JPS5848711B2 - How to build an underground tank - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for constructing an underground tank that prevents heaving and reduces the amount of spring water during excavation.

More specifically, a temporary slab is installed with piles on the bottom that reach the supporting ground at the lower part of the underground tank, and water of a weight that can counteract heaving is stored on this slab, and this water load is transferred through the piles. The present invention relates to a method of constructing an underground tank that reduces heaving and spring water by conveying supporting ground and pressurizing the temporary slab and excavated space as necessary to lower the groundwater level.

When excavating underground to construct an underground tank, there is a phenomenon in which the soil at the bottom rises due to the influence of the surrounding earth pressure and water pressure, which is called heaving, and it is impossible to build by leaving this as it is. Conventionally, the methods used were to deepen the retaining structure to balance the earth pressure and water pressure between the inside and outside of the retaining structure, or to lower the groundwater level by pumping and amplifying groundwater. In the former case, there is a limit to the scope of application, and in the latter case, the pump amplifier equipment, costs, etc. increase, and various conditions of construction such as ground subsidence are worsened.

From this point of view, the inventor of the present invention has invented a method for constructing an underground tank that can prevent heaving and water leakage by a simple method, and hereby proposes the method.

Hereinafter, as an embodiment of the present invention, the most preferable example of a method for constructing an underground tank installed in permeable ground will be described in detail.

First, as shown in Fig. 1, a retaining structure 1 that also serves as a water stopper is installed up to the support ground 2 of the tank, and the side wall 3 is installed inside this retaining structure 1 while being excavated one after another. Let's go.

The depth of this excavation shall be the limit at which heaving occurs or the depth at which spring water treatment is possible.

Next, as shown in FIG. 2, piles 4 that can withstand water loads and slab loads are appropriately driven, and temporary slabs 5 that can withstand slab loads and water loads are installed on top of these piles 4. Install the air lock and shaft 6.

Next, as shown in FIG. 3, water is poured into the temporary slab 5 and side wall 3.

Note that this water has a weight that can resist heaving.

Then, the space under the temporary slough 5 is pressurized via an airlock and shaft 6 to prevent spring water, and the side wall 3 is installed and excavated to a predetermined position, and the pile is placed in the predetermined position. Install the foundation bottom plate 7 including the

Next, as shown in Figure 4, the water in the tank (temporary slab 5, inside the side wall 3) is drained, the temporary slab 5, airlock, and shaft 6 are removed, and the piles on the foundation bottom plate 7 are removed. do.

With the above work, the basic construction of the underground tank has been completed.
Complete other necessary incidental works.

In addition, in the above embodiment, when performing excavation work without pressurizing the space under the temporary slab 5, the air pressure is increased to 1.0 k.
If it exceeds g/cI1t, various problems will occur, such as decreasing the work duration and limiting the work to specific workers.
If necessary, a method of suppressing spring water that does not rely on air pressure is adopted.

This method involves freezing the ground below the planned excavation depth to increase the ground strength and create a completely impermeable layer.

Furthermore, if the ground below the planned excavation depth is an impermeable layer (for example, a clay layer), air pressure is not necessary and there is no need to create an impermeable layer.

As described above, according to the construction method of the present invention, the temporary slab 5 and the supporting piles 4 reaching the supporting ground 2 transmit the water load to the supporting ground 2 via the piles 4, thereby suppressing heaving. The heaving prevention measures are simple and reliable, and have the effect of improving the safety and work efficiency of underground tank construction, as well as preventing surrounding ground subsidence.

Next, if the ground is a permeable layer, the space under the temporary slab 5 is pressurized to lower the groundwater level and prevent water from springing up, and if necessary, this pressure is used to prevent water from becoming impermeable due to frozen soil. Since it forms a layer and suppresses spring water, compared to conventional spring water treatment measures, the equipment is simpler, the cost is lower, and there is less work noise (for example, the sound of operating pumps, etc.). .

[Brief explanation of drawings]

1 to 4 are step-by-step explanatory diagrams of the construction method of the present invention. 1...Water stop, mountain retaining works, 2...Supporting ground,
3...Side wall, 4...Pile, 5...
・Temporary slab, 6...Air lock, shaft, 7...Foundation bottom plate.

Claims (1)

[Claims] 1 At the predetermined location for tank construction, install a retaining structure that also serves as a water stopper, and excavate the inside of this while installing side walls to a depth that limits the occurrence of heaving or allows for the treatment of spring water, and then At the bottom of this excavated hole, a supporting pile is driven down to the supporting ground, a temporary slab is installed on the top of this pile, and water is poured into the space formed by the temporary slab and the side wall. , this water load is transferred to the supporting ground via the temporary slab and piles to prevent the occurrence of heaving, and the underground tank is excavated under the temporary slab to the location where the foundation bottom plate will be constructed, and the foundation bottom plate is constructed at the bottom of this excavation. The construction method of