JP5723558B2 - Ground improvement method - Google Patents

Description

  The present invention relates to a ground improvement method for improving the ground in an area where a tank for liquefied natural gas (LNG) is installed, and more specifically, a site where an existing facility such as a tank for crude oil has been removed is one. It is related with the ground improvement method when installing the tank for LNG so that it may be included in a section.

  In recent years, demand for LNG, which is clean energy, is increasing from the viewpoint of eliminating global warming due to an increase in carbon dioxide. Therefore, in the future, in the coastal industrial area and the like, it is presumed that the need to install an LNG tank in the site where the existing equipment has been removed is expected to increase.

  LNG tanks can be roughly classified into an underground type and an above-ground type, and an example of an above-ground type LNG tank will be described with reference to FIG. This LNG tank 10 is a prestressed concrete (PC) outer tank system, and is an inner tank 11 made of low-temperature steel, an outer tank 12 made of room-temperature steel, and between the inner tank 11 and the outer tank 12. It is comprised by the cold insulating material (pearlite and nitrogen gas) 13 with which it fills, and the bottomed cylindrical concrete structure 14 surrounding the side part and bottom part of the outer tank 12. FIG.

  Although the bottom part 14a of the concrete structure 14 is not shown in the figure, the center side may be recessed from the outer peripheral part and the outer peripheral part may protrude slightly from the central side. And the foundation pile 20,20 ... like a steel pipe pile is driven in the ground which supports the bottom part 14a of the concrete structure 14, and the foundation pile 20,20 ... supports the tank 10 for LNG. , So that it does not sink unevenly.

  In addition, when crude oil tanks are installed on soft ground such as the coastal industrial area, ground improvement by the sand drain method or the like is carried out only in the area where the crude oil tanks are installed. In the sand drain method, a number of sand columns with high water permeability are created in the vertical direction in soft ground. The sand column is constructed so that it is easy to pass water in a loose state.

JP-A-9-279565

  Since LNG is transported by sea by an LNG ship, the tank 10 for LNG is installed in the coastal industrial area. On the other hand, a tank for crude oil is also installed in the coastal industrial area, and if the tank 10 for LNG is installed on the site of the removed crude oil tank, the land can be used effectively.

  However, the LNG tank 10 may not be installed so as to completely overlap with the removed crude oil tank due to the layout. In other words, the LNG tank 10 may need to be installed across the area where the crude oil tank was installed and the area where it was not installed.

  However, the ground in the area where crude oil tanks were installed was improved by the sand drain method, etc., and consolidated and consolidated, while the ground in areas where crude oil tanks were not installed, The ground is not improved and is soft. Therefore, if the tank 10 for LNG is installed across the area where the crude oil tank was installed and the area where it was not installed, it is not possible to clearly analyze how it behaves during an earthquake. . In addition, the LNG tank 10 sinks in the region where the crude oil tank was not installed (unequal subsidence), and uneven stress is applied to the inner tank 11, the outer tank 12, or the concrete structure 14. The tank 10 can be damaged.

  Therefore, the present invention provides a ground for uniformizing the ground in the entire region where the LNG tank is installed when the LNG tank is installed across the ground improved region and the region where the ground is not improved. It is an object to provide an improved method.

The ground improvement method according to the present invention is a ground improvement method for installing a tank for LNG having a circular bottom surface across a ground improved area and a non-ground improved area. By placing a large number of sand piles on the ground in a non-region, the ground in the entire region where the tank for LNG is installed is made uniform, and the ground improved by placing the large number of sand piles, calculating a number of foundation piles for supporting a tank for LNG by sand pile to measure the soil strength between the region which has been ground improvement before being pouring, there in the region of the entire region A plurality of foundation piles spaced in the circumferential direction in the region along the outer periphery, and arranged in a matrix in the region within the entire region, the region inside the region along the outer periphery And laying multiple foundation piles That.

  According to this ground improvement method, a large number of sand piles are placed on the ground in the area where the ground is not improved, so that the ground in this area is compacted and improved. That is, the ground improved region becomes a ground that has been made uniform with the already ground improved region by the sand piles that have been laid. Therefore, the tank for LNG installed over both these regions has a clear behavior at the time of an earthquake, and can prevent unequal settling.

Moreover, according to this ground improvement method, it is supported by the foundation pile in which the tank for LNG was laid. The foundation pile is calculated by measuring the ground strength of both the area where the ground improvement was made by placing many sand piles and the area where the ground improvement was made before many sand piles were placed. Therefore, the number necessary and sufficient to support the tank for LNG can be placed.

  In the ground improvement method, the sand pile is preferably placed by a sand compaction pile method.

  According to this ground improvement method, sand piles are placed by the sand compaction pile method, so that consolidation settlement and unequal settlement in areas where ground improvement has not been completed converge in a short period of time. The horizontal resistance can be increased. The sand compaction pile method creates a compacted sand pile by press-fitting and expanding sand (including similar materials such as cohesive soil) in soft ground by vibration loading or impact loading. It is a kind of compaction method that compacts and compacts.

  In the ground improvement method, the sand pile may be placed in a region along the outer periphery of the LNG tank.

  According to this ground improvement method, sand piles are also placed in the area along the outer periphery of the LNG tank, so that the ground in the area along the outer periphery of the LNG tank is also made uniform, The behavior of the tank for LNG can be further clarified. The width of the region along the outer periphery of the LNG tank is preferably about 0.6 to 0.8 times the length of the sand pile.

  According to the present invention, a large number of sand piles are placed on the ground in an area where the ground is not improved, and the entire area in the tank for LNG installed across the ground improved area and the area where the ground is not improved As a result, the LNG tank installed by effectively using the site where the existing equipment such as a crude oil tank has been removed is clarified in the event of an earthquake. In addition, since the installed LNG tank is installed on a uniform ground, it does not sink unevenly, and the LNG tank does not generate uneven stress. It is possible to prevent an accident of spilling.

  In addition, the present invention makes it possible to use existing pier equipment, cooling equipment, power receiving equipment, fire prevention related equipment, and other various equipment by making it possible to install a tank for LNG at the site of the crude oil tank. Construction costs can be reduced compared to when the crude oil tank site is not used.

It is a top view including the ground which implements the present invention. It is a top view which shows the state of the ground before implementing this invention. It is a top view which shows the state of the ground in the middle of implementing this invention. It is a top view which shows the state of the ground improved by this invention. It is a schematic sectional drawing of the tank for LNG.

  An embodiment of the ground improvement method according to the present invention will be described with reference to FIGS. As shown in FIG. 1, this ground improvement method is carried out when, for example, a crude oil tank in an idle state is removed from a landfill 1 in a coastal industrial zone, and an LNG tank 10 is installed in the site 2. To do. In the coastal industrial zone, the pier facility 3 and other facilities (not shown) are left, and these facilities can be used. And the tank 10 for LNG is installed so that the ruins 2 from which the tank for crude oil was removed may be included in part because of the layout.

  As shown in FIG. 2, the site 2 from which the crude oil tank has been removed has already been improved by sand piles 9 and 9 placed by the sand drain method (illustrated by halftone dots). The ground 4 is not improved. Hereinafter, the site 2 from which the crude oil tank has been removed is referred to as “ground improved region 2”, and the periphery 4 of the ground improved region 2 is referred to as “region not improved” 4.

  When the LNG tank 10 is installed across the ground improved region 2 and the ground unimproved region 4, the LNG tank 10 behaves when an earthquake occurs because different types of ground are subject to evaluation. Becomes unclear and sinks on the region 4 side where the ground is not improved.

  Therefore, first, as shown in FIG. 3, a region (Crescent Moon in the drawing) 7 that protrudes from the ground-improved region 2 and a region along the outer periphery of the LNG tank 10 ( A number of sand piles 9, 9... Are placed at equal intervals on the ground of C-shaped in the drawing. By the large number of sand piles 9, 9,..., The entire area 5 where the LNG tank 10 is installed, that is, the ground 2 in the ground improved area and the ground 4 in the area 4 where the ground is not improved is made uniform. Note that the width of the region 8 (more specifically, the distance between the inner edge of the region 8 (coincident with the outer surface of the tank 10) and the outer edge of the region 8) is determined in relation to the length of the sand pile 9, for example, a sand pile It is preferable to set it in the range of 0.6 to 0.8 times the length of 9, particularly preferably 2/3 times.

  A large number of sand piles 9, 9... Are laid by a sand compaction pile method excellent in various characteristics such as settlement prevention, liquefaction prevention, improvement effect, construction period, design accuracy and the like. The sand compaction method is to place sand piles 9, 9 ... by pressing and expanding the sand (including similar materials such as cohesive soil) into the soft ground by vibration loading or impact loading. It is a kind of compaction method that tightens firmly.

  More specifically, a casing pipe (not shown) is buried in a soft ground at a predetermined position to a predetermined depth, and then the casing pipe is filled with sand and finally the sand is left in the ground. The sand piles 9, 9... Are driven into the soft ground by pulling out the pipe (see Patent Document 1).

  The sand piles 9, 9... Use a means of compacting sand, such as a vibro flotation method or a rod conversion method, or drainage, such as a sand drain method or a quick lime pile method, depending on the condition of the ground. You may drive by means.

  Next, by measuring the ground strength of the entire region 5 of the region 2 where the ground improvement and the multiple sand piles 9, 9... Are placed, the foundation piles 6, 6. The number of is calculated. And based on this calculation result, as shown in FIG. 4, many foundation piles 6,6 ... like a steel pipe pile are driven into the ground of the whole area | region 5 which installs the tank 10 for LNG at equal intervals. In this way, the LNG tank 10 has the entire area 5 where the entire bottom 14a (see FIG. 5) of the concrete structure 14 is installed and the surrounding area ground are made uniform by the sand piles 9, 9,. It is supported by these foundation piles 6, 6.

  When the LNG tank 10 is recessed at the center side of the bottom portion 14a of the concrete structure 14, sand piles 9, 9... Are driven in accordance with the shape of the surrounding protruding bottom portion 14a. The foundation piles 6, 6 ... are driven in.

  Thus, the entire region 5 of the LNG tank 10 installed across the ground improved region 2 and the non-ground improved region 4 is the same as the LNG at the time of the occurrence of the earthquake. The behavior of the tank 10 can be clarified. Further, even if LNG is stored in the LNG tank 10, the LNG tank 10 does not sink unevenly, and safety is ensured. Furthermore, the LNG tank 10 can store LNG using various facilities such as the existing jetty facility 3.

  In addition, this invention can be variously changed within the range of the technical matter described in the claim, without being limited to the said embodiment. For example, the present invention can be implemented not only when the crude oil tank is used, but also when the LNG tank 10 is installed across various areas of the building where the ground has been improved. Moreover, arrangement | positioning of the sand piles 9,9 ... and the foundation piles 6,6 ... can be designed suitably.

2 ... Ground improvement area 4 ... Ground improvement area 5 ... All areas where tanks for LNG are installed 6 ... Foundation piles 9 ... Sand piles 10 ... LNG tanks

Claims (3)

A ground improvement method when installing a tank for LNG having a circular bottom surface across a ground improved region and a region not ground improved,
By placing a large number of sand piles on the ground in the area where the ground has not been improved, the ground in all areas where LNG tanks are installed is made uniform,
The number of the sand pile is pouring soil improvement area, a tank for LNG by a large number of sand pile to measure the soil strength between the region which has been ground improvement before being pouring support Calculate the number of foundation piles to
A plurality of foundation piles that are circumferentially spaced in a region along the outer periphery, the region within the entire region, the region within the entire region, and more than the region along the outer periphery A ground improvement method characterized by placing a plurality of foundation piles in a matrix in the inner region.   The ground improvement method according to claim 1, wherein the sand pile is driven by a sand compaction pile method. The ground improvement method according to claim 1 or 2, wherein the sand pile is also placed in a region along an outer periphery of a tank for LNG.

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