JPH02128010A - Improvement method for soft ground - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a construction method for improving soft ground such as waterfronts.

"Prior Art and its Issues" In general, it is desirable to construct various structures on waterfronts such as coastal areas due to their favorable location, but most of these waterfronts are located on reclaimed land. Therefore, a thick layer of soft soil (soft soil layer) containing a lot of clay, organic matter, and water content is deposited, resulting in a large amount of ground subsidence, and is extremely resistant to external forces such as earthquakes. It is weak. Therefore, when creating a housing site on soft ground and constructing a structure there, it is necessary to take measures such as increasing the strength of the ground and increasing its resistance to external forces, and therefore the ground must be improved.

For this reason, as a conventional ground improvement method,
The so-called surcharge construction method involves filling the planned construction site with soft ground in advance, increasing the bearing capacity of the foundation ground through consolidation, removing the embankment, and then constructing the structure on top of the ground. There is. However, this construction method requires additional soil costs for loading, leveling work costs, remaining soil disposal costs for removal, etc., and the work is also large-scale and takes a long time, resulting in high costs. I tended to.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for improving soft ground such as a waterfront, which can be easily and inexpensively improved by consolidation.

"Means for solving the problem" The method for improving soft ground according to the present invention is to drive sheet piles around soft ground to be improved such as waterfronts, and to waterproof the soft ground surrounded by the sheet piles. A sheet is laid, then both ends of the tie opening and rad are fixed on the inner surfaces of the opposing sheet piles, water is drawn from the sea or river to the inside of the sheet piles, and the loaded water is removed after the consolidation period is over. It was designed to do so.

"Operation" According to the soft ground improvement method of the present invention, water is easily drawn from the sea or river using a pump or other means and spread over the waterproof sheet on the soft ground to be improved inside the sheet pile, thereby reducing the water load. It can be completed quickly, and after the consolidation is completed, the water can be pumped out using a pump or the like and the load can be quickly removed.

"Embodiment" FIGS. 1 and 2 show an embodiment of the present invention. The soft ground improvement method according to the present invention is a loading method using water pressure as the loading load, and in this embodiment, when improving a reclaimed land such as a waterfront (soft ground 1), An example of construction using this method in combination with a certain atmospheric pressure construction method will be explained.

The atmospheric pressure construction method is a method in which the improved ground area is completely sealed with an impermeable vinyl membrane, etc., and then a vacuum pump is used to create negative pressure between the membrane and the ground to reduce atmospheric pressure. This is a construction method that uses it as a load to improve the geology.

The method for improving soft ground according to the present invention will be explained below in the order of steps. Enter.

The material of this sheet pile 3 is wooden, t14'b
J. Although reinforced concrete is available, lightweight steel sheet piles are the most suitable as they are inexpensive and easy to install and remove.

Furthermore, a drain 4 for drainage is driven into the improved ground area 2 inside the sheet pile 3, and a layer of sand 5 with good water permeability is spread on top of it to a thickness of 0°5 to 1 m. , A vibro for collecting air and water is installed in this sand bed 5. The area around the base end of the sheet pile 3 is backfilled and sealed with bentonite, muddy water, etc. to prevent air from leaking. In addition, holes 3a penetrating through the sheet pile 3 in the thickness direction are pre-drilled at equal intervals in the upper end of the sheet pile 3.

Next, a covering waterproof sheet 7 is spread over the inner circumferential surface of the sheet pile 3 and the upper surface of the improved ground 2 therein. Types of waterproof sheets 7 include plastic waterproof sheets mainly made of plastics such as polyisobutylene, vinyl chloride, and polyethylene, and asphalt waterproof sheets made of organic fiber base paper infiltrated with heated asphalt. be. Further, the outlet of the vibro for collecting air and water from the waterproof sheet 7 is particularly connected to the warehouse and connected to the vacuum pump 8.

Next, the holes 3a of the opposing sheet piles 3, 3,
Both ends of the tie rod 9 are inserted into the sheet piles 3, 3a, respectively, and fixing nuts 10 are screwed onto both ends from the outside of the sheet piles 3, 3, thereby fixing both ends of the tie rod 9 to the sheet piles 3, 3. This tie rod 9 functions to suppress the sheet pile 3 from expanding outward due to water pressure due to its tension, and the number of tie rods 9 is determined based on the load ff1ffi (water pressure applied to each sheet pile 3... ) is determined by Furthermore, a tie pull may be used instead of the tie rod 9.

Next, a predetermined meter of seawater (or river water) 11 serving as a loading object is pumped up from the sea 13 by the pump 12 and spread onto the waterproof sheet 7 inside the sheet vile 3. For example, when building a structure on soft ground 2, the amount of seawater 11 to be pumped is set to a load value greater than the final planned load.

If this state is left as it is for a predetermined period (for example, 2 to 3 months), the consolidation settlement of the improved ground area 2 will gradually be promoted and the strength of the ground will increase. The degree of vacuum between the waterproof sheet 7 and the ground during this loading period can be controlled by installing a mercury manometer in the sand bed 5 in addition to the Bourdon gauge of the drainage pump and passing it under the waterproof sheet 7. , for example, in the observation room.

(2) Removal of loaded load When the consolidation settlement amount and ground strength of the improved ground 2 due to the seawater 11 reach the target and the consolidation period ends, the seawater 11 in the seat vile 3 is pumped up by a pump drive to restore the original seawater 13. It can be returned and removed immediately.

After that, by removing the waterproof sheet 7 and the sheet pile 3, the ground improvement of the soft ground 2 is completed. Further, the sheet pile 3 may be completely buried in the ground as it is.

According to this embodiment, the following excellent effects can be achieved.

■In ground improvement using only atmospheric pressure method, consolidation using atmospheric pressure as a load does not work effectively in the deep part of the ground, but by adding water as a load as in this example, the improved soil can be consolidated deeper. can be promoted.

- Pumping up of the seawater 11 can be done by operating the pump 12 day and night, so loading can be completed quickly.

Furthermore, once the consolidation period has ended, the pump 12 is operated day and night to pump out the seawater 11 inside the sheet pile 3.
Since all you have to do is return it to Therefore, the pre-treatment and post-treatment steps during the consolidation period are easy, and these periods can be significantly shortened.

■Unlike when embankments are used as a load, a large amount of soil is not required, and water, which is the object of the load, can be used for free.
Soil costs can be significantly reduced.

■ Since transportation by truck is not required, the loading cost is only the operating cost of the pump, and there is no need to consider traffic conditions, and the sheet pile 3 and waterproof sheet 7 can be used repeatedly. The cost required for ground improvement can be significantly reduced in addition to various expenses such as. Further, noise problems caused by trucks and the like do not occur.

■ By using water as the load object, consolidation settlement can proceed evenly over the improved area of Landfill 1,
A stable improved ground can be constructed.

"Effects of the Invention" As explained above, according to the soft ground improvement method of the present invention, sheet piles are driven around the soft ground to be improved such as waterfronts, and the soft ground surrounded by the embankment is A tarpaulin sheet is laid on the inside of the sheet pile, and then water is pumped from the sea or river to the inside of the sheet pile, and after the consolidation period, the embankment is cut and the loaded water is removed. This simplifies processing and significantly shortens the period.

In addition, water, which is the object of the load, can be used freely, and there is no need to pay for additional soil as in the case of embankments.
In combination with the effects mentioned above, a significant cost reduction can be achieved.

[Brief explanation of the drawing]

FIGS. 1 and 2 show an embodiment of the present invention. FIG. 1 is an explanatory diagram showing a method for improving soft ground, and FIG. 2 is a sectional view of the soft ground in FIG. 1. 2... Soft ground, 3... Sheet pile, 7... Waterproof sheet, 8... Tie rod 11... Seawater (water).

Claims (1)

[Claims] Driving sheet piles around soft ground that needs to be improved, such as a waterfront, and laying a waterproof sheet over the soft ground surrounded by the sheet piles, then fixing both ends of tie rods or tie rods to the inner surfaces of the opposing sheet piles. This is a construction method for improving soft ground, which is characterized by drawing water from the sea or river to the inside of the sheet pile and removing the loaded water after the consolidation period is over.