Method for reinforcing dry silty-fine sand foundation through water circulation vibroflotation method

Abstract

The invention discloses a method for reinforcing a dry silty-fine sand foundation by a water circulation vibroflotation method, which comprises the following steps of: dividing a construction area into a foundation area and a cofferdam, and surveying the geology of the foundation area; the optimal water content is calculated according to the geology, obtained through exploration, of the foundation area, a plurality of irrigation holes are formed in the foundation area, and irrigation is conducted on the foundation area through the irrigation holes according to the optimal water content; a plurality of vibroflotation points are arranged in the foundation area, vibroflotation is conducted on the vibroflotation points in the foundation area after irrigation is completed, waste water generated during vibroflotation is discharged into the cofferdam every time vibroflotation is conducted, and water circulation vibroflotation is conducted on the follow-up vibroflotation points through the waste water in the cofferdam till vibroflotation is completed on all the vibroflotation points in the foundation area. According to the method, the vibroflotation area and the cofferdam area are arranged in the dry silty-fine sand area, waste water is accumulated and utilized through the cofferdam during vibroflotation, water circulation vibroflotation is conducted, and the problems that when the water source is limited, the dry silty-fine sand soil layer foundation treatment efficiency is low, and the construction effect is poor are solved.

Description

Technical Field

[0001] The invention relates to the technical field of foundation reinforcement, and in particular to a method for reinforcing a dry powdery fine sand foundation using a water circulation vibratory method. Background Art

[0002] Dry fine sand layers are widely distributed in coastal desert areas such as South America and the Middle East. The particles are small and non-viscous, the natural moisture content is extremely low, and the natural foundation bearing capacity is insufficient. In such areas, due to the low initial relative density of loose dry fine sand and the poor bearing capacity of the natural foundation, it is difficult to meet the settlement and bearing capacity requirements of the project. In addition, vibro-compaction zoning has high requirements for the frequency of vibration. The traditional dynamic compaction method has large vibrations that will affect the surrounding existing buildings and structures; the use of composite foundations such as gravel piles or pile foundations will result in high project costs. In addition, although deserts and coastal areas are close to water sources (such as oceans and groundwater), the on-site water level in some areas is low, and there is a thick layer of dry fine sand on the surface of the foundation. The traditional vibro-compaction foundation treatment technology has low construction efficiency and poor construction results, which is difficult to meet the needs of the project.

[0003] Therefore, a foundation reinforcement method is needed that can make full use of limited water resources and adapt to dry geological conditions to meet the needs of engineering construction in coastal desert areas. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a method for reinforcing a dry fine sand foundation by a water circulation vibration method. A vibration zone and a cofferdam zone are set in the dry fine sand area, and waste water is stored and utilized by the cofferdam during vibration to perform water circulation vibration. This solves the problem of low efficiency and poor construction effect of dry fine sand foundation treatment when water sources are limited.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for consolidating dry fine sand foundation by water circulation vibration method comprises the following steps:

[0007] Divide the construction area into the foundation area and cofferdam, and conduct geological survey on the foundation area;

[0008] Calculate the optimum moisture content based on the geology of the foundation area obtained through survey, open a number of irrigation holes in the foundation area, and irrigate the foundation area through the irrigation holes according to the optimum moisture content;

[0009] Several vibration points are set in the foundation area, and the vibration points in the foundation area are vibrated after the water filling is completed. The wastewater generated during the vibration is discharged into the cofferdam each time, and the wastewater in the cofferdam is used to perform water circulation vibration on subsequent vibration points until all the vibration points in the foundation area are completed.

[0010] Furthermore, the geological survey of the foundation area specifically includes: surveying the thickness of the dry, loose, fine sand layer in the foundation area to obtain the thickness of the dry, loose, fine sand layer.

[0011] Furthermore, the specific implementation method of opening a plurality of irrigation holes in the foundation area is as follows: for each irrigation hole, after drilling is completed, bentonite is backfilled into the bottom of the hole to seal the hole, and after sealing is completed, gravel is backfilled into the hole until the irrigation hole is filled to form a gravel irrigation hole.

[0012] Furthermore, the depth of the irrigation hole is greater than the thickness of the dry loose fine sand layer.

[0013] Furthermore, after the drilling is completed, bentonite is backfilled into the bottom of the hole to seal the hole, and the implementation method also includes: filling low-permeability fine sand into the bottom of the hole and then filling bentonite.

[0014] Furthermore, the vibro-compaction points in the foundation area after the watering is completed are vibrated, and the specific implementation method is as follows: for each vibro-compaction point, a hole is made by using a vibro-compaction machine until the vibro-compaction machine reaches a preset depth and then vibrates, and after the vibration is completed, the hole is lifted up, and the on-site sand produced by the vibration is backfilled into the hole during the lifting process, and after each lifting to a certain height, a reverse insertion and vibration is performed, and the reverse insertion depth is less than the lifting height, until it is lifted to the ground, and the vibro-compaction of the vibro-compaction point is ended.

[0015] Furthermore, the wastewater in the cofferdam is used to perform water circulation vibration on subsequent vibration points, and its specific implementation method is: the wastewater in the cofferdam is precipitated, the water obtained after precipitation is used for vibration, and the sediment is used for drilling irrigation holes.

[0016] Furthermore, it also includes: arranging a plastic film at the bottom of the cofferdam for waterproofing.

[0017] Furthermore, it also includes: dividing the foundation area into a number of vibro-impact zones, and performing rolling construction according to the vibro-impact zones.

[0018] Furthermore, the specific implementation method of the rolling construction according to the vibration zone is: fill the vibration zone with water one by one, and after each vibration zone is filled with water, vibrate the vibration zone that has been filled with water, and while vibrating the vibration zone that has been filled with water, fill the next vibration zone with water.

[0019] Through the above technical scheme, the present invention has the following beneficial effects: by combining hydraulic compaction and vibration reinforcement technology, the bearing capacity of the foundation is improved, while optimizing the utilization of water resources, cyclically vibrating, adapting to the special geological conditions and resource limitations of coastal desert areas, reducing the consumption of water resources during construction and reducing costs, and improving the strength and uniformity of the foundation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is a schematic diagram of the overall process of a method for reinforcing a dry fine sand foundation by a water circulation vibration method. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Example 1

[0024] See also Figure 1 A method for consolidating dry fine sand foundation by water circulation vibration method comprises the following steps:

[0025] Divide the construction area into the foundation area and cofferdam, and conduct geological survey on the foundation area;

[0026] Calculate the optimum moisture content based on the geology of the foundation area obtained through survey, open a number of irrigation holes in the foundation area, and irrigate the foundation area through the irrigation holes according to the optimum moisture content;

[0027] Several vibration points are set in the foundation area, and the vibration points in the foundation area are vibrated after the water filling is completed. The wastewater generated during the vibration is discharged into the cofferdam each time, and the wastewater in the cofferdam is used to perform water circulation vibration on subsequent vibration points until all the vibration points in the foundation area are completed.

[0028] In an optional embodiment, the surveying of the geology of the foundation area specifically includes: surveying the thickness of the dry, loose, fine sand layer in the foundation area to obtain the thickness of the dry, loose, fine sand layer.

[0029] Survey the geological conditions at the construction site, confirm the distribution of soil layers, and survey the water level, ground elevation, thickness of dry loose fine sand layer and natural moisture content of dry fine sand.

[0030] According to the survey results, survey points are set in the foundation area, and drilling survey is carried out according to the survey points. The drilling depth of the survey points is greater than the thickness of the dry loose fine sand layer. The distribution of the survey points is determined according to the on-site geological conditions. The more complex the geological conditions, the denser the survey points, and the simpler the geological conditions, the sparser the survey points.

[0031] Specifically, the survey points are distributed every 250m 2 A survey point, wherein the depth of the survey point exceeds the thickness of the dry loose fine sand layer by 1m.

[0032] In an optional embodiment, after exploration, the optimal moisture content on site is 10%, the thickness of the dry loose fine sand layer is 8m, and the dry density of the on-site dry sand is 1650kg / m 3 , the surplus coefficient is 1.1, and it is calculated that each site needs to be irrigated with 726 tons of water in advance.

[0033] The surplus coefficient may also be 1 to 1.3.

[0034] In an optional embodiment, a plurality of irrigation holes are opened in the foundation area, and the specific implementation method is: for each irrigation hole, after the drilling is completed, bentonite is backfilled into the bottom of the hole to seal the hole. After the sealing is completed, gravel is backfilled into the hole until the irrigation hole is filled to form a gravel irrigation hole.

[0035] Specifically, the irrigation hole is drilled at the exploration point. After the exploration of the drilling hole at the exploration point is completed, bentonite is backfilled to seal the hole, and then the casing is pulled out and gravel is backfilled into the hole. The role of the bentonite bottom seal is to ensure that the water in the irrigation hole does not leak vertically into the dense soil layer, that is, the non-reinforced area.

[0036] In actual application, the bentonite landfill thickness is generally 20 to 100 cm to ensure that the interface between the reinforced fine sand layer and the original stratum is sealed by bentonite.

[0037] In an optional embodiment, the depth of the irrigation hole is greater than the thickness of the dry loose fine sand layer.

[0038] In an optional embodiment, after the drilling is completed, bentonite is backfilled into the bottom of the hole to seal the hole, and the implementation method also includes: filling low-permeability fine sand into the bottom of the hole and then filling bentonite.

[0039] When the depth of the irrigation hole exceeds the loose fine sand layer to be reinforced, some low-permeability fine sand can be filled first, and then bentonite can be filled to ensure complete closure without affecting the non-reinforced area.

[0040] In an optional embodiment, the vibro-compaction points in the foundation area after the watering is completed are vibrated, and the specific implementation method is: for each vibro-compaction point, a hole is made by using a vibro-compaction machine until the vibro-compaction machine reaches a preset depth and then vibrates, and after the vibration is completed, the hole is lifted up, and the on-site sand produced by the vibration is backfilled into the hole during the lifting process, and after each lifting to a certain height, a reverse insertion and vibration is performed, and the reverse insertion depth is less than the lifting height, until it is lifted to the ground, and the vibration of the vibro-compaction point is ended.

[0041] Vibroflotation, also known as vibration water flushing, refers to a foundation reinforcement method developed based on the principle that sandy soil foundations can be compacted by adding water and vibration. Vibroflotation is a foundation reinforcement treatment method to improve poor foundations to meet the foundation requirements of buildings. The vibroflotation equipment is selected according to the on-site geological conditions, and the power of the vibroflotation equipment is generally not less than 75kw. Specifically, the spacing between on-site vibroflotation points is 3m, and the vibroflotation depth is the depth of the soil layer to be reinforced, that is, the dry, loose, fine sand layer.

[0042] The vibration retention time should be determined in the test area according to the required reinforcement effect. The better the required reinforcement effect, the longer the vibration retention time. The same applies to the spacing between lifting and reverse insertion. The better the required reinforcement effect, the higher the requirement, the smaller the required spacing, and the longer the time.

[0043] The vibro-impact stage includes four parts: the start of vibro-impact, the hole-making stage, the lifting stage and the completion of vibro-impact. In the start of vibro-impact and the hole-making stage, the vibro-impact equipment uses high water pressure to increase the hole-making rate. At the same time, a pump is used to extract the overflowing water in the hole to the cofferdam. When the preset depth is reached, it enters the lifting stage, reduces the water pressure and repeats the steps of retaining vibration-lifting-reverse insertion-retaining vibration, and recovers the water in the hole to lower the water level in the hole. The loader simultaneously backfills the hole with on-site sand until the vibro-impact equipment reaches the ground to complete the vibro-impact.

[0044] In an optional embodiment, the maximum water pressure of the vibroflotation equipment is set to 0.8MPa. After reaching the preset depth, the water pressure is reduced to 0.3MPa and the vibration is retained for 30 seconds. Then, every time the vibroflotation equipment is lifted up by 1m, it is inserted back by 0.5m and the vibration is retained for 30 seconds until the vibroflotation equipment returns to the ground.

[0045] In an optional embodiment, the wastewater in the cofferdam is used to perform water circulation vibration on subsequent vibration points, and its specific implementation method is: the wastewater in the cofferdam is precipitated, the water obtained after precipitation is used for vibration, and the sediment is used for drilling irrigation holes.

[0046] The wastewater in the cofferdam can also be seawater near the construction area. If the seawater does not meet the requirements, it should be purified. If necessary, high-salinity water resources should be partially desalinated to ensure that no corrosive damage is caused to the equipment and soil.

[0047] In an optional embodiment, the cofferdam is located at the center of the construction area, and the cofferdam volume is determined according to the pre-watering demand.

[0048] Specifically, the capacity of the cofferdam is 1,200 tons, and the water reservoir is determined based on on-site usage to meet actual on-site usage. In theory, the larger the better. In addition, wastewater or seawater in different areas at different times can be managed in different areas to improve sedimentation effect and efficiency.

[0049] In an optional embodiment, the method further includes: providing a plastic film at the bottom of the cofferdam for waterproofing.

[0050] In an optional embodiment, the method further includes: dividing the foundation area into a plurality of vibro-impact zones, and performing rolling construction according to the vibro-impact zones.

[0051] Specifically, the area of ​​each vibro-zone is 500m 2 .

[0052] In an optional embodiment, the specific implementation method of the rolling construction according to the vibration zone is: fill the vibration zone with water one by one, vibrate the vibration zone that has been filled with water after each vibration zone is filled with water, and while vibrating the vibration zone that has been filled with water, fill the next vibration zone with water.

[0053] Specifically, the sign of completion of the irrigation is that there is no obvious water accumulation on the surface of the irrigation area, which means that the irrigation penetration is completed.

[0054] The present invention has the following beneficial effects: in view of the low moisture content of dry fine sand, the soil performance is improved by water injection, creating suitable conditions for the vibroflotation method, solving the problem of low efficiency of traditional construction methods in such areas, and improving the strength and uniformity of the foundation. The increase in moisture content optimizes the liquefaction characteristics of the soil, making the vibroflotation construction more efficient, the foundation density is higher, the bearing capacity of the foundation can be greatly improved, differential settlement can be reduced, and it is suitable for various types of heavy-loaded structures. At the same time, pre-watering of the irrigation holes can assist in reducing the energy consumption and construction time of the vibroflotation equipment, especially under dry soil conditions, to avoid reduced efficiency due to excessive looseness of the soil. In addition, the present invention adopts a cyclic construction process, optimizes resource utilization, seamlessly connects between regions, and avoids repeated operations.

[0055] In addition, the present invention can accurately control the moisture content distribution of the target area by reasonably designing the injection volume and hole spacing, adapt to various soil conditions, and through cofferdams and pumping devices, the water flowing out during the injection process can be directly used in other areas, reducing the waste of water resources.

[0056] The embodiment disclosed in this specification is only an example of a unilateral feature of the present invention, and the protection scope of the present invention is not limited to this embodiment, and any other functionally equivalent embodiments fall within the protection scope of the present invention. For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all of these changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. A method for consolidating dry fine sand foundation by water circulation vibration method, characterized in that: The following steps are involved: Divide the construction area into the foundation area and cofferdam, and conduct geological survey on the foundation area; Calculate the optimum moisture content based on the geology of the foundation area obtained through survey, open a number of irrigation holes in the foundation area, and irrigate the foundation area through the irrigation holes according to the optimum moisture content; Several vibration points are set in the foundation area, and the vibration points in the foundation area are vibrated after the water filling is completed. The wastewater generated during the vibration is discharged into the cofferdam each time, and the wastewater in the cofferdam is used to perform water circulation vibration on subsequent vibration points until all the vibration points in the foundation area are completed.

2. The method for consolidating dry fine sand foundation by water circulation vibration method according to claim 1, characterized in that: The geological survey of the foundation area specifically includes: surveying the thickness of the dry, loose, fine sand layer in the foundation area to obtain the thickness of the dry, loose, fine sand layer.

3. The method for consolidating dry fine sand foundation by water circulation vibration method according to claim 2, characterized in that: The specific implementation method of opening a plurality of irrigation holes in the foundation area is as follows: for each irrigation hole, after drilling is completed, bentonite is backfilled into the bottom of the hole to seal the hole, and after sealing is completed, gravel is backfilled into the hole until the irrigation hole is filled to form a gravel irrigation hole.

4. The method for consolidating dry fine sand foundation by water circulation vibration method according to claim 3, characterized in that: The depth of the irrigation hole is greater than the thickness of the dry loose fine sand layer.

5. The method for consolidating dry fine sand foundation by water circulation vibration method according to claim 3, characterized in that: After the drilling is completed, bentonite is backfilled into the bottom of the hole to seal the hole. The implementation method also includes: filling low-permeability fine sand into the bottom of the hole and then filling bentonite.

6. The method for consolidating dry fine sand foundation by water circulation vibration method according to claim 1, characterized in that: The vibro-compaction points in the foundation area after the watering is completed are vibrated. The specific implementation method is: for each vibro-compaction point, a hole is made by using a vibro-compaction machine until the vibro-compaction machine reaches a preset depth and then vibrates. After the vibration is completed, the hole is lifted up. During the lifting process, the on-site sand produced by the vibration is backfilled into the hole. After each lifting to a certain height, a reverse insertion and vibration is performed, and the reverse insertion depth is less than the lifting height, until it is lifted to the ground, and the vibro-compaction of the vibro-compaction point is ended.

7. The method for consolidating dry fine sand foundation by water circulation vibration method according to claim 1, characterized in that: The method of using the wastewater in the cofferdam to perform water circulation vibration on subsequent vibration points is specifically implemented as follows: the wastewater in the cofferdam is precipitated, the water obtained after precipitation is used for vibration, and the sediment is used for drilling irrigation holes.

8. The method for consolidating dry fine sand foundation by water circulation vibration method according to claim 1, characterized in that: Also includes: A plastic film is set at the bottom of the cofferdam for waterproofing.

9. The method for consolidating dry fine sand foundation by water circulation vibration method according to claim 1, characterized in that: Also includes: The foundation area is divided into several vibro-impact zones, and rolling construction is carried out according to the vibro-impact zones.

10. The method for consolidating dry fine sand foundation by water circulation vibration method according to claim 9, characterized in that: The specific implementation method of the rolling construction according to the vibro-compaction zones is: water is poured into the vibro-compaction zones one by one, and after each pair of vibro-compaction zones are filled with water, the vibro-compaction zones that have been filled with water are vibrated, and while the vibro-compaction zones that have been filled with water are vibrated, the next vibro-compaction zones are filled with water.

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