JP6770398B2 - Subsidence suppression method for embankment on the back of the abutment - Google Patents

Description

The present invention relates to a method for suppressing the subsidence of the embankment on the back of the abutment, which is a connection between the abutment and the embankment. Specifically, the present invention is a method for suppressing the subsidence of the embankment by injecting an improved material into the embankment on the back of the abutment. It is about.

The embankment on the back of the abutment is prone to land subsidence and depression due to the loosening phenomenon of the ground caused by insufficient compaction during construction, aging deterioration of the embankment material, and outflow of the embankment material due to rainfall. In addition, when an earthquake occurs, the relative displacement between the pier and the back embankment becomes remarkable, which may reduce the running performance of trains and the like. In order to eliminate such a phenomenon, measures have been taken to inject a chemical solution such as cement milk into the embankment.

As a technique for reinforcing the embankment on the back surface of the abutment, for example, there are techniques described in Patent Document 1, Patent Document 2, and Patent Document 3. The technique described in Patent Document 1 removes the back embankment of the pier by an appropriate distance after installing a temporary line of the railroad and the road near the pier of the railroad and the road to interrupt the passage of the pier. A reinforced embankment will be constructed in the space at intervals from the back of the pier. Then, by placing back concrete between the back of the pier and the front of the reinforced embankment to integrate the pier and the reinforced embankment, the pier and the back embankment can be reinforced.

In the technique described in Patent Document 2, a rod-shaped reinforcing material is placed from the front surface of the abutment to the back embankment substantially parallel to the axial direction of the bridge girder. Furthermore, by placing a rod-shaped reinforcing material in the direction orthogonal to the axial direction of the bridge girder from the slope of the embankment, it is possible to reinforce the embankment and the embankment on the back of the pier while maintaining the traffic conditions of railways and rolling stock. It is said that it can be done.

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

Japanese Unexamined Patent Publication No. 2011-247060 Japanese Unexamined Patent Publication No. 2011-247064 JP 2015-55082

However, there are various problems that have not yet been solved by the above-mentioned conventional techniques. For example, as a countermeasure by injecting a chemical solution with cement milk or the like, it is necessary to inject the chemical solution at a pressure lower than the normal pressure in consideration of the influence on the train track. For this reason, it is difficult to effectively inject the chemical solution into the loosened area in the ground, and there are cases where the reliability of quality cannot be ensured.

In addition, since it is unknown where the loosened area in the ground exists, the number of constructions is often large when injecting chemicals. Therefore, as measures against loosening areas of the ground, it is conceivable to improve cement by mechanical stirring and cement improvement by high-pressure jet stirring. In the case of cement improvement by mechanical stirring, it is often possible to perform only a limited range of improvement, but high-pressure jet stirring is adopted in which cement milk is sprayed and stirred at high pressure (for example, 20 to 30 MPa) from a rod with a small diameter. If this is the case, it is possible to effectively take measures against the loosened area of the ground whose position is unclear.

However, when high-pressure jet agitation is performed horizontally, there is a high possibility that ground displacement (particularly subsidence phenomenon) will occur if the general construction method is used. In addition, there is a high possibility that the temporary loosening inside the improved body after construction will promote the displacement of the ground over time. Therefore, it is necessary to prevent the ground from being displaced during and immediately after the construction.

Further, in each prior art listed as the prior art document, there is room for further ingenuity, such as limited construction conditions and time-consuming construction.

The present invention has been proposed in view of the above circumstances, and there are few restrictions on the construction conditions, and the subsidence of the embankment on the back surface of the abutment is surely and easily suppressed with almost no displacement of the ground during and after the construction. The purpose is to provide a possible construction method.

The subsidence suppression method for the back embankment of the abutment according to the present invention has the following features in order to achieve the above-mentioned object. That is, the subsidence suppression method for the back embankment of the abutment according to the present invention is a high-pressure stirring injection method in which a chemical solution injection rod is inserted into the embankment on the back surface of the abutment to be improved and the chemical solution is injected from the chemical solution injection rod into the embankment on the back surface of the abutment. This is a construction method that forms a ground improvement body to suppress the subsidence of the embankment on the back of the pier.

In this subsidence suppression method, first, the step of forming the preceding ground improvement body at regular intervals in the substantially horizontal direction and the insertion position and insertion depth of the chemical injection rod at the same height are shifted to form the preceding ground improvement body. Is repeated to form a trailing ground improvement body at different positions to form a series of ground improvement bodies in a substantially horizontal direction.

Then, by shifting the insertion height of the chemical injection rod and repeating the process of forming a series of ground improvement bodies in a substantially horizontal direction, the ground improvement bodies are formed for the entire abutment back embankment to be improved. It is characterized by forming.

In the above-described method for suppressing the settlement of the back embankment of the abutment, when the chemical solution is injected into the embankment on the back surface of the abutment from the chemical injection rod, it is preferable to inject the chemical solution downward from the substantially horizontal direction.

Further, in the above-mentioned subsidence suppression method for the back embankment of the abutment, it is preferable to inject the chemical solution into the embankment on the back surface of the abutment while removing mud from the chemical injection portion of the chemical injection rod.

According to the subsidence suppression method for the back embankment of the abutment according to the present invention, the insertion position and insertion depth of the chemical injection rod are shifted at the same height as the step of forming the preceding ground improvement body at regular intervals in the substantially horizontal direction. By repeating the process of forming the trailing ground improvement body at a position different from that of the preceding ground improvement body, a series of ground improvement bodies is formed in a substantially horizontal direction, so that one unit of ground improvement is formed. Since the body formation process is divided in a staggered pattern and the ground to be improved is not disturbed at once over the entire length, it is possible to suppress the displacement of the embankment on the back of the abutment to be improved.

Further, by carrying out such a staggered division improvement, it becomes possible to surely form a ground improvement body over the entire embankment on the back surface of the abutment to be improved. Further, by carrying out such staggered division and improvement, the improved bodies in each region are formed independently, so that it is possible to prevent variations in the strength of the improved bodies.

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

In addition, when injecting the chemical solution from the chemical solution injection rod into the embankment on the back of the abutment, the chemical solution is injected downward from the substantially horizontal direction (so-called downward improvement), so that the chemical solution is not injected upward. , It is possible to prevent the upper ground forming the ground improvement body from collapsing, and it is possible to suppress the displacement of the embankment on the back surface of the abutment to be improved.

In addition, by draining 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 suppress the displacement (especially uplift) of the embankment on the back of the abutment to be improved. Become.

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

The side view explaining the subsidence suppression method of the embankment on the back of the abutment which concerns on embodiment of this invention. The front view explaining the subsidence suppression method of the embankment on the back surface of the abutment which concerns on embodiment of this invention. The plan view explaining the settlement suppression method of the embankment on the back surface of the abutment which concerns on embodiment of this invention. The explanatory view which shows the procedure of forming the ground improvement body in the subsidence suppression method of the embankment on the back surface of the abutment which concerns on embodiment of this invention. The explanatory view which shows the procedure of forming the ground improvement body in the subsidence suppression method of the embankment on the back surface of the abutment which concerns on embodiment of this invention. A schematic cross-sectional view of the embankment on the back of the abutment as seen from the side. A schematic cross-sectional view of the embankment on the back of the abutment as seen from the front.

Hereinafter, the subsidence suppression method for the embankment on the back surface of the abutment according to the embodiment of the present invention will be described with reference to the drawings. 1 to 5 show a method of suppressing the settlement of the back embankment of the abutment according to the 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. 4 and 5 are. It is explanatory drawing which shows the procedure of forming the ground improvement body. 6 and 7 are schematic cross-sectional views of the embankment on the back of the abutment.

<Outline of subsidence suppression method for embankment on the back of the pier>
The subsidence suppression method for the back embankment of the abutment according to the embodiment of the present invention is to form a ground improvement body inside the back embankment 80 of the abutment by using a high pressure injection stirring method, and precedes the embankment in the substantially horizontal direction at regular intervals. By forming the ground improvement body 10 and the trailing ground improvement body 20 in a staggered manner, the ground improvement body group 30 having the same height is formed. Then, by shifting the position in the height direction and repeatedly forming the ground improvement group 30 which is a series in the substantially horizontal direction, the ground improvement group 30 is formed with respect to the entire abutment back embankment 80 to be improved. It is designed to do. In particular, by using the high-pressure injection stirring method for forming the ground improvement body, it is possible to reliably form the ground improvement body in the loosened area of the ground whose position is unclear.

<Embankment on the back of the pier>
The abutment 90 is a foundation structure that supports an upper structure such as a railway bridge, and an embankment (embankment 80 on the back of the abutment) 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 by using a high-pressure injection stirring method. For example, the height of the abutment back embankment 80 is about 3 m, and the ground improvement group 30 formed inside is formed over about 1 m from the upper surface of the abutment back embankment 80 and about 5 m from the back of the abutment 90.

<Installation of construction machine>
Prior to forming the ground improvement group 30 inside the embankment 80 on the back of the abutment, a scaffold 40 for installing construction equipment is constructed. For example, as shown in FIG. 1, a scaffold 40 is assembled on the side of the embankment 80 on the back surface of the abutment using a single pipe or the like. In the present embodiment, since the positions in the height direction are shifted to form a plurality of ground improvement body groups 30 in a series in the substantially horizontal 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 by using a single pipe or the like which is easy to assemble and disassemble.

Further, in the present embodiment, since the construction equipment smaller than the construction equipment used in the general high-pressure injection stirring method (for example, the machine weight is about 1.0 ton) is used, it is sufficient that the strength is commensurate with the construction equipment. .. The height of the scaffold 40 is sequentially increased or decreased in accordance with the formation process of the ground improvement group 30.

Although not shown in detail on the scaffold 40, as construction equipment for forming the ground improvement body group 30, a small high-pressure injection agitator 50, a power supply device, a compressor, a hardening agent, water, and the like are sent out. Install pumps, vacuum devices to promote mud drainage, etc. In the present embodiment, in order to form the ground improvement body group 30 in the substantially horizontal direction, the chemical solution injection rod 60 of the high-pressure injection stirring device 50 is in the substantially horizontal direction (horizontal direction).

<Formation of ground improvement body>
In the present embodiment, as shown in FIGS. 1 to 3, the chemical solution injection rod 60 is formed at the same height as the step of forming the preceding ground improvement body 10 at a predetermined height at regular intervals in the substantially horizontal direction. By repeating the process of forming the trailing ground improvement body 20 at a position different from that of the preceding ground improvement body 10 by shifting the insertion position and the insertion depth, the ground improvement body group becomes a series in a substantially horizontal direction. Form 30.

For example, as shown in FIG. 4, the preceding ground improvement body 10 is formed at an arbitrary position at a predetermined interval in the insertion / removal direction of the chemical solution injection rod 60. Subsequently, the construction position is shifted in the lateral direction (direction orthogonal to the insertion / removal direction of the chemical injection rod 60 (the same applies hereinafter)) 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 trailing ground improvement body 20 is formed by repeating the same steps in the region where the preceding ground improvement body 10 is not formed at the same height. Then, when the formation of the ground improvement body group 30 at the same height is completed, the position in the height direction is shifted, and as shown in FIG. 2, a step of forming a series of ground improvement body groups 30 in the substantially horizontal direction is performed. By repeating this, the ground improvement group 30 is formed on the entire abutment back embankment 80 to be improved.

Further, as another procedure for forming 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 solution injection rod 60 at an arbitrary position, the construction position is shifted in the lateral direction. The trailing 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 a process, the ground improvement group 30 is formed at the same height.

Subsequently, in a region where the preceding ground improvement body 10 and the trailing ground improvement body 20 are not formed at the same height, a series of ground improvement bodies 30 are formed at the same height by repeating the same steps. .. Then, when the formation of the ground improvement body group 30 at the same height is completed, the position in the height direction is shifted, and as shown in FIG. 2, a step of forming a series of ground improvement body groups 30 in the substantially horizontal direction is performed. By repeating this, the ground improvement group 30 is formed for the entire abutment back embankment 80 to be improved.

As shown in FIG. 2, it is preferable to form the improved body in each place so as to form a fan shape downward by injecting the chemical solution downward from the substantially horizontal direction. This makes it possible to prevent the upper ground that forms the ground improvement body from collapsing. The ground improvement body group 30 including the preceding ground improvement body 10 and the trailing ground improvement body 20 may be formed from the upper side to the lower side or from the lower side to the upper side.

Further, as shown in FIG. 1, it is preferable that the vacuum pipe 70 is arranged along the chemical solution injection rod 60 to drain mud from the chemical solution injection portion at the time of chemical solution injection. As a result, it is possible to prevent the pressure increase inside the ground improvement body and suppress the displacement (particularly uplift) of the abutment back embankment 80 to be improved.

In addition, it is preferable to inject the hardening accelerator into the ground improvement body via the chemical injection rod 60 immediately after forming the various board improvement bodies. As a result, the setting time of the ground improvement body can be shortened, and the displacement of the abutment back embankment 80, which increases with time, can be suppressed.

10 Preceding ground improvement body 20 Trailing ground improvement body 30 Ground improvement body group 40 Scaffolding 50 High-pressure injection agitator 60 Chemical injection rod 70 Vacuum pipe 80 Bridge back embankment 90 Bridge

Claims (3)

A ground improvement body is formed by a high-pressure stirring injection method in which a chemical injection rod is inserted into the embankment on the back of the abutment to be improved and the chemical is injected into the embankment on the back of the abutment from the chemical injection rod to suppress subsidence of the embankment on the back of the abutment. It is a construction method to be performed
The step of forming the preceding ground improvement body at a constant interval in the substantially horizontal direction and the insertion position and insertion depth of the chemical solution injection rod are shifted at the same height to move backward to a position different from the preceding ground improvement body. By repeating the process of forming the ground improvement body, a series of ground improvement bodies is formed in a substantially horizontal direction.
By shifting the insertion height of the chemical solution injection rod and repeating the step of forming a series of ground improvement bodies in a substantially horizontal direction, the ground improvement body is used for the entire abutment back embankment to be improved. A subsidence control method for the embankment on the back of the abutment, which is characterized by forming a group. The method for suppressing the settlement of the back embankment of the abutment according to claim 1, wherein when the chemical is injected into the embankment on the back of the abutment from the chemical injection rod, the chemical is injected downward from the substantially horizontal direction. .. The method for suppressing subsidence of the embankment on the back surface of the abutment according to claim 1 or 2, wherein the chemical solution is injected into the embankment on the back surface of the abutment while draining mud from the chemical solution injection portion of the chemical solution injection rod.

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