JPH0525828A - Final excavation level lift-preventive construction - Google Patents

Abstract

PURPOSE:To reduce a construction cost of an earth retaining wall and to curtail a construction period by fixing a final excavation level to the lower layer of a non-water permeable layer with steel pipe piles, etc., as an anchor, and preventing the final excavation level lift due to lifting pressure of pressurized water in the water-bearing ground. CONSTITUTION:An earth retaining wall 5 is provided around an excavated place, the inside thereof is excavated to form the final excavation level 6, and steel pipe piles 10, etc., as an anchor are arranged in parallel with the earth retaining wall 5 and are fixed to the hard ground 4. After that, a special head introducing prestress is provided to a pile head integrated with the final excavation level 6, and reinforcing members 15 are arranged around the head. The reinforcing 15 are so formed that cement milk is injected into the peripheral ground cut by jet injection to solidify. In addition, prestress is introduced to the steel pipe piles 10, and a prestress introduction amount or a number of steel pipe piles to be installed are decided in advance. Dead weight of the floor mounted ground 6 or a prestress amount is in excess of lifting pressure of pressurized water from a poor subsoil 2 occuring in the floor mounted ground 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention allows a grounded ground formed by excavating the ground on the inside of a mountain retaining wall to be lifted by the lifting pressure of pressured water existing in the aquifer. The structure for preventing

[0002]

2. Description of the Related Art When excavating the ground, a mountain retaining wall is provided in order to prevent collapse of the surrounding ground. However, in the case of an aquifer where pressured water exists, the inside of the mountain retaining wall is There is a problem that the floor-attached ground formed on the bottom of the excavated ground floats up due to the lifting pressure of the pressurized water.

Therefore, conventionally, as a first method, the pressured water existing in the ground is drained to reduce the lifting pressure to stabilize the grounded ground so that the grounded floor does not float up. . Also, as the second method,
The mountain retaining wall is rooted to the impermeable layer located at the depth where the lifting pressure of the pressurized water and the weight of the ground are in harmony to stabilize the grounded floor. Furthermore, as a third method, the chemical solution is injected to a depth where the lifting pressure of the pressurized water and the weight of the ground are harmonized to improve the ground, and the improved ground is used as an impermeable layer. I am trying to do it.

[0004]

[Problems to be Solved by the Invention] However, the above 3
According to one method, there were the following problems. In the first method, in addition to drainage at the time of excavation, drainage for reducing the water pressure is performed, so that there is a problem that the amount of drainage increases and the cost required for drainage increases. The second method adopts this method if the immovable layer does not exist at an appropriate depth because the cost of embedding the retaining wall is high because the retaining wall is deeper than necessary. There is a problem that cannot be done. In the third method, since the chemical solution is injected to an appropriate depth by boring or the like, the cost and the construction period for forming the impermeable layer are extra, and it is difficult to form a complete impermeable layer. .

The present invention has been made in view of the above-mentioned problems, and provides a structure for preventing floating of a floor-laying ground which can shorten the rooting dimension of a mountain retaining wall and can be obtained at a low cost and in a short construction period. The purpose is to do.

[0006]

Therefore, according to the present invention, the flooring ground formed at the bottom of the ground inside the mountain retaining wall is excavated by the pressure of the pressurized water existing in the aquifer. With a structure to prevent floating, the flooring ground is provided in a position above the impermeable layer, and for fixing the flooring ground to the hard ground located below the impermeable layer, The provision of the anchor means was the means for solving the above problems.

[0007] It is desirable to introduce into the anchor means a pre-stress that gives a larger fixing force to the hard ground than the lifting pressure of the pressurized water existing in the aquifer ground to the floor ground with its own weight. .

[0008]

In the present invention, since the floor-attached ground is fixed to the hard ground by the anchoring means, the above-mentioned water is placed on the impermeable layer at a shallow position where the lifting pressure of the pressured water becomes larger than the own weight of the ground. Even if the grounded floor is formed, it is possible to resist the lifting pressure of the pressured water, which makes it necessary to insert the retaining wall up to the impermeable layer at a depth where the lifting pressure of the pressured water and the ground's own weight are in harmony. Therefore, it is possible to make the root retaining dimension of the Yamadome wall shallow. In addition, since the above structure prevents the floor-mounted ground from rising, it is not necessary to drain the pressurized water for reducing the pressure or to form a new impermeable layer by injecting the chemical liquid.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

In the figure, reference numeral 1 is a ground having a ground 2 made of a sand layer and the like, and an impermeable layer 3 made of a hard clay layer and a pressure-fixed fixing layer 4 made of a gravel layer under the ground 2, and a reference numeral 5
Is a mountain retaining wall provided around the excavation site, and reference numeral 6 is a floor-attached ground formed on the bottom formed by excavating the inside of the mountain retaining wall 5.

The mountain retaining wall 5 is a water retaining mountain retaining wall which is driven so that its tip reaches the impermeable layer 3. Further, in the present embodiment, the flooring ground 6 is fixed to the hard ground, that is, the fixing layer 4 by a large number of anchor piles (anchor means) 10, so that the flooring ground 6 is lifted by the lifting pressure of the pressurized water. It is designed to prevent this.

The anchor piles 10 are arranged in parallel with each other between the mountain retaining walls 5, 5 along the long side direction of the excavation site, for example.
The 0 pile head is integrated with the grounded floor 6. As the anchor piles 10, for example, steel pipe piles, concrete construction piles having H-shaped steel or steel pipe as a core material, and the like are appropriately adopted, but in the present embodiment, as shown in FIG.
An unbonded steel wire is used for and a pile in which the grout material 12 is filled is used.

The anchor pile 10 used in this embodiment will be described in detail. The pile head 1 integrated with the upper end of the ground with ground 6 is formed.
3 is equipped with a special head 14 for introducing prestress to the anchor pile 10, and a reinforcing material 15 is provided around the pile head 13 to reinforce it. The reinforcing material 15 is formed by, for example, a method (jet grout pile) in which the surrounding ground is cut by jet injection and cement milk is injected into this portion to be solidified. Then, the prestress is introduced into the anchor pile 10 by the special head 14. The amount of prestress introduced is
The total weight of the floor-bearing ground 6 and the total amount of prestresses of the anchor piles 10 ... is larger than the lifting pressure of the pressurized water from the soft-ground 2 generated on the floor-bearing ground 6, that is, the floor-bearing ground 6 Is set to such a value that does not raise. Further, the number of anchor piles 10 is also determined in consideration of the introduction amount of the prestress.

FIG. 3 shows the appearance of the special head 14. One end of a core material 11 made of unbonded steel wire is fixed to the upper end of the special head 14 via a chuck 16. The core material 11 reaches the fixing layer 4, is folded back from there, and the other end of the core material 11 is fixed to the upper end of the special head 14. The other end of the core material 11 is sandwiched by a chuck 17 and an unbonded sheath 18 in a state where a predetermined tensile force is applied from the ground, and is fixed to the upper end of the special head 14. In addition, in FIG. 3, reference numeral 30 denotes the grout material 1.
2 shows a packer for preventing leakage of the grout material when filling 2 into the hole 20.

Next, the procedure for constructing the floor-attached ground having the above structure will be described.

(1) After constructing the mountain retaining walls 5 and 5, as shown in FIG. 2, a hole 20 is drilled to the root cutting bottom by a large diameter boring machine. (2) A sleeve 21 made of vinyl chloride or the like is inserted into the hole 20 from the ground to protect the hole wall of the hole 20. (3) The surrounding ground is cut from the bottom of the hole 20 by jet injection, cement milk is injected into the removed portion, and solidification is performed around the pile head of the anchor pile 10 to reinforce the reinforcing material 1
5 is formed. (4) When the cement milk is solidified, boring is further performed from the bottom of the hole 20 to pass through the hard clay layer 3 to extend the hole 20 to the gravel layer 4. (5) The unbonded steel wire 11 is inserted into the hole 20 in a loop state, and the special head 14 is attached to the unbonded steel wire 11. (6) The grout material 12 is pressure-filled to the bottom of the hole 20 through the grout pipe 19 of the special head 14. (7) After waiting for the grout material 12 to solidify, the unbonded steel wire 11 is pulled from the ground, and the unbonded steel wire 11 is fixed to the special head 14 by the chucks 16 and 17 and the unbonded sheath 18, and the anchor pile 10 has a desired amount. Introduce prestress. The amount of prestress introduction per anchor pile 10 is set to a value such that the total amount of prestress introduction and the total weight of the ground with ground is larger than the lifting pressure of the pressurized water. (8) The unbonded steel wire 11 above the special head 14 is cut. (9) In this way, the anchor piles 10 with the prestress introduced are installed every several meters.

According to this embodiment, by appropriately increasing the amount of prestress to be introduced into the anchor pile 10, the fixing force exceeding the lifting pressure of the pressurized water generated in the floor-laying ground 6 at an arbitrary depth can be obtained. 6 can have. Therefore, the floor imbedded ground 6 can be formed on the shallow impermeable layer in which the lifted pressure of the pressurized water becomes larger than the weight of the ground in comparison with the deep layer, and the ground retaining wall 5 can be formed. The rooting dimension of can be shortened. In addition, when the floor-attached ground is formed at such a position, the work for preventing the floor-attached ground from being lifted up by draining or injecting a chemical liquid, which is conventionally required, is unnecessary, and the construction period and the construction cost can be shortened.

In the above embodiment, the anchor pile 10 is applied to prevent the floor-attached ground 6 from rising, but the application of the anchor pile 10 is not limited to this, and the upper end of the anchor pile 10 is attached to the floor-attached ground. By fixing it to the bottom plate of the skeleton constructed on 6, it is also possible to prevent the skeleton from rising.

[0019]

As described above, according to the present invention,
The anchoring means is used to fix the floor-attached ground to the fixed layer below the impermeable layer, so that the weight of the floor-attached ground and the lifting pressure of the pressurized water do not match up You can prevent floating. This makes it possible to shorten the rooting dimension of the mountain retaining wall for forming the ground with floor,
The construction cost of the Yamadome wall can be reduced. In addition, since it is not necessary to take measures for preventing floating due to conventional drainage work or chemical injection work, it is possible to further reduce the construction cost and the construction period. In addition, by directly fixing the anchor means to the bottom plate of the skeleton constructed on the ground with floor, it is possible to prevent the skeleton from rising.

[Brief description of drawings]

FIG. 1 is an elevational view showing an example of a lift-up prevention structure for a floor-mounted ground according to the present invention.

FIG. 2 is an elevational view showing a main part of the same structure.

FIG. 3 is a perspective view showing a special head of an anchor pile used in the structure.

[Explanation of symbols] 1 ground 2 ground 3 impermeable layer 4 Fixing layer (hard ground) 5 Yamadome wall 6 floor ground 10 Anchor pile (anchor means).

Claims (3)

[Claims] 1. A structure for preventing a grounded ground formed at the bottom of a ground inside a mountain retaining wall from being lifted by the lifting pressure of the pressurized water existing in the aquifer, The floor-laying ground is provided at an upper layer of the impermeable layer, and an anchor means for fixing the floor-laying ground to a hard ground located at a lower layer of the impermeable layer is provided. A structure to prevent the ground from floating. 2. The floating prevention structure for grounded ground according to claim 1, wherein a desired prestress is introduced into the anchor means. 3. The amount of prestress introduced to the anchor means is fixed to the floor-bearing ground including its own weight with respect to the hard ground rather than the lifting pressure of the pressurized water in the ground occurring in the floor-bearing ground. The floating prevention structure for the floor-attached ground according to claim 1, wherein the force is set to a value that increases.