Pile testing structure, pile testing method and construction method for cast-in-situ bored pile of shoal foundation

Abstract

The invention discloses a shoal foundation cast-in-situ bored pile test pile structure, method and construction method.The pile test method comprises the steps that S100, it is checked and determined that a pile head protection cylinder is stably installed, and it is ensured that all connecting pieces are correctly in place; s200, equipment for providing stable loading is arranged above the test pile, a distributive girder or a steel plate is used for dispersing the load, and it is ensured that the load can be evenly transmitted to the test pile; s300, loads are gradually applied in a graded mode according to the preset loading rate, and after each stage of load is applied, a certain time is waited to observe the settlement condition of the pile; s400, the settlement amount of the pile top is monitored, and test data including the settlement amount of the pile top under each stage of load are recorded; s500, analyzing the relation curve of pile top settlement and load in the loading process, determining the ultimate bearing capacity of the test pile, and continuing loading until the preset maximum test load is reached; and S600, when the test meets the termination standard, final data are unloaded and recorded, and after loading equipment is dismantled, the pile head pile casing is dismantled. One-time forming of the pile head is achieved, and construction cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of building construction, and more specifically, relates to a test pile structure, a test pile method and a construction method of a bored cast-in-place pile of a seabed foundation. Background Art

[0002] With the development of cities, the concentration of human production and life, and the growth of urban land demand have made the trend of urban expansion increasingly obvious. When urban development is restricted by terrain, breaking through the constraints of bad geology on construction through technological innovation has become an important development direction for urban expansion, such as using coastal tidal flats for construction. Coastal tidal flats belong to marine landforms, with deep soft soil distribution areas, and have both sea and land characteristics, with relatively special hydrodynamic, topographic and soil characteristics. The most important thing for construction projects on coastal tidal flats is to ensure that the bearing capacity of the foundation meets the design requirements. At present, the most commonly used foundation type for high-rise buildings in coastal tidal flat foundation construction is pile foundation. The pile type used is generally reinforced concrete cast-in-place piles, and the hole-making process is mostly positive circulation drilling rig drilling. Due to the complex geological conditions, the compressive bearing capacity test of cast-in-place piles usually adopts single pile static load test.

[0003] The principle of the single pile vertical compressive static load test is to apply loads step by step to the top of the pile, observe the settlement of the pile under load, and thus detect the vertical compressive bearing capacity of the single pile. The single pile vertical compressive test equipment is mainly composed of a reaction device, a loading device, a load measuring device, and a displacement measuring device. When conducting static load tests on tidal flat foundations, on the one hand, due to the process and structural limitations of traditional test piles, the pile heads are not formed in one go, which has a great impact on the total construction period; on the other hand, if the concrete construction or maintenance of the top of the test pile is not in place, and there is an uneven loose layer on the surface, the reaction device may destroy part of the loose concrete during the loading process, resulting in eccentric stress, and in severe cases, it may cause broken piles.

[0004] The Chinese patent with publication number CN117779861A discloses an engineering pile test structure and a pile test method, comprising an inner cylinder with openings at both ends and an outer cylinder with openings at both ends, the outer diameter of the inner cylinder is smaller than the inner diameter of the outer cylinder, the inner cylinder and the outer cylinder are coaxially sleeved together, the length of the outer cylinder is smaller than the length of the inner cylinder, the upper and lower ends of the outer cylinder are both between the upper and lower ends of the inner cylinder, and the two ends of the outer cylinder are sealed and connected to the outer wall of the inner cylinder through a sealing member; when in use, the assembled and welded steel sleeve is first hoisted into a borehole on the ground that accommodates the engineering foundation pile; then the steel cage that has been tied in advance is hoisted into the inner cylinder, and concrete is poured; finally, when the concrete strength reaches the design strength, the sealing member on the top of the outer sleeve is cut off with a cutting machine to conduct the test. The present application solves the problem that the test results are affected by the contact between the surface fill of the ground and the concrete poured on the foundation pile.

[0005] However, the Chinese patent with publication number CN117779861A still has the problem that it cannot be formed in one time, which has a great impact on the total construction period. Therefore, a structure and method for testing bored piles on a seabed foundation are needed to achieve one-time forming of the pile head, enhance the strength and surface stiffness of the pile head during static load testing, reduce material waste, and reduce construction costs. Summary of the invention

[0006] In view of the above defects or improvement needs of the prior art, the present invention provides a test pile structure, test pile method and construction method for bored piles on a seashore foundation. The test pile head is formed in one step, which shortens the inspection cycle and thus the total construction period, avoids material waste caused by secondary construction and quality problems in secondary pouring, simplifies the overall process and saves labor.

[0007] To achieve the above purpose, according to a first aspect of an embodiment of the present invention, a method for testing bored piles on a coastal land foundation is provided, which specifically comprises the following steps:

[0008] S100, check and make sure that the pile casing is firmly installed and that all the connectors are properly in place;

[0009] S200. Set up equipment to provide stable loading above the test pile, use distribution beams or steel plates to disperse the load, and ensure that the load can be evenly transferred to the test pile;

[0010] S300, gradually applying loads in stages according to a predetermined loading rate, and waiting for a certain period of time after each level of load is applied to observe the settlement of the pile;

[0011] S400, monitor the settlement of the pile top and record the test data including the settlement of the pile top under each level of load;

[0012] S500, analyzing the relationship curve between pile top settlement and load during loading, determining the ultimate bearing capacity of the test pile, and continuing loading until the pile shows signs of damage or reaches a predetermined maximum test load;

[0013] S600. When the test meets the termination criteria, unload and record the final data, remove the loading equipment and then remove the pile head casing.

[0014] Furthermore, in step S200, the loading rate R(t) of the loading device needs to be set, and the loading rate R(t) is:

[0015] R(t)=R0·(1+α T (T-T0)+α H (H-H0)+β W W):

[0016] Where R0 is the standard loading rate,

[0017] α T is the temperature coefficient,

[0018] α H is the humidity coefficient,

[0019] β W is the wear coefficient,

[0020] T0 is the standard temperature,

[0021] H0 is the standard humidity,

[0022] T is the actual ambient temperature,

[0023] H is the actual ambient humidity,

[0024] W is the degree of wear of the equipment.

[0025] Furthermore, it is necessary to simulate the distributed load in the actual test, where the distributed load is f(x, t):

[0026]

[0027] Where f0 is the standard value of load distribution,

[0028] x0, y0, z0 are the coordinates of the center of the load distribution along the x, y, and z directions respectively.

[0029] σ x is the distribution width of the load in the x direction,

[0030] σ z is the load distribution width in the z direction,

[0031] g(t) is a function of time.

[0032] Furthermore, the load fluctuates periodically over time, and the time function g(t) is:

[0033] g(t)=A sin(ωt+φ)+B;

[0034] Where A is the amplitude,

[0035] ω is the angular frequency,

[0036] φ is the phase,

[0037] B is the base load level.

[0038] Furthermore, in step S300, the step of applying load in stages is specifically:

[0039]

[0040] Among them, Ptotal (t) is the total applied load at time t,

[0041] R(t′, X) is the loading rate, which is equal to R(t).

[0042] Furthermore, the settlement of the observed test pile is based on the average settlement rate of the monitored test pile, specifically:

[0043]

[0044] Among them, v s (t) is the average sedimentation velocity in time t,

[0045] t w is the length of the observation window,

[0046] is the sedimentation rate at time t,

[0047] g(t′) is the correction factor of sedimentation rate, which is used to describe the change characteristics of sedimentation rate with time.

[0048] Furthermore, in step S400, the monitoring pile top settlement S(t) is specifically:

[0049]

[0050] in,

[0051]

[0052] Where c is a constant,

[0053] p is the order of the autoregressive term,

[0054] φ i is the autoregression coefficient,

[0055] q is the order of the sliding average term,

[0056] θ j is the sliding average coefficient,

[0057] ∈(t) is a white noise term, representing random disturbance,

[0058] X(t) is the external input variable,

[0059] β is the coefficient of the external input variable X(t).

[0060] Furthermore, in step S500, the ultimate bearing capacity Q of the test pile u for:

[0061]

[0062] Among them, E[S(t)] is the expected value of the settlement S(t),

[0063] Var[S(t)] is the variance of the settlement S(t),

[0064] is the additional variance caused by environmental factors,

[0065] is the additional variance caused by measurement error.

[0066] According to a second aspect of an embodiment of the present invention, there is provided a test pile structure of bored piles for a coastal land foundation, comprising:

[0067] A pile head casing, the pile head casing comprises a first guard plate and a second guard plate, and a plurality of groups of the first guard plates and the second guard plates are connected by a support shaft to form a casing wall; after the support shaft passes through the first guard plate and the second guard plate and is connected, the two form a hinge-like structure, and both ends of the support shaft are provided with threads and fixed by nuts;

[0068] The first guard plate and the second guard plate are also provided with fasteners, and the fasteners on the two adjacent first guard plates and the second guard plates are connected and fixed by supporting bolts to ensure that the pile head casing does not deform during use; the plate bodies of the first guard plate and the second guard plate are welded by an arc plate with a sleeve and an arc plate without a sleeve, and sleeves are provided on both side ends of the arc plate with the sleeve. The two arc plates on the first guard plate and the second guard plate are staggered to ensure that on the same cross-section, there is only one arc plate with a sleeve between the adjacent first guard plates and the second guard plates; the support shaft passes through the sleeves on both sides of the arc plate with the sleeve to realize the connection between the adjacent first guard plates and the second guard plates.

[0069] According to a third aspect of an embodiment of the present invention, a construction method for a test pile structure of a bored cast-in-place pile on a coastal land foundation is provided, which specifically comprises the following steps:

[0070] T100, Construction preparation: After the pile position is staked out, a test pile pit needs to be excavated with the test pile as the center. After the test pile pit is completed, the pile position is rechecked and staked out, and the borehole casing is buried;

[0071] T200, pile construction: the process includes mud preparation, drilling rig placement, drilling, first hole cleaning, steel cage installation, second hole cleaning and underwater concrete pouring. The longitudinal reinforcement, spiral stirrups and pile reinforcement in the top of the test pile are formed at one time;

[0072] T300, Pile head construction: After the concrete pouring of the pile body is completed, the drilled casing is pulled out, the debris including mud skin at the hole mouth is cleaned, the steel mesh is installed on the pile top, the release agent is applied to the inside of the pile head casing, and then the pile head casing is hoisted and installed, the pile head concrete is poured, and the pile head is smoothed after initial setting; the concrete around the pile head casing is manually cleaned, and the steel cover is installed, and the maintenance period begins;

[0073] T400, casing removal: After the static load test is completed, unscrew the nut, remove the steel cover plate, rotate and pull out one of the support shafts and remove all support bolts, so that the first and second guard plates rotate along the other support shafts to remove the pile head casing.

[0074] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0075] 1. The pile test method of the present invention enables the pile head of the test pile to be formed at one time, uses a distribution beam or a steel plate to disperse the load, ensures that the load can be evenly transferred to the test pile, analyzes the relationship curve between the pile top settlement and the load during the loading process, determines the ultimate bearing capacity of the test pile, shortens the detection cycle and thus shortens the total construction period, avoids material waste caused by secondary construction and quality problems existing in secondary pouring.

[0076] 2. The pile test method of the present invention uses a special sleeve as the supporting sleeve, which has a high degree of toolization and is made of common materials, and is easy to produce and process; the structural design is simple and ingenious, and the functions are practical and diverse. The casing fasteners can simultaneously reinforce the cylinder body and serve as a lifting point. The components are designed to be mechanically connected, and the cylinder body can rotate along the support shaft, which is easy to install and dismantle and has strong turnover.

[0077] 3. The pile test method of the present invention uses a steel casing and a steel cover plate to reinforce the pile head, so that the pile head concrete can meet the test pile requirements without increasing the strength grade. The pile body and the pile head concrete have the same grade, and the pouring interval is short, and the integrity is strong, avoiding the pile head concrete chiseling after the pile test, which causes greater waste. In addition, since the pile top is a steel cover plate with high and uniform strength, it can avoid the uneven loose layer on the pile head surface being damaged during the loading process, thereby avoiding the eccentric stress. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1 This is a schematic diagram of the overall structure of a bored cast-in-place pile test pile structure for a coastal land foundation according to an embodiment of the present invention;

[0079] Figure 2 An exploded view of the overall structure of a bored cast-in-place pile test pile structure for a seashore foundation according to an embodiment of the present invention;

[0080] Figure 3 A schematic diagram of a pile head casing structure of a bored cast-in-place pile test structure for a coastal land foundation according to an embodiment of the present invention;

[0081] Figure 4 It is a schematic diagram of the installation of a construction method of a bored cast-in-place pile test pile structure for a seashore foundation according to an embodiment of the present invention;

[0082] Figure 5 A schematic diagram of the dismantling of a construction method of a bored cast-in-place pile test pile structure for a seashore foundation according to an embodiment of the present invention;

[0083] Figure 6 A schematic diagram of a construction method of a bored cast-in-place pile test pile structure for a coastal foundation according to an embodiment of the present invention;

[0084] Figure 7 The present invention is a flowchart of a method for testing bored cast-in-place piles on a tidal flat foundation according to an embodiment of the present invention.

[0085] In all the drawings, the same reference numerals represent the same technical features, specifically: 1-pile head casing, 11-first guard plate, 12-second guard plate, 2-support shaft, 3-support bolt, 4-cover plate. DETAILED DESCRIPTION

[0086] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0087] Example 1

[0088] like Figure 1-3 As shown, an embodiment of the present invention provides a structure and method for testing bored piles on a tidal flat foundation, including a pile head casing 1, wherein the pile head casing 1 includes a first guard plate 11 and a second guard plate 12, and a plurality of groups of the first guard plates 11 and the second guard plates 12 are connected by a support shaft 2 to form a casing wall. After the support shaft 2 passes through the first guard plate 11 and the second guard plate 12 and is connected, the two form a hinge-like structure, and the two ends of the support shaft 2 are provided with threads and fixed by nuts. The pile head of the test pile is formed in one step, and a distribution beam or a steel plate is used to disperse the load to ensure that the load can be evenly transferred to the test pile. The relationship curve between the pile top settlement and the load during the loading process is analyzed to determine the ultimate bearing capacity of the test pile, thereby shortening the detection cycle and thus shortening the total construction period, and avoiding material waste caused by secondary construction and quality problems in secondary pouring.

[0089] The first guard plate 11 and the second guard plate 12 are also provided with fasteners, and the fasteners on the two adjacent first guard plates 11 and the second guard plates 12 are connected and fixed by support bolts 3 to ensure that the pile head casing 1 does not deform during use. The plate bodies of the first guard plate 11 and the second guard plate 12 are welded by an arc plate with a sleeve and an arc plate without a sleeve. Sleeves are provided on both sides of the arc plate with a sleeve. The two arc plates on the first guard plate 11 and the second guard plate 12 are staggered to ensure that there is only one arc plate with a sleeve between the adjacent first guard plates 11 and the second guard plates 12 on the same cross section. The support shaft 2 passes through the sleeves on both sides of the arc plate with a sleeve to achieve the connection between the adjacent first guard plates 11 and the second guard plates 12. The matching sleeve is a special sleeve with a high degree of tooling. The materials are all common materials and are easy to produce and process. The structural design is simple and ingenious, with practical and diverse functions. The casing fasteners can both reinforce the cylinder and serve as lifting points. The components are designed as mechanical connections, and the cylinder can rotate along the support shaft. It is easy to install and dismantle and has strong turnover.

[0090] The top of the pile head casing 1 is also provided with a cover plate 4, which is a circular thin steel plate with multiple connection holes equidistantly opened in the circumferential direction. After the support shaft 2 passes through the connection hole, it is fixed to the top of the pile head casing 1 with a nut. Ensure that the pile head is uniformly stressed as a whole, and increase the rigidity of the cylinder. The pile head is reinforced with a steel casing and a steel cover plate, so that the pile head concrete does not need to increase the strength grade to meet the test pile requirements. The pile body and the pile head concrete have the same grade, and the pouring interval time is short, and the integrity is strong, avoiding greater waste caused by chiseling out the pile head concrete after the test pile is completed. In addition, since the pile top is a steel cover plate with high and uniform strength, it can avoid the uneven loose layer on the surface of the pile head being damaged during the loading process, thereby avoiding the situation of eccentric stress.

[0091] Example 2

[0092] like Figure 4-6 As shown, the embodiment of the present invention provides a construction method for a test pile structure of a bored cast-in-place pile on a seashore foundation, which specifically includes the following steps:

[0093] T100, Construction preparation: After the pile position is staked out, a test pile pit needs to be excavated with the test pile as the center. After the test pile pit is completed, the pile position is rechecked and staked out, and the borehole casing is buried;

[0094] T200, pile construction: the process includes mud preparation, drilling rig placement, drilling, first hole cleaning, steel cage installation, second hole cleaning and underwater concrete pouring. The longitudinal reinforcement, spiral stirrups and pile reinforcement in the top of the test pile are formed at one time;

[0095] T300, Pile head construction: After the concrete pouring of the pile body is completed, the drilled casing is pulled out, the debris including mud skin at the hole mouth is cleaned, the steel mesh is installed on the pile top, the mold release agent is applied to the inside of the pile head casing 1, and then the pile head casing 1 is hoisted and installed, the pile head concrete is poured, and the pile head is smoothed after the initial setting; the concrete around the pile head casing is manually cleaned, and the steel cover plate is installed, and the maintenance period begins;

[0096] T400, casing removal: After the static load test is completed, unscrew the nut, remove the steel cover plate, rotate and pull out one of the support shafts 2 and remove all the support bolts 3, so that the first guard plate 11 and the second guard plate 12 rotate along the other support shafts, thereby removing the pile head casing 1.

[0097] Example 3

[0098] like Figure 7 As shown, the embodiment of the present invention provides a method for testing bored piles on a seashore foundation, which is a static load test and is used after step T300, specifically comprising the following steps:

[0099] S100, check and make sure that the pile casing is firmly installed and that all the connectors are properly in place;

[0100] S200. Set up equipment to provide stable loading above the test pile, use distribution beams or steel plates to disperse the load, and ensure that the load can be evenly transferred to the test pile;

[0101] S300, gradually applying loads in stages according to a predetermined loading rate, and waiting for a certain period of time after each level of load is applied to observe the settlement of the pile;

[0102] S400, monitor the settlement of the pile top and record the test data including the settlement of the pile top under each level of load;

[0103] S500, analyzing the relationship curve between pile top settlement and load during loading, determining the ultimate bearing capacity of the test pile, and continuing loading until the pile shows signs of damage or reaches a predetermined maximum test load;

[0104] S600, when the test meets the termination criteria, unload and record the final data, remove the loading device and then remove the pile head casing 1.

[0105] In step S200, the loading rate R(t) of the loading device needs to be set, and the loading rate R(t) is:

[0106] R(t)=R0·(1+α T (T-T0)+α H (H-H0)+β W W);

[0107] Where R0 is the standard loading rate,

[0108] α T is the temperature coefficient,

[0109] α H is the humidity coefficient,

[0110] β W is the wear coefficient,

[0111] T0 is the standard temperature,

[0112] H0 is the standard humidity,

[0113] T is the actual ambient temperature,

[0114] H is the actual ambient humidity,

[0115] W is the degree of wear of the equipment.

[0116] It is also necessary to simulate the distributed load in the actual test, which is f(x, t):

[0117]

[0118] Where f0 is the standard value of load distribution,

[0119] x0, y0, z0 are the coordinates of the center of the load distribution along the x, y, and z directions respectively.

[0120] σ x is the distribution width of the load in the x direction,

[0121] σ z is the load distribution width in the z direction,

[0122] g(t) is a function of time.

[0123] The load fluctuates periodically over time, and the time function g(t) is:

[0124] g(t)=A sin(ωt+φ)+B;

[0125] Where A is the amplitude,

[0126] ω is the angular frequency,

[0127] φ is the phase,

[0128] B is the base load level.

[0129] In step S300, the step of applying load in stages is as follows:

[0130]

[0131] Among them, P total(t) is the total applied load at time t,

[0132] R(t′, X) is the loading rate, which is equal to R(t).

[0133] The settlement of the observed test pile is based on the average settlement rate of the monitored test pile, specifically:

[0134]

[0135] Among them, v s (t) is the average sedimentation velocity in time t,

[0136] t w is the length of the observation window,

[0137] is the sedimentation rate at time t,

[0138] g(t′) is the correction factor of sedimentation rate, which is used to describe the change characteristics of sedimentation rate with time.

[0139] The correction factor g(t′) for the sedimentation rate is:

[0140] g(t′)=exp(-λt′);

[0141] Among them, λ is the sedimentation rate attenuation coefficient, which reflects the trend of sedimentation rate gradually decreasing over time.

[0142] In step S400, the monitoring pile top settlement S(t) is specifically:

[0143]

[0144] in,

[0145]

[0146] Where c is a constant,

[0147] p is the order of the autoregressive term,

[0148] φ i is the autoregression coefficient,

[0149] q is the order of the sliding average term,

[0150] θ j is the sliding average coefficient,

[0151] ∈(t) is a white noise term, representing random disturbance,

[0152] X(t) is the external input variable,

[0153] β is the coefficient of the external input variable X(t).

[0154] The external input variable X(t) specifically includes: changes in ambient temperature over time, changes in ambient humidity over time, and changes in equipment wear over time.

[0155] In step S400, the test data also includes: displacement data, stress data, strain data, and equipment status.

[0156] The displacement data includes the rate of change of displacement over time, specifically:

[0157]

[0158] in, is the integrated displacement change at time t,

[0159] is the rate of change of horizontal displacement at time t,

[0160] is the rate of change of vertical displacement at time t,

[0161] is the rate of change of displacement in the depth direction at time t.

[0162] Δr(t) is the integrated displacement at time t,

[0163] Δx(t) is the horizontal displacement at time t,

[0164] Δy(t) is the vertical displacement at time t,

[0165] Δz(t) is the displacement in the depth direction at time t.

[0166] The integrated displacement Δr(t) at time t is:

[0167]

[0168] In step S500, the ultimate bearing capacity Q of the test pile u for:

[0169]

[0170] Among them, E[S(t)] is the expected value of the settlement S(t),

[0171] Var[S(t)] is the variance of the settlement S(t),

[0172] is the additional variance caused by environmental factors,

[0173] is the additional variance caused by measurement error.

[0174] The expected value E[S(t)] of the settlement S(f) is specifically:

[0175]

[0176] Among them, β0, β1, and β2 are all constants.

[0177] X i (t) is the external factor variable,

[0178] γ i is the external factor variable X i The coefficient of (t).

[0179] Among them, the external factor variable X i (t)Including temperature, humidity and air pressure.

[0180] Among them, η is the safety factor, which ensures that the actual load does not exceed the ultimate bearing capacity.

[0181] In step S500, the Bayesian method is also needed to update the estimate of the ultimate bearing capacity and establish the ultimate bearing capacity Q u The prior distribution P(Q u ), according to the test data D, it is updated to the posterior distribution P(Q u |D), specifically:

[0182] P(Q u |D)∝P(D|Q u )·P(Q u );

[0183] At this time, the maximum test load P is predicted max Specifically:

[0184] P max =E[Q u |D]·(1-η);

[0185] Among them, E[Q u |D] is the ultimate bearing capacity Q u expected value.

[0186] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for testing bored piles on a coastal land foundation, characterized in that: The specific steps include: S100, check and make sure that the pile casing is firmly installed and that all the connectors are properly in place; S200. Set up equipment to provide stable loading above the test pile, use distribution beams or steel plates to disperse the load, and ensure that the load can be evenly transferred to the test pile; S300, gradually applying loads in stages according to a predetermined loading rate, and waiting for a certain period of time after each level of load is applied to observe the settlement of the pile; S400, monitor the settlement of the pile top and record the test data including the settlement of the pile top under each level of load; S500, analyzing the relationship curve between pile top settlement and load during loading, determining the ultimate bearing capacity of the test pile, and continuing loading until the pile shows signs of damage or reaches a predetermined maximum test load; S600. When the test meets the termination criteria, unload and record the final data, remove the loading equipment and then remove the pile head casing.

2. A method for testing bored piles on a coastal land foundation according to claim 1, characterized in that: In step S200, the loading rate R(t) of the loading device needs to be set, and the loading rate R(t) is: R(t)=R0·(1+α T (T-T0)+a H (H-H0)+β W W); Where R0 is the standard loading rate, α T is the temperature coefficient, α H is the humidity coefficient, β W is the wear coefficient, T0 is the standard temperature, H0 is the standard humidity, T is the actual ambient temperature, H is the actual ambient humidity, W is the degree of wear of the equipment.

3. A method for testing bored piles on a seashore foundation according to claim 2, characterized in that: It is also necessary to simulate the distributed load in the actual test, which is f(x, t): Where f0 is the standard value of load distribution, x0, y0, z0 are the coordinates of the center of the load distribution along the x, y, and z directions respectively. σ x is the distribution width of the load in the x direction, σ z is the load distribution width in the z direction, g(t) is a function of time.

4. A method for testing bored piles on a seashore foundation according to claim 3, characterized in that: The load fluctuates periodically over time, and the time function g(t) is: g(t)=A sin(ωt+φ)+B; Where A is the amplitude, ω is the angular frequency, φ is the phase, B is the base load level.

5. A method for testing bored piles on a coastal land according to any one of claims 1 to 4, characterized in that: In step S300, the step of applying load in stages is as follows: Among them, P total (t) is the total applied load at time t, R(t′, X) is the loading rate, which is equal to R(t).

6. A method for testing bored piles on a coastal land foundation according to claim 5, characterized in that: The settlement of the observed test pile is based on the average settlement rate of the monitored test pile, specifically: Among them, v s (t) is the average sedimentation velocity in time t, t w is the length of the observation window, is the sedimentation rate at time t, g(t′) is the correction factor of sedimentation rate, which is used to describe the change characteristics of sedimentation rate with time.

7. A method for testing bored piles on a coastal land according to any one of claims 1 to 4, characterized in that: In step S400, the monitoring pile top settlement S(t) is specifically: in, Where c is a constant, p is the order of the autoregressive term, φ i is the autoregression coefficient, q is the order of the sliding average term, θ j is the sliding average coefficient, ∈(t) is a white noise term, representing random disturbance, X(t) is the external input variable, β is the coefficient of the external input variable X(t).

8. A method for testing bored piles on a coastal land according to any one of claims 1 to 4, characterized in that: In step S500, the ultimate bearing capacity Q of the test pile u for: Among them, E[S(t)] is the expected value of the settlement S(t), Var[S(t)] is the variance of the settlement S(t), is the additional variance caused by environmental factors, is the additional variance caused by measurement error.

9. A test pile structure of bored piles on a tidal flat foundation, used to implement a test pile method of bored piles on a tidal flat foundation as claimed in any one of claims 1 to 8, characterized in that: include: A pile head casing (1), the pile head casing (1) comprising a first guard plate (11) and a second guard plate (12), wherein a plurality of groups of the first guard plates (11) and the second guard plates (12) are connected via a support shaft (2) to form a casing wall; after the support shaft (2) passes through the first guard plate (11) and the second guard plate (12) and connects them, the two form a hinge-like structure, and both ends of the support shaft (2) are provided with threads and fixed by nuts; The first guard plate (11) and the second guard plate (12) are also provided with fasteners, and the fasteners on the two adjacent first guard plates (11) and the second guard plates (12) are connected and fixed by support bolts (3) to ensure that the pile head casing (1) does not deform during use; the plate bodies of the first guard plate (11) and the second guard plate (12) are welded by an arc plate with a sleeve and an arc plate without a sleeve, and sleeves are provided on both side ends of the arc plate with a sleeve. The two arc plates on the first guard plate (11) and the second guard plate (12) are staggered to ensure that on the same cross-section, there is only one arc plate with a sleeve between the adjacent first guard plates (11) and the second guard plates (12); the support shaft (2) passes through the sleeves on both sides of the arc plate with a sleeve to achieve the connection between the adjacent first guard plates (11) and the second guard plates (12).

10. A construction method for a bored pile test pile structure of a seashore foundation as claimed in claim 9, characterized in that: The specific steps include: T100, Construction preparation: After the pile position is staked out, a test pile pit needs to be excavated with the test pile as the center. After the test pile pit is completed, the pile position is rechecked and staked out, and the borehole casing is buried; T200, pile construction: the process includes mud preparation, drilling rig placement, drilling, first hole cleaning, steel cage installation, second hole cleaning and underwater concrete pouring. The longitudinal reinforcement, spiral stirrups and pile reinforcement in the top of the test pile are formed at one time; T300, pile head construction: after the concrete pouring of the pile body is completed, the drilled casing is pulled out, the hole opening including the mud skin is cleaned, a steel mesh is installed on the pile top, a release agent is applied to the inside of the pile head casing (1), and then the pile head casing (1) is hoisted and installed, the pile head concrete is poured, and the pile head is smoothed after initial setting; Manually clean the concrete around the pile head casing, install the steel cover plate, and enter the maintenance period; T400, casing removal: After the static load test is completed, unscrew the nut, remove the steel cover plate, rotate and pull out one of the support shafts (2) and remove all the support bolts (3), so that the first guard plate (11) and the second guard plate (12) rotate along the other support shafts, thereby removing the pile head casing (1).

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