EP3406802A1

EP3406802A1 - Offshore rock-drilling redriving-type large-diameter pile structure and construction method

Info

Publication number: EP3406802A1
Application number: EP18168006.7A
Authority: EP
Inventors: Na LV; Hu ZHOU; Haifeng Qi; Jinping LUO; Danshan WANG; Hongbao RONG; Ning LIANG; Yu Li
Original assignee: PowerChina Huadong Engineering Corp Ltd
Current assignee: PowerChina Huadong Engineering Corp Ltd
Priority date: 2017-05-25
Filing date: 2018-04-18
Publication date: 2018-11-28
Also published as: CN107299632A

Abstract

An offshore rock-drilling redriving-type large-diameter pile structure is provided, which is suitable for a foundation including a loose cover soil layer, a compact soil layer and a rock layer from top to bottom, wherein a pile hole (3) is drilled into the rock layer, and a steel pipe pile (1) is driven into the pile hole (3); the pile hole (3) being sequentially divided into a loose soil layer section corresponding to the loose cover soil layer, a compact soil layer section corresponding to the compact soil layer and a rock layer section corresponding to the rock layer from top to bottom, wherein the loose soil layer section is formed after the steel pipe pile is subjected to pile driving, and the compact soil layer section and the rock layer section are formed after the steel pipe pile driven in the loose cover soil layer and drilling is performed on the compact soil layer and the rock layer for a construction channel.

Description

TECHNICAL FIELD

The present invention relates to an offshore rock-drilling redriving-type large-diameter pile structure and construction method. It is suitable for the technical fields of offshore wind power and other ocean engineering.

BACKGROUND ART

The monopile foundation is a structural form most widely applied in the field of offshore wind power, and it has such advantages as simple structure, convenient construction and high construction efficiency. With the large-scale construction of offshore wind power industry, as engineering sea areas like those in Fujian province and Guangdong province in China are featured by complex geologic conditions, the depths of sand deposits in some submarine formations are limited, and weathered rock formations are found in lower portions, so that it is relatively more difficult for a pile foundation to be driven to the designed depth once for all, and the traditional method in which pile driving is conducted merely by means of hammering limits the application of monopile foundations in these engineering sea areas.
In view of the above geologic conditions, some engineering employs traditional high-piled cap rock-socketed pile foundations or jacket rock-socketed foundations. But the high-piled cap rock-socketed foundations are featured by complex construction processes, numerous procedures, low efficiency and high overall construction costs of foundation; for the jacket foundation structures, as pile tops are below the water surface, boring construction is rendered inconvenient.

SUMMARY OF THE INVENTION

In view of the existing problems mentioned above, the technical problem to be solved by the present invention is to provide an offshore rock-drilling redriving-type large-diameter pile structure featured by simple structure and convenient construction, and construction method, so as to improve construction efficiency and reduce construction costs.
The technical solution adopted by the present invention is as follows: an offshore rock-drilling redriving-type large-diameter pile structure is provided, which is suitable for a foundation including a loose cover soil layer, a compact soil layer and a rock layer from top to bottom, and it is characterized in that the foundation is provided with a pile hole extending into the rock layer, and a steel pipe pile is driven into the pile hole;
the pile hole is sequentially divided into a loose soil layer section corresponding to the loose cover soil layer, a compact soil layer section corresponding to the compact soil layer and a rock layer section corresponding to the rock layer from top to bottom, wherein the loose soil layer section is formed after the steel pipe pile is subjected to pile driving, and the compact soil layer section and the rock layer section are formed after the steel pipe pile driven in the loose cover soil layer conducts drilling on the compact soil layer and the rock layer for a construction channel.
The compact soil layer section of the pile hole has a hole diameter smaller than the pile diameter of the steel pipe pile, and the rock layer section of the pile hole has a hole diameter slightly larger than the pile diameter of the steel pipe pile.
The rock layer section of the pile hole is filled with underwater concrete, and the steel pipe pile is integrated with the rock layer section of the pile hole by means of the underwater concrete.
A construction method for offshore rock-drilling redriving-type large-diameter pile structure is provided, which is characterized in that the construction method comprises the steps of:

S1 of conducting pile driving at the top of a steel pipe pile by means of the pile driving hammer until a lower end of the steel pipe pile is supported on the surface of the compact soil layer;
S2 of setting up a driller apparatus at the top of the steel pipe pile, wherein a rock-socketed driller bit of the driller apparatus conducts drilling within and under the steel pipe pile through a channel within the steel pipe pile until it reaches the designed bottom elevation in the rock layer, wherein the drilled hole has a hole diameter smaller than the pile diameter of the steel pipe pile; and of conducting hole broadening for the drilled hole within the rock layer until its hole diameter is slightly larger than the pile diameter of the steel pipe pile;
S3 of removing the driller apparatus and cleaning the drilled hole;
S4 of filling the drilled hole in the rock layer with underwater concrete;
S5 of conducting pile driving at the top of the steel pipe pile by means of the pile driving hammer until the lower end of the steel pipe pile reaches the designed bottom elevation in the rock layer.

An offshore rock-drilling redriving-type large-diameter pile structure is provided, which is suitable for a foundation including a loose cover soil layer, a compact soil layer and a rock layer from top to bottom, and it is characterized in that the foundation is provided with a pile hole extending into the compact soil layer, and a steel pipe pile is driven into the pile hole;
the pile hole is sequentially divided into a loose soil layer section corresponding to the loose cover soil layer and a compact soil layer section corresponding to the compact soil layer from top to bottom, wherein the loose soil layer section is formed after the steel pipe pile is subjected to pile driving, and the compact soil layer section is formed after the steel pipe pile driven in the loose cover soil layer conducts drilling on the compact soil layer for a construction channel.
The compact soil layer section of the pile hole has a hole diameter smaller than the pile diameter of the steel pipe pile.
A construction method for offshore rock-drilling redriving-type large-diameter pile structure is provided, which is characterized in that the construction method comprises the steps of:

S1 of conducting pile driving at the top of a steel pipe pile by means of a pile driving hammer until a lower end of the steel pipe pile is supported on the surface of a compact soil layer;
S2 of setting up a driller apparatus at the top of the steel pipe pile, wherein a rock-socketed driller bit of the driller apparatus conducts drilling within and under the steel pipe pile through a channel within the steel pipe pile until it reaches the designed bottom elevation in the compact soil layer, wherein the drilled hole has a hole diameter smaller than the pile diameter of the steel pipe pile;
S3 of removing the driller apparatus and cleaning the drilled hole;
S4 of conducting pile driving at the top of the steel pipe pile by means of the pile driving hammer until the lower end of the steel pipe pile reaches the designed bottom elevation in the compact soil layer.

The present invention has the following beneficial effects: in the present invention, the driller apparatus is directly set up at the top of the steel pipe pile, thus making the steel pipe pile both a driller supporting mechanism and a drilled hole protection structure; in this manner, the construction procedure of setting up a rock-socketed platform is omitted, thus shortening the construction period and reducing the costs of rock-socketed construction. In the present invention, the steel pipe pile is subjected to pile driving and made to pass through the loose cover soil layer to be supported on the compact soil layer. Here, the steel pipe pile itself can stand stably, which meet the requirements for setting up a driller apparatus. The present invention is featured by simple structure form and less drilling workload, which effectively shortens the construction period, thus greatly reducing the engineering investments.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic diagram illustrating the structure of Embodiment 1.
Figs. 2-4 are schematic diagrams illustrating the construction process of Embodiment 1.
Fig. 5 is a schematic diagram illustrating the structure of Embodiment 2.

DETAILED DESCRIPTION OF THE INVENTION

Embodiment 1: As shown in Fig. 1, the present embodiment is an offshore rock-drilling redriving-type large-diameter pile structure. This structure is suitable for a foundation including a loose cover soil layer 9 (into which a pile can be driven), a compact soil layer 10 (difficult for a pile to be driven) and a rock layer 11 from top to bottom, and the geologic condition of the foundation is that the depth of sand deposits is limited. Therefore, a pile foundation may be driven to a certain depth, but can't be sunk down to the designed bottom elevation once for all. In the present embodiment, the foundation is provided with a pile hole 3, and the designed bottom elevation of this pile hole is located within the rock layer 11. The bottom portion of the pile hole 3 is filled with underwater concrete 6, a steel pipe pile 1 is driven into the pile hole 3 by means of a pile driving hammer 4, and a lower end of the steel pipe pile 1 is integrated with the rock layer 11 by means of the underwater concrete 6.
In the present embodiment, the pile hole 3 is sequentially divided into a loose soil layer section 31 located within the loose cover soil layer 9, a compact soil layer section 32 located within the compact soil layer 10 and a rock layer section 33 located within the rock layer 11 from top to bottom, wherein the loose soil layer section 31 is formed within the loose cover soil layer 9 after the steel pipe pile 1 is driven by the pile driving hammer 4 to be supported on the compact soil layer 10, and the compact soil layer section 32 and the rock layer section 33 are formed after the steel pipe pile 1, whose lower end is supported on the compact soil layer 10 after pile driving, conducts drilling on the compact soil layer 10 and the rock layer 11 under the bottom portion of the steel pipe pile 1 for the construction channel. In the present embodiment, the compact soil layer section 32 of the pile hole 3 has a hole diameter smaller than the pile diameter of the steel pipe pile 1, and the rock layer section 33 of the pile hole 3 has a hole diameter slightly larger than the pile diameter of the steel pipe pile 1.
The construction method of the present embodiment is as follows:

1. Similar to a normal foundation pile, pile driving is conducted at the top of the steel pipe pile 1 by means of the pile driving hammer 4. This requires no additional auxiliary apparatuses or measures, but pile driving must be controlled in strict accordance with the hammer-stopping standard so as to prevent the pile body from being damaged as a result of forcible pile driving. The pile driving may be continued until the lower end of the steel pipe pile 1 is supported on the surface of the compact soil layer 10 (see Fig. 2), and the initially driven depth for the pile foundation of the steel pipe pile 1 can meet the stability requirement of the driller during its construction process;
2. The steel pipe pile 1 itself is taken as both a driller supporting structure and a drilled hole protection structure. The driller apparatus 5 is set up at the top of the steel pipe pile 1, wherein a rock-socketed driller bit 5-1 of the driller apparatus conducts drilling on the compact soil layer 10 and the rock layer 11 within and under the steel pipe pile 1 through the channel within the steel pipe pile 1 until it reaches the designed bottom elevation within the rock layer 11, wherein the drilled hole has a hole diameter smaller than the pile diameter of the steel pipe pile 1, and specific sizes may be properly adjusted according to on-site drilling conditions; hole broadening is conducted for the drilled hole within the rock layer 11 (the rock layer section of the pile hole) until its hole diameter is slightly larger than the pile diameter of the steel pipe pile (see Fig. 3);
3. Rmoving the driller apparatus 5 , cleaning the drilled hole;
4. The underwater concrete 6 is filled in the drilled hole of the rock layer 11, and its filling height is slightly above the top surface of the rock layer section 33;
5. Pile driving is conducted at the top of the steel pipe pile 1 by means of the pile driving hammer 4 until the lower end of the steel pipe pile 1 sinks down to the designed bottom elevation within the rock layer 11 (see Fig. 4).

Embodiment 2: As shown in Fig. 5, the present embodiment is an offshore rock-drilling redriving-type large-diameter pile structure. This structure is suitable for a foundation including a loose cover soil layer 9 (into which a pile can be driven), a compact soil layer 10 (difficult for a pile to be driven) and a rock layer 11 from top to bottom, and the geologic condition of the foundation is that the depth of sand deposits is limited. Therefore, a pile foundation may be driven to a certain depth, but can't be sunk down to the designed bottom elevation once for all. In the present embodiment, the foundation is provided with a pile hole 3, the designed bottom elevation of this pile hole is located within the compact soil layer 10, and a steel pipe pile 1 is driven into the pile hole 3 by means of a pile driving hammer 4.
In the present embodiment, the pile hole 3 is sequentially divided into a loose soil layer section 31 located within the loose cover soil layer, a compact soil layer section 32 located within the compact soil layer and a rock layer section 33 corresponding to the rock layer from top to bottom, wherein the loose soil layer section 31 is formed within the loose cover soil layer after the steel pipe pile is driven by the pile driving hammer to be supported on the compact soil layer, and the compact soil layer section 32 is formed after the steel pipe pile, whose lower end is supported on the compact soil layer upon pile driving, conducts drilling on the compact soil layer and the rock layer under the bottom portion of the steel pipe pile for the construction channel. In the present embodiment, the compact soil layer section of the pile hole has a hole diameter smaller than the pile diameter of the steel pipe pile.
The construction method of the present embodiment is as follows:

1. Similar to a normal foundation pile, pile driving is conducted at the top of the steel pipe pile 1 by means of the pile driving hammer 4. This requires no additional auxiliary apparatuses or measures, but pile driving must be controlled in strict accordance with the hammer-stopping standard so as to prevent the pile body from being damaged as a result of forcible pile driving. The pile driving may be continued until the lower end of the steel pipe pile is supported on the surface of the compact soil layer, and the initially driven depth for the pile foundation of the steel pipe pile can meet the stability requirement of the driller during its construction process;
2. The steel pipe pile 1 itself is taken as both a driller supporting structure and a drilled hole protection structure. The driller apparatus 5 is set up at the top of the steel pipe pile 1, wherein a rock-socketed driller bit 5-1 of the driller apparatus conducts drilling on the compact soil layer 10 within and under the steel pipe pile through a channel within the steel pipe pile until it reaches the designed bottom elevation within the compact soil layer, wherein the drilled hole has a hole diameter smaller than the pile diameter of the steel pipe pile 1, and specific sizes may be properly adjusted according to on-site drilling conditions;
3. Removing the driller apparatus 5, and cleaning the drilled hole;
4. Pile driving is conducted at the top of the steel pipe pile 1 by means of the pile driving hammer 4 until the lower end of the steel pipe pile 1 sinks down to the designed bottom elevation within the compact soil layer 10.

In the implementation process of the present invention, parameters of geological exploration are required to be analyzed, and related software is employed to analyze the initially driven depth of the foundation and the feasibility of the manner in which pile driving is conducted upon hole cleaning. Then, numerical simulations or other manners are employed to analyze the overall stability of foundation + driller during drilling and under the action of wave and current loads as well as vibration loads of the driller, and the vertical bearing capacity of the foundation after the drilled hole is cleaned. For geologic conditions under which piles can be successfully redriven after holes are drilled, the construction process of Embodiment 2 is employed; for those situations in which hard rock layers are required to be broken and redriving is still faced with difficulties even after holes are drilled, the construction process of Embodiment 1 may be employed.
The above embodiments and construction processes are mainly applied to monopile foundations for offshore wind power, but they are not limited thereto. For other foundation structures to which oceaneering structures pertain, they can also be designed and constructed through the technical solution of the present invention.

Claims

An offshore rock-drilling redriving-type large-diameter pile structure suitable for a foundation including a loose cover soil layer (9), a compact soil layer (10) and a rock layer (11) from top to bottom, characterized in that the foundation is provided with a pile hole extending into the rock layer (11), and a steel pipe pile (1) is driven into the pile hole;
the pile hole (3) is sequentially divided into a loose soil layer section (31) corresponding to the loose cover soil layer (9), a compact soil layer section (32) corresponding to the compact soil layer (10) and a rock layer section (33) corresponding to the rock layer (11) from top to bottom, wherein the loose soil layer section (31) is formed after the steel pipe pile (1) is subjected to pile driving, and the compact soil layer section (32) and the rock layer section (33) are formed after the steel pipe pile (1) driven in the loose cover soil layer (9) conducts drilling on the compact soil layer (10) and the rock layer (11) for a construction channel.
The offshore rock-drilling redriving-type large-diameter pile structure according to claim 1, characterized in that the compact soil layer section (32) of the pile hole (3) has a hole diameter smaller than the pile diameter of the steel pipe pile (1), and the rock layer section (33) of the pile hole has a hole diameter slightly larger than the pile diameter of the steel pipe pile (1).
The offshore rock-drilling redriving-type large-diameter pile structure according to claim 1 or 2, characterized in that the rock layer section (33) of the pile hole (3) is filled with underwater concrete (6), and the steel pipe pile (1) is integrated with the rock layer section of the pile hole by means of the underwater concrete.
A construction method for the offshore rock-drilling redriving-type large-diameter pile structure according to any one of claims 1-3, characterized in that the construction method comprises the steps of:
S4.1 of conducting pile driving at the top of a steel pipe pile (1) by means of a pile driving hammer (4) until a lower end of the steel pipe pile is supported on the surface of the compact soil layer (10);

S4.2 of setting up a driller apparatus (5) at the top of the steel pipe pile (1), wherein a rock-socketed driller bit (5-1) of the driller apparatus conducts drilling within and under the steel pipe pile through a channel within the steel pipe pile until it reaches the designed bottom elevation in the rock layer (11), wherein a drilled hole has a hole diameter smaller than the pile diameter of the steel pipe pile; and of conducting hole broadening for the drilled hole within the rock layer until its hole diameter is slightly larger than the pile diameter of the steel pipe pile;

S4.3 of removing the driller apparatus (5) and cleaning the drilled hole;

S4.4 of filling the drilled hole of the rock layer (11) with underwater concrete (6);

S4.5 of conducting pile driving at the top of the steel pipe pile (1) by means of the pile driving hammer until the lower end of the steel pipe pile reaches the designed bottom elevation in the rock layer (11).
An offshore rock-drilling redriving-type large-diameter pile structure suitable for a foundation including a loose cover soil layer (9), a compact soil layer (10) and a rock layer (11) from top to bottom, characterized in that the foundation is provided with a pile hole (3) extending into the compact soil layer (10), and a steel pipe pile (1) is driven into the pile hole;
the pile hole (3) is sequentially divided into a loose soil layer section (31) corresponding to the loose cover soil layer (9) and a compact soil layer section (32) corresponding to the compact soil layer (10) from top to bottom, wherein the loose soil layer section (31) is formed after the steel pipe pile (1) is subjected to pile driving, and the compact soil layer section (32) is formed after the steel pipe pile (1) driven in the loose cover soil layer (9) conducts drilling on the compact soil layer for a construction channel.
The offshore rock-drilling redriving-type large-diameter pile structure according to claim 5, characterized in that the compact soil layer section of the pile hole (3) has a hole diameter smaller than the pile diameter of the steel pipe pile (1).
A construction method for the offshore rock-drilling redriving-type large-diameter pile structure according to claim 5 or 6, characterized in that the construction method comprises the steps of:
S7.1 of conducting pile driving at the top of a steel pipe pile (1) by means of the pile driving hammer (4) until a lower end of the steel pipe pile is supported on the surface of the compact soil layer (10);

S7.2 of setting up a driller apparatus (5) at the top of the steel pipe pile (1), wherein a rock-socketed driller bit (5-1) of the driller apparatus conducts drilling within and under the steel pipe pile through a channel within the steel pipe pile (1) until it reaches the designed bottom elevation in the compact soil layer (10), wherein a drilled hole has a hole diameter smaller than the pile diameter of the steel pipe pile;

S7.3 of removing the driller apparatus (5) and cleaning the drilled hole;

S7.4 of conducting pile driving at the top of the steel pipe pile (1) by means of the pile driving hammer (4) until the lower end of the steel pipe pile reaches the designed bottom elevation in the compact soil layer (10).