JP3579807B2 - Method of reducing lateral pressure on underground structures in aerial landfill method - Google Patents

Description

[0001]
[Industrial applications]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing lateral pressure on an underground structure in an aerial landfill method in which a landfill area is closed, drainage is performed, and landfilling and construction of facilities in the landfill are performed.
[0002]
[Problems to be solved by the invention]
The conventional landfill method used for construction of artificial offshore islands, etc., was based on Tsukishima, which dumped sediment into the water and thrived from the sea surface to a uniform ground height.
[0003]
In this underwater landfill method, the subsidence time of the foundation ground is extended or the ground improvement is increased. Insufficient landfill strength due to underwater landfill, risk of liquefaction, and increase in ground improvement. Pollution of water quality and destruction of ecosystems by dumping sediment into water. Deterioration of landfill board quality due to landfill with bad soil and difficulty in early use. Extension of construction period due to the inability to carry out parallel work for Tsukishima and facility construction. There are issues such as rework and re-digging in the construction of underground facilities.
[0004]
In addition, due to the excavation and construction of the underground structure after the completion of landfill, earth pressure and water pressure are applied to the side wall of the underground structure in proportion to the depth from the ground surface. There is also a problem that it becomes extremely thick as compared with a side wall on the ground that does not hang.
[0005]
As a solution to the problem of such underwater reclamation method, the reclamation area is closed, drainage within the deadline is performed, and the ground in the reclamation area appears. The aerial landfill method was developed to construct facilities in the landfill.
・ Since the inside of the deadline is drained and then compacted one by one by rolling, it is not necessary to improve the landfill ground and high quality landfill with little settlement is possible. Therefore, the maintenance after completion is reduced, and the landfill can be used early.
・ Due to the pre-load due to the aerial landfill where the amount of landfill increases, the local density is promoted and the ground improvement is not required or required.
・ Since landfilling is performed after draining the deadline, water pollution is reduced compared to the case of dumping soil into the water, and the impact on the environment and fisheries around the landfill area due to changes in water quality is almost eliminated.
・ It is possible to use poor soil such as soil generated by construction. In addition, since the reclamation work and the facility construction can be performed simultaneously, the construction can be shortened.
・ Eliminating piers and secondary excavation for the construction of facilities is not required, and the foundation piles for facilities are not required or short.
The underwater reclamation method has an effect that cannot be solved, but for the construction of underground structures, construction by open-cutting after completion of reclamation has been adopted.
[0006]
The present invention was conceived in order to solve the problem of the construction of the underground structure in the aerial landfill method, and an object of the invention is to reduce the earth pressure applied to the side wall of the underground structure around the underground structure. It is an object of the present invention to provide a new method that can be reduced by making the soil layer an impermeable soil layer.
[0007]
[Means for Solving the Problems]
The feature of the present invention according to the above object is that embankment of a stabilized soil with coal ash or cement or the like whose earth pressure is reduced is constructed on the ground around the underground structure to be constructed, and between the stabilized soil and the underground structure. Is to use lightweight embankment.
[0008]
In such a side pressure reduction method, the structure of the underground structure can be made into a slit, and the coal ash can be effectively used. In addition, since the soil layer around the underground structure is strong, it does not liquefy even during an earthquake, and becomes an impermeable layer. Therefore, it is possible to reduce the lifting pressure on the underground structure and produce a high-quality structure without water leakage.
[0009]
The construction of the above facilities will be based on direct foundations or pile foundations, etc., depending on the condition of the underwater ground. In addition, the roof load of the underground structure can be reduced by using a truss roof, a block of styrofoam, lightweight embankment, etc., and the roof structure can be reduced by reducing the load on the roof. Embankment can be realized by using lightweight embankment.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Improvement of revetment ground (Fig. 1)
The water area of the terrain where watertight seawalls or temporary cutoffs and the reinforcement can be constructed is set as a landfill area, and the geology of the water bottom 1 in that water area is weak and the subsidence of the seawall part 2 is long, When the part 2 cannot be constructed, the ground improvement of the water bottom 1 which becomes the revetment part 2 of the landfill area A is first performed. However, when the ground in the water area is of good quality or when long-term land subsidence time can be ensured, the ground improvement of the water bottom 1 can be omitted.
[0011]
In this ground improvement, the required number of vertical drain piles 4 is cast at regular intervals to the ground 101 serving as a stratum using the work boat 3. At the time of ground improvement, the pollution prevention curtain 5 is provided from the work boat 3 in the surrounding water of the pile being constructed to prevent pollution of seawater due to the soaring soil. The formation of the vertical drain pile 4 promotes the compaction of the soft layer, improves the bearing capacity, and increases the strength of the on-site bed 6 of the seawall 2.
[0012]
Cut-off sheet pile driving process (Fig. 2)
A water-resistant steel sheet pile 7 is single- or double-poured on the ground 6 where the revetment is to be made, and the outer periphery of the landfill area A is shut off. The steel sheet pile 7 is cast by suspending the steel sheet pile 7 from the turret of the barge 8 with a crane located at an offshore position, and driving the steel sheet pile 7 into the field board 6 with a vibro hammer or a hydraulic hammer 9.
[0013]
Deadline filling process (Fig. 3)
In the case of closing with double steel sheet piles, after the steel sheet piles 7 inside and outside of the completed driving portion are connected at regular intervals by tie rods 10, the stuffed soil 12 or rubble stones carried by the gut ship 11 are removed. It is put in between 7 and thereby shuts off watertightly.
[0014]
Deadline reinforcement process (Fig. 4)
Further, for the purpose of wave breaking and stabilizing the cut-off, rubble 13 is put offshore of the cut-off sheet pile, and a covering stone and a wave-breaking block are installed thereon to form a seawall 14. In some cases, embankment is also performed on the inside with rubble or earth and sand to ensure stability.
[0015]
Improving the soil in the local area in the landfill area (Fig. 5)
All the drainage in the closed landfill area is drained to make the water bottom 1 appear, and the soft layer is improved with the stabilizer 15 or the like. Further, a deep wall 16 for the purpose of spring water treatment and consolidation promotion is installed as required.
[0016]
Improvement process of local panel (Fig. 6)
In a place where the soft layer is thick, a ground improvement pile 17 such as a vertical drain is constructed by a pile driver 18 for the purpose of consolidation settlement and improvement of bearing capacity.
[0017]
Landfill process (Fig. 7)
After the improvement of the on-site board has been completed, the landfill soil 19 transported by the soil transport ship is lifted by the dumper 20 into the deadline and landfilled. The landfill soil at this time is not limited to mountain soil, but may be construction-generated soil including defective soil. The defective soil is alternately laid with high-quality sandy soil in a sandwich form by the bulldozer 21 and sufficiently compacted.
[0018]
Facility construction process (Fig. 8)
Construction of the facilities in the landfill will begin at the same time as the reclamation within the deadline. In the case where this facility is an underground structure 22, first, the improved ground is removed to the periphery of the site where the facility is to be constructed, and the ground 101 is made to appear. The underground structure 22 of a concrete frame is directly built on the ground 101 on the foundation. I do.
[0019]
Lateral pressure reduction process (Fig. 9)
Next, on the ground 101 around the underground structure 22, an embankment 23 made of a stabilized soil such as coal ash or cement whose earth pressure is reduced to the landfill base surface is provided with a required space between the underground structure 22 and the ground. Leave 24 open. This construction is performed after the thin water blocking wall 25 is provided on the ground 101 on the side of the underground structure at the embankment position.
When the construction of the stabilized soil is completed, a lightweight embankment 26 is constructed up to the landfill base surface in the space 24 between the underground structure 22 and the embankment 23, and a normal embankment 27 is constructed outside the embankment 23.
[0020]
When planting is performed using the roof portion of the underground structure 22, the roof is a truss roof 27 to reduce the roof load, and an intermediate layer 28 such as a block of polystyrene foam or lightweight embankment is placed thereon. A topsoil 29 is applied on the intermediate layer 28 to a thickness (50 cm) necessary for planting.
[0021]
As described above, when the surroundings of the underground structure 22 are constituted by the embankment 23 of the stabilized treatment soil such as coal ash or cement and the lightweight embankment 26, the surrounding soil layer of the underground structure 22 becomes an impermeable layer. Therefore, the water pressure applied to the side wall of the underground structure 22 disappears, the side pressure due to the earth pressure and the water pressure is reduced, and the thickness of the side wall of the underground structure 22 can be reduced.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a process diagram of a revetment portion ground improvement process in an aerial landfill method.
FIG. 2 is a view showing a process of driving a cut-off sheet pile.
FIG. 3 is a diagram showing a process for closing during closing.
FIG. 4 is a process diagram of a cut-off reinforcement process.
FIG. 5 is a drawing showing a process of improving a soil in a local area in a landfill area.
FIG. 6 is a process chart of a local board improvement process in a landfill area.
FIG. 7 is a landfilling process chart.
FIG. 8 is a facility construction process diagram.
FIG. 9 is a schematic longitudinal sectional view showing the periphery of an underground structure constructed by the lateral pressure reducing method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Ground of reclamation area 2 Revetment part 4 Vertical drain pile 6 Local base of revetment part 14 Revetment 17 Soil improvement 22 Underground structure 23 Embankment of stabilization treatment soil 25 Water stop wall 26 Lightweight embankment 27 Truss roof 28 Intermediate layer 29 Topsoil 101 Soil

Claims (1)

A deadline for the reclamation area, drainage within the deadline to reveal the ground in the reclamation area, improve the ground of the local area, and then reclaim the land within the deadline and construct facilities in the landfill. In the landfill method,
The embankment of the stabilized soil with coal ash or cement that reduces the earth pressure is constructed on the ground around the underground structure to be constructed, and a lightweight embankment is used between the stabilized soil and the underground structure. Method to reduce lateral pressure on underground structures in the aerial landfill method.

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