) is installed on the top surface of the base (1); In the second step, the test soil sample is evenly filled in the soil sample cavity (3) above the base (1) in layers, the cantilever end of the piezoelectric bending element exciting element (12) is inserted into the soil sample, and the top surface of the soil sample is leveled; In the third step, the upper ring-shaped permeable stones (11) are placed on the top surface of the soil sample, the pressure cap (9) is added on the upper part, the piezoelectric bending element receiving element (16) has been installed on the bottom surface of the pressure cap (9), and the cantilever end of the piezoelectric bending element receiving element (16) on the pressure cap (9) is inserted into the soil sample; Then, the two thin film pressure gauges (6), the piezoelectric bending element exciting element (5) and the piezoelectric bending element receiving element (13) on the inner walls of the two sides of the rigid ring (7) are installed; Fourth step, according to the stress test design, the pressure cap (9) applies vertical effective stress σ' to the soil sample in the soil sample cavity (3) v ; using the film pressure gauge (6) to measure the horizontal effective stress σ' h ; In the fifth step, after the consolidation is stable, the piezoelectric bending element is used to measure the shear wave velocity of the vertical and horizontal planes, and the small strain shear modulus G max,vh with G max,hh ; Sixth step, calculate the void ratio e according to the compression of soil sample, and finally calculate the small strain shear modulus G max,vh With G max,hh , vertical effective stress σ' v and horizontal effective stress σ' h The structural parameters A of soil body are calculated by the following formula vh With A hh : F(e) = 1 / (0.3 + 0.7e 2 ) where F(e) is a function of void ratio e; P a is the reference stress; OCR is the overconsolidation ratio; n is the stress exponent; k is the overconsolidation ratio exponent; A vh represents the soil structural parameter in the vertical plane, A hh represents the soil structural parameter in the horizontal plane.

2. The method for accurately measuring the structural parameters of soil mass based on the multifunctional oedometer according to claim 1, characterized in that: The base (28) of the first piezoelectric bending element receiving element (16) is embedded in the installation groove (21) at the center of the circular boss of the base (1), and the cantilever end (27) of the first piezoelectric bending element receiving element (16) is inserted into the soil sample in the soil sample cavity (3) upwards; the base (28) of the first piezoelectric bending element exciting element (12) is embedded in the installation groove (22) at the center of the circular boss of the pressure cap (9), and the cantilever end (27) of the first piezoelectric bending element exciting element (12) is inserted into the soil sample in the soil sample cavity (3) downwards.

3. The method for accurately measuring the structural parameters of soil mass based on the multifunctional oedometer according to claim 1, characterized in that: The first piezoelectric bending element receiving element (16) is electrically connected with the external test system, the bottom of the mounting groove (21) of the base (1) mounting the first piezoelectric bending element receiving element (16) is provided with a wiring hole (19) for leading to the outside, and the wire between the first piezoelectric bending element receiving element (16) and the test system passes through the wiring hole (19).

4. The method for accurately measuring the structural parameters of soil mass based on the multifunctional oedometer according to claim 1, characterized in that: The base (28) of the second piezoelectric bending element receiving element (13) is provided with a shock-absorbing rubber sleeve (15) between the groove walls of the mounting groove (24), and the second piezoelectric bending element receiving element (13) is wrapped by the shock-absorbing rubber sleeve (15).

5. The method for accurately measuring the structural parameters of soil mass based on the multifunctional oedometer according to claim 1, characterized in that: The long axis of the cantilever end of the first piezoelectric bending element exciting element (12) and the long axis of the cantilever end of the first piezoelectric bending element receiving element (16) are in the same plane. The long axis of the cantilever end of the first piezoelectric bending element exciting element (12) and the long axis of the cantilever end of the first piezoelectric bending element receiving element (16) are in the same plane.

6. The method for accurately measuring the structural parameters of soil mass based on the multifunctional oedometer according to claim 1, characterized in that: ​ 7. The method for accurately measuring the structural parameters of soil mass based on the multifunctional oedometer according to claim 1, characterized in that: ​ 8. The method for accurately measuring the structural parameters of soil mass based on the multi-function consolidator according to claim 1, characterized in that: ​ 9. The method for accurately measuring the structural parameters of soil mass based on the multifunctional oedometer according to claim 1, characterized in that: ​ 10. The method for accurately measuring the structural parameters of soil mass based on the multifunctional oedometer according to claim 1, characterized in that: The second piezoelectric bending element exciting element (5) and the second piezoelectric bending element receiving element (13) are arranged in diametric opposition, and the long axes of the cantilevered ends of the second piezoelectric bending element exciting element (5) and the second piezoelectric bending element receiving element (13) are in the vertical direction.

Images