JP6352120B2 - Ground reinforcement method using perforated steel pipe with blades - Google Patents

Description

  The present invention relates to a ground reinforcement method using a perforated steel pipe with spiral blades having a drainage function.

  Due to topographical factors, groundwater is supplied into the ground, which increases the pore water pressure and reduces the effective stress between soil particles, resulting in many cases in which the slope surface collapses during heavy rains or earthquakes. .

  Conventionally, measures have been taken to lower the water level in the embankment with drainage pipes using vinyl chloride pipes and the like. In addition, when stability is not satisfied only by lowering the water level, there are cases where deterrence measures using steel pipes or ground anchors are implemented as necessary.

For example, in Patent Document 1, a cylindrical shape is formed, a tip opening is closed by a closing plate, a digging blade is fixed to the closing plate, and one or a plurality of spiral blades are provided on the outer periphery near the tip. A plurality of through holes are formed on the peripheral wall, and the steel pipe anchor body is formed with a male screw on the outer periphery near the head, and has a mesh smaller than the hole diameter of the through hole of the anchor body, A mesh-like cylinder inserted into the interior space of the anchor body, and a through-hole through which the head of the anchor body is inserted in the center, and a nut to be screwed into the male screw of the anchor body is positioned on the upper surface of the through-hole. There is disclosed an inclined ground stabilizer comprising a supported bearing plate and a cap that detachably closes the head opening end of the anchor body.
In this inclined ground stabilizer, a drilling drill is connected to the head of the anchor body and rotated, and the anchor body is screwed into the ground by a forward force acting on the spiral blade. As the screwing direction of the anchor body, in addition to the vertical direction and the obliquely downward direction, it is shown that the anchor body is screwed in a substantially horizontal direction when the drainage function by the through holes is important.

  In Patent Document 2, a pile main body made of a steel pipe, a spiral blade provided spirally on the tip or peripheral surface of the pile main body, provided on the peripheral surface of the pile main body, and in contact with the ground surface or A through-hole that is disposed in the ground and has a pressure-bearing portion that generates a compressive force on the ground between the spiral blades and allows water from the ground to pass through the inside of the pile body. A landslide prevention pile provided with is disclosed.

  In Patent Document 3, a hollow steel pipe, a spiral blade formed in a spiral shape on the outer circumference of the steel pipe continuously from one end side to the other end side of the steel pipe, and one end side of the steel pipe, A first cutout portion in which a part of the entire circumference of the steel pipe is cut out along the spiral blade, and a circumference of the other part of the whole circumference of the steel pipe other than the circumference of the part is the first. The steel pipe provided with the 2nd notch part notched by connecting the start end part and termination | terminus part of this notch part is disclosed.

JP 2006-226051 A JP 2012-2012 A JP 2012-136823 A

The slope ground stabilizer disclosed in Patent Document 1 described above discharges ground water from the ground through a plurality of through holes formed in the peripheral wall of the steel anchor body, and the anchor body is grounded by the spiral wing at the tip. In addition, the ground is supported by the spiral blade and the bearing plate, so that the inclined ground is supported. However, in this construction method using an inclined ground stabilizer, a restraining effect can be obtained by tightening the pressure bearing plate at the base end of the anchor body and the spiral wing at the distal end penetrating the support ground. It is necessary to penetrate, but the method is not disclosed. If you try to penetrate a steel pipe with a spiral blade with a tip bit attached to it, it will work well in clay layers and sandy soil layers (which will not be a supporting ground), but in most embankments, there will be a mix of gravel. In addition, since the ground is somewhat solid (standard penetration test value of about 10 or more), it is difficult to penetrate horizontally or slightly upward.
There is also a method to fix the slit at the tip of the steel pipe for wedge tightening by hitting the proximal end with a hammer etc. without using a spiral blade, but if the steel pipe is short, it can be expected to have some effect, but it is long If it is a case (about 10 m or more), it is often impossible to expect the effect due to the resistance of the pile peripheral surface friction (it cannot be sufficiently expanded) by hitting with human power.
Further, when there is no bearing plate at the base end of the anchor body, the restraining effect is lost, and the resistance force of the anchor to the displacement of the ground is only the frictional force of the anchor peripheral surface, and the effect of the spiral blade at the tip is not exhibited.

  Similarly to Patent Document 1, the landslide prevention pile disclosed in the above-mentioned Patent Document 2 has a structure in which a spiral blade is provided at the distal end of the pile body, a supporting portion is provided at the proximal end, and a through hole is provided therebetween. Therefore, there is a problem similar to that of Patent Document 1.

  The above-mentioned Patent Document 3 discloses a steel pipe provided with spiral blades continuously from one end side to the other end side of a hollow steel pipe, and in order to ensure penetration into the ground and strength, along the spiral blades. However, it has no function of discharging groundwater in the ground.

  Furthermore, the slope stabilization method using the anchor body or the steel pipe disclosed in the above-mentioned Patent Documents 1 to 3 is to provide a through hole for draining water, to provide a spiral blade on the peripheral wall, and to be horizontal to the ground. Although the general technique of driving in is disclosed, there are differences in the ground conditions such as soil quality, strength, moisture content, etc., so in actual construction, the diameter and density of the through holes, the spiral blades The installation length, height, pitch, etc. must be designed to suit the ground conditions.

  However, although the general concept of the construction method is shown in the above-mentioned patent document, a specific design method according to the ground conditions necessary for actual construction, for example, the diameter, length, and driving of the steel pipe The method for determining construction conditions such as spacing, driving angle, through-hole diameter and density is not disclosed, and in most grounds, gravel is mixed and the ground is somewhat solid (standard penetration test value of about 10 or more). Therefore, it is difficult to penetrate horizontally or slightly upward, but a method for reliably penetrating even in such ground is not disclosed.

  The present invention determines the construction conditions of a perforated steel pipe having a drainage function and a ground restraint function at the same time, and adapts the determined perforated steel pipe to viscous soil, sandy soil, gravel mixed material. The purpose of the construction is to make sure that even artificial ground or natural ground that has been constructed with any kind of soil such as ground, composites of them, etc. It is intended to improve surface stability and reduce construction costs.

In order to solve the above problems, the present invention is characterized by the following configuration.
<1> A ground reinforcement method using a perforated steel pipe with a blade provided with a spiral blade on the outer periphery of a steel pipe body and further provided with a drain hole on the outer periphery of the tube body,
A ground constant setting step for setting ground constants such as unit volume weight of the ground, shear resistance force, shear resistance angle, etc. for the ground to be constructed,
Safety factor setting step to set the current safety factor and the planned safety factor,
Necessary deterrence calculation step for calculating necessary detergency from the planned safety factor in each state at the time of earthquake and earthquake,
The perforated steel pipe arrangement calculating step for calculating the installation length of the bladed perforated steel pipe, the installation density, and
A necessary tensile force per one perforated steel pipe with blades, and a tensile force calculating step for calculating an allowable tensile force,
The ground using the bladed perforated steel pipe, wherein the bladed perforated steel pipe having the installation length obtained in the bladed perforated steel pipe arrangement calculation step is screwed into the ground at the installation density. Reinforcement method.

<2>
By placing the bladed perforated steel pipe into the ground, the water in the ground is guided into the bladed perforated steel pipe by a drain hole provided in the outer periphery of the pipe body, and is installed horizontally or slightly upward. In addition, the inside of the perforated steel pipe with blades is allowed to flow down to the outside of the ground, and the adhesion effect based on the peripheral frictional resistance between the perforated steel pipe with blades and the ground is used for the collapse or deformation of the ground. The ground reinforcing method using the bladed perforated steel pipe according to <1>, characterized by increasing resistance.

<3>
In order to drive the perforated steel pipe with blades horizontally or slightly upward to the ground, a rotational force is applied to the perforated steel pipe with blades and driven using the screw action of a spiral blade, <2> Ground reinforcement method using a perforated steel pipe with a blade according to 2>.

<4>
The ground reinforcement construction method using a perforated steel pipe with a blade according to <3>, wherein the perforated steel pipe with a blade is driven by using a pushing force in addition to the screw action of a spiral blade.

<5>
The ground reinforcement construction method using the bladed perforated steel pipe according to <4>, wherein the bladed perforated steel pipe is driven by using vibration in addition to the screw action and pushing force of the spiral blade.

<6>
Drilling with a diameter slightly smaller than the outer diameter of the spiral blade of the bladed perforated steel pipe, and then applying rotational force to the bladed perforated steel pipe along the drilled hole, screw action of the spiral blade, pushing force, vibration The ground reinforcement construction method using a perforated steel pipe with a blade according to <1>, which is driven by using any one or more of the above.

<7>
Drilling with a slightly smaller diameter or the same diameter or slightly larger diameter than the outer diameter of the spiral blade of the bladed perforated steel pipe, after filling the hole with a filler, along the hole filled and drilled, <1> The blade according to <1>, wherein the bladed perforated steel pipe is driven by applying a rotational force to the bladed perforated steel pipe and using one or both of the screw action, pushing force, and vibration of the spiral blade. Ground reinforcement method using perforated steel pipes with holes.

<8>
Both the perforated steel pipe with blades is driven by applying a rotational force and an indentation force, and the bit or striking hammer attached to the tip of the lot is subjected to a rotational force and an indentation force or an impact force for drilling. The ground reinforcement method using the perforated steel pipe according to <1>, wherein the perforated steel pipe with blades is driven using a driving machine capable of performing the above.

<9>
The bladed perforated steel pipe according to <8>, wherein the bladed perforated steel pipe is driven using a driving machine capable of using both vibration for driving and drilling. The ground reinforcement method used.

<10>
A ground reinforcement construction method using a perforated steel pipe with blades according to <1>, wherein a pull-out test is performed and the adhesion strength related to the perforated steel pipe circumference is set according to the ground classification and the ground condition.

<11>
A perforated steel pipe with a certain length of blade is screwed into the ground in advance and left for a certain period of time, and then a pull-out test is performed using a hydraulic jack to set the ultimate peripheral friction resistance. 2> Ground reinforcement method using a perforated steel pipe with a blade according to 2>.

<12>
The filler is one selected from materials having good water permeability, such as sand, sandy soil, gravel, crushed stone, and blast furnace slag, which are slightly smaller than the hole diameter, and packed in a biodegradable plastic bag. The ground reinforcement method using a perforated steel pipe with a blade according to <7>, wherein two or more are used to fill the entire length of the hole.

The present invention has the following effects.
(1) The ground water level and saturation can be lowered by installing a perforated steel pipe with a blade having a drainage function.
(2) The effect of restraint (adhesion) with the ground is improved by installing spiral blades on the outer periphery of the perforated steel pipe.
(3) The ground restraint function and the drainage function can be further improved by filling a filler (sand) between the ground and the bladed perforated steel pipe.
(4) By conducting a pull-out test and setting the adhesion strength related to the perforated steel pipe circumference according to the ground classification and ground condition, it is possible to construct a perforated steel pipe with blades suitable for the ground to be installed.
(5) Not only the general method of installation by the rotational force and the screw action of the spiral blades, but also the method of installation by using indentation force and vibration (vibro), or the method of installation after previously drilling the holes to be installed In addition, by any one of the methods of installing after filling a hole that has been drilled in advance, any soil soil of any soil can be reliably constructed.
(6) Although the above-mentioned Patent Document 2 aims to stabilize the ground by generating a compressive force on the ground, in the present invention, the entire surface is bonded by the peripheral frictional resistance generated between the ground and the steel pipe. The deterrent effect can be expected.
(7) Moreover, in patent document 2, although it is supposed that the sand pipe | tube previously filled with sand is penetrated, and it is supposed that a steel pipe is rotationally penetrate | introduced after that, in this invention, a shape a little smaller than the outer diameter of a perforated steel pipe with a spiral feather or This is a method of drilling with the same diameter or a slightly larger diameter, then filling the hole with a filler, and then applying rotational force to the perforated steel pipe with spiral blades, and screwing it in. There are advantages.

The perforated steel pipe which concerns on embodiment of this invention is shown, (a) is a side view, (b) is front sectional drawing. The construction example of the perforated steel pipe with a blade | wing which concerns on embodiment of this invention is shown, (a) is a side view, (b) is a front view. It is a side view showing the state where two perforated steel pipes with a blade concerning an embodiment of the invention are connected in the longitudinal direction. It is a side view which shows the state which connected two perforated steel pipes with a blade | wing concerning embodiment of this invention in the longitudinal direction, and attached the cone for excavation to the front-end | tip. It is a design flow figure of the ground reinforcement construction method using the perforated steel pipe with a blade concerning an embodiment of the invention. It is a principal part side view of the perforated steel pipe with a blade | wing which shows the example of a drain hole. It is a graph which shows the relationship between N value and ultimate circumference resistance.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
As shown in FIG. 1, a perforated steel pipe with blades according to an embodiment of the present invention (hereinafter sometimes simply referred to as “perforated steel pipe”) 10 is a spiral blade 2 on the outer periphery of a pipe body 1 made of steel pipe. Further, the drain hole 3 is provided on the outer periphery of the pipe body 1. The spiral blade 2 is formed on the side of the tube main body 1 in the propulsion direction so as to be close to the end of the tube so that when it is screwed in while rotating to the ground, a propulsive force into the ground can be obtained. The front side of the tube body 1 forms a portion where the spiral blade 2 is not provided for mounting a steel tube rotating metal fitting for engaging with a chuck of a screwing machine (not shown) of the perforated steel tube 10. . The diameter of the pipe body 1, the height and pitch of the spiral blades 2, and the diameter and number of the drain holes 3 are set according to the calculation formula described later.

  FIG. 2 shows a state in which the perforated steel pipe 10 of the present invention is screwed into the slope surface. The perforated steel pipe 10 is provided on the slope surface with an inclination so that the base end side is lowered in the horizontal direction, preferably the base end side. By screwing, groundwater and moisture in the ground flow into the inside of the pipe body 1 through the drainage holes 3 and are drained from the outside of the slope surface. The spiral blade 2 provided on the outer periphery of the tube body 1 exerts a propulsive force into the ground when screwed into the slope surface, and after the screwing, the effect of restraining (adhering) to the ground is the spiral blade 2. Compared with the case where no is provided, it is remarkably increased.

  FIG. 3 is intended to secure a necessary length when a plurality of perforated steel pipes 10 having a predetermined length are connected in the longitudinal direction and screwed into the ground. The perforated steel pipe 10 is connected by attaching the insertion bolt type joint 12 to one pipe end and inserting the other pipe end and bolting it through a bolt hole that has been opened in advance. FIG. 4 shows a state after connection by the insertion bolt type joint 12. In the figure, 11 is a steel tube rotating metal fitting for engaging with a chuck of a screwing machine (not shown) of the perforated steel pipe 10, and 13 is a ground propulsion member that is welded and fixed to the tip of the perforated steel pipe 10. The cone. In the present embodiment, the tip of the steel pipe is shaped like a cone, the length per pipe is 1 to 2 m, and a bolt-type joint structure is used to connect them to improve workability.

In addition to the above-described insertion bolt type joints, there are screw types.
Steel pipe rotating metal fittings for engaging the chuck of the driving machine have different shapes (not shown) for each joint.

  When the perforated steel pipe 10 is screwed into the ground, the steel pipe rotating metal fitting 11 welded to the base end portion is engaged with the chuck of the screwing machine and rotated to be pushed into the ground. When screwed, a steel pipe rotating metal fitting 11 welded to the base end portion of the perforated steel pipe 10 to which the next perforated steel pipe 10 is connected by an insertion bolt type joint 12 and added is inserted into the screwing machine. The required length is screwed by repeatedly engaging and rotating the chuck and screwing it into the ground.

  The perforated steel pipe is driven by applying a rotational force to the perforated steel pipe by a driving machine and utilizing the screw action of the spiral blade.

  The perforated steel pipe is driven by the above method. However, in the case where gravels are mixed or hard ground (standard penetration test value of about 10 or more), it is difficult to drive only by the rotational force and the screw action of the spiral blade. In such a case, a perforating steel pipe is driven to a predetermined length by applying a pushing force to the rotational force to assist the driving.

  If it is difficult to drive a perforated steel pipe using the above-mentioned rotational force and the screw action of the spiral blade, it is difficult to drive the perforated steel pipe. The perforated steel pipe is driven to a predetermined length by assisting the driving.

  If the perforated steel pipe of the specified length cannot be driven even with the above-mentioned vibration method, drill a hole with a diameter slightly smaller than the outer diameter of the blade of the perforated steel pipe before screwing in the perforated steel pipe. Then, using the hole, it is driven so that part or all of the blades of the perforated steel pipe bite into the original ground. The driving is performed by applying a rotational force to the perforated steel pipe with a driving machine, utilizing the screw effect of the spiral blade, and in some cases using a pressing force and vibration (vibro) together.

  The above-mentioned pre-drilling is done by using a driving machine to blow and rotate the hollow lot with a drilling bit or hammer to the tip by air pressure and hydraulic pressure to cut the ground at the tip. With the compressed air blown in, the shaved soil is discharged to the outside and a predetermined required length is installed.

A rotating force is applied to the perforated steel pipe and the screw action of the spiral blade is used. The adhesion strength (peripheral surface frictional resistance) with the original ground of the perforated steel pipe installed using the hole is reduced to about half.
If you want to increase the adhesion strength (peripheral frictional resistance) per pile by design, drill a hole in advance using a casing, fill the hole with a filler, then pull out only the casing and fill with the filler. If the perforated steel pipe is screwed into the hole, the adhesion strength (circumferential frictional resistance) between the filler and the perforated steel pipe is obtained, so that the adhesion strength (peripheral frictional resistance) can be improved.

The filler is packed in a full length of the hole using a push rod or the like, which is packed in a vinyl bag whose main component is denatured polyvinyl alcohol (PVOH) having a diameter slightly smaller than the hole diameter.
Since this bag is a biodegradable plastic that is decomposed by bacteria in the water and soil, it does not affect the drainage effect from the ground after the perforated steel pipe is installed. Since the dissolution time can be set from several seconds to about 2 years depending on the thickness of the bag and the composition of the components, it is preferable to use the one set to about 1 to 10 days in consideration of the construction time and the water content of the ground.

  As the filler, materials having good water permeability such as sand, sandy soil, gravel, crushed stone, or blast furnace slag can be used. The adhesion strength (circumferential frictional resistance) between the filler and the perforated steel pipe varies depending on the type of filler used and the filling rate of the drilled hole.

  Next, the design of the ground reinforcement method using the perforated steel pipe 10 having the above configuration will be described with reference to FIG.

Step 100: Grasping design and construction conditions In order to rationalize the design and construction of this construction method, the site reconnaissance and drawings are read, and the ground conditions, groundwater conditions and surrounding environment of the target ground are grasped. In order to grasp the ground conditions, the state and characteristics of the ground are examined in a test for determining the physical properties of the target ground, and the strength of the soil is determined in a test for determining the mechanical properties of the target ground.
To understand groundwater conditions, the amount of spring water and the increase or decrease in groundwater level due to rainfall conditions are investigated by monitoring the groundwater level and groundwater level by survey boring.
To understand the surrounding environment, the surrounding land use situation, existing structures and buried objects, approach roads necessary for construction, electric power, noise, vibration, working time, etc. are investigated.

Step 110: Judgment whether application of this method is appropriate Judgment is made based on the scale of ground reinforcement targeted for applicability of this method. If the deterrence required to reinforce the ground is 300 KN / m or if the length of the slip line is more than 30 m, other deterrence methods such as ground anchors and deterrence piles may become economical. is assumed.
If the application is appropriate, proceed to the next. If the application is not appropriate, the design is terminated.

Step 120: Examination of stability analysis method Stability analysis is performed using the limit balance method.
Stability analysis is performed using seismic intensity method.
Stability analysis is performed using the Newmark method.

Step 130: Setting the ground constant The ground constants necessary for the design such as unit volume weight, shear resistance force and shear resistance angle are in principle physical and mechanical tests based on samples taken from the target ground. Shall be determined by However, in the case of targeting general ground, it can be set with reference to Table 1.

Step 140: Setting of safety factor, etc. The current safety factor (F _s ) in the target ground is calculated by the limit balance method based on Step 100 and Step 130. The planned safety factor (F _sp ) for long-term stability is generally Fsp = 1.2 to 1.25 for artificial ground such as embankment, and F _{sp for} natural ground such as cut soil. = 1.2 is targeted, so we quoted them.

ここに、（Ｗ）は分割片の重量、（α）はすべり面の傾斜角である。
地震時における必要抑止力は、Ｆ_sp＝１．０とし、次式から算定する。

ここに、（ｈ）は分割片の重心とすべり円との中心との鉛直距離、（ｒ）はすべり円の半径、（ｋ_h）は設計水平震度である。 Step 150: Calculation of necessary deterrence In calculating the necessary deterrence by this method, in addition to long-term stability, each planned safety factor should be satisfied in the event of abnormal rainfall and earthquake that are subject to short-term stability. Set.
The necessary deterrence (P _r ) at the time of abnormal rain is set to F _sp = 1.05 to 1.1 and is calculated from the following equation.

Here, (W) is the weight of the divided piece, and (α) is the inclination angle of the sliding surface.
The necessary deterrence in the event of an earthquake is _Fsp = 1.0 and is calculated from the following formula.

Here, (h) the vertical distance between the center of a circle and sliding the center of gravity of the divided piece, (r) is the sliding circle radius, (k _h) is a design horizontal seismic.

Steps 160-180
When considering the arrangement of perforated steel pipes, the installation length and the arrangement density (interval) are assumed in advance, and examination is performed so that the most reasonable arrangement is obtained in repeated calculations.
At that time, it is necessary to set the permissible tensile force per one perforated steel pipe, and {the peripheral friction resistance with the ground, the tensile strength of the perforated steel pipe, the welding strength between the spiral blade and the effective steel pipe} The smallest one is adopted.

Step 190: Judgment of whether or not the stability can be secured It is judged whether or not the stability can be secured when the necessary tensile force assumed to act on the perforated steel pipe is equal to or less than the allowable tensile force. If secured, proceed to the next. If not secured, the process returns to step 160.
The necessary deterring force calculated in step 150 is shared by the arrangement density (interval) assumed in step 160, the necessary tensile force per piece that the perforated steel pipe is responsible for is calculated, and the allowable tensile per piece adopted in step 180 is calculated. Make sure you are satisfied.

Step 200: Calculation of the yield seismic intensity The yield horizontal seismic intensity is calculated by the seismic intensity method using the limit balance method.

Step 210: Calculation of ground surface waveform The ground surface waveform to be used for the design is selected with reference to the seismic waveform described in the road bridge specifications / explanation (seismic design).

Step 220: Calculation of residual deformation amount The residual deformation amount of the ground is calculated by the Newmark method using the seismic waveform selected in step 210.

Step 230: Judgment of whether or not the allowable deformation amount is satisfied If the residual deformation amount calculated in Step 210 is less than 100 cm, the allowable deformation amount is satisfied. And review the arrangement density (interval).

  The perforated steel pipe having the installation length determined in step 160 is screwed into the ground with the installation density also determined in step 160.

In order to reduce the groundwater level and saturation of the target ground, a slit-shaped long hole 4 with an opening ratio of 10% is installed on the outer periphery of the pipe body 1 as shown in FIG. . In this example, the outer diameter of the tube main body 1 is 50 mm, the long holes 4 are 6 × 50 mm, and the zigzag is arranged at a pitch of 90 ° in the circumferential direction of the tube main body 1 and 78 mm in the longitudinal direction. An open area ratio of 10% is equivalent to 10 ^-3 to 10 ^-2 m / s in terms of hydraulic conductivity, and in a mixed ground of silt and sand, which is said to have poor hydraulic conductivity when the hydraulic permeability is 10 ^-9 to 10 ^-5 m / s. It greatly contributes to the drainage effect.
Changing the aperture ratio will change the effect of draining groundwater in the ground to the outside of the slope. Therefore, it will be necessary to consider whether to review the arrangement of effective steel pipes.
Drain holes to be opened on the outer periphery of the pipe body 1 are selected by applying the provisions of “Road Civil Engineering-Drainage Guideline” (published by the Japan Road Association) and “Construction of underground drainage facilities-Selection of filter materials”. It is good. In addition to the slit shape, it may be circular.

ここでτ；極限周面摩擦抵抗（ＫＮ/ｍ²）
Ｎ；盛土の平均Ｎ値 Here, the constraint (adhesion) effect of the perforated steel pipe on the ground is quantitatively evaluated by the following pull-out test.
That is, a perforated steel pipe having a certain length (6 m in this example) is screwed into the ground, left for a certain period of time, then excavated around a 1 m long portion of the perforated steel pipe, and the remaining 5 m long A perforated steel pipe is subjected to a pull-out test using a hydraulic jack, and the ultimate peripheral friction resistance is set.
The ultimate peripheral frictional resistance is an N value that is frequently used as an indicator of the strength of the ground (a 63.5 kg weight hammer is dropped from a height of 75 cm and a cylindrical sampler. The number of drops required for driving 30 cm into the soil and the number of drops required for driving 30 cm) was obtained as shown in FIG.

Where τ: Ultimate circumferential frictional resistance (KN / m ² )
N: Average N value of the embankment

  The present invention provides a technique capable of determining the construction conditions of a perforated steel pipe having a drainage function and a ground restraint function at the same time, and is suitably used for various ground reinforcement works. be able to.

DESCRIPTION OF SYMBOLS 1 Pipe body 2 Spiral blade 3 Drain hole 4 Long hole 10 Perforated steel pipe 11 Steel pipe rotation metal fitting 12 Insertion bolt type joint 13 Cone for ground propulsion

Claims (11)

A perforated steel pipe with a blade provided with a spiral blade on the outer periphery of a steel tube main body, and further provided with a drain hole for discharging water in the ground on the outer periphery of the tube main body , the spiral blade is the tube main body Over the entire length of the tube body, the tube body is formed on the propulsion direction side up to the end of the tube so that when it is screwed in while rotating to the ground, a propulsion force into the ground can be obtained. On the front side of the blade is a perforated steel pipe with a blade forming a portion not provided with a spiral blade for mounting a steel pipe rotating metal fitting for fitting a steel pipe rotating metal fitting for engaging with a chuck of a screwing machine. By using the perforated steel pipe with blades into the ground, the water in the ground is guided into the perforated steel pipe with blades horizontally or slightly upward by the drain holes provided on the outer periphery of the pipe body. It flows naturally through the installed perforated steel pipe with blades. Te drained to ground out, by utilizing the adhering effect based on the peripheral surface frictional resistance between the bladed perforated steel tube and the ground without providing a bearing capacity Release the proximal end, increasing the resistance to collapse and Deformation of the ground A ground reinforcement method,
A ground constant setting step for setting ground constants such as unit volume weight of the ground, shear resistance force, shear resistance angle, etc. for the ground to be constructed,
Safety factor setting step to set the current safety factor and the planned safety factor,
Necessary deterrence calculation step for calculating necessary detergency from the planned safety factor in each state at the time of earthquake and earthquake,
The perforated steel pipe arrangement calculating step for calculating the installation length of the bladed perforated steel pipe, the installation density, and
A necessary tensile force per one perforated steel pipe with blades, and a tensile force calculating step for calculating an allowable tensile force,
A ground reinforcement method using a bladed perforated steel pipe, characterized in that a bladed perforated steel pipe having the installation length obtained in the bladed perforated steel pipe arrangement calculation step is driven into the ground at the installation density. . In order to drive the bladed perforated steel pipe horizontally or slightly upward into the ground, a rotational force is applied to the bladed perforated steel pipe and driven using the screw action of a spiral blade. Item 1. Ground reinforcement method using the perforated steel pipe with a blade according to Item 1 . 3. The ground reinforcement method using a bladed perforated steel pipe according to claim 2 , wherein the bladed perforated steel pipe is driven using a pushing force in addition to the screw action of the spiral blade. The ground reinforcing method using the bladed perforated steel pipe according to claim 3 , wherein the bladed perforated steel pipe is driven by using vibration in addition to the screw action and pushing force of the spiral blade.   Drilling with a diameter slightly smaller than the outer diameter of the spiral blade of the bladed perforated steel pipe, and then applying rotational force to the bladed perforated steel pipe along the drilled hole, screw action of the spiral blade, pushing force, vibration A ground reinforcement method using a bladed perforated steel pipe according to claim 1, wherein the method is driven by using any one or two or more of them together.   Drilling with a slightly smaller diameter or the same diameter or slightly larger diameter than the outer diameter of the spiral blade of the bladed perforated steel pipe, after filling the hole with a filler, along the hole filled and drilled, 2. The blade according to claim 1, wherein the bladed perforated steel pipe is driven by applying a rotational force to the bladed perforated steel pipe and using one or a combination of screw action, pushing force, and vibration of the spiral blade. Ground reinforcement method using perforated steel pipes with holes.   Both the perforated steel pipe with blades is driven by applying a rotational force and an indentation force, and the bit or striking hammer attached to the tip of the lot is subjected to a rotational force and an indentation force or an impact force for drilling. 2. The ground reinforcement method using a perforated steel pipe according to claim 1, wherein the perforated steel pipe with blades is driven using a driving machine capable of performing the following. 8. The bladed perforated steel pipe according to claim 7 , wherein the bladed perforated steel pipe is driven using a driving machine capable of using both vibration for driving and drilling. The ground reinforcement method used.   The ground reinforcement construction method using a bladed perforated steel pipe according to claim 1, wherein a pulling test is performed to set the adhesion strength related to the perforated steel pipe perimeter according to the ground classification and the ground condition. A perforated steel pipe with a certain length of blade is screwed into the ground in advance and left for a certain period of time, then a pull-out test is performed using a hydraulic jack, and the ultimate peripheral friction resistance is set. Item 1. Ground reinforcement method using the perforated steel pipe with a blade according to Item 1 . The filler is one selected from materials having good water permeability, such as sand, sandy soil, gravel, crushed stone, and blast furnace slag, which are slightly smaller than the hole diameter, and packed in a biodegradable plastic bag. The ground reinforcement construction method using a perforated steel pipe with blades according to claim 6 , wherein two or more are used to fill the entire length of the hole.

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