WO2019218115A1

WO2019218115A1 - New lightweight dynamic mounting anchor and mounting method

Info

Publication number: WO2019218115A1
Application number: PCT/CN2018/086701
Authority: WO
Inventors: 刘君; 韩聪聪
Original assignee: 大连理工大学
Priority date: 2018-05-14
Filing date: 2018-05-14
Publication date: 2019-11-21

Abstract

A new lightweight dynamic mounting anchor and a mounting method therefor. Said anchor comprises a wing plate (11), an anchor shank (12) and a connecting rod (14). The wing plate (11) is composed of two triangular flat plates symmetrically spliced together, and the connecting rod (14) is mounted on the tail of the wing plate (11). The anchor shank (12) is an inverted V-shaped structure composed of two trapezoidal flat plates which are symmetrically fixed to the wing plate (11). A propeller (2) may be secured to the tail of the anchor by means of a shear pin (3), forming a combined anchor with the anchor. During mounting, the combined anchor is first launched into seawater, and a mounting anchor chain (4) is released, so that the combined anchor penetrates into the soil, then the mounting anchor chain (4) is tensioned, the shear pin (3) is sheared off, the propeller (2) is pulled out, and the anchor is left in the soil; a working anchor chain (5) is tensioned to adjust the angle of the anchor; and the propeller (2) is taken out for the mounting of the next anchor. The anchor above has the advantages of light weight, high loading efficiency, deep penetration depth in soil, and low cost.

Description

Novel lightweight power installation anchor and installation method

Technical field

The invention belongs to the technical field of marine engineering and relates to a novel lightweight power installation anchor and installation method.

Background technique

With the rapid development of the social economy and the gradual depletion of oil and gas resources in the shallow sea, people have gradually turned the development of oil and gas resources into the deep sea. In deep-sea environments with water depths in excess of 300–500 m, oil and gas exploration, collection and storage equipment are primarily connected by anchoring systems to anchoring foundations acting on the surface of the seabed or embedded in the seabed. Therefore, the anchoring foundation is the root of the mooring system and is the premise guarantee for the safe operation of the superstructure. The anchoring foundations suitable for deep sea mooring systems mainly include suction caisson, tow anchor, suction mounting plate anchor and power mounting anchor. The suction caisson needs to be pumped outward from the valve at the top of the caisson to create a negative pressure inside the caisson, thus pressing the caisson into the seabed to the required depth. Towing anchors need to be towed from the surface of the seabed to a certain depth in the seabed by means of a tugboat. Suction mounting plate anchors need to be lifted by suction caisson. After the installation, the caisson is pulled out, and then the anchor chain is tensioned to turn the anchor to the angle required for working. The power installation anchor does not need to rely on external force during installation. The kinetic energy obtained by the free fall of the anchor in the water and the self-gravity potential penetrate into the soil to a certain depth, and rely on the anchoring force of the surrounding soil to provide the pull-out bearing capacity. Therefore, compared with the first three anchoring foundations, the power mounting anchor has the advantages of short installation time and low installation cost, so it has broad development prospects in marine engineering.

The power anchors currently used in practical engineering are mainly torpedo anchors (US Patent, Patent No. 6106199) and multidirectional load anchors (US Patent, Patent No. 7052923, B1). The torpedo anchor consists of a cylindrical central shaft with a semi-ellipsoidal or tapered front end and a few empennages. The central shaft is used to provide the weight of the anchor so that the anchor can penetrate into the soil without the aid of external forces. Improve the orientation stability of the anchor when it falls in the water. However, since the anchor eye position is located at the uppermost end of the anchor axis, the uplift bearing capacity of the anchor is mainly provided by the frictional force on the anchor-soil contact surface when subjected to the uplift load, so the anchor bearing efficiency is low. The multiple load anchors are composed of three plates that are mutually 120°. The surface area of the anchor is larger, which increases the contact area between the anchor and the surrounding soil, and the anchor eye position is close to the front end of the anchor, so the anchor is subjected to the uplift load. Rotation occurs at this time, thereby increasing the projected area of the anchor in a direction perpendicular to the upward pulling load to increase the uplift bearing capacity. However, multiple load-bearing anchors are light in weight and have a large surface area, resulting in a limited depth of anchoring in the soil. The soft clay of the seabed is generally normal consolidated soil or slightly over-consolidated soil, and the soil strength increases linearly with depth, so the smaller the installation depth of the anchor, the smaller the corresponding pull-out bearing capacity.

The invention absorbs the advantages of the power anchor and proposes a new light-weight deep penetrating plate anchor (L-DPPA). The anchor is mainly composed of a wing plate, an anchor handle and an anchor eye. The wing plate is composed of two triangular plates, which increases the anchor-soil contact area and thus increases the bearing capacity. In order to increase the depth of penetration of the anchor in the seabed, the anchor needs to be driven by means of a propeller. The propeller is mainly composed of a cylindrical central shaft, a empennage and an anchor eye. It can be attached to the tail of the anchor to increase the penetration speed and depth of the anchor. After the installation, the propeller can be recycled for the installation of the next anchor. . By adjusting the size of the anchor and the weight of the propeller, the anchor can be applied to the seabed of various strengths and various soils including clay and sand.

Summary of the invention

In order to solve the above problems, the present invention proposes a new lightweight power installation anchor and installation method, including a new lightweight power installation anchor (L-DPPA) and a power installation method for anchor installation by means of a propeller.

The technical solution of the invention:

The utility model relates to a novel lightweight power installation anchor, which is mainly composed of a wing plate 11, an anchor handle 12 and a connecting rod 14; the wing plate 11 is composed of two triangular plates symmetrically spliced, and the angle between the two is adjusted according to engineering requirements. The two triangular plates of the wing 11 are symmetrically provided with a plurality of openings a15; the connecting rod 14 is mounted on the tail of the wing 11, and the connecting rod 14 is provided with an opening b17, which is connected by the shear pin 3. The rod 14 is fixedly connected with the pusher 2; the anchor handle 12 is an inverted V-shaped structure composed of two trapezoidal flat plates, and the bottom of the anchor handle 12 is provided with a plurality of openings c18, and the opening c18 and the opening a15 cooperate with each other. The anchor shank 12 is symmetrically fixed to the two triangular flat plates of the wing 11 by bolts 16; the top of the anchor shank 12 is provided with an anchoring eye 13 for connecting the working anchor chain 5 to provide a pull-out bearing capacity; In the fixed position, the anchor shank 12 moves up and down along the axial direction of the flap 11, thereby changing the offset of the anchor eye 13, that is, the distance from the anchor eye 13 to the soil resistance center of the flap 11 in the axial direction of the flap 11. , so that the new lightweight power installation anchor has the ability to dive when subjected to the uplift load, new Dynamic light thereby mounting anchor embedded in the soil bearing capacity is obtained.

A new lightweight power installation anchor mounting method, the installation anchor chain 4 is connected to the propeller anchor eye 23; the connecting rod 14 is fixed in the front end slot 25 of the propeller shaft by the shear pin 3, so that the new light The mass-powered mounting anchor 1, the pusher 2 and the shear pin 3 are assembled in combination to form a combined anchor; the working anchor chain 5 is connected to the anchor eye 13;

Specific steps are as follows:

Firstly, the combined anchor is released into the seawater, so that the combined anchor is located above the surface of the seabed, then the anchor chain 4 is loosened, the combined anchor is free to fall in the water, and the kinetic energy obtained by the free fall and the gravitational potential of the combined anchor itself penetrate the soil. In the middle, the installation is completed; after the installation is completed, the anchor chain 4 of the tail of the pusher 2 is tensioned, and when the shearing force of the shear pin 3 is greater than its own allowable shearing force, the shear pin 3 is cut, so that the pusher 2 is Pull out, and the new lightweight power installation anchor 1 remains in the soil; when the working anchor chain 5 is tensioned, the force transmitted to the anchor eye 13 by the working anchor chain 5 exceeds the initial pull-out bearing capacity of the new lightweight power-mounted anchor 1 At the time, the new lightweight power installation anchor 1 begins to move in the soil to adjust the angle of the new lightweight power installation anchor 1; the thruster 2 is removed for installation of the next new lightweight power installation anchor.

The allowable shear force of the shear pin 3 is 1.5 - 2.0 times the weight of the new lightweight power mounting anchor 1 .

The weight of the propeller 2 is adjusted according to actual engineering needs, so that the anchor can penetrate into the seabed of different strength and soil quality.

The propeller 2 adopts a propeller in the patent application No. 201610648708.7, which is mainly composed of a propeller shaft 21, a propeller tail 22 and a propeller anchor eye 23; the front end of the propeller center shaft 21 is provided with a lateral direction. The front end opening 24 of the shaft of the propeller and the front end slot 25 of the longitudinal shaft of the propeller, the front end opening 24 of the shaft of the propeller is used for placing the shear pin 3, and the front end slot 25 of the shaft of the propeller is used for connecting the new light The connecting rod 14 of the anchor 1 of the mass power; the front end opening 24 of the shaft of the propeller is coaxial with the opening b17 of the connecting rod 14 and cooperates with each other;

The propeller tail 22 is mounted at the tail of the propeller middle shaft 21, and a propeller anchor eye 23 is provided at the center of the tail of the propeller middle shaft 21 for connecting the installation anchor chain 4; the width and number of the propeller tail 22 Increase or decrease according to actual needs to ensure the directional stability of the whole when falling in water.

The shaft 21 of the propeller is a hollow cylinder, the tail portion is a gradually contracting truncated cone, and the front end is semi-ellipsoidal or hemispherical; the inner filling material of the hollow cylinder is mercury, lead or concrete.

The material of the propeller tail 22 is an alloy material, a composite material or a plastic, and the position of the center of gravity is reduced by reducing the density of the propeller tail 22 .

Advantageous Effects of Invention: The novel lightweight power mounting anchor proposed in the present invention has the advantages of light weight, high load bearing efficiency, and dive under appropriate conditions. In addition, the power mounting method proposed by the present invention for anchor installation by means of a propeller can significantly increase the depth of penetration of the anchor in the soil to accommodate different soil and soil strengths. Although the installation of the anchor of the present invention by means of a propeller increases the installation cost to some extent, the load carrying efficiency of a single anchor is significantly improved. The installation of all anchors is accomplished with one pusher, saving production costs. Therefore, the number of anchors required for the entire mooring system can be reduced, and the production, transportation, and installation costs can be reduced, thereby reducing the total project cost. The anchor and installation method in the invention are not affected by the water depth, and have wide applicability, and can be used for anchoring foundations of marine floating platforms, floating fans and the like. The invention contributes to the advancement of China's development process in anchoring foundations of deep-sea mooring systems.

DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a three dimensional schematic view of a novel lightweight power mounting anchor of the present invention.

Figure 2 is a front elevational view of the new lightweight power mounting anchor of the present invention.

Figure 3 is a side elevational view of the novel lightweight power mounting anchor of the present invention.

4 is a top plan view of a novel lightweight power mounting anchor of the present invention.

Figure 5 is a three dimensional schematic view of the pusher of the present invention.

Figure 6 is a front elevational view of the pusher of the present invention.

Figure 7 is a side view of the pusher of the present invention.

Figure 8 is a plan view of the pusher of the present invention.

Figure 9 is a schematic illustration of a new lightweight power mounting anchor and thruster connection.

Figure 10 is a flow chart showing the installation of the new lightweight power mounting anchor with the aid of a propeller.

Figure 11(a) shows the predicted results of the dynamic penetration process of the new lightweight power-mounted anchor and composite anchor in the soil.

Fig. 11(b) is a graph showing the curve of the speed of the combined anchor as a function of depth at different penetration speeds.

In the figure: 1 new lightweight power installation anchor; 2 propeller; 3 shear pin; 4 installation anchor chain; 5 working anchor chain; 11 wing plate; 12 anchor handle; 13 anchor eye; 14 connecting rod; ; 16 bolts; 17 holes b; 18 holes c; 2 propellers; 21 propeller shafts; 22 propeller tails; 23 propeller anchor eyes; 24 propeller shaft front end openings; 25 propeller shaft front ends Slotted.

Detailed ways

The specific embodiments of the present invention are further described below in conjunction with the drawings and technical solutions.

1. New lightweight power mounting anchor

Figure 1–4 is a schematic diagram of a new lightweight power installation anchor 1 which is mainly composed of a wing plate 11, an anchor handle 12 and a connecting rod 14. The wing 11 is composed of two triangular plates symmetrically spliced, and the two right-angled sides of the triangular plate can be adjusted according to actual conditions to adapt to different soil strength and soil quality. The two triangular plates can be joined by welding, riveting, hinged and the like to form the flaps 11. The angle between the two triangular plates is greater than 180° in order to balance the eccentricity caused by the anchor shank 12. The angle between the two triangular plates is determined by the size of the wings 11 and the anchor shank 12 such that the center of gravity of the anchor falls on the axis X-X of the anchor, as shown in FIG. The front end of the flap 11 forms a pointed end which reduces the soil resistance experienced by the anchor as it initially penetrates into the soil, helping to give the anchor a deeper depth of penetration. In addition, according to the processing needs or transportation needs, the three vertices of the wing 11 can be processed into a shape with a certain curvature, which reduces the problems of abrasion, buckling and the like of the anchor during transportation.

The anchor handle 12 is mainly composed of two trapezoidal flat plates, and the top end of the anchor handle 12 is opened to form an anchor eye 13. The working anchor chain 5 is taken out from the anchoring eye 13, and the upper load acts on the new lightweight power mounting anchor 1 through the working anchor chain 5. When the new lightweight power mounting anchor 1 is installed, the initial axis direction of the new lightweight power mounting anchor 1 is vertical. The working anchor chain 5 is then tensioned. When the force transmitted by the working anchor chain 5 to the anchor eye 13 exceeds the initial uplift bearing capacity of the new lightweight power mounting anchor 1, the new lightweight power mounting anchor 1 begins to move in the soil. Since the point of application of the uplift load is at the anchor eye 13 rather than the tail of the wing 11, the uplift load creates a moment on the center of the soil resistance of the wing 11. The resistance center point of the soil refers to the earth body resistance to the point when the anchor tangential motion (movement along the XX axis direction) or the normal motion (perpendicular to the plane direction composed of the three vertices of the wing 11) The torque value is zero. The distance from the anchor eye 13 to the axis of the wing 11 can be adjusted according to actual engineering needs, which is also referred to as the anchor eye eccentricity. The anchor will rotate in the soil under the action of the upward force on the force formed by the center of the soil resistance. The anchor tip position will rotate toward the initial position of the anchor eye, and the anchor tail will rotate toward the initial position away from the anchor eye. As the anchor rotates, the projected area of the flap 11 in the direction perpendicular to the upward pulling load increases, thereby increasing the normal bearing capacity. Therefore, compared with the torpedo anchor, the new lightweight power mounting anchor 1 of the present invention is mainly subjected to the normal force of the soil rather than the tangential force in the soil, and thus has a higher bearing efficiency, that is, the anchorage resistance of the anchor. The ratio of force to anchor weight is higher. The larger the eccentricity of the anchor eye, the smaller the buried depth loss generated during the rotation of the anchor plate.

The bottom of the anchor shank 12 is connected to the wing 11 by bolts 16. The bottom of the anchor shank 12 is provided with an opening c18, and the wing 11 is also provided with a matching opening a15. The wing 11 and the anchor shank 12 are connected by bolts 16, as shown in FIG. Alternatively, the attachment of the flap 11 and the anchor shank 12 may be performed by other methods, such as rivet anchoring. In the present invention, the position of the anchor shank 12 can be adjusted along the X-X axis direction to change the position of the anchor eye 13 relative to the center of the soil resistance. The projection of the distance from the anchor eye 13 to the soil resistance center in the X-X axis direction is referred to as the anchor eye offset. The anchor eye offset is a key factor in determining whether the anchor has a submersible property when subjected to an uplift load. Where appropriate, the anchor will dive into a deeper soil layer when subjected to a pull-up load, resulting in a higher pull-out capacity. Therefore, the position of the anchor shank 12 on the wing 11 can be determined according to actual engineering needs and on-site soil quality and soil strength.

The tail of the wing 11 is provided with a connecting rod 14 having an opening b17 as shown in FIG. The action of the connecting rod 14 and the opening b17 is specifically described in the pusher portion.

2, propeller

Figures 5-8 are schematic views of the pusher 2. The propeller 2 is mainly composed of a propeller shaft 21, a propeller tail 22 and a propeller anchor eye 23. The shaft 21 of the propeller is a cylindrical structure, and the front end is designed to be semi-ellipsoidal or hemispherical, so that the water flow can evenly transition around the front end of the shaft of the propeller to reduce the drag resistance of the propeller when it falls in the water, thereby improving The penetration speed; the tail of the shaft 21 of the propeller is designed to be gradually contracted in a truncated cone shape, so that the water flow smoothly flows through the tail of the propeller, reducing the vortex area, thereby increasing the penetration speed. The shape of the shaft 21 of the propeller is approximately streamlined, in order to reduce the drag resistance of the propeller 2 in the water, thereby helping the new lightweight power mounting anchor 1 to achieve higher penetration speed and deeper depth of penetration. . The diameter and length of the shaft 21 of the propeller can be adjusted according to the soil quality and soil strength. When the soil strength is high, it is recommended to lengthen the length of the propeller or increase the diameter of the propeller to increase the weight of the propeller and help the anchor reach the required depth of the design. In addition, the propeller shaft 21 can be made hollow, filled with a denser material such as lead, mercury, etc., to increase the density and quality of the propeller, and to improve the depth of penetration of the anchor in the soil.

The propeller tail 22 is used to increase the directional stability of the composite anchor as it falls in the water. The tail 22 shown in Fig. 5 has three pieces which are 120 degrees apart from each other. According to actual needs, the number, shape and size of the tail fins can be adjusted to meet the needs of different projects. When the anchor falls in the water, the lower the center of gravity, that is, the closer the center of gravity is to the anchor tip, the better the orientation stability of the anchor in the water. The good orientation stability of the anchor means that when the anchor falls in the water, the axial direction of the anchor does not deviate from the vertical direction. Even if it deviates from the vertical direction, the anchor will gradually rotate and adjust during the falling process, so that the axis of the anchor is rotated again to the vertical. Straight direction. Therefore, in addition to the above-described reduction of the center of gravity by filling a denser material in the shaft 21 of the pusher, the position of the center of gravity can be lowered by reducing the density of the tail 22. The tail 22 can be made of a lighter material such as a high strength alloy material, a composite material, a high strength plastic, and the like.

The front end of the propeller middle shaft 21 is provided with a longitudinal thruster middle shaft front end slot 25, as shown in FIG. The front end slot 25 of the pusher shaft and the connecting rod 14 are matched to ensure that the connecting rod 14 is just inserted into the front end slot 25 of the propeller shaft. At this time, the opening b17 of the connecting rod 14 of the new lightweight power mounting anchor 1 is coaxial with the front end opening 24 of the propeller middle shaft. The shear pin 3 is passed through the opening b17 and the front end opening 24 of the pusher center shaft, so that the new lightweight power mounting anchor 1 and the pusher 2 are as shown in FIG. The allowable shearing force of the shear pin 3 should be about 1.5–2.0 times the weight of the anchor 1, so as to ensure that the new lightweight power-mounted anchor 1 will not leave the propeller 2 when the combined anchor is released in the water, and that the installation is completed. When the pusher 2 is pulled out, the shear pin 3 can be cut in time without pulling up the new lightweight power mounting anchor 1.

The propeller anchor eye 23 is used to attach the anchor chain 4. The installation anchor chain 4 is also used to recover the propeller after installation. When the combined anchor is installed, the anchor chain 4 is tensioned and the propeller 2 can be pulled out of the soil, leaving only the anchor in the soil.

3, the installation method

Figure 10 shows the power installation process for the anchor 1 installation using the propeller 2. First, the new lightweight power mounting anchor 1 and the pusher 2 are connected by a shear pin 3 to form a combined anchor. The combined anchor is then released from the installation vessel to a certain height from the surface of the seabed, waiting for installation. The switch on the installation anchor chain 4 is triggered to make the combined anchor fall in the water to obtain kinetic energy, and the kinetic energy obtained by the movement of the combined anchor in the water and the self-gravity potential energy penetrate into the soil to complete the installation. After the installation is completed, the anchor chain 4 is tensioned, and after the shear pin 3 is cut, the propeller 2 is pulled out of the seabed, leaving only the new lightweight power installation anchor 1 in the seabed. Subsequently, the working anchor chain 5 attached to the anchor eye 13 is tensioned by the tugboat at a certain upward pulling angle, so that the new lightweight power mounting anchor 1 is rotated from a vertical direction to a certain angle, thereby providing a pull-out bearing capacity. The pusher 2 can be used for the installation of the next anchor.

4, invention design verification

In order to verify the practicability of the novel power anchor proposed by the present invention and the power installation method for anchor installation by means of a propeller, the following is an investigation of the working performance and working efficiency of the anchor from the two stages of anchor drop in water and dynamic penetration in soil. .

a. Hydrodynamic characteristics

When the combined anchor falls freely in the water, it will be dragged by the water. The dragging resistance of water to the anchor can be expressed by the formula (1).

Where F _D,w is the drag resistance of the water to the anchor, C _D,w is the drag drag coefficient, ρ _w is the density of water, and A _F is the projected area of the anchor in the direction perpendicular to the axis. It can be seen from equation (1) that the drag drag is proportional to the square of the speed. As the drop speed of the anchor increases, the drag resistance increases rapidly, and when the drag resistance is equal to the effective weight of the anchor in the water, the acceleration of the anchor is reduced to zero. The corresponding speed at this time is called the ultimate speed of the anchor, v _T . The expression of the ultimate speed of the anchor is shown in equation (2).

Where W _A ' is the effective weight of the anchor in the water.

Table 1 main parameters of anchors and thrusters

The hydrodynamic characteristics of the anchor during its falling in the water include the drag drag coefficient of the anchor, the limit speed, the orientation stability, and the like. The inventors studied the hydrodynamic properties of the combined anchor in water based on the fluid dynamics software FLUENT 17.0. The relevant dimensions of the anchor and thruster are shown in Table 1. The numerical results show that the orientation of the composite anchor is very good. Once the axis direction of the anchor deviates from the vertical direction, the anchor will gradually adjust, so that the axial direction returns to the vertical direction. In addition, the numerical calculation results show that the corresponding drag coefficient is 0.71 when the combined anchor falls freely in water, and the limit speed is 33.5m/s.

b. The depth of the anchor in the soil

The following is a theoretical analysis method to predict the depth of penetration of a new power installation anchor in the soil. The main dimensions of the anchor and thruster are shown in Table 1. The speed at which the anchor reaches the soil surface is called the penetration speed, v ₀ . The force acting on the anchor when the anchor is motivated in the soil includes the effective weight W' of the anchor in the water, the overburden pressure F _{b of the} anchor, the end bearing resistance F _bear , the frictional resistance F _frict , and the drag of the soil to the anchor Resistance F _{D, s} . The force of the anchor in the soil can be expressed by the formula (3).

Where z is the depth at which the anchor tip penetrates into the soil and t is time. For the new power installation anchor, m=m _A , W′=W _A ′, corresponding combination anchor m=m _A +m _B , W′=W _A ′+W _B ′, W _B ′ is the effective effect of the propeller in water weight. The values of each force are described below.

(1) The end bearing resistance F _bear is the earth resistance that the anchor receives in the direction perpendicular to the axis XX, as shown in the formula (4).

F _bear =N _c s _u A _t (4)

Wherein, the coefficient N _c is the bearing capacity, varies with changes in the depth of embedment, N _c is calculated as Equation (5a-5c) as shown in, s _u of soil undrained shear strength, A _t is the anchor The area of contact with the soil in a direction perpendicular to the axis XX.

Where c ₁ and c ₂ are parameters related to the basic shape, B is the base width, L is the base length, and z is the anchor plate depth. For the novel anchor of the present invention, B is the thickness t _A of the triangular wing and L is the width w _F of the triangular wing. For the thruster, both B and L are taken as the diameter D _{B of the} shaft in the thruster.

(2) The frictional resistance F _frict is the soil resistance received by the side of the anchor as shown in the formula (6). In the formula, α is the friction coefficient between the anchor-soil interface, and A _s is the area where the anchor side contacts the soil.

F _frict =αs _u A _s (6)

(3) The overburden pressure F _b is the effective weight of the anchor row open soil.

(4) The drag resistance of the soil to the anchor F _D,s can be calculated by the formula (7).

Where C _{D, s} is the towing drag coefficient of the soil to the anchor, ρ _s is the saturation density of the soil, and v is the velocity of the anchor at any one time.

In addition, when the anchor penetrates into the seabed at high speed, the soil around the anchor has a high shear strain rate. Soil exhibits a rate effect at high shear strain rates, ie soil strength increases with increasing shear strain rate. Therefore, the undrained shear strength considering the soil rate effect can be expressed as equation (8).

Where R _f is the rate effect coefficient and s _{u, ref} is the reference shear strain rate

The undrained shear strength of the soil obtained is called the reference soil strength, and λ is the rate effect parameter.

For the shear strain rate, it can be expressed by the formula (9).

Where d is the reference length. In the field test, the undrained shear strength of the soil was measured mainly by Cone, T-bar and Ball penetrometer, which can be considered as the reference soil strength. At this time, the reference shear strain rate is taken as the ratio of the penetration speed to the diameter of the penetration gauge. For the anchor, d is taken as the thickness of the wing; for the shaft of the thruster, d is taken as the diameter of the shaft in the thruster.

Assume that the anchorage interface friction coefficient α = 0.33, the rate effect parameter λ = 0.14, the reference soil strength s _{u, ref} = 2.4 + 3z kPa, the parameters of the anchor and propeller are shown in Table 1, according to formula (3) can be determined The relationship between the velocity and depth of an anchor or a composite anchor when it is dynamically penetrated into the soil. According to formula (2), the ultimate speed of the anchor and the combined anchor can be calculated, which are 18.3 and 33.5 m/s, respectively. So for the anchor, take two different penetration speeds, 17 and 18 m/s respectively. For the combined anchor, take five different speeds, 17, 18, 20, 25 and 30 m/s. The relationship between the velocity of the anchor and the combined anchor as a function of depth is shown in Fig. 11.

As can be seen from Fig. 11(a), when the penetration speed is 17 m/s, the penetration depth of the anchor is 7.56 m; after the thruster is added, the penetration depth of the anchor is 18.56 m. Fig. 11(b) is a graph showing the velocity of the combined anchor as a function of depth at different penetration speeds. As mentioned earlier, the penetration speed of the anchor in the water is also improved by means of the pusher. When the penetration speed is 30 m/s, the final penetration depth of the composite anchor is 24.88 m. This shows that the thruster can improve the penetration depth of the anchor from two aspects: one increases the overall weight, thereby increasing the overall gravitational potential energy to increase the anchor depth of the anchor; the second is to increase the overall penetration in the water. The speed, which increases the overall kinetic energy, can also increase the depth of penetration of the anchor in the soil. The greater the depth of the anchor, the higher the corresponding load carrying efficiency. Therefore, although the installation of the anchor of the present invention by means of a propeller increases the installation cost to some extent, the load carrying efficiency of a single anchor is significantly improved. Therefore, the number of anchors required for the entire mooring system can be reduced, and the production, transportation, and installation costs can be reduced, thereby reducing the total project cost.

Claims

A novel lightweight power mounting anchor characterized in that the new lightweight power mounting anchor is mainly composed of a wing plate (11), an anchor handle (12) and a connecting rod (14); the wing plate (11) is composed of Two triangular plates are symmetrically spliced, and the angle between the two is adjusted according to engineering requirements; two triangular plates on the wing plate (11) are symmetrically provided with a plurality of openings a (15); the connecting rods (14) Mounted on the tail of the wing (11), the connecting rod (14) is provided with an opening b (17), and the connecting rod (14) is fixedly connected with the pusher (2) by the shearing pin (3); The anchor handle (12) is an inverted V-shaped structure composed of two trapezoidal flat plates. The bottom of the anchor handle (12) is provided with a plurality of openings c (18), and the opening c (18) and the opening a (15) are mutually Cooperating, the anchor shank (12) is symmetrically fixed on the two triangular plates of the wing plate (11) by bolts (16); the top of the anchor shank (12) is provided with an anchor eye (13) for connecting the working anchor chain ( 5) to provide a pull-out bearing capacity; by adjusting the fixed position of the anchor shank (12), the anchor shank (12) moves up and down along the axis of the wing (11), thereby changing the offset of the anchor eye (13), ie The distance between the anchor eye (13) and the soil resistance center of the wing (11) is in the wing (11) projected in the axial direction, so that the performance of new lightweight power installation having a dive when the anchor on the pulling load by, new lightweight power thereby mounting anchor embedded in the soil bearing capacity is obtained.
A new method for installing a lightweight power mounting anchor, characterized in that the mounting anchor chain (4) is connected to the propeller anchor eye (23); the connecting rod (14) is fixed by the shear pin (3) In the front end slot (25) of the shaft, the new lightweight power mounting anchor (1), the pusher (2) and the shear pin (3) are assembled into a combined anchor; the working anchor chain (5) is connected to the anchor eye. (13) above;

Specific steps are as follows:

Firstly, the combined anchor is released into the seawater, so that the combined anchor is located above the surface of the seabed, then the anchor chain (4) is loosened, the combined anchor is free to fall in the water, and the kinetic energy obtained by free fall and the gravitational potential energy of the combined anchor itself are firstly released. Through the soil, complete the installation; after the installation, tighten the mounting anchor chain (4) at the end of the thruster (2), when the shear pin (3) receives the shear force greater than its own allowable shear force, the shear pin ( 3) is cut so that the thruster (2) is pulled out, and the new lightweight power mounting anchor (1) remains in the soil; the working anchor chain (5) is tensioned, when the working anchor chain (5) is transmitted to the anchor eye (13) When the force above the initial pull-up bearing capacity of the new lightweight power-mounted anchor (1), the new lightweight power-mounted anchor (1) begins to move in the soil to adjust the new lightweight power-mounted anchor (1) Angle; the thruster (2) is removed for installation of the next new lightweight power mounting anchor.
A method of installing a novel lightweight power mounting anchor according to claim 2, wherein the shearing force of said shear pin (3) is 1.5 - the weight of the new lightweight power mounting anchor (1) 2.0 times.
A method for installing a novel lightweight power installation anchor according to claim 2 or 3, characterized in that the weight of the pusher (2) is adjusted according to actual engineering requirements, so that the anchor can penetrate different strengths. And the earthy seabed.
A method of installing a novel lightweight power mounting anchor according to claim 2 or 3, characterized in that

The propeller (2) is mainly composed of a propeller shaft (21), a propeller tail (22) and a propeller anchor eye (23); the front end of the propeller middle shaft (21) is provided with a lateral direction The front end opening of the shaft of the propeller (24) and the front end of the longitudinal shaft of the propeller (25), the front end opening of the shaft of the propeller (24) for placing the shear pin (3), the front end of the shaft of the propeller Slot (25) is used to connect the connecting rod (14) of the new lightweight power mounting anchor (1); the front end opening (24) of the propeller shaft and the opening b (17) on the connecting rod (14) Coaxial, mutual cooperation;

The propeller tail (22) is mounted at the tail of the propeller middle shaft (21), and a propeller anchor eye (23) is provided at the center of the propeller middle shaft (21) at the tail end for connecting the installation anchor chain (4) The width and number of the propeller tail (22) are increased or decreased according to actual needs to ensure the directional stability of the whole when falling in water.
A method of installing a novel lightweight power mounting anchor according to claim 4, wherein

The propeller (2) is mainly composed of a propeller shaft (21), a propeller tail (22) and a propeller anchor eye (23); the front end of the propeller middle shaft (21) is provided with a lateral direction The front end opening of the shaft of the propeller (24) and the front end of the longitudinal shaft of the propeller (25), the front end opening of the shaft of the propeller (24) for placing the shear pin (3), the front end of the shaft of the propeller Slot (25) is used to connect the connecting rod (14) of the new lightweight power mounting anchor (1); the front end opening (24) of the propeller shaft and the opening b (17) on the connecting rod (14) Coaxial, mutual cooperation;

The propeller tail (22) is mounted at the tail of the propeller middle shaft (21), and a propeller anchor eye (23) is provided at the center of the propeller middle shaft (21) at the tail end for connecting the installation anchor chain (4) The width and number of the propeller tail (22) are increased or decreased according to actual needs to ensure the directional stability of the whole when falling in water.
A method for installing a novel lightweight power mounting anchor according to claim 2, 3 or 6, wherein the propeller central shaft (21) is a hollow cylinder, and the tail portion is a gradually contracting truncated cone. It is semi-ellipsoidal or hemispherical; the interior of the hollow cylinder is filled with mercury, lead or concrete.
The method for installing a novel lightweight power mounting anchor according to claim 4, wherein the propeller central shaft (21) is a hollow cylinder, the tail portion is a gradually contracting circular table, and the front end is a semi-ellipsoidal shape. Or hemispherical; the interior of the hollow cylinder is filled with mercury, lead or concrete.
The method for installing a novel lightweight power mounting anchor according to claim 5, wherein the propeller central shaft (21) is a hollow cylinder, the tail portion is a gradually contracting circular table, and the front end is a semi-ellipsoidal shape. Or hemispherical; the interior of the hollow cylinder is filled with mercury, lead or concrete.
A method of installing a novel lightweight power mounting anchor according to claim 2, 3, 6, 8 or 9, wherein the material of the thruster tail (22) is an alloy material, a composite material or a plastic material. The position of the center of gravity is lowered by reducing the density of the propeller tail (22).