JP2011256534A - Water cut-off method for reservoir - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water cut-off method for a reservoir capable of forming water shielding layers to prevent water leakage from the reservoir even if net-like connected crevices on rocks reach to deep parts.SOLUTION: The water cut-off method for the reservoir comprises: a first process which forms plural first grout injection holes 2 at a prescribed interval approximately along a shoreline direction from surrounding natural ground of a reservoir 1 in a direction inclined to the reservoir 1 side, injects a grout material into the deeper part of the natural ground than a high water level WL2 in the reservoir 1 from the first grout injection holes 2, under a condition that the water level is at a low water level WL1 in the reservoir, so as to grout the whole depth range, and forms water shielding layers not to be overlapped with each other within the natural ground in an area I and the water shielding layers to be overlapped with each other within the natural ground in an area II; and a second process which, under a condition that the water level is at the high water level WL2 in the reservoir 1, forms second grout injection holes 3 at each of central positions between the first grout injection holes 2 in a direction inclined to the reservoir side and injects the grout material into at least the natural ground in the area I from the second grout injection holes 3 so as to form the water shielding layers.

Description

  The present invention relates to a grouting method for preventing water from a reservoir such as a dam lake or a regulating pond from infiltrating and flowing through an opening split of a natural mountain, and more specifically, an opening split connected to a net is present to the deep part. The present invention relates to a water stoppage construction method for a reservoir by grouting, which is suitable for a bedrock.

  Conventionally, a grouting method is known in which a grout material is injected into an open split of a natural ground in order to prevent water from leaking into a ground from a reservoir such as a dam lake or a regulating pond. In this grouting method, a plurality of boring holes are arranged in the ground, and a grout material such as a cement grout material and a chemical grout material is injected into the ground from the boring holes to form a water shielding layer.

  Even in this grouting method, many improvements have been attempted so far. For example, a dynamic injection method for increasing the permeability (increase in reach distance) of the grout material, an improvement of the grout material for improving the closing performance of a large opening split, and the like can be mentioned.

  As an example of the former dynamic injection method, in Patent Document 1 below, cement and bentonite grout materials are pumped at a predetermined injection pressure by an injection pump, and drilled in a cracked rock mass through a terminal injection pipe. In grouting for injecting the grout material into the injection hole, a pulsation pressure having a specific frequency selected from a frequency range of 5 Hz to 30 Hz is added to the injection pressure in a superimposed manner to excite the constituent particles of the grout material. Grout construction methods have been proposed. Further, in Patent Document 2 below, when a grout material is injected into an injection target region while periodically changing the injection pressure, the frequency is changed to a long-wave injection pressure fluctuation having a frequency of 0.05 to 1 Hz. A grout injection method has been proposed in which the grout material is injected with a fluctuation in injection pressure in which a short wave injection pressure fluctuation having a period of 1 to 10 Hz is superimposed.

  As a method for improving the blocking performance of the latter, conventionally, cotton fibers (for example, trade name “Uragomer”), bentonite (swelling clay), and a setting accelerator (for example, trade name “Sanko-Hard”) are mixed. Although many methods have been adopted, it is considered that the blockage of the large opening split is insufficient in these methods, the following Patent Document 3 is a rock grout material used to inject into the crack portion of the rock, It consists of a mixed solution containing cement, water, and water-swellable fibers. The water-swellable fibers have a water absorption amount that is several times or more than their own weight, and sufficiently absorb and swell the fibers that have fluid smoothness due to water absorption beforehand. Proposed rock grout materials have been proposed.

Japanese Patent No. 3096244 JP 2007-247389 A JP-A-8-113938

  However, even with the dynamic injection method as described in Patent Documents 1 and 2 above, in a rock where a large opening split exists in a net shape and extends to a deep part, sufficient permeability cannot be secured. Also, the grout pump itself has a problem of using a special device.

  In addition, even in the case of a construction method using a special grout material proposed in Patent Document 3 above, the convergence of water permeability in the direction of the deep part is observed in rocks where a large opening split exists in a net shape and extends to the deep part. In many cases, expensive grout materials are used in this case, and there is a problem that the construction cost is enormous.

  In addition, when the rock mass where the open slits connected to the net exist to the deep part, osmotic water from the reservoir tends to flow out to the underground when the flow channel that is most likely to flow (called the primary flow channel) is selected. Show. Therefore, when the clot is closed by the grouting method described above, even if the primary flow path is blocked, there is a water channel in the mesh shape. Since the permeated water flows through the secondary channel), and even if it is blocked, it flows through another water channel (tertiary channel). It is desirable that the grouting method be compatible with

  Therefore, the main problem of the present invention is to efficiently combine the permeability of the grout material and the blockage performance, so that even if the bedrock is open to the deep part, the water break layer is formed from the reservoir. The purpose of the present invention is to provide a water stop construction method for a reservoir by a grouting method capable of effectively suppressing water leakage.

In order to solve the above-mentioned problem, as the present invention according to claim 1, there is a water stop construction method of a reservoir by grouting for suppressing the water of the reservoir from seeping out through the opening split of the natural mountain,
A plurality of first grout injection holes are formed in a direction inclined toward the reservoir side at a predetermined interval along a substantially shoreline direction from a natural ground around the reservoir, and when the water level of the reservoir is at a low water level, the high water level of the reservoir Grouting material is injected into the deeper ground area from the first grout injection hole, grouting is performed over the entire depth range, and in the ground depth shallower than the water level of the reservoir, the grout material reaches in the horizontal direction. Forming a water shielding layer that does not overlap with each other, and forming a water shielding layer in which the horizontal reach of the grout material overlaps with each other in a deeper ground than the water level of the reservoir;
Under the condition that the water level of the reservoir is at a high water level, a second grout injection hole is formed at a central position between the first grout injection holes in the first step in a direction inclined toward the reservoir, and at least the first step And a second step of forming a water shielding layer by injecting a grout material from a second grout injection hole into a ground shallower than the water level of the reservoir at the time. .

  The invention according to claim 1 performs grouting in two steps to form a water shielding layer that eliminates water that permeates and flows out from the reservoir. First, in the first step, a plurality of first grout injection holes are formed in a direction inclined toward the reservoir side at a predetermined interval along a substantially shoreline direction from a natural mountain around the reservoir, and the water level of the reservoir is in a low water level state. Occasionally, grout material is injected from the first grouting hole into the ground area deeper than the high water level of the reservoir, grouting is performed over the entire depth range, and the ground is shallower than the water level of the reservoir. A water shielding layer in which the horizontal reach of the material does not overlap each other is formed, and a water shield layer in which the horizontal reach of the grout material overlaps in a deeper mountain than the water level of the reservoir is formed. In the present specification, the “low water level” refers to a water level lower than the highest level in the range where water stop treatment is desired. In addition, the “high water level” means a water level that is higher than or equal to the highest level in the range where water stop treatment is desired.

  In the subsequent second step, under the condition that the water level of the reservoir is at a high water level, the second grout injection hole is inclined in the direction inclined toward the reservoir at the center position between the first grout injection holes in the first step. And a grouting material is injected from the second grouting hole into the ground at least shallower than the water level of the reservoir at the time of the first step to form a water shielding layer.

Inventors of the present application consider that grouting that depends on the injection pressure of a conventional grout material has a limit on the expansion of the permeation range, and the grout material cannot penetrate into a wide range of apertures. The idea was that if the particles were placed on the permeation flow rate of the water that permeates and flows out of the reservoir, the permeability of the grout material was improved and the grout material could be injected over a wide range. In the case of pressure-dependent grouting, the cement particles settle and settle when the critical sedimentation rate (D ₁₀ = 5 μm and Vc = 1 cm / sec if the effective diameter of the cement particles is 10%). It will close the split. According to the test, if the opening width is 3 mm, the cement milk reachable distance is about 10 m at an injection pressure of 10 kgf / cm ² .

  On the other hand, if the flow rate of the osmotic water is equal to or higher than the critical sedimentation rate, the sedimentation of the cement particles is suppressed, and the osmotic flow rate transports and settles far away, so that the grout material can be injected over a wide range. Depending on the level of the infiltration flow rate, if there is an infiltration flow rate of about 1 cm / sec, the reach distance can be increased to about 15 to 20 m under the same conditions.

  Moreover, in this invention, in order to utilize the flow velocity of the osmotic water which flows out from a reservoir to a natural ground, a grout injection hole is formed in the direction inclined to the reservoir side from the natural ground around a reservoir. That is, under the condition that the grouting hole is formed in the ground downstream area where the osmotic water leaking from the reservoir flows at a flow rate of a certain level (above the limit settling velocity), and the grouting target area is deeper than the water level of the reservoir, In this region, cement grout material is injected into the ground from the grout injection hole, and grouting is performed utilizing the flow rate of the permeated water.

  The present invention is directed to grouting utilizing the flow rate of the osmotic water as the injection pressure, but by effectively utilizing the grouting depending on the injection pressure, efficient grouting work is realized.

  In the first step, a first grout injection hole is formed, and when the water level of the reservoir is in a low water level state, a grout material is injected from the first grout injection hole into a natural ground region deeper than the high water level of the reservoir, Grouting over the entire depth range. In this case, grouting depending on the injection pressure is performed in the ground (region I) shallower than the water level of the reservoir, and a water-impervious layer in which the reach ranges in the horizontal direction of the grout material do not overlap each other is formed. Moreover, in the ground (region II) deeper than the water level of the reservoir, a water-impervious layer is formed in which the horizontal reach of the grout material overlaps by grouting using the flow rate of the osmotic water as the injection pressure. become.

  In the region I, there are regions where the water shielding layer is not formed at regular intervals or intermittently, but the outflow of water from the reservoir is suppressed by the amount of the formed water shielding layer, and the water level is reduced as much as possible. Can be maintained. Therefore, even if the reservoir has a large amount of seepage and outflow, it is possible to satisfy the “condition that the reservoir water level is high” in the next second step easily and in a short period of time.

  In the second step, a second grout injection hole is formed in a direction inclined to the reservoir side at a central position between the first grout injection holes in the first step under the condition that the water level of the reservoir is in a high water level state. In addition, a grout material is injected from a second grout injection hole into a ground mountain shallower than the water level of the reservoir at the time of the first step, and grouting utilizing the flow rate of the permeated water is performed to form a water shielding layer.

  From the above, even in rocks where the opening splits connected in a net form exist to the deep part, grouting using the flow rate of the permeated water performs blockage of the flow path in order from the deep side of the natural ground by the mechanism described later. It is possible to effectively close the splits and form a water-impervious layer in the natural ground, preventing water from flowing out of the reservoir.

  As the present invention according to claim 2, the first grout injection hole is formed in a direction inclined from the altitude position above the high water level of the reservoir toward the reservoir side, and the tip thereof is also an altitude above the high water level of the reservoir on the opposite bank. The water stop construction method for a reservoir according to claim 1, wherein the water stop construction method is formed so as to intersect with a grout injection hole formed in a direction inclined from the position toward the reservoir.

  The invention according to claim 2 is characterized in that the first grout injection hole is formed in a direction inclined from the altitude position above the high water level of the reservoir to the reservoir side, and the tip of the same is the altitude above the high water level of the reservoir on the opposite bank. A water shielding layer having a substantially V-shaped cross section is formed so as to surround the reservoir by forming it so as to intersect with the grout injection hole formed in a direction inclined from the position toward the reservoir. It is effective to form the water shielding layer in such a manner when the water leaking portion of the reservoir extends over the whole.

  As described above in detail, according to the present invention, by efficiently combining the permeability of the grout material and the blockage performance, even if it is a bedrock in which the opening splits connected in a net form exist deeply, a water shielding layer is formed. It becomes possible to effectively suppress water leakage from the reservoir.

FIG. 3 is a layout diagram of a first grout injection hole 2 and a second grout injection hole 3 with respect to a reservoir 1. It is the II-II arrow directional view. FIG. 3 is a layout view of a first grout injection hole 2 and a second grout injection hole 3. It is sectional drawing of the reservoir 1 which shows the example of a setting of the maximum injection pressure. It is a flowchart which shows the switching point of the mixture ratio of a grout material. It is a longitudinal cross-sectional view which shows the injection | pouring procedure of the 1st process by this invention grouting. It is a longitudinal cross-sectional view which shows the injection | pouring point of the 2nd process by this invention grouting. It is a conceptual diagram for demonstrating the injection mechanism depending only on injection pressure. It is a graph which shows the relationship between the injection pressure P and the cement reach distance R. It is a graph which shows the particle size distribution of cement. It is a conceptual diagram for demonstrating the injection | pouring mechanism using the osmosis | permeation flow rate of this invention. It is a figure for demonstrating the obstruction | occlusion process of grouting of this invention using an osmosis | permeation flow velocity.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

As shown in FIGS. 1 and 2, the water stopping method by grouting according to the present invention is to prevent the water in the reservoir 1 such as a dam lake or a regulating pond from penetrating and flowing out through the opening split of the natural ground. A plurality of first grout injection holes 2, 2... Are formed in a direction inclined to the reservoir 1 side at a predetermined interval along a substantially shoreline direction from a natural mountain around the reservoir 1, and the water level of the reservoir 1 is formed. When the water level is low, grouting material is injected from the first grouting holes 2, 2... Into the natural ground region deeper than the high water level of the reservoir 1, and grouting over the entire depth range. In the ground mountain shallower than the water level, the horizontal reach of the grout material forms a water shielding layer, and in the ground mountain deeper than the water level of the reservoir 1, the horizontal reach range of the grout material is mutual. The first work to form a water shielding layer that overlaps And,
Under the condition that the water level of the reservoir 1 is high, the second grout injection holes 3 and 3 are inclined in the direction inclined toward the reservoir 1 at the center position between the first grout injection holes 2, 2. ... and at least a second step of injecting a grout material from the second grout injection holes 3, 3 ... into a ground mountain shallower than the water level of the reservoir 1 at the time of the first step to form a water shielding layer. It will be.

  In the present invention, in particular, in order to enable effective grouting for a rock in which the opening splits connected in a net form exist to the deep part, it will be described in detail in the section of (Grouting mechanism) at the later stage in order to enable effective grouting. Thus, in addition to the injection pressure of the grout material, the flow rate of osmotic water is utilized to direct effective injection into the water channel. If the flow rate of the osmotic water is equal to or higher than the critical settling rate, the settling of cement particles will be suppressed, and the osmotic flow rate will cause the grouting material to be injected over a wide range by being transported and settled far away. In addition, in the bedrock where the opening splits connected to the mesh form exist deeply, the flow path is formed in a multi-dimensional manner as described above, so that the permeability of the grout material is increased and the flow formed at each blockage is formed. By closing the road in order, it is possible to effectively close the split.

  In this grouting, the grouting holes 2 and 3 are formed in a direction inclined from the natural ground around the reservoir 1 to the reservoir 1 side. That is, since the flow rate of the osmotic water is closer to the bottom of the reservoir 1 or directly below it, the grouting hole 2 is used to utilize the flow rate of the osmotic water. It forms toward the direction which inclines to the reservoir 1 side.

  In the grouting in the first step, when the water level of the reservoir 1 is in the low water level WL1, the grouting material is injected from the first grout injection holes 2, 3... Into the natural ground region deeper than the high water level WL2 of the reservoir 1. Grouting over the entire depth range. Here, grouting depending on the injection pressure is performed in the ground mountain shallower than the water level of the reservoir 1, and grouting using the flow rate of the osmotic water in addition to the injection pressure is performed in the ground mountain deeper than the water level of the reservoir 1.

  The first grout injection hole 2 is formed with a hole diameter of about 40 to 80 mm using a boring machine, and may be either non-core boring or core boring. The mouth position of the injection hole 2 is desirably set to a position higher than the elevation of the high water level WL2 of the reservoir 2. As shown in FIG. 2, the injection hole 2 is formed in a direction inclined toward the reservoir 1 from a point above the high water level WL <b> 2 of the reservoir 1, and a tip of the grout injection hole 2 formed from the opposite bank direction. It is preferable to be formed so as to overlap the tip portion. As a result, a water shielding layer is formed in a V-shaped longitudinal section from both banks below the reservoir 1. In this embodiment, it is assumed that water leak points are scattered throughout the reservoir 1, and a V-shaped impermeable layer is formed on the entire lower ground of the reservoir 1 in plan view. If the location is specified as a partial area, a water shielding layer may be formed only in that portion.

  In the case of grouting utilizing the flow rate of permeated water, it is considered possible to inject grout material up to a range of about 15 to 20 m in the horizontal direction around the first grout injection hole 2 from the mechanism described later. The first grout injection holes 2, 2... Are formed at an interval that allows an overlap allowance in the grout material injection range by the 1 grout injection holes 2, 2. Specifically, as shown in FIG. 3, the first grout injection holes 2, 2... Are formed at intervals of about 25 m.

  As the grout material, a cement grout material such as cement milk or mortar is used from the viewpoint of construction cost and the mechanism of the present grouting. It is desirable that the concentration can be arbitrarily adjusted in the blending ratio of cement: water according to the lugion value at the injection site.

  As a result of the grouting in the first step described above, as shown in FIG. 6, the flow rate of the osmotic water cannot be used in the ground (shallow region I) shallower than the low water level WL1 of the reservoir 1, and thus depends on the injection pressure. It becomes grouting and a water shielding layer is formed in which the horizontal reach of the grout material does not overlap each other. In the ground (region II) deeper than the low water level WL1 of the reservoir 1, grouting is performed by utilizing the flow rate of the osmotic water as the injection pressure, so that the horizontal reach of the grouting material is mutually Overlapping water shielding layers are formed.

  In the region I, there are regions where the water shielding layer is not formed at regular intervals or intermittently, but the outflow of water from the reservoir is suppressed by the amount of the formed water shielding layer. It becomes possible to maintain the water level as much as possible. Therefore, even if the reservoir has a large amount of seepage and outflow, it is possible to satisfy the “condition that the reservoir water level is high” in the next second step easily and in a short period of time.

  Next, in the second step, as shown in FIG. 7, the center position between the first grout injection holes 2, 2... In the first step under the condition that the water level of the reservoir 1 is in the high water level state WL2. Are formed in the direction inclined to the reservoir 1 side, and the second grout is injected into the ground (region I) shallower than the low water level WL1 of the reservoir 1 at least during the first step. A grout material is injected from the holes 3, 3... And grouting utilizing the flow rate of the permeated water is performed to form a water shielding layer. In addition, in order to set the water level of the reservoir 1 to the high water level state WL2, the water level is artificially increased by grouting during rainy season or the like when there is a lot of rainfall, or by pumping or power generation in the adjustment pond of the pumped storage power plant, for example. Like that. By performing grouting under the condition of the high water level WL2, grouting is performed by utilizing the flow rate of the osmotic water in addition to the injection pressure, and also in the region I, the horizontal reach ranges of the grouting materials overlap each other. An aqueous layer is formed.

  By the above procedure, as shown in FIG. 7, an improved range in which the grout material is filled over the entire depth range is formed. The adjacent grout injection holes 2... (3 ...) are provided so that the reach range of the grout material in the horizontal direction, that is, the improvement ranges by the respective injection holes overlap each other. The grouting in these regions I and II is grouting utilizing the flow rate of the permeated water. As will be described later, the channel is closed in order from the deeper side of the natural ground, so that the opening ratio formed around the reservoir 1 is By filling the grout material without gaps in the eyes and closing the water channel, the permeation and outflow of water in the reservoir 1 can be suppressed.

[Grouting work instructions]
First of all, we will conduct drilling surveys of natural grounds as necessary, and understand the hydrological and geological characteristics of natural grounds, such as the distribution status of opening splits, permeability tests, groundwater behavior, etc. The investigation hole formed at this time can be used as a part of the grout injection holes 2, 2.

  In grouting, either a single packer method in which one packer is provided in an injection tube and a grout material is press-fitted, or a double packer method in which packers are provided in the upper and lower portions of the injection section can be used. As a grouting method, stage grouting in which the depth is divided into several stages and boring and grouting are repeated from the hole opening toward the hole bottom is preferable. However, as a result of the water permeability test, a stage having a pre-injection lugeon value of 1 Lu or less may be injected together with the next stage (one stage 10 m).

In the grouting of the first step according to the present invention, as described above, the grouting material is injected from the first grouting holes 2, 2,. Injection pressure of the grout is preferably between 3kgf / cm ² ~30kgf / cm ² according to suffer minimum land mountain thickness d (minimum distance between the bottom of the water grouting hole 2 and reservoirs 1). For example, as shown in FIG. 4 and Table 1, it can be increased in steps with respect to an increase in the minimum ground cover thickness d. In addition, the inside of the reservoir 1 is constantly monitored at the time of injection, and when the grout material leaks to the reservoir 1 side, the pressure at that time is taken as the injection pressure.

  In injecting the grout material, as shown in FIG. 5, after mixing the grout injection hole 2 and pushing the water, the blending ratio of cement milk to be injected (cement (C): water (W)) is switched. This initial formulation is C: W = 1: 6 to 1: 2 depending on the pre-injection lugeon value of the natural ground, and when a predetermined amount (400 liters in the illustrated example) of cement milk of this initial formulation is injected, stepwise Change the blending ratio to high-concentration cement milk. And when it becomes a predetermined | prescribed mixture ratio (C: W = 1: 1 in the example of illustration), it inject | throws in unlimited by this mixture ratio. Thereafter, in accordance with the total cement amount, the injection flow rate Q and the concern of a packer accident due to long-time injection or a natural ground leak, the injection is completed or switched to a high-concentration cement milk (C: W = 1 in the illustrated example) : 0.8). Even in this case, when the injection flow rate Q does not converge and there is a concern about a packer accident or a natural ground leak, the injection is interrupted, and the injection is repeated again from the initial stage after washing with water. In addition, when the injection pressure P tends to increase and P> 0.8 Pmax, it is preferable not to switch the blending. Further, when the injection pressure reaches the specified pressure and the flow rate tends to decrease, it is preferable not to switch the blending.

[Grouting mechanism]
The grouting according to the first step of the present invention is a combination of (1) grouting depending on the injection pressure and (2) grouting utilizing the flow rate of the osmotic water in addition to the injection pressure. (2) Grouting using the flow rate of osmotic water in addition to the injection pressure. When the grouting material is injected into the shallower region than the water level of the reservoir 1 as a boundary, (1) grouting depending on the injection pressure is executed, and the grouting material is injected into the region deeper than the water level of the reservoir 1. In the case of the injection, (2) grouting utilizing the flow rate of the osmotic water in addition to the injection pressure is executed, and the grouting material can reach far in the horizontal direction by the flow rate of the osmotic water.

  Hereinafter, these grouting mechanisms will be described in detail by dividing into (1) grouting that depends only on the injection pressure and (2) grouting in which the osmotic flow rate is added to the injection pressure.

(1) Grouting dependent only on injection pressure In this case, the grouting material filling mechanism with respect to the opening split is within the opening split (assuming a horizontal parallel plate, opening width a) as shown in the conceptual diagram of FIG. Assuming that the cement milk (viscosity coefficient μ) expands concentrically from the injection hole (injection pressure P, injection flow rate Q, radius r), the relationship between the distance R to the tip and the flow velocity V at the tip is It is expressed as 1).

Q = 2πRaV (1)
That is, when R increases, V decreases, and sedimentation starts from a location where the cement particle has reached a critical sedimentation velocity _Vc or less, and cement sedimentation progresses toward the injection hole to close the opening split.

  In this case, assuming a laminar flow, the relationship between the injection pressure and the injection flow rate is expressed by the following equation (2).

P = [6 μQ / (πa ³ )] · log (R / r) (2)
However, since cement milk is not a Newtonian fluid such as water and has non-Newtonian flow characteristics, it is not possible to directly calculate the reach distance R of cement milk according to the injection pressure from the above two formulas. . Therefore, considering the relationship between the experimental shear rate and viscosity, considering the laminar flow and turbulent flow for horizontal parallel plates with smooth walls, the opening width a, injection pressure P, cement milk reach distance R The relationship is conventionally known (FIG. 9). The aperture width a = 3 mm is obtained by interpolation.

According to this, in the case of the opening split with an opening width a = 3 mm, the cement milk reaching distance is about 10 m in the horizontal direction at an injection pressure of 10 kgf / cm ² .

Depending on the type of cement to be used, even there (see FIG. 10) greater than 10% particle diameter D ₁₀ is the effective diameter of cement particles, the limit settling velocity Vc is also expected to become faster. For this reason, the reach | attainment distance of cement milk is fully considered also when it becomes shorter than 10 m in a horizontal direction.

(2) Grouting in which the osmotic flow rate is added to the injection pressure In the case of grouting that depends only on the injection pressure, as described above, the flow rate at the tip of the cement milk is the critical sedimentation rate of the cement particles (Vc if the effective diameter is 10% particle size). = 1 cm / sec), the cement particles begin to settle and blockage proceeds toward the injection hole.

However, as shown in FIG. 11, when the flow rate v of osmotic water is added in addition to the above injection pressure, if the flow rate v of osmotic water at the tip of the cement milk is equal to or higher than the critical sedimentation velocity Vc, cement particles Sedimentation is suppressed, transported further by the permeation flow velocity v, settles at a permeation flow rate lowering portion (below the critical settling velocity) such as the network crossing portion of the opening split, and the blockage to the upstream side develops. The arrival distance of cement milk is about 15 to 20 m in the horizontal direction at an injection pressure of 10 kgf / cm ² .

  The clogging process of the split when this osmotic flow velocity is added will be described with reference to FIG. First, in the initial stage of injection, the cement particles move through the opening split through the channels A to B which are most likely to flow by the permeated water. At this time, the movable region of the cement particles is in a range equal to or higher than the critical sedimentation velocity Vc of the cement particles. Even if there is a flow path from the branch points A to D, the permeated water does not flow much in this flow path, and the flow velocity v is less than the critical sedimentation velocity Vc of the cement particles. In the region of the flow paths A to B, the cement particles settle, clog, and condense, and the cracks are closed. When the flow paths A to B are closed, as shown in the column of the injection process, the upstream potential of the closed portion is increased, and the permeation flow rates of the opening splits A to D intersecting on the upstream side are increased. If the increased flow velocity is equal to or higher than the critical sedimentation velocity Vc, the cement particles newly move in the directions of the flow paths A to D. Also in this flow path, sedimentation of cement particles begins at a position where the cement particle is less than the critical sedimentation velocity Vc, causing clogging and condensation, and closing the flow paths A to D. If such occlusion is repeated sequentially and becomes less than the critical sedimentation velocity Vc in almost every division, only the injection depending on the injection pressure is performed and the injection converges as shown in the column of the injection end stage.

  DESCRIPTION OF SYMBOLS 1 ... Reservoir, 2 ... 1st grout injection hole, 3 ... 2nd grout injection hole, WL1 ... Low water level, WL2 ... High water level

Claims (2)

Reservoir construction method of the reservoir by grouting to prevent the water of the reservoir from seeping out through the opening split of the natural mountain,
A plurality of first grout injection holes are formed in a direction inclined toward the reservoir side at a predetermined interval along a substantially shoreline direction from a natural ground around the reservoir, and when the water level of the reservoir is at a low water level, the high water level of the reservoir Grouting material is injected into the deeper ground area from the first grout injection hole, grouting is performed over the entire depth range, and in the ground depth shallower than the water level of the reservoir, the grout material reaches in the horizontal direction. Forming a water shielding layer that does not overlap with each other, and forming a water shielding layer in which the horizontal reach of the grout material overlaps with each other in a deeper ground than the water level of the reservoir;
Under the condition that the water level of the reservoir is at a high water level, a second grout injection hole is formed at a central position between the first grout injection holes in the first step in a direction inclined toward the reservoir, and at least the first step A waterstop construction method for a reservoir, comprising a second step of injecting a grout material into a ground mountain shallower than the water level of the reservoir at the time to form a water shielding layer by injecting a grout material from the second grout injection hole.   The first grout injection hole is formed in a direction inclined to the reservoir side from an altitude position higher than the high water level of the reservoir, and a tip portion thereof is inclined to the reservoir side from an altitude position equal to or higher than the high water level of the opposite bank. The water stop construction method for a reservoir according to claim 1, wherein the water stop construction method is formed so as to intersect the formed grout injection hole in a longitudinal section.

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