KR20120012503A - Reverse Circulation Drill Method With precast type Caisson and Jacket - Google Patents

Abstract

PURPOSE: A reverse circulation drill method using a prefabricated caisson and a jacket is provided to reduce resistance to stress and differential settlement using a pile foundation. CONSTITUTION: A reverse circulation drill method using a prefabricated caisson and a jacket is as follows. A concrete structure of a prefabricated caisson(10) is put into a sea bottom. The inner part of the prefabricated caisson is dredged using a clamshell bucket and a sand pump. A jacket(15) having a guide steel pipe(33) is installed in the dredged part, and underwater concrete is placed.

Description

Reverse Circulation Drill Method With precast type Caisson and Jacket}

The present invention is a construction method that replaces and reinforces the foundation construction part and the marine soft ground in the bridge construction made in the seabed and the sea, and solves the various problems that occur during the construction of the cast-in-place pile. Assembled caisson which can increase structural stability and save time and economics of targets by using RCD (Reverse Circulation Drill) by adopting excerpts and collecting and supplementing constraints of each method by changing construction method. And it relates to an Alcidi (RCD) method using a jacket.

In the soil and foundation fields, deep foundations are divided into pile foundations, cast-in-place piles and caisson foundations, which are divided into steel pipes, PHC and RC piles according to the material, Driven) It is divided into pile and purchase pile. In general, when the bearing capacity is the pile pile, the construction conditions are not easy due to the noise and vibration. In addition, when driving when there is gravel or a hard layer on the strata, the piles are broken, so the application conditions are not easy.

Therefore, when it does not meet the above conditions, it is necessary to use the embedding or on-site pour pile. The embedding is a method of inserting the pile after pre-excavation of the ground. . The cast-in-place piles are not ready-made products, so they are difficult to install and quality control, and are generally used as large diameters in bridges.

On the other hand, the site foundation pile foundation method by RCD (Reverse Circulation Drill) is also impossible to construct large-diameter foundations with a limited diameter, and it is difficult to check the quality of the finished foundation structure when underwater casting, It is not possible to supplement or modify the soil, and many other types of conventional Pier Foundation methods are also easy to excavate from soil layers such as soft ground. However, if the caisson is settled to the supporting layer such as weathered rock or soft rock, Due to the infiltration of infiltrated water and the placing of underwater concrete, quality control is restricted.

The direct foundation method, which is applied when the depth of excavation to the support layer is relatively shallow, also requires a wide range of basic types such as an enlarged foundation to secure horizontal bearing capacity, or uses sheet piles in deep waters such as rivers, lakes, and seas. As additional provision of temporary installations or steel cladding is required, the construction of foundation structures is greatly limited.

The steel pipe is released from the initial point in the state that the steel pipe is not fully seated due to the effects of algae and scouring during the installation of the RCD when the steel pipe is entered during the construction of the cast-in-place pile. Do the same to get it back on. In addition, it is greatly affected by the stratum state of the sea bottom.

It is adaptable to the reduction of load and installs the direct foundation pier footing on the sea floor, which transmits the upper and vertical loads of the bridge directly to the support layer in equal distribution. It is a method of using a combination of deformations of the shape of the caisson, which has a large cross-sectional friction force. In this case, it is possible to construct a predetermined depth by mounting an RCD that can be excavated to the soft rock layer.

Therefore, there are various construction problems that occur during the recession of piles around the piles due to scour phenomena which are inevitably generated in pile foundations that are frequently used as foundations of bridges, and when the steel pipes enter and excavate. In addition, consideration will be given to the manufacturing problems involved in the caisson work, the conditions of onshore land, the means and method of transportation to the berthing facilities, and the constraints of weather conditions and transportation equipment that are restricted by sea transport.

Design and construction of working civil engineering foundation, civil engineering research society. Book Publishing Construction Information, Road Design Manual, Part 5 Bridges, Ministry of Land, Transport and Maritime Affairs. Latest Basic Design Construction Handbook, Construction Culture History p758 / 804. Explanation of Construction of Marine R.C.D Basic Construction Method 2006 Korean Society of Civil Engineers Regular Conference. Production construction launching method using factory slim form, Hyundai Construction Technology Development Office.

The present invention has been made in view of the above circumstances, and by installing a footing used as an extension base of the direct foundation method on the bottom or the bottom surface, it is possible to offset the bearing force, bending moment, and eccentric load in the vertical or horizontal direction. In order to provide the RCD method using the assembly caisson and jacket, the resistance to stress and uneven settlement due to the ground reaction force can be reduced to the pile foundation to increase the coping force according to the reduction of the overhead load of the upper bridge. There is a purpose.

In order to achieve the above object, the present invention, by dropping and casing the caisson to bind the assembly caisson and dredging the inside of the weathered rock using the cram shell bucket, and then install the jacket with the guide steel pipe attached and poured the concrete underwater Configured to integrate; Drop the concrete structure of the assembled caisson on the sea floor, dredge the inner area of the caisson assembly using the cramshell bucket and sand pump, immerse the jacket, then pour the primary concrete, press-fit the steel pipe, excavate the bedrock and reinforce the It is characterized by the fact that the net pressure, after the concrete is poured secondary concrete, and installed artificial reefs.

As described above, according to the present invention, the pier foundation can be easily installed on the bottom or the bottom of the seabed, and the steel pipe indentation and Alcidi (RCD) excavation can be easily performed, and the effect of reducing the scour caused by the scour can be reduced. have.

1 is an installation diagram for explaining the RCD method using the assembly caisson and jacket according to an embodiment of the present invention,
2 is a plan view and a cross-sectional view showing the assembly caisson and jacket shown in FIG.
Figure 3 is a flow chart of the work of Alcidi (RCD) method in the site of the pile.

Preferred embodiments of the present invention will be described in detail with reference to the drawings.

1 is an installation diagram for explaining the RCD method using the assembly caisson and jacket according to an embodiment of the present invention. Figure 2 is a plan view and a cross-sectional view showing the assembly caisson and jacket shown in Figure 1, Figure 3 is a work flow chart of the Alcidi (RCD) method in the site-pouring pile.

The present invention is a construction method that replaces and reinforces the foundation construction part and the marine soft ground in the bridge construction made in the seabed and the sea, and solves the various problems that occur during the construction of the cast-in-place pile. By using the introduction of Alcidi (RCD) by extracting the merits, and using the assembly caisson and jacket that can improve the structural stability of the target and save time and economics by collecting and supplementing the constraints of each method by changing the construction method. Alcidi (RCD) method.

As shown in Figure 1, in the construction method of the present invention by dropping the caisson to bind to the assembly caisson 10, the inside of the dredging to the upper weathered rock using the cram shell bucket. After that, the steel jacket 15 to which the guide steel pipe 33 is attached is installed, and the water concrete pouring 37 is integrated. Therefore, it increases the role and function of the footing of the piers, and reduces the range of errors in the inductance of the steel pipe, thereby securing time stability and saving time.

A hole in the upper portion of the guide steel pipe 33 is attached to the bushing roller 36 to reduce the load of the traction crane when entering the inlet steel pipe 31. The upper welding ring 32 is removed after the installation is completed. The wire rope 35 is fastened from the crane of the barge 20 to the traction hole 34 of the guide steel pipe 33, and the guide steel pipe 33 enters the RCD drilling depth 38 by a dotted line in the sea bottom.

In manufacturing the assembly caisson 10 shown in Figure 2, the existing caisson is large in size itself and its structural form is indispensable to maintain the bulkhead, it is indispensable for various difficulties, such as constraints of the working space. It is impossible to install in deep areas because its height must also be higher than the surface due to the nature of the process. Therefore, it can be installed in the water, and the scale is reduced to make it easy to manufacture, transport and install.

In manufacturing and installing the jacket 15 shown in FIG. 2, the apparatus for inducing and inducing the steel pipe to secure the construction base on the sea floor in order to overcome the constraints of various natural phenomena which appear during the steel pipe ingress and excavation And steel assembly to support it can be manufactured and installed. Underwater concrete placement in an assembly can eliminate the effects of wave forces by increasing its own weight to meet its functional effects of shrinking caissons.

Figure 2 (a) is a plan view of the assembly caisson 10, the male caisson 12 and the female caisson 14 is fastened to the connection portion (a) and the corner caisson 13 is also fastened, Figure 2 (b) is assembled An upper sloped surface 19 is formed as a sectional view of the caisson 10. Figure 2 (c) (d) is a male caisson 12 at the time of the connection to the four holes 17 and the underwater transmitter 18 around the circular hole 16 is formed, the left and right connecting portion (m) is formed.

Figure 2 (e) is a jacket 15 to fix the four guided steel pipes 33 using a plurality of H beams 101 and the support 102 and the spacing connecting connecting plate 103 is installed on the slope. 6 (f) is a cross section of the jacket 15, the inlet steel pipe 31 is introduced into the guide steel pipe 33.

As the work flow chart of the RCD method in the cast-in-place method, Figure 3 (a) is a steel pipe indentation process, Figure 3 (b) is a Vibro hammer work process, Figure 3 (c) is an RCD work process, Figure 3 ( d) is a rebar network entry process, Figure 3 (e) is a tremi pipe assembly process, Figure 3 (f) is a concrete pouring process.

Looking at the order of working the RCD method of the cast-in-place pile method, as shown in Figure 3 (a) is a guide frame of the sea level installed in the upper part of the steel pipe 31 welded to the survey point on the tweeter barge 40 ( 30).

As shown in FIG. 3 (b), the vibrating hammer 42 is fitted with a vibro hammer 42 by a crane in the trough barge 40 and press-fits the bottom of the seabed. The hammer 42 is put down by the vibro and excavated to the soil layer with a hammer grab.

At this time, when the rock appears, as shown in Figure 3 (c) is set to the top of the steel pipe RCD (43) proceeds the excavation work to a predetermined depth. Here, the drilling bit 44 of the RCD is used.

After the excavation work, the RCD 43 is dismantled, and the assembled reinforcing bar 45 as shown in FIG. Subsequently, the tremi pipe 46 is assembled and installed as shown in FIG. Thereafter, the concrete placing (see FIG. 3 (f)) is poured to a predetermined height using the tremi pipe 46 for underwater concrete placement.

As described above, the RCD method using the assembled caisson and the jacket of the present invention will be described with reference to FIGS. 1 to 3 as follows.

First, the concrete structure of the assembly caisson 10 is dropped on the sea bottom.

Installation of the assembly caisson is done by completing the largest caisson in order of priority from one side and then alternately on both sides, and finally in the order of the opposite installation first. Woodwork should be attached to the joint, ie the female caisson contact, to facilitate the joining process. At this time, the measurement can be fine-tuned DGPS using the underwater transmitter 18 and the low frequency sonar imaging apparatus attached to both corners of the caisson assembly.

Each caisson assembly is connected and tied with a coring wire rope through the loop shown in FIG. 2 (c) (d), and the last connection is finished with a wire socket. When it is necessary to keep the bottom flat, use a large sand spigot and adjust the filling amount according to its size and quantity.

Second, dredging the interior area of the caisson assembly using a cramshell bucket and a sand pump. It dredges to the top of weathered rock (sandstone) layer or to the top of bedrock.

Third, immerse the jacket (15). The frame of the jacket is made of H beam (eg 300 * 300 * 9 * 12), the reinforcement is made of a-beam (Angle: 90 * 90 * 6), and a plurality of induction steel pipes are installed therein. The diameter of the induction steel pipe is used with a diameter of 300m / m larger than the diameter of the near entrance steel pipe. The height must be at least 1.5D (D = diameter).

The size of the jacket is made 300m / m less than the width of the inside of the caisson assembly. As shown in Figure 2, each hole in the upper side of the mold to make a hole to hold the spacing plate for two places, each side edge is made to support the assembly so as to cover the fabricated rebar mesh. The lower part of the induction steel pipe is attached with a protective film using a polyethylene material so that it does not flow in the concrete pouring, the upper part is attached to the bushing roller as shown in Fig.

Fourth is the induction of induction steel pipe. Install the steel pipe using a traction crane as shown in FIG. The height of the welded ring shall be installed at least 500 m / m higher than the guided steel pipe and removed after installation. Primary concrete pouring. In order to prevent the flow between each caisson assembly, it is poured into underwater concrete using Tremi pipe. The pouring height is up to one third of the prefabricated caisson.

Fifth is the primary concrete pouring. In order to prevent the flow between each caisson assembly, it is poured into underwater concrete using Tremi pipe. The pouring height is up to one third of the prefabricated caisson.

Sixth is steel pipe indentation. As shown in Figure 3 using a vibro hammer and hammer grep is repeatedly excavated indentation until the top of the bedrock appeared.

Seventh is bedrock excavation. The RCD is mounted to grind the bedrock to a predetermined depth.

Eighth is the reinforcement network. Install rebar network assembled from the ground.

Ninth is concrete pouring, using the Tremi pipe to the desired height.

The tenth is secondary concrete pouring. That is, to the top of the prefabricated caisson. At this time, the empty space between the guided steel pipe and the adjacent steel pipe is also filled. The outflow of concrete to the outside through the assembly connection portion is in the form of uneven structure, and is prevented due to the characteristics of the aggregate specification of the concrete.

When the installation point of the jacket is lowered by about more than the ground due to the state of the stratum in the zone, as shown in FIG. The finishing of the upper surface is done by lowering and filling the air content in the concrete using an underwater vibrator to uniformly treat the surface.

Eleventh installs artificial reefs. The artificial reefs are installed up to the level above the surface of the water so that the naked eye can identify them.

As described above, the present invention facilitates steel pipe intrusion and RCD excavation. In other words, in the area where the shellfish is exposed immediately after invading the steel pipe or in the area where the tide is high, the guide frame installed on the work barge is subjected to excessive load due to the buoyancy and the load according to the cross-sectional area of the steel pipe in contact with the water. The adjustment of the seating point itself is difficult, and the larger the diameter of the steel pipe is proportional. It's even worse when it comes to getting involved.

As a countermeasure, a guide frame with a pin pile is manufactured and operated, but even the pin pile is not fully entered. However, the pin pile ring is torn in the tide region. Even if it is settled down, it is unusual to be dragged while attempting to insert a vibratory hammer and swing indentation.

Therefore, it is necessary to lift and reset the leg of the tweet-up barge from the initial survey point. This can be a lot of time because the same task must be repeated many times. The advantage of the excavation is that it removes various soil layers and other sediments with large porosity around the seating point and wraps the surroundings with concrete of uniform media, which increases the consolidation effect. Increase the efficiency of work.

In addition, the weather conditions should be good when entering the steel pipe, and if the work is not preceded, no subsequent work is performed, so the time and economic loss during the waiting time is enormous. Therefore, by installing the structure to set the starting point on the sea floor in advance, the construction can be performed within the tolerance range, and the quality can be improved, and the air can be reduced by working without being affected by the blue.

The present invention can reduce depression due to scour. In other words, by increasing the cross-sectional area corresponding to the sewer and current of the support layer, the depth of scour depth inevitably followed by pile foundation holes is canceled, and the approach angle of the currents flowing around the piers is slowed, and the concentration of the vortices is reduced to reduce the concentration of vortices. Scour can be prevented.

10: assembly caisson
12: male caisson
13: corner caisson
14: cancer caisson
15: jacket
16: round hole
17: ring
18: underwater transmitter
19: slope
20: barge
30: guide frame
31: near-mouth steel pipe
32: link
33: induction steel pipe
34: round hole
36: bushing roller
38: RCD excavation
40: Tit-Up Barge
42: Vibro Hammer
43: RCD
44: RCD bit
45: rebar network
46: tremi pipe
47: concrete pouring
101: H-beam
102: angle (a section steel)
103: connecting iron plate

Claims (1)

Caisson dropping and binding to the assembly caisson and the inside of the dredging to the upper end of the soft rock using the cramshell bucket, after which the jacket with the guide steel pipe is installed, and it is configured to be integrated by pouring concrete under water;
Drop the concrete structure of the assembled caisson on the sea floor, dredge the inner area of the caisson assembly using the cramshell bucket and sand pump, immerse the jacket and pour the primary concrete, intrude the induction steel pipe and press in the steel pipe, Alcidi (RCD) method using assembling caisson and jacket, characterized in that the foundation rock excavation, reinforcing the reinforcing bar network, and after the concrete is poured secondary concrete, and installed artificial reefs.

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