JP7602501B2 - Embankment construction method - Google Patents

Description

The present invention relates to a method for constructing embankments for use in railways and other applications, and more specifically, to a method for constructing embankments using liquefied soil.

For example, railway embankments, by their very nature, often require construction in places with poor workability, such as narrow areas, or in limited time slots, such as at night, so there is a demand for labor-saving and rapid construction. In addition, with the increase in damage from torrential rains in recent years, there is also a growing demand for the early restoration of collapsed embankments.

Fluidized soil, which is made by mixing construction waste soil with water, cement, and other solidifying agents, has high fluidity and filling properties, and using fluidized soil as an embankment material can reduce the labor required for embankment construction and speed up the process compared to using soil materials.

When constructing embankments using liquefied treated soil, it is necessary to set up formwork on the sides to prevent the soil from flowing out when it is poured. Traditionally, large sandbags or PC retaining walls have been used as formwork. However, large sandbags are merely temporary materials and cannot be used as permanent structures, so when large sandbags are used, they must be removed after the liquefied treated soil has hardened and the slope must be constructed. On the other hand, PC retaining walls are limited in size due to transportation and construction, and it takes a long time to construct a large PC retaining wall. Therefore, these methods do not fully utilize the advantages of using liquefied treated soil as an embankment material, such as labor-saving and rapid construction.

As an example of a method for constructing embankments using liquefied treated soil, Patent Document 1 discloses a method for constructing embankments in which liquefied treated soil is poured into a dam made of multiple boxes or bags filled with a filling material.

JP 2002-21083 A

However, liquefied treated soil has the tendency to deteriorate due to external factors such as water retention from rainwater and drying out due to the outside air. For example, to ensure that it can support the load of trains over the long term as railway embankments, it is necessary to have a method of protecting it from these external factors and improving its durability.

The present invention was made in consideration of the above circumstances, and aims to provide a method for constructing embankments using liquefied treated soil that allows for simple and quick construction and is durable against external factors such as water retention from rainwater and drying.

In order to solve the above problems, the present invention provides a method for constructing embankments using liquefied treated soil, which comprises placing bags around the periphery of an embankment construction site, filling the inside of the bags with filler to form a bag formwork, stacking the bag formwork to the height of the first stage, and then pouring the first stage of liquefied treated soil up to the top height of the bag formwork. After the first stage of liquefied treated soil has hardened to a predetermined uniaxial compressive strength, a bag formwork is installed on top of the first stage of liquefied treated soil, as in the first stage, and the bag formwork is stacked to the height of the second stage and the second stage of liquefied treated soil is poured. This process is repeated until the liquefied treated soil has been poured to a predetermined height, after which the upper end of the top layer of the liquefied treated soil is covered with a protective layer having drainage, water retention and load dispersion effects, and the protective layer is composed of two types of layers with different permeabilities, with a lower layer with high permeability directly above the liquefied treated soil and an upper layer with low permeability above that .
Another aspect of the present invention is a method for constructing embankments using liquefied treated soil, which comprises placing bags around the periphery of an embankment construction site, filling the inside of the bags with filler to form a bag formwork, stacking the bag formwork to the height of the first stage, and then pouring the first stage of liquefied treated soil up to the top height of the bag formwork, and after the first stage of liquefied treated soil has hardened to a predetermined uniaxial compressive strength, dismantling the first stage of the bag formwork, placing the bags of the dismantled bag formwork on top of the first stage of liquefied treated soil, filling the inside of the bags with filler to form a bag formwork, and pouring the second stage of liquefied treated soil, and repeating this process to pour the liquefied treated soil up to a predetermined height, and then covering the upper end of the topmost layer of the liquefied treated soil with a protective layer that has drainage, water retention and load distribution effects.

The 28-day unconfined compressive strength of the liquefied soil may be 600 kPa or more.

The unconfined compressive strength of the poured liquefied treated soil when it hardens can be determined by measuring the subgrade reaction coefficient of the liquefied treated soil in a small-scale FWD test, determining the deformation coefficient from the relationship between the subgrade reaction coefficient and the deformation coefficient, and then determining the unconfined compressive strength of the liquefied treated soil from the relationship between the deformation coefficient and the uniaxial compressive strength.

A rod-shaped reinforcing material may be provided, one end of which is fixed to the bag formwork and the other end of which is fixed within the liquefied treated soil.

The bag may be made of synthetic fibers.

The filler may be concrete.

A retaining wall may be provided on the slope of the embankment. The embankment may also be a railway embankment.

According to the present invention, it is possible to easily and quickly construct embankments using liquefied treated soil that are durable against external factors such as rainwater retention and drying, and that can be used for railways and other purposes.

FIG. 2 is a perspective view showing an example of a bag form used in the present invention. FIG. 2 is a cross-sectional view illustrating an example of a construction procedure for embankment according to an embodiment of the present invention. 1 is a graph showing the relationship between the subgrade reaction coefficient _KP.FWD value and the deformation coefficient _E50 . 1 is a graph showing the relationship between unconfined compressive strength q _u and deformation modulus E ₅₀ . FIG. 1 is a cross-sectional view showing an example of construction of a railway embankment. FIG. 1 is a perspective view showing an example of a reinforcement method when constructing a steeply sloping embankment. FIG. 11 is a cross-sectional view showing an example of construction of a steep embankment. FIG. 13 is a perspective view showing an example of an anchoring rebar having an anchoring portion at its tip. 13 is an oblique view showing an example in which long anchoring members are attached to the ends of multiple anchoring steel bars. FIG. 10A to 10C are cross-sectional views for explaining an example of a construction procedure for embankment according to a different embodiment of the present invention.

The following describes an embodiment of the present invention with reference to the drawings. In this specification and the drawings, elements having substantially the same functional configuration are designated by the same reference numerals to avoid redundant description.

Figure 1 shows an example of a bag formwork 2 used in the present invention. The bag formwork 2 is formed by placing a bag body 2a around the periphery of the area where the embankment is to be constructed, and then filling the interior of the bag body 2a with a filling material such as concrete through an injection port 2b. The bag formwork 2 can be used as is as the main structure of the embankment after construction of the embankment, and the bag body 2a is preferably made of a material with excellent weather resistance and strength, such as synthetic fiber. In addition, the bag body 2a before being filled with the filling material is preferably light enough to be folded, for example, and transported and set up manually.

Below, an example of the procedure for the embankment construction method according to an embodiment of the present invention will be described with reference to Figure 2. This embodiment is a method for constructing embankments for railways.

First, a bag body 2a made of synthetic fiber, for example, is placed at a predetermined position on-site, and a filler such as concrete is filled into the bag body 2a and shaped into the shape shown in FIG. 1 to form the bag body formwork 2. The filler is pressed in, for example, by a pump truck. The bag body formwork 2 filled with the filler has a height of, for example, about 500 mm. The width is determined according to the width and height of the embankment to be constructed, the unit volume weight of the filler, and the like, and is, for example, about 1,000 to 4,000 mm, so as to be able to resist the lateral pressure when pouring the liquefied treated soil. The longitudinal dimension of the bag body formwork 2 is not particularly limited, but it may be an elongated shape arranged along the longitudinal direction of the embankment, for example, about 50 m.

Next, another bag 2a is placed on top of the bag form 2 filled with the filler, and the filler is filled in the same way to form the bag form 2. Then, for example, when the two bag form 2 are stacked, curing is performed until the filler hardens. When concrete with a nominal strength of 24 N/ ^mm2 is used as the filler, curing for about one day is recommended. In the same manner, as shown in Fig. 2(a), bag form 2 is piled up on both ends of the embankment to a height of, for example, about 2 m. In the embodiment of Fig. 2(a), four layers of bag form 2 with a height of 500 mm are stacked.

Then, between the bag-shaped forms 2 piled up to a predetermined height as the first stage, liquefied treated soil 3 is poured up to the top height of the bag-shaped forms 2 (FIG. 2(b)). The liquefied treated soil 3 may be a general one made by mixing construction waste soil with water and cement or other solidifying materials. Conventionally, when using liquefied treated soil as a railway embankment material, there is no clear regulation regarding the design standard strength of the liquefied treated soil. For example, in the tunnel invert section, liquefied treated soil with a uniaxial compressive strength of about 6,000 kPa was used in consideration of sufficient safety. However, in recent years, experimental research by the inventors has confirmed that if a protective layer is provided on the embankment made of liquefied treated soil and the uniaxial compressive strength q _u of about 600 kPa or more, the structure can withstand the repeated action of train loads. In this embodiment, liquefied treated soil 3 with a 28-day strength of 1,200 kPa is used.

The poured liquefied treated soil 3 is allowed to harden until it reaches an unconfined compressive strength determined according to the weight of the bag formwork 2, etc. In this embodiment, it is allowed to harden until the unconfined compressive strength reaches approximately 50 kPa. For example, if the mix is designed for a 28-day strength of 1,200 kPa, it will usually reach 50 kPa or more after about one day of age.

To perform the uniaxial compression test, a dedicated testing machine is required, which takes time, and the number of specimens for the uniaxial compression test is limited, making it difficult to perform a test that reflects the on-site conditions. Therefore, in this embodiment, a small-scale FWD test is used as a method for easily confirming the strength of the liquefied treated soil 3 after casting at the site. First, the ground reaction coefficient _KP.FWD value is measured by the small-scale FWD test, and the deformation coefficient _E50 is obtained from the relationship between the ground reaction coefficient _KP.FWD value and the deformation coefficient _E50 as shown in FIG. 3. Furthermore, the uniaxial compressive strength _qu is obtained from the relationship between the previously confirmed uniaxial compressive strength _qu and the deformation coefficient _E50 as shown in FIG. 4. The strength of the liquefied treated soil 3 can be grasped from the uniaxial compressive strength _qu thus obtained.

Once it is confirmed that the liquefied treated soil 3 has hardened to a predetermined strength, the bag formwork 2 is piled on top of it in the same manner as described above at a position that provides a predetermined slope as the second layer (Fig. 2(c)), and then liquefied treated soil 3 with a composition that has a 28-day strength of 1,200 kPa is poured up to the height of the top of the bag formwork 2 (Fig. 2(d)). In this embodiment, the height of one layer of liquefied treated soil 3 poured at once is 2 m, and the stacking of the bag formwork 2 and pouring of liquefied treated soil 3 are repeated in three layers as shown in Figs. 2(e) and (f). When pouring the top layer of liquefied treated soil 3, a specimen for a uniaxial compression test to be tested after construction of the embankment is taken.

As shown in Figure 2 (f), after the casting of the third layer of liquefied treated soil 3 is completed, heavy machinery work is carried out to lay railway tracks and the like on the liquefied treated soil 3. In this embodiment, when carrying out this heavy machinery work, the uniaxial compressive strength q _{u of the liquefied treated soil 3 is set to 100 kPa or more so that general spreading and compaction machines can work on the liquefied treated soil 3. In the case of liquefied treated soil 3 with a composition having a 28-day strength of 1,200 kPa, the uniaxial compressive strength q u usually} reaches 100 kPa or more after about 2 days of curing.

If the unconfined compressive strength q _u of the topmost liquefied treated soil 3 after curing for about two days does not reach 100 kPa, curing is continued for another day or so and a small-scale FWD test is conducted again to confirm the unconfined compressive strength q _u of the liquefied treated soil 3. This process is repeated until the desired strength is confirmed.

When it is confirmed that the uniaxial compressive strength q _u is 100 kPa or more, a protective layer 4 is constructed on the top surface of the liquefied treated soil 3 of the top layer to prevent rainwater from accumulating, protect against drying, and disperse train loads, etc. In this embodiment, the protective layer 4 is formed by stacking two types of layers 5 and 6 with different permeabilities, as shown in FIG. 2(g), and the lower layer 5 directly above the liquefied treated soil 3 is made to have high permeability, for example, a coarse gravel layer, and the upper layer 6 is made to have fine sand. By lowering the permeability of the upper layer 6 in this way, drainage at the upper layer 6 and the boundary between the upper layer 6 and the lower layer 5 is promoted, and rainwater is less likely to soak into the liquefied treated soil 3 through the lower layer 5. The thickness of the entire protective layer 4 is, for example, about 300 mm. The protective layer 4 can also prevent the liquefied treated soil 3 from drying excessively and disperse the load of trains, etc. The protective layer 4 is provided in an area that covers at least the upper surface of the liquefied treated soil 3, and may also cover the upper surface of the bag formwork 2 as shown in Fig. 5(a). In this way, the upper surface of the liquefied treated soil 3 is protected by the protective layer 4, and the sides are protected by the bag formwork 2 to form an embankment 10.

Furthermore, when used as a railway embankment, a crushed stone roadbed 7 and a track 8 are constructed on the upper surface of the protective layer 4 as shown in Fig. 5. Then, a uniaxial compression test is performed on the uniaxial compression test specimen taken when pouring the topmost liquefied treated soil 3, and it is confirmed that the uniaxial compressive strength q _{u of the liquefied treated soil 3 is a predetermined strength, i.e., 1,200 kPa or more in this embodiment. After the uniaxial compressive strength q u is} confirmed, it is confirmed that the support performance for train operation is secured by running a test train, etc., and train operation is started.

As described above, according to this embodiment, the bag body 2a, which can be transported and installed manually, is placed along the area of the embankment 10, and the filler is pressed into the bag body 2a using a pump truck or the like, allowing the bag body formwork 2 to be easily installed. Furthermore, since the installed bag body formwork 2 can be used as the main structure as is, removal of the formwork and slope work can be omitted. This allows the construction period to be shortened and the embankment to be constructed quickly. Furthermore, if concrete is used as the filler for the bag body formwork 2, a weed-prevention effect on the slope can also be expected.

Furthermore, by constructing a protective layer 4 on the top surface of the liquefied treated soil 3, the liquefied treated soil 3 is protected from external factors such as rainwater retention and drying due to the outside air, improving the durability of the liquefied treated soil 3 and also having the effect of dispersing the train load. Therefore, while liquefied treated soil with a 28-day strength q _u28 of about 6,000 kPa has been used in the past in tunnel invert sections, it is now possible to use liquefied treated soil with lower strength (q _u28 = 600 kPa or more, for example 1200 kPa), improving versatility. The sides of the liquefied treated soil 3 can be protected from external factors by leaving the continuous bag formwork 2 in place.

Furthermore, by checking the strength of the liquefied treated soil 3 using a small-scale FWD test, it is possible to evaluate the strength of the liquefied treated soil 3 more easily and at the right time than by checking the strength using a conventional uniaxial compression test. Therefore, work on the liquefied treated soil 3, such as the protective layer 4 and the track 8, can be carried out at the right time, and the embankment 10 can be constructed quickly.

Figure 6 shows a different embodiment of the present invention, illustrating the construction procedure for the bag formwork 2 when the slope is steep.

First, as in the example of Figure 2, the bag body 2a is placed at a predetermined position on-site, and a filler such as concrete is poured into the injection port 2b of the bag body 2a to form the bag body formwork 2 (Figure 6 (a)).

In this embodiment, the bag formwork 2 and the liquefied treated soil 3 are integrated by attaching a rod-shaped reinforcing material to the bag formwork 2, which is fixed to the liquefied treated soil 3. This prevents the bag formwork 2 from collapsing due to an earthquake or the like, and improves the stability of the steeply sloping embankment 10 made of the liquefied treated soil 3. In this embodiment, an anchoring reinforcing bar 22 is used as a rod-shaped member. First, as shown in FIG. 6(b), fixing reinforcing bars 21 are arranged vertically at appropriate intervals in the longitudinal direction on the surface of the bag formwork 2 that will be the outer side of the embankment. Then, fixing reinforcing bars 22 are arranged to be fixed to the fixing reinforcing bars 21 and fixed to the liquefied treated soil 3. One end of the fixing reinforcing bar 22 is bent, and the bent portion 22a is hooked onto the fixing reinforcing bar 21, and the other end is arranged to extend horizontally (FIG. 6(c)). Then, the next bag 2a is placed on top of this anchoring rebar 22 and filled with filler to form the bag formwork 2 (Figure 6(d)).

In this way, the anchoring rebars 22 are sandwiched between the bag formwork 2 and fixed in a state where they extend horizontally. In the same manner, the anchoring rebars 22 are placed on top of the bag formwork 2 of each stage (Figure 6 (e)). When the bag formwork 2 has been piled up to a specified height, for example 2 m (Figure 6 (f)), liquefied treated soil 3 is poured up to the top height of the bag formwork 2, as in Figure 2 (b). The diameter and number (installation interval) of the anchoring rebars 22 and the length of their anchorage into the liquefied treated soil 3 are designed so that the embankment 10 has the strength to stably withstand earthquakes and the like as a permanent structure.

After repeating the above steps until the desired embankment height is reached, as shown in Figure 7, a retaining wall 9 is constructed of concrete or the like on the outside of the bag formwork 2 according to the gradient of the slope, and multiple piled up bag formwork 2 are integrated. If the gradient is relatively gentle, a sprayed material or a planar or mesh-like reinforcing material that is weather-resistant to ultraviolet rays, rainwater, etc. may be laid instead of the retaining wall 9. Note that in the case of a mesh-like reinforcing material, a separate means is required to protect the reinforcing bars 21, 22 exposed on the surface.

Furthermore, after checking the strength of the liquefied treated soil 3, a protective layer 4 is constructed on top of the liquefied treated soil 3, similar to the embodiment shown in Figure 2 (g).

When constructing steep embankments using liquefied treated soil, it was necessary to construct a strong wall such as a PC retaining wall, but there was a problem that the construction of PC retaining walls takes time and there is a limit to transportation. In addition, when using large sandbags to construct steep embankments, measures must be taken to ensure stability during construction corresponding to the steep slope. On the other hand, according to the embodiment shown in FIG. 6, for embankments with steep slopes, the stability of the structure of the embankment 10 can be increased by placing rod-shaped reinforcing materials between the bag formwork 2 and pouring the liquefied treated soil 3. Furthermore, the stability of the embankment 10 is improved by integrating multiple bag formworks 2 by constructing a retaining wall 9 or laying a planar reinforcing material on the surface of the slope. The embankment 10 reinforced in this way can be applied when the land area is limited or when sufficient area cannot be secured, such as when restoring an existing embankment with a steep slope.

In order to strengthen the fixation of the anchoring rebars 22 to the liquefied soil 3, a rectangular or circular plate-shaped anchoring portion 22b may be provided at the tip of the anchoring rebars 22 as shown in FIG. 8. Alternatively, the tips of multiple anchoring rebars 22 may be attached to a long anchoring member 23, such as an L-shaped angle as shown in FIG. 9.

Figure 10 also shows the steps of a construction method for embankment 10 according to yet another embodiment of the present invention.

The bag body 2a is placed at a predetermined position on-site and filled with a filler to form the bag body formwork 2 (Figure 10 (a)). In this embodiment, water is used as the filler. The bag body formwork 2 filled with the filler has a height and width of, for example, about 1,500 mm.

Then, liquefied treated soil 3 is poured between the bag formwork 2 to a height equal to or lower than the top height of the bag formwork 2, for example, to a height of 1,000 mm (Figure 10 (b)). The liquefied treated soil 3 may be the same as that in the above-mentioned embodiment.

After pouring the liquefied treated soil 3 and curing it for about a day until it reaches the required strength, the water is drained from the first layer of the bag formwork 2 and the bag formwork 2 is dismantled (Figure 10(c)). The bag 2a of the dismantled bag formwork 2 is then placed on top of the first layer of the liquefied treated soil 3 and filled with filler to form the bag formwork 2 (Figure 10(d)). Thereafter, liquefied treated soil 3 is poured in the same way as the first layer (Figure 10(e)), and after curing for about a day, the water is drained from the bag formwork 2 and the bag formwork 2 is dismantled (Figure 10(f)).

The same process is repeated to pile up the liquefied treated soil 3 to a specified height (Fig. 10(g)). Once it has been confirmed that the uniaxial compressive strength q _u of the liquefied treated soil 3 satisfies the specified strength, a protective layer 4 formed by stacking two types of layers 5, 6 with different permeabilities is constructed on the top surface of the topmost layer of the liquefied treated soil 3. Furthermore, a retaining wall 9 is constructed of concrete or the like on the side of the liquefied treated soil 3 to integrate the piled up multiple layers of liquefied treated soil 3. When used as an embankment for a railway, a crushed stone roadbed 7 and tracks 8 are constructed on the top surface of the protective layer 4 (Fig. 10(h)).

In this embodiment, water is used as the filler for the bag formwork 2, and the same bag formwork 2 is used repeatedly for each stage, making it possible to construct the embankment at low cost.

The above describes preferred embodiments of the present invention, but the present invention is not limited to these examples. It is clear that a person skilled in the art can come up with various modified or revised examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

The present invention is useful as a method for constructing embankments for railways and other applications.

2 Bag formwork 3 Fluidized treated soil 4 Protective layer 9 Retaining wall 10 Embankment 21 Fixing reinforcing bar 22 Anchoring reinforcing bar

Claims (9)

A method for constructing embankments using liquefied treated soil, comprising the steps of:
A bag is placed around the periphery of the embankment construction site, and a filler is filled into the bag to form a bag formwork;
After stacking the bag formwork to the height of the first stage, pour the first stage of liquefied treated soil up to the top height of the bag formwork,
After the first stage of liquefied soil has hardened to a specified uniaxial compressive strength,
A bag formwork is installed on the first layer of liquefied treated soil in the same manner as the first layer, and the bag formwork is piled up to the height of the second layer and the second layer of liquefied treated soil is poured in.
This process is repeated until the liquefied treated soil is poured to a specified height, and then
The upper end of the top layer of the liquefied treated soil is covered with a protective layer having drainage, water retention and load dispersion effects.
The method for constructing embankments is characterized in that the protective layer is composed of two types of layers with different permeabilities, with a lower layer with high permeability being placed directly above the liquefied treated soil, and an upper layer with low permeability being placed on top of that . 2. The method for constructing embankments according to claim 1 , further comprising providing a rod-shaped reinforcing material having one end fixed to the bag formwork and the other end anchored in the liquefied treated soil. 3. The method for constructing a bank as claimed in claim 1 , wherein the bag body is made of synthetic fiber. The method for constructing a bank as claimed in any one of claims 1 to 3 , characterized in that the filling material is concrete. A method for constructing embankments using liquefied treated soil, comprising the steps of:
A bag is placed around the periphery of the embankment construction site, and a filler is filled into the bag to form a bag formwork;
After stacking the bag formwork to the height of the first stage, pour the first stage of liquefied treated soil up to the top height of the bag formwork,
After the first stage of liquefied soil has hardened to a specified uniaxial compressive strength,
The first stage of the bag body formwork is dismantled, the bag body of the dismantled bag body formwork is placed on the first stage of the liquefied treated soil, a filler material is filled inside the bag body to form a bag body form, and the second stage of the liquefied treated soil is poured in.
This process is repeated until the liquefied treated soil is poured to a specified height, and then
A method for constructing embankments, characterized in that the upper end of the topmost layer of the liquefied treated soil is covered with a protective layer that has drainage, water retention and load dispersion effects. The method for constructing embankments according to any one of claims 1 to 5 , characterized in that the 28-day unconfined compressive strength of the liquefied treated soil is 600 kPa or more. The uniaxial compressive strength of the cast liquefied treated soil when hardened is as follows:
The subgrade reaction coefficient of the liquefied treated soil was measured in a small FWD test.
The deformation coefficient is calculated from the relationship between the subgrade reaction coefficient and the deformation coefficient.
The method for constructing embankments according to any one of claims 1 to 6 , characterized in that the unconfined compressive strength of the liquefied treated soil is determined from the relationship between the deformation coefficient and the unconfined compressive strength. The method for constructing an embankment according to any one of claims 1 to 7 , further comprising providing a retaining wall on the slope of the embankment. The embankment construction method according to any one of claims 1 to 8 , characterized in that the embankment is an embankment for a railway.

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