阅读说明：本技术 一种混凝土管桩海上沉桩施工方法 (Concrete pipe pile offshore pile sinking construction method ) 是由 刁钰 朱鹏宇 郑刚 于 2019-10-25 设计创作，主要内容包括：本发明属于海上沉桩技术领域,公开了一种混凝土管桩海上沉桩施工方法,首先将高压喷嘴作业的注浆旋喷管和预制的混凝土管桩垂直放置在沉桩位置正上方,混凝土管桩套放在注浆旋喷管的外部并由抱桩器夹持固定；然后进行钻孔和高压旋喷作业,注浆旋喷管下降一个区段深度后,利用抱桩器将混凝土管桩向下放送同样的区段深度,如此重复直至混凝土管桩达到设计标高位置；再将注浆旋喷管由混凝土管桩中向上提出；最后静置养护至水泥砂土强度达到要求。本发明可有效解决由高应力状态砂土对桩壁的强摩阻力导致的混凝土管桩沉桩困难问题,能够有效提升砂土与桩界面的连接强度,扩大混凝土管桩有效桩径,提高承载力,还能够实现海上沉桩的一次性施工,节省工期。(The invention belongs to the technical field of offshore pile sinking, and discloses a concrete pipe pile offshore pile sinking construction method, which comprises the following steps of firstly vertically placing a grouting rotary spray pipe operated by a high-pressure nozzle and a prefabricated concrete pipe pile right above a pile sinking position, sleeving the concrete pipe pile outside the grouting rotary spray pipe and clamping and fixing the concrete pipe pile by a pile gripper; then drilling and high-pressure rotary spraying operation are carried out, after the grouting rotary spraying pipe descends by a section depth, the concrete pipe pile is placed downwards by the same section depth by using the pile gripper, and the operation is repeated until the concrete pipe pile reaches the designed elevation position; then the grouting rotary spraying pipe is lifted upwards from the concrete pipe pile; and finally, standing and maintaining until the strength of the cement sand reaches the requirement. The invention can effectively solve the problem of difficult pile sinking of the concrete pipe pile caused by strong frictional resistance of high-stress state sand on the pile wall, can effectively improve the connection strength of the sand and the pile interface, enlarge the effective pile diameter of the concrete pipe pile, improve the bearing capacity, realize one-time construction of offshore pile sinking and save the construction period.)

1. A concrete pipe pile offshore pile sinking construction method is characterized by comprising the following steps:

(1) positioning a pile sinking position, and vertically placing a grouting rotary spray pipe for high-pressure rotary spraying operation and a prefabricated concrete pipe pile right above the pile sinking position; the concrete pipe pile is sleeved outside the grouting rotary spray pipe, and the concrete pipe pile is clamped by the pile gripper; the bottom of the grouting rotary spray pipe is provided with a rotary nozzle and a drill bit, and the drill bit is positioned below the rotary nozzle;

(2) drilling and high-pressure rotary spraying operation are carried out, drilling and rotary spraying are carried out while the grouting rotary spraying pipe is rotated and lowered, so that the prepared cement slurry and the sandy soil at the position of the pile to be sunk are fully stirred and mixed, and cement sandy soil with lower stress level is formed; when the grouting rotary spraying pipe descends to a section depth, the concrete pipe pile is placed downwards by the pile gripper to the same section depth, and the operation is repeated until the concrete pipe pile reaches a designed elevation position;

(3) lifting a grouting rotary spray pipe with a rotary nozzle and a drill bit upwards from the concrete pipe pile;

(4) and standing and maintaining the cement sand until the strength of the cement sand meets the requirement.

2. The offshore pile sinking construction method for the concrete pipe pile as claimed in claim 1, wherein the cement grout has a water cement ratio of not more than 0.4.

3. The offshore pile sinking construction method for the concrete pipe pile as claimed in claim 1, wherein the pressure value of the slurry pump in the high-pressure jet grouting operation is not lower than the water and soil pressure value of the sandy soil below the seawater.

4. The offshore pile sinking construction method for the concrete pipe pile as claimed in claim 1, wherein the impermeability grade of the concrete pipe pile is not less than P8.

Technical Field

The invention belongs to the technical field of offshore pile sinking, and particularly relates to a concrete pipe pile offshore pile sinking construction method which is particularly suitable for a dense sand soil environment below the sea surface.

Background

When the platform is operated on the sea, the platform foundation needs to be driven into a soil layer below seawater. Compared with land construction, the sea water pressure action exists above the soil layer of the marine pile foundation, so that the compactness of the soil body is higher, and a stronger stress field exists, so that the pile sinking of the marine concrete pipe pile is more difficult. The sandy soil has rough surface, and can generate great friction resistance in the pile sinking process of the precast pile under a high stress field, so that the problem is more obvious in the sandy soil layer. Therefore, the offshore pile foundation generally adopts steel piles, and compared with concrete pipe piles, the offshore pile foundation can reduce pile sinking frictional resistance as much as possible. However, how to finish pile sinking of the concrete pipe pile in the offshore high-stress sandy soil is not well solved, and the stress level of the sandy soil and the friction coefficient between the sandy soil and the pile side should be reduced by successfully finishing pile sinking of the concrete pipe pile in the undersea sandy soil.

The high-pressure rotary spraying method is a foundation treatment method commonly used in onshore construction, and is a chemical reinforcing method which adopts high-pressure cement slurry to form a jet flow by spraying through a nozzle, so as to cut soil and prefabricate and mix the soil with cement reinforcing bodies. The high-pressure rotary spraying technology on land is generally used for reinforcing and treating soft foundation soil.

Disclosure of Invention

The invention aims to solve the technical problem that the offshore concrete pipe pile is difficult to sink in foundation soil below seawater, particularly sand, and provides a offshore pile sinking construction method for the concrete pipe pile.

In order to solve the technical problems, the invention is realized by the following technical scheme:

a concrete pipe pile offshore pile sinking construction method comprises the following steps:

(1) positioning a pile sinking position, and vertically placing a grouting rotary spray pipe operated by a high-pressure nozzle and a prefabricated concrete pipe pile right above the pile sinking position; the concrete pipe pile is sleeved outside the grouting rotary spray pipe, and the concrete pipe pile is clamped by the pile gripper; the bottom of the grouting rotary spray pipe is provided with a rotary nozzle and a drill bit, and the drill bit is positioned below the rotary nozzle;

(2) drilling and high-pressure rotary spraying operation are carried out, drilling and rotary spraying are carried out while the grouting rotary spraying pipe is rotated and lowered, so that the prepared cement slurry and the sandy soil at the position of the pile to be sunk are fully stirred and mixed, and cement sandy soil with lower stress level is formed; when the grouting rotary spraying pipe descends to a section depth, the concrete pipe pile is placed downwards by the pile gripper to the same section depth, and the operation is repeated until the concrete pipe pile reaches a designed elevation position;

(3) lifting a grouting rotary spray pipe with a rotary nozzle and a drill bit upwards from the concrete pipe pile;

(4) and standing and maintaining the cement sand until the strength of the cement sand meets the requirement.

Further, the cement slurry has a water-cement ratio of not greater than 0.4.

Further, the pressure value of the grouting pump in the high-pressure rotary spraying operation is not lower than the water and soil pressure value of the sand below the seawater.

Further, the impermeability grade of the concrete pipe pile is not less than P8.

The invention has the beneficial effects that:

the invention firstly treats the sandy soil with high stress level and high compactness by high-pressure rotary spraying to destroy the original soil structure and form a looser soil structure; the cement paste and the sandy soil are fully mixed to form cement sandy soil with lower stress level, and the roughness of the surface of sandy soil particles is reduced; after treatment, the filling resistance of the concrete pile during pile sinking is obviously reduced, and the sinking of the concrete pipe pile in a sand soil body in a seawater environment can be smoothly realized.

After the high-pressure rotary spraying treatment, the sandy soil and the cement slurry are mixed into the cement sandy soil, and compared with the contact surface of untreated sandy soil and a pile body, the mechanical connection effect of the cement sandy soil and the pile body is obviously improved; after the cement sand is cured, the cement sand is effectively connected with the outer wall of the concrete pipe pile, the effective stress range of the concrete pipe pile is enlarged, and the bearing capacity of the concrete pipe pile is obviously improved.

The concrete pipe pile can be prefabricated and maintained in advance to form a pile by adopting impervious and corrosion-resistant concrete, concrete maintenance is not needed to be carried out under the sea water, higher pile forming quality is ensured, and adverse effects of various harmful ions in the sea water on the durability of the concrete pipe pile when the drilled pile is maintained under the underwater environment can be avoided.

The invention realizes the one-time pile sinking of the concrete pipe pile in offshore construction, saves the construction period and reduces the cost of manpower and material resources.

Drawings

FIG. 1 is a flow chart of the construction operation of the present invention;

FIG. 2 is a schematic view of the invention in an unfinished state;

FIG. 3 is a schematic view of the in-place state of the rotary spraying steel pipe and the pipe pile of the invention;

FIG. 4 is a schematic view of the drilling and rotary jetting operation of the present invention;

FIG. 5 is a schematic view illustrating the pile sinking operation of the present invention;

FIG. 6 is a schematic view of the present invention showing the pile bottom sinking to a designed elevation;

FIG. 7 is a schematic view showing the state of the present invention in which the rotary sprayed steel pipe is taken out;

fig. 8 is a horizontal sectional view of a concrete pipe pile and cement sand mixed structure.

In the above figures: 1-sandy soil; 2-seawater; 3-a drill bit; 4-rotating the nozzle; 5-pile gripper; 6-a roller; 7-concrete pipe pile; 8-grouting rotary spray pipes; 9-cement grout; 10-cement sand soil.

Detailed Description

In order to further understand the contents, features and effects of the present invention, the following embodiments are illustrated and described in detail with reference to the accompanying drawings:

as shown in fig. 1, the embodiment provides a concrete pipe pile offshore pile sinking construction method, which mainly solves the problems that when an offshore pile foundation is constructed, as shown in fig. 2, due to the pressure effect of seawater 2, the density of sandy soil 2 below the seawater is high, a strong stress field exists, and meanwhile, the surface of sandy soil 2 is rough, and a large friction resistance is generated in the pile sinking process under the high stress field.

The concrete precast pile offshore pile sinking construction method of the embodiment applies the high-pressure jet grouting technology to offshore concrete pipe pile construction, and comprises the following specific steps:

step one, as shown in fig. 3, positioning the pile sinking position, and vertically placing the grouting rotary jet pipe 8 for high-pressure nozzle operation right above the pile sinking position. Grouting rotary spray pipe 8 is made of steel, rotary spray port 4 and drill bit 3 which are connected integrally are arranged at the bottom of grouting rotary spray pipe, drill bit 3 is located below rotary spray port 4, and the maximum outer diameters of drill bit 3, rotary spray port 4 and grouting rotary spray pipe 8 are all smaller than the inner diameter of concrete pipe pile 7, so that the three parts can move freely independently of concrete pipe pile 7, and high-pressure rotary spray operation is performed while drilling.

And (3) placing the prefabricated concrete pipe pile 7 outside the grouting rotary spray pipe 8 in a sleeving manner, clamping the concrete pipe pile 7 by using the pile gripper 5, and fixing the concrete pipe pile 7 right above the pile sinking position. The axial line of the grouting rotary spray pipe 8 and the axial line of the concrete pipe pile 7 are on the same straight line with the pile sinking position.

The pile gripper 5 comprises a plurality of rollers 6 extending inwards, the rollers 6 are distributed on the same circle on the plane, and the inner diameter of the circle is the same as the outer diameter of the concrete pipe pile 7. The pile gripper is used for righting the concrete pipe pile 7 on one hand and ensuring that the concrete pipe pile 7 is kept in a vertical state in the pile sinking process; on the other hand, the pile gripper 5 slides downwards through a plurality of rollers 6 to realize the downward release of the concrete pipe pile 7.

The concrete pipe pile 7 is prefabricated before the pile sinking operation in offshore construction, the concrete pipe pile 7 in the embodiment adopts cement with impermeability grade of P10, the concrete grade depends on the seawater pressure on the pile top, and the impermeability grade is not less than P8.

In addition, the concrete pipe pile 7 can be prefabricated and maintained in advance to form a pile by adopting impervious and corrosion-resistant concrete, concrete maintenance is not needed to be carried out under the sea water, higher pile forming quality is ensured, and adverse effects of various harmful ions in the sea water on the durability of the concrete pipe pile 7 during maintenance of the bored pile in an underwater environment can be avoided.

And step two, as shown in fig. 4, performing drilling and high-pressure rotary spraying operation, drilling while performing rotary spraying in the process of lowering the grouting rotary spraying pipe 8, vertically downwards drilling the sandy soil 2 by using the drill bit 3, and simultaneously pumping the prepared cement slurry 9 into the grouting rotary spraying pipe 8 through a grouting pump, so that the prepared cement slurry 9 with high concentration is fully stirred and mixed with the sandy soil 2 at the position of the pile to be sunk, the sandy soil 2 is changed into a loose state from a high-stress tight state, and the cement sandy soil 10 with lower stress level is formed. Wherein, the water-cement ratio of the cement slurry 9 used for the rotary spraying is not more than 0.4 in consideration of the dilution effect of seawater on the slurry. The pressure value of the grouting pump for high-pressure rotary spraying is set to be 30MPA, and the specific pressure value is determined according to the strength of effective stress in the sandy soil 2 and generally should not be lower than the water and soil pressure value of the sandy soil 2 below seawater 1.

The grouting rotary spraying pipe 8 is controlled to rotate and descend, cement slurry 9 is sprayed and stirred from top to bottom in a rotary mode, and the rotary spraying speed can be adjusted at any time and the cement slurry ascends and descends in the process. Dividing the concrete pipe pile into a plurality of same or different section depths according to the designed elevation, and after the grouting rotary jet pipe 8 descends by one section depth, as shown in fig. 5, utilizing the pile gripper 5 to place the concrete pipe pile 7 downwards by the same section depth (the pile sinking depth of the concrete pipe pile 7 is not more than the depth of the position of the drill bit 3), and repeating the operation until the concrete pipe pile 7 reaches the designed elevation position, as shown in fig. 6.

In the invention, the sandy soil 2 in a high stress state in seawater is treated by using a high-pressure rotary spraying technology, and the sandy soil 2 is loosened and softened by using a rotary spraying method instead of forming a high-pressure rotary spraying pile, so that the compactness of the sandy soil 2 in a treatment area is reduced, the pile-soil contact surface is lubricated, and the pile end resistance and the pile side resistance in pile sinking are reduced.

And step three, as shown in fig. 7, lifting the grouting rotary spraying pipe 8 with the rotary spraying opening 4 and the drill bit 3 upwards from the concrete pipe pile 7.

And step four, as shown in fig. 8, standing and maintaining the cement sand soil 10 until the strength of the cement sand soil 10 meets the requirement.

After standing and maintaining, the cement sand 10 and the concrete pipe pile 7 form effective connection with enough strength to form a stressed working whole, and the bearing capacity of the concrete pipe pile 7 is increased.

Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and those skilled in the art can make various changes and modifications within the spirit and scope of the present invention without departing from the spirit and scope of the appended claims.