JP5155930B2 - Underground wall excavator and impermeable wall construction method using the same - Google Patents

Description

  The present invention relates to an underground wall excavator and a impermeable wall construction method using the same.

  When constructing a structure such as a waste disposal facility or a highway in the basement, a water shielding layer may be formed around the structure for the purpose of containment of pollutants or groundwater countermeasures. Various studies have been made so far on a method for constructing a water shielding wall by stirring and mixing a solidified material such as bentonite, cement and lime or a solidified liquid and sand mud in situ. For example, a TRD method (Trench Cutting Re-mixing Deep Wall Method) using a chain cutter type excavator and an SMW method (Soil Mixing Wall) using a multi-axis kneading auger machine are known (Patent Document 1 below). , 2).

JP 2006-249929 A JP-A-10-331188

  By the way, when the chain cutter type excavator as shown in FIG. 8 of Patent Document 1 is used, there is room for improvement in that the adaptability to construction at a deep depth and construction of hard ground is insufficient. It was. That is, since the length of the chain cutter in the vertical direction is limited, there is a circumstance that the depth at which the impermeable wall can be constructed is limited. In addition, when constructing a water-impervious wall on hard ground, prior to the use of a chain cutter type excavator, work such as forming an excavation hole in advance by an all casing rock excavation method (CD method) or the like is necessary.

  On the other hand, the suspended underground wall excavator as shown in FIG. 1 of Patent Document 2 can be excavated to a deep position and can be applied to a relatively hard ground. . However, when bentonite is used, there is a problem that the performance of the water-impervious wall to be constructed is insufficient. Compared with cement and the like that harden by a chemical reaction, the fluidity of the mixture of bentonite and sand mud decreases early. For this reason, in order to construct a water-impervious wall exhibiting high water-impervious performance, it is required to sufficiently uniformly mix bentonite and sand mud in a state where fluidity is lowered.

  The present invention has been made in view of such a situation, and it is possible to construct a water shielding wall having a sufficiently high water shielding performance, and to excavate an underground wall capable of constructing a water shielding wall even for hard ground. An object is to provide a machine and a method for constructing a water shielding wall using the same.

  The underground wall excavator according to the present invention includes a cutter for excavating the ground, a cutter holding plate on which the cutter is mounted at the tip, a rotating drum having a plurality of cutter holding plates standing on the outer peripheral surface, and a rotating drum And at least one cutter holding plate is characterized in that an angle formed between the longitudinal direction of the plate and the rotation direction of the rotary drum is freely changeable.

  The underground wall excavator according to the present invention can change the angle formed by the longitudinal direction of at least one cutter holding plate and the rotation direction of the rotary drum to a predetermined value (for example, 0 to 10 °). Yes. By rotating the rotating drum having the cutter holding plate whose angle is changed, the cutter holding plate functions as a stirring blade, and the bentonite and sand mud can be forcibly stirred in the excavation hole. For this reason, according to the underground wall excavator of the present invention, the impermeable wall having sufficiently high impermeable performance that can sufficiently uniformly mix bentonite and sand mud contained in the liquid supplied at the time of excavation at the original position. Can be built.

  The cutter holding plate of the conventional underground wall excavator is erected on the rotating drum so that the longitudinal direction thereof coincides with the rotating direction of the rotating drum from the viewpoint of achieving high excavation capability. In the underground wall excavator of the present invention, the excavation capability can be sufficiently maintained by appropriately setting the number of cutter holding plates whose angles are changed as described above and the angle among the plurality of cutter holding plates. For this reason, it is possible to construct a water-impervious wall even on relatively hard ground. In addition, the excavation capability of the underground wall excavator tends to decrease as the number of cutter holding plates whose angles are changed is increased and the angle is increased.

  The underground wall excavator of the present invention preferably further includes a nozzle that is disposed in the vicinity of the rotating drum and injects powdered bentonite that is transferred from the ground. By providing such a nozzle, powdered bentonite can be supplied into the borehole. By supplying powdered bentonite into the excavation hole and increasing the content of bentonite in the impermeable wall, it is possible to construct a impermeable wall having particularly excellent impermeable performance.

  The underground wall excavator of the present invention preferably further includes a comb plate having an opposing surface at a position separated from the side surface of the cutter holding plate that moves with the rotation of the rotating drum and fixed to the main body. By providing the comb plate of the above configuration in the main body, the lump of excavated soil and bentonite can be crushed between the cutter holding plate and the comb plate whose angle has been changed, and these can be mixed evenly. The effect that it can be produced.

  The underground wall excavator of the present invention may be one in which the rotating drum having the above-described configuration is further provided on the upper portion of the main body. By adopting such a configuration, for example, even if there is a boulder after the excavation hole is formed, the underground wall excavator can be pulled up smoothly by rotating the rotating drum at the top of the main body. In addition, by setting up cutter holding plates with different angles on the rotating drums provided at the lower and upper parts of the main body, and rotating these rotating drums, a mixture of bentonite and sand mud is formed in the excavation hole. It can be convected and these can be mixed more uniformly.

  The impermeable wall construction method of the present invention constructs the impermeable wall using the underground wall excavator. That is, the impermeable wall construction method according to the present invention excavates the underground wall in which the cutter holding plate is fixed to the rotating drum so that the longitudinal direction of at least one cutter holding plate is inclined with respect to the rotating direction of the rotating drum. The excavation process for excavating the ground while supplying the bentonite-containing water or the bentonite-containing solidified material or liquid into the excavation hole, and when the underground wall excavator is pulled up, And a stirring step of mixing sand mud and bentonite in the excavation hole by rotating.

  According to the impermeable wall construction method of the present invention, bentonite and sand mud can be forcibly agitated by the cutter holding plate whose angle has been changed. It is possible to construct a water-impervious wall with high water-impervious performance.

  When using the underground wall excavator provided with the nozzle which injects powdery bentonite, the following aspects may be sufficient as the impermeable wall construction method of this invention. That is, the impermeable wall construction method according to the present invention excavates the underground wall in which the cutter holding plate is fixed to the rotating drum so that the longitudinal direction of at least one cutter holding plate is inclined with respect to the rotating direction of the rotating drum. The excavation process of excavating the ground by moving the machine downward, and when pulling up the underground wall excavator, the bentonite is supplied from the nozzle into the excavation hole, and the rotation hole is rotated to rotate the excavation hole. And an agitation step of mixing the sand mud and bentonite.

  According to this impermeable wall construction method, since bentonite in powder form can be supplied from the nozzle into the excavation hole, the content of bentonite in the impermeable wall can be increased, and the impermeable wall having particularly excellent impermeable performance You can build a wall.

  According to the present invention, it is possible to construct a water-impervious wall having a sufficiently high water-impervious performance and to construct a water-impervious wall even on hard ground.

It is a front view which shows embodiment of the underground wall excavator which concerns on this invention. It is sectional drawing which shows a mode that the underground wall excavator shown in FIG. 1 excavates the ground. It is a front view which shows the structure of the lower part of the underground wall excavator shown in FIG. It is a side view which shows the structure of the lower part of the underground wall excavator shown in FIG. It is a schematic diagram which shows the state which expand | deployed the outer peripheral surface of the rotating drum on the plane. It is a front view which shows the structure of the cutter holding plate which can change an angle freely. It is a schematic diagram which shows the cutter holding plate and comb-tooth plate which can change an angle freely. (A)-(d) is a figure which shows the shape of a nozzle, respectively. It is a perspective view which shows other embodiment of the underground wall excavator which concerns on this invention.

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

<Underground wall excavator>
As shown in FIG. 1, the underground wall excavator 50 includes a plurality of rotating drums 10, a main body 20 and the like that are rotatably provided. The underground wall excavator 50 is suspended from an arm 52 extending above the vehicle 51 and is movable in the vertical direction. As shown in FIG. 2, the underground wall excavator 50 excavates the ground to a predetermined depth by its own weight. When excavation is completed at a certain location, the continuous water-impervious wall 1 can be constructed by moving the vehicle 51 by a certain distance and excavating again. The underground wall excavator 50 can be used as a so-called horizontal multi-axis continuous underground wall excavator.

  3 and 4 are a front view and a side view showing the rotating drum 10 that is rotatably provided at the lower portion of the main body 20 and at the corresponding portion. As shown in FIG. 3, the rotary drum 10 includes a plurality of cutter holding plates 12 erected on the outer peripheral surface 10 </ b> F. As shown in FIG. 4, the rotating drum 10 is provided in front and rear of the main body 20, and a total of four rotating drums 10 are provided in the lower part of the main body 20. On the outer peripheral surface 10F of the rotary drum 10, cutter holding plates 12 are erected in three rows in the direction of the rotation axis, and a total of twelve cutter holding plates 12 are erected in each row (four in total). (See FIG. 5). The tip of the cutter holding plate 12 can be fitted with a cutter 12a.

  FIG. 5 is a schematic diagram showing a state in which the outer peripheral surface 10F of the rotary drum 10 is developed on a plane. As shown in the figure, among the 12 cutter holding plates 12, some of the cutter holding plates can freely change the angle between the longitudinal direction and the rotation direction of the rotary drum 10 (the direction of the arrow R in FIG. 5). It is. In addition, about the cutter holding plate 12 which can change the said angle, in FIGS. 5-7, it describes with the cutter holding plate 12A.

  FIG. 6 is a front view showing the configuration of the cutter holding plate 12A. As shown in the figure, the cutter holding plate 12A has a hole 13 into which a cylindrical pin 11 provided on the outer peripheral surface 10F of the rotating drum 10 is inserted, and an angle (FIG. Can be arbitrarily changed within a predetermined range. As shown in FIG. 6, the cutter holding plate 12 </ b> A is fixed to the outer peripheral surface 10 </ b> F of the rotary drum 10 via the fixing members 15 and 16 by tightening the bolts 14. As shown in FIG. 7, grooves are formed on the contact surfaces of the fixing member 16 and the cutter holding plate 12A with the fixing member 16 so that the angle α can be set by fitting the grooves together. It has become.

  The angle α formed by the longitudinal direction of the cutter holding plate 12A and the rotation direction R of the rotary drum 10 is preferably 1 to 10 °, and more preferably 2 to 6 °. When the angle α is less than 1 °, the stirring force of the cutter holding plate 12A tends to be insufficient, and when it exceeds 10 °, the excavation ability tends to be insufficient. Moreover, it is preferable to use the cutter holding plate 12A (the cutter holding plate functioning as a stirring blade) for about 1/3 to 1/2 of all the cutter holding plates. By rotating the rotary drum 10 having the cutter holding plate 12A whose angle has been changed, the solidified material and the sand mud can be forcibly stirred in the excavation hole. That is, the movement of excavated earth and sand toward the horizontal direction of the underground wall excavator 50 and the direction of the wall surface of the excavation hole is promoted, and it is possible to construct a impermeable wall having a high impermeable performance.

  As shown in FIG. 5, the direction in which the cutter holding plate 12A is inclined may be changed depending on the row. For example, in the case of the setting shown in FIG. 5, when the rotary drum 10 rotates in the R direction, the cutter holding plates 12A in the left row cause a flow in the right direction, and the cutter holding plates 12A in the center and right rows Create a flow in the left direction. By adopting such a configuration, there is an advantage that bentonite and earth and sand can be mixed more uniformly in the excavation hole.

  In addition, about all the cutter holding plates, the structure shown in FIG. 6 is adopted, and the angle α of each cutter holding plate 12A is appropriately set in a range of about 0 to 10 ° according to the required performance of the water shielding layer, the hardness of the ground, and the like. May be. The excavation capability of the underground wall excavator 50 can be sufficiently maintained by appropriately setting the number of the cutter holding plates 12A and the angle thereof. For this reason, it is possible to construct a water-impervious wall even on relatively hard ground. Moreover, the row | line | column and the number of sheets of the cutter holding plate 12 are not limited to said 3 rows and 12 sheets. For example, it can be appropriately changed to 3 to 6 rows according to the wall thickness of the impermeable wall 1 to be constructed, and a maximum of 24 cutter holding plates 12 may be erected on one rotating drum 10.

  As shown in FIG. 1, the underground wall excavator 50 is provided with the rotary drum 10 having the above-described configuration also on the upper portion of the main body 20. By providing a plurality of rotating drums 10 on the upper part of the main body 20, even if there is a rock having a diameter of about 200 mm after the formation of the excavation hole, the rotating wall 10 on the upper part of the main body 20 can be rotated to rotate the underground wall The excavator 50 can be pulled up smoothly. In addition, the cutter holding plate 12A is erected on the rotating drums 10 provided at the lower part and the upper part of the main body part 20, respectively, and by rotating these rotating drums 10, the mixture of solidified material and sand mud is formed in the excavation hole. It can be convected and these can be mixed more uniformly.

  As shown in FIG. 3, from a ground bentonite silo (not shown) in the vicinity of the rotating drum 10 provided in the lower part of the main body 20, that is, in the vicinity of the center of the main body 20 and above the rotating drum 10. A nozzle 30 for injecting the powdered bentonite to be transferred is provided. By providing the nozzle 30 at such a position, powdered bentonite can be supplied into the excavation hole. By supplying powdered bentonite into the excavation hole and increasing the content of bentonite in the impermeable wall, it is possible to construct a impermeable wall having particularly excellent impermeable performance. The injection of powder by the nozzle 30 is not limited to the central injection method using a cylindrical shape as shown in FIG. 8A, and from the viewpoint of efficiently mixing with sand mud, FIGS. The flat injection method or the multiple-aperture simultaneous injection method may be employed as in (1). The nozzle 30 may be selected according to the hardness of the ground, and when excavating the hard ground, it is preferable to adopt a configuration as shown in FIG. In the case of excavation, it is preferable to adopt a configuration as shown in FIGS.

  4 and 7, the underground wall excavator 50 has a facing surface 40F at a position separated from the side surface of the cutter holding plate 12A that moves in the R direction as the rotating drum 10 rotates. A comb tooth plate 40 fixed to the main body 20 is further provided. By providing the comb plate 40 of such a configuration in the main body 20, as shown in FIG. 7, the lump of excavated soil and solidified material can be crushed between the cutter holding plate 12A and the comb plate 40, There is an effect that these can be mixed more uniformly.

<Construction method of impermeable walls>
Next, a method for constructing the impermeable wall using the underground wall excavator 50 will be described. The impermeable wall construction method according to the present embodiment moves the underground wall excavator 50 configured as described above downward while supplying bentonite-containing water, bentonite-containing solidified material, or solidified liquid into the excavation hole. When the underground wall excavator 50 is pulled up after the excavation process by excavating the ground, the bentonite is supplied from the nozzle 30 into the excavation hole, and the four rotating drums 10 are rotated. A stirring step of mixing sand mud and bentonite in the borehole. In addition, as a solidification material or a solidification liquid, what contains a bentonite can be used, You may use what further contains cement, lime, fly ash, slag, etc. Examples of bentonite include those produced from bentonite ore.

  In the excavation process, excavation is performed while supplying water containing bentonite into the excavation hole together with air. The underground wall excavator 50 can excavate to a depth of about 60 m. When excavation is completed to a predetermined depth, the underground wall excavator 50 is pulled up while rotating the rotary drum 10 at a rotational speed of about 20 to 30 times / minute. The speed at which the underground wall excavator 50 is pulled up is preferably about 15 to 35 cm / min. If the pulling rate is excessively high, the mixing of bentonite and sand mud tends to be insufficient, while if it is excessively slow, the working efficiency tends to decrease. By repeatedly performing a series of steps including such excavation step and stirring step, the impermeable wall 1 having a predetermined width can be constructed in the ground.

  According to the impermeable wall construction method according to the present embodiment, the cutter holding plate 12A functions as a stirring blade and can forcibly stir bentonite and sand mud, so that the bentonite and sand mud are sufficiently uniform in the original position. Can be mixed. Further, in the stirring step, by supplying powdered bentonite from the nozzle 30 into the excavation hole, the content of bentonite in the impermeable wall can be increased, and the impermeable wall 1 having particularly excellent impermeable performance. Can be built.

  The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the above embodiment. For example, in the above embodiment, the hanging type underground wall excavator 50 is illustrated, but the present invention may be a push-in type underground wall excavator as shown in FIG. The underground wall excavator 60 shown in FIG. 9 includes a rotary drum 10 having a plurality of cutter holding plates 12 on the outer peripheral surface, a main body portion 62 on which the plurality of rotary drums 10 are rotatably provided, and the main body portion 62 at the lower end. Provided with a rod 64 and the like. A part of the plurality of cutter holding plates 12 is a cutter holding plate (cutter holding plate 12A) that can change the angle α and functions as a stirring blade (see FIG. 7). The rod 64 is movable in the vertical direction with respect to the support column 72 of the vehicle 70, and an excavation hole can be formed by pushing the main body 62 into the ground via the rod 64. When the underground wall excavator 60 is pulled up, the rotating drum 10 is rotated so that the bentonite and sand mud can be mixed sufficiently uniformly as in the underground wall excavator 50 according to the above-described embodiment, and high water shielding performance is achieved. It is possible to construct a water shielding wall having. When excavation by the underground wall excavator 60 is completed at a certain location, a continuous impermeable wall can be constructed by moving the vehicle 65 a certain distance and excavating again.

  Moreover, in the said embodiment, although the underground wall excavator provided with the nozzle 30 was illustrated as a particularly preferable example, in the case of forming the impermeable wall with low bentonite content, the underground wall excavator is You may use what does not comprise the nozzle 30. FIG.

  Furthermore, although the fixing members 15 and 16 are exemplified as the mechanism for setting the angle α, any mechanism may be adopted as long as the cutter holding plate 12A can be sufficiently fixed to the rotating drum 10. . Furthermore, the number of the cutter holding plates 12 and 12A provided on the outer peripheral surface 10F of the rotating drum 10 is not limited to the above embodiment, and may be set as appropriate according to the excavation depth, ground strength, and the like.

<Evaluation test>
(Evaluation of drilling capacity)
The present inventors evaluated the excavation capability of the underground wall excavator in the above embodiment. The conventional underground wall excavator (chain cutter method) has been difficult to apply to ground having an N value of 100 (uniaxial compressive strength 5 N / mm ² ). On the other hand, according to the excavator having the same configuration as the underground wall excavator 50, the impermeable wall is constructed even in the ground having an N value exceeding 100 (uniaxial compressive strength 30 N / mm ² ). I was able to.

(Evaluation of stirring force)
A rotating drum (model) having eight cutter holding plates on the outer peripheral surface was produced. A container for housing the rotating drum was prepared, and a lever was attached so that the rotating drum could be manually rotated from the outside of the container. After putting the sample soil (15 L) and the pigment into the container, the rotating drum was rotated at a rotational speed of about 20 times / minute for about 2 minutes. The degree of coloring of the sample soil after the stirring / mixing treatment was visually observed. Also, except that bentonite powder was put into the container instead of the pigment, the sample soil and bentonite were stirred and mixed in the same manner as described above, and then the sample soil was removed from several locations in the container after the treatment. Collected. The flow value of the sample soil after mixing with bentonite was measured according to the method described in JIS R5201. That is, first, a flow cone (upper inner diameter 70 mm, lower inner diameter 100 mm, height 60 mm) was placed on the surface of a mortar flow tester, and sample soil was filled in the flow cone. Thereafter, the flow cone was pulled up, and then the dropping motion was given 15 times to the flow table. The diameter of the sample soil spread on the flow table in two directions at right angles was measured, and the average value was taken as the flow value. Table 1 shows the flow value of the sample soil before blending bentonite and the presence or absence of variation in the flow value after blending bentonite.

  DESCRIPTION OF SYMBOLS 1 ... Water shielding wall, 10 ... Rotating drum, 10F ... Outer peripheral surface of rotating drum, 12, 12A ... Cutter holding plate, 12a ... Cutter, 20, 62 ... Main part, 30 ... Nozzle, 40 ... Comb tooth plate, 50, 60: underground wall excavator, R: rotational direction, α: angle.

Claims (6)

A cutter for excavating the ground,
A cutter holding plate on which the cutter is mounted at the tip;
A rotating drum in which a plurality of the cutter holding plates are erected on the outer peripheral surface;
The rotating drum includes a main body portion rotatably provided at a lower portion,
The underground wall excavator characterized in that at least one of the cutter holding plates is capable of changing an angle between a longitudinal direction of the plate and a rotating direction of the rotary drum.   2. The underground wall excavator according to claim 1, further comprising a nozzle that is disposed in the vicinity of the rotating drum and that injects powdered bentonite transferred from the ground.   The apparatus further comprises a comb-tooth plate having a facing surface at a position spaced apart from a side surface of the cutter holding plate that moves as the rotating drum rotates and is fixed to the main body. Underground excavator as described in.   The underground wall excavator according to any one of claims 1 to 3, wherein the rotating drum is further provided on an upper portion of the main body. A impermeable wall construction method using the underground wall excavator according to claim 1,
Moving the underground wall excavator with the cutter holding plate fixed to the rotating drum downward so that the longitudinal direction of at least one of the cutter holding plates is inclined with respect to the rotating direction of the rotating drum; A drilling step of excavating the ground while supplying solidified material or liquid containing bentonite containing water or bentonite into the drilling hole;
When pulling up the underground wall excavator, the stirring step of mixing sand mud and bentonite in the excavation hole by rotating the rotating drum,
A method for constructing a impermeable wall, comprising: A impermeable wall construction method using the underground wall excavator according to claim 2,
The ground excavator with the cutter holding plate fixed to the rotating drum is moved downward so that the longitudinal direction of at least one cutter holding plate is inclined with respect to the rotating direction of the rotating drum. Drilling process to drill,
When pulling up the underground wall excavator, the stirring step of supplying the bentonite from the nozzle into the drilling hole and mixing the sand mud and bentonite in the drilling hole by rotating the rotating drum When,
A method for constructing a impermeable wall, comprising:

Images