JP3051716B2 - Construction method for underground structures - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for constructing an underground structure in which structures such as a water storage tank and a basement are buried underground.

[0002]

2. Description of the Related Art When digging the ground and burying a water tank underground, for example, it is necessary to block water in a portion to be digged, but a typical water blocking method is a well point method and a well point method. There is an earth retaining sheet pile method.

The well point method is, for example, shown in FIGS.
As shown in FIG. 6, a well point c is formed in the ground at a pitch of 1 to 1.5 m so as to surround a portion b where the ground a is to be dug.
And a tube d extending upward from the well point c
Is connected to an annular pipe e on the ground, and groundwater is lowered by forcibly sucking groundwater with a vacuum pump f attached to the annular pipe e, thereby blocking the groundwater. Then, while ensuring this water-blocking state, the water tank structure g is gradually settled as shown by the dashed line in FIG. 5 while digging the ground a, and is installed at a predetermined depth as shown by the solid line in FIG. ,
A water tank bottom h was formed by casting in place, and then closed with a top plate i to construct a water tank j buried underground.

The earth retaining sheet pile method is described in, for example, FIGS.
As shown in Fig. 5, a steel sheet pile k is driven into the ground continuously in the circumferential direction so as to surround a portion b where the ground a is to be dug, thereby blocking water. Then, while ensuring this water-blocking state, the water tank structure g is gradually settled as shown by the dashed line in FIG. 7 while digging the ground a, and is installed at a predetermined depth as shown by the solid line in FIG. A water tank bottom h was formed by casting in place, and then closed with a top plate i to construct a water tank j buried underground.

[0005]

However, the following problems have been encountered when using the above-described conventional water-blocking method. (1) Problems with the well point method The well point method can be adopted without being affected by the level of the groundwater level, and has the advantage of being able to be constructed at relatively low cost. there were. In addition, since the ground level lowers and the surrounding ground subsidence is caused, it cannot be adopted when houses and structures exist in the surrounding area. Furthermore, due to the clogging of the pump, this construction method had soil conditions suitable for a granular sand layer and a sandy silt layer but not a clay layer.

(2) Problems of the earth retaining sheet pile method The earth retaining sheet pile method is advantageous in that it is not affected by the level of the groundwater level and can avoid the influence on the surroundings due to the decrease in the groundwater level as in the well point method. However, the following problems have been pointed out. There is a drawback that the construction period is prolonged because it takes days to drive and pull out the steel sheet pile, and the construction cost has risen due to the need for such construction days. Since the sheet pile driving is performed while applying vibration, not only the ground around the driving portion of the steel sheet pile is loosened, but also the ground is further loosened by pulling out the sheet pile after the water tank is sunk to a predetermined level. Such loosening of the ground may adversely affect the side wall of the buried water tank, or may cause the ground around the water tank to sink.

An object of the present invention is to provide a construction method of an underground structure capable of simultaneously solving the above-mentioned problems of the well point method and the earth retaining sheet pile method.

[0008]

In order to solve the above-mentioned problems, the present invention employs the following means. That is, the method of constructing an underground structure according to the present invention (hereinafter referred to as a construction method) is a method of constructing an underground structure in which a ground is dug and a structure is buried underground. In order to completely surround the water impervious wall, a water impervious wall having an annular shape in plan view is to be constructed in advance. A soil cement-like columnar material obtained by curing the stirring mixture of the above is continuously formed in the circumferential direction in an arrangement in which the side portions overlap each other, and the depth of the impermeable wall is set at the lower end of the impermeable wall. In order to prevent the boiling phenomenon in which water and sand boil inside the impermeable wall, the depth is set downward from the lower end of the underground structure, and the impermeable wall constructed in this way is buried under the structure. Characterized by being left in the ground after A.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings, taking as an example the case where a structure as a water storage tank is buried underground. In FIG. 1, the construction method according to the present invention involves digging a ground 1 and burying a water storage tank structure 2 underground. In order to perform the burying work by blocking groundwater, the construction method is shown in FIGS. As described above, the impermeable wall 5 is formed in advance so as to completely surround the portion 3 to be dug into the ground in the circumferential direction.

The water impervious wall 5 is provided with a soil cement-like columnar material 6 formed by drilling the ground in the vertical direction and hardening a stirring mixture of drilled soil and cement milk inside the soil, as shown in FIG.
As shown in the figure, the side portions 7, 7 are constructed so as to be continuous in the circumferential direction in an overlapping arrangement.

The concrete construction method is to drill a hole while injecting cement milk with an auger screw, and after reaching a predetermined depth, reciprocate the auger screw up and down to sufficiently separate the drilled soil and cement milk. Stir and mix to form a soil cement. Thereafter, the auger screw is gradually pulled up while continuously injecting the cement milk to maintain the stability of the hole wall. Thereafter, the auger screw is moved, and in a state where the side portions of the drilling overlap each other,
A hole is drilled in the same manner as described above to form a soil cement-like column. This is sequentially repeated to construct the impermeable wall 5.

The depth of the impermeable wall 5 constructed in this way can prevent a boiling phenomenon in which water and sand boil over the impermeable wall beyond the lower end of the impermeable wall 5, as shown in FIG. 1, for example. It is assumed that the water tank structure 2 is set to be deeper downward from the lower end 9 of the water tank structure 2 to be buried.

After constructing the annular water-impervious wall 5 in plan view in this way, as shown in FIG. 4, the water-reservoir structure whose upper and lower ends are open while digging down the inner part of the impervious wall 5 is shown. 2 is gradually settled underground. This subsidence is performed by digging down the inside of the water tank structure 2. At that time, since a reliable groundwater blocking effect is obtained by the water blocking wall 5, the settling of the structure can be performed safely without being affected by the groundwater. After the water tank structure 2 is buried underground at a predetermined depth, as shown in FIG. 1, a water tank bottom 10 is formed by casting in place, and then closed with a top plate 11 to bury the water tank. The water tank 12 is constructed.

The impermeable wall 5 is left underground as a permanent structure even after the water tank is constructed. Thus, the impermeable wall 5 remaining in the ground functions as a kind of earth retaining, not only contributing to the reduction of the earth pressure on the water storage tank, but also exerts the water shielding function, and protects the water storage tank.

The construction method according to the present invention can be widely applied to the construction of a basement or other underground buried structure in addition to the water tank. The impermeable wall may be constructed so as to completely surround the digging portion of the ground in the circumferential direction, and it is not specified to be an annular shape in plan view as described above, but an elliptical annular shape. It may be annular or rectangular.

[0016]

According to the present invention, not only the underground structure can be constructed while the groundwater is reliably blocked by the annular impermeable wall in plan view, but also the construction can be performed safely and reliably in a short construction period. In addition, the construction cost can be reduced. More specifically, it is as follows.

[0017] Since the soil-cement-like columnar material forming the impermeable wall has a property close to that of the soil, it can be left as a permanent structure in the ground, as in the conventional earth retaining sheet pile method. No need to lift from the ground. Therefore, the number of construction days can be shortened and the construction cost can be reduced as compared with the earth retaining sheet pile method.

[0018] The construction of the impermeable wall does not have the risk of loosening the surrounding ground as in the earth retaining sheet pile method involving the driving and pulling out of steel sheet piles, and is not restricted by the soil properties as in the well point method in which groundwater is drained. In addition, since there is no problem that the ground level is lowered and the surrounding ground subsidence is not caused, there is an advantage that the construction can be performed safely even in a residential area. As described above, the present invention has high reliability that can be performed safely and reliably without adversely affecting the surrounding ground.

Since the impermeable wall remains in the ground as a permanent structure even after the water tank is constructed, it functions as a kind of earth retaining, not only contributing to reducing the earth pressure on the water tank, but also a water impervious function. Therefore, it is possible to further improve the safety of the underground structure after the construction.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a construction method according to the present invention.

FIG. 2 is a plan view thereof.

FIG. 3 is a plan view for explaining a step of constructing the impermeable wall.

FIG. 4 is a cross-sectional view illustrating a step of digging down the ground to settle a structure.

FIG. 5 is a cross-sectional view illustrating a conventional well point method.

FIG. 6 is a plan view thereof.

FIG. 7 is a cross-sectional view illustrating a conventional earth retaining sheet pile method.

FIG. 8 is a plan view thereof.

[Explanation of symbols]

 Reference Signs List 1 ground 2 structure 5 impermeable wall 6 soil cement column

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) E02D 29/04 E02D 5/18-5/20 E02D 19/06-19/20

Claims (1)

(57) [Claims] 1. A method of constructing an underground structure in which a ground is dug down and a structure is buried underground, wherein a water-impervious structure having an annular shape in plan view is formed so as to completely surround a portion to be dug down in the ground in a circumferential direction. The wall is to be constructed in advance, and the impermeable wall is a soil-cement-like columnar material obtained by drilling the ground in the vertical direction and hardening the stirring mixture of the drilling soil and the cement milk therein. The side walls overlap each other and are formed continuously in the circumferential direction, and the depth of the impermeable wall is such that the water and sand boil up inside the impermeable wall beyond the lower end of the impermeable wall. An underground structure characterized by being set deep downward from the lower end of the underground structure to such an extent that it can be prevented, and the impermeable wall thus constructed is left in the ground even after the structure is buried underground. Construction method.