Method for treating vibro-replacement gravel pile composite foundation in silt gravel liquefied stratum and improving bearing capacity of vibro-replacement gravel pile composite foundation
The vibro-compaction stone pile treatment method, which involves precise design and real-time monitoring, solves the problem of controlling the pile penetration depth in silty gravel liquefaction strata, thereby improving the bearing capacity of the foundation and achieving efficient, environmentally friendly, and economical construction.
Patent Information
- Application Number
- CN202511860287.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-10
- Publication Date
- 2026-03-20
AI Technical Summary
Existing technologies struggle to precisely control the penetration depth of piles when treating silty gravel liquefaction strata, resulting in insufficient bearing capacity and easy damage to surrounding strata during construction, failing to meet the requirements for efficient, environmentally friendly, and economical foundation treatment.
By precisely designing the layout and length of the vibratory compaction stone piles, selecting suitable crushed stone fill materials, and combining measurement equipment to ensure the accuracy of pile positioning and construction precision, the working current of the vibratory compactor motor is monitored in real time to control the sinking speed and suspension vibration time. Intermittent filling material is vibrated to compact the piles, ensuring the density of the pile body, and the bearing capacity is verified.
It improves the bearing capacity and stability of the foundation, reduces the amount of construction work and costs, reduces disturbance to the surrounding environment, has strong adaptability, and meets the bearing capacity and stability requirements of engineering structures.
Smart Images
Figure CN121700798A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of foundation treatment technology, specifically to a method for treating and enhancing the bearing capacity of a composite foundation using vibratory compaction and stone piles in liquefied silty gravel strata. Background Technology
[0002] In the field of civil engineering, the stability and bearing capacity of the foundation are the basic prerequisites for ensuring the safety and normal use of various engineering structures. Among them, silty gravel liquefaction strata, as a special and complex geological type, are widely distributed in many water conservancy projects, building projects and other construction areas. They are mainly composed of silt and gravel, which makes this stratum prone to a series of problems that are detrimental to the stability of the project when subjected to external loads or vibration. When subjected to dynamic forces such as earthquakes and mechanical vibrations, the structure between soil particles will quickly become unstable. The stress originally borne by the contact between particles will be quickly transferred to the pore water, causing the pore water pressure to rise sharply. Once the pore water pressure exceeds the effective stress of the soil, the soil will lose its shear strength and liquefy, causing uneven settlement, tilting or even failure of the engineering structure, seriously threatening the safety and stability of the project.
[0003] Existing treatment technologies for liquefiable silty gravel strata have many limitations. While conventional crushed stone pile construction is a common method, it's difficult to precisely control the depth of pile penetration into the liquefied layer. Due to the complex and variable geological conditions, the pile's density is affected by factors such as particle size distribution and water content during penetration, making it difficult to guarantee a stable bearing system. This not only affects the overall bearing capacity of the foundation but may also lead to safety hazards during the project's use. Replacement is another traditional foundation treatment method; however, this method requires large-scale excavation and replacement of the liquefied strata, increasing construction workload and costs. Furthermore, the excavation process can easily damage the original structure of surrounding strata, causing geological disturbances that may trigger secondary disasters in the surrounding strata, further increasing the complexity and risk of the project. In addition, replacement is difficult to balance in terms of construction feasibility, economy, and geological adaptability, failing to meet the modern engineering requirements for efficient, environmentally friendly, and economical foundation treatment. Therefore, a new foundation treatment technology solution that can specifically address these problems is urgently needed. Summary of the Invention
[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for treating and enhancing the bearing capacity of vibratory compaction stone pile composite foundations in liquefiable silty gravel strata. This method, through comprehensive geological survey results during the preliminary parameter design and site preparation stages, precisely designs the layout and length of the vibratory compaction stone piles. It also rigorously selects suitable crushed stone fill materials and carefully treats the construction site to ensure that construction conditions meet requirements. During the measurement, positioning, and pile driver calibration stages, measuring equipment and techniques are used to ensure the accuracy of pile location and the precision of pile driver calibration, laying a solid foundation for subsequent construction. During the vibratory compaction drilling process, the electrical conductivity of the vibratory compactor is monitored in real time. By controlling the operating current of the vibratory compactor and the suspension vibration time, the quality of hole drilling is ensured. During the intermittent filling and compaction stage of pile formation, the density of each section of the pile is precisely controlled to ensure the stability of the pile's bearing capacity. In the top treatment and bearing capacity verification stage, the foundation treatment area is subjected to overall compaction and rigorous bearing capacity tests to ensure the quality of the composite foundation. This reduces the amount of construction work and costs, minimizes disturbance to the surrounding environment, and allows for flexible adjustment of parameters according to actual geological conditions. It has strong engineering adaptability and can effectively improve the foundation bearing capacity of silty gravel liquefaction strata, meeting the bearing and stability requirements of engineering structures.
[0005] To solve the above-mentioned technical problems, this invention provides the following technical solution: a method for treating and enhancing the bearing capacity of a composite foundation of vibro-compacted crushed stone piles in silty gravel liquefaction strata, comprising the following specific steps:
[0006] Preliminary parameter design and site preparation: Parameters of liquefiable silty gravel strata and underlying non-liquefiable soil layers were obtained through geological survey. The layout and length of vibro-compacted crushed stone piles were designed, qualified crushed stone filler was selected, and the site was leveled, the groundwater level was controlled, and soft areas were compacted to meet construction requirements.
[0007] Measurement and positioning and pile driver calibration: Use professional equipment to measure the pile position outline and control points, mark the boundary of the liquefaction zone and locate the pile hole. After the vibratory pile driver is in place, adjust the verticality and calibrate the pile tip and the pile position mark point to ensure that the deviation meets the requirements.
[0008] Vibro-compaction drilling construction: Start the water supply system and vibro-compactor of the vibro-compactor, control the vibro-compactor to sink at a uniform speed and suspend it to expand the hole, monitor the motor current during construction, and when the vibro-compactor reaches the designed pile length, lift the vibro-compactor and clean the loose soil at the bottom of the hole.
[0009] Intermittent filling compaction pile formation: Clean the pile hole, lift the vibratory compactor away from the hole, fill with the preset volume of crushed stone filling, start the vibration function to compact the filling, repeat the process until the top surface elevation of the pile reaches the design requirements.
[0010] Top treatment and bearing capacity verification: The treated area is compacted with a road roller. After the pile body is cured to the specified age, a bearing capacity test is carried out. After passing the test, a crushed stone cushion layer is laid and compacted by vibration rolling.
[0011] Furthermore, in the preliminary parameter design and site preparation steps, the distribution range, thickness, physical and mechanical parameters of the liquefiable silty gravel strata, and the burial depth and properties of the underlying non-liquefiable soil layers are obtained through geological surveys. Based on the survey results, the layout of the vibro-compacted crushed stone piles is designed, and it is determined that the piles must completely penetrate the liquefied layer and extend to a predetermined depth within the non-liquefied soil layer. At the same time, crushed stone with continuous gradation, hard particles, no weathering, and no soil impurities is selected as filler to meet the requirements of pile strength and permeability. The construction site is leveled to ensure that the construction surface elevation reaches the design preset value. A drainage system or dewatering measures are used to control the groundwater level below the preset depth below the construction surface to avoid the water level being too high and affecting the quality of pile formation. For the soft areas in the site, the layered compaction method with slag is used for compaction.
[0012] Furthermore, in the measurement, positioning, and pile driver calibration steps, engineering surveying equipment is used to measure and set the outline of the pile positions in different areas according to the design drawings. Control points and leveling points marked with durable materials are set simultaneously to ensure stability during the construction period. The position of a single pile hole is determined by marking with steel rods or grouting lime into the hole. During construction, the principle of positioning while constructing is followed, that is, the next pile hole is positioned after the construction of one pile hole is completed. At the same time, markers are set at the boundary between liquefied and non-liquefied strata. The vibratory pile driver is moved to the designated pile position. The verticality of the pile driver body meets the design specifications by adjusting the height of the pile driver's outriggers and the angle of the guide rod. Then, a plumb bob or laser calibrator is used to align and calibrate the pile tip with the pile position marking point to ensure that the deviation between the center of the pile tip and the pile position marking point is within the design allowable range.
[0013] Furthermore, in the vibratory compaction drilling process, the water supply system of the vibratory compaction equipment is started and the water pressure and flow rate are adjusted to preset parameters. After a stable water flow is formed at the lower outlet of the vibratory compactor, the vibratory compactor is started and put into normal vibration operation. First, the warning value of the vibratory compactor motor current is calculated, and then the vibratory compactor is controlled to sink vertically into the silty gravel layer. During the sinking process, the sinking is paused after penetrating to a preset depth, so that the vibratory compactor is suspended at that position and vibrates for a preset time to use the vibration to enlarge the hole wall. After the mud mixed with soil particles in the hole overflows naturally from the hole opening, the downward penetration continues. During the construction process, the operating current of the vibratory compactor motor is monitored in real time. If the current value exceeds the warning value, the vibratory compactor will be activated. If necessary, immediately reduce the sinking speed of the vibratory compactor or stop sinking. Continue operation only after the current returns to normal. Once the vibratory compactor has sunk to the designed pile length, raise it upwards by a preset distance to leave space at the bottom of the hole for subsequent filling. At the same time, use the vibratory compactor's small vibrations to clean up any loose soil remaining at the bottom of the hole.
[0014] Furthermore, in the vibratory compaction drilling construction step, the warning value of the vibratory compactor motor current is first calculated, and then the vibratory compactor is controlled to sink vertically into the silty gravel stratum. The calculation formula is as follows: ,in, This is the warning value for the vibratory motor current. The rated current of the vibratory beater motor The density is the natural density of the silty gravel liquefaction layer, measured by the ring sampler method or a density meter. It is the sinking speed of the vibratory impactor.
[0015] Furthermore, in the intermittent filling compaction pile formation step, the already constructed pile holes are cleaned by using a vibratory compactor and water flushing to remove residual mud, loose soil, and impurities from the holes. The compaction time for each section of filling is then determined. After lifting the vibratory compactor away from the orifice, fill the orifice with a preset volume of crushed stone filler. Then, lower the vibratory compactor into the filler layer inside the orifice and start the vibration function to compact the filler.
[0016] Furthermore, in the intermittent fill compaction pile forming step, the compaction time for a single section of fill is determined. After lifting the vibratory compactor away from the orifice, a preset volume of crushed stone filler is inserted into the orifice, and the compaction time of a single section of filler is determined. The calculation formula is: ,in, It is the vibration compaction time of a single section of packing. It is the basic vibration time; the larger the particle size, The larger, It refers to the thickness of a single section of filler material. It refers to the vibration frequency of the vibratory compactor; the higher the frequency, the higher the vibration efficiency. The smaller, It is the residual resistance coefficient of the formation.
[0017] Furthermore, in the intermittent filling compaction pile forming step, the motor current and vibration frequency of the vibratory compactor are monitored in real time during the compaction process. When the current value stabilizes within a preset range and the duration reaches a certain threshold, the vibration frequency is determined. After determining that the compaction of the fill material in this section meets the standard, the vibration compaction operation of this section is completed. The above fill material-vibration compaction process is repeated, and construction is carried out gradually upward until the top surface elevation of the pile reaches the design requirements, forming a continuous and dense vibratory crushed stone pile.
[0018] Furthermore, in the top treatment and bearing capacity verification steps, a road roller is used to perform overall compaction of the foundation treatment area according to the design requirements, controlling the number of compaction cycles and the compaction speed. After the piles have been cured to the age specified in the design and the piles and the soil between the piles have completed preliminary consolidation, a predetermined number of representative pile positions are selected according to the foundation bearing capacity testing specifications to conduct single-pile composite foundation bearing capacity tests. If the test results show that the bearing capacity does not meet the design requirements, the piles in that area are tested and the reasons for the failure to meet the standards are analyzed, and then supplementary piles or rework measures are taken. After the bearing capacity test is qualified, a crushed stone cushion layer of predetermined thickness is laid on the top surface of the composite foundation, and a vibratory road roller is used to compact the cushion layer in layers.
[0019] Compared with existing technologies, this method for treating and enhancing the bearing capacity of vibro-compacted stone pile composite foundations in silty gravel liquefaction strata has the following advantages:
[0020] I. This invention replaces liquefiable silty gravel strata with vibro-compacted stone piles. During construction, the vibration generated by the vibro-compactor produces a compaction effect on the surrounding soil, greatly improving the density of the strata and making the soil particles more closely arranged, reducing pore space and thus improving the overall bearing capacity of the foundation. At the same time, the stone piles act as efficient drainage channels in the liquefied strata, accelerating the discharge of pore water. As the pore water is discharged, the foundation soil gradually consolidates, and the strength and stability of the soil are significantly enhanced, thereby effectively improving the strata's resistance to liquefaction. This dual mechanism enables the composite foundation to better withstand external loads and vibrations, providing a solid and reliable foundation support for the engineering structure.
[0021] Second, this invention employs a pile-forming method using intermittent filling material vibration compaction, which allows for precise control of the compaction of each section of the pile during construction. By monitoring the motor current and vibration frequency of the vibratory compactor in real time, the compaction of the filling material in that section is determined to be up to standard once the current value stabilizes within a preset range for a certain period of time. This ensures the stable and reliable bearing capacity of the pile. Furthermore, this technical solution eliminates the need for large-scale excavation, significantly reducing the amount of construction work and cost. At the same time, by reducing the damage to the surrounding environment caused by excavation, it minimizes geological disturbance and effectively protects the ecological environment.
[0022] Other advantages, objectives and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination or study, or may be learned from the practice of the invention. Attached Figure Description
[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.
[0024] Figure 1 A flowchart of a method for treating and improving the bearing capacity of a composite foundation using vibratory compaction stone piles in liquefiable silty gravel strata.
[0025] Figure 2 A flowchart illustrating the steps of vibratory compaction drilling for composite foundation treatment and bearing capacity enhancement using vibratory compaction of gravel piles in silty gravel liquefaction strata. Detailed Implementation
[0026] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.
[0027] Example 1
[0028] A geological survey of a reservoir dam foundation of a certain water conservancy project confirmed the presence of a large area of silty gravel liquefaction strata. As the core bearing foundation of the reservoir's water-retaining structure, the dam foundation must not only bear the weight of the dam body and the water storage pressure of the reservoir, but also resist external forces such as seasonal water level fluctuations and earthquakes. The method of vibro-compaction crushed stone pile composite foundation treatment and bearing capacity enhancement for silty gravel liquefaction strata of the present invention was adopted to carry out the dam foundation treatment work.
[0029] like Figure 1 As shown, geological exploration methods such as drilling and in-situ testing were used to determine the lateral distribution range of the liquefiable strata in the dam foundation, the longitudinal liquefaction degree classification, and the lithology, burial depth, and bearing characteristics of the underlying non-liquefiable soil layer. Combined with the bearing requirements of the foundation in the dam structure design, the planar layout and extension depth of the vibro-compacted stone piles were determined to ensure that the piles could completely penetrate strata with different degrees of liquefaction while also forming stable anchorage within the non-liquefiable soil layer. High-strength and reasonably permeable crushed stone was selected as filler material. The dam foundation construction area was leveled in sections. Considering the proximity of the dam foundation to the water source, a combination of wellpoint dewatering and open ditch drainage was used to control the groundwater level and prevent water level rise from soaking the construction area. For the soft areas at the dam foundation edge and where it connects to the bank slope, layered slag padding and heavy compaction were used to prevent pile displacement due to uneven settlement of the foundation during vibro-compacting equipment operation.
[0030] Using specialized equipment that meets the accuracy requirements for water conservancy engineering surveying, and in conjunction with design drawings such as the dam foundation axis and dam body zoning, the pile position outlines were surveyed for each dam section. Permanent control points and leveling points were set at key locations such as the dam crest and toe to facilitate repeated verification of pile position accuracy during construction. Considering the large construction area and numerous piles in the dam foundation, the pile hole positions were marked by dividing the area into sections and advancing section by section. During construction, the principle of positioning while constructing was followed, and the next section was positioned only after the pile construction of each section was completed, reducing the disturbance of the already positioned pile positions caused by the vibration of the large vibro-compactor moving back and forth on the dam foundation. At the boundary between the liquefiable and non-liquefiable zones, concrete marker piles were inserted to clarify the treatment boundary, ensuring that the treatment range completely covers all liquefaction risk areas of the dam foundation. After the vibro-compactor pile driver was moved to the designated pile position, the verticality of the pile driver was made in accordance with the accuracy specifications for foundation treatment in water conservancy engineering by adjusting the extension length of the pile driver's outriggers and the tilt angle of the guide rod. Then, a laser calibrator was used to repeatedly check the alignment between the pile tip and the pile position marker point to ensure that the deviation was controlled within the allowable range.
[0031] Before starting the high-pressure water supply system of the vibratory compaction equipment, first follow the formula. Calculate the warning value of the oscillator motor current (wherein) This is the rated current of the vibratory motor. The natural density of the liquefaction layer in different areas of the dam foundation. (This refers to the sinking speed of the vibratory compactor). After a uniform and stable water flow is formed at the lower outlet of the vibratory compactor (which serves to cool the vibratory compactor and assist in cutting the soil and preventing borehole wall collapse), the vibratory compactor is started and adjusted to the preset vibration frequency. The vibratory compactor is controlled to sink vertically into the silty gravel layer at a uniform speed. During the sinking process, the suspension time of the vibratory compaction is adjusted according to the density difference of the liquefiable strata in different areas of the dam foundation. The suspension time is appropriately extended in areas with higher density to fully expand the borehole, and the suspension time is shortened in areas with loose and easily collapsed boreholes to maintain a stable water flow for wall protection. After the mud mixed with soil particles in the borehole naturally overflows from the borehole opening, the vibratory compactor continues to penetrate downwards. The working status and current change of the vibratory compactor motor are monitored in real time. If the current exceeds the calculated value, the vibratory compactor is activated. Immediately reduce the sinking speed or stop sinking until the cause is identified and dealt with before continuing the operation; after the vibratory compactor sinks to the designed depth, slowly lift the vibratory compactor a certain distance while maintaining low-frequency vibration to clean the loose soil and impurities remaining at the bottom of the hole, creating a clean bottom environment for subsequent filling.
[0032] The pile holes are cleaned by a combination of high-pressure water jet flushing and low-frequency vibration of a vibratory compactor, ensuring that there is no mud layer adhering to the hole wall and no loose accumulation at the bottom of the hole, thus preventing the subsequent filler from not bonding tightly to the hole wall. The vibratory compactor is lifted to a suitable height above the hole opening, and crushed stone is evenly poured into the hole through a special filler funnel to avoid local accumulation or gaps in the filler. The vibratory compactor is slowly lowered to the filled crushed stone layer, and the vibration function is activated to compact the crushed stone. During the compaction process, the vibration feedback and current stability of the vibratory compactor are closely observed. Once the current stabilizes within the preset range, the compaction of that section is stopped. The above filler-compaction process is repeated cyclically to gradually advance the pile construction upwards until the top surface of the pile reaches the design elevation of the dam foundation, forming a continuous, uniform, and dense vibratory crushed stone pile body, ensuring that the pile body and the soil between the piles can work together to bear the dam load.
[0033] After all piles are constructed, heavy-duty rollers suitable for large-area dam foundation construction are used to compact the dam foundation treatment area in multiple passes. During compaction, special attention is paid to the loose soil around the pile tops (to avoid stress concentration caused by voids between the pile tops and the cushion layer), ensuring that the flatness and compaction of the top surface of the treatment area meet the requirements of subsequent dam construction. After the piles have cured to the specified age, representative pile locations are selected in key areas such as the middle of the dam body, the dam toe, and the bank slope connection, according to the hydraulic engineering foundation testing specifications, to conduct single-pile composite foundation bearing capacity tests, verifying whether the foundation bearing capacity meets the requirements of the combined loads such as the dam body's self-weight and water storage pressure. After the test is passed, a crushed stone cushion layer is laid on the top surface of the composite foundation, and compacted in layers using a vibratory roller. During the laying of the cushion layer, attention is paid to the connection with the dam's seepage prevention structure to avoid the formation of seepage channels. The final composite foundation of the dam foundation not only completely eliminates the risk of liquefaction but also adapts to the load changes caused by reservoir water level fluctuations, ensuring the long-term safe operation of the reservoir.
[0034] Example 2
[0035] Geological surveys revealed that a silty gravel liquefaction stratum exists in the site of a heavy machinery manufacturing plant. The heavy equipment in the plant has a large single unit weight and may generate periodic vibration loads during operation. Furthermore, the installation of the equipment places extremely high demands on the flatness and settlement control of the foundation.
[0036] Through geological surveys, the distribution boundaries, thickness variations, and underlying non-liquefiable soil properties of the liquefiable silty gravel strata within the factory site were clarified. Considering the load differences of equipment in different areas of the factory, the density of vibro-compacted stone piles was optimized. In the processing area where heavy equipment is concentrated, the pile density was appropriately increased, while in auxiliary areas, the piles were arranged at a conventional density to ensure that the foundation bearing capacity matched the load distribution. Crushed stone with continuous particle size distribution and high compressive strength was selected as filler. The factory construction site was leveled as a whole, and multiple construction zones were divided according to the industrial factory construction schedule to facilitate simultaneous operation of multiple pieces of equipment. For potential underground pipelines within the site, the pipeline routes and depths were determined before measurement and positioning, and the pile placement was adjusted to avoid the pipelines. A combination of open ditch drainage and collection wells was used to control the groundwater level to prevent excessively high water levels from affecting the quality of pile formation. For the soft foundations in temporary heavy vehicle passage areas such as factory entrances and equipment transport channels, pre-compaction with slag was carried out to prevent foundation deformation caused by transport vehicles.
[0037] Based on the factory floor plan and equipment foundation layout, high-precision equipment specifically designed for industrial building surveying was used to survey the pile locations in different construction zones. Semi-permanent leveling points were established at key corner locations of the factory column foundations and equipment foundations to facilitate subsequent verification of the foundation elevation during equipment installation. Considering the large number of piles within the factory and the high accuracy requirements for pile locations in the equipment foundations, a one-pile-one-measurement method was adopted to mark the pile hole locations. Each pile location was measured and marked individually, using a steel rod driven in and surrounded by lime to enhance the marking's resistance to disturbance. During construction, the principle of simultaneous construction and positioning was followed to locate the pile holes. In the liquefaction zone... The boundaries are marked with wooden stakes painted red to ensure that the treatment area completely covers all areas of the factory that need to support heavy equipment, especially the liquefied soil layer under the equipment foundation. After the vibratory compaction pile driver is moved to the designated pile position, since the construction space in the factory may be limited by the reserved position of the column foundation and temporary facilities, a compact vibratory compaction machine is selected. By adjusting the horizontal and vertical position of the pile driver and the angle of the guide rod, the verticality of the pile driver meets the accuracy requirements of the industrial factory foundation treatment. Then, by using a combination of plumb bob and level, the alignment between the pile tip and the pile position mark is repeatedly calibrated to ensure that the deviation is within the allowable range of equipment installation.
[0038] like Figure 2As shown, start the water supply system of the vibratory compactor and adjust the water pressure to a moderate level. After a stable water flow is formed at the lower end of the vibratory compactor, start the vibratory compactor and adjust the vibration frequency. Control the vibratory compactor to sink into the silty gravel layer at a uniform speed. During the sinking process, adjust the number of suspension vibrations according to the differences in particle composition of the strata in different areas of the plant. Reduce the number of suspensions in areas with coarser particles and better permeability, and increase the number of suspensions in areas with cohesive soil and poor permeability to fully expand the hole. After the mud in the hole slowly overflows from the hole opening, continue to penetrate downwards. Monitor the operating noise and current changes of the vibratory compactor in real time. If abnormal noise or current fluctuations occur, stop the operation immediately and use high-pressure water to flush the hole or use a slag bucket to clean impurities. When the vibratory compactor sinks to the designed depth, slowly lift the vibratory compactor while maintaining slight vibration to clean the loose soil at the bottom of the hole and avoid the residue at the bottom of the hole affecting the bearing performance of the pile.
[0039] The pile holes are cleaned by flushing the hole walls with low-pressure water while a vibratory compactor is moved up and down slightly inside the hole to remove residual mud, loose soil, and other impurities, ensuring smooth hole walls and a clean bottom. After removing the vibratory compactor, crushed stone is filled into the hole using an automatic filling device. The filling speed is controlled to prevent voids from forming in the hole due to excessive filling speed. The vibratory compactor is lowered to the filling layer, and the vibration function is activated to compact the crushed stone. During compaction, the vibration time of the vibratory compactor is adjusted according to the load requirements of different areas in the plant. The vibration time is appropriately extended for piles under heavy equipment to ensure higher pile density. Once the vibratory compactor current stabilizes within the preset range, the compaction is stopped for that section. The filling-compacting process is repeated until the top surface of the pile reaches the design elevation of the plant foundation, forming a dense vibratory crushed stone pile, ensuring that the pile can withstand the static and vibration loads of heavy equipment for a long time.
[0040] After all pile construction is completed, a small vibratory roller is used to compact the foundation treatment area. During compaction, the compaction proceeds from the equipment foundation area to the surrounding auxiliary areas, focusing on compacting the soil at the contact point between the pile top and the equipment foundation to prevent poor contact after subsequent equipment installation. After the piles have cured to the specified age, multiple test points are selected under each heavy equipment foundation according to the industrial building foundation testing specifications to conduct composite foundation bearing capacity tests and settlement observations. This verifies whether the foundation bearing capacity meets the load requirements for long-term equipment operation and whether the settlement is controlled within the allowable range of equipment accuracy. After the tests are passed, a crushed stone cushion layer is laid on top of the composite foundation. The cushion layer is laid and compacted in layers. After compaction, the surface flatness of the cushion layer is tested. The final treated factory foundation not only completely eliminates the risk of liquefaction but also meets the stringent requirements of heavy equipment for foundation bearing capacity, flatness, and settlement control, ensuring the normal production operation and processing accuracy of the factory equipment.
[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.
Claims
1. A method for treating and enhancing the bearing capacity of a composite foundation using vibro-compacted crushed stone piles in silty gravel liquefaction strata, characterized in that... The method includes the following specific steps: Preliminary parameter design and site preparation: Parameters of liquefiable silty gravel strata and underlying non-liquefiable soil layers were obtained through geological survey. The layout and length of vibro-compacted crushed stone piles were designed, qualified crushed stone filler was selected, and the site was leveled, the groundwater level was controlled, and soft areas were compacted to meet construction requirements. Measurement and positioning and pile driver calibration: Use professional equipment to measure the pile position outline and control points, mark the boundary of the liquefaction zone and locate the pile hole. After the vibratory pile driver is in place, adjust the verticality and calibrate the pile tip and the pile position mark point to ensure that the deviation meets the requirements. Vibro-compaction drilling construction: Start the water supply system and vibro-compactor of the vibro-compactor, control the vibro-compactor to sink at a uniform speed and suspend it to expand the hole, monitor the motor current during construction, and when the vibro-compactor reaches the designed pile length, lift the vibro-compactor and clean the loose soil at the bottom of the hole. Intermittent filling compaction pile formation: Clean the pile hole, lift the vibratory compactor away from the hole, fill with the preset volume of crushed stone filling, start the vibration function to compact the filling, repeat the process until the top surface elevation of the pile reaches the design requirements. Top treatment and bearing capacity verification: The treated area is compacted with a road roller. After the pile body is cured to the specified age, a bearing capacity test is carried out. After passing the test, a crushed stone cushion layer is laid and compacted by vibration rolling.
2. The method for treating and improving the bearing capacity of vibro-compacted stone pile composite foundation in silty gravel liquefaction strata according to claim 1, characterized in that, In the preliminary parameter design and site preparation steps, the distribution range, thickness, physical and mechanical parameters of the liquefiable silty gravel strata, and the burial depth and properties of the underlying non-liquefiable soil layers are obtained through geological exploration. Based on the exploration results, the layout of the vibro-compacted crushed stone piles is designed, and it is determined that the piles must completely penetrate the liquefiable layer and extend to a predetermined depth within the non-liquefied soil layer. At the same time, crushed stone with continuous gradation, hard particles, no weathering, and no soil impurities is selected as filler to meet the requirements of pile strength and permeability. The construction site is leveled to ensure that the construction surface elevation reaches the design preset value. A drainage system or dewatering measures are used to control the groundwater level below the preset depth below the construction surface to avoid the water level being too high and affecting the quality of pile formation. For the soft areas in the site, the layered compaction method of pad slag is used for compaction.
3. The method for treating and enhancing the bearing capacity of vibro-compacted stone pile composite foundations in silty gravel liquefaction strata according to claim 1, characterized in that, In the measurement, positioning, and pile driver calibration steps, engineering surveying equipment is used to measure and set the outline of the pile positions in different areas according to the design drawings. Control points and leveling points marked with durable materials are set simultaneously to ensure stability during the construction period. The position of a single pile hole is determined by marking with steel rods or grouting lime into the hole. During construction, the principle of positioning while constructing is followed, that is, the next pile hole is positioned after the construction of one pile hole is completed. At the same time, markers are set at the boundary between liquefied and non-liquefied strata. The vibratory pile driver is moved to the designated pile position. The verticality of the pile driver body meets the design specifications by adjusting the height of the pile driver's outriggers and the angle of the guide rod. Then, a plumb bob or laser calibrator is used to align and calibrate the pile tip with the pile position marking point to ensure that the deviation between the center of the pile tip and the pile position marking point is within the design allowable range.
4. The method for treating and enhancing the bearing capacity of vibro-compacted stone pile composite foundations in silty gravel liquefaction strata according to claim 1, characterized in that, In the vibratory compaction drilling process, the water supply system of the vibratory compaction equipment is started and the water pressure and flow rate are adjusted to preset parameters. After a stable water flow is formed at the lower outlet of the vibratory compactor, the vibratory compactor is started and put into normal vibration operation. First, the warning value of the vibratory compactor motor current is calculated, and then the vibratory compactor is controlled to sink vertically into the silty gravel layer. During the sinking process, the sinking is paused after penetrating to a preset depth, so that the vibratory compactor is suspended at that position and vibrates for a preset time to use the vibration to enlarge the hole wall. After the mud mixed with soil particles in the hole overflows naturally from the hole opening, the downward penetration continues. During the construction process, the operating current of the vibratory compactor motor is monitored in real time. If the current value exceeds the warning value, the vibratory compactor will be activated. If necessary, immediately reduce the sinking speed of the vibratory compactor or stop sinking. Continue operation only after the current returns to normal. Once the vibratory compactor has sunk to the designed pile length, raise it upwards by a preset distance to leave space at the bottom of the hole for subsequent filling. At the same time, use the vibratory compactor's small vibrations to clean up any loose soil remaining at the bottom of the hole.
5. The method for treating and improving the bearing capacity of vibro-compacted stone pile composite foundation in silty gravel liquefaction strata according to claim 4, characterized in that, In the vibratory compaction drilling process, the warning value of the vibratory compactor motor current is first calculated, and then the vibratory compactor is controlled to sink vertically into the silty gravel stratum. The calculation formula is as follows: ,in, This is the warning value for the vibratory motor current. The rated current of the vibratory beater motor The density is the natural density of the silty gravel liquefaction layer, measured by the ring sampler method or a density meter. It is the sinking speed of the vibratory impactor.
6. The method for treating and improving the bearing capacity of vibro-compacted crushed stone pile composite foundation in silty gravel liquefaction strata according to claim 1, characterized in that, In the intermittent fill compaction pile construction step, the constructed pile holes are cleaned by using a vibratory compactor and water flushing to remove residual mud, loose soil, and other impurities from the holes. The compaction time for a single section of fill is determined first. After lifting the vibratory compactor away from the orifice, fill the orifice with a preset volume of crushed stone filler. Then, lower the vibratory compactor into the filler layer inside the orifice and start the vibration function to compact the filler.
7. The method for treating and improving the bearing capacity of vibro-compacted stone pile composite foundation in silty gravel liquefaction strata according to claim 6, characterized in that, In the intermittent fill compaction pile construction step, the compaction time of a single section of fill is determined. After lifting the vibratory compactor away from the orifice, a preset volume of crushed stone filler is inserted into the orifice, and the compaction time of a single section of filler is determined. The calculation formula is: ,in, It is the vibration compaction time of a single section of packing. It is the basic vibration time; the larger the particle size, The larger, It refers to the thickness of a single section of filler material. It refers to the vibration frequency of the vibratory compactor; the higher the frequency, the higher the vibration efficiency. The smaller, It is the residual resistance coefficient of the formation.
8. The method for treating and enhancing the bearing capacity of vibro-compacted stone pile composite foundations in silty gravel liquefaction strata according to claim 6, characterized in that, In the intermittent filling compaction pile forming step, the current and vibration frequency of the vibratory compactor motor are monitored in real time during the compaction process. When the current value stabilizes within the preset range and the duration reaches a certain threshold, the vibration frequency is determined. After determining that the compaction of the fill material in this section meets the standard, the vibration compaction operation of this section is completed. The above fill material-vibration compaction process is repeated, and construction is carried out gradually upward until the top surface elevation of the pile reaches the design requirements, forming a continuous and dense vibratory crushed stone pile.
9. The method for treating and improving the bearing capacity of vibro-compacted stone pile composite foundation in silty gravel liquefaction strata according to claim 1, characterized in that, In the top treatment and bearing capacity verification steps, a road roller is used to control the number of rolling times and rolling speed according to the design requirements to carry out overall rolling operations on the foundation treatment area. After the pile body is cured to the age specified in the design and the pile body and the soil between the piles are initially consolidated, a preset number of representative pile positions are selected according to the foundation bearing capacity testing specifications to carry out single pile composite foundation bearing capacity tests. If the test results show that the bearing capacity does not meet the design requirements, the piles in the area will be inspected and the reasons for the failure will be analyzed. Then, measures such as adding piles or rework will be taken. After the bearing capacity test is qualified, a crushed stone cushion layer of a preset thickness will be laid on the top surface of the composite foundation, and a vibratory roller will be used to compact the cushion layer in layers.