Construction method of foundation rotary digging pile for water conservancy and hydropower engineering

Abstract

This invention discloses a construction method for rotary drilling piles used in water conservancy and hydropower engineering. The method involves setting up a first row and a second row of rotary drilling piles at a predetermined elevation on the river-facing side of the foundation pit. These piles interlock and their tops are flush. A capping beam is also included at the top of the first and second rows of rotary drilling piles, connecting and fixing them into a vertical, closed wall. A diaphragm wall is also installed inside the foundation pit, with one end connected to the solid wall and the other end connected to the bedrock. The interlocking of the two rows of rotary drilling piles, along with the construction of the capping beam and diaphragm wall at the top of the piles, forms a continuous, closed foundation pit protection structure. The entire construction process facilitates the excavation and layout of the outlet retaining wall foundation after the flood season, saves construction time, reduces construction costs, and provides functions such as cofferdam seepage prevention, scour prevention, soil retention, foundation pit protection, and foundation bearing capacity.

Description

Technical Field

[0001] This invention relates to the field of water conservancy engineering technology, and in particular to a construction method for rotary drilling piles used in water conservancy and hydropower projects. Background Technology

[0002] The spillway energy dissipation structure of conventional hydropower stations is usually located on the riverside, where the overburden layer is often thick and the geological conditions are complex. Furthermore, the construction period for continuous anti-seepage walls is long, and the construction site layout is limited, making it difficult to complete the excavation, foundation treatment, and concrete pouring processes within a single dry season. Summary of the Invention

[0003] To overcome the shortcomings of the existing technology, the technical problem to be solved by the present invention is to solve the problems of low construction efficiency, long construction period and high cost of the foundation excavation of the outlet sill.

[0004] The technical solution adopted by this invention to solve its technical problem is: A construction method for rotary drilling piles in water conservancy projects includes the following steps: S1: Prepare the rotary drilling pile construction platform; S2: Measure and locate the lead point and pile point of the first row of rotary drilling piles; S3: Install the casing according to the set guide points and pile points; S4: Drill holes according to the location of the casing, and clean the holes after drilling is completed; S5: Install a reinforcing cage inside the drilled hole; S6: Pour concrete into the hole to complete the construction of the first row of rotary drilling piles; S7: Construct the second row of rotary drilling piles using the same steps as steps S2 - S6, with adjacent piles of the first and second rows interlocking in pairs. S8: A cap beam reinforcement frame is installed on the top of the first row of rotary drilling piles and the second row of rotary drilling piles; S9: Cast the cap beam.

[0005] Furthermore, in step S3, the process of installing the casing specifically includes: using a full-rotation drilling rig to excavate the hole, and installing the casing every 2m after rotary drilling until the bottom of the overburden layer is reached. The top of the casing is 0.3m above the ground or 1.0 to 2.0m above the water surface.

[0006] Furthermore, in step S4, before the drilling rig is positioned, the filler around the casing is compacted, the crosshairs of the protective piles around the casing are hung out, and then the drill bit and drill rod are adjusted by the drilling rig's automatic control device so that the drill bit is precisely aligned with the crosshairs.

[0007] Furthermore, during the drilling process, the drilling speed should be controlled according to the geological conditions. When drilling from hard rock to soft rock, the drilling speed can be increased appropriately; when the soft rock turns into hard rock, the speed should be reduced.

[0008] Furthermore, after drilling to the designed depth, the hole depth, bottom sediment, and hole inclination should be checked; the hole depth is measured or verified using a measuring rope; the bottom sediment is detected using the cone disc method or a sediment analyzer; and the hole inclination is detected using a slewing instrument or an ultrasonic logging instrument.

[0009] Furthermore, in step S5, the reinforcing cage is manufactured in sections; during assembly, the upper end of the lower section of the reinforcing cage protrudes 1m from the operating platform; the connection points of the main reinforcement bars of the upper and lower sections of the reinforcing cage are aligned and the upper and lower sections of the cage are kept vertical before connection; the connection is carried out symmetrically on both sides; after each section of the reinforcing cage is connected, the stirrups at the connection points are supplemented; after all the reinforcing cages are placed into the holes, the installation position is checked, and after confirming that it meets the requirements, the reinforcing cage lifting bars are fixed; positioning bars are set every 3m on the main reinforcement bars around the reinforcing cage.

[0010] Furthermore, in step S6, the pouring process includes: first, lowering the guide pipe into the hole, and then pouring concrete into the hole through the guide pipe. The elevation of the pile top after pouring should be 0.8 to 1.0 m higher than the design elevation.

[0011] Furthermore, the substandard concrete at the top of the pile was removed.

[0012] Furthermore, in step S9, the cap beam pouring process specifically includes: after breaking the pile heads of the first row of rotary drilling piles and the second row of rotary drilling piles, fixing the steel cages on the two broken rotary drilling pile heads, and then setting up the formwork to pour concrete.

[0013] The beneficial effects of this invention are: The first and second rows of rotary drilling piles interlock to form a continuous, closed anti-seepage wall structure in complex geological conditions. This structure can be applied to foundation pits with deep overburden layers, where the upper part of the pit is mainly composed of colluvial gravel soil, the middle and lower parts are alluvial boulders and alluvial sand and gravel soil, and the lower bedrock is granite. The first and second rows of rotary drilling piles, the capping beam, and the diaphragm wall form an integrated structure, which facilitates the excavation and construction of the outlet retaining wall foundation after the flood season, saves construction time, reduces construction costs, and can also play the roles of cofferdam seepage prevention, scour prevention, soil retention, foundation pit protection, and foundation bearing capacity. As a relatively advanced construction machine, rotary drilling rigs have obvious advantages. Compared with conventional bored pile machines, rotary drilling rigs have advantages such as faster hole formation speed, wider applicability, and controllable construction period. Attached Figure Description

[0014] Figure 1 This is a flowchart of the construction method of the present invention; Figure 2 This is a schematic diagram of the reinforcing cage of the present invention; Figure 3 This is a schematic diagram of the planar cross-section of the present invention; Figure 4 This is a schematic diagram showing the positions of the first row of rotary drilling piles and the second row of rotary drilling piles in this invention; Figure 5 This is a schematic diagram showing the positional relationship between the first row or second row of rotary drilling piles and the overburden layer of the present invention; Figure 6 This is a schematic diagram of the longitudinal cross-section of the present invention; The markings in the diagram are: 1-overburden layer, 2-first row of rotary drilling piles, 3-second row of rotary drilling piles, 4-cap beam, 5-pile top, 6-reinforcing cage. Detailed Implementation

[0015] The invention will be further described below with reference to the accompanying drawings.

[0016] like Figures 1-6 As shown, this application proposes a foundation rotary drilling pile structure for water conservancy projects, including a cover layer 1. The cover layer 1 is vertically provided with a first row of rotary drilling piles 2 and a second row of rotary drilling piles 3 at a preset elevation. The first row of rotary drilling piles 2 and the second row of rotary drilling piles 3 are interlocked and their tops are flush. The application also includes a capping beam 4 disposed at the top of the first row of rotary drilling piles 2 and the second row of rotary drilling piles 3. The capping beam 4 connects and fixes the first row of rotary drilling piles 2 and the second row of rotary drilling piles 3 in series to form a vertical closed structure.

[0017] It should be noted that the first row of rotary drilling piles 2 and the second row of rotary drilling piles 3 interlock to form a continuous, closed seepage-proof wall structure in complex geological conditions. After the foundation pit excavation is completed, the capping beam 4 at the top of the rotary drilling piles is constructed to form a continuous, closed foundation pit protection structure. Finally, after the foundation pit construction is completed, the first row of rotary drilling piles 2, the second row of rotary drilling piles 3, and the capping beam 4 form the foundation. The entire construction process facilitates the layout of the post-flood outlet retaining wall foundation excavation, saves construction time, and reduces construction costs. Moreover, it can play the roles of cofferdam seepage prevention, scour prevention, soil retention, foundation pit protection, and foundation bearing capacity, maximizing the stability and safety of the foundation pit.

[0018] This application also proposes a construction method for rotary drilling piles in water conservancy and hydropower projects, corresponding to the above-described structure, including the following steps: S1: Prepare the rotary drilling pile construction platform; the construction platform mainly utilizes the original ground surface, which is compacted using a vibratory roller. After excavating the structural slope to the design elevation, the site is leveled and compacted to serve as the rotary drilling pile foundation construction platform.

[0019] S2: Measure and locate the reference points and pile points of the first row of rotary drilling piles 2; use a total station for positioning measurement, and measure the reference points and pile points according to the coordinates during the measurement process; divided into elevation control, plane control and pile position protection.

[0020] S3: Install casing according to the set guide points and pile points; use a full-rotation drilling rig for direct installation or excavation, and install casing every 2m after rotary drilling until the bottom of the overburden layer is reached. The top elevation of the casing should be 0.3m above the ground or 1.0-2.0m above the water surface.

[0021] S4: Drill holes according to the casing position, and clean the holes after drilling is completed; before the drilling rig is in place, compact the fill material around the casing to ensure that the drilling rig does not sink or tilt during drilling. Before drilling, hang the crosshairs around the casing, and then adjust the drill bit and drill rod through the automatic control device of the drilling rig to make them accurately aligned with the crosshairs.

[0022] Two types of drill bits were used in circulation: an 18-tooth core drill and a flat-bottomed slag remover. The drill bits were cutting teeth adapted to a borehole diameter of 150 MPa or higher. During drilling, the drilling speed was controlled according to the geological conditions. When drilling from hard rock to soft rock, the drilling speed could be increased appropriately; when soft rock turned into hard rock, the speed was reduced. In strata prone to borehole narrowing, the number of scavenging passes was increased appropriately to prevent borehole narrowing.

[0023] After drilling to the designed depth, the hole depth, bottom sediment, and hole inclination should be checked. Hole depth is checked using a measuring rope or by verifying the height of the drill bit and drill pipe; bottom sediment is checked using the cone disc method or a sediment analyzer; and hole inclination is checked using a directional measuring instrument or an ultrasonic logging instrument.

[0024] S5: Install the reinforcing cage 6 inside the drilled hole; the reinforcing cage 6 is manufactured in sections; during assembly, the upper end of the lower section of the reinforcing cage 6 should protrude about 1m above the operating platform to ensure connection with the capping beam 4; the connection points of the main reinforcement bars of the upper and lower sections of the reinforcing cage should be aligned and the upper and lower sections of the cage should be vertical before connection; the connection should be symmetrical on both sides; after each section of the reinforcing cage 6 is connected, add stirrups to the connection points; after all the reinforcing cages 6 are installed in the hole, check the installation position, and after confirming that it meets the requirements, fix the lifting bars of the reinforcing cage 6. Positioning bars are installed every 3m on the main reinforcement bars around the reinforcing cage 6, with 4 bars installed in the transverse circumference.

[0025] S6: Pour concrete into the hole to complete the construction of the first row of rotary drilling piles 2; first, lower the guide pipe into the hole, and pour concrete into the hole through the guide pipe. The elevation of the top 5 of the pile after pouring should be 0.8 to 1.0m higher than the design elevation.

[0026] Before using the conduit, a water tightness and pressure test should be conducted to check for sand holes, deformation of the flange, and poor sealing. The test water pressure is 0.6 to 1.0 MPa. After the conduit is placed at the bottom of the contact hole, it should be raised 0.5 m.

[0027] The concrete pouring frame, made of structural steel, supports the suspended guide pipe and holds the concrete funnel on top. A crane is also used to dismantle the guide pipe. The top elevation of the completed pile should be 0.8–1.0 m higher than the design elevation.

[0028] S7: Construct the second row of rotary drilling piles using the same steps as steps S2-S6, with adjacent piles of the first and second rows interlocking.

[0029] The first row of rotary drilling piles 2 and the second row of rotary drilling piles 3 are both composed of multiple rotary drilling piles arranged in rows. The construction of the first row of rotary drilling piles 2 is carried out by intermittent skip-piling construction, and the two adjacent first row of rotary drilling piles 2 are in interlocking contact to ensure sufficient sealing. The composition and size specifications of the second row of rotary drilling piles 3 are the same as those of the first row of rotary drilling piles 2. The same set of equipment is used for sequential pouring construction, resulting in lower construction costs.

[0030] Specifically, the first row of rotary drilling piles 2 and the second row of rotary drilling piles 3 are closely interlocked to form a contact structure that abuts against each other. The first row of rotary drilling piles 2 and the second row of rotary drilling piles 3 are cast in sequence without interfering with each other during the casting process, which can improve construction efficiency and reduce construction costs.

[0031] S8: A cap beam 4 steel reinforcement frame is installed at the top 5 of the first row of rotary drilling piles 2 and the second row of rotary drilling piles 3.

[0032] S9: Cast the cap beam 4. After breaking the pile heads of the first row of rotary drilling piles 2 and the second row of rotary drilling piles 3, fix the steel reinforcement frame on the two broken rotary drilling pile heads, and then set the formwork to pour concrete.

[0033] In summary, the double-row rotary drilling pile with capping beam structure can serve multiple functions, including cofferdam seepage prevention, unilateral retaining, foundation pit support, structural load-bearing, and external scour prevention. It can solve problems related to foundation pit construction and the safe and stable operation of spillway structures. This structure and construction method are suitable for situations with tight schedules and complex geological conditions. It can effectively reduce construction difficulty, create dry construction conditions, and facilitate the seamless transition between work processes.

Claims

1. A construction method for rotary drilling piles in water conservancy and hydropower projects, characterized in that, Includes the following steps, S1: Prepare the rotary drilling pile construction platform; S2: Measure and locate the lead point and pile point of the first row of rotary drilling piles (2); S3: Install the casing according to the set guide points and pile points; S4: Drill holes according to the location of the casing, and clean the holes after drilling is completed; S5: Install a steel cage (6) inside the drilled hole; S6: Pour concrete into the hole to complete the construction of the first row of rotary drilling piles (2); S7: Construct the second row of rotary drilling piles using the same steps as steps S2-S6, with adjacent piles of the first and second rows interlocking in pairs. S8: A cap beam (4) steel reinforcement frame is set at the top (5) of the first row of rotary drilling piles (2) and the second row of rotary drilling piles (3); S9: Cast the cap beam (4).

2. The construction method for rotary drilling piles in water conservancy and hydropower projects according to claim 1, characterized in that, The process of installing the casing includes: using a full-rotation drilling rig to dig holes, and installing the casing every 2m after rotary drilling until the bottom of the overburden (1); the top elevation of the casing is 0.3m above the ground or 1.0 to 2.0m above the water surface.

3. The construction method for rotary drilling piles in water conservancy and hydropower projects according to claim 1, characterized in that, In step S4, before the drilling rig is positioned, the filler around the casing is compacted, the crosshairs of the protective piles around the casing are hung out, and then the drill bit and drill rod are adjusted by the drilling rig's automatic control device so that the drill bit is precisely aligned with the crosshairs.

4. The construction method for rotary drilling piles in water conservancy and hydropower projects according to claim 3, characterized in that, During drilling, the drilling speed should be controlled according to the geological conditions. When drilling from hard rock to soft rock, the drilling speed can be increased appropriately; when the soft rock turns into hard rock, the speed should be reduced.

5. A construction method for rotary drilling piles in water conservancy and hydropower projects according to claim 4, characterized in that, After drilling to the designed depth, the hole depth, bottom sediment, and hole inclination should be checked. The hole depth is measured by measuring rope or verification. The bottom sediment is detected by cone disc method or sediment meter. The hole inclination is detected by inclinometer or ultrasonic sidetracking instrument.

6. The construction method for rotary drilling piles in water conservancy and hydropower projects according to claim 1, characterized in that, In step S5, the steel cage (6) is made in sections; during assembly, the upper end of the lower section of the steel cage (6) protrudes 1m from the operating platform; the main reinforcement connection points of the upper and lower sections of the steel cage are aligned and the upper and lower sections are in a vertical state before they can be connected; the connection is carried out symmetrically on both sides; after each section of the steel cage (6) is connected, the stirrups at the connection points are supplemented; after all the steel cages (6) are placed into the holes, the installation position is checked, and after confirming that it meets the requirements, the lifting bars of the steel cage (6) are fixed; positioning bars are set every 3m on the main reinforcement around the steel cage (6).

7. A construction method for rotary drilling piles in foundation engineering for water conservancy and hydropower projects according to claim 1, characterized in that, In step S6, the pouring process includes: first, lowering the guide pipe into the hole, and then pouring concrete into the hole through the guide pipe. The elevation of the top of the pile (5) after pouring should be 0.8 to 1.0 m higher than the design elevation.

8. A construction method for rotary drilling piles in water conservancy and hydropower projects according to claim 7, characterized in that, Remove the substandard concrete at the top of the pile (5)(5).

9. A construction method for rotary drilling piles in water conservancy and hydropower projects according to claim 1, characterized in that, In step S9, the concrete pouring process of the cap beam (4) specifically includes: after breaking the pile heads of the first row of rotary drilling piles (2) and the second row of rotary drilling piles (3), fixing the steel cage (6) on the two broken rotary drilling pile heads, and then setting the formwork to pour concrete.

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