JPH0324637B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides a method for detecting the presence of underground objects such as sewer pipes that may be damaged by ground improvement work, and This invention relates to a method for detecting underground objects to protect underground objects.

[Technical background of the invention and its problems]

BACKGROUND OF THE INVENTION In ground improvement work in cities, such as chemical injection work, it is often necessary to avoid existing underground structures. However,
Because the buried object itself is underground, it is not possible to determine much from above ground. Even if there are construction drawings for existing buried structures, they may not match the reality. Furthermore, even if holes are drilled to avoid underground objects during chemical injection work, if the injection pipe itself becomes bent, there is a risk of damaging the underground objects.

On the other hand, when detecting the presence or absence of underground objects from the ground, electrical resistivity methods and acoustic methods can be considered, but high detection accuracy cannot be expected.

[Purpose of the invention]

An object of the present invention is to provide a detection method that can detect underground objects with high precision and reliability.

[Summary of the Invention] The purpose of this invention is to approach an underground object from above ground while rotating an insertion tube having a jet nozzle opening diagonally forward at its tip, and in this approach process, the jet This is achieved by letting the fluid flow out into the surrounding ground from the outlet and detecting the presence or absence of the underground object based on the pressure change of the supplied fluid as the underground object approaches.

[Specific examples of the invention]

The present invention will be explained in more detail below with reference to the drawings.

FIGS. 1 and 2 show examples of insertion tubes that are suitably applied to carry out the method of the present invention. However, both figures show only the tip, and a double pipe DP and swivel S of the desired length are connected to the base.

Reference numeral 1 denotes an outer tube, and a tip shoe 2 is screwed onto the tip of the outer tube. A guide 3 is housed inside the outer tube 1, and a joint 4 that is inserted into the inner tube of the double tube is screwed to the base thereof. A tubular spool 5 is housed inside the guide 3, and is normally urged toward the base by a spring 6 as shown in FIG. When the tubular spool 5 is not moving, a narrow annular discharge opening 7 is secured between it and the distal end shoe 2, as shown in FIG. 2, and when it is moving, it is closed, as shown in FIG. It is said that the configuration is as follows. Further, the tip of the tubular spool 5 is a small-area jet nozzle 8, and an annular groove 9 is formed near the base.

On the other hand, a plurality of communication ports 10 are formed in the wall surface of the guide 3 in the circumferential direction, which communicate with the annular groove 9 when the tubular spool 5 moves. This communication port 10
is connected to a flow path 11 formed between the tubular spool 5 and the outer tube 1, and further to a detection liquid spout 12 formed in the tip shoe 2. 13 is a guide path formed between the guide 3 and the tubular spool 5 and communicating with the annular discharge port 7.

During construction, first, drilling is performed while pumping a drilling fluid W into the inner flow path and a detection fluid W', such as water, into the outer flow path using a pump P. At this time, since the diameter of the ejection nozzle 8 is small, the tubular spool 5 is pushed down by the pressure of the drilling fluid W against the biasing force of the spring 6, and the annular discharge port 7 is closed.
In this state, when the high-pressure drilling liquid W is ejected from the ejection nozzle 8, the ground is excavated and a hole is drilled. During this drilling, the detection liquid W' is pumped continuously or intermittently. This detection liquid W' is
0, the spout 1 through the annular groove 9 and the flow passage 11
It is ejected from 2 at high speed.

During this drilling process, if there is an underground object X near the drilling zone, the detected liquid from the spout 12
Since the ejected liquid W' is blocked by the underground object X, back pressure acts on the supply system of the detection liquid W°, and the supply pressure suddenly increases. Therefore, while monitoring this with the pressure gauge 13, the presence or absence of the underground object X is determined.

Here, the spout 12 is located on the outer circumferential portion of the distal end shoe 2 and is oriented diagonally outward, and by rotating the insertion tube around its axis, a wide range of detection is possible. It is also possible to detect the pressure increase in the drilling fluid W supply system from the jet nozzle 8, or to use this together.

If, as mentioned above, underground objects
Once the existence of the hole is confirmed, the drilling operation is stopped and the insertion (injection) pipe is removed. At this time, it is not preferable to leave a hole in the cavity, so it is preferable to inject and fill the hole with a chemical solution during the process of pulling up and removing the search tube. If underground object X does not exist, the injection work is performed as prescribed.

At the time of injection, the feeding fluid is switched, and both liquids A and B of the two-component curable chemical liquid are fed at low pressure. At this time, since the feeding pressure of liquid A is low, the biasing force of the spring 6 prevails, and the tubular spool 5 moves toward the base, and liquid B passes through the conduit 13 to the annular discharge port 7.
On the other hand, liquid A is ejected from the ejection nozzle 8.
As a result, both AB and AB liquids meet at the front.
It is mixed and injected into the surrounding ground.

By the way, if the purpose is only to detect underground objects, a single nozzle attached to a single pipe will suffice, but if the purpose is to inject chemical liquid, it is better to have the injection function. desirable. In addition, even if a single nozzle is attached to a single pipe, 1.5
There are no problems with the shot construction method.

Figures 4a and 4b show the results of the ground test. 3
From the spout 12 of mmφ, (a) one port flow rate approximately 4/
min, total 8/min When the pressure is approximately 11Kg/ ^m2 , (b)
At a single port flow rate of approximately 6/min, total of 12/min, and a pressure of approximately 22 Kg/ ^cm2 , while spouting water with
Steel pipe, () Huium pipe with outer diameter 114mmφ, ()
Acrylic tubes with an outer diameter of 60 mmφ are placed close to each other,
The pressure changes at the _P1 port and _P2 port were observed. Note that the pressure gauge installed at the P ₂ port _is
It has higher sensitivity than the pressure gauge installed in the port.

According to the results, it can be seen that as the pipe is detected, the pressure clearly increases while the discharge flow rate remains constant. Therefore, it will be understood that such a method can be effectively used for detecting objects buried underground.

However, in ground experiments, pressure changes clearly appear even at low pressures, but in the ground,
Because it is necessary to distinguish between the surrounding soil and buried objects, the pressure (feeding pressure) must be 10 kg/ ^cm2 or more, especially 20 kg/cm2.
Kg/cm2 or ^more is desirable, and the flow rate from the spout is 10
m/sec or more, particularly 25 m/sec or more is preferable.

Note that in the present invention, air can also be used instead of liquid such as water, but this is not so preferred in terms of accuracy.

〔Effect of the invention〕

As described above, according to the present invention, the presence or absence of an underground object can be directly detected with high precision and reliability, although it is a non-contact method, since detection is performed based on pressure changes in the supplied fluid.

Furthermore, in the present invention, the spout is opened diagonally forward and the insertion tube is inserted while being rotated around its axis, so that buried objects can be buried not only forward in the axial direction but also in a wide area around the periphery. The presence or absence can be detected, thereby reducing the number of explorations. Moreover, as shown in FIG. 1 above, if detection were to rely solely on the back pressure at the jet nozzle 8, only the buried object could be detected in front of it.
If there is a buried object on the side, it cannot be detected.
If the excavation were to continue as is, the buried objects on the side would be damaged by the outer pipe 1. On the other hand, according to the present invention, at least the buried object in the insertion region of the insertion tube is not damaged.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an example of an insertion tube that can be suitably used for carrying out the method of the present invention in a state in which a detection fluid is being supplied; FIG. 2 is a longitudinal sectional view showing a state in which a drug solution is being injected; Figure 3 is a schematic diagram of the method of the present invention, Figure 4 a, b
is a chart showing the results of ground experiments. 12...Blowout nozzle, 13...Pressure gauge, X...Underground object, W'...detection liquid.

Claims (1)

[Claims] 1. Approach an underground object from above the ground while rotating an insertion tube having a spout opening diagonally forward at its tip about its axis, and during this approach process fluid is directed from the spout to the surrounding ground. A method for detecting an underground object, characterized in that the presence or absence of the underground object is detected by detecting the presence or absence of the underground object based on a change in the pressure of the supplied fluid as the underground object approaches.