In-situ vane shear test device in deep sea and method for analyzing strength of different shear surfaces of sediment

Abstract

In-situ vane shear test device for deep sea and method for analyzing strengths of different shear planes of sediments, belonging to the technical field of submarine sediment strength testing. The device includes a bottom-mounted carrier platform, a connecting rod, an operation control cable, a data transmission cable, a pressure sensor, a torque sensor, an intelligent control motor, a speed reducer, a telescopic probe, a connection port and a vane probe. The device enables the coordinated and efficient operation of the pressure sensor and the torque sensor, achieving the ability to simultaneously measure the penetration resistance of the vane probe along the penetration depth and the torque at a specified depth with a single penetration. The device and its sediment strength analysis method achieve the efficient testing and accurate analysis of the undrained shear strengths of the horizontal and vertical shear planes of submarine sediments at different depths, especially solving the problems of discontinuous test data and overly rough strength analysis faced by existing vane shear test technologies, and having significant advantages in the field of in-situ strength testing and application of submarine sediments.

Description

Technical Field

[0001] The present invention relates to a deep - sea in - situ vane shear test device and a method for analyzing the strength of different shear surfaces of sediments, belonging to the technical field of submarine sediment strength testing. Background Art

[0002] The seabed contains a large amount of resources, including mineral resources such as oil, natural gas, combustible ice, manganese nodules, cobalt - rich crusts, rare metals and non - metals; environmental resources such as low temperature and weak interference required for installing equipment such as servers; space resources for meeting communication, power transportation and storage; physical resources for obtaining scientific data (such as earthquakes) and biological, chemical, geological and other resources. To realize the rational utilization of these resources, a large number of projects and their supporting facilities need to be built on the seabed, such as mining tracks, drilling, pipe - cable systems, observation networks, submarine foundations, etc. Therefore, the undrained shear strength of submarine sediments, especially the undrained shear strength of shallow - surface sediments, is crucial, which is one of the most important parameters for engineering design, construction and disaster assessment.

[0003] At present, the methods for obtaining the undrained shear strength of submarine sediments mainly include two categories: in - situ tests and laboratory tests after sampling. Compared with laboratory tests, in - situ tests can avoid disturbing the original structure of sediments during sampling and transportation, and can also maintain the thermal (temperature state) - water (water environment) - force (stress state) environment of the sediments to be measured during the test process, and can obtain the strength parameters of submarine sediments in the real state more accurately and quickly. Among many in - situ test methods, the vane shear test (VST), the cone penetration test (CPT) and the full - flow penetration test (Ball and T - bar) have been widely used.

[0004] VST is a method for testing the undrained shear strength of submarine sediments with simple principle, few influencing factors and wide application. It has been used for more than 100 years and is still active in the fields of strength testing, calibration and verification. The principle of VST is to insert a vane probe with a standard shape and size into a certain depth of the sediments to be measured, and then rotate the vane probe at a uniform speed. By measuring the torque received by the vane probe during rotation, the undrained shear strength of the sediments can be indirectly obtained. Specifically, VST assumes that the undrained shear strength of the sediments on the shear column failure surface (side, top and bottom) formed by the rotation of the vane head during the test is equal. As Figure 1 shown, τ v = τ H . By dividing the measured torque by the coefficient related to the vane - head size, the undrained shear strength of the sediments is evaluated, as shown in formula (1.1).

[0005]

[0006] where: s u is the undrained shear strength of the sediment measured by the vane shear test; M is the torque measured by the vane shear test; D is the diameter of the vane probe; H is the height of the vane probe.

[0007] In fact, the shear strength of submarine sediments is related to the stress state they are in, that is, it is determined by the normal stress on the shear plane (the side, top and bottom of the shear cylinder), as Figure 2 shown. In the natural environment, considering the formation process of submarine sediments, there are three consolidation states of natural sediments: under-consolidated, normally consolidated and over-consolidated. The basis for dividing these three sediment consolidation states is the ratio of the consolidation pressure that the sediment has experienced historically to the current overlying pressure; when it is greater than 1, the sediment is in an over-consolidated state; when it is equal to 1, the sediment is in a normally consolidated state; when it is less than 1, the sediment is in an under-over-consolidated state. In fact, the torque of the VST should be divided into two parts, corresponding to the sediment strength τ H on the horizontal plane and the sediment strength τ v on the vertical plane, as shown in formulas (1.2) and (1.3). Generally, the normal stress on the horizontal plane of the sediment is greater than the normal stress on the vertical plane, that is, τ v < τ H , and for sediments in an over-consolidated state, this gap will become even larger [Bonet J L, Barros M, Romero M L. Comparative study of analytical and numerical algorithms for designing reinforced concrete sections under biaxial bending [J]. Computers & Structures, 2006, 84: 2184 - 2193; Dundar C, Tokgoz S, Tanrikulu A K, et al. Behaviour of reinforced and concrete-encased composite columns subjected to biaxial bending and axial load [J]. Building and environment, 2008, 43(6): 1109 - 1120.].[[]]

[0008]

[0009]

[0010] Where: τ H is the undrained shear strength of the sediments above and below the shear column; τ v M is the undrained shear strength of the sediment on the side (vertical surface) of the shear column; H M is the torque acting on the upper and lower horizontal surfaces of the shear column; v is the torque acting on the side of the shear column; here M = M v +M H .

[0011] However, existing VSTs assume that seafloor sediments are isotropic, meaning that the shear strength of sediments on the surfaces (side, top, and bottom) of the shear cylinder is equal, as shown in Equation (1.4). This is significantly different from actual conditions, resulting in a rough and inaccurate VST strength analysis theory. Furthermore, existing VSTs can only test discrete points along the depth direction and cannot achieve continuous testing and strength assessment. This is a major issue restricting the development of VSTs and an application bottleneck that urgently needs to be overcome. Therefore, it is imperative to develop new testing devices and technologies to address practical issues such as discontinuous test data and overly rough strength analysis faced by cross-plate shear testing technology.

[0012] s u =τ v =τ H (1.4) Summary of the Invention

[0013] The purpose of the present invention is to address the shortcomings of the current cross-plate shear strength test of seabed sediments, provide a deep-sea in-situ cross-plate shear test device and sediment strength analysis method, and elaborate on the undrained shear strength analysis principle and usage method in detail, in order to meet the needs of marine resource development, engineering construction and geological disaster assessment.

[0014] In order to achieve the above object, the technical solution of the present invention is:

[0015] A deep-sea in-situ cross-plate shear test device, characterized by comprising a bottom-mounted carrying platform, an operating control cable, a data transmission cable, and a connecting rod located below the platform. A pressure sensor, a torque sensor, and an intelligent control motor with a reducer are sequentially mounted at the lower end of the connecting rod. The intelligent control motor and its reducer drive a retractable probe rod, the lower end of which is connected to a cross-plate probe via a connecting port.

[0016] The pressure sensor collects the penetration resistance of the cross-plate probe during the entire process of the cross-plate probe penetrating into the seabed sediment from the mudline until it stops;

[0017] The described torque sensor collects the torque on the vane probe during the rotation process after the vane probe stops penetrating the seabed sediment.

[0018] The described intelligent control motor has the functions of penetration, rotation and recovery, so as to penetrate the vane probe and the telescopic rod into the specified depth of the seabed sediment, then rotate the telescopic rod and the vane probe, and finally recover the telescopic rod and the vane probe.

[0019] The described vane probe is the main tool for testing the strength of seabed sediment. The height H of the vane probe is usually twice its diameter D, and the specific dimensions can be determined according to the range and accuracy of the pressure sensor and the torque sensor and the strength of the seabed sediment to be measured.

[0020] A method for analyzing the undrained shear strength of different shear planes of seabed sediment using the above device is characterized by including the following steps:

[0021] First, set the accuracy and range of the pressure sensor and the torque sensor, the data acquisition frequency of the bottom-mounted platform, the length of the telescopic rod, the size of the vane probe, and the working modes of the intelligent control motor and its reducer. The working modes include: penetration depth, penetration speed, penetration time, rotational angular velocity, rotational time.

[0022] Second, deploy the in-situ vane shear test device in the sea area to be measured, start the pre-set operation program, carry out the test work, and recover it after the work is completed.

[0023] Finally, analyze the test data to obtain the undrained shear strength of the seabed sediment at different depths. The specific analysis process is as follows:

[0024] 1) As the penetration depth h of the vane probe increases, the undrained shear strength τ v (h) of the vertical shear plane at different depths can be calculated according to the penetration resistance Q(h) varying with depth, as shown in formula (1.5):

[0025]

[0026] Among them, τ v (h) is the undrained shear strength of the vertical shear plane at different depths; h is the penetration depth of the bottom surface of the vane probe starting from the contact with the mud line, as Figure 3 shown, this penetration depth is determined by multiplying the penetration speed of the motor by the time; D is the diameter of the vane probe; H is the height of the vane probe; Q(h) is the penetration resistance at different penetration depths.

[0027] For a specified depth, the undrained shear strength τ′ of the vertical shear plane at the specified depth can also be calculated according to the penetration resistance Q′ at that depth v , as shown in formula (1.6):

[0028]

[0029] where Q′ is the penetration resistance at the specified depth; τ′ v is the undrained shear strength of the vertical shear plane at the specified depth;

[0030] According to the stress distribution characteristics of the shear column, the undrained shear strength τ v (h) can also be expressed by formula (1.7):

[0031]

[0032] where M v is the torque acting on the side of the shear column;

[0033] Substituting formula (1.5) into formula (1.7), formula (1.7) is obtained:

[0034]

[0035] 2) Based on the penetration resistance Q′ and torque M′ at the specified depth, and based on the relationship, the undrained shear strength τ′ of the horizontal shear plane at the specified depth can be calculated H , as shown in formula (1.9):

[0036]

[0037] where τ′ H is the undrained shear strength of the horizontal shear plane at the specified depth; Q′ is the penetration resistance at the specified depth; M′ is the torque at the specified depth;

[0038] 3) Define the relationship between the undrained shear strengths τ′ v and τ′ H of different shear planes at the specified depth, as shown in formula (1.10):

[0039] τ′ v = η · τ′ H (1.10)

[0040] where η is the ratio of the undrained shear strength of the vertical shear plane to the undrained shear strength of the horizontal shear plane at the specified depth;

[0041] Substituting formula (1.9) and formula (1.6) into formula (1.10), formula (1.11) is obtained:

[0042]

[0043] 4) According to τ shown in formula (1.12) v (h) and τ H (h) relationship:

[0044] τ v (h) = η · τ H (h) (1.12)

[0045] Among them, τ H (h) is the undrained shear strength of the horizontal shear plane at different depths;

[0046] Substitute formula (1.11) and formula (1.5) into formula (1.12) again, and the undrained shear strength τ of the horizontal shear plane at different depths can be analyzed H (h), as shown in formula (1.13), the undrained shear strength τ of the horizontal shear plane at different depths H (h) varies along the penetration depth;

[0047]

[0048] Finally, the calculation formulas are as shown in formulas (1.14) and (1.15), where the penetration depth h should be greater than twice the height H of the vane probe;

[0049]

[0050]

[0051] Start the pre-set operation program. In the steps of carrying out the test work, the operation program is set as follows: Penetrate into the specified depth of the seabed sediment at a preset speed uniformly, and collect the penetration resistance during the penetration process at the same time; then stand still for two minutes, start to rotate at a low angular velocity uniformly for 10 minutes, and rotate at a high angular velocity uniformly for 5 minutes, obtain the peak torque and the residual torque respectively, and obtain the peak strength and the residual strength correspondingly. The ratio of the two is the sensitivity.

[0052] The specified depth should be greater than twice the height H of the vane probe 11.

[0053] The preset speed is 20 mm / s; the low angular velocity is 12° / min, and the high angular velocity is 144° / min.

[0054] In addition, the shear strain rate, i.e., the shear rate, in the shear column (band) around the vane is unevenly distributed. Different rotational angular velocities will affect the strength analysis results of submarine sediments. The method for evaluating the shear rate of submarine sediments is shown in Equation (1.16)

Einav I, Randolph M F. Combining upper bound and strain path methods for evaluating penetration resistance[J]. International Journal for Numerical Methods in Engineering, 2005, 63(14): 1991 - 2016.

[0055]

[0056] In the formula: is the shear rate of the sediment; ω is the angular velocity of the vane.

[0057] The present invention focuses on the problems faced by the existing vane shear test technology, such as discontinuous test data, overly rough strength analysis, and inability to obtain the undrained shear strength of submarine sediments on different shear planes. A new in-situ vane shear test device for deep sea is designed. The pressure sensor and the torque sensor in the device exist simultaneously, and can measure the penetration resistance varying along the penetration depth and the torque at a specified depth. And based on this device, a method for continuously measuring the undrained shear strength of submarine sediments on different shear planes at different depths is provided.

[0058] By adding the real-time penetration resistance test technology along the penetration depth direction, the present invention obtains the penetration resistance at different penetration depths, overcomes the drawback of the existing VST assuming the isotropy of sediment strength, solves the problem that the existing VST can only measure the undrained shear strength of sediments at a specific position at a certain depth (continuous measurement cannot be achieved), and realizes the efficient and continuous measurement of the undrained shear strength of submarine sediments at different depths and the accurate analysis of the strength of different shear planes, having significant advantages in the field of in-situ strength testing and application of submarine sediments. Description of the Drawings

[0059] Figure 1 is the shear stress state of the column unit during the vane shear test.

[0060] Figure 2 are the normal stress and shear stress of the column unit.

[0061] Figure 3 is the schematic diagram of the in-situ vane shear test device for deep sea of the present invention.

[0062] In the figure: 1 is a bottom-mounted platform; 2 is a connecting rod; 3 is an operation control cable; 4 is a data transmission cable; 5 is a pressure sensor; 6 is a torque sensor; 7 is an intelligent control motor; 8 is a speed reducer; 9 is a telescopic probe; 10 is a connection port; 11 is a vane probe. Detailed implementation manners

[0063] The following will describe in detail the specific implementation manners of the present invention in conjunction with the accompanying drawings.

[0064] As Figure 3 shown, a deep-sea in-situ vane shear test device, characterized in that it includes a bottom-mounted platform 1, an operation control cable 3, a data transmission cable 4, and a connecting rod 2 located below the platform. A pressure sensor 5, a torque sensor 6, and an intelligent control motor 7 with a speed reducer 8 are successively installed at the lower end of the connecting rod 2. The intelligent control motor and its speed reducer 8 drive a telescopic probe 9, and the lower end of the probe 9 is connected to a vane probe 11 through a connection port 10;

[0065] The pressure sensor 5 collects the penetration resistance received by the vane probe 11 during the entire process from the mud line to the stop of the vane probe 11 penetrating into the seabed sediment;

[0066] The torque sensor 6 collects the torque received by the vane probe 11 during the rotation process after the vane probe 11 stops penetrating into the seabed sediment;

[0067] The intelligent control motor 7 has the functions of penetration, rotation, and recovery, to penetrate the vane probe 11 and the telescopic probe 9 into the seabed sediment to a specified depth, then rotate the telescopic probe 9 and the vane probe 11, and finally recover the telescopic probe 9 and the vane probe 11;

[0068] The vane probe 11 is the main tool for testing the strength of seabed sediment. The height H of the vane probe 11 is usually 2 times its diameter D, and the specific dimensions can be determined according to the ranges and precisions of the pressure sensor 5 and the torque sensor 6 and the strength of the seabed sediment to be measured.

[0069] Through the collation and analysis of multiple indoor test and in-situ test data, the following value-taking rules for the vane size and sensors are obtained: when the strength of the seabed sediment is low, a larger vane probe 11 size and lower ranges of the pressure sensor 5 and the torque sensor 6 should be selected to obtain higher test accuracy, and vice versa.

[0070] The bottom-mounted platform 1 is connected to the vane probe 11 through devices such as the connecting rod 2 to form an integral body, thereby realizing the function of stably deploying the entire device to a specified sea area and safely recovering it; at the same time, the bottom-mounted platform 1 can also provide the power supply, control system, data acquisition system, and necessary stability required for the operation of the vane probe 11.

[0071] The connecting rod 2 connects the bottom-mounted carrying platform 1 with the cross-plate probe 11 and ensures that the cross-plate probe 11 is in a vertical position.

[0072] The operation control cable 3 sends the preset operation instructions from the control system of the bottom-mounted carrying platform 1 to the intelligent control motor 7 to ensure the accurate conduct of the test.

[0073] The data transmission cable 4 transmits all data collected by the pressure sensor 5 and the torque sensor 6 during the test, ensuring the security of the data obtained from the test.

[0074] The speed reducer 8 adjusts the high angular velocity output by the intelligent control motor 7 to the angular velocity ω after the optimal setting.

[0075] One end of the telescopic probe rod 9 is connected to the reducer 8, and the other end connection port 10 is connected to the cross plate probe 11. The length of the telescopic probe rod 9 can also be freely adjusted according to the test depth.

[0076] The probe rod connection port 10 is composed of two parts, one part is at one end of the telescopic probe rod 9, and the other part is at one end of the cross plate probe 11, which plays the role of connecting the telescopic probe rod 9 with the cross plate probe 11.

[0077] A method for analyzing the undrained shear strength of seabed sediments at different shear planes using the above device is characterized by comprising the following steps:

[0078] First, a suitable bottom-mounted carrying platform 1 is determined based on the specific conditions of the sea area to be measured (including working water depth, bottom environment, and operation time) and the above-mentioned detailed working requirements for the bottom-mounted carrying platform 1.

[0079] For example, the "in-situ testing device for mechanical properties of seabed sediments" which successfully completed sea trials in December 2021.

[0080] Then, according to the working conditions to be measured, the data acquisition system in the bottom-mounted platform 1 is set to acquire data at a frequency, the accuracy and range of the pressure sensor 5 and torque sensor 6, the operating mode (penetration depth, penetration speed, penetration time, rotation angular velocity, rotation time) of the intelligent control motor 7 and reducer 8, the length of the retractable probe 9, and the size of the cross-plate probe 11.

[0081] Then connect the cross-plate probe 11 to the bottom-mounted carrying platform 1 through the connecting rod 2, and check the test accuracy and stability of the entire system;

[0082] The deep-sea in-situ cross-plate shear test device will then be deployed to the sea area to be tested, and the test will be carried out according to the pre-set operating procedures and safely recovered.

[0083] Set up an operation procedure in the control system of the submersible platform 1: First, penetrate into the specified depth of the seabed sediment at a constant speed of 20 mm / s, and at the same time collect the penetration resistance Q (including Q′) during the penetration process; then, after standing still for two minutes, start to rotate at a low angular velocity ω at a constant speed (such as 12° / min) for 10 minutes, and then rotate at a high angular velocity ω at a constant speed (recommended 144° / min) for 5 minutes, respectively obtain the peak torque and the residual torque, and correspondingly obtain the peak undrained shear strength and the residual (disturbed) undrained shear strength, and the ratio of the two is the sensitivity.

[0084] Finally, analyze the test data to obtain the undrained shear strength of the seabed sediment at different depths. The specific strength analysis process is as follows:

[0085] The derivation process of the calculation method for the undrained shear strength of the seabed sediment is shown in formulas (1.5) to (1.15). Specifically, as the penetration depth h of the vane shear probe 11 continuously increases, the undrained shear strength τ of the vertical shear plane at different depths can be calculated according to the penetration resistance Q (changing along the penetration depth) v (changing along the penetration depth), as shown in formula (1.5).

[0086] Then, based on the functional relationship between the penetration resistance Q′ and the torque M′ at the specified depth, as shown in formula (1.7), the undrained shear strength τ′ of the horizontal shear plane at the specified depth can be calculated H , as shown in formula (1.9); furthermore, according to τ′ v =η·τ′ H The functional relationship, as shown in formulas (1.10) and (1.11), can be used to analyze the undrained shear strength τ of the horizontal shear plane at different depths H (changing along the penetration depth), as shown in formula (1.13). The final calculation formulas are shown in formulas (1.14) and (1.15).

[0087]

[0088]

[0089]

[0090]

[0091]

[0092] τ′ v =η·τ′ H (1.10)

[0093]

[0094] τ v (h) = η·τ H (h) (1.12)

[0095]

[0096]

[0097]

[0098] where: τ v (h) is the undrained shear strength of the vertical shear plane at different depths; h is the penetration depth of the bottom surface of the vane probe starting from the contact with the mud line, as Figure 3 shown, this penetration depth is determined by multiplying the penetration speed of the motor by the time; D is the diameter of the vane probe; H is the height of the vane probe; Q(h) is the penetration resistance at different penetration depths; Q′ is the penetration resistance at the specified depth; τ′ v is the undrained shear strength of the vertical shear plane at the specified depth; M v is the torque acting on the side surface of the shear column; τ′ H is the undrained shear strength of the horizontal shear plane at the specified depth; Q′ is the penetration resistance at the specified depth; M′ is the torque at the specified depth; η is the ratio of the undrained shear strength of the vertical shear plane to the undrained shear strength of the horizontal shear plane at the specified depth; τ H (h) is the undrained shear strength of the horizontal shear plane at different depths.

Claims

1. A method for analyzing the strength of submarine sediments with different shear surfaces, characterized in that This method utilizes an in-situ vane shear test device in the deep sea. The device includes a bottom-mounted platform (1), an operation control cable (3), a data transmission cable (4), and a connecting rod (2) located below the platform. At the lower end of the connecting rod (2), a pressure sensor (5), a torque sensor (6), and an intelligent control motor (7) with a speed reducer (8) are successively installed. The intelligent control motor and its speed reducer (8) drive a telescopic probe (9), and the lower end of the probe (9) is connected to a vane probe (11) through a connection port (10). The pressure sensor (5) collects the penetration resistance received by the vane probe (11) during the entire process from the mud line to the stop of the vane probe (11) penetrating into the seabed sediment. The torque sensor (6) collects the torque received by the vane probe (11) during the rotation process after the vane probe (11) stops penetrating into the seabed sediment. The intelligent control motor (7) has the functions of penetration, rotation, and recovery, so as to penetrate the vane probe (11) and the telescopic probe (9) into a specified depth of the seabed sediment, then rotate the telescopic probe (9) and the vane probe (11), and finally recover the telescopic probe (9) and the vane probe (11). The vane probe (11) is the main tool for testing the strength of seabed sediment, and the height H of the vane probe (11) is twice its diameter D. It includes the following steps: First, set the accuracy and range of the pressure sensor (5) and the torque sensor (6), the data acquisition frequency of the bottom-mounted platform (1), the length of the telescopic probe (9), the size of the vane probe (11), and the working mode of the intelligent control motor (7) and its speed reducer (8). The working mode includes: penetration depth, penetration speed, penetration time, rotational angular velocity, and rotation time. Secondly, deploy the in-situ vane shear test device in the deep sea to the sea area to be measured, start the pre-set operation program, carry out the test work, and recover it after the work is completed. Finally, analyze the test data to obtain the undrained shear strength of the seabed sediment at different depths. The specific analysis process is as follows: 1) As the penetration depth h of the vane probe (11) increases, the undrained shear strength τ of the vertical shear plane at different depths can be calculated according to the penetration resistance Q(h) varying with depth v (h), as shown in formula (1.5): where τ v (h) is the undrained shear strength of the vertical shear plane at different depths; h is the penetration depth of the bottom surface of the vane probe starting from the contact with the mud line. As shown in Figure 3, this penetration depth is determined by multiplying the penetration speed of the motor by the time; D is the diameter of the vane probe; H is the height of the vane probe; Q(h) is the penetration resistance at different penetration depths; For a specified depth, the undrained shear strength τ′ of the vertical shear plane at the specified depth can also be calculated according to the penetration resistance Q′ at that depth v , as shown in formula (1.6) where Q′ is the penetration resistance at a specified depth; τ′ v is the undrained shear strength of the vertical shear plane at a specified depth; According to the stress distribution characteristics of the shear column, the undrained shear strength τ of the vertical shear plane v (h) can also be expressed by formula (1.7): Among them, M v is the torque acting on the side of the shear column; Substitute formula (1.5) into formula (1.7) to obtain formula (1.7): 2) Based on the penetration resistance Q′ and torque M′ at a specified depth, according to the relationship, the undrained shear strength τ′ of the horizontal shear plane at the specified depth can be calculated H , as shown in formula (1.9): where τ′ H is the undrained shear strength of the horizontal shear plane at a specified depth; Q′ is the penetration resistance at a specified depth; M′ is the torque at a specified depth; 3) Define the undrained shear strength τ′ of different shear planes at a specified depth v and the relationship with τ′ H is as shown in formula (1.10): τ′ v = η·τ′ H (1.10) Among them, η is the ratio of the undrained shear strength of the vertical shear plane to the undrained shear strength of the horizontal shear plane at a specified depth. Substitute formula (1.9) and formula (1.6) into formula (1.10) to obtain formula (1.11); 4) According to τ shown in formula (1.12) v (h) and τ H (h) relationship: τ v (h) = η·τ H (h)(1.12) where τ H (h) is the undrained shear strength of the horizontal shear plane at different depths; Substituting Equation (1.11) and Equation (1.5) into Equation (1.12) again, the undrained shear strength τ of the horizontal shear plane at different depths can be solved H (h), as shown in Equation (1.13), where the undrained shear strength τ of the horizontal shear plane at different depths H (h) varies along the penetration depth; Finally, the calculation formulas are as shown in formulas (1.14) and (1.15), where the penetration depth h should be more than twice the height H of the vane probe. 。 2. The method for analyzing the strength of submarine sediments with different shear planes according to claim 1, characterized in that In the step of starting the pre-set operation program and carrying out the test work, the operation program is set as follows: penetrate into the specified depth of the seabed sediment at a preset speed uniformly, and collect the penetration resistance during the penetration process at the same time; then stand still for two minutes, start to rotate at a low angular velocity uniformly for 10 minutes, and then rotate at a high angular velocity uniformly for 5 minutes to obtain the peak torque and the residual torque respectively, and obtain the peak strength and the residual strength correspondingly. The ratio of the two is the sensitivity.

3. The method for analyzing the strength of submarine sediments with different shear surfaces according to claim 2, characterized in that The specified depth shall be greater than twice the height H of the vane probe 11.

4. The method for analyzing the strength of submarine sediments with different shear surfaces according to claim 2, characterized in that The preset speed is 20 mm / s; the low angular velocity is 12° / min, and the high angular velocity is 144° / min.

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