JPS58101922A - Control or air pressure in hollow pipe for sand pile construction - Google Patents

Abstract

PURPOSE:To optimize the control of air pressure by using a control system in which air supply and discharge operations are automatically controlled in such a way that the air pressure inside a hollow pipe is regulated between the lower set pressure corresponding to soil pressure at the lower end of the hollow pipe and the upper set pressure. CONSTITUTION:An air supply pipe 5 with a switch valve 9 and a discharge pipe 6 with an air exhaust valve 7 are connected to a hollow pipe 1 through which sand is discharged into soft ground. Signal of a pressure sensor 8 provided to the pipe 1 is put, together with signals of a depth meter 11, etc., in a meter 13. In the drawing process of the pipe 1 (discharge process of sand), while regulating the air pressure inside the pipe 1, detected by the sensor 8, by the meter 13 in such a way that the air pressure is set within the lower limit set pressure corresponding to the soil pressure at the lower end of the pipe 1 and the upper limit set pressure slightly greater than the lower limit set pressure, detected by the depth meter, the pipe 1 is drawn and sand is discharged.

Description

[Detailed Description of the Invention] Conventionally, it has been said from experience that when constructing sand piles on soft ground, supplying compressed air into hollow pipes improves the removal of sand inside the pipes. In this case, air pressure control relied solely on the operator's experience and intuition, and was therefore dependent on the operator's ability.
Inevitably, the amount of sand removed will vary! There were many.

The present invention is intended to overcome the above problems, and includes:
The feature is that in the process of supplying compressed air into the hollow pipe for sand pile construction and discharging it into the soft ground of the sand bank inside the pipe, the air pressure inside the hollow pipe is set at a lower limit that corresponds to the earth pressure at the lower end of the hollow pipe. The point is that the supply and exhaust operations are automatically controlled so that the pressure falls between the upper limit set pressure and the slightly larger upper limit set pressure.

Hereinafter, the present invention will be explained in detail based on the drawings.

Fig. 1 shows an example of a device for constructing sand piles according to the present invention. is an air valve, 5 is an air supply pipe, 6 is an exhaust pipe, 7 is an exhaust valve, 8 is a pressure sensor, 9 is a switching valve, 10
is the receiver tank, 11 is the depth gauge, 12 is the sand level gauge, 1
3 is an instrument (control panel), 14 is a recorder, 15 is an outer tube, 16
17 is a sand discharge and compaction member, and 17 is a forced vertical movement mechanism (for example, a hydraulic cylinder).

Figure 2 shows the locus of leakage of the hollow pipe 1 in one construction example in which sand piles are constructed in soft ground using the equipment shown in Figure 1.
This trajectory is obtained from the depth meter 11.

In Fig. 2, a-+b is receiving, b-+c is building a sand pile while pulling out the hollow tube 1, c-+d is replenishing sand after stopping pulling out the hollow tube 1, and d→e is the same as b-+c, and after that, sand replenishment and sand pile construction are repeated to form a sand pile extending from point b to the ground surface, but in this construction example, the pneumatic pressure control of the present invention is performed. is mainly the drawing process of the hollow tube 1 (b-+c, d→e,...
).

In each drawing process (sand discharge process) of the hollow fl, the air pressure inside the pipe is automatically controlled to be between the lower limit setting pressure corresponding to the earth pressure at the lower end of the pipe and the upper limit setting pressure slightly larger than this. The set pressure is shown by line segments A and A' (between b-+0) in FIGS. 3 and 4.

In general, the earth pressure σr at depth 2 is expressed as σ2=12+β where γ: unit volume weight of ground soil β: 2c when considering passive earth pressure (C: ground strength) O when considering static earth pressure Therefore, if we assume that γ does not change between b-+0 and consider static earth pressure.

Line segment A is ua=12 Line segment A' is ua=γz+Δua However, z=zb−2゜ It is indicated by.

Next, the air pressure control in the pipe between l) −+ (4 is shown in Fig. 1,
This will be explained in detail with reference to FIG.

Air supply ■: Prior to drawing out the hollow pipe 1, the exhaust valve 7 is closed by a signal, and the switching valve 9 is activated to open the receiver.
Compressed air from the tank 10 is sent into the hollow tube 1 via the air supply pipe 5. The rising air pressure inside the pipe is detected moment by moment by the pressure sensor 8 and inputted to the meter 13.

Since the depth at the lower end of the tube is inputted as a signal from the depth gauge 11 into the gauge 13, that l! ! ! Air supply continues in the pressure cylinder of line segment A' at degree (Zb).

Canceling air supply and exhaust (2): When the pipe air pressure ua reaches around the pressure of line segment A', a signal is given from the meter 13, the switching valve 9 is operated, and the supply of compressed air is stopped.

The drawing of the hollow tube 1 is started, and as the hollow tube 1 is drawn out, the sand is discharged, so that the air pressure ua in the tube decreases. The pressure is detected every moment by the pressure sensor 8 and inputted to the meter 13.

Since the constantly changing depth of the lower end of the pipe is detected by the depth gauge and VC and inputted to the meter 13, air supply is not performed until the pressure of line segment A is reached.

Air supply ■: The switching valve 9 is activated by a signal from the meter 13, and compressed air is sent into the pipe from the air supply pipe 5 (same as air supply ■).

Suspension of supply/exhaust ■ and air supply ■ are the same as (2) and ■.

Exhaust ■: This is a case where the pressure of A' is exceeded by the supply air ψ), the switching valve 9 is closed, the exhaust valve 7 is opened, and the air inside the pipe is discharged to the outside of the pipe via the exhaust pipe 6.

Suspension of supply/exhaust ■: When the air pressure ua in the tube becomes less than the pressure A', the exhaust valve 7 is closed and the condition is maintained until the pressure A'kua reaches the pressure A'.

Air supply ■ and stopping supply/exhaust ■ are the same as ■ and (2).

Exhaust ■: 2 When the depth gauge 1.1 detects the length of the hollow tube 101 times, the extraction is stopped, and at the same time the exhaust valve 7 is opened to discharge the air inside the tube to the outside of the tube.

Note that if the air is being supplied at the time when L is detected, the switching valve 9 is operated to stop the air supply, and the exhaust valve 7 is opened to exhaust the air. According to one invention,
Since the air pressure inside the tube is controlled as described above, sand is properly discharged when the hollow tube 1 is pulled out, and even if the operator is Nagisa with little experience, the same inconvenience will not occur.

As described above, the sand discharge and compaction member 16t in the device shown in Fig. 1
- Although we have described the case of discharging sand with the same diameter as the diameter of the outer pipe 15 without activating it, the sand discharge/compaction member 16 is operated to discharge compacted sand piles with a diameter larger than the diameter of the outer pipe 15. In the case of land reclamation, if we consider the passive earth pressure using the earth pressure formula on page 3, it will be as follows.

Generally, the passive earth pressure at depth Z is σ2 = γZ + 2c, but since ua6γZ glue and atmospheric pressure are fully acting inside the pipe, the passive earth pressure σj at the lower end of the hollow pipe 1 is σ3 = γZ + 2C - ua = 2c Therefore, the pushing force F of the forced vertical movement mechanism 17 can be reduced by the amount of earth cover.

Then, if σ3 is equal to 20 and b, the pushing force F is detected by the hydraulic pressure of the forced vertical movement mechanism 17, and the cross-sectional area of the sand pile being constructed is detected by the depth gauge 11 and the sand level gauge 12, the three-axis By fully applying the compression theory, C, that is, the full strength of the original ground can be detected.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing an example of device 01 used in the implementation of the present invention, Fig. 2 is a locus diagram of the lower end of the hollow tube, Fig. 3 is an explanatory diagram of the set pressure, and Fig. 4 is the supply/exhaust operation. FIG. In addition, in the figure 1: hollow tube, 2: sand charging hopper, 3: penetration machine,...
...is... Agent Patent Attorney Hiroshi Sometani

Claims (1)

[Claims] In the process of supplying compressed air into a hollow pipe for sand pile construction and discharging it into the soft ground of gold dust inside the pipe, the air pressure inside the hollow pipe is set at a lower limit corresponding to the earth pressure at the lower end of the hollow pipe, and an upper limit set slightly higher than this. To fit between the pressure,
A method for controlling air pressure in a hollow pipe for sand pile construction, characterized by automatically controlling supply and exhaust operations.