JP2008150859A - Reinforcing structure of ground level different part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reinforcing structure of a ground level difference, capable of exhibiting the reducing effect of a load acting on an underground structure on a high level, by improving soil of a refilling part, regardless of a position of an upper structure. <P>SOLUTION: Improved earth 7 is filled in a space between a cantilever retaining wall 3 and the existing ground 6. The improved earth 7 is rolled and solidified after mixing and agitating by inputting a cement-based solidifying material to refilled surplus soil by a hydraulic excavator, after refilling the surplus soil generated by excavation work at a job site. A foundation 4 of the upper structure is arranged over an improved part 8 and the existing ground 6, and unimproved ordinary earth 9 is also refilled in the improved part 8 so as to become the same level as the existing ground. A form of the foundation 4 of the upper structure is a continuous footing, and an inclined face 10 (a boundary surface between the improved part 8 and the existing ground 6) of the existing ground 6 and the foundation 4 are substantially orthogonally constituted. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a reinforcing structure when an underground structure such as a retaining wall is constructed to reinforce a step portion of the ground.

  Conventionally, underground structures such as retaining walls have been constructed for the purpose of preventing the collapse of the ground and effective use of the land at the level difference portion of the ground. When constructing underground structures such as retaining walls, (a) If there is a ground that obstructs the construction of the underground structure, excavate the relevant part, and (b) construct the underground structure (C) The back surface of the underground structure is backfilled, and the ground surface is restored or newly constructed.

  In this case, what is used for backfilling the back of underground structures is generally the remaining soil or mountain sand generated by excavating the ground, but when constructing a structure above the backfill, Sometimes crushed stone is used to prevent sinking of the return part. In any case, since a lateral pressure such as earth pressure acts on the underground structure in the horizontal direction, it is necessary to consider the lateral pressure when designing the underground structure.

  Moreover, as disclosed in Patent Document 1, when a building is constructed on the ground surface near the stepped portion, the earth pressure acting on the rising portion of the retaining wall is reduced as much as possible by the load of the building. For this reason, the soil layer directly under the foundation of the building has been improved. In this case, the earth pressure due to the load of the building can be reduced.

JP 2001-164557 A

  However, in the technique disclosed in Patent Document 1, the earth pressure of the improved soil layer does not act on the retaining wall, but the soil pressure of the non-improved soil layer acts on the retaining wall directly or through the improved soil layer. Retaining walls must be designed in consideration of this earth pressure. In particular, the smaller the aspect ratio of the improved soil layer (the longer it becomes longer), the more the improved soil layer is against the earth pressure caused by the unmodified soil layer. There was a problem that the function as the “shield” was weakened and the effect of the improved soil layer formation was impaired.

  In addition, since the improved soil layer is limited to just below the foundation of the superstructure, if the superstructure is rebuilt, the foundation may be placed in an area other than the modified soil layer. There was also a problem that the soil quality had to be improved again according to the layout of the foundation after rebuilding because the soil pressure due to the load of the building would act in addition to the soil pressure of the unimproved soil layer.

  The present invention solves the above-described problems of the prior art, and can provide a high level of effect of reducing the load acting on the underground structure by improving the soil quality of the backfill portion regardless of the position of the upper structure. It aims at providing the reinforcement structure of a level | step-difference part.

  A first configuration of a ground level difference portion reinforcing structure according to the present invention for solving the above-described problem is a ground level difference portion reinforcing structure constituted by an underground structure capable of resisting earth pressure, and has a predetermined structure. An underground structure is constructed in such a manner that the bottom plate edge is in contact with or near the starting point of the slope on the ground step portion where the slope with the inclined angle is formed. The gap between the ground and the ground is backfilled with improved soil having a predetermined compressive strength and shear strength to a predetermined height.

  Moreover, the 2nd structure of the reinforcement structure of the ground level | step-difference part which concerns on this invention uses the improved soil as a low water absorption material in the said 1st structure, It is characterized by the above-mentioned.

  Further, the third structure of the reinforcing structure of the ground step portion according to the present invention is the same as that of the first or second structure, the existing ground with respect to the foundation beam of the upper structure constructed on the high side of the ground step portion. The inclined surfaces are set so as to be substantially orthogonal.

  Moreover, the 4th structure of the reinforcement structure of the ground level | step-difference part which concerns on this invention is the root cutting bottom surface of the foundation of the said upper structure, or ground work in any one of the said 1st-3rd structure. It is characterized by being substantially the same as the height of the surface.

  According to the reinforcing structure of the first ground level difference portion according to the present invention, the earth pressure acting on the underground structure can be reduced by backfilling with the improved soil having the predetermined compressive strength and shear strength. Furthermore, since the existing ground forms an inclined surface having a predetermined inclination angle, it is possible to eliminate as much as possible the influence of the earth pressure of the existing ground having a larger earth pressure coefficient than the improved portion. In addition, since the backfill portion is entirely improved, construction can be performed without considering the arrangement of the upper structure.

  According to the reinforcement structure of the 2nd ground level | step-difference part which concerns on this invention, the increase in the side pressure by water | moisture content can also be suppressed with respect to an underground structure by making improved soil a thing with low water absorption.

  According to the reinforcing structure of the third ground level difference portion according to the present invention, the upper structure is different by arranging the boundary portion between the existing ground and the improved portion so as to be substantially orthogonal to the foundation beam of the upper structure. Even when arranged over the existing ground showing the properties and the improved portion, the rigidity of the foundation beam can sufficiently function to enhance the structural safety.

  According to the fourth ground level difference reinforcement structure of the present invention, since the improved surface is made to coincide with the rooted bottom surface or the groundwork surface of the foundation of the upper structure, the foundation can be constructed directly on the improved surface. The labor of construction is reduced.

  Hereinafter, the best mode for carrying out the reinforcing structure of a ground level difference portion according to the present invention will be described. The present invention realizes a reinforcing structure for a ground step portion that can exert a high level of effect of reducing the load acting on the underground structure by improving the soil regardless of the position of the upper structure regardless of the position. To do.

  In the present invention, the underground structure constructed in the ground level difference part is not in a state of being completely embedded in the ground, but is constructed in the level difference part of the ground, and is the soil by the high side or the upper structure. This refers to structures such as retaining walls that receive pressure, underground garages, and cloth foundations of buildings.

  When the underground structure is a retaining wall, the structure type is not particularly limited, and cantilevered retaining walls such as L-shape and inverted T-shape made of reinforced concrete, gravity-type retaining walls made of concrete, It can be applied to various types such as leaning type retaining walls constructed by stacking slanting stones and wisdom blocks.

  The improved soil filled in the improved portion on the back side of the underground structure may have a predetermined compressive strength and shear strength, as long as it can reduce the earth pressure acting on the underground structure, A material obtained by adding an improving material to the remaining soil generated during excavation, mixing, stirring, and solidifying is preferable from the viewpoint of reducing the disposal amount of the remaining soil. As the improvement material, a powdered cement-based solidification material is preferable, and by adjusting the components and mixing ratio of the solidification material, the compressive strength and shear strength of the improved soil can be set to desired values, and vertical load is applied. Even so, it is possible to provide strength that does not cause earth pressure. Further, by mixing and stirring with the improving material and rolling and solidifying, it is possible to limit the water absorption such as rainwater and to reduce the lateral pressure acting on the underground structure as much as possible.

  It is preferable that the slope formed in the step portion of the ground has an inclination angle based on the stress dispersion angle of the soil constituting the ground in the existing ground on the high place side. Here, the stress dispersion angle is an angle at which a stress spreads when a downward vertical load is applied to a certain point on the ground and the load is transmitted downward to the ground.

  The inclination angle of the existing ground (the elevation angle formed by the straight line connecting the tip of the bottom of the bottom plate of the underground structure and the tip of the existing ground) is a value based on the stress dispersion angle (α), that is, (90−α) degrees or less By doing so, the weight of the existing ground and the vertical load applied to the existing ground are not transmitted to the improved soil, and the earth pressure acting on the underground structure can be reduced. In addition, since the stepped portion is stabilized, temporary work such as a parent pile and a sheet pile for preventing the stepped portion from collapsing can be omitted or simplified. The stress dispersion angle varies depending on the soil composition, but in the case of general clay soil in the Kanto region, it can be regarded as approximately 30 to 45 degrees.

  The underground structure constructed in the ground level difference portion is located at a position where the bottom plate end is in contact with the starting point of the slope or in the vicinity of the starting point. When the bottom plate end is in a position in contact with the starting point of the slope, the amount of earth and sand excavated at the stepped portion can be reduced, which is preferable. Although the end of the bottom slab is not in contact with the starting point of the slope, the reinforcement structure intended by the present invention can be realized, but the amount of excavation of the sand increases as the bottom slab end separates from the starting point of the slope. It is preferable that it is the vicinity.

  When constructing an upper structure such as a building across the existing ground and the improved portion on the high side of the ground stepped portion reinforced with the above configuration, the compressive strength, spring constant, etc. of the existing ground and the improved portion It is preferable that a foundation having high rigidity is provided in order to reduce the influence on the superstructure due to the difference. The foundation type for giving high rigidity is preferably a continuous foundation (cloth foundation), and the inclined surface of the existing ground (boundary surface between the existing ground and the improved part) is set so that it is substantially orthogonal to the foundation. Is preferred. By comprising in this way, the rigidity which a foundation has fully functions can improve the structural safety | security of a superstructure.

In addition, when constructing an upper structure such as a building on the high side of the ground stepped portion reinforced with the above structure, the improved soil is equal to the height of the bottom root of the foundation of the upper structure or the groundwork surface. It is preferable to do. By comprising in this way, when constructing the foundation of the superstructure, it is possible to construct the foundation directly without adjusting the level of the improved portion, and to reduce the labor of construction.

  Next, the first embodiment of the reinforcing structure of the ground level difference portion according to the present invention will be specifically described with reference to the drawings. The present embodiment is a reinforcing structure in a ground step portion constructed with an L-shaped cantilever retaining wall, FIG. 1 is a plan view of the first embodiment of the reinforcing structure of the ground step portion, and FIG. 2 is a sectional view. .

  In FIG. 1, the alternate long and short dash line indicates the range of the site 1 where the upper structure is constructed by applying the reinforcing structure of the present embodiment, and the adjacent land 2 on the left side of the drawing is lower than the site 1. In order to reinforce the step portion of the ground, a cantilever retaining wall 3 that is an underground structure is constructed along the boundary of the adjacent land. The cantilever retaining wall 3 is made of reinforced concrete, and has an L-shaped cross section consisting of a bottom plate 3a and a rising wall 3b, as shown in FIG. 2, and is composed of cracked stone, crushed stone, discarded concrete, etc. It is constructed in the upper part of the business surface 3c.

  Prior to the construction of the cantilever retaining wall 3, excavation work is performed on the ground. The excavation work is performed at a height above the ground step 3c and a predetermined angle from the tip of the bottom slab 3a. It is applied to a region above the line 5 indicated by a two-dot chain line drawn to the side. Here, the predetermined angle is based on the stress dispersion angle α of the ground constituting the site 1 described above. For example, when the stress dispersion angle α is 30 degrees, the angle is 90-30 = 60 degrees or less. It is. This angle may be 60 degrees or less. However, the smaller the angle, the greater the amount of excavation of the ground, which increases labor and cost. Therefore, it is preferable to set the angle close to 60 degrees.

As shown in FIG. 2, the space between the cantilever retaining wall 3 and the existing ground 6 on the high place side is filled with the improved soil 7. The improved soil 7 is obtained by refilling residual soil generated by excavation work on site, adding cement-based solidification material to the backfilled residual soil, mixing and agitating with a hydraulic excavator, and then rolling and solidifying. The input amount of the solidifying material is 50 to 150 kg with respect to 1 m ³ of the remaining soil, the compressive strength of the improved soil 7 after solidification is 0.073 N / mm ² or more, and the shear strength is 0.036 N / mm ² or more. is there. This is sufficiently strong if the upper structure is of a size of a medium- and low-rise housing, and the influence of earth pressure on the underground structure such as the cantilever retaining wall 3 is negligible. Further, the level of the upper end of the improved soil 7 is set in advance equal to the level of the bottom surface of the footing 4b of the foundation 4 of the superstructure described later, and the foundation 4 is constructed directly on the improved portion 8 without level adjustment. can do.

  The base 4 of the superstructure is reinforced concrete, and has an inverted T-shaped cross section consisting of a base beam 4a and a footing 4b as shown in FIG. In the upper part of the improved portion 8, ordinary soil 9 that has not been improved is backfilled so as to be at the same level as the existing ground 6.

  Since the improved portion 8 has improved compressive strength and shear strength compared to ordinary soil that is not improved, the improved portion 8 acts on the rising wall 3b of the cantilever retaining wall 3 due to the weight of the improved soil 7 or a load caused by an upper structure. The earth pressure to be reduced is reduced. Furthermore, since the existing ground 6 has an inclination angle based on the stress dispersion angle, even if a load due to the weight of the existing ground 6 or an upper structure is applied, the load exceeds the range of the existing ground 6 and enters the improved portion 8 side. It is never transmitted. Therefore, the earth pressure that the rising wall 3b of the cantilever retaining wall 3 receives from the improved soil 7 and the existing ground 6 is reduced, the thickness of the rising wall 3b and the amount of reinforcing bars are reduced, and the length of the bottom plate 3a is reduced. Therefore, the labor and cost for constructing the cantilever retaining wall 3 can be greatly reduced. Such an effect is exhibited regardless of the position of the ground structure, and it is also possible to deal with a case where the value of the vertical load or the position where it acts changes due to rebuilding of the ground structure or the like. Further, since the improved soil 7 has a lower water absorption than ordinary soil that is not improved, it is possible to reduce as much as possible the side pressure acting on the rising wall 3b due to water absorption during rainfall.

The upper structure is arranged in parallel with the cantilever retaining wall 3 and the improved portion 8 is also formed in parallel with the cantilever retaining wall 3. Are arranged so as to be orthogonal to the inclined surface 10 of the existing ground 6 (the boundary surface between the improved portion 8 and the existing ground 6). By configuring in this way, even if the upper structure is arranged across the improved portion 8 having different strength and hardness and the existing ground 6, the rigidity of the foundation 4 functions sufficiently to increase the structural safety. Can do.

  Next, the second embodiment of the ground level difference reinforcing structure according to the present invention will be described in detail with reference to the drawings. The present embodiment is a reinforcing structure in a ground step portion in which a leaning type retaining wall using a cognitive block is constructed, and FIG. 3 is a cross-sectional view of a second embodiment of the reinforcing structure of the ground step portion.

  In FIG. 3, 11 is a leaning type retaining wall using a cognitive block, 11 a is a concrete bottom slab, 11 b is a cognitive block, and 11 c is a geotechnical surface. Since other configurations are the same as those of the first embodiment, description thereof is omitted. Since the cognitive block 11c has a structure that does not stand on its own, it cannot be constructed according to the procedure of filling the improved soil after the stacking of the cognitive blocks has been completed. In this embodiment, (a) the knowledge block 11c is stacked one stage. (B) The improved soil 7 is filled to a level at which the upper knowledge block 7 can be placed. By repeating this process a plurality of times until the cognitive block 11b reaches a predetermined height, the ground level stepped portion reinforcement structure in which the leaning type retaining wall 11 using the cognitive block 11b is constructed is realized. In addition, in FIG. 3, 12 is earth retaining concrete.

  Since the improvement part 8 has improved compressive strength and shear strength compared with the soil which does not improve, the earth pressure which acts on the cognitive block 11b by the load by the dead weight of the improvement soil 7, an upper structure, etc. is reduced. . Further, since the existing ground 6 has an inclination angle based on the stress dispersion angle α, even if a load due to the weight of the existing ground 6 or an upper structure acts, the load exceeds the range of the existing ground 6 and the improved portion 8 side. Will not be transmitted. Therefore, the earth pressure received by the knowledge block 11b from the improved soil 7 and the existing ground 6 is reduced, and the effective angle of the site 1 can be increased by increasing the inclination angle of the knowledge block 11b. Further, since the improved soil 7 has a lower water absorption than ordinary soil that is not improved, it is possible to reduce as much as possible the increase in the side pressure acting on the knowledge block 11b due to water absorption during rainfall.

  Further, since the superstructure is arranged in parallel with the leaning type retaining wall 11 and the improved portion 8 is also formed in parallel with the leaning type retaining wall 11, the foundation 4 is continuous in the left-right direction in FIG. Is arranged so as to be orthogonal to the inclined surface 10 of the existing ground 6 (the boundary surface between the improved portion 8 and the existing ground 6). By configuring in this way, even if the upper structure is arranged across the improved portion 8 having different strength and hardness and the existing ground 6, the rigidity of the foundation 4 functions sufficiently to increase the structural safety. Can do.

  Since the present invention is a reinforcing structure that reduces the influence of earth pressure on underground structures, it has a high utility value particularly in a retaining wall whose cross-sectional shape is determined by investigation of overturning and sliding.

It is a top view of the 1st example of the reinforcement structure of the ground level difference part concerning the present invention. It is sectional drawing of the 1st Example of the reinforcement structure of the ground level | step-difference part which concerns on this invention. It is sectional drawing of the 2nd Example of the reinforcement structure of the ground level | step-difference part which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Site 2 ... Neighboring land 3 ... Cantilever retaining wall 3a ... Bottom plate 3b ... Rising wall 3c ... Groundwork surface 4 ... Foundation 4a ... Foundation beam 4b ... Footing 5 ... Line 6 ... Existing ground 7 ... Improvement soil 8 ... Improvement part DESCRIPTION OF SYMBOLS 9 ... Ordinary soil 10 ... Inclined surface 11 ... Leaning type retaining wall 11a ... Bottom plate 11b ... Machi block 11c ... Groundwork surface 12 ... Earth retaining concrete α ... Stress dispersion angle

Claims (4)

Reinforcement structure of ground level difference part composed of underground structures that can resist earth pressure, and the bottom plate end touches the starting point of the slope or the ground level difference part where the slope with a predetermined inclination angle is formed. An underground structure is constructed so as to be located in the vicinity, and the gap between the underground structure and the existing ground on the high place side is improved soil having a predetermined compressive strength and a shear strength up to a predetermined height. A structure for reinforcing a ground level difference portion, characterized by being backfilled. The reinforcing structure of a ground level difference part according to claim 1, wherein the improved soil is made of a low water absorption material. The ground level difference according to claim 1 or 2, wherein an inclined surface of the existing ground is set to be substantially orthogonal to a base beam of an upper structure constructed on a high side of the ground level difference part. Reinforcement structure of the part. 4. The structure for reinforcing a ground level difference portion according to claim 1, wherein the predetermined height is substantially the same as a height of a rooted bottom surface or a geotechnical surface of a foundation of the superstructure. .

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