JPH0796783B2 - Pier settlement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a submergence device for a pier that is erected on soft ground such as a river.

(Prior Art) Generally, a bridge pier for mounting a bridge or an elevated road is constructed by a concrete structure or a reinforced concrete structure. And in the place where the ground is weak, such as a river, this pier is erected by sinking deep into the ground. Usually, the caisson method is used to sink the pier, and the caisson with a substantially circular blade bottom is pushed downward by a heavy machine to sink, and the pier is further constructed above it.

In such a conventional caisson method, as the caisson deeply sinks, the earth pressure and water pressure applied to the caisson become higher, making it difficult to sink, and the sinking work becomes difficult. It was also very difficult to adjust so that

Therefore, Japanese Patent Publication No. 31-5334 proposes a gas injection type settlement device for a basic well. This subsidence device is provided with a plurality of air supply pipes that open at each stage around the well, and an injection pipe having a plurality of injection ports is attached to the open end of the air supply pipe. The air supply pipe descends along the inner circumference of the well, bends outward in the radial direction, and opens to the outer circumference of the well. The injection pipe is attached to an injection pipe attachment groove provided on the outer periphery of the well, and is attached to the opening end of the air supply pipe at a right angle or at an angle. And the injection pipes are in four stages up and down, and there are three groups along the circumference of the well, and the range of each group is
It is about 60 °. Further, each injection pipe is provided with three to four injection ports on its upper side surface, and these injection ports are covered with a stretchable plate made of rubber. On the other hand, each air supply pipe is connected to the main air distribution pipe via a pressure regulating valve and a distribution valve.

Then, by ejecting compressed air from the injection port of the injection pipe around the well, the friction resistance due to earth pressure or water pressure is weakened, and the well is sunk. At this time, for example, when the frictional resistance in each part is different in the soft ground, by appropriately adjusting the pressure of the compressed air to each injection pipe, it is possible to prevent the well pipe from tilting due to unbalanced sinking.

(Problems to be Solved by the Invention) However, the conventional settlement device has the following problems. First, the injection pipes are divided into three groups around the well and are only within the range of about 60 °, respectively, and they do not cover the entire circumference of the well, so the efficiency is poor. Further, the ejection pipes are provided in four upper and lower stages for the purpose of enhancing the effect of reducing the earth pressure and the water pressure, but as a result, the number of ejection pipes increases and the manufacturing becomes difficult. At the same time, by adjusting the pressure for each of the ejection pipes, it is intended to perform the optimal air injection according to the ground condition, etc., but in reality, a large number of ejection pipes arranged vertically and horizontally are appropriate. Difficult to control. Furthermore, the upper and lower ejection pipes are arranged in a zigzag shape in order to prevent a decrease in efficiency due to a short circuit between the upper and lower ejection air.
Arranging the ejection pipes in a zigzag shape itself causes a decrease in working dynamic pressure, resulting in a decrease in efficiency. In addition to that, in order to prevent the inflow of earth and sand into the ejection pipe, the injection port is covered with a stretchable plate made of rubber, but this stretchable plate makes the jet direction of air oblique and indefinite, and also reduces efficiency. ing.

On the other hand, an object of the present invention is to provide an efficient pier subsidence device that can obtain a large settlement effect with a structure as simple as possible and can also correct an inclined caisson in the vertical direction.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention provides a jet pipe provided on the outer periphery of a caisson provided at the lower part of a pier and air to the jet pipe The caisson has an air supply pipe and a compressor for sending high-pressure air to the air supply pipe, and the caisson has one upward outer peripheral shoulder portion at the lower outer periphery over the entire circumference, and the ejection pipe is an outer peripheral shoulder of the caisson. Is provided only on the part and over the entire circumference of the outer peripheral shoulder, and has a large number of ejection holes with the direction of the fumes directed upward and is divided into a plurality of sections that are mutually shielded in the axial direction. The air supply pipes are vertically embedded in the caisson, a plurality of the air supply pipes communicate with the ejection pipes in each of the sections, and the compressor supplies high pressure air to the air supply pipes independently of each other. Is.

(Operation) In the present invention, when the caisson is sunk, the compressor is driven, and when the high pressure air is sent through the air supply pipe to the ejection pipe located all around the outer peripheral shoulder at the lower part of the caisson, the high pressure air is ejected. It spouts upward from a large number of spouts on the entire circumference of the pipe and rises along the entire outer circumference of the caisson. This weakens the earth pressure and water pressure applied to the caisson,
Subsidence of caisson becomes easier. Further, when the caisson is tilted, the tilt can be easily adjusted by appropriately blowing or stopping the air blowing for each section divided in the axial direction of the ejection pipe.

(Example) Hereinafter, one example of the present invention will be described in detail with reference to the drawings. In FIG. 1 to FIG. 3, reference numeral 1 is a substantially elliptically cylindrical pier,
A caisson 3 having a blade 2 is provided at the lower part thereof, and this pier 1 is erected so as to bury the caisson 3 in the excavated ground. A jet pipe 6 having a large number of jet holes 5 formed around the entire circumference of the caisson 3 is attached to an upward facing outer circumferential shoulder portion 4 provided around the entire lower circumference of the caisson 3. The ejection hole 5 has its ejection direction directed upward. Further, the ejection pipe 6 is divided into four sections A, B, C, D in the axial direction as shown in FIG. 2, and the same sections A, B,
It is connected in C and D. An air supply pipe 8 is provided in communication with the ejection pipe 6 for each of the sections A, B, C and D. These air supply pipes 8 are vertically embedded in the caisson 3, and the upper ends thereof extend to the upper part of the pier 1 and are connected to the compressors 9 on the ground. In order to attach the air supply pipe 8 and the ejection pipe 6, the air supply pipe 8 is arranged in the formwork of the caisson 3 and concrete is placed, and immediately thereafter, the ejection pipe 6 is attached to the outer peripheral shoulder portion 4 and the air supply pipe 6 is attached. 8 and the ejection pipe 6 are connected to each other, and after the concrete is hardened, the ejection hole 5 is formed right above.

In the apparatus of this embodiment configured as described above, the caisson 3 sinks by its own weight or by pushing downward from above with a heavy machine. When the caisson 3 sinks deeply, earth pressure and water pressure are applied toward the caisson 3, so that the caisson 3 becomes difficult to sink. In this case, when four compressors are operated and high-pressure air is sent to the ejection pipes 6 of the sections A, B, C, and D through the air supply pipe 8, the high-pressure air is ejected upward from the ejection holes 5. ,
Then, this high-pressure air rises from the lower part of the caisson 3 along the entire outer circumference of the caisson 3. Therefore, earth pressure and water pressure toward the caisson 3 are weakened, and the caisson 3 is likely to sink. If the caisson 3 is tilted during this subsidence, if high-pressure air is not blown to the ejection pipes 6 in the tilted sections A, B, C, and D, a high earth pressure is applied to the caisson 3 on this side. On the opposite side, high-pressure air is ejected upward from the ejection pipe 6 in the large-diameter outer peripheral shoulder portion 4, and the fumes rise along the caisson 3, so that torque acts in the direction to correct the inclination. At this time, high-pressure air is discharged from the jet holes 5 into the caisson 3
Since it rises along with, the inclination can be easily corrected.
Therefore, in the present embodiment, the jet pipe 6 is divided into four sections and the high-pressure air is sent independently. Therefore, the inclination of the caisson 3 can be easily corrected by appropriately feeding the high-pressure air or not sending the high-pressure air. It can be carried out.

According to the configuration of the above embodiment, a large settlement effect can be obtained by the settlement device having a simple structure. That is, caisson 3
Since the ejection pipe 6 is provided all around the outer peripheral shoulder portion 4 at the lower part of this, and a large number of ejection holes 5 in which the direction of the fumes is directed upward are provided all around the ejection pipe 6, Since the air rises from the lower part of the caisson 3 along the entire circumference of the caisson 3, the earth pressure and water pressure applied to the caisson 3 can be efficiently reduced. Further, the jet pipe 6 is divided into four sections A, B, C, D in the axial direction, and high-pressure air can be independently sent to each section A, B, C, D, so that it is inclined. It is also easy to straighten the caisson vertically. That is, it is easy to control the blowing and non-blowing of the four sections A, B, C, and D. Further, since the ejection pipe 6 is provided only on the outer peripheral shoulder portion 4 of the caisson 3, it is easy to manufacture. Moreover, at the time of construction, after the air supply pipe 8 was arranged in the formwork of the caisson 3 and the concrete was placed, the ejection pipe 6 was immediately attached to the outer peripheral shoulder portion 4 and connected to the air supply pipe 8 to harden the concrete. After that, since the ejection holes 5 are formed, the construction can be performed easily and surely, and the ejection holes 5 can be formed easily.

Although one embodiment of the present invention has been described in detail above, it can be appropriately modified within the scope of the present invention. For example, the pier 1 may have a substantially cylindrical shape. Further, the number of sections of the ejection pipe can be appropriately set to other than four sections.

[Effects of the Invention] As described in detail above, according to the present invention, in particular, the ejection pipe is provided over the entire circumference only on the outer peripheral shoulder portion at the lower part of the caisson, and the ejection direction is upward in this ejection pipe. By providing a large number of ejection holes for the entire circumference, the earth pressure applied to the caisson can be efficiently reduced and the caisson can be submerged smoothly,
A large settlement effect can be obtained with a simple structure. Further, since the ejection pipe is divided into a plurality of sections in the axial direction and high-pressure air is sent to each section independently from the compressor via the air supply pipe in the caisson, it is easy to adjust the inclination of the caisson to sink. You can definitely. Furthermore, it is easy to manufacture.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the present invention, FIG. 2 is a horizontal sectional view, and FIG. 3 is a vertical sectional view of an essential part. 1 ... Pier 3 ... Caisson 4 ... Outer shoulder 5 ... Jet hole 6 ... Jet pipe 8 ... Air pipe 9 ... Compressor A, B, C, D ... Section

Claims (1)

[Claims] 1. A caisson provided at the outer periphery of a caisson provided at the lower part of a pier, an air supply pipe for sending air to the ejection pipe, and a compressor for sending high pressure air to the air supply pipe, wherein the caisson comprises: It has one upward outer peripheral shoulder part on the lower peripheral part over the entire circumference, and the ejection pipe is provided only on the outer peripheral shoulder part of the caisson and over the entire peripheral part of the outer peripheral shoulder part. It has a large number of upward ejection holes over the entire circumference and is divided into a plurality of compartments that are shielded from each other in the axial direction, and the air supply pipe is vertically embedded in the caisson, and there are a plurality of them. A pier subsidence device characterized in that each section communicates with the jet pipe, and the compressor sends high-pressure air to each of the air supply pipes independently.