JPS60246915A - Method of constructing underground wall through introducing prestress - Google Patents

Abstract

PURPOSE:To produce necessary given prestress, by a method wherein a bottom plate, secured to the lower end of a PC steel wire is hung down into a groove, and after concrete is placed on the bottom plate and is cured, prestress is produced at an underground wall. CONSTITUTION:A bottom plate 2, secured to the lower end of a PC steel material 3, is hung down into a groove 1 in a manner to form a space chamber 5, and a reinforcing cage is hung down into the groove 1. When concrete is poured in the groove 1, the bottom plate 2, on which the weight of the concrete is applied, is lowered in the space chamber 5, and the steel material 3 is sufficiently stretched. Thereafter, the space chamber 5 is filled with mortar. Further, after the concrete is cured, by exerting a force, by a dint of which the upper end of the steel material 3 is hung, directly on the concrete, a shrinkage force, due to which the steel material 3 is going to shrink, is exerted on a concrete underground wall. Since the one surface of the underground wall is released by a cutting work, a force, by which deformation of the concrete is restrained, is removed, and the release side of the concrete is shrunk to produce prestress.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of constructing an underground wall using prestress.

■〉Purpose of the invention [Industrial application field] Construction field [Conventional technology J Conventionally, when introducing prestress into underground walls, the boss tension method has been used.

In other words, as shown in FIG.
After the concrete has hardened, the prestressed steel is tensed to introduce prestress.

L Problems to be Solved by the Present Invention] In the method described above, since the frictional force between the underground wall W and the ground G acts greatly, it is difficult to introduce the necessary prestress.

That is, applying prestress means that the concrete contracts by an amount commensurate with the force, but the concrete cannot contract sufficiently because of the large friction with the ground G.

[Object of the present invention] The purpose of the present invention is to provide a construction method for an underground wall that introduces prestress, which can freely introduce a required prestress as the ground is excavated. shall be.

<■> Structure of the invention [Means for solving problems] An embodiment of the construction method of the present invention will be described.

(a) Excavation of underground wall (Fig. 1) A trench 1 corresponding to the shape of the wall is excavated underground using a known construction method.

(b) Lowering of the bottom plate (Fig. 2) The bottom plate 2 is suspended at the deepest part of the groove 1.

At this time, the lower end of the PC steel material 3 is fixed to the bottom plate 2,
This PC steel material 3 is lowered into the groove 1 while holding the upper end thereof.

The upper end of the PC steel material 3 is fixed on the ground.

Simultaneously with or after suspending the PC steel material 3, a quantity of reinforcing bars is suspended into the groove 1.

Rather than lowering the bottom plate 2 completely to the bottom of the groove 1,
A certain distance S is provided between the groove bottom 4 and the bottom plate 2 to form a void 5.

(c) Placing concrete (Figure 3) Concrete is poured into the groove 1 by a known method.

Then, all the weight of the concrete is added to the bottom plate 2, so the return plate 2 moves down inside the empty space 5 under the weight of the concrete.
The PC steel material 3 will be in a fully stretched state.

At this time, since the concrete is in a fluid state without hardening, all the weight acts on the PC steel material 3 without experiencing any frictional resistance with the surrounding ground.

(d) Filling the bottom edge The cavity 5 between the bottom plate 2 and the groove bottom 4 is filled with mortar.

At this time, if the bottom plate 2 is positioned not horizontally but in an inclined position, it is possible to completely fill up to the ends.

(E) Introduction of prestress After the concrete 1 has hardened, the force that was suspending the upper end of the PC steel material 3 is applied directly to the concrete.

Then, a contraction force is applied to the concrete underground wall so that the stretched PC steel material 3 tries to contract.

However, as mentioned above, prestress will not be introduced due to the frictional resistance of the ground.

Since one side of the Roga basement wall is released by the root cutting work, the force that was restraining the deformation of the concrete is removed, and the free side of the concrete contracts and becomes prestressed, as shown in Figure 4. will be introduced.

In other words, as the rooting work progresses, stress is gradually introduced into the underground walls.

<■> Effects of the invention Since the present invention is as described above, the following effects can be expected.

(a) Due to the frictional resistance of the surrounding ground, it has been difficult to introduce sufficient prestress into conventional underground walls.

In the construction method of the present invention, prestress is introduced using the dead weight of concrete, and as a result, prestress is introduced as the cutting work progresses.

(b) If prestress is introduced, cracks in the concrete will be restrained and the entire cross section will work effectively. Therefore, the amount of deformation of the underground wall can be reduced, the amount of reinforcing bars can be reduced, and in some cases, the wall thickness can also be reduced.

[Brief explanation of drawings]

No. 173N: Explanatory diagram of the construction order of the construction method of the present invention Figure 4: Explanatory diagram when introducing nibrest stress Figure 5: Illustration of the conventional method 1: Groove 2: Bottom plate 3: PC steel 5: Vacant room Figure 2 Figure 4

Claims (1)

[Claims] A bottom plate fixed to the lower end of the PC steel material is suspended into a trench excavated for the underground wall, concrete is poured on top of this bottom plate, and after the concrete hardens, prestress is applied to the underground wall. A construction method for underground walls that incorporates prestressing.