JP2015030970A - Hole wall protection body of cast-in-place pile, and construction method of the same - Google Patents
Hole wall protection body of cast-in-place pile, and construction method of the same Download PDFInfo
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- JP2015030970A JP2015030970A JP2013158634A JP2013158634A JP2015030970A JP 2015030970 A JP2015030970 A JP 2015030970A JP 2013158634 A JP2013158634 A JP 2013158634A JP 2013158634 A JP2013158634 A JP 2013158634A JP 2015030970 A JP2015030970 A JP 2015030970A
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- 238000010276 construction Methods 0.000 title claims abstract description 21
- 230000001012 protector Effects 0.000 claims description 27
- 230000001681 protective effect Effects 0.000 claims description 15
- 238000000034 method Methods 0.000 claims description 8
- 238000003756 stirring Methods 0.000 claims description 7
- 239000000463 material Substances 0.000 claims description 3
- 239000002689 soil Substances 0.000 abstract description 70
- 239000004568 cement Substances 0.000 abstract description 69
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 9
- 239000008267 milk Substances 0.000 description 8
- 210000004080 milk Anatomy 0.000 description 8
- 235000013336 milk Nutrition 0.000 description 8
- 239000002245 particle Substances 0.000 description 6
- 238000005553 drilling Methods 0.000 description 4
- 239000003673 groundwater Substances 0.000 description 4
- 238000009412 basement excavation Methods 0.000 description 3
- 238000006073 displacement reaction Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 230000000087 stabilizing effect Effects 0.000 description 3
- 238000005266 casting Methods 0.000 description 2
- 239000004567 concrete Substances 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 230000001133 acceleration Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000010907 mechanical stirring Methods 0.000 description 1
- 239000011178 precast concrete Substances 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
Landscapes
- Consolidation Of Soil By Introduction Of Solidifying Substances Into Soil (AREA)
- Piles And Underground Anchors (AREA)
- Bulkheads Adapted To Foundation Construction (AREA)
Abstract
Description
本発明は、場所打ち杭の孔壁防護体、及びその構築方法に関する。 The present invention relates to a hole wall protective body for a cast-in-place pile and a construction method thereof.
近隣に既設構造物が存在する狭隘な敷地で場所打ち杭を施工する場合、孔壁が崩壊すると近隣の既設構造物に影響が及ぶ可能性があるため、孔壁を防護する必要がある。そこで、特許文献１に記載の孔壁防護方法では、複数の柱状改良体を円環状に連結した孔壁防護体を、杭孔を囲うように構築することで孔壁を防護している。 When cast-in-place piles are constructed on a narrow site where existing structures exist in the vicinity, it is necessary to protect the hole walls because the collapse of the hole walls may affect the existing existing structures. Therefore, in the hole wall protection method described in Patent Document 1, the hole wall is protected by constructing a hole wall protective body in which a plurality of columnar improvement bodies are connected in an annular shape so as to surround the pile hole.
本願の発明者等が、特許文献１に記載の孔壁防護体の施工コストを低減することを目的として、柱状改良体を１本おきに間隔を空けて構築することを検討し、実際の応力場・ひずみ場および外力条件を模擬した遠心模型実験を実施したところ、地表面の沈下や変形等の地盤の変状が発生した。 The inventors of the present application examined the construction of every other columnar improvement body at intervals in order to reduce the construction cost of the hole wall protection body described in Patent Document 1, and the actual stress When a centrifugal model experiment simulating the field / strain field and external force conditions was carried out, ground deformation such as subsidence and deformation of the ground surface occurred.
本発明は、上記事情に鑑みなされたものであり、場所打ち杭の施工時における周囲の地盤変状を抑制すると共に、孔壁防護体の施工コストを低減することを課題とするものである。 This invention is made | formed in view of the said situation, and makes it a subject to reduce the construction cost of a hole wall protective body while suppressing the surrounding ground deformation at the time of construction of a cast-in-place pile.
本発明に係る場所打ち杭の孔壁防護体は、複数の柱状改良体が場所打ち杭の杭孔を囲うように配されて接合された孔壁防護体であって、天端から所定長さの上部では、複数の柱状改良体の強度が全周に亘って一様であり、前記上部より下側では、前記複数の柱状改良体のうちの一部の強度が、前記上部と同等であるのに対して、その他の前記複数の柱状改良体の強度が、前記上部よりも低いことを特徴とする。 The cast-in-place pile wall protector according to the present invention is a perforated wall protector in which a plurality of columnar improvement bodies are arranged so as to surround the cast-in-place pile hole, and have a predetermined length from the top. In the upper part, the strength of the plurality of columnar improvement bodies is uniform over the entire circumference, and below the upper part, the strength of a part of the plurality of columnar improvement bodies is equal to the upper part. On the other hand, the strength of the other plurality of columnar improvements is lower than that of the upper part.
また、本発明に係る場所打ち杭の孔壁防護体の構築方法は、複数の柱状改良体を場所打ち杭の杭孔を囲うように配して接合することにより、孔壁防護体を構築する方法であって、前記孔壁防護体の天端から所定長さの上部は、前記複数の柱状改良体の強度が全周に亘って一様となるように構築し、前記孔壁防護体の上部より下側は、前記複数の柱状改良体のうちの一部の強度が、前記上部と同等となるのに対して、その他の前記複数の柱状改良体の強度が、前記上部よりも低くなるように構築することを特徴とする。 Further, the method for constructing a hole wall protective body for a cast-in-place pile according to the present invention constructs a hole wall protector by arranging and joining a plurality of columnar improvement bodies so as to surround the pile hole of the cast-in-place pile. The upper portion of the hole wall protector having a predetermined length from the top is constructed so that the strength of the plurality of columnar improvement bodies is uniform over the entire circumference, and the hole wall protector On the lower side from the upper part, the strength of a part of the plurality of columnar improvement bodies is equal to that of the upper part, whereas the strength of the other plurality of columnar improvement bodies is lower than that of the upper part. It is characterized by constructing as follows.
上記場所打ち杭の孔壁防護体の構築方法において、前記柱状改良体を、地盤内に改良材を注入しながら削孔攪拌することにより構築してもよく、前記柱状改良体の前記上部よりも低強度の部分を攪拌する時間及び回数を、前記柱状改良体の前記上部及び該上部と同程度の強度の部分よりも減らしてもよい。 In the method for constructing the hole wall protective body of the cast-in-place pile, the columnar improvement body may be constructed by agitating a hole while injecting the improvement material into the ground, than the upper part of the columnar improvement body. You may reduce the time and frequency | count which stir a low intensity | strength part from the said upper part of the said columnar improvement body, and a part of the intensity | strength comparable to this upper part.
本発明によれば、場所打ち杭の施工時における周囲の地盤変状を抑制すると共に、孔壁防護体の施工コストを低減することができる。 ADVANTAGE OF THE INVENTION According to this invention, while the surrounding ground deformation at the time of construction of a cast-in-place pile is suppressed, the construction cost of a hole wall protective body can be reduced.
以下、本発明の一実施形態を、図面を参照しながら説明する。図１は、一実施形態に係る孔壁防護体１０を示す斜視図である。この図に示すように、孔壁防護体１０は、場所打ち杭１を造成する際に掘削する杭孔を囲うように円環状に、地上から地下水位以深で掘削孔の下端に達しない深さまで構築されている。 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a hole wall protector 10 according to an embodiment. As shown in this figure, the hole wall protector 10 is formed in an annular shape so as to surround the pile hole to be excavated when the cast-in-place pile 1 is constructed, to a depth that does not reach the lower end of the excavation hole from the ground to a depth below the groundwater level. Has been built.
ここで、本実施形態では、場所打ち杭１を、鉄道等の既設構造物が近隣に存在する狭隘な敷地で施工するため、孔壁が崩壊して近隣の既設構造物に影響が及ぶことを防止する必要がある。そこで、孔壁防護体１０を構築して孔壁を防護している。 Here, in this embodiment, since the cast-in-place pile 1 is constructed on a narrow site where existing structures such as railways exist in the vicinity, the hole wall collapses and the existing structures in the vicinity are affected. There is a need to prevent. Therefore, the hole wall protector 10 is constructed to protect the hole wall.
孔壁防護体１０は、複数の円柱状のソイルセメント柱１２、１４が円環状に配されて連結されたソイルセメント柱列壁である。ソイルセメント柱１２が１本おきに構築され、隣合ったソイルセメント柱１２の間にソイルセメント柱１４が構築されている。ここで、隣合ったソイルセメント柱１２、１４の中心間距離は、これらの直径よりも短くなっており、隣合ったソイルセメント柱１２、１４は、互いに側部同士が重なり合った状態で接合されている。 The hole wall protection body 10 is a soil cement column wall in which a plurality of columnar soil cement columns 12 and 14 are arranged in an annular shape and connected. Every other soil cement column 12 is constructed, and a soil cement column 14 is constructed between adjacent soil cement columns 12. Here, the distance between the centers of the adjacent soil cement columns 12 and 14 is shorter than their diameters, and the adjacent soil cement columns 12 and 14 are joined with their side portions overlapping each other. ing.
ソイルセメント柱１２は、天端から下端まで一様の強度であるのに対して、ソイルセメント柱１４は、天端から下方に所定長さＬ（例えば、２０００〜３０００ｍｍあるいは杭長の１／３〜１／５の長さ）の範囲はソイルセメント柱１２と同等の強度、当該範囲よりも下側の範囲はソイルセメント柱１２よりも低強度となっている。即ち、孔壁防護体１０における天端から下方に上記所定長さＬの範囲（以下、上部１０Ａという）は、全周に亘って同等の強度のソイルセメント柱が配された構成であるのに対して、孔壁防護体１０における上部１０Ａよりも下側の範囲は、上部１０Ａと同等の強度のソイルセメント柱とそれよりも低強度のソイルセメント柱とが交互に配された構成となっている。 The soil cement column 12 has a uniform strength from the top to the bottom, whereas the soil cement column 14 has a predetermined length L (for example, 2000 to 3000 mm or 1/3 of the pile length) downward from the top. The range of ˜1 / 5 length) has the same strength as the soil cement column 12, and the range below the range has a lower strength than the soil cement column 12. That is, the range of the predetermined length L (hereinafter referred to as the upper portion 10A) below the top end of the hole wall protector 10 is a structure in which soil cement columns having the same strength are arranged over the entire circumference. On the other hand, the range below the upper part 10A in the hole wall protection body 10 is configured such that soil cement columns having the same strength as the upper part 10A and soil cement columns having lower strength are alternately arranged. Yes.
ここで、孔壁防護体１０の上部１０Ａの強度は、周囲の地盤の土水圧に対して抵抗して円環状の形状を保持できる程度に設定されている。なぜなら、上部１０Ａの形状が崩壊した場合には、地表面近傍で孔壁が崩壊して近隣の既設構造物に影響が及ぶ可能性があるからである。また、場所打ち杭１の頭部については、先打ちコンクリートの斫り作業、及び後打ちコンクリートの打設作業を実施する必要があり、上部１０Ａの内側での作業が発生するからである。 Here, the strength of the upper part 10A of the hole wall protection body 10 is set to such an extent that it can resist the soil water pressure of the surrounding ground and can maintain an annular shape. This is because, when the shape of the upper part 10A collapses, the hole wall may collapse near the ground surface and affect nearby existing structures. Moreover, about the head of the cast-in-place pile 1, it is necessary to carry out the work of casting the pre-cast concrete and the work of placing the post-cast concrete, and the work inside the upper part 10A occurs.
それに対して、孔壁防護体１０における上部１０Ａよりも下側の範囲の強度は、周囲の地盤の土水圧で崩壊することがなく、周囲の地盤から杭孔への土粒子の流入を止めることができる程度に設定されている。なぜなら、周囲の地盤から杭孔へ土粒子が流れ込んだ場合には、周囲の地盤が変形して地表面が沈下することで、近隣の既設構造物に影響が及ぶ可能性があるからである。 On the other hand, the strength in the range below the upper part 10A in the hole wall protection body 10 is not collapsed by the soil water pressure of the surrounding ground, and stops the inflow of soil particles from the surrounding ground to the pile hole. It is set to the extent that can be. This is because when soil particles flow into the pile hole from the surrounding ground, the surrounding ground is deformed and the ground surface sinks, which may affect existing nearby structures.
つまり、孔壁防護体１０の上部１０Ａの形状が維持されると共に、上部１０Ａより下側において周囲の地盤から杭孔への土粒子の流入が防止されれば、周囲の地盤の変形や地表面の沈下等の地盤変状が抑制されて近隣の既設構造物に影響が及ぶことはない。そこで、孔壁防護体１０の上部１０Ａについては、全周に亘って一様に高強度のソイルセメント柱を設けているのに対して、上部１０Ａよりも下側については、高強度のソイルセメント柱と低強度のソイルセメント柱とを１本おきに交互に設けることで、近隣の既設構造物に影響が及ぶような地盤変状の発生を防止すると共に、孔壁防護体１０の施工コストを低減することを可能にしている。 In other words, if the shape of the upper part 10A of the hole wall protection body 10 is maintained and the inflow of soil particles from the surrounding ground to the pile hole is prevented below the upper part 10A, the deformation of the surrounding ground and the ground surface The ground deformation such as subsidence of the ground is suppressed and the existing existing structures are not affected. Therefore, the upper 10A of the hole wall protective body 10 is uniformly provided with a high-strength soil cement column over the entire circumference, whereas the lower 10-A is provided with a high-strength soil cement. By alternately providing pillars and alternate low-strength soil cement pillars, it is possible to prevent the occurrence of ground deformation that affects nearby existing structures and to reduce the construction cost of the perforated wall protector 10. It is possible to reduce.
なお、孔壁防護体１０の止水性については、上部１０Ａへの地下水の流入や杭孔から周囲の地盤への安定液の流出を抑えるために高く設定することが望ましいが、これは必須ではない。 It should be noted that the waterstop of the hole wall protection body 10 is preferably set high in order to suppress the inflow of groundwater to the upper part 10A and the outflow of the stabilizing liquid from the pile hole to the surrounding ground, but this is not essential. .
図２及び図３は、孔壁防護体１０の施工手順を示す平面図である。これらの図に示すように、ソイルセメント柱１２を１本おきに構築して、構築済みのソイルセメント柱１２の間にソイルセメント柱１４を構築する。施工機械は、狭隘かつ空頭制限のある敷地での施工に対応可能であるコンパクトな機械攪拌式地盤改良機、例えば、ボーリングマシーンの先端にビットのある削孔攪拌翼と、セメントミルクの吐出口とを設けたもの等を使用する。 2 and 3 are plan views showing a construction procedure of the hole wall protection body 10. FIG. As shown in these drawings, every other soil cement column 12 is constructed, and a soil cement column 14 is constructed between the constructed soil cement columns 12. The construction machine is a compact mechanical stirring type ground improvement machine that can handle construction in a narrow and empty space, for example, a drilling stirring blade with a bit at the tip of a boring machine, a discharge port for cement milk, Use the one provided with.
ここで、ソイルセメント柱１４を構築するために地盤を削孔する際には、上記例の削孔攪拌翼等により構築済みのソイルセメント柱１２の側部を切削する。そして、掘削孔内においてセメントミルクと掘削土とを攪拌混合することで、ソイルセメント柱１４を構築すると共に、該ソイルセメント柱１４とその両側のソイルセメント柱１２とを連結する。 Here, when the ground is drilled to construct the soil cement column 14, the side portion of the constructed soil cement column 12 is cut by the drilling stirring blade of the above example. Then, by mixing the cement milk and the excavated soil in the excavation hole, the soil cement column 14 is constructed, and the soil cement column 14 and the soil cement columns 12 on both sides thereof are connected.
ここで、ソイルセメント柱１２は、下端から上端まで、一定の回転数で攪拌すると共に一定の単位時間当たりの量でセメントミルクを吐出させながら一定の速度Ｖで下降もしくは上昇させることによって、下端から上端まで強度が一様になるように構築する。それに対して、ソイルセメント柱１４は、一定の回転数で攪拌すると共に一定の単位時間当たりの量でセメントミルクを吐出させながら、上部１０Ａよりも下側の範囲では、ソイルセメント柱１２を構築する際の速度Ｖよりも速い速度Ｖ´で下降もしくは上昇させ、上部１０Ａの範囲では、ソイルセメント柱１２を構築する際の速度Ｖで下降もしくは上昇させることによって構築する。これにより、ソイルセメント柱１４における上部１０Ａの範囲の強度はソイルセメント柱１２の全体と同程度に、ソイルセメント柱１４における上部１０Ａより下側の範囲の強度は、その上側の範囲及びソイルセメント柱１２よりも低強度になる。また、ソイルセメント柱１４の上部１０Ａよりも下側の範囲のセメント量（ｋｇ／ｍ３）は、その上の範囲及びソイルセメント柱１２よりも少なくなる。 Here, the soil cement pillar 12 is stirred from a lower end to an upper end at a constant rotational speed and is lowered or raised at a constant speed V while discharging cement milk at a constant amount per unit time. It is constructed so that the intensity is uniform up to the top. On the other hand, the soil cement pillar 14 constructs the soil cement pillar 12 in a range below the upper part 10A while stirring the milk at a constant rotational speed and discharging cement milk at a constant amount per unit time. It is constructed by lowering or raising at a speed V ′ that is faster than the actual speed V, and descending or raising at the speed V when constructing the soil cement column 12 in the range of the upper part 10A. Thereby, the strength of the range of the upper part 10A in the soil cement column 14 is almost the same as that of the entire soil cement column 12, and the strength of the range below the upper part 10A of the soil cement column 14 is the upper range and the soil cement column. The strength is lower than 12. Further, the cement amount (kg / m 3 ) in the range below the upper portion 10A of the soil cement column 14 is smaller than the range above and the soil cement column 12.
以上のようにして構築される孔壁防護体１０の効果を確認するために、実際の応力場・ひずみ場および外力条件を模擬した遠心模型実験を実施したので、以下説明する。図４は、模型の孔壁防護体１００を示す立面図であり、図５は、実物の孔壁防護体１０と模型の孔壁防護体１００との関係を示す表である。図４の立面図及び図５の表に示すように、実物の孔壁防護体１０の内径すなわち本設杭の直径は３０００ｍｍであるのに対して、模型の本設杭の直径は１２０ｍｍである。また、実物の本設杭の長さは１００００ｍｍであるのに対して、模型の本設杭の長さは４００ｍｍである。また、実物のソイルセメント柱１２、１４の直径は６００ｍｍであるのに対して、模型のソイルセメント柱１２０、１４０の直径は２４ｍｍである。さらに、実物のソイルセメント柱１２、１４のラップ長（交点間の長さ）は１３０ｍｍであるのに対して、模型のソイルセメント柱１２０、１４０のラップ長は５．２ｍｍである。即ち、模型の孔壁防護体１００は、実物の孔壁防護体１０の１／２５のサイズである。 In order to confirm the effect of the hole wall protection body 10 constructed as described above, a centrifugal model experiment simulating an actual stress field / strain field and external force conditions was performed, which will be described below. FIG. 4 is an elevational view showing the model hole wall protector 100, and FIG. 5 is a table showing the relationship between the actual hole wall protector 10 and the model hole wall protector 100. As shown in the elevation view of FIG. 4 and the table of FIG. 5, the diameter of the actual hole wall protection body 10, that is, the diameter of the permanent pile is 3000 mm, whereas the diameter of the permanent pile of the model is 120 mm. is there. Further, the length of the actual main pile is 10000 mm, whereas the length of the model main pile is 400 mm. The actual soil cement columns 12 and 14 have a diameter of 600 mm, whereas the model soil cement columns 120 and 140 have a diameter of 24 mm. Further, the wrap length (length between intersections) of the actual soil cement columns 12 and 14 is 130 mm, whereas the wrap length of the model soil cement columns 120 and 140 is 5.2 mm. That is, the model hole wall protector 100 is 1/25 the size of the actual hole wall protector 10.
ここで、模型のソイルセメント柱１２０の全体及びソイルセメント柱１４０の天端から所定深さ（１００ｍｍ）までの強度は１．０Ｎ／ｍｍ２程度に設定し、ソイルセメント柱１４０の所定深さ以深の範囲の強度は０．５Ｎ／ｍｍ２程度に設定した。このため、模型のソイルセメント柱１２０の全体及びソイルセメント柱１４０の天端から所定深さ（１００ｍｍ）までのセメント量は２００ｋｇ／ｍ３程度で作製し、ソイルセメント柱１４０の所定深さ以深の範囲のセメント量は７５ｋｇ／ｍ３程度で作製した。また、水セメント比Ｗ／Ｃは、ソイルセメント柱１２０、１４０の全体を１００％程度としている。 Here, the strength from the top of the model soil cement column 120 and the top of the soil cement column 140 to a predetermined depth (100 mm) is set to about 1.0 N / mm 2 , and the depth of the soil cement column 140 is greater than the predetermined depth. The strength in the range was set to about 0.5 N / mm 2 . For this reason, the cement amount from the top of the model soil cement column 120 and the top of the soil cement column 140 to a predetermined depth (100 mm) is about 200 kg / m 3 , and the soil cement column 140 is deeper than the predetermined depth. The cement amount in the range was prepared at about 75 kg / m 3 . The water cement ratio W / C is about 100% for the entire soil cement columns 120 and 140.
図６は、遠心模型実験の全体計画を示す平面図であり、図７は、遠心模型実験の全体計画を示す立面図である。これらの図に示すように、本実験では、幅１９００ｍｍ、奥行き８００ｍｍ、深さ７００ｍｍの剛土槽１１０を幅方向及び奥行き方向について等分することで４等分に分割し、その中の一つの領域１１０Ａに模型の孔壁防護体１００を設置した。なお、他の領域１１０Ａは、他形状の孔壁防護体についての実験で使用した。 FIG. 6 is a plan view showing the overall plan of the centrifugal model experiment, and FIG. 7 is an elevation view showing the overall plan of the centrifugal model experiment. As shown in these figures, in this experiment, the hard earth basin 110 having a width of 1900 mm, a depth of 800 mm, and a depth of 700 mm is divided into four equal parts in the width direction and the depth direction. A model hole wall protector 100 was installed in the area 110A. The other region 110A was used in an experiment for a hole wall protector having another shape.
剛土槽１１０の模型地盤は、砂質土系試料（Ｇｓ＝２．６７４）を地盤材料として用いて空中落下法により作成した。この模型地盤の上部は相対密度Ｄｒ＝４０％程度で作成し、模型地盤の下部は、孔壁防護体１００の支持地盤にすることを想定して相対密度Ｄｒ＝６０％程度で作成した。そして、地下水位が高いことを想定して、孔壁防護体１００の周囲を、下部から通水管１０２を通して通水することにより模型地盤の表面まで飽和状態とした。 The model ground of the hard soil tank 110 was created by an air drop method using a sandy soil sample (G s = 2.674) as the ground material. The upper part of this model ground was created with a relative density D r = 40%, and the lower part of the model ground was created with a relative density D r = 60% assuming that it would be the supporting ground for the hole wall protector 100. . Then, assuming that the groundwater level is high, the periphery of the hole wall protection body 100 was saturated to the surface of the model ground by passing water through the water pipe 102 from the lower part.
本実験では、剛土槽１１０に所定の遠心加速度（２５Ｇ）を付与した後に、孔壁防護体１００の内部の模擬安定液（塩水、比重１．０５）の水位を低下させた。また、図８に示すように、孔壁防護体１００の中心から１００ｍｍ、２００ｍｍの位置での地表面の沈下量をレーザー変位計１０４で計測した。 In this experiment, after applying a predetermined centrifugal acceleration (25G) to the hard earth tank 110, the water level of the simulated stabilizing liquid (salt water, specific gravity 1.05) inside the hole wall protective body 100 was lowered. Further, as shown in FIG. 8, the laser displacement meter 104 was used to measure the amount of ground surface settlement at positions of 100 mm and 200 mm from the center of the hole wall protector 100.
図９は、実験結果を示すグラフである。なお、このグラフでは、実験体をレーザー変位計で計測して得た数値を実物のスケールに換算して表示している。また、杭芯から２．５ｍの位置の結果を黒色の線で示し、杭芯から５ｍの位置の結果を灰色の線で示している。このグラフに示すように、安定液の水位の低下に伴って地表面の沈下量が徐々に増加する傾向があるが、地表面の沈下量の最大値は１ｃｍ程度と非常に小さい。 FIG. 9 is a graph showing experimental results. In this graph, the numerical value obtained by measuring the experimental body with a laser displacement meter is converted into a real scale and displayed. Moreover, the result of the position 2.5 m from a pile core is shown with the black line, and the result of the position 5 m from a pile core is shown with the gray line. As shown in this graph, the amount of settlement on the ground surface tends to increase gradually as the water level of the stabilizing liquid decreases, but the maximum amount of ground settlement is as small as about 1 cm.
図１０は、実験実施後の模型地盤を示す写真である。この写真から、孔壁防護体１００の周辺の地盤では大きな変形や沈下は生じていないことが確認された。 FIG. 10 is a photograph showing the model ground after the experiment. From this photograph, it was confirmed that there was no significant deformation or settlement in the ground around the hole wall protection body 100.
以上説明したように、本実施形態に係る場所打ち杭１の孔壁防護体１０では、複数のソイルセメント柱１２、１４が場所打ち杭１の杭孔を囲うように配されて連結されている。ここで、孔壁防護体１０の上部１０Ａでは、複数のソイルセメント柱１２、１４の強度が全周に亘って一様であり、上部１０Ａより下側では、複数のソイルセメント柱１２、１４のうちの一部のソイルセメント柱１２の強度が、上部１０Ａと同等であるのに対して、その他の複数のソイルセメント柱１４の強度が、上部１０Ａよりも低くなっている。 As described above, in the hole wall protection body 10 of the cast-in-place pile 1 according to the present embodiment, the plurality of soil cement columns 12 and 14 are arranged and connected so as to surround the pile hole of the cast-in-place pile 1. . Here, in the upper part 10A of the hole wall protection body 10, the strength of the plurality of soil cement columns 12 and 14 is uniform over the entire circumference, and below the upper part 10A, the strength of the plurality of soil cement columns 12 and 14 is increased. The strength of some of the soil cement columns 12 is equal to that of the upper portion 10A, whereas the strength of the other plurality of soil cement columns 14 is lower than that of the upper portion 10A.
即ち、孔壁防護体１０の上部１０Ａについては、形状を維持できる程度に全周に亘って高強度にしているのに対して、孔壁防護体１０の上部１０Ａよりも下側の範囲については、周囲の地盤から杭孔への土粒子の流入を止めることができる程度に、１本おきに交互に高強度部分（通常の強度の部分）と低強度部分とを設けている。これによって、近隣の既設構造物に影響が及ぶような地盤変状の発生を防止できる。また、上部１０Ａの形状の崩壊を防止できることによって、上部１０Ａの内側で場所打ち杭頭部の斫り作業、及び後打ちコンクリートの打設作業等を安全に実施できる。さらに、孔壁防護体１０の低強度の部分を、攪拌時間及び回数を減らしたり、セメントミルクの量を少なくしたりして構築することにより、孔壁防護体１０の施工コストを低減できる。 That is, the upper portion 10A of the hole wall protector 10 is made strong enough to maintain the shape, whereas the range below the upper portion 10A of the hole wall protector 10 is high. The high strength portions (normal strength portions) and the low strength portions are alternately provided every other line to such an extent that the inflow of soil particles from the surrounding ground to the pile hole can be stopped. As a result, it is possible to prevent the occurrence of ground deformation that affects existing nearby structures. Further, by preventing the shape of the upper portion 10A from collapsing, it is possible to safely carry out the work of casting the cast-in-place pile head, the work of placing the post-cast concrete, etc. inside the upper portion 10A. Furthermore, the construction cost of the hole wall protector 10 can be reduced by constructing the low-strength portion of the hole wall protector 10 by reducing the stirring time and the number of times or by reducing the amount of cement milk.
ここで、孔壁防護体１０の低強度の部分を構築する際に、攪拌時間及び回数を減らすことにより、施工時間を短縮でき、それによるコスト低減効果を得ることができる。 Here, when constructing the low-strength portion of the hole wall protection body 10, the construction time can be shortened by reducing the stirring time and the number of times, and thereby the cost reduction effect can be obtained.
なお、上述の実施形態は、本発明の理解を容易にするためのものであり、本発明を限定するものではない。本発明はその趣旨を逸脱することなく、変更、改良され得ると共に本発明にはその等価物が含まれることは勿論である。例えば、上述の実施形態では、孔壁防護体１０の上部１０Ａより下側の範囲に、低強度部分を１本おきに構築したが、土粒子の掘削孔への流入を防止できるのであれば、例えば、低強度部分を複数本連続で構築したり、逆に、高強度部分を複数本連続で構築したりしてもよい。 In addition, the above-mentioned embodiment is for making an understanding of this invention easy, and does not limit this invention. It goes without saying that the present invention can be changed and improved without departing from the gist thereof, and that the present invention includes equivalents thereof. For example, in the above-described embodiment, every other low-strength portion is constructed in the range below the upper portion 10A of the hole wall protector 10, but if it can prevent the inflow of soil particles into the excavation hole, For example, a plurality of low strength portions may be constructed continuously, or conversely, a plurality of high strength portions may be constructed continuously.
また、実験でのセメントミルクの配合は、一例であり、原位置の土質や地下水圧等に応じて適宜決めればよい。ここで、上記実験では、低強度部分の強度を、高強度部分の強度の１／２としたが、高強度部分の強度の１／３、１／４、１／５等、周囲の地盤から杭孔への土粒子の流入を止めることができる範囲で適宜設定すればよい。 In addition, the blending of cement milk in the experiment is an example, and may be determined as appropriate according to the in situ soil quality, groundwater pressure, and the like. Here, in the above experiment, the strength of the low-strength portion was set to 1/2 of the strength of the high-strength portion, but 1/3, 1/4, 1/5, etc. of the strength of the high-strength portion from the surrounding ground. What is necessary is just to set suitably in the range which can stop the inflow of the soil particle to a pile hole.
また、施工機械の一例として、ボーリングマシーンの先端にビットのある削孔攪拌翼と、セメントミルクの吐出口とを設けたものを挙げたが、オーガーで削孔攪拌するもの等、施工機械は適宜選択すればよい。 In addition, as an example of the construction machine, a drilling machine with a drilling stirrer blade with a bit at the tip of the boring machine and a discharge port for cement milk was mentioned. Just choose.
さらに、上述の実施形態では、改良体をラップ施工した場合を想定しているが、隣接する改良体同士が点で接するような状態で施工されていても同じ効果を得ることは可能である。 Furthermore, in the above-described embodiment, it is assumed that the improved body is lapped, but the same effect can be obtained even when the adjacent improved bodies are in contact with each other at points.
１ 場所打ち杭、１０ 孔壁防護体、１０Ａ 上部、１２、１４ ソイルセメント柱、１００ 孔壁防護体、１０２ 通水管、１０４ レーザー変位計、１１０ 剛土槽、１１０Ａ 領域、１２０、１４０ ソイルセメント柱 DESCRIPTION OF SYMBOLS 1 Cast-in-place pile, 10 hole wall protection body, 10A upper part, 12, 14 soil cement pillar, 100 hole wall protection body, 102 water pipe, 104 laser displacement meter, 110 rigid earth tank, 110A area, 120, 140 soil cement pillar
Claims (3)
天端から所定長さの上部では、複数の柱状改良体の強度が全周に亘って一様であり、
前記上部より下側では、前記複数の柱状改良体のうちの一部の強度が、前記上部と同等であるのに対して、その他の前記複数の柱状改良体の強度が、前記上部よりも低いことを特徴とする場所打ち杭の孔壁防護体。 A hole wall protective body in which a plurality of columnar improvement bodies are arranged and joined so as to surround a pile hole of a cast-in-place pile,
In the upper part of the predetermined length from the top, the strength of the plurality of columnar improvements is uniform over the entire circumference,
Below the upper part, the strength of some of the plurality of columnar improvement bodies is equal to that of the upper part, whereas the strength of the other plurality of columnar improvement bodies is lower than that of the upper part. A cast-in-place pile wall protector.
前記孔壁防護体の天端から所定長さの上部は、前記複数の柱状改良体の強度が全周に亘って一様となるように構築し、
前記孔壁防護体の上部より下側は、前記複数の柱状改良体のうちの一部の強度が、前記上部と同等となるのに対して、その他の前記複数の柱状改良体の強度が、前記上部よりも低くなるように構築することを特徴とする場所打ち杭の孔壁防護体の構築方法。 A method of constructing a hole wall protection body by arranging and joining a plurality of columnar improvement bodies so as to surround a pile hole of a cast-in-place pile,
The upper part of the predetermined length from the top end of the hole wall protective body is constructed so that the strength of the plurality of columnar improvement bodies is uniform over the entire circumference,
On the lower side from the upper part of the hole wall protective body, the strength of a part of the plurality of columnar improvement bodies is equivalent to the upper part, whereas the strength of the other columnar improvement bodies is A construction method for a hole wall protective body of a cast-in-place pile, wherein the construction is such that the lower part is lower than the upper part.
前記柱状改良体の前記上部よりも低強度の部分を攪拌する時間及び回数を、前記柱状改良体の前記上部及び該上部と同程度の強度の部分よりも減らすことを特徴とする請求項２に記載の場所打ち杭の孔壁防護体の構築方法。 The columnar improvement body is constructed by agitating a hole while injecting the improvement material into the ground,
The time and the number of times of stirring the lower strength portion than the upper portion of the columnar improvement body are reduced as compared with the upper portion of the columnar improvement body and a portion having the same strength as the upper portion. The construction method of the hole wall protection body of the cast-in-place pile described.
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| JP2002266343A (en) * | 2002-01-30 | 2002-09-18 | Tenox Corp | Method for controlling soil improving method, and apparatus for controlling soil improving machine |
| JP2005282043A (en) * | 2004-03-29 | 2005-10-13 | Takenaka Komuten Co Ltd | Earth retaining wall reinforcing method |
| JP2011074675A (en) * | 2009-09-30 | 2011-04-14 | Ohbayashi Corp | Method for constructing soil cement structure, and the soil cement structure |
| JP2011132689A (en) * | 2009-12-22 | 2011-07-07 | Shimizu Corp | Structure of earth retaining wall serving also as footing and construction method of the same |
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| JP2002266343A (en) * | 2002-01-30 | 2002-09-18 | Tenox Corp | Method for controlling soil improving method, and apparatus for controlling soil improving machine |
| JP2005282043A (en) * | 2004-03-29 | 2005-10-13 | Takenaka Komuten Co Ltd | Earth retaining wall reinforcing method |
| JP2011074675A (en) * | 2009-09-30 | 2011-04-14 | Ohbayashi Corp | Method for constructing soil cement structure, and the soil cement structure |
| JP2011132689A (en) * | 2009-12-22 | 2011-07-07 | Shimizu Corp | Structure of earth retaining wall serving also as footing and construction method of the same |
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