JPH11323926A - Evaluating method for ground anchor fixation area - Google Patents

Abstract

PROBLEM TO BE SOLVED: To grasp the ground state of an anchor insertion hole and to evaluate an anchor fixation area by drilling the anchor insertion hole with a hydraulic drill, calculating a breakdown energy coefficient from drilling data, and generating a depth distribution map. SOLUTION: A hydraulic percussion drill A is provided with a depth measuring device 1 which is a depth/speed sensor, a bit load pressure sensor 2, a torque pressure sensor 3, a feed water pressure sensor 4 and a pressure switch 5 for preventing an idle feed, and they are connected to a magnetic recording device 6 respectively. When a ground anchor insertion hole is to be drilled in the ground by percussion boring, drilling data are obtained when the anchor insertion hole is drilled by a hydraulic drill, a breakdown energy coefficient is calculated from the drilling data to generate a depth distribution map, the ground state of the anchor insertion hole is grasped, and the eligibility of a fixation area is judged. The execution cost for percussion boring is low, percussion boring allows the evaluation of the anchor fixation area by accurately grasping the ground state, thereby it serves to shorten the construction period and reduce the construction cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a technique for evaluating a fixing area of a ground anchor.

[0002]

2. Description of the Related Art When installing a ground anchor, which is a reinforcement work that stabilizes the ground by inserting a steel wire into a hole drilled in the ground, fixing the tip, and tightening and fixing, the ground condition of the anchored area It is important to accurately grasp and evaluate

[0003] Conventionally, in rock masses, holes for anchor insertion have been drilled by percussion boring, and a lugion test (injecting water of a constant pressure into a certain section of the hole,
A type of permeability test, which evaluates the permeability of the rock mass based on the injection amount at that time, was conducted, and the eligibility of the anchor anchoring area was evaluated based on the Luzion value. For example, if the lugion value of the ground in which the anchor insertion hole is drilled is 3 lugion or more, the ground in the fixing area is not suitable. In such a case, the ground has been conventionally improved by improving the ground by grouting or increasing the anchor length to the ground where sufficient adhesion strength can be obtained.

[0004] In addition, in earth and sand pits, an anchor insertion hole is drilled by rotary percussion boring, and the collected slime is observed, or a boring core by rotary boring is observed. Samples were collected and the rest was drilled by percussion boring to evaluate the condition of the ground at the anchor anchorage area, and the anchor length was extended to a good ground where sufficient adhesion strength between mortar and rock was obtained.

[0005] However, according to the conventional method in the rocky ground, since a lugion test is performed using the hole after drilling the anchor insertion hole, the construction period and cost are high.

[0006] In addition, even in the case of a soil pile, slime observation is not sufficient for grasping the ground condition, and when performing rotary boring, it is more expensive than percussion boring.

[0007] For this reason, when constructing a ground anchor, there is a demand for a technique capable of drilling the anchor insertion hole by percussion boring, which is inexpensive to construct, and also capable of grasping the condition of the ground and evaluating the anchor fixing area. Was. However, at present, such a technique has not been proposed.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has been proposed to meet the demands of the related art. It is possible to drill an anchor insertion hole by percussion boring. The purpose of the present invention is to provide a method for evaluating the ground anchor anchorage area so that the ground condition can be grasped and the anchor anchorage area can be evaluated.

[0009]

According to the method for evaluating the anchorage area of a ground anchor according to the present invention, when drilling a ground anchor insertion hole in the ground using percussion boring, a drilling logging is performed to determine a fracture energy coefficient. It is characterized in that the ground condition of the anchor insertion hole is grasped based on the obtained fracture energy coefficient.

As a result of various studies, the inventors measured and analyzed data such as drilling speed and impact energy obtained when drilling the ground with a hydraulic drill, and evaluated the state of the ground at the drilled depth. It has been found that the above-mentioned problem of the prior art can be solved and the conventional request can be satisfied by using the “drilling logging” which is a technique for performing the drilling. "Drilling well"
Is described, for example, in Japanese Patent Publication No. 7-49756, entitled "Method of Rock Mass Evaluation and Geological Prediction of Face in Front of Face Using Hydraulic Drilling Data".

In practicing the present invention, the ground is preferably a rock mass or a soil mass. The method for evaluating the anchor area of a ground anchor according to the present invention can be widely applied to a ground such as a rock slope, a soil slope, and a rock underground cavity.

According to the present invention having the above-described configuration, when drilling a ground anchor insertion hole in the ground using percussion boring, drilling logging is performed.
The fracture energy coefficient is obtained from the data at the time of drilling the anchor insertion hole, the ground condition of the anchor anchorage area can be grasped based on the obtained fracture energy coefficient, and it is possible to evaluate whether or not the anchor area is appropriate.

In other words, according to the present invention, the anchor insertion hole can be drilled by percussion boring, which is inexpensive to construct, and at the same time, by drilling logging and determining the fracture energy coefficient, the condition of the ground can be reduced. It is possible to grasp and evaluate the anchor fixing area.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. First, drilling logs are those that measure and analyze data (drilling speed, impact energy, etc.) obtained when drilling the ground with a hydraulic drill, and evaluate the condition of the ground at the drilled depth. It is.

FIG. 1 shows an example of a hydraulic drill A used for borehole logging. Depth measuring device 1, which is a depth / speed sensor,
A pressure sensor 2 for bit load, a pressure sensor 3 for torque, a pressure sensor 4 for water supply pressure, and a pressure switch 5 for preventing idle feed are provided, which are respectively connected to a magnetic recording device 6 having a built-in timer. ing.

The evaluation uses the fracture energy coefficient shown in FIG. As shown in this figure, the fracture energy coefficient represents the energy required to destroy a unit-volume ground. The fracture energy coefficient increases when the ground at the excavation position is hard, and decreases when the ground at the excavation position is soft.

This embodiment is an example in which the present invention is implemented in a rocky underground cavity, but an anchor is to be installed on the cavity wall surface. When drilling the anchor insertion hole, drilling logging was performed, and the fracture energy coefficient was determined as an average value for each 1 m section. An example with one hole is shown in FIG. 10m depth
The fracture energy coefficient is small in the vicinity, and large in the vicinity of the hole depth 20 m.

FIG. 4 shows an example in which a lugion test was conducted in the same hole as in FIG. The lugion value is large in the 10-15 m section (large water permeability) and small in the 15-20 m section (small water permeability).

For reference, FIG. 5 shows an example in which velocity logging is performed in the same hole as in FIGS. 3 and 4 and the section velocity (P-wave velocity) for each 1 m is calculated. The speed is small near the depth of 10 m,
It becomes large near the hole depth of 20 m.

FIG. 6 shows the relationship between the fracture energy coefficient at a plurality of holes at this site and the lugion value. The fracture energy coefficient is an average value in a section corresponding to a section in which the Lugion test was performed (5 m in this case). As shown in FIG. 6, a strong negative correlation is observed.

FIG. 7 shows the relationship between the fracture energy coefficient and the P-wave velocity. The P-wave velocity, which is a good index of the hardness of the ground, and the fracture energy coefficient obtained by drilling show a good correlation. You can see that.

Therefore, based on these relationships, it is possible to evaluate the water permeability of the ground from the fracture energy coefficient of the borehole logging and to estimate the elastic wave velocity (P-wave velocity). Therefore, if drilling logging is performed when drilling the anchor insertion hole and the fracture energy coefficient is determined, the eligibility of the anchor fixing area in the hole can be evaluated. As a result, measures such as ground improvement by grouting and extension of the anchor length can be taken.

The procedure of the method for evaluating the anchor construction and the fixing area will be described with reference to FIG. The working steps are shown in FIGS.

First, an anchor insertion hole is drilled by a hydraulic drill. At this time, drilling data is acquired simultaneously (step S1, FIG. 9). Calculate the fracture energy coefficient from the drilling data and create a distribution map for each depth (step S
2), the ground condition of the anchor insertion hole is grasped (step S3), and the eligibility of the fixing area is determined (step S4, FIG. 10).

If ineligible, it is examined from existing geological data or the like whether there is a possibility that the ground condition of the anchorage area may be improved by slightly extending the anchor length (step S5). For example, the current anchorage area is earth and sand, but this is the case where it is certain that it will reach rock mass if it is slightly extended, and it is certain that it will reach fresh rock if it is slightly weathered rock. In this case, a design change is performed to extend the anchor length (step S6).

If the above conditions are not met, grout is performed on the anchor insertion hole as shown in FIG. 11 to improve the ground around the anchor insertion hole (step S7).

In the case of the extension of the anchor length, drilling and drilling are performed on the extended portion, and a new fixing area is similarly evaluated.

If the anchor fixing area is determined to be qualified, the anchor will be installed. In the case of ground improvement by grouting, an anchor is to be constructed after reboring (step S8).

First, the anchor is inserted into the hole (step S9, FIG. 12). Next, the fixing area is fixed by injection (step S10, FIG. 13). After the base plate is set, the anchor is tensioned and fixed (step S11, FIG. 13).
(FIG. 14).

[0030]

As described above, according to the present invention, the anchor insertion hole can be drilled by percussion boring, which is inexpensive to construct. At the same time, when drilling the ground anchor insertion hole, drilling logging is performed to determine the fracture energy coefficient, so that the condition of the ground can be grasped and the anchor anchoring area can be evaluated. Therefore, it is useful for shortening the construction period and the construction cost.

The present invention can be widely applied to rock slopes, earth and sand slopes, rock underground cavities, and the like.

[Brief description of the drawings]

FIG. 1 is a side view showing an example of a hydraulic drill used for drilling logs.

FIG. 2 is a diagram showing a method of calculating a fracture energy coefficient in a borehole logging.

FIG. 3 is a diagram showing an example of a distribution of fracture energy coefficient by depth obtained by drilling.

FIG. 4 is a diagram showing an example of a distribution of lugeone values by depth according to a lugeon test.

FIG. 5 is a diagram showing an example of a distribution of P-wave velocities by depth obtained by velocity logging.

FIG. 6 is a diagram showing a relationship between a fracture energy coefficient and a lugion value.

FIG. 7 is a diagram showing a relationship between a breaking energy coefficient and a P-wave velocity.

FIG. 8 is a diagram showing a procedure of anchor construction and evaluation of a fixing area.

FIG. 9 is a process chart showing a drilling operation and a drilling logging operation.

FIG. 10 is a diagram illustrating an evaluation operation process based on a fracture energy coefficient.

FIG. 11 is a process chart showing ground improvement work using grout.

FIG. 12 is a process chart showing an anchor insertion operation.

FIG. 13 is a process chart showing an anchor fixing operation.

FIG. 14 is a process chart showing an anchor tensioning operation.

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[Procedure amendment]

[Submission date] March 17, 1999

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

[0009]

According to the present invention, there is provided a method for evaluating a ground anchor fixing area when a ground anchor is inserted and fixed by drilling an anchor insertion hole in the ground by percussion boring. The anchor insertion hole is drilled, the fracture energy coefficient is calculated from the drilling data, a distribution map for each depth is created, and the ground condition of the anchor insertion hole is grasped.

Claims (2)

[Claims] When drilling a ground anchor insertion hole in the ground using percussion boring, drilling logging is performed to determine a fracture energy coefficient, and the ground condition of the anchor insertion hole is determined based on the determined fracture energy coefficient. The method of evaluating the ground anchor anchorage area, characterized by grasping the ground. 2. The method according to claim 1, wherein the ground is a rock mass or a soil mass.