Method for reinforcing loose soil foundation through variable-frequency vibration water vapor compaction method

Abstract

According to the method for reinforcing the loose soil foundation through the variable-frequency vibration water vapor compaction method, when a vibration rod drills downwards, longitudinal control is applied to the vibration rod, the longitudinal control comprises the longitudinal vibration frequency and the longitudinal amplitude, and during the period, the transverse vibration frequency and the transverse amplitude of the vibration rod are controlled to be within a certain range; and spraying high-pressure air, high-pressure water or high-pressure water vapor when the vibration rod drills downwards, wherein the spraying medium is selected according to the soil body water content of the current soil layer, when the soil body water content is high, the high-pressure air is sprayed, when the soil body water content is low, the high-pressure water is sprayed, and when the soil body water content is moderate, the high-pressure water is sprayed. High-pressure water vapor formed by alternately spraying high-pressure air and high-pressure water is adopted; by means of the frequency conversion technology and spraying of different media, the work efficiency is improved, the construction cost is reduced, other types of reinforcing materials are not needed during construction, during lifting, loose soil particles in the reinforcing range are distributed more evenly under the combined action of vibration of the vibration rod and the air spraying pressure, the compactness of a soil body is improved, and the reinforcing quality is greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of loose soil foundation treatment, in particular to a method for reinforcing a loose soil foundation by using a variable frequency vibration water vapor compaction method. Background Art

[0002] Loose soil is not a specific soil classification, but a relative concept used to describe the physical state of soil. Loose soil usually refers to soil with no cohesion between particles and loose properties. It is mainly composed of particles of 0.075 mm to 2 mm and has no plasticity. This type of soil is widely distributed in Quaternary sediments, as well as modern coastal, river, lake, and desert areas. Sandy soil is a typical example. It is a kind of loose soil because there is no cohesion between its particles. It is loose in nature, mainly composed of particles of 0.075~2 mm and has no plasticity. Sandy soil can be divided into coarse sand, medium sand, fine sand and silt according to the particle size composition. In addition, the looseness of the soil can also be judged by other indicators, for example, according to the number of standard penetration test hammers (N value) or other in-situ test indicators. For example, if the Ps value of silt or fine sand is less than 5.0MPa or the N value is less than 10, it can be considered loose. These indicators reflect the mechanical properties of the soil and are of great significance for foundation treatment and earthwork in engineering practice.

[0003] The conventional methods for reinforcement of loose soil mainly include the following: 1. Replacement cushion method: dig out the soft soil layer within a certain range under the bottom of the foundation, and then fill in the strong sand, gravel, soil, lime soil and other stable and non-corrosive materials in layers, and tamp to the required density. This method is suitable for the treatment of shallow soft foundation and uneven foundation. Its main function is to improve the bearing capacity of the foundation, reduce the settlement, accelerate the drainage and consolidation of the soft soil layer, prevent frost heave and eliminate the expansion and contraction of expansive soil.

[0004] 2. Dynamic compaction method: A method in which a heavy hammer (100-2000 kN) is lifted to a certain height (10-40 m) and allowed to fall freely to generate strong dynamic stress to compact the soil. It is suitable for treating foundations such as gravel soil, sandy soil, low-saturation silt and clay soil, collapsible loess, miscellaneous fill and plain fill. Dynamic compaction method is mainly used to increase soil strength, reduce compressibility, improve soil resistance to vibration liquefaction and eliminate collapsibility.

[0005] 3. Sand and gravel pile method: It is suitable for compacting loose sand, silt, clay, plain fill, miscellaneous fill and other foundations to improve the bearing capacity of the foundation and reduce compressibility. It can also be used to treat liquefiable foundations. Sand and gravel pile replacement treatment can also be used for projects on saturated clay foundations with poor deformation control, so that sand and gravel piles and soft clay form a composite foundation, accelerate the drainage and consolidation of soft soil, and improve the bearing capacity of the foundation.

[0006] 4. Vibroflotation: The method with filler is usually called vibroflotation crushed stone pile method. The vibroflotation method is suitable for treating foundations such as sand, silt, silty clay, plain fill and miscellaneous fill. Vibroflotation crushed stone piles are mainly used to increase the bearing capacity of the foundation, reduce the foundation settlement, and can also be used to improve the anti-sliding stability of loess slopes or improve the shear strength of the soil.

[0007] 5. Cement soil mixing method: It is divided into slurry deep mixing method (referred to as wet method) and powder spray mixing method (referred to as dry method). It is suitable for treating normally consolidated silt and silty soil, clay soil, silt soil, saturated loess, plain fill soil and saturated loose sand foundation without flowing groundwater. It is not suitable for treating peat soil, clay with plasticity index greater than 25, corrosive groundwater and foundation with high organic matter content.

[0008] 6. High-pressure jet grouting method: suitable for treating silt, muddy soil, clay soil, silt soil, and sandy soil foundation. This method uses high-pressure jetting of cement slurry to reinforce the soil and improve its density and bearing capacity.

[0009] Through a large number of engineering practices, it is found that the traditional method is basically to use reinforcement materials to deal with loose soil, which has high construction costs; or it causes large noise and vibration, and has a serious impact on the surrounding environment. Summary of the invention

[0010] The technical problem to be solved by the present invention is to address the drawbacks of conventional loose soil reinforcement methods, such as high cost and serious environmental impact, and propose a low-carbon, environmentally friendly variable frequency vibration water vapor compaction method for reinforcing loose soil with intelligent operation, so as to achieve a variable frequency vibration water vapor compaction method for reinforcing loose soil foundation that solves the above problems.

[0011] The technical problem to be solved by the present invention is achieved through the following technical scheme: a method for strengthening loose soil foundation by variable frequency vibration water vapor compaction method. When the vibration rod is drilling, longitudinal control is applied to the vibration rod. The drilling speed corresponds to the longitudinal control. The longitudinal control includes longitudinal vibration frequency and longitudinal amplitude. The longitudinal vibration frequency is proportional to the drilling speed. During this period, the lateral vibration frequency and lateral amplitude of the vibration rod are controlled within a certain range; and high-pressure air, high-pressure water or high-pressure water vapor is sprayed during the drilling of the vibration rod. The selection of the spraying medium is based on the soil moisture content of the current soil layer. When the soil moisture content is high, high-pressure air is sprayed. When the soil moisture content is low, high-pressure water is sprayed. When the soil moisture content is moderate, high-pressure water vapor is sprayed alternately with high-pressure air and high-pressure water.

[0012] The technical problem to be solved by the present invention can also be achieved by the following technical scheme: the above-mentioned variable frequency vibration water vapor compaction method for strengthening loose soil foundation has a longitudinal vibration frequency of 14-18 Hz and a longitudinal amplitude of 5-10 cm.

[0013] The technical problem to be solved by the present invention can also be achieved by the following technical scheme: the above-mentioned variable frequency vibration water vapor compaction method for strengthening loose soil foundation has a lateral vibration frequency of 20~22Hz and a lateral amplitude of 1~2cm.

[0014] The technical problem to be solved by the present invention can also be achieved by the following technical scheme: the variable frequency vibration water vapor compaction method for reinforcing loose soil foundation has a drilling speed of 100-150 cm / min.

[0015] The technical problem to be solved by the present invention can also be achieved by the following technical solutions. In the above-mentioned variable frequency vibration water vapor compaction method for strengthening loose soil foundation, when the moisture content of the soil is above 20%, high-pressure air is sprayed, and the spraying mode is pulsed, that is, the time interval between each spraying is 3-5s; when the moisture content of the soil is below 12%, high-pressure water is sprayed, and the spraying mode is pulsed, that is, the time interval between each spraying is 3-5s; when the moisture content of the soil is between 12 and 20%, high-pressure water vapor is sprayed, and the spraying mode is alternating, that is, when the single water spraying volume reaches 5-10kg, high-pressure air is sprayed for 2-3s, and the spraying of high-pressure water and high-pressure air is carried out alternately, thereby forming high-pressure water vapor composed of multiple streams of high-pressure water and multiple streams of high-pressure air.

[0016] The technical problem to be solved by the present invention can also be achieved by the following technical scheme. In the above-mentioned variable frequency vibration water vapor compaction method for reinforcing loose soil foundation, the vibration rod is not frequency-controlled when the drill is lifted, and high-pressure air needs to be sprayed, and the jet pressure is 0.1~0.2Mpa.

[0017] The technical problem to be solved by the present invention can also be achieved by the following technical scheme. The above-mentioned variable frequency vibration water vapor compaction method for reinforcing loose soil foundation, when lifting the drill, every 4m is lifted and then sunk 2m, and soil backfilling is required at the hole mouth during sinking.

[0018] The technical problem to be solved by the present invention can also be achieved by the following technical solutions: the above-mentioned variable frequency vibration water vapor compaction method for strengthening loose soil foundation also includes a system for implementing the method, which includes a pile driver and a water and air supply system; The pile driver comprises a chassis, on which a stand, a winch, a cab with an intelligent control cabinet, a hydraulic workstation and a frequency converter are arranged, the bottom end of the stand is hinged on the chassis, a vibrating hammer is installed on the top end, a vibrating rod is installed at the lower end of the vibrating hammer, and a nozzle is arranged at the lower end of the vibrating rod; The water and air supply system comprises an air compressor, an air storage tank and a water storage tank. The air compressor is connected to the air storage tank through a pipeline. The top of the air storage tank is connected to the top of the water storage tank through a pipeline. A pneumatic valve I is installed on the pipeline between the top of the air storage tank and the top of the water storage tank. A water supply pipeline is provided at the bottom of the water storage tank. A pneumatic valve II is installed on the water supply pipeline. An air supply pipeline is provided at the bottom of the air storage tank. A pneumatic valve III is installed on the air supply pipeline. The outlet ends of the water supply pipeline and the air supply pipeline are connected to a delivery pipe, which is connected to the inside of the vibration pipe, so as to supply water and air through the nozzle at the lower end of the vibration rod. It also includes a water pump, the inlet end of the water pump is connected to a water source, the outlet end of the water pump is connected to a water storage tank through a pipeline, and a pneumatic valve IV is arranged on the pipeline between the outlet end of the water pump and the water storage tank; A pneumatic valve V is provided on the top of the water storage tank through a pipeline; A gas flow meter is also provided on the gas supply pipeline; The water and gas supply system is also equipped with a weight sensor for detecting weight changes of the water storage tank.

[0019] Compared with the prior art, the beneficial technical effects of the present invention are: (1) By using frequency conversion technology and spraying different media, the work efficiency is improved, the project cost is reduced, and no other types of reinforcement materials are required during construction. During the lifting process, the vibration of the vibrating rod and the jet pressure make the loose soil particles in the reinforcement range more evenly distributed, the density of the soil is improved, and the reinforcement quality is greatly improved; (2) The vibration frequency of the vibratory hammer is automatically adjusted according to the speed of drilling to achieve a frequency close to the natural vibration frequency of the soil, making it easier to break the soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a construction schematic diagram of the present invention; Figure 2 It is a numerical ratio diagram of the drilling speed and the longitudinal vibration frequency of the present invention; Figure 3 It is a structural schematic diagram of the pile driver and the water and air supply system of the present invention; Figure 4 It is a schematic diagram of the intelligent operation and remote monitoring management system of the present invention; Figure 5 Schematic diagram of the monitoring and management system of the present invention.

[0021] In the figure, 1. vibration rod; 2. chassis; 3. stand; 4. winch; 5. intelligent control cabinet; 6. cab; 7. hydraulic workstation; 8. frequency converter; 9. vibration hammer; 10. nozzle; 11. air compressor; 12. gas storage tank; 13. water storage tank; 14. pneumatic valve I; 15. water supply pipeline; 16. pneumatic valve II; 17. gas supply pipeline; 18. pneumatic valve III; 19. delivery pipe; 20. water pump; 21. pneumatic valve IV; 22. pneumatic valve V; 23. gas flow meter; 24. weight sensor. DETAILED DESCRIPTION

[0022] The specific technical solutions of the present invention are further described below with reference to the accompanying drawings, so as to facilitate further understanding of the present invention by those skilled in the art, and do not constitute a limitation on the rights thereof.

[0023] Example 1, reference Figure 1-3 , a variable frequency vibration water vapor compaction method for reinforcing loose soil foundation. When the vibration rod is drilling, longitudinal control is applied to the vibration rod 1. The drilling speed corresponds to the longitudinal control. The longitudinal control includes longitudinal vibration frequency and longitudinal amplitude. The longitudinal vibration frequency is proportional to the drilling speed. The longitudinal vibration frequency is 14-18Hz, the longitudinal amplitude is 5~10cm, and the drilling speed is 100~150cm / min. During this period, the lateral vibration frequency and lateral amplitude of the vibration rod 1 are controlled within a certain range. The lateral vibration frequency is 20~22Hz, and the lateral amplitude is 1~2cm; and high-pressure air, high-pressure water or high-pressure water vapor is sprayed during the drilling of the vibration rod 1. The selection of the spraying medium is based on the soil moisture content of the current soil layer; When the soil moisture content is above 20%, high-pressure air is sprayed in a pulsed manner, i.e., the time interval between each spraying is 3-5s; when the soil moisture content is below 12%, high-pressure water is sprayed in a pulsed manner, i.e., the time interval between each spraying is 3-5s; when the soil moisture content is between 12% and 20%, high-pressure water vapor is sprayed in an alternating manner, i.e., when the single water spraying volume reaches 5-10kg, high-pressure air is sprayed for 2-3s, and high-pressure water spraying and high-pressure air spraying are performed alternately, thereby forming high-pressure water vapor composed of multiple streams of high-pressure water and multiple streams of high-pressure air; When lifting the drill, the vibration rod 1 is not frequency-controlled, the longitudinal frequency is 14-18Hz, and the lateral frequency is 20-22Hz. High-pressure air needs to be sprayed, and the jet pressure is 0.1~0.2Mpa. When lifting the drill, it is lifted by 4m and then sunk by 2m. When sinking, the soil needs to be backfilled at the hole mouth; It also includes a system for implementing the method, which includes a pile driver and a water and air supply system; the pile driver includes a chassis 2, on which a stand 3, a winch 4, a cab 6 with an intelligent control cabinet 5, a hydraulic workstation 7 and a frequency converter 8 are arranged, the bottom end of the stand 3 is hinged on the chassis 2, and a vibrating hammer 9 is installed on the top, a vibrating rod 1 is installed at the lower end of the vibrating hammer 9, and a nozzle 10 is arranged at the lower end of the vibrating rod 1; the water and air supply system includes an air compressor 11, an air tank 12 and a water tank 13, the air compressor 11 is connected to the air tank 12 through a pipeline, the top of the air tank 12 is connected to the top of the water tank 13 through a pipeline, a pneumatic valve I 14 is installed on the pipeline between the top of the air tank 12 and the top of the water tank 13, and a water supply pipeline 15 is arranged at the bottom of the water tank 13, A pneumatic valve II 16 is installed on the water supply pipe 15, an air supply pipe 17 is arranged at the bottom of the air tank 12, and a pneumatic valve III 18 is installed on the air supply pipe 17. The outlet ends of the water supply pipe 15 and the air supply pipe 17 are connected with a delivery pipe 19, and the delivery pipe 19 is connected to the inside of the vibration tube, so as to supply water and air through the nozzle 10 at the lower end of the vibration rod 1; it also includes a water pump 20, the inlet end of the water pump 20 is connected to the water source, and the outlet end of the water pump 20 is connected to the water tank 13 through a pipeline, and a water pneumatic valve IV 21 is arranged on the pipeline between the outlet end of the water pump 20 and the water tank 13; a pneumatic valve V 22 is arranged on the top of the water tank 13 through a pipeline; a gas flow meter 23 is also arranged on the air supply pipe 17; the water and air supply system is also equipped with a weight sensor 24 for detecting the weight change of the water tank 13.

[0024] During the specific construction: 1. The air compressor 11 starts automatically. At this time, the pneumatic valve I 14 and the pneumatic valve III 18 are in the closed state. The air storage tank 12 is restarted. When the pressure reaches the preset value, the air compressor 11 is automatically closed. 2. The water pump 20 starts automatically. At this time, the water pneumatic valve IV21 and the pneumatic valve V22 are opened, while the pneumatic valve II16 is in a closed state, so that water is transported to the water storage tank 13. The water entering the water storage tank 13 is weighed by the weight sensor 24 installed on the water storage tank 13. When the weight of the water reaches the set value, the water pump 20 is automatically closed. At this time, the pneumatic valve II16, the water pneumatic valve IV21 and the pneumatic valve V22 are in a closed state; 3. The pneumatic valve I14 is opened, and the high-pressure air in the air tank 12 enters the water tank 13 to pressurize the water tank 13. When the pressure in the water tank 13 reaches the set value, the pneumatic valve I14 is closed. The opening and closing of the pneumatic valve I14 is based on ensuring the pressure in the water tank 13; 4. Start the vibrating hammer 9 and the hoist 4. At this time, the wire rope on the hoist 4 releases the vibrating hammer 9, causing the vibrating rod 1 to enter the soil. The drilling speed is determined by the density of the soil layer. When the soil layer density is large, the drilling difficulty increases, resulting in a slower drilling speed. At this time, the frequency converter automatically adjusts the vibration frequency of the vibrating hammer 9, resulting in a longitudinal vibration frequency of 14-18Hz, a longitudinal amplitude of 1.5~2m / min, a lateral vibration frequency of 20~22Hz, and a lateral amplitude of 1~2cm, so that it is close to the natural frequency of the soil layer, achieving a resonance effect, and keeping the vibrating rod 1 drilling at a uniform speed; 5. According to the geological survey data and the water content of each soil layer, the spray mode is automatically switched to spray different media: (1) When the soil moisture content is high, high-pressure air is sprayed, the pneumatic valve II 16 is closed, the pneumatic valve III 18 is opened, and pulsed high-pressure air is sprayed. The interval between each air supply is 3-5 seconds, and the amount of gas is automatically controlled by the gas flow meter 23; (2) When the soil moisture content is low, high-pressure water is sprayed, the pneumatic valve III 18 is closed, the pneumatic valve II 16 is opened, and pulsed high-pressure water is sprayed. The interval between each water supply is 3-5 seconds. The amount of water can be automatically controlled by the weight sensor 24 on the water storage tank 13; (3) When the soil moisture content is moderate, high-pressure water vapor is sprayed, and the pneumatic valve II16 is opened to deliver high-pressure water. The water volume is automatically controlled by the weight sensor 24 on the water storage tank 13. When the water volume reaches the set value, which is generally set to 5-10 kg, the pneumatic valve II16 is closed, and the pneumatic valve III18 is opened to deliver high-pressure air. When the air volume reaches the set value, it generally lasts for 2-3 seconds, and the pneumatic valve III18 is closed. This process is carried out alternately, and a stream of high-pressure water and a stream of high-pressure air are formed in the delivery pipe 19, and are sprayed out from the nozzle 10 at the lower end of the vibration rod 1 through the delivery pipe 19 to form high-pressure water vapor; 6. The vibrating rod 1 vibrates and sinks in the soil. Under the combined action of the vibration of the vibrating rod 1 and high-pressure air, high-pressure water or high-pressure water vapor, the original soil structure of the soil particles is destroyed and reassembled into a new soil structure. The porosity of the loose soil is reduced and the soil begins to become dense. 7. When the drilling reaches the designed depth, start to lift the drill (lift the vibration rod 1); 8. When lifting the vibration rod 1, the vibration hammer 9 maintains a fixed vibration frequency of the vibration rod 1. At this time, the vibration rod 1 and the soil within the influence range of the spray medium become a mixture. In the lifting process, frequency conversion control is not required, and jetting is required. The pressure is generally 0.1-0.2Mpa. Its function is to prevent the nozzle 10 from being blocked. At the same time, the soil particles are more evenly distributed under the action of the gas; 9. When lifting the vibrating rod 1, in order to ensure the compactness of the soil, the reverse insertion process needs to be adopted, that is, every time it is lifted by 4m, it sinks 2m, so that a cavity is formed. When performing the reverse insertion process, it is necessary to fill the hole with filler, and the filler can be the soil at the hole; 10. Follow the reverse insertion process until the vibration rod 1 is lifted out of the ground to complete the reinforcement of the loose soil foundation.

[0025] For monitoring and management systems, refer to Figure 4-5 , which can be composed of the following parts: on-site inspection, on-site monitoring management, and monitoring center; (1) When Internet terminal devices such as mobile phones, tablets, PCs, platform monitoring centers, and on-site inspection equipment obtain data, the application server directly reads data from the cache database by dispatching the server to the application server, which can greatly reduce the reading pressure of the database server and return data results more quickly.

[0026] (2) Since the frequency of modular data transmission is 1-3 seconds, the number of data is large. We write the collected real-time data into files and store them in the attachment server. If conditions permit, multiple attachment servers can be clustered. The files stored in the attachment server contain the piling process data of all pile drivers. Therefore, in the application system, this stored data can be called to simulate the dynamic process of the original operation.

[0027] (3) The data page display platform integrates a camera video monitoring system, and the food flow data is broadcast online to display the construction site conditions in real time. At the same time, after the data transmitted from the Internet of Things module is collected, the websocket technology is integrated to synchronize it to each terminal device in real time, dynamically displaying the progress of the construction work.

[0028] (4) The on-site monitoring management and monitoring center automatically generates original on-site construction records and statistical tables based on the received on-site construction parameters, eliminating human factors, ensuring the authenticity of the data, and significantly reducing labor costs.

[0029] (5) For completed loose soil reinforcement foundations, if there are any disputes after testing, the construction process can be replayed to find out the problem.

[0030] (6) For irregular operations and special circumstances on site, instructions can be sent to the control cabinet of the variable frequency vibration water vapor compaction method intelligent pile driver to terminate the on-site construction and reduce losses.

Claims

1. A method for strengthening loose soil foundation by variable frequency vibration water vapor compaction method, characterized in that: When the vibration rod is drilling, longitudinal control is applied to the vibration rod, and the drilling speed corresponds to the longitudinal control. The longitudinal control includes longitudinal vibration frequency and longitudinal amplitude. The longitudinal vibration frequency is proportional to the drilling speed. During this period, the lateral vibration frequency and lateral amplitude of the vibration rod are controlled within a certain range; and high-pressure air, high-pressure water or high-pressure water vapor is sprayed during the vibration rod drilling. The selection of the spraying medium is based on the soil moisture content of the current soil layer. When the soil moisture content is high, high-pressure air is sprayed. When the soil moisture content is low, high-pressure water is sprayed. When the soil moisture content is moderate, high-pressure water vapor is sprayed alternately with high-pressure air and high-pressure water.

2. The method for strengthening loose soil foundation by variable frequency vibration water vapor compaction method according to claim 1 is characterized in that: The longitudinal vibration frequency is 14-18 Hz, and the longitudinal amplitude is 5~10 cm.

3. The method for strengthening loose soil foundation by variable frequency vibration water vapor compaction method according to claim 1 is characterized in that: The lateral vibration frequency is 20~22Hz, and the lateral amplitude is 1~2cm.

4. The method for strengthening loose soil foundation by variable frequency vibration water vapor compaction method according to claim 1 is characterized in that: The drilling speed is 100~150cm / min.

5. The method for strengthening loose soil foundation by variable frequency vibration water vapor compaction method according to claim 1 is characterized in that: When the moisture content of the soil is above 20%, high-pressure air is sprayed in a pulsed manner, that is, the time interval between each spraying is 3-5s; when the moisture content of the soil is below 12%, high-pressure water is sprayed in a pulsed manner, that is, the time interval between each spraying is 3-5s; when the moisture content of the soil is between 12 and 20%, high-pressure water vapor is sprayed in an alternating manner, that is, when the single water spraying volume reaches 5-10kg, high-pressure air is sprayed for 2-3s, and the spraying of high-pressure water and high-pressure air is carried out alternately to form high-pressure water vapor composed of multiple streams of high-pressure water and multiple streams of high-pressure air.

6. The method for strengthening loose soil foundation by variable frequency vibration water vapor compaction method according to claim 1 is characterized in that: When lifting the drill, the vibration rod is not frequency-controlled and high-pressure air needs to be sprayed, with the jet pressure being 0.1~0.2Mpa.

7. The method for strengthening loose soil foundation by variable frequency vibration water vapor compaction method according to claim 1, characterized in that: When lifting the drill, it should be lifted by 4m and then sunk by 2m. When sinking, the soil should be backfilled at the hole mouth.

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