JP2008150774A - Two step high/low concentration grout construction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a two step high/low concentration grout construction method for enlarging a scope of pouring of a water cut-off material and filling all the cracks including large and small cracks with sufficient amount of mixture of water and the material to obtain high water cut-off performance in the ground around a structure while shortening a construction term and reducing costs of construction. <P>SOLUTION: This two step high/low concentration grout construction method comprises a primary grouting process for pouring the first mixture having comparatively high target concentration selected from among the concentrations (ratio of the material to water) of 1/1-1/10 into a grout hole using pressure as low as possible being 0.1-0.5 MPa (megapascal) while a packer is provided at a mouth of the grout hole to stop roughly the crack in which water permeates to a large extent in the ground around the grout hole and a secondary grouting process for pouring the second mixture having comparatively low target concentration selected from among the concentrations (ratio of the material to water) of 1/30-1/100 into the grout hole using pressure being 0.1-1.0 MPa after the primary grouting process without changing the depth of the drilled grout hole. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high and low concentration two-step grout method capable of reliably stopping water when a structure such as a dam is provided on a water-permeable ground.

  In general, a method of injecting a water-stopping material made of cement milk for water-stopping work on permeable rock is called a grout method.

  In the following description, grout officially means grouting, and means that a water-stopping material is injected into the rock mass (injected at a pressure higher than the spring pressure of the rock mass).

Grout / water (ratio) means concentration (for example, 1/10 is water 10 to material 1 and weight ratio). Also, cement milk or milk officially refers to infusion material milk (slag, fly ash is officially distinguished from cement, but this expression is used because it is a material used in cement is doing). Blaine refers to fineness and the unit is cm ² / g.

  As shown in FIGS. 10 and 11, normally, when a dam a is built on the rocks b and d, a grout curtain (grouting) is used to prevent water from leaking from the permeable rock b around the lower part of the dam a. It is usual to provide a curtain) c.

  In addition to the grout curtain c, the type of grout to be constructed for water stoppage of the dam bedrock is adjacent to the grout curtain c for the purpose of preventing leakage of cement milk during the construction of the grout curtain. The auxiliary curtain grout f for injecting high-concentration cement milk into the rock mass b, the consolidation grout g1 for the purpose of improving the water shielding of the lower rock mass b where the dam a levee rests, and the fault crushed material, etc. There is a consolidation grout g2 to be constructed for the purpose of reinforcing weak parts. The symbol h is a basic drainage hole through which drainage from the lower rock mass of the dam a dam body is passed.

In the above-mentioned grout curtain c, as shown in FIG. 10A, a hole (grouting hole) e is drilled to reach the poorly permeable (or impermeable) rock mass d, and cement milk is permeable to water from the hole e. By injecting into the natural rock b, the area is shown in the hatched area shown in FIG.
In this way, the grout curtain c blocks the flow of the water permeation indicated by the arrow in FIG.

  In this way, the method of injecting cement milk into the parts that need to be stopped is the basis of today's grout method.

  For the purpose of ensuring the necessary water shielding and strength for the foundation ground of the dam, the “Grouting Technical Guidelines” issued by the former Ministry of Construction's River Bureau have been issued. Conventionally, safe and reliable grouting has been implemented for all dams. As a result, the construction results were standardized.

  However, in recent years, in response to requests for diversification of individual dam sites and cost reductions for social capital development, grouting planning, design and construction are carried out according to the geological conditions of individual dam sites to reduce the cost of grouting construction. In 2003, the “Grouting Technical Guidelines” were revised (see Non-Patent Document 1) and notified by the Ministry of Land, Infrastructure, Transport and Tourism's River Bureau.

  The revision of the technical guidelines for grouting has drastically changed the degree of improvement of water permeability and the range of improvement by the grouting of dams compared to the conventional guidelines.

The purpose of the above revision is based on the past results of grout, on the premise that the safety of the dam is not impaired, as described on pages 32 to 34 of the above-mentioned Patent Document 1, “improvement range of water permeability H / 2 (H is the dam height) within 2-5 Lu (Ludion), and up to H may be 5-10 Lu ”. The permeability of rock mass is expressed by a hydraulic conductivity of 1 × 10 ^-6 (cm / sec) for underground structures such as tunnels, while 10 (kg / cm ² ) is applied for dams. It displays with the flow rate per 1 grout hole at the time. The water permeability of 1 (l / m: liter per meter) at 10 (kg / cm ² ) is 1 (Lu: Luzione), and this 1 (Lu) is approximately 1 × 10 ⁻⁵ (cm / sec) in terms of the water permeability coefficient. ).

However, the technical items shown in the above revision of the “Groaching Technical Guidelines” follow the conventional methods for the spacing of the grout holes, the injection section, the injection material, the construction method, etc. There was only an advantage to the extent that it was reduced, and it was not possible to achieve a significant cost reduction while ensuring sufficient water stopping performance. In addition, water stoppage could not be effectively performed on rocks with small cracks.
In addition, as for the injection method (order) in the case of conventional grout, there is a description in the above technical guideline (for example, see 2.5.2) that “the blending of cement milk is poured in order from a thin blend”. Concentration (material / water ratio) starts with a small concentration of 1/10 (for the purpose of closing small cracks), and every time the prescribed injection amount is exceeded, 1/8 → 1/6 → 1/4 → 1 The general method is to switch the density to 1/2, which is larger, and close the grout hole with cement milk in the last 1/1.
Grouting technical guidelines and explanation (edited by National Institute for Land and Infrastructure Research, Taisei Publishing Co., Ltd. issued in July 2003)

  The present invention has been made in view of the above circumstances, and shortens the construction period and construction cost when water-permeable ground including open cracks close to the ground surface where structures such as dams are provided is stopped by grouting. However, it is possible to expand the injection range of the water-stopping material, and to fill the mixture of water and material uniformly from large cracks to small cracks, and to obtain high water-stopping performance on the ground around the structure We intend to provide a high and low concentration two-stage grout method.

The present invention relates to a high / low concentration two-step grout method.
The present invention relates to a grout method in which a plurality of grout holes are drilled in the ground, and a mixture of material and water is pressed into a gap in the ground from the grout holes to stop the ground, and a packer is provided at the mouth of the grout hole. In the provided state, the first mixture having a relatively high concentration selected from a concentration (material / water ratio) of 1/1 to 1/10 (preferably 1/2 to 1/5) is 0.1 to 0.00. It is injected into the grouting hole at a pressure as low as 5 MPa (megapascal), and a primary grouting step for roughening cracks of high water permeability in the ground around the grouting hole, and after the primary grouting step, the concentration ( The second mixture having a relatively low concentration selected from (material / water ratio) of 1/30 to 1/100 (preferably 1/50 to 1/100) is grooved at a pressure of 0.1 to 1.0 MPa. A secondary grouting process for injecting into the grouting By performing without changing the drilling depth, the high and low density 2 step grout method, characterized by the water stopping the ground near the grout holes.
The “lowest possible pressure” in the primary grouting process is 0 when the injection pressure of the first mixture is 0 when a low limit pressure is assumed due to the properties of the ground (soft rock, weathering zone, alteration zone, fault clay zone, etc.). The pressure is set so that the ground is not loosened as much as possible within the range of 1 to 0.5 MPa, including the case where the first mixture is poured into the cracks of the rock at almost zero pressure.

  In the present invention, it is preferable that the concentration of the first mixture and the concentration of the second mixture are set to one target concentration and the primary grouting step and the secondary grouting step are respectively performed.

  In the present invention, the packer provided at the mouth of the grout hole for injecting the mixed liquid is composed of a double pipe consisting of an inner pipe and an outer pipe, a gap between the inner pipe and the outer pipe, and an outer wall of the outer pipe and the grout hole. A double packer having a packing body that shields water between each, and when injecting the mixture into the grout hole, the intubation pipe connected to the inner pipe is inserted into the grout hole, and the intubation pipe is mixed The mixture is pressed into the grout hole from the tip of the intubation tube as an injection path, while the space between the inner wall of the grout hole and the outer wall of the intubation tube is used as a mixture return path, and the mixture is returned to the tank from between the inner tube and the outer tube. It is preferable to adjust the concentration of the mixture in the tank and press the mixture after concentration adjustment into the grout hole again via the intubation.

  In the present invention, it is preferable that the inside of the grout hole be washed with water or subjected to diameter-expanded boring after the primary grout process and before the start of the secondary grout process.

  Further, in the present invention, the material of the mixture includes fine slag having a setting time / setting time slower than cement and an average particle size of 4 to 5 (μm), or the fine slag and fine particles. It is preferred to use a mixture of fly ash or a powder material of these performances and particle sizes.

  In the present invention, the plurality of grout holes are formed at a standard interval of 3 (m) pitch, and when the water stop effect is not sufficient, the grout holes are inserted between the standard interval grout holes. It is preferable to drill grout holes at a pitch of 5 (m).

  Further, in the present invention, the grout hole after the mixture is injected by the first grout process and the second grout process is washed with water, and the grout hole after the water washing is connected to the grout hole adjacent to the first grout hole. It is preferable to use the drainage hole or the induction hole when the mixture is injected by the grouting process and the second grouting process.

  In the present invention, it is preferable to provide a pressure control means for a grout hole into which a mixture of a plurality of grout holes has not been injected, and to control the amount of excess water discharged from the grout hole.

  The present invention is applied to water stoppage, prevention of water leakage, reinforcement of weathered part of bedrock, etc., where the packer (means to control the pressure inside the hole by closing the grout hole entrance) cannot be applied. Thus, the ground improvement effect is improved while significantly reducing the construction period and construction labor.

  And in the construction of dams, if divided into large scale (over 50 m) and small scale (below 50 m), today there are overwhelmingly many plans for small dams. For such small-scale dams (including the depth at which the intubation can be inserted from the grouting position even if the dam height exceeds 50 m), a completely new rationalization that reviewed the injection method from the construction method A method can be provided.

  According to the high / low concentration two-step grouting method of the present invention, with a packer provided at the mouth of the grouting hole, the concentration (material / water ratio) is a relatively high concentration selected from 1/1 to 1/10. A primary mixture is injected into the grout hole at a relatively low pressure of 0.1 to 0.5 MPa (megapascal) to prevent rough cracks in the ground around the grout hole. After the grouting step and the primary grouting step, a second mixture having a relatively low concentration selected from a concentration (material / water ratio) of 1/30 to 1/100 is applied to the grouting at a pressure of 0.1 to 1.0 MPa. The ground around the grouting hole is water-stopped by performing the secondary grouting step of injecting into the hole without changing the drilling depth of the grouting hole.

  As described above, the injection method (order) in the case of the conventional grout is “the blending of cement milk is carried out in order from a thin blend”. On the other hand, in the present invention, from the primary grouting step of injecting the first mixture having a relatively high concentration with the concentration (material / water ratio) selected from 1/1 to 1/10, 1/30 to 1 As the second grouting step of injecting a second mixture having a relatively low concentration selected from / 100 (extremely low compared to the concentration of normal cement milk) is performed, the concentration is reduced and 2 The concentration is changed in stages.

  In the present invention, the concentration of the first mixture and the concentration of the second mixture are set to one target concentration, respectively, and the primary grout step and the secondary grout step are performed respectively. It is easy to predict the grouting results for cracks.

  Cement grouts mainly composed of conventional ordinary cement and blast furnace cement (Type B) are closely arranged with an injection hole interval of 1.5 (m), and divided into 5 (m) stages and injected carefully. However, in the present invention, the pore spacing is reduced by using a material (particle size 4 to 5 μm) that is finer and slower in curing time than the cement (particle size 10 to 20 μm). Even if the entire length of one hole is grouted once, the improvement of about 1 Lu is possible.

  In addition, the present invention greatly reduces the number of grout holes and the number of times of grouting to the grout holes, so that the construction period and construction costs can be greatly reduced.

  In the present invention, the primary grouting step and the secondary grouting step are performed through the grouting hole without changing the piercing depth of the grouting hole with the packer provided at the mouth of the grouting hole. If the grout of the grout hole is completed, it is not necessary to grout up and down, that is, in order from the shallow part to the deep part as in the conventional method, and the construction period can be shortened and the cost can be reduced as compared with the conventional method. .

  For example, when a grout hole is provided as a standard section 5 (m), conventionally, grout holes in each section 5 (m) are deeply excavated after cement milk is poured into the grout hole, and the ground is deeper. Grouting to the side. On the other hand, in the present invention, grout holes are collectively drilled to a necessary ground depth, and the grout is completed by performing construction without adding and drilling a primary grout process and a secondary grout process.

In the present invention, the packer provided at the mouth of the grout hole for injecting the mixed liquid is composed of a double pipe consisting of an inner pipe and an outer pipe, a space between the inner pipe and the outer pipe, and an outer pipe and an inner wall of the grout hole. A double packer having a packing body for shielding water between each;
When injecting the mixture into the grouting hole, an intubation tube connected to the inner tube is inserted into the grouting hole, and the mixture is pressed into the grouting hole as an intubation tube through the grouting hole. Using the space between the inner wall of the grout hole and the outer wall of the intubation tube as the mixture return path, the mixture is returned to the tank from between the inner tube and the outer tube, and the concentration of the mixture is adjusted in the tank. By press-fitting into the grout hole again through the intubation, the mixture flows upward and downward in the grout hole drilled up and down, so that the mixture prevents sedimentation and sedimentation by breathing and at the same time cleans the crack entrance. Clogging can be prevented.

  Further, after the primary grouting step, before the secondary grouting step is started, it is preferable that the inside of the grouting hole is subjected to water cleaning (including cleaning water circulation or water jet cleaning in the cleaning) or a boring machine for diameter expansion. By washing the excess mixture in the primary grouting step, the mixture enters cracks in the secondary grouting step, and water can be effectively stopped. In addition, when a material has entered the crack from the crack entrance opening in the borehole inner wall, clogging cannot be removed only by cleaning. Then, clogging can be effectively removed.

  In addition, the material injected into the crack in the ground during the primary grouting process may be pushed back at the time of cleaning. In that case, a packer is provided at the mouth of the grouting hole, and the water pressure in the grouting hole is constant until the material of the mixture is cured. (Example: About 10 to 20 hours).

  Further, in the present invention, the plurality of grout holes are formed at a standard interval of 3 (m) pitch, and when the water stop effect is not sufficient, the grout holes are inserted between the grout holes of the standard interval. (M) Grout holes can be drilled at a pitch. In the conventional construction method, the standard interval of the grout holes is 1.5 (m), and the grout holes are formed at a pitch of 0.75 (m) when interpolated. Thus, the number of grout holes can be reduced, the construction period can be shortened, the construction load can be reduced, and the cost can be reduced.

  Further, in the present invention, a drain hole / guide hole is provided separately by using the grout hole after the completion of the first grout process and the second grout process as a drain hole / guide hole when other grout holes are processed. Efficient and effective grouting can be performed without any problems. In addition, when grout construction is completed at nearby grout holes, it is preferable to fill the plurality of grout holes together with inexpensive mortar and fill the holes.

  In the present invention, the material of the mixture is a powder material (preferably a fine slag or fine particle having a performance and a particle size, which has a setting time / setting time slower than that of cement and an average particle size of 4 to 5 μm. Grout slag and fine fly ash) can be used to significantly increase the grout injection time and thus fill the finer cracks without increasing the injection pressure, At the same time, the injection range is expanded, so that the grout hole interval can be increased.

  Usually, the dam site forms a valley, so the water level is generally lowered from the ground surface on both sides, but a large amount of water is injected into the ground with low concentration grout according to the present invention. Therefore, the groundwater level can be raised and the unsaturated part can be eliminated at the same time, and the effect of the grout can be further ensured.

  In addition, in the injection of one grout hole, since the position of the packer is close to the ground surface, the injection pressure can be reduced at both banks where the groundwater level is lowered, and the effective pressure of the hole can be increased.

In general, as shown in FIG. 1, the target of the hydraulic conductivity is in the deep underground of tunnels and shafts, so the groundwater pressure is relatively high, and the improvement target of the hydraulic conductivity is 1 × 10 ⁻⁶ (cm / sec) (0 .1Lu) is preferable. On the other hand, in the present invention, since the dam is on the ground surface, the hydraulic conductivity may be higher than that of a tunnel or the like, and the improvement target can be set to 1 × 10 ⁻⁵ (cm / sec). Although the degree of improvement is small, it can be set to a hydraulic conductivity that can provide sufficient water stopping for the grouting of the dam.

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

  FIG. 2 is an overall view of a grouting plant according to an embodiment of the high / low concentration two-step grouting method of the present invention. FIG. 3 is a detailed explanatory view around the grout hole into which grout is injected by this plant. 4 is an explanatory diagram of the two-step grout method of the above embodiment, FIG. 5 is a process flow diagram of the two-step grout method of the embodiment, FIG. 6 is an explanatory diagram of a conventional grout method for comparison, and FIG. 7 is the present invention. FIG. 8 is an explanatory view showing the particle size curves of various materials, and FIG. 9 is an explanatory view of the injection pressure of the curtain grout.

  As shown in FIG. 2, in the grout injection plant, a plurality of grout holes 12 are drilled in the ground 10 of the dam, and a mixture of material and water (cement milk) is inserted into the gaps in the ground 10 from the grout holes 12. The ground 10 is pressed to stop the water. The dam in this case is a dam similar to the dam (a) shown in FIG. 10, and performs curtain grout.

  In the grout injection plant, a concentrate production plant 14 for producing cement milk having a material / water ratio of 1/1 is provided on the upstream side, and the cement milk sent from the concentrate solution production plant 14 via a feed pipe 14a and The water sent from the water source 16 through the water pipe 16a is fed to the mixing and stirring tank 18 at a predetermined ratio.

In the mixing stirring layer 18, the material / water ratio (mixing ratio) of cement milk and water is 1/2 (1 / 1-1 / 10, preferably 1 / 2-1 / 5) corresponding to the primary grout process. 1 example) selected from among them, and 1/100 (one example selected from 1/30 to 100, preferably 1/50 to 1/100) corresponding to the secondary grouting process Set to ratio.
The material / water ratio is set by adjusting the opening degree of the valves 20a and 20b provided to the feed pipe 14a and the water feed pipe 16a flowing downward from the stock solution production plant 14 and the water source 16 (an operator or opening degree control not shown). Means). In this case, it is preferable to feed the required amount of cement milk or water by a feed pump if it cannot be washed out naturally.

  In the mixing and stirring layer 18, stirring is performed so that the entire cement milk accommodated by the stirring propeller 18a has a uniform concentration.

  Below the mixing and stirring layer 18 is provided a temporary storage stirring tank 22 for re-stirring the cement milk to further uniform the concentration and temporarily storing it before injecting the grout, and the cement milk in the mixing and stirring tank 18 is supplied with a feeding pipe. 24 and the temporary storage stirring tank 22 are entered through the adjustment valve 24a. In this temporary storage stirring layer 22, a stirring propeller 22a is provided, and stirring is performed so that the contained cement milk has a uniform concentration.

  A water tank 26 is provided below the temporary storage agitation tank 22, and water from the water supply pipe 16a is stored in the water tank 26.

  A cement milk feed pipe 28 a from the temporary storage agitation tank 22 and a water feed pipe 28 b from the water tank 26 are connected to the grout pump 32 entry side via a switching valve 30. At the time of injecting grout in the grout hole 12, the switching valve 30 is switched to the feed pipe 28 a side of the temporary storage agitation tank 22 to send cement milk having a set concentration in the temporary storage agitation tank 22 to the grout pump 32. On the other hand, when the grout hole 12 is washed with water, the switching valve 30 is switched to the feed pipe 28 b side of the water tank 26 and feeds the water in the water tank 26 to the grout pump 32.

  The grout pump 32 sets the cement milk through the pressure feed line 34 at a set feed pressure (0.1 to 0.5 MPa in the primary grouting process and 0.1 to 1.0 MPa in the secondary grouting process). Pump to the supply side. Further, from the return side of the grout hole 12, the return line 36 returns the cement milk to the temporary storage agitation tank 22.

  In order to accurately control the grout, a pressure-feeding state detection sensor 38 for detecting the pressure and flow rate of cement milk provided in the pressure-feed line 34 and a return pressure and flow rate of cement milk provided in the return line 36 are detected. The return state detection sensor 40 and the electric valve 42 for controlling the opening degree of the return pipe 36 and the output signals of both detection sensors 38 and 40 are taken, and based on the signals, printing is recorded on the recording paper. And a controller 44 for controlling the valve opening degree of the electric valve 42 so that the pressure and flow rate of the cement milk become set values.

  In the embodiment, as shown in FIGS. 2 and 3, the grout hole 12 is provided with a packer (also referred to as “packer device”) 46 at the mouth of the grout hole 12 in order to inject cement milk (mixed liquid). The packer 46 includes an inner packer 46i, which shuts off water between the double pipe composed of the inner pipe 46b and the outer pipe 46a, between the inner pipe 46b and the outer pipe 46a, and between the outer pipe 46a and the inner wall 12i of the grout hole 12. This is a double packer having an outer packer 46o (packing body).

When injecting cement milk, which is a mixture of material and water, into the grout hole 12, the intubation pipe 48 connected to the inner pipe 46b is inserted into the grout hole 12, and the grout hole is used as the infusion pipe 48 as a mixture injection path. 12, the mixture is pressed into the inner tube 48 from the tip of the inner tube 48, while the space 50 between the inner wall 12 i of the grout hole 12 and the outer wall 48 o of the inner tube is used as a mixture return path, and the mixture is temporarily put between the inner tube 46 b and the outer tube 46 a It returns to the storage stirring layer (tank) 22.
And the density | concentration of a mixture is adjusted in this temporary storage stirring layer 22, and the mixture after density | concentration adjustment is press-fitted in the grout hole 12 again via an intubation, and is primary with respect to the said grout hole 12. In this method, the grouting step and the secondary grouting step are performed without changing the depth of the grouting hole 12.

Specifically, the packer (packer device) 46 is a double tube comprising an inner tube 46b and an outer tube 46a, and is of a double packer type in which the packer is provided inside and outside the outer tube 46a (inner packer 46i, outer packer 46o). It is.
The packer 46 is inserted into the inlet portion of the grout hole 12, and an outer packer 46o is closely disposed between the outer tube 46a and the inner wall 12i of the grout hole 12, and the inner side between the outer tube 46a and the inner tube 46b. The packer 46i is disposed in close contact with the grout hole 12 so as to be disposed.
Although not shown, each of the packers 46i, 46o is firmly clamped by a clamping member from the vertical axis direction and swelled in the radial direction so as to ensure the liquid tightness between them. Yes.

  An inner tube 48 is connected to the tip of the inner tube 46b in the grout hole 12 by the joint 46c, while a supply-side pressure feed line 34 is connected to the outer tail end of the inner tube 46b.

  Further, the tip of the outer tube 46a in the grout hole 12 opens toward the space 50 between the inner wall of the grout hole 12 and the inner tube 48, while the outer tail end of the outer tube 46a has a return side. The return line 36 is connected. The outer packer 46o ensures liquid tightness between the inner wall of the grout hole 12 and the outer pipe 12a, and prevents cement milk (mixture) from leaking between the inner wall of the grout hole 12 and the outer pipe 12a. It has become.

  When the mixed solution is injected into the grout hole 12, the inner tube 48 is inserted into the grout hole 12 via the inner tube 46b, and the inner tube 48 is inserted into the grout hole 12 from the pressure feed line 34 as the mixture injection path. 48 Cement milk is press-fitted from the tip. The space 50 between the inner wall 12i of the grout hole 12 and the outer wall 48o of the inner tube 48 is used as a cement milk return path, and the cement milk passes through the outer pipe 46b and the return pipe 36 from the space 50 of the return path. Return to (temporary storage stirring layer 22).

  In the temporary storage agitation tank 22, the concentration of the cement milk therein is adjusted, and the adjusted cement milk is press-fitted into the grout hole 12 again from the grout pump 32 via the pressure feed line 34 and through the intubation pipe 48. The circulation injection method is used.

FIG. 4 is an explanatory diagram of a state in which cement milk is filled in the ground gap with a circulation grout when performing the high / low concentration two-step grout method according to the embodiment. In FIG. 4, in the front view, the state where the left side is performing the primary grouting process and the state where the right side is performing the secondary grouting process are shown together.
FIG. 5 is a detailed explanatory view of each process of the high / low concentration two-step grout method. In the embodiment, grouting is performed according to this process chart, and the dam ground 10 is stopped.

As shown in FIG. 4, the cement milk is fed to the inner tube 48 connected to the inner tube 46 b of the packer 46 via the supply-side pressure feeding line 34, and the inner tube inserted deeply into the grout hole 12. Cement milk enters the grout hole 12 from the tip of 48.
Through the cement milk return path in the space 50 between the inner wall 12i of the grout hole 12 and the outer wall 48o of the inner tube 48, the tank (temporary storage agitation) passes through the outer pipe 46a and the return pipe 36 from the space 50 of the return path. Return to layer 22).
The cement milk in the space 50 presses the concentration and pressure into the space in the ground 10 in two steps.

  The grouting method of the embodiment is intended to rationalize the grouting of a small-scale dam, and a grouting hole is formed (step S1). As will be described later, the grout hole 12 is subjected to the grout according to the present invention for every grout hole such as a pilot hole or a specified hole.

One set concentration (first set concentration) in which the concentration (material / water ratio) is set to a relatively high concentration selected from 1/1 to 1/10 with the packer 46 provided at the mouth of the grout hole 12 A first grouting step of injecting the first mixture (cement milk) into the grouting hole 12 at a pressure as low as 0.1 to 0.5 MPa (megapascal) is performed (step S2).
In the primary grouting step, as shown on the left side of FIG. 4, large cracks p1 to p2 having a high water permeability in the ground 10 around the grouting hole 12 are filled with cement milk having a first concentration of high concentration and stopped. Do water.

Next, the inside of the grout hole 12 is washed with water (step S3). The cement remains in the large crack but is not completely stopped at this stage.
In addition, since the entrance of a crack may cause clogging with cement in the fine cracks p3 and p4 among the cracks p1 to p4, the clogging can be eliminated by washing with water in the grout hole 12. The grout hole 12 can be cleaned by various other methods such as cleaning with jet water in addition to water cleaning.

Then, after the primary grouting step, the concentration (material / water ratio) is composed of cement milk having one target concentration (second set concentration) set to a relatively low concentration selected from 1/30 to 1/100. A second grouting step of injecting the mixture of 2 into the grouting holes at a pressure of 0.1 to 1.0 MPa, and a relatively low concentration second of concentration (material / water ratio) of 1/30 to 1/100. A secondary grouting step of injecting the mixture into the grouting holes 12 at a pressure of 0.1 to 1.0 MPa is performed (step S4).
In the above-described primary grouting process, large gaps such as p1 and p2 are formed by breathing that is caused by cement milk sinking.
In this secondary grouting process, large cracks or the like in which voids r and r ′ remain due to breathing as indicated by symbols p5 and p6 corresponding to symbols p1 and p2 are selected from a low concentration (1/30 to 1/100). The second set concentration of cement milk is filled at 0.1 to 1.0 MP. In this case, it is preferable that the injection pressure in the secondary grouting process is larger than the injection pressure in the primary grouting process.

The individual grout holes 12 are washed after the above-described primary and secondary grout processes are completed and used as drain outlets when grouting other adjacent grout holes 12.
The grouting in the above two steps is performed for all the initially set grout holes 12 such as the pilot holes P1 and P2 and the defined holes 1 to 3 without changing the drilling depth (step S5).

After the primary and secondary grouting processes have been completed for all of the initially set grout holes 12, check holes are drilled as shown by broken lines in FIG. 7 and a water permeability test is performed (step S6).
As a result of the water permeation test, for example, when it is determined that the water permeation amount is larger than a prescribed amount, the grout hole 12 is formed at the same position as the check hole, and the above-described primary and secondary grout processes are performed in the grout hole 12. The process proceeds from step S1 (step S7).

  After the grouting is completed for all of the grouting holes that have been initially set and the grouting holes that have been added, the grouting holes 12 are filled with mortar to complete the grouting of the ground 10 around the grouting holes 12 (step S8).

  Here, as described in Non-Patent Document 1 mentioned above, the revision of the grout guideline in 2003 significantly improved the degree of improvement in water permeability and the extent of improvement due to the grouting of the dam compared to the previous guideline. It was.

  The purpose of the revision is based on the past results of grout, assuming that the safety of the dam is not impaired. “With regard to the range of improved permeability, the depth is within H / 2 (H is the height of the dam) in the ground. In the range of 2 to 5Lu (Lujion), 5 to 10Lu may be used until the depth is H ", and the range of permeability of the improvement target is changed depending on the dam height, and it is strongly conscious of cost reduction of grout (See FIG. 1).

  However, because the grout hole interval, injection section length, injection material, construction method, etc. are just following the conventional method, the number of additional holes is reduced and the cost is reduced significantly. Absent.

  The dams that will be constructed from the present time are overwhelmingly planned for small-scale dams of 50 (m) or less, if divided into large-scale (height of more than 50 (m)) and small-scale (less than 50 (m)). For streamlined dams of 50 m or less (it is good enough to insert an intubation even if the dam height exceeds 50 m), a completely new rationalization that has been fundamentally reviewed from construction methods to injection materials The method of construction is proposed.

The main differences between the high / low concentration two-step grout method and the conventional method according to the present invention are as follows.
1. The injection unit is not a section every 5 m (refer to FIG. 6 of the conventional method) but a single hole unit (refer to FIG. 7 of the present method).
That is, in the conventional construction method, as shown in FIG. 6, when a grout hole is initially drilled in a 5 (m) section (indicated by reference numerals x1, X2,...) And the section x1 ends, an additional 5 (m) section Growing by digging x2 and performing grouting by repeating drilling and grouting in the section from x1 to Xn.
On the other hand, in the method of the present invention, as shown in FIG. 7, grouting holes are collectively drilled to the required depth and grouting is performed in a circulating manner.

2. In the present invention, the minimum prescribed hole interval is 1.5 (m) (see FIG. 6), and is 3.0 (m) in the present invention (see FIG. 7).
That is, in the conventional construction method, in each grout hole shown in FIG. 6, “◎” is a pilot hole, and is drilled at an interval of 12.0 (m). Check the geology at the pilot hole and determine the drilling pattern of the grout hole. Of the grout holes, “◯” is a defined hole (primary hole) that is first drilled between pilot holes, and “□” is a defined hole (2 that is drilled next between the pilot hole and primary hole). Secondary hole), “black △” is a pilot hole that is further drilled between the pilot hole, primary hole, and secondary hole (third hole), and “×” is a pilot hole, primary hole, 2 This is an additional hole (quaternary hole) that is further drilled at a necessary position between the secondary hole and the tertiary hole.

In contrast, in the method of the present invention, in each of the grout holes shown in FIG. 7, “◎” is pilot holes P ₁ and P ₂ , and “◯” is a rule to be drilled between the pilot holes P ₁ and P _2. Holes 1 to 3. In this case, unlike the conventional method, the pilot holes are set to 12.0 (m), the grout holes of the specified holes 1 to 3 are set to 3 (m), and the pilot holes P ₁ and P ₂ and the specified holes 1 to For No. 3, the ground grout around the grout hole is completed by performing the primary grout and the secondary grout in the method of the present invention without changing the drilling depth of the grout hole.

In the ground where grouting is performed, assuming that there is no drain outlet in the vicinity at the time of injection, first, the drilling order is P ₁ → P ₂ → 1 → 2 → 3. That is, grout holes are sequentially drilled in order of 1 → 2 → 3 from the _one pilot hole P ₁ side (left side of the drawing in FIG. 7) every 3.0 (m), and the first and second in the method of the present invention. The next grout is performed, and the construction sequence is to complete the ground grout around the grout hole. P ₁ at the time of grout between defined bore 1 and the pilot holes P ₁ becomes drain port is mainly filled from the specified hole 1. During grouting from the defined hole 2, the defined hole 1 becomes a drain outlet and the space between the defined hole 1 and the defined hole 2 is mainly filled. Defined at the time of the grout from the hole 3 defined hole 2 and the pilot holes P ₂ becomes drain outlet defining holes 2, while the pilot holes P ₂ is grout simultaneously.
In FIG. 7, “black circles” are check holes for inspecting the water stoppage state due to grout, and 1 or 2 holes are formed at intervals of 12 (m).

3. Holes that have been injected by primary grouting and secondary grouting are left unfilled and used as drainage / permeation holes during grouting of adjacent holes.

In this case, the inside of the grout hole is washed to ensure the performance as a drainage / guide hole.
As shown in Fig. 7, the grout hole where the grout has been finished is used as a drainage / guide hole without being backfilled. Therefore, when cement milk grouts into the specified hole 1, it passes through the ground and is drained from the pilot hole. Therefore, the grout spreads in a curtain shape from the defined hole 1 to the pilot hole. Also when the specified hole 2 is grouted, the grout spreads from the specified hole 2 to the specified hole 1 in a curtain shape. Also, when the specified hole 3 is grouted, the grout spreads in a curtain shape from the specified hole 3 to the specified hole 2 and the pilot hole.
When the grouting of all the defined holes is completed, the grouting holes are filled with mortar and closed.

4). As the injection material, instead of the currently used ordinary Portland cement and blast furnace cement (Type B) (both 50% particle size 10-20 μm, Blaine value of about 3,000), the price does not change much. Granule slag, fine fly ash (both 50% particle size 4 to 5 μm, brain value 6,000) or powder material (equivalent product) having equivalent performance and particle size are used (see FIG. 8).

Slag has a relatively slow setting / setting time compared to cements, but is self-hardening, so adjust the setting time. Since fly ash is not self-hardening, it cannot be used alone, but the 50% particle size is the same as slag, the 100% particle size is as small as 20 (μm), and the shape is spherical without being crushed. The price is almost the same as slag, so mix it with slag. In both cases, the compressive strength is smaller than that of cement (σ28≈10 N / mm ² ), but there is no problem as a filler.

  The point of this grouting method of the present invention is that fine material is injected at a low concentration of 1/50 to 1/100 over a long period of time in the final secondary grouting process, so that it is within the injection time (about 20 to 30 hours). ) Is required that condensation and hardening do not start.

5. The injection is carried out separately in a primary grouting process for large cracks and a secondary grouting process for fine cracks.
In the primary grouting process, a high concentration material selected from a material / water ratio, 1/2 to 1/5, is injected at the ultra-low pressure of 0.1 to 0.5 MPa as if flowing into a crack. To do. This ensures a small gap at the top of the large crack that was not filled with breathing, while at the same time preventing the milk (first mixture) from running too far.
Also, small cracks are left without being injected.

  Next, as a secondary grouting step, a milk (second mixture) having a very low concentration (concentration (material / water ratio) of 1/50 to 1/100 is selected from 0.1 to 1.0 MPa and set as much as possible. At low pressure, all voids / cracks that were not injected in the primary grouting process are injected into the target.

  FIG. 9 is an explanatory diagram of the groundwater pressure at both banks of the dam which is the target of the embodiment grout method. As shown in FIG. 9, the groundwater level is at a position lower than the ground surface. When the packer 46 is set at the mouth of the grout hole 12 and pressure is applied, as shown in FIG. Since the pressure is generated, the groundwater level is raised (increase from W1 to W2), and effective grouting is possible.

  As a result, it is possible to improve evenly from a crack with a high Lu (lugion) value to a fine crack with a low Lu without applying a large pressure. Since the improvement target is macro management for each hole, 1Lu is stricter than the guideline, and the target value of the check hole placed in the center of the specified hole is 2Lu.

6). The grout hole is a long hole with a maximum length of 40 to 50 m, and the grout is injected for a long time. Therefore, in order to make the concentration in the hole uniform and prevent sedimentation / precipitation, it is shown in FIGS. Thus, the circulation injection method using the double tube double packer 46 and the internal intubation 48 is adopted. In addition, as shown in FIGS. 1 to 4, by adopting a circulation injection method, even when using high-concentration milk, not only prevents precipitation and enables long-time injection, but also the primary injection. The combined use of cleaning in the hole at the end of the grout can also prevent clogging at the entrance of fine cracks.

  In the grouting of the dam, the hole is vertically oriented and the position of the packer 46 is the uppermost portion where the pressure is small. Therefore, the pressure applied to the packer is reduced, and the packer has a complicated structure but can be reduced in weight.

7). Two of the biggest concerns with high-concentration primary grouts are whether the milk flows out far away and whether the filled milk in the cracks flows backward when the pressure is reduced However, the former is poured at a low pressure as much as possible, and if there is a large amount of spillage, it takes time for condensation and is interrupted for about half a day to cope with intermittent injection.
For the latter, even though the pressure is low, the pressure of about several kg / cm ² is applied, so the deposit in the crack should be stabilized by dehydration, and even if the pressure is released, the hole is more pressure than the outer periphery. It is considered that there is almost no back flow in the hole because it becomes equal or higher, but if there is a possibility, the final injection pressure is used, and the injection is not performed and left in the pressurized state for about 10 hours. Therefore, measures such as waiting for stabilization can be considered.

  8). If the pre-grouting is performed prior to the curtain grouting and the opening crack is sufficiently high and the water permeability coefficient at the start of grouting is 5Lu or less, the primary grouting step is omitted. It can be started from the process.

The effects of the high / low concentration two-step grout method according to the embodiment will be described.
The construction method of the present invention is a construction method of two birds with one stone, that is, the effect of improving the improvement effect while significantly reducing the construction period / construction cost as compared with the conventional construction method.

Here, the effect is described.
1. By injecting every hole instead of every 5m section, the number of injections is greatly reduced (for example, if the average hole length is 30m, the number of injections is 1/6), and construction / technical management Will be simplified and construction period and construction costs will be greatly reduced.

2. A circulation system that uses a double-pipe double packer and an internal intubation. By supplying grouting liquid into the hole, it prevents bleeding, settling / sedimentation, and clogging at the crack entrance even in high-concentration liquid. Since milk having a uniform concentration is supplied over the entire length of the grout hole, the quality of the grout can be improved and homogenized.

3. As a grout material, instead of the usual 3,000 brane grade ordinary cement and blast furnace cement (type B), fine slag with a fine setting and hardening rate of 6,000 brane grade. Or a material in which fine fly ash is mixed with fine slag, or a powder material (equivalent product) having performance and particle size equivalent to those (FIG. 8). As a result, 1. 1. Can fill narrower cracks (improvement of water permeability). 2. The injection range can be expanded (groove hole pitch expansion). It has the effect of enabling long-time injection (it cannot be injected unless time is required for fine cracks), and it is possible to simultaneously improve the quality of the grout and reduce the construction period and construction cost.

4). The grouting of the dam, which covers the rock near the surface of the ground, has to achieve filling of both large permeable cracks and small permeable fine cracks, so the problem can be solved by dividing the injection into two stages. Resolve.

First, fill a large crack with high concentration milk of 1/2 to 1/5 as the primary grout (since it is injected at ultra-low pressure, the crack will leave voids due to breathing), and after cleaning in the hole, the secondary grout The finishing grout is carried out with a low concentration milk of 1/50 to 1/100.
By thus injecting the fine-grained material in two stages (two steps), a homogeneous improvement can be achieved at a relatively low pressure (0.1 to 1.0 MPa).

5. As a secondary effect of injecting at a low concentration for a long time, the width of the curtain can be expanded, and in the part where the groundwater level on both banks of the dam is lowered, the groundwater level is raised and at the same time the unsaturation is eliminated, The grout effect can be enhanced (see FIG. 9).

6). Since the number of injections is greatly reduced, technical management such as Lu value and injection amount becomes easy.
The permeability or permeability unit of the rock described above is expressed as kg / cm ² as the permeability coefficient for underground structures, but is simplified to 10 (kg / cm ² without considering the bore diameter etc. for dams. The indication of 1.0 Lu (1 ludione) is used for the injection amount per 1 m of the hole length when the pressure of) is applied. It is approximately 1.0 × 10 ⁻⁵ (kg / cm ² ) ≈1.0 Lu.

  In addition, in the dam, 1Lu is considered to be a poorly permeable zone that cannot be improved by the grout, but the underground structure is a highly permeable zone that requires improvement (FIG. 1).

In addition, since the above terms are difficult to read in technical terms, the following expressions are used.
[Official] → [This]
Grouting → Grout Grout / Water ratio → Concentration (for example, 1/10 is water 10 to material 1 and weight ratio)
Permeability Coefficient → Permeability, Permeability, Lu value Injection material milk → Cement milk, or just milk (Slag, fly ash is officially distinguished from cement, but is a material used mixed with cement Use this expression)
Blaine → Splashiness (Unit: cm ² / g)

  Note that the high / low concentration two-step grout method of the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the scope of the present invention. FIG. 2 shows an example of a grout injection system for carrying out the present invention. If the system can change the cement milk concentration and the injection pressure in the primary grout process and the secondary grout process, a system having another configuration is used. be able to.

It is a graph which compares and shows the improvement target of the hydraulic conductivity of a tunnel and a dam. 1 is an overall view of a grout injection plant according to an embodiment of a high / low concentration two-step grout method of the present invention. FIG. 3 is a detailed explanatory view around a grout hole into which grout is injected by the plant of FIG. 2. FIG. 4 is an explanatory diagram of the state of filling the ground void with cement milk to explain the details of the circulating grout when performing the high / low concentration two-step grout method according to the embodiment. The left shows the injection state of the primary grouting process and the right shows the injection state of the secondary grouting process. It is a process flow figure of 2 step grout construction method concerning an embodiment. It is explanatory drawing of the conventional grout construction method for a comparison. It is explanatory drawing of the 2 step grout construction method of the said embodiment. It is explanatory drawing which shows the particle size curve of various materials. It is explanatory drawing of the injection pressure of the curtain grout in a dam ground. It is explanatory drawing of the grout with respect to the ground of a dam, (a) is front sectional drawing, (b) is side sectional drawing. It is explanatory drawing of the various grout with respect to the ground of a dam.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Ground 12 Grout hole 12i Grout hole inner wall 14 Stock solution manufacturing plant 14a Feed pipe 16 Water source 16a Water feed pipe 18 Mixing stirring tank 18a Stirring propeller 20a, 20b Valve 22 Temporary storage stirring tank 22a Stirring propeller 24 Feeding pipe 24a Adjustment valve 26 Water tank 28a Feed pipe 28b Feed pipe 30 Switching valve 32 Grout pump 34 Pressure feed line 36 Pipe line 38 Pressure feed state detection sensor 40 Return state detection sensor 42 Electric valve 44 Controller 46 Packer (double pipe double packer)
46a Outer tube 46b Inner tube 46c Joint 46i Inner packer 46o Outer packer 48 Inner tube 48o Inner tube outer wall 50 Space P between inner tube outer wall and grout hole inner wall P Pilot hole

Claims (5)

In the grout method of drilling a plurality of grout holes in the ground and pressing the mixture of material and water from the grout holes into the gap in the ground to stop the ground,
In a state where a packer is provided at the mouth of the grout hole, the first mixture having a relatively high concentration selected from a concentration (material / water ratio) of 1/1 to 1/10 is 0.1 to 0.5 MPa (megapascals). A primary grouting step of injecting into the grouting hole at a pressure as low as possible to prevent the cracking of high water permeability in the ground around the grouting hole;
After the primary grouting step, a second mixture having a relatively low concentration selected from a concentration (material / water ratio) of 1/30 to 1/100 is injected into the grouting hole at a pressure of 0.1 to 1.0 MPa. A secondary grouting process to
A high and low concentration two-step grout method characterized in that the ground around the grout hole is stopped by changing the depth of the grout hole without changing the drilling depth.   2. The high / low ratio according to claim 1, wherein the concentration of the first mixture and the concentration of the second mixture are set to one target concentration, and the primary grout process and the secondary grout process are respectively performed. Concentration 2 step grout method. The packer provided at the mouth of the grout hole for injecting the mixed liquid shields water between the double pipe consisting of the inner pipe and the outer pipe, between the inner pipe and the outer pipe, and between the outer pipe and the inner wall of the grout hole. A double packer having a packing body,
When injecting the mixture into the grouting hole, an intubation tube connected to the inner tube is inserted into the grouting hole, and the mixture is pressed into the grouting hole as an intubation tube through the grouting hole. Using the space between the inner wall of the grout hole and the outer wall of the intubation tube as the mixture return path, the mixture is returned to the tank from between the inner tube and the outer tube, and the concentration of the mixture is adjusted in the tank. 3. The high / low concentration two-step grouting method according to claim 1, wherein the grouting hole is press-fitted again through intubation.   2. The high / low concentration two-step grout method according to claim 1, wherein the inside of the grout hole is washed with water or expanded in diameter after the primary grout process and before the start of the secondary grout process.   The material of the mixture is a fine slag having a particle size with an average particle size of 4-5 (μm) or a mixture of fine slag and fine fly ash. Alternatively, a powder material having such performance and particle size is used, and the high / low concentration two-step grout method according to claim 1.

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