Telescopic self-mounting dynamic penetrometer, method of operation and applications thereof

Abstract

The present application belongs to the technical field of ocean engineering, and relates to a telescopic self-installation dynamic penetrometer, an operation method and application thereof to seabed soil strength parameter calculation. The present application overcomes the defect of insufficient penetration depth of the dynamic penetrometer, provides soil reaction force by setting extendable blades inside the lower booster and the upper booster, and realizes continuous penetration of the dynamic penetrometer in seabed soil by relying on motor driving. The present application basically does not change the weight of the dynamic penetrometer, and has no special requirements for the survey ship; measurement in any depth range can be realized, and the application prospect of the dynamic penetrometer is greatly expanded. The present application also proposes a seabed soil strength parameter interpretation method based on the measurement data of the dynamic penetrometer, which can interpret the seabed soil strength parameters in the stage of high-speed penetration of the dynamic penetrometer into seabed by relying on self-weight and the stage of continuous penetration of the dynamic penetrometer into seabed by relying on motor, and provides a basis for marine geotechnical engineering design.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of ocean engineering, and relates to a telescopic self-installed dynamic penetrometer, an operation method and application thereof to seabed soil strength parameter calculation. BACKGROUND

[0002] With the continuous development of ocean oil and gas resources and the use of ocean space, a series of structures need to be built on the seabed, such as submarine pipelines and cables, shallow foundations, anchoring foundations, and production wells. Before the size design and stability analysis of the seabed structure, the variation trend of the seabed soil strength along the depth needs to be determined. Due to the difficulty of sampling at sea and the unavoidable sampling disturbance, the cost of sampling is high and the measured soil strength parameters have large dispersion. Therefore, seabed in-situ testing technology has emerged. Seabed in-situ testing methods include static penetration and dynamic penetration: the static penetrometer needs to use a large counterforce frame, which is first released from a professional survey ship to the seabed surface, and then the penetrometer probe is uniformly penetrated into the deep seabed, and the seabed soil strength parameters are obtained through the counterforce on the probe; the dynamic penetrometer is free from the restriction of a large counterforce frame, and relies on its own weight to quickly fall freely in seawater and penetrate into the seabed soil, and the seabed soil strength parameters are obtained by inversion of the measured acceleration. The dynamic penetrometer is simple and fast to operate, and does not require a professional survey ship, so it has received widespread attention in the industry in recent years.

[0003] Patent ZL201711448424.4 relates to a free-fall type spherical penetrometer with a propeller, which belongs to the category of dynamic penetrometers. The penetrometer is composed of a spherical probe, a connecting rod, and a propeller. A force sensor is arranged between the spherical probe and the connecting rod to measure the interaction force between the spherical probe and the connecting rod. An acceleration sensor is arranged inside the propeller to measure the acceleration of the penetrometer. The falling velocity and penetration depth of the penetrometer can be determined by integrating the acceleration. The propeller increases the weight of the penetrometer, thereby increasing the penetration depth of the penetrometer. However, relying on the self-weight of the penetrometer can only obtain a limited penetration depth, and the penetration depth can only be further increased by increasing the weight of the penetrometer, which undoubtedly increases the requirements for the survey ship. SUMMARY

[0004] In view of the shallow penetration depth of the dynamic penetrometer and the inability to measure the strength parameters of deep soil, the present application proposes a telescopic self-installed dynamic penetrometer and a corresponding operation method to expand the use range of the dynamic penetrometer, and proposes a seabed soil strength parameter interpretation method based on the measurement data of the dynamic penetrometer. After the dynamic penetrometer penetrates into the seabed at a high speed relying on its own weight, the device is started to make the dynamic penetrometer continue to penetrate into the deeper seabed continuously, without the need for a large counterforce device, thereby expanding the measurement depth range of the dynamic penetrometer.

[0005] The technical solution of the present application is as follows.

[0006] 1. Telescopic self-installing powered penetrometer

[0007] The telescopic self-mounted dynamic penetrometer (MPP) consists of a spherical probe, connecting rod, booster, tail fin, and hook from bottom to top. The spherical probe is a sphere, and the connecting rod is a cylinder. The ratio of the connecting rod's cross-sectional area to the maximum cross-sectional area of ​​the spherical probe is less than 0.1 to ensure that the flow mechanism of the soil around the spherical probe is not affected by the connecting rod. Furthermore, the length of the connecting rod should be no less than twice the diameter of the spherical probe to ensure that the flow mechanism of the soil around the spherical probe is not affected by the booster. The booster is a cylindrical section with a semi-ellipsoidal front end connected to the connecting rod and a gradually tapering frustum-shaped rear end. The hook is fixed to the rear end of the booster and used to connect the cable. The other end of the cable is connected to the survey vessel; an automatic release hook is installed in the middle of the cable to release the MPP. At least three tail fins are required, fixed at equal angles to the tail of the booster to ensure the directional stability of the MPP during freefall in water. A force sensor is placed between the spherical probe and the connecting rod to measure the interaction force between them. An acceleration sensor is placed inside the booster to monitor the acceleration of the dynamic penetrometer. A pore pressure sensor is placed on the spherical probe to measure the water pressure experienced by the dynamic penetrometer when it falls into the water and the pore water pressure experienced when it penetrates into the seabed soil.

[0008] A device for retractable self-installation of a powered penetrometer mainly consists of blades, a motor, a push rod, and a measurement and control acquisition cabin. The booster is cut in half, into an upper booster and a lower booster. Both the upper and lower boosters have slots cut at equal angles along the axial direction, with blades arranged within these slots. When the blades are fully retracted within the slots, their outer edges do not extend beyond the slots; when the blades are extended, they protrude from the slots. The rear end of the lower booster is hollowed out into a cylindrical cavity to accommodate the front end of the upper booster. A flange is located near the bottom of the cylindrical cavity. The upper booster has a hollow cylinder at its front end, which fits inside the cylindrical cavity of the lower booster. A gap exists between the outer wall of the hollow cylinder and the inner wall of the cylindrical cavity to allow the lower booster to move relative to the upper booster. An arc-shaped groove is located at the top of the cylindrical cavity to house a sealing ring, which seals the gap between the outer wall of the hollow cylinder and the inner wall of the cylindrical cavity, preventing water and soil from entering. A motor and push rod are installed inside the hollow cylinder. The upper end of the push rod is connected to the motor via a flange, and the lower end of the push rod is connected to the lower booster via a flange. The blades in both the upper and lower boosters extend or retract into slots via motor rotation.

[0009] The measurement and acquisition cabin integrates data transmission and acquisition modules and a motor control module. Depending on the actual water depth, it can be externally mounted on the survey vessel or internally encapsulated within the dynamic penetrometer (MPP). Force sensors, acceleration sensors, and pore pressure sensors are connected to the data transmission and acquisition module in the measurement and acquisition cabin to collect data on the interaction force between the spherical probe and the connecting rod, the acceleration of the MPP, and the water pressure experienced by the spherical probe as it falls through the water and the pore water pressure it experiences during penetration into the seabed. The motor is connected to the motor control module in the measurement and acquisition cabin to control its rotation, thereby driving the push rod and blades to achieve continuous penetration of the MPP into the seabed. The motor operates as follows under the drive of the motor control module: First, the motor rotates forward, causing the upper booster blades to extend out of the slot. Once the blade extension reaches a preset value, the motor continues to rotate forward, driving the push rod downward, which in turn drives the lower booster downward, thus extending the dynamic penetrometer. Second, once the push rod extension reaches its maximum value, the motor continues to rotate forward, causing the lower booster blades to extend out of the slot. Then, the motor begins to rotate in reverse, causing the upper booster blades to retract into the slot. Once the upper booster blades have retracted into the slot, the motor continues to rotate in reverse, causing the upper booster to move downward, thus retracting the dynamic penetrometer.

[0010] 2. Operating Instructions for Telescopic Self-Mounting Powered Penetrometer

[0011] The penetration process of the dynamic cone penetrator into the seabed soil consists of two stages: a high-speed penetration stage relying on its own weight, and a stage where the push rod is driven by the internal motor of the booster to penetrate the seabed at a constant speed. The specific operating steps are as follows:

[0012] (1) Release the powered cone penetrometer from the survey vessel into the seawater, gradually release the cable to lower the powered cone penetrometer to a predetermined height above the seabed surface, and then activate the automatic release mechanism. The powered cone penetrometer falls freely from the water and penetrates the seabed soil at high speed. During this process, the blades in the upper and lower boosters are in a retracted state. At the same time, the acceleration of the powered cone penetrometer and the interaction force between the spherical probe and the connecting rod are measured in real time.

[0013] (2) When the dynamic penetrometer comes to rest after penetrating the seabed soil by its own weight, the motor rotates forward under the drive of the motor control module, causing the blades of the upper booster to extend out of the slot; when the blade extension reaches the preset value, the motor continues to rotate forward to drive the push rod to move downward, thereby pushing the lower booster, connecting rod and spherical probe to move downward. Since the upper surface of the blades extending from the upper booster is subjected to passive earth pressure, the upper booster remains stationary in the seabed soil. At this time, the upper booster is equivalent to a reaction frame. During this process, the interaction force between the spherical probe and the connecting rod is monitored.

[0014] (3) When the push rod elongation reaches its maximum value, the motor continues to rotate forward to make the lower booster blades extend out of the slot; then, the motor starts to rotate in reverse to make the upper booster blades retract into the slot; when the upper booster blades retract into the slot, the motor continues to rotate in reverse to make the upper booster move downward. At this time, the lower booster, connecting rod and spherical probe are equivalent to a reaction frame and remain stationary in the seabed, while the upper booster moves downward against the soil resistance.

[0015] (4) Repeating steps (2) and (3) can enable the dynamic penetrating instrument to continuously penetrate the seabed, thereby measuring the strength parameters of deep seabed soil;

[0016] (5) When the measurement depth reaches the design depth, retract the blades on the booster, tension the cable from the survey vessel, pull the powered cone probe out of the seabed and retrieve it to the survey vessel.

[0017] The power supply for the motor can be built into the telescopic self-mounted powered penetrometer or externally mounted on the survey vessel and connected to the motor via wires.

[0018] 3. Calculation of seabed soil strength parameters based on dynamic cone penetrometer measurement data

[0019] (1) During the high-speed penetration stage of the telescopic self-mounted dynamic cone penetrator into the seabed by its own weight, it is necessary to measure the interaction force between the spherical probe and the connecting rod and the acceleration of the dynamic cone penetrator. The process of interpreting the seabed soil strength parameters based on the measurement data is as follows:

[0020] The force balance equation for the spherical probe when a telescopic self-mounted dynamic cone penetrometer penetrates into the seabed soil is as follows:

[0021] (m+m * A cc =W+F int -F b -F d -F t (1)

[0022] Where m is the mass of the spherical probe, m * For added mass; A cc The acceleration is measured by an accelerometer; W is the weight of the spherical probe; F int The interaction force between the spherical probe and the connecting rod is measured by a force sensor; F b F represents the differential pressure resistance of the soil acting on the spherical probe. d F is the drag resistance experienced by the spherical probe. t The end bearing resistance experienced by the spherical probe. Additional mass m. * The calculation formula is:

[0023] m * =Cm ρ s V dis (2)

[0024] Among them, C m For the additional mass coefficient, ρ s V is the density of soil. dis This represents the volume of seabed soil displaced when the spherical probe penetrates the seabed. The pressure resistance F exerted by the soil on the spherical probe is also represented. b The calculation formula is:

[0025] F b =ρ s gV dis (3)

[0026] Where g is the acceleration due to gravity. Dragging resistance F d The calculation formula is:

[0027]

[0028] Among them, C d A is the drag coefficient, v is the velocity of the dynamic penetrometer, obtained by integrating the acceleration data. p This represents the maximum cross-sectional area of ​​the spherical probe. End bearing resistance F. t The calculation formula is:

[0029] F t =s uo A p N c R fb S fb (5)

[0030] Among them, s uo N represents the undrained shear strength of seabed soil. c R is the bearing capacity coefficient. fb S is the rate effect coefficient. fb This represents the softening effect coefficient.

[0031] When a spherical probe penetrates from the seabed surface to deeper layers, the flow mechanism of the surrounding soil transitions from a shallow mode to a deep mode. The depth at which this transition occurs is called the critical depth z. t The calculation formula is:

[0032] z t =(3.169α+3.127)·(0.670λ+1)·(1-0.402(1-δ rem )α 0.538 )·D (6)

[0033] Where α is the friction coefficient at the interface between the spherical probe and the seabed soil, λ is the seabed soil ratio parameter, and δrem The softening strength ratio of the seabed soil is given by , and D is the diameter of the spherical probe. Bearing capacity coefficient N. c The calculation formula for the soil flow mechanism around the spherical probe being in deep mode is as follows:

[0034] N c =3.975α + 10.660 (7)

[0035] Bearing capacity coefficient N c The calculation formula for the shallow soil flow mechanism around the spherical probe is as follows:

[0036]

[0037] Where z is the soil penetration depth of the lowest point of the spherical probe, which is obtained by integrating the acceleration data twice, and e is the natural logarithm.

[0038] drag coefficient C d The calculation formula for the soil flow mechanism around the spherical probe being in deep mode is as follows:

[0039]

[0040] Among them, Re n For non-Newtonian fluids, the Reynolds number is calculated using the following formula:

[0041] drag coefficient C d The calculation formula for the shallow soil flow mechanism around the spherical probe is as follows:

[0042] Rate effect coefficient R fb The calculation formula is:

[0043]

[0044] Among them, v ref / D represents the reference shear strain rate, and the velocity v within the reference shear strain rate is... ref The speed is the same as that of subsequent dynamic penetrometers that rely on motors for continuous penetration. Softening effect coefficient S fb The calculation formula for the soil flow mechanism around the spherical probe being in deep mode is as follows:

[0045]

[0046] Where, ξ 95 This represents the cumulative plastic shear strain corresponding to a softening degree of 95% in the seabed soil.

[0047] Softening effect coefficient S fbThe calculation formula for the shallow soil flow mechanism around the spherical probe is as follows:

[0048]

[0049] Undrained shear strength s of seabed soil uo This can be derived from equation (15):

[0050]

[0051] In formulas (5-15), the undrained shear strength s of the seabed soil uo , Spherical probe-seabed soil interface friction coefficient α, seabed soil ratio effect parameter λ, seabed soil softening strength ratio δ rem The cumulative plastic shear strain ξ corresponding to the softening degree of seabed soil reaching 95% 95 The unknowns are the mass m and acceleration A of the spherical probe. cc The weight W of the spherical probe and the interaction force F between the spherical probe and the connecting rod. int Additional quality coefficient C m Density ρ of seabed soil s The volume V of seabed soil displaced when a spherical probe penetrates the seabed. dis , gravitational acceleration g, dynamic penetrometer velocity v, and maximum cross-sectional area A of the spherical probe p The diameter D of the spherical probe, the penetration depth z of the lowest point of the spherical probe, and the speed v of the dynamic penetrometer when it achieves continuous penetration using a motor. ref Given a known quantity, the critical depth z t Bearing capacity coefficient N c Driving drag coefficient C d Rate effect coefficient R fb Softening effect coefficient S fb The undrained shear strength s of seabed soil uo , Spherical probe-seabed soil interface friction coefficient α, seabed soil ratio effect parameter λ, seabed soil softening strength ratio δ rem The cumulative plastic shear strain ξ corresponding to the softening degree of seabed soil reaching 95% 95 Related. The acceleration A of the dynamic penetrometer. cc Velocity v, and the interaction force F between the spherical probe and the connecting rod. int Substituting the depth z of the lowest point of the spherical probe into equation (17), and iteratively solving it using a global optimization algorithm, the undrained shear strength s of the seabed soil is determined. uo , Spherical probe-seabed soil interface friction coefficient α, seabed soil ratio parameter λ, seabed soil softening strength ratio δ rem The cumulative plastic shear strain ξ corresponding to the softening degree of seabed soil reaching 95% 95 .

[0052] (2) During the stage when the dynamic cone penetrator penetrates the seabed at a continuous and uniform speed using a motor, the force sensor monitors the interaction force F between the spherical probe and the connecting rod. int This refers to the soil resistance experienced by the spherical probe. The formula for calculating the strength of seabed soil is:

[0053]

[0054] The interaction force F between the spherical probe and the connecting rod int Substituting into equation (16) and iteratively solving using a global optimization algorithm, the undrained shear strength s of the seabed soil is determined. uo The friction coefficient α between the spherical probe and the seabed soil interface, and the ratio of the softening strength of the seabed soil to its δ value. rem The cumulative plastic shear strain ξ corresponding to the softening degree of seabed soil reaching 95% 95 .

[0055] The beneficial effects of this invention are:

[0056] This invention overcomes the limitation of insufficient penetration depth of dynamic cone penetrometers (MPPs) by providing soil reaction force through extendable blades inside the lower and upper boosters, thereby enabling continuous penetration of the MPP into the seabed. This invention essentially does not change the weight of the MPP and places no special requirements on the survey vessel; it can achieve measurements at any depth range, greatly expanding the application prospects of MPPs. This invention also proposes a method for interpreting seabed soil strength parameters based on MPP measurement data. This method can interpret seabed soil strength parameters during the high-speed penetration stage relying on its own weight and the continuous penetration stage relying on a motor, providing a basis for marine geotechnical engineering design. Attached Figure Description

[0057] Figure 1 This is a schematic diagram of a dynamic penetrometer.

[0058] Figure 2 This is a partial longitudinal section view of the lower booster of the powered penetrometer.

[0059] Figure 3 This is a partial longitudinal section view of the upper booster of the powered penetrometer.

[0060] Figure 4 This is a partial diagram showing the connection between the lower and upper boosters.

[0061] Figure 5 This is a partial view of the motor driving the push rod to move downwards.

[0062] Figure 6a This is a schematic diagram of the blade in a contracted state.

[0063] Figure 6b This is a schematic diagram of the blades in the extended position.

[0064] Figure 7 This is a schematic diagram of a powered cone penetrometer being released into the sea from a survey vessel.

[0065] Figure 8 This is a schematic diagram of a dynamic penetrometer penetrating the seabed soil at high speed.

[0066] Figure 9 This is a schematic diagram of a dynamic cone penetrator continuously penetrating the seabed.

[0067] Figure 10 It is the process for interpreting the strength parameters of seabed soil during the high-speed penetration stage of the dynamic penetrometer into the seabed soil.

[0068] In the diagram: 100 Power Penetrometer; 200 Survey Vessel; 300 Cable; 400 Automatic Unhooking; 1 Spherical Probe; 2 Connecting Rod; 3 Lower Booster; 4 Upper Booster; 5 Tail Fin; 6 Hook and Ring; 7 Force Sensor; 8 Accelerometer; 9 Pore Pressure Sensor; 10 Measurement and Control Acquisition Cabin; 31 Lower Blade; 32 Cylindrical Cavity; 33 Flange; 34 Arc-shaped Groove; 35 Sealing Ring; 41 Upper Blade; 42 Hollow Cylinder; 43 Motor; 44 Sleeve; 45 Push Rod; 46 Disc. Detailed Implementation

[0069] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0070] 1. Telescopic self-installing powered penetrometer

[0071] like Figure 1As shown, the dynamic penetrometer 100 consists of, from bottom to top, a spherical probe 1, a connecting rod 2, a lower booster 3, lower booster blades 31, an upper booster 4, upper booster blades 41, a tail fin 5, and a hook 6. The spherical probe 1 is a sphere, and the connecting rod 2 is a cylinder. The ratio of the cross-sectional area of ​​the connecting rod 2 to the maximum cross-sectional area of ​​the spherical probe 1 is less than 0.1 to ensure that the flow mechanism of the soil around the spherical probe 1 is not affected by the connecting rod 2. Furthermore, the length of the connecting rod 2 should be no less than twice the diameter of the spherical probe 1 to ensure that the flow mechanism of the soil around the spherical probe 1 is not affected by the lower booster 3. The booster is a cylindrical section with a semi-ellipsoidal front end connected to the connecting rod 2 and a gradually tapering frustum shape at the rear end. The booster is cut in half, becoming the lower booster 3 and the upper booster 4. The spherical probe 1, the connecting rod 2, and the booster are all collinear. The hook 6 is welded to the rear end of the booster and is used to connect the release cable 300. The other end of the cable is connected to the survey vessel 200, and an automatic release hook 400 is connected in the middle of the cable. The automatic release hook 400 is used to release the powered penetrometer 100. Multiple tail fins 5 are fixed at equal angles to the tail of the booster to ensure the directional stability of the powered penetrometer 100 during free fall in the water. The dimensions of the tail fins 5 need to meet certain requirements: that is, to ensure that the hydrodynamic center of the powered penetrometer 100 is higher than the center of gravity displacement, thereby ensuring the directional stability of the powered penetrometer 100 during free fall in the water. At least three tail fins 5 are required, and more can be added appropriately to ensure the overall rigidity of the powered penetrometer 100.

[0072] A force sensor 7 is arranged between the spherical probe 1 and the connecting rod 2 to measure the interaction force between them. An acceleration sensor 8 is arranged inside the booster to monitor the acceleration of the dynamic penetrometer 100. A pore pressure sensor 9 is arranged on the spherical probe 1 to measure the water pressure experienced by the dynamic penetrometer 100 when it falls into the water and the pore water pressure experienced when it penetrates the seabed soil. The pore pressure sensor 9 can be installed at the bottom of the spherical probe 1 at its largest diameter position, or arranged according to measurement requirements.

[0073] A device for continuously increasing the penetration depth of a dynamic penetrometer 100 mainly consists of blades, a motor 43, a push rod 45, and a measurement and control acquisition cabin 10. The lower booster 3 and the upper booster 4 have slots formed at equal angles along the axial direction, and lower fan-shaped blades 31 and upper fan-shaped blades 41 are respectively arranged in the slots, such as... Figure 2 and Figure 3 As shown. When the blades are fully retracted within the slot, the outer edge of the blades will not extend beyond the slot; when the blades are open, they extend radially outward from the slot along the booster. The rear end of the lower booster 3 is hollowed out into a cylindrical cavity 32, as shown. Figure 2As shown, the upper booster 4 is housed in a hollow cylinder 42. A flange 33 is located near the bottom of the cylindrical cavity 32. The front end of the upper booster 4 is a hollow cylinder 42 with a slightly smaller diameter so that it can fit into the cylindrical cavity 32 of the lower booster 3. A gap is left between the outer wall of the hollow cylinder 42 and the inner wall of the cylindrical cavity 32 to allow the lower booster 3 to move relative to the upper booster 4. An arc-shaped groove 34 is provided on the upper inner wall of the cylindrical cavity 32 to hold a sealing ring 35. The sealing ring 35 can block the gap between the outer wall of the hollow cylinder 42 and the inner wall of the cylindrical cavity 32 to prevent water and soil from entering the gap. A motor 43 and a push rod 45 are installed inside the hollow cylinder 42 at the front end of the upper booster 4. One end of the push rod 45 is connected to the motor 43 via a flange, and the other end is a disc 46, which is fixed to the flange 33 of the lower booster 3. The upper part of the push rod 45 is located inside the sleeve 44, such as... Figure 4 As shown. When motor 43 is started, push rod 45 is pushed out of sleeve 44, driving disk 46 to move downward, thereby driving lower booster 3, connecting rod 2, and spherical probe 1 to move downward, as shown. Figure 5 As shown. The upper blade 41 and lower blade 31 in the upper booster and lower booster are also extended and retracted by the motor 43.

[0074] The measurement and control acquisition cabin 10 integrates a data transmission and acquisition module and a motor control module. Depending on the actual water depth, it can be externally mounted on the survey vessel 200 or internally encapsulated within the dynamic penetrometer 100. Force sensor 7, acceleration sensor 8, and pore pressure sensor 9 are connected to the data transmission and acquisition module of the measurement and control acquisition cabin 10 to collect data on the interaction force between the spherical probe 1 and the connecting rod 2, the acceleration of the dynamic penetrometer 100, and the water pressure experienced by the spherical probe 1 as it falls into the water and the pore water pressure experienced during penetration into the seabed. Motor 43 is connected to the motor control module of the measurement and control acquisition cabin 10 to control the rotation of motor 43, thereby driving the push rod 45 and the blades to move, thus realizing the continuous penetration process of the dynamic penetrometer 100 into the seabed. The motor 43 operates as follows under the drive of the motor control module: First, the motor 43 rotates forward, causing the upper blade 41 in the upper booster 4 to extend out of the slot. When the extension of the upper blade 41 reaches a preset value, the motor 43 continues to rotate forward, driving the push rod 45 to move downward, thereby driving the lower booster 3 to move downward, so as to achieve the extension of the power penetrometer 100. Second, when the extension of the push rod 45 reaches its maximum value, the motor 43 continues to rotate forward, causing the lower blade 31 in the lower booster to extend out of the slot. Then, the motor 43 begins to reverse, causing the upper blade 41 in the upper booster 4 to retract into the slot. When the upper blade 41 in the upper booster 4 retracts into the slot, the motor 43 continues to reverse, causing the upper booster 4 to move downward, so as to achieve the retraction of the power penetrometer 100.

[0075] Figure 6a and Figure 6bThe diagrams show the lower blade 31 in its retracted and extended states, respectively. The lower blade 31 can be extended radially along the booster by the motor 43, or it can be designed as a rotating opening and closing device to rotate out of the booster. To increase the soil resistance on the blades, multiple layers of blades can be installed on both the lower booster 3 and the upper booster 4. The number of blade layers needs to be determined based on the weight of the dynamic penetrometer 100.

[0076] 2. Operating procedures for a telescopic self-installing powered penetrometer

[0077] The specific operating steps are as follows:

[0078] (1) Release the powered cone penetrometer 100 from the survey vessel 200 into the seawater, and gradually release the cable 300 to lower the powered cone penetrometer 100 to a predetermined height above the seabed surface, such as... Figure 7 As shown; then the release mechanism 400 is activated, and the powered penetrometer 100 falls freely from the water and penetrates the seabed soil at high speed, as shown. Figure 8 As shown, during this process, the blades in the upper booster 4 and the lower booster 3 are in a retracted state, and at the same time, the measurement data of the force sensor 7 and the acceleration sensor 8 are obtained in real time to measure the interaction force between the spherical probe 1 and the connecting rod 2 and the acceleration of the dynamic penetrometer 100.

[0079] (2) After the dynamic penetrometer 100 penetrates the seabed soil by its own weight, the upper blade 41 of the upper booster 4 extends outward through the narrow slot, such as Figure 9 As shown, the motor 43 is then started to push the push rod 45 downward, pushing the lower booster 3, connecting rod 2 and spherical probe 1 to continue moving downward. Since the upper surface of the blade 41 extending from the upper booster 4 is subjected to passive earth pressure, the upper booster 4 remains stationary in the seabed soil. At this time, the upper booster 4 is equivalent to a reaction frame. During this process, the interaction force between the spherical probe 1 and the connecting rod 2 is monitored.

[0080] (3) The upper blade 41 of the upper booster 4 is retracted, and then the lower blade 31 of the lower booster 3 is extended. At this time, the three parts of the lower booster 3, the connecting rod 2 and the ball probe 1 are equivalent to a reaction frame. The motor 43 is started in the opposite direction to retract the push rod 45. At this time, the upper booster 4 moves downward against the soil resistance.

[0081] (4) Repeating steps (2) and (3) can enable the dynamic penetrating probe 100 to continuously penetrate the seabed, thereby measuring the strength parameters of deep seabed soil;

[0082] (5) When the measurement depth reaches the design depth, the cable 300 is tensioned on the survey vessel 200, the power cone probe 100 is pulled out of the seabed and retrieved to the survey vessel 200.

[0083] 3. Calculation of seabed soil strength parameters based on dynamic cone penetrometer measurement data

[0084] (1) During the stage where the dynamic cone penetrator 100 penetrates the seabed at high speed by its own weight, the interaction force between the spherical probe 1 and the connecting rod 2 is measured by the force sensor 7, and the acceleration of the dynamic cone penetrator 100 is measured by the acceleration sensor 8. The process of interpreting the seabed soil strength parameters based on the measurement data is as follows.

[0085] The force equilibrium equation for the spherical probe 1 when the dynamic cone penetrometer 100 penetrates the seabed soil is as follows:

[0086] (m+m * A cc =W+F int -F b -F d -F t (1)

[0087] Where m is the mass of the spherical probe 1, m * For added mass; A cc The acceleration is measured by acceleration sensor 8; W is the weight of spherical probe 1; F int The interaction force between the spherical probe 1 and the connecting rod 2 is measured by the force sensor 7; F b F is the differential pressure resistance of the soil acting on the spherical probe 1. d F is the drag resistance experienced by the spherical probe 1. t The end bearing resistance experienced by the spherical probe 1. Additional mass m. * The calculation formula is:

[0088] m * =C m ρ s V dis (2)

[0089] Among them, C m As an additional mass coefficient, it is usually taken as 0.5, ρ s V is the density of soil. dis Let F be the volume of seabed soil displaced when the spherical probe 1 penetrates the seabed. The pressure resistance F exerted by the soil on the spherical probe 1 is also given. b The calculation formula is:

[0090] F b =ρ s gV dis (3)

[0091] Where g is the acceleration due to gravity. Dragging resistance F d The calculation formula is:

[0092]

[0093] Among them, C d A is the drag coefficient; v is the velocity of the dynamic penetrometer 100, obtained by integrating the acceleration data; A p This represents the maximum cross-sectional area of ​​the spherical probe 1. End bearing resistance F. t The calculation formula is:

[0094] F t =s uo A p N c R fb S fb (5)

[0095] Among them, s uo N represents the undrained shear strength of seabed soil. c R is the bearing capacity coefficient. fb S is the rate effect coefficient. fb This represents the softening effect coefficient.

[0096] When the spherical probe 1 penetrates from the seabed surface to the deeper layers, the flow mechanism of the surrounding soil transitions from a shallow mode to a deep mode. The depth at which this transition occurs is called the critical depth z. t The calculation formula is:

[0097] z t =(3.169α+3.127)·(0.670λ+1)·(1-0.402(1-δ rem )α 0.538 )·D (6)

[0098] Where α is the friction coefficient at the interface between the spherical probe and the seabed soil, λ is the seabed soil ratio parameter, and δ rem The ratio of softening strength to the seabed soil is given, and D is the diameter of the spherical probe 1. Bearing capacity coefficient N. c The calculation formula for the soil flow mechanism around spherical probe 1 in the deep mode is as follows:

[0099] N c =3.975α + 10.660 (7)

[0100] Bearing capacity coefficient N c The calculation formula for the soil flow mechanism around spherical probe 1 when it is in the shallow mode is as follows:

[0101]

[0102] Where z is the depth of the bottom of the spherical probe 1 relative to the seabed surface, called the penetration depth of the spherical probe 1, which is obtained by integrating the acceleration data twice, and e is the natural logarithm.

[0103] drag coefficient C d The calculation formula for the soil flow mechanism around spherical probe 1 in the deep mode is as follows:

[0104]

[0105] Among them, Re n For non-Newtonian Reynolds numbers, the calculation formula is:

[0106]

[0107] drag coefficient C d The calculation formula for the soil flow mechanism around spherical probe 1 when it is in the shallow mode is as follows:

[0108]

[0109] Rate effect coefficient R fb The calculation formula is:

[0110]

[0111] Among them, v ref / D represents the reference shear strain rate, and the velocity v within the reference shear strain rate is... ref The speed is the same as when the subsequent dynamic penetrometer 100 achieves continuous penetration using motor 43. Softening effect coefficient S fb The calculation formula for the soil flow mechanism around spherical probe 1 in the deep mode is as follows:

[0112]

[0113] Where, ξ 95 This represents the cumulative plastic shear strain corresponding to a softening degree of 95% in the seabed soil.

[0114] Softening effect coefficient S fb The calculation formula for the soil flow mechanism around spherical probe 1 when it is in the shallow mode is as follows:

[0115]

[0116] Undrained shear strength s of seabed soil uo This can be derived from equation (15):

[0117] In formulas (5-15), the undrained shear strength s of the seabed soil uo , Spherical probe-seabed soil interface friction coefficient α, seabed soil ratio effect parameter λ, seabed soil softening strength ratio δ rem The cumulative plastic shear strain ξ corresponding to the softening degree of seabed soil reaching 95% 95For unknowns, the spherical probe has a mass m and an acceleration A. cc The weight W of the spherical probe and the interaction force F between the spherical probe and the connecting rod. int Additional quality coefficient C m Density ρ of seabed soil s The volume V of seabed soil displaced when a spherical probe penetrates the seabed. dis , gravitational acceleration g, dynamic penetrometer velocity v, and maximum cross-sectional area A of the spherical probe p The diameter D of the spherical probe, the penetration depth z of the spherical probe, and the speed v of the dynamic penetrometer when it relies on a motor to achieve continuous penetration. ref Given a known quantity, the critical depth z t Bearing capacity coefficient N c Driving drag coefficient C d Rate effect coefficient R fb Softening effect coefficient S fb The undrained shear strength s of seabed soil uo , Spherical probe-seabed soil interface friction coefficient α, seabed soil ratio parameter λ, seabed soil softening strength ratio δ rem The cumulative plastic shear strain ξ corresponding to the softening degree of seabed soil reaching 95% 95 Related.

[0118] The calculation process for seabed soil strength parameters is as follows: Figure 10 As shown, the specific steps are as follows:

[0119] ①Based on the interaction force F between the spherical probe and the connecting rod int The measurement data is divided into j segments based on the variation trend of the spherical probe's insertion depth z. Each segment contains two control points, where the i-th segment contains the (i-1)-th and i-th control points. The interaction force F between the spherical probe and the connecting rod is extracted based on the depth of the selected control points. int,i Dynamic penetrometer acceleration A cc,i and the speed v of the dynamic penetrometer i ;

[0120] ② Select q data points between every two control points, including the interaction force F between the spherical probe and the connecting rod. int Dynamic penetrometer acceleration A cc Combine the velocity v of the powered penetrometer to form a dataset. The superscript p represents the p-th data point selected between the (i-1)-th and ith control points, where p = 1, 2, ..., q;

[0121] ③ Undrained shear strength s of unknown seabed soil uo , Spherical probe-seabed soil interface friction coefficient α, seabed soil ratio effect parameter λ, seabed soil softening strength ratio δ remThe cumulative plastic shear strain ξ corresponding to the softening degree of seabed soil reaching 95% 95 Assign initial values;

[0122] ④ Calculate the critical depth z t Bearing capacity coefficient N c Driving drag coefficient C d Rate effect coefficient R fb Softening effect coefficient S fb ;

[0123] ⑤ Substitute the initial value assigned in ③ and the calculation result in ④ into formula (1) to obtain the interaction force F' between the spherical probe and the connecting rod. int,i The superscript '′' indicates a calculated value rather than an actual measured value, and is related to the actual measured interaction force F' between the spherical probe and the connecting rod. int,i contrast;

[0124] ⑥ Repeat steps ④ and ⑤ based on the global optimization algorithm and update the unknown undrained shear strength s of the seabed soil. uo , Spherical probe-seabed soil interface friction coefficient α, seabed soil ratio parameter λ, seabed soil softening strength ratio δ rem The cumulative plastic shear strain ξ corresponding to the softening degree of seabed soil reaching 95% 95 ;

[0125] ⑦ When the number of iterations reaches the maximum number of iterations set by the global optimization algorithm, stop the iteration and output the undrained shear strength s of the seabed soil. uo , Spherical probe-seabed soil interface friction coefficient α, seabed soil ratio effect parameter λ, seabed soil softening strength ratio δ rem The cumulative plastic shear strain ξ corresponding to the softening degree of seabed soil reaching 95% 95 .

[0126] (2) During the stage when the dynamic cone penetrator 100 continuously and uniformly penetrates the seabed by the motor 43, the interaction force F between the spherical probe and the connecting rod is monitored by the force sensor 7. int This refers to the soil resistance experienced by the spherical probe 1. The formula for calculating the strength of seabed soil is:

[0127] The interaction force F between the spherical probe and the connecting rod int Substituting into equation (16) and iteratively solving using a global optimization algorithm, the undrained shear strength s of the seabed soil is determined. uo The friction coefficient α between the spherical probe and the seabed soil interface, and the ratio of the softening strength of the seabed soil to its δ value. rem The cumulative plastic shear strain ξ corresponding to the softening degree of seabed soil reaching 95% 95 .

[0128] The specific embodiments described above are merely preferred embodiments of the present invention and should not be considered as limiting the scope of the present invention. All equivalent variations and improvements made within the scope of the present invention should still fall within the scope of the claims of the present invention.

Claims

1. A telescopic self-installing dynamic penetrometer characterized in that: the penetrometer is composed of a spherical probe, a connecting rod, a booster, a tail wing and a hook ring from bottom to top; the spherical probe is a sphere and the connecting rod is a cylinder, and the ratio of the cross-sectional area of the connecting rod to the maximum cross-sectional area of the spherical probe is less than 0.1; the length of the connecting rod is not less than 2 times the diameter of the spherical probe; the booster is a cylinder, the front end of the booster is processed into a semi-ellipsoidal shape and connected with the connecting rod, and the tail end of the booster is a gradually tapered circular truncated cone; the hook ring is fixed at the tail end of the booster; the tail wing is fixed at the tail end of the booster at equal angles; a force sensor is arranged between the spherical probe and the connecting rod to measure the interaction force between the spherical probe and the connecting rod, an acceleration sensor is arranged inside the booster to monitor the acceleration of the penetrometer, and a pore pressure sensor is arranged on the spherical probe to measure the water pressure when the penetrometer freely falls in water and the pore water pressure when the penetrometer penetrates into seabed soil; the telescopic self-installing dynamic penetrometer further comprises a device for realizing telescopic self-installation of the penetrometer, which is composed of a blade, a motor, a push rod and a measurement and control collection cabin; the booster comprises an upper booster and a lower booster; both the upper booster and the lower booster are provided with slots at equal angles along the axial direction, and the slots are arranged with fan-shaped blades; when the blades are completely retracted into the slots, the outer edges of the blades do not exceed the slots, and when the blades are opened, they extend out of the slots along the radial direction of the booster; the rear end of the lower booster is hollowed out into a cylindrical cavity to accommodate the front end of the upper booster; a flange is arranged near the lower end of the cylindrical cavity; the front end of the upper booster is a hollow cylinder, and a motor and a push rod are installed in the hollow cylinder; the upper end of the push rod is connected with the motor through the flange; the lower end of the push rod is connected with the lower booster through the flange; the upper part of the push rod is located in a sleeve, and when the motor is started, the push rod is pushed out of the sleeve; the extension and retraction of the blades to the slots are also driven by the motor; a data transmission and collection module and a motor control module are integrated in the measurement and control collection cabin; the force sensor, the acceleration sensor and the pore pressure sensor are connected to the data transmission and collection module; the motor is driven by the motor control module.

2. A telescoping self-installing dynamic penetrometer according to claim 1, wherein, a cable is connected to the hook ring, and the other end of the cable is connected to a survey ship to release and recover the penetrometer; an automatic unhooking device is connected in the middle of the cable.

3. A telescoping self-installing dynamic penetrometer according to claim 1, wherein, The number of tail wings is at least 3.

4. A telescoping self-installing dynamic penetrometer according to claim 1, wherein, The actions of the motor driven by the motor control module are as follows: firstly, the motor is turned on to make the blades of the upper booster extend out of the slots, and when the extension amount of the blades reaches a preset value, the motor continues to be turned on to drive the push rod to move downward, thereby driving the lower booster to move downward to realize the elongation of the dynamic penetrometer; secondly, when the extension amount of the push rod reaches the maximum value, the motor continues to be turned on to make the blades of the lower booster extend out of the slots; then, the motor is reversed to make the blades of the upper booster retract into the slots, and when the blades of the upper booster retract into the slots, the motor continues to be reversed to make the upper booster move downward to realize the contraction of the dynamic penetrometer.

5. A method of operating a telescoping self-installing dynamic penetrometer according to any one of claims 1 to 4, characterised in that, The penetration process of the penetrometer in seabed soil includes two stages of high-speed penetration into seabed soil relying on its own weight and uniform-speed penetration into seabed soil relying on the extension of the booster, which is specifically as follows: (1) The power penetrometer is released from the survey ship into the sea water until a predetermined height above the seabed surface, and then the automatic unhooking is opened, the power penetrometer falls freely from the water and penetrates into the seabed soil at high speed, in the process, the blades in the upper booster and the lower booster are in the retracted state, and the acceleration of the power penetrometer and the interaction force between the spherical probe and the connecting rod are measured in real time; (2) When the power penetrometer penetrates into the seabed soil by relying on the self weight and is static, the blades in the upper booster are extended out of the slot, and then the motor is started to push the push rod downward, pushing the lower booster, the connecting rod and the spherical probe to continue to move downward, because the upper surface of the extended blades in the upper booster is subjected to passive earth pressure, so that the upper booster remains static in the seabed soil, at this time the upper booster is equivalent to a counterforce frame, in the process the interaction force between the spherical probe and the connecting rod is monitored; (3) The blades of the lower booster are extended, and then the blades of the upper booster are retracted, at this time the lower booster, the connecting rod and the spherical probe are equivalent to a counterforce frame, the motor is reversed to retract the push rod, at this time the upper booster moves downward against the resistance of the soil; (4) Steps (2) and (3) are repeated to realize the continuous penetration of the power penetrometer in the seabed soil, so as to measure the strength parameters of the deep seabed soil; (5) When the measured depth reaches the designed depth, the blades on the booster are retracted, the cable is tensioned from the survey ship, the power penetrometer is pulled out of the seabed and recovered to the survey ship.

6. A method of operating a telescoping self-installing dynamic penetrometer according to claim 5, wherein, The power supply of the motor has two modes of built-in and external, the built-in power supply is directly packaged in the telescopic self-installed power penetrometer, and the external power supply is placed on the survey ship.

7. The telescopic self-installed power penetrometer according to any one of claims 1-4 is applied to a seabed soil strength parameter calculation method, and the data obtained by the telescopic self-installed power penetrometer is calculated, characterized in that, (1) The telescopic self-installed power penetrometer penetrates into the seabed at high speed by relying on its own weight: The force balance equation of the spherical probe when the telescopic self-installed power penetrometer penetrates into the seabed soil by relying on its own weight is: (m+m * )A cc = W + F int - F b - F d - F t (1) Wherein, m is the mass of the spherical probe, m * is the additional mass; A cc is the acceleration, measured by the acceleration sensor; W is the weight of the spherical probe; F int is the interaction force between the spherical probe and the connecting rod, measured by the force sensor; F b is the differential pressure resistance of the soil on the spherical probe, F d is the drag resistance on the spherical probe, F t is the end bearing resistance on the spherical probe; The additional mass m * The calculation formula is: m * =C m ρ s V dis (2) where C m is the added mass coefficient, p s is the seabed soil density, V dis is the volume of the seabed soil displaced by the spherical probe as it penetrates the seabed; the pressure resistance F b experienced by the soil on the spherical probe is calculated as: F b = p s gV dis (3) Wherein, g is the acceleration of gravity; Drag force F d The formula for calculating the drag force F is: where C d is the drag coefficient, v is the velocity of the dynamic penetrometer, obtained by integrating the acceleration data, A p is the maximum cross-sectional area of the spherical probe; End resistance F t The calculation formula is: F t = s uo A p N c R fb S fb (5) where s uo cu is the undrained shear strength of seabed soil, N c R is a bearing capacity coefficient fb S is a rate effect coefficient fb is a softening effect coefficient The flow mechanism of the seabed soil around the spherical probe transits from the shallow layer mode to the deep layer mode when the spherical probe penetrates into the deep layer from the seabed surface. The depth of the transition from the shallow layer to the deep layer is called the critical depth z t , and the calculation formula is: z t = (3.169a + 3.127) · (0.670l + 1) · (1 - 0.402(1 - d rem )a 0.538 ) · D (6) wherein a is the spherical probe-seabed soil interface friction coefficient, λ is the seabed soil rate parameter, δ rem is the softening strength ratio of seabed soil, and D is the diameter of the spherical probe. Coefficient of bearing capacity N c The formula for the case when the seabed soil flow mechanism around the spherical probe is in the deep mode is: N c ＝3.975α+10.660 (7) Coefficient of bearing capacity N c The formula for the case when the seabed soil flow mechanism around the spherical probe is in the shallow layer mode is: Wherein, z is the penetration depth of the bottom end of the spherical probe relative to the seabed surface, referred to as the soil penetration depth of the spherical probe, obtained by integrating the acceleration data twice, e is the natural logarithm; Drag coefficient C d The formula for the flow mechanism around the spherical probe in the deep layer mode of seabed soil is as follows: where Re n is the Reynolds number for non-Newtonian fluids, calculated as: Drag coefficient C d The formula for the flow mechanism around the spherical probe in the shallow layer mode is as follows: Rate effect coefficient R fb The formula for calculating R is: where v ref D is the reference shear strain rate, the velocity v ref The same as the speed of the subsequent dynamic penetrometer relies on the motor to achieve continuous penetration. Softening effect coefficient S fb The formula for the seabed soil flow mechanism around the spherical probe in the deep mode is: where ξ 95 is the cumulative plastic shear strain corresponding to 95% softening of the seabed soil. Softening effect coefficient S fb The formula for the case when the seabed soil flow mechanism around the spherical probe is in the shallow layer mode is: undrained shear strength s of the seabed soil uo From equation (15) we have: In formula (5-15), the undrained shear strength s of seabed soil uo , the friction coefficient α of the spherical probe-seabed soil interface, the rate effect parameter λ of seabed soil, and the softening strength ratio δ of seabed soil rem , the cumulative plastic shear strain ξ corresponding to the softening degree of seabed soil reaching 95% 95 are unknown, the mass m and acceleration A of the spherical probe cc , the weight W of the spherical probe and the interaction force F between the spherical probe and the connecting rod int , the additional mass coefficient C m , the density ρ of seabed soil s , the volume V of seabed soil displaced by the spherical probe when penetrating into seabed dis , the gravitational acceleration g, the movement speed v of the dynamic penetration tester, and the maximum cross-sectional area A of the spherical probe p , the diameter D of the spherical probe, the soil penetration depth z of the spherical probe, and the speed v of the dynamic penetration tester when continuously penetrating by means of the motor ref are known, and the critical depth z t , the bearing capacity coefficient N c , the drag resistance coefficient C d , the rate effect coefficient R fb , the softening effect coefficient S fb , and the undrained shear strength s of seabed soil uo , the friction coefficient α of the spherical probe-seabed soil interface, the rate effect parameter λ of seabed soil, and the softening strength ratio δ of seabed soil rem , the cumulative plastic shear strain ξ corresponding to the softening degree of seabed soil reaching 95% 95 are related. The power penetrometer acceleration A cc , the velocity v, the interaction force F between the spherical probe and the connecting rod int and the spherical probe penetration depth z into the seabed soil into equation (15) and iteratively solved by a global optimization algorithm to determine the undrained shear strength s of the seabed soil uo , the spherical probe-seabed soil interface friction coefficient α, the seabed soil rate parameter λ, the seabed soil softening strength ratio δ rem , the cumulative plastic shear strain ξ corresponding to the seabed soil softening degree reaching 95% 95 ; (2) The power penetrometer continuously penetrates into the seabed by relying on the motor drive: The interaction force F between the spherical probe and the connecting rod monitored by the force sensor int The soil resistance on the spherical probe is obtained, and the seabed soil strength calculation formula is: The interaction force F between the spherical probe and the connecting rod is measured by a load cell int Substitute into equation (16) and solve iteratively by a global optimization algorithm to determine the undrained shear strength s of the seabed soil uo The friction coefficient α between the spherical probe and the seabed soil, the softening strength ratio δ of the seabed soil rem The cumulative plastic shear strain ξ corresponding to the softening degree of 95% of the seabed soil 95 .

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