Hydraulic engineering foundation construction method

Abstract

The invention belongs to the field of water conservancy projects, and particularly relates to a water conservancy project foundation construction method, which comprises the following steps: carrying out foundation investigation on a to-be-constructed area, designing a construction plan according to an investigation result, carrying out layered vibroflotation construction according to the geological condition of the to-be-constructed area, dynamically adjusting construction parameters, leveling the foundation and laying a sand-gravel cushion layer. The special micro vibroflot reinforcing assembly is adopted, the construction problem which cannot be solved through a vibroflot construction method of a traditional vibroflot can be solved when structural sandy soil, a medium-compressibility pebble soil layer or an alluvial-flood pebble layer, a soil layer gradation curve located outside a standard distribution area and other special geologies exist, and the construction effect is improved.

Description

Technical Field

[0001] This invention relates to the field of water conservancy engineering technology, and specifically to a method for foundation construction of water conservancy projects. Background Technology

[0002] The conventional methods for foundation construction in water conservancy projects are as follows: 1. Natural consolidation type (mainly for large water conservancy projects such as reservoirs) Natural consolidation: This method utilizes the water pressure and compaction effect of the soil's own weight after the reservoir is filled, allowing the foundation soil to naturally compact, drain, and consolidate. This is the most economical and primary method of reinforcing reservoir foundations, and usually requires no artificial construction.

[0003] High-pressure jet grouting: Cement grout is injected under high pressure, and the cement grout fills the pores by binding. It is suitable for situations where the foundation cement is unstable or there are karst caves.

[0004] 2. Forced Consolidation Type (Applicable to dam, gate foundations, etc.) Replacement method: Excavate the soft soil layer and replace it with high-strength soil or gravel to solve the problem of low bearing capacity.

[0005] Pile foundation construction: including cast-in-place piles, precast piles, bored cast-in-place piles, etc., used to solve extremely poor soft soil problems or areas requiring high bearing capacity.

[0006] Vibro-compaction method: using vibration energy to replace soil and form crushed stone piles or driven pipe piles.

[0007] Vibro-compaction has significant advantages in hydraulic engineering, especially for treating large areas of loose sandy or gravelly soil layers. Its advantages include lower equipment and construction costs compared to bored piles or large-area replacement, shorter construction period, and suitability for addressing large-area foundation softening problems.

[0008] Vibro-compaction (vibratory water jetting) is a foundation treatment technology that uses the combined action of horizontal vibration of a vibro-compactor and high-pressure water jetting to reinforce soft foundations. Its core structure consists of a submersible motor inside the vibro-compactor driving an eccentric block to generate horizontal vibration force. A nozzle at the lower end sprays high-pressure water. Foundation reinforcement is achieved through the synergistic action of "vibratory compaction - drilling - mud removal - wall protection - filling with crushed stone (pebbles, etc.) - vibro-compactor sinking and compaction." It can be divided into vibro-compaction replacement method and vibro-compaction compaction method. Vibro-compaction has replacement, compaction, and vibration compaction effects on different soil layers. For medium and fine sand and silt, in addition to replacement, it also has a compaction effect. For cohesive soil foundations, it has a replacement effect. In construction with medium and fine sand, silt, plain fill, and miscellaneous fill, crushed stone (pebbles, etc.) is added as backfill material into the vibro-compactor hole, and the vibro-compactor compacts it to form vibro-compacted piles. The soil between the piles is compacted to varying degrees, forming a composite foundation between the piles and the soil between the piles. When vibratory compaction is performed in medium-coarse sand layers, the surrounding sand may collapse due to the collapse of the holes. Therefore, in-situ vibratory compaction without filler can also be used to densify the sand. This method is suitable for relatively pure medium-coarse sand.

[0009] Because existing vibratory compactors have limitations in foundation construction for water conservancy projects with special geological conditions, such as structural sand, medium compressible gravel soil or alluvial gravel layer, and soil gradation curves located outside the standard distribution area, vibratory compaction with existing vibratory compactors is difficult and is basically not used. Instead, other construction methods are used.

[0010] Therefore, the purpose of this invention is to overcome the construction difficulties of existing vibro-compaction methods for special geological conditions such as structural sand, medium compressibility gravel soil or alluvial gravel layer, and soil gradation curves located outside the standard distribution area, and to expand the construction scope of vibro-compaction methods in the foundation of water conservancy projects. Summary of the Invention

[0011] The purpose of this invention is to provide a method for foundation construction in water conservancy projects to solve the above-mentioned problems.

[0012] The purpose of this invention is to provide a method for foundation construction in water conservancy projects, which can be achieved through the following technical solutions: A method for foundation construction of a water conservancy project includes the following steps: Step 1: Conduct a foundation survey of the construction area, design a construction plan based on the survey results, clear the site and lay drainage facilities, install vibratory compaction equipment, and arrange vibratory compaction points. Step 2: Perform layered vibro-compaction construction according to the geological conditions of the area to be constructed. Vibro-compaction construction includes one or more of the following: hole drilling, vibro-compaction compaction, and vibro-compaction grouting. Step 3: Set up settlement and horizontal displacement observation points, dynamically adjust construction parameters, and use dynamic penetration tests to detect compaction. Step 4: Level the foundation and lay a sand and gravel cushion layer.

[0013] Furthermore, the vibratory compaction equipment includes one or more of a vibratory compactor and a micro vibratory compactor reinforcement assembly.

[0014] Furthermore, the micro vibratory shock absorber reinforcement assembly includes three sets of micro vibratory shock absorbers, a hanging platform for connecting the tops of the three sets of micro vibratory shock absorbers, and a lifting system for lifting the hanging platform and the three sets of micro vibratory shock absorbers. The three sets of micro vibratory shock absorbers are arranged in an equilateral triangle shape. The micro vibratory impactor includes a cylindrical vibratory impactor body, a cone head, and jet holes arranged on the surface of the cone head; a hollow buffer plate is installed between any two adjacent sets of vibratory impactor bodies, and a discharge chamber is formed between the three sets of vibratory impactor bodies and the three hollow buffer plates.

[0015] Furthermore, the micro vibratory compactor reinforcement assembly also includes a grouting system, which includes a grouting pump and a grouting hose. The grouting pump delivers concrete slurry into the discharge chamber through the grouting hose.

[0016] Furthermore, the hollow buffer plate includes multiple corrugated metal plates, and two adjacent sets of vibratory impactor bodies are sealed and connected by corrugated metal plates, forming a cavity between two adjacent corrugated metal plates; sealing plugs are installed at the upper and lower ends of the hollow buffer plate; the cavity is filled with a liquid medium.

[0017] Furthermore, the top of the vibratory compactor body is fixedly connected to the hanging platform by installing multiple steel wire ropes. The top of the hanging platform is equipped with a lifting ring that matches the lifting system, and a flexible hose connector that communicates with the discharge chamber is embedded in the center of the hanging platform.

[0018] Furthermore, when the geological conditions of the area to be constructed are one or more of the following: soft plastic clay layer, silt layer, loose sand layer, artificial fill layer, peat layer, and fine sand layer, vibratory compaction is carried out using a vibratory compactor.

[0019] Furthermore, when the geological condition of the area to be constructed is structural sand, the clay content in the sand exceeds 10% and the content of cement between soil particles exceeds 5%, wherein the cement is one or more of iron-manganese nodules and carbonate cement. Vibratory compaction is carried out using miniature vibratory compactors with reinforced components. When vibratory grouting is performed, the corresponding densification currents for the three sets of micro vibrators are I1, I2, and I3, respectively, where I1 = I2 and I3 > I1.

[0020] Furthermore, when the geological conditions of the area to be constructed are moderately compressible gravelly soil or alluvial gravelly soil, the compressibility coefficient of the soil layer is less than 0.13 MPa. -1 Furthermore, the content of medium-sized pebbles in the soil layer is 33% to 47%; A miniature vibratory punch is used to reinforce the hole-making process. During hole-making, the vibration frequencies of the three sets of miniature vibratory punches are set to increase or decrease proportionally in a first direction. The first direction refers to the arrangement of the three sets of miniature vibratory punches in a clockwise or counterclockwise direction.

[0021] Furthermore, when the geological conditions of the area to be constructed are such that the soil gradation curve is outside the standard distribution area, a micro vibratory compactor reinforced with components is used for vibratory compaction. When vibratory grouting is performed, the vibration frequencies of the three sets of micro vibrators are all equal, and their values ​​are all less than or equal to 20Hz.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. High adaptability and targeted solutions for the foundation needs of water conservancy projects: Based on the geological parameters of the foundation layers, this invention designs differentiated vibro-compaction parameters and construction methods for different soil properties. In particular, for poor soils such as soft soil and sand-mud mixture, different construction schemes are designed to improve the vibro-compaction reinforcement effect, while strengthening the foundation's impermeability and liquefaction resistance, thus adapting to the special needs of water conservancy projects subjected to long-term water loads.

[0023] 2. Excellent disturbance control, ensuring the safety of surrounding structures: By optimizing the layout of points, monitoring settlement and horizontal displacement in real time, and dynamically adjusting construction parameters, the disturbance of the surrounding soil caused by vibro-compaction construction is effectively controlled, avoiding secondary damage caused by local heave and displacement. It is especially suitable for foundation reinforcement projects near existing water conservancy structures. The settlement of the surrounding soil can be controlled within 50mm, and the horizontal displacement can be controlled within 30mm.

[0024] 3. High construction efficiency and controllable cost: This invention uses a specially designed micro vibratory compactor reinforcement component, which can solve the construction problems that traditional vibratory compaction methods cannot solve in special geological conditions such as structural sand, medium compressible gravel soil or alluvial gravel layer, and soil gradation curve outside the standard distribution area. The construction effect is good, and the construction efficiency is increased by 20-30% compared with other foundation construction methods. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the micro-vibrator reinforcement assembly described in this invention; Figure 2 This is a schematic diagram of the structure of an existing micro-vibrating shock absorber; Figure 3 This is a schematic diagram of the hollow buffer plate described in this invention; Figure 4 This is a schematic diagram showing the distribution of the three sets of micro-vibrators described in this invention. Detailed Implementation

[0026] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0027] The following detailed description of embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0028] In the description of the embodiments of this application, it should be noted that if terms such as "upper," "lower," "left," "right," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0029] In the description of the embodiments of this application, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0030] Example 1

[0031] A method for foundation construction of a water conservancy project includes the following steps: 1. Foundation Investigation and Layer Division: A comprehensive geological investigation is conducted on the construction area, using a combination of drilling and in-situ testing to obtain parameters such as the layer thickness, particle size distribution, mud content, permeability coefficient, and bearing capacity characteristics of the foundation soil. Based on the investigation results, the foundation is divided into different layers from top to bottom, and a construction plan is designed according to the geological characteristics of different layers. For example, the geology of a certain area may be subdivided into sandy soil sublayer, soft soil sublayer, and sand-mud mixed sublayer according to soil properties, all of which can be constructed using existing conventional vibratory compactors.

[0032] 2. Construction Preparation and Equipment Debugging: Clean the surface of the construction area, removing debris and standing water. Level the site and lay temporary drainage facilities to prevent rainwater or groundwater accumulation from affecting construction. Select an electric / hydraulic vibratory compactor suitable for the water conservancy project requirements. Currently, the outer diameter of common vibratory compactors is usually 30cm~50cm. Before construction, it is necessary to debug the vibration intensity, lifting speed, flushing pressure, and other parameters of the vibratory compactor. At the same time, prepare the filler material, which is a mixture of crushed stone, graded sand and gravel and curing agent, or concrete with aggregate.

[0033] 3. Vibro-compaction point layout: Based on the foundation reinforcement requirements and layered geological parameters, vibro-compaction points are arranged with a spacing of 1.5~3.0m. For sandy soil sublayers, the spacing is 1.5~2.0m; for soft soil sublayers and sand-mud mixed sublayers, the spacing is 2.0~3.0m; for points near the edge of hydraulic structure foundations, the spacing is shortened to 1.2~1.5m to form a dense reinforcement zone and enhance the stability of the foundation surrounding the foundation.

[0034] 4. Based on the geological conditions of the area to be constructed, layered vibro-compaction construction shall be carried out. Vibro-compaction construction includes one or more of the following: hole drilling, vibro-compaction compaction, and vibro-compaction grouting.

[0035] Using a vibratory compactor to create holes is called vibratory compaction, or simply hole making. It is the first step in vibratory compaction foundation treatment. It breaks up and empties the soil by using water jetting and vibration of the vibratory compactor to form holes, which are then used for filling and pile making.

[0036] Vibro-compaction is divided into non-filled compaction and filled compaction. Non-filled compaction is a foundation treatment technique that uses the vibration of a vibratory compactor and the action of high-pressure water jetting to liquefy the original foundation soil (mainly sand) and rearrange the particles to reduce porosity and increase density. Filled compaction involves continuously pouring crushed stone into the pile hole obtained after vibro-compaction, while the vibratory compactor is descending or ascending. The vibration of the vibratory compactor will squeeze the crushed stone into the surrounding soil, filling the hole.

[0037] Vibro-compaction grouting is a foundation treatment process that combines vibro-compaction with traditional grouting techniques. Vibro-compaction loosens the soil, removes the mud from the borehole, and forms a "water-absorbing layer" on the borehole wall, which is then reinforced by grouting.

[0038] Layered vibratory compaction: This method employs a top-down, layered vibratory compaction and layered filling approach, adjusting construction parameters for different sub-layers of soil. For example: Sandy soil sub-layer: The sinking speed of the vibratory compactor is controlled at 0.8-1.2 m / min, and the flushing pressure is 0.3-0.5 MPa. After sinking to the bottom of the sub-layer, the vibratory compactor is kept vibrating for 30-60 seconds to compact it. Then, the vibratory compactor is slowly raised at a speed of 0.5-0.8 m / min, and the filler is evenly filled at the same time. Every 0.5 m is raised, the vibratory compactor is held for 20-30 seconds to ensure that the filler is fully compacted and integrated with the surrounding sandy soil.

[0039] Soft soil sub-layer: Before the vibratory compactor is lowered, a hole can be drilled at the location to the top of the sub-layer (to increase the construction speed). The hole diameter should be slightly larger than the vibratory compactor diameter to reduce the adsorption resistance of the soft soil to the vibratory compactor. The lowering speed should be controlled at 0.5-0.8 m / min, and the flushing pressure should be increased to 0.5-0.7 MPa. After lowering to the bottom, vibrate for 60-90 seconds to disrupt the soft soil structure. During the lifting process, fill the material in layers at a lifting speed of 0.3-0.5 m / min. Vibrate for 30-40 seconds every 0.3 m of lifting, while simultaneously adding flushing water to ensure that the fill material is densely packed and forms a composite pile.

[0040] Sand and mud mixed sub-layer: The "vibratory compaction-static pressure combination" method is adopted. The sinking speed of the vibratory compactor is 0.6-1.0m / min, the flushing water pressure is 0.4-0.6MPa, and after sinking to the bottom, it vibrates for 45-60s. Then, a vertical pressure of 50-80kN is applied by the external static pressure device (such as a hydraulic device) of the vibratory compactor and maintained for 30s. During the lifting process, the filling material is carried out synchronously with the vibration. The lifting speed is 0.4-0.6m / min, and the vibration is paused for 25-35s every 0.4m of lifting.

[0041] 5. Disturbance Control and Quality Monitoring: During construction, settlement and horizontal displacement observation points are set up within a 5m radius of the vibratory compaction points. After vibratory compaction at every 3 points, the settlement and horizontal displacement of the surrounding soil are observed. If the settlement exceeds 50mm or the horizontal displacement exceeds 30mm, construction is stopped immediately, and the vibratory compaction parameters are adjusted (reducing the vibration intensity and increasing the spacing between points). At the same time, a super-heavy dynamic penetration test is used to test the compaction of the soil after each vibratory compaction layer to ensure that the compaction of the sandy soil sublayer is ≥95% and the compaction of the soft soil sublayer and the sand-mud mixture sublayer is ≥90%.

[0042] 6. Post-construction treatment: After all vibratory compaction points are completed, the foundation surface is leveled, and a 30-50cm thick layer of graded sand and gravel is laid. This layer is then compacted using a plate vibrator, achieving a compaction degree of ≥96%. If concrete is used during construction, it requires 7-14 days of curing, during which time regular watering is necessary to prevent cracking. After curing, the foundation bearing capacity and permeability coefficient are tested. Once these parameters are met, the next construction step can proceed.

[0043] In other embodiments, for foundation areas with high groundwater levels, dewatering wells are arranged around the construction area before vibro-compaction, and a lightweight wellpoint dewatering method is used to lower the groundwater level to 0.5m below the bottom of the intermediate reinforcement layer, so as to prevent the groundwater level from being too high and affecting the vibro-compaction compaction effect and the stability of the fill material.

[0044] In some embodiments, when the geological conditions of the area to be constructed are one or more of the following: soft plastic clay layer, silt layer, loose sand layer, artificial fill layer, peat layer, and fine sand layer, vibro-compaction is performed. The following are common applicable geological types for vibro-compaction: 1) Soft plastic clay layer It has a wide range of applications, especially for improving the bearing capacity of cohesive soils.

[0045] 2) Silt layer Silt is one of the ideal soils for vibro-compaction, and its bearing capacity can be significantly improved after construction.

[0046] It is often used to improve the bearing capacity of silty soil foundations and prevent buildings from sinking.

[0047] 3) Loose sandy soil layer Vibro-compaction is very suitable for loose sandy soils, especially saturated loose sandy soils.

[0048] Vibro-compaction or vibro-replacement methods can significantly improve the density and liquefaction resistance of sandy soil.

[0049] 4) Artificial fill layer This includes miscellaneous fill and plain fill.

[0050] Vibro-compaction is suitable for treating artificial fill, especially for replacement or compaction.

[0051] 5) Peat layer Peat is a special type of soft soil, and vibro-compaction is also used to treat this type of geology, usually as a replacement reinforcement method.

[0052] 6) Fine sandy soil layer For foundations containing a large amount of coarse sand and moisture, vibro-compaction piles (such as crushed stone piles) are suitable to increase the density of the foundation.

[0053] Example 2

[0054] The vibro-compaction construction performed in Example 1 was carried out using conventional vibro-compaction equipment, and the applicable strata were all within the areas where conventional vibro-compaction equipment could be readily applied. However, in water conservancy projects, some strata have complex geological conditions, and special strata are easily encountered, such as structural sand, moderately compressible gravelly soil or alluvial gravel layers, and soil gradation curves located outside the standard distribution area. In such cases, conventional vibro-compaction construction is extremely difficult, or even impossible. Therefore, it is worth considering optimizing and improving existing conventional vibro-compaction equipment to expand the construction range of the existing vibro-compaction method, thereby improving the construction effect and quality of water conservancy project foundations.

[0055] Miniature vibratory compactors typically refer to vibratory compaction devices with lower power, suitable for small-diameter holes or special applications (such as small-diameter monitoring holes, ultra-small piles, and bored piles). Compared to conventional vibratory compactors, miniature vibratory compactors are simply vibratory compactors with a smaller outer diameter. The main differences between miniature vibratory compactors and traditional foundation treatment vibratory compactors (such as ZCQ-30, ZCQ-55, and ZCQ-75) are their lower power and more compact size. They are primarily used for treating piles with smaller diameter holes (the outer diameter of a miniature vibratory compactor is typically less than 30cm), or in situations where space is limited and load requirements are low. Compared to conventional vibratory compactors, miniature vibratory compactors eliminate the water channel plates on both sides, instead incorporating internal water channels (which also provide heat dissipation). Their working principle is the same as conventional vibratory compactors: a submersible motor drives an eccentric block to generate horizontal excitation force, while simultaneously spraying high-pressure water to scour the soil, disrupting its structure and filling it with crushed stone.

[0056] In this invention, a micro-vibrator reinforcement component is fabricated by optimizing the design of an existing micro-vibrator, such as... Figures 1-3 As shown, the micro vibratory compactor reinforcement assembly includes three sets of micro vibratory compactors 10, a lifting platform 30 for connecting the top of the three sets of micro vibratory compactors 10, and a lifting system for lifting the lifting platform 30 and the three sets of micro vibratory compactors 10. The three sets of micro vibratory compactors 10 are arranged in an equilateral triangle shape. The lifting system includes a winch, lifting ropes, and a mast, etc.

[0057] The miniature vibratory compactor 10 includes a cylindrical vibratory compactor body 11, a conical head 13, and jet holes 12 arranged on the surface of the conical head 13. Hollow buffer plates 20 are installed between any two adjacent sets of vibratory compactor bodies 11, and the three sets of vibratory compactor bodies 11 and the three hollow buffer plates 20 together form a discharge chamber 50. The jet holes 12 can spray water jets or compressed air as needed. The discharge chamber 50 can spray water, air jets, or concrete slurry as needed; for example, it can be connected to a corresponding water source, air source, or grouting system by installing a four-way connector.

[0058] In some embodiments, the micro vibratory compactor reinforcement assembly further includes a grouting system, which includes a grouting pump and a grouting hose, wherein the grouting pump delivers concrete slurry into the discharge chamber 50 via the grouting hose.

[0059] Because the vibration effects (vibration frequency, encryption current, etc.) of the three sets of miniature vibratory shock absorbers 10 can be different according to the design of this invention, in order to avoid strong interference caused by them being close together, a certain buffering mechanism must be installed between the adjacent sets of vibratory shock absorber bodies 11. Therefore, in some embodiments, the hollow buffer plate 20 includes multiple corrugated metal plates 21, and the adjacent sets of vibratory shock absorber bodies 11 are sealed and connected by the corrugated metal plates 21, forming a cavity 22 between the adjacent sets of corrugated metal plates 21; sealing plugs are respectively installed at the upper and lower ends of the hollow buffer plate 20; the cavity 22 is filled with a liquid medium. The corrugated metal plates 21 are preferably steel plates with a corrugated cross-section, which can provide a certain degree of buffering compared to flat steel plates. The corrugated metal plates 21 are fixed and sealed to the vibratory shock absorber bodies 11 by full welding.

[0060] In other embodiments, the sealing plug is made of several steel sheets and resin, with the steel sheets forming a framework and resin encapsulating between them. The resin cures to form a seal. The steel sheets primarily provide mechanical strength, thereby minimizing wear on the resin between the steel sheets, while also providing a degree of cushioning.

[0061] In some other embodiments, the liquid medium is preferably water, and the cavity 22 is not completely filled; the filling volume is about 95% of the internal volume of the cavity 22.

[0062] In some other embodiments, the top of the vibratory compactor body 11 is fixedly connected to the hanging platform 30 by installing multiple steel wire ropes. The top of the hanging platform 30 is equipped with a lifting ring that matches the lifting system, and a flexible hose connector that communicates with the discharge chamber 50 is embedded in the center of the hanging platform 30.

[0063] As a control group, the control micro-vibrator group was made of three sets of micro-vibrators 10 welded together with flat steel plates.

[0064] Test Group 1: When the geological condition of the area to be constructed is structural sand, the clay content in the sand exceeds 10% and the cement content between soil particles exceeds 5%. The cement is one or more of iron-manganese nodules and carbonate cement. This type of sand, which simultaneously possesses high fine-grain content and significant cement, belongs to structural cemented sand, a special type of soil and rock material with high strength and low deformation characteristics. Construction is difficult: Due to its strong structure, treating this type of soil is difficult, requiring attention to crack control and stress distribution. The specific characterization method is as follows: If obvious cracks appear during vibro-grouting, obvious grout flow will occur. Grout flow is determined by comparing the difference between the output of the grouting pump and the theoretical consumption of concrete grout at the specified vibro-grouting depth. If the difference is not within a predetermined range, grout flow is indicated. Grout flow rate = number of piles where grout flow occurs / total number of piles selected in the test process.

[0065] Miniature vibratory compactors with reinforced components were used for vibratory grouting. When vibratory grouting was performed on the above-mentioned geological conditions, the corresponding densification currents for the three sets of miniature vibratory compactors were I1, I2, and I3, respectively, where I1 = I2 and I3 > I1. The corresponding grout flow rate was 7.7%.

[0066] In control group 11, a set of micro vibratory compactors was used for vibratory grouting. When vibratory grouting was performed on the above-mentioned geological conditions, the corresponding densification currents for the three sets of micro vibratory compactors were I1, I2, and I3, respectively, where I1 = I2 and I3 > I1. The corresponding grout flow rate was 100%. This indicates that even with the same construction parameters, without the buffering effect of the hollow buffer plate 20, the strong interference between the three sets of micro vibratory compactors was very severe, leading to very obvious cracks during vibratory grouting and thus grout flow.

[0067] In comparison group 11, a micro vibratory compactor with reinforced components was used for vibratory compaction. When vibratory compaction grouting was performed on the artificial fill layer, the corresponding densification currents for the three micro vibratory compactors were I1, I2, and I3, respectively, where I1 = I2 and I3 > I1. The corresponding grout flow rate was 0%.

[0068] Comparative group 13: Vibratory compaction was carried out using miniature vibratory compactors with reinforced components. When vibratory compaction grouting was performed on the artificial fill layer, the corresponding densification currents for the three miniature vibratory compactors were I1, I2, and I3, respectively, with I1=I2=I3, and the corresponding grout flow rate was 0%.

[0069] In comparison group 14, a micro vibratory compactor was used to reinforce the vibratory compaction process. When vibratory compaction grouting was performed on the structural sand layer described in test group 1, the corresponding densification currents for the three micro vibratory compactors were I1, I2, and I3, respectively, with I1=I2=I3, and the corresponding grout flow rate was 76.2%.

[0070] Comparative group 15 uses micro vibratory compactors with reinforced components for vibratory compaction construction; when vibratory compaction grouting is performed on the structural sand layer described in test group 1, the corresponding densification currents of the three micro vibratory compactors are I1, I2, and I3, respectively, with I1 > I2 > I3, and the corresponding grout flow rate is 100%.

[0071] As can be seen from the above, for artificial fill layers, which are very suitable for vibratory compaction, grout flow generally does not occur. When using a micro-vibratory compactor with reinforced components for vibratory grouting, artificial fill layers, regardless of whether the special intensified current technology of test group 1 is used, are unlikely to develop significant cracks during construction. Only when vibratory grouting is performed on structural sandy soil layers, which are extremely difficult to construct, as shown in test group 1, must the specially designed intensified current technology of test group 1 be used; otherwise, significant cracks are likely to appear during construction.

[0072] Test Group 2: When the geological conditions of the area to be constructed are moderately compressible gravelly soil or alluvial gravelly soil, the compressibility coefficient of the soil layer is less than 0.13 MPa. -1 Furthermore, the medium-sized gravel content in the soil layer is 33%~47%. This type of stratum is characterized by gravel and cemented compaction, making vibro-compaction a highly challenging task. The difficulties lie in the high strength and density of the soil, making it difficult for ordinary vibro-compactors to penetrate and prone to jamming. During the experiment, we encountered a 2.4~3.1m thick layer of moderately compressible gravelly soil. We recorded whether jamming occurred at each pile location. The jamming incidence rate was calculated as: (Number of pile locations experiencing jamming) / (Total number of pile locations selected during the experiment).

[0073] A micro-vibratory compactor assembly was used to vibrate-compact in medium-compressible gravelly soil layers to create boreholes. During borehole creation, the vibration frequencies of the three sets of micro-vibratory compactors were set to increase or decrease proportionally in a first direction, where the three sets of micro-vibratory compactors were arranged in a clockwise or counterclockwise direction. Figure 4 As shown, the first direction refers to the three sets of micro vibratory compactors arranged in a clockwise direction. The vibration frequencies corresponding to the three sets of micro vibratory compactors are f1=25Hz, f2=30Hz, and f3=36Hz, respectively. The medium compressible gravel soil layer was penetrated, and the jamming rate was 7.4%.

[0074] In comparison group 21, a micro vibratory compactor reinforced component was used to vibrate and compact the medium compressible gravelly soil layer. During the hole making, the vibration frequencies corresponding to the three micro vibratory compactors were f1=30Hz, f2=30Hz, and f3=30Hz, respectively. The medium compressible gravelly soil layer was penetrated, and the jamming rate was 77.8%.

[0075] In comparison group 22, a micro vibratory compactor reinforced component was used to vibrate and compact the medium compressible gravelly soil layer. During the compaction, the vibration frequencies of the three micro vibratory compactors were f1=36Hz, f2=36Hz, and f3=36Hz, respectively. The medium compressible gravelly soil layer was not penetrated, and the jamming rate was 100%.

[0076] In comparison group 23, a micro vibratory compactor reinforced component was used to vibrate and compact the medium compressible gravelly soil layer. During the hole making, the vibration frequencies corresponding to the three micro vibratory compactors were f1=25Hz, f2=35Hz, and f3=45Hz, respectively. The medium compressible gravelly soil layer was not penetrated, and the jamming rate was 100%.

[0077] In comparison group 24, a micro vibratory compactor was used to vibrate and compact the silt layer to create holes. During hole creation, the vibration frequencies of the three micro vibratory compactors were f1=25Hz, f2=35Hz, and f3=45Hz, respectively. The silt layer was penetrated, and the jamming rate was 0%.

[0078] It should be noted that medium-sized pebbles are pebbles with a diameter of approximately 128-256 mm. For test group 2, if the diameter of the pebbles in the soil layer is greater than 30 cm and the content exceeds 25%, even the special vibratory compaction frequency matching technology used in test group 2 cannot penetrate this type of soil layer.

[0079] As can be seen from the above, for medium compressible gravel soil layers, which are very difficult to construct with vibro-compaction, the special vibro-compaction frequency matching technology in test group 2 must be used. Otherwise, it is difficult to penetrate the medium compressible gravel soil layer, and the vibro-compaction device body 11 is easily stuck during hole drilling.

[0080] Test Group 3: When the geological conditions of the area to be constructed are as follows: the soil gradation curve is outside the standard distribution area (area B) (i.e., area C), it indicates that the soil particle gradation is unreasonable, mainly due to an excessive amount of fine particles or a lack of suitable medium particles. When using conventional vibratory compactors for vibratory compaction, this type of soil layer will liquefy or become fluid, leading to "hole slippage" of the vibratory compactor or excessively fast hole formation, making it difficult to form a dense pile body, and easily resulting in voids or quicksand phenomena. The cumulative duration of continuous slurry flow is used to characterize this. If the cumulative duration of continuous slurry flow is greater than 15 minutes, it indicates that the slurry flow phenomenon has not been controlled and is still serious. In general, in this case, it is necessary to abandon the vibratory compaction grouting method, either abandon the pile location, or adopt technical improvements such as vibratory compaction of crushed stone piles combined with driven pipe grouting.

[0081] In this experimental example, a miniature vibratory compactor reinforced with components was still used for vibratory compaction. When performing vibratory grouting, the vibration frequencies corresponding to the three sets of micro vibrators are all equal, and their values ​​are all less than or equal to 20Hz. For example, the vibration frequencies corresponding to the three sets of micro vibrators are f1=15Hz, f2=15Hz, and f3=15Hz, respectively; the cumulative duration of continuous grout flow is less than 15 minutes.

[0082] In comparison group 31, when the soil gradation curve is outside the standard distribution area, the micro vibratory compactor reinforced components are still used for vibratory compaction. When vibratory grouting is performed, the vibration frequencies corresponding to the three micro vibratory compactors are f1=25Hz, f2=25Hz, and f3=25Hz, respectively; the cumulative duration of continuous grout flow is greater than 15min.

[0083] In comparison group 32, when the soil gradation curve is outside the standard distribution area, the micro vibratory compactor reinforced components are still used for vibratory compaction. When vibratory grouting is performed, the vibration frequencies corresponding to the three micro vibratory compactors are f1=15Hz, f2=21Hz, and f3=30Hz, respectively; the cumulative duration of continuous grout flow is greater than 15min.

[0084] In comparison group 33, when the soil gradation curve is within the standard distribution area (such as well-graded loose sandy soil), the micro vibratory compactor reinforced components are still used for vibratory compaction. When vibratory grouting is performed, the vibration frequencies corresponding to the three sets of micro vibratory compactors are f1=15Hz, f2=21Hz, and f3=30Hz, respectively; no grout flow phenomenon occurs.

[0085] Example 3

[0086] In a foundation treatment project for a dam at a water conservancy hub, the foundation of a certain construction area is divided from top to bottom into: a shallow layer (1.2m thick), an intermediate layer (4.5m thick, subdivided into a 2.0m sandy soil sublayer and a 2.5m soft soil sublayer), and a silty clay layer (bearing capacity ≥200kPa). The groundwater level in this area is relatively high, 1.0m below the surface. The original foundation bearing capacity is 78kPa, and the permeability coefficient is 1×10⁻⁶. -4 At a speed of cm / s, vibratory compaction is required to increase the foundation bearing capacity to over 150 kPa and reduce the permeability coefficient to 1×10⁻⁶. -6 Below cm / s.

[0087] The specific steps for construction using the method of this invention are as follows: Foundation investigation and stratification: The parameters of each soil layer were determined by a combination of drilling and standard penetration tests. The sandy soil sublayer had a mud content of 5%; the soft soil sublayer had a water content of 38% and a mud content of 25%.

[0088] Construction preparation and equipment commissioning: After clearing the site, light well point dewatering wells are set up to lower the groundwater level to 0.5m below the bottom of the intermediate reinforcement layer (5.7m from the ground surface); a 150kW vibratory compactor with a vibration frequency of 40Hz is selected; the filler is a graded aggregate of gravel (45%), medium sand (35%), and fine sand (20%), and the curing agent is cement (5%, accounting for the filler mass) + fly ash (25%, accounting for the cement mass) + slag powder (8%, accounting for the cement mass).

[0089] Vibro-compaction point layout: the spacing between points in the sandy soil sub-layer is 1.8m, the spacing between points in the soft soil sub-layer is 2.5m, and the spacing between points at the edge of the dam foundation is 1.4m, forming a dense reinforcement zone.

[0090] Layered vibratory compaction construction: Sandy soil sub-layer: sinking speed 1.0m / min, flushing pressure 0.4MPa, bottom vibration 45s, lifting speed 0.6m / min, vibration pause for 25s every 0.5m lifting, synchronous filling.

[0091] Soft soil sub-layer: sinking speed 0.6m / min, flushing pressure 0.6MPa, bottom vibration 75s, lifting speed 0.4m / min, vibration pause for 35s every 0.3m lifting, replenish flushing water and fill material.

[0092] Disturbance control and quality monitoring: Eight observation points were set up within 5m of the vibratory compaction point. Observations were conducted every 3 points. The maximum settlement was 38mm and the maximum horizontal displacement was 22mm, which met the requirements. The ultra-heavy dynamic penetration test showed that the compaction of the sandy soil sublayer was 96% and the compaction of the soft soil sublayer was 92%.

[0093] Post-construction treatment: After construction, lay a 40cm graded sand and gravel cushion layer, compact it with a plate vibrator to a compaction degree of 97%; cure for 10 days and sprinkle water to keep it moist.

[0094] Test results: After reinforcement, the bearing capacity of the foundation is 165 kPa, and the permeability coefficient is 8 × 10⁻⁶. -7 With a flow rate of cm / s and a liquefaction resistance rating of Class C, it meets the requirements for use in the foundation of water conservancy hub dams. The construction period is shortened by 25% compared to traditional methods, and the cost of filler material is reduced by 18%.

[0095] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0096] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for foundation construction of a water conservancy project, characterized in that: Includes the following steps: Step 1: Conduct a foundation survey of the construction area, design a construction plan based on the survey results, clear the site and lay drainage facilities, install vibratory compaction equipment, and arrange vibratory compaction points. Step 2: Perform layered vibro-compaction construction according to the geological conditions of the area to be constructed. Vibro-compaction construction includes one or more of the following: hole drilling, vibro-compaction compaction, and vibro-compaction grouting. Step 3: Set up settlement and horizontal displacement observation points, dynamically adjust construction parameters, and use dynamic penetration tests to detect compaction. Step 4: Level the foundation and lay a sand and gravel cushion layer.

2. The method for foundation construction of a water conservancy project according to claim 1, characterized in that: The vibratory compaction equipment includes one or more of a vibratory compactor and a micro vibratory compactor reinforcement assembly.

3. The method for foundation construction of a water conservancy project according to claim 2, characterized in that: The micro vibratory impactor reinforcement assembly includes three sets of micro vibratory impactors, a hanging platform for connecting the tops of the three sets of micro vibratory impactors, and a lifting system for lifting the hanging platform and the three sets of micro vibratory impactors. The three sets of micro vibratory impactors are arranged in an equilateral triangle shape. The micro vibratory impactor includes a cylindrical vibratory impactor body, a cone head, and jet holes arranged on the surface of the cone head; a hollow buffer plate is installed between any two adjacent sets of vibratory impactor bodies, and a discharge chamber is formed between the three sets of vibratory impactor bodies and the three hollow buffer plates.

4. The method for foundation construction of a water conservancy project according to claim 3, characterized in that: The micro vibratory compactor reinforcement assembly also includes a grouting system, which includes a grouting pump and a grouting hose. The grouting pump delivers concrete slurry to the discharge chamber through the grouting hose.

5. A method for constructing a foundation for a water conservancy project according to claim 3, characterized in that: The hollow buffer plate includes multiple corrugated metal plates, and two adjacent sets of vibratory impactor bodies are sealed and connected by corrugated metal plates, forming a cavity between two adjacent corrugated metal plates; sealing plugs are installed at the upper and lower ends of the hollow buffer plate; the cavity is filled with a liquid medium.

6. A method for foundation construction of a water conservancy project according to claim 3, characterized in that: The top of the vibratory compactor body is fixedly connected to the hanging platform by multiple steel wire ropes. The top of the hanging platform is equipped with a lifting ring that matches the hoisting system. A flexible hose connector that communicates with the discharge chamber is embedded in the center of the hanging platform.

7. A method for constructing a foundation for a water conservancy project according to claim 2, characterized in that: When the geological conditions of the area to be constructed are one or more of the following: soft plastic clay layer, silt layer, loose sand layer, artificial fill layer, peat layer, and fine sand layer, vibratory compaction is carried out.

8. A method for constructing a foundation for a water conservancy project according to claim 3, characterized in that: When the geological condition of the area to be constructed is structural sandy soil, the clay content in the sandy soil exceeds 10% and the content of cement between soil particles exceeds 5%, and the cement is one or more of iron-manganese nodules and carbonate cement. Vibratory compaction is carried out using miniature vibratory compactors with reinforced components. When vibratory grouting is performed, the corresponding densification currents for the three sets of micro vibrators are I1, I2, and I3, respectively, where I1 = I2 and I3 > I1.

9. A method for constructing a foundation for a water conservancy project according to claim 3, characterized in that: When the geological conditions of the area to be constructed are moderately compressible gravelly soil or alluvial gravelly soil, the compressibility coefficient of the soil layer is less than 0.13 MPa. -1 Furthermore, the content of medium-sized pebbles in the soil layer is 33% to 47%; A miniature vibratory punch is used to reinforce the hole-making process. During hole-making, the vibration frequencies of the three sets of miniature vibratory punches are set to increase or decrease proportionally in a first direction. The first direction refers to the arrangement of the three sets of miniature vibratory punches in a clockwise or counterclockwise direction.

10. A method for constructing a foundation for a water conservancy project according to claim 3, characterized in that: When the geological conditions of the area to be constructed are such that the soil gradation curve is outside the standard distribution area, a micro vibratory compactor reinforced with components is used for vibratory compaction. When vibratory grouting is performed, the vibration frequencies of the three sets of micro vibrators are all equal, and their values ​​are all less than or equal to 20Hz.

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