A foundation reinforcing device and construction method for vacuum drainage and high-pressure gas lift combined vibration and pulse hole making

Abstract

This invention relates to a foundation reinforcement device and construction method using a combination of vacuum drainage and high-pressure air lift for vibratory compaction, belonging to the field of foundation construction. The device includes a vibratory compactor, a high-pressure air lift system, and a vacuum drainage system; the vacuum drainage system has a vacuum suction pipe with a filter structure installed outside the vibratory compactor. During construction, the high-pressure air lift assists in borehole formation and forms an air curtain for wall protection, while the vacuum drainage system forcibly pumps out pore water, and the vibratory compactor vibrates and compacts the soil. This invention also includes a dual-pulse control module. When the drainage flow rate drops below 50% of the initial value, a dual-pulse coupled unblocking command is triggered: by alternating changes in vacuum and air pressure, and with the synergistic effect of vibratory compaction, the mud cake on the filter screen surface fatigues and detaches under alternating stress. This invention is specifically designed for silty clay soils, effectively solving the problems of borehole wall collapse and filter layer blockage during vibratory compaction. The drainage flow rate maintenance rate reaches over 80%, the bearing capacity improvement can reach 200%, significantly shortening the construction period and reducing energy consumption.

Description

Technical Field

[0001] This invention relates to the field of foundation construction technology, specifically to a foundation reinforcement device and construction method that combines vacuum drainage and high-pressure air lift with vibratory compaction. Background Technology

[0002] Existing technologies typically employ the following methods for construction on silty clay soils:

[0003] ① The combination of plastic drainage boards and surcharge preloading works by using the load of the upper soil pile to squeeze out the water from the soft soil, allowing the soil to gradually solidify and increase in strength; settlement is completed in advance, and there is no settlement in the later stage of use. The characteristics of this construction method are that it is the most mature, reliable, and cheapest method; the disadvantage is that it usually takes 3 to 6 months or even longer to complete the construction, which is very slow.

[0004] ② The combination of plastic drainage boards and vacuum preloading technology. Its function is to use vacuum negative pressure to draw out water without piling up soil, relying on atmospheric pressure for solidification; its advantage is that it is much faster than surcharge, and construction can generally be completed in 1.5 to 3 months; it is the first choice for silt and ultra-soft soil geology; it has uniform settlement, is not easy to slide sideways, and has little impact on the surrounding area.

[0005] ③ Combined vacuum and surcharge preloading; its effect is that vacuum negative pressure and surcharge positive pressure work together; the drainage efficiency is the sum of the two; its characteristics are that it is the fastest drainage and most thorough consolidation conventional method in soft soil treatment, the construction period can be compressed to 1-2 months, and the bearing capacity is improved most significantly; it is suitable for construction conditions with high requirements, tight schedules, and ultra-soft silt.

[0006] ④ The bagged sand well / sand well preloading method uses sand wells as vertical drainage channels, combined with surcharge drainage consolidation; it is a relatively outdated old technology, now basically replaced by plastic drainage boards; it is more expensive, slower to construct, prone to clogging, and the drainage effect is not as good as drainage boards; it can only be seen in some old specifications and old projects.

[0007] ⑤ Vibro-compaction. Vibro-compaction is a mature foundation treatment method that uses vibratory compactors to compact the soil, significantly improving the bearing capacity of the foundation. However, it generally presents the following technical challenges when treating silty clay:

[0008] 1) Silt-like soil has low cohesion, and the borehole wall is prone to collapse during vibro-compaction, resulting in difficulty in borehole formation and extremely low construction efficiency.

[0009] 2) The pore water in the saturated silt is trapped and difficult to drain in time, which makes the soil softer the more it is vibrated, making it difficult for the pore water to drain out and the density to meet the standard.

[0010] 3) Conventional hole-making methods (such as mechanical hole-making) cause significant soil disturbance and cannot quickly remove mud and sand, resulting in high resistance to the sinking of the vibratory compactor and high energy consumption.

[0011] Currently, the industry lacks a specialized device that can integrate hole drilling, drainage, and compaction, and there is an urgent need for an efficient reinforcement technology solution for silty clay.

[0012] Based on this, the present invention is proposed. Summary of the Invention

[0013] During vibro-compaction construction, it was found that while vacuum-assisted drainage can accelerate water runoff, the fine particles in the silty soil easily form a dense mud cake on the surface of the filter pipe under negative pressure. Once the mud cake forms, its permeability coefficient can be 2-3 orders of magnitude lower than that of the original soil, rendering the drainage channel ineffective. Currently, the industry standard for solving this problem is to stop the machine and lift and flush the mud cake from the filter pipe surface, which significantly impacts construction efficiency.

[0014] This invention addresses the shortcomings of existing technologies by providing a foundation reinforcement device and construction method that combines vacuum drainage and high-pressure air lift for vibratory compaction drilling. The technical solution is as follows:

[0015] A foundation reinforcement device combining vacuum drainage and high-pressure air lift for vibratory compaction drilling includes a vibratory compactor, wherein a shock absorber is installed at the lower end of the guide rod of the vibratory compactor, and further includes:

[0016] The high-pressure air lift system includes a high-pressure air pipeline arranged inside the vibratory impactor and an air nozzle located at the bottom of the vibratory impactor head.

[0017] The vacuum drainage system includes at least four vacuum suction pipes installed on the outside of the vibratory impactor 1, a water collection box located outside the vibratory impactor, and a vacuum suction pump. The upper ends of the vacuum suction pipes are all connected to the water collection box, the water collection box is connected to the vacuum suction pump, and the lower ends of the vacuum suction pipes are provided with a water filter structure.

[0018] Furthermore, the vacuum suction pipe includes an inner pipe and an outer pipe sleeved outside the lower section of the inner pipe. The lower section of the inner pipe and the side wall of the outer pipe are provided with through holes, and the inner pipe and the outer pipe are connected through the through holes. The water filtration structure includes a filter screen and a filter cloth, which are arranged from the outside to the inside between the inner pipe and the outer pipe.

[0019] Furthermore, an upper end cap is installed at the upper end of the outer tube, and a lower end cap is installed at the lower end of the outer tube.

[0020] Furthermore, both the upper end of the upper end cap and the lower end of the lower end cap are provided with a pointed structure with an inclined surface.

[0021] Furthermore, it also includes a dual-pulse control module, which comprises a frequency converter, a pressure regulating valve, a vacuum regulating valve, a drainage flow sensor, and a central controller. The frequency converter is used to adjust the vibration frequency of the vibratory impactor; the pressure regulating valve is used to adjust the output pressure of the high-pressure air lift system; the vacuum regulating valve is used to adjust the output vacuum of the vacuum suction pump; the drainage flow sensor is used to monitor the drainage flow of the vacuum suction pipe 2 in real time; and the central controller receives the drainage flow signal and sends control commands to the frequency converter, the pressure regulating valve, and the vacuum regulating valve according to preset logic. The control commands include a dual-pulse coupling unblocking command.

[0022] Secondly, a foundation reinforcement construction method combining vacuum drainage and high-pressure air lift with vibratory compaction includes the following steps:

[0023] Step S1: Pre-construction preparation, determine the permeability coefficient k of the soil layer to be treated, set the benchmark working parameters, including the benchmark frequency f0, benchmark air pressure P0 and benchmark vacuum degree V0, and record the initial drainage flow rate Q0.

[0024] Step S2: In the air-lift hole-making stage, the high-pressure air-lift system is turned on, the jet nozzle sprays high-pressure airflow to assist hole-making and form an air curtain to protect the wall, and the vibratory impactor vibrates and sinks to the design depth at the reference frequency f0.

[0025] Step S3: During the settling and compaction and forced drainage stage, start the vacuum drainage system, maintain normal operating parameters, and monitor the drainage flow rate Q in real time. When Q drops to less than 50% of the initial flow rate Q0, trigger the dual-pulse coupling unblocking command to perform pulse unblocking operation.

[0026] Step S4: During the lifting, densification, and pile formation stage, aggregate is filled into the hole, and the vibratory compactor is vibrating and lifting simultaneously. The vacuum drainage system continues to operate, and the drainage flow rate Q is monitored in real time. When Q drops to less than 50% of the initial flow rate Q0, a dual-pulse coupling unblocking command is triggered to perform pulsating unblocking operations.

[0027] Furthermore, the dual-pulse coupling unblocking command includes:

[0028] The coupling pulsation frequency f is calculated using the following formula. pulse :

[0029] ;

[0030] Where: f is the vibration frequency of the current vibratory oscillator, ΔV is the vacuum pulsation amplitude, V0 is the reference vacuum degree, ΔP is the air pressure pulsation amplitude, and P0 is the reference air pressure;

[0031] The calculated f pulseThe frequency is adjusted by alternating between the pressure regulating valve and the vacuum regulating valve, causing the output pressure of the high-pressure air lift system and the output vacuum of the vacuum water pump to change periodically in the following manner:

[0032] First half of the cycle: Output vacuum V = V0 + ΔV / 2, output pressure P = P0 - ΔP / 2;

[0033] Second half of the cycle: Output vacuum V = V0 - ΔV / 2, output gas pressure P = P0 + ΔP / 2.

[0034] Furthermore, the vacuum pulsation amplitude ΔV and the gas pressure pulsation amplitude ΔP are determined based on the permeability coefficient k measured in step S1:

[0035] When k>10 -5 When the speed is cm / s, it is classified as Class I geological condition, and the dual-pulse coupling unblocking command is not used for pulse unblocking operation;

[0036] When 10 -6 cm / s≤k≤10 -5 When the speed is cm / s, it is classified as Class II geological condition, and the initial ΔP is set to 0.10MPa and the initial ΔV to 15kPa.

[0037] When k < 10 -6 When the speed is cm / s, it is classified as Class III geological condition, with initial ΔP = 0.20 MPa and initial ΔV = 30 kPa.

[0038] Furthermore, after the pulsating unblocking operation lasts for 5-10 seconds, it is assessed whether the drainage flow rate Q has recovered to above 0.8Q0:

[0039] If recovery occurs, stop the pulsation and restore constant parameters;

[0040] If the problem persists, increase ΔP by 0.05 MPa and ΔV by 10 kPa, and recalculate f. pulse And execute the dual-pulse coupling unblocking command again.

[0041] Furthermore, in step S4, a preventative hole cleaning operation is actively performed every 2m of elevation, with ΔV=10kPa and ΔP=0.05MPa substituted into the coupling pulsation frequency f. pulse The calculation formula for f pulse Execute dual pulses for 3 seconds.

[0042] Furthermore, in step S2, the high-pressure air lift system operates at maximum air pressure P. max High-pressure airflow is continuously injected; in step S2, the vacuum drainage system is shut off or maintained at low power.

[0043] In this invention, high pressure refers to a gas pressure state with a gauge pressure greater than or equal to 0.5 MPa relative to standard atmospheric pressure. In this invention, the operating gas pressure range of the high-pressure gas lift system is 0.6~0.8 MPa. Wherein, 0.6 MPa is the reference operating gas pressure P0, and 0.8 MPa is the maximum operating gas pressure P... max This pressure range ensures that the airflow ejected from the bottom nozzle has sufficient kinetic energy to create an effective airlift slag removal effect and an air curtain wall protection effect.

[0044] Low-power maintenance refers to the vacuum drainage system not actively draining water during the air-lift pore-forming stage (step S2), but instead operating at the minimum power required to maintain the system in standby mode. Specifically, low-power maintenance means the vacuum suction pump operates at 10%~20% of its rated power, maintaining a slight negative pressure of 0~10 kPa within the vacuum pipeline. The function of this slight negative pressure is:

[0045] 1) Prevent external mud from flowing back in under gravity;

[0046] 2) Keep the pipeline filled with air rather than mud so that a baseline vacuum V0 can be quickly established when transitioning to step S3;

[0047] 3) Avoid equipment damage and current surges caused by frequent start-stop of vacuum water pumps.

[0048] When step S3 requires vacuum drainage, the system directly increases power from the low power maintenance state to the normal working state, establishes the reference vacuum level V0 (80kPa), and the response time does not exceed 3 seconds.

[0049] Furthermore, the reference operating parameters are: f0=30Hz, P0=0.6MPa, V0=80kPa.

[0050] In this invention, the vibration of the vibratory compactor provides an alternating stress field, causing a slight relative displacement between the cake unit and the filter screen interface. Since the filter screen is made of stainless steel and the filter cloth is made of 200g geotextile layers, a certain gap redundancy exists between the inner and outer tubes, allowing the stainless steel filter screen to move slightly under various forces. Therefore, the alternating suction force caused by vacuum pulsation can further promote the detachment of the cake unit from the filter screen surface; the external scouring force caused by air pressure pulsation creates an alternating flow field, flushing loose particles away from the orifice; or, when the negative pressure suction is at its lowest point, the external scouring force caused by air pressure pulsation can accelerate the detachment of the cake unit. With these multiple effects acting alternately, the cake unit is repeatedly subjected to these forces, preventing it from forming a stable adhesion.

[0051] Compared with the prior art, the beneficial effects of the present invention are:

[0052] 1. This invention utilizes high-pressure air lift to form an air curtain for wall protection, combined with vacuum drainage to reduce soil moisture content, thus minimizing the risk of borehole collapse in silty clay soils. High-pressure air lift borehole creation is highly efficient, eliminating the need for traditional mud wall protection, saving on mud preparation and treatment steps, and shortening the construction period by more than 30%.

[0053] 2. The present invention uses a control method corresponding to the dual-pulse coupling unblocking command to actively disrupt the dynamic conditions of mud cake unit formation during construction, so that the through holes used for water filtration can remain unobstructed to the maximum extent within a single construction cycle, and the drainage flow rate can be maintained at over 80%.

[0054] 3. Due to the continuous unobstructed drainage channels, pore water is forcibly discharged, and the soil is fully compacted under vibration. For silty clay, the bearing capacity can be increased from 60 kPa to over 180 kPa, an increase of over 200%.

[0055] 4. The construction method of the present invention is less prone to large-scale blockage within a single construction cycle, thus eliminating the need to stop the machine to clean the filter element or replace the pipeline, resulting in good construction continuity and a significant reduction in the construction time of a single pile.

[0056] 5. This invention significantly reduces the sinking resistance of the vibratory flusher. Compared to the disproportionate water absorption effect and energy consumption caused by using constant parameters for forced water absorption when slight blockage occurs, the energy consumption of the equipment of this invention is relatively low (dual pulse control), making it economical and environmentally friendly. Attached Figure Description

[0057] Figure 1 This is a schematic diagram of the foundation reinforcement device for combined vacuum drainage and high-pressure air lift vibration drilling as described in this invention.

[0058] Figure 2 This is a schematic diagram of the structure of the vacuum water suction pipe described in this invention;

[0059] Figure 3 for Figure 2 AA view;

[0060] Figure 4 for Figure 3 Enlarged view of section B in the middle. Detailed Implementation

[0061] The present invention will be described in detail below with reference to specific embodiments. These embodiments are merely some, not all, implementations of the present invention. All other implementations obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0062] Example 1

[0063] like Figures 1-4 As shown, a foundation reinforcement device combining vacuum drainage and high-pressure air lift for vibratory drilling includes a vibratory drill 1, with a shock absorber 4 installed at the lower end of the guide rod of the vibratory drill 1. Firstly, the vibratory drill itself has an internal circulating cooling water channel responsible for cooling the motor.

[0064] The high-pressure air lift system includes a high-pressure air pipeline arranged inside the vibratory impactor 1, and an air nozzle located at the bottom of the vibratory impactor 1 head.

[0065] High-pressure air is injected downwards from the nozzle at the bottom through external pipelines and high-pressure air pipelines to achieve functions such as cooling the motor, assisting in hole making, protecting the hole wall, and removing mud and sand entrained in the hole.

[0066] The vacuum drainage system includes at least four vacuum suction pipes 2 installed on the outside of the vibratory impactor 1, a water collection box 3 set outside the vibratory impactor 1, and a vacuum suction pump. The upper ends of the vacuum suction pipes 2 are all connected to the water collection box 3, the water collection box 3 is connected to the vacuum suction pump, and the lower ends of the vacuum suction pipes 2 are provided with a water filter structure.

[0067] The vacuum suction pump provides negative pressure to the vacuum suction pipe 2. After the vibratory compactor squeezes out the pore water in the soil, it will be discharged to the ground through the vacuum suction pipe 2, the water collection box, the external water pipe, and the vacuum suction pump under the action of negative pressure.

[0068] In other embodiments, the foundation reinforcement device combining vacuum drainage and high-pressure air lift with vibratory compaction can be used in the following ways:

[0069] 1. High-pressure air lift drilling: When the vibratory compactor sinks, the jet nozzle at the bottom sprays out high-pressure airflow, forming an air lift effect, which liquefies the soil at the bottom of the hole and carries it upward and out. At the same time, the high-pressure airflow forms an air film, which effectively protects the wall and prevents collapse.

[0070] 2. Synchronous vacuum drainage: While high-pressure air lift drilling is being carried out, a vacuum water pump is started to extract pore water around the hole through the lower water filter structure, quickly reducing the soil moisture content.

[0071] 3. Vibro-compaction reinforcement: Utilizing the vibration energy of a 180kW high-power vibro-compactor, the dehydrated soil is forcefully compacted, achieving rapid soil compaction and significantly improving the bearing capacity of the foundation.

[0072] Example 2

[0073] Based on Embodiment 1, the vacuum suction pipe 2 includes an inner pipe 21 and an outer pipe 22 sleeved outside the lower section of the inner pipe 21. The lower section of the inner pipe 21 and the side wall of the outer pipe 22 are both provided with through holes 27, and the inner pipe 21 and the outer pipe 22 are connected through the through holes 27. The water filtration structure includes a filter screen 25 and a filter cloth 26, which are arranged from the outside to the inside between the inner pipe 21 and the outer pipe 22.

[0074] The upper end of the inner pipe is connected to the water collection box.

[0075] The filter screen 25 is preferably an 80-mesh stainless steel filter screen (to prevent clogging by fine particles). It is protected by an outer tube. In some embodiments, the upper end of the outer tube 22 is fitted with an upper end cap 23, and the lower end of the outer tube 22 is fitted with a lower end cap 24.

[0076] The upper end cap 23 and the lower end cap 24 are designed to facilitate sealing the tube and to facilitate fixing the outer tube to the vibratory compactor.

[0077] In some other embodiments, the lower end cap may also be provided with a threaded hole; when drainage is required, this threaded hole is plugged with a screw. In geological conditions where drainage is not required, this vacuum suction pipe 2 can be used to spray water and air, thereby effectively broadening the application scope of the invention.

[0078] In some other embodiments, the upper end of the upper endcap 23 and the lower end of the lower endcap 24 are both provided with a pointed structure with a bevel. This design helps to reduce resistance at this point during lifting and lowering.

[0079] Example 3

[0080] Based on Embodiment 1 or Embodiment 2, in this example, the foundation reinforcement device for combined vacuum drainage and high-pressure air lift vibratory compaction further includes a dual-pulse control module. This module includes a frequency converter, a pressure regulating valve, a vacuum regulating valve, a drainage flow sensor, and a central controller. The frequency converter is used to adjust the vibration frequency of the vibratory compactor; the pressure regulating valve is used to adjust the output pressure of the high-pressure air lift system; the vacuum regulating valve is used to adjust the output vacuum of the vacuum suction pump; the drainage flow sensor is used to monitor the drainage flow rate of the vacuum suction pipe 2 in real time; and the central controller receives the drainage flow rate signal and sends control commands to the frequency converter, pressure regulating valve, and vacuum regulating valve according to preset logic. The control commands include a dual-pulse coupling unblocking command.

[0081] Based on Example 1, the construction method can be further extended as follows:

[0082] A foundation reinforcement construction method combining vacuum drainage and high-pressure air lift with vibratory compaction includes the following steps:

[0083] Step S1: Pre-construction preparation, determining the permeability coefficient k of the soil layer to be treated, classifying the geological structure based on the permeability coefficient k, and determining the initial parameters for the vacuum pulsation amplitude:

[0084] Set the reference operating parameters, including reference frequency f0, reference pressure P0 and reference vacuum V0; f0=30Hz, P0=0.6MPa, V0=80kPa.

[0085] Record the first stable reading of the drainage flow rate after construction begins, as the initial drainage flow rate Q0.

[0086] Step S2: The vibratory impactor vibrates at a reference frequency and sinks to the designed depth;

[0087] Once the vibratory impactor is in place, the high-pressure air lift system is activated, and the air lift hole-forming stage begins.

[0088] The jet nozzle operates at maximum air pressure P max (e.g., 0.8MPa) Continuously inject high-pressure air to form an air lift effect to assist in hole formation, while simultaneously forming an air curtain to protect the wall.

[0089] The vibratory impactor vibrates and sinks at a reference frequency f0.

[0090] During this stage, the vacuum drainage system is either shut down or maintained at low power.

[0091] After the vibratory compactor is lowered to the designed depth, proceed to step S3.

[0092] Step S3: During the settling and compaction and forced drainage stage, turn on the vacuum water pump to establish a reference vacuum level V0, and the vacuum water suction pipe begins to extract pore water around the hole.

[0093] Maintain normal operating parameters: vibration frequency f=f0, air pressure P=P0, vacuum degree V=V0 (constant).

[0094] Real-time monitoring of drainage flow rate Q.

[0095] When the monitored drainage flow rate Q drops to below 50% of the initial flow rate Q0, a dual-pulse coupling deblocking command is triggered to perform a pulse deblocking operation.

[0096] The dual-pulse coupling unblocking command includes:

[0097] The coupling pulsation frequency f is calculated using the following formula. pulse :

[0098] ;

[0099] In the formula: f is the current vibration frequency of the vibratory shock, in Hz; ΔV is the vacuum pulsation amplitude, in kPa; V0 is the reference vacuum degree, in kPa; ΔP is the air pressure pulsation amplitude, in MPa; P0 is the reference air pressure, in MPa;

[0100] The calculated f pulse The frequency is adjusted by alternating between the pressure regulating valve and the vacuum regulating valve, causing the output pressure of the high-pressure air lift system and the output vacuum of the vacuum water pump to change periodically in the following manner:

[0101] First half of the cycle: Output vacuum V = V0 + ΔV / 2, output pressure P = P0 - ΔP / 2;

[0102] Second half of the cycle: Output vacuum V = V0 - ΔV / 2, output gas pressure P = P0 + ΔP / 2.

[0103] In addition, the vacuum pulsation amplitude ΔV and the gas pressure pulsation amplitude ΔP are determined based on the permeability coefficient k measured in step S1:

[0104] When k>10 -5 When the speed is cm / s, it is classified as Class I geological condition, and the dual-pulse coupling unblocking command is not used for pulse unblocking operation;

[0105] When 10 -6 cm / s≤k≤10 -5 When the speed is cm / s, it is classified as Class II geological condition, and the initial ΔP is set to 0.10MPa and the initial ΔV to 15kPa.

[0106] When k < 10 -6 When the speed is cm / s, it is classified as Class III geological condition, with initial ΔP = 0.20 MPa and initial ΔV = 30 kPa.

[0107] Through extensive testing and analysis, it was found that: Class I geological conditions generally do not experience blockages and do not require pulsed unblocking operations; Class II geological conditions have a moderate risk of blockage and are the main geological types to which this invention is applicable; Class III geological conditions have a high risk of blockage and require a larger pulse amplitude.

[0108] After the pulsating unblocking operation lasts for 5-10 seconds, assess whether the drainage flow rate Q has recovered to above 0.8Q0:

[0109] If recovery occurs, stop the pulsation and restore constant parameters;

[0110] If the problem persists, increase ΔP by 0.05 MPa and ΔV by 10 kPa, and recalculate f. pulse And execute the dual-pulse coupling unblocking command again.

[0111] The vibratory compactor continues to sink until it reaches the designed depth.

[0112] Step S4: The vacuum drainage system continues to operate and monitors the drainage flow rate Q in real time. When Q drops to less than 50% of the initial flow rate Q0, a dual-pulse coupling deblocking command is triggered to perform a pulse deblocking operation.

[0113] During the reinforcement and pile formation stage, crushed stone and other aggregates are filled into the hole in batches, and the vibratory compactor is used to lift the pile while vibrating.

[0114] The vacuum drainage system operates continuously, maintaining V=V0.

[0115] Real-time monitoring of drainage flow rate Q; when Q < 0.5Q0, execution of dual-pulse coupling unblocking command.

[0116] For every 2m elevation, a preventative hole cleaning operation is proactively performed, with ΔV=10kPa and ΔP=0.05MPa substituted into the coupling pulsation frequency f. pulse The calculation formula for f pulse The system performs a dual-pulse cycle for 3 seconds to prevent mud cake from gradually accumulating during long-term construction.

[0117] After the vibratory impactor is pulled out of the orifice, the high-pressure air lift system is shut off, and the vacuum water pump continues to run for 30 seconds to drain the remaining water from the pipeline before shutting it off.

[0118] Move the machine to the next pile location and repeat steps S2 to S4.

[0119] In this example, one method of implementing preventative hole cleaning is as follows:

[0120] S4.1 Pause the vibratory impactor lifting, maintain the current depth position, and continue vibration;

[0121] S4.2, Set the mild pulsation parameter: ΔV temp =10kPa, ΔP temp =0.05MPa.

[0122] S4.3 Read the current vibration frequency f and substitute it into the core formula to calculate the coupling pulsation frequency f at this time. pulse :

[0123] ;

[0124] The calculated f pulse Frequency, perform pulsed unblocking operation, lasting 3 seconds:

[0125] First half of the cycle: Vacuum degree V = V0 + 5 kPa, air pressure P = P0 - 0.025 MPa;

[0126] Second half of the cycle: Vacuum degree V = V0 - 5 kPa, Gas pressure P = P0 + 0.025 MPa;

[0127] S4.5 After 3 seconds, the pulsation stops and the constant parameters f=f0, P=P0, V=V0 are restored.

[0128] S4.6 Resume vibratory compactor lifting and continue the packing densification construction.

[0129] Example 4

[0130] This example is a specific application example. Both this example and the comparative example use the same equipment:

[0131] The vibratory impactor power is 180kW; the reference frequency f0 is 30Hz; the reference air pressure P0 is 0.6MPa; the maximum air pressure P max The initial pulsation amplitude (when enabled) is 0.8 MPa; the reference vacuum level V0 is 80 kPa; the initial pulsation amplitude is ΔP = 0.1 MPa and ΔV = 15 kPa.

[0132] The performance evaluation indicators are as follows:

[0133] Drainage flow maintenance rate, the ratio of drainage flow at the end of construction to the initial flow;

[0134] Unblocking success rate: the percentage of times traffic recovers to more than 80% of the initial traffic after unblocking is triggered out of the total number of triggers;

[0135] Single pile construction time is the total time from the start of drilling to the completion of pile construction.

[0136] Final bearing capacity, characteristic value of the bearing capacity of the soil between piles after pile completion.

[0137] The geological conditions in this example are: silty clay with a permeability coefficient k = 3.2 × 10⁻⁶. -6 cm / s, average particle size d 50 =0.025mm, natural moisture content 58%, initial bearing capacity 60kPa. It belongs to Class II geology.

[0138] The specific construction process in this example is as follows:

[0139] The method described in Example 3 is executed according to steps S1 to S4 as described above. When the flow rate drops to 0.5Q0, f is calculated. pulse =30×(15 / 80)×(0.1 / 0.6)=0.94Hz, the pressure and vacuum alternate at a frequency of 0.94Hz with opposite phases for 5 seconds. The flow rate returns to normal parameters after recovering to above 0.8Q0.

[0140] The experimental results are shown in Table 1:

[0141] Table 1

[0142]

[0143] Comparative Example 1

[0144] The geological conditions were exactly the same as in Example 4, only the construction in different areas was compared (the purpose was to use multiple construction methods simultaneously to speed up the construction period; silty clay, k=3.2×10). -6 (cm / s).

[0145] The construction process uses traditional constant parameter control and does not enable the pulsating unblocking function. When the drainage flow rate decreases, no parameter adjustment is made, and the original parameters are maintained forcibly for construction (the reason is that the appropriate parameters were not properly calibrated in the early stage, and the forced construction is to collect data).

[0146] The experimental results are shown in Table 2:

[0147] Table 2

[0148]

[0149] A comparison between Example 4 and this example shows that, under the same silty soil geological conditions, without the construction method of this invention, the drainage flow rate begins to drop sharply after about 8 minutes of construction. Once the filter holes are completely blocked by silt, pore water cannot drain, and the vibratory compactor becomes increasingly soft in the saturated soil, failing to effectively compact it. The final bearing capacity only increases to 95 kPa, far below the design requirement of 150 kPa. The construction time is significantly prolonged due to the increased resistance to the vibratory compactor's sinking after blockage.

[0150] Comparative Example 2

[0151] Geological conditions: Sandy silt, permeability coefficient k = 5.8 × 10⁻⁶ -4 cm / s, average particle size d 50 =0.12mm, natural moisture content 22%, initial bearing capacity 110kPa. Belongs to Class I geology.

[0152] The construction process uses the same method as in Example 4 (that is, the method in Example 3).

[0153] The experimental results are shown in Table 3:

[0154] Table 3

[0155]

[0156] A comparison between Example 4 and this example shows that when the geology is sandy silt, unblocking is triggered only once during the entire construction process, and even without triggering pulsation, the flow rate can recover on its own. Using the method of this invention, the construction time is only shortened by about 2 minutes compared to normal construction, a negligible effect. The pulsation unblocking operation of this invention has almost no chance of being effective in such geological conditions; frequent pulsation may actually increase equipment wear and tear.

[0157] Comparative Example 3

[0158] The geological conditions in this example are: stiff plastic clay with a permeability coefficient k = 8.5 × 10⁻⁶. -8 cm / s, average particle size d 50 =0.003mm, natural moisture content 35%, initial bearing capacity 180kPa. Belongs to Class III geology.

[0159] The construction process employed the same dual-pulse coupling unblocking command as in Example 4, with initial ΔP = 0.1 MPa and ΔV = 15 kPa. If unblocking failed, ΔP was progressively increased to 0.3 MPa and ΔV to 50 kPa.

[0160] The test results are shown in Table 4:

[0161] Table 4

[0162]

[0163] A comparison of Example 4 and this example shows that the permeability coefficient of stiff plastic clay is two orders of magnitude lower than that of silty clay, and the soil itself is almost impermeable. The vacuum drainage system could not extract much water from the outset, and the surface of the pores was quickly and completely sealed by a dense mud cake formed by the clay particles. Even when the pulsation amplitude was increased to a value far exceeding the safe operating range of the equipment, the drainage flow rate could not be restored. The reason for this may be that the cohesive force of the mud cake in the stiff plastic clay far exceeds the maximum shear force that the pulsating shear force can provide, and the physical premise on which the method of this invention relies is not valid.

[0164] As can be seen from the above, the method of the present invention is specifically designed for special geological conditions where fine particles such as silty clay can form mud cakes, but the mud cakes have limited cohesiveness.

[0165] As can be seen from the above embodiments and comparative examples, the construction method provided by the present invention has significant technical effects specifically for silty soil, and can alleviate the blockage problem of vacuum suction pipes during construction to the greatest extent, thereby achieving smooth drainage and a significant increase in bearing capacity.

[0166] Furthermore, it should be understood that those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A foundation reinforcement device combining vacuum drainage and high-pressure air lift for vibratory compaction, comprising a vibratory compactor, wherein a shock absorber is installed at the lower end of the guide rod of the vibratory compactor, characterized in that, Also includes: The high-pressure air lift system includes a high-pressure air pipeline arranged inside the vibratory impactor and an air nozzle located at the bottom of the vibratory impactor head. The vacuum drainage system includes at least four vacuum suction pipes installed on the outside of the vibratory impactor 1, a water collection box located outside the vibratory impactor, and a vacuum suction pump. The upper ends of the vacuum suction pipes are all connected to the water collection box, the water collection box is connected to the vacuum suction pump, and the lower ends of the vacuum suction pipes are provided with a water filter structure.

2. The foundation reinforcement device for combined vacuum drainage and high-pressure air lift vibratory drilling according to claim 1, characterized in that: The vacuum suction pipe includes an inner pipe and an outer pipe sleeved outside the lower section of the inner pipe. The lower section of the inner pipe and the side wall of the outer pipe are provided with through holes, and the inner pipe and the outer pipe are connected through the through holes. The water filtration structure includes a filter screen and a filter cloth, which are arranged from the outside to the inside between the inner pipe and the outer pipe.

3. The foundation reinforcement device for combined vacuum drainage and high-pressure air lift vibratory drilling according to claim 2, characterized in that: The upper end of the outer tube is fitted with an upper end cap, and the lower end of the outer tube is fitted with a lower end cap.

4. The foundation reinforcement device for combined vacuum drainage and high-pressure air lift vibratory drilling according to claim 3, characterized in that: The upper end of the upper end cap and the lower end of the lower end cap are both provided with a pointed structure with a bevel.

5. The foundation reinforcement device for combined vacuum drainage and high-pressure air lift vibratory drilling according to claim 1, characterized in that, It also includes a dual-pulse control module, which comprises a frequency converter, a pressure regulating valve, a vacuum regulating valve, a drainage flow sensor, and a central controller. The frequency converter is used to adjust the vibration frequency of the vibratory impactor, the pressure regulating valve is used to adjust the output pressure of the high-pressure air lift system, the vacuum regulating valve is used to adjust the output vacuum of the vacuum suction pump, the drainage flow sensor is used to monitor the drainage flow of the vacuum suction pipe 2 in real time, and the central controller receives the drainage flow signal and sends control commands to the frequency converter, the pressure regulating valve, and the vacuum regulating valve according to preset logic.

6. A foundation reinforcement construction method using a combination of vacuum drainage and high-pressure air lift for vibro-compaction drilling, wherein the foundation reinforcement device using a combination of vacuum drainage and high-pressure air lift for vibro-compaction drilling as described in any one of claims 1 to 5 is employed, characterized in that... Includes the following steps: Step S1: Pre-construction preparation, determine the permeability coefficient k of the soil layer to be treated, set the benchmark working parameters, including the benchmark frequency f0, benchmark air pressure P0 and benchmark vacuum degree V0, and record the initial drainage flow rate Q0. Step S2: In the air-lift hole-making stage, the high-pressure air-lift system is turned on, the jet nozzle sprays high-pressure airflow to assist hole-making and form an air curtain to protect the wall, and the vibratory impactor vibrates and sinks to the design depth at the reference frequency f0. Step S3: During the settling and compaction and forced drainage stage, start the vacuum drainage system, maintain normal operating parameters, and monitor the drainage flow rate Q in real time. When Q drops to less than 50% of the initial flow rate Q0, trigger the dual-pulse coupling unblocking command to perform pulse unblocking operation. Step S4: During the lifting, densification, and pile formation stage, aggregate is filled into the hole, and the vibratory compactor is vibrating and lifting simultaneously. The vacuum drainage system continues to operate, and the drainage flow rate Q is monitored in real time. When Q drops to less than 50% of the initial flow rate Q0, a dual-pulse coupling unblocking command is triggered to perform pulsating unblocking operations.

7. The foundation reinforcement construction method of vacuum drainage and high-pressure air lift combined vibratory compaction drilling according to claim 6, characterized in that, The dual-pulse coupling unblocking command includes: The coupling pulsation frequency f is calculated using the following formula. pulse : ； Where: f is the vibration frequency of the current vibratory oscillator, ΔV is the vacuum pulsation amplitude, V0 is the reference vacuum degree, ΔP is the air pressure pulsation amplitude, and P0 is the reference air pressure; The calculated f pulse The frequency is adjusted by alternating between the pressure regulating valve and the vacuum regulating valve, causing the output pressure of the high-pressure air lift system and the output vacuum of the vacuum water pump to change periodically in the following manner: First half of the cycle: Output vacuum V = V0 + ΔV / 2, output pressure P = P0 - ΔP / 2; Second half of the cycle: Output vacuum V = V0 - ΔV / 2, output gas pressure P = P0 + ΔP / 2.

8. The foundation reinforcement construction method of vacuum drainage and high-pressure air lift combined vibratory compaction drilling according to claim 7, characterized in that, The vacuum pulsation amplitude ΔV and the gas pressure pulsation amplitude ΔP are determined based on the permeability coefficient k measured in step S1: When k>10 -5 When the speed is cm / s, it is classified as Class I geological condition, and the dual-pulse coupling unblocking command is not used for pulse unblocking operation; When 10 -6 cm / s≤k≤10 -5 When the speed is cm / s, it is classified as Class II geological condition, and the initial ΔP is set to 0.10MPa and the initial ΔV to 15kPa. When k < 10 -6 When the speed is cm / s, it is classified as Class III geological condition, with initial ΔP = 0.20 MPa and initial ΔV = 30 kPa.

9. The foundation reinforcement construction method of vacuum drainage and high-pressure air lift combined vibratory compaction drilling according to claim 7, characterized in that, After the pulsating unblocking operation lasts for 5-10 seconds, assess whether the drainage flow rate Q has recovered to above 0.8Q0: If recovery occurs, stop the pulsation and restore constant parameters; If the problem persists, increase ΔP by 0.05 MPa and ΔV by 10 kPa, and recalculate f. pulse And execute the dual-pulse coupling unblocking command again.

10. The foundation reinforcement construction method of vacuum drainage and high-pressure air lift combined vibratory drilling according to claim 7, characterized in that, In step S4, a preventative hole cleaning operation is performed every 2m of lifting. The coupling pulsation frequency f is substituted with ΔV=10kPa and ΔP=0.05MPa. pulse The calculation formula for f pulse Execute dual pulses for 3 seconds.

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