JP2005290714A - Check dam raising method for check dam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a check dam raising method for an existing check dam, which overcomes the problems, associated with constructibility, safety, environment preservation, etc., of a conventional technology. <P>SOLUTION: This check dam raising method comprises: a first step of demolishing a wing section of the existing check dam to be subjected to levee raising; an second step of placing concrete so that a surface can be made vertical, after existing concrete and new concrete are integrated together on an inclined plane on the downstream side of the check dam by using a joint bar etc.; a third step of performing oblique boring toward foundation ground on the upstream side from a top section of the check dam, of inserting a tension member into a bored hole so as to fix it to the foundation ground, and of applying a tensile force, great enough to almost cancel out a tensile force generated by a newly planned silt pressure, to the tension member after that; and a fourth step of placing the concrete to an upper section of the check dam so that a newly planned sedimentation surface can be secured. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for raising an existing sabo dam.

  The height of the gravity concrete type sabo dam is determined by the height of the sedimentation surface at the time of construction planning. Therefore, if the height of the planned sedimentation surface increases after construction, the newly planned sedimentation surface must be dealt with. Conventionally, in such a case, a new sabo dam has been constructed or the existing sabo dam has been raised so as to conform to the newly planned sedimentation surface.

Raising the existing sabo dam is a more efficient method than constructing a new sabo dam because the development volume that can be newly deposited is larger than the volume of the bank required for raising the dam, but the following issues are encountered: Have.
(1) In order to construct a concrete body on the upstream side of an existing sabo dam, it is necessary to remove the sediment, so construction is difficult.
(2) In order to construct a concrete body downstream of an existing sabo dam, the section where the sabo dam is installed generally has a steep river. In some cases, the shape may be stable (shown as A in FIG. 3). In such a case, the volume of the levee body becomes large, and it is necessary to ensure safety during construction (especially during excavation directly downstream). There is.
(3) Since there is a shortage of de-energizing chiefs and full-scale renovation work of de-energizing works occurs, there is a lot of construction in the river channel, which involves large-scale river flow treatment and earthwork, and has a large impact on the surrounding environment. (See FIG. 3).
(4) When the top concrete is cast and raised in an existing sabo dam, tensile stress is generated on the upstream side, which causes structural safety problems.

On the other hand, when a new sabo dam is constructed, there are problems in environmental conservation, such as the need for an access road to the dam construction site, in addition to the economic problems described above.
Under such circumstances, a method for repairing a sabo dam that overcomes problems such as workability, safety, and environmental conservation is desired.

  Accordingly, an object of the present invention is to provide a method for raising an existing sabo dam that overcomes problems such as workability, safety, and environmental conservation in the prior art.

  The method for raising a sabo dam according to claim 1 of the present invention is the first step of demolishing the sleeve portion of an existing sabo dam to be raised, and the integration of old and new concrete such as incisors on the inclined surface downstream of the sabo dam. After the second step, the concrete is placed so that the surface is almost vertical, and the boring is performed obliquely from the top of the sabo dam toward the upstream foundation ground, and a tension member is inserted into the borehole. Then, after fixing on the foundation ground, the third step of applying a tensile force to the tension member to a magnitude that almost cancels the tensile force generated by the newly planned sediment pressure, and the sabo to secure the newly planned sediment surface And a fourth step of placing concrete on top of the dam.

  The method for raising a sabo dam according to claim 2 of the present application further includes a step of providing a water hitting protection part at the bottom of the sabo dam downstream of the fourth step in the method of claim 1. It is a feature.

  According to the present invention, construction is mainly performed in the existing dam dam, and the influence on the downstream side of the dam, such as de-energization work, is greatly reduced. Is also advantageous. Further, even if the top concrete is cast and raised, no tensile stress is generated on the upstream side, which is advantageous in terms of structure.

  Next, a method for raising a sabo dam according to a preferred embodiment of the present invention will be described in detail with reference to the drawings. First, the sleeve part 10a of the existing sabo dam 10 (illustrated by a long broken line) to be raised is demolished (see FIG. 1B). Next, the lower construction on the downstream side of the existing sabo dam 10 is performed. Specifically, after the old and new concrete such as the reinforcing bar 12 is integrated on the inclined surface on the downstream side of the existing sabo dam 10, the concrete 14 is placed so that the inclined surface is substantially vertical (FIG. 1 ( c)). Thereby, the space (upper surface of the concrete 14) for performing the diagonal boring operation | work and tension | tensile_strength operation mentioned later is ensured.

  Next, oblique boring is performed from the top of the existing sabo dam 10 toward the upstream foundation ground, and a tension member 16 such as a PC steel material is inserted into the bore hole and fixed on the foundation ground, and then pulled to the tension member 16. Apply force (see FIG. 1 (d)). The tensile force applied to the tension member 16 is set to a magnitude that substantially cancels the tensile force generated by the newly planned sedimentation pressure.

  Next, concrete 18 is placed on top of the existing sabo dam 10 in order to secure the newly planned sedimentation surface (see FIG. 1 (e)).

  The raised sabo dam 20 is completed as described above (see FIG. 1 (f)). In the lower part of the raised sabo dam 20, the upstream side remains the existing slope, and the downstream side has a substantially vertical slope. Moreover, the upper part of the sabo dam 20 is made into the shape which can ensure required safety | security as a gravity type concrete type.

FIG. 2 is an overall view of the sabo dam 20 subjected to the raising method of the present invention and a diagram showing a reaction force on the bottom surface of the sabo dam 20. That is, FIG. 2B is a reaction force diagram (downstream side: compressive force C ₁ ) due to the old planned sedimentation pressure of the existing sabo dam, and FIG. 2C is a new planned sedimentation of the raised sabo dam 20. FIG. 2D is a reaction force diagram (upstream side: compression force C ₃ ≈T ₁ ) of the tension member 16. FIG. 2D is a reaction force diagram due to pressure (downstream side: compression force C ₂ , upstream side: T ₁ ). FIG. 2 (e) is a composite reaction diagram (downstream side: compression force C ₄ = C ₁ + C ₂ ) of the raised sabo dam 20. As can be seen from FIG. 2 (e), no tensile force is generated on the bottom surface of the sabo dam 20.

  In addition, in the raised sabo dam 20, since the depressurization method has a shape close to free fall, it may be preferable to provide the water hitting protection part 22 at the bottom of the sabo dam 20 on the downstream side. A concrete lump, a block, or the like is used as the water hitting protection unit 22.

  In addition, for management purposes, when the tension member 16 is accompanied by a re-tensioning operation, the operation can be performed by installing a work hole on the upper extension of the tension member 16.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the invention described in the claims, and these are also included in the scope of the present invention. Needless to say, it is something.

It is the schematic which showed typically a series of processes about the raising method of the sabo dam which concerns on preferable embodiment of this invention. 2A is an overall view of the sabo dam subjected to the raising method of FIG. 1, and FIGS. 2B to 2E are reaction forces in each case on the bottom surface of the sabo dam subjected to the raising method. FIG. It is the figure which showed the concept of the raising plan of the conventional sabo dam.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Existing sabo dam 10a Sleeve part 12 Reinforcing bar 14 Lower concrete 16 Tension member 18 Upper concrete 20 Raised sabo dam 22 Water hitting protection part

Claims (2)

A method for raising a sabo dam,
A first step of demolishing a sleeve of an existing sabo dam to be raised;
A second step of placing the concrete so that the surface is substantially vertical after integrating the old and new concrete, such as incisors, on the inclined surface on the downstream side of the sabo dam;
After drilling diagonally from the top of the sabo dam toward the upstream foundation ground, inserting a tension member into the borehole and fixing it with the foundation ground, the tensile force generated by the newly planned sedimentation pressure is almost canceled. A third step of applying a tensile force of magnitude to the tension member;
A fourth step of placing concrete on top of the sabo dam so as to secure the newly planned sand surface;
A method comprising the steps of: The method according to claim 1, further comprising a step of providing a water hitting protection portion at a bottom portion on the downstream side of the sabo dam after the fourth step.

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