JPH08209704A - Construction of banking - Google Patents

Abstract

PURPOSE: To provide a method with which a banking that is higher and steeper than a stabilized gradient on the slope of a banking made of ordinary earth can be constructed without allowing cost therefor to rise. CONSTITUTION: Ordinary earth obtained by cutting through natural ground on a construction site is used for banking, and a banking main body 21 having a side slope 2a1 without reinforcement in the thickness of ΔH is constructed, and a filter layer 31 is formed thereon with drainage material such as gravels or crushed stones in small grain size laid with an appropriate thickness along the side slope 2a1 . A form 4 having a sheathing board 41 inclining toward the side slope 2a1 is erected, and a waterproof sheet 51 is laid on the surface of the filter layer 31 . Cement 6, highly deformative and low in strength, made up by mixing cement, bentonite, sand and water in appropriate ratios, is placed into a placement space S1 between the sheathing board 41 and the waterproof sheet 51 , and a reinforced area 61 is formed after hardening of the cement. A series of processes as mentioned above is repeated for forming upper layers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a steep embankment which has a high height and is stable.

[0002]

2. Description of the Related Art In the case of forming an embankment, according to a conventional method of forming an embankment, the embankment material made of a general earth material such as earth and sand is piled up and compacted to a predetermined density to consolidate it. A stable calculation is carried out, and as a result, the slope gradient required to satisfy the specified safety factor is obtained, or empirically depending on the soil quality of the embankment material such as whether it is good quality soil or soft soil such as loam. The embankment having the slope of the predetermined slope is formed by sprinkling and compacting the embankment material so that the slope has a predetermined slope. In this case, it is common to construct the embankment material only by compacting it by compaction, without performing soil improvement or reinforcement for strength improvement, but especially with a steep slope and a high slope. When embankment is to be constructed, a reinforced earth construction method or the like is used in which a reinforcing material (so-called geotextile) made of a synthetic polymer material that is resistant to pulling is laid at every constant layer thickness in the embankment to embank.

[0003]

Among the conventional construction methods described above, in the case of giving only the strength that the embankment material can originally exhibit by the usual method of only compacting the embankment material, a steep high embankment is used. Since it cannot be constructed, that is, the slope must be graded to a certain degree in order to construct a high embankment, it is necessary to acquire a large land for construction.

Further, among the conventional construction methods described above, the reinforced earth construction method of embedding a reinforcing material in the embankment has an advantage that a steep high embankment can be formed, but the height of the embankment is high. The higher the price, the narrower the embedding interval of the reinforcing material and the large amount of reinforcing material required, and the reinforcing material itself is expensive, so it is not suitable for large-scale civil engineering work, and therefore, There is a problem that the height of the embankment that can be constructed is limited.

The present invention has been made under the above circumstances, and its technical problem is that the construction cost is high and the slope is steeper than the stable slope. It is to provide a method capable of forming an embankment.

[0006]

Means for Solving the Problems As a means for effectively solving the above-mentioned technical problems, a method for forming an embankment according to the present invention is a method in which a material for embankment is squeezed out and compacted to form a predetermined layer thickness having a slope. The embankment main body is piled up, and the weir plate is assembled at an appropriate distance from the slope to form a mold inclined to the slope.
Between the formwork and the slope, cement, bentonite,
It comprises a step of forming low-strength, high-deformability mortar in which sand and water are mixed in an appropriate ratio to form a reinforced region. In this construction method, more preferably, a filter layer made of drainage material is formed on the slope of the raised embankment body, a waterproof sheet is laid on the surface of the filter layer, and a low-strength, high-deformability mortar is used as a formwork. And the waterproof sheet. Further, the low-strength and high-deformability mortar may be mixed with locally generated soil or reinforcing fibers.

[0007]

In other words, the construction method of the present invention ensures that the area of a certain thickness on the slope surface layer portion of the embankment is deformable to the same extent as the embankment material such as earth and sand or rock crushed material, and the slope is stable. The embankment body, which is the other part of the reinforcement area with the required strength, is made of only embankment material that does not undergo the same improvements or reinforcements as before, so that the embankment has a steeper slope than the conventional one. It enables the creation of.

The reinforced region must have strength so that the entire embankment slope including the reinforced region satisfies a predetermined safety factor and is in a stable state. Therefore, in the formation of the reinforced region, a low-strength and high-deformability mortar having sufficient strength to stabilize the entire embankment slope and having deformability capable of following the subsidence deformation and shear deformation of the embankment To use. This low-strength, high-deformability mortar is, for example, a mortar that is generally used in earth retaining walls and dam-blocking walls of dam foundations, in which bentonite, sand and water are mixed at an appropriate ratio. In addition to water and soil, soil cement added with locally generated soil, fiber reinforced mortar or fiber reinforced soil cement in which steel fibers or plastic fibers are mixed with the mortar or soil cement to improve durability against cracks, etc. It is preferably used.

Such low strength and high deformability mortar is
Although it has lower strength than ordinary concrete, it is a solidified body with required toughness due to adhesive strength. On the other hand, general soil materials such as earth and sand and rock-crushed materials used as embankment materials are granular aggregates with low mutual adhesiveness between particles and a large internal friction angle. The ground of the embankment is most likely to suffer a shallow slip failure such that an arc-shaped slip surface is formed inside the ground near the slope. Therefore, it is extremely effective to prevent slip failure by forming a reinforced region with low-strength and high-deformability mortar with excellent toughness due to adhesive force on the slope of the embankment raised by such an embankment material. Therefore, the slope can be made steeper than the stable slope in the normal embankment.

In a preferred embodiment of the present invention, the filter layer interposed between the embankment main body and the reinforced region promotes drainage of pore water from the embankment main body due to rainfall or the like, and a slope portion of the embankment main body. The deformation is absorbed, and an effect of mitigating a local increase in pressure load on the reinforced region is exerted.
Further, the waterproof sheet laid on the surface of the filter layer prevents the cement from flowing out to the filter layer and lowering the drainage function when the low-strength and high-deformability mortar is cast.

[0011]

FIG. 1 shows a first embodiment of a method of forming embankment according to the present invention in the order of steps. That is, in the method of this embodiment, first, the ground foundation or the bedrock 1 is leveled, and then, as shown in FIG. 1 (a), a predetermined gradient θ is formed on the foundation ground or the bedrock 1 to a height of an appropriate layer thickness ΔH. with make prime the embankment body portion 2 ₁ of the unreinforced first layer having a _second slope face 2a _1, suitable thickness drainage material of crushed stone, such as gravel or small particle size along the slopes 2a ₁ To form the filter layer 3 ₁ . In prime fresh embankment body portion 2 _1, for example, as a fill material generally soil generated by Cut the natural ground of the field, out inoculated by the thickness of which is suitable for compaction of single, tightened by compacting The work of solidifying and then spreading the embankment material again is repeated a required number of times. The filter layer 3 ₁ is a drainage layer whose lower end is formed on the foundation ground or the bedrock 1 (not shown).
Outside the filter layer 3 ₁ , a casting space S ₁ for forming a reinforced region 6 ₁ described later, which is shown by a chain line in the figure, is set.

Next, as shown in FIG. 1B, the form 4 is assembled at a position which is an end of the placing space S ₁ , that is, a position which is appropriately separated from the slope 2a ₁ of the embankment body 2 _1. A waterproof sheet 5 ₁ is laid on the surface of the filter layer 3 ₁ . Formwork 4
Comprises a dam plate 41 and a support 42 for fixing and supporting the dam plate 41, and the dam plate 41 is provided in an inclined state substantially corresponding to the slope 2a ₁ . The barrier plate 41 and the waterproof sheet 5 ₁ have a height equal to or larger than the layer thickness ΔH of the embankment body 2 ₁ .

Next, as shown in FIG. 1C, cement, bentonite, sand and water are appropriately mixed in the casting space S ₁ defined by the dam plate 41 of the formwork 4 and the waterproof sheet 5 ₁ . Pour the low-strength, high-deformability mortar 6'mixed in. This low-strength / high-deformability mortar 6'has developed an appropriate viscous strength (toughness) by being cured for a predetermined time after being placed, and as a result, as shown in FIG. The reinforced region 6 ₁ of the first layer is formed.

The first-layer embankment body 2 ₁ and the reinforced region 6
_{When 1} is created, move the creation work to the upper layer, and repeat the series of steps from Fig. 1 (a) again. That is, as shown in FIG. 1 (d), on the embankment body portion 2 ₁ of the first layer, leaving a striking設空between S ₂ to form a reinforcing region of the second layer, the first with make prime the embankment body portion 2 ₂ of the second layer having a thickness of ΔH having slope 2a ₂ consecutive modulo surface 2a ₁ of the embankment body portion 2 ₁ of the layers first, the slopes 2a
₂ along the formwork having a weir plate continuous with the filter layer 3 ₁ of the first layer to form the filter layer 3 _2, to form a continuous surface with the slope 6a of the reinforcing region ₆₁ (not shown) with assembling, after laying a waterproof sheet (not shown) to the filter layer 3 ₂ of the surface of the second layer, and Da設low strength and high deformability mortar 6 'on the punching設空between S ₂ cured By doing so, the formation of the second layer is performed. Hereinafter, by repeating the same steps up to the n-layer,
The height H = n · ΔH
And the embankment body 2 made of unreinforced embankment material,
The embankment having the filter layer 3 and the reinforced region 6 formed on the slope surface layer portion is formed.

The horizontal thickness L of the reinforced region 6 should be calculated from the height H of the embankment to be formed, the slope of the embankment, and the strength of the embankment body 2 obtained by compacting the embankment material. Is calculated from the combination with the mortar strength of the reinforcement region 6 necessary for the whole embankment to satisfy the predetermined safety factor and be stable, and is set to a fixed ratio to the height H, that is, L = m · H. .

According to this embodiment, the formation of the reinforced region 6 improves the stability of the embankment slope and increases the shear strength of the embankment against slip failure. Therefore, as shown by the alternate long and short dash line in FIG. It is possible to create a bank with a steeper slope than the conventional bank shown in. Therefore, since the land area a taken up on the slope portion is small,
As shown in (a), it is possible to increase the usable area of the top surface of the embankment even with the same business land area, or, as shown in FIG. 3 (b), create a bank having the required top surface area. It is possible to save the land area for business.

The embankment is Construction by the inventive method, the slope theta ₆ of the outer slopes of the slope gradient theta ₂ and the reinforcing region 6 of the embankment body portion 2 are the same, the thickness L of the reinforcement region 6 and below However, even if the ratio of the cross section of the reinforcement region 6 in the cross section of the embankment is the same, as shown in FIG. 4, the thickness L _{T of the} lower end is larger than the thickness L _T of the upper end of the reinforcement region 6. _By increasing _B , that is, the following equation L _T <L _B ... (1) (L _T + L _B ) / 2 = M · H (2), the ratio of L _T and L _B is variously examined to determine an appropriate value, and the thickness of the reinforced region 6 is set to L _T and L _B. The stability of the embankment slope can be more effectively increased by gradually changing the height depending on the height. This is because the slip surface LS at the time of slip collapse of the embankment slope is the slope A at the lower end of the outer slope in the reinforced region 6 as shown by the alternate long and short dash line in FIG.
Also, since it occurs in an arc shape passing through the shoulder C of the embankment body 2 and centered on the point O, the thickness L is uniform in the vertical direction as shown by the broken line.
When (= m · H), the length of the slip surface LS in the reinforced region 6 is A to P ₁ , whereas the reinforced region 6 is
The thickness of the slip surface LS in the reinforced region 6 is increased to A to P ₂ by changing the thickness so that the thickness L _B at the lower end is larger than the thickness L _T at the upper end, and Slip surface LS in the embankment body 2 which is a reinforced area
Is reduced from P ₁ -B to P ₂ -B.

As shown in FIG. 5, the stability of the entire slope including the reinforced area 6 is evaluated by the shear strength along the portion which becomes the slip surface LS, that is, the low strength in the reinforced area 6.
Shear strength τ _{C of the} highly deformable mortar 6 ′ and shear strength τ _S of the embankment material in the embankment body 2 which is the unreinforced region τ (=
c + σ _N · tan φ, where c; adhesive strength of embankment material, φ;
The internal friction angle of the embankment material) from A to S on the slip surface LS
The stability calculation is performed by calculating the slip resistance force integrated along P and P to B. In order for this slip resistance to act effectively and stably on the entire embankment slope, the shear strength τ _C in the reinforced region 6 and the shear strength τ _S in the embankment body 2 must be simultaneously exhibited. For this reason,
The reinforced region 6 is formed of a low-strength, high-deformability mortar 6'having sufficient strength to stabilize the entire embankment slope and having the same deformability as the embankment material. Therefore, as the low-strength, high-deformability mortar 6 ′, in addition to the above-mentioned cement mixed with bentonite, sand and water, according to the characteristics of the embankment material of the embankment main body 2, Soil cement mixed with part of ordinary soil used as embankment material by cutting earth's ground, fiber reinforced mortar mixed with steel fiber or plastic fiber,
Alternatively, a fiber-reinforced soil cement in which steel fibers or plastic fibers are mixed with the soil cement is preferably used.

[0019] FIG In Construction of embankment structures such as 5, for example, than the slope gradient theta ₂ of the embankment body portion 2 shown in FIG. 2, the gradient of the outer slopes theta ₆ That mold 4 of the reinforcement region 6
The inclination angle of the dam plate 41 is made gentle, and the width of the casting space for the low-strength, high-deformability mortar 6'is gradually narrowed as the construction moves to the upper layer.

The present invention is not limited to the illustrated embodiment. For example, by setting the horizontal thickness (average thickness in FIG. 4) L of the reinforcing region 6 to be L> m · H, the strength against slip collapse can be further improved.

[0021]

According to the present invention, the following effects are realized. 1. Since the strength of the embankment slope against slip failure increases, it is possible to create a high embankment with a steep slope, thus increasing the site area on the embankment or saving the business site area necessary for creation. Can be achieved. 2. The construction cost can be reduced by eliminating the need for a special reinforcement material for embankment formation. 3. In order to form a reinforced area on the slope surface of the embankment body with low-strength and high-deformability mortar, which has the same degree of deformability as the embankment material and the strength required for stable slope, subsidence deformation and shearing of the ground Deformation can be followed and slope erosion due to rainfall does not occur.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a first embodiment of a method for forming embankment according to the present invention in process order.

FIG. 2 is a cross-sectional view showing an embankment formed by the forming method of the above embodiment.

FIG. 3 is a diagram for explaining the effect of the forming method of the above embodiment.

FIG. 4 is a diagram for explaining a change in shear strength depending on the thickness of a reinforced region of the embankment created.

FIG. 5 is a diagram for explaining a change in shear strength along a slip surface that occurs in the constructed embankment.

[Explanation of symbols]

1 foundation ground or rock 2, 2 _1, 2 ₂ ... 2 _n embankment body portion 2a _1, 2a ₂ slopes 3,3 _1, 3 ₂ filter layer 4 Formwork 41 dam 5,5 ₁ tarp 6,6 ₁ Reinforcement area 6'Low strength and high deformability mortar

Claims (4)

[Claims] 1. A fill material is sprinkled out and compacted to form a fill main body having a slope having a predetermined layer thickness, and a weir plate is assembled at a proper distance from the slope to the slope. , Cement between the formwork and the slope, bentonite,
A method for forming embankment, which comprises a step of forming low-strength / high-deformability mortar in which sand and water are mixed in an appropriate ratio to form a reinforced region. 2. A filter layer made of drainage material is formed on the slope of the raised embankment main body, a waterproof sheet is laid on the surface of the filter layer, and a low-strength, high-deformability mortar is used for the mold and the waterproof. The embankment forming method according to claim 1, wherein the embankment is placed between the sheet and the sheet. 3. The method for forming embankment according to claim 1, wherein the locally generated soil is mixed with the low-strength and high-deformability mortar. 4. The embankment construction method according to claim 1, wherein the reinforcing fiber is mixed with the low-strength, high-deformability mortar.