JP3224503B2 - Road construction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a construction method for constructing a road by embankment on soft ground.

[0002]

2. Description of the Related Art As shown in FIG. 4, when a road is constructed by embankment on a soft ground where the thickness of a buried layer or an alluvial layer is thick, a ground improved in rigidity by performing a shallow ground improvement as shown in FIG. It is a common practice to provide a floor, a subgrade made of various crushed stones and the like by embankment, and paving the floor. (In the present specification, the roadbed and the pavement are not separated, and the two are collectively referred to as road pavement.) In some cases, a friction pile is further provided below the improved ground to suppress settlement due to consolidation.

[0003]

On the roadbed of a road, a dynamic load due to traffic is applied together with a static load due to embankment.
These are combined and transmitted to the subgrade. Therefore, if the degree of improvement is not sufficient, the road will not be able to withstand the dynamic load several times as large as it can withstand the consolidation settlement due to the static load, and the road will continue to consolidate due to the dynamic load. Become. On the other hand, if the ground is sufficiently improved, it is of course possible to suppress consolidation settlement due to dynamic loads, but the relationship between the degree of ground improvement and the effect of suppressing consolidation settlement due to dynamic loads has been well understood. Because of the lack of consolidation settlement, excessive ground improvement often resulted in useless construction periods and wasteful expenditures.

[0004]

SUMMARY OF THE INVENTION The present invention was made as a result of studying an efficient ground improvement method for substantially eliminating consolidation settlement due to dynamic load of a road constructed thereon. .

[0005] That is, the present invention is applied to soft ground on a road foundation.
A soil cement columnar body is constructed at a planar view improvement rate of 20 to 60% as a lattice arrangement or a non-contact staggered arrangement as a planar arrangement, and a consolidated soil is mixed therewith to lay an improved consolidated soil, and This is a road construction method characterized in that a road pavement is constructed thereon, and the height from the tip of the soil cement column to the road pavement surface is 4 m or more. And
When the plane arrangement is a grid arrangement, the grid spacing is set to less than twice the height from the upper end of the soil cement column to the road pavement surface, and when the plane arrangement is a non-contact staggered arrangement, two adjacent The interval between the soil cement pillars is set to not more than twice the height from the upper end of the soil cement pillars to the road pavement surface.

When a combination of forming a soil cement column for improving the deep ground and laying an improved soil consolidated with a consolidating material for improving the shallow ground is adopted, the length of the soil cement column plus the shallow length is used. The thickness of the layer-improved soil (roadbed) + the thickness of the road pavement is a large condition for suppressing consolidation settlement due to dynamic load. When this value exceeds 4 m, consolidation settlement due to dynamic load is substantially reduced. Can be eliminated. Furthermore, it is sufficient that the soil cement columnar body is formed in an improvement ratio in plan view of 20 to 60%, and there is no need to particularly increase the improvement ratio.

In the present invention, the value of the above-mentioned length of the soil cement column + thickness of the improved shallow soil (roadbed) + thickness of the road pavement needs to be at least 4 m, but it is necessary to increase the value. The effect of suppressing dynamic consolidation settlement is not so large. However, the larger the size, the greater the effect of suppressing static consolidation settlement. Usually, the length of soil cement column is 3 ~
5 m, the thickness of the shallow layer improved soil is set to 0.5-1 m, the thickness of the road pavement is set to 10-50 cm, and the height from the tip of the soil cement column to the road pavement surface is set to 4-7 m. Is set.

[0008] The purpose of the present invention is to prevent the lateral flow of the ground due to the dynamic load in the soil cement columnar body constructed for deep ground improvement, but the planar arrangement is a lattice-like arrangement or a non-contact staggered arrangement. The improvement rate in plan view is kept as low as possible. In the case where the grid-like arrangement is employed in the range of the planar view improvement rate of 20 to 60%, the grid interval is 2 times the height from the upper end of the soil cement column to the road pavement surface.
If it is less than twice, the static load and the dynamic load can be reliably transmitted to the soil cement columnar body, and the lateral flow of the ground can be sufficiently prevented.

Similarly, when the non-contact staggered arrangement is adopted, the distance between two soil cement pillars adjacent in the direction of the road axis and the direction perpendicular thereto is also the height from the upper end of the soil cement pillar to the road pavement surface. If it is less than twice the static load and the dynamic load can be reliably transmitted to the soil cement columnar body, and it is possible to sufficiently prevent lateral flow of the ground.

The above is a case where there is no buried structure in the foundation ground on which a road is constructed. However, when constructing a road, it is necessary to cross over an existing underground structure such as a culvert or to construct a road. In many cases, existing underground structures such as culverts are laid, and then roads are built across them. The underground structure is usually supported by a support pile reaching the support layer, and does not sink, and the sink is very small. If consolidation subsidence due to dynamic load occurs on a road constructed over an underground structure that hardly sinks, a step will occur on the road between the upper part of the underground structure and the part adjacent to it. Dangerous on traffic.

The present invention is also used for eliminating such a step. That is, in the vicinity of the underground structure, a long soil cement column having a height from the tip of the soil cement column to the roadbed pavement surface of 4 m or more is constructed, and the longer the distance from the underground structure, the shorter the soil cement column becomes. By constructing the body, measures will be taken to minimize consolidation settlement near the underground structure and to allow some degree of consolidation settlement gradually as it moves away. Even in this case, the step-elimination method needs to be efficient and economical.Therefore, various conditions for ground improvement near the underground structure, that is, in the case of the planar arrangement of the soil cement pillars to be constructed and the lattice arrangement The grid spacing, the spacing between adjacent soil cement columns in the case of non-contact staggered arrangement, the improvement rate in plan view, the mixing conditions of shallow-layer improved soil, etc. apply the same conditions as when improving over the entire length of the road described above. The difference is that the length of the soil cement column gradually decreases as the distance from the underground structure increases.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view of a road constructed according to the present invention. FIG. 1A is a cross-sectional view of a general portion in a direction perpendicular to a road axis.
(B) is a cross-sectional view of a cross section of the underground structure in the direction of the road axis. FIG. 2 is a graph showing the relationship between the amount of consolidation settlement of a road constructed according to the present invention and the conventional method, and time. 3A and 3B show an example of a planar arrangement of the soil cement pillars, wherein FIG. 3A shows an example of a lattice arrangement, and FIG. 3B shows an example of a non-contact staggered arrangement. FIG. 4 is a cross-sectional view in a direction perpendicular to the road axis of a road constructed by two slightly different conventional methods.

Referring to FIG. 1 (a), an example of a general road construction method according to the present invention will be described along with construction procedures.

(1) The target soft ground is slightly excavated, and a soil cement columnar body 1 having a diameter of 80 cm is formed in a non-contact staggered manner at a pitch of 200 cm (both in the road axis direction and in the orthogonal direction) by a normal soil cement column method. Constructed with 25% improvement in plan view. The length of the soil cement column 1 is 350 cm. The length of the soil cement column 1 is set to 200 cm depending on the construction section, assuming that the length is short.

(2) A 70-cm-thick improved shallow soil layer 11 is formed by mixing a cement-based solidifying material with excavated soil and earth and sand conveyed from another place and consolidating it.

(3) A particle size adjusting crushed stone layer 15 is laid in a thickness of 10 cm, and the crushed stone layer 15 is paved with an asphalt concrete 16 having a thickness of 5 cm.

With the above, the construction of the general road according to the present invention is completed, and a road having a height of 435 cm from the tip of the soil cement pillar to the road pavement surface is constructed. Even when a soil cement column is constructed, if the length is 200 cm, the height from the tip of the soil cement column to the road pavement surface is 285 cm.

In the case of the cross section of the underground structure shown in FIG. 1B, the length of the soil cement column 1 of the above (1) is set to 35.
Construction is performed in the same manner as described above except that the number of steps is reduced in several steps from 0 cm to 200 cm.

FIG. 2 is a time subsidence curve showing the relationship between the elapsed time and the amount of subsidence of a road constructed by various methods. 1-In the case of the present invention, the m-soil cement column is constructed, but the soil cement column is constructed. The height from the tip of the road to the road pavement is 2
In the case of 85 cm, n—the case of the conventional method shown in FIG.

As is apparent from the graph, the settlement amount due to the static load until the start of operation is small and no significant difference is recognized, but the settlement amount due to the dynamic load after the start of operation has a large difference. It can be seen that the effect of suppressing the consolidation settlement by the dynamic load of the road constructed by the present invention is great.
By the way, even if the soil cement column is constructed, when the length is short, it is understood that there is not much difference between the case where the conventional shallow ground is sufficiently improved and the effect of suppressing the consolidation settlement by the dynamic load.

FIG. 3 illustrates the grid spacing in the case of a grid arrangement and the spacing between two adjacent soil cement columns in the case of employing the non-contact staggered arrangement in relation to the planar arrangement of the soil cement columns. As shown in (a), when the grid is rectangular, the longer interval d is the grid interval. In addition, as shown in (b), the interval between two adjacent soil cement pillars is such that when the pitch of the non-contact staggered arrangement is different between the road axis direction and the direction orthogonal thereto, the longer distance d 'is columnar. It is body spacing.

[0023]

According to the present invention, a combination of forming a soil cement column for improving the deep ground and laying improved soil consolidated with a consolidating material for improving the shallow ground, and adopting a planar arrangement in a grid-like configuration. Soil at a planar view improvement rate of 20 to 60%, with the grid spacing of soil cement columns or the spacing between adjacent soil cement columns being no more than twice as large as the road pavement surface from the top of the soil cement columns as an arrangement or non-contact staggered arrangement By constructing a cement column and setting the value of the thickness of the shallow-layered improved soil (roadbed) + the thickness of the road pavement to 4 m or more, despite the fact that the improved area of the deep ground is small, It is possible to suppress the consolidation settlement due to the dynamic load. As a result, it is possible to construct an efficient road with low construction costs.

When a road is constructed by crossing over an existing underground structure which hardly sinks, a pavement surface near the underground structure buried in the soft ground of the road foundation from the tip of the soil cement columnar body. To construct a long soil-cement column having a height of at least 4 m, and gradually constructing a short soil-cement column as the distance from the underground structure increases, and the plane of the soil-cement column. When the arrangement is grid-like or non-contact staggered, the grid spacing or the spacing between two adjacent soil cement pillars is less than twice the height from the top of the soil cement pillar to the road pavement surface, and the improvement rate in plan view is reduced. A soil cement column is constructed at 20 to 60%, and the improved soil laid by mixing a solidifying material to improve the shallow ground is laid on it, and a road pavement is further laid on it. By building, it is possible to prevent the generation of steps that occurred road crossing the existing underground structure Butsujo not sink. That is, in the vicinity of the existing underground structure, consolidation settlement is suppressed as much as possible, and a certain degree of consolidation settlement is allowed gradually as the distance increases. As a result, it is possible to construct an efficient road with low construction costs.

[Brief description of the drawings]

FIG. 1 is a sectional view of a road constructed according to the present invention;
FIG. 3 is a cross-sectional view of a general part in a direction orthogonal to a road axis, and FIG. 4B is a cross-sectional view of a crossing part of an underground structure in a road axial direction.

FIG. 2 is a graph showing a relationship between a consolidation settlement amount and time of a road constructed by the present invention and a conventional method.

FIG. 3 shows an example of a planar arrangement of a soil cement pillar,
(A) is an example of a lattice arrangement, and (b) is an example of a non-contact staggered arrangement.

FIG. 4 is a cross-sectional view of a road constructed by two slightly different conventional methods in a direction perpendicular to the road axis.

[Explanation of symbols]

1. Soil cement column, 2. Support pile, 3. Underdrain, 11. Cement-based solidified dry mixed shallow layer improved soil layer, 12. Quick lime dry mixed shallow layer improved soil layer, 13.
Fe lime dry-mixed shallow layer improved soil layer, 14. Crusher run layer, 15. Crushed stone layer, 16. Asphalt concrete layer.

──────────────────────────────────────────────────続 き Continuing on the front page (73) Patent holder 591072949 Tokyo Hoso Kogyo Co., Ltd. 2-4-2-4 Sotokanda, Chiyoda-ku, Tokyo (72) Inventor Tetsuhiko Miura 850-4, Hatsujo-cho, Honjo-cho, Saga-shi, Saga ( 72) Inventor Kazuyuki Fujikawa 1-7-5, Einomaru-minami-cho, Yahata-nishi-ku, Kitakyushu-shi, Fukuoka (72) Inventor Akira Hamake 1-82, Yayoi, Kasuga-shi, Fukuoka San-ai City Life No. 3-311, Kasuga (72) Invention Person Hideki Tanaka 380-2 Amagi, Omuta-shi, Fukuoka (72) Inventor Fukuda 6-13-7 Akasaka, Minato-ku, Tokyo Inside Tenox Co., Ltd. (72) Inventor Shigeru Yoshida 6-13, Akasaka, Minato-ku, Tokyo No. 7 Inside Tenox Co., Ltd. (56) References JP-A-50-44629 (JP, A) JP-A-60-152718 (JP, A) JP-A-51-93515 (JP, A) (58) Investigated Field (Int.Cl. ^7, DB name) E01C 3/00 - 3/04 E02D 3/00 101 E02D 3/12 101

Claims (4)

(57) [Claims] 1. A soil cement column having a lattice arrangement in a plane arrangement on a soft ground of a road foundation, and a lattice interval of 2 heights from the upper end of the soil cement column to a road pavement surface.
It is constructed at an improvement rate of 20 to 60% in plan view, and a consolidated soil is mixed with a consolidated material to lay the improved soil, and a road pavement is further constructed thereon, and the soil cement columnar body is constructed. A road construction method characterized in that the height from the tip of the road to the road pavement surface is 4 m or more. 2. A soil cement column having a non-contact staggered plane arrangement on a soft ground of a road foundation, and an interval between two adjacent soil cement columns arranged on a road pavement surface from an upper end of the soil cement column. Up to twice the height up to the height of 20 to 60% in plan view, laying the improved soil that has been mixed with the consolidated material and consolidated, and then the road pavement The height from the tip of the soil cement column to the road pavement surface is 4 m or more. 3. A method of constructing a road on a soft ground of a road foundation by crossing over an underground structure with little settlement buried in the soft ground of a road foundation, wherein the road is buried in the soft ground of a road foundation. In the vicinity of an underground structure with little settlement, a long soil cement column having a height from the tip of the soil cement column to the roadbed pavement surface of 4 m or more is gradually reduced as the distance from the underground structure increases. While constructing the pillars, the planar arrangement of the soil cement pillars is set as a grid arrangement, and the grid spacing is set to be not more than twice the height from the upper end of the soil cement pillars to the road pavement surface. %, Constructing a soil cement columnar body, laying a consolidated soil mixed with a consolidating material, laying the consolidated soil, and constructing a road pavement on the underground structure and the modified soil. Characteristic road construction method. 4. A method of constructing a road on soft ground of a road foundation by crossing over an underground structure with little settlement embedded in the soft ground of a road foundation, wherein the road is buried in the soft ground of a road foundation. In the vicinity of an underground structure with little settlement, a long soil cement column having a height from the tip of the soil cement column to the roadbed pavement surface of 4 m or more is gradually reduced as the distance from the underground structure increases. While constructing the pillars, the soil cement pillars are arranged in a non-contact staggered plane, and the interval between two adjacent soil cement pillars is set at the height of the height from the upper end of the soil cement pillars to the road pavement surface. 2 times or less and improvement rate in plan view 20
Constructing a soil cement column at about 60%, laying a consolidated soil mixed with a consolidating material, laying the consolidated soil, and constructing a road pavement on the underground structure and the modified soil. Characteristic road construction method.