In recent years, there are mainly two ways to reclaim land for land reclamation. One way is to open a mountain for reclamation, and the other is to make land by dredging the dredged soil. The former method is more and more damaging to the environment due to high cost, and its use is increasingly restricted by government departments. The latter method is not only low in cost, relatively environmentally friendly, but also has a short construction period. More importantly, with the increase of port construction, the landfilling of dredged soil can minimize the external throwing of dredged soil in port engineering. While greatly reducing the cost of dredging projects, the use of dredged soil as a reclamation resource, so that the dredged soil that should be discarded has a value, can be described as a multi-pronged.
Because landfilling by dredging and filling land has great advantages in both technical and economic benefits, this land reclamation method is more and more accepted by people and has been widely used in reclamation projects in coastal areas. . This land reclamation method also brings greater application prospects to vacuum pre-loading foundation treatment technology.
The application prospect of vacuum pre-loading in land reclamation
The purpose of reclamation is to provide land areas that can be used for economic construction. If the site is to meet the requirements of use, ground treatment must be carried out. Vacuum preloading is widely used in large reclamation projects because the technology has the following characteristics:
1) Save pre-compressed materials and reduce project cost. Vacuum preloading uses atmospheric pressure as the motive force for preloading. On the one hand, it does not need to use a large amount of piled materials, such as sand and stone, as preloading load, which solves the trouble of supplying preloaded materials, and on the other hand, the atmosphere Pressure is a free resource, which reduces engineering costs, especially for large-area soft-base treatments, which can greatly save engineering investment.
2) Fast consolidation and short construction period. Since the foundation does not undergo shear deformation under the action of vacuum pressure, no matter the degree of vacuum during the loading process, the foundation will not be unstable when applied once. With the maturity of vacuum preloading reinforcement technology in China, the vacuum degree under the film can reach about 85 kPa. Although the speed of consolidation does not depend on the magnitude of the preloading load, the overload is greater when the load is equal. The speed of residual settling must be faster. Since the load of the vacuum preload is large and the loading process is fast, the reinforcement time is short.
3), The construction is simple, the vacuum preloading is achieved by pumping air, then the unloading can be stopped as long as the pumping is stopped, that is, there is no problem that a large amount of unloading sand needs to be treated, which is in areas with poor external traffic conditions, It looks very good. In addition, vacuum preloading does not require the use of a large number of construction machines during loading, construction disturbance is small, construction accidents are not easy to occur, and after the required vacuum is stably maintained, the remaining work is only daily inspection and maintenance.
4), The reinforcement effect is good, the degree of consolidation of the vacuum preload can reach more than 90%, which can eliminate most of the settlement of the foundation. Moreover, since the atmospheric pressure is evenly distributed throughout the reinforced zone, the vertical deformation of the soil is also uniform throughout the reinforced zone (constrained by the surrounding soil, and the settlement at the boundary of the reinforced zone is slightly smaller), so The vacuum preloading strengthens the soft foundation, and the uneven settlement of the site will be smaller.
For sites with large ground design loads, such as container yards, if the preloading scheme is used, when the treatment area is large, the amount of earthwork used for the loading will be very amazing. Due to the impact of the stacking process, the construction period will be It has become very amazing. Due to the impact of the stacking process, the construction period will become very long. For example, in a project in Nansha, Guangzhou, the disposable treatment area is 1.50*10~5 square meters. If the preloading scheme is used, the purchased heap is required. Load sand 4*40~5 cubic meters, then divide the treatment area into three large blocks and use the piled sand in stages. The required construction period is not less than 2 years, and the construction cost reaches 400 million yuan. In the case of increasingly tight supply of sand and gravel resources, It is very difficult to obtain such a large amount of sand in a short period of time. The handling of a large amount of unloading sand is also extremely difficult. What is more important is that even if the engineering cost and construction difficulty are aside, such a long period of time cannot be used for investors or Accepted by the owner.
Because the vacuum preloading soft soil improvement has the advantages of low cost, short construction period, saving earthwork and ensuring the reinforcing effect, the treatment of large-area deep soft soil, especially the port engineering with relatively high ground design load, has the advantage that the preloading can not be compared. As mentioned above, the Guangzhou Nansha foundation project uses the vacuum preloading scheme to not only greatly reduce the project cost, but also the total processing time is only one year. Obviously, the application prospect of vacuum preloading in the landfilling project of dredging and filling soil is Very bright.
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