JP2010090532A - Method for restricting head of earth retaining wall - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for restricting or reinforcing the head of an earth retaining wall so as not to be deformed inward. <P>SOLUTION: The surface soil of the rear surface side ground of the head of the earth retaining wall is improved in a soil cement by mixing the original soil with cement or replaced with a soil cement. A plurality of anchor steel members 5 are buried in the surface-improved ground 4 improved in the soil cement generally horizontally in the rear surface direction, and at pitches promoting a reinforcement effect in the longitudinal direction of the earth retaining wall. One ends of the anchor steel members 5 are joined to the head of the earth retaining wall. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a construction method for constructing a retaining wall in the ground and excavating the inner ground of the retaining wall so as to restrain or reinforce the retaining wall so that the head of the retaining wall does not fall inwardly. It belongs to the technical field.

  As a mountain wall excavation method for excavating the ground by constructing a retaining wall around the ground to be excavated, conventionally, a method of constructing a retaining wall by placing a so-called sheet pile into the ground in a continuous wall state, or H In addition to implementing a method of constructing a retaining wall by placing a steel column into the ground and installing a retaining plate between the H-shaped steel columns, in the case of soft ground, Build a retaining wall made of continuous soil improvement pillars made of soil cement mixed and mixed with stabilizer (cement), or insert a core material into the ground improvement pillars to reinforce and stiffen it. A construction method for constructing a wall is widely implemented (see Patent Documents 1 to 3 below).

In addition, in Patent Document 4 below, a retaining wall is constructed in which ground improvement columns made of soil cement are connected, and abandoned concrete is placed on the surface of the ground on the back side of the head of the ground improvement columns. There is disclosed a mountain retaining wall method that is combined with the head of the ground improvement pillar and eliminates the need to build a core material in the ground improvement pillar, thereby reducing the cost.
Furthermore, in Patent Document 5 below, the ground side (back side ground) is used so that the beam supporting the soil cement pillar row retaining wall with core material from the inside becomes unnecessary or the number of steps of the beam can be reduced. ) Soil cement columns that are driven by a string material parallel to the core material of the soil cement column array, and the string material and the core material are connected by a bundle material and a diagonal material to reinforce and stiffen the side pressure on the natural ground side. A row retaining wall method is disclosed.

Japanese Patent Laid-Open No. 2-74715 Japanese Patent Laid-Open No. 4-115016 JP-A-7-197450 JP-A-11-350491 JP 2003-55959 A

The wall of the mountain wall built for the purpose of excavating the ground is a temporary structure, and is constructed and used on the assumption that it will be demolished and removed after the fact. Therefore, it is desirable that the temporary construction can be performed in as short a time as possible.
In that respect, the mountain wall wall construction method disclosed in Patent Documents 1 to 3 is effective as a construction method utilizing the characteristics of so-called soft ground. However, because it is originally soft ground, when a ground retaining wall is constructed and excavation of the ground begins, backhoes used for excavating the ground, crawler cranes used for erection of cut beams and excavation soil, dump trucks, etc. Heavy machinery rests on the back ground of the head of the retaining wall and operates close to the retaining wall, so that the side pressure against the head of the retaining wall increases due to the weight and work load of such heavy machinery. The head will be deformed to fall to the excavation side, resulting in significant deformations and subsidence of the surrounding ground, and serious problems such as the load exceeding the proof stress acting on the retaining wall.

  In that respect, the invention disclosed in the above-mentioned Patent Document 4 is abandoned concrete placed on the surface layer of the ground on the back side of the ground improvement column head and joined with the head of the ground improvement column. It is easy to misunderstand that it can be expected to have the effect of suppressing the deformation of. However, since the discarded concrete is only a concrete structure having a thickness of about 5 to 30 cm, when the above heavy machinery is placed on the discarded concrete on the head of the retaining wall, it is easily determined by the weight and work load of such heavy machinery. Since it cracks and breaks, it is difficult to expect the effect of suppressing an increase in lateral pressure on the head of the retaining wall. In addition, it is difficult to disassemble and remove post-mortem concrete. For example, it is impossible to expect to dismantle with a backhoe.

Instead of the above-mentioned discarded concrete, as a countermeasure when the back side ground of the head of the retaining wall is soft, the same applies to the case where the surface ground is modified to soil cement that can be easily disassembled and removed. It will collapse due to weight and work load, and it cannot be expected to reduce the lateral pressure load on the retaining wall.
Once the mountain retaining wall starts to be deformed to fall inward, the surface improvement body by the above-mentioned discarded concrete or soil cement starts to collapse easily, and the effect of dispersing the loading load (side pressure) disappears.

  Further, as in the invention disclosed in the above-mentioned Patent Document 5, a chord material parallel to the core material is driven into the ground mountain side (back side ground) from the soil cement pillar row retaining wall containing the core material, and the chord material and the core material The soil cement pillar row retaining wall constructed by connecting the two with a bundle material and an oblique member can also pay attention to the reinforcement and stiffening effect of the retaining wall. However, it cannot be said to be very effective for restraint and reinforcement that suppresses deformation of the head of the ground improvement pillar. In addition, it is cumbersome to drive and reinforce the string material and connect the string material and the core material with a bundle material and a diagonal material, which increases the construction cost, prolongs the work period, and requires time for disassembly and removal after the fact. There is a problem that it takes.

The object of the present invention is to reinforce the heavy machinery so that it does not crack or collapse due to the weight or work load of heavy machinery even if the heavy machinery rests on the backside ground of the retaining wall head and operates close to the retaining wall. It is possible to prevent the lateral pressure on the head of the retaining wall from increasing, and the deformation that the retaining wall head falls to the excavation side can be positively suppressed, so that the surrounding ground is not deformed or subsidized, Another object of the present invention is to provide a restraining method for a head of a retaining wall that can effectively prevent a load exceeding its proof stress from acting on the retaining wall.
The next object of the present invention is to provide a restraining method for the head of a retaining wall that is easy to construct and can be carried out in a short construction period, is easy to be disassembled and removed afterwards, and does not generate industrial waste. .

As means for solving the above-described problems of the prior art, the restraint method for the head of the retaining wall according to the invention described in claim 1 is:
A construction method for constructing a retaining wall 1 in the ground and restraining the head of the retaining wall 1 from being deformed in a retaining mechanism for excavating the inner ground of the retaining wall 1.
The surface soil of the back side ground of the mountain retaining wall head is improved to soil cement mixed with in situ soil and cement, or replaced with soil cement.
In the surface improvement ground 4 improved to soil cement, a plurality of anchoring steel materials 5 are embedded in a substantially horizontal arrangement in the back direction and in the longitudinal direction of the retaining wall at a pitch that provides a reinforcing effect. One end of the steel material 5 is connected to the head of the retaining wall.

The invention described in claim 2 is a method for restraining a mountain retaining wall head according to claim 1,
The construction of the surface soil on the back side of the mountain retaining wall head with soil cement is improved or replaced with soil cement. The construction method is to stir the surface soil in situ and mix with cement, or excavate the surface soil to improve. The soil transported to the facility, or excavated elsewhere and transported to the improved facility is mixed with cement in the improved facility and improved to soil cement, and the soil cement is refilled to the position of the surface soil. It is characterized by.
The invention described in claim 3 is the restraint method for the head of the retaining wall described in claim 1,
Reinforcing steel or PC steel material is used as the anchoring steel material 5, and the anchoring steel material 5 is embedded in the surface improvement ground 4 at a pitch suitable for reinforcement of the surface improvement ground 4 improved to soil cement, and is fastened therein. One end of the steel material 5 facing the core material 6 of the wall 1 is connected to the head of the core material 6.
The invention described in claim 4 is the restraint method of the head of the retaining wall described in claim 1,
Reinforcing steel or PC steel material is used as the anchoring steel material 5, and a plurality of anchoring steel materials 5 are embedded in the surface improvement ground 4 at a pitch suitable for reinforcement of the surface improvement ground 4 improved to soil cement. The end of the steel material 5 is connected to the head of the retaining wall 1 via the reaction force receivers 10 and 11.

  The method of restraining the head of the retaining wall according to the present invention is to improve the surface soil of the back side ground of the retaining wall head to a soil cement mixed with in-situ soil and cement, or to replace the soil cement with the soil cement. A plurality of anchor steel materials 5 are embedded in the improved surface layer improved ground 4 at a pitch that exerts a reinforcing effect substantially horizontally in the back direction and in the longitudinal direction of the retaining wall, and one end of the anchor steel material 5 is embedded. Is coupled to the head of the retaining wall 1, firstly, the anchoring steel material 5 works as a reinforcing material for the surface-improved ground 4 and exhibits a strong shear reinforcement effect against the load. Therefore, even if heavy machinery rests on the back side ground of the retaining wall head and operates close to the retaining wall 1, the surface improvement ground 4 exhibits strength and rigidity that can withstand the weight and work load of such heavy machinery. In addition, since the load distribution effect is exhibited, even if the load of heavy machinery is received, the side pressure action of depressing the head of the retaining wall 1 to the excavation side is reduced, and a load exceeding the proof stress acts on the retaining wall 1. Can be effectively suppressed.

Secondly, the anchoring steel material 5 strongly adheres and closely adheres to the surface improvement ground 4 and generates a large resistance to pulling out the anchoring steel material 5 and exerts an anchor function. As an effect combined with the head of the retaining wall 1, the restraining effect of the retaining wall head is exhibited by resisting the deformation that the head of the retaining wall 1 falls to the excavation side.
As a result of effectively restraining the deformation of the head of the retaining wall, it is possible to effectively prevent deformation and subsidence in the surrounding natural ground, and to enable highly safe ground excavation work.

Moreover, in the restraint method of the present invention, the surface soil of the back side ground of the retaining wall head is improved to soil cement mixed with in-situ soil and cement, or replaced with soil cement, and a plurality of steel materials for anchors are used. Since it can be carried out in the process of the existing technique of burying 5 almost horizontally in the back direction, construction is easy and can be carried out at a low cost and in a short construction period.
Moreover, even if the surface improvement ground 4 improved to soil cement is embedded with the anchor steel material 5, the subsequent dismantling and removal work can be easily dismantled by a method of excavating with a backhoe, for example, and the anchor steel material. Separation from 5 is easy.

This is a construction method for constraining the head of the retaining wall 1 from being deformed in the retaining retaining excavation method in which the retaining wall 1 is constructed in the ground and the inner ground of the retaining wall 1 is excavated.
The surface soil on the back side ground of the head of the retaining wall will be improved with soil cement mixed with in-situ soil and cement, or replaced with soil cement.
A plurality of anchoring steel materials 5 are embedded in the surface improvement ground 4 improved to soil cement substantially horizontally in the back direction and in the longitudinal direction of the retaining wall 1 at a pitch that exhibits a reinforcing effect. One end of the steel material 5 is coupled to the head of the retaining wall 1.
The surface soil on the back side of the head of the retaining wall is modified with soil cement or replaced with soil cement. The surface soil is stirred in place and mixed with cement, or the surface soil is excavated. The soil that has been transported to the improved facility, or excavated elsewhere and transported to the improved facility is mixed with cement at the improved facility to improve the soil cement, and then the soil cement is refilled to the surface soil location. Do.
Reinforcing steel or PC steel is used as the anchoring steel 5, and the anchoring steel 5 is embedded in the surface improvement ground 4 at a pitch suitable for reinforcement of the surface improvement ground 4 improved by soil cement. One end of the steel material corresponding to the core material 6 of the retaining wall 1 is coupled to the head of the concentric material 6 of the retaining wall 1.
Or the edge part of some steel materials 5 in the steel materials 5 for anchors embed | buried as mentioned above is couple | bonded with the head part of the retaining wall 1 via the reaction force receptacles 10 and 11. FIG.

Next, the method of restraining the head of the retaining wall according to the present invention will be described based on the illustrated embodiment. First, FIG. 1 is a plan view showing the state of implementation of a mountain retaining excavation method in which a retaining wall 1 is constructed in the ground at the outer peripheral position of the ground to be excavated and the inner ground of the retaining wall 1 is excavated. Reference numerals 2 and 3 in the figure indicate a cut beam and an upset erected in the inside of the retaining wall 1.
Further, reference numeral 4 in the figure indicates that the soft soil on the outer periphery of the retaining wall 1 is modified with a soil cement in which the soil on the back side of the retaining wall head is mixed with in situ soil and cement, or a site, etc. Fig. 1 shows the surface improved ground where the soil cement improved at the improved facility prepared in 1 is refilled and replaced.

The above-described construction in which the surface soil on the back side ground of the retaining wall head is replaced with soil cement mixed with in-situ soil and cement, or replaced with soil cement is performed as follows.
Specifically, a ground improvement processing machine such as a stabilizer (not shown) is carried in, and a ground improvement method is carried out in which the surface soil in the original position is directly stirred and mixed with cement to a depth of about 70 cm to 150 cm.
Alternatively, the surface soil on the back side ground of the retaining wall head is excavated to about 70 cm to 150 cm underground by heavy machinery such as a backhoe, bulldozer, and yumbo, and the excavated soil is once transported to an improved facility prepared at the site. Or, the soil excavated elsewhere is carried to the site improvement facility, and the excavated soil is uniformly stirred and mixed with the cement in the improvement facility to improve the soil cement. Carry out the construction method of transporting back to the surface soil of the side ground.
Which construction method is employed is selected as appropriate according to the construction conditions and environmental conditions at the site. The surface improvement ground 4 thus formed has a width W of about 4 m to 6 m and a depth H (layer thickness) of about 70 cm to 150 cm.

A feature of the present invention is that a plurality of anchoring steel materials 5 are placed in the surface improvement ground 4 formed by directly improving the in-situ soil as described above or replacing the surface soil with soil cement. As shown in FIG. 3, the surface of the mountain retaining wall 1 is embedded at a pitch that exhibits the reinforcing effect of the surface improvement ground 4 substantially horizontally in the rear direction and in the longitudinal direction of the mountain retaining wall 1. As the steel material 5 for anchors, a rebar or PC steel material having an outer diameter of about 32 mm can be suitably used. As shown in FIG. 2, the length of the steel for anchor 5 is set to be slightly shorter than the width W of the surface improved ground 4.
Of the planar arrangement of the anchoring steel material 5, embedding at a pitch that exerts the reinforcing effect of the surface improvement ground 4 is specifically arranged at a pitch of about 45 cm in the longitudinal direction of the mountain retaining wall 1 with the above-mentioned reinforcing steel or PC steel material. To be buried (see FIG. 3). The anchoring steel material 5 is embedded at a position approximately in the middle of the layer thickness of the surface improved ground 4.
And when the mountain retaining wall 1 is a ground improvement pillar containing a core material, the inner end of the anchor steel material 5 at a position facing the core material 6 inserted into the mountain retaining wall 1 in the anchor steel material 5 is The core member 6 and the contact 7 of the head of the retaining wall are joined by a method such as welding. However, the planar arrangement, number, and length of the steel materials 5 for anchors are determined and implemented together with the thickness, material, and pitch according to the material constituting the retaining wall 1.

As a method of burying the anchor steel material 5 in the middle of the improved surface layer improved ground 4, it can be carried out as follows.
When the surface layer improved ground 4 is formed, the surface soil of the back side ground of the retaining wall head is excavated, and once carried out, the soil cement is improved at the improved facility, and the construction method for refilling back is performed. As illustrated in FIG. 3, when the soil cement is spread to about ½ of the layer thickness of the surface improved ground 4, the anchor steel materials 5 are placed in the above arrangement on the surface of the soil cement, A part of the steel material 5 is joined at its inner end to the core material 6 of the mountain retaining wall head by a method such as welding. After that, backfilling of the soil cement is performed for the remaining 1/2 layer thickness, and compacted and integrated.

When the construction method of excavating the surface soil of the back side ground of the mountain retaining wall head directly with a ground improvement processing machine such as a stabilizer and mixing with cement is improved, according to the progress of the construction method, A groove for embedding an anchor steel material 5 is dug in the surface improved ground 4 immediately after the construction, and the anchor steel material 5 is placed on the bottom of the groove and joined to the core material 6 of the retaining wall head by welding or the like. After that, it is possible to suitably carry out a construction method in which the groove is backfilled, and the work of reinforce and compacting is repeated.
Thus, when the anchoring steel material 5 is buried in the middle of the layer thickness of the surface improvement ground 4, each anchoring steel material 5 is strongly bonded or adhered to and integrated with the surface improvement ground 4 and is used as a reinforcing material for the surface improvement ground 4. Work and effect as an effective shear reinforcement for the load on the surface improvement ground 4 is achieved.

Here, the anchor effect when the anchor steel material 5 is strongly bonded to or adhered to the surface-improved ground 4 and integrated is shown by the following strength design method.
First, the strength qu of the surface improved ground 4 improved by soil cement can be assumed to be qu = 0.1 N / mm ² based on the past results.
Under this condition, assuming that the adhesive strength τu of the anchoring steel material 5 is about 1/6 of the strength qu of the surface improved ground 4, it is possible to secure about τu = qu / 6 = 0.177 N / mm ^2. Conceivable.
When the thickness of the anchoring steel material 5 is D32 and the length L = 6 m, and the entire length is deeply buried in the middle of the layer thickness of the surface improvement ground 4 as shown in FIG. According to the above example, the adhesive strength Fu per reinforcing bar is calculated as Fu = π · D · L × τu = 10.2 KN. That is, by this adhesive strength Fu, the core material 6 of the head of the retaining wall can be constrained and its deformation can be suppressed.

Next, when the surface soil of the back side ground of the mountain retaining wall head is formed by the surface improved ground 4, the frictional resistance with the surface soil on which the surface improved ground 4 is placed is calculated.
The surface soil existing under the surface improvement ground 4 is a loose sand ground, the angle of repose φ is about 25 °, and the unit volume weight γ of the surface improvement ground 4 is about γ = 17 KN / m ² . When the layer thickness h is 70 cm, the friction stress τr with the surface soil on which the surface improved ground 4 is placed is
τr = γ · h · tanφ = 17 × 0.7 × tan25 ° = 5.5 KN / m ²
It can be asked.
It is considered that the displacement of the head of the retaining wall falling inward is greatly affected by the initial excavation. Therefore, assuming that the displacement due to excavation up to 5m underground is restrained by the restraint method of the present invention and assuming 45 ° main dynamic collapse, the width W1 of the surface improvement ground 4 is only 6m out of the width W. Assume resistance. Then, the sharing width L required for the bottom surface of the surface improved ground 4 corresponding to the adhesive strength τu of the anchor steel material 5 can be obtained as follows.
L = Fu / (W1 · τr) = 10.2 / 4.0 × 5.5 = 0.46 m.
Therefore, when the mountain retaining wall 1 is constructed of a ground improvement column with a core material and the pitch of the core material 6 is about 45 cm, the anchor steel materials 5 arranged so as to face each other one by one with respect to the entire core material are respectively improved in the surface layer improvement ground. 4 shows that the maximum restraint effect of the retaining wall head can be obtained.

Next, FIG. 4 shows the Example from which the coupling | bonding of the steel material 5 for anchors and the head of the retaining wall 1 differs.
That is, a plurality of anchor steel members 5 are arranged in the longitudinal direction of the retaining wall 1 at a pitch suitable for reinforcement of the surface improvement ground 4 and embedded in the middle of the surface thickness of the surface improvement ground 4. The inner ends of some of the anchor steel materials 5 selected in consideration of the restraining effect are respectively penetrated through the heads of the retaining walls 1 inward in the horizontal direction. Then, a reaction force receiver 10 and a cradle 11 are installed on the inner side surface of the head of the retaining wall 1 and the inner end of the anchoring steel member 5 is coupled by a coupling tool 12 used for binding a so-called ground anchor. This is an example fixed.

  Although the present invention has been described above based on the illustrated embodiment, the present invention is not limited to the illustrated embodiment. It should be noted that the present invention extends to design changes, modifications, and application variations as required by those skilled in the art without departing from the scope and spirit of the present invention.

It is the top view which showed notionally the ground excavation construction whole view which implemented the restraint method of the retaining wall head by this invention. It is sectional drawing of the II-II line | wire arrow of FIG. It is a perspective view which shows the point which embeds the steel material for anchors to a surface improvement ground. FIG. 5 is a cross-sectional view illustrating a second embodiment having a configuration different from that of FIG. 2.

Explanation of symbols

1 Mountain retaining wall 4 Surface improved ground (soil cement)
5 Steel materials 10 and 11 for anchors

Claims (4)

It is a construction method that constructs a retaining wall in the ground and restrains the head of the retaining wall from being deformed in the retaining mechanism for excavating the inner ground of the retaining wall,
The surface soil of the back side ground of the mountain retaining wall head is improved to soil cement mixed with in situ soil and cement, or replaced with soil cement.
In the surface improvement ground improved to soil cement, a plurality of anchoring steel materials are embedded in a horizontal direction in the back direction and at a pitch that exerts a reinforcing effect in the longitudinal direction of the retaining wall. A constraining method for a mountain retaining wall head, wherein one end is coupled to the head of the mountain retaining wall.   The construction of the surface soil on the back side of the mountain retaining wall head with soil cement is improved or replaced with soil cement. The construction method is to stir the surface soil in situ and mix with cement, or excavate the surface soil to improve. The soil transported to the facility, or excavated elsewhere and transported to the improved facility is mixed with cement in the improved facility and improved to soil cement, and the soil cement is refilled to the position of the surface soil. The method for restraining a mountain retaining wall head according to claim 1, wherein:   Reinforcing steel or PC steel is used as the anchoring steel, and the anchoring steel is embedded in the surface improvement ground at a pitch suitable for reinforcement of the surface improvement ground improved to soil cement, and the core material of the retaining wall therein 2. The method of restraining a mountain retaining wall head according to claim 1, wherein one end of a steel material facing the surface is coupled to the head of the core. Reinforcing steel or PC steel is used as the anchoring steel, and the anchoring steel is embedded in the surface improvement ground at a pitch suitable for reinforcement of the surface improvement ground improved to soil cement. The restraint method for a mountain retaining wall head according to claim 1, wherein the end portion is coupled to the head of the mountain retaining wall via a reaction force receiver.

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