JP2018071093A - Construction method to suppress subsidence of back fill on abutment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress subsidence of back fill on an abutment surely and easily, with little constraints on construction conditions, causing little displacement of ground during construction and after construction.SOLUTION: A construction method to suppress subsidence of back fill on an abutment comprises: repeating a step of forming a preceding soil improvement body 10 at a predetermined interval in a substantially horizontal direction; step of forming a subsequent soil improvement body 20 at a position different from the preceding soil improvement body 10 by shifting an insertion position and an insertion depth of a chemical injection rod 60 at a same height, so as to form a series of soil improvement body groups 30 in a substantially horizontal direction; and repeating a step of shifting an insertion height of the chemical injection rod 60 to form a series of soil improvement body groups 30 in the substantially horizontal direction, so as to form the soil improvement body groups 30 for the whole of back fill 80 on abutment to be improved.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an abutment backfill settlement settlement method that is a connection between an abutment and embankment, and more specifically, a construction method for suppressing settlement of the embankment by injecting an improved material into the abutment backfill high-pressure injection. It is about.

  Abutment backfill is prone to ground subsidence or depression due to ground compaction due to insufficient compaction during construction, aging deterioration of the embankment material, or outflow of embankment material due to rain. In addition, when an earthquake occurs, relative displacement between the abutment and the back embankment becomes prominent, which may reduce the traveling performance of a train or the like. In order to eliminate such a phenomenon, measures are taken to inject a chemical solution with cement milk or the like during the embankment.

  As a technique for reinforcing the abutment back embankment, for example, there are techniques described in Patent Document 1, Patent Document 2, and Patent Document 3. The technique described in Patent Document 1 is to remove the backfill of the abutment by an appropriate distance after installing the temporary line of the railway and the road and interrupting the abutment in the vicinity of the abutment of the railway and the road. In the space, build a reinforced embankment with a gap from the back of the abutment. And, it is said that the abutment and the back embankment can be reinforced by placing the back concrete between the abutment back and the front of the reinforce embankment and integrating the abutment and the reinforce embankment.

  In the technique described in Patent Document 2, a rod-shaped reinforcing material is driven substantially parallel to the axial direction of the bridge girder from the front surface of the abutment toward the back embankment. Furthermore, by placing rod-shaped reinforcements in the direction perpendicular to the axial direction of the bridge girder from the slope of the embankment, it is possible to reinforce the abutment and the embankment on the back of the abutment while maintaining the traffic state of the railway or vehicle. I can do it.

  The technique described in Patent Document 3 is based on the back embankment of the anti-earth pressure abutment of a railway bridge. On the both sides of the track, a plurality of embankment improvement bodies penetrating the embankment along the track direction are provided at predetermined intervals. Arrange and create an improved track group. Then, the head of the embankment improvement body is integrally rigidly connected with a connecting body. The improved track group along the track divides the earth pressure during the earthquake along the track, and further reduces the earth pressure during the earthquake by attenuating the earth pressure during the earthquake by friction between the back embankment and the embankment improved body. As a result, the earthquake resistance of the bridge can be improved without relatively reinforcing the anti-earth pressure abutment itself.

JP 2011-247060 A JP 2011-247064 A Japanese Patent Laying-Open No. 2015-55082

  However, the above-described conventional techniques have various problems that have not been solved yet. For example, in a countermeasure by chemical liquid injection using cement milk or the like, it is necessary to perform chemical liquid injection at a pressure lower than a normal pressure in consideration of the influence on the train track. For this reason, it is difficult to effectively inject chemicals into a loose area in the ground, and quality reliability may not be ensured.

  In addition, since it is unclear where the loose region in the ground exists, in many cases, the number of constructions is large in the case of chemical injection. For this reason, it is conceivable to implement cement improvement by mechanical agitation and cement improvement by high-pressure jet agitation as countermeasures against the loosening area of the ground. In the case of cement improvement by mechanical agitation, there are many cases where only a limited range of improvement can be made, but high-pressure jet agitation is used in which cement milk is injected from a small diameter rod at high pressure (for example, 20 to 30 MPa) and agitated. In this case, it is possible to effectively take measures against the loose area of the ground whose position is unclear.

  However, when the high-pressure jet agitation is applied horizontally, the general construction method is likely to cause ground displacement (particularly the settlement phenomenon). In addition, there is a high possibility that the displacement of the ground will be promoted with the passage of time due to temporary loosening inside the improved body after construction. Therefore, it is necessary to perform construction that prevents displacement of the ground during construction and immediately after construction.

  Furthermore, each prior art cited as the prior art document has room for further contrivance, such as construction conditions being limited or construction being troublesome.

  The present invention has been proposed in view of the above-described circumstances, has few restrictions on construction conditions, and reliably and easily suppress settlement of the abutment backside embankment without causing substantial displacement of the ground during and after construction. The purpose is to provide a construction method that can be used.

  The settlement suppression method for abutment backfill according to the present invention has the following features in order to achieve the above-described object. That is, the subsidence suppression method of the abutment back embankment according to the present invention is a high pressure stirring injection method in which a chemical injection rod is inserted into the abutment back embankment to be improved, and the chemical solution is injected into the abutment back embankment from the chemical injection rod. It is a construction method that suppresses settlement of the abutment backfill by forming a ground improvement body.

  In this subsidence suppression construction method, first, the step of forming the preceding ground improvement body at a constant interval in a substantially horizontal direction, and the preceding ground improvement body by shifting the insertion position and the insertion depth of the chemical injection rod at the same height, And repeatedly forming the subsequent ground improvement body at different positions, thereby forming a ground improvement body group that is a series of substantially horizontal directions.

  And, by shifting the insertion height of the chemical solution injection rod and repeating the process of forming a series of ground improvement bodies in a substantially horizontal direction, the ground improvement body group is applied to the entire abutment back embankment to be improved. It is characterized by forming.

  In the above-described settlement suppression method for the abutment backfill, it is preferable to inject the chemical solution downward from the substantially horizontal direction when the chemical solution is injected from the chemical injection rod into the abutment backfill.

  Moreover, in the settlement suppression method of the abutment back embankment described above, it is preferable to inject the chemical into the abutment back embankment while discharging mud from the chemical injection portion of the chemical injection rod.

  According to the settlement suppression method of the abutment backfill according to the present invention, the insertion position and the insertion depth of the chemical injection rod are shifted at the same height as the step of forming the preceding ground improvement body at a constant interval in the substantially horizontal direction. In addition, by repeating the process of forming the subsequent ground improvement body at a position different from the preceding ground improvement body, a group of ground improvement bodies is formed in a substantially horizontal direction. Since the body formation process is divided in a zigzag pattern and the ground to be improved is not disturbed at once, the displacement of the abutment back embankment to be improved can be suppressed.

  Moreover, by implementing such a staggered division improvement, it becomes possible to reliably form a ground improvement body over the entire abutment back embankment to be improved. Further, by implementing such a staggered division improvement, each board improvement body is formed independently, and thus it is possible to prevent variations in the improvement body strength.

  Moreover, by adopting the high-pressure jet stirring method, cement milk can be jetted and stirred from a small-diameter rod at a high pressure (for example, 20 to 30 MPa), which is effective for the loose region of the ground where the position is unclear. It is possible to implement measures to prevent settlement.

  In addition, when injecting the chemical solution from the chemical injection rod into the abutment backside embankment, the chemical solution is not injected upward by injecting the chemical solution downward from the substantially horizontal direction (so-called downward improvement). In addition, the upper ground forming the ground improvement body can be prevented from collapsing, and the displacement of the abutment back embankment to be improved can be suppressed.

  Also, by discharging mud from the chemical injection part of the chemical injection rod, it is possible to prevent the pressure rise inside the ground improvement body and to suppress the displacement (particularly uplift) of the abutment back embankment to be improved Become.

  Furthermore, since the ground improvement body has strength, it is possible to suppress the ground subsidence of the abutment backside embankment and to cope with the slack area, and to perform seismic reinforcement.

The side view explaining the settlement suppression construction method of the abutment back embankment which concerns on embodiment of this invention. The front view explaining the settlement suppression construction method of the abutment back embankment concerning the embodiment of the present invention. The top view explaining the settlement suppression construction method of the abutment back embankment concerning the embodiment of the present invention. Explanatory drawing which shows the procedure which forms a ground improvement body in the settlement suppression construction method of the abutment back embankment which concerns on embodiment of this invention. Explanatory drawing which shows the procedure which forms a ground improvement body in the settlement suppression construction method of the abutment back embankment which concerns on embodiment of this invention. The cross-sectional schematic diagram of the state which looked at the abutment back embankment from the side. The cross-sectional schematic diagram of the state which looked at the abutment back embankment from the front.

  Hereinafter, with reference to the drawings, a method for suppressing settlement of an abutment backfill according to an embodiment of the present invention will be described. 1 to 5 are diagrams for explaining the settlement control method for abutment back embankment according to an embodiment of the present invention. FIG. 1 is a side view, FIG. 2 is a front view, FIG. 3 is a plan view, and FIGS. It is explanatory drawing which shows the procedure which forms a ground improvement body. Moreover, FIG.6 and FIG.7 is a cross-sectional schematic diagram of abutment back embankment.

<Outline of settlement control method for abutment backfill>
The abutment backfill settlement suppression method according to the embodiment of the present invention is to form a ground improvement body inside the abutment backfill 80 using a high-pressure jet agitation method, and is preceded at a certain interval in a substantially horizontal direction. A ground improvement body group 30 having the same height is formed by dividing and forming the ground improvement body 10 and the subsequent ground improvement body 20 in a zigzag pattern. And the ground improvement body group 30 is formed with respect to the whole abutment back embankment 80 to be improved by shifting the position in the height direction and repeatedly forming a series of ground improvement body groups 30 in a substantially horizontal direction. It is supposed to be. In particular, by using the high-pressure jet stirring method for forming the ground improvement body, it is possible to reliably form the ground improvement body in the loose region of the ground whose position is unclear.

<Abutment rear embankment>
The abutment 90 is a basic structure that supports an upper structure such as a railway bridge, for example, and a banking (backing abutment 80) is formed on the back side of the abutment 90. As shown in FIGS. 1 and 2, a ground improvement body group 30 is formed inside the abutment back embankment 80 according to the embodiment of the present invention using a high-pressure jet stirring method. For example, the height of the abutment back embankment 80 is about 3 m, and the ground improvement body group 30 formed therein is formed over about 1 m from the top surface of the abutment back embankment 80 and about 5 m from the back surface of the abutment 90.

<Installation of construction machines>
Prior to forming the ground improvement body group 30 inside the abutment back embankment 80, a scaffold 40 for installing construction equipment is constructed. For example, as shown in FIG. 1, the scaffold 40 is assembled on the side of the abutment back embankment 80 using a single pipe pipe or the like. In this embodiment, since the plurality of ground improvement body groups 30 that are arranged in a substantially horizontal direction are formed by shifting the position in the height direction, it is necessary to change the height of the scaffold 40 according to the progress of the construction. Therefore, the scaffold 40 is preferably formed using a single pipe or the like that can be easily assembled and disassembled.

  Moreover, in this embodiment, since construction equipment smaller in size than construction equipment used in a general high-pressure jet stirring method is used (for example, a machine weight of about 1.0 t), it is only necessary to have strength corresponding to that. . The scaffold 40 sequentially increases in height or decreases in height in accordance with the formation process of the ground improvement body group 30.

  Although not shown in detail on the scaffold 40, as a construction device for forming the ground improvement body group 30, a small high-pressure jet agitating device 50, a power supply device, a compressor, a curing agent, water and the like are sent out. Install a pump, a vacuum device, etc. to promote waste mud. In the present embodiment, since the ground improvement body group 30 is formed in a substantially horizontal direction, the chemical solution injection rod 60 of the high-pressure jet agitating device 50 is in a substantially horizontal direction (lateral direction).

<Formation of ground improvement body>
In this embodiment, as shown in FIGS. 1 to 3, at a predetermined height, the step of forming the preceding ground improvement body 10 at a predetermined interval in the substantially horizontal direction is the same as the step of forming the chemical injection rod 60 at the same height. The ground improvement body group which becomes a series in a substantially horizontal direction by shifting the insertion position and the insertion depth and repeatedly performing the process of forming the subsequent ground improvement body 20 at a position different from the preceding ground improvement body 10. 30 is formed.

  For example, as shown in FIG. 4, the preceding ground improvement body 10 is formed at a predetermined interval in the insertion / removal direction of the chemical solution injection rod 60 at an arbitrary position. Subsequently, the construction position is shifted in the horizontal direction (the direction orthogonal to the insertion / removal direction of the chemical injection rod 60 (hereinafter the same)) at the same height, and the preceding ground is separated by a predetermined interval in the insertion / removal direction of the chemical injection rod 60. The improved body 10 is formed.

  Subsequently, the succeeding ground improvement body 20 is formed by repeating the same process in a region where the preceding ground improvement body 10 is not formed at the same height. And when formation of the ground improvement body group 30 in the same height is complete | finished, the process of forming the ground improvement body group 30 which shifts the position of a height direction and becomes a series in a substantially horizontal direction, as shown in FIG. By repeating, the ground improvement body group 30 is formed with respect to the whole abutment back embankment 80 used as improvement object.

  As another formation procedure of the ground improvement body, as shown in FIG. 5, when the preceding ground improvement body 10 is formed in the insertion / removal direction of the chemical injection rod 60 at an arbitrary position, the construction position is shifted in the lateral direction. The following ground improvement body 20 is formed at a position where the insertion depth of the chemical injection rod 60 is different from the formation position of the preceding ground improvement body 10. By repeating such steps, the ground improvement body group 30 is formed at the same height.

  Subsequently, in a region where the preceding ground improvement body 10 and the succeeding ground improvement body 20 are not formed at the same height, the ground improvement body group 30 which is a series at the same height is formed by repeating the same process. . And when formation of the ground improvement body group 30 in the same height is complete | finished, the process of forming the ground improvement body group 30 which shifts the position of a height direction and becomes a series in a substantially horizontal direction, as shown in FIG. By repeating, the ground improvement body group 30 is formed with respect to the whole abutment back embankment 80 used as improvement object.

  As shown in FIG. 2, it is preferable that the local board improvement body is formed so as to have a fan-like shape downward by injecting the chemical solution downward from the substantially horizontal direction. Thereby, collapse of the upper ground which forms the ground improvement body can be prevented. In addition, the ground improvement body group 30 including the preceding ground improvement body 10 and the following ground improvement body 20 may be formed from the upper side to the lower side, or may be formed from the lower side to the upper side.

  Moreover, as shown in FIG. 1, it is preferable to arrange | position the vacuum pipe | tube 70 along the chemical | medical solution injection rod 60, and to discharge mud from a chemical | medical solution injection | pouring part at the time of chemical | medical solution injection | pouring. Thereby, the pressure rise in the inside of a ground improvement body can be prevented, and the displacement (especially raising) of the abutment back embankment 80 used as improvement object can be suppressed.

  Moreover, it is preferable to inject a curing accelerator into the ground improvement body via the chemical solution injection rod 60 immediately after the formation of the local improvement body. Thereby, the setting time of a ground improvement body can be shortened, and the displacement of the abutment back embankment 80 which increases with time can be suppressed.

DESCRIPTION OF SYMBOLS 10 Prior ground improvement body 20 Trailing ground improvement body 30 Ground improvement body group 40 Scaffolding 50 High pressure injection stirring apparatus 60 Chemical solution injection rod 70 Vacuum pipe 80 Abutment back embankment 90 Abutment

Claims (3)

Insert a chemical injection rod into the abutment back embankment to be improved, and form a ground improvement body by high-pressure stirring injection method that injects the chemical into the abutment back embankment from the chemical injection rod to suppress settlement of the abutment back embankment. A construction method to be performed,
The step of forming the preceding ground improvement body at a certain interval in a substantially horizontal direction, and the insertion position and the insertion depth of the chemical injection rod are shifted at the same height, and the subsequent ground improvement body is moved to a different position. By repeating the step of forming a ground improvement body, a ground improvement body group that is a series in a substantially horizontal direction is formed,
By shifting the insertion height of the chemical solution injection rod and repeating the step of forming a series of ground improvement bodies in the substantially horizontal direction, the ground improvement body for the whole abutment back embankment to be improved A subsidence control method for backfilling of abutment, characterized by forming a group.   The method for suppressing settlement of an abutment backside embankment according to claim 1, wherein when injecting the chemical solution from the medicinal solution injection rod into the abutment backside embankment, the chemical solution is injected downward from a substantially horizontal direction. .   The method for suppressing settlement of an abutment backside embankment according to claim 1 or 2, wherein the chemical solution is injected into the abutment backside embankment while discharging mud from a chemical solution injecting portion of the medicinal solution injection rod.

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