A method for graded treatment and composite pile construction of bridge pile foundations in strongly developed karst geology

Abstract

The present invention belongs to the technical field of karst geological bridge foundation construction and foundation treatment, and discloses a method for graded treatment and composite pile construction of bridge pile foundations in strongly developed karst geological conditions. Through advanced geological exploration and karst grade classification, construction methods are reasonably selected for different cave types to achieve on-demand treatment and graded construction, effectively avoiding material waste and excessive grouting caused by construction; conventional bored piles are directly used for areas with tiny pores to simplify the process and save costs; low-pressure grouting and synchronous grouting are designed for isolated caves and through caves respectively to reduce treatment difficulty and improve on-site resource utilization; this method has extremely strong on-site adaptability and can flexibly cope with complex and changeable karst structures. By adopting a multi-segment isolation conduit structure and combining it with an intelligent grouting-grouting synchronous control system, segmented independent grouting is effectively achieved to prevent slurry cross-flow or concrete loss between different construction depths.

Description

Technical Field

[0001] The present invention belongs to the technical field of karst geological bridge foundation construction and foundation treatment, and specifically relates to a method for graded treatment and composite pile construction of strongly developed karst geological bridge pile foundations. Background Art

[0002] In existing bridge pile foundation construction, when encountering a strongly developed karst geological environment, the traditional pile foundation treatment technologies commonly used, such as conventional cast-in-place piles, rock-embedded piles, grouting reinforcement, and pile end expansion methods, are difficult to simultaneously meet the requirements of pile foundation quality, construction safety, and engineering economy.

[0003] Strongly developed karst areas usually have the typical characteristics of irregular karst distribution, complex cave morphology, and multi-level penetration. If conventional processes are used, concrete loss, broken piles and pile structure defects are very likely to occur during the grouting process, seriously affecting project safety. Especially when dealing with large or highly penetrated caves, the existing grouting technology often has poor reinforcement effect and high construction risk due to factors such as difficulty in controlling the grouting volume, high grouting costs, and interference of flowing water in the grouting effect.

[0004] In addition, the traditional single pile type is difficult to effectively adapt to different cave levels, and the existing construction plan lacks specificity and flexibility, which easily leads to problems such as strong construction rigidity, large economic investment, and low construction efficiency. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for graded treatment and composite pile construction of bridge pile foundations in strongly developed karst geology to solve the problems raised in the above background technology.

[0006] To achieve the above-mentioned object, the present invention provides the following technical solution: a method for graded treatment and composite pile construction of bridge pile foundations in strongly developed karst geology. The specific steps of the method for graded treatment and composite pile construction of bridge pile foundations in strongly developed karst geology are as follows:

[0007] S1, Advanced geological exploration and karst classification: Through advanced geological exploration, the karst distribution and water flow conditions in the pile foundation path are understood, and the karst is divided into three categories, providing a basis for subsequent process selection;

[0008] S2, Karst graded treatment process design: formulate graded treatment plans according to karst grade, design reasonable grouting pressure and construction technology for different karst types to ensure targeted treatment;

[0009] S3, drilling construction and dynamic karst verification: real-time monitoring of drilling parameters during drilling construction, dynamic verification of karst grade, and timely adjustment of construction plan if it does not match the design to ensure accurate matching;

[0010] S4, installation of segmented isolation conduits and construction of grouting system: Install segmented isolation conduits in the borehole. The conduits are equipped with remote grouting valves and grouting stoppers to achieve multi-segment independent grouting and effectively prevent cross-flow of slurry.

[0011] S5, Segmented Grouting and Sealing of Caves: Prioritize segmented grouting for Grade II and Grade III caves, monitor the grouting status in real time, seal the caves segment by segment, and automatically close the grouting valves after grouting is completed.

[0012] S6, grouting-pouring synchronous intelligent control construction: After grouting is stable, concrete pouring is started. The grouting and pouring rhythm are controlled in real time through the intelligent linkage system to ensure synchronous construction and prevent concrete loss;

[0013] S7, Composite pile structure construction and pile type optimization configuration: A composite pile structure is set up in the through-cavern area, with a reasonable configuration of main cast-in-place piles, auxiliary grouting piles, and cavity control piles to meet the bearing requirements of complex strata;

[0014] S8, real-time monitoring and dynamic adjustment of construction parameters throughout the entire process: Various parameters are collected in real time during the construction process and monitoring records are established. If the detection data is abnormal, the construction parameters are adjusted in time or the operation is suspended to ensure safety;

[0015] S9, pile quality inspection and construction closed-loop feedback: After the construction is completed, pile quality inspection is carried out, and the pile foundation quality is verified through sound wave transmission, grouting filling rate and core drilling inspection to ensure the quality of the project construction.

[0016] Preferably, the specific steps of the advanced geological exploration and karst delineation in S1 are as follows:

[0017] S11. Determination of advanced geological exploration paths and information acquisition: Prior to bridge pile foundation construction, advance geological exploration along the construction path is prioritized. Using a combination of geological radar scanning, advanced horizontal drilling, and core drilling, the distribution of karst, pore development characteristics, and groundwater flow within the pile foundation area can be fully understood. This exploration process not only reveals the extent of karst development but also identifies the rock layer structure and karst cave media in advance, providing key guidance for the subsequent hierarchical construction process design.

[0018] S12, Karst grade classification and reasonable design of grouting pressure: Based on the results of geological exploration, the identified karst is classified into grades according to pore size, cave structure and through-flow conditions. The karst is divided into Grade I micro-pore area, Grade II isolated cave area and Grade III through-flow large cave area. For caves of different grades, the grouting pressure is reasonably designed. It is necessary to fully consider the static pressure formed by the slurry's own weight and the cave depth. At the same time, ensure that an additional safety pressure is set to overcome the internal resistance of the complex karst and prevent slurry loss.

[0019] Preferably, the specific steps of the karst graded treatment process design in S2 are as follows:

[0020] S21. Overall formulation of karst graded treatment processes: Based on the results of advanced geological surveys and karst grade classification, rationally formulate graded treatment processes for different karst grades. For Grade I micro-pore areas, conventional cast-in-place pile penetration construction is used. Such pores have little impact on pile foundation formation and do not require additional reinforcement. For Grade II isolated karst cave areas, local grouting reinforcement of the caves is required before pile foundation construction to prevent slurry loss or pile fracture during concrete pouring.

[0021] S22, grouting reinforcement parameter design and level III complex cave treatment: low-pressure grouting technology is used for grouting in level II cave areas. The grouting pressure needs to comprehensively consider the depth of the cave and the gravity of the grouting material itself to ensure that the slurry enters the cave smoothly, while avoiding damage to the cave structure caused by excessive pressure. For level III through-type large cave areas, multi-section isolation conduits are designed, and segmented grouting and concrete simultaneous pouring technology are adopted to ensure that caves of different depths are effectively blocked step by step to prevent concrete loss and slurry cross-flow.

[0022] The construction method of the present invention follows the treatment principle of "adapting to local conditions, grading and classification, reasonable reinforcement, economy and high efficiency", that is, according to the results of advanced geological exploration, karst is divided into different types such as tiny pores, isolated caves and through caves, and targeted selection of conventional grouting, low-pressure grouting or segmented grouting and synchronous grouting processes; through the graded treatment method that varies according to the cave, the pile type and reinforcement means are scientifically configured, effectively improving the construction quality, reducing the construction difficulty and cost, and realizing the safe and efficient construction of bridge pile foundations in complex karst areas.

[0023] Preferably, the specific steps of the drilling construction and dynamic karst verification in S3 are as follows:

[0024] S31, Drilling Construction and Real-time Data Collection: Drilling construction is carried out along the designed path of the bridge pile foundation. By real-time monitoring of drilling resistance, drilling rate, and changes in rock debris during the drilling process, drilling process parameters are continuously collected. By comparing the current drilling status with the estimated rock formation resistance data obtained from advanced geological surveys, the actual distribution of karst in the drilling path can be dynamically monitored. This monitoring process provides basic data support for determining whether the on-site karst grade meets the design, ensuring real-time control of the construction process.

[0025] The expression formula of drilling pressure dynamic deviation is:

[0026] ;

[0027] Where, Drilling pressure deviation (kN), Actual drilling resistance (kN), Advance detection of expected drilling resistance (kN);

[0028] During the drilling process, the karst grade or drilling status can be identified in real time to determine whether the drilling has entered an unexpected weak stratum or cave area.

[0029] Drilling resistance deviation directly reflects the formation changes along the drilling path. By continuously comparing real-time resistance with the resistance predicted by advance detection, drilling path anomalies can be quickly detected, facilitating dynamic adjustment of drilling parameters or suspension of construction to ensure drilling quality and construction safety.

[0030] S32, drilling deviation analysis and dynamic process adjustment: During the drilling process, dynamic deviation analysis is performed based on the difference between real-time monitoring data and the design predicted resistance. By real-time judgment of the amplitude of change in drilling resistance, the deviation between the size or structure of the cave and the design prediction can be identified in time. When the resistance deviation is monitored to exceed the allowable range, the drilling operation should be suspended immediately, and the subsequent treatment process should be adjusted according to the actual karst situation to ensure that the pile foundation construction path is accurately matched with the karst grade to prevent construction risks caused by deviations.

[0031] Preferably, the specific steps of installing the segmented isolation conduit and constructing the grouting system in S4 are as follows:

[0032] S41, Segmented Isolation Conduit Structure Design and Installation Process: After drilling is completed, a segmented isolation conduit is installed in the pile hole according to the predetermined design. The isolation conduit consists of multiple independent grouting chambers, which are rationally separated along the depth direction and stably connected via dedicated interfaces. The isolation conduit structure ensures segmented and independent grouting operations at different construction depths, while meeting the requirements for precise control of the grouting path in complex karst environments and effectively supporting subsequent staged plugging construction.

[0033] S42, grouting valve control and grouting stop structure function: Each grouting section of the isolation conduit is equipped with a mechanical or electrically controlled grouting valve. The grouting valve supports remote opening and closing control to ensure that the grouting operation of each section can be carried out independently and orderly. Stepped grouting stop gaskets are set between the grouting sections of the conduit. The grouting stop gaskets are sealed through the structure to effectively prevent the slurry from flowing and diffusing between different grouting sections, ensuring a clear slurry filling path. This structural design is conducive to grouting multiple caves in sequence, improving the sealing accuracy and grouting quality.

[0034] Preferably, the specific steps of the segmented grouting and plugging construction of the cave in S5 are as follows:

[0035] S51, grouting process parameter monitoring and grouting section priority control: Prioritize grouting construction in Grade II and Grade III cave areas. Use a real-time grouting monitoring system to continuously monitor grouting pressure, flow rate, and slurry filling rate. Real-time monitoring ensures that the grouting process is within a safe and effective range to prevent abnormal pressure or uncontrolled grouting speed. During construction, grouting is carried out step by step in strict accordance with the segmented design, with priority given to plugging larger caves. The grouting path is effectively controlled to ensure that the slurry enters the designated cave area smoothly and does not diffuse ineffectively.

[0036] The calculation formula of grouting design pressure is:

[0037] ;

[0038] Where, Grouting design pressure (MPa), Unit weight of grouting slurry (kN / m3), Depth of slurry static pressure action (m), The additional safety pressure required for cave plugging (MPa) is usually 0.1-0.3MPa;

[0039] Ensure that the grouting pressure matches the cave depth, slurry density, and actual on-site working conditions to ensure that the slurry can fully enter the cave for effective filling, while avoiding rock damage or further cave expansion due to excessive grouting pressure;

[0040] Karst strata have different pore connectivity, so the grouting pressure must be compatible with the static pressure of the slurry and the additional pressure required to seal the caves. Too low a pressure will result in incomplete filling, while too high a pressure may damage the surrounding rock structure. Therefore, designing reasonable grouting parameters by combining static pressure and safety pressure is a necessary means to control construction risks.

[0041] The calculation formula of grouting filling rate is:

[0042] ;

[0043] Where, Grouting filling rate The actual volume of slurry injected (m3), Target cave design volume , used to monitor in real time whether the grouting has achieved the designed filling effect, and automatically adjust the grouting when the filling rate is lower than the warning value;

[0044] Real-time monitoring of grouting construction results to ensure that the grout filling the cave reaches the designed saturation, and to prevent the grout from not effectively filling the target space or excessive injection resulting in material waste;

[0045] The filling rate is a key indicator for judging grouting quality. By calculating the ratio of the actual grouting volume to the designed volume of the target cave, it can accurately reflect whether the grouting has met the standards. Real-time understanding of the filling rate helps to dynamically adjust the grouting flow rate or suspend construction, preventing excessive or insufficient grouting and improving the reinforcement effect.

[0046] S52, grouting diffusion control and valve closure management: Based on the grouting flow rate, grouting time, cave porosity, and formation permeability, scientifically evaluate the reasonable diffusion range of slurry in the karst, ensure that each grouting section has an effective grouting radius, and prevent slurry from spreading to non-construction areas. By controlling the slurry diffusion range and actual filling conditions, the grouting is guaranteed to be full and without excess loss. After grouting is completed, the grouting valve automatically closes, promptly sealing the current grouting section to prevent slurry backflow and cross-flow between sections.

[0047] The formula for estimating the grouting diffusion radius is:

[0048] ;

[0049] Where, Slurry diffusion radius (m), Grouting flow rate (m³ / min), Grouting time (min), Karst porosity (value ranges from 0.01 to 0.1), Karst unit water discharge rate (m / min);

[0050] Reasonably control the diffusion range of slurry in karst structures to ensure that the slurry effectively fills the target caves without excessive diffusion into non-construction areas, thereby avoiding slurry loss and grouting failure;

[0051] The grouting flow rate, time, karst porosity and formation permeability jointly determine the actual diffusion range of the slurry; by setting the diffusion radius control, it is ensured that the grouting operation only exerts a reinforcement effect within the designed area, preventing the slurry from entering unrelated cavities or channels, thereby ensuring construction safety and material utilization.

[0052] Preferably, the specific steps of the grouting-pouring synchronous intelligent control construction in S6 are as follows:

[0053] S61, Synchronous Construction Start and Grouting Stability Confirmation: When the segmented grouting construction is completed and the monitoring system confirms that the grouting pressure is stable, the concrete pouring operation is immediately started. The concrete pouring must be kept continuous with the grouting operation to avoid construction interruptions, slurry backflow, or local instability of the cave. To ensure the overall coordination of the construction rhythm, an intelligent linkage control system is used to synchronize the grouting and pouring processes to ensure that the slurry is continuously sealed while the concrete is smoothly poured into the pile hole.

[0054] The synchronous expression formula of injection speed and grouting flow rate is:

[0055] ;

[0056] Where, Concrete pouring speed (m³ / min), Grouting flow rate (m³ / min), Synchronous adjustment coefficient (recommended value 0.8~1.0);

[0057] Ensure that the concrete pouring speed is consistent with the grouting flow rate to avoid the concrete breaking through the grout due to excessively rapid pouring or the grout backflow due to excessively slow pouring;

[0058] Grouting and pouring are synchronous construction processes. Mismatched rhythms can easily lead to quality defects. By setting a reasonable synchronization adjustment coefficient, a dynamic linkage relationship between the pouring speed and the grouting flow rate is established to ensure that the slurry and concrete are formed and advanced synchronously, maintaining pouring stability.

[0059] S62, real-time synchronous adjustment and grouting rhythm control: The intelligent linkage control system collects grouting flow rate and grouting rate data in real time, and maintains a dynamic matching relationship between the two according to preset construction parameters; synchronous control requires reasonable adjustment of the concrete pouring speed to form a coordinated ratio with the current grouting flow rate to prevent the concrete from breaking through the slurry defense line due to fast pouring speed, or the slurry from backflowing due to slow pouring. The system effectively guarantees the stability and quality reliability of the synchronous construction process through linkage ratio adjustment and real-time feedback.

[0060] Preferably, the specific steps of the composite pile structure construction and pile type optimization configuration in S7 are as follows:

[0061] S71. Rational configuration and pile type design of composite pile structures: For through-hole karst cave areas, composite pile structures are preferred to ensure that the pile foundation can stably penetrate large-span karst caves and meet stress safety requirements. The composite pile structure consists of main cast-in-place piles, auxiliary grouting piles, and cavity control piles. The main cast-in-place piles are located at the core of the pile hole to carry the main vertical load. The auxiliary grouting piles are placed below the karst cave to enhance the stability of the lower blockage. The cavity control piles are placed above the karst cave to effectively support the cave roof and prevent collapse.

[0062] S72, Coordinated force mechanism and bearing capacity assessment of composite piles: The various types of composite piles are rationally arranged according to the karst cave morphology, load transfer path and foundation bearing characteristics. The main cast-in-place piles mainly provide end bearing, while the auxiliary grouting piles and cavity control piles jointly participate in the bearing through side friction resistance. During the construction design phase, the overall bearing capacity needs to be scientifically assessed based on the force-bearing area and force transfer path of each pile type. The total bearing capacity of the composite pile is composed of the end resistance of the main pile and the side friction resistance of each pile, ensuring that the pile foundation structure has sufficient stability and safety margin in the complex karst environment.

[0063] Preferably, the specific steps of real-time monitoring and dynamic adjustment of construction parameters throughout the entire process in S8 are as follows:

[0064] S81, Establishment of a full-process data collection and construction monitoring system: During the construction of bridge pile foundations, all stages of drilling, grouting, and concrete pouring must be monitored in real time. By installing drilling parameter acquisition devices, grouting pressure and flow rate monitors, and a concrete pouring status tracking system, key data from the construction process can be comprehensively recorded. The construction monitoring system simultaneously collects dynamic parameters such as drilling resistance, grouting filling ratio, and pouring rate, establishing detailed construction monitoring records to ensure complete and traceable data from each process step.

[0065] S82, monitoring data analysis and real-time response to abnormal working conditions: During construction, various parameters collected by the monitoring system should be continuously compared and analyzed in real time, and abnormal working conditions should be identified in a timely manner through preset safety thresholds; when the monitoring results show that the drilling resistance, grouting pressure or injection speed exceeds the reasonable design range, the system will immediately issue an early warning; the construction parameters should be adjusted in a timely manner according to the type of abnormality on site, and the drilling speed, grouting flow rate or injection rhythm should be adjusted. If necessary, construction should be suspended for inspection to ensure that the construction process is always in a controllable and safe state.

[0066] Preferably, the specific steps of pile quality detection and construction closed-loop feedback in S9 are as follows:

[0067] S91, Pile Quality Inspection Methods and Data Confirmation: After construction is completed, a comprehensive quality inspection of the bridge pile foundation should be conducted. The accuracy of the inspection results should be verified through the acoustic transmission method, grouting filling rate testing, and drill core sampling. The acoustic transmission method measures the propagation time of sound waves within the pile body to determine whether there are voids, interlayers, or defects in the pile structure. Changes in propagation time are closely related to the density of the pile material. Combined with the grouting filling rate and drill core structure test results, it can effectively confirm whether the karst cave is completely blocked.

[0068] The formula for sound wave transmission time is:

[0069] ;

[0070] Where, Sound wave propagation time (ms), Sound wave transmission path distance (mm), Sound wave propagation speed (mm / ms);

[0071] Accurately test the quality of piles to determine whether there are cavities, interlayers or structural defects in the pile body, ensuring that the integrity of the pile body meets the design standards;

[0072] The propagation time of acoustic waves is highly correlated with the density of the material within the pile. Using acoustic transmission to measure the propagation delay can effectively determine the location and extent of pile defects. This is a mature and intuitive quality inspection method currently used in the industry.

[0073] S92, Handling of detection anomalies and subsequent process adjustments: During the detection process, if the sound wave transmission time is obviously abnormal, the grouting is insufficiently filled, or there are structural defects in the drill core sample, it should be promptly identified as an abnormal pile quality. For abnormal detection situations, the construction unit needs to analyze the cause of the abnormality in detail and promptly feedback the test results to the process adjustment link. In the subsequent construction of the same type of pile foundation, it is necessary to optimize the grouting pressure, pouring rhythm or composite pile configuration parameters based on the problems that have been found to ensure the stable and reliable quality of the entire bridge foundation project.

[0074] The beneficial effects of the present invention are as follows:

[0075] 1. The present invention uses advanced geological exploration and karst grade classification to rationally select construction methods for different cave types, realize on-demand treatment and graded construction, and effectively avoid material waste and excessive grouting caused by construction; conventional bored piles are directly used for areas with tiny pores, simplifying the process and saving costs; low-pressure grouting and synchronous grouting are designed for isolated caves and through caves respectively, reducing the difficulty of treatment and improving on-site resource utilization; this construction method has strong on-site adaptability and can flexibly cope with complex and changeable karst structures, ensuring both construction efficiency and economic benefits.

[0076] 2. The present invention adopts a multi-section isolation conduit structure and combines it with an intelligent grouting-pouring synchronous control system to effectively realize segmented independent grouting, prevent slurry cross-flow or concrete loss between different construction depths, and reduce the risk of broken piles and voids; the real-time monitoring system can dynamically feedback the grouting flow rate, pressure and pouring rate to ensure the precise synchronization of grouting and pouring rhythm, and further control the safety of the construction process; through the full process control of this method, the integrity of the pile body and the quality of the pile body molding can be greatly improved, reducing the uncontrollable risks of bridge pile foundation construction in karst areas.

[0077] 3. The present invention introduces a composite pile structure and realizes all-round support for different cave spaces through a reasonable combination of main cast-in-place piles, auxiliary grouting piles and cavity control piles. The auxiliary grouting piles effectively reinforce the weak area below the cave to prevent the pile foundation from sinking; the cavity control piles provide continuous support for the upper arch structure of the cave to prevent the cave from collapsing in the later period; a multi-path joint bearing system is formed between the main cast-in-place piles, side friction resistance and auxiliary structure piles, which greatly improves the overall bearing capacity of the pile foundation and the foundation reinforcement effect, and significantly improves the long-term use stability and anti-destruction ability of the bridge foundation in karst areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1This is a flow chart of the method for graded treatment and composite pile construction of bridge pile foundations in strongly developed karst geology according to the present invention. DETAILED DESCRIPTION

[0079] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0080] like Figure 1 As shown, the embodiment of the present invention provides a method for graded treatment and composite pile construction of bridge pile foundations in strongly developed karst geology. The specific steps of the method for graded treatment and composite pile construction of bridge pile foundations in strongly developed karst geology are as follows:

[0081] S1. Advanced geological exploration and karst classification: At a bridge pile foundation construction site, high-frequency geological radar was used to scan the entire pile foundation path. Combined with horizontal drilling sampling, the drilling depth reached 40 meters, and core drilling was carried out at intervals along the path. On-site testing results showed the presence of multiple karst development zones along the drilling path. Based on the advanced exploration data, the karst was divided into Class I micropore areas, Class II isolated cave areas, and Class III through-hole large cave areas. A detailed karst distribution profile was generated as a basis for subsequent processing.

[0082] S2, Karst graded treatment process design. Based on the on-site karst zoning results, the Class I area is designed to use conventional bored piles for direct penetration; the Class II area uses a local low-pressure grouting process, controlling the grouting pressure at around 0.4 MPa to prevent the slurry from spreading too quickly; the Class III area is equipped with multiple isolation conduits, and a staged grouting and simultaneous grouting process is designed to ensure that the through caves can be blocked in sequence. The grouting segment division and conduit installation depth are optimized based on the on-site cave distribution and pile diameter.

[0083] S3, drilling construction and dynamic karst verification: Pile holes were drilled using an impact drill, with real-time monitoring of drilling resistance and footage speed. At 12 meters, the drilling resistance decreased significantly, exceeding the warning value with the preset resistance. Drilling was immediately suspended on-site, and testing confirmed that the Class II karst cave area had been entered ahead of schedule. The construction plan was adjusted, and grouting reinforcement was carried out in advance before drilling continued. The final drilling depth met the design requirements.

[0084] S4, Installation of Segmented Isolation Conduits and Construction of Grouting System: After drilling is completed, three sections of isolation conduits are installed along the borehole. Each section is equipped with a mechanical grouting valve, which is remotely controlled via an external electrical control box. The isolation conduits are segmented and sealed with grouting gaskets to ensure that grouting at different depths does not interfere with each other. After the conduit is installed, the grouting valve opening and closing functions are debugged on-site to confirm that each grouting section is unobstructed and controllable.

[0085] S5, Segmented Grouting and Sealing of Karst Caves: For Grade II and Grade III karst caves, cement-water glass composite slurry is used for grouting. The flow rate and pressure of the grouting system are preset before grouting begins. During the grouting process, the grouting flow rate, pressure, and filling rate are tracked in real time through the grouting monitoring system to control the segmented grouting. When the filling rate reaches the designed value, the grouting valve of the current segment is automatically closed and the next segment grouting is started to ensure the effective segmented sealing effect of the grouting.

[0086] S6, grouting and pouring synchronous intelligent control construction: After the grouting pressure stabilizes, concrete pouring is immediately started. The grouting and pouring processes are synchronously managed by an intelligent linkage control system. The concrete pouring speed is matched with the grouting flow rate in real time, and the linkage system dynamically adjusts the rhythm to ensure the continuous advancement of slurry and concrete. Slurry backflow or concrete loss is avoided during construction to ensure the continuous formation of the pile foundation.

[0087] S7, Composite Pile Structure Construction and Pile Type Optimization: In the Class III through-hole area, main cast-in-place piles were constructed with a designed diameter of 1.2 meters. Auxiliary grouting piles with a diameter of 0.8 meters were placed on both sides of the main piles and reinforced grouting was injected below the cave. Cavity control piles with a diameter of 0.7 meters were installed above the cave to control the stability of the upper arch structure. Based on the finite element simulation results, the spacing between the auxiliary piles and the control piles was adjusted on-site to ensure coordinated force distribution across the composite pile structure.

[0088] S8, real-time monitoring and dynamic adjustment of construction parameters throughout the entire construction process: A monitoring system records data such as drilling pressure, grouting flow rate, grouting pressure, and concrete injection rate throughout the construction process. The monitoring system sets safety thresholds for each parameter and determines in real time whether there are any anomalies. If a sudden increase in local pressure is detected during grouting, the system issues an early warning, adjusts the grouting flow rate on-site, and temporarily suspends grouting. Construction continues only after confirming that the construction status has returned to normal.

[0089] S9, pile quality inspection and construction closed-loop feedback: After construction, the pile quality is inspected using the acoustic wave transmission method, with the inspection points spaced 50 cm apart. The acoustic wave transmission results show that the overall propagation time of the pile body is uniform and the pile body integrity is good. The grouting filling rate test confirms that the slurry is fully filled, and core sampling verifies that the pile body has no obvious defects. For areas with low local density found during the inspection, the grouting flow rate and pouring rhythm parameters of subsequent similar pile foundations are adjusted to ensure the overall project quality.

[0090] The specific steps of advanced geological exploration and karst delineation in S1 are as follows:

[0091] S11. Determination of advanced geological exploration paths and information acquisition: Prior to bridge pile foundation construction, advance geological exploration along the construction path is prioritized. Using a combination of geological radar scanning, advanced horizontal drilling, and core drilling, the distribution of karst, pore development characteristics, and groundwater flow within the pile foundation area can be fully understood. This exploration process not only reveals the extent of karst development but also identifies the rock layer structure and karst cave media in advance, providing key guidance for the subsequent hierarchical construction process design.

[0092] S12, Karst grade classification and reasonable design of grouting pressure: Based on the results of geological exploration, the identified karst is classified into grades according to pore size, cave structure and through-flow conditions. The karst is divided into Grade I micro-pore area, Grade II isolated cave area and Grade III through-flow large cave area. For caves of different grades, the grouting pressure is reasonably designed. It is necessary to fully consider the static pressure formed by the slurry's own weight and the cave depth. At the same time, ensure that an additional safety pressure is set to overcome the internal resistance of the complex karst and prevent slurry loss.

[0093] The specific steps of the karst graded treatment process design in S2 are as follows:

[0094] S21. Overall formulation of karst graded treatment processes: Based on the results of advanced geological surveys and karst grade classification, rationally formulate graded treatment processes for different karst grades. For Grade I micro-pore areas, conventional cast-in-place pile penetration construction is used. Such pores have little impact on pile foundation formation and do not require additional reinforcement. For Grade II isolated karst cave areas, local grouting reinforcement of the caves is required before pile foundation construction to prevent slurry loss or pile fracture during concrete pouring.

[0095] S22, grouting reinforcement parameter design and level III complex cave treatment: low-pressure grouting technology is used for grouting in level II cave areas. The grouting pressure needs to comprehensively consider the depth of the cave and the gravity of the grouting material itself to ensure that the slurry enters the cave smoothly, while avoiding damage to the cave structure caused by excessive pressure. For level III through-type large cave areas, multi-section isolation conduits are designed, and segmented grouting and concrete simultaneous pouring technology are adopted to ensure that caves of different depths are effectively blocked step by step to prevent concrete loss and slurry cross-flow.

[0096] The specific steps of drilling construction and dynamic karst verification in S3 are as follows:

[0097] S31, Drilling Construction and Real-time Data Collection: Drilling construction is carried out along the designed path of the bridge pile foundation. By real-time monitoring of drilling resistance, drilling rate, and changes in rock debris during the drilling process, drilling process parameters are continuously collected. By comparing the current drilling status with the estimated rock formation resistance data obtained from advanced geological surveys, the actual distribution of karst in the drilling path can be dynamically monitored. This monitoring process provides basic data support for determining whether the on-site karst grade meets the design, ensuring real-time control of the construction process.

[0098] The expression formula of drilling pressure dynamic deviation is:

[0099] ;

[0100] Where, Drilling pressure deviation (kN), Actual drilling resistance (kN), Predicted drilling resistance (kN) is detected in advance; it is used to determine in real time whether the drilling process has entered karst or abnormally weak formations. When the deviation exceeds the limit, the drilling process is automatically suspended and the process is adjusted.

[0101] S32, drilling deviation analysis and dynamic process adjustment: During the drilling process, dynamic deviation analysis is performed based on the difference between real-time monitoring data and the design predicted resistance. By real-time judgment of the amplitude of change in drilling resistance, the deviation between the size or structure of the cave and the design prediction can be identified in time. When the resistance deviation is monitored to exceed the allowable range, the drilling operation should be suspended immediately, and the subsequent treatment process should be adjusted according to the actual karst situation to ensure that the pile foundation construction path is accurately matched with the karst grade to prevent construction risks caused by deviations.

[0102] The specific steps for installing the segmented isolation duct and constructing the grouting system in S4 are as follows:

[0103] S41, Segmented Isolation Conduit Structure Design and Installation Process: After drilling is completed, a segmented isolation conduit is installed in the pile hole according to the predetermined design. The isolation conduit consists of multiple independent grouting chambers, which are rationally separated along the depth direction and stably connected via dedicated interfaces. The isolation conduit structure ensures segmented and independent grouting operations at different construction depths, while meeting the requirements for precise control of the grouting path in complex karst environments and effectively supporting subsequent staged plugging construction.

[0104] S42, grouting valve control and grouting stop structure function: Each grouting section of the isolation conduit is equipped with a mechanical or electrically controlled grouting valve. The grouting valve supports remote opening and closing control to ensure that the grouting operation of each section can be carried out independently and orderly. Stepped grouting stop gaskets are set between the grouting sections of the conduit. The grouting stop gaskets are sealed through the structure to effectively prevent the slurry from flowing and diffusing between different grouting sections, ensuring a clear slurry filling path. This structural design is conducive to grouting multiple caves in sequence, improving the sealing accuracy and grouting quality.

[0105] The specific steps for the segmented grouting and plugging of the S5 cave are as follows:

[0106] S51, grouting process parameter monitoring and grouting section priority control: Prioritize grouting construction in Grade II and Grade III cave areas. Use a real-time grouting monitoring system to continuously monitor grouting pressure, flow rate, and slurry filling rate. Real-time monitoring ensures that the grouting process is within a safe and effective range to prevent abnormal pressure or uncontrolled grouting speed. During construction, grouting is carried out step by step in strict accordance with the segmented design, with priority given to plugging larger caves. The grouting path is effectively controlled to ensure that the slurry enters the designated cave area smoothly and does not diffuse ineffectively.

[0107] The calculation formula of grouting design pressure is:

[0108] ;

[0109] Where, Grouting design pressure (MPa), Unit weight of grouting slurry (kN / m3), Depth of slurry static pressure action (m), Additional safety pressure required for cave plugging (MPa), usually 0.1-0.3MPa; used to calculate the reasonable grouting pressure for Class II and Class III caves, to ensure that the grouting pressure can fill the cave without being too high to cause rock damage;

[0110] The calculation formula of grouting filling rate is:

[0111] ;

[0112] Where, Grouting filling rate The actual volume of slurry injected (m3), Target cave design volume , used to monitor in real time whether the grouting has achieved the designed filling effect, and automatically adjust the grouting when the filling rate is lower than the warning value;

[0113] S52, grouting diffusion control and valve closure management: Based on the grouting flow rate, grouting time, cave porosity, and formation permeability, scientifically evaluate the reasonable diffusion range of slurry in the karst, ensure that each grouting section has an effective grouting radius, and prevent slurry from spreading to non-construction areas. By controlling the slurry diffusion range and actual filling conditions, the grouting is guaranteed to be full and without excess loss. After grouting is completed, the grouting valve automatically closes, promptly sealing the current grouting section to prevent slurry backflow and cross-flow between sections.

[0114] The formula for estimating the grouting diffusion radius is:

[0115] ;

[0116] Where, Slurry diffusion radius (m), Grouting flow rate (m³ / min), Grouting time (min), Karst porosity (value ranges from 0.01 to 0.1), Karst unit water discharge rate (m / min); used to evaluate the diffusion effect of slurry in karst and prevent excessive grouting or slurry loss.

[0117] The specific steps of the S6 grouting-pouring synchronous intelligent control construction are as follows:

[0118] S61, Synchronous Construction Start and Grouting Stability Confirmation: When the segmented grouting construction is completed and the monitoring system confirms that the grouting pressure is stable, the concrete pouring operation is immediately started. The concrete pouring must be kept continuous with the grouting operation to avoid construction interruptions, slurry backflow, or local instability of the cave. To ensure the overall coordination of the construction rhythm, an intelligent linkage control system is used to synchronize the grouting and pouring processes to ensure that the slurry is continuously sealed while the concrete is smoothly poured into the pile hole.

[0119] The synchronous expression formula of injection speed and grouting flow rate is:

[0120] ;

[0121] Where, Concrete pouring speed (m³ / min), Grouting flow rate (m³ / min), Synchronous adjustment coefficient (recommended value 0.8~1.0); used for grouting-pouring synchronous control to ensure the same rhythm of the two and prevent concrete loss;

[0122] S62, real-time synchronous adjustment and grouting rhythm control: The intelligent linkage control system collects grouting flow rate and grouting rate data in real time, and maintains a dynamic matching relationship between the two according to preset construction parameters; synchronous control requires reasonable adjustment of the concrete pouring speed to form a coordinated ratio with the current grouting flow rate to prevent the concrete from breaking through the slurry defense line due to fast pouring speed, or the slurry from backflowing due to slow pouring. The system effectively guarantees the stability and quality reliability of the synchronous construction process through linkage ratio adjustment and real-time feedback.

[0123] The specific steps for the construction of composite pile structures and pile type optimization in S7 are as follows:

[0124] S71. Rational configuration and pile type design of composite pile structures: For through-hole karst cave areas, composite pile structures are preferred to ensure that the pile foundation can stably penetrate large-span karst caves and meet stress safety requirements. The composite pile structure consists of main cast-in-place piles, auxiliary grouting piles, and cavity control piles. The main cast-in-place piles are located at the core of the pile hole to carry the main vertical load. The auxiliary grouting piles are placed below the karst cave to enhance the stability of the lower blockage. The cavity control piles are placed above the karst cave to effectively support the cave roof and prevent collapse.

[0125] S72, Coordinated force mechanism and bearing capacity assessment of composite piles: The various types of composite piles are rationally arranged according to the karst cave morphology, load transfer path and foundation bearing characteristics. The main cast-in-place piles mainly provide end bearing, while the auxiliary grouting piles and cavity control piles jointly participate in the bearing through side friction resistance. During the construction design phase, the overall bearing capacity needs to be scientifically assessed based on the force-bearing area and force transfer path of each pile type. The total bearing capacity of the composite pile is composed of the end resistance of the main pile and the side friction resistance of each pile, ensuring that the pile foundation structure has sufficient stability and safety margin in the complex karst environment.

[0126] The specific steps for real-time monitoring and dynamic adjustment of construction parameters throughout the entire process in S8 are as follows:

[0127] S81, Establishment of a full-process data collection and construction monitoring system: During the construction of bridge pile foundations, all stages of drilling, grouting, and concrete pouring must be monitored in real time. By installing drilling parameter acquisition devices, grouting pressure and flow rate monitors, and a concrete pouring status tracking system, key data from the construction process can be comprehensively recorded. The construction monitoring system simultaneously collects dynamic parameters such as drilling resistance, grouting filling ratio, and pouring rate, establishing detailed construction monitoring records to ensure complete and traceable data from each process step.

[0128] S82, monitoring data analysis and real-time response to abnormal working conditions: During construction, various parameters collected by the monitoring system should be continuously compared and analyzed in real time, and abnormal working conditions should be identified in a timely manner through preset safety thresholds; when the monitoring results show that the drilling resistance, grouting pressure or injection speed exceeds the reasonable design range, the system will immediately issue an early warning; the construction parameters should be adjusted in a timely manner according to the type of abnormality on site, and the drilling speed, grouting flow rate or injection rhythm should be adjusted. If necessary, construction should be suspended for inspection to ensure that the construction process is always in a controllable and safe state.

[0129] The specific steps for pile quality inspection and construction closed-loop feedback in S9 are as follows:

[0130] S91, Pile Quality Inspection Methods and Data Confirmation: After construction is completed, a comprehensive quality inspection of the bridge pile foundation should be conducted. The accuracy of the inspection results should be verified through the acoustic transmission method, grouting filling rate testing, and drill core sampling. The acoustic transmission method measures the propagation time of sound waves within the pile body to determine whether there are voids, interlayers, or defects in the pile structure. Changes in propagation time are closely related to the density of the pile material. Combined with the grouting filling rate and drill core structure test results, it can effectively confirm whether the karst cave is completely blocked.

[0131] The formula for sound wave transmission time is:

[0132] ;

[0133] Where, Sound wave propagation time (ms), Sound wave transmission path distance (mm), Sound wave propagation speed (mm / ms); used to detect pile integrity and determine whether there are defects in the pile body by the sound wave propagation time;

[0134] S92, Handling of detection anomalies and subsequent process adjustments: During the detection process, if the sound wave transmission time is obviously abnormal, the grouting is insufficiently filled, or there are structural defects in the drill core sample, it should be promptly identified as an abnormal pile quality. For abnormal detection situations, the construction unit needs to analyze the cause of the abnormality in detail and promptly feedback the test results to the process adjustment link. In the subsequent construction of the same type of pile foundation, it is necessary to optimize the grouting pressure, pouring rhythm or composite pile configuration parameters based on the problems that have been found to ensure the stable and reliable quality of the entire bridge foundation project.

[0135] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0136] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for graded treatment and composite pile construction of bridge pile foundations in strongly developed karst geology, characterized by: The specific steps of the graded treatment and composite pile construction method for the strongly developed karst geological bridge pile foundation are as follows: S1, Advanced geological exploration and karst classification: Through advanced geological exploration, the karst distribution and water flow conditions in the pile foundation path are understood, and the karst is divided into three categories, providing a basis for subsequent process selection; S2, Karst graded treatment process design. A graded treatment plan is formulated according to the karst grade. For Grade I micro-pore areas, conventional cast-in-place pile penetration construction is adopted. For Grade II isolated cave areas, local grouting reinforcement of the cave is required before pile foundation is completed. For Grade III through-hole large cave areas, multi-section isolation conduits are designed, and segmented grouting and concrete simultaneous pouring are adopted. Appropriate grouting pressure and construction technology are designed for different karst types to ensure targeted treatment. S3, drilling construction and dynamic karst verification: real-time monitoring of drilling parameters during drilling construction, dynamic verification of karst grade, and timely adjustment of construction plan if it does not match the design to ensure accurate matching; S4, installation of segmented isolation conduits and construction of grouting system: Install segmented isolation conduits in the borehole. The conduits are equipped with remote grouting valves and grouting stoppers to achieve multi-segment independent grouting and effectively prevent cross-flow of slurry. S5, Segmented Grouting and Sealing of Caves: Prioritize segmented grouting for Grade II and Grade III caves, monitor the grouting status in real time, seal the caves segment by segment, and automatically close the grouting valves after grouting is completed. S6, grouting-pouring synchronous intelligent control construction: After grouting is stable, concrete pouring is started. The grouting and pouring rhythm are controlled in real time through the intelligent linkage system to ensure synchronous construction and prevent concrete loss; S7, Composite pile structure construction and pile type optimization configuration: A composite pile structure is set up in the through-cavern area, with a reasonable configuration of main cast-in-place piles, auxiliary grouting piles, and cavity control piles to meet the bearing requirements of complex strata; S8, real-time monitoring and dynamic adjustment of construction parameters throughout the entire process: Various parameters are collected in real time during the construction process and monitoring records are established. If the detection data is abnormal, the construction parameters are adjusted in time or the operation is suspended to ensure safety; S9, pile quality inspection and construction closed-loop feedback: After the construction is completed, pile quality inspection is carried out to verify the quality of the pile foundation through sound wave transmission, grouting filling rate and core drilling inspection to ensure the quality of the project construction.

2. The method for graded treatment and composite pile construction of bridge pile foundations in highly developed karst geology according to claim 1 is characterized by: The specific steps of advanced geological exploration and karst delineation in S1 are as follows: S11, Determination of advanced geological exploration paths and information acquisition: Prior to bridge pile foundation construction, advance geological exploration along the construction path is prioritized. Using a combination of geological radar scanning, advanced horizontal drilling, and core drilling techniques, the distribution of karst within the pile foundation area, pore development characteristics, and groundwater flow conditions are fully understood. This exploration process not only determines the extent of karst development but also identifies the rock layer structure and karst cave media in advance. S12, Karst grade classification and reasonable design of grouting pressure: Based on the geological exploration results, the identified karst is classified according to pore size, cave structure and through-flow conditions. The karst is divided into Grade I micro-pore area, Grade II isolated cave area and Grade III through-flow large cave area.

3. The method for graded treatment and composite pile construction of bridge pile foundations in highly developed karst geology according to claim 2 is characterized by: The specific steps of the karst graded treatment process design in S2 are as follows: S21. Overall formulation of karst graded treatment processes: Based on the results of advanced geological surveys and karst grade classification, rationally formulate graded treatment processes for different karst grades. For Grade I micro-pore areas, conventional cast-in-place pile penetration construction is used. Such pores have little impact on pile foundation formation and do not require additional reinforcement. For Grade II isolated cave areas, local grouting reinforcement of the caves is required before pile foundation construction. S22, grouting reinforcement parameter design and level III complex cave treatment: low-pressure grouting technology is used for grouting in level II cave areas. The grouting pressure needs to comprehensively consider the depth of the cave and the gravity of the grouting material itself to ensure that the slurry enters the cave smoothly. For level III through-type large cave areas, multi-section isolation conduits are designed, and segmented grouting and concrete simultaneous pouring technology are adopted to ensure that caves of different depths are effectively blocked step by step.

4. The method for graded treatment and composite pile construction of bridge pile foundations in highly developed karst geology according to claim 1 is characterized by: The specific steps of drilling construction and dynamic karst verification in S3 are as follows: S31, Drilling Construction and Real-Time Data Collection: Drilling construction is carried out along the designed path of the bridge pile foundation. By real-time monitoring of drilling resistance, drilling rate, and changes in rock cuttings during the drilling process, drilling process parameters are continuously collected. By comparing the current drilling status with the estimated rock formation resistance data obtained from advanced geological surveys, the actual distribution of karst along the drilling path can be dynamically understood. The expression formula of drilling pressure dynamic deviation is: ； Where, Drilling pressure deviation (kN), Actual drilling resistance (kN), Predicted drilling resistance (kN) is detected in advance; it is used to determine in real time whether the drilling process has entered karst or abnormally weak formations. When the deviation exceeds the limit, the drilling process is automatically suspended and the process is adjusted. S32, drilling deviation analysis and dynamic process adjustment: During the drilling process, dynamic deviation analysis is performed based on the difference between real-time monitoring data and the design predicted resistance. By real-time judgment of the amplitude of change in drilling resistance, the deviation between the size or structure of the cave and the design prediction can be identified in time. When the resistance deviation is monitored to exceed the allowable range, the drilling operation should be suspended immediately, and the subsequent treatment process should be adjusted according to the actual karst situation to ensure that the pile foundation construction path is accurately matched with the karst grade to prevent construction risks caused by deviations.

5. The method for graded treatment and composite pile construction of bridge pile foundations in highly developed karst geology according to claim 1 is characterized by: The specific steps for installing the segmented isolation conduit and constructing the grouting system in S4 are as follows: S41, Segmented Isolation Conduit Structure Design and Installation Process: After drilling is completed, a segmented isolation conduit is installed in the pile hole according to the pre-determined design. The isolation conduit consists of multiple independent grouting chambers, which are rationally separated along the depth direction and stably connected via dedicated interfaces. The isolation conduit structure ensures segmented and independent grouting operations at different construction depths, while meeting the requirements for precise control of the grouting path in complex karst environments. S42, grouting valve control and grouting stop structure function: Each grouting section of the isolation conduit is equipped with a mechanical or electrically controlled grouting valve. The grouting valve supports remote opening and closing control to ensure that the grouting operation of each section can be carried out independently and orderly. A stepped grouting stop gasket is set between the grouting sections of the conduit. The grouting stop gasket is sealed through the structure to effectively prevent the slurry from flowing and diffusing between different grouting sections, ensuring a clear slurry filling path.

6. The method for graded treatment and composite pile construction of bridge pile foundations in highly developed karst geology according to claim 1 is characterized by: The specific steps of the segmented grouting and plugging construction of the S5 cave are as follows: S51, grouting process parameter monitoring and grouting section priority control: Prioritize grouting construction in Grade II and Grade III cave areas. Use a real-time grouting monitoring system to continuously monitor grouting pressure, flow rate, and slurry filling rate. Real-time monitoring ensures that the grouting process is within a safe and effective range. During construction, grouting is carried out step by step in strict accordance with the segmented design, with priority given to plugging larger caves. The grouting path is effectively controlled to ensure that the slurry enters the designated cave area smoothly and prevents ineffective diffusion. The calculation formula of grouting design pressure is: ； Where, Grouting design pressure (MPa), Unit weight of grouting slurry (kN / m 3 ), : Depth of slurry static pressure action (m), : Additional safety pressure required for cave plugging (MPa), usually 0.1-0.3MPa; used to calculate the reasonable grouting pressure for Class II and Class III caves, ensuring that the grouting pressure can fill the cave without being too high to cause rock damage; The calculation formula of grouting filling rate is: ； Where, Grouting filling rate , : Actual slurry volume injected (m 3 ), , used to monitor in real time whether the grouting has achieved the designed filling effect, and automatically adjust the grouting when the filling rate is lower than the warning value; S52, grouting diffusion control and valve closure management: Based on the grouting flow rate, grouting time, cave porosity and formation permeability characteristics, scientifically evaluate the reasonable diffusion range of slurry in karst, ensure that each grouting section forms an effective grouting radius, avoid slurry diffusion to non-construction areas, and control the slurry diffusion range and actual filling conditions to ensure that the grouting is full and there is no excess loss. After grouting is completed, the grouting valve automatically closes, and the current grouting section is closed in time to prevent slurry backflow and cross-flow between sections.

7. The method for graded treatment and composite pile construction of bridge pile foundations in highly developed karst geology according to claim 1 is characterized by: The specific steps of the grouting-pouring synchronous intelligent control construction in S6 are as follows: S61, simultaneous construction start and grouting stability confirmation: When the segmented grouting construction is completed and the monitoring system confirms that the grouting pressure is stable, the concrete pouring operation is immediately started. The concrete pouring must be kept continuous with the grouting operation to avoid construction interruptions. The intelligent linkage control system is used to synchronize the grouting and pouring processes to ensure that the slurry continues to seal and the concrete is smoothly poured into the pile hole. The synchronous expression formula of injection speed and grouting flow rate is: ； Where, :Concrete pouring speed (m³ / min), : Grouting flow rate (m³ / min), : Synchronous adjustment coefficient, used for grouting-pouring synchronous control to ensure the same rhythm of the two and prevent concrete loss; S62, real-time synchronous adjustment and grouting rhythm control: The intelligent linkage control system collects grouting flow rate and grouting rate data in real time, and maintains a dynamic matching relationship between the two according to preset construction parameters; synchronous control requires reasonable adjustment of the concrete pouring speed to form a coordinated ratio with the current grouting flow rate to prevent the concrete from breaking through the slurry defense line due to fast pouring speed, or the slurry from backflowing due to slow pouring. The system adjusts the linkage ratio and provides real-time feedback.

8. The method for graded treatment and composite pile construction of bridge pile foundations in highly developed karst geology according to claim 1 is characterized by: The specific steps of the composite pile structure construction and pile type optimization configuration in S7 are as follows: S71. Rational configuration and pile type design of composite pile structures: For through-hole karst cave areas, composite pile structures are preferred to ensure that the pile foundation can stably penetrate large-span karst caves and meet stress safety requirements. The composite pile structure consists of main cast-in-place piles, auxiliary grouting piles, and cavity control piles. The main cast-in-place piles are located at the core of the pile hole to carry the main vertical load. The auxiliary grouting piles are placed below the karst cave to enhance the stability of the lower blockage. The cavity control piles are placed above the karst cave. S72, Coordinated load-bearing mechanism and bearing capacity assessment of composite piles: The various types of composite piles are rationally arranged according to the cave morphology, load transfer path, and foundation bearing characteristics. The main cast-in-place piles mainly provide end bearing, while the auxiliary grouting piles and cavity control piles jointly participate in the bearing through side friction resistance. During the construction design phase, the overall bearing capacity must be scientifically assessed based on the load-bearing area and force transfer path of each pile type. The total bearing capacity of the composite pile is composed of the end resistance of the main pile and the side friction resistance of each pile.

9. The method for graded treatment and composite pile construction of bridge pile foundations in highly developed karst geology according to claim 1 is characterized by: The specific steps of real-time monitoring and dynamic adjustment of construction parameters throughout the entire process in S8 are as follows: S81, Establishment of a full-process data collection and construction monitoring system: During the construction of bridge pile foundations, all stages of drilling, grouting, and concrete pouring must be monitored in real time. By installing drilling parameter acquisition devices, grouting pressure and flow rate monitors, and a concrete pouring status tracking system, key data from the construction process can be comprehensively recorded. The construction monitoring system simultaneously collects dynamic parameters such as drilling resistance, grouting filling ratio, and pouring rate, establishing detailed construction monitoring records to ensure complete and traceable data from each process step. S82, monitoring data analysis and real-time response to abnormal working conditions: During construction, various parameters collected by the monitoring system should be continuously compared and analyzed in real time, and abnormal working conditions should be identified in a timely manner through preset safety thresholds; when the monitoring results show that the drilling resistance, grouting pressure or injection speed exceeds the reasonable design range, the system will immediately issue an early warning; the construction parameters should be adjusted in a timely manner on site according to the type of abnormality, and the drilling speed, grouting flow rate or injection rhythm should be adjusted. If necessary, construction should be suspended for inspection.

10. The method for graded treatment and composite pile construction of bridge pile foundations in highly developed karst geology according to claim 1, characterized in that: The specific steps of pile quality inspection and construction closed-loop feedback in S9 are as follows: S91, Pile Quality Inspection Methods and Data Verification: After construction is completed, a comprehensive quality inspection of the bridge pile foundation should be conducted. This should be verified through acoustic transmission testing, grouting filling rate testing, and core sampling to ensure the accuracy of the test results. The acoustic wave transmission method measures the propagation time of sound waves inside the pile to determine whether there are cavities, interlayers, or defects in the pile structure. The change in propagation time is closely related to the density of the pile material. Combined with the grouting filling rate and the drill core structure test results, it can effectively confirm whether the cave is completely blocked. The formula for sound wave transmission time is: ； Where, Sound wave propagation time (ms), : Sound wave transmission path distance (mm), : Sound wave propagation speed; used to detect pile integrity and determine whether there are defects in the pile body quality by the sound wave propagation time; S92, Handling of detection anomalies and subsequent process adjustments: During the detection process, if the sound wave transmission time is obviously abnormal, the grouting is insufficient, or there are structural defects in the drill core sample, it should be promptly identified as an abnormal pile quality. For abnormal detection situations, the construction unit needs to analyze the cause of the abnormality in detail and promptly feedback the test results to the process adjustment link. In the subsequent construction of the same type of pile foundation, it is necessary to optimize the grouting pressure, pouring rhythm or composite pile configuration parameters based on the problems that have been discovered.

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