Method for testing dynamic and static bearing capacity of sediment based on marine static sounding

Abstract

According to the method for testing the dynamic and static bearing capacity of the sediment based on the ocean static sounding, an ocean static sounding instrument is provided with a spherical probe with the cross section area being 100 cm < 2 > and is provided with a penetration resistance sensor, a pore water pressure sensor, an attitude sensor and the like which are arranged on a conventional static sounding instrument; a penetration device, a power supply and an acquisition system of the static penetrometer are used for data acquisition, and the dynamic bearing capacity characteristics of the sediments are obtained through multiple times of penetration at different penetration speeds, calculation of the rate effect coefficient of the sediments and service of the dynamic bearing capacity characteristics of the sediments at different walking speeds of a mine car in the submarine manganese nodule mining process.

Description

Technical Field:

[0001] This application relates to the field of determining the mechanical properties of deep-sea soft soil. Specifically, it particularly relates to a method for testing the static and dynamic bearing capacities of sediments based on marine static cone penetration testing. Background Art:

[0002] In the fields of marine oil and gas, mineral resource development, and submarine engineering construction, the bearing capacity characteristics of deep-sea soft soil are one of the important parameters determining the construction of engineering facilities and the safe operation of equipment. With the deepening of deep-sea development, the demands for deep-sea mining and energy development are also continuously increasing, especially for the exploitation of mineral resources such as manganese nodules. During the process of deep-sea manganese nodule mining, it is necessary to place the ore vehicle on the seabed for ore collection operations, and its safety and operational stability are directly affected by the bearing capacity of the seabed surface soil. When the ore vehicle operates in the deep sea, it needs to move and position on the seabed. The bearing characteristics of the surface soil are related to both the safety and stability of the ore vehicle equipment and the efficiency of the entire ore collection process.

[0003] Moreover, when the seabed ore vehicle is in a non-operating state, the bearing capacity of the seabed surface soil will still affect it, affecting the safety and stability of the ore vehicle during long-term static periods. And when the ore vehicle is in an operating state, as the operating speed changes, the bearing capacity of the sediment will also change accordingly. This characteristic will cause settlement or uplift phenomena during the movement of the ore vehicle, affecting the smooth operation of the equipment. The settlement or uplift problems of the ore vehicle will make it difficult for the ore vehicle to maintain a stable operating posture, thereby affecting the operation efficiency and accuracy, and at the same time increasing the wear of the ore vehicle and its system components under different working conditions, greatly increasing the equipment maintenance and operation costs. Due to the complexity of the deep-sea environment and the limitations of traditional assessment methods, it is difficult to obtain accurate parameters suitable for deep-sea working conditions only relying on existing bearing capacity prediction means. Therefore, developing a bearing capacity assessment technology based on deep-sea static cone penetration data and precisely testing and interpreting the data of the bearing capacity characteristics of deep-sea surface soft soil can not only improve the operation efficiency and safety of ore vehicles in the deep-sea environment, but also effectively reduce the costs of deep-sea mining and submarine engineering. The application of this technology will provide a more reliable design basis and operation guarantee for deep-sea mining equipment and other submarine engineering facilities, and contribute to the efficient development and sustainable utilization of deep-sea resources. Summary of the Invention:

[0004] To make up for the deficiencies of the existing technology, this application provides a method for testing the static and dynamic bearing capacities of sediments based on marine static cone penetration testing and its...

[0005] The static cone penetration system of this application is equipped with a cross-sectional area of 100 cm 2The spherical probe is designed specifically for deep - sea use and has the characteristics of corrosion resistance, pressure resistance, and low - temperature resistance to adapt to the deep - sea environment with high pressure, high salinity, and low temperature. In addition, a variety of sensors are integrated on the probe, including a penetration resistance sensor, a pore water pressure sensor, and an attitude sensor, etc., which can monitor the penetration resistance, pore water pressure, and equipment attitude of the probe in real time. These sensors are connected to the penetration device, power supply, and data acquisition system to ensure that data can be recorded and transmitted quickly and accurately. The device is also designed with a multi - layer protection structure and a stability system to ensure the reliability of long - term operation in the deep - sea environment.

[0006] The specific test method is as follows:

[0007] Step S1, deployment, including the installation and release of the static cone penetrometer. First, connect the static cone penetrometer to the geological winch, start all the sensors inside the device to ensure the normal function of the equipment. After the device is started, use the geological winch to lower the static cone penetrometer to the seabed. During the lowering process, the device monitors parameters such as water depth, pressure, and position in real time to ensure that the instrument is stably parked after reaching the seabed. This step ensures the stability of the static cone penetrometer and provides a reliable basis for subsequent penetration tests.

[0008] Step S2, primary penetration test. After the static cone penetrometer is stable on the seabed, set the penetration speed of the probe to 0.02 m / s through the deck unit to ensure that the probe can enter the sediment layer smoothly and evenly, avoiding disturbing the natural state of the sediment. After the probe penetrates to the predetermined depth, keep it static for 5 minutes to ensure the stable contact between the soil and the probe and achieve ideal data acquisition accuracy. After the static period, use the winch to gradually recover the drill rod to the seabed surface position.

[0009] Step S3, secondary penetration test, mainly for the secondary penetration at adjacent stations to obtain the in - situ rate effect coefficient. Raise the static cone penetrometer 5 meters with the geological winch, and after ensuring the stable position of the device, conduct the penetration test again. At this time, set the penetration speed of the probe to 0.05 m / s, repeat the penetration step, and collect the penetration resistance data at different speeds. This test also maintains a 5 - minute static period, and then recover the drill rod again.

[0010] Step S4, data reading and device cleaning. After the test is completed, use the geological winch to recover the device to the deck and clean the test equipment to remove sediments and other attachments. After cleaning, read all the collected data from the data acquisition system, including parameters such as penetration resistance, pore water pressure, and attitude, to provide raw data support for data interpretation and analysis.

[0011] Step S5, calculation and adjustment of the penetration angle. Calculate the penetration angle of the probe using the data from the attitude sensor to ensure the validity of the data during the penetration test. When the penetration angle of the probe is greater than 15°, re - execute the penetration step until the angle is less than 15° to improve the data accuracy and reliability. The calculation formula for the penetration angle is as follows:

[0012]

[0013] where θ h is the penetration angle of the probe, and φ and θ are the rotation angles in two mutually perpendicular directions in the horizontal direction of the attitude sensor. This step ensures that the probe enters the soil mass at an angle close to vertical, avoiding measurement errors caused by the inclination of the probe.

[0014] Optionally, it also includes:

[0015] Determination of the velocity effect coefficient. This application introduces the velocity effect coefficient λ to characterize the influence of different penetration velocities on the bearing capacity characteristics of sediments. The calculation formula is as follows:

[0016]

[0017] where λ is the rate effect coefficient, q t0.02 is the penetration resistance measured at a penetration velocity of 0.02 m / s, q t0.02 is the penetration resistance measured at a penetration velocity of 0.05 m / s, v 1 is the penetration velocity during the first penetration, and v 2 is the penetration velocity during the second penetration.

[0018] Determination of the undrained shear strength. By calculating the in - situ undrained shear strength s u of the sediment, further evaluate the bearing capacity strength of the soil mass. The calculation formula for this parameter is:

[0019]

[0020] where s u is the in - situ undrained shear strength of the sediment, and N t is the penetration resistance coefficient.

[0021] Determination of the static bearing capacity and dynamic bearing capacity. This application provides calculation methods for the static bearing capacity and dynamic bearing capacity to help evaluate the performance of sediments under different loads. Under static load, the static bearing capacity of the sediment is:

[0022] Q s = s u ·S (4)

[0023] where Q sis the static bearing capacity of the sediment, and S is the cross-sectional area of ​​the probe. Under dynamic loads, such as when a mine car is moving on the seabed, the dynamic bearing capacity of the sediment is as follows:

[0024] Q w =s u ·S·(1+λlg(v / v 2 )) (5)

[0025] Among them, Q w is the dynamic bearing capacity of sediment, v is the dynamic bearing capacity of sediment under a certain velocity to be calculated. The dynamic bearing capacity of sediment under different velocities can be calculated according to formula (5).

[0026] The method for testing the dynamic and static bearing capacity of sediments based on marine static penetration provided in this application has the following advantages:

[0027] 1. Enhanced adaptability and reliability in deep-sea environments. This application uses a special spherical probe and a high-pressure and corrosion-resistant design, which can work for a long time in complex deep-sea environments, avoiding data distortion and equipment damage caused by environmental factors. Equipped with a variety of sensors to monitor penetration resistance, pore water pressure and probe posture in real time, ensuring accurate measurement of the equipment in various water depths and pressure environments, and improving the adaptability of the system.

[0028] 2. Improve data accuracy and consistency. Through precise penetration speed control and penetration angle monitoring functions, this application effectively reduces the error caused by probe tilt or speed fluctuation. The design of multiple penetrations and automatic adjustment of penetration angles ensures the accuracy and consistency of data, which is especially suitable for mechanical property testing of deep-sea soft soil. The bearing capacity data obtained is more reliable, providing a more reliable data basis for engineering applications.

[0029] 3. Solve the impact of velocity effect and improve the applicability of results. By introducing the calculation of velocity effect coefficient (λ), this application can correct the impact of different penetration velocities on test results. This innovative design ensures the applicability of the measured undrained shear strength and dynamic bearing capacity of sediments under different velocity conditions, making it possible to evaluate the impact of equipment on seabed sediments under dynamic loads, especially suitable for the engineering needs of dynamic equipment such as deep-sea mining vehicles.

[0030] 4. Supports comprehensive evaluation of static and dynamic bearing capacity, expanding the scope of application. This application can not only obtain the static bearing capacity of sediments, but also provide a method for calculating dynamic bearing capacity, which can evaluate the response of sediments under the action of mine car movement or other dynamic loads. This method is particularly suitable for scenarios that require comprehensive bearing capacity evaluation, such as deep-sea mining operations, submarine pipeline and platform construction, and provides comprehensive data support for submarine equipment design.

[0031] 5. It improves the safety and economy of deep-sea operations. The high-precision bearing capacity data provided by this application can help optimize the selection and design of deep-sea equipment, reduce problems such as equipment damage and reduced mining efficiency caused by settlement or uplift, and thus significantly reduce the safety hazards and operating costs of deep-sea operations. This has important economic and safety significance for equipment such as deep-sea mining vehicles and oil and gas platforms working in the deep-sea environment. Description of the Drawings:

[0032] The above and / or additional aspects and advantages of this application will become apparent and easy to understand from the description of the embodiments in conjunction with the following drawings, where:

[0033] Figure 1 It is a schematic diagram of a static cone penetration instrument for the method of testing the static and dynamic bearing capacities of sediments based on marine static cone penetration provided by this application;

[0034] Figure 2 It is a schematic flow diagram of the method of testing the static and dynamic bearing capacities of sediments based on marine static cone penetration provided by this application;

[0035] Figure 3 It is a comparison chart of the static bearing capacity and dynamic bearing capacity of sediments for the method of testing the static and dynamic bearing capacities of sediments based on marine static cone penetration provided by this application. Detailed Embodiments:

[0036] In order to be able to more clearly understand the above objects, features, and advantages of this application, the following further detailed description of this application is made in conjunction with the drawings and specific embodiments. It should be noted that, without conflict, the embodiments of this application and the features in the embodiments can be combined with each other.

[0037] Many specific details are set forth in the following description in order to fully understand this application. However, this application can also be implemented in other ways different from those described herein. Therefore, the protection scope of this application is not limited by the specific embodiments disclosed below.

[0038] As Figure 1 shown, it is a static cone penetration instrument diagram for the method of testing the static and dynamic bearing capacities of sediments based on marine static cone penetration provided by this application. The static cone penetration instrument is equipped with a cross-sectional area of 100 cm 2The spherical probe is designed for deep - sea use. It has the characteristics of corrosion resistance, pressure resistance and low - temperature resistance to adapt to the deep - sea environment with high pressure, high salinity and low temperature. In addition, a variety of sensors are integrated on the probe, including a resistance sensor, a pore - water pressure sensor (piezometer) and an attitude sensor, etc., which can monitor the penetration resistance, pore - water pressure and the attitude of the device in real time. These sensors are connected to the penetration device, power supply and data acquisition device to ensure that data can be recorded and transmitted quickly and accurately. The device is also designed with a multi - layer protection structure and a stabilization system to ensure the reliability of long - term operation in the deep - sea environment.

[0039] Combined with Figure 2 The specific steps of the method for testing the static and dynamic bearing capacities of sediments based on marine piezocone penetration test provided by this application are as follows:

[0040] First, release the piezocone penetrometer, which mainly includes the installation and release of the piezocone penetrometer. First, connect the piezocone penetrometer to the geological winch, start all the sensors inside the device to ensure the normal function of the equipment. After the device is started, use the geological winch to lower the piezocone penetrometer to the seabed. During the lowering process, the device monitors parameters such as water depth, pressure and position in real time to ensure that the instrument is stably parked after reaching the seabed. This step ensures the stability of the piezocone penetrometer and provides a reliable basis for subsequent penetration tests.

[0041] Secondly, conduct a primary penetration test. After the piezocone penetrometer is stable on the seabed, set the penetration speed of the probe to 0.02 m / s through the deck unit to ensure that the probe can smoothly and evenly enter the sediment layer and avoid disturbing the natural state of the sediment. After the probe penetrates to the predetermined depth, keep it static for 5 minutes to ensure the stable contact between the soil and the probe and achieve ideal data acquisition accuracy. After static, use the winch to gradually recover the drill rod to the seabed surface position.

[0042] Thirdly, conduct a secondary penetration test, mainly for the secondary penetration at similar stations to obtain the in - situ rate effect coefficient. Raise the piezocone penetrometer 5 meters with the geological winch, and after ensuring the stable position of the device, conduct the penetration test again. At this time, set the penetration speed of the probe to 0.05 m / s, repeat the penetration step, and collect the penetration resistance data at different speeds. This test also maintains a static time of 5 minutes, and then recover the drill rod again.

[0043] Data reading and device cleaning. After the test is completed, use the geological winch to recover the device to the deck and clean the test equipment to remove sediments and other attachments. After cleaning, read all the collected data from the data acquisition system, including parameters such as penetration resistance, pore - water pressure and attitude, to provide raw data support for data interpretation and analysis.

[0044] Calculation and adjustment of the penetration angle. The attitude sensor data is used to calculate the penetration angle of the probe to ensure the validity of the data during the penetration test. When the penetration angle of the probe is greater than 15°, the penetration step is re-executed until the angle is less than 15° to improve the data accuracy and reliability. The calculation formula for the penetration angle is as follows:

[0045]

[0046] where θ h is the penetration angle of the probe, and φ and θ are the rotation angles in two mutually perpendicular directions in the horizontal direction of the attitude sensor. This step ensures that the probe enters the soil mass at an angle close to vertical, avoiding measurement errors caused by the tilt of the probe.

[0047] Determination of the velocity effect coefficient. This application introduces the velocity effect coefficient λ to characterize the influence of different penetration velocities on the bearing capacity characteristics of sediments. The calculation formula is as follows:

[0048]

[0049] where λ is the rate effect coefficient, q t0.02 is the penetration resistance measured at a penetration velocity of 0.02 m / s, q t0.02 is the penetration resistance measured at a penetration velocity of 0.05 m / s, v 1 is the penetration velocity during the first penetration, v 2 is the penetration velocity during the second penetration.

[0050] Determination of the undrained shear strength. By calculating the in-situ undrained shear strength s u of the sediment, the bearing capacity strength of the soil mass is further evaluated. The calculation formula for this parameter is:

[0051]

[0052] where s u is the in-situ undrained shear strength of the sediment, and N t is the penetration resistance coefficient.

[0053] Determination of the static bearing capacity and dynamic bearing capacity. This application provides calculation methods for the static bearing capacity and dynamic bearing capacity to help evaluate the performance of sediments under different loadings. Under static loading, the static bearing capacity of the sediment is:

[0054] Q s =s u ·S (4)

[0055] where Q s$Q_{s}$ is the static bearing capacity of the sediment, and $S$ is the cross-sectional area of the probe. Under dynamic loads, for example, when a mining cart travels on the seabed, the formula for the dynamic bearing capacity of the sediment is as follows:

[0056] $Q$ w $= s$ u $\cdot S\cdot(1 + \lambda\lg(v / v$ 2 $))\ (5)$

[0057] Where $Q$ w is the dynamic bearing capacity of the sediment, and $v$ is the dynamic bearing capacity of the sediment at a certain speed to be calculated. The dynamic bearing capacity of the sediment under different speed conditions can be calculated according to formula (5).

[0058] Figure 3 This is a calculation example of this method, which calculates the difference between the static bearing capacity calculated by the conventional static cone penetration test and the dynamic bearing capacity calculated by this method. The test point of this figure is located in a certain sea area of the South China Sea. Among them, the blue line represents the bearing capacity measured by the static cone penetration test technology, the red line represents the bearing capacity characteristics when the traveling speed of the mining cart is 0.6 m / s, and the black line represents the bearing capacity characteristics when the traveling speed of the mining cart is 1 m / s. It can be seen that the greater the traveling speed of the mining cart, the greater its bearing capacity, but as the traveling speed of the mining cart increases, the increase in the bearing capacity becomes less. Based on this, a reasonable traveling speed of the mining cart can be designed to ensure that the bearing capacity of the sediment is large enough and the collection efficiency of the mining cart is high enough as much as possible.

[0059] In the description of this application, the term "a plurality" means two or more. Unless otherwise clearly defined, the orientation or positional relationship indicated by terms such as "upper", "lower", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to this application; terms such as "connection", "installation", "fixation", etc. should all be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0060] In the description of this specification, the description of terms such as "one embodiment", "some embodiments", "specific embodiments", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of this application. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0061] The above are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A method for testing the dynamic and static bearing capacity of sediments based on marine static penetration, characterized in that: The specific steps include: Step S1: deployment; mainly includes the installation and release of the static penetration instrument. First, the static penetration instrument is connected to the geological winch, and all sensors inside the static penetration instrument are started to ensure that the equipment functions normally. After the device is started, the geological winch is used to lower the static penetration instrument to the seabed. During the lowering process, the device monitors the water depth, pressure and position parameters in real time to ensure that the instrument is stably parked after reaching the seabed. This step ensures the stability of the static penetration instrument and provides a reliable basis for subsequent penetration tests. Step S2: a penetration test; after the static penetration instrument is stable on the seabed, the penetration speed of the probe is set to 0.02m / s through the deck unit to ensure that the probe can enter the sediment layer smoothly and evenly to avoid disturbing the natural state of the sediment. After the probe penetrates to the predetermined depth, it is kept still for 5 minutes to ensure that the contact between the soil and the probe is stable so that the data acquisition can achieve the desired accuracy; after standing still, the probe rod is gradually recovered to the seabed surface using a winch, which can realize the parameters required for calculating the penetration resistance of the seabed sediment; Step S3: secondary penetration test; mainly secondary penetration at similar positions is carried out to obtain the in-situ rate effect coefficient, the static penetration instrument is raised by 5 meters with a geological winch, and the penetration test is carried out again after ensuring that the position of the device is stable. At this time, the probe penetration speed is set to 0.05m / s, the penetration steps are repeated, and the penetration resistance data at different speeds are collected; the test also maintains a static time of 5 minutes, and then the probe is recovered again. The secondary penetration test mainly carries out secondary penetration at similar positions to obtain the in-situ rate effect coefficient, the static penetration instrument is raised by 5 meters with a geological winch, and the penetration test is carried out again after ensuring that the position of the device is stable. At this time, the probe penetration speed is set to 0.05m / s, the penetration steps are repeated, and the penetration resistance data at different speeds are collected; the test also maintains a static time of 5 minutes, and then the probe is recovered again. This step can obtain the variation characteristics of the penetration resistance under different penetration speeds with the penetration speed in this environment, which is used to calculate the rate effect coefficient. This method overcomes the deficiency that the static penetration technology can only test static process parameters; Step S4: Data reading and device cleaning: After the test is completed, the device is recovered to the deck using a geological winch, and the test equipment is cleaned to remove sediments and other attachments. After cleaning, all collected data are read from the data acquisition system, including parameters such as penetration resistance, pore water pressure, and attitude, to provide raw data support for data interpretation and analysis; Step S5: Calculation and adjustment of the penetration angle; use the data of the attitude sensor to calculate the penetration angle of the probe to ensure the validity of the data during the penetration test; when the penetration angle of the probe is greater than 15°, re-execute the penetration step 2 until the angle is less than 15° to improve the data accuracy and reliability; the calculation formula of the penetration angle is as follows: Among them, θ h is the penetration angle of the probe, φ and θ are the rotation angles of the attitude sensor in two mutually perpendicular directions in the horizontal direction. This step ensures that the probe enters the soil at a nearly vertical angle to avoid measurement errors caused by probe tilt.

2. The method for testing the dynamic and static bearing capacity of sediments based on marine static penetration according to claim 1, characterized in that: It is necessary to introduce the velocity effect coefficient λ to characterize the influence of different penetration velocities on the sediment bearing capacity characteristics. The calculation formula is as follows: Among them, λ is the rate effect coefficient, q t0.02 is the penetration resistance measured at a penetration velocity of 0.02 m / s, q t0.05 is the penetration resistance measured at a penetration velocity of 0.05 m / s, v1 is the penetration velocity at the first penetration, and v2 is the penetration velocity at the second penetration.

3. The method for testing the dynamic and static bearing capacity of sediments based on marine static penetration as claimed in claim 2, characterized in that: The bearing capacity characteristics of sediments require the use of the undrained shear strength of sediments. The formula for the undrained shear strength of sediments based on static penetration technology is: Among them, s u is the in-situ undrained shear strength of sediment, N t is the penetration resistance coefficient.

4. The method for testing the dynamic and static bearing capacity of sediments based on marine static penetration as claimed in claim 3, characterized in that: By determining the static bearing capacity and dynamic bearing capacity, the calculation method of the static bearing capacity and dynamic bearing capacity can help evaluate the performance of sediments under different loads. Under static load, the static bearing capacity of sediments is: Q s =s u ·S (4) Among them, Q s is the static bearing capacity of sediment, S is the cross-sectional area of ​​the probe; Under dynamic loads, such as when a mine car travels on the seabed, the dynamic bearing capacity of the sediment is as follows: Q w =s u ·S·(1+λlg(v / v2)) (5) Among them, Q w is the dynamic bearing capacity of the sediment, v is the dynamic bearing capacity of the sediment at a certain velocity to be calculated, and the dynamic bearing capacity of the sediment at different velocities can be calculated according to formula (5).

5. The method for testing the dynamic and static bearing capacity of sediments based on marine static penetration according to claim 1, characterized in that: The static penetration instrument consists of a penetration device, a power system, a collection system and a probe. The probe of the seabed static penetration technology uses a cross-sectional area of ​​100cm 2 The spherical probe is designed for deep-sea use and is corrosion-resistant, pressure-resistant and low-temperature-resistant to adapt to the deep-sea environment of high pressure, high salinity and low temperature. The probe is integrated with a variety of sensors, including penetration resistance sensors, pore water pressure sensors and attitude sensors, which can monitor the penetration resistance, pore water pressure and equipment attitude of the probe in real time. The sensors are connected to the penetration device, power supply and data acquisition system to ensure that data can be recorded and transmitted quickly and accurately. The equipment is also designed with a multi-layer protection structure and a stabilization system to ensure the reliability of long-term operation in the deep-sea environment.

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