JP2533722B2 - Hole bottom condensation method for drilling holes - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of excavation method for ground investigation.

[0002]

2. Description of the Related Art In recent years, as for excavation work for ground investigation, an air excavation system has been provided in which bubbles are sent together with air to the tip of a sampler inserted into the ground. As one of the air excavation methods, the applicant has proposed an air bubble generation apparatus and method of Japanese Patent Application No. 03-101052 as an improvement of the air excavation method. In this air excavation method (hereinafter referred to as the JFB method), a blowing agent is jetted at high speed into compressed air flowing at high speed. As a result, uniform and fine air bubbles in the active micelle state (primary foaming) are formed and are supplied to the sampler tip together with the compressed air. Here, as shown in FIG. 2, the sampler 11 is an outer pipe 1 to which a drill bit 12 is attached.
It is configured as a double core tube by 1a and an inner tube 11b for accommodating the collected sample. This inner pipe 11
The b is configured so as not to rotate together with the outer pipe 11a by using a bearing or the like. Bubbles (primary foaming) 13 pass in a laminar flow state between the two types of pipes thus configured. And the foaming agent in the active micelle state is
High-speed jetting from the bit port at the tip of the sampler produces fine uniform bubbles (secondary bubbles) 14. Due to the bubbles, rock powder generated during excavation is smoothly carried out of the hole. At this time, the bit 12 at the tip of the sampler rotates to perform excavation, and at the same time, a sample is sampled and stored inside the sampler inner tube 11b.

Further, recently, there is also provided one in which a resin tube folded inside the sampler inner tube is provided. Due to the provision of this tube, when the sample is inserted into the inner tube, the material is wrapped in the tube and is securely stored. This improves the core collection rate.

In such a JFB method, since the sampler and members for holding the sampler are hardly shaken during excavation, the disturbance of the hole wall can be minimized, and the quality of the disturbance is good. Samples can be collected, and various tests such as soil condition for soil condition can be measured with high accuracy. Therefore, compared with the conventional air excavation method, since the hole wall itself is self-supporting, collapse of the hole wall can be suppressed.

[0005]

However, in order to sample a good quality sample, the stability of the hole wall is not sufficient, and is influenced by other drilling conditions. One of them is the stability of the bottom surface of the hole.

That is, a gravel layer, a crush zone, an extreme weathering layer, a crack (soil) layer, etc. in which the ground to be sampled is unstable are considerably disturbed by sampling the bottom surface of the hole. Moreover, this phenomenon is exacerbated by the release of underground stress.

In this way, when the deep sampling is newly performed with the bottom of the hole disturbed, the ground on the excavated surface of the hole collapses before the ground around the sample is excavated by the rotation of the bit. Will be broken into pieces. This is because when the bottom of the hole is disturbed, the ground around this hole loses the supporting force in the horizontal direction. Therefore, it becomes impossible to collect the data.

Conventionally, in order to deal with such a problem,
As shown in FIG. 3, the structure of the sampler 11 is modified,
A method has also been proposed in which a reflection piston 15 or the like is provided and the bottom surface of the hole is pressed by this to perform sampling. In this method, by pressing the bottom surface of the hole, the ground at the bottom surface of the hole can be stabilized horizontally and vertically to prevent collapse.

However, when the bottom surface of the hole is disturbed, the pressing is partial and cannot be completely stabilized. For this reason, as the bit rotates, the ground fragments whose bottom of the hole collapses also rotate, and the ground below the hole bottom that has not been excavated (virgin) is also in a disordered state.

Therefore, it is considered that the sample collected in such a state is inferior in quality as a sample for ground investigation. In addition, the actual work is rather inefficient and troublesome, and in this method, it is necessary to prepare a dedicated sampler, so that it has not spread.

The present invention has been proposed in order to solve the problems of the prior art as described above, and the purpose thereof is to collapse by making the bottom of a drill hole having poor stability stable. It is an object of the present invention to provide an excavation method that can easily collect a high-quality sample with little turbulence. Further, in the above-mentioned excavation method, it is also an object to easily and easily collect a good quality sample with a minimum number of members.

[0012]

DISCLOSURE OF THE INVENTION The present invention relates to an excavation method for stabilizing and excavating a hole wall, and when a hole bottom reaches an unstable ground portion by excavation work, a block blocker is already added. It is characterized in that it is a hole bottom condensation method in which it is poured into the hole bottom through the stabilized hole wall portion, and the blocking agent is scattered at the hole bottom surface to stabilize and stabilize the hole bottom surface.

[0013]

The operation of the present invention having the above construction is as follows.

That is, in the excavation method for stabilizing and excavating the hole wall, the hole bottom reaches the unstable ground portion by the excavation work, and when the unstable ground portion is excavated, collapse occurs and the hole bottom is broken. When it becomes disordered due to such factors as the above, a block blocker is added to the bottom of the hole. This block-shaped blocking agent passes through the already stabilized hole wall portion to reach the hole bottom, and is scattered at the hole bottom surface to set and stabilize the hole bottom surface. As a result, the bottom surface of the hole becomes stable, and excavation deeper than the unstable ground area can be performed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the hole bottom condensation method of the present invention will be described below with reference to the drawings.

The sampling is carried out by an outer pipe 1a to which a drill bit 2 is attached and an inner pipe 1b for accommodating the sample collected.
Is performed by the sampler 1 configured as a double core tube. When excavating with such a sampler 1,
The ground has an unstable gravel layer, a crush zone, an extreme weathering layer, a crack (soil) layer, etc. as shown in (1-1) of FIG.
When the collapsed portion X is formed and the hole bottom portion Y is disturbed, the excavation is temporarily stopped at that position.

Then, as shown in FIG. 1 (1-2), after the sampler is taken out, a blocking agent 3 such as bentonite-cement, which is appropriately kneaded into a dumpling shape, is dropped into the formed drill hole. Here, Table 1 shows an example of a condensed material corresponding to the ground property.

[0018]

[Table 1] As shown in this table, the blocking agent 3 is prepared by using a material suitable for the ground property.

Next, as shown in FIG. 1 (1-3), after confirming that the ground debris near the bottom of the hole has been appropriately condensed by the dropped blocking agent 3, the sampler 1 is inserted again,
Perform sampling work. The time required for this condensation is J
In the case of the FB method, the time is about 5 to 30 minutes. The sampling work is performed on the disintegration part X which is solidified by the blocking agent
Further, the hole bottom portion Y in a disordered state and the ground (virgin layer) Z therebelow are also excavated and sampled by the conventional method. Here, Tables 2 and 3 show examples of construction standards when the present embodiment is applied to the JFB method. Table 2 shows
Material and construction method suitable for extreme weathering layer and gravel layer.
Further, Table 3 relates to a cracked rock mass and a crush zone.

[0020]

[Table 2]

[Table 3] The effects of the construction of this embodiment as described above are as follows. That is, in the excavation method of stabilizing and excavating the hole wall, the hole bottom reaches the unstable ground part by excavation work,
When the bottom of the hole is disturbed by fragments or the like due to excavation of the unstable part of the ground and the bottom of the hole is disturbed, a blocker in block form is added to the bottom surface of the hole. The block agent passes through the already stabilized hole wall portion to reach the bottom of the hole and is scattered at the bottom surface of the hole, so that the broken pieces of ground and slime are condensed. In addition, when no water is originally charged, the bottom surface of the hole is simply blocked by this.
Therefore, since the bottom surface of the hole is in a stable ground state, sufficient excavation can be performed even in an unstable depth, and a high-quality sample with little disturbance can be easily collected. In addition, since this embodiment does not require any special mechanical equipment, it can be easily installed and is time-consuming.
It is also very economically advantageous.

The hole bottom condensing method of the present invention is as follows:
The present invention is not limited to the above embodiment. For example, the property of the blocking agent is not limited to the dumpling, and a fluid or soft one such as a suspension may be wrapped in a wrap material or the like so as to be applied in a lump form, depending on the ground property. When wrapped in wrap material, etc., when dropped and hit the bottom of the hole,
The wrapped barrier material is scattered all over the bottom surface of the hole, and the same effect as that of this embodiment can be obtained.

When it becomes necessary to further solidify the vicinity of the bottom of the hole, or when the ground requires a higher blocking effect, a blocking agent having excellent permeability such as fine particle cement is first used, and then A better effect can be obtained by using the barrier material adjusted by the material suitable for the ground conditions.

[0023]

As described above, in the hole bottom condensation method of the present invention, the hole bottom reaches the unstable ground portion by the excavation work,
If the bottom of the hole is disturbed by debris or the like due to excavation of the unstable ground part and the bottom of the hole is disturbed, a blocker is injected into the bottom of the hole. This block blocker passes through the already stabilized hole wall and reaches the bottom of the hole, and is scattered at the bottom of this hole to condense and stabilize the fragments and slime of the collapsed ground at the bottom of the hole. It As a result, excavation can be easily performed even in an unstable depth, and a high-quality sample with little disturbance can be easily obtained.

Further, according to the method of the present invention, a member such as a special machine or the like is not required at the time of charging the blocking agent, and the unstable ground can be stabilized in a short time.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of a hole bottom condensation method of an excavation hole of the present invention.

FIG. 2 is an explanatory view showing a general ground excavation sampler.

FIG. 3 is an explanatory diagram showing a conventional technique when excavating unstable ground.

[Explanation of symbols]

 X ... Disintegration part Y ... Ground at the bottom of the disintegration part 1,11 ... Sampler 2, 12 ... Bit 3 ... Blocking agent 13 ... Bubbles (primary foaming) 14 ... Bubbles (secondary foaming) 15 ... Reflection piston

Claims (1)

(57) [Claims] 1. An excavation method for stabilizing a hole wall for excavation, when the hole bottom reaches an unstable ground part due to excavation work,
A lump-shaped blocking agent is introduced into the hole bottom by passing through the already stabilized hole wall portion, and the blocking agent is scattered at the hole bottom surface to stabilize and condense the hole bottom surface. Bottom setting method.