JP2017180085A - Construction method of underground wall - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a construction method of an underground wall that enhances ease of insertion of a core material into a wall body and suppresses increase of generated sludge.SOLUTION: A construction method of an underground wall is a construction method of an underground wall comprising a wall body formed by cement-based solidification material injected into a ground, and at least one core material including a first core material embedded inside the wall body. The construction method includes: a solidification material injection step for injecting the cement-based solidification material into the ground; and a core material insertion step for inserting the first core material to a targeted depth into the wall body before the cement-based solidification material injected into the ground hardens. The core material insertion step includes a voltage application step for applying direct current voltage between the first core material and a conductive body, with the first core material functioning as an anode and the conductive body buried in the ground as a cathode, before the first core material reaches the targeted depth.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a construction method of an underground wall (underground continuous wall) including a wall body formed of a cement-based solidified material injected into the ground and a core material embedded in the wall body.

  As a construction method for constructing earth retaining walls and water retaining walls in the ground, a core material is used as a stress material, depending on the design strength, inside the wall formed by cement-based solidified material injected into the ground. An underground continuous wall construction method for constructing an underground wall by inserting (for example, H-shaped steel) is known.

  In this underground continuous wall construction method, the wall formed of the cement-based solidification material adjusts the water-cement ratio (weight ratio (w / c) of water (w) and cement (c)) of the cement-based solidification material. Thus, the strength of the underground wall after the cement-based solidified material is cured and the insertability of the core material into the wall body before the cement-based solidified material is cured can be adjusted. In general, the water-cement ratio of the cement-based solidifying material is set in consideration of the insertability of the core material. When the standard water cement ratio is, for example, 200 to 300%, the amount of cement-based solidifying material injected into the ground increases, and as a result, the amount of generated mud increases. The waste mud needs to be treated as industrial waste, resulting in an increase in cost.

  In recent years, environmental load reduction has been demanded in construction work, and various methods have been proposed for reducing the amount of sludge in the underground continuous wall method. For example, the bubble excavation method is a method of improving the fluidity and water shielding property of excavated soil by adding bubbles during excavation, and reducing the water cement ratio to achieve a reduction in the amount of mud. In addition, a method in which the bubble excavation method is applied to a columnar soil cement wall has been proposed. This construction method is a construction method capable of reducing the amount of generated mud by reducing the water cement ratio by excavating with cement slurry and bubbles and defoaming the bubbles with an antifoaming agent.

Japanese Patent No. 5790091

  However, even in such a construction method, there is a limit to reducing the water-cement ratio of the cement-based solidified material in consideration of the insertability of the core material. In order to reduce the amount of generated sludge, it is desired to develop a technology that can further reduce the water-cement ratio while ensuring the insertability of the core material.

  In Patent Document 1, when a core material is extracted from a wall body formed of a cement-based solidified material injected into the ground, a voltage is applied between the core material to be extracted and another core material. A technique that facilitates drawing has been proposed (see Patent Document 1). However, this Patent Document 1 does not describe that this technique can be applied when a core material is inserted into a wall body formed of a cement-based solidifying material.

  At least one embodiment of the present invention is an invention made on the basis of such a state of the art, and its object is to improve the insertability of the core material into the wall body, thereby It is in providing the construction method of the underground wall which can suppress the increase in the generation amount.

(1) A method for constructing an underground wall made of soil cement according to at least one embodiment of the present invention is as follows.
A method for constructing an underground wall comprising a wall formed of a cement-based solidified material injected into the ground and at least one core including a first core embedded in the wall. There,
A solidifying material injection step of injecting the cement-based solidifying material into the ground;
A core material inserting step of inserting the first core material to a target depth inside the wall body before the cement-based solidified material injected into the ground is hardened;
The core material insertion step includes
In a state where the first core material does not reach the target depth, the first core material is a negative electrode, and the conductor embedded in the ground is a positive electrode, and the first core material and the conductor And a voltage applying step of applying a DC voltage between the two.

  According to the underground wall construction method described in (1) above, when the first core member is inserted into the wall body, the first core member has not reached the target depth. A DC voltage is applied between the first core member and the conductor by the voltage application step. Here, when a negative electrode is electrically connected to a core member inserted in a wall formed of a cement-based solidified material, a positive electrode is electrically connected to a conductor, and a voltage is applied between both electrodes, Due to the permeation phenomenon, moisture moves from the conductor as the positive electrode to the first core material as the negative electrode. Thereby, moisture collects around the first core material to be inserted. As a result, the frictional resistance with the surroundings can be reduced, and the insertability of the first core material can be improved. Therefore, even if it is a cement-based solidified material with a low water cement ratio and low core material insertability, the first core material can be inserted to the target depth, and the increase in the amount of waste mud can be suppressed. A method of constructing an underground wall can be realized.

(2) In some embodiments, in the construction method of the underground wall according to (1) above,
The at least one core material is a second core material different from the first core material, and the interior of the wall body before the first core material is inserted into the wall body. Including a second core member inserted into
The conductor is configured to be the second core material.

  According to the underground wall construction method of the present embodiment, the core material (second core material) embedded in the wall body can be used as the conductor. Thereby, it is not necessary to embed a conductor separately in the ground, and the workability is excellent. In addition, when a voltage is applied between the conductor (second core material) and the first core material, the periphery of the first core material is caused by the accumulation of moisture on the first core material side due to the electroosmosis phenomenon described above. While moisture collects, the periphery of the second core material is dehydrated. Thereby, the adhesiveness of a 2nd core material and its circumference | surroundings can be improved.

(3) In some embodiments, in the underground wall construction method according to (1) or (2) above,
The first core member and the second core member are embedded in the wall body in an adjacent state.

  According to the embodiment described in (3) above, the first core material and the second core material are embedded in the wall body in an adjacent state, so that the distance between these core materials is shortened. Can be For this reason, if a voltage is applied between both core materials, a voltage can be made to act effectively in the ground between both core materials, and the insertability of the 1st core material used as insertion object can be improved more. it can. Moreover, the workability | operativity at the time of connecting an electrode between both core materials can be improved.

(4) In some embodiments, in the underground wall construction method according to any one of (1) to (3) above,
The underground wall construction method includes a first underground wall construction step of constructing a first underground wall, and a second underground wall constructed after the first underground wall. Including a second underground wall construction process,
Each of the first underground wall construction step and the second underground wall construction step includes the solidifying material injection step and the core material insertion step,
In the solidification material injection step in the second underground wall construction step, the cement-based solidification injected into the ground in consideration of the construction status of the core material insertion step in the first underground wall construction step Adjust the water-cement ratio of the material.

  The underground wall is constructed in order for each of the plurality of construction unit sections such that the second underground wall is constructed after the construction of the first underground wall when the extension exceeds a predetermined value. . According to the embodiment described in the above (4), in the solidifying material injecting step in the second underground wall construction step, the construction status of the core material insertion step in the first underground wall construction step is considered, By adjusting the water cement ratio of the cement-based solidifying material to be injected therein, the water cement ratio can be appropriately set so that the water cement ratio can be made as small as possible while ensuring the insertability of the core material.

  According to at least one embodiment of the present invention, it is possible to provide a method for constructing an underground wall that can improve the insertability of a core material into a wall body and can suppress an increase in the amount of generated mud. it can.

It is a top view of the underground wall constructed | assembled by the construction method of the underground wall concerning one Embodiment of this invention. It is a whole flowchart for demonstrating the construction method of the underground wall concerning one Embodiment of this invention. It is a fragmentary sectional view for demonstrating the solidification material injection | pouring process and core material insertion process of a construction method of an underground wall. It is a flowchart for demonstrating the core material insertion process of the construction method of an underground wall. It is a fragmentary sectional view for demonstrating a voltage application process. It is a top view of the underground wall for demonstrating the voltage application process concerning other embodiment. It is a top view of the underground wall constructed | assembled by the construction method of the underground wall concerning other embodiment. It is a whole flowchart for demonstrating the construction method of the underground wall concerning other embodiment. It is a flowchart for demonstrating the solidification material injection | pouring process concerning other embodiment. It is the figure which showed schematic structure of the experimental apparatus for demonstrating the effect of the construction method of the underground wall concerning one Embodiment of this invention. It is the graph which showed the relationship between the insertion depth and the load at the time of insertion in each case from which the magnitude | size of the DC voltage to apply differs. It is the graph which showed the relationship between the magnitude | size of the DC voltage to apply, and the stress ratio of a core material. It is the plot figure which showed the relationship between electrode space | interval (space | interval of a conductor and a core material) and the stress ratio of a core material. It is the graph which showed the relationship between the amount of sand in earth and sand, and the stress ratio of a core material. It is the graph which showed the relationship between the magnitude | size of the direct-current voltage applied and the stress ratio of a core material in two cases of normal earth and sand and the mixed earth and sand which mixed the cement-type solidification material in normal earth and sand.

  Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, material properties, shapes, relative arrangements, and the like of the components described in the embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples. Only. For example, expressions expressing relative or absolute arrangements such as “in a certain direction”, “along a certain direction”, “parallel”, “orthogonal”, “center”, “concentric” or “coaxial” are strictly In addition to such an arrangement, it is also possible to represent a state of relative displacement with an angle or a distance such that tolerance or the same function can be obtained. For example, an expression indicating that things such as “identical”, “equal”, and “homogeneous” are in an equal state not only represents an exactly equal state, but also has a tolerance or a difference that can provide the same function. It also represents the existing state. For example, expressions representing shapes such as quadrangular shapes and cylindrical shapes represent not only geometrically strict shapes such as quadrangular shapes and cylindrical shapes, but also irregularities and chamfers as long as the same effects can be obtained. A shape including a part or the like is also expressed. On the other hand, the expressions “comprising”, “comprising”, “comprising”, “including”, or “having” one constituent element are not exclusive expressions for excluding the existence of the other constituent elements. In the following description, the same components may be denoted by the same reference numerals and detailed description thereof may be omitted.

  FIG. 1 is a plan view of an underground wall constructed by an underground wall construction method according to an embodiment of the present invention. FIG. 2 is an overall flowchart for explaining a construction method of an underground wall according to an embodiment of the present invention. FIG. 3 is a partial cross-sectional view for explaining the solidifying material injecting step and the core material inserting step of the underground wall construction method.

  In one embodiment of the present invention, a method for constructing an underground wall in the case of constructing an underground wall made of soil cement connected to the underground will be described.

  As shown in FIG. 1, the underground wall construction method according to an embodiment of the present invention includes a wall body 10 formed of a cement-based solidified material S injected into the underground Gi, and an interior of the wall body 10. It is a construction method of the underground wall 1 comprising at least one core member 20 including the first core member 20a to be embedded. As shown in FIG. 2, the construction method of the underground wall 1 includes a solidifying material injection process (step 100) and a core material insertion process (step 200).

  In the solidifying material injection step (step 100), the cement-based solidifying material S adjusted to a predetermined water-cement ratio is injected into the underground Gi. In the embodiment shown in FIG. 3, the apparatus for injecting the cement-based solidifying material S is a multi-axis kneading auger machine 30 used in, for example, a columnar soil cement continuous wall construction method. The multi-shaft kneading auger machine 30 excavates the ground with an earth auger, and discharges the cement-based solidified material S from the tip of the ground to a ground Gi. As shown in FIG. 1, the wall body 10 formed by the cement-based solidified material S injected into the underground Gi is arranged so that the side portions of the pillars 11 having a circular cross section overlap each other. It is formed in a shape. In addition, the apparatus which inject | pours the cement-type solidification material S in underground Gi may be a construction apparatus used by the equal thickness type soil-cement continuous wall construction method etc., for example.

  In the core material insertion step (step 200), the first core material 20a is inserted to the target depth inside the wall body 10 before the cement-based solidified material S injected into the underground Gi is cured. In the core material insertion step (step 200), in a state where the first core material 20a has not reached the target depth, the first core material 20a is the negative electrode, and the conductor embedded in the underground Gi is the positive electrode. And a voltage applying step (step 300) to be described later, in which a DC voltage is applied between the first core member 20a and the conductor.

  In the illustrated embodiment, the conductor is the second core member 20b of the core member 20 different from the first core member 20a.

  FIG. 4 is a flowchart for explaining a core material insertion step of the underground wall construction method.

  As shown in FIG. 4, the first core member 20 of the plurality of core members 20 is inserted into the wall body 10 to the target depth (steps 400 and 401). For example, as shown in FIG. 3, the first core 20 is moved above the wall 10 in a state where the first core 20 is suspended by a lifting device 40 such as a crane, and then the first core is lifted by the lifting device 40. The material 20 is moved downward, and the first core material 20 is inserted from the upper end of the wall body 10 to the target depth. When the first core member 20 cannot be inserted to the target depth by its own weight, the core member 20 is forcibly pressed downward by a heavy machine or the like to be inserted to the target depth.

  In the core material insertion step (step 200), when the first core material 20 is inserted to the target depth, the second core material 20 is inserted into the columnar wall 10 adjacent to the first core material 20 ( Step 201). At this time, it is determined whether it is necessary to apply a voltage when the second core member 20 is inserted (step 202). In this determination, for example, when the core material 20 cannot be inserted to the target depth even by a heavy machine or the like, or when it takes too much time to insert the core material to the target depth, it is determined that it is necessary to apply a voltage. And when it is judged that it is necessary to apply a voltage, it transfers to the voltage application process (step 300) demonstrated below.

  In step 300, the negative electrode of the DC power supply 43 is electrically connected to the second core member 20 (first core member 20a) described above, and a direct current is connected to the first core member 20 (second core member 20b). The positive electrode of the power supply 43 is electrically connected (step 301). Then, a voltage is applied between the first core material 20 (second core material 20b) and the second core material 20 (first core material 20a) (step 302). The applied voltage is set in advance. Note that the DC power supply 43 is configured to be able to adjust the magnitude of the applied voltage.

  When a voltage is applied between the first core material 20 (second core material 20b) and the second core material 20 (first core material 20a), the second core material will be described later. Friction resistance with the periphery of 20 (first core material 20a) is reduced. Thus, the second core member 20 (first core member 20a) is inserted to the target depth only by being lightly pressed downward by its own weight or heavy machinery (step 203).

  Then, it is determined whether there is another core material 20 to be inserted (step 204). If there is another core material 20 to be inserted (for example, the third core material 20), the third core material 20 is determined. Steps 201 to 203 and Step 300 are repeated using the first core member 20a described above as the second core member 20b described above as the second core member 20 described above. If there is no core material 20 to be newly inserted in step 204, the flowchart of FIG. 4 ends.

  In the embodiment illustrated in FIG. 1, the case where the core member 20 is inserted into each of the wall bodies 10 including the columns 11 that are arranged in a row is illustrated. The core material 20 may not be inserted into some of the columns 11 of the wall body 10 made of 11.

  According to such a construction method of the underground wall 1, when the second (n + 1) core member 20 is inserted into the wall body 10, the second core member 20 does not reach the target depth. In the voltage application step (step 300), a DC voltage is applied between the second core member 20 (first core member 20b) and the first (n-th) core member 20 (second core member 20a). Applied. Then, as shown in FIG. 5, due to the electroosmosis phenomenon, the first core material 20 (second core material 20b) that is the positive electrode to the second core material 20 (first core material 20a) that is the negative electrode. Moisture moves to Thereby, moisture collects around the second core material 20 (first core material 20a) to be inserted. As a result, the frictional resistance with the surroundings is reduced, and the insertability of the second core member 20 (first core member 20a) can be improved. Therefore, even if it is the cement-type solidification material S with a small water cement ratio and the insertion property of the core material 20 low, it becomes possible to insert the 2nd core material 20 (1st core material 20a) to the target depth. The construction method of the underground wall 1 which can suppress the increase in the generated amount of mud can be realized.

  Further, as described above, the conductor is configured to be the second core member 20b of the first core member 20. Thereby, it is not necessary to embed an electric conductor separately in the underground Gi, and it is excellent in workability. Further, when a voltage is applied between the first core member 20 (second core member 20b) and the second core member 20 (first core member 20a), the second moisture due to the electroosmosis phenomenon described above is applied. The accumulation on the core material 20 (first core material 20a) side collects moisture around the second core material 20 (first core material 20a), while the first core material 20 (second core material 20a). The periphery of the core material 20b) is cured. Thereby, the adhesiveness of the 1st core material 20 (2nd core material 20b) embed | buried previously and its circumference | surroundings can be improved.

  In addition, when the third core member 20 is inserted into the wall body 10, the second core member 20 may be used as the positive electrode (as the above-described second core member 20b). The second core material 20 that was the negative electrode first has low adhesion with the surrounding cementitious solidified material S, but by using this second core material 20 as the positive electrode after that, Adhesiveness between the second core material 20 and its surroundings can be enhanced.

  In the above-described embodiment, the conductor serving as the positive electrode is the first core member 20 (second core member 20b). However, as shown in FIG. The rod-shaped conductor 22 may be used. Here, FIG. 6 is a plan view of the underground wall for explaining a voltage application process according to another embodiment.

  In the illustrated embodiment, the rod-shaped conductor 22 is inserted into the underground Gi outside the intermediate portion in the longitudinal direction of the wall body 10 formed of the cement-based solidified material S. The rod-like conductor is connected to the positive electrode of the DC power supply 43, and the negative electrode of the DC power supply 43 is electrically connected to the core member 20. Each time the core member 20 is inserted into the wall body 10, the negative electrode is connected to the core member 20 to be inserted. On the other hand, the positive electrode is always connected to the rod-shaped conductor 22. For this reason, the work burden of the electrode connection work can be reduced. However, the distance X between the rod-shaped conductor 22 and each of the inserted core members 20 is different. For this reason, the magnitude of the voltage applied between the rod-shaped conductor 22 and the core member 20 needs to be adjusted according to the distance X between the electrodes.

  In some embodiments, as shown in FIGS. 1 and 6, the first core member 20 a and the second core member 20 b are embedded in the wall body 10 in an adjacent state.

  In the illustrated embodiment, when the second core member 20b is the first core member 20 inserted into the column 11 formed at one end in the longitudinal direction of the wall body 10, the first core member 20a is The second core member 20 is inserted into the pillar 11 adjacent to the pillar 11.

  Thus, since the 1st core material 20a and the 2nd core material 20b are embed | buried in the inside of the wall body 10 in the adjacent state, the distance between these core materials can be shortened. For this reason, when a voltage is applied between both core materials, a voltage can be effectively applied to the underground Gi between the both core materials, and the second core material 20 (first core material 20a) to be inserted. ) Can be further improved. Moreover, the workability | operativity at the time of connecting an electrode between both core materials can be improved.

  FIG. 7 is a plan view of the underground wall constructed by the underground wall construction method according to another embodiment. FIG. 8 is an overall flowchart for explaining a construction method of an underground wall according to another embodiment. FIG. 9 is a flowchart for explaining a solidifying material injecting step according to another embodiment.

  In some embodiments, the underground wall construction method includes a first underground wall 1A constructed by the first underground wall construction step and a second underground wall construction as shown in FIG. It is the construction method of the underground wall 1 containing the 2nd underground wall 1B constructed | assembled by the process. As shown in FIG. 8, the construction method of the underground wall 1 includes a first underground wall construction process (step 1) and a second underground wall construction process (step 2). And the 1st underground wall construction process (step 1) is equipped with the solidification material injection | pouring process (step 100) and the core material insertion process (step 200). The second underground wall construction process (step 2) includes a solidifying material injection process (step 100a) and a core material insertion process (step 200).

  Among these, the solid material injection process (step 100) of the first underground wall construction process (step 1), the core material insertion process (step 200), and the core of the second underground wall construction process (step 2). Since the material insertion step (step 200) conforms to the above-described embodiment, the description thereof is omitted.

  As shown in FIG. 9, the solid material injection process (step 100a) of the second underground wall construction process (step 2) is a core material insertion process (step 200) in the first underground wall construction process (step 1). ) Is determined whether it is possible to reduce the water-cement ratio of the cement-based solidifying material S injected in the solidifying material injection step (step 100a) of the second underground wall construction step (step 2). (Step 100a1). If the water-cement ratio can be lowered, the process proceeds to step 100a2.

  On the other hand, if it is determined in step 100a1 that the water-cement ratio cannot be lowered, the process proceeds to step 100a3 and the predetermined water produced in the first underground wall construction process (step 1) is performed. The cement-based solidification material S having a water cement ratio higher than the cement-based solidification material S having the same water cement ratio as the cement-based solidification material S adjusted to the cement ratio or the cement-based solidification material S adjusted to the predetermined water-cement ratio Is made.

  In step 100a2, a cement-based solidified material S having a lower water cement ratio than the cement-based solidified material S prepared in the first underground wall construction step (step 1) and adjusted to a predetermined water-cement ratio is prepared. To do. Then, the cement-based solidified material S produced in either step 100a2 or step 100a3 is injected into the underground Gi (step 100a4).

  Here, whether or not it is possible to reduce the water-cement ratio in step 100a1 described above is determined as follows, for example. That is, in the solidification material injection process (step 100) of the first underground wall construction process (step 1), the first core material 20 (second core material 20b) and the second core material 20 (first When the second core material 20 (first core material 20a) is inserted into the ground while a predetermined voltage is applied between the core materials 20a), the time required for the insertion is less than the specified time. In step 100a1, it is determined that the water cement ratio can be lowered. The second core material 20 (second core material 20 (second core material 20 b) and the second core material 20 (first core material 20 a) are applied with a predetermined voltage between them. When the core material 20a) is inserted into the ground and the pressing force when pressing with a heavy machine or the like falls below a specified pressing force, it is determined in step 100a1 that the water cement ratio can be lowered.

  In this way, the underground wall 1 has a plurality of construction unit sections such that the second underground wall 1B is constructed after the construction of the first underground wall 1A when the extension is greater than or equal to a predetermined value. Each is built in turn. According to the embodiment described above, in the solidifying material injection process (step 100a) in the second underground wall construction process (step 2), the core material insertion process in the first underground wall construction process (step 1). In consideration of the construction status of (Step 200), by adjusting the water cement ratio of the cement-based solidified material S injected into the ground, the water cement ratio can be made as small as possible while ensuring the insertability of the core material 20. Thus, the water cement ratio can be set appropriately.

  As mentioned above, although the preferable form of this invention was demonstrated, this invention is not limited to said form, A various change in the range which does not deviate from the objective of this invention is possible.

  The effect of the underground wall construction method according to one embodiment of the present invention will be specifically described based on the following examples.

  FIG. 10: is the figure which showed schematic structure of the experimental apparatus for demonstrating the effect of the construction method of the underground wall concerning one Embodiment of this invention. In the experimental apparatus 50 shown in FIG. 10, earth and sand 60 are accommodated in a container 58, and the container 58 is configured to be movable upward by an elevating device 56. The amount of upward movement of the container 58 can be measured by a displacement meter 55. Further, a conductor 53 embedded in the earth and sand 60 is electrically connected to the positive electrode side of the DC power supply 51 via a resistor 54, and a core material 52 is electrically connected to the negative electrode side thereof. It is connected. In the initial state before the container 58 moves upward, the core material 52 is not inserted into the earth and sand 60 and is supported at an upper position of the earth and sand 60. A load meter is arranged on the upper part of the core material 52, and an axial load acting on the core material 52 when the container 58 moves upward (insertion required for inserting the core material 52 into the earth and sand 60). (Hour load) can be measured.

FIG. 11 is a graph showing the relationship between insertion depth and insertion load in each case where the magnitude of the DC voltage to be applied is different. 11A shows a case where no DC voltage is applied, FIG. 11B shows a case where a DC voltage of 5V is applied, FIG. 11C shows a case where a DC voltage of 10V is applied, and FIG. 11D shows a case where a DC voltage of 20V is applied. (E) shows a case where a DC voltage of 30 V is applied. In each case of (a) to (e), the distance between the core member 52 and the conductor 53 is the same distance (10 cm).
As shown in FIG. 11, by applying a DC voltage between the core material 52 and the conductor 53 (cases b to e), no DC voltage is applied between the core material 52 and the conductor 53. Compared with (Case a), the insertion load is smaller, and it can be seen that the insertability of the core material 52 is improved.

FIG. 12 is a graph showing the relationship between the magnitude of the applied DC voltage and the stress ratio of the core material. Here, the stress ratio is the ratio of the stress of the core material 52 in each case when the stress of the core material 52 when no DC voltage is applied is 1, and the smaller the stress ratio, the above-described load at the time of insertion. Means small. In addition, in FIG. 12, the graph of two types of earth and sand (clay A, clay B) from which a property differs is shown.
As shown in FIG. 12, it can be seen that the greater the DC voltage applied, the smaller the stress ratio (load during insertion).

FIG. 13 is a plot diagram showing the relationship between the electrode interval (interval between the conductor and the core material) and the stress ratio of the core material. Note that FIG. 13 shows two cases of a case where the applied DC voltage is 10 V and a case where the DC voltage is 30 V.
As shown in FIG. 13, when the voltage was 30 V, no significant difference could be confirmed between the electrode interval and the stress ratio. This is presumably because the electrode spacing is small with respect to the magnitude of the voltage. On the other hand, when the voltage is 10 V, the stress ratio when the electrode interval is 30 cm is significantly larger than when the electrode interval is 10 cm and 20 cm. The stress ratio when the electrode spacing is 10 cm and 20 cm is about 0.8, but the stress ratio when the electrode spacing is 30 cm is close to 1, and the effect of reducing the stress ratio (load during insertion) is hardly seen. . From this, it is presumed that there is a preferable upper limit of the electrode interval for reducing the stress ratio (load at the time of insertion) with respect to the magnitude of the applied DC voltage.

FIG. 14 is a graph showing the relationship between the amount of sand in earth and sand and the stress ratio of the core material. FIGS. 11 to 13 described above are experimental results in the case where the kind of earth and sand is clay. FIG. 14 shows experimental results performed to evaluate the influence of the amount of sand contained in the earth and sand on the stress ratio. Here, the amount of sand means the percentage by weight of sand contained in the earth and sand (particles having a particle size of 2.00 mm to 0.075 mm). FIG. 14 shows three cases: a case where the applied DC voltage is 10 V, a case where the DC voltage is 20 V, and a case where the DC voltage is 30 V.
As shown in FIG. 14, when the amount of sand exceeds 40%, the stress ratio (load during insertion) tends to increase as the amount of sand increases. This means that the effect of improving the insertability of the core material 52 becomes smaller as the sand content becomes higher than 40%. This is because clay particles tend to be negatively charged, which is thought to lead to a reduction in the stress ratio (load during insertion) when a voltage is applied, whereas sand particles The reason is that such a charging property is not provided.

  That is, in the construction method of the underground wall according to one embodiment of the present invention, clay (particles having a particle size of 0.005 mm or less) and silt (particles having a particle size of 0.074 to 0.005 mm) are contained in the earth and sand. The present invention can be particularly suitably applied to a viscous ground (a ground having a total amount of clay and silt of 50% or more) that is contained in a large amount.

FIG. 15 is a graph showing the relationship between the magnitude of DC voltage applied and the stress ratio of the core material in two cases of normal earth and sand and mixed earth and sand mixed with cement-based solidified material. The comparative example of FIG. 15 is an experimental result in soil (40% clay content, 60% sand content) simulating normal soil, and the example is the soil (40% clay content, 60% sand content) simulating normal soil. The experimental results of the mixed soil mixed with a specified amount of cementitious solidifying material are shown. Here, the cement-based solidifying material is obtained by adjusting a cement obtained by adding bentonite to a predetermined water cement ratio. The weight of cement or bentonite to be mixed with the specified amount of earth and sand is predetermined according to the properties of the earth and sand (for example, SMW Association website <http://www.smw-kyokai.jp/page/smwkikai /oshiire.htm>) In this example, 250 kg of cement and 15 kg of bentonite were mixed with 1 m ^{3 of} earth and sand. On the other hand, the water cement ratio was adjusted to 50%, which is lower than the specified amount.
As shown in FIG. 15, the stress ratio is smaller in the example than in the comparative example. It is inferred that this is because the bentonite contained in the cement-based solidified material functions in the same manner as the clay particles described above, leading to a reduction in the stress ratio (load during insertion) when a voltage is applied.

  That is, the underground wall construction method according to one embodiment of the present invention includes a ground in which the sand content is 40% or more in the earth and sand, and a sandy ground in which the sand content is 50% or more. Also, it can be suitably applied.

1, 3, 5 underground wall 10 wall body 11 pillar 20 core material 20a first core material 20b second core material (conductor)
22 Bar-shaped conductor 30 Multi-axis mixed auger machine 40 Lifting device 43 DC power supply Gi Underground S Cement-based solidification material X Distance W Water

Claims (4)

A method for constructing an underground wall comprising a wall formed of a cement-based solidified material injected into the ground and at least one core including a first core embedded in the wall. There,
A solidifying material injection step of injecting the cement-based solidifying material into the ground;
A core material inserting step of inserting the first core material to a target depth inside the wall body before the cement-based solidified material injected into the ground is hardened;
The core material insertion step includes
In a state where the first core material does not reach the target depth, the first core material is a negative electrode, and the conductor embedded in the ground is a positive electrode, and the first core material and the conductor Including a voltage application step of applying a DC voltage between
The construction method of the underground wall characterized by this. The at least one core material is a second core material different from the first core material, and the interior of the wall body before the first core material is inserted into the wall body. Including a second core member inserted into
The conductor is the second core material,
The construction method of the underground wall of Claim 1 characterized by the above-mentioned. The first core member and the second core member are embedded in the wall body in an adjacent state.
The construction method of the underground wall of Claim 1 or 2 characterized by the above-mentioned. The underground wall construction method includes a first underground wall construction step of constructing a first underground wall, and a second underground wall constructed after the first underground wall. Including a second underground wall construction process,
Each of the first underground wall construction step and the second underground wall construction step includes the solidifying material injection step and the core material insertion step,
In the solidification material injection step in the second underground wall construction step, the cement-based solidification injected into the ground in consideration of the construction status of the core material insertion step in the first underground wall construction step Adjust the water-cement ratio of the material,
The construction method of the underground wall of any one of Claim 1 to 3 characterized by the above-mentioned.

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