A reverse construction method for internal frame column cap pile foundation

Abstract

This invention relates to the field of building construction technology, specifically disclosing a reverse construction method for internal frame column cap pile foundations, comprising: First, a pre-construction preparation stage: determining the soil layers and steel pile locations at the construction site, and designing earthwork excavation and foundation cushion treatment; Next, pile cap construction: pouring the pile cap at the designed construction location and reserving pile driving holes and pre-embedding anchors at the designed pile locations, ensuring that the pull-out resistance of the anchors meets the pile driving force requirements; Then, anchor static pressure pile construction: installing a pile driving frame and determining the pile driving time, and setting up a monitoring system to monitor changes in pile driving pressure; Based on the monitoring results from step three, sealing the piles and determining the sealing time; Finally, using temporary pile sealing to obtain the sealing pressure in real time, adjusting it according to the construction status of the superstructure, and finally sealing the piles after the superstructure construction is completed; This invention improves construction efficiency and reduces costs by real-time monitoring and timely adjustment of the pile driving pressure.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, specifically to a reverse construction method for internal frame column foundation pile foundations. Background Technology

[0002] The reverse construction method for pile foundations is commonly used in pile-raft foundations for high-rise buildings. This construction method involves first pouring a raft slab (with pre-reserved pile driving holes on the raft slab), and then, after the superstructure has been constructed to a certain number of stories, anchor static pressure piles are installed in the pre-reserved holes. Finally, the anchor static pressure piles are connected to the raft slab. Compared with conventional forward construction pile-raft foundations, the raft slab is constructed first, ensuring the bearing capacity of the soil at the bottom of the slab, thereby reducing the number of piles and lowering the cost. At the same time, the construction of the pile foundations and the construction of the superstructure can be carried out simultaneously, thus saving construction time.

[0003] Because dynamic monitoring is required during construction to control the appropriate pile sealing time, construction typically involves three stages: pre-pile driving, pile driving, and post-sealage construction. A monitoring system is used to monitor the pile driving process in real time. However, existing monitoring methods rely solely on workers' experience, adjusting the verticality and settlement of the piles visually. This dependence on workers' experience requires significant manpower, leading to slow project progress, long construction periods, and high manual monitoring costs. Summary of the Invention

[0004] The purpose of this invention is to provide a reverse construction method for pile foundations with internal frame columns, solving the following technical problems:

[0005] How to monitor the status of pile driving construction in real time and make timely adjustments based on the pile driving pressure to improve construction efficiency and reduce costs.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for constructing an internal frame column cap pile foundation using a reverse construction method, the method comprising:

[0008] Step 1, Pre-construction preparation stage: Determine the distribution of soil layers and steel pile locations at the project site, and design earthwork excavation and foundation cushion treatment;

[0009] Step 2, Pile cap construction: Pile caps are poured at the construction design location, and pile driving holes and anchor rods are reserved at the designed pile positions, ensuring that the pull-out force of the anchor rods meets the pile driving force requirements;

[0010] Step 3, Static Pressure Pile Construction with Anchor Bolts: Install the pile driving frame and determine the pile driving time, and set up a monitoring system to monitor changes in pile driving pressure;

[0011] Step 4: Pile sealing construction: Based on the monitoring results from Step 3, pile sealing will be carried out and the sealing time will be determined;

[0012] Step 5: Use temporary pile sealing to obtain the pile sealing pressure in real time, and adjust it according to the construction of the superstructure. After the superstructure construction is completed, finally seal the pile.

[0013] Preferably, the pile driving stress in step two includes two stages: the stress on the foundation and the stress on the foundation soil.

[0014] The first stage involves the existing foundation soil bearing the self-weight of the foundation and the existing n1-story structure above, as well as the construction load P1; the first time period is set from 0 to t0.

[0015] The second stage involves the soil between the piles and the piles jointly bearing the weight of P1 and the self-weight and live load P2 of the later-constructed n2-story structure; the second time period is set from t0 to t1. m ;

[0016] Where t0 is the start time of pile driving; t m This is the time when the pile driving process ends.

[0017] Preferably, the monitoring content of the monitoring system in step three includes pile side earth pressure monitoring, and the monitoring method is as follows:

[0018] S1. Install steel wire pressure sensors on the pile to measure the magnitude of the pile side pressure in real time;

[0019] S2. Obtain curve E1 based on the change of pile side pressure P1' during the first time period 0 to t0;

[0020] S3, based on the second time period t0~t m The magnitude of the pile side pressure P m 'Change yields curve E2;'

[0021] S4. Calculate the area deviation value D corresponding to the coincidence time of curves E1 and E2 in the same coordinate system; compare D with the preset deviation threshold D0. thi Compare:

[0022] If D < D thi If the steel wire pressure sensor is in normal condition, the monitoring strategy will be executed.

[0023] Otherwise, the monitoring status of the steel wire pressure sensor is determined to be abnormal, and a first abnormal command is issued to perform a test on the steel wire pressure sensor.

[0024] Before burying the steel wire pressure sensor, it is necessary to conduct tests on stability, waterproof sealing, pressure calibration, and temperature calibration.

[0025] Preferably, the monitoring strategy acquisition includes:

[0026] According to the formula Calculate the pile stability coefficient S pil Where T(t) is the real-time pile pressure intensity, [t n , t m [t] represents the time period during pile driving operation. i , t j [] represents the time period of the pile driving interval state, and δ and ε are weighting coefficients;

[0027] The pile stability coefficient S pil With preset threshold [S] A S B Compare sizes:

[0028] If S pil ∈[S A S B If the pile stability is normal, work can continue.

[0029] like If the pile stability is deemed abnormal, a second abnormality command is generated to regulate the pile stability.

[0030] Preferably, the monitoring system further includes monitoring of the pile driving process, pile top settlement, pile side friction, pile stress, and pile deformation; the pile side earth pressure monitoring also includes monitoring the earth pressure values ​​P inside and outside the foundation pit. sio and pore water pressure value P w Monitoring.

[0031] Preferably, the method for controlling the stability of the pile body is as follows:

[0032] Through formula Calculate the pile body adjustment coefficient U pil Where f is a preset function, γ1, γ2, and γ3 are weighting coefficients, and γ1, γ2, and γ3 are all greater than 0; P0 is the standard earth pressure value inside and outside the foundation pit; Pw0 is the standard pore water pressure value; and ΔP is the preset deviation value of earth pressure inside and outside the foundation pit.

[0033] Preferably, the pile body adjustment coefficient U pil With preset threshold (U) A U B Compare:

[0034] If U pil ≤U A If the pressure around the pile is too high, insert a plastic drainage board to drain and reduce the pressure.

[0035] If U A <U pil ≤U BIf the pressure around the pile is normal, then the current pressure value is obtained.

[0036] If U pil >U B If the pressure around the pile is too low, then pile top settlement monitoring should be performed.

[0037] Preferably, the monitoring of pile top settlement includes:

[0038] The first part is the consolidation settlement S1 of the shallow foundation at time t0 under the action of P1;

[0039] The second part is the foundation uplift S that may occur during pile driving due to the soil squeezing effect. r ;

[0040] The third part is the settlement S2 that continues to occur in the pile foundation under the action of P1 after the sealing pile is completed;

[0041] Part Four is the foundation settlement S3 under the action of P2;

[0042] Adding the above components together, we obtain the final settlement: S tfp =S1-S r +S2+S3.

[0043] Preferably, the real-time acquisition method for the pile sealing pressure in step five is as follows:

[0044] SS1. Real-time pile driving pressure value is obtained by setting a steel wire pressure sensor at the jack position between the steel pipe piles installed between the wall of the pile cap and the foundation.

[0045] SS2. The load of the upper structural steel columns is transferred to the piles, temporary pile sealing is carried out, and the pile sealing pressure value is adjusted according to the real-time calculation results;

[0046] The force value is determined by the numerical change of the vibrating wire strain gauges arranged on the steel pile, and transmitted through the data transmission line. When the force value is applied, the vertical displacement of the steel column is guaranteed not to change.

[0047] SS3. After the superstructure construction is completed, the structural pile sealing is carried out, the jacks are removed, and the pile sealing reinforcement is welded.

[0048] The beneficial effects of this invention are:

[0049] (1) The present invention solves the problem that the existing monitoring process relies solely on the construction experience of workers and makes adjustments by visually observing the verticality and settlement of the pile itself. Due to the reliance on the construction experience of existing workers, a large amount of human resources are required, which leads to slow project progress, long construction period and high cost of manual monitoring. Specifically, by setting up a monitoring system, it is beneficial to analyze the real-time stress state of the pile foundation during the pile driving process and make further judgments based on the stress state. The specific monitoring tool used is a steel wire pressure sensor. The data obtained by the steel wire pressure sensor is further monitored to obtain analysis results.

[0050] (2) The present invention obtains a monitoring strategy by detecting the first abnormal command, and uses the monitoring strategy to detect the stability of pile driving. It obtains the stability coefficient of the pile body and judges to obtain the second abnormal command. The two abnormal commands are conducive to obtaining real-time monitoring of the pile driving status and judging the situation, reducing the consumption of manual and human resources. Finally, according to the needs of the detailed test results, further monitoring of pile top settlement is carried out to ensure that the pile driving meets the reasonable construction standards.

[0051] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0052] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0053] Figure 1 This is a schematic diagram illustrating the construction steps of a reverse construction method for an internal frame column cap pile foundation according to the present invention;

[0054] Figure 2 This is a schematic diagram of the sealing process steps of the present invention;

[0055] Figure 3 This is a schematic diagram of the pressure sealing pile structure of the present invention. Detailed Implementation

[0056] 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.

[0057] Building sites with historical value and cultural memory require a certain degree of renovation during the renovation process, especially the pile foundation. The original, more traditional pile foundations adopted the construction method of piling first and then pile cap, assuming that the piles bear the entire load of the superstructure without considering the bearing capacity of the soil between the piles. However, this often leads to an increase in the number of piles and thus an increase in cost. How to minimize costs and shorten the construction period has become a practical problem facing the engineering industry.

[0058] By considering the interaction between piles and soil, and allowing the soil between piles to share part of the external load, it is one of the important ways to reduce the cost of pile foundations and to achieve reasonable and optimized design. The reverse construction method of pile foundation is a new type of foundation construction method that first constructs the pile cap and a certain number of superstructures before driving the piles. Therefore, the design considers that the load is shared by the piles and soil. This invention uses this method to conduct dynamic monitoring during construction to control the time of pile sealing. This can achieve reasonable load distribution and control the construction period, thus showing great economic and social benefits.

[0059] Please see Figure 1 As shown, this invention is a reverse construction method for pile foundations with internal frame columns, the specific method including:

[0060] Step 1, Pre-construction preparation stage: Determine the distribution of soil layers and steel pile locations at the project site, and design earthwork excavation and foundation cushion treatment;

[0061] Step 2, Pile cap construction: Pile caps are poured at the construction design location, and pile driving holes and anchor rods are reserved at the designed pile positions, ensuring that the pull-out force of the anchor rods meets the pile driving force requirements;

[0062] Step 3, Static Pressure Pile Construction with Anchor Bolts: Install the pile driving frame and determine the pile driving time, and set up a monitoring system to monitor changes in pile driving pressure;

[0063] Step 4: Pile sealing construction: Based on the monitoring results from Step 3, pile sealing will be carried out and the sealing time will be determined;

[0064] Step 5: Use temporary pile sealing to obtain the pile sealing pressure in real time, and adjust it according to the construction of the superstructure. After the superstructure construction is completed, finally seal the pile.

[0065] The above technical solution addresses the problems of existing monitoring processes that rely solely on workers' construction experience and involve visually observing the verticality and settlement of the piles. This process is dependent on the workers' experience, requires a large amount of manpower, and consequently leads to slow project progress, long construction periods, and high manual monitoring costs.

[0066] The specific implementation method of this invention involves the following steps: First, a pre-construction preparation stage is established: the distribution of soil layers and steel pile locations at the construction site is determined, and earthwork excavation and foundation cushion treatment design are carried out; then, pile cap construction is performed: the pile cap is poured at the designed construction location, and pile driving holes and anchor rods are reserved at the designed pile locations, ensuring that the pull-out force of the anchor rods meets the pile driving force requirements; next, static pile driving is performed using anchor rods: a pile driving frame is installed, the pile driving time is determined, and a monitoring system is set up to monitor changes in pile driving pressure; pile sealing is performed: based on the monitoring results from step three, pile sealing is carried out, and the sealing time is determined; finally, temporary pile sealing is used to obtain the sealing pressure in real time, and adjustments are made according to the construction status of the superstructure. After the superstructure construction is completed, the pile is finally sealed.

[0067] In one embodiment of the present invention, the pile driving force in step two includes two stages: the force on the foundation and the force on the foundation soil.

[0068] The first stage involves the existing foundation soil bearing the self-weight of the foundation and the existing n1-story structure above, as well as the construction load P1; the first time period is set from 0 to t0.

[0069] The second stage involves the soil between the piles and the piles jointly bearing the weight of P1 and the self-weight and live load P2 of the later-constructed n2-story structure; the second time period is set from t0 to t1. m ;

[0070] Where t0 is the start time of pile driving; t m This is the time when the pile driving process ends.

[0071] Through the above technical solution, since the stress characteristics of the pile foundation during the reverse construction process are relatively complex, and the time interval between pile pressing and sealing is generally short, in order to facilitate calculation and analysis, the stress stage of the composite foundation is ignored in this implementation process. Therefore, the stress of the foundation and the foundation soil is simplified into two stages for analysis. The first stage is that the original foundation soil bears the self-weight of the foundation and the existing n1-layer structure above it, as well as the construction load P1; the first time period is set from 0 to t0. The second stage is that the soil between the piles and the piles jointly bear P1 and the self-weight of the later-constructed n2-layer structure, as well as the live load P2; the second time period is set from t0 to t2. m Where t0 is the start time of pile driving; t m This is the time when the pile driving process ends.

[0072] In one embodiment of the present invention, the monitoring content of the monitoring system in step three includes pile side earth pressure monitoring, and the monitoring method is as follows:

[0073] S1. Install steel wire pressure sensors on the pile to measure the magnitude of the pile side pressure in real time;

[0074] S2. Obtain curve E1 based on the change of pile side pressure P1' during the first time period 0 to t0;

[0075] S3, based on the second time period t0~t m The magnitude of the pile side pressure P m 'Change yields curve E2;'

[0076] S4. Calculate the area deviation value D corresponding to the coincidence time of curves E1 and E2 in the same coordinate system; compare D with the preset deviation threshold D0. thi Compare:

[0077] If D < D thi If the steel wire pressure sensor is in normal condition, the monitoring strategy will be executed.

[0078] Otherwise, the monitoring status of the steel wire pressure sensor is determined to be abnormal, and a first abnormal command is issued to perform a test on the steel wire pressure sensor.

[0079] Before burying a steel wire pressure sensor, it is necessary to conduct tests on its stability, waterproof sealing, pressure calibration, and temperature calibration.

[0080] The above technical solution utilizes a monitoring system to analyze the real-time stress state of the pile foundation during pile driving and to make further judgments based on this stress state. The specific monitoring tool used is a steel wire pressure sensor. The monitoring process is as follows: First, a steel wire pressure sensor is installed on the pile to measure the pile side pressure in real time; then, curve E1 is obtained based on the change in pile side pressure P1' during the first time period (0–t0); next, curve E1 is obtained based on the change in pile side pressure P1' during the second time period (t0–t1). m The magnitude of the pile side pressure P m The change yields curve E2; finally, by calculating the area deviation value D corresponding to the coincidence time of curves E1 and E2 in the same coordinate system; D is then compared with a preset deviation threshold D0. thi Compare the sizes, and then further determine: if D < D thi If the condition is normal, the steel wire pressure sensor is judged to be in normal condition and the monitoring strategy is executed; otherwise, the steel wire pressure sensor is judged to be in abnormal condition and the first abnormal command is issued to perform a test on the steel wire pressure sensor. Before the steel wire pressure sensor is buried, tests such as stability, waterproof sealing, pressure calibration, and temperature calibration need to be performed.

[0081] The area deviation value D is calculated based on the cumulative overlapping area of ​​curves E1 and E2 within the same time period, and is not limited to a single overlapping area. Therefore, the area deviation value D should be the result of the cumulative calculation of the overlapping area.

[0082] As one embodiment of the present invention, the monitoring strategy acquisition includes:

[0083] According to the formula Calculate the pile stability coefficient Spil Where T(t) is the real-time pile pressure intensity, [t n , t m [t] represents the time period during pile driving operation. i , t j [] represents the time period of the pile driving interval state, and δ and ε are weighting coefficients;

[0084] The pile stability coefficient S pil With preset threshold [S] A S B Compare sizes:

[0085] If S pil ∈[S A S B If the pile stability is normal, work can continue.

[0086] like If the pile stability is deemed abnormal, a second abnormality command is generated to regulate the pile stability.

[0087] Using the above technical solution, this embodiment detects pile driving stability through a monitoring strategy. Specifically, it first obtains the pile stability coefficient and then calculates it using the formula... Calculate the pile stability coefficient S pil Where T(t) is the real-time pile pressure intensity, [t n , t m [t] represents the time period during pile driving operation. i , t j [ ] represents the time interval of pile driving, where δ and ε are weighting coefficients; then, the pile stability coefficient S... pil With preset threshold [S] A S B The values ​​are compared to determine whether pile body adjustment is needed in the current state. Specifically, the analysis involves determining whether the pile body stability coefficient falls within a preset threshold range. If S... pil ∈[S A S B If the pile stability is normal, then work can continue; if... If the pile stability is deemed abnormal, a second abnormality command is generated to regulate the pile stability.

[0088] As one embodiment of the present invention, the monitoring system's monitoring scope also includes monitoring of the pile driving process, pile top settlement, pile side friction, pile stress, and pile deformation; the pile side earth pressure monitoring also includes the earth pressure value P inside and outside the foundation pit. sio and pore water pressure value P w Monitoring.

[0089] To ensure comprehensive monitoring of the pile driving process using the above technical solutions, the system also includes monitoring of pile driving, pile top settlement, pile side friction, pile stress, and pile deformation. This allows for the acquisition of construction status data such as pile driving and sealing during the reverse construction method, and data analysis to promptly address any issues that arise during pile construction. The pile side earth pressure monitoring also includes monitoring the earth pressure values ​​P inside and outside the foundation pit. sio and pore water pressure value P w Monitoring was conducted by acquiring the soil pressure values ​​P inside and outside the foundation pit. sio and pore water pressure value P w It can obtain more detailed information about the stability of the pile body and make real-time adjustments.

[0090] As one embodiment of the present invention, the pile stability control method is specifically as follows:

[0091] Through formula Calculate the pile body adjustment coefficient U pil Where f is a preset function, γ1, γ2, and γ3 are weighting coefficients, and γ1, γ2, and γ3 are all greater than 0; P0 is the standard earth pressure value inside and outside the foundation pit; Pw0 is the standard pore water pressure value; and ΔP is the preset deviation value of earth pressure inside and outside the foundation pit.

[0092] Using the above technical solution, pile body adjustment is performed after the second abnormal command is generated. The specific adjustment method is determined by the formula. Calculate the pile body adjustment coefficient U pil By adjusting the pile body coefficient U pil The judgment and analysis can obtain the factors affecting pile stability and determine the direction of control; where f is a preset function, which is an adjustment function set according to historical data to ensure that the adjustment coefficient is within a specific and reasonable range. γ1, γ2, and γ3 are weight coefficients, and γ1, γ2, and γ3 are all greater than 0. P0 is the standard earth pressure value inside and outside the foundation pit; Pw0 is the standard pore water pressure value; both are standard data values ​​obtained based on historical experience; ΔP is the preset deviation value of earth pressure inside and outside the foundation pit; where the deviation value of earth pressure inside and outside the foundation pit is preset in advance based on the historical database, it will not be elaborated here.

[0093] As one embodiment of the present invention, the pile body adjustment coefficient U pil With preset threshold (U) A U B Compare:

[0094] If U pil ≤U A If the pressure around the pile is too high, insert a plastic drainage board to drain and reduce the pressure.

[0095] If U A <Upil ≤U B If the pressure around the pile is normal, then the current pressure value is obtained.

[0096] If U pil >U B If the pressure around the pile is too low, then pile top settlement monitoring should be performed.

[0097] Through the above technical solution, the obtained adjustment coefficient U pil With preset threshold (U) A U B A comparison is performed, and the current pile condition is adjusted according to the range of the comparison control coefficients to ensure that the overall adjustment area is within a reasonable range required for construction. Specifically, the comparison method involves judging U... pil Is it within the preset threshold (U)? A U B Within the range, determine if it is less than or equal to U. A If the pressure around the pile is too high, it is because the pore water pressure value P w If the pressure is too high, consider excessive pore water and drain the water by inserting a plastic drainage plate; if U A <U pil ≤U B If the pressure around the pile is normal, the current pressure value is obtained, the status is recorded, parameter data is generated and stored; if it is greater than U... B If the pressure around the pile is too low, the earth pressure P inside and outside the foundation pit is determined. sio and pore water pressure value P w The abnormal changes indicate that further monitoring of pile top settlement is needed to ensure that the pile driving meets reasonable construction standards.

[0098] As one embodiment of the present invention, the monitoring content of pile top settlement includes:

[0099] The first part is the consolidation settlement S1 of the shallow foundation at time t0 under the action of P1;

[0100] The second part is the foundation uplift S that may occur during pile driving due to the soil squeezing effect. r ;

[0101] The third part is the settlement S2 that continues to occur in the pile foundation under the action of P1 after the sealing pile is completed;

[0102] Part Four is the foundation settlement S3 under the action of P2;

[0103] Adding the above components together, we obtain the final settlement: S tfp =S1-S r +S2+S3.

[0104] Using the above technical solution, pile top settlement monitoring is conducted. The monitoring content includes four parts. The first part is the consolidation settlement S1 of the shallow foundation at time t0 under the action of P1, and the theoretical final settlement under the corresponding load is S. tfp The second part describes the foundation uplift S that may occur during pile driving due to the soil squeezing effect. r The third part is the settlement S2 of the pile foundation under the action of P1 after the sealing piles are completed. The calculation of S2 needs to consider the effect of the increased foundation stiffness caused by the combined action of the piles and soil. The fourth part is the settlement S3 of the foundation under the action of P2. Adding the above parts together gives the final settlement: S tfp =S1-S r +S2+S3; The settlement of the foundation of the pile foundation on site will affect the pile driving process and even the final state of the encapsulated piles. Obviously, if the pile driving time is early, the soil consolidation time is short, the final settlement of the foundation is small, the load on the piles is large, and the number of piles required is large. Conversely, if the pile driving time is late, the foundation settlement is large, and the number of piles required is small. Therefore, there is an optimization relationship between controlling settlement and selecting the number of piles.

[0105] The detailed formula for calculating the settlement in this embodiment is as follows:

[0106]

[0107] In the formula, n is the number of piles; Vp is the volume of concrete driven into the ground by a single pile; A is the total area of ​​the foundation; K1 is the volume change coefficient, generally taken as 0.7 to 0.95; K2 is the soil displacement construction coefficient, generally taken as 0.55 to 0.8, which is related to the number of piles, density, and driving direction; K3 is the vertical displacement coefficient, generally taken as 0.33 to 0.4; K r For the original foundation stiffness; K pr For the stiffness of the pile foundation; S tf1 Let K be the theoretical final settlement value of the original shallow foundation under the action of P1; for the stiffness K of the shallow foundation r The calculation can be replaced by Winkler coefficients.

[0108] As one embodiment of the present invention, please refer to Figure 2-3 As shown, the real-time acquisition method for the pile sealing pressure in step five is as follows:

[0109] SS1. Real-time pile driving pressure value is obtained by setting a steel wire pressure sensor at the jack position between the steel pipe piles installed between the wall of the pile cap and the foundation.

[0110] SS2. The load of the upper structural steel columns is transferred to the piles, temporary pile sealing is carried out, and the pile sealing pressure value is adjusted according to the real-time calculation results;

[0111] The force value is determined by the numerical change of the vibrating wire strain gauges arranged on the steel pile, and transmitted through the data transmission line. When the force value is applied, the vertical displacement of the steel column is guaranteed not to change.

[0112] SS3. After the superstructure construction is completed, the structural pile sealing is carried out, the jacks are removed, and the pile sealing reinforcement is welded.

[0113] With the above technical solution, the static pressure pile construction is completed, but the superstructure has not yet been constructed. If the pressure is too high during pile sealing, it will inevitably cause cracks in the wall supporting the pile cap; if the pressure is too low, settlement will occur after the load is applied later. Therefore, this embodiment adopts temporary pile sealing measures during the superstructure construction period. The pile sealing pressure is adjusted according to the superstructure construction situation to ensure that the temporary pile sealing pressure is equal to the superstructure load. The piles are finally sealed after the superstructure construction is completed. The specific process flow is as follows:

[0114] Cleaning of pile driving holes → Treatment of the inverted funnel-shaped interface of pile opening → Installation of pile sealing reaction frame and jacks → Loading of pile sealing → Temporary pile sealing → Adjustment of pile sealing pressure → Waiting for completion of superstructure construction → Pouring of KL-80 high-strength material → Removal of pile sealing reaction frame and jacks → Welding of cross reinforcement bars at pile top → Formwork erection and pouring of concrete at pile top for protection.

[0115] Construction steps include

[0116] 1) Cleaning of pile driving holes

[0117] Clean the debris, soil, and original template inside the press hole.

[0118] 2) Treatment of the inverted funnel-shaped interface at the pile opening

[0119] To ensure the punching shear resistance of the connection surface between the sealing concrete and the original pile cap, the inverted bell-shaped opening of the pile hole is treated with interface treatment.

[0120] 3) Installation of pile sealing reaction frame and jacks

[0121] After the interface processing is completed and the opening is cleaned, a small press-fit reaction frame for sealing piles is installed on the original pre-embedded screw rod of the pile using a connector, and a sealing steel pipe is set on the steel pipe pile. A sealing steel beam is set on the upper part of the sealing steel pipe, and a jack is designed between the sealing steel pipe and the reaction frame.

[0122] 4) Temporary pile sealing

[0123] By adjusting the pressure of the jacks, the load of the upper structural steel columns is transferred to the piles, ensuring that all the upper load transmitted from the columns is borne by the piles. The force value is determined by calculating the numerical changes of the vibrating wire strain gauges arranged on the steel piles, ensuring that the vertical displacement of the steel columns does not change when the force is applied. Furthermore, the pile sealing pressure is adjusted in a timely manner according to the construction progress of the upper floors during implementation.

[0124] 5) Structural pile sealing

[0125] After the superstructure construction is completed, the sealing pile pressure is adjusted to the design value, the sealing pile opening is moistened with water, and then KL-80 high-strength non-shrinkage material is used for sealing pile pouring, with the pouring surface 150mm lower than the top of the pile cap.

[0126] 6) Pile cap beam pouring

[0127] After the concrete for sealing the piles has reached the design strength, the pile-sealing reaction frame and jacks are removed. The surface of the press-fitted anchor rods is cleaned of loose dust and impurities, and the pile-sealing reinforcement is welded. After the reinforcement welding is completed, formwork is erected in the area of ​​the pile-sealing reinforcement, and concrete is poured for protection.

[0128] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A construction method for reverse-construction of pile foundations for internal frame columns, characterized in that, The method includes: Step 1, Pre-construction preparation stage: Determine the distribution of soil layers and steel pile locations at the project site, and design earthwork excavation and foundation cushion treatment; Step 2, Pile cap construction: Pile caps are poured at the construction design location, and pile driving holes and anchor rods are reserved at the designed pile positions, ensuring that the pull-out force of the anchor rods meets the pile driving force requirements; Step 3, Static Pressure Pile Construction with Anchor Bolts: Install the pile driving frame and determine the pile driving time, and set up a monitoring system to monitor changes in pile driving pressure; Step 4: Pile sealing construction: Based on the monitoring results from Step 3, pile sealing will be carried out and the sealing time will be determined; Step 5: Temporary pile sealing is used to obtain the sealing pressure in real time, and adjustments are made according to the construction progress of the superstructure. The piles are finally sealed after the superstructure construction is completed. In step three, the monitoring system monitors the pile side earth pressure, and the monitoring method is as follows: S1. Install steel wire pressure sensors on the pile to measure the magnitude of the pile side pressure in real time; S2. Obtain curve E1 based on the change of pile side pressure P1' during the first time period 0 to t0; S3, based on the second time period t0~t m The magnitude of the pile side pressure P m 'Change yields curve E2;' S4. Calculate the area deviation value D corresponding to the time when curves E1 and E2 coincide in the same coordinate system; compare D with the preset deviation threshold D0. thi Compare: If D < D thi If the steel wire pressure sensor is in normal condition, the monitoring strategy will be executed. Otherwise, the monitoring status of the steel wire pressure sensor is determined to be abnormal, and a first abnormal command is issued to perform a test on the steel wire pressure sensor. Before installation, the steel wire pressure sensor needs to undergo stability, waterproof sealing, pressure calibration, and temperature calibration tests. The acquisition of the monitoring strategy includes: According to the formula Calculate the pile stability coefficient S pil Where T(t) is the real-time pile pressure intensity, [t n , t m [t] represents the time period during pile driving operation. i , t j [] represents the time period of the pile driving interval state, and δ and ε are weighting coefficients; The pile stability coefficient S pil With preset threshold [S] A S B Compare sizes: If S pil ∈[S A S B If the pile stability is normal, work can continue. like If the pile stability is deemed abnormal, a second abnormality command is generated to adjust the pile stability. The specific method for controlling pile stability is as follows: Through formula Calculate the pile body adjustment coefficient U pil Where f is a preset function, γ1, γ2, and γ3 are weighting coefficients, and γ1, γ2, and γ3 are all greater than 0; P0 is the standard earth pressure value inside and outside the foundation pit; Pw0 is the standard pore water pressure value; and ΔP is the preset deviation value of earth pressure inside and outside the foundation pit. Adjust the pile body coefficient U pil With preset threshold (U) A U B Compare: If U pil ≤U A If the pressure around the pile is too high, insert a plastic drainage board to drain and reduce the pressure. If U A <U pil ≤U B If the pressure around the pile is normal, then the current pressure value is obtained. If U pil >U B If the pressure around the pile is too low, then pile top settlement monitoring should be performed.

2. The construction method of the reverse construction method for the pile foundation of the inner frame column as described in claim 1, characterized in that, The pile driving stress in step two includes two stages: the stress on the foundation and the stress on the foundation soil. The first stage involves the existing foundation soil bearing the self-weight of the foundation and the existing n1-story structure above, as well as the construction load P1; the first time period is set from 0 to t0. The second stage involves the soil between the piles and the piles jointly bearing the weight of P1 and the self-weight and live load P2 of the later-constructed n2-story structure; the second time period is set from t0 to t1. m ; Where t0 is the start time of pile driving; t m This is the time when the pile driving process ends.

3. The construction method of the reverse construction method for the pile foundation of the inner frame column as described in claim 1, characterized in that, The monitoring system's monitoring scope also includes monitoring of the pile driving process, pile top settlement, pile side friction, pile stress, and pile deformation; the pile side earth pressure monitoring also includes the earth pressure value P inside and outside the foundation pit. sio and pore water pressure value P w Monitoring.

4. The construction method of the reverse construction method for the pile foundation of the inner frame column as described in claim 1, characterized in that, The monitoring of pile top settlement includes: The first part is the consolidation settlement S1 of the shallow foundation at time t0 under the action of P1; The second part is the foundation uplift S that may occur during pile driving due to the soil squeezing effect. r ; The third part is the settlement S2 that continues to occur in the pile foundation under the action of P1 after the sealing pile is completed; Part Four is the foundation settlement S3 under the action of P2; Adding all the above parts together, we get the final settlement: S tfp =S1-S r +S2+S3.

5. The construction method of the reverse construction method for the pile foundation of the inner frame column as described in claim 1, characterized in that, The real-time acquisition method for the pile sealing pressure in step five is as follows: SS1. Real-time pile driving pressure value is obtained by setting a steel wire pressure sensor at the position of the jack supporting the steel pipe piles between the wall and the foundation of the pile cap. SS2. The load of the upper structural steel columns is transferred to the piles, temporary pile sealing is carried out, and the pile sealing pressure value is adjusted according to the real-time calculation results; The force value is determined by the numerical change of the vibrating wire strain gauges arranged on the steel pile, and transmitted through the data transmission line to ensure that the vertical displacement of the steel column does not change when the force value is applied. SS3. After the superstructure construction is completed, the structural pile sealing is carried out, the jacks are removed, and the pile sealing reinforcement is welded.

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