Pile foundation construction method for seabed high-strength inclined rock surface

Abstract

The invention discloses a pile foundation construction method for a seabed high-strength inclined rock surface, which comprises the following steps of: 1, hoisting a measure steel casing to a pile foundation construction position and sinking to a designed elevation, and fixing the upper part of the measure steel casing on a construction platform; 2, on the inner side of the measure steel casing, downward rotary digging is carried out from the top of the bearing stratum to a first depth so as to form a rock breaking hole channel, and slag removal is carried out; then, a variable-diameter hole channel is formed in a chambering and rotary digging mode on the basis of the rock breaking hole channel, and slag removal is conducted; and finally, on the basis of the variable-diameter hole channel, chambering and rotary excavating are conducted to a second depth so as to form a peripheral hole channel, and slag removal is conducted. The diameter of the peripheral hole channel is equal to the outer diameter of the permanent steel casing, and the second depth is the designed bottom elevation of the permanent steel casing; 3, the permanent steel casing is hoisted into the measure steel casing and lowered to a second depth; and then gravelly soil is backfilled between the permanent steel casing and the measure steel casing to the position above the seabed surface, then the measure steel casing is pulled out, and the upper portion of the permanent steel casing is fixed to the construction platform.

Description

Technical Field

[0001] The invention relates to the technical field of pile foundation construction, and in particular to a pile foundation construction method for a high-strength inclined rock surface on the seabed. Background Art

[0002] In submarine engineering construction, bored piles need to be constructed on the seabed as the bearing foundation of the upper structure. On the high-strength submarine rock formation, the bearing layer is very hard, which makes it difficult for the drill bit of the rotary drilling rig to complete the one-time hole drilling. Forced drilling not only causes great wear and tear on the equipment and easily causes failures, but also has low drilling construction efficiency and delays the construction period.

[0003] During the construction of bored piles, due to the large depth of the borehole and the complex geological conditions on both sides of the hole, it is often necessary to set up wall protection mud to prevent the hole from collapsing, which will inevitably cause pollution to the marine environment. Secondly, since the drilling construction will produce a large amount of debris or gravel and other debris, it is necessary to use flushing mud to remove the debris and debris from the hole, otherwise it will affect the construction progress. Both wall protection mud and flushing mud will have an impact on the marine environment. Moreover, the above operations are time-consuming and labor-intensive, and also affect the efficiency of pile foundation construction to a certain extent. Summary of the invention

[0004] The main technical problem to be solved by the present invention is to provide a pile foundation construction method for a high-strength inclined rock surface on the seabed to increase the hole-forming efficiency and realize green construction.

[0005] In order to solve the above technical problems, the present invention provides a pile foundation construction method for a high-strength inclined rock surface on the seabed, comprising the following steps:

[0006] Step 1: Construction of steel casing; this step includes the following steps:

[0007] Step 11: hoist the steel casing to the pile foundation construction site and lower it vertically; the bottom of the steel casing is located in the covering layer above the bearing layer; Step 12: sink the steel casing to the designed elevation; Step 13: fix the upper part of the steel casing on the construction platform;

[0008] Step 2: Pile hole construction; this step includes the following steps:

[0009] Step 21: Position the rotary drilling rig to the inner side of the said measure steel casing, use the slag removal drill bit to drill downward, and remove the slag to the top of the bearing layer; Step 22: Rotate and drill to a first depth in the bearing layer to form a rock-breaking channel, and remove the slag from the said rock-breaking channel; Step 23: Based on the said rock-breaking channel, expand and rotary drill a variable diameter channel in the bearing layer, and remove the slag; the said variable diameter channel is single or multiple arranged in a stepped manner; Step 24: Based on the said variable diameter channel with the largest diameter, expand and rotary drill to a second depth in the bearing layer to form a peripheral channel, and remove the slag; the diameter of the said peripheral channel is equal to the outer diameter of the permanent steel casing, and the second depth is the designed bottom elevation of the permanent steel casing; the bottom elevation of any variable diameter channel is not lower than the first depth and not higher than the second depth;

[0010] Step 3: Construction of permanent steel casing; the diameter of the permanent steel casing is smaller than that of the measure steel casing; this step includes the following steps:

[0011] Step 31: inspect the outer hole, then hoist the permanent steel casing into the measure steel casing, and lower it to the second depth; Step 32: backfill between the permanent steel casing and the measure steel casing; Step 33: release the fixation between the measure steel casing and the construction platform, and pull out the measure steel casing; Step 34: fix the upper part of the permanent steel casing on the construction platform.

[0012] In a preferred embodiment, in step 2, the first depth is less than the designed bottom elevation of the pile foundation; and after step 3, there is step 4, which includes:

[0013] Step 41: Continue drilling the rock-breaking hole in step 22 to the designed bottom elevation of the pile foundation, and clean the slag; Step 42: Based on the rock-breaking hole formed in step 41, each of the variable-diameter holes is respectively rotary-drilled to the designed bottom elevation, and clean the slag; wherein the designed bottom elevation of the variable-diameter hole with the smallest diameter is equal to the designed bottom elevation of the pile foundation.

[0014] In a preferred embodiment, in step 2, the first depth is equal to the designed bottom elevation of the pile foundation; the bottom elevations of each variable diameter channel are their respective designed bottom elevations; wherein the bottom elevation of the variable diameter channel with the smallest diameter is equal to the first depth.

[0015] In a preferred embodiment, in step 12, a vibratory hammer is installed on the top of the measure steel casing, and the vibratory hammer is started to vibrate the measure steel casing down to the designed elevation.

[0016] In a preferred embodiment, in step 32, gravel soil is backfilled between the permanent steel casing and the protective steel casing until the backfill height is higher than the top of the covering layer.

[0017] In a preferred embodiment, in step 12, after the steel casing is sunk to the designed elevation, the top height is higher than the construction platform.

[0018] In a preferred embodiment, in step 34, the permanent steel casing is fixed by welding the top of the permanent steel casing to the construction platform in the circumferential direction using steel sections.

[0019] In a preferred embodiment, a pick-tooth slag bucket drill bit is used to clean slag from each channel.

[0020] In a preferred embodiment, the rock breaking channel or the peripheral channel is drilled by a cone drill.

[0021] In a preferred embodiment, the variable diameter hole is drilled by a roller cutter.

[0022] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0023] The method provided by the present invention first uses a small-diameter drill bit with the strongest rock-breaking ability to drill a channel in a hard medium-weathered rock layer, and then uses a larger drill bit to expand the hole and drill to the designed elevation, thereby obtaining a pile hole that meets the requirements. For high-strength bearing rock layers, this method can effectively solve the problems of drilling difficulties and high equipment failure rates in traditional one-time drilling methods. It not only greatly improves construction efficiency and shortens construction period, but also alleviates the wear of drill bits and drilling rigs, and extends the service life of equipment. Secondly, before the final permanent steel casing is put into place, the temporary support of the measure steel casing solves the problem of composite piles being difficult to embed in the rock in existing projects, avoids the risk of hole collapse, and thus improves construction safety and quality. For this reason, the method only needs to directly drill holes in the measure casing or the permanent steel casing, and there is no need to add mud walls on the seabed, which not only simplifies the process but also reduces environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 to Figure 5 This is a schematic diagram of the construction of the steel casing of the embodiment 1 of the present invention;

[0025] Figure 6 to Figure 9 It is a construction schematic diagram of the 3.0-meter pile hole section described in Example 1 of the present invention;

[0026] Figure 10 to Figure 12 This is a schematic diagram of the construction of the permanent steel casing described in Example 1 of the present invention;

[0027] Figure 13-14 It is a construction schematic diagram of the 2.7-meter pile hole section described in Example 1 of the present invention;

[0028] Figure 5 to Figure 17 It is a schematic diagram of the construction of the variable diameter pile hole described in Example 2 of the present invention;

[0029] Fig.18 This is a schematic diagram of the construction of the permanent steel casing described in Example 2 of the present invention.

[0030] Markings in the figure are: 11-measure steel casing, 12-permanent steel casing, 21-first crane, 22-second crane, 31-construction platform, 32-guide frame, 33-steel bracket, 4-vibratory hammer, 41-clamp, 51-cover layer, 52-medium-weathered rock layer, 53-backfill layer, 6-rotary drilling rig, 7-3.0-meter pick-tooth slag bucket drill bit, 81-1.5-meter roller drill, 82-3.0-meter roller drill, 83-2.7-meter roller cutter bit, 91-rock breaking channel, 92-variable diameter channel, 93-peripheral channel. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments, and all other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making creative work are within the scope of protection of the present invention.

[0032] In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "top / bottom" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0033] In the description of the present invention, it should be noted that, unless otherwise clearly stipulated and limited, the terms "installed", "provided with", "installed / connected", "connected", etc. should be understood in a broad sense. For example, "connection" can be a wall-mounted connection, a detachable connection, or an integral connection. It can be a mechanical connection or an electrical connection. It can be a direct connection or an indirect connection through an intermediate medium. It can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0034] like Figure 1 to Figure 14 As shown, an embodiment of the present invention provides a pile foundation construction method for a high-strength inclined rock surface on the seabed, which uses a "measure steel casing combined with direct rotary drilling + multi-stage hole expansion drilling" method to drill pile foundation holes in the hard medium-weathered rock layer 52 on the seabed.

[0035] The following takes the drilling construction of 3.0-2.7m variable diameter piles as an example to illustrate the method. The equipment and devices involved in the construction method mainly include: a first crane 21, a second crane 22, a vibrating hammer 4, a rotary drilling rig 6; a measure steel casing 11: an inner diameter of 3.3 meters and a wall thickness of 2 centimeters, a permanent steel casing 12: an inner diameter of 3.0 meters and a wall thickness of 3 centimeters; a roller drill: diameters of 1.5 meters and 3.0 meters, respectively, a roller cutter drill bit 83: a diameter of 2.7 meters, and a pick slag bucket drill bit: a diameter of 1.5 meters, 2.7 meters or 3.0 meters. Corresponding to the claims, in this embodiment, the slag removal drill bit adopts the pick slag bucket drill bit. For general submarine engineering, the working faces in the vertical direction are seawater, silt layer, clay layer, gravel layer, strongly weathered rock layer, and medium weathered rock layer 52 from high to low. In this embodiment, the medium weathered rock layer 52 is the bearing layer of the pile foundation. For the convenience of the following description, the silt layer, clay layer, gravel layer and strongly weathered rock layer are collectively referred to as a covering layer 51 .

[0036] In this embodiment, the method uses a multi-stage drilling method to drill a 2.7-meter pile hole, which specifically includes the following steps:

[0037] Step 1: Construction of the steel casing 11. It specifically includes the following steps:

[0038] Step 11: Figure 1 As shown, the main hook of the first hoist 21 is connected to one end of the measure steel casing 11 , and the second hoist 22 is connected to the lifting lug close to the other end of the measure steel casing 11 .

[0039] Step 12: Figure 2 As shown, slowly lift the main hook of the first crane 21, and with the cooperation of the second crane 22, slowly lift the steel casing 11 to a vertical state. After the steel casing 11 is completely vertical, the main hook of the second crane 22 is separated from the lifting lug. Then, only the first crane 21 operates the steel casing 11.

[0040] Step 13: Figure 3 As shown, the steel casing 11 is hoisted into the guide frame 32 and lowered to the seabed. Figure 4 After lowering, the bottom of the steel casing 11 is located in the covering layer 51.

[0041] Step 14: Figure 4As shown, the first crane 21 or the second crane 22 is used to hoist the vibrating hammer 4 to the top of the steel casing 11. The specific connection method is: a clamp 41 is provided at the bottom of the vibrating hammer 4, and the clamp 41 is clamped on the wall of the steel casing 11. Then the vibrating hammer 4 is started to sink the steel casing 11 to the designed elevation. The top elevation of the steel casing 11 should be 3150-80 cm higher than the construction platform, so as to facilitate subsequent extraction for turnover construction.

[0042] Step 15: Figure 5 As shown, a plurality of steel brackets 33 are symmetrically welded on the outer periphery of the steel casing 11 to fix the steel casing 11 on the top of the construction platform 31 to prevent it from suddenly falling into the formed borehole during subsequent construction.

[0043] Step 2: Construction of the 3.0-meter pile hole section. Specifically includes the following steps:

[0044] Step 21: Figure 6 As shown, the rotary drilling rig 6 is positioned at the steel casing 11 and adjusted to make its verticality and center position meet the requirements. The overburden 51 is drilled and slag removed using a 3.0-meter pick-tooth slag bucket drill bit 7 until the top surface of the medium-weathered rock layer 52 is drilled.

[0045] Step 22: Figure 7 As shown, a 1.5-meter cone drill 81 is used to drill into the medium-weathered rock layer 52 to a first depth to form a rock-breaking channel 91. The first depth is 3 to 5 meters lower than the designed bottom elevation of the permanent steel casing 12. During this process, a 1.5-meter pick-tooth slag bucket drill bit is used for slag removal.

[0046] Step 23: Figure 8 As shown, on the basis of the rock-breaking channel 91, a 2.7-meter roller cutter drill bit 83 is used to drill from the top of the medium-weathered rock layer 52 to form a variable-diameter channel 92, the bottom elevation of which is 0.5 to 1 meter lower than the designed bottom elevation of the permanent steel casing 12. In this process, a 1.5-meter pick-tooth slag bucket drill bit is used for slag removal. In this embodiment, the variable-diameter channel 92 is in a single-stage form.

[0047] Step 24: Fig. 9 As shown, on the basis of the variable diameter channel 92, a 3.0-meter cone drill 82 is used to drill into the medium weathered rock layer 52 to a second depth to form a peripheral channel 93. In this process, a pick dredger drill bit of any of the above specifications is used to remove slag. The second depth is the designed bottom elevation of the permanent steel casing 12. At this point, the construction of the 3.0-meter pile hole is completed.

[0048] Step 3: Construction of permanent steel casing 12. Specifically includes the following steps:

[0049] Step 31: For the peripheral hole 93 formed in step 2, an ultrasonic hole forming detector is used to detect the hole depth, hole diameter and verticality.

[0050] Step 32: Fig.10 As shown, after passing the inspection, the permanent steel casing 12 is hoisted into the measure steel casing 11 by using the first crane 21 and the second crane 22, referring to the method described in steps 11 to 13, and lowered to the designed elevation.

[0051] Step 33: Fig.11 As shown, the gap between the permanent steel casing 12 and the protective steel casing 11 is backfilled with gravel soil, and the upper height of the backfill layer 53 is not lower than the top of the cover layer 51. Preferably, the upper part of the backfill layer 53 is 1 to 2 meters above the seabed surface. During the backfilling process, a conical cover needs to be installed on the top of the permanent steel casing 12 to prevent gravel from falling in.

[0052] Step 34: Fig.12 As shown, after the gravel soil backfill is completed, the fixing of the measure steel casing 11 and the construction platform 31 is released. The first crane 21 or the second crane 22 is used to cooperate with the vibrating hammer 4 to pull out the measure steel casing 11 to transfer to the next pile foundation construction.

[0053] Step 35: Within the height range of the cover layer 51, the permanent steel casing 12 is fixed by radially limiting the cover layer 51 through a circle of backfill layer 53 on the periphery. As for the top section of the permanent steel casing 12, it may shake due to the flow of seawater or disturbance during subsequent drilling. Therefore, it is necessary to use steel sections to weld the top of the permanent steel casing 12 to the construction platform 31 in the circumferential direction to achieve fixation.

[0054] Step 4: Construction of the 2.7-meter pile hole section. Specifically includes the following steps:

[0055] Step 41: Fig.13 As shown, based on the rock-breaking hole 91 formed in step 22, a 1.5-meter cone drill 81 is used to drill to the designed bottom elevation of the pile foundation, and a 1.5-meter pick-tooth slag bucket drill bit is used to remove slag.

[0056] Step 42: Fig.14As shown, based on the rock-breaking hole 91 formed in step 41, a 2.7-meter roller cutter drill bit 83 is used to expand the hole and drill to the designed bottom elevation of the pile foundation. During the drilling process, a 1.5-meter pick-tooth slag bucket drill bit is used to remove slag. After drilling completely to the designed bottom elevation of the pile foundation, a 2.7-meter pick-tooth slag bucket drill bit is used to remove the sediment deposited at the bottom of the hole. At this point, the drilling construction of the 3.0-meter-2.7-meter variable-diameter pile is completed.

[0057] It should be understood that what is exemplified in this article is only a specific working condition in an actual project. For variable diameter piles of other sizes and more grades, the method is still applicable. As an extension of this working condition, in another embodiment, the variable diameter pile is multi-level, that is, the variable diameter channels 92 drilled in step 23 are multiple, and the depth of each variable diameter channel 92 is shallower as the diameter increases, and the whole is arranged in a stepped shape. Then in step 23, the variable diameter channel 92 can be drilled by sequentially expanding the hole and rotary drilling, and the bottom elevation of any variable diameter channel 92 is not lower than the first depth and not higher than the second depth. In step 42, each of the variable diameter channels 92 needs to be rotary drilled to the designed bottom elevation and slag removed; it should be understood that the designed bottom elevation of the variable diameter channel 92 with the smallest diameter is equal to the designed bottom elevation of the pile foundation.

[0058] Example 2

[0059] As an alternative to implementation 1, a method for pile foundation construction on a high-strength inclined rock surface on the seabed provided in an embodiment of the present invention has the same working conditions and equipment and devices as those in embodiment 1. Different from embodiment 1, the method provided in this embodiment is to drill a 2.7-meter pile hole to the bottom of the pile foundation at one time. The method comprises the following steps:

[0060] Step 1: Construction of the protective steel casing 11. This step is the same as that in Example 1 and will not be described in detail herein.

[0061] Step 2: Construction of variable diameter pile holes. The specific steps include:

[0062] Step 21: As in Example 1, the rotary drilling rig 6 is put in place and debugged to ensure that its verticality and center position meet the requirements. The overburden layer 51 is drilled and slag removed using a 3.0-meter pick-tooth slag bucket drill bit 7 until the top surface of the medium-weathered rock layer 52 is reached.

[0063] Step 22: Fig.15 As shown, a 1.5-meter cone drill 81 is used to drill into the medium-weathered rock layer 52 to a first depth to form a rock-breaking channel 91. The first depth is the designed bottom elevation of the pile foundation. In this process, a 1.5-meter pick-tooth slag bucket drill bit is used to remove slag.

[0064] Step 23: Fig.16As shown, based on the rock-breaking channel 91 formed in step 22, a 2.7-meter roller cutter drill bit 83 is used to drill from the top of the medium-weathered rock layer 52 to form a variable-diameter channel 92. In this embodiment, the variable-diameter channel 92 is a single-stage channel, so its bottom should be drilled to the first depth, that is, the designed bottom elevation of the pile foundation. In this process, a 1.5-meter pick-tooth slag bucket drill bit is used for slag removal.

[0065] Step 24: Fig.17 As shown, based on the variable diameter channel 92 formed in step 23, a 3.0 m roller drill 82 is used to drill into the medium weathered rock layer 52 to a second depth to form a peripheral channel 93. The second depth is the designed bottom elevation of the permanent steel casing 12.

[0066] Step 25: Use a 2.7-meter pick-tooth dredger to remove the sediment deposited at the bottom of the 2.7-meter hole.

[0067] Step 3: Construction of the permanent steel casing 12. Fig.18 This step is the same as that in Example 1 and will not be described in detail herein. At this point, the drilling construction of the 3.0-m-2.7-m variable diameter pile is completed.

[0068] Similarly, in other working conditions, the variable diameter holes 92 may be multiple and arranged in a stepped manner. Correspondingly, in step 23, each of the variable diameter holes 92 needs to be respectively excavated to the designed bottom elevation and slag removed; wherein the designed bottom elevation of the variable diameter hole 92 with the smallest diameter is equal to the first depth, i.e., the designed bottom elevation of the pile foundation.

[0069] Example 3

[0070] The pile foundation construction method for a high-strength inclined rock surface on the seabed provided in an embodiment of the present invention is different from that in Embodiment 1 or Embodiment 2 in that the working condition involved is a non-variable diameter pile.

[0071] The method can be used to drill holes in one go in the manner of Example 2. The construction steps are different from those of Example 2 in that: in steps 23 and 24, the bottom elevations of the rock-breaking channel 91, the variable-diameter channel 92 and the peripheral channel 93 are equal, and are all the designed bottom elevations of the pile foundation; in step 25, a pick-tooth slag bucket drill bit of any of the above specifications is used to remove the sediment deposited at the bottom of the peripheral channel 93; in step 3, the installation bottom elevation of the permanent steel casing 12 is the designed bottom elevation of the pile foundation.

[0072] Of course, the method can also be used to drill holes in multiple stages, and the construction process is equivalent to multiple repetitions of the above-mentioned one-time drilling operation, except that the bottoms of the rock-breaking hole 91, the variable-diameter hole 92, and the peripheral hole 93 gradually approach the designed bottom elevation of the pile foundation. This article will not elaborate on this.

[0073] In summary, the method provided in the above embodiments first uses a small-diameter drill bit with the strongest rock-breaking ability to drill a channel in a hard medium-weathered rock layer 52, and on this basis, uses a larger drill bit to expand the hole and drill to the designed elevation, thereby obtaining a pile hole that meets the requirements. For high-strength bearing rock formations, this method can effectively solve the problems of drilling difficulties and high equipment failure rates in traditional one-time drilling methods, which not only greatly improves construction efficiency and shortens construction periods, but also alleviates the wear of drill bits and drilling rigs, and extends the service life of equipment. Secondly, before the final permanent steel casing 12 is placed, the temporary support of the measure steel casing 11 solves the problem of difficulty in embedding composite piles in existing projects, avoids the risk of hole collapse, and thus improves construction safety and construction quality. For this reason, the method only needs to directly drill holes in the measure steel casing 11 or the permanent steel casing 12, and there is no need to add mud wall protection on the seabed, which not only simplifies the process but also reduces environmental pollution.

[0074] The above description is only a preferred specific implementation mode of the present invention, and does not limit the patent scope of the present invention. Any technical equivalent changes made using the contents of the present invention specification shall fall within the protection scope of the present invention.

Claims

1. A pile foundation construction method for high-strength inclined rock surface on the seabed, characterized in that: The following steps are involved: Step 1: Construction of steel casing; this step includes the following steps: Step 11: hoist the steel casing to the pile foundation construction site and lower it vertically; the bottom of the steel casing is located in the covering layer above the bearing layer; Step 12: sink the steel casing to the designed elevation; Step 13: fix the upper part of the steel casing on the construction platform; Step 2: Pile hole construction; this step includes the following steps: Step 21: Position the rotary drilling rig to the inner side of the said measure steel casing, use the slag removal drill bit to drill downward, and remove the slag to the top of the bearing layer; Step 22: Rotate and drill to a first depth in the bearing layer to form a rock-breaking channel, and remove the slag from the said rock-breaking channel; Step 23: Based on the said rock-breaking channel, expand and rotary drill a variable diameter channel in the bearing layer, and remove the slag; the said variable diameter channel is single or multiple arranged in a stepped manner; Step 24: Based on the said variable diameter channel with the largest diameter, expand and rotary drill to a second depth in the bearing layer to form a peripheral channel, and remove the slag; the diameter of the said peripheral channel is equal to the outer diameter of the permanent steel casing, and the second depth is the designed bottom elevation of the permanent steel casing; the bottom elevation of any variable diameter channel is not lower than the first depth and not higher than the second depth; Step 3: Construction of permanent steel casing; the diameter of the permanent steel casing is smaller than that of the measure steel casing; This step includes the following steps: Step 31: Inspect the outer hole, then hoist the permanent steel casing into the measure steel casing, and lower it to the second depth; Step 32: Backfill between the permanent steel casing and the measure steel casing; Step 33: Release the fixation between the measure steel casing and the construction platform, and pull out the measure steel casing; Step 34: Fix the upper part of the permanent steel casing on the construction platform.

2. A pile foundation construction method for a high-strength inclined rock surface on the seabed according to claim 1, characterized in that: In step 2, the first depth is less than the designed bottom elevation of the pile foundation; after step 3, there is step 4, which includes: Step 41: Continue drilling the rock-breaking hole in step 22 to the designed bottom elevation of the pile foundation, and clean the slag; Step 42: Based on the rock-breaking hole formed in step 41, each of the variable-diameter holes is respectively rotary-drilled to the designed bottom elevation, and clean the slag; wherein the designed bottom elevation of the variable-diameter hole with the smallest diameter is equal to the designed bottom elevation of the pile foundation.

3. The method for pile foundation construction on a high-strength inclined rock surface on the seabed according to claim 1, characterized in that: In step 2, the first depth is equal to the designed bottom elevation of the pile foundation; the bottom elevations of the various variable-diameter holes are their respective designed bottom elevations; wherein the bottom elevation of the variable-diameter hole with the smallest diameter is equal to the first depth.

4. A pile foundation construction method for a high-strength inclined rock surface on the seabed according to any one of claims 1 to 3, characterized in that: In step 12, a vibrating hammer is installed on the top of the measure steel casing, and the vibrating hammer is started to vibrate the measure steel casing down to the designed elevation.

5. A pile foundation construction method for a high-strength inclined rock surface on the seabed according to any one of claims 1 to 3, characterized in that: In step 32, gravel soil is backfilled between the permanent steel casing and the protective steel casing until the backfill height is higher than the top of the covering layer.

6. A pile foundation construction method for a high-strength inclined rock surface on the seabed according to any one of claims 1 to 3, characterized in that: In step 12, after the steel casing is sunk to the designed elevation, the top height is higher than the construction platform.

7. A pile foundation construction method for a high-strength inclined rock surface on the seabed according to any one of claims 1 to 3, characterized in that: In step 34, the permanent steel casing is fixed by welding the top of the permanent steel casing to the construction platform in the circumferential direction using steel sections.

8. A pile foundation construction method for a high-strength inclined rock surface on the seabed according to any one of claims 1 to 3, characterized in that: Use a pick-tooth slag bucket drill bit to clean the slag from each channel.

9. A pile foundation construction method for a high-strength inclined rock surface on the seabed according to any one of claims 1 to 3, characterized in that: The rock breaking hole or the peripheral hole is drilled by using a roller drill.

10. A pile foundation construction method for a high-strength inclined rock surface on the seabed according to any one of claims 1 to 3, characterized in that: The variable diameter hole is drilled by using a roller cutter bit.

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