KR20150037005A - sedment control dam including grouting filling hole and method therefor - Google Patents

Abstract

The present invention relates to a sediment control dam including a grouting filling part and a grouting method for the same. The sediment control dam including a grouting filling part comprises: an embankment main body (10) built by banking gravel, sand, and soil on the foundation ground (30) to store water in one side; a core barrier wall (20) which is made of viscous mud materials and of which the cross section is shaped into a trapezoid with a narrow top and a wide bottom to be installed at the internal center of the embankment main body (10); a plurality of grouting injection parts (40) installed in an injection hole (41) bored at a predetermined distance from the core barrier wall (20); and a grouting filling part (50) injected into a filling hole (51) bored through a space between the plurality of grouting injection parts (40) to fill up a destroyed part of the embankment main body (10). Therefore, the sediment control dam including a grouting filling part cuts off running water leaking from an embankment by carrying out leakage prevention and reinforcement for the embankment, which can cause the collapse of the embankment, thereby preventing the embankment from being weakened and collapsed.

Description

[0001] The present invention relates to a grooved filling hole and method therefor,

The present invention relates to a four-way dam having a grouting filling part and a grouting method for the same, and more particularly, to a method for preventing the leakage of a running water and a collapse of a levee by weakening a dam, a reservoir or a river bank, And a grouting filling portion for infiltrating the cement milk, the waterproofing binder and the filling yarn into the lost or collapsed portion of the bank by injecting the milk, the filler and the filling yarn, thereby regenerating and reinforcing the bank body.

Sasang Dam is a dam made by using rock as a main material. It is a method commonly used in reservoirs or multi-purpose dams in our country. Because there are mountains nearby, it is possible to obtain rock and earth resources from the mountains. It is easy to procure and construction cost is also low Since the construction period was short, about 4,000 reservoirs scattered throughout the country were constructed by this method.

At the beginning of the construction, the proper material is selected for the core and the core wall, so that it is constructed to be water-tight. Therefore, the leakage through the core is within the allowable range, but the water penetrates into the core and the core wall When the infiltration line is generated and the pore water pressure becomes high and the amount of leaking water becomes large, the leakage of the soil particles along with the leaking water will break the reservoir or the dam dam.

Therefore, after a considerable period of time has elapsed since the construction of the levee dam, the ability of the levee to resist water and water pressure is reduced, and the leaking water through the levee may lead to the collapse of the levee.

The major factors involved in the stability of the duck dam are the settlement deformation of the embankment body and the pore water pressure. During the construction, the total stress and the pore pressure increase due to the increase of the overburden load, so that settlement starts to occur in the embankment, and deformation occurs in the vertical direction of the longitudinal section and in the axial direction of the embankment.

This type of dams have many leaks in their characteristics, and leaks generated in leaks due to leaks can cause problems in various forms of stability of the dirt structure. Especially in the dams, Penetration through the ground occurs.

Pore water pressure and penetration force occur due to the action of infiltration water. If the design or construction is inappropriate, it is a factor that adversely affect the stability of the dam such as infiltration failure and reduction of shear resistance. Therefore, in order to minimize the amount of leakage, basic treatment and construction of water walls should be taken into consideration.

Reservoirs constructed in Korea are aged due to years of use, and are affected by internal factors such as cracks, collision, penetration, erosion and activity, and external factors such as earthquakes, heavy rain, overflow due to climate change, erosion of cover, , And the leakage and embankment erosion caused by the heavy rain, seismic pore water pressure, and aging account for most of the damage causes of the dam.

In order to repair the leakage or damage of the reservoir or duck dam, grouting reinforcement for the embankment was carried out by grouting method when a problem occurred in the embankment. In the conventional art, the curing of the grout material may be incomplete after the grouting is completed by using the cement grout, and the soil may be contaminated by the grout. In the substitution method, the body of the embankment must be completely removed and reinstalled The reservoir could not be used during the replacement period.

In order to solve all of the above problems, Korean Patent Laid-Open No. 10-2003-0037829 discloses a water leakage prevention method for a reservoir or a duck dam. In the conventional water leakage prevention method, the permeate of a cement or an inorganic- Reinforcement is carried out.

FIG. 1A is a side cross-sectional view showing a structure of a core water wall of a reservoir or a resilient dam according to a conventional technique.

The reservoir or duck dam is usually constructed to store water (4), so it usually stores a certain amount of water during use. The core (2) is provided inside the embankment (1) so that the water (4) stored therein does not leak through the embankment (1), and a material having a low permeability coefficient such as clay is used. When the water reservoir or the dynamo-electric dam is aged and water is leaked through the damper body 1 or the core water wall 2 to damage the damper body 1, the water barrier wall 3 to which the conventional technique is applied, 1 or the inside of the core wall 2.

1B is a cross-sectional view of a core provided with a water wall according to a conventional technique.

The bearing 1 of the reservoir or the resilient dam is installed in contact with the slopes 6 and 7 in the valley or the mountain and the bearing wall 3 is pierced (50 to 200Ø) in the bearing 1 or the core 2, And then the inorganic liquid ceramic permeable waterproofing binder according to the conventional technique is injected.

Here, as shown in FIG. 1B, the perforations are made from the upper surface to the bottom of the core 2, but are zigzagged and then injected into the holes so that the boundaries of the inorganic liquid ceramic permeable waterproof binder cured as a cylindrical shape overlap each other. In other words, the inorganic liquid ceramic permeable waterproofing binder injected into the perforated hole can be easily penetrated into the clay particles of the core made of clay because it is ultra-fine particles of 40 nm or less, The edges of the inorganic liquid ceramic permeable waterproofing binder cured by the above-mentioned method are overlapped with each other when the distance between the perforated holes and the holes is less than 150 mm.

Therefore, the leakage water reaching the water level wall 3 through the cracks of the body 1 or the core 2 can not pass through the water level wall.

In this conventional technique, the inorganic liquid ceramic permeable waterproofing binder is injected into the hole after zigzag punching, so that the boundaries of the inorganic liquid ceramic permeable waterproofing binder in the form of a cylinder are superimposed on each other so that the bank body itself becomes an impermeable water- It is possible to shorten the construction air for the leakage prevention, improve the workability, and drastically reduce the construction cost. However, since the boundaries of the cylindrical waterproofing binder overlap each other at two stages, So that there is a problem that the stress on the embankment is weakened by leakage through the boundary.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a water jet pump for a water jet pump, which comprises a double- And a grouting filling portion for injecting a plurality of coupling chambers through the grouting filling portion and connecting the grouting injection portion columns restored by the grouting to each other, and a grouting method for the grouting filling portion.

It is another object of the present invention to provide a method and apparatus for forming a plurality of grouting injection portions having a certain width and depth at the side of a four-way dam, and forming a plurality of grouting filling portions therebetween to tightly connect the grouting injection portion columns, And a grouting filling portion for filling a gap or a void portion caused by the grouting filling portion and the grouting method.

In order to accomplish the above object, according to the present invention, there is provided a four-way dam having a grouting filling part, comprising: a basin main body formed by filling gravel, sand and soil on a foundation ground to contain water stored on one side; A core water wall having a vertically long trapezoidal cross section with a narrow upper side made of a viscous clay material at an inner center of the bankhouse main body; A plurality of grouting injection portions installed in the injection holes drilled at a predetermined distance from the core water wall; And a grouting filling portion injected into a filling hole drilled between the plurality of grouting injection portions and filled in a loss portion of the bankhouse main body.

According to an embodiment of the present invention, an apparatus for constructing a grouting injection unit includes: an expansion bag which is excellent in stretchability and excellent in tensile strength and is not damaged while being inserted into an injection hole; A first pecker plate inserted into the upper portion of the expansion bag and tied to the first binding rope from the outside; A binding rope that binds and seals a first pecker plate inserted in an upper portion of the expansion bag outside the expansion bag; A second pecker plate inserted under the first pecker plate at an upper portion of the expansion bag and tied to a second binding rope at the outside; A second binding rope that binds and seals a second pecker plate inserted in an upper portion of the expansion bag outside the expansion bag; A first grouting injection pipe extending inward from the first pecker plate and the second pecker plate to a lower end of the expansion bag; An air discharging pipe inserted into the inside of the expansion bag through the first and second pecker plates and discharging air to the outside; And a second grouting injection pipe inserted into the space between the first pecker plate and the second pecker plate through the first pecker plate to inject cement milk.

According to an embodiment of the present invention, the grouting filling portion has at least one filling hole formed between a plurality of injection holes, a casing outer tube and an inner tube are inserted into the filling hole, and the cement milk, And filling the gaps and voids caused by the leakage of the main body of the bank.

According to an embodiment of the present invention, a cement milk pump is connected to an inner pipe, and the inner pipe is enclosed in a paker at the lower end of the inner pipe to expand the inner pipe. And a water jet pump nozzle is connected to the side of the inner pipe to supply a water-dispersible material through the water-feeding pipe, and a cement milk and a plurality of water- The filling yarn is mixed and injected into the filling hole to be injected into the gap and the void formed due to the leakage of the main body of the bank.

(A) drilling a plurality of filling holes with a predetermined distance d2 from the core water wall by drilling, inserting a casing exterior into the plurality of filling holes; (b) a water jet pump nozzle and a water-feeding pipe are connected to the outer surface of the casing, and an inner pipe having a paker attached to the lower end thereof is inserted, and when the inner pipe reaches a desired depth, the pucker is expanded to adhere the pucker to the outer surface of the casing ; (c) mixing the cement milk and the filling yarn through the water jet pump nozzle while injecting the cement milk through the inner pipe, and supplying the filling material through the feeding pipe; (d) shrinking the pellet to raise the outer and inner pipes, the water jet pump nozzle, and the dispenser pipe together by a distance D1 between the pellets, and re-expanding the pellet to adhere the pellet to the outer surface of the casing; (e) filling the cement milk and the filling yarn up to the upper surface of the four-sided dam body by repeating the steps (c) and (d).

According to the present invention, cement milk, filling yarn and filler are injected into gaps and voids that can cause the bank to collapse, thereby filling the gaps and voids of the bank body with the leakage, Thereby preventing leakage of leaking water from the levee, thereby preventing the levee from becoming soft and consequently preventing the levee from collapsing.

FIG. 1A is a side cross-sectional view showing a structure of a core water wall of a reservoir or a damping dam according to a conventional technique,
1B is a cross-sectional view of a core provided with a water wall according to a conventional technique,
FIG. 2A is a cross-sectional view of a four-way dam having a grouting injection pipe formed by a grouting method according to the present invention,
FIG. 2B is a horizontal sectional view of a four-way dam having a grouting injection pipe formed by a grouting method according to the present invention,
3 is a schematic view showing the construction of an injection unit construction apparatus according to the present invention,
FIG. 4 is a cross-sectional view of a casing outer tube and an inner tube constituting a filling part construction apparatus according to the present invention,
FIG. 5 is a perspective view of one embodiment of a filling yarn according to the present invention,
6A to 6F are flowcharts for constructing a filling part by a filling part construction apparatus in a four-way dam according to the present invention.

While the present invention has been described with reference to particular embodiments, it is capable of being embodied in many different forms and is not limited to the embodiments set forth herein. Hereinafter, the present invention will be described with reference to the drawings.

FIG. 2A is a cross-sectional view of a four-way dam having a grouting injection part and a filling part formed by a grouting method according to the present invention, FIG. 2B is a plan view showing a four- Sectional view is shown.

The four-way dam 100 according to the present embodiment includes a basin 10 having a foundation ground 30 formed of a gravel, sand, earth or the like so as to contain water stored on one side; A core water wall 20 formed of a viscous clay material and having a narrow upper side and a lower side wide trapezoidal cross-sectional shape at an inner center of the bankhouse main body 10; A plurality of grouting injection portions 40 installed in the injection holes 41 spaced apart from the core water wall 20 by a predetermined distance; And a grouting filling part 50 injected into the filling hole 51 drilled between the plurality of grouting injection parts 40 and filled in the loss part of the bank body 10.

The bankhouse body 10 is constructed by dugging soil, gravel, sand, etc. from a nearby mountain and sloping on the foundation ground 30, thereby reserving water on the upstream side. An intermediate layer consisting of gravel on both sides of the core water wall 20 formed in the middle, a small rock layer composed of small rocks, and an intermediate rock layer of medium size rock are covered with several layers and are formed at a height of several tens meters according to the topography.

The core water wall (20) is composed of viscous clay so as to prevent the stored water from being leaked, and is installed in a trapezoidal cross-sectional shape having a narrow upper side and a lower side.

The grouting injection unit 40 drills a plurality of injection holes 41 at a predetermined distance from the lower end of the core water wall 20 with a predetermined distance d from the core water wall 20 as shown in FIG. The grouting with cement milk is injected into the injection hole 41 thus drilled.

The grouting filling portion 50 is formed by forming at least one filling hole 51 between the plurality of injection holes 41 and inserting the casing outer tube 61 and the inner tube 62 into the filling hole 51, The cement milk and the filler 74 and the filler are injected through the inner pipe 62 so as to be filled in gaps and voids due to the oil chamber of the bank body 10.

Fig. 3 is a schematic view showing the construction of an injection unit construction apparatus according to the present invention.

The injection apparatus constructing apparatus 200 according to the present invention comprises: an expansion bag 42 which is excellent in stretchability and excellent in tensile strength and is not damaged by being inserted into the injection hole 41; A first pecker plate 43 inserted into the upper part of the expansion bag 42 and bound to the first binding rope 44 from the outside; A first binding rope (44) which binds and seals a first pecker plate (43) inserted in an upper part of the expansion bag (42) outside the expansion bag (42); A second pecker plate (48) inserted below the first pecker plate (43) and tied to the second binding rope (49) from the outside on the top of the expansion bag (42); A second binding rope (49) for tying and sealing a second pecker plate (48) inserted in the upper part of the expansion bag (42) outside the expansion bag (42); A first grouting injection pipe 45 extending inward from the first pecker plate 43 and the second pecker plate 48 to a lower end of the expansion bag 42; An air discharge pipe 46 inserted into the inflatable bag 42 through the first and second petacarbon plates 43 and 48 to discharge air to the outside; And a second grouting injection pipe 47 inserted into a space between the first pecker plate 43 and the second pecker plate 48 through the first pecker plate 43 to inject cement milk.

The grouting injection unit 40 according to the present invention is formed by drilling a plurality of injection holes 41 from the lower end of the core water wall 20 to a foundation ground 30 by drilling at a predetermined distance, As shown in FIG. 3, the injection unit constructing apparatus 200 is inserted to form a grout grout made of cement milk.

The inflatable bag 30 according to the present invention is characterized in that it has a stretchability of 150 to 250% and is excellent in stretchability and has a strong paragraphic aramid fiber or a cocoa wood and a fruit tree which can maintain its performance even under strong pressure of tensile strength of 1167 N / , And hemp fibers.

The infusion section constructing apparatus 200 according to the present invention is inserted into the injection hole 41 of the grouting infusion section 40 pierced in the bankhouse main body 10 and is installed in the inflating bag 42 as a grout material, Is supplied and filled.

The second grouting injection pipe 47 is inserted to the vicinity of the second pecker plate 48 and the grout material (cement milk) supplied from the second grouting injection pipe 47 is inserted into the first pecker plate 43 When the grout material (cement milk) is filled in the space between the first pecker plate 43 and the second pecker plate 48, air (foreign matter) flows upward And is discharged to the outside through the hole of the expansion bag 42.

At this time, the water contained in the grout material is also discharged to the outside to reduce the ratio of water contained in the cement milk, thereby increasing the strength of the cement.

When the grout material is supplied to the space between the first and second pecker plates 43 and 48 through the second grouting injection pipe 47, the first pecker plate 43 and the second pecker plate 48 The air inside the space between the first and second pecker plates 43 and 48 is discharged through the primary exhaust hose 28 And is discharged to the outside of the grouting hole 2.

The space between the first pecker plate 43 and the second pecker plate 48 filled with the grout material 35 is sufficiently expanded and expanded in volume to become larger than the inner periphery (surface) of the injection hole 41, The primary pressurizing field formed by the grout material between the first pecker plate 43 and the second pecker plate 48 which is bulged (expanded) from the inner periphery (surface) of the hole 41 is completely solidified after several minutes, So that the state in which the inlet of the hole 41 is closed is maintained.

When the grout material is supplied to the inflatable bag 42 through the first grouting infusion pipe 45, the grout material is gradually filled inside the inflatable bag 30, and when the grout material is gradually filled into the inflatable bag 30, The air (including foreign matter) inside the turret 42 is discharged to the outside of the injection hole 41 of the grouting injection unit 40 through the air discharge pipe 46.

Since the inflatable bag 42 filled with the grout material includes a hole through which water can pass, water contained in the cement milk is discharged through the hole of the inflatable bag 42 to reduce the proportion of water contained in the cement milk, (The surface) of the pouring hole 41 and the volume of the pouring hole 41 is larger than that of the inner periphery (surface) of the pouring hole 41 ) The grout material injected into the inflatable bag 30 is completely solidified after a few minutes and the injection hole 41 is completely filled (closed).

FIG. 4 is a cross-sectional view of a casing outer tube and an inner tube which constitute a filling part construction apparatus according to the present invention.

In order to carry out the present invention, the casing outer tube 61 is inserted into the perforated filling hole 51 until the outer surface of the casing outer tube 61 touches the ground 30, and then the inside of the casing outer tube 61 is filled with a water jet pump nozzle 70 And the inner pipe 62 connected by welding the water-dispersing pipe 75 by welding or the like is inserted.

A cement milk pump is connected to the inner pipe 62 and the inner pipe 62 is wrapped with a paker 80 at the lower end of the inner pipe 62 so as to be in close contact with the inside of the casing outer pipe 61 to seal the inside of the casing outer pipe 61, 62 are prevented from flowing back up through the casing outer tube 61.

A cement milk pump is connected to the inner pipe 62 to feed the cement milk through the acupuncture pipe 75 while feeding the cement milk, and a cement milk and a plurality of fillers (75) are mixed and injected into gaps, voids and the like which are created due to the oil chamber of the bank body (10).

As shown in FIG. 5, the filling yarn 74 is made of a natural fiber such as cotton, hemp, and the like, a chemical fiber material such as nylon, a short filling yarn 74a having a short length and a medium diameter, 50 cm length and 2 to 3 mm diameter long filling yarn (74b), 20 to 30 cm in length, 2 to 3 mm in diameter in the middle filling yarn (74 c), a length in the range of 40 to 50 cm and a diameter of 4 A large filling yarn 74d of ~ 5 mm is used and longer, thinner or shorter and thicker filling yarns 74 may be used if desired.

In this embodiment, the length is in the range of 10 to 50 cm and the thickness is 1 to 5 mm. The thickness is injected together with the cement milk through the water jet pump nozzle 70, It is filled and hardened together with cement milk to compensate for the strength that the cement does not have.

Here, the cement milk and the plurality of fillers 75 having various lengths are mixed through the inner pipe 62 without connecting the water jet pump nozzle 70 to the inner pipe 62 of the filling part installing apparatus, 51, it is possible to inject it into a gap, a void or the like which is created due to the oil chamber of the bank body 10.

6A to 6F are flowcharts showing the construction of the filling part by the filling part installing device in the four-way dam according to the present invention.

6A, a plurality of fill holes 51 are drilled from the core water wall 20 by a predetermined distance d2 (see FIG. 2B), and in step S2, the plurality of fill holes 51 The casing outer tube 61 is inserted.

In Step S3, the casing outer tube 61 is inserted into the filling hole 51, the pellet 85 is attached to the lower end portion, and the water jet pump nozzle 70 and the water-feeding pipe 75 are connected to each other by welding or the like. 6B, when the inner pipe 62 reaches a desired depth, the pucker 85 is expanded as shown in FIG. 6C to attach the pucker 85 to the casing outer pipe 61, So that the cement milk injected through the inner pipe 62 does not flow back over the kettle 85.

In step S4, the cement milk and the filling yarn 74 are mixed and injected through the water jet pump nozzle 70 while injecting the cement milk through the inner pipe 62, and the water-absorbing material is fed through the water feeding pipe 75 The filling hole 51 is filled with the cement milk and the filling yarn 74 as shown in FIG. 6D so that the filling hole 51 is filled with a gap, a void or the like created by the oil chamber of the bank body 10.

In step S5, as shown in Fig. 6E, the outer pipe 61 and the inner pipe 62, the water jet pump nozzle 70 and the water supplying pipe 75 are raised together by a distance D1 between one pair, The paker 85 is expanded so that the paker 85 is brought into close contact with the casing outer surface 61 so that the cement milk injected through the inner pipe 62 does not flow back over the paker 85.

 The cement milk and the filling yarn 74 are mixed and injected through the water jet pump nozzle 70 while the cement milk is injected through the inner pipe 62 in the step S6 and the water- The cement milk and the filling yarn 74 are injected into the filling hole 51 of the new section and the filling hole 51 is filled with the cement milk and the filling yarn 74 as shown in Fig. And filled in gaps and voids created by the oil chamber of the bank body 10.

The cement milk and the filling yarn 74 are mixed and injected by raising the outer pipe 61, the inner pipe 62, the water jet pump nozzle 70 and the water supplying pipe 75 together by the distance D1 between the adjacent pipes, And the cement milk and the filling yarn 74 are filled up to the upper surface of the four-sided dam body 10 by filling the holes 51 repeatedly.

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 in the appended claims and their equivalents. Of course, such modifications are within the scope of the claims as long as they are for the technical idea of forming.

10: the embankment main body 20:
30: foundation foundation 40: grouting injection part
41: injection hole 42: expansion bag
43: first pecker plate 44: first binding rope
45: first grouting injection pipe 46: air discharge pipe
47: second grouting injection pipe 48: second pecker plate
49: second binding rope
50: grouting filling part 51: filling hole
61: casing appearance 62: inner pipe
70: Water jet pump nozzle 74: Filler
75: A quick-paying pipe 100:

Claims (5)

A basin main body formed of a mixture of gravel, sand, and earth on a foundation ground to contain water stored on one side;
A core water wall having a vertically long trapezoidal cross section with a narrow upper side made of a viscous clay material at an inner center of the bankhouse main body;
A plurality of grouting injection portions installed in the injection holes drilled at a predetermined distance from the core water wall;
And a grouting filling portion injected into the filling holes drilled between the plurality of grouting injection portions and filled in the loss portion of the bankhouse main body. The method according to claim 1,
The apparatus for constructing the grouting injection unit comprises: an expansion bag which is excellent in stretchability and excellent in tensile strength and is not damaged while being inserted into the injection hole; A first pecker plate inserted into the upper portion of the expansion bag and tied to the first binding rope from the outside; A binding rope that binds and seals a first pecker plate inserted in an upper portion of the expansion bag outside the expansion bag; A second pecker plate inserted under the first pecker plate at an upper portion of the expansion bag and tied to a second binding rope at the outside; A second binding rope that binds and seals a second pecker plate inserted in an upper portion of the expansion bag outside the expansion bag; A first grouting injection pipe extending inward from the first pecker plate and the second pecker plate to a lower end of the expansion bag; An air discharging pipe inserted into the inside of the expansion bag through the first and second pecker plates and discharging air to the outside; And a second grouting filler pipe inserted into the space between the first pecker plate and the second pecker plate through the first pecker plate to inject cement milk. The method according to claim 1,
The grouting filling part forms at least one filling hole between a plurality of injection holes, inserts a casing outer tube and an inner tube into the filling hole, injects cement milk, a filling yarn and a filler through the inner tube, Wherein the grouting filling portion is filled with a gap and a void portion caused by the grouting filling portion. 3. The method of claim 2,
A cement milk pump is connected to the inner pipe, and the inner pipe is wrapped with a pecker to expand the inner pipe so as to be brought into close contact with the inside of the outer casing, thereby sealing the inside of the casing. A water-feeding pipe and a water jet pump nozzle are connected to the side of the inner pipe, a water-feeding material is supplied through a water-feeding pipe, and a cement milk and a plurality of fillers having various lengths are mixed through a water- So as to be injected into the gaps and voids created by the leakage of the main body of the bank. (a) drilling a plurality of filling holes with a drill having a constant separation distance d2 from the core water wall, and inserting a casing appearance into the plurality of filling holes;
(b) a water jet pump nozzle and a water-feeding pipe are connected to the outer surface of the casing, and an inner pipe having a paker attached to the lower end thereof is inserted, and when the inner pipe reaches a desired depth, the pucker is expanded to adhere the pucker to the outer surface of the casing ;
(c) mixing the cement milk and the filling yarn through the water jet pump nozzle while injecting the cement milk through the inner pipe, and supplying the filling material through the feeding pipe;
(d) shrinking the pellet to raise the outer and inner pipes, the water jet pump nozzle, and the dispenser pipe together by a distance D1 between the pellets, and re-expanding the pellet to adhere the pellet to the outer surface of the casing;
(e) repeating the steps (c) and (d) to fill the upper surface of the four-legged dam main body with cement milk and filling yarn.

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