KR101118518B1 - Construction method for pressurized grouting compression ground anchor - Google Patents

Abstract

The present invention relates to a construction method of a pressure-type compression ground anchor, comprising: forming a drilling hole using a casing and a mill at a target ground to be reinforced; Filling a primary grout into a casing inserted into the drilling hole; Inserting a ground anchor comprising a steel wire and a load bearing body into the drilling hole; Drawing the casing to the position of the lower body; And a pressure grouting step of installing a pressure cap at the rear end of the casing and injecting a grout agent at an injection pressure and an injection time suitable for ground conditions through an injection tube connected to the pressure cap, wherein the grout agent is used in the pressure grouting step. The injection pressure is characterized in that it is monitored through a pressure gauge, through which the grouting pressure is reliably transmitted to the fixing station without pressure loss during pressurized grouting, thereby suppressing the occurrence of cavities and eliminating the poor filling of the grouting, thereby improving grouting quality. In addition, the ultimate pullout resistance can be increased by the expansion of the pore size and the residual stress effect.

Description

Construction of Pressurized Compression Ground Anchors {CONSTRUCTION METHOD FOR PRESSURIZED GROUTING COMPRESSION GROUND ANCHOR}

The present invention relates to a method for constructing a pressurized compressed ground anchor, and more particularly, by performing quantitative pressure grouting, the grouting pressure is reliably transmitted to the fixing station without pressure loss, thereby suppressing the occurrence of cavities and poor filling of grouting. The present invention relates to a construction method of a pressurized compression ground anchor that can improve the quality of grouting by solving the problem.

Ground anchors (ground anchors) are used as an effective method for applying a high tension force to the steel of high strength in order to fix the target structure on the ground to apply the restraining force and pre-stress in the transverse or vertical direction to the structure. In addition, there are many other methods such as strut, raker, and soil nailing as the supporting structure of black film, but considering the ease of construction associated with securing excavation internal working space and subsequent structure process Anchor is the most preferred method.

Ground anchors can be classified according to the type of ground to be settled, the installation direction, grout pressure, the shape of the anchor body, and in particular divided into tension type anchor and compression type anchor based on the way of applying the tension force of the anchor.

In case of installation of ground anchors adjacent to existing buildings or facilities in urban excavation work, there are many cases where anchors need to be installed by violating site boundaries. In this case, the removed ground anchors should be considered from the planning stage since the anchors must be removed after the body structure is completed. Removable ground anchors are mainly developed as compressed ground anchors because of the need to remove PC strands.

This compressed ground anchor has a structure in which fish strands are completely covered to facilitate removal, and one or more load bearing bodies are fixed to the fish strand fixing unit. Appears differently. However, in Korea, a design method or construction method corresponding to the drawing characteristics of the compressed ground anchor is not known. In particular, in the case of the conventional gravity-type (non-pressure) grouting anchor method, when the anchoring ground is soil ground or soft ground, the frictional resistance between the anchor and the ground is small, it is often not possible to secure a predetermined design anchor force. Therefore, in this case, since the anchor interval is narrowed during construction or the free field of the anchor is extended to settle in a relatively hard ground or rock, the increase in the total cost of construction due to the increase in the depth of drilling, the length of the anchor body, and the increase in the number of anchors is significant. to be.

For this reason, the pressurized grouting method has been developed as a method to secure greater ultimate pulling force in domestic and overseas soil and soft ground. However, until now, most of the construction such as injection pressure, injection time, injection volume, etc. As it depends only on the experience of skilled workers, the evaluation of construction methods such as pressure, time, and injection amount according to the condition and condition of the ground cannot be made quantitatively.

In the case of pressure-type pressure grouting, if the proper injection pressure, injection time, and injection range cannot be applied according to the ground conditions, it may cause problems such as hydraulic fracturing, which may impair the stability of the structure. There was a problem that it is difficult to secure stability due to additional reinforcement cases.

Therefore, the problem to be solved by the present invention is that the pressure is surely transmitted to the anchorage during pressure grouting to increase the ultimate pullout resistance of the ground anchor and pressurized compression type that can quantify the injection pressure and injection time to increase the economics and stability of construction It is to provide a construction method of ground anchors.

In order to achieve the above object,

Forming a drilling hole using a casing and a fabric mill in the target ground to be reinforced;

Filling a primary grout into a casing inserted into the drilling hole;

Inserting a ground anchor comprising a steel wire and a load bearing body into the drilling hole;

Drawing the casing to the position of the lower body; And

And a pressure grouting step of installing a pressure cap at the rear end of the casing and injecting a grout agent at an injection pressure and an injection time suitable for ground conditions through an injection tube connected to the pressure cap.

The injection pressure of the grout agent in the pressure grouting step provides a construction method of the pressure-type compressed ground anchors, characterized in that the pressure gauge is monitored.

Here, the injection pressure of the grout agent in the pressure grouting step is preferably 100kPa to 500kPa.

In addition, the minimum injection time of the grout agent in the pressure grouting step is 30 seconds to 270 seconds when the ground water permeability coefficient is 5.0 × 10 ⁻³ cm / sec to 5.0 × 10 ⁻⁵ cm / sec. It is desirable to decrease the minimum injection time as it decreases.

In addition, the inside of the pressing cap is provided with a packing in contact with the casing, it is preferable to seal the pressing cap and the casing by pressing the upper pressure cap.

In the forming of the perforation hole, it is preferable to drill the target ground using a double casing composed of inner and outer casings, and to remove the inner casing so that the outer casing and the perforated ground are in close contact with each other.

In addition, when the ground anchor includes a plurality of inner bodies, the drawing of the casing and the pressing grouting step may be performed step by step for the plurality of inner bodies.

In addition, after the pressure grouting step, it may further comprise the step of tensioning and fixing the ground anchor by tensioning the steel wire.

In addition, when the ground anchor includes a plurality of inner bodies, it is preferable that the ground anchors are sequentially stretched from the steel wire surrounding the inner bodies positioned at the tip of the ground anchors.

In addition, after the tension and fixing step of the ground anchors, the ultimate pull resistance (P _u ) of the ground anchors can be calculated by the following equation.

(Wherein, D is the perforation diameter, L Chapter fixation of the ground anchor length, τ _u is a main surface frictional resistance per unit area of the ground anchor, Ge refers to group efficiency due to close-up the construction of the ground anchor, and the τ _u and the Ge Is defined by

Where N _52.5 is the standard penetration test value,

Here, a = distance of ground anchors, R = anchor length x tan β, β = 2/3 x φ (soil), 45 ° (rock), φ = internal friction angle).

According to the present invention, the pressure is not lost during pressure grouting, and the grouting pressure is reliably transmitted to the fixing station, whereby the generation of the cavity is suppressed, and the poor filling of the grouting can be eliminated to improve the grouting quality. In addition, by performing pressure grouting step by step for each load bearing body, it is possible to expect the effect of the expansion of the drilling diameter, the increase in the roughness of the ground anchor, thereby increasing the ultimate pull resistance compared to the pressureless grouting anchor.

Hereinafter, the present invention will be described in more detail with reference to preferred examples. However, these examples are intended to illustrate the present invention in more detail, it will be apparent to those skilled in the art that the scope of the present invention is not limited thereby.

1 is a structural diagram of a ground anchor according to the present invention. The ground anchor 10 comprises a load bearing body 1 and a steel wire 2, and the steel wire 2 made of a wire 4 and a sheath 3 surrounding the outside thereof is fastened along the load bearing body 1. It is bound by (5), and is extended.

As shown in FIG. 1, the ground anchor 10 may include a plurality of load bearing bodies 1a, 1b, ..., and steel wires 2a, 2b, ... fastened thereto. That is, after installing a plurality of inner body body and the front end of the lower body body to each steel wire, and each fixed body and the steel wire installed at regular intervals to each other fixed to each other, the steel wire can be configured to extend to a certain length. .

As used herein, the term "leading end" means one end in a direction far from the index, ie, in the depth direction of the hole, and vice versa.

2a to 2e is a diagram showing a step-by-step method of construction of the pressurized compression ground anchor according to the present invention. That is, FIG. 2A is a view illustrating a state in which the casing 11 is inserted into the drilling hole after the drilling hole h is formed in the ground using the casing 11 and the drilling device (not shown). Figure 1 is a view showing a state in which the primary grout is filled in the casing inserted into the drilling hole, Figure 2c is a view showing a pressurized compressed ground anchor inserted into the drilling hole, Figure 2d is a housing (1b) Figure 2e is a view showing a state drawn to the position, Figure 2e is a pressure cap 20 attached to the rear end of the casing 11 is installed, and a predetermined time using the injection pipe 23 connected to the pressure cap for a predetermined injection time Figure 2f is a view showing a state of injecting grout agent in the injection pressure of, Figure 2f is a view showing the tension and fixing step of the ground anchor after the pressure cap and the casing is completely removed.

First, the construction method of the pressure-type compression ground anchor according to the present invention forms a drilling hole (h) by using a casing 11 and a drilling device (not shown) in the target ground to reinforce the bearing capacity of the ground. The casing can be adjusted to the depth of the drilling hole by connecting a plurality of casing in the longitudinal direction. Forming the hole (h) may use a double casing (not shown) consisting of the inner and outer casing. That is, it is possible to perforate the ground by attaching a drilling bit of high strength material such as diamond to the inner casing tip and supplying water through the inner casing, and the supplied water is casing through the gap between the inner casing and the outer casing. It can drain from the inside.

After the drilling is completed, the inner casing is removed so that the outer casing is located in the drilled hole. As such, since the drilling method using the double casing can be inserted such that the casing (outer casing) is substantially in close contact with the excavated ground after drilling, there is an advantage that the grouting pressure can be reliably transmitted to the anchorage during pressure grouting.

Next, the primary grout is filled into the casing 11 inserted into the drilling hole. The mixing of the grout is such that the mixing weight ratio of water and cement is 1: 2, and it is preferable that no other admixture including the expanding agent is added. After inserting the hose 12 to the end of the drilling hole, the pressure-free grout is filled into the drilling hole, and at this time, the grout is preferably filled until the grout flows out of the casing 11.

After the primary grout is filled, the ground anchor 10 including the steel wire and the lower body is inserted into the drilling hole. The ground anchor 10 may be connected to a plurality of internal bodies in multiple stages, the total length of the ground anchor is preferably left 1.5 to 2.0m longer than the anchor length. In addition, it is preferable to mark the pair of steel wires that surround the same load-bearing body for convenience in tensioning the steel wire later.

After insertion of the ground anchors 10 into the casing 11 is completed, the casing 11 is pulled out to the position of the lower body 1b. At this time, some of the casing protruding out of the surface can be separated and dismantled.

Thereafter, the pressure cap 20 is installed at the rear end of the casing 11 and pressure grouting is performed at a proper injection pressure for a predetermined injection time. During pressure grouting, the pressure of the grout agent supplied using the pressure gauge 21 can be monitored, and when the proper injection pressure is not reached, the supply pressure of the grout agent supply pump 22 is increased.

The proper injection pressure and injection time of the grout agent may vary depending on the type of the ground, and the injection time may also vary according to the permeability coefficient of the target ground. Specific values for the proper injection pressure and injection time will be described later.

The pressurized cap 20 used in the pressurized grouting step is installed at the rear end of the casing, and an injection pipe 23 for supplying pressurized grout to one side is connected. The pressure cap is preferably made of the same material as the casing, for example metal.

And this injection pipe is provided with the pressure gauge 21 which displays the injection pressure of the pressurized grout injected into a drilling hole. The pressure gauge allows the operator to adjust the pressure of the grouting agent supplied in the pressurized grouting step by adjusting the pressure of the pump when the grouting agent is below the proper injection pressure or exceeds the proper injection pressure.

On the other hand, the pressure gauge 21 may be installed in the pressure cap 20, the mounting position is not limited as long as it can measure the injection pressure of the grout injected into the drilling hole.

In the pressurized grouting operation in the conventional compressed ground anchor, the operator decides the pressure of the grout agent to be injected only depending on the experience. However, in the present invention, the pressure gauge can be used to monitor the pressure of the grout agent injected into the hole. have.

On the other hand, during pressure grouting, in order to prevent pressure loss of the grout material supplied into the drilling hole, the packing 24 may be installed inside the pressure cap. The packing is preferably made of a rubber material, so as to maintain airtightness when the casing 11 and the pressure cap are coupled to each other to prevent the pressure of the grout pressurized from the pressure cap and the casing from dropping. In addition, in order to further enhance the airtight effect between the pressure cap and the casing, it is preferable to press the upper portion of the pressure cap. For example, the pressure grouting step may be performed while pressing the pressure cap upper portion using the insertion rod 25 of the punching device.

On the other hand, when the ground anchor 10 includes a plurality of inner body (1a, 1b, ...), the step of drawing the casing and the pressure grouting step may be divided step by step by a plurality of inner body position.

For example, when a ground anchor including two stages of inner body is inserted, the casing is drawn out stepwise to the lower body 1b, and then the pressure grouting step is repeated. Thereafter, the pressure cap 20 is separated from the casing 11 and the casing is completely removed from the drilling hole.

Figure 2f is a view showing the tension and fixing step of the ground anchor after the pressure cap and the casing is completely removed.

Tensile order of the steel wire is, in order when the load body (1a, 1b, ...) consists of a plurality, the tension in order from the steel wire (2a) surrounding the first lower body (1a) located at the tip of the ground anchor 10 It is desirable to. That is, first, a tensile force is applied to an end portion of the first steel wire 2a wrapping the first load bearing body 1a to tension a predetermined amount, and a tension is applied to an end portion of the second steel wire 2b wrapping the second load body 1b. Tension the ground anchors in this order. Then, the ground anchor construction is completed while fixing the fixed first and second steel wires as described above to the fixing plate 32 provided on the pressure plate 31 disposed on the ground.

Hereinafter, the process of calculating the ultimate pull-out resistance of the pressurized grout-type ground anchor constructed by the injection method, the injection pressure and the construction method according to the present invention will be described based on the experimental results.

Estimation of the minimum injection time for pressurized grouting according to the ground permeability coefficient

The rate at which excess pore water pressure in the grout dissipates as the water exits the surrounding ground due to pressure grouting is determined by the permeability coefficient of the surrounding ground. The average density of the grout (the degree of dissipation of excess pore water pressure) according to the grout consolidation model is determined by the consolidation coefficient, the grout-base permeability coefficient ratio, the drilling radius, and the like. Among them, the grout-ground permeability ratio and the perforation radius are factors that are determined through actual measurements, and thus, the grout consolidation coefficient needs to be corrected. Since the consolidation coefficient of cement grout will change according to the water / cement ratio of cement paste, the process of finding a value consistent with the experimental results was repeated while changing the consolidation coefficient value. As a result, when the mixing weight ratio of water and cement is 1: 2, when the consolidation coefficient is 0.38 ~ 0.45cm2 / sec, the results are consistent with the experimental results, and the modified consolidation coefficient is applied as 0.42cm2 / sec. 3 shows the relationship between the "time-grout average density" according to the permeability coefficient of the ground by using the basic consolidation equation of the grout represented by Equation (1).

Where r is any distance radially from the center of the puncture, and c is the consolidation coefficient of the cement grouting agent.

Although the mixing weight ratio of water / cement in the field is 50%, it is known that the water content decreases as the water flows out to the surrounding ground due to the pressurized grouting and finally decreases to about 30%.

The state of the grout changes greatly with the moisture content of the cement, and the roughness of the solid-liquid can be seen as about 35% of the cement moisture content. Therefore, it is possible to estimate the function ratio at which the stiffness of the grouting agent is expressed as 35% as water is released from the grouting agent due to the pressurized grouting, and when this value is reached, the average density of the grouting agent is calculated as follows. Can be.

Therefore, in general, the time to reach the average density of 75% in the interval of 5 × 10 ^-3 ~ 5 × 10 ^-5 cm / sec, which is the permeability coefficient range of the field weathered soil layer using the graph shown in Figure 3 Same as 1.

Therefore, the minimum injection time of the grout agent during the pressure grouting is preferably 30 seconds to 270 seconds when the ground water permeability coefficient is 5.0 × 10 ⁻³ cm / sec to 5.0 × 10 ⁻⁵ cm / sec. It can be seen that the minimum injection time should be increased as the coefficient decreases.

On the other hand, the proper injection time of the pressurized grouting may be approached from the viewpoint that the pressurized grouting injection should be made at least during the time when the grouting agent exhibits rigidity as water is released from the grouting agent due to the pressurized grouting. Therefore, if the pressurized grouting is stopped before the time of reaching the average density of 75% according to the ground permeability coefficient of Table 1, the expansion of the pore that has been expanded due to the pressurized grout decreases rapidly, and the effect of residual stress cannot be expected. That is, only when pressure grouting is performed over the minimum injection time, the pullout resistance may be improved due to pressure grouting.

Given that expansion factors caused by pressurized grouting and residual stress acting on the perforated wall are important factors that increase the pullout resistance of ground anchors, pressurized grouting injection over minimum injection time is essential to increase pullout resistance of ground anchors. It can be seen that.

Field test

Field tests were conducted to investigate the effect of pressure grouting of compressed ground anchors. In order to establish an efficient method of pressurized grouting for compressed ground anchors by searching for efficient pressure grouting methods, the site location and ground were analyzed for a total of 5 times. It was performed with different kinds. In addition, in the third and fourth field tests, the group effect (interference effect due to mutual influence between ground anchors) test was performed in parallel.

1) Measurement of standard penetration

The standard penetration test measures the hammer strike frequency (N value) required to penetrate a 63.5kg hammer at 76cm in height to penetrate a cylindrical sampler of specified size 30cm in a borehole. It is an in-situ test method that evaluates the degree, further estimates the ground constants such as ground strength, relative density, internal friction angle, etc., and obtains a sample in a disturbed state.

In the field test, the N value was measured through the standard penetration test, and in Korea, the energy ratio of the standard penetration test defined as the ratio of the energy used for the penetration of the free fall energy of the theoretical hammer is assumed to be 52.5%. It is denoted by N _52.5 .

2) Specifications of grout

At the time of the test, the cement used for the grout was general portland cement, having a water-cement mixing weight ratio (W / C) of 50%, and no other admixture was added.

3) Field test result

In order to analyze the effect by the pressure grouting, the field test results when the grouting is performed under pressureless and pressurization are described in Tables 2a to 2e. Here, the expansion ratio means a value obtained by dividing the difference value between the measured diameter and the punched diameter by the punched diameter, and k means the ground permeability coefficient. And, "anchor length" means the length of the ground anchors in which the ground anchors are embedded in the drilling hole, "settling ground" means the length of the ground anchors fixed in the drilling holes by the grout injected pressure, "Anchor length" means the length of the ground anchors excluding "fixing point".

In addition, the ground conditions of the field test are described in Table 3.

In pressurized grouting, the grouting injection is carried out at an injection pressure of approximately 100 to 250 kPa, but depending on the ground conditions, the injection pressure can be increased up to 500 kpa. That is, the grouting injection pressure is preferably 100 to 500 kPa, and if the grout agent is injected below the injection pressure, the effect of pressure grouting cannot be obtained, and if the grout agent is injected beyond the range of the injection pressure, the ground Cracks are generated and the grout flows out between the cracks, thereby reducing the effect of pressure grouting.

Comparing the results of pressurized grouting and non-pressurized grouting, the ultimate pullout resistance in the case of pressurization was 1.36 ~ 1.93 times (average 1.66 times) and N _52.5 value in the case of sedimentary soil (silt sand, N _52.5 = 9). Weathered soil layers below 50 show 1.19 ~ 1.74 times (1.47 times average), whereas weathered soil layers with N _{52.5 and} above 50 show 0.93 ~ 0.95 (0.94 times average). There was no. As a result, it can be seen that the effect of increasing the pullout resistance by pressure grouting is effective in the ground of 50% or less of N _52.5 , and the more loose the ground and the better the permeability, the greater the effect.

On the other hand, it is confirmed that the better the water permeability of the ground, the greater the effect of increasing the ultimate pullout resistance of the pressure grouting ground anchors compared to the pressureless grouting case. In addition to the effect of small standard penetration (N value) on the ground where the field test was carried out, the ground where the field test was conducted had a grout to the surrounding ground as well as the expansion of the pore due to the increase of radial stress due to the pressure grouting injection. Since the actual diameter of the anchor body is expected to increase due to the penetration of the agent, it can be analyzed that the better the permeability due to this effect, the greater the effect of increasing the ultimate pullout resistance of the pressurized grouting anchors compared to the unpressurized grouting. .

In addition, when comparing the expansion rate by pressurized grouting, the expansion ratio was generally larger than the punching diameter when pressurization was applied, and in that case, 20.15 to 24.52% (average 21.5) for the sedimentary soil (silt sand). %), Weathered soil layers with N _{52.5 and} below 50 showed an increase of 21.48 ~ 22.67% (average 21.9%), while the expansion by pressure grouting was insufficient at 4.9% over weathered soils with N _{52.5 and} above. On the other hand, even when the pressure-free grouting is carried out, the bulb diameter is increased by 3.9 ~ 15.56% depending on the stiffness and permeability coefficient of the ground compared to the drilling diameter. As described above, the effect on the expansion of pore size by pressure grouting is similar to that of the ultimate pullout resistance. That is, it can be seen that the looser the ground, the greater the perforation magnification effect.

Calculation formula for ultimate pullout resistance of pressure grouting ground anchor

1) Calculation of principal surface frictional resistance per unit area

As described above, it can be seen that the effects of increasing the pullout resistance and expanding the pore size due to the pressurized grouting are larger as the surrounding ground is loosened (smaller N value) and the larger permeability coefficient.

Therefore, the main surface frictional resistance τ _u per unit area can be assumed as a function of N value (N _52.5 ). Based on the results of the first to fifth field experiments, the principal surface frictional resistance (τ _u ) per unit area according to the N value (N _52.5 ) is shown in FIG. 4, and the formula for calculating the ultimate pullout resistance is shown in Equation 3 below.

2) Consideration of the military effect of the ground anchor

In the third test, the separation distances of ground anchors were 3.0m, 1.0m, and 0.5m, respectively, to examine the group effects of the ground anchors. In the fourth test, the separation distance for each ground anchor was 2.0m, 1.75m, 1.50m, 1.25m, 1.0m, 0.75m, and 0.50m, respectively.

As a method to consider the military effect, the ultimate pullout reduction rate of the ground anchor proposed by Habib was used, and a graph of the military efficiency derived through the third and fourth field test results is shown in FIG. 4 is described.

Here, "a = separate distance of ground anchor, R = anchor length xtan (beta), (beta) = 2 / 3x (soil), 45 degrees (rock), (phi) = internal friction angle" means.

Internal friction angle can be measured through the experiment on the site ground, as the ground conditions of the site as shown in Table 3.

3) Ultimate pullout resistance formula

Based on the above-described contents, the ultimate pullout resistance of the ground anchors constructed by the pressure-type compression ground anchor construction method according to the present invention can be calculated by the following equation.

Here, "D is the drilling diameter, L is the anchorage length of the ground anchor, τ _u is the main surface frictional resistance per unit area of the ground anchor, Ge is the group efficiency due to the near construction of the ground anchor".

In the present invention, the ultimate pullout resistance calculation formula expressed by Equation 5 is derived based on the test result, and the ultimate pullout resistance can be used in the design of the compression type ground anchor for N _52.5 or less. have.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

1 is a schematic view of a pressure compression ground anchor.

2a to 2f is a step-by-step view showing the construction method of the pressure-type compression ground anchor according to an embodiment of the present invention.

Figure 3 is a graph showing the relationship between the "time- grout average pressure density" according to the ground permeability coefficient.

4 is a graph showing the principal friction resistance per unit area derived from the field test results.

5 is a group efficiency graph derived through the field test results.

Claims (9)

Forming a drilling hole using a casing and a fabric mill in the target ground to be reinforced; Filling a primary grout into a casing inserted into the drilling hole; Inserting a ground anchor comprising a steel wire and a load bearing body into the drilling hole; Drawing the casing to the position of the lower body; A pressure grouting step of installing a pressure cap at the rear end of the casing and injecting a grout agent at an injection pressure and an injection time suitable for ground conditions through an injection tube connected to the pressure cap; And And tensioning and anchoring the ground anchors by tensioning the steel wires. In the pressure grouting step, the injection pressure of the grout agent is monitored through a pressure gauge, After the tension and fixing step of the ground anchors, the ultimate pull resistance (P _u ) of the ground anchors constructed can be calculated by the following equation.

(Wherein, D is the perforation diameter, L Chapter fixation of the ground anchor length, τ _u is a main surface frictional resistance per unit area of the ground anchor, Ge refers to group efficiency due to close-up the construction of the ground anchor, and the τ _u and the Ge Is defined by

Where N _52.5 is the standard penetration test value,

Where a = ground anchor distance, R = anchor length x tanβ, β = 2/3 x φ (soil), 45 ° (rock), φ = internal friction angle) The method of claim 1, The injection pressure of the grout agent in the pressure grouting step is a construction method of the pressurized compressed ground anchor, characterized in that 100kPa to 500kPa. The method of claim 1, The minimum injection time of the grout agent in the pressure grouting step is 30 seconds to 270 seconds when the water permeability of the ground is 5.0 × 10 ⁻³ cm / sec to 5.0 × 10 ⁻⁵ cm / sec, and as the water permeability decreases. Construction method of the pressurized compressed ground anchors, characterized in that the minimum injection time is increased. The method of claim 1, The inside of the pressure cap is provided with a packing in contact with the casing, The pressurizing cap pressurizes the upper portion of the pressurized cap and the casing is characterized in that the construction method of the compression type ground anchor. The method of claim 1, The forming of the punching hole may be performed by using a double casing formed of an inner casing and an outer casing, and pressurizing and compressing the outer casing and the perforated ground by closely removing the inner casing. Construction method of ground anchor. The method of claim 1, When the ground anchor includes a plurality of load bearing body, the step of drawing the casing and the pressure grouting step is a step of construction of a pressurized compressed ground anchor characterized in that the step is made for each of the plurality of load body position. delete The method of claim 1, When the ground anchor includes a plurality of load bearing body, the construction method of the pressure-type compressed ground anchor characterized in that the tension in order from the steel wire surrounding the load bearing body located at the tip of the ground anchor. delete

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