JP2014025315A - Banking construction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To construct banking with which shaking-down settlement of a banking support foundation or long-term banking settlement is suppressed and which has high stability so as to prevent functionality from being impaired even in the case of a major earthquake.SOLUTION: A source foundation A is excavated, the excavated part is filled back by a replacement material B of (i) or (ii) and banking C is constructed thereon by using sediment generated by the excavation. The replacement material B of (i) includes earth and stones comprised of one kind or more of a concrete recycled material, an artificial earth and stone material obtained by mixing a solidification material into sea-bottom soil or dredge soil and solidifying the soil, and the like and having a grain size of an average grain diameter D50>10 mm or a grain size of a 10% grain diameter D10>1 mm. The replacement material B of (ii) includes soil which is comprised of one kind or more of construction resultant soil, soil which is modified by mixing a modifier into the construction resultant soil, and the like, has a grain size in which the ratio of a grain diameter smaller than 0.075 mm exceeds 35 mass% or a gain size in which the ratio of a grain diameter smaller than 0.075 mm exceeds 30 mass% and is equal to or less than 35 mass%, and the ratio of a grain diameter smaller than 0.005 mm exceeds 15 mass%, and has a cone index being equal to or more than 400kN/m.

Description

  The present invention relates to a banking construction method for improving the ground by replacing the supporting ground of the bank with a replacement material by excavation and replacement, and constructing the bank on the ground in order to improve the stability of the bank.

The embankment structure has been widely used for roads, railways, river embankments, coastal embankments, etc. since a very old age because it is economical and it is relatively easy to obtain and construct materials.
When a bank is constructed, design calculations are generally omitted, and it is constructed so as to satisfy the specifications such as bank support ground conditions, gradient, material, etc., and the improvement of the support ground is limited to a very soft case.

Conventionally, there is a known method of constructing the embankment using the soil generated by excavation and replacement by improving the ground of the embankment support ground by excavation and replacement method in order to prevent consolidation settlement due to its own weight and stabilizing the embankment. Patent Document 1 discloses a construction method in which a replacement material used for ground improvement is a lighter material than the embankment material.
In addition, for embankment materials, measures were taken to prevent elution of heavy metals, etc., in construction-generated soils that partially contain heavy metals of natural origin, etc., using construction-generated soils associated with tunnel construction, subway construction, sewerage construction, etc. There are known methods such as using a material, or using a material in which waste tire chips and sand are mixed (Patent Documents 2 and 3, etc.).

JP-A-11-229380 JP 2009-249554 A JP 2008-184808 A

In the conventional embankment structure, if a large earthquake motion occurs, in addition to the embankment subsidence, the support ground will also subsidize, and these combine to greatly subsidize and deform the entire embankment structure. The embankment function may be greatly impaired by sliding or collapse.
In addition, as in Patent Document 1, when the support ground is improved with a material that is lighter than the embankment material by excavation and replacement method, generally, the deformation of the embankment tends to increase with respect to the horizontal external force, In particular, during an earthquake in which horizontal forces are applied repeatedly, the embankment function may be greatly impaired due to sliding or collapse due to large deformation.

In addition, as disclosed in Patent Documents 2 and 3, if the material of the embankment is construction-generated soil with measures for preventing the dissolution of construction-generated soil or heavy metals, or a mixture of waste tire chips and sand, etc., the eluted components are environmental standards. Even if the above conditions are satisfied, it is difficult to obtain a sufficient level of security for local residents, and the use cases are limited.
Therefore, the object of the present invention is to suppress the rock subsidence of the embankment support ground and the subsidence of the embankment over a long period of time, and has high stability that does not impair its function even in the event of a large earthquake, and also has an environmental load and environmental risk An object of the present invention is to provide a banking construction method capable of constructing a small banking.

The gist of the present invention for solving the above problems is as follows.
[1] Excavating the original ground (A) where the embankment is to be constructed, refilling the excavated part with the replacement material (B) of (i) or (ii) below, and then the earth and sand generated by the excavation The embankment construction method characterized by constructing embankment (C) using.
(I) From recycled concrete material, artificial debris material that has been solidified by mixing solidified material with seabed soil or dredged soil, artificial debris material that has been modified by mixing steel slag with seabed soil or dredged soil, and steel slag A debris material consisting of one or more selected particles and having an average particle size D50> 10 mm or a 10% particle size D10> 1 mm. (Ii) Construction-generated soil; It is composed of one or more selected from among the selected soils, and the particle size with a particle size of less than 0.075 mm exceeds 35% by mass, or the particle size with a particle size of less than 0.075 mm exceeds 30% by mass and is 35% by mass or less. And a soil having a particle size of more than 15% by mass with a particle size of less than 0.005 mm and a cone index of 400 kN / m ² or more.

[2] The embankment construction method according to the construction method of [1], wherein a thickness of the embankment portion covering the end portion of the upper surface of the replacement material (B) backfilled with the excavation portion is 30 cm or more.
[3] The embankment construction method according to [2], wherein the upper surface of the replacement material (B) in which the excavated portion is backfilled is at a position deeper than the original ground surface by 30 cm or more.
[4] In the construction method according to any one of [1] to [3] above, by mixing at least one selected from solidified material and steel slag into the earth and sand generated by excavation of the original ground (A) The embankment construction method characterized by constructing embankment (C) using this earth and sand, after improving to cone index 400kN / m < ² > or more.

[5] A banking construction method according to any one of the above [1] to [4], wherein the banking is constructed by sequentially performing the following steps (a) to (c).
(A) Construction is started from a position on one end side in the longitudinal direction of the embankment to be constructed, the original ground (a ₁ ) at the position is excavated, and at least a part of the excavated part (d ₁ ) is replaced with a replacement material (b ₁ ) Backfill.
(B) along the longitudinal direction of the embankment to be construction, excavating excavation of the "pre-step (d _n) to an adjacent original ground (a n _{+ 1),} using a sand generated by the excavation, before step in addition to constructing the backfilled substituted material (b _n) a part of the embankment on the (c _n), backfilled with the drilling unit (d n _{+ 1)} at least a portion of the replacement material (b n _{+ 1)} "that By repeating the above several times, the embankment is sequentially constructed in the longitudinal direction. (N is an integer of 1 or more)
(C) At the position on the other end side in the longitudinal direction of the embankment to be constructed, the end portion (c _END ) of the embankment is constructed using the earth and sand generated from the excavation part (d ₁ ) of the step (a).

[6] A banking construction method according to any one of the above [1] to [5], wherein the banking is constructed so as to satisfy the following formula (1).
(S2 / S1) (X2 / X1) ≧ 0.8 (1)
However, S1: Cross-sectional area in the width direction of the constructed embankment (C) (m ² )
S2: Cross-sectional area (m ² ) in the fill width direction of the replacement material (B) backfilled in the excavation part
X1: Unit volume weight of raw ground (A) (kN / m ³ )
X2: Unit volume weight (kN / m ³ ) of the replacement material (B)

According to the embankment construction method of the present invention, by replacing the original ground on which the embankment is installed with a specific material and improving the ground, the embankment supporting ground can be prevented from swaying and sinking over a long period of time, and a large earthquake. An embankment structure with high stability that does not impair its function sometimes can be constructed, and in addition, the following effects are obtained.
(I) As a substitute material for the original ground where the embankment is to be installed, such as concrete reclaimed material, artificial debris material that solidifies or modifies the seabed soil and dredged soil, steel slag, construction generated soil, modified construction soil, etc. Since only recycled materials are used and natural earth and sand materials are not used, environmental impact can be reduced.
(Ii) Even if the replacement material is a recycled material with an environmental risk, it is always used in the soil, and it is used in a place where it is almost impossible to dig up even during an artificial or natural disaster. Can be used with confidence.
(Iii) Since the embankment material is earth and sand of the original natural ground (original ground), it has little influence on the surrounding environment and is also effective for the growth of vegetation.
Therefore, according to the method of the present invention, these effects can be obtained in combination, so that an embankment suitable for vegetation can be obtained that has high stability and has low environmental burden and environmental risk while effectively using recycled materials. Can be constructed at low cost.

Explanatory drawing which shows typically the longitudinal cross-section of the embankment width direction about one embodiment of the embankment constructed by this invention method Explanatory drawing which shows typically the longitudinal cross-section of the embankment width direction about other embodiment of the embankment constructed by this invention method Explanatory drawing which shows typically the longitudinal cross-section of the embankment width direction about the case where the embankment of embodiment of FIG. 2 is applied to a road. Explanatory drawing which shows typically the longitudinal cross-section of the embankment width direction about the case where the embankment of embodiment of FIG. 2 is applied to a seawall. Explanatory drawing which shows the embankment height h and the substitution depth z by a substitution material about the embankment constructed by this invention method FIG. 6 (a) shows the scale of a generally assumed bank, and FIG. 6 (b) is an explanatory diagram showing cross-sectional views in the width direction of the bank of the maximum scale. Chart of influence values for determining vertical stress in semi-infinite body due to embankment load (Osterburk chart) Graph showing the relationship between the shear resistance angle φ of the ground and the bearing capacity factor Figure to find slope stability coefficient (Taylor chart) Explanatory drawing which shows the concrete example of the construction procedure of this invention method

FIG. 1 shows one embodiment of the method of the present invention, and schematically shows a longitudinal section in the width direction of a constructed embankment.
The embankment construction method of the present invention excavates the original ground A where the embankment is to be constructed, and backfills this excavated portion with the replacement material B of (i) or (ii) below, and is generated by the excavation thereon. The embankment C is constructed using earth and sand.
(I) "Concrete reclaimed material", "Artificial stone material solidified by mixing solidified material with seabed soil or dredged soil", "Artificial stone material modified by mixing steel slag with seabed soil or dredged soil" , A debris material consisting of one or more selected from “steel slag” and having an average particle size D50> 10 mm or a 10% particle size D10> 1 mm (ii) “construction generated soil”, “construction generated” It consists of one or more materials selected from “modified soil mixed with a modifying material”, and a particle size with a particle size of less than 0.075 mm exceeds 35% by mass, or a particle size with a particle size of less than 0.075 mm. Is a soil having a particle size of more than 30% by mass and not more than 35% by mass and a particle size of less than 0.005 mm exceeding 15% by mass and having a cone index of 400 kN / m ² or more.

  The above materials (i) and (ii) (substitution materials) are obtained by effectively using so-called recycled materials. Among these, the debris material (i) above has a particle size of a predetermined level or more so that the replacement material backfilled in the excavation part of the original ground can be sufficiently compacted, thereby improving the stability of the embankment structure. It is intended to be enhanced. On the other hand, the soil of (ii) above has a strength of a predetermined level or more so that the replacement material buried in the excavation part of the original ground is sufficiently compacted, thereby improving the stability of the embankment structure. It is intended to be.

  In the present invention, it is important to selectively use the material (i) and the material (ii) as the replacement material B. That is, since the material of (i) has high water permeability, it is possible to design by the concept of effective stress that bears external stress only by the particle skeleton constituting the replacement material, and the material of (ii) has water permeability. Since the design is based on the concept of total stress that bears external stress with the particle skeleton constituting the replacement material and the water in the gap, the design is appropriate for each material characteristic and stable improvements are made. The ground can be installed. On the other hand, when the materials (i) and (ii) are mixed and used, the stress state of the replacement material becomes complicated, and the design may become unstable.

Among the materials of (i) above, “concrete recycled material” is a material obtained by crushing waste concrete and adjusting the particle size according to the intended use, and is used as recycled aggregate, recycled crushed stone, recycled backfill material, etc. And quality standards established by local governments.
When this recycled concrete material is used, an appropriate amount of sulfur-containing steel slag such as blast furnace slow-cooled slag or desulfurized slag (for example, elution level) is used to fix hexavalent chromium contained in trace amounts in concrete and prevent its elution. (About 1 to 10% by mass depending on the condition)), or it is preferably installed so as to coexist. Thereby, the amount of elution can be reduced significantly and it can be used in a state with a sufficiently low environmental risk.

  In addition, “artificial debris that has been solidified by mixing solidification material with seabed soil or dredged soil” means bottom mud excavated from the seabed (seafloor soil) or bottom mud excavated from the bottom of the dredging work ( It is a debris material obtained by adding a solidifying material to dredged soil and mixing it thoroughly and curing it as necessary. Examples of the solidifying material include cement, cement-based solidified material, lime-based solidified material, and the like, and one or more of these can be used. Here, cement-based solidified material and lime-based solidified material are solidified by adding one or more active ingredients (solidification accelerator) using cement as a base material in order to deal with soil and sites that are difficult to solidify with cement and lime. It is a solidified material (lime-based solidified material) in which one or more active ingredients (solidification accelerator) are added using lime as a base material (cement-based solidified material). The blending amount of the solidifying material is suitably about 5 to 30% (mass ratio) of the seabed soil or dredged soil depending on the water content of the seabed soil or dredged soil.

  In addition, “artificial debris modified by mixing steel slag with seabed soil or dredged soil” means that steel slag is added to seabed soil or dredged soil as described above and mixed thoroughly, and cured as necessary. A debris material obtained by adjusting the particle size. Examples of the steel slag (slag generated in the steel manufacturing process) include blast furnace slag, steelmaking slag, ore reduction slag, and one or more of these can be used. Blast furnace slag includes blast furnace slow cooling slag and blast furnace granulated slag. In addition, as steelmaking slag, steelmaking slag generated in the processes such as hot metal pretreatment, decarburization blowing, casting (for example, decarburization slag, dephosphorization slag, desulfurization slag, desiliconization slag, ingot slag, etc.), Examples include electric furnace slag. Among these slags, converter steelmaking slag, such as decarburized slag and dephosphorized slag, is suitable for the modification of seabed soil and dredged soil, and among them, particularly contains 30% by mass or more of CaO. And a particle size of 40 mm or less is desirable. This is because the Ca component in the steelmaking slag reacts with the Si component in the seabed soil or dredged soil to accelerate the solidification and improve the reforming effect. In practice, the particle size of the steelmaking slag is 40 mm or less. If so, the mixing operation is easy, and the solidification reaction proceeds promptly. The blending amount of steel slag is appropriately about 20 to 50% (mass ratio) of the seabed soil or dredged soil depending on the water content of the seabed soil or dredged soil.

Moreover, also about the "iron and steel slag" used as the material itself of said (i), 1 or more types of the various slag mentioned above can be used. Among these slags, steel slag other than granulated blast furnace slag is preferable from the viewpoint of securing a predetermined particle size, and converter steelmaking slag such as decarburized slag and dephosphorized slag is particularly preferable. preferable.
The material (i) must have “average particle size D50> 10 mm particle size” or “10% particle size D10> 1 mm particle size”. Here, the average particle diameter D50 is generally referred to as the median particle diameter. The cumulative particle size distribution is plotted with the horizontal axis as a logarithmic scale and the vertical axis as the mass percentage of the material passing through the sieve. In a curve, it is a particle size (a sieve opening) with a mass fraction of 50%. D10 is the particle size at which the mass fraction is 10% in the cumulative particle size distribution curve. If the particle size of the material of (i) is smaller than this condition, when the replacement material is saturated with groundwater and receives vibration, the water pressure of the groundwater rises and the groundwater moves accordingly. Decreases and loses stability. The upper limit of the particle size of the material (i) is not particularly in terms of design or function, but if it is too large, the construction becomes difficult.

Among the materials of (ii) above, “the soil modified by mixing the modifying material with the construction generated soil” means that the modifying material is applied to the construction generated soil so that the cone index is 400 kN / m ² or more. In addition, it was obtained by thoroughly mixing and curing as necessary. Examples of the modifier include cement, cement-based solidified material, lime-based solidified material, and the like, and one or more of these can be used. Here, cement-based solidified material and lime-based solidified material are solidified by adding one or more active ingredients (solidification accelerator) using cement as a base material in order to deal with soil and sites that are difficult to solidify with cement and lime. It is a solidified material (lime-based solidified material) in which one or more active ingredients (solidification accelerator) are added using lime as a base material (cement-based solidified material). The blending amount of the modifying material is suitably about 5 to 30% (mass ratio) of the construction generated soil depending on the moisture content of the construction generated soil.

The material of (ii) above is “a particle size in which the ratio of particle size less than 0.075 mm exceeds 35% by mass” or “the ratio of particle size less than 0.075 mm exceeds 30% by mass and is 35% by mass or less. It is necessary that the ratio of the diameter less than 0.005 mm has a particle size exceeding 15% by mass and the cone index is 400 kN / m ² or more. When the particle size of the material of (ii) is larger than the above conditions, the water permeability is generally improved, and when the replacement material is saturated with ground water and receives vibration as described above, the strength decreases as a whole. , Lose stability. If the cone index is less than 400 kN / m ² , (a) the strength is insufficient and the embankment load cannot be supported, (b) compaction is difficult, (c) the construction machine is easy to sink and stable. Cause problems such as being unable to operate.
The cone index is a value determined by JIS-A-1228 “Testing method for cone index of compacted soil” and is a kind of penetration resistance.

In the embankment structure constructed by the method of the present invention, the replacement material B in which the excavation part is backfilled so that the replacement material B is not exposed when a part of the embankment C is lost for some reason. The thickness of the embankment portion covering the end 20 of the upper surface 2 is 30 cm or more, preferably 50 cm or more.
When the replacement material B is backfilled to substantially the same level as the original ground surface 1 as in the embodiment of FIG. 1, the end portions 20 of the upper surface 2 of the replacement material B are close to the ground surface at both side positions in the embankment width direction. In order to make the thickness of the embankment part which covers the edge part 20 30 cm or more (preferably 50 cm or more), it is necessary to make the embankment width larger than originally required as a embankment structure. Therefore, as in the embodiment of FIG. 2, it is preferable to place the upper surface 2 of the replacement material B backfilled with the excavated portion at a position deeper than the original ground surface 1, thereby increasing the embankment width more than necessary. The thickness of the embankment part which covers the edge part 20 can be ensured without. In particular, the upper surface 2 of the replacement material B in which the excavated portion is backfilled is positioned 30 cm or more, more preferably 50 cm or more deeper than the original ground surface 1 (that is, the depth x in FIG. 2 is more than 30 cm, more preferably Is preferably 50 cm or more.
As described above, the thickness of the embankment portion that covers the end 20 of the upper surface 2 of the replacement material B that has backfilled the excavation part is sufficiently increased (preferably, the upper surface 2 of the replacement material B is made to be larger than the original ground surface 1. The replacement material B will not be exposed even if a part of the embankment C is lost for some reason, and vegetation such as windbreak forest or tide forest is applied to the embankment. In the case of providing, the main vegetation base can be the soil of the original ground, which is advantageous for the growth of vegetation.

In addition, the soil generated by excavation of the original ground A is mixed with at least one selected from solidified material and steel slag to improve it to a cone index of 400 kN / m ² or more, and then filled with this soil It is preferable to construct C.
When the solidifying material is mixed with the earth and sand, the solidifying material as mentioned above is added and sufficiently mixed so that the cone index is 400 kN / m ² or more. The blending amount of the solidifying material is suitably about 5 to 30% (mass ratio) of the earth and sand depending on the moisture content of the earth and sand.
Moreover, when mixing steel slag with earth and sand, the steel slag as mentioned above is added and mixed sufficiently so that the cone index becomes 400 kN / m ² or more. The blending amount of steel slag is appropriately about 20 to 50% (mass ratio) of the earth and sand depending on the moisture content of the earth and sand.
Thus, the stability of the embankment itself can be improved by modifying the earth and sand for constructing the embankment C to a cone index of 400 kN / m ² or more.

In the method of the present invention, it is preferable to apply the embankment so as to satisfy the following formula (1), desirably the following formula (2). Thereby, it can be set as the structure where stability of the whole embankment structure is high, and subsidence does not arise easily.
Reducing the vibration amplitude of the embankment in the event of an earthquake is effective for the stability of the entire embankment structure and suppression of settlement, and for this purpose, the entire embankment is required to be lighter than the entire replacement material. As a result of numerical simulation, it was found that if the equation (1) is satisfied, preferably the equation (2) is satisfied, the vibration amplitude is relatively small, the settlement of the embankment is small, and the entire embankment structure is stable. Therefore, it was defined as a preferable condition.
(S2 / S1) (X2 / X1) ≧ 0.8 (1)
(S2 / S1) (X2 / X1) ≧ 1.0 (2)
However, S1: Cross-sectional area in the width direction of the constructed embankment (C) (m ² )
S2: Cross-sectional area (m ² ) in the fill width direction of the replacement material (B) backfilled in the excavation part
X1: Unit volume weight of raw ground (A) (kN / m ³ )
X2: Unit volume weight (kN / m ³ ) of the replacement material (B)

Next, (A) the safety factor of the bearing capacity of the original ground, (B) the stability of the improved ground by the replacement material, and (C) the stability of the embankment will be described for the embankment structure constructed by the present invention method. In addition, the improved ground by a substitute material means the ground which backfilled the excavation part of the original ground with the substitute material B.
(A) Safety factor of the bearing capacity of the original ground The area where harmful settlement does not occur due to the weight of the embankment shall be improved (replacement with the replacement material B), and as shown in Fig. 5, it is almost the same as the embankment height h The ground up to the depth (replacement depth z) is to be improved (replacement by the replacement material B).
FIG. 6 shows the generally assumed scale of the embankment. FIG. 6 (a) shows a minimum scale embankment, and FIG. 6 (b) shows a cross-sectional view in each width direction of the maximum scale embankment. The embankment height h is 5-10 m, and the embankment width W is 25-45 m.

As a design matter of important structures, the safety factor of the bearing capacity of the ground is generally set to 3 for long-term (always) and 1.5 for short-term (during earthquake). When the replacement depth z is the same as the embankment height h (z = h), the assumed embankment scale is 5-10 m in height, and the normal gradient is 1: 2 (see FIG. 6), FIG. , “New edition of soil mechanics”, Morikita Publishing, 1978, p.171), from the Osterbark chart (the chart of influence values for determining vertical stress in semi-infinite bodies due to embankment load) The stress increase σz1 due to embankment in the original ground is as follows, where unit volume weight of embankment material = unit volume weight of replacement material = γ.
σz1 = 0.47 ～ 0.44γz
・ When the height is 5m
a / z = 10/5 = 2, b / z = 5/5 = 1
From the Osterburk chart I = 0.47
・ When the height is 10m
a / z = 20/10 = 2, b / z = 5/10 = 0.5
From Osterburk chart I = 0.44

On the other hand, the weight σz0 of the improved ground by the replacement material B having the replacement depth z is σz0 = γz. Therefore, the ground stress σ of the original ground just below the improved ground due to the replacement material B is as follows.
σ = σz1 + σz0 = (1.47-1.44) γz
This value is below the short-term (earthquake) safety factor of 1.5, which means that the embankment can be safely supported.

(B) Stability of improved ground with replacement material The stability of the improved ground is evaluated by the bearing capacity of the improved ground surface (Tertuagi's bearing capacity formula) as follows. As shown in FIG. 6, the assumed embankment has an embankment height h of 5 to 10 m and an embankment width W of 25 to 45 m. The unit volume weight γ of the embankment is 16 kN / m ³ .
Note that the shear strength s and adhesive strength c (shear strength) of the soil, the stress σ perpendicular to the shear plane, and the shear resistance angle φ are in the relationship of the following equations.
s = c + σ · tanφ
Table 1 shows the bearing capacity coefficients Nc and Nr at each shear resistance angle φ of the soil. FIG. 8 shows the relationship between the ground shear resistance angle φ and the bearing force coefficient.

First, the own weight σz of the embankment is calculated as follows from the unit volume weight γ and the embankment height h.
σz = γ ・ h = 16 × (5-10) = 80-160kN / m ²
When the replacement material B is the material (i) above, assuming that the adhesive force c = 0 of the replacement material B and the shear resistance angle φ = 25 °, the support force qd of the improved ground by the replacement material B is the support force coefficient Nc = 9.9 and Nr = 3.3, it is calculated as follows.
Supporting force qd = c · Nc + (1/2) · γ · W · Nr = (1/2) × 16 × (25 to 45) × 3.3 = 660 to 1180 kN / m ²
Here, since the weight σz of the embankment is 80 to 160 kN / m ² as described above, the improved ground composed of the material (i) (substitution material B) has a sufficient supporting force (supporting force qd: 660 to 1180 kN). / m ² ). That is, it is stable.

Further, when the replacement material B is the material (ii) above, assuming that the adhesive force c of the replacement material B is 40 kN / m ² and the shear resistance angle φ = 0, the bearing capacity qd of the improved ground by the replacement material B is From the bearing force coefficient Nc = 5.3 and Nr = 0, calculation is performed as follows.
Supporting force qd = c ・ Nc + (1/2) ・ γ ・ W ・ Nr = 40 × 5.3 ＝ 212kN / m ²
Here, as described above, since the weight σz of the embankment is 80 to 160 kN / m ² , the improved ground made of the material (ii) (substitution material B) has sufficient supporting force (supporting force qd: 212 kN / m). ² ) will have. That is, it is stable.

On the other hand, in the case where the ground improvement by the replacement material B as in the present invention is not performed, assuming that the adhesion force c = 25 kN / m ^{2 of} the ground soil and the shear resistance angle φ = 0, the bearing capacity of the ground qd is calculated as follows from the bearing capacity coefficient Nc = 5.3 and Nr = 0.
Supporting force qd = c ・ Nc + (1/2) ・ γ ・ W ・ Nr = 25 × 5.3 = 133kN / m ²
Here, since the weight σz of the embankment is 80 to 160 kN / m ² as described above, when the ground height is not improved by the replacement material B, the supporting force of the ground is insufficient when the embankment height is close to 10 m. . That is, it is unstable.

(C) Stability of embankment (C-1) When the replacement material B is the material of (i) above Adhesive strength c of the soil before the ground improvement c = 25kN / m ² , Unit volume weight γ = 16kN / m ^3. Adhesive strength c of improved ground replacement material B c = 25kN / m ² , unit volume weight γ = 16kN / m ³ , shear resistance angle φ = 5 °, ground improvement with replacement material B and ground improvement For each case, the limit height Hc of each embankment is obtained from the tailor chart (figure for calculating the slope stability coefficient) in Fig. 9 (Toyohiro Yamauchi, "Soil Mechanics", Science and Engineering Book, 1977, p.166-168). And the following.
・ When the ground is not improved (Nc = 5.5)
Hc = c ・ Nc / γ = 25 × 5.5 / 16 = 8.6m
・ When the ground is improved (Nc = 9.5)
Hc = c ・ Nc / γ = 25 × 9.5 / 16 = 14.8m
Here, the height of the assumed embankment is 5 to 10 m. Therefore, if the ground is not improved, the height of the embankment is not stable at 10 m, but the limit height of the embankment is about 1.7 times higher due to the ground improvement (replacement). Stable even on 10m bank.

(C-2) When the replacement material B is the material of (ii) above, the soil adhesion of the ground before the ground improvement is c = 25kN / m ² and the unit volume weight γ = 16kN / m ³ to replace the improved ground Adhesive strength of material B c = 40kN / m ² (≒ cone index 400kn / m ² ), unit volume weight γ = 16kN / m ³ When the limit height Hc is determined from the tailor chart of FIG. 9, it is as follows.
・ When the ground is not improved (Nc = 5.5)
Hc = c ・ Nc / γ = 25 × 5.5 / 16 = 8.6m
・ When the ground is improved (Nc = 5.5)
Hc = c ・ Nc / γ = 40 × 5.5 / 16 = 12.5m
Here, the height of the assumed embankment is 5 to 10m. Therefore, if the ground is not improved, the height of the embankment is not stable at 10m. Stable even on 10m bank.

(D) Comprehensive evaluation of the above (A) to (C) Comprehensive evaluation of the stability of the embankment structure constructed by the method of the present invention is as shown in Table 2. According to the present invention, a very stable embankment structure is obtained. It turns out that it is obtained.

FIG. 3 schematically shows a vertical section in the width direction of the embankment when the embankment of the embodiment of FIG. 2 is applied to a road (embankment road), and 3 is a road. In this case, since the embankment supporting ground has been improved, deformation of the embankment can be minimized during and after the earthquake, and can be sufficiently utilized as a lifeline without impairing road functions.
FIG. 4 schematically shows a longitudinal section in the width direction of the embankment when the embankment of the embodiment of FIG. 2 is applied to a tide bank forest, and 4 is vegetation. In this case, even if a tsunami caused by a large earthquake hits, the deterioration of the embankment function due to the earthquake is minimal, and the tsunami can be suppressed. Naturally, it is possible to control drowning even during a heavy flood due to stormy weather.

The basic procedure for constructing banking for roads and seawalls according to the method of the present invention is shown below. However, it is not limited to the following procedure.
(1) Preparatory work (2) Ground improvement work (i) Excavation of the original ground A: Excavate the natural ground (original ground A) with excavators such as bulldozers and backhoes.
(Ii) Transport excavated soil and construct by temporary placement or embankment.
(Iii) soil excavated material characterization: Review Cone Index, etc. (400 kN / m ² or more, etc.).
(Iv) Construction of the replacement material B (backfilling of the excavation part): The replacement material B is put into the excavation part, and is rolled out and compacted (the construction method and construction management satisfying the specifications are taken). Repeat sprinkling and compaction as necessary.

(3) Embankment work (i) Construction of embankment material: After improving the soil quality of the excavated soil as necessary based on the results of (2)-(iii) above, the embankment material (the excavated soil of the original ground A) Rolling out, rolling and compacting (Use construction method and construction management that satisfy the specifications.) Repeat rolling and compacting and compacting as necessary.
(Ii) In the case of embankment roads, general road works (roadbed work, roadbed work, pavement work) are performed. In the case of a seawall, general vegetation is performed.
In addition, in order to suppress the outflow of pore water to the surrounding soil, a water shielding sheet may be laid under the replacement material B.

Since the embankment constructed by the method of the present invention is used as an embankment road, a seawall, etc., it is constructed with a certain length (for example, about several kilometers to several tens of kilometers). In order to construct such banking efficiently, it is preferable to adopt the following method. That is, this construction method constructs the embankment by sequentially performing the following steps (a) to (c).
(A) Construction is started from a position on one end side in the longitudinal direction of the embankment to be constructed, the original ground (a ₁ ) at the position is excavated, and at least a part of the excavated part (d ₁ ) is replaced with a replacement material (b ₁ ) Backfill.
(B) Along the longitudinal direction of the embankment to be constructed, “excavate the original ground (a _{n + 1} ) following the excavation part (d _n ) of the previous process, and use the earth and sand generated by this excavation, in the previous process with building a backfilled substituted material part of embankment on the _{(b n) (c n)} , that the at least a portion of the drilling unit (d n _{+ 1)} backfilled with replacement material (b n _{+ 1)} " By repeating a plurality of times, the embankment is sequentially constructed in the longitudinal direction. (N is an integer of 1 or more)
(C) at the location of the other end side in the longitudinal direction of the embankment to be construction, constructing the terminal portion c _END of embankments using sediment generated from excavation d ₁ of the step (A).

FIG. 10 is an explanatory diagram showing a specific example of the construction procedure of the construction method.
As shown in FIG. 10 (1) and FIG. 10 (2), construction is started from a position on one end in the longitudinal direction of the embankment to be constructed, and the original ground a ₁ at the position is excavated with a certain length (excavation) Part d ₁ ) and the excavated earth and sand e ₁ are temporarily placed in an arbitrary place. Then, as shown in FIG. 10 (3), backfilled at least a portion of the drilling unit d ₁ substituted material b _1.
10 (4) and FIG. 10 (5), along the longitudinal direction of the embankment to be construction, the original ground a ₂ adjacent to the digging unit d ₁ was drilled at a predetermined length (excavation d ₂ ) Using the earth and sand generated by the excavation, a part c ₁ of the embankment is constructed on the replacement material b ₁ that is first backfilled, and the excavation part is shown in FIG. 10 (6). At least part of d ₂ is backfilled with the replacement material b ₂ . By repeating this step a plurality of times, as shown in FIGS. 10 (7) to 10 (9), the embankment is sequentially applied in the longitudinal direction. Here, in FIG. 10 (9), second a b _N of the substituent material backfilled second from last in a series of steps, the b N _{+ 1-substituted} material which also finally backfilled, c _N is also the last The embankment part (part of embankment) to be constructed is shown respectively. Then, at the end of the series of steps, as shown in FIG. 10 (9), at the location of the other end side in the longitudinal direction of the embankment to be construction (construction end position embankment), generated from the first excavation d ₁ The bank c1 _END is constructed using the earth and sand e ₁ to complete the banking.

A Original ground B Replacement material C Embankment a _{1 to} a ₃ Original ground b ₁ , b ₂ , b _N , b _{N + 1} Replacement material c ₁ , c ₂ , c _N , c _END Part of embankment d _{1 to} d ₃ excavation part e ₁ earth and sand 1 raw ground surface 2 replacement material top surface 3 road 4 vegetation 20 edge of replacement material top surface

Claims (6)

Excavate the original ground (A) where the embankment is to be constructed, backfill the excavated part with the replacement material (B) of (i) or (ii) below, and then use the earth and sand generated by the excavation A banking construction method characterized by constructing banking (C).
(I) From recycled concrete material, artificial debris material that has been solidified by mixing solidified material with seabed soil or dredged soil, artificial debris material that has been modified by mixing steel slag with seabed soil or dredged soil, and steel slag A debris material consisting of one or more selected particles and having an average particle size D50> 10 mm or a 10% particle size D10> 1 mm. (Ii) Construction-generated soil; It is composed of one or more selected from among the selected soils, and the particle size with a particle size of less than 0.075 mm exceeds 35% by mass, or the particle size with a particle size of less than 0.075 mm exceeds 30% by mass and is 35% by mass or less. And a soil having a particle size of more than 15% by mass with a particle size of less than 0.005 mm and a cone index of 400 kN / m ² or more.   The embankment construction method according to claim 1, wherein the thickness of the embankment part covering the end of the upper surface of the replacement material (B) backfilling the excavation part is 30 cm or more.   The embankment construction method according to claim 2, wherein the upper surface of the replacement material (B) in which the excavated portion is backfilled is at a position deeper than the original ground surface by 30 cm or more. The soil generated by excavation of the original ground (A) is mixed with at least one selected from solidified material and steel slag to improve the cone index to 400 kN / m ² or more, and then embankment using the soil The embankment construction method according to claim 1, wherein (C) is constructed. The embankment construction method according to claim 1, wherein the embankment is constructed by sequentially performing the following steps (a) to (c).
(A) Construction is started from a position on one end side in the longitudinal direction of the embankment to be constructed, the original ground (a ₁ ) at the position is excavated, and at least a part of the excavated part (d ₁ ) is replaced with a replacement material (b ₁ ) Backfill.
(B) along the longitudinal direction of the embankment to be construction, excavating excavation of the "pre-step (d _n) to an adjacent original ground (a n _{+ 1),} using a sand generated by the excavation, before step in addition to constructing the backfilled substituted material (b _n) a part of the embankment on the (c _n), backfilled with the drilling unit (d n _{+ 1)} at least a portion of the replacement material (b n _{+ 1)} "that By repeating the above several times, the embankment is sequentially constructed in the longitudinal direction. (N is an integer of 1 or more)
(C) At the position on the other end side in the longitudinal direction of the embankment to be constructed, the end portion (c _END ) of the embankment is constructed using the earth and sand generated from the excavation part (d ₁ ) of the step (a). The embankment construction method according to any one of claims 1 to 5, wherein the embankment is constructed so as to satisfy the following expression (1).
(S2 / S1) (X2 / X1) ≧ 0.8 (1)
However, S1: Cross-sectional area in the width direction of the constructed embankment (C) (m ² )
S2: Cross-sectional area (m ² ) in the fill width direction of the replacement material (B) backfilled in the excavation part
X1: Unit volume weight of raw ground (A) (kN / m ³ )
X2: Unit volume weight (kN / m ³ ) of the replacement material (B)

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