JPH02296930A - Construction of manhole for underground power transmission line - Google Patents

Abstract

PURPOSE:To lower a block by a method wherein with the inside of a cylindrical concrete block provided with a cutting edge on the lower end exposed to the atmosphere ground water is taken into the block so that sediment in the block can be dug. CONSTITUTION:A friction cut 10 is formed on the outer periphery of the lower end of a vertically cylindrical concrete block 2 in a rectangle shape while a cutting edge 1 is formed or the inner periphery of the lower end. A supporting stage 12 of a concrete bottom plate 11 is formed on the upper end of the cutting edge 1' while a concrete engaging groove 13 is formed on the inner peripheral face immediately above the stage 12. A horizontal pneumatic tube 14 is buried on the bottom face 1'' formed on the lowered end of the cutting edge 1', and pneumatic exhaust nozzles 6 are provided with constant intervals to have them opened on the bottom face 1''. Further a plurality of vertical pneumatic tubes 14' are buried on the side wall of the block 2 to have their lower ends communicated with the horizontal tube 14. The upper end is protruded from the upper end face of the side wall to be connected to an air presser 17 via a compressed air tube 15.

Description

[Detailed Description of the Invention] ``Industrial Application Field'' The present invention relates to a method for implementing a connecting manhole in an underground power transmission line duct.``Prior Art'' In order to bury it underground, a construction method was used in which a rectangular cylindrical concrete block with a cutting edge at the bottom was pushed downward. In other words, the earth and sand on the inner periphery of the cutting edge and directly below it are manually removed to allow it to settle under its own weight. When the water is pushed below the groundwater level, groundwater will gush out into the blocks, which must be drained with a pump. However, there is a problem in that the work often has to be interrupted due to the so-called boiling phenomenon in which the earth and sand just below the block collapses together with the groundwater due to the water pressure of the groundwater level, causing groundwater to leak into the block all at once.

"Problems to be Solved by the Invention" The present invention aims to prevent the above-mentioned boiling phenomenon and to construct a manhole for the underground transmission line N without requiring human labor.

"Means for Solving the Problems" In order to achieve the above object, the present invention has a structure in which the inside of a cylindrical concrete block having a cutting edge at the lower end is opened to the atmosphere when the block is propelled downward below the groundwater level. Under this condition, groundwater is taken into the block, the earth and sand in the center of the block is excavated without draining the groundwater, and pressurized air is ejected from the cutting edge. A method for constructing a manhole for an underground power transmission line, characterized in that the block is removed toward the center and the block is propelled downward by its own weight. Construction method The manhole construction method for an underground power transmission line is performed according to the first or second aspect of the invention, in which the underground water in the block is drained after completing the downward movement and filling the inner periphery of the cutting hole with foundation stones.

``Function'' Therefore, inside the cylindrical concrete block 2 that has been pushed below the groundwater level 3, the groundwater 4 on the outside gushes out from below the cutout I, and the water surface 4' rises to approximately the water level 4 below the groundwater level 3. (Fig. 1, Fig. 7 to Fig. 8). In this state, if the earth and sand 5 inside is removed from the water to the ground 9 by an excavator 8 such as a backhoe without removing the groundwater 4, four parts are formed in the center as shown in FIGS. 1 and 7. In this state, pressurized air is ejected from the downward pressurized air outlet 6 of the cutting edge l, and by this pressure, the earth and sand 5 located directly below the cutting edge l and on the inner periphery of the cutting edge 1 can be removed toward the above-mentioned recess. (The state is shown in FIG. 8).

In this way, a space S is formed directly below the cutting edge l, so that the block 2 descends by its own weight and is propelled downward by the space S. Repeat this operation or repeat this operation at mM
By doing so, the block 2 can be propelled to a predetermined depth. Thereafter, as shown in Fig. 9, the foundation stone 7 is thrown in and filled into the inner circumference of the cutting edge l, thereby supporting the groundwater pressure at the inner circumference of the cutting edge l (see Fig. 9). ), in this state, when the groundwater 4 in the block 2 is drained, the groundwater pressure balances with the weight of the foundation stone 7, or the weight of the foundation stone 7 overcomes, and the boiling phenomenon is prevented. In this state, water is stopped and the bottom of the block 2 is formed.

"Example" A frixillan cut 10 is formed on the outer periphery of the lower end of a rectangular vertical cylindrical concrete block 2, and a cutting surface l' is formed on the inner periphery of the lower end.
A cutting edge l is formed. A support step 12 for the concrete bottom plate 1) is formed at the upper end of the blade surface 1', and a concrete engagement groove 13 facing the side surface of the bottom plate 11 is formed on the inner circumferential surface directly above the support step 12. A concrete engagement groove 13' facing the engagement groove 13 is formed. A bottom surface l# of the blade l is formed at the lower end of the blade surface 1', and a horizontal pressure trachea 14 is buried in the bottom surface 1'', and pressure air jet ports 6 are bored in the pressure trachea 14 at regular intervals. Open the bottom 1". A plurality of vertical pressure trachea 14' are embedded in the side wall of the block 2, and the lower ends thereof are communicated with the horizontal pressure trachea 14. The upper end projects from the upper end surface of the side wall and is connected to an air compressor 17 via a compressed air pipe 15 and an on-off valve 16. In this way, the block 2 is placed on the ground 9 (Fig. 6), and the block 2 is removed by removing the earth and sand 5 directly below the cutting edge l and inside the block 2.
When propelled into the ground while descending under its own weight, it reaches groundwater level 3. When the block 2 is further propelled, groundwater 4 springs and accumulates in the block 2, and the water surface 4' reaches approximately the groundwater level 3 and becomes balanced. An excavation packet 8 such as a small backhoe is inserted into this accumulated water, and the earth and sand 5 at the center of the inner periphery of the cutting edge 1 is excavated and disposed of on the ground 9. A lower recess is formed (phantom line in Figure 1, solid line in Figure 7).In this state, when the on-off valve 16 is opened and pressurized air is jetted downward from the jet nozzle 6, the pressure causes the air to flow directly below the blade l. The dirt 5 on the inner circumference is pushed toward the recess and removed, leaving an empty space r' below the bottom surface 1'' of the cutting edge 1.
Since t s is generated, the block 2 descends by its own weight and is propelled downward by the depth of the space S. Although this operation is repeated, the above-mentioned propulsion operation can be performed continuously by continuously ejecting pressurized air and excavating the earth and sand 5 in this state.

Then, after driving to a predetermined depth, a foundation stone 7 such as chestnut stone is thrown in, and as shown in FIG. be able to. In this state, the accumulated groundwater 4 is removed by a pump, the concrete bottom plate 1) is supported on the support stage 12 and the foundation stone 7, and the bottom plate 1) is filled with concrete 18 between the engagement grooves 13 and 13'. It forms the bottom of the block 2, which can be fixed in position and watertight. After that, the upper end opening of the block 2 is closed with the root 19, and the! [Support the inlet/outlet tube 21.21 at the entrance/exit 20.20 formed in 19, close the inlet/outlet tube 21.21 with M22.22, and backfill with earth and sand as shown in Fig. 12 to carry out the construction work. It ends.

"Effects of the Invention" Since the present invention is based on the method described above, when constructing a manhole for an underground power transmission line below the groundwater level, there is no accident (boiling phenomenon) of water coming out from below the cutting edge 1, and therefore the work is carried out smoothly. It is not necessary to interrupt the process, and the cylindrical concrete block 2 can be quickly propelled to a predetermined depth without requiring human power.

In addition to the above-mentioned effects, there is an effect of safely and quickly forming the bottom part of the block 2 of the block 2, which is propelled to a predetermined depth.

[Brief explanation of drawings]

Fig. 1 is a cutaway front view showing the manhole for underground power transmission lines and its construction method according to the present invention, Fig. 2 is a cutaway perspective view of the above manhole, Fig. 3 is a diagram of the blade opening state, and Fig. 4 is Fig. 3. A-A
Fig. 5 is a vertical sectional view of the concrete engagement groove, Fig. 6 is a front view of the cylindrical concrete block placed on the ground, Fig. 7 is a front view of the state of propulsion below the groundwater level, Figure 8 is a front view of the state of removing dirt from the area directly below the cutting edge and the inner periphery.
Fig. 9 is a front view of the foundation stone filling state, Fig. 10 is a front view of the bottom forming state, Fig. 1.1 is a front view of the loading/unloading cylinder mounted state,
FIG. 12 is a front view of the backfilling state. l...Blade mouth, 2...Tubular concrete block, 3...
Groundwater level, 4. Groundwater, 5. Sediment, 6. Downward pressure air outlet, 7. Foundation stone.

Claims (3)

[Claims] (1) When a cylindrical concrete block with a cutting edge at the lower end is propelled downward below the groundwater level, groundwater is taken into the block and drained while the block is open to the atmosphere. The earth and sand in the center of the block is excavated without any problem, and the pressurized air is ejected from the cutting edge, which removes the earth and sand directly below the cutting edge and around the inner periphery of the cutting edge toward the center, and the block is propelled downward by its own weight. A method of constructing manholes for underground power transmission lines. (2) Claim (1) in which the cutting edge has a plurality of downward pressure air outlets
) Manhole construction method for underground power transmission lines. (3) Claim (1) in which the underground water in the block is drained after finishing the downward propulsion and filling the inner periphery of the cutting edge with foundation stones.
) or the underground power transmission line manhole construction method described in (2).