Rapid reinforcement construction method for deep ultra-soft foundation

Abstract

The invention belongs to the technical field of foundation treatment construction, and particularly relates to a rapid reinforcement construction method for a deep ultra-soft foundation. Comprising the following steps: step 1, in-situ sludge solidification; 2, leveling and partitioning are carried out; 3, construction of the cutoff wall; 4, well point dewatering; 5, high-pressure jet grouting reinforcement is conducted; 6, a geogrid reinforced broken stone hardcore is laid; and 7, leveling and rolling. According to the method, the three key steps of sludge in-situ solidification, well-point dewatering and high-pressure jet grouting pile construction are combined, the construction period is effectively shortened, the construction cost is reduced, the environmental protection property is good, the bearing capacity of the foundation can be remarkably improved, the stability and safety of a building are ensured, and an innovative solution is provided for reinforcement treatment of the ultra-soft soil foundation.

Description

Technical Field

[0001] The invention belongs to the technical field of foundation treatment construction, and in particular relates to a deep and ultra-soft foundation rapid reinforcement construction method. Background Art

[0002] With the development and utilization of marine resources, the demand for offshore engineering construction is growing. In offshore engineering, foundation treatment is a crucial link, especially for the extremely soft foundation formed by new filling, which has low bearing capacity and poor stability, bringing great challenges to engineering construction. The treatment of ultra-soft soil foundation has always been a technical problem. In particular, the newly filled silt land, due to its special physical properties, such as strong fluidity, extremely low strength, high water content, low sand content and large thickness, makes the reinforcement treatment of this type of foundation particularly complex and difficult, especially this kind of geological foundation has extremely poor bearing capacity, construction machinery does not have the conditions for construction, and the reinforcement period is often relatively long.

[0003] Traditional methods for reinforcing newly filled silt land may include simple drainage consolidation and replacement filling, but these methods have obvious limitations when dealing with thick ultra-soft soil. For example, drainage consolidation is inefficient when dealing with silt with high water content, while replacement filling may be uneconomical due to material costs and construction difficulties. In summary, when dealing with thick ultra-soft soil, traditional foundation treatment methods often fail to achieve the desired reinforcement effect, or do not have advantages in terms of cost and time.

[0004] Chinese invention patent 201910202405.6 discloses a method and structure for rapid reinforcement of soft foundation in fill area, but it is not suitable for newly filled extremely soft foundation, and the reinforcement cycle is relatively long, which has certain limitations. Summary of the invention

[0005] In order to solve the deficiencies of the prior art and overcome these technical difficulties, the present invention provides a method for rapid reinforcement of deep and ultra-soft foundations, which uses scientific and effective technical means to efficiently and economically reinforce newly filled silt land.

[0006] To achieve the above purpose, the technical solution of the present invention is as follows: A deep ultra-soft foundation rapid reinforcement construction method, characterized in that it comprises the following steps: Step 1: In-situ silt solidification: In-situ silt solidification is carried out on the newly filled silt land. The depth of in-situ silt solidification is 3m, forming a stable working layer in the working area; Step 2: Leveling and zoning: Level the reinforced area where the silt has been solidified to ensure that the foundation surface is flat, and divide the reinforced area into several construction units, each with an area of ​​10m×10m; Step 3: Watertight wall construction: cement mixing pile watertight wall construction is carried out at the partition connection and the outer edge of the soft foundation treatment area; the cement mixing pile watertight wall is constructed using three-axis cement mixing piles, and two adjacent cement mixing piles are overlapped with each other; the diameter of the cement mixing piles is 850 mm, the center spacing is 600 mm, the overlap width is 300 mm, and the verticality deviation is not more than 1 / 250; Step 4: Well point dewatering. After a stable working layer is formed, well point dewatering operation is carried out. This process includes setting a certain number of well points in the working layer and extracting groundwater through these well points to lower the groundwater level and create favorable conditions for the next step of high-pressure jet grouting pile construction. Step 5: High-pressure jet grouting reinforcement. After the well point is dewatered, high-pressure jet grouting pile construction is carried out. When the groundwater level drops to 3.5m below the construction plane, high-pressure jet grouting technology is used to construct high-pressure jet grouting piles. This step can further improve the bearing capacity of the soil and enhance the stability of the foundation. The specific parameters of high-pressure jet grouting pile construction are: slurry pressure 0.6~0.8MPa, air pressure 30~35Mpa, and lifting speed 10~15cm / min. Step 6: Lay the geogrid reinforced gravel cushion. After completing the reinforcement treatment of the rotary grouting reinforcement area, first lay the geogrid. The laying of the geogrid requires precise measurement and positioning to ensure that its position is accurate. When laying, the grid should be spread out flat to avoid wrinkles or distortions to ensure that it can fully play its role in enhancing the stability of the foundation. Then, lay a layer of gravel cushion on top of the geogrid. The selection of gravel should meet the specified particle size and quality requirements. It should be laid evenly and densely to provide good bearing capacity and prevent the geogrid from being subjected to direct pressure and damage. Step 7: Leveling and rolling. After the geogrid reinforced gravel cushion layer is laid, leveling work is carried out. Use a roller to level the surface of the gravel cushion layer to ensure that its flatness meets the subsequent construction requirements.

[0007] In step 1, one or more of an inorganic compound curing agent, an organic compound curing agent, and a composite curing agent are used.

[0008] In step 4, the number and location of the well points are accurately calculated and determined based on the specific conditions of the working layer and construction requirements, and one well point is set every 100 square meters to ensure maximum precipitation effect and construction efficiency.

[0009] In step 6, the reinforcing material in the geogrid reinforced cushion layer is a unidirectional geogrid with a tensile strength of not less than 50 kN / m, which is determined during the design calculation. The unidirectional geogrids are filled with crushed stone fillers, the compaction degree of the crushed stone fillers is greater than 96%, and the spacing between adjacent unidirectional geogrids is 0.2~0.3m.

[0010] The newly blown silt land refers to a silt layer foundation that is in a fluid state, has extremely low strength, a water content greater than 130%, a sand content less than 5% and a thickness greater than 10m.

[0011] The present invention has the following beneficial effects: 1. The present invention firstly performs in-situ silt solidification on the newly filled thick ultra-soft soil, which can form a fast working cushion layer and greatly improve the construction progress.

[0012] 2. The present invention forms a water-blocking wall by setting cement mixing piles between each partition, which can effectively reduce the circulation and penetration of groundwater into the soft foundation treatment area and improve the well point dewatering effect of subsequent well points.

[0013] 3. The present invention extracts groundwater through well points to lower the groundwater level, creating favorable conditions for the next step of high-pressure rotary jet grouting pile construction, and can significantly improve the strength of the high-pressure rotary jet grouting pile.

[0014] 4. The strength and rigidity of the dam material are increased by setting a geogrid reinforced gravel cushion layer. On the other hand, as a cushion layer, it diffuses the overlying stress, reduces the stress acting on the foundation soil and makes it more uniform, which can effectively reduce the uneven settlement of the dam.

[0015] The method of the present invention combines the three key steps of in-situ solidification of sludge, well point dewatering and high-pressure rotary jet pile construction, effectively shortens the construction period, reduces construction costs, has good environmental protection, can significantly improve the bearing capacity of the foundation, ensure the stability and safety of the building, and provides an innovative solution for the reinforcement treatment of ultra-soft soil foundations. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the rapid reinforcement structure of deep and ultra-soft foundation; Figure 2 It is a flow chart of the construction method of the present invention; Figure 3 It is the construction unit division diagram; Figure 4 This is the layout diagram of the pile positions of the triaxial mixing pile watertight wall; In the figure: 1. Silt in-situ solidification area, 2. Watertight wall, 3. High-pressure rotary jet reinforcement area, 4. Geogrid reinforced gravel cushion layer. DETAILED DESCRIPTION

[0017] The present invention is further described below in conjunction with the accompanying drawings, but the present invention is not limited to the specific embodiments.

[0018] Example 1

[0019] Reference Figure 1 to Figure 4 A method for rapid reinforcement of a deep and ultra-soft foundation is shown, comprising the following steps: Step 1: In-situ silt solidification: In-situ silt solidification is carried out on the newly filled silt land. The depth of in-situ silt solidification is 3m, forming a stable working layer in the working area; Step 2: Leveling and zoning: Level the reinforced area where the silt solidification has been completed to ensure that the foundation surface is flat, and divide the reinforced area into 9 construction units, each with an area of ​​10m×10m; Step 3: Watertight wall construction: cement mixing pile watertight wall construction is carried out at the partition connection and the outer edge of the soft foundation treatment area; the cement mixing pile watertight wall is constructed using three-axis cement mixing piles, and two adjacent cement mixing piles are overlapped with each other; the diameter of the cement mixing piles is 850 mm, the center spacing is 600 mm, the overlap width is 300 mm, and the verticality deviation is not more than 1 / 250; Step 4: Well point dewatering. After a stable working layer is formed, well point dewatering operation is carried out. This process includes setting a certain number of well points in the working layer and extracting groundwater through these well points to lower the groundwater level and create favorable conditions for the next step of high-pressure jet grouting pile construction. Step 5: High-pressure jet grouting reinforcement. After the well point is dewatered, high-pressure jet grouting pile construction is carried out. When the groundwater level drops to 3.5m below the construction plane, high-pressure jet grouting technology is used to construct high-pressure jet grouting piles. This step can further improve the bearing capacity of the soil and enhance the stability of the foundation. The specific parameters of high-pressure jet grouting pile construction are: slurry pressure 0.6MPa, air pressure 30Mpa, and lifting speed 10cm / min. Step 6: Lay the geogrid reinforced gravel cushion. After completing the reinforcement treatment of the rotary grouting reinforcement area, first lay the geogrid. The laying of the geogrid requires precise measurement and positioning to ensure that its position is accurate. When laying, the grid should be spread out flat to avoid wrinkles or distortions to ensure that it can fully play its role in enhancing the stability of the foundation. Then, lay a layer of gravel cushion on top of the geogrid. The selection of gravel should meet the specified particle size and quality requirements. It should be laid evenly and densely to provide good bearing capacity and prevent the geogrid from being subjected to direct pressure and damage. Step 7: Leveling and rolling. After the geogrid reinforced gravel cushion layer is laid, leveling work is carried out. Use a roller to level the surface of the gravel cushion layer to ensure that its flatness meets the subsequent construction requirements.

[0020] In step 1, one or more of an inorganic compound curing agent, an organic compound curing agent, and a composite curing agent are used.

[0021] In step 4, the number and location of the well points are accurately calculated and determined based on the specific conditions of the working layer and construction requirements, and one well point is set every 100 square meters to ensure maximum precipitation effect and construction efficiency.

[0022] In step 6, the reinforcing material in the geogrid reinforced cushion layer is a unidirectional geogrid with a tensile strength of not less than 50 kN / m, which is determined during the design calculation. The unidirectional geogrids are filled with crushed stone fillers, the compaction degree of the crushed stone fillers is greater than 96%, and the spacing between adjacent unidirectional geogrids is 0.2~0.3m.

[0023] The newly blown silt land refers to a silt layer foundation that is in a fluid state, has extremely low strength, a water content greater than 130%, a sand content less than 5% and a thickness greater than 10m.

[0024] Example 2

[0025] The steps of the rapid reinforcement construction method for deep and ultra-soft foundation described in this embodiment are the same as those in Example 1, except that the specific parameters of the high-pressure jet grouting pile construction are: slurry pressure 0.7MPa, air pressure 32Mpa, and lifting speed 12cm / min.

[0026] Example 3

[0027] The steps of the rapid reinforcement construction method for deep and ultra-soft foundation described in this embodiment are the same as those in Example 1, except that the specific parameters of the high-pressure jet grouting pile construction are: slurry pressure 0.8MPa, air pressure 35Mpa, and lifting speed 15cm / min.

[0028] Example 4

[0029] The construction structure adopted by the construction method described in Examples 1-3 includes: a silt in-situ solidification area 1 formed after the new blown silt land area is solidified, a watertight wall 2, a high-pressure rotary grouting reinforcement area 3, and a geogrid reinforced gravel cushion layer 4, wherein the silt in-situ solidification area 1 is divided into a plurality of small areas, and the watertight wall 2 is arranged at the connection of the small areas and at the outer edge of the soft foundation treatment area; the high-pressure rotary grouting reinforcement area 3 is located at the bottom layer of the silt in-situ solidification area 1, and the geogrid reinforced gravel cushion layer 4 is located at the top layer of the silt in-situ solidification area 1; The reinforcing material in the geogrid reinforced gravel cushion layer 4 is a unidirectional geogrid with a tensile strength of not less than 50 kN / m, which is determined during the design calculation. The unidirectional geogrids are filled with gravel fillers, the compaction degree of the gravel fillers is greater than 96%, and the spacing between adjacent unidirectional geogrids is 0.2~0.3m.

[0030] The present invention is not limited to the above-mentioned embodiments. If various changes or modifications to the present invention do not depart from the spirit and scope of the present invention, and if these changes and modifications fall within the scope of the claims and equivalent technologies of the present invention, the present invention is also intended to include these changes and modifications.

Claims

1. A method for rapid reinforcement of deep and ultra-soft foundation, characterized in that: The following steps are involved: Step 1: In-situ silt solidification: In-situ silt solidification is carried out on the newly filled silt land. The depth of in-situ silt solidification is 3m, forming a stable working layer in the working area; Step 2: Leveling and zoning: Level the reinforced area where the silt has been solidified to ensure that the foundation surface is flat, and divide the reinforced area into several construction units, each with an area of ​​10m×10m; Step 3: Watertight wall construction: cement mixing pile watertight wall construction is carried out at the partition connection and the outer edge of the soft foundation treatment area; the cement mixing pile watertight wall is constructed using three-axis cement mixing piles, and two adjacent cement mixing piles are overlapped with each other; the diameter of the cement mixing piles is 850 mm, the center spacing is 600 mm, the overlap width is 300 mm, and the verticality deviation is not more than 1 / 250; Step 4: Well point dewatering. After a stable working layer is formed, well point dewatering operation is carried out. This process includes setting well points in the working layer and extracting groundwater through these well points to lower the groundwater level and create favorable conditions for the next step of high-pressure jet grouting pile construction. Step 5: High-pressure jet grouting reinforcement, high-pressure jet grouting pile construction is carried out after the well point is dewatered; when the groundwater level drops to below 3.5m above the construction plane, high-pressure jet grouting technology is used to construct high-pressure jet grouting piles; the specific parameters of high-pressure jet grouting pile construction are: slurry pressure 0.6~0.8MPa, air pressure 30~35Mpa, and lifting speed 10~15cm / min; Step 6: Lay the geogrid reinforced gravel cushion. After the reinforcement treatment of the rotary grouting reinforcement area is completed, the geogrid is laid first. The laying of the geogrid requires precise measurement and positioning to ensure that its position is accurate. When laying, the grid is spread out flat to avoid wrinkles or distortions. Then, a layer of gravel cushion is laid on top of the geogrid. The selection of gravel should meet the specified particle size and quality requirements. Step 7: Leveling and rolling. After the geogrid reinforced gravel cushion layer is laid, leveling work is carried out. Use a roller to level the surface of the gravel cushion layer to ensure that its flatness meets the subsequent construction requirements.

2. A deep ultra-soft foundation rapid reinforcement construction method according to claim 1, characterized in that: In step 1, one or more of an inorganic compound curing agent, an organic compound curing agent, and a composite curing agent are used.

3. A deep ultra-soft foundation rapid reinforcement construction method according to claim 1, characterized in that: In step 4, the number and location of the well points are accurately calculated and determined based on the specific conditions of the working layer and construction requirements, and one well point is set every 100 square meters to ensure maximum precipitation effect and construction efficiency.

4. A deep ultra-soft foundation rapid reinforcement construction method according to claim 1, characterized in that: In step 6, the reinforcing material in the geogrid reinforced gravel cushion layer is a unidirectional geogrid with a tensile strength of not less than 50 kN / m, which is determined during the design calculation. The unidirectional geogrids are filled with gravel fillers, the compaction degree of the gravel fillers is greater than 96%, and the spacing between adjacent unidirectional geogrids is 0.2~0.3m.

5. A method for rapid reinforcement of deep ultra-soft foundation according to any one of claims 1 to 4, characterized in that: The newly blown silt land refers to a silt layer foundation that is in a fluid state, has extremely low strength, a water content greater than 130%, a sand content less than 5%, and a thickness greater than 10m.

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