JP5505959B2 - A slanted group pile method using a large-diameter core with a bearing plate structure at the head to allow pile deformation - Google Patents

Description

  The present invention has the effect of deflection reinforcement by using a large-diameter core material, the effect of tension reinforcement by having a head-supported plate structure, and the deformation of the sliding surface within the moving layer by not loading prestress. It is related to the oblique group pile construction method that improves the stability of the entire slope that has been loosened due to the integration effect of the ground and core material.

  In general, the end of the slope where the landslide has occurred often exhibits an unstable slope after completion of the landslide countermeasure work on the main body. The destabilized slope is subjected to earth pressure and landslide thrust from the back, and the shear zone due to passive fracture forms a multi-layer structure, and the moving landslide of the main landslide forms a steep cliff with a rocky outcrop with a top ring There are a wide variety of things, such as those where the earth and sand supplied from the steep slope part forms a thick cliff with a cliff face.

  Also, in recent years when the rainfall pattern has changed and the risk of heavy rain disasters has increased, the slopes that have left such unstable elements at the end of the landslide will be collapsed or eroded in the future. The risk of destabilization is increasing.

  However, planning the countermeasures for the purpose of eliminating destabilizing elements that may occur in the future against the behavior of the landslide end may result in a business volume that is comparable to the construction cost of the main unit. There are few cases where special countermeasures are introduced, except when refraining from behind.

When applying the conventional method to such applications, we face several problems. First, the “pile method” and “anchor method” are designed to guide the integrated sliding body to stop by arranging a large deterrent force in a row, and the stabilization target spreads over the entire slope. Is difficult to apply. In addition, the soil layer that causes destabilization reaches the base rock surface and is deep, and the existing “Reinforced Earth Construction Method” with a moving layer thickness of up to 3 m is not applicable.
"New landslide steel pipe pile design guidelines", supervised by the Japan Landslide Society, published by the Japan Landslide Countermeasure Technology Association, revised edition 30 June 2003 “Geotechnical Society Standards Ground Anchor Design and Construction Standards, JGS4101 ・ 2000”, (edited by Geotechnical Society, published by Geotechnical Society, March 30, 2000) “Guidelines for Design and Construction of Cut Reinforced Earth Construction Method” (supervised by the Japan Highway Public Corporation, issued by the Road Welfare Society, June 2004, 5th print)

  Extruded, steep, steep and unstable slopes generated at the end of the landslide due to active landslide activity are generally large because the construction area to ensure internal stability is large and the landslide strength is small. Pile work and anchor work whose design is based on local placement of deterrence is uneconomical because the design load per piece must be reduced. Conversely, when considering the application of a reinforced earth method in which the moving layer thickness has an advantage in terms of surface response, the moving layer thickness was 5 to 10 m, exceeding the range of application, and it was difficult to respond.

Accordingly, the first aspect of the present invention is to grout the clearance around the large-diameter core material in the oblique group pile construction method that allows deformation of the pile body using the large-diameter core material having a bearing plate structure at the head. In addition to the effect of the tension reinforcement developed by the top plate support plate structure on the fixing length section and the core head, the top plate is restrained by the top plate support plate without prestressing Therefore, the large-diameter core is flexed greatly during sliding on the landslide, and is arranged in a zigzag arrangement or a square zigzag arrangement, so that the deformation resistance of the moving layer generated in the ground during this deflection process and the bending resistance of the large-diameter core In addition to the reinforcing force as a flexural reinforcement effect, it is designed to share the proportion of the tensile reinforcement effect and the flexural reinforcement effect at the maximum allowable deformation .

Moreover, this invention prevents a prestress from being loaded on the head of the said large diameter core material .

Furthermore, the present invention selects the staggered staggered or square staggered arrangement of the stiffeners and bearing plates in consideration of the design stiffening force consisting of the flexural stiffening force and the tensile stiffening force based on the analysis considering the amount of ground deformation. It is what you want to do.

In the present invention, a self-supporting pressure plate is used when installing on a sloping slope.

  The arrangement is planned to ensure the internal stability of the entire unstable slope, and the landslide of a large depth (up to about 10 m depth) is a reinforced earth method for natural slopes by making the core material a large cross section. Can be made a design object. In addition, the slanted pile structure has enabled the effect of retaining and tightening the axial force component to strengthen the reinforcing force. In addition, by evaluating the ratio of the axial force and bending shear resistance based on the stress-strain relationship and the yield criterion of the reinforcing material, the reinforcement considering the manifestation of the axial force and bending shear resistance due to the bending of the core material. Achieved strength evaluation.

  Also, by deliberately applying prestress and allowing deformation of the core material and natural ground until the reinforcement effect appears (up to 5% of the core material length in the moving layer), the core material The integration effect of the ground and the core material generated in the deformation process was expressed, and the cost reduction was realized by expanding the reinforcement placement distance to a maximum of 4 m.

  In addition, a rectangular arrangement and a square arrangement based on the staggered arrangement can be selected, and an arrangement with excellent reinforcement efficiency is selected according to the slope length / construction extension ratio, further reducing costs.

  In addition, by adopting a top-end type bearing plate shape, it has become possible to develop tensile reinforcement efficiently even on sloping slopes with small earth bearing strength.

The application range of the present invention can be introduced to slopes that satisfy the following conditions regardless of whether they are natural slopes or artificial slopes.
(1) Loose layer thickness of 3m or more and 10m or less (2) Non-viscous soil slope (3) Even if there is a mainland landslide behind, the activity has already stopped completely.
(4) Permissible pile head displacement (about 5% of pile length in moving layer)

  An embodiment of the present invention will be described with reference to “Table 1” shown in paragraph “0031” described later and the drawings. In the “Table 1”, the present invention has two types of specifications in order to cope with loose slopes having various forms.

  First, on slopes where the slip displacement of the block type is dominant, the A type mainly composed of bending shear is effective, in which several rows of GCPs are arranged at construction positions that increase the cross-sectional strength of the core material, overcome the block, and do not generate small blocks. .

  On the other hand, in areas where mudging and fluidization are conspicuous and small-scale slope failures occur frequently, adopting the B type, which induces the ground integration effect mainly by pulling, increases the diameter of the entire slope. Stability can be improved by placing steel bars and tightening loose slopes.

  In addition, in areas where mudification has progressed extremely partly, it will be possible to respond flexibly to slope conditions by increasing the number of hits.

  FIG. 1 is an application determination flow of the present invention. The present invention reduces the looseness by expecting the effect of deflection reinforcement by using a large-diameter core material, the effect of tension reinforcement by having a head bearing plate structure, and the integration effect of the ground and core material. This is a method to improve the stability of the entire slope. Therefore, in adopting this construction method, the looseness state, soil quality, variation form, depth of basement surface (loose layer thickness), block scale, slope direction, spring condition, and the presence of landslide main body block behind If it is clear, it is important to examine the activity of this and examine whether it can be introduced and the method specifications.

  In addition, because it is a method that does not load prestress, the reinforcement by this method will be gradually exerted as the loosening of the ground progresses. For this reason, a moderate loose displacement is allowed before the expected reinforcement force is exhibited. Therefore, when the object to be maintained is adjacent to a sloping slope, it is necessary to judge the application of this method.

  The conventional method (pile, anchor if landslide prevention method, non-frame method, etc. as a representative of earth and mountain reinforced earth for reinforced earth works) can be used properly. The loose layer thickness is more than 5m and the sloping slope is small. When collapse, deformation, and erosion are repeated on the scale, the advantage of this method is demonstrated, and the cost reduction effect is high as the total construction cost to ensure the internal stability of the entire slope.

FIG. 2 is a standard structure diagram of the present invention “GCP = Geo Coat Piling” -A type). 1 is a core material according to the present invention, and a specification using a steel pipe 1 'as the core material is called A type, and a diameter φ = 101.6 mm, a wall thickness t = 25 mm, and a fixing length L = 3 m or more is used. . Further, in the case of the specification using the deformed steel bar 1 ″ for the core material 1, the case of using the one having a diameter of about D51 (diameter = 50.8 mm) is referred to as B type. 2 is a head cap with an injection hole, and when the steel pipe 1 'is used as the core material 1, the steel pipe itself is used as an injection pipe for the grout material g. the holes 2 ₁ is provided.

3 is a full thread PC steel rod Gevin desturb that is provided to cut off the steel pipe 1 'that becomes the bearing plate and the core material 1. The connection between the Gevin desturb and the core material 1 is the case of the steel pipe 1' and Gevin desturb. 2 and 3, a screw-in type is allowed, and a cap 9 which is center-threaded is attached to the surface side end side which is the head of the steel pipe 1 ', and the Gevin Destab 3 is screwed into this screw hole. It is fixed with a nut 6 '. Reference numeral 4 denotes a self-supporting type pressure bearing plate that is attached to the distal end portion of the length of the Gevin desturb 3.
The above-mentioned Gevin Destave 3 is installed to cut the top plate-type bearing plate 4 and the steel pipe 1 '. The “edge cutting” means that when the force is applied to the bearing plate 4 from the ground part. This means that a buffer area is provided between the two 4 1 'in order to prevent the grout g around the material 1 from being broken.

  Next, when the core material 1 is the deformed bolt 1 "and the Gevin desturb 3, the coupler joint 12 is used for connection (FIG. 5).

Reference numeral 5 denotes a head plate to be attached to the top plate 4 from the ground surface G, 6 is a nut attached to the tip of the Gevin desturb 3 and fixed to the head plate 5, 7 is an oil cap, and 8 is in the oil cap. It is a rust preventive. The length of the Gebin desturb 3 connected to the tip of the pile length L ′ in the moving layer is at least the thickness of the head plate 5 and the nut 6 of the upper structure L ″ of the pile length in the moving layer. The height is set to the added dimension.
In Type A, the clearance around the core material in the section of the fixing length L and the pile length L ′ in the moving bed is closed with cement milk, and the core material 1 and grout g, and the grout g and the hole 10 wall are adhered. Realize.

  Next, in type B, the core material 1 becomes a deformed bar 1 ″ and is connected via a coupler-type joint 12. The head structure is such that the deformed bar 1 ″ which becomes the core 1 becomes the top plate 4 Directly linked. Further, an injection pipe 11 is provided along the deformed bolt, and the grout g is filled up to the back surface of the bearing plate 4 by using the injection pipe 11.

  FIG. 4 shows a specific design flow. In designing the present invention, it is necessary to sufficiently consider ground conditions, groundwater conditions, surrounding structures, and the like so as to be sufficiently stable and not cause harmful deformation.

  First, in assuming the collapse form and slip, the collapse form and slip surface are assumed based on the ground conditions, etc., and the stability is examined by the limit balance method considering the reinforcement effect of the reinforcing material accordingly. . The slope stability calculation is performed by the stability calculation according to the assumed slip, such as the arc slip method, the linear slip method, the non-arc slip method, and the composite slip method, and the slope safety factor is examined.

  Moreover, this invention presupposes integration of a reinforcing material and the ground. Therefore, it is necessary to pay attention to the following points so that integration will occur as expected and the expected reinforcing force will be exhibited. First, the viscous ground is less likely to cause arch action and it is difficult to expect integration of the ground and the reinforcing material. Since the integration effect is strongly exerted in the vicinity of the depth 3/4 below the pile length L ′ in the moving layer, the degree of viscosity of the moving layer ground at the depth is confirmed. In addition, when the deformation restraining effect of the reinforcing material acts on the slope due to the integration, the slope does not break inside the reinforcement region. Therefore, in the present invention, it is not necessary to examine internal stability such as hollowing out.

  Furthermore, the required deterrence is calculated from the balance on the slip surface of the design section, and the planned safety factor must be satisfied. The design cross-sectional load is determined by multiplying the required deterrent by the load factor.

Next, the type (A, B) and core material are selected in consideration of the stability of the current slope, the thickness of the moving layer, and the required deterrence. A type (mainly bending shear) is considered for slips with a thick moving layer, and B type (mainly tensile) is considered for slips that are not.
“Table 1” is a table showing features and types of the present invention.

In addition, as a control condition for integration, the combination of reinforcing material interval and bearing plate is studied.
(1) Stiffener spacing B, stiffener angle θ
A type (mainly bending shear)
-Reinforcement space | interval B shall be the range of 2.0-4.0m.
-Reinforcement material angle [theta] = 0 to 30 [deg.].
B type (mainly tension)
-It is set as the range of the reinforcement material space | interval B = 1.0-3.0m.
・ In order to exert tensile reinforcement, the reinforcement angle θ is basically 30 ° ~ 45 °.
(2) Pressure plate
A type (mainly bending shear)
・ In the case of a top type support plate, the support plate size is 1.0 m.
・ For bearing plates other than the top-of-the-game type, the bearing plate size is 1.5 m.
B type (mainly tension)
・ Based on a bearing plate size of 1.0m.
(3) Arrangement • Staggered arrangement. Considering design reinforcement and workability, select a layout with excellent efficiency from rectangular layout and square layout.

  Set the penetration length to satisfy the design section load.

Reinforcement force occurs only after deformation of the natural ground, and the value of the reinforcing force changes due to deformation of the natural ground and interaction with the reinforcing material. In the present invention, based on the analysis in consideration of natural ground deformation amount, to evaluate the reinforcement force pulling the design maximum pull-out resistance force T _max, to evaluate the shear reinforcement bending force by the maximum deflection reinforcing force .SIGMA.R _max design. After that, the design strength R _ud is calculated, compared with the design cross-sectional load R _rd, and the safety is checked against the ultimate limit state of the reinforcement.

The displacement y _Smax corresponding to the design strength is defined as the design deformation, and the assumed maximum deformation of the natural ground. During and after construction, the natural ground deformation is required to be within the design deformation y _Smax .

Ri by the present invention, method of promoting stabilization of loose slope which are created in not belonging landslide end the scope of conventional landslide control method and reinforced earthwork method, and also to small and medium-sized landslide, the deformation As a landslide countermeasure method with a high cost reduction effect due to the introduction of the support mechanism in consideration, a new option for the method has arisen.

These are the application determination flow of this invention. These are the structural drawings (GCP-A type) based on this invention which used the steel pipe for the core material. These are expanded sectional views which show the connection state of a steel pipe head, the lower end part of a Gevin desturb, and a head. FIG. 3 is an enlarged sectional view showing the tip of FIG. 2. These are structural drawings (B type) using a deformed steel bar as the core material. These are the flow of the design procedure of this invention.

1. Core material (steel pipe 1 'or deformed steel bar 1 ")
2 …… Head cap with injection hole 3 …… Gevin de star 4 …… Self-supporting pressure plate 5 …… Head plate 6 ・ 6 '…… Nut 7 …… Oil cap 8 …… Rust prevention material 9 …… Connection cap 10 ... Drilling hole 11 ... Injection pipe 12 ... Coupler type joint

Claims (1)

By grouting the clearance around the large-diameter core material, pre-stress is applied to the core material head, along with the effect of the tension reinforcement that is manifested by the section of the fixing length and the self-supporting pressure plate structure of the core material. The large-diameter core material is deflected greatly when sliding on the landslide by restraining it with a topless support plate without loading, and the moving layer generated in the ground during this deflection process is arranged in a zigzag arrangement or a square zigzag arrangement. For the head, which is designed to share the deformation resistance and the bending strength of the core as a flexural reinforcement effect, as well as the share of the tensile reinforcement effect and the flexural reinforcement effect at the maximum allowable deformation. A slanted group pile construction method that allows deformation of pile bodies using a large-diameter core material having a bearing plate structure.