JP2011208484A - Method of injecting grout in soil improvement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of injecting a grout in a soil improvement which can build a solidified improved body of a desired size in a ground by well injecting the grout into the ground even if the coefficient of permeability of the ground is considerably small.SOLUTION: This method of injecting a grout in soil improvement includes a prior injection step of building a loose area T in the ground by penetrating an injection rod 1 into the ground, and injecting a high-pressure fluid W therearound from the injection rod 1 at a predetermined depth of ground in a plurality of stages while slightly shifting the injection of the high-pressure fluid W in the vertical direction so as to loosen the ground therearound and performing the building of the loose area T for each required predetermined depth, and a solidified improved body building step of building a solidified improved body P of a desired size in the ground by inserting an injection pipe 3 into the ground and injecting the grout M from the injection pipe 3 into the loose area T of the ground built in the prior injection step so as to penetrate the grout M into the ground on the outside thereof through the loose area T of the ground.

Description

  The present invention aims to strengthen the ground such as prevention of liquefaction of the ground by injecting an injecting material such as a solution-type injecting material and a suspension-type injecting material into the ground, and creating a consolidated improvement body in the ground. The present invention relates to an injection material injection method in ground improvement.

  Conventionally, there has been a double pipe double packer method as a method widely used in the injection material injection method for ground improvement. This double pipe double packer construction method uses a double injection pipe 23 composed of an outer pipe 24 and an inner pipe 26. After installing the outer pipe 24 on the ground, an inner pipe 26 fitted with a double packer 27 at the tip. Is inserted into the outer tube 24, and an injection material is injected into the ground from the double packer 27 inserted into the outer tube 24 through the valve portion 25 of the outer tube 24, thereby forming a consolidated improvement body in the ground. It is.

  As shown in FIG. 10 (a), the ground is drilled by the casing pipe 20, and as shown in FIG. 10 (b), the inside is filled with a sealing material G. As shown in FIG. 10C, an outer tube 24 is inserted therein, and a plurality of valve portions 25 are provided in the outer tube 24 at regular intervals. After the outer tube 24 is installed, the casing pipe 20 is pulled out, and an inner tube 26 with a double packer 27 attached to the tip is inserted into the outer tube 24 as shown in FIG. Next, as shown in FIG. 10 (e), the double packer 27 attached to the tip of the inner tube 26 is aligned with the valve portion 25 of the outer tube 24. Then, the injection material M is pumped into the inner tube 26, the injection material M is discharged from the double packer 27 at the tip, and the injection material M is injected into the ground through the valve portion 25 of the outer tube 24. After the injection of the injection material M to the ground is completed, as shown in FIG. 10 (f), the double packer 27 is aligned with the valve portion 25 in the lower stage of the outer tube 24, and the injection material M is grounded as before. inject. By repeating this, a large number of consolidated improvement bodies P can be created in the ground, and ground reinforcement such as prevention of liquefaction of the ground is performed.

However, in the conventional method for injecting an injection material in ground improvement, there are cases in which the injection material cannot be injected well into the ground depending on the properties of the ground. This is because the infiltration distance of the injection material when the injection material is injected into the ground is extremely high in the case where the ground material contains a lot of fine particles and has a low water permeability coefficient, for example, a water permeability coefficient of k = 10 ⁻³ cm / sec or less. There is a possibility that the phenomenon of shortening, and further, the phenomenon of splitting of the ground may occur when the injection material is injected at a high speed. In particular, these phenomena are prominent when a suspension type injection material is used as the injection material.

  Therefore, measures have been taken to reduce the injection rate of the injection material or to increase the injection cross section of the injection part in the vertical direction. However, if the injection rate is reduced, the work time increases and the injection cross section is increased. Increasing the size causes problems such as labor and complexity of the working device. In addition, it has been difficult to increase the penetration distance of the injection material into the ground, and it has been difficult to create a consolidation improvement body having a large diameter in the ground. Since it is impossible to create a consolidation improvement body with such a large diameter in the ground, it was attempted to improve the ground by creating a large number of small improvement consolidation bodies with a small diameter. However, there is a problem that the construction cost for the ground improvement increases by creating such a large number of consolidated improvement bodies.

  In view of such a conventional problem, the present invention can inject an injection material well into the ground even in a ground having a relatively small hydraulic conductivity, and create a consolidated improvement body of a desired size in the ground. It is an object of the present invention to provide an injection material injection method for ground improvement that can be performed.

  The first invention penetrates the injection rod into the ground, injects high-pressure fluid from the injection rod to the surroundings at a predetermined depth of the ground, and performs the injection of this high-pressure fluid over a plurality of stages while slightly shifting up and down, A pre-injection step in which the surrounding ground is loosened to create a loose region in the ground, and this loose region is made at every required depth, and an injection tube is inserted into the ground, and the pre-injection step from the injection tube By injecting the injection material into the loose area of the ground made in step, the injection material penetrates into the outer ground through the loose area of the ground and creates a consolidated improvement body of the desired size in the ground. An improved material creation process, and an injection material injection method in ground improvement.

  The second invention is a method for injecting an injection material in ground improvement in which a loosened area of the ground is created in the pre-injecting step in the first invention and then the loosened area is filled with sand.

  According to the third invention, the size of the slack area created in the pre-injection step in the first or second invention is controlled according to the properties of the ground by controlling the injection conditions of the high-pressure fluid injected from the injection rod. This is a method for injecting an injection material in ground improvement by changing the size of the loosened region to create a consolidated improvement body having a desired size in the ground.

  According to the first invention, in the pre-injection step, the high-pressure fluid is injected around the ground at the required predetermined depth of the ground, and the ground is loosened to create a loosened area on the ground. Even in the ground, when injecting the injection material from the injection tube into the ground in the subsequent consolidation improvement body formation process, the injection material penetrates well into the loose area created in the pre-injection process, and the injection Since the material penetrates from the end of the loosened region to the ground outside thereof, the final penetration distance of the injected material can be increased, and a consolidated improvement body of a desired size can be reliably formed. . Thereby, it is possible to eliminate the phenomenon such as splitting that occurs when the injection material is injected into the ground, and there is no such thing as creating a large number by narrowing the interval of the small diameter consolidation improvement bodies as in the past, Since the number of consolidation improvement bodies can be reduced by creating a consolidation improvement body with a large diameter in the ground at a certain interval, the construction period in the ground improvement work will be shortened and the construction cost will be greatly reduced. be able to.

  In addition, according to the second invention, the loose region created in the pre-injection process is filled with sand having a larger hydraulic conductivity than the surrounding ground, for example, sand having a large particle size, so that a strong earth pressure is externally applied to the loose region. Even if it takes, it is possible to eliminate the blockage of the loosened area by the filled sand, which makes it possible to very well and reliably inject the injection material to be performed in the subsequent consolidation improvement body forming step. .

  In addition, according to the third invention, by changing the size of the slack area created in the pre-injection step according to the nature of the ground, even if the ground has a small hydraulic conductivity, the desired size A consolidated improvement body can be created, and an optimum ground improvement work can always be performed.

It is explanatory drawing which shows the construction procedure of the injection material injection | pouring method in the ground improvement of this invention. It is explanatory drawing which shows the construction procedure of the injection material injection | pouring method in the ground improvement of this invention. It is explanatory drawing which shows the construction procedure of the injection material injection | pouring method in the ground improvement of this invention. It is explanatory drawing which shows the construction procedure of the injection material injection | pouring method in the ground improvement of this invention. It is explanatory drawing which shows the construction procedure of the injection material injection | pouring method in the ground improvement of this invention. It is explanatory drawing which shows the construction procedure of the injection material injection | pouring method in the ground improvement of this invention. It is explanatory drawing which shows the state of the consolidation improvement body created in the ground. It is explanatory drawing which shows creation of the consolidation improvement body in case the property of the ground is different. It is explanatory drawing which shows a part of construction procedure of another example of the injection material injection | pouring method in the ground improvement of this invention. It is explanatory drawing which shows the construction procedure of the conventional double pipe double packer construction method.

An embodiment of an injection material injection method for ground improvement according to the present invention will be described.
The injection material injection method in this ground improvement includes a pre-injection step of injecting a high-pressure fluid W around the ground at a necessary predetermined depth of the ground to loosen the ground to create a loose region T in the ground, and a loose region T of the ground. A consolidation improvement body forming step of injecting an injection material M into the ground to create a consolidation improvement body P in the ground.

This will be described along the construction procedure.
First, a pre-injection process for creating a loose region T on the ground is performed. As shown to Fig.1 (a), this penetrates the injection rod 1 in the ground with the construction machine which is not shown in figure. The injection rod 1 has a diameter of about 60 to 90 mm, and includes an injection nozzle 2 capable of injecting a high-pressure fluid W. The high-pressure fluid W is supplied from a supply plant such as a high-pressure pump or a generator (not shown), The high pressure fluid W is ejected from the ejection nozzle 2 of the ejection rod 1. The high-pressure fluid W is high-pressure water and air, in which high-pressure water is injected from the center side of the injection nozzle 2 and air is injected from the periphery thereof. The high-pressure fluid W is not limited to this, and only high-pressure water may be used. Further, the number of spray nozzles 2 is not limited to one, and a plurality of spray nozzles 2 may be provided along the circumferential direction of the spray rod 1.

  And after penetrating the injection rod 1, as shown in FIG.1 (b), the high pressure fluid W is injected around from the injection nozzle 2 of the injection rod 1 in the predetermined depth of the ground. This injection continues to inject the high-pressure fluid W for a predetermined time while rotating the injection rod 2. And as shown in FIG.1 (c), injecting the high pressure fluid W, the injection rod 1 is pulled out slightly upwards, and this upward drawing is about 2-10 cm. Then, as shown in FIG. 1 (d), the high-pressure fluid W is continuously ejected for a predetermined time while the ejection rod 1 is rotated. By injecting the high-pressure fluid W in this way and loosening the surrounding ground, the first loosened region T is created on the ground. In addition, the injection of the high-pressure fluid W when creating the first slack region T is performed in two stages while shifting up and down, but depending on the properties of the ground such as the N value and the hydraulic conductivity k, A plurality of stages, four stages or more may be used. In short, by performing the process over two or more stages, it is possible to produce a slack region T having a thickness in the vertical direction.

  In actuality, although depending on the properties of the ground, when the N value is about 20 or less, the nozzle diameter of the injection nozzle 2 is about 3 to 6 mm, the air injection pressure is about 0.1 to 1.0 MPa, and high-pressure water The injection pressure is about 10 to 40 MPa, the discharge flow rate of high pressure water is about 10 to 200 L / min, the injection time is about 10 to 300 sec, and the rotation speed of the injection rod is about 3 to 6 rpm. A loose region T having a desired size (large diameter) is created in the lateral direction by appropriately selecting and controlling conditions such as the injection amount and the injection time according to the properties of the ground.

  Next, as shown in FIG. 2 (e), the injection rod 1 is pulled out by a predetermined length, for example, 1 to 2 m, and as shown in FIG. 2 (f), the injection rod 1 is again formed at a predetermined depth of the ground. The high pressure fluid W is sprayed from the spray nozzle 2 to the surroundings. Also in this injection, the high pressure fluid W is continuously injected for a predetermined time while rotating the injection rod 1, and as shown in FIG. 2 (g), the injection rod 1 is slightly pulled upward, and shown in FIG. 2 (h). As described above, the high pressure fluid W is continuously ejected for a predetermined time while the ejection rod 1 is rotated. The second slack area T is created above the first slack area T by injecting the high-pressure fluid W in this way and loosening the surrounding ground.

  Furthermore, if necessary, the slack areas T such as the third and fourth are created, so that the slack areas T are created for each necessary predetermined depth. When the necessary number of loose areas T are created in the ground as described above, the injection rod 1 is pulled out as shown in FIG. 2 (i), thereby completing the preliminary injection process.

  Next, when this pre-injection process is completed, the consolidation improvement body formation process which forms the consolidation improvement body P in the ground is performed. In addition, as a construction method adopted in this step, a double pipe double packer construction method using a double injection pipe 3 comprising an outer pipe 4 provided with a valve portion 5 and an inner pipe 6 fitted with a double packer 7 is used.

  As shown to Fig.3 (a), the casing pipe 10 is penetrated in the place which made the slack area | region T in the preliminary injection process. And as shown in FIG.3 (b), the inside of the casing pipe 10 is filled with the sealing material G, and after filling, as shown in FIG.3 (c), the outer tube | pipe 4 of the injection tube 3 is inserted there. . The outer tube 4 is provided with a plurality of valve portions 5 at regular intervals, and the positions of the valve portions 5 provided on the outer tube 4 are substantially aligned with the positions of the plurality of loose regions T produced in the pre-injection process. Make the same position. And after installing this outer tube | pipe 4, the casing pipe 10 is pulled out as shown in FIG.3 (d), and the double packer 7 was mounted | worn at the front-end | tip in the outer tube | pipe 4 as shown in FIG.4 (e). Insert the inner tube 6. The double packer 7 attached to the tip of the inner pipe 6 is provided with a number of discharge ports 8, and an injection material M is supplied from an injection plant such as a material storage tank or an injection pump (not shown) to discharge the double packer 7. The injection material M is discharged from 8. The injection material M is a suspension type injection material containing suspended particles such as cement, bentonite and slag. However, the present invention is not limited to this, and a solution type injection material mainly composed of water glass may be used.

  Next, the inner tube 6 is inserted to the lower end, and as shown in FIG. 4 (f), the double packer 7 attached to the tip of the inner tube 6 is placed at the lowermost valve portion 5 of the outer tube 4 and the pre-injection step. Align with the lowermost slack area T produced by Then, the injection material M supplied from the injection plant is pumped into the inner pipe 6, and the injection material M is discharged from the discharge port 8 of the double packer 7 at the tip. The discharged injection material M is injected into the loose region T of the ground through the valve portion 5 of the outer tube 4, whereby the end of the loose region T is passed through the loose region T as shown in FIG. The infusion material M permeates into the outer ground. At this time, even if it is a suspension type injection material, it penetrates well in the loose region T of the ground created in the pre-injection process, and after passing through the loose region T, from the end of the loose region T The injection material M is infiltrated into the outer ground, and as shown in FIG. 5 (h), a large diameter consolidated improvement body P having a desired size is created in the ground.

  When the formation of the lower consolidated improvement body P is finished, as shown in FIG. 5 (i), the inner pipe 6 is pulled out and doubled into the upper valve portion 5 and the upper loose area T of the outer pipe 4. Matching the packer 7, the injection material M is discharged from the double packer 7 in the same manner as described above, and the injection material M is infiltrated into the outer ground through the valve portion 5 of the outer tube 4 through the loose region T of the ground, As shown in FIG. 5 (j), a consolidation improvement body P having a desired size is created in the ground in the same manner as before.

  And by performing injection | pouring of this injection material M for every slack area | region T built in the ground, as shown in FIG. 6, many consolidation improvement bodies P connected up and down in the ground can be created, Thereby, a consolidation improvement body creation process is completed.

  Thus, the ground reinforcement | strengthening, such as prevention of liquefaction of a ground, can be performed by creating the consolidation improvement body P of a desired magnitude | size in a ground.

  In addition, as a construction method adopted in the consolidation improvement body formation process, although it was a double pipe double packer construction method using the double injection pipe 3 which consists of the outer pipe 4 and the inner pipe 6, it is limited to this. Instead, for example, another injection method in which an injection material is injected by providing packers that can be deformed into a bag shape above and below the injection section may be used.

  As described above, in the pre-injection step, the high-pressure fluid W is injected around and the loose region T is created in the ground, so that the consolidation of the post-process is possible even on the ground having a small hydraulic conductivity k. When the injection material M is injected into the ground from the injection pipe 3 in the improved body formation process, the injection material M penetrates well into the surrounding ground from the loosened region T created in the preliminary injection process, and the injection material M Since it penetrates into the ground outside from the end of the loosened region T, the final penetration distance of the injection material M can be lengthened, and a consolidation improvement body P having a desired size and a large diameter is created. be able to.

  This will be described with reference to the drawings. In the case of the conventional injection material injection method for ground improvement, as shown in FIG. 7A, the penetration distance of the injection material M when the injection material M is injected into the ground is u. Therefore, the final penetration distance of the injection material M is also u, and the diameter of the consolidation improvement body P formed in the ground is 2 × u, and this consolidation improvement body P is moved up and down at a predetermined interval h. A large number will be created. On the other hand, when the injection material M is injected into the ground through the slack region T in the consolidation improvement body formation step after the slack region T is created in the ground in the pre-injection step, as shown in FIG. Although the penetration distance of the injection material M is u, r which is the size of the created loosened region T is also added, so that the final penetration distance of the injection material M becomes u + r, and the consolidation improvement body formed in the ground Since the diameter of P is 2 × (u + r), the consolidation improvement body P having a larger diameter than that of the consolidation improvement body P created by the conventional method can be created.

  Moreover, when creating the slack area T on the ground in the pre-injection step, the thickness in the vertical direction of the slack area T is increased by performing it over a plurality of stages of two or more stages. In this way, by creating the slack area T having a thickness in the vertical direction, the pouring of the injection material M in the slack area T in the consolidation improvement body forming process of the subsequent process can be made much better. Thus, the injection material M can be satisfactorily penetrated into the ground outside the loosened region T, and the consolidated improvement body P having a large diameter and thickness which is a desired size can be reliably formed.

  Furthermore, in the injection | pouring material injection | pouring method in the ground improvement of this invention, while using the injection rod 1 in the preliminary injection process, the injection pipe 3 is used in the consolidation improvement body formation process, and the injection rod 1 and the injection pipe 3 are connected. Since each device is used separately, the device does not become complicated or expensive, and the device can be simple and inexpensive, and the construction cost can be reduced.

  In addition, because the pre-injection process and the consolidation improvement body creation process are performed independently, the construction method adopted in the consolidation improvement body construction process may be a double pipe double packer construction method or other injection construction methods, As a result, a wide variety of constructions are possible, and any construction site can be handled.

  Next, if the properties of the ground, for example, the permeability coefficient k of the ground is different, the penetration distance of the injection material M is also different. The creation of the consolidation improvement body P in the ground having such different properties will be described with reference to FIG. ) When the ground permeability coefficient k is large, the penetration distance of the injection material M is ua, so that the lateral size of the slack area T created in the pre-injection process is set as ra. By setting the final penetration distance of the material M to ua + ra, a consolidation improvement body P having a diameter of 2 × (ua + ra), which is a desired size, is created in the ground.

  On the other hand, as shown in FIG. 8B, when the water permeability coefficient k of the ground is small, the infiltration distance of the injection material M becomes ub shorter than the ua, so that the loose region T created in the pre-injection step The lateral size is increased to rb longer than the ra, and the final penetration distance of the injection material M is set to ub + rb, so that a desired diameter of 2 × (ub + rb) is fixed in the ground. A knot improvement body P is formed. Since the permeation distance ub of the injection material M is short, the interval h between the consolidated improvement bodies P formed up and down is also shortened, and a large number of consolidation improvement bodies P are created up and down.

  In this way, by changing the lateral size of the slack area T created in the pre-injection process in accordance with the ground properties (in this case, the hydraulic conductivity k), the ground has a large hydraulic conductivity k. The size of the consolidation improvement body P having a diameter of 2 × (ua + ra) and the consolidation improvement body P having a diameter of 2 × (ub + rb) formed on the ground having a small water permeability coefficient k is It can be the same, that is, even if the properties of the ground are different, by changing the size in the lateral direction of the slack area T created in the pre-injection process, the consolidated improvement body P finally created The size of can be set to a desired size, and the optimum consolidation improvement body P can be formed on the ground of any property.

  In addition, as described above, the lateral size of the slack region T created in the preliminary injection process is the nozzle diameter of the injection nozzle 2, the injection pressure of air, the injection pressure and discharge flow rate of high-pressure water, and the injection time. By appropriately selecting and controlling the injection conditions of the high-pressure fluid W injected from the injection rod 1, such as the number of rotations of the injection rod 1, the size is changed according to the properties of the ground.

  Next, another embodiment of the injection material injection method in the ground improvement according to the present invention will be described. The high pressure fluid W is sprayed around the ground at a required predetermined depth of the ground, and the ground is loosened to create a loosened region T in the ground. The above-described embodiment in that it comprises a pre-injecting step, and a consolidation improvement body forming step of injecting an injection material M into the ground through a loosened area T of the ground to create a consolidation improvement body P in the ground. However, in the pre-injection step, after the slack area T of the ground is created, the slack area T is filled with sand S.

  Specifically, in the pre-injection step, after the necessary number of loose areas T have been created on the ground and the injection rod 1 is pulled out, as shown in FIG. The filling rod 11 having a size (diameter of about 60 to 90 mm) is penetrated. The filling rod 11 is provided with a discharge hole 12 for discharging the sand S. Sand S is produced by adding an additive such as water, a fluidizing agent, and a plasticizer that returns the fluidized state to a normal state after a certain period of time, and is supplied from a supply plant (not shown), Sand S is discharged from the discharge hole 12 of the filling rod 11. And as shown in FIG.9 (b), the sand S is discharged from the discharge hole 12 of the filling rod 11 to the slack area | region T built in the predetermined depth of the ground, and the slack area | region T is filled with the sand S. FIG. In addition, as shown in FIG.9 (c), the filling of this sand S is performed sequentially from the lower area | region T of a lower side. Further, when the sand S is filled, by managing the sand press-fitting amount and the press-fitting pressure, it is possible to grasp the filling state of the sand S into the loose region T. This is because, when the sand S is sufficiently filled in the loosened region T, the press-fitting pressure increases. Therefore, the increase of the press-fitting pressure is used as a criterion for determination, and the sand S is reliably filled in the entire loosened region T. Yes. After the sand S is filled in all the loose regions T, the filling rod 11 is pulled out to complete the pre-injection step, and the subsequent consolidation improvement body forming step is performed. The sand S to be filled is sand having a larger water permeability than that of the surrounding ground, for example, having a larger particle diameter, and may be in the form of grains as an alternative.

  By filling the slack area T with the sand S in this manner, the loosened area T thus produced is not blocked by earth pressure, and the injection material M to be formed in the subsequent consolidation improvement body forming step is performed. The injection is not disturbed.

  DESCRIPTION OF SYMBOLS 1 ... Injection rod, 2 ... Injection nozzle, 3 ... Injection pipe, 4 ... Outer pipe, 5 ... Valve part, 6 ... Inner pipe, 7 ... Double packer, 8 ... Discharge port, 10 ... Casing pipe, 11 ... Filling rod, DESCRIPTION OF SYMBOLS 12 ... Discharge hole, 20 ... Casing pipe, 23 ... Injection pipe, 24 ... Outer pipe, 25 ... Valve part, 26 ... Inner pipe, 27 ... Double packer

Claims (3)

The injection rod penetrates the ground, high pressure fluid is injected from the injection rod to the surroundings at a predetermined depth of the ground, and the surrounding ground is loosened by performing the injection of this high pressure fluid over several stages while slightly shifting up and down. A pre-injection step in which a loose area is created in the ground, and this loose area is created at every required depth;
Inserting the injection tube into the ground, and injecting the injection material from the injection tube into the loose region of the ground created in the pre-injection step, infiltrate the injection material into the outer ground through the loose region of the ground, A consolidation improvement body creation step of creating a consolidation improvement body of a desired size in the ground;
An injection material injection method for ground improvement, comprising:   2. The method for injecting an injection material in ground improvement according to claim 1, wherein in the pre-injection step, a loosened area of the ground is created and then the loosened area is filled with sand.   The size of the slack area created in the pre-injection process is changed according to the properties of the ground by controlling the injection conditions of the high-pressure fluid injected from the injection rod, and the size of the slack area is changed. 3. A method for injecting an injection material in ground improvement according to claim 1, wherein a consolidated improvement body having a desired size is created in the ground.

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