KR100939311B1 - Prestressed quay wall and construction method thereof - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PC wall and a quay wall in which prestressing is introduced into a steel pipe, and a construction method thereof. To reduce the cross-section of the wall by providing a, and to provide a quay wall and pre-stressing method to the PC block and steel pipe that can flexibly cope with impact load by connecting the seismic device to the tension member.

In order to achieve the above object, the present invention, in the construction of the inner wall, the foundation is formed by dredging the bottom surface and put the sandstone into the dredged bottom surface; A first wall portion and a second wall portion disposed above the foundation to be spaced apart in the width direction of the inner wall; A drainage layer filled between the first wall portion and the second wall portion; Horizontal tension member that supports the back earth pressure by the drainage layer by connecting the first wall portion and the second wall portion horizontally and applying a tension force in the horizontal direction; A vertical tension member installed to vertically penetrate the first wall portion and the second wall portion, and having both ends fixed to upper and lower ends of the first and second wall portions after introduction of a tensile force in a vertical direction; The technical gist of the present invention includes a cover part covering the first and second wall parts and an upper surface of the drainage layer.

PC Block, Wall, Vertical Tensile, Horizontal Tensile, Interior Fixing, Prestressing, Steel Jacket, Steel Pipe

Description

Prestressed quay wall and construction method using prestressing in PC blocks and steel pipes

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quay wall in which prestressing is introduced into a PC block and a steel pipe, and a construction method thereof, wherein a PC block is laminated through a steel pipe, and prestressing is introduced into the stacked PC block to reduce the cross section of the quay wall. The present invention relates to a PC wall and a steel pipe in which prestressing is applied to a steel pipe so as to improve the workability by linearizing the linearity thereof, and a construction method thereof.

In general, because the coastline is in contact with the sea, the line is very irregular.

When constructing a coastal road on such a coastline, the road should be installed along a coastline with an irregular linearity, so that the linearity of the road is irregular and narrow.

Conventionally, in order to construct the coastal road as described above, the inner wall was formed along the coastline, and the coastal road was constructed on the upper portion of the inner wall, and the inner wall was constructed as a gravity type wall by self-weight.

Since the gravity wall is supported by self-weight by stacking or prefilling precast concrete blocks, a large number of precast concrete blocks are stacked and a large amount of soil is injected.

As the conventional quay wall as described above has to be constructed in accordance with the topography of the coastline, the linearity of the quay wall is very irregular. When the coastal road is constructed on the upper part of the quay wall after the formation of the quay, the linearity of the coastal road is very irregular and curved. This is an uncomfortable problem.

In addition, since the inner wall is a gravity type wall, a phenomenon in which the cross section of the inner wall becomes very large is generated, and because of this, a large amount of precast concrete blocks or soil is introduced, resulting in a long construction period, a large increase in construction cost, and a poor workability.

In addition, since the size of the cross section of the quay wall is very large, there are many restrictions on the place of the quay wall, there is a lot of problems that can be lost.

The present invention for solving the conventional problems as described above is to be built so that the construction of the PC block to the steel pipe installed in the ground through the steel jacket to facilitate the construction, the tension material on the two facing walls formed by the PC block In order to reduce the cross section of the quay wall by introducing prestressing in the vertical and horizontal directions, the quay wall and its construction method which adopt prestressing on the PC block and steel pipe which can flexibly cope with the impact load by installing the seismic device in the tension member to provide.

The present invention to achieve the object as described above and to perform the problem for removing the conventional drawbacks, in the construction of the inner wall, the foundation is formed by dredging the bottom surface and put the sandstone into the dredged bottom surface; A first wall portion and a second wall portion disposed above the foundation to be spaced apart in the width direction of the inner wall; A drainage layer filled between the first wall portion and the second wall portion; Horizontal tension member that supports the back earth pressure by the drainage layer by connecting the first wall portion and the second wall portion horizontally and applying a tension force in the horizontal direction; A vertical tension member installed to vertically penetrate the first wall portion and the second wall portion, and having both ends fixed to upper and lower ends of the first and second wall portions after introduction of a tensile force in a vertical direction; And a cover part covering the first and second wall parts and the upper surface of the drainage layer.

In addition, the first wall portion and the second wall portion, the steel jacket is provided in the upper portion of the base portion, a plurality of guide holes in the longitudinal direction of the inner wall is formed at a predetermined interval; A seismic device installed on an outer surface of the steel jacket, the seismic device being fluidly connected to an upper portion of the steel jacket so as to absorb a shock applied to the wall part; One end is fixed to the lower portion of the earthquake-resistant device, the other end is fixed to the ground in the form of a ground anchor through the base portion fixed steel jacket for fixing a steel jacket on the upper portion of the base; A plurality of steel pipes guided through the guide holes of the steel jacket and driven into the ground, exposed to the ground by the installation height of the inner wall, and into which concrete is injected; A plurality of PC blocks stacked on both sides of the adjacent steel pipe to form walls; Characterized in that comprises a.

In addition, the seismic device, the outer case is coupled to the outside of the steel jacket; A flow connection part installed to be movable by a spring on an inner upper side of the outer case and connected to the vertical tension member to provide elastic force to the vertical tension material; A wedge portion formed at an inner lower side of the outer case to fix the steel jacket fixing tension member by a wedge having a cone shape; It will be configured to include.

In another aspect, the present invention is the step of forming the foundation to form a foundation by dredging the bottom surface and sandstone; Installing a steel jacket positioned on the upper portion of the foundation to be spaced apart in the width direction of the inner wall, having a plurality of guide holes formed thereon, and having a seismic device attached to an outer surface thereof; A steel jacket fixing step of connecting one end of the steel jacket fixing tension member to the seismic device and fixing the other end to the ground in the form of a ground anchor; A steel pipe installation step of driving the steel pipe into the base part to be guided through the guide hole; Reinforcing foundation forming step of forming a reinforcement base by inserting the sandstone as high as the steel jacket; A wall part forming step of forming a first wall part and a second wall part which are stacked to face each other by stacking PC blocks so as to be fitted into steel pipes installed through the steel jacket on one side and steel pipes installed through the steel jacket on the other side; A horizontal tension member installation step of connecting steel pipes installed in the first wall portion and the second wall portion facing each other when the PC block is laminated using horizontal tensile strength and applying the tensile force to fix the horizontal tensile strength; A drainage layer forming step of filling a space between the first wall portion and the second wall portion to form a drainage layer; Inserting a vertical tensile member to vertically penetrate the PC block, connecting the seismic device, introducing a tensile force, and then installing and fixing the vertical tensile material; A cover part forming step of covering the first and second wall parts and an upper surface of the drainage layer; Characterized in that comprises a.

The present invention constituted as described above by applying prestressing in the vertical and horizontal direction to the inner wall through the vertical tension and horizontal tension, thereby reducing the overall cross section of the inner wall, thereby improving the construction of the inner wall, material saving and construction period shortening The construction cost is reduced and the steel pipe is guided to the steel jacket so that the steel pipe can be installed at regular intervals, the steel pipe can be installed stably, and the seismic device can flexibly cope with external shocks. It is a useful invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view showing a construction state of the quay wall according to an embodiment of the present invention, Figure 2 is a front view showing a construction state of a quay wall according to an embodiment of the present invention, Figure 3 is according to an embodiment of the present invention Figure 4 is a plan view showing the construction state of the quay, Figure 4 is an exemplary view showing the installation of the seismic in detail, Figure 5 is a perspective view showing the installation state of the steel jacket, steel pipe according to an embodiment of the present invention,

The quay wall of the present invention, the base portion 10 is formed by putting the sandstone in the dredged bottom surface as shown in the figure, and is positioned to be spaced apart at regular intervals on the upper portion of the base portion 10, a plurality of PC blocks 42 The first wall portion 40 and the second wall portion 41 formed by stacking the plurality of layers), the drainage layer 50 filled between the first wall portion 40 and the second wall portion 42, A horizontal tension member 61 for horizontally connecting the first wall portion 40 and the second wall portion 41 and applying the tensile force in the horizontal direction so as to be supported against the back earth pressure; and the PC block 42 ) Is installed to vertically penetrate the vertical tension member 60 and both ends are fixed to the upper and lower ends of the first and second wall parts 40 and 41 after the tensile force is introduced in the vertical direction, and the first and second wall parts. 40 and 41 and a cover portion 80 covering the upper surface of the drainage layer 50 is configured.

The first wall portion 40 and the second wall portion 41 are installed on the upper portion of the base portion 10, the steel jacket in which a plurality of guide holes 21 are formed at regular intervals in the longitudinal direction of the inner wall. 20, the seismic device 70 is installed on the outer surface of the steel jacket 20, the vertical tension member 60 is fixed to the upper side to be movable, and one end of the lower side of the seismic device 70 The other end is fixed to the ground in the form of a ground anchor in the base portion 10, the steel jacket fixing tension member 63 for fixing the steel jacket 20 to the top of the base portion 10, and the steel jacket Guided through the guide hole 21 of 20 and driven to the ground, but to be exposed to the ground by the installation height of the inner wall, the steel pipe 30 is installed by injecting concrete therein, and the neighboring steel pipe A plurality of PC tablets stacked so that both ends are fitted to 30 to form a wall. It is configured to include a 42.

The steel jacket 20 maintains the installation interval of the steel pipe 30 at a predetermined interval through the guide hole 21.

In addition, the steel jacket 20 is firmly fixed to the upper portion of the base portion 10 by the tension member 63 for fixing the steel jacket to stably guide the steel pipe 30 at the time of installation of the steel pipe 30 The pipe 30 is to be supported to be installed underground.

The seismic device 70 is formed in the outer case 71 coupled to the outer both sides of the steel jacket 20 and the groove shape inclined toward the lower side in the lower side of the inner case 70, the steel jacket Fixing tension member 63 is coupled to the upper portion of the wedge portion 73 is fixed by the wedge 74 of the cone shape, the outer case 71 in the interior of the outer case 71 by the spring 72 It is installed to be movable, and comprises a flow connection portion 75 is connected to the vertical tension member 60 to one side.

One side of the fluid connection portion 75 is coupled to the wedge cone 77 is integrally formed at the end of the vertical tension material 60, the wedge cone coupling groove 76 is fixed and fixed by the resin 78 is Formed.

The seismic device 70 is configured as described above, the steel jacket fixing tension member 63 is installed underground, the steel jacket 20 is to be stably fixed to the upper portion of the base (10).

In addition, since the flow connecting portion 75 to which the vertical tension member 60 is connected is installed to flow up and down inside the outer case 71 by a spring 72, the elastic force is provided to the vertical tension member 60 by impact. It absorbs and alleviates, thereby stably supporting the first wall portion 40 and the second wall portion 41.

On the other hand, the PC block 42 is installed so as to be fitted to the steel pipe 30 is prevented from falling, and is properly installed at regular intervals, the construction is made simple.

The horizontal tension member 61 connects the steel pipe 30 of the first wall portion 40 and the steel pipe 30 of the second wall portion 41 to be horizontally fixed, and is fixed after the tensile force is introduced. , So that the supporting force against the back earth pressure applied to the two wall parts 40 and 41 is improved.

In this case, the horizontal tensile material 61 allows the two steel pipes 30 to be wound and fixed.

The PC block 42 has a body portion having a fixing key 48 and a fixing groove 49 corresponding to each other on both sides so that side coupling with another neighboring PC block 42 can be easily combined and more firmly. 43, a pair of through-holes 44 formed in the vertical direction of the body portion 43 so that the steel pipe 30 can be stacked and inserted therein, and the vertical tension member 60 may be inserted. To concave on the upper surface of the body portion 43 to enable the installation of a number of tension member insertion holes 45 and the horizontal pipe member 61 of the horizontal tension member 61 so as to be perpendicular to the body portion 43 It is configured to include an installation groove 46 is formed.

The PC block 42 is stably supported by being fitted at both ends of the steel pipe 30, and is manufactured and constructed on land, thereby improving the workability of the inner wall and thereby shortening the construction period.

On the other hand, the PC block 42 configured as described above is further formed with a concave sofa 47 in the front of the body portion 43 to reduce the intensity of the blue.

The drainage layer 50 is formed by laying the earth and sand, the geosynthetic fiber facing the PC block 42 of the first wall portion 40 and the second wall portion 41 to prevent the loss of the earth and sand (51) is attached, and the inside is to be made to fill.

The horizontal tension member 61 is to be settled after applying a tensile force by horizontally connecting the steel pipe 30 facing each other among the steel pipe 30 installed in the first wall portion 40 and the second wall portion 41 A plurality of steel pipes 30 are installed in the height direction so that the first wall portion 40 and the second wall portion 41 can be more stably supported by the back earth pressure.

The horizontal tension member 61, the vertical tension member 60 and the tension member 63 for fixing the steel jacket is to selectively use a common steel bar, rebar, strand wire, etc. according to the construction environment, vertical and horizontal to the quay wall (100) By applying a tensile force in the direction is to reduce the cross section of the entire inner wall 100 is to improve the workability.

On the other hand, the cover portion 80 is formed by pouring concrete, it can be further constructed a coastal road to the upper surface of the cover portion (80).

That is, as shown in Figure 6, the inner wall 100 of the present invention can be straightened construction by reducing the width of the cross section of the inner wall 100 by the vertical tension member 60 and the horizontal tension member 61, according to the shoreline 101 Irrespective of the irregular shape of the straightened quay wall (100) can be installed and to be able to construct a coastal road on the top of the quay wall (100).

Referring to the quay wall construction method of the present invention configured as described above are as follows.

First, the bottom surface of the sea is dredged and the sandstone is put into the dredged bottom surface to form the foundation 10.

When the base portion 10 is formed as described above, a plurality of guide holes are disposed to be spaced apart in the width direction of the inner wall 100 so as to form the first wall portion and the second wall portion on the upper portion of the base portion 10 ( 21) is installed steel jacket 20 is formed.

At this time, both sides of the steel jacket 20, the seismic device 70 is coupled to enable the installation of the vertical tension member and the tension member for fixing the steel jacket.

When the steel jacket 20 is installed, the steel jacket fixing tension member 63 is inserted into the ground so that one end is fixed to the ground in the form of a ground anchor, and after the tension is introduced, the wedge 74 is inserted into the other end. It is fixed to the wedge portion 73 of the seismic device 70.

Such steel jacket 20 is stably fixed to the upper portion of the base portion 10 by the steel jacket fixing tension member 63.

When the steel jacket 20 is installed as described above, the steel pipe 30 is inserted into the base 10 so as to be guided through the guide hole 21 of the steel jacket 20, but the steel pipe being driven ( 30) to be exposed to the ground by the construction height of the quay wall (100).

As described above, the steel pipe 30 is installed in the ground while being guided by the steel jacket 20 and is arranged at regular intervals and is stably installed.

As described above, when the installation of the steel pipe 30 is completed, the reinforcement foundation 11 is formed by injecting sandstone as much as the height of the steel jacket 20.

Then, the first wall portion 40 is formed by stacking the both ends of the PC block 42 in the steel pipe 30 installed through the steel jacket 20 on one side, and at the same time, the steel jacket 20 on the other side. The second wall part 40 is formed by stacking the both ends of the PC block 42 in the steel pipe 30 installed through the fitting.

At this time, the seismic device 70 is located in the lower portion of the tension member insertion hole 45 of the PC block 42 to enable the installation of the vertical tension member (60).

In addition, when the PC block 42 is stacked, the steel pipe 30 installed on the first wall part 40 and the second wall part 42 is connected by using a horizontal tension member 61 to introduce a tensile force. Then settle down.

At this time, a plurality of the horizontal tensile material 61 is installed in the height direction of the inner wall 100 to connect the first wall portion 40 and the second wall portion 41 more stably to respond to the back earth pressure.

In addition, the horizontal tensile material 61 is installed to be wound around the steel pipe 30 through the installation groove 46 formed in the upper portion of the PC block 42 so as not to interfere with the other PC block 42 stacked on the upper. do.

As described above, the PC block 42 is installed to construct the first and second wall parts 40 and 41, and at the same time, the first and second wall parts 40 and 41 are buried between the drain layers 50. Form.

When the installation of the PC block 42, the horizontal tension member 61 and the drainage layer 50 is completed in the same manner as above, the vertical tension member 60 is inserted through the tension member insertion hole 45 of the PC block 42. To be connected to the interior of the seismic device (70).

At this time, the wedge cone 77 is formed at one side end of the vertical tension member 60 to be fixed in the wedge cone coupling groove 76 formed in the flow connection portion 75 of the seismic device 70, After installation in the wedge cone coupling groove 76 is fixed and bonded by a resin (78).

In this case, it is preferable to use water glass resin in general so that the resin can exhibit strong adhesive force.

When one end of the vertical tension member 60 is fixed as described above, the vertical tension member 60 is tensioned to introduce tension in the vertical direction, and then fixed to the upper surface of the PC block 42 located at the upper end using the anchorage 62. do.

Then, the first and second wall parts 40 and 41 are completed by constructing a cover part 50 covering the upper surface of the drainage layer 50.

Meanwhile, the steel pipe 30 is grouted to fill the inside of the steel pipe 30 so as to improve the bearing force of the steel pipe 30.

In addition, when the steel pipe 30 is grouted, grouting is performed by the through hole 44 of the PC block 42 so that the outer circumferential surface of the steel pipe 30 is covered by the grout, thereby causing rust on the surface of the steel pipe 30. To prevent it.

Meanwhile, when the drainage layer 50 is formed, the geotextiles 51 are attached to opposite surfaces of the first wall portion 40 and the second wall portion 41, and are deposited in the interior of the drainage layer 50. Prevents soil from being lost to the outside of the quay wall (100).

In addition, if necessary for the protection of the vertical tension member 60 may be installed by covering the vertical tension member 60 with a duct or tube.

On the other hand because the flow connection portion 75 of the seismic device 70 is configured to be moved up and down by a spring 72 in the interior of the outer case (71). When an impact is applied in the vertical direction, the tensile force of the vertical tension member 60 is adjusted to absorb and reduce the impact load applied in the vertical direction.

In addition, the present invention is to minimize the construction cross-section of the inner wall 100 by supporting the inner wall 100 by using the vertical tension member 60 and the horizontal tension member 61 as described above, thereby improving the construction properties.

In addition, the air is shortened compared to the existing gravity-type quay wall, construction cost is reduced, it is possible to flexibly respond to the impact load by the earthquake-resistant device (70).

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by any person having ordinary skill in the art without departing from the gist of the present invention claimed in the claims. Of course, such changes will fall within the scope of the claims.

1 is a cross-sectional view showing a construction state of the quay wall according to an embodiment of the present invention,

2 is a front view showing a construction state of the quay wall according to an embodiment of the present invention,

3 is a plan view showing a construction state of the quay wall according to an embodiment of the present invention,

4 is an exemplary view showing the seismic device installation state in detail;

5 is a perspective view schematically showing a coupling state of the steel jacket, steel pipe according to an embodiment of the present invention,

Figure 6 is a plan view showing a coastline installation state of the quay wall according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

(10): foundation part (11): reinforcement foundation part

(20): Steel Jacket (21): Guide Hole

(30): steel pipe (40): first wall portion

(41): second wall portion (42): PC block

(43): body portion 44: through hole

(45): Tension material insertion hole (46): Installation groove

(47): couch ball (48): fixed key

(49): fixing groove (50): drainage layer

(51): Geotextile (60): Vertical Tensile Material

(61): horizontal tensile material (62): anchorage

(63): Tension material for fixing steel jacket (70): Seismic device

(71): outer case (72): spring

(73): Wedge portion 74: Wedge

(75): flow connection portion (76): wedge cone coupling groove

(77): Wedge cone (78): Resin

80: cover part 100: the inner wall

101: shoreline

Claims (9)

delete In the quay, A foundation portion formed by dredging the bottom surface and inserting sandstone into the dredged bottom surface; It is installed to be spaced apart in the width direction of the inner wall in the upper portion of the base portion, the steel jacket is formed in the longitudinal direction of the inner wall a plurality of guide holes at a predetermined interval, and is provided on the outer surface of the steel jacket, applied to the wall portion A seismic device in which the vertical tension member is fluidly connected to an upper portion to absorb a shock, and one end is fixed to the lower part of the seismic device, and the other end is fixed to the ground in the form of a ground anchor through the base portion is steel Steel jacket fixing tension member for fixing the jacket on the upper part of the base, guided through the guide hole of the steel jacket is driven into the ground, but a number of strokes to be exposed to the ground by the installation height of the inner wall and the concrete is injected into Steel pipes and a plurality of PC tablets stacked on both sides of the neighboring steel pipes to form walls A first wall portion and the second wall portion is configured to include; A drainage layer filled between the first wall portion and the second wall portion; Horizontal tension member that supports the back earth pressure by the drainage layer by connecting the first wall portion and the second wall portion horizontally and applying a tension force in the horizontal direction; A vertical tension member installed to vertically penetrate the first wall portion and the second wall portion, and having both ends fixed to upper and lower ends of the first and second wall portions after introduction of a tensile force in a vertical direction; A pre-stressing wall is introduced into the PC block and the steel pipe, characterized in that it comprises a cover portion covering the first and second wall portion and the upper surface of the drainage layer. The method of claim 2, The seismic device, the outer case is coupled to the outside of the steel jacket; A flow connection part installed to be movable by a spring on an inner upper side of the outer case and connected to the vertical tension member to provide elastic force to the vertical tension material; A wedge portion formed at an inner lower side of the outer case to fix the steel jacket fixing tension member by a wedge having a cone shape; A quay wall in which prestressing is introduced into a PC block and a steel pipe, characterized in that the configuration comprises a. The method of claim 2 or 3, The horizontal tension member is a horizontal wall connecting the steel pipe of the first wall portion and the steel pipe of the second wall portion horizontally and is fixed after the introduction of the tension of the PC block and the steel pipe introduced prestressing the steel pipe. The method of claim 4, wherein The PC block may include: a body portion having fixing keys and fixing grooves corresponding to each other on both sides thereof so as to be easily coupled to other neighboring PC blocks; A pair of through-holes formed in the body portion in a vertical direction so as to be fitted into the steel pipes; A plurality of tension member insertion holes formed in the body portion in a vertical direction so that the vertical tension member can be inserted therein; An installation groove formed in a concave shape on an upper surface of the body portion to enable the steel pipe of the horizontal tensile material to be installed; A sofa ball formed concave on the front of the body to reduce the strength of the wave; A quay wall in which prestressing is introduced into a PC block and a steel pipe, characterized by comprising a. A foundation portion forming step of dredging a bottom surface and inserting sandstone to form a foundation; Installing a steel jacket positioned on the upper portion of the foundation to be spaced apart in the width direction of the inner wall, having a plurality of guide holes formed thereon, and having a seismic device attached to an outer surface thereof; A steel jacket fixing step of connecting one end of the steel jacket fixing tension member to the seismic device and fixing the other end to the ground in the form of a ground anchor; A steel pipe installation step of driving the steel pipe into the base part to be guided through the guide hole; Reinforcing foundation forming step of forming a reinforcement base by inserting the sandstone as high as the steel jacket; A wall part forming step of forming a first wall part and a second wall part which are stacked to face each other by stacking PC blocks so as to be fitted into steel pipes installed through the steel jacket on one side and steel pipes installed through the steel jacket on the other side; A horizontal tension member installation step of connecting steel pipes installed in the first wall part and the second wall part facing each other when the PC block is laminated using horizontal tension material, and applying a tensile force to fix the horizontal tension material; A drainage layer forming step of filling a space between the first wall portion and the second wall portion to form a drainage layer; Inserting a vertical tensile member to vertically penetrate the PC block, connecting the seismic device, introducing a tensile force, and then installing and fixing the vertical tensile material; A cover part forming step of covering the first and second wall parts and an upper surface of the drainage layer; Construction method of the quay wall introduced pre-stressing to the PC block and the steel pipe, characterized in that comprises a. The method of claim 6, In the vertical tensile material installation step, the vertical tensile material is installed in the inner wall of the seismic device so as to relieve the impact load applied in the vertical direction, the quay wall introduced pre-stressing to the steel block. Construction method. The method of claim 6, The step of forming the drainage layer, a method of constructing a quay wall introduced pre-stressing to the PC block and the steel pipe, characterized in that the geosynthetic fiber is attached to the surface facing the first wall portion and the second wall portion, the land is embedded therein. The method of claim 6, The steel pipe installation step in the pre-stressing the PC block and the steel pipe, characterized in that the inside of the steel pipe by grouting the inside of the steel pipe in the steel pipe installation step.

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