JP2008248649A - Soil improvement method in vicinity of underground structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly decide a soil improvement area in a soil improvement method for the vicinity of an underground structure when a track is constructed on the earth surface. <P>SOLUTION: In this soil improvement method, a method for constructing a box culvert 1 serving as an underground structure is investigated for specifying whether it is constructed by an open-cut method or a non-open-cut method. Subsequently, if the box culvert 1 is constructed by the open-cut method, a virtual slope 3 diagonally extending upward from the lower edge of an earth retaining wall 2 built in construction to the earth surface on the opposite side to the box culvert 1 is assumed, and a triangular cross section area surrounded by the virtual slope, a vertical plane wherein the earth retaining wall 2 is built, and the earth surface is decided as a soil improvement area 4a. If the box culvert 1 is constructed by a pipe jacking method, a cylindrical cross section area spread from the circumferential face of the box culvert 1 to the position separated by a distance d equivalent to a wall thickness of the box culvert is decided as a soil improvement area 5. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention mainly relates to a ground improvement method in the vicinity of underground structures when a track is laid on the ground surface.

  Tunnel-like underground structures built in transportation tunnels, sewer tunnels, urban common trenches and other grounds are constructed in various uses and scales. It is roughly divided into the open-cut method.

  The excavation method is a method of constructing mountain retaining walls and digging between them, laying underground structures at the bottom of the root, and then backfilling the surroundings.

  On the other hand, the non-cut-off method is employed when the open-cut method cannot be adopted due to roads, railways and other circumstances existing on the ground, and is classified into a shield method, a propulsion method, a traction method, and the like.

JP-A-1-226913

  Here, regardless of whether it is an open-cut method or a non-open-cut method, if a track is laid on the ground surface on which the underground structure is constructed, ground subsidence may occur due to a moving load when the vehicle passes.

  In such a case, from the viewpoint of vehicle running safety, the ground spreading around the underground structure must be improved to increase the ground strength.

  However, in the past, there is no specific indication of how much ground should be improved around the underground structure, and therefore, ground improvement that is too safe is performed, resulting in uneconomical construction. There was a problem that it had to be.

  The present invention has been made in consideration of the above-described circumstances, and an object of the present invention is to provide a ground improvement method in the vicinity of an underground structure that can appropriately determine a ground improvement range.

  In order to achieve the above object, the ground improvement method in the vicinity of the underground structure according to the present invention is the ground improvement method for improving the ground spreading around the underground structure as described in claim 1,

  Investigate the construction method where the underground structure was constructed,

  When the construction method is an open-cut method, assuming a virtual slope extending obliquely upward from the lower edge of the retaining wall built at the time of construction toward the ground surface opposite to the underground structure, The triangular cross-sectional area surrounded by the vertical surface and the ground surface where the mountain retaining wall was built as a ground improvement area,

  When the construction method is a non-cutting construction method, a cylindrical cross-sectional area extending from the peripheral surface of the underground structure to a position separated by a distance corresponding to the wall thickness of the underground structure is defined as a ground improvement area. ,

  The ground improvement area is ground improved.

  In the ground improvement method in the vicinity of the underground structure according to the present invention, the angle formed between the virtual slope and the horizontal plane is an internal friction angle or repose angle determined from the soil properties of the ground in the triangular cross-sectional area. is there.

  Further, the ground improvement method in the vicinity of the underground structure according to the present invention, as described in claim 3, in the ground improvement method for improving the ground spreading around the underground structure constructed by the open-cut method,

  Assuming a virtual slope extending obliquely upward from the lower edge of the retaining wall built at the time of construction toward the ground surface opposite to the underground structure, the vertical slope where the virtual slope and the retaining wall were built The ground improvement is performed using the triangular cross-sectional area surrounded by the surface and the ground surface as the ground improvement area.

  Further, the ground improvement method in the vicinity of the underground structure according to the present invention, as described in claim 4, in the ground improvement method for improving the ground spreading around the underground structure constructed by the non-opening method,

  The ground improvement is performed using a cylindrical cross-sectional area extending from the peripheral surface of the underground structure to a position separated by a distance corresponding to the wall thickness of the underground structure as a ground improvement area.

  In the ground improvement method in the vicinity of the underground structure according to the present invention, first, the construction method in which the underground structure was constructed was investigated as necessary, whether it was constructed by the open-cut method or was constructed by the non-open-cut method. To identify.

  Here, the excavation method is a method of constructing a retaining wall, excavating, building an underground structure in the excavated space, and then refilling the excavated space. It is common to build underground structures by installing mountain retaining walls on both sides, but if earth retaining using existing structures is possible, it is not always necessary to build mountain retaining walls on both sides In addition, the excavation method of the present invention also includes a case where the underground structure is constructed by installing the retaining wall only on one side of the construction planned region.

  Non-open cutting methods include shield method, propulsion method and traction method. Here, in the shield method, the strength reduction caused by the disturbance of the surrounding ground caused when the shield machine moves forward occurs in the case of press-fitting or towing the box or element in the propulsion method and the traction method. Improving the strength reduction due to disturbance of the surrounding ground is the purpose of ground improvement.

  The shield method is a method of assembling the segments from the tail side while excavating the ground in front with a shield machine, and the propulsion method using a box is a hydraulic propulsion jack installed on a start-up shaft. In addition to excavating the ground at the tip, the box is pushed into the ground one after another while connecting the boxes at the rear end. In this method, the hollow space is formed in the space surrounded by them. The element may be pressed into the ground not only by towing but also by propulsion.

  The box means a cylindrical member that is configured so that it can be continuously joined in the material axis direction, and in which the hollow passage is integrally formed in the joined state. For example, a box culvert or a tube corresponds to the box.

  If the construction method in which the underground structure is constructed is specified, the ground improvement area is determined as follows, depending on which of them is used.

  In other words, if the underground structure was constructed by the open-cut method, a hypothetical slope extending diagonally upward from the lower edge of the retaining wall built at the time of construction toward the ground surface opposite to the underground structure was assumed. A triangular cross-sectional area surrounded by the vertical plane where the virtual slope and the retaining wall are built and the ground surface is defined as a ground improvement area.

  Here, the angle formed between the virtual slope and the horizontal plane is the internal friction angle determined from the soil properties of the ground in the triangular cross-sectional area, and the repose angle on the safer side.

  On the other hand, if the underground structure is constructed by the non-open cutting method, a cylindrical cross section that extends from the peripheral surface of the underground structure to a position separated by a distance corresponding to the wall thickness of the underground structure. The area is the ground improvement area.

  Next, ground improvement is performed on the specified ground improvement area.

  If it does in this way, it will become possible to set appropriately the ground area which has loosened according to a construction method, and it can improve a necessary and sufficient ground area.

  Embodiments of a ground improvement method in the vicinity of an underground structure according to the present invention will be described below with reference to the accompanying drawings. Note that components that are substantially the same as those of the prior art are assigned the same reference numerals, and descriptions thereof are omitted.

  FIG. 1 is a flowchart showing a ground improvement method in the vicinity of an underground structure according to the present embodiment. As can be seen in the figure, in the ground improvement method according to this embodiment, first, the construction method in which the underground structure was constructed was investigated, and whether it was constructed by the open-cut method or non-open-cut method. Specify (step 101).

  Fig.2 (a) is sectional drawing which showed the condition at the time of construction in case the box culvert 1 which is an underground structure was constructed by the open-cut method. To construct the box culvert 1 using the open-cut method, build the retaining walls 2 and 2, then dig down the space surrounded by the retaining walls, construct the box culvert 1 in the excavated space, and finally dig Refill the space.

  FIG. 5B is a cross-sectional view showing the situation at the time of construction when the box culvert 1 is constructed by the propulsion method which is a non-open cutting method. In order to construct the box culvert 1 by the propulsion method which is a non-open-cut method, the block body which is a component of the box culvert 1 is pushed into the ground with a propulsion jack (not shown) installed on the start shaft, By excavating the natural ground, the block bodies are pushed into the ground one after another while being connected at the rear end.

  If the construction method in which the box culvert 1 is constructed is specified, the ground improvement area is determined as follows, depending on which of them is used.

  That is, if the box culvert 1 is constructed by the open-cut method (step 102, YES), it is obliquely upward from the lower edge of the retaining wall 2 built during construction toward the ground surface opposite to the box culvert 1 Assuming an extending virtual slope 3, a triangular cross-sectional area surrounded by the virtual slope and the vertical surface where the retaining wall 2 is built and the ground surface is defined as a ground improvement area 4a (step 103).

  Here, the angle θ formed by the virtual slope 3 and the horizontal plane is an internal friction angle determined from the soil properties of the ground in the triangular cross-sectional area, and a repose angle on the safer side, for example, 30 degrees.

  Of course, the backfill region 4b sandwiched between the retaining walls 2 and 2 is an object of ground improvement.

  On the other hand, if the box culvert 1 is constructed by the propulsion method (step 102, NO), the cylinder that extends from the peripheral surface of the box culvert 1 to a position separated by a distance d corresponding to the wall thickness of the box culvert. The cross-sectional area is designated as ground improvement area 5 (step 104).

  Next, the ground improvement is performed on the ground improvement area 4a and the backfilling region 4b in the case of the open-cut method, and the ground improvement area 5 is performed in the case of the non-cut-off method (step 105). The injection material and the injection method used for ground improvement can be appropriately selected from known ones. For example, the injection material may be appropriately selected from a chemical system such as a polymer system or a water glass system, or a non-chemical system such as cement milk or bentonite.

  For ground improvement, it is sufficient to return soil loosening due to excavation and disturbance during box culvert construction to the state before construction, and any further improvement may be performed as necessary.

  As described above, according to the ground improvement method in the vicinity of the underground structure according to the present embodiment, the ground improvement is performed depending on whether the construction method in which the box culvert 1 is constructed is an open-cut method or a non-cut-open method. Since the area 4a or 4b is selected and determined, it is possible to appropriately set the ground area where the looseness has occurred according to the construction method, and the necessary and sufficient ground area can be improved.

  Next, an indoor experiment demonstrating the ground improvement method according to the present invention will be described.

  The experimental model is shown in FIG. As shown in the figure, the experiment was carried out using silica sand No. 6 (Gs = 2.652, emax = 0.903, emin = 0.582) in a fixed soil tank having a width of 210 cm, a height of 60 cm and a depth of 100 cm. A model embankment having a height of 25 cm and a gradient of 1: 1.5 was prepared, and a cross-sectional structure model under the track having a width of 40 cm, a height of 20 cm, and a depth of 60 cm was installed at the center.

  Here, 16 divided two-way load cells were arranged around the crossing structure model under the track, and normal force and tangential force acting on the structure were measured. In addition, accelerometers and displacement meters were installed on the embankment to measure dynamic behavior. The sampling frequency is 500 Hz.

  The experiment was conducted for three cases with different ground conditions around the structure, and the characteristics of the external force acting on the crossing structure under the track due to the difference in embankment properties and the installation position of the structure under the track were verified. A sine wave (3 Hz) was used as the input wave, and the acceleration was continuously increased to 400 gal every 10 waves with 100 gal as an initial value. The excitation direction is the line direction.

  The embankment was made of wet sand (water content ratio 10%) with a relative density Dr = 80% as a target. The slack area was created with a target of Dr = 40%.

  A graph showing the relationship between the excitation time and the settlement rate is shown in FIG. As can be seen in the figure, with 20 seconds of vibration, the settlement rate is approximately 0.003 with the open-cut method and approximately 0.001 with the non-cut method, but when the ground is improved, it is about 0.0002. It can be seen that it is improved.

  FIG. 5 is a graph showing the results of analyzing the above-described experiment. As can be seen from Fig. 5 (a), in the excavation method, the ground sinks about -30mm in the vicinity of the retaining wall, and the amount of settlement decreases as it moves away from the retaining wall. However, it can be said that the result of the analysis performed separately represents the result of this experiment.

  In addition, as can be seen in FIG. 5 (b), in the non-open cutting method, the subsidence amount is -20 mm at the maximum at the center of the underground structure, and decreases as the distance from the center decreases. When the wall thickness of the underground structure is separated, it is almost negligible. However, the results of the analysis performed separately can be said to represent the experimental results well, similar to the open-cut method.

  In this embodiment, the construction method in which the underground structure was constructed was investigated, and the ground improvement area was determined separately depending on whether the construction method was an open-cut method or a non-cut-off method. If the method is already known, the step of investigating the method may be omitted.

  In such a configuration, the ground improvement area may be specified by a method corresponding to each construction method, and the ground improvement may be performed on the specified ground improvement area.

The flowchart which showed the procedure of the ground improvement method which concerns on this embodiment. Explanatory drawing which showed how to determine a ground area area. It is the figure which showed the fixed soil tank used for experiment, and a structure model under a track, (a) is a top view, (b) is a sectional view which meets an AA line, (c) is along a BB line Sectional drawing. The graph which showed the relationship between excitation time and settlement rate. It is the graph which showed the settlement amount obtained by experiment and analysis, (a) is the graph which showed the settlement amount of the open-cut method, (b) The graph which showed the sink amount of the non-cut method.

Explanation of symbols

1 Box culvert (underground structure)
2 Mountain retaining wall 3 Virtual slope 4a Ground improvement area 5 Ground improvement area

Claims (4)

In the ground improvement method for improving the ground spreading around underground structures,
Investigate the construction method where the underground structure was constructed,
When the construction method is an open-cut method, assuming a virtual slope extending obliquely upward from the lower edge of the retaining wall built at the time of construction toward the ground surface opposite to the underground structure, The triangular cross-sectional area surrounded by the vertical surface and the ground surface where the mountain retaining wall was built as a ground improvement area,
When the construction method is a non-cutting construction method, a cylindrical cross-sectional area extending from a peripheral surface of the underground structure to a position separated by a distance corresponding to the wall thickness of the underground structure is defined as a ground improvement area. ,
A ground improvement method in the vicinity of an underground structure, wherein the ground improvement area is improved. The ground improvement method according to claim 1, wherein an angle formed between the virtual slope and a horizontal plane is an internal friction angle or a repose angle determined from a soil property of the ground in the triangular cross-sectional area. In the ground improvement method to improve the ground spreading around the underground structure constructed by the open-cut method,
Assuming a virtual slope extending obliquely upward from the lower edge of the retaining wall built at the time of construction toward the ground surface opposite to the underground structure, the vertical slope where the virtual slope and the retaining wall were built A ground improvement method in the vicinity of an underground structure, characterized by performing ground improvement using a triangular cross-sectional area surrounded by a surface and a ground surface as a ground improvement area. In the ground improvement method to improve the ground spreading around the underground structure constructed by the non-open cutting method,
A ground improvement is performed using a cylindrical cross-sectional area extending from a peripheral surface of the underground structure to a position separated by a distance corresponding to a wall thickness of the underground structure as a ground improvement area. Ground improvement method near the structure.

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