Sand layer geologic pile foundation hole forming process

Abstract

The application relates to the technical field of building construction, and discloses a sand layer geological pile foundation hole-forming process, which comprises the following steps: step one, steel casing embedding pretreatment: the embedding depth and wall thickness of the steel casing are determined according to the stratum distribution and compactness characteristics of the dense sand layer, the outer wall of the casing is roughened, and then the casing is embedded in layers in cooperation with a sand layer compaction process; after embedding, the top of the casing is fixed and reinforced to prevent the casing from deviating or sinking during hole forming; step two, parameterized hole forming construction; step three, fine cleaning of the mud skin on the inner wall of the steel casing; step four, hole bottom sediment treatment, which optimizes the construction environment in the hole; step five, optimized concrete pouring; and step six, pile foundation maintenance and forming. Through multi-link collaborative optimization, the application stabilizes the casing, considers the hole forming efficiency and the stability of the hole wall, optimizes the environment in the hole, strengthens the stress performance of the pile foundation, and improves the construction quality and structural reliability of the sand layer pile foundation.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, specifically to a drilling process for pile foundations in sandy geological layers. Background Technology

[0002] The pile foundation drilling process under dense sand geological conditions is a key technology to ensure the quality of drilling and the bearing capacity of pile foundations in sandy soil. It is widely applicable to various building pile foundation projects involving dense sand layers.

[0003] In the construction of pile foundations in dense sand layers, steel casings are often installed using a uniform layout. While simple fixing methods are used to ensure the casing position during construction, it is difficult to achieve effective adhesion between the casing and the sand layer, which can easily lead to casing displacement and subsidence, affecting the stability of subsequent drilling operations. Drilling operations are carried out using fixed drilling and mud wall protection parameters. Some construction attempts to improve the performance of mud wall protection to ensure borehole stability, but this reduces the drilling speed. It is impossible to balance drilling efficiency and borehole stability, which can easily lead to slow drilling or borehole collapse. Therefore, a new drilling technology for pile foundations in sandy geological layers is proposed. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a drilling process for pile foundations in sandy geological layers, thereby solving the problems mentioned in the background section.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a hole-forming process for pile foundations in sandy geological layers, comprising the following steps: Step 1: Pre-treatment for steel casing installation: The burial depth and wall thickness of the steel casing are determined based on the stratigraphic distribution and compaction characteristics of the dense sand layer. After roughening the outer wall of the casing, it is buried in layers in conjunction with the sand layer compaction process. After burial, the top of the casing is fixed and reinforced to prevent the casing from shifting or sinking during the drilling process. Step 2: Parametric Hole Formation Construction Rotary drilling rigs are used for hole-forming operations. Drilling parameters are dynamically and collaboratively adjusted according to the real-time density of the sand layer, and the wall-protecting performance of the mud is controlled simultaneously. Sand particles and impurities are filtered during the mud circulation process to ensure the stability of the hole wall while accelerating the hole-forming speed. Step 3: Fine cleaning of mud cake on the inner wall of the steel casing: After the hole is formed, the inner wall of the casing is first flushed with high-pressure water, and then a flexible scraper is used to scrape the wall to remove mud skin layers of different thicknesses layer by layer, so as to avoid the mud skin from blocking the effective bonding between the pile foundation and the sand layer. Step 4: Treatment of sediment at the bottom of the borehole: After the mud skin is cleaned, the sediment at the bottom of the hole is pumped out and cleaned using the mud circulation and replacement method to control the thickness of the sediment at the bottom of the hole and optimize the construction environment inside the hole. Step 5: Optimized Concrete Pouring: After the sediment is treated, the grouting pipe is quickly lowered and concrete is poured using a continuous grouting method. The burial depth of the pipe is dynamically adjusted to ensure the continuity and compactness of the concrete pouring. Step Six: Pile Foundation Curing and Shaping After the grouting is completed, targeted moisturizing and curing measures are taken according to the on-site temperature and humidity conditions of the sand layer geology. At the same time, the sand layer around the pile is compacted to strengthen the lateral restraint of the sand layer around the pile and improve the overall bearing capacity of the pile foundation. Each construction step is progressively connected and coordinated to adapt to the geological characteristics of the dense sand layer, effectively avoiding problems such as casing instability, borehole wall collapse, mud cake residue, excessive sediment, and concrete pouring defects during hole drilling in the sand layer. This comprehensively optimizes the construction quality of pile foundations in sandy geological layers, strengthens the bond between the pile foundation and the sandy stratum, improves the overall stress performance and structural reliability of the pile foundation, and ensures the stability and effectiveness of pile foundation construction in sandy geological layers.

[0006] Preferably, in the pretreatment of steel casing installation in step one, the sand compaction process uses a vibratory hammer to compact the sand layer around the casing in layers. The vibration height of each layer is matched with the segmented depth of the casing installation. After vibration compaction, graded sand is used to fill the gap between the casing and the stratum. After filling, a small compaction device is used for preliminary compaction to ensure that the casing and the sand layer are in contact, thus preventing the sand layer from collapsing around the casing and causing instability of the borehole wall during drilling.

[0007] Preferably, in the steel casing installation pretreatment in step one, the roughening treatment of the outer wall of the casing is carried out by sandblasting. The particle size of the sandblasting is selected according to the density of the sand layer. After the roughening treatment, a thin layer of sand-fixing agent is applied to the outer wall of the casing. The casing installation is completed before the sand-fixing agent initially sets, which further enhances the adhesion between the casing and the sand layer and prevents gaps between the casing and the sand layer from causing grout leakage.

[0008] Preferably, in the parameterized hole-forming construction of step two, the dynamic adjustment of the drilling parameters includes the coordinated control of drilling speed, drilling pressure and drilling rate. When the sand layer density is high, the drilling speed is reduced and the drilling pressure is increased, and the specific gravity and viscosity of the mud are increased simultaneously to enhance the wall protection effect. When the sand layer density is low, the drilling speed is increased and the drilling pressure is reduced, and the specific gravity of the mud is appropriately reduced to avoid excessive mud sediment, thus balancing the hole-forming speed and the stability of the hole wall.

[0009] Preferably, in the parameterized drilling construction of step two, the sand impurity filtration of the mud circulation adopts a multi-stage filter screen structure. The pore size of the filter screen is dynamically changed according to the actual particle size of the returned sand during the drilling process. After the filtered mud is purified by sedimentation, it is reinjected into the hole to realize the recycling of mud and at the same time ensure that the wall protection effect of the hole does not decrease with the circulation of mud.

[0010] Preferably, in the fine cleaning of the mud skin on the inner wall of the steel casing in step three, the high-pressure water flushing uses a multi-angle high-pressure nozzle to move vertically and uniformly along the inner wall of the casing. The flushing pressure is adjusted in real time according to the tightness of the mud skin adhesion. The mud impurities generated by the flushing naturally flow into the bottom of the hole with the water flow. After the high-pressure water flushing is completed, a flexible scraper is used to scrape the inner wall of the casing in a circular motion. During the scraping process, the scraper and the inner wall of the casing are kept in consistent contact.

[0011] Preferably, in the fine cleaning of mud on the inner wall of the steel casing in step three, the flexible scraper is made of wear-resistant rubber material, and the scraping surface of the scraper is toothed to improve the scraping effect. After the toothed scraping is completed, the inner wall of the casing is rinsed with low-pressure water again to flush all the scraped mud debris to the bottom of the hole, thus completing the thorough cleaning of the mud on the inner wall of the casing.

[0012] Preferably, in the bottom sediment treatment of step four, the mud circulation replacement method adopts a reverse circulation mud process, in which the sediment, mud cake debris and mud slurry at the bottom of the hole are pumped together to a sedimentation tank outside the hole. During the pumping process, the circulation flow rate of the mud slurry is strictly controlled to avoid the flow rate being too fast and disturbing the hole wall, causing the sand layer to collapse. After the pumping is completed, the thickness of the sediment at the bottom of the hole is checked. If it does not meet the standard, the replacement and cleaning operation is repeated until the sediment thickness meets the specifications for sand layer pile foundation construction.

[0013] Preferably, in the optimized concrete pouring of step five, the water tightness and pressure bearing capacity of the entire pipe section are tested before the pouring pipe is lowered. It is lowered only after the test is qualified. During the lowering, the pipe is ensured to be centered in the hole. The pouring rate is uniformly controlled during the continuous concrete pouring process. The burial depth of the pipe is dynamically adjusted according to the real-time rise of the concrete pouring surface to avoid concrete segregation, pile breakage or slag inclusion caused by the pipe being buried too deep or too shallow.

[0014] Preferably, in the pile foundation curing and forming process of step six, the targeted moisturizing curing measures involve tightly wrapping the exposed part of the pile body with geotextile and regularly sprinkling water to keep it moist. The curing time is adjusted according to the ambient temperature of the sand layer. The sand layer around the pile is compacted in layers using a small vibratory roller. The compaction range is the sand layer area with a preset radius around the pile foundation, which further enhances the density and lateral restraint capacity of the sand layer around the pile, and effectively improves the vertical bearing capacity and pull-out performance of the pile foundation.

[0015] Compared with the prior art, the present invention provides a drilling process for pile foundations in sandy geological layers, which has the following beneficial effects: This invention achieves a tight fit between the casing and the dense sand layer and a stable embedded structure through customized parameter design and reinforcement measures for the pre-treatment of steel casing installation. This avoids casing displacement and sinking, solving the problem of casing instability in the early stage of drilling in sand layers. Through dynamic synergistic control of drilling parameters and mud wall performance, it achieves a balance between drilling efficiency and borehole wall stability, accelerating drilling speed and solving the problems of slow drilling and easy borehole wall collapse caused by fixed drilling parameters in sand layers. Through refined mud cake cleaning and bottom sediment treatment, it optimizes the construction environment inside the borehole, eliminating mud cake obstruction and strictly controlling sediment thickness, solving the problem of mud cake and sediment weakening the bond between the pile foundation and the sand layer. Through optimized concrete pouring and compaction curing of the sand layer around the pile, it improves the pile density and lateral constraint around the pile, enhancing the overall load-bearing capacity of the pile foundation and solving the core problem of insufficient bearing capacity of pile foundations in sandy geological conditions. Overall, it improves the construction quality and structural reliability of sandy pile foundations. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the hole-forming process for sand layer geological pile foundations according to the present invention; Figure 2 This is a flowchart of the overall process for drilling sand layer geological pile foundations according to the present invention; Figure 3 This is a schematic diagram of the pretreatment process for embedding the steel casing according to the present invention; Figure 4 This is a schematic diagram of the core construction process of drilling, slag removal, and grouting according to the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] This invention provides a technical solution: a drilling process for pile foundations in sandy geological layers. Please refer to [link / reference]. Figure 1 , Figure 2 , Figure 3 and Figure 4 It includes the following steps: Step 1: Pre-treatment for steel casing installation: The burial depth and wall thickness of the steel casing are determined based on the stratigraphic distribution and compaction characteristics of the dense sand layer. After roughening the outer wall of the casing, it is buried in layers in conjunction with the sand layer compaction process. After burial, the top of the casing is fixed and reinforced to prevent the casing from shifting or sinking during the drilling process. Step 2: Parametric Hole Formation Construction Rotary drilling rigs are used for hole-forming operations. Drilling parameters are dynamically and collaboratively adjusted according to the real-time density of the sand layer, and the wall-protecting performance of the mud is controlled simultaneously. Sand particles and impurities are filtered during the mud circulation process to ensure the stability of the hole wall while accelerating the hole-forming speed. Step 3: Fine cleaning of mud cake on the inner wall of the steel casing: After the hole is formed, the inner wall of the casing is first flushed with high-pressure water, and then a flexible scraper is used to scrape the wall to remove mud skin layers of different thicknesses layer by layer, so as to avoid the mud skin from blocking the effective bonding between the pile foundation and the sand layer. Step 4: Treatment of sediment at the bottom of the borehole: After the mud skin is cleaned, the sediment at the bottom of the hole is pumped out and cleaned using the mud circulation and replacement method to control the thickness of the sediment at the bottom of the hole and optimize the construction environment inside the hole. Step 5: Optimized Concrete Pouring: After the sediment is treated, the grouting pipe is quickly lowered and concrete is poured using a continuous grouting method. The burial depth of the pipe is dynamically adjusted to ensure the continuity and compactness of the concrete pouring. Step Six: Pile Foundation Curing and Shaping After grouting, targeted moisturizing and curing measures are taken according to the on-site temperature and humidity conditions of the sand layer geology. At the same time, the sand layer around the pile is compacted to strengthen the lateral restraint of the sand layer around the pile and improve the overall bearing capacity of the pile foundation. The density of the sand layer is detected in real time by ground-penetrating radar. Flexible scrapers are used to scrape the vertical layer along the wall of the casing. The thickness of the sediment at the bottom of the hole is controlled according to the construction specifications for sand layer pile foundations. The grouting pipe is lowered to keep the hole centered. The frequency of curing and moisturizing is dynamically adjusted according to the on-site temperature and humidity. The entire process of progressive construction is precisely adapted to the geological characteristics of dense sand layers. The high degree of coordination between the steel casing pretreatment and the pile foundation curing and forming solves the core problems such as slow hole formation in sand layers, incomplete mud cleaning, and insufficient bearing capacity of the pile foundation. It strengthens the bonding force between the pile foundation and the sand layer, comprehensively improves the construction quality and overall bearing capacity of the pile foundation, and is suitable for various dense sand layer pile foundation construction scenarios.

[0019] Please see Figure 1 , Figure 2 , Figure 3 and Figure 4In the pretreatment of steel casing installation in step one, the sand compaction process uses a vibratory hammer to compact the sand layer around the casing in layers. The vibration height of each layer matches the segment depth of the casing installation. After vibration compaction, graded sand is used to fill the gap between the casing and the stratum. After filling, a small compaction device is used for preliminary compaction to ensure that the casing and the sand layer are in close contact. This prevents the sand layer from collapsing around the casing during drilling and causing instability of the borehole wall. A high-frequency, low-amplitude vibratory hammer is used for compaction. The height of each layer of vibration compaction is ≤1.5m. Medium and coarse sand is used for the graded sand. A plate compactor is used for the small compaction device. Targeted layered vibration compaction and gap filling compaction ensure that the steel casing and the sand layer are in close contact. This fundamentally avoids the problem of borehole wall instability caused by the collapse of the sand layer around the casing during drilling, greatly improves the structural stability of the steel casing installation, lays a solid foundation for the subsequent whole-process drilling construction, and reduces drilling failures.

[0020] Please see Figure 1 , Figure 2 , Figure 3 and Figure 4 In the pretreatment of steel casing installation in step one, the outer wall of the casing is roughened by sandblasting. The particle size of the sandblasting is selected according to the density of the sand layer. After roughening, a thin layer of sand-fixing agent is applied to the outer wall of the casing. The casing installation is completed before the sand-fixing agent initially sets. This further enhances the adhesion between the casing and the sand layer, preventing gaps between the casing and the sand layer that could lead to grout leakage. 20-80 mesh corundum is used for sandblasting, with the particle size selected according to the density of the sand layer. The thin sand-fixing agent is inorganic, with a coating thickness of 0.5-1mm. The initial setting time of the sand-fixing agent is controlled at 30-60 minutes. Sandblasting roughens the surface area between the casing and the sand layer. Combined with the application of the sand-fixing agent, this significantly enhances the adhesion between the two, fundamentally avoiding grout leakage caused by gaps between the casing and the sand layer. This further improves the sealing and stability of the steel casing installation, ensuring the continuity of subsequent drilling operations.

[0021] Please see Figure 1 , Figure 2 , Figure 3 and Figure 4In the parametric drilling process of step two, the dynamic adjustment of drilling parameters includes the coordinated control of drilling speed, drilling pressure, and drilling rate. When the sand layer density is high, the drilling speed is reduced and the drilling pressure is increased, while the mud density and viscosity are increased simultaneously to enhance the wall protection effect. When the sand layer density is low, the drilling speed is increased and the drilling pressure is reduced, while the mud density is appropriately reduced to avoid excessive mud sediment. This balances drilling speed and borehole stability. The drilling parameters are coordinated and controlled by the drilling rig's intelligent control system. The sand layer density is fed back in real time by the in-hole detector. The mud density and viscosity are dynamically adjusted by increasing or decreasing the bentonite content. The drilling parameters and mud wall protection performance are dynamically adapted according to the real-time sand layer density, breaking the drawbacks of traditional fixed parameter construction. This achieves a dual balance between drilling speed and borehole stability, effectively preventing sand layer collapse and significantly improving the drilling efficiency in dense sand layers.

[0022] Please see Figure 1 , Figure 2 , Figure 3 and Figure 4 In the parametric drilling process of step two, a multi-stage filter structure is used for filtering sand impurities in the mud circulation. The pore size of the filter screen is dynamically changed according to the actual particle size of the returned sand during the drilling process. After the filtered mud is purified by sedimentation, it is reinjected into the hole to realize the recycling of mud. At the same time, it ensures that the wall protection effect of the hole does not decrease with the circulation of mud. The multi-stage filter screen has 2-3 filtration layers, and the pore size of the filter screen is selected according to the actual particle size of the returned sand, which is 0.5-2mm. The sedimentation tank adopts a three-stage sedimentation structure. After purification, the mud is reinjected after passing the index test. The multi-stage filter screen dynamically filters sand impurities, and together with the three-stage sedimentation, the mud is recycled. This reduces the waste of mud raw materials, ensures that the wall protection effect of mud does not decrease during the circulation process, continuously maintains the stability of the hole wall structure, and reduces the amount of sediment accumulation at the bottom of the hole during the drilling process.

[0023] Please see Figure 1 , Figure 2 , Figure 3 and Figure 4 In step three, the fine cleaning of the mud skin on the inner wall of the steel casing, high-pressure water flushing is carried out using multi-angle high-pressure nozzles that move vertically and uniformly along the inner wall of the casing. The flushing pressure is adjusted in real time according to the tightness of the mud skin adhesion. The mud impurities generated by flushing naturally flow into the bottom of the hole with the water flow. After the high-pressure water flushing is completed, a flexible scraper is used to scrape the inner wall of the casing in a circular motion. During the scraping process, the scraper is kept in consistent contact with the inner wall of the casing. The multi-angle high-pressure nozzles are set with 3-6 water outlet angles, a vertical movement speed of 0.2-0.5m / min, and a flushing pressure of 3-8MPa. Multi-angle high-pressure water flushing can evenly remove mud skin of different thicknesses. The uniform vertical movement ensures no dead corners in the flushing. The circular wall scraping and strict control of the contact ensure more uniform mud skin removal and avoid local mud skin residue. This reduces the obstruction effect of mud skin on the bonding between the pile foundation and the sand layer.

[0024] Please see Figure 1 , Figure 2 , Figure 3 and Figure 4 In step three, the fine cleaning of the mud skin on the inner wall of the steel casing, the flexible scraper is made of wear-resistant rubber. The scraping surface of the scraper is toothed to improve the scraping effect. After the toothed scraping is completed, the inner wall of the casing is rinsed again with low-pressure water to flush all the scraped mud skin debris to the bottom of the hole, thus completing the thorough cleaning of the mud skin on the inner wall of the casing. The wear-resistant rubber has a hardness of 60-80 Shore A, the tooth pitch of the toothed scraping surface is 5-10 mm, and the low-pressure water rinsing pressure is 0.3-0.8 MPa. During rinsing, the scraper moves in a circular and vertical reciprocating motion. The toothed wear-resistant rubber scraper greatly improves the scraping effect on the compacted mud skin. The second low-pressure water reciprocating rinse can thoroughly remove the scraped mud skin debris, achieving a thorough cleaning of the mud skin on the inner wall of the steel casing without dead angles, completely eliminating mud skin obstruction, and significantly improving the side friction resistance between the pile foundation and the sand layer.

[0025] Please see Figure 1 , Figure 2 , Figure 3 and Figure 4 In step four, the treatment of sediment at the bottom of the borehole, the mud circulation replacement method employs a reverse circulation mud process. Sediment, mud cake debris, and mud slurry at the bottom of the borehole are pumped together to a sedimentation tank outside the borehole. During the pumping process, the circulation flow rate of the mud slurry is strictly controlled to avoid disturbing the borehole wall and causing the sand layer to collapse. After pumping, the thickness of the sediment at the bottom of the borehole is checked. If it does not meet the standard, the replacement and cleaning operation is repeated until the sediment thickness meets the specifications for sand layer pile foundation construction. The circulation flow rate of the reverse circulation mud process is controlled at 1.0-1.5 m / s. The sediment thickness is measured using a measuring hammer. The specifications for sand layer pile foundations require a sediment thickness ≤ 50 mm. If the standard is not met, the number of pumping operations is repeated ≤ 2 times. The reverse circulation mud process precisely controls the circulation flow rate, efficiently pumping sediment while avoiding disturbance of the borehole wall and preventing borehole collapse. Repeated cleaning operations after testing ensure that the sediment thickness at the bottom of the borehole strictly meets the construction specifications, optimizes the construction environment inside the borehole, and provides good foundation conditions for subsequent concrete pouring.

[0026] Please see Figure 1 , Figure 2 , Figure 3 and Figure 4In the optimized concrete pouring process of step five, the water tightness and pressure bearing capacity of the entire pipe section are tested before the pouring duct is lowered. The duct is lowered only after passing the tests. During lowering, the duct is kept centered within the hole. The pouring rate is uniformly controlled during continuous concrete pouring. The duct depth is dynamically adjusted based on the real-time rise of the concrete surface to avoid concrete segregation, pile breakage, or slag inclusion caused by excessively deep or shallow duct burial. The water tightness and pressure bearing capacity of the pouring duct are tested using a water pressure test at a pressure of 0.6-1.0 MPa. The concrete pouring rate is controlled at 1-3 m³ / h, and the duct burial depth is maintained at 2-6 m. Early testing of the pouring duct prevents leakage problems from the outset. The combination of centered lowering, uniform pouring rate, and dynamic burial depth adjustment effectively avoids quality problems such as concrete segregation, pile breakage, and slag inclusion, ensuring the continuity and density of concrete pouring and significantly improving the quality of the pile foundation structure.

[0027] Please see Figure 1 , Figure 2 , Figure 3 and Figure 4 In step six, pile foundation curing and shaping, targeted moisturizing measures include tightly wrapping the exposed part of the pile body with geotextile and regularly sprinkling water to keep it moist. The curing time is adjusted according to the ambient temperature of the sand layer. The sand layer around the pile is compacted in layers using a small vibratory roller. The compaction range is the sand layer area with a preset radius around the pile foundation, which further enhances the density and lateral restraint of the sand layer around the pile, effectively improving the vertical bearing capacity and pull-out performance of the pile foundation. Non-woven geotextile is selected. The water sprinkling frequency is 1-2 hours / time in summer and 3-4 hours / time in winter. The layer compaction thickness of the small vibratory roller is ≤300mm, and the preset compaction radius around the pile is ≥2m. The moisturizing curing with appropriate temperature and humidity can ensure the steady development of concrete strength. The layer compaction of the sand layer around the pile effectively enhances the density and lateral restraint of the sand layer, allowing the pile foundation and the sand layer to form an integral force system, significantly improving the vertical bearing capacity and pull-out performance of the pile foundation, and meeting the engineering design requirements of dense sand layer pile foundations.

[0028] This scheme: Based on the geological characteristics of dense sand layers with poor cohesion and weak stability, this process focuses on full-process collaborative optimization. It establishes a stable construction foundation through pre-treatment with embedded steel casings, followed by parametric drilling to achieve efficient and stable borehole formation. Subsequently, it meticulously cleans the mud cake from the inner wall of the steel casing and treats sediment at the bottom of the borehole, thoroughly optimizing the construction environment within the borehole. Optimized concrete pouring ensures the density of the pile concrete. Finally, pile curing enhances the bond between the pile foundation and the sand layer, thereby improving bearing capacity. When using this method, first... The parameters of the steel casing are determined based on the distribution and density of the sand layer, and roughening, compaction, and reinforcement are completed. During hole formation, drilling parameters are dynamically adjusted by real-time monitoring of density, and mud filtration and circulation are carried out simultaneously. Mud cake removal is carried out by combining high-pressure water flushing with flexible scraping. Sediment treatment adopts reverse circulation mud technology and the thickness is monitored until it meets the standard. Before grouting, the guide pipe is inspected, and continuous grouting is carried out during construction with dynamic adjustment of the burial depth. Curing is carried out with appropriate moisturizing measures according to the site temperature and humidity, and the sand layer around the pile is compacted in layers. Each step is carried out in a progressive order.

[0029] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0030] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A drilling process for pile foundations in sandy geological layers, characterized in that, Includes the following steps: Step 1: Pre-treatment for steel casing installation: The burial depth and wall thickness of the steel casing are determined based on the stratigraphic distribution and compaction characteristics of the dense sand layer. After roughening the outer wall of the casing, it is buried in layers in conjunction with the sand layer compaction process. After burial, the top of the casing is fixed and reinforced. Step 2: Parametric Hole Formation Construction Rotary drilling rigs are used for hole formation operations. Drilling parameters are dynamically and collaboratively adjusted according to the real-time density of the sand layer, and the wall protection performance of the mud is controlled simultaneously. Sand particles and impurities are filtered during the mud circulation process. Step 3: Fine cleaning of mud cake on the inner wall of the steel casing: After the hole is formed, the inner wall of the casing is first flushed with high-pressure water, and then a flexible scraper is used to scrape the wall to remove the mud skin layers of different thicknesses layer by layer. Step 4: Treatment of sediment at the bottom of the borehole: After the mud skin is cleaned, the sediment at the bottom of the hole is pumped out and cleaned using the mud circulation and replacement method to control the thickness of the sediment at the bottom of the hole and optimize the construction environment inside the hole. Step 5: Optimized Concrete Pouring: After the sediment is treated, the grouting pipe is quickly lowered and concrete is poured using a continuous grouting method, with the burial depth of the pipe being dynamically adjusted. Step Six: Pile Foundation Curing and Shaping After the grouting is completed, targeted moisturizing and curing measures are taken according to the on-site temperature and humidity conditions of the sand layer geology. At the same time, the sand layer around the pile is compacted to strengthen the lateral restraint of the sand layer around the pile.

2. The pile foundation drilling process in sandy geological layers according to claim 1, characterized in that: In the pretreatment of steel casing installation in step one, the sand compaction process uses a vibratory hammer to compact the sand layer around the casing in layers. The vibration height of each layer is matched with the segmented depth of the casing installation. After vibration compaction, graded sand is used to fill the gap between the casing and the stratum. After filling, a small compaction device is used for preliminary compaction to make the casing fit with the sand layer.

3. The pile foundation drilling process in sandy geological layers according to claim 2, characterized in that: In the pretreatment of steel casing installation in step one, the roughening treatment of the outer wall of the casing is carried out by sandblasting. The particle size of the sandblasting is selected according to the density of the sand layer. After the roughening treatment, a thin layer of sand-fixing agent is applied to the outer wall of the casing. The casing installation is completed before the sand-fixing agent initially sets, which further enhances the adhesion between the casing and the sand layer.

4. The pile foundation drilling process in sandy geological layers according to claim 1, characterized in that: In the parameterized hole-forming construction of step two, the dynamic adjustment of drilling parameters includes the coordinated control of drilling speed, drilling pressure and drilling speed. When the sand layer density is high, the drilling speed is reduced and the drilling pressure is increased, and the specific gravity and viscosity of the mud are increased simultaneously. When the sand layer density is low, the drilling speed is increased and the drilling pressure is reduced, and the specific gravity of the mud is appropriately reduced to avoid excessive mud sediment.

5. The pile foundation drilling process in sandy geological layers according to claim 4, characterized in that: In the parameterized drilling construction of step two, the sand impurity filtration of the mud circulation adopts a multi-stage filter structure. The pore size of the filter is dynamically changed according to the actual particle size of the returned sand during the drilling process. The filtered mud is purified by sedimentation and then reinjected into the hole.

6. The pile foundation drilling process in sandy geological layers according to claim 1, characterized in that: In the third step of the fine cleaning of the mud skin on the inner wall of the steel casing, the high-pressure water flushing uses a multi-angle high-pressure nozzle to move vertically and uniformly along the inner wall of the casing. The flushing pressure is adjusted in real time according to the tightness of the mud skin adhesion. The mud impurities generated by the flushing naturally flow into the bottom of the hole with the water flow. After the high-pressure water flushing is completed, a flexible scraper is used to scrape the inner wall of the casing in a circular motion.

7. The pile foundation drilling process in sandy geological layers according to claim 6, characterized in that: In the third step of the fine cleaning of the mud on the inner wall of the steel casing, the flexible scraper is made of wear-resistant rubber. The scraping surface of the scraper is toothed to improve the scraping effect. After the toothed scraping is completed, the inner wall of the casing is rinsed again with low-pressure water to flush all the scraped mud debris to the bottom of the hole.

8. The pile foundation drilling process in sandy geological layers according to claim 1, characterized in that: In step four, the treatment of sediment at the bottom of the borehole, the mud circulation replacement method adopts a reverse circulation mud process, in which sediment, mud cake debris, and mud slurry at the bottom of the borehole are pumped together to a sedimentation tank outside the borehole. During the pumping process, the circulation flow rate of the mud slurry is strictly controlled to avoid disturbing the borehole wall due to excessive flow rate and causing the sand layer to collapse. After the pumping is completed, the thickness of sediment at the bottom of the borehole is checked. If it does not meet the standard, the replacement and cleaning operation is repeated until the sediment thickness meets the specifications for sand layer pile foundation construction.

9. The pile foundation drilling process in sandy geological layers according to claim 1, characterized in that: In the optimized concrete pouring of step five, the water tightness and pressure bearing capacity of the entire pipe section are tested before the pouring pipe is lowered. It is lowered only after the test is qualified. During the lowering, the pipe is arranged in the center of the hole. The pouring rate is uniformly controlled during the continuous concrete pouring process. The burial depth of the pipe is dynamically adjusted according to the real-time rise of the concrete pouring surface.

10. The pile foundation drilling process in sandy geological layers according to claim 1, characterized in that: In the pile foundation curing and forming process of step six, the targeted moisturizing curing measures involve tightly wrapping the exposed part of the pile body with geotextile and sprinkling water to keep it moist at regular intervals. The curing time is adjusted according to the ambient temperature of the sand layer. The sand layer around the pile is compacted in layers using a small vibratory roller, and the compaction range is the sand layer area with a preset radius around the pile foundation.

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