Construction method of steel pipe pile boring under deep water and bare rock geological conditions

Abstract

The present invention discloses a method for drilling and constructing steel pipe piles under deep-water bare rock geological conditions, which is applied to the technical field of deep-water engineering construction. The method mainly comprises: S0, modeling with finite element software, and verifying construction safety; S1, first positioning and installing a small-sized steel pipe, and then preliminarily fixing the steel pipe pile by sleeve-fitting the steel pipe pile outside the small-sized steel pipe; S2, vibrating and fixing the steel pipe pile, first drilling a hole from the steel pipe pile to the bottom of the deep-water bed, and then vibrating and fixing it; when the drilling effect needs to be checked, S3, performing a tensile test on two adjacent steel pipe piles, obtaining a horizontal load-displacement curve of the steel pipe pile, and ensuring the steel pipe pile's ability to resist horizontal loads; the method can efficiently realize steel pipe pile drilling, reduce the difficulty of steel pipe pile insertion, and ensure stable installation, effectively solving a series of problems existing in traditional construction processes, such as complicated construction procedures, long construction period, large environmental pollution, and high cost.

Description

Technical Field

[0001] The present invention relates to the technical field of deepwater engineering construction, in particular to a steel pipe pile boring construction method under deepwater bare rock geological conditions. Background Art

[0002] In recent years, with the rapid development of bridge technology in my country, the number of bridges spanning major rivers has continued to increase. Steel trestles, as the lifeline for transporting materials and equipment for bridge construction, are increasingly being used in projects. Designing and constructing trestles under diverse hydrological and geological conditions, particularly those in complex and harsh conditions, is crucial to project success. Rapidly constructing steel trestles in deepwater, rapid, and bare rock environments is relatively rare in China, requiring frequent overhead work, high construction risks, and significant difficulty. This presents new challenges for steel trestles in deepwater, bare rock environments.

[0003] Steel trestle construction requires setting up a working platform in advance, followed by the "fishing method" technique. This construction technique is simple in principle and low in cost, but the limited working surface limits construction speed. Furthermore, in deepwater, bare rock geological environments, using the traditional "fishing method" for steel trestle construction makes it difficult to drive steel pipe piles, ensuring the embedding depth and structural stability. Currently, the steel pipe pile drilling techniques used in steel trestle construction primarily include bench piles, gravity piles, ring-cut rock-embedded piles, punch piles, and anchor rock-embedded piles.

[0004] Bench piles are formed by connecting two rows of piles horizontally and vertically to form a bench structure, which improves the stability and anti-overturning ability of the structure and reduces the rock embedding depth of steel pipe piles. Gravity pile planting first prefabricates the steel pipe piles and concrete into a whole, and then hoisted the whole to the designated location. This method has simple procedures and convenient construction, but usually requires large machinery to lift prefabricated components, resulting in high construction costs. The ring-cut rock-embedded pile planting method is based on the drilling principle of a water well drilling rig. Multiple steel drill teeth are pre-installed at the bottom of the steel pipe pile, and then the steel pipe pile is rotated by rotating the drill rod to achieve hole guidance. This method is theoretically feasible, but the process is complicated, and the steel drill teeth embedded in the steel pipe pile are usually impossible to remove, resulting in high construction costs. The punching pile method uses a large-hole-to-small-hole construction technique. A large steel pipe is hoisted to a designated location, then a percussion drill is used to punch a hole to a specified distance below the seabed. Concrete is then poured through a funnel and conduit. Steel pipe piles are then driven in before the concrete sets. When the steel pipe piles are driven to the designated location, the large steel pipe is removed. This process is simple in principle, but places high demands on the performance of the punching equipment, resulting in low hole-forming efficiency. The punching slurry can easily contaminate surrounding water sources. Furthermore, the concrete left after construction can easily scratch passing ships, affecting their safe navigation. The anchor-embedded rock pile method is constructed based on the principle of prefabricated anchor-embedded rock piles. An operating platform is set up at the top of the steel pipe pile, and a geological drill is used to drill into the steel pipe. Anchors are then planted and concrete is poured in to form a stable rock-anchor-column system. This method also has the problems of polluting the surrounding environment during construction and of scraping passing ships with the concrete left after construction.

[0005] In recent years, with the development of society, higher requirements for environmental protection have been put forward. Traditional construction techniques that have a significant impact on the surrounding environment are not allowed to be used in marine or aquatic environments with strict environmental protection requirements. Therefore, it is necessary to develop a drilling construction technology for steel pipe piles in deepwater bare rock geological conditions. While meeting environmental requirements, it is necessary to fundamentally solve the construction difficulties of steel pipe piles in deepwater turbulent bare rock geological conditions and improve the quality and effectiveness of drilling. Summary of the Invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art such as the difficulty in driving steel pipe piles, insufficient embedding depth, and poor stability, and to provide a steel pipe pile drilling construction method under deep-water bare rock geological conditions, which can efficiently realize steel pipe pile drilling, reduce the difficulty of driving steel pipe piles, and ensure stable installation, effectively solving a series of problems existing in traditional construction processes such as complicated construction procedures, long construction period, large environmental pollution, and high cost.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The method for constructing steel pipe pile holes under deep-water bare rock geological conditions comprises the following steps:

[0009] S1. First, lower a steel pipe with a diameter smaller than that of the steel pipe pile vertically to the deep waterbed corresponding to the pile position and secure it. Then, by sleeve-tying the steel pipe pile outside the steel pipe, lower the steel pipe pile vertically to the pile position and secure it preliminarily. Measure and verify the position of the steel pipe pile, and then remove the steel pipe.

[0010] S2. Use a vibration device to vibrate and fix the steel pipe pile. When the steel pipe pile can no longer sink by vibration, use a drilling rig to drill a hole in the steel pipe pile toward the bottom of the deep water bed. After drilling the hole, use a vibration device to vibrate and fix the steel pipe pile until the steel pipe pile is installed in place.

[0011] By first drilling a small-sized steel pipe and then positioning and fixing the steel pipe pile, the position of the steel pipe pile can be accurately located. The steel pipe pile is positioned to the position of the small-sized steel pipe and fixed, avoiding deviation and error in the installation and fixation of the steel pipe pile, which can improve the accuracy of construction and the effectiveness of the next step of installing the steel pipe pile; by lowering a drilling rig into the steel pipe pile, further drilling holes based on the pile position, and based on the principle of "small holes leading to large holes", a rotary drill or impact drill is used to crush the bare rock in the steel pipe pile. When a small hole is drilled in the deep water bed below, the sinking resistance of the steel pipe pile is reduced, and it can be vibrated and sunk stably and continuously, which improves the quality of the drilling and the positioning and installation effect of the steel pipe pile, significantly reduces the difficulty of inserting the steel pipe pile, and can smoothly vibrate and sink the steel pipe pile to the design standard depth, accurately install the steel pipe pile to meet the standards, and quickly and effectively complete the installation and positioning construction of the steel pipe pile.

[0012] In a preferred embodiment of the present invention, the hole-drawing method adopted in the above-mentioned step S2 includes impact drilling and rotary drilling. Through the drilling depth standard, the steel pipe pile can be firmly installed at the bottom of the deep water bed, providing sufficient supporting strength. Through impact drilling and rotary drilling, two different hole-drawing methods are provided, which can be applicable to different geological conditions and construction requirements.

[0013] In a preferred embodiment of the present invention, in the above step S1, after the steel pipe is lowered and fixed, the verticality of the steel pipe needs to be tested: a number of reflective sheets are set on the outer wall of the steel pipe along the parallel axial direction, and the reflected light of the reflective sheets is measured by measuring instruments on the shore to ensure the verticality of the steel pipe; by setting the reflective sheets, the verticality of the steel pipe can be quickly tested, thereby improving the installation and positioning accuracy of the steel pipe.

[0014] In a preferred embodiment of the present invention, the above-mentioned construction method also includes step S3: setting a number of reflective sheets on the outer wall of the steel pipe pile along the parallel axial direction, using a fall chain to connect adjacent steel pipe piles, performing a tensile test on two adjacent steel pipe piles, measuring the reflected light of the reflective sheet by a measuring instrument, and obtaining a horizontal load-displacement curve of the steel pipe pile, thereby ensuring the rationality and feasibility of the construction process and ensuring that the steel pipe pile has sufficient ability to resist horizontal loads; through the setting of the reflective sheet, the verticality of the steel pipe pile can be quickly detected, thereby improving the installation and positioning accuracy of the steel pipe pile.

[0015] In a preferred embodiment of the present invention, the reflective sheet is marked with points, lines, or a pattern composed of points and lines for measuring and positioning, and the pattern reflected by the reflective sheet is positioned and measured by a measuring instrument; the marking of the reflective sheet can improve the efficiency of the measuring instrument's detection and the accuracy of the measurement.

[0016] In a preferred embodiment of the present invention, when performing the tensile test in step S3, a horizontal static load is applied to two adjacent steel pipe piles in the following manner:

[0017] S31. First, apply a first-level load to two adjacent steel pipe piles. The first-level load is 1.8 to 2.2 times the graded load, and the graded load is 0.08 to 0.12 times the preset maximum load.

[0018] S32. Then adopt the form of graded loading, increase the graded loading load step by step, and maintain each load for 25 to 35 minutes. During the load maintenance period, monitor the tension between adjacent steel pipe piles and the horizontal displacement of adjacent steel pipe piles every 5 to 15 minutes.

[0019] This method continuously applies load to the fall chain to make the two steel pipe piles move inward, and uses a total station to measure the horizontal displacement corresponding to each level of load during the loading process. The tensile test is carried out by loading the horizontal static load in equal amounts in a graded manner. During loading, the load is transferred evenly, continuously and without impact, and the variation range of each level of load during the maintenance process shall not exceed 10% of the graded load. This can minimize the influence of the tensile test on the stress of the steel pipe piles and can effectively verify the installation effect of the guide hole and the steel pipe piles.

[0020] In a preferred embodiment of the present invention, when performing the tensile test in step S3, the unloading method of the horizontal static load is:

[0021] S33. Use a graded unloading method, reducing the graded unloading load by an equal amount step by step. The graded unloading load is 1.5 to 2.5 times the graded loading load. Each load level is maintained for 10 to 20 minutes. During the load maintenance period, the tension between adjacent steel pipe piles and the horizontal displacement of adjacent steel pipe piles are monitored at intervals of 5 to 10 minutes.

[0022] S34. After unloading the load to zero, measure the horizontal displacement of adjacent steel pipe piles for 25 to 35 minutes, with an interval of 5 to 15 minutes between each measurement.

[0023] This method continuously releases the applied load to restore the displacement of the two steel pipe piles, and uses a total station to measure the horizontal displacement corresponding to each level of load during the loading process. By unloading the horizontal static load in equal amounts in stages, the load is transferred evenly, continuously and without impact during unloading, and the variation range of each level of load during the maintenance process shall not exceed 10% of the graded load. This method can minimize the influence of the tensile test on the stress of the steel pipe piles, and can effectively verify the installation effect of the guide hole and the steel pipe piles.

[0024] In a preferred embodiment of the present invention, before the above step S1, a security verification is also included:

[0025] Finite element software is used for modeling, and the load conditions when drilling holes at the cantilever end are calculated. Verification parameters include the stress at the cantilever end, the maximum displacement of the structure, and stability. Modeling can restore the real construction environment, and stress, displacement, and stability testing can be used to fully consider the safety of the structure. Safety testing can ensure that construction can proceed smoothly and that construction is safe.

[0026] In a preferred embodiment of the present invention, the above construction method further comprises:

[0027] Fix the construction equipment on the ship, move the ship to the preset pile position, drop anchor, preliminarily fix the ship, and perform hole drilling operations using the construction equipment; the construction equipment includes a drilling rig and auxiliary equipment. By fixing the construction equipment on the ship, the steel pipes and steel pipe piles can be constructed independently, ensuring that the installation of the steel pipes and steel pipe piles is not affected by external forces.

[0028] In a preferred embodiment of the present invention, in the above step S1, a floating crane is used to load and operate the steel pipes and steel pipe piles when they are moved, positioned, and lowered; the floating crane can smoothly complete the operation of the steel pipes and steel pipe piles and meet the lowering requirements.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. This construction method is based on the principle of "small hole leading to big hole". A drilling rig is inserted into the steel pipe pile to guide the hole, and then the steel pipe pile is installed and fixed. This significantly reduces the sinking resistance of the steel pipe pile, and can stably and continuously vibrate and sink it, improving the quality of the guide hole and the positioning and installation effect of the steel pipe pile. It significantly reduces the difficulty of inserting and driving the steel pipe pile, and can smoothly vibrate and sink the steel pipe pile to the design standard depth, accurately install the steel pipe pile to the standard, and can quickly and effectively complete the installation and positioning construction of the steel pipe pile.

[0031] 2. This construction method, which is carried out at the cantilever end, can significantly save construction costs. At the same time, it can be adapted to different geological conditions and construction requirements, providing an efficient, pollution-free, low-cost steel pipe pile boring construction method. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the steps of Example 1 of the steel pipe pile boring construction method under deep-water bare rock geological conditions of the present invention;

[0033] Figure 2 A cross-sea bridge to which the steel pipe pile boring construction method under deep-water bare rock geological conditions of the present invention is applied;

[0034] Figure 3 Schematic diagram of modeling and verification of the finite element software of the present invention;

[0035] Figure 4 A schematic diagram of the construction method of the steel pipe pile boring construction method under deep-water bare rock geological conditions of the present invention;

[0036] Figure 5 Schematic diagram of step S1 of the steel pipe pile boring construction method under deep-water bare rock geological conditions of the present invention;

[0037] Figure 6 Schematic diagram of the construction of step S2 in the steel pipe pile boring construction method under deep-water bare rock geological conditions of the present invention;

[0038] Figure 7 Schematic diagram of the steps of Example 2 of the steel pipe pile boring construction method under deep-water bare rock geological conditions of the present invention;

[0039] Figure 8 Schematic diagram of the tensile test of step S3 in the steel pipe pile boring construction method under deep-water bare rock geological conditions of the present invention;

[0040] Markings in the figure: 1-steel pipe; 2-steel pipe pile; 3-construction equipment; 4-ship; 5-deep waterbed; 6-reflective sheet; 7-tensile gauge; 8-fall chain. DETAILED DESCRIPTION

[0041] The present invention will be further described in detail below in conjunction with test examples and specific embodiments. However, this should not be understood as limiting the scope of the present invention to the following embodiments, and all technologies implemented based on the present invention fall within the scope of the present invention.

[0042] Example 1

[0043] Please refer to Figure 1 and Figure 2This embodiment provides a method for constructing steel pipe pile boreholes in deepwater, bare rock geological conditions. This method was applied to a project involving a sea-crossing bridge with a length of 7 km. The main bridge consists of prestressed concrete continuous box girders with spans of 50m and 80m. While the deepwater area used in this embodiment is the ocean, the method can also be applied to deepwater areas of inland lakes or rivers. Deepwater generally refers to areas with a water depth exceeding 3.8m. To ensure the transportation of construction materials and equipment and protect the natural ecological environment, a steel trestle was constructed along the mudflats and water levels at the bridge site. The steel trestle has a single span of 12m, five spans per unit, and an 8m deck width. The superstructure utilizes Bailey sheet steel, and the substructure utilizes a steel pipe pile 2+ steel cap beam structure. The water depth along the route is primarily 8-12m, with the deepest reaching 20m. The lithology revealed by drilling includes mudstone, shale, argillaceous siltstone, and sandstone. The deepwater areas are primarily bare rock (highly weathered shale). The small-size steel pipe 1 that can be used is φ300 steel pipe, φ450 steel pipe or φ600 steel pipe, and the steel pipe pile 2 can be φ600 steel pipe, φ630 steel pipe or φ650 steel pipe. In this embodiment, the steel pipe pile 2 is φ630 steel pipe and the small-size steel pipe 1 is φ300 steel pipe.

[0044] The construction method comprises the following steps:

[0045] S0. Before the actual construction of the steel pipe pile 2, safety verification is required. Please refer to Figure 3 : The large-scale finite element software Midas civil is used to model the cross-sea bridge of this embodiment. The steel pipe pile 2 drilling construction is carried out at the cantilever end during the construction of the cross-sea bridge. Relevant calculations are carried out on the load conditions when the drilling rig is located at the cantilever end, that is, the load conditions when drilling at the cantilever end are calculated. According to the actual situation on site and considering the dynamic load factor multiplied by the amplification factor, a single impact drill is considered to be 12.5 tons, and the cantilever end is considered to be constructed simultaneously with two sets of impact drills, that is, the cantilever end is considered to be 25 tons. The verification parameters include the stress at the cantilever end, the maximum displacement of the structure and the stability.

[0046] (1) Stress calculation

[0047] According to the simulation of finite element software, the calculation results show that under the simultaneous action of two impact drills, the maximum stress of the structure is 128.5MPa, located at the lower chord position of the Bailey plate. The Bailey plate is made of Q345 steel and has a safety factor of 2.68, which meets the construction requirements.

[0048] (2) Displacement

[0049] The calculation results show that under the action of two impact drills, the maximum displacement of the structure is 48 mm, which just meets the regulatory limit of L / 250=48 mm. Since the on-site construction impact drill is about 2 m away from the cantilever end itself, the structural modeling fully considers construction safety and applies the load to the top of the cantilever end. Therefore, the structural displacement meets the requirements and is safe.

[0050] (3) Stability

[0051] Furthermore, the stability of the structure is analyzed, and four modes are considered. The calculated structure is shown in Table 1 below:

[0052] Table 1 Buckling calculation results under various modes

[0053]

[0054] Software calculations show that the minimum stability coefficient of the cantilever hole construction method is 9.2, which is greater than the limit of 4.0 allowed by the specification, indicating that the structure has good stability.

[0055] In summary, modeling can restore the real construction environment, stress, displacement and stability testing can comprehensively consider the safety of the structure, and safety testing can ensure that the construction can proceed smoothly and ensure safe construction.

[0056] S1. After calculating and verifying the construction safety, carry out the actual construction. Please refer to Figure 4 Before operating the steel pipe 1 and the steel pipe pile 2, the construction equipment 3 is fixed on the ship 4, the ship 4 is moved to the preset pile position, anchored, and the ship 4 is preliminarily fixed. The steel pipe 1 and the steel pipe pile 2 are drilled using the construction equipment 3; the construction equipment 3 is a drilling rig and construction auxiliary equipment. The drilling rig includes an impact drill rig, a rotary drill rig, etc. By fixing the construction equipment 3 on the ship 4, the steel pipe 1 and the steel pipe pile 2 can be constructed independently, ensuring that the installation of the steel pipe 1 and the steel pipe pile 2 is not affected by external forces.

[0057] Please refer to Figure 5 First, lower the steel pipe 1 with a diameter smaller than that of the steel pipe pile 2 vertically to the deep water bed 5 corresponding to the pile position and fix it. Then, put the steel pipe pile 2 outside the steel pipe 1 and lower the steel pipe pile 2 vertically to the pile position and preliminarily fix it. Measure and verify the position of the steel pipe pile 2 and pull out the steel pipe 1. By first positioning and fixing the small-sized steel pipe 1 and then the steel pipe pile 2, the position of the steel pipe pile 2 can be accurately located. The steel pipe pile 2 is positioned to the position of the small-sized steel pipe 1 and fixed, avoiding deviation and error in the installation and fixation of the steel pipe pile 2, and improving the accuracy of the construction and the effectiveness of the next step of installing the steel pipe pile 2.

[0058] In step S1, when the steel pipe 1 and the steel pipe pile 2 are moved, positioned, and lowered, a floating crane 4 is used to load and operate them; the floating crane 4 can smoothly complete the operation of the steel pipe 1 and the steel pipe pile 2 to meet the lowering requirements. After the steel pipe 1 is lowered and fixed, the verticality of the steel pipe 1 needs to be tested: a number of reflective sheets 6 are set on the outer wall of the steel pipe 1 along the parallel axial direction, and the reflected light of the reflective sheet 6 is measured by a measuring instrument on the shore to ensure the verticality of the steel pipe 1; by setting the reflective sheet 6, the verticality of the steel pipe 1 can be quickly tested, thereby improving the installation and positioning accuracy of the steel pipe 1.

[0059] S2. Use a vibration device to vibrate and fix the steel pipe pile 2. When the steel pipe pile 2 can no longer sink by vibration, use a drilling rig to drill a hole in the steel pipe pile 2 toward the deep water bed bottom 5. After drilling, use a vibration device to vibrate and fix the steel pipe pile 2 until the steel pipe pile 2 is installed in place.

[0060] Please refer to Figure 6 In this step, when a drilling rig is used to drill a hole, the depth of the hole drilled into the deep-water bottom 5 is 5 to 10 meters. The drilling depth is determined according to the geological conditions, and the drilling methods include impact drilling and rotary drilling. The drilling method is specifically as follows: insert the drill bit of an impact drill or rotary drilling into the large-sized steel pipe pile 2. The drill bit is smaller than the inner diameter of the steel pipe pile 2, and the hole is drilled in the vertical downward direction of the deep-water bottom 5 corresponding to the steel pipe pile 2. Through the drilling depth standard, the steel pipe pile 2 can be firmly installed in the deep-water bottom 5, providing sufficient supporting strength. By using impact drilling and rotary drilling, two different drilling methods are provided, which can be adapted to different geological conditions and construction requirements.

[0061] When drilling holes with an impact drill, it is necessary to set up an operating platform in advance, and then use the "fishing method" cantilever drilling construction process. In this embodiment, it is carried out at the cantilever end of the erected steel trestle. The vibratory hammer and the impact drill are both set on the steel trestle. A guide frame is set up at the cantilever end to locate the position of the steel pipe pile 2. The steel pipe pile 2 is initially inserted and fixed by the vibratory hammer. Then, the impact drill is lifted to the cantilever end by a crawler crane, and a 600mm diameter impact drill (the steel pipe pile 2 is φ630) is used to drill the steel pipe pile 2. When the impact drill drills the hole to the specified depth, the vibratory hammer is used to insert and drive the steel pipe pile 2 to the specified depth. The construction process is simple in principle and has low construction cost. However, due to the limited working surface, the construction speed is limited.

[0062] When the construction period is tight and a large amount of manpower and material equipment are needed to realize the simultaneous start of construction on multiple work surfaces, a rotary drilling can be used for hole-guiding construction, and a vibratory hammer is fixed on the ship. This method first drives the pile-driving ship 4 to the specified position, drops anchor and fixes it, and uses a φ300 small steel pipe 1 to accurately locate the position of the steel pipe pile 2. Then, according to the position of the small steel pipe 1, the large steel pipe 1 is lowered into place, and the position is verified by using measuring equipment. When the position is correct, a vibratory hammer is used to fix the φ630 steel pipe. When the vibratory hammer cannot vibrate and sink it, a small pile diameter rotary drilling drill (φ600 drill diameter rotary drilling drill) is used to guide the hole. When the rotary pile guide hole reaches the specified position, a vibratory hammer is used to construct the steel pipe pile 2, thereby realizing the guide hole of the steel pipe pile 2.

[0063] By lowering a drilling rig into the steel pipe pile 2, further drilling a hole based on the pile position, and based on the principle of "small hole leading to big hole", a rotary drill or impact drill is used to crush the bare rock in the steel pipe pile 2. When a small hole is drilled in the deep water bed 5 below the steel pipe pile 2, the sinking resistance of the steel pipe pile 2 is reduced, and the pile can be vibrated and sunk stably and continuously, thereby improving the quality of the drilling and the positioning and installation effect of the steel pipe pile 2, significantly reducing the difficulty of inserting the steel pipe pile 2, and allowing the steel pipe pile 2 to be vibrated and sunk smoothly to the design standard depth, accurately installing the steel pipe pile 2 to meet the standards, and completing the installation and positioning construction of the steel pipe pile 2 quickly and effectively.

[0064] If a drilling rig is used to drill holes at the cantilever end of the embodiment, construction costs can be significantly saved.

[0065] Using a cantilevered drilling rig for drilling, equipment and materials can be transported overland. The cost of constructing a single steel pipe pile includes the following: monthly rental of the percussion drill, 10,000 yuan; monthly salary of the operator, 6,000 yuan; and monthly rental of a crawler crane for auxiliary construction, 150,000 yuan. Since a single crawler crane can simultaneously handle two percussion drills, the monthly cost is 75,000 yuan. The construction of a single steel pipe pile requires one day: half a day for drilling the hole and half a day for setting the pile and transporting the equipment. Therefore, the total cost of a single steel pipe pile is (10,000 + 6,000 + 75,000) / 300,000 = 3,030,000 yuan.

[0066] Using a rotary drilling rig to guide the hole requires four vessels to assist with construction and transport materials, serving as construction platforms. The monthly rental cost for four 500-ton civilian vessels is NT$300,000. Regulations require four crew members to operate each vessel, each earning NT$35,000 per month. The monthly rental cost for a small rotary drill is NT$80,000 per unit, and the monthly salary for the operator is NT$10,000. The waste generated during drilling must be removed, requiring the monthly rental cost of four small slag dredgers. Since the construction of a single steel pipe pile requires one day: half a day for drilling, half a day for driving, and repositioning the four vessels, the drilling process is performed by the rotary drilling rig, while the steel pipe pile is driven using the fishing method. Therefore, the total cost per pile is (NT$300,000 + NT$35,000 + NT$80,000 + NT$10,000 + NT$50,000) / NT$300,000 = NT$15,800.

[0067] Using conventional construction methods, such as bench piers, would cost 170,000 yuan per month. Assuming each pile takes 2 hours to build, and a 12-hour workday, each bench pier would take 12 hours to build. The additional material cost would be 152.89 kg / m * 18 m * 3 piers * 6,000 yuan / ton = 49,536.4 yuan. Therefore, the additional cost per bench pier is (49,536,400 yuan + 170,000 yuan * 12 / (30 * 12)) / 3 = 18,500 yuan.

[0068] Therefore, the costs of cantilever hole construction, rotary drilling hole construction, and bench pier construction are 30,300, 15,800, and 18,500 respectively. Therefore, compared with rotary drilling hole construction and cantilever hole construction, the cantilever hole construction technology should be considered as much as possible for deep-water bare rock construction. However, when the construction period is limited and steel trestle operations need to be constructed simultaneously on multiple working surfaces at sea, rotary drilling holes have unique advantages.

[0069] Example 2

[0070] Please refer to Figure 7 This embodiment provides a method for drilling holes for steel pipe piles under deep-water bare rock geological conditions. The construction method is applied to deep-water areas of inland lakes. Steel pipes and steel pipe piles are φ400 and φ650 steel pipes, respectively. The method also includes S0 to S2 in Example 1: S0, using finite element software to model and perform construction safety verification; S1, first positioning and installing small-sized steel pipes, and then preliminarily fixing them by sleeves of steel pipe piles outside the small-sized steel pipes; S2, vibrating and fixing the steel pipe piles, first drilling holes in the steel pipe piles toward the bottom of the deep water bed, and then vibrating and fixing them.

[0071] Please refer to Figure 8 The construction method of this embodiment further includes step S3:

[0072] S3. After the steel pipe pile 2 is installed, a tensile test is performed. Two or more adjacent positions of the installed steel pipe piles are selected and tested. First, a plurality of reflective sheets 6 are set on the outer wall of the steel pipe pile 2 along a parallel axial direction. In this embodiment, two spaced reflective sheets 6 are affixed to the outer wall of each steel pipe pile 2 at equal heights. The reflective sheets 6 are marked with points, lines, or a pattern composed of points and lines for measurement and positioning. In this embodiment, a cross symbol is used. The intersection of the cross symbol reflected by the reflective sheet 6 is positioned and measured by a measuring instrument. The marking of the reflective sheet 6 can improve the efficiency of the measuring instrument's detection and the accuracy of the measurement. In this way, the verticality of the steel pipe pile 2 can be quickly detected, and the installation and positioning accuracy of the steel pipe pile 2 can be improved.

[0073] First, a solid water platform is set up. The platform is separated from the steel pipe piles 2 and cannot be connected to each other, so as to facilitate accurate testing. A fall chain 8 is used to connect adjacent steel pipe piles 2. Both ends of the fall chain 8 are connected to the steel pipe piles 2 with a dynamometer 7. Then, a tensile test is performed on the two adjacent steel pipe piles 2. The measuring instrument is a total station or a theodolite. The reflected light of the reflective sheet 6 is measured by the measuring instrument to obtain the horizontal load-displacement curve of the steel pipe pile 2, thereby ensuring the rationality and feasibility of the construction process and ensuring that the steel pipe pile 2 has sufficient ability to resist horizontal loads.

[0074] During the tensile test in this step, a horizontal static load is applied to two adjacent steel pipe piles 2, and then the load is unloaded after completion. During the loading and unloading process, the load is transferred evenly, continuously, and without impact, and the variation range of each level of load during the maintenance process shall not exceed 10% of the graded load. This can minimize the influence of the tensile test on the stress of the steel pipe piles 2 and effectively verify the installation effect of the guide hole and the steel pipe piles 2. The loading and unloading process includes:

[0075] S31. First, apply the first level load to the two adjacent steel pipe piles 2. The first level load is 1.8 to 2.2 times the graded loading load. In this embodiment, the first level load is taken as 2 times the graded loading load. The graded loading load is 0.08 to 0.12 times the preset maximum loading load. The graded loading load in this embodiment adopts 1 / 10 of the maximum loading load.

[0076] S32. A graded loading method is adopted to increase the graded load step by step. Each load level is maintained for 25 to 35 minutes. In this embodiment, the load maintenance time is 0.5 hours. During the load maintenance period, the tension between adjacent steel pipe piles 2 and the horizontal displacement of adjacent steel pipe piles 2 are monitored every 5 to 15 minutes. Specifically, the horizontal displacement of the steel pipe pile 2 is measured at the 5th, 15th and 30th minute after each load level.

[0077] S33. A graded unloading method is adopted to reduce the graded unloading load by an equal amount step by step. The graded unloading load is 1.5 to 2.5 times the graded loading load, and the graded unloading load is 2 times the graded loading load. Each load level is maintained for 10 to 20 minutes. In this embodiment, the load maintenance time is 15 minutes. During the load maintenance period, the tension between adjacent steel pipe piles 2 and the horizontal displacement of adjacent steel pipe piles 2 are monitored every 5 to 10 minutes. Specifically, the horizontal displacement of the steel pipe pile 2 is measured at the 5th and 15th minutes after each level of unloading.

[0078] S34. After unloading the load to zero, measure the horizontal displacement of the adjacent steel pipe piles 2 for 25 to 35 minutes. The measurement and reading time is 0.5 hours, and the measurement and reading are performed every 5 to 15 minutes. Specifically, the measurement and reading are performed at 5, 15, and 30 minutes after unloading to zero.

[0079] This method continuously releases the applied load to restore the displacement of the two steel pipe piles 2, and uses a total station to measure the horizontal displacement corresponding to each level of load during the loading process, and finally obtains the horizontal load-displacement curve of the steel pipe pile 2. Based on this curve, the installation effect of the steel pipe pile 2 is judged.

[0080] The bridge in this embodiment is located in a deep-water, bare rock environment at a depth of over 20 meters. The water velocity is 1.5 m / s, the tidal range is 3 m, and the wave height is 0.5 m. The geology consists of highly weathered muddy siltstone with no overburden. The prevailing wind direction throughout the year is from the north, with an average annual wind speed of 3.8 m / s, a maximum wind speed of 31.0 m / s, and a peak wind speed of 38.5 m / s. The temperature is approximately 35.0°C. Due to the actual structural conditions, the steel trestle bridge is subject to loads such as tank trucks, crawler cranes, rotary drilling rigs, percussion drills, wind loads, water flow forces, and horizontal forces (braking loads and impact loads from tank trucks and transport vehicles). The maximum transport load is a 135-ton crawler crane load. The maximum horizontal load is generated when two transport vehicles are operating side by side. The steel trestle bridge is designed as follows: the standard span is five spans per unit, each span is 12 m, each unit is 60 m long, and the bridge deck is 8 m wide. The steel trestle pile foundations all use φ630×10mm steel pipe piles 2, with bench piles at both ends, and the rest are in a single row, with a total of 6 bench piles and a single row of 3 piles. The bench piles are 3.2m apart horizontally.

[0081] Calculations show that φ630 steel pipe piles 2, with a rock penetration depth of 5m, can withstand a horizontal tensile load of approximately 20T. According to JTG D60-2015, "General Specification for Highway Bridge and Culvert Design," and referring to measured statistical data from other bridges, the maximum horizontal load is 10T, carried by three steel pipe piles 2, with each pile bearing an average load of 3.3T. Based on these tests, when the borehole depth is 5m, the maximum horizontal tensile load is 3T, resulting in a horizontal displacement of approximately 345mm; when the maximum horizontal tensile load is 6T, the horizontal displacement is approximately 570mm, indicating that the steel pipe piles 2 for the steel trestle can withstand the horizontal loads during construction with a significant safety margin.

[0082] 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 scope of protection of the present invention.

Claims

1. A method for constructing steel pipe pile holes under deep-water bare rock geological conditions, characterized in that: The following steps are involved: S1. First, lower a steel pipe with a diameter smaller than that of the steel pipe pile vertically to the deep waterbed corresponding to the pile position and secure it. Then, by sleeve-tying the steel pipe pile outside the steel pipe, lower the steel pipe pile vertically to the pile position and secure it preliminarily. Measure and verify the position of the steel pipe pile, and then remove the steel pipe. S2. Use a vibrating device to vibrate and fix the steel pipe pile. When the steel pipe pile can no longer sink by vibration, use a drilling rig to drill a hole in the steel pipe pile toward the bottom of the deep water bed. After drilling the hole, use a vibrating device to vibrate and fix the steel pipe pile until the steel pipe pile is installed in place. The method further includes step S3: providing a plurality of reflective sheets on the outer wall of the steel pipe pile along a parallel axial direction, connecting adjacent steel pipe piles with a fall chain, performing a tensile test on two adjacent steel pipe piles, measuring the reflected light of the reflective sheets with a measuring instrument, obtaining a horizontal load-displacement curve of the steel pipe pile, and ensuring the steel pipe pile's ability to resist horizontal loads; When performing the tensile test in step S3, a horizontal static load is applied to two adjacent steel pipe piles in the following manner: S31. First, apply a first-level load to two adjacent steel pipe piles. The first-level load is 1.8 to 2.2 times the graded load, and the graded load is 0.08 to 0.12 times the preset maximum load. S32. Then adopt the form of graded loading, increase the graded loading load step by step, and maintain each load for 25 to 35 minutes. During the load maintenance period, monitor the tension between adjacent steel pipe piles and the horizontal displacement of adjacent steel pipe piles every 5 to 15 minutes.

2. The method for constructing steel pipe pile holes under deep-water bare rock geological conditions according to claim 1, characterized in that: The hole-drilling method in step S2 includes percussion drilling and rotary drilling.

3. The method for constructing steel pipe pile holes under deep-water bare rock geological conditions according to claim 1, characterized in that: In step S1, after the steel pipe is lowered and fixed, the verticality of the steel pipe needs to be tested: a number of reflective sheets are set on the outer wall of the steel pipe along the parallel axial direction, and the reflected light of the reflective sheets is measured by a measuring instrument on the shore to ensure the verticality of the steel pipe.

4. The method for constructing steel pipe pile holes under deep-water bare rock geological conditions according to claim 1, characterized in that: The reflective sheet is marked with points, lines, or a pattern composed of points and lines for measuring and positioning, and the pattern reflected by the reflective sheet is positioned and measured by a measuring instrument.

5. The method for constructing steel pipe pile holes under deep-water bare rock geological conditions according to claim 1, characterized in that: When performing the tensile test in step S3, the unloading method of the horizontal static load is: S33. Use a graded unloading method, reducing the graded unloading load by an equal amount step by step. The graded unloading load is 1.5 to 2.5 times the graded loading load. Each load level is maintained for 10 to 20 minutes. During the load maintenance period, the tension between adjacent steel pipe piles and the horizontal displacement of adjacent steel pipe piles are monitored at intervals of 5 to 10 minutes. S34. After unloading the load to zero, measure the horizontal displacement of adjacent steel pipe piles for 25 to 35 minutes, with an interval of 5 to 15 minutes between each measurement.

6. The method for constructing steel pipe pile holes under deep-water bare rock geological conditions according to claim 1, characterized in that: Before step S1, security verification is also included: Finite element software was used to build the model and calculate the load conditions when drilling a hole at the cantilever end. The verification parameters included the stress at the cantilever end, the maximum displacement of the structure, and stability.

7. The method for constructing steel pipe pile holes under deep-water bare rock geological conditions according to claim 1, characterized in that: Also includes: Fix the construction equipment on the ship, move the ship to the preset pile position, drop anchor, preliminarily fix the ship, and use the construction equipment to perform drilling operations.

8. The method for constructing steel pipe pile holes under deep-water bare rock geological conditions according to claim 1, characterized in that: In step S1, when the steel pipes and steel pipe piles are moved, positioned, and lowered, a floating crane is used to load and operate them.

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