JP2020056192A - Landslide prevention pile and design method thereof - Google Patents
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Abstract
Description
本発明は、地中に推定されるすべり面を境にして、すべり面より下方の不動層に対して、すべり面より上方の移動層が、すべり面に沿って滑る地すべりを抑止するための地すべり抑止用杭およびその設計方法に関するものである。 The present invention relates to a landslide for suppressing a landslide that slides along a slip surface with respect to a stationary layer below the slip surface with respect to a slip surface estimated underground. The present invention relates to a deterrent pile and a design method thereof.
地すべり抑止用杭に関しては、例えば特許文献１に、杭本体の経済性を高めると共に、効率よく設置することができること目的としたものが開示されている。
特許文献１に開示されたものを含め、一般的に地すべり抑止用杭は、推定されるすべり面に対する安全率の不足分を必要抑止力として設定し、必要抑止力を外力として杭に作用させたときの応力度の検討が行われる。
Regarding a landslide prevention pile, for example, Patent Literature 1 discloses a pile that aims to increase the economical efficiency of a pile main body and to be able to efficiently install the pile main body.
In general, landslide prevention piles, including those disclosed in Patent Literature 1, set the estimated safety deficiency for the slip surface as a necessary deterrent, and applied the required deterrent to the pile as an external force. A study of the degree of stress at the time is performed.
必要抑止力が作用したときに発生する応力の算定方法は、くさび杭、抑え杭、補強杭、せん断杭の４種類あり、地盤の条件や杭の設置位置によって設計式を選択する（非特許文献１参照）。これらの設計方法のうち、せん断杭を除く３種類の杭における設計式は、杭のたわみに一次比例した地盤反力が杭に作用するという考え方に基づいている。 There are four types of methods for calculating the stress generated when the necessary deterrent is applied: wedge piles, holding piles, reinforcing piles, and shear piles. The design formula is selected according to the ground conditions and the pile installation position (Non-patent Document 1). Among these design methods, the design formulas for the three types of piles except for the shear pile are based on the idea that a ground reaction force that is linearly proportional to the deflection of the pile acts on the pile.
地すべり抑止用杭として鋼管を用いる場合、従来はSKK400（長期許容曲げ応力度140N/mm2）、SKK490（長期許容曲げ応力度185N/mm2）、SM570（長期許容曲げ応力度255N/mm2）等が用いられ、発生応力に応じて管径や板厚が決定される。 When steel pipes are used as landslide prevention piles, SKK400 (long-term allowable bending stress 140 N / mm 2 ), SKK490 (long-term allowable bending stress 185 N / mm 2 ), SM570 (long-term allowable bending stress 255 N / mm 2 ) Are used, and the tube diameter and the plate thickness are determined according to the generated stress.
また、用途上、地すべり抑止用杭は山間部に設置されることが多いため、運搬の容易性と施工の簡易性の観点から、多くの場合は直径550mm以下の鋼管であることが多い。それゆえ、杭の剛性の向上に管径を大きくするには限界があり、一般的には板厚を大きくすることで剛性を確保する必要がある。このため、発生する応力が大きい箇所では、板厚が大きくなり、それ故に鋼材重量が大きくなるという問題がある。 In addition, since landslide prevention piles are often installed in mountainous areas due to their applications, steel pipes with a diameter of 550 mm or less are often used in many cases from the viewpoint of ease of transportation and simplicity of construction. Therefore, there is a limit in increasing the pipe diameter in improving the rigidity of the pile, and it is generally necessary to secure the rigidity by increasing the plate thickness. For this reason, there is a problem that the plate thickness becomes large at the place where the generated stress is large, and hence the weight of the steel material becomes large.
前述のとおり、くさび杭、抑え杭、補強杭の手法で設計される地すべり抑止用杭は、杭のたわみに比例した地盤反力を抵抗力として考慮する。この点を、図７に基づいて説明する。なお、図７において、１は移動層、３は不動層、５はすべり面、９は地すべり抑止用杭（以下、単に「杭」という場合あり）であり、図７（ａ）では地すべり抑止用杭９に作用する地盤反力を矢印で、地すべり抑止用杭９に作用する曲げモーメントを曲線で示し、図７（ｂ）は地すべり抑止用杭９が作用力を受けたときのたわみを模式的に示している。
図７に示すように、板厚が薄い薄肉杭の場合には剛性が小さく、地すべり抑止用杭９のたわみが大きいので抵抗力として考慮する地盤反力が大きくなる。
As described above, landslide prevention piles designed using wedge piles, holding piles, and reinforcing piles consider the ground reaction force proportional to the deflection of the piles as resistance. This will be described with reference to FIG. In FIG. 7, 1 is a moving layer, 3 is an immobile layer, 5 is a slip surface, 9 is a landslide prevention pile (hereinafter sometimes simply referred to as a “pile”), and FIG. 7A shows a landslide prevention pile. The ground reaction force acting on the pile 9 is indicated by an arrow, and the bending moment acting on the landslide prevention pile 9 is indicated by a curve. FIG. 7 (b) schematically shows the deflection when the landslide prevention pile 9 receives the action force. Is shown in
As shown in FIG. 7, in the case of a thin-walled pile having a small thickness, the rigidity is small and the deflection of the landslide prevention pile 9 is large, so that the ground reaction force considered as the resistance becomes large.
作用力が一定である場合、板厚を厚くして地すべり抑止用杭９の剛性を大きくすると、図８（ｂ）で示すように、地すべり抑止用杭９のたわみが小さくなるため、抵抗力として考慮する地盤反力が小さくなる。その結果、地すべり抑止用杭９に発生する曲げモーメントが更に大きくなり、地すべり抑止用杭９の剛性を大きくするため、更に板厚を厚くしなければならず鋼材重量が益々増加するという悪循環に陥る。 In the case where the acting force is constant, if the rigidity of the landslide prevention pile 9 is increased by increasing the plate thickness, as shown in FIG. 8B, the deflection of the landslide prevention pile 9 decreases, so that the resistance force becomes The ground reaction force to be considered becomes smaller. As a result, the bending moment generated in the landslide prevention pile 9 further increases, and in order to increase the rigidity of the landslide prevention pile 9, the plate thickness must be further increased, and a vicious circle occurs in which the steel material weight increases more and more. .
また、地すべり抑止用杭９の剛性を大きくすると、杭のたわみが十分発揮されるために必要となる杭の不動層３への根入長も大きくなるため、この点でも鋼材重量が大きく不経済な設計となる。 In addition, when the rigidity of the landslide prevention pile 9 is increased, the length of the pile required to sufficiently exhibit the deflection of the pile into the immovable layer 3 is also increased. Design.
本発明はかかる課題を解決するためになされたものであり、抑え杭で設計される場合に、鋼材重量を低減して建設コストを抑制できる地すべり抑止用杭およびその設計方法を提供することを目的とする。 The present invention has been made to solve such a problem, and an object of the present invention is to provide a landslide prevention pile capable of reducing the steel material weight and suppressing the construction cost when designing with a holding pile and a method of designing the same. And
（１）本発明に係る地すべり抑止用杭は、地中のすべり面を境にして、該すべり面より下方の不動層に対して、前記すべり面より上方の移動層が、前記すべり面に沿って滑る地すべりを抑止するためのものであって、
前記地すべり抑止用杭は抑え杭である鋼管杭であり、かつ鋼管杭を構成する鋼材の許容応力度σａと鋼管杭の剛性EIが下式を満たすものである。
300≦σa・・・（１）
EI≦109.16Pcosθ・H0.8-20783・・・（２）
但し、σa：許容応力度(N/mm2)
E：鋼材のヤング率(kN/m2)
I：鋼管杭の断面二次モーメント(m4)
EI：鋼管杭の剛性(kN・m2)
H：移動層の厚み(m)
P：地すべりを抑止するために必要な単位奥行あたりの抑止力(kN/m)
θ：すべり面の傾斜角(°)
(1) In the landslide prevention pile according to the present invention, a moving layer above the slip surface is located along the slip surface with respect to an immovable layer below the slip surface with respect to the underground slip surface. To prevent landslides,
The landslide restraining pile is steel pipe is suppressed pile, and allowable stress sigma a and rigidity EI of the steel pipe pile of steel constituting the steel pipe pile are those that satisfy the following expression.
300 ≦ σ a ... (1)
EI ≦ 109.16Pcosθ · H 0.8 -20783 ・ ・ ・ (2)
Where σ a : allowable stress (N / mm 2 )
E: Young's modulus of steel material (kN / m 2 )
I: Second moment of area of steel pipe pile (m 4 )
EI: the rigidity of the steel pipe pile (kN · m 2)
H: Thickness of moving bed (m)
P: Deterrent force per unit depth required to suppress landslide (kN / m)
θ: Slope inclination angle (°)
（２）本発明に係る地すべり抑止用杭の設計方法は、地中のすべり面を境にして、該すべり面より下方の不動層に対して、前記すべり面より上方の移動層が、前記すべり面に沿って滑る地すべりを抑止するためのものであって、
前記地すべり抑止用杭は抑え杭の設計手法で設計された鋼管杭であり、かつ鋼管杭を構成する鋼材の許容応力度σａと鋼管杭の剛性EIが下式を満たすように設計するものである。
300≦σa・・・（１）
EI≦109.16Pcosθ・H0.8-20783・・・（２）
但し、σa：鋼材の許容応力度(N/mm2)
E：鋼材のヤング率(kN/m2)
I：鋼管杭の断面二次モーメント(m4)
EI：鋼管杭の剛性(kN・m2)
H：移動層の厚み(m)
P：地すべりを抑止するために必要な単位奥行あたりの抑止力(kN/m)
θ：すべり面の傾斜角(°)
(2) The method for designing a landslide-preventing pile according to the present invention is characterized in that, with respect to the immovable layer below the slip surface, the moving layer above the slip surface is separated from the immovable layer below the slip surface. To prevent landslides along the surface,
The landslide restraining pile is steel pipe designed with design method of suppressing pile, and in which the stiffness EI of the allowable stress sigma a and steel pipe pile steel constituting the steel pipe pile is designed to meet the following formula is there.
300 ≦ σ a ... (1)
EI ≦ 109.16Pcosθ · H 0.8 -20783 ・ ・ ・ (2)
Where σ a : allowable stress of steel (N / mm 2 )
E: Young's modulus of steel material (kN / m 2 )
I: Second moment of area of steel pipe pile (m 4 )
EI: the rigidity of the steel pipe pile (kN · m 2)
H: Thickness of moving bed (m)
P: Deterrent force per unit depth required to suppress landslide (kN / m)
θ: Slope inclination angle (°)
本発明によれば、鋼材の許容応力度が大きく、鋼管杭の剛性が小さい地すべり抑止用杭となり、杭のたわみ性が十分に発揮され、鋼材重量を低減することができ、建設コストの抑制を実現できる。 ADVANTAGE OF THE INVENTION According to this invention, the permissible stress degree of steel material is large, it becomes a landslide prevention pile with small rigidity of a steel pipe pile, the flexibility of a pile is fully exhibited, the steel material weight can be reduced, and the construction cost can be reduced. realizable.
本実施の形態に係る地すべり抑止用杭は、地中のすべり面を境にして、該すべり面より下方の不動層に対して、前記すべり面より上方の移動層が、前記すべり面に沿って滑る地すべりを抑止するための地すべり抑止用杭であって、
前記地すべり抑止用杭は抑え杭の設計手法で設計された鋼管杭であり、かつ鋼管杭を構成する鋼材の許容応力度σａと鋼管杭の剛性EIが下式（１）、（２）を満たすことを特徴とするものである。
300≦σa・・・（１）
EI≦109.16Pcosθ・H0.8-20783・・・（２）
但し、σa：鋼材の許容応力度(N/mm2)
E：鋼材のヤング率(kN/m2)
I：鋼管杭の断面二次モーメント(m4)
EI：鋼管杭の剛性(kN・m2)
H：移動層の厚み(m)
P：地すべりを抑止するために必要な単位奥行あたりの抑止力(kN/m)
θ：すべり面の傾斜角(°)
The landslide prevention pile according to the present embodiment is configured such that a moving layer above the slip surface moves along the slip surface with respect to an immovable layer below the slip surface with respect to an underground slip surface. A landslide deterrent stake for deterring a sliding landslide,
The landslide restraining pile is steel pipe designed with design method of suppressing pile and the steel constituting the steel pipe pile allowable stress sigma a and rigidity EI is the formula of the steel pipe pile (1), (2) It is characterized by satisfying.
300 ≦ σ a ... (1)
EI ≦ 109.16Pcosθ · H 0.8 -20783 ・ ・ ・ (2)
Where σ a : allowable stress of steel (N / mm 2 )
E: Young's modulus of steel material (kN / m 2 )
I: Second moment of area of steel pipe pile (m 4 )
EI: the rigidity of the steel pipe pile (kN · m 2)
H: Thickness of moving bed (m)
P: Deterrent force per unit depth required to suppress landslide (kN / m)
θ: Slope inclination angle (°)
以下、上記の数式を導き出した経緯について説明する。
地すべり抑止用杭が抑え杭で設計される場合に、鋼材重量を低減して建設コストを抑制するため、従来よりも降伏点の高い鋼管を、地すべり抑止用杭として活用することを考えた。すなわち、(ａ)鋼管杭を構成する鋼材として高強度鋼を用いて降伏点を高くする、換言すれば許容応力度を大きくして、杭が大きくたわんでも破壊しないようにするとともに、(ｂ)鋼管杭の剛性を小さくして鋼管杭を大きくたわませることで、十分な地盤反力を得ることにより合理的な設計にしようというものである。
Hereinafter, the process of deriving the above formula will be described.
When landslide prevention piles are designed with restraining piles, we considered using steel pipes with a higher yield point than before as landslide prevention piles in order to reduce steel material weight and reduce construction costs. That is, (a) the yield point is increased by using high-strength steel as a steel material constituting the steel pipe pile, in other words, the allowable stress is increased so that the pile is not broken even if it is greatly bent, and (b) By reducing the rigidity of the steel pipe pile and causing the steel pipe pile to flex greatly, it is intended to obtain a sufficient ground reaction force to achieve a rational design.
そこで、さまざまな設計条件における、抑え杭の試計算を行った。試計算のモデルの概要を図１に示す。試計算のモデルは、厚みHの移動層１（N値=N1）が不動層３（N値=N2）の上方に傾斜角度θのすべり面５を介して配置され、地すべり抑止用杭である鋼管杭７は、移動層１からすべり面５を貫通して不動層３まで貫入されているものとした。 Therefore, trial calculation of retaining piles was performed under various design conditions. FIG. 1 shows an outline of the model of the trial calculation. In the model of the trial calculation, the moving layer 1 (N value = N 1 ) having the thickness H is disposed above the immobile layer 3 (N value = N 2 ) via the slip surface 5 having the inclination angle θ, and the landslide prevention pile is provided. The steel pipe pile 7, which penetrates the sliding surface 5 from the moving layer 1 and penetrates to the immobile layer 3.
試計算の条件は次に示すとおりである。
奥行1mあたりの必要抑止力の大きさは700kN/m、800kN/mの２種類で、移動層１の厚みHは5m、7mの2種類とした。また、すべり面５の傾斜角θは15°、30°の2種類とした。さらに、不動層３は硬質な地盤であることを想定し、N値は50で固定した。
鋼管杭７は奥行1mにつき1本設置すると仮定し、管径を100mm〜550mmの範囲で変化させたときに必要となる板厚を計算した。
鋼材の長期曲げ許容応力度は、SKK400は140N/mm2、SKK490は185N/mm2、SM570は255N/mm2とした。それ以上の高強度材料については、300N/mm2、350N/mm2、400N/mm2、450N/mm2、500N/mm2、550N/mm2、600N/mm2とした。
The conditions for the trial calculation are as follows.
The magnitude of the required deterrent force per 1 m of depth was 700 kN / m and 800 kN / m, and the thickness H of the moving layer 1 was 5 m and 7 m. In addition, the inclination angle θ of the sliding surface 5 was set to two types, 15 ° and 30 °. Further, assuming that the immobile layer 3 is hard ground, the N value is fixed at 50.
Assuming that one steel pipe pile 7 is installed for every 1 m in depth, the required thickness was calculated when the pipe diameter was changed in the range of 100 mm to 550 mm.
Long bending allowable stress of the steel, SKK400 is 140N / mm 2, SKK490 is 185N / mm 2, SM570 was 255N / mm 2. For more high strength material, it was 300N / mm 2, 350N / mm 2, 400N / mm 2, 450N / mm 2, 500N / mm 2, 550N / mm 2, 600N / mm 2.
試計算の結果を表１、２に示す。表中には、種々の地盤条件と鋼種に対して、抑え杭としての設計条件を満たすことで杭の安全性が確保され、かつ鋼材重量が最も小さくなった管径と板厚の組み合わせを代表して示している。 Tables 1 and 2 show the results of the trial calculation. In the table, the combination of pipe diameter and plate thickness that ensured the safety of the pile by satisfying the design conditions as a retaining pile for various ground conditions and steel types and that minimized the steel material weight is represented. Is shown.
表１、２に示した各数値の算出根拠となる数式は以下の通りである。 Numerical expressions that are the basis for calculating each numerical value shown in Tables 1 and 2 are as follows.
表１、２に示したNo.１〜No.80の全てについて、横軸を鋼材の許容応力度σa(N/mm2)、縦軸を鋼種ごとの鋼材重量W(t)の同じ地盤条件におけるSKK400での鋼材重量W0(t)に対する鋼材重量比率(W/W0)としたグラフに表示すると、図２に示す通りである。
図２のグラフにおいて、累乗近似すると近似式としてのW/W0=704.55σa -1.338と高い相関が得られることが分かった。
For all of No. 1 to No. 80 shown in Tables 1 and 2, the horizontal axis represents the allowable stress of steel σ a (N / mm 2 ), and the vertical axis represents the same ground with the steel weight W (t) for each steel type. FIG. 2 shows a graph showing the steel material weight ratio (W / W 0 ) to the steel material weight W 0 (t) at SKK400 under the conditions.
In the graph of FIG. 2, it was found that a high correlation of W / W 0 = 704.55σ a -1.338 as an approximate expression was obtained by power approximation.
この近似式から、抑え杭の設計においては、鋼材の許容応力度が大きいほど鋼材重量を小さくできるが、許容応力度の増加に対して鋼材重量を小さくできる割合（累乗近似曲線の接線の傾きの絶対値）は、徐々に小さくなることが分かる。 From this approximation formula, in the design of the retaining pile, the steel material weight can be reduced as the allowable stress of the steel increases, but the ratio of decreasing the steel weight to the increase of the allowable stress (the slope of the tangent of the tangent of the power approximate curve) (Absolute value) gradually decreases.
この近似式を基に許容応力度をどのように設定することが、抑え杭として合理的な設計となるかについて検討した。
まず、鋼材の許容応力度が大きいほど鋼材重量を小さくできることから、鋼材重量を低減するという観点からは、許容応力度をできるだけ大きくすることが好ましい。
そして、許容応力度の増加に対して鋼材重量を小さくできる割合（累乗近似曲線の接線の傾きの絶対値）は、徐々に小さくなること、換言すれば、許容応力度が小さい領域では、許容応力度を少し大きくするだけで大きな鋼材重量低減が実現できることを考慮すれば、鋼材重量の低減率が高い領域、換言すれば許容応力度が小さい領域ではさらなる合理化ができることになるので、許容応力度としては下限値を設定することが、合理的な設計となる。
We examined how to set the allowable stress based on this approximation formula to obtain a reasonable design for the retaining pile.
First, since the weight of the steel material can be reduced as the allowable stress of the steel material increases, it is preferable to increase the allowable stress as much as possible from the viewpoint of reducing the weight of the steel material.
The rate at which the steel material weight can be reduced with respect to the increase in the allowable stress (the absolute value of the slope of the tangent of the power approximation curve) gradually decreases. In other words, in the region where the allowable stress is small, the allowable stress is small. Considering that a large reduction in steel material weight can be realized by only slightly increasing the degree, the region where the rate of reduction in steel material weight is high, in other words, the region where the allowable stress level is small, can be further rationalized. It is reasonable to set a lower limit.
図２のグラフを見ると、例えば既往の技術として用いられているSM570（許容応力度255N/mm2）の段階では、鋼材重量を小さくする割合は比較的大きいため、この許容応力度よりもさらに大きな許容応力度にすることが合理的であると言える。
前述したように、許容応力度が大きくなればなるほど、許容応力度の増加に対して鋼材重量を小さくできる割合（累乗近似曲線の接線の傾きの絶対値）は、徐々に小さくなる。そして、許容応力度が300N/mm2（接線の傾き：−0.00152）あたりから曲線の接線の傾きが小さくなっており、このことから許容応力度が300N/mm2よりも小さい領域は鋼材重量低減率が高いので、この領域では十分な合理化が達成できていない、換言すれば許容応力度を300N/mm2以上に設定することが、合理的な設計となると言える。
Referring to the graph of FIG. 2, for example, at the stage of SM570 (allowable stress level of 255 N / mm 2 ) used as a conventional technique, the ratio of reducing the steel material weight is relatively large. It can be said that it is rational to set a large allowable stress.
As described above, as the allowable stress level increases, the ratio (absolute value of the slope of the tangent of the power approximate curve) in which the weight of the steel material can be reduced with respect to the increase in the allowable stress level gradually decreases. The slope of the tangent of the curve becomes smaller from the allowable stress level of around 300 N / mm 2 (the slope of the tangent: -0.00152). Therefore, the area where the allowable stress level is smaller than 300 N / mm 2 is reduced in steel weight. Since the rate is high, sufficient rationalization has not been achieved in this region. In other words, setting the allowable stress to 300 N / mm 2 or more is a reasonable design.
次に、抑え杭として合理的な設計となるためには、杭の剛性をどの程度まで小さくする必要があるかについて検討した。設計の成り立つ杭の剛性は、地盤条件ごとに異なるため、各地盤条件に応じた杭の剛性の評価式が必要となる。
まず、試設計の結果をもとに、各地盤条件において、縦軸：杭の剛性(kN/m2)、横軸：鋼材の許容応力度で整理したところ、こちらも累乗近似で整理できることが分かった。一例として、地盤条件が共通する表１におけるNo.1〜No.10についての整理結果を図３のグラフに示す。図３中の点線は、累乗近似曲線を示す。ここで近似式は、EI=8.572×107×σa -1.024であった。
Next, we examined how much the rigidity of the pile had to be reduced in order to obtain a reasonable design for the retaining pile. Since the stiffness of the pile for which the design holds is different for each ground condition, an evaluation formula for the stiffness of the pile according to the ground conditions at each location is required.
First, based on the results of the trial design, the vertical axis: the rigidity of the pile (kN / m 2 ) and the horizontal axis: the allowable stress of the steel under the conditions of each area, the results can be summarized by the power approximation. Do you get it. As an example, the graph of FIG. 3 shows the results of rearranging No. 1 to No. 10 in Table 1 having common ground conditions. The dotted line in FIG. 3 indicates a power approximation curve. Here, the approximate expression was EI = 8.572 × 10 7 × σ a -1.024 .
表１、２の全ての地盤条件について、前述したように合理的な杭の設計となるための条件として鋼材の許容応力度を求めているので（図２参照）、この許容応力度を導出したときの条件を前提として、各地盤条件について許容応力度と杭の剛性との関係を求める必要がある。
表１、２の全ケースの検討において、許容応力度を300N/mm2以上としたのは、累乗近似曲線の接線の傾きに基づくものである。したがって、各地盤条件についても全ケースの場合と同様に、許容応力度と鋼材重量の比率との関係を示す近似式（近似曲線）を求め、この近似曲線の接線の傾きが−0.00152となるとき、すなわち図２において求めた許容応力度の下限値のとなるときの許容応力度を、近似式より算出する。
そして、算出した許容応力度のときの、杭の剛性を累乗近似式によって求める。
これらの手順を各地盤条件について行って、各地盤条件における杭の剛性を求め、全ての地盤条件における杭の剛性を整理することで、杭の剛性が満たすべき条件を求める。
以上のような手順によって、杭の剛性を求めたものが、式（２）の条件である。
As described above, for all the ground conditions in Tables 1 and 2, the allowable stress level of the steel material is determined as a condition for designing a reasonable pile (see FIG. 2). Assuming the conditions at that time, it is necessary to find the relationship between the allowable stress level and the stiffness of the pile for each of the board conditions.
In all of the cases in Tables 1 and 2, the reason why the allowable stress was set to 300 N / mm 2 or more is based on the slope of the tangent of the power approximation curve. Therefore, as in all cases, an approximate expression (approximate curve) indicating the relationship between the allowable stress and the ratio of the weight of the steel material is obtained for each local area condition, and when the slope of the tangent of the approximate curve is -0.00152. That is, the allowable stress at which the lower limit of the allowable stress obtained in FIG. 2 is reached is calculated from the approximate expression.
Then, the stiffness of the pile at the calculated allowable stress is determined by a power approximation formula.
These procedures are performed for each ground condition, the stiffness of the pile in each ground condition is obtained, and the stiffness of the pile in all the ground conditions is arranged to obtain the condition that the stiffness of the pile should satisfy.
The condition of equation (2) is obtained by determining the stiffness of the pile by the above procedure.
上記の手順を地盤条件が共通するNo.1〜No.10について、図４に基づいて具体的に説明する。
図４（ａ）は、地盤条件が共通するNo.1〜No.10について、横軸を鋼材の許容応力度σa(N/mm2)、縦軸を図２と同様に、鋼種ごとの鋼材重量W(t)の同じ地盤条件におけるSKK400での鋼材重量W0(t)に対する鋼材重量比率(W/W0)としてグラフ表示したものであり、図４（ｂ）は、図３と同一のものである。また、図４（ａ），（ｂ）中の点線は、それぞれのデータの組に対する累乗近似曲線を示す。
図４（ａ）に示す近似曲線において、接線の傾きが-0.00152となるときの許容応力度を求めると、302N/mm2となり、許容応力度が302N/mm2のときの杭の剛性EIを図４（ｂ）で求めると、247556(kN・m2)となる。
The above procedure will be specifically described with reference to FIG. 4 for No. 1 to No. 10 having common ground conditions.
FIG. 4 (a) shows the allowable stress σ a (N / mm 2 ) of the steel material on the horizontal axis and the vertical axis on each steel type for No. 1 to No. 10, which have the same ground conditions, as in FIG. FIG. 4B is a graph showing the steel material weight W (t) as a steel material weight ratio (W / W 0 ) to the steel material weight W 0 (t) at SKK400 under the same ground conditions, and FIG. 4B is the same as FIG. belongs to. Dotted lines in FIGS. 4A and 4B indicate power approximate curves for the respective data sets.
In the approximate curve shown in FIG. 4 (a), when determining the allowable stress when the tangent slope is -0.00152, 302N / mm 2, and the rigidity EI of the pile when allowable stress of 302N / mm 2 When calculated in FIG. 4B, it is 247556 (kN · m 2 ).
以上の手順に従って地盤条件が共通するもの毎に杭の剛性EIを求め、求められた杭の剛性に対して近似式で整理できる地盤条件に応じたパラメータを探索したところ下式（３）に示すパラメータを発見した。 Following the above procedure, the pile stiffness EI was calculated for each of the ground conditions common to each other, and the parameters corresponding to the ground conditions that could be arranged by an approximate expression were searched for the obtained pile stiffness. Found parameters.
Pcosθ・H0.8 ・・・（３）
但し、P:地すべりを抑止するために必要な単位奥行きあたりの抑止力(kN/m)
θ：すべり面の傾斜角(°)
H:移動層の厚み(m)
Pcosθ ・ H 0.8・ ・ ・ (3)
However, P: Deterrent force per unit depth required to suppress landslide (kN / m)
θ: Slope inclination angle (°)
H: thickness of moving bed (m)
図５は、縦軸が抽出した杭の剛性(kN・m2)であり、横軸が上記の式（３）のパラメータの値を示しており、表１、２の全ケースについてプロットしたものである。なお、図５において、プロットが大きくなっているのは、複数のプロットが重なっているためである。
図５を直線近似すると、下式（４）が求まる。
In FIG. 5, the vertical axis represents the extracted stiffness (kN · m 2 ) of the pile, and the horizontal axis represents the parameter values of the above equation (3), plotted for all cases in Tables 1 and 2. It is. In FIG. 5, the plots are large because a plurality of plots overlap.
By linearly approximating FIG. 5, the following equation (4) is obtained.
EI=109.16Pcosθ・H0.8-20783・・・（４）
但し、E：鋼材のヤング率(kN/m2)
I：鋼管杭の断面二次モーメント(m4)
EI：鋼管杭の剛性(kN・m2)
H：移動層の厚み(m)
P：地すべりを抑止するために必要な単位奥行あたりの抑止力(kN/m)
θ：すべり面の傾斜角(°)
EI = 109.16Pcosθ · H 0.8 -20783 ・ ・ ・ (4)
Where E: Young's modulus of steel (kN / m 2 )
I: Second moment of area of steel pipe pile (m 4 )
EI: the rigidity of the steel pipe pile (kN · m 2)
H: Thickness of moving bed (m)
P: Deterrent force per unit depth required to suppress landslide (kN / m)
θ: Slope inclination angle (°)
図５に示す直線よりも下方の領域（図中に示す丸が存在する領域）が、許容応力度を踏まえた杭の剛性の満たすべき領域である。
この領域を数式で示すと下式（２）となり、杭の剛性が（２）式を満たしていれば、合理的な設計となっているといえる。
The area below the straight line shown in FIG. 5 (the area where the circle shown in the figure exists) is an area where the rigidity of the pile should be satisfied in consideration of the allowable stress.
This area is expressed by the following equation (2), and if the rigidity of the pile satisfies the equation (2), it can be said that the design is reasonable.
EI≦109.16Pcosθ・H0.8-20783・・・（２）
但し、E：鋼材のヤング率(kN/m2)
I：鋼管杭の断面二次モーメント(m4)
EI：鋼管杭の剛性(kN・m2)
H：移動層の厚み(m)
P：地すべりを抑止するために必要な単位奥行あたりの抑止力(kN/m)
θ：すべり面の傾斜角(°)
EI ≦ 109.16Pcosθ · H 0.8 -20783 ・ ・ ・ (2)
Where E: Young's modulus of steel (kN / m 2 )
I: Second moment of area of steel pipe pile (m 4 )
EI: the rigidity of the steel pipe pile (kN · m 2)
H: Thickness of moving bed (m)
P: Deterrent force per unit depth required to suppress landslide (kN / m)
θ: Slope inclination angle (°)
（２）式の妥当性を調べるため、試設計の結果を、縦軸：杭の剛性(kN・m2)、横軸：（２）式のパラメータの値として図６のように整理した。なお、図６においては、全ケースのプロットのうち、図６に示した縦軸と横軸の範囲を逸脱するものは除外している。
許容応力度が300N/mm2以上では、概ね図６の破線の直線の下方の領域にあり、（２）式を満たす杭の剛性となっており、評価式に問題はないと言える。
In order to check the validity of the equation (2), the results of the trial design were arranged as shown in FIG. 6 with the vertical axis: pile rigidity (kN · m 2 ) and the horizontal axis: parameter values of the equation (2). Note that, in FIG. 6, those plots that deviate from the range of the vertical axis and the horizontal axis shown in FIG. 6 are excluded from the plots of all cases.
When the allowable stress degree is 300 N / mm 2 or more, it is generally in a region below the broken straight line in FIG. 6, and the stiffness of the pile satisfies the expression (2), and it can be said that there is no problem in the evaluation expression.
以上のように、本発明によれば、鋼材の許容応力度が大きく、鋼管杭７の剛性が小さい地すべり抑止用杭となり、杭のたわみ性が十分に発揮され、鋼材重量を低減することができ、建設コストの抑制を実現できる。 As described above, according to the present invention, a landslide-preventing pile having a large allowable stress of steel and a small rigidity of the steel pipe pile 7 is provided, the flexibility of the pile is sufficiently exhibited, and the weight of the steel can be reduced. In addition, the construction cost can be reduced.
表１、２に示されたものの一部について考察すると、例えば必要抑止力が700kN/m、移動層の厚みが5m、すべり面の傾斜角が15°の場合（表１のNo.1〜No.10）、鋼管の管径、板厚、鋼材重量、（２）式の上限値と杭剛性の比率は、SKK400（許容応力度140N/mm2）では、それぞれ管径550mm板厚58mm、8.32t、2.06である。また、同条件において、SKK490（許容応力度185N/mm2）では、鋼管の管径、板厚、鋼材重量、（２）式の上限値と杭剛性の比率は、それぞれ管径550mm板厚39mm、5.51t、1.54である。これらに対して、許容応力度300kN/mm2のものでは、鋼管の管径、板厚、鋼材重量、（２）式の上限値と杭剛性の比率は、それぞれ管径550mm板厚21mm、2.86t、0.92となる。使用鋼材重量の比率をみると、SKK400を1.0とすると、SKK490は0.66、許容応力度300kN/mm2は0.34となり、許容応力度を300kN/mm2にすると、大幅に鋼材重量を低減出来ることができる。 Considering a part of those shown in Tables 1 and 2, for example, when the required deterrent is 700 kN / m, the thickness of the moving layer is 5 m, and the inclination angle of the sliding surface is 15 ° (No. 1 to No. .10), the pipe diameter, plate thickness, steel material weight, and the ratio between the upper limit of equation (2) and the pile rigidity are S550 (permissible stress: 140 N / mm 2 ) with a pipe diameter of 550 mm and a plate thickness of 58 mm and 8.32, respectively. t, 2.06. Under the same conditions, for SKK490 (permissible stress level: 185N / mm 2 ), the pipe diameter, plate thickness, steel weight, and the upper limit of equation (2) and the ratio of pile rigidity are respectively pipe diameter 550mm and plate thickness 39mm , 5.51t and 1.54. For these, those of the allowable stress 300 kN / mm 2, the pipe diameter of the steel tube, thickness, steel weight, (2) the upper limit value and the ratio of the pile stiffness, respectively pipe diameter 550mm thickness 21 mm, 2.86 t, 0.92. Looking at the ratio of use steel weight, when 1.0 SKK400, SKK490 0.66, allowable stress 300 kN / mm 2 is 0.34, that when the allowable stress to 300 kN / mm 2, can significantly reduce the steel weight it can.
なお、高強度鋼を用いることによる、鋼材重量の低減割合は、許容応力度が大きくなるほど小さくなるが、その一方で材料コストが上昇するため、好ましくは、許容応力度が（５）式を満たすことがより望ましい。
300≦σa≦400 ・・・（５）
In addition, the reduction rate of the steel material weight by using the high-strength steel decreases as the allowable stress increases, but on the other hand, the material cost increases. Therefore, the allowable stress preferably satisfies the expression (5). It is more desirable.
300 ≦ σ a ≦ 400 ・ ・ ・ (5)
また、杭に発生する最大曲げモーメントの作用点は、理論上はすべり面５の付近であり、地表面付近や杭の下端に大きな曲げモーメントは発生しないが、実際は地点によってすべり面５の位置や地中の地盤条件が変化するため、杭の剛性および許容応力度は一律であることが望ましい。 In addition, the point of application of the maximum bending moment generated on the pile is theoretically near the slip surface 5 and a large bending moment does not occur near the ground surface or the lower end of the pile, but actually the position of the slip surface 5 depends on the point. Since the underground ground conditions change, it is desirable that the rigidity of the pile and the allowable stress are uniform.
１ 移動層
３ 不動層
５ すべり面
７ 鋼管杭
９ 地すべり抑止用杭(従来例)
Reference Signs List 1 moving bed 3 immobile layer 5 slip surface 7 steel pipe pile 9 landslide prevention pile (conventional example)
Claims (2)
前記地すべり抑止用杭は抑え杭である鋼管杭であり、かつ鋼管杭を構成する鋼材の許容応力度σａと鋼管杭の剛性EIが下式を満たす地すべり抑止用杭。
300≦σa・・・（１）
EI≦109.16Pcosθ・H0.8-20783・・・（２）
但し、σa：鋼材の許容応力度(N/mm2)
E：鋼材のヤング率(kN/m2)
I：鋼管杭の断面二次モーメント(m4)
EI：鋼管杭の剛性(kN・m2)
H：移動層の厚み(m)
P：地すべりを抑止するために必要な単位奥行あたりの抑止力(kN/m)
θ：すべり面の傾斜角(°) With the underground slip surface as a boundary, with respect to the immobile layer below the slip surface, the moving layer above the slip surface is a landslide prevention pile for suppressing a landslide that slides along the slip surface. So,
The landslide restraining pile is steel pipe is suppressed piles, and the allowable stress sigma a and steel pipe pile steel constituting the steel pipe pile rigidity EI is pile for landslide suppress satisfies the following equation.
300 ≦ σ a ... (1)
EI ≦ 109.16Pcosθ · H 0.8 -20783 ・ ・ ・ (2)
Where σ a : allowable stress of steel (N / mm 2 )
E: Young's modulus of steel material (kN / m 2 )
I: Second moment of area of steel pipe pile (m 4 )
EI: the rigidity of the steel pipe pile (kN · m 2)
H: Thickness of moving bed (m)
P: Deterrent force per unit depth required to suppress landslide (kN / m)
θ: Slope inclination angle (°)
前記地すべり抑止用杭は抑え杭の設計手法で設計された鋼管杭であり、かつ鋼管杭を構成する鋼材の許容応力度σａと鋼管杭の剛性EIが下式を満たすように設計する地すべり抑止用杭の設計方法。
300≦σa・・・（１）
EI≦109.16 Pcosθ・H0.8-20783・・・（２）
但し、σa：鋼材の許容応力度(N/mm2)
E：鋼材のヤング率(kN/m2)
I：鋼管杭の断面二次モーメント(m4)
EI：鋼管杭の剛性(kN・m2)
H：移動層の厚み(m)
P：地すべりを抑止するために必要な単位奥行あたりの抑止力(kN/m)
θ：すべり面の傾斜角(°) A landslide prevention pile for suppressing a landslide that slides along the slip surface, with respect to an immobile layer below the slip surface, with the underground slip surface as a boundary. A design method,
The landslide restraining pile is steel pipe designed with design method of suppressing pile and landslide deterrence rigidity EI of allowable stress sigma a and steel pipe pile steel constituting the steel pipe pile is designed to meet the following formula Design method for piles.
300 ≦ σ a ... (1)
EI ≦ 109.16 Pcosθ · H 0.8 -20783 ・ ・ ・ (2)
Where σ a : allowable stress of steel (N / mm 2 )
E: Young's modulus of steel material (kN / m 2 )
I: Second moment of area of steel pipe pile (m 4 )
EI: the rigidity of the steel pipe pile (kN · m 2)
H: Thickness of moving bed (m)
P: Deterrent force per unit depth required to suppress landslide (kN / m)
θ: Slope inclination angle (°)
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111648387A (en) * | 2020-06-10 | 2020-09-11 | 广东省工程勘察院 | Construction method of stiffness variable-section high-pressure jet grouting pile slide-resistant wall |
| CN114235566A (en) * | 2021-11-08 | 2022-03-25 | 中国电建集团华东勘测设计研究院有限公司 | Model test system and method for testing multiple arc model calculation design thrust effect |
Citations (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS53148105A (en) * | 1977-05-30 | 1978-12-23 | Taisei Corp | Method of preventing landslide |
| JPS60104437U (en) * | 1983-12-21 | 1985-07-16 | 株式会社クボタ | Deterrent piles for landslide prevention |
| JPH08184058A (en) * | 1994-12-28 | 1996-07-16 | Ohbayashi Corp | Landslide protection construction |
| JPH0978575A (en) * | 1995-09-14 | 1997-03-25 | Kubota Corp | Landslide suppressing pile |
| JP2002146778A (en) * | 2000-11-09 | 2002-05-22 | Nippon Steel Corp | Full-scale type inspection method for steel-pipe pile welding section |
| US20090080983A1 (en) * | 2007-08-14 | 2009-03-26 | Richard Donovan Short | Methods and devices for ground stabilization |
| JP2010101159A (en) * | 2008-09-29 | 2010-05-06 | Jfe Steel Corp | Steel pipe-concrete composite pile and steel pipe used for the steel pipe-concrete composite pile |
| JP2012017648A (en) * | 2010-06-07 | 2012-01-26 | Jfe Steel Corp | Foundation pile group |
| JP2012097415A (en) * | 2010-10-29 | 2012-05-24 | Jfe Steel Corp | Steel pipe sheet pile quaywall |
| JP2012144951A (en) * | 2011-01-14 | 2012-08-02 | Jfe Steel Corp | Steel pipe pile type landing pier |
| JP2015193887A (en) * | 2014-03-31 | 2015-11-05 | Ｊｆｅスチール株式会社 | Low yield ratio high strength spiral steel pipe pile and manufacturing method therefor |
| JP2017002609A (en) * | 2015-06-12 | 2017-01-05 | 東京製綱株式会社 | Pipe-type shallow landslide prevention facility |
-
2018
- 2018-10-01 JP JP2018186366A patent/JP6958528B2/en active Active
Patent Citations (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS53148105A (en) * | 1977-05-30 | 1978-12-23 | Taisei Corp | Method of preventing landslide |
| JPS60104437U (en) * | 1983-12-21 | 1985-07-16 | 株式会社クボタ | Deterrent piles for landslide prevention |
| JPH08184058A (en) * | 1994-12-28 | 1996-07-16 | Ohbayashi Corp | Landslide protection construction |
| JPH0978575A (en) * | 1995-09-14 | 1997-03-25 | Kubota Corp | Landslide suppressing pile |
| JP2002146778A (en) * | 2000-11-09 | 2002-05-22 | Nippon Steel Corp | Full-scale type inspection method for steel-pipe pile welding section |
| US20090080983A1 (en) * | 2007-08-14 | 2009-03-26 | Richard Donovan Short | Methods and devices for ground stabilization |
| JP2010101159A (en) * | 2008-09-29 | 2010-05-06 | Jfe Steel Corp | Steel pipe-concrete composite pile and steel pipe used for the steel pipe-concrete composite pile |
| JP2012017648A (en) * | 2010-06-07 | 2012-01-26 | Jfe Steel Corp | Foundation pile group |
| JP2012097415A (en) * | 2010-10-29 | 2012-05-24 | Jfe Steel Corp | Steel pipe sheet pile quaywall |
| JP2012144951A (en) * | 2011-01-14 | 2012-08-02 | Jfe Steel Corp | Steel pipe pile type landing pier |
| JP2015193887A (en) * | 2014-03-31 | 2015-11-05 | Ｊｆｅスチール株式会社 | Low yield ratio high strength spiral steel pipe pile and manufacturing method therefor |
| JP2017002609A (en) * | 2015-06-12 | 2017-01-05 | 東京製綱株式会社 | Pipe-type shallow landslide prevention facility |
Non-Patent Citations (1)
| Title |
|---|
| 新日鐵住金 建設用資材ハンドブック２０１８年４月改訂版 建築構造用鋼管, JPN6021017340, April 2018 (2018-04-01), pages 133 - 3, ISSN: 0004503415 * |
Cited By (4)
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| CN111648387A (en) * | 2020-06-10 | 2020-09-11 | 广东省工程勘察院 | Construction method of stiffness variable-section high-pressure jet grouting pile slide-resistant wall |
| CN111648387B (en) * | 2020-06-10 | 2021-09-14 | 广东省工程勘察院 | Construction method of stiffness variable-section high-pressure jet grouting pile slide-resistant wall |
| CN114235566A (en) * | 2021-11-08 | 2022-03-25 | 中国电建集团华东勘测设计研究院有限公司 | Model test system and method for testing multiple arc model calculation design thrust effect |
| CN114235566B (en) * | 2021-11-08 | 2023-09-15 | 中国电建集团华东勘测设计研究院有限公司 | Model test system and method for checking multiple circular arc model calculation design thrust effect |
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