Underwater reef limestone pile foundation ballast enlarged end accessory structure and construction method

Abstract

The application discloses an underwater reef limestone pile foundation ballast enlarged end accessory structure and method, and belongs to the field of marine civil engineering. The main purpose of the application is to make up for the shortage of the bearing capacity of the reef limestone pile foundation pile end by setting an expansion accessory. The upper load is effectively compacted in the foundation below the expansion accessory, thereby increasing the side friction resistance between the pile foundation and the foundation. The side friction resistance and the end resistance are better exerted with the increase of the late-stage pile load, the steel pipe pile rock penetration depth is effectively shortened, the consumption of the steel pipe pile is greatly saved, and the pile body settlement is better controlled. The expansion accessory is a whole, and is convenient for recycling after the structure failure. The application is widely applied, and is mainly applied to the marine reef limestone foundation. The application can also be applied to the single-pile structure of the offshore wind turbine, the land pile foundation engineering with insufficient foundation bearing capacity, and has the advantages of less construction process, high speed, assembly, high pile foundation bearing capacity, good economic benefits and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of marine civil engineering, in particular to a water reef limestone pile foundation ballast enlarged end accessory structure and construction method. BACKGROUND

[0002] The following defects exist in the traditional method of sinking piles on reef limestone:

[0003] 1) The porosity of coral reef limestone is large, and the structure is prone to brittle failure. The steel pipe pile has strong penetration and large penetration depth in coral reef limestone, and the sinking depth is difficult to control. 2) When sinking piles on coral reef limestone, post-treatment methods are often used due to insufficient pile foundation bearing capacity. The more common post-treatment method is post-grouting to improve the pile side friction and pile end resistance. However, there are many disadvantages in the grouting process: it is difficult to grasp the grouting pressure, grouting amount, slurry concentration and grouting rhythm. 3) The steel pipe pile side friction of reef limestone stratum is very limited. The deeper the stratum distribution and the higher the cementation degree, the greater the side friction. Therefore, the side friction is highly dependent on the soil penetration depth of the steel pipe pile and the type of reef limestone. In actual engineering, steel pipe piles with a length of several tens of meters or even hundreds of meters are often needed to ensure the bearing capacity of the pile foundation, which easily leads to an increase in engineering cost due to excessive pile length. The weathering degree of coral reef limestone geology is uneven, and soft and hard alternations occur, making it difficult to grasp the pile end resistance, and there is a risk of pile body penetration failure under ultimate load. 4) Marine pile foundation is also subject to water wave dynamic load, overturning moment and poor overall stability.

[0004] In view of the above shortcomings, an optimized pile foundation means is needed to improve the mechanical properties and economic benefits of sinking piles on reef limestone. SUMMARY

[0005] In view of the many shortcomings of the existing post-grouting method, a water reef limestone pile foundation ballast enlarged end accessory structure is provided, which is simple in structure, high in construction efficiency, has no backflow of slurry, and has a certain assembly.

[0006] In view of the complexity of the physical properties of coral reef limestone and the bearing characteristics of pile foundation, a water reef limestone pile foundation ballast enlarged end accessory structure is provided to control the soil penetration depth of pile foundation, save steel, and improve the bearing capacity of pile foundation.

[0007] In view of the frequent water wave and wind dynamic load, the difficulty in ensuring the stability of sinking piles, and the existence of overturning moment, a water reef limestone pile foundation ballast enlarged end accessory structure is provided to solve the above problems.

[0008] To solve the above technical problems, the present application realizes the following technical scheme:

[0009] The application relates to a reef limestone pile foundation ballast enlarged end accessory structure, which comprises a steel pipe pile and an expansion accessory sleeved on the steel pipe pile, a support is fixed on the outer wall of the steel pipe pile, the expansion accessory comprises an annular accessory base and a stress table fixed on the inner side wall of the accessory base, and an empty space is arranged between the stress table and the inner side wall of the accessory base; the support is arranged in a limiting fit relationship with the stress table in the length direction of the steel pipe pile when the support overlaps with the stress table after rotation, and the support can shuttle in the empty space in the length direction of the steel pipe pile when the support overlaps with the empty space after rotation; the top surface of the stress table is spaced from the top surface of the accessory base; the support is arranged in a limiting fit relationship with the accessory base in the radial direction of the steel pipe pile when the support is embedded in the space.

[0010] Preferably, the bottom surface of the expansion accessory is provided with sharp corners for inserting into reef limestone.

[0011] Further preferably, the sharp corners comprise large-angle sharp corners with an angle of 45-60 degrees with the horizontal and small-angle sharp corners with an angle less than 45 degrees with the horizontal, the large-angle sharp corners are arranged on the outer edge of the bottom surface of the accessory base and the inner edge of the bottom surface of the stress table respectively, and the small-angle sharp corners are arranged on the bottom surface of the expansion accessory between the outer edge of the accessory base and the inner edge of the stress table.

[0012] Preferably, a plurality of the supports are uniformly fixed on the outer wall of the steel pipe pile in the circumferential direction, a plurality of the stress tables are uniformly fixed on the inner side wall of the accessory base in the circumferential direction, and the supports and the stress tables are arranged in one-to-one correspondence.

[0013] Preferably, the planes of the support and the stress table are in the shape of a sector, the outer arc surface of the support is tightly fitted with the inner side wall of the accessory base when the support is embedded in the space, and the plane width of the support is smaller than the plane width of the stress table.

[0014] Preferably, the reef limestone is provided with gravel in the range of the pile body and the pile end of the steel pipe pile.

[0015] Further preferably, the gravel is selected from special fine gravel with a nominal particle size range of 5-10 mm, a mud content controlled within 0.5%, a mud block content of 0 and a porosity controlled within 43%, or the gravel is selected from special fine pebbles with the same particle size grading.

[0016] A construction method of a reef limestone pile foundation ballast enlarged end accessory structure, comprising the following steps:

[0017] S1: calculating and designing the rock insertion depth of the steel pipe pile;

[0018] S2: prefabricated steel pipe pile and support on the pile body, prefabricated expansion accessory;

[0019] S3: when the steel pipe pile is inserted to the designed depth, the expansion accessory is sleeved from the upper part of the steel pipe pile downwards, and after the empty mouth passes through the support, it is rotated and placed under the support;

[0020] S4: continue to insert the steel pipe pile until the support is seated and pressed on the stress platform, so that the sharp corners of the bottom surface of the expansion accessory are inserted into the reef limestone.

[0021] Preferably, in step S3, before the expansion accessory is sleeved, the gravel is blown from the pile end of the steel pipe pile upwards to the top of the foundation, and the gravel is compacted at the top of the foundation.

[0022] Preferably, when the fully weathered coral reef limestone is soft as the bearing layer, the expansion accessory is designed to be wide and thin in size; when the strongly weathered coral reef limestone is hard as the bearing layer, the expansion accessory is designed to be narrow and thick in size.

[0023] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0024] The underwater reef limestone pile foundation ballast enlarged end accessory structure of the present application has the advantages of simple structure, strong water wave dynamic load resistance and overturning moment resistance, good overall stability, and the like. The expansion accessory makes up for the deficiency of the reef limestone pile foundation pile end bearing capacity, the upper load is effectively compacted and expanded by the expansion accessory below the foundation, thereby increasing the side friction resistance between the pile foundation and the foundation, and the side friction resistance and the end resistance are better with the increase of the later-stage pile load, effectively shortening the rock insertion depth of the steel pipe pile, greatly saving the material consumption of the steel pipe pile, and better controlling the pile body settlement. The expansion accessory as a whole is convenient for recycling after structural failure. The present application is widely applicable, and the main purpose is to be applied to the marine reef limestone foundation, and can also be applied to the single pile structure of the offshore wind turbine, the land pile foundation engineering with insufficient foundation bearing capacity, and the like, and has the advantages of less construction process, fast speed, assembly, high pile foundation bearing capacity, good economic benefits, and the like.

[0025] The underwater reef limestone pile foundation gravel physical compaction disposal technology uses the method of physical blowing and compaction of gravel to replace the traditional grouting foundation, protects the reef limestone foundation and seawater from chemical pollution, and overcomes the disadvantage of grouting foundation "back grouting". Simulation tests prove that the blowing and compaction of gravel effectively improves the total bearing capacity of the pile, including the pile side resistance and the pile end resistance, thereby reducing the soil insertion depth of the pile and saving the steel material. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The structure diagram of the pile foundation ballast enlarged end accessory involved in the embodiment 1 of the present application.

[0027] Figure 2The pile foundation ballast enlarged end accessory of the embodiment 1 of the present application relates to a top view.

[0028] Figure 3 The pile foundation ballast enlarged end accessory of the embodiment 1 of the present application relates to a bottom view.

[0029] Figure 4 The pile foundation ballast enlarged end accessory of the embodiment 1 of the present application relates to a sectional view.

[0030] Figure 5 The pile foundation ballast enlarged end accessory of the embodiment 1 of the present application relates to an elevation view.

[0031] Figure 6 The pile foundation ballast enlarged end accessory of the embodiment 1 of the present application relates to a plan view.

[0032] Figure 7 The pile foundation ballast enlarged end accessory of the embodiment 1 of the present application relates to a structural schematic view.

[0033] Figure 8 The pile foundation ballast enlarged end accessory of the embodiment 1 of the present application relates to a structural schematic view.

[0034] Figure 9 The pile foundation ballast enlarged end accessory of the embodiment 1 of the present application relates to a sectional view.

[0035] Figure 10 The pile foundation ballast enlarged end accessory of the embodiment 1 of the present application relates to an elevation view.

[0036] Figure 11 The pile foundation ballast enlarged end accessory of the embodiment 1 of the present application relates to an elevation view.

[0037] Figure 12 The pile foundation ballast enlarged end accessory of the embodiment 1 of the present application relates to a structural schematic view at the construction process S4.

[0038] Figure 13 The pile foundation ballast enlarged end accessory of the embodiment 1 of the present application relates to a force diagram.

[0039] Figure 14 The pile foundation ballast enlarged end accessory of the embodiment 1 of the present application relates to a bearing capacity curve diagram of each part.

[0040] Figure 15 The pile foundation ballast enlarged end accessory of the embodiment 1 of the present application relates to a FLAC model sectional view.

[0041] Figure 16 The pile foundation ballast enlarged end accessory of the embodiment 1 of the present application relates to a sectional view.

[0042] Figure 17 The pile foundation ballast enlarged end accessory of the embodiment 1 of the present application relates to a sectional view.

[0043] Figure: 1, steel pipe pile; 11, support; 2, expansion accessory; 21, accessory base; 22, stress platform; 23, spacing; 24, air opening; 25, sharp corner; 251, large-angle sharp corner; 252, small-angle sharp corner; 3, foundation; 4, stress influence area; 5, gravel. DETAILED DESCRIPTION

[0044] To make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described below in a clear and complete manner with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0045] The above description is made in combination with the accompanying drawings of the embodiments of the present application. Figures 1-17 The embodiments of the present application are further described in detail.

[0046] Embodiment one:

[0047] According to the existing technical deficiencies, the present application aims to provide a reef limestone pile foundation ballast expansion end accessory structure, the present application provides a reef limestone pile foundation ballast expansion end accessory structure as shown in Figures 1-12 The reef limestone pile foundation ballast expansion end accessory structure is provided for the pile foundation bearing characteristics on coral reef limestone, frequent dynamic load, and insufficient post-processing technology, and a reef limestone pile foundation ballast expansion end accessory with less construction steps, simple structure, high application efficiency, prefabrication, and good bearing characteristics is proposed, which more efficiently provides help for piling on reef limestone.

[0048] The expansion accessory 2 is applied on the marine reef limestone foundation 3, and can also be applied to single pile structures of offshore wind turbines and land pile foundation engineering with insufficient foundation 3 bearing capacity, has the advantages of less construction process, fast speed, assembly, high pile foundation bearing capacity, good economic benefits, etc.

[0049] As shown in Figures 1-12As shown, the underwater reef limestone pile foundation ballast enlarged end accessory structure includes a steel pipe pile 1 and an expansion accessory 2 sleeved on the steel pipe pile 1, a support 11 is fixed on the outer wall of the steel pipe pile 1, the expansion accessory 2 includes an annular accessory base 21 and a stress platform 22 fixed on the inner side wall of the accessory base 21, and an air gap 24 is arranged between the stress platform 22 and the inner side wall of the accessory base 21; the support 11 is arranged in a manner that when the support 11 overlaps with the stress platform 22 after rotation, a limiting fit relationship is formed between the support 11 and the stress platform 22 in the length direction of the steel pipe pile 1, and when the support 11 overlaps with the air gap 24 after rotation, the support 11 can shuttle in the air gap 24 in the length direction of the steel pipe pile 1. The top surface of the stress platform 22 and the top surface of the accessory base 21 have a spacing 23; the support 11 is arranged in a manner that when the support 11 is embedded in the spacing 23, a limiting fit relationship is formed between the support 11 and the accessory base 21 in the radial direction of the steel pipe pile 1.

[0050] As can be known from the above structural design, the steel pipe pile 1 and the expansion accessory 2 jointly bear the wave load, the overturning moment and the upper structure load, and the expansion accessory 2 effectively controls the later-stage settlement of the steel pipe pile 1.

[0051] Specifically, when the support 11 is pressed on the top surface of the stress platform 22, the upper part of the stress platform 22 bears the load of the support 11 and the load transmitted by the support 11, and due to the limiting fit between the support 11 and the stress platform 22 in the vertical direction and the limiting fit between the support 11 and the accessory base 21 in the horizontal direction, the assembly between the steel pipe pile 1 and the expansion accessory 2 is more compact, meanwhile, the setting of the expansion accessory 2 increases the contact area with the reef limestone, the expansion accessory 2 makes up for the deficiency of the reef limestone pile foundation pile end bearing capacity, the upper load is effectively compacted into the foundation 3 below the expansion accessory 2 through the expansion accessory 2, thereby increasing the side friction resistance between the pile foundation and the foundation 3, and the side friction resistance and the end resistance play better with the increase of the later-stage pile load, effectively shortening the rock penetration depth of the steel pipe pile 1, greatly saving the material consumption of the steel pipe pile 1, and better controlling the pile body settlement. The underwater reef limestone pile foundation ballast enlarged end accessory structure has simple structure, strong water wave dynamic load resistance and overturning moment resistance, and good overall stability.

[0052] As shown in Figs. Figure 4 , 8 and 9, the bottom surface of the expansion accessory 2 is provided with a sharp corner 25 for inserting into the reef limestone. The sharp corner 25 includes a large-angle sharp corner 251 with a horizontal angle of 45-60° and a small-angle sharp corner 252 with a horizontal angle less than 45°, the large-angle sharp corner 251 is arranged on the bottom surface of the accessory base 21 and the bottom surface of the stress platform 22 respectively, and the small-angle sharp corner 252 is arranged on the bottom surface of the expansion accessory 2 between the outer edge of the accessory base 21 and the inner edge of the stress platform 22.

[0053] From the above structural design, due to the easy brittleness of the reef limestone, the expansion accessory only needs to be inserted and fixed into the foundation under the vertical load and the sharp corner. The large-angle sharp corner 251 is designed to easily insert into the reef limestone, and the small-angle sharp corner 252 is designed to closely contact with the reef limestone foundation 3. The sharp corner 25 can easily insert into the reef limestone under the self-weight of the expansion accessory 2, so that the expansion accessory 2 closely contacts with the reef limestone foundation 3, and the expansion accessory has better grip on the ground, and is not easy to relatively displace with the foundation under the influence of water waves or other factors.

[0054] As shown in Figure 6 and 7 , a plurality of supporting members 11 are uniformly fixed on the outer wall of the steel pipe pile 1 in the circumferential direction, and a plurality of force receiving platforms 22 are uniformly fixed on the inner side wall of the accessory foundation 21 in the circumferential direction, and the supporting members 11 and the force receiving platforms 22 are one-to-one corresponding.

[0055] From the above structural design, a plurality of supporting members 11 and force receiving platforms 22 are respectively and uniformly arranged, so that the upper load is uniformly transmitted to the accessory foundation 21 and the foundation 3 through the supporting members 11 and the force receiving platforms 22, and the problem of easy overturning due to uneven stress is avoided.

[0056] As shown in Figure 2 and 3 , the planes of the supporting members 11 and the force receiving platforms 22 are fan-shaped, the outer arc surface of the supporting member 11 closely abuts against the inner side wall of the accessory foundation 21 when the supporting member 11 is embedded in the spacing 23, and the plane width of the supporting member 11 is smaller than the plane width of the force receiving platform 22.

[0057] From the above structural design, the outer arc surface of the fan-shaped supporting member 11 can closely abut against the inner side wall of the accessory foundation 21, which is more conducive to conducting horizontal load, and can also increase the frictional resistance between the supporting member 11 and the accessory foundation 21 to resist the upward pulling force of the pile body in the seabed soil due to the buoyancy; when the horizontal load (small, random dynamic load) acts on the pile foundation above the foundation, the (small) bending moment generated is transmitted to the expansion accessory through the supporting member; and then transmitted to the foundation by the expansion accessory; because of the existence of the sharp corners at the lower part of the expansion accessory, the expansion accessory has better grip on the ground, and is more likely to transmit the horizontal load to the foundation. The plane width of the supporting member 11 is smaller than the plane width of the force receiving platform 22, which can increase the movement range of the supporting member 11 on the force receiving platform 22, and avoid the situation that the supporting member 11 and the force receiving platform 22 are misaligned due to accidental rotation of the steel pipe pile 1 or the expansion accessory 2.

[0058] As shown in Figure 2 and 3 , the expansion accessory 2 is integrally formed, and is made of reinforced concrete or steel; the plane of the expansion accessory 2 is circular.

[0059] From the above structural design, the structural strength and stability of the integrally formed expansion accessory 2 are better, and the expansion accessory 2 with a circular shape can better offset the severe scouring effect of seawater.

[0060] The stress mechanism of the pile foundation ballast expansion end accessory is as follows: after the upper load Q is transmitted to the steel pipe pile 1, the upper load Q is divided into three parts, and a part of the upper load Q is transmitted to the expansion accessory 2 through the support member 11 and then to the lower reef limestone of the expansion accessory 2, which is called the base pressure (i.e., the end resistance of the expansion accessory); a part of the upper load Q is transmitted to the pile end (i.e., the end resistance of the pile foundation); and a part of the upper load Q is transmitted to the friction between the pile and the soil (i.e., the side resistance of the pile). The base pressure compacts the soil around the pile and further improves the side friction resistance. The stress diagram is shown in Figure 13 .

[0061] The vertical bearing capacity of the pile foundation and the expansion accessory 2 is composed of:

[0062] Q = Qend + Qside + Qend

[0063] Based on the above structural design, the application provides a construction method of a underwater reef limestone pile foundation ballast expansion end accessory structure, which comprises the following steps:

[0064] S1: calculating and designing the rock entering depth of the steel pipe pile 1;

[0065] S2: prefabricating the steel pipe pile 1 and the support member 11 on the pile body, and prefabricating the expansion accessory 2;

[0066] S3: when the steel pipe pile 1 is inserted to the designed depth, the expansion accessory 2 is sleeved downward from the upper part of the steel pipe pile 1, and then is rotated and placed under the support member 11 after the empty opening 24 passes through the support member 11, as shown in Figure 12 .

[0067] S4: continuing to insert the steel pipe pile 1 until the support member 11 is seated and pressed on the stress platform 22, so that the sharp corner 25 of the bottom surface of the expansion accessory 2 is inserted into the reef limestone.

[0068] The traditional method is to first enter the barrel and then sink the pile, which is easy to cause pile inclination, position deviation and other conditions during the sinking process, thereby disturbing the barrel. Therefore, after entering the barrel, it is difficult to control the pile driving without disturbing the barrel. The present application first forms the pile, then enters the barrel, and after the pile forming is basically completed (a small downward displacement is required in the later period, so that the pile and the expansion accessory can better act on the foundation), the expansion accessory is placed on the foundation from top to bottom along the pile body, and then is rotated. During this process, only the vertical descent and rotation of the expansion accessory need to be controlled, and the operation is relatively easy, and the correction difficulty is relatively small.

[0069] As shown in Figure 15As shown, in order to verify the pile foundation bearing capacity of the pile foundation ballast enlarged end accessory, the present application is compared with the pile foundation bearing capacity without pile foundation ballast enlarged end accessory, and the simulation test is carried out, as shown in the following table: Figure 17 As shown, under the same geological conditions and pile sinking conditions, the effect of the pile foundation ballast enlarged end accessory on improving the pile foundation bearing capacity is extremely significant, and with the increase of the soil depth, the pile foundation bearing capacity of the present application is improved, therefore, the present application has obvious advantages in the application of super-long soil depth pile foundation, and greatly saves the consumption of steel materials.

[0070] The bearing capacity of each part of the pile foundation ballast enlarged end accessory is as shown in the following table: Figure 14 As shown, it is found that the expansion accessory 2 is very obvious for improving the pile side resistance.

[0071] Example two

[0072] The difference between this example two and example one is that: example one is designed to be applied to relatively weak fully weathered coral reef limestone as the bearing stratum foundation 3, the contact area of the expansion accessory 2 and the foundation 3 needs to be increased, therefore, the design size is "wide and thin", as shown in the following table: Figure 10 a; example two is designed to be applied to relatively strong weathered coral reef limestone as the bearing stratum foundation 3, the contact area of the expansion accessory 2 and the foundation 3 is smaller than that of example one, therefore, the design size is "narrow and thick", as shown in the following table: Figure 10 b; on the relatively weak fully weathered coral reef limestone, thin can reduce the self weight of the expansion accessory 2, on the relatively strong weathered coral reef limestone, thick can increase the self weight of the expansion accessory 2, and improve the stability of itself.

[0073] Among them, the diameter of the marine pile foundation ranges from 1-2 meters for small diameter to 5-7 meters for large diameter, specifically, when the pile diameter is small, the width of the expansion accessory can be slightly smaller (2.5-4 times the diameter of the pile); when the pile group foundation is considered, the spacing between the piles and the effective range of the pile, the diameter of the expansion accessory can also be set smaller; when the foundation is in strong weathered coral reef limestone as the bearing stratum (good foundation), the width of the expansion accessory can also be set smaller. Thick: because it needs to have sufficient thickness to resist bending moment and shear force acting on the expansion accessory. When the pile group is large in diameter, fully weathered coral reef limestone is used as the bearing stratum (the foundation is soft), and the single pile structure (wind turbine) is large in diameter, on the one hand, it is suitable for large diameter piles, on the other hand, it increases the end resistance of the expansion accessory to save pile materials, and on the other hand, it increases the planar area of the large expansion accessory so as not to insert (pierce) into the foundation, the diameter is generally 5-6 times the diameter of the pile body. Here, thin is relative to width, and relative to the expansion accessory of small diameter piles.

[0074] Example three

[0075] The statistical analysis of the gradation of the coral reef sand in the construction site shows that the coarse aggregate of the reef limestone has a particle size range of 10-30 mm, the coarse aggregate of the coral has a high irregular particle type composition, and the reef limestone has a high porosity, which makes it possible to compact the reef limestone foundation by filling the broken stones.

[0076] The difference between the second embodiment and the first embodiment is that, as shown in Figure 16 , the reef limestone is provided with broken stones 5 in the range of the pile body and the range of the pile end of the steel pipe pile 1. The broken stones are selected from the special fine broken stones with a nominal particle size range of 5-10 mm, a clay content controlled within 0.5%, a mud content of 0, and a porosity controlled within 43%, or the broken stones are selected from the special fine pebbles with the same particle size gradation. The special fine broken stones or pebbles are mainly selected because the particle size of the special fine broken stones or pebbles is relatively small, which is suitable for the size of the voids of the reef limestone and is easy to be blown into the broken reef limestone. The broken stones can also resist the upward uplift force of the pile body in the seabed soil caused by the buoyancy.

[0077] A construction method of an underwater reef limestone pile foundation ballast expanded end accessory structure, comprising the following steps:

[0078] S1: calculating and designing the rock insertion depth of the steel pipe pile 1;

[0079] S2: prefabricating the steel pipe pile 1 and the support 11 on the pile body, and prefabricating the expanded accessory 2;

[0080] S3: inserting the steel pipe pile 1 into the designed depth, filling the broken stones 5 from the bottom of the pile end of the steel pipe pile 1 to the top of the foundation 3, compacting the broken stones at the top of the foundation, then putting the expanded accessory 2 into the steel pipe pile 1 from the top, and rotating and placing the expanded accessory under the support 11 after the empty hole 24 passes through the support;

[0081] S4: continuing to insert the steel pipe pile 1 until the support 11 is seated and compacted on the stress platform 22, so that the sharp corner 25 of the bottom surface of the expanded accessory 2 is inserted into the reef limestone.

[0082] The compaction method of the broken stones can be the traditional dynamic compaction and vibration compaction method. The filling device for the broken stones uses the filling device described in the patent "blowing and filling combined polymer solidification track bed maintenance device", and one filling device is arranged on the left and right and front and back of the pile body to blow the broken stones into the pile body and the pile end by using high-speed airflow.

[0083] In order to verify the effect of the third embodiment, the FLAC software is used to simulate the pile sinking, and the working condition without the filling of the broken stones and the expanded accessory is compared, as shown in Figure 17 , the third embodiment working condition has improved the bearing capacity of the pile foundation, and the effect of the combination of the filling of the broken stones and the expanded accessory is the most obvious, and the improvement of the bearing capacity of the pile foundation reaches the maximum degree.

[0084] To verify the effect of underwater reef limestone pile foundation crushed stone physical compaction treatment technology on improving the pile foundation bearing capacity, this invention was compared with a working condition without dredged crushed stone and without extended attachments, such as... Figure 17 As shown, under the same geological conditions and pile driving conditions, the dredged crushed stone compaction treatment technology of this invention improves the bearing capacity of the pile foundation. The effect is most obvious when dredged crushed stone is used in conjunction with extended attachments, maximizing the improvement of the pile foundation bearing capacity. Especially in the case of shallow pile driving depth, the physical compaction treatment technology of crushed stone for underwater reef limestone pile foundations performs even better. Therefore, the advantages of this invention in applying to pile foundations with shallow driving depth are extremely obvious, and it also saves a great deal of steel consumption.

[0085] The above are merely specific embodiments of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features of the invention herein.

Claims

1. An underwater reefal limestone pile foundation ballast enlarged toe accessory structure comprising a steel pipe pile (1) and an expansion accessory (2) fitted on the steel pipe pile (1), characterized in that: The steel pipe pile (1) is fixed with a support (11) on the outer wall, the expansion accessory (2) includes an annular accessory base (21) and a stress platform (22) fixed on the inner side wall of the accessory base (21), and an air gap (24) is arranged between the stress platform (22) and the inner side wall of the accessory base (21); the support (11) is arranged so that when the support (11) overlaps with the stress platform (22) after rotation, a limiting fit is formed between the support (11) and the stress platform (22) in the length direction of the steel pipe pile (1), and when the support (11) overlaps with the air gap (24) after rotation, the support (11) can shuttle in the air gap (24) along the length direction of the steel pipe pile (1); the top surface of the stress platform (22) and the top surface of the accessory base (21) have a spacing (23); the support (11) is arranged so that when the support (11) is embedded in the spacing (23), a limiting fit is formed between the support (11) and the accessory base (21) in the radial direction of the steel pipe pile (1).

2. The underwater reefal limestone pile foundation bulb extension appendage structure of claim 1, wherein: The bottom surface of the expansion accessory (2) is provided with a sharp corner (25) for inserting into the reef limestone.

3. The underwater reefal limestone pile foundation bulb extension appendage structure of claim 2, wherein: The sharp corner (25) includes a large-angle sharp corner (251) with a horizontal included angle of 45-60° and a small-angle sharp corner (252) with a horizontal included angle less than 45°, and the large-angle sharp corner (251) is arranged on the outer edge of the bottom surface of the accessory base (21) and the inner edge of the bottom surface of the stress platform (22) respectively, and the small-angle sharp corner (252) is arranged on the bottom surface of the expansion accessory (2) between the outer edge of the accessory base (21) and the inner edge of the stress platform (22).

4. The underwater reefal limestone pile foundation bulb extension appendage structure of claim 1, wherein: A plurality of supports (11) are uniformly fixed on the outer wall of the steel pipe pile (1) in the circumferential direction, and a plurality of stress platforms (22) are uniformly fixed on the inner side wall of the accessory base (21) in the circumferential direction, and the support (11) and the stress platform (22) are arranged one-to-one.

5. The underwater reefal limestone pile foundation bulb extension appendage structure of claim 1, wherein: The planes of the support (11) and the stress platform (22) are all in the shape of a sector, the outer arc surface of the support (11) is closely attached to the inner side wall of the accessory base (21) when the support (11) is embedded in the spacing (23), and the plane width of the support (11) is smaller than the plane width of the stress platform (22).

6. The underwater reefal limestone pile foundation bulb extension appendage structure of claim 1, wherein: The reef limestone is provided with gravel (5) within the range of the pile body and the pile end of the steel pipe pile (1).

7. The underwater reefal limestone pile foundation bulb extension appendage structure of claim 6, wherein: The gravel (5) is selected from special fine gravel with a nominal particle size range of 5-10 mm, a mud content controlled within 0.5%, no mud block content, and a porosity controlled within 43%, or special fine pebbles with the same particle size gradation.

8. A method of construction of a reefed limestone pile weight- enl argement end attachment structure as claimed in claim 2, c h a r a c t e r i s e d b y, The method comprises the following steps: S1: calculating and designing the rock penetration depth of the steel pipe pile (1); S2: prefabricating the steel pipe pile (1), the support (11) on the pile body, and the expansion accessory (2); S3: When the steel pipe pile (1) is inserted to the designed depth, the expansion accessory (2) is sleeved downward from the upper part of the steel pipe pile (1), and then is rotated and placed under the support member (11) after the empty mouth (24) passes through the support member (11); S4: Continue to insert the steel pipe pile (1) until the support member (11) is seated and pressed on the stress platform (22), so that the sharp corner (25) of the bottom surface of the expansion accessory (2) is inserted into the reef limestone.

9. A method of construction of a reefed limestone pile weight- enl argement end attachment structure according to claim 8, c h a r a c t e r i s e d i n that: In step S3, before sleeving the expansion accessory (2), the gravel (5) is blown from the pile end of the steel pipe pile (1) to the top of the foundation (3) from bottom to top, and the gravel is compacted on the top of the foundation.

10. The method of construction of a reefed limestone pile weight- enl argement end attachment structure according to claim 8, c h a r a c t e r i z e d b y: When the fully weathered coral reef limestone is soft as the bearing layer, the size of the expansion accessory (2) is designed to be wide and thin; when the strongly weathered coral reef limestone is hard as the bearing layer, the size of the expansion accessory (2) is designed to be narrow and thick.

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