JPH04293817A - Managing method in constructing column wall - Google Patents

Abstract

PURPOSE:To obtain an exactly continuous column wall by excavating the ground by means of an auger and attaching a neutron moisture gauge to the head section of the auger when constructing the continuous column wall integrally. CONSTITUTION:Cement milk is jetted from the head of an auger while excavating by the use of three shaft auger 1 to repeatedly form soil mortar unit column wall 3 with the cement milk mixed with the soil of the original position by a mixing blade. At this moment, a neutron moisture gauge is built in the head section of a center auger 1-2. This neutron moisture measures the distribution of the counting rate of the neutrons of the excavated ground, the excavation being conducted while comparing the value with the preset managing value. This method makes it possible to construct an exactly continuous column wall in a body.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for managing the construction of columnar walls underground using the columnar continuous wall construction method or the in-situ stirring pile method.

0002

[Prior Art] To construct a column wall, the ground is excavated with a single or multiple auger, and the drilled hole is filled with a solidifying material such as cement milk, or the solidifying material is added while excavating. They were mixed together to create a pillar wall, which was then repeatedly constructed horizontally to create a continuous row of pillar walls.

[0003] In order to create a continuous column wall, the positional accuracy and homogeneity of the unit column walls in the depth direction are required, but it is necessary to ensure continuity between the unit column walls in the lateral direction. Must.

Conventionally, means for ensuring continuity in the lateral direction have largely depended on the posture of the auger before excavation. Furthermore, with this method, the auger tip position underground is likely to shift, and it is difficult to detect the auger tip position, making it difficult to accurately ensure continuity.

Recently, there is a technology that detects the posture by installing an inclinometer inside the auger, but the structure of the inclinometer makes it difficult to measure while the auger is rotating. I had to make it stand still.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems. The purpose is to continuously check lateral continuity during the excavation process without stopping the rotation of the auger, and to propose a management method during column wall construction that can ensure accurate continuity. be.

[0007]

[Means for solving the problem] This control method during construction of column walls involves excavating the ground with an auger, injecting and mixing solidifying material into the excavated hole, and repeating the process laterally to form unit column walls. When constructing a continuous column wall, a neutron moisture meter is attached to the auger tip, and when excavating the ground adjacent to the preceding unit column wall, the count rate of the excavated ground at the auger tip is equal to the preceding unit column wall layer. It is characterized by selecting an excavation position that takes a control value set between the counting rate of the ground and the counting rate of the mountain ground.

This control method measures the count rate distribution of the excavated ground with a neutron moisture meter attached to the tip of the auger, and uses this value as a clue to confirm the exact excavation position while excavating.

A neutron moisture meter uses a radiation source (for example, 252Cf
) is an application of the phenomenon in which fast neutrons (several MeV) emitted from a hydrogen atom collide with a hydrogen atom with a small atomic mass and are converted into a thermal neutron (0.025 eV) with a lower energy.If the amount of thermal neutrons is counted, From the counting rate (count number Ncpm), the amount of hydrogen atoms in the substance (g/cm3
), that is, the water content can be measured. The mixing amount of a solidifying agent using water such as cement milk as a medium can be measured from this counting rate (number of counts).

However, if the excavated ground has a high water content ratio or is saturated, there will be no significant difference between the soil and the solidification material mixture, making it difficult to distinguish. For this reason, in the case of ground with a high moisture content, a tracer substance such as boron that absorbs thermal neutrons is added to the solidification material. Since thermal neutrons are absorbed by the tracer substance and the counting rate decreases, the concentration of the tracer substance, that is, the concentration of the solidifying material can be detected using the counting rate.

[0011]

[Example] Fig. 1 shows that while excavating the ground 2 using a triaxial auger 1, cement milk is injected from the tip of the auger and mixed with in-situ soil by a mixing blade, repeatedly forming a unit column wall 3 made of soil mortar. An example will be shown in which a column wall 4 that is integrally continuous in the lateral direction is constructed. In this construction, a neutron moisture meter 5 is installed at the tip of the central auger 1-2 of the triaxial auger 1.
is built-in.

FIGS. 2 and 3 show 3
This is a step of forming a subsequent unit column wall 3' adjacent to the preceding unit column wall 3 consisting of columns of columnar soil mortar 3-1, 3-2, 3-3. Auger 1-1 on the 1 side of the triaxial auger 1
is the columnar soil mortar layer 3 on the first side of the preceding unit column wall 3
- Duplicate excavation at 3 positions, columnar soil mortar 3'-1
, and continuity between the unit column walls 3 and 3' is achieved. When forming the following unit column wall 3', the distribution of the neutron count rate in the excavated ground is measured with the neutron moisture meter 5 built into the tip of the central auger 1-2 of the triaxial auger 1, and the value Excavation proceeds while comparing the values with preset control values.

[0013] In this construction, the counting rate (A) of the ground 2
has been measured in advance, and the counting rate (
B) was measured at the time of construction. Figure 2(b) shows the depth and counting rate, and the counting rate (B) of the preceding unit column wall 3 made of soil mortar mixed with cement milk containing boron tracer is compared to the counting rate (A). It shows a low value, and the control value (C) is set in the middle.

When forming the trailing unit column wall 3', the steps shown in FIG.
As shown in (b), the counting rate (D) of the excavated ground is set to the control value (
C) Excavation will be carried out while maintaining the controlled area (between c and c) centered on. When the first side auger 1-1 of the three-shaft auger 1 overlaps and excavates with the columnar soil mortar layer 3-3 on the first side of the preceding unit column wall 3, the ground excavated at the tip of the central auger 1-2 is the same as that of the preceding unit. Since the soil mortar of the pillar wall 3 and the ground are mixed, the distribution of the counting rate (D) falls within the control range (between c and c) centered on the control value (C).

However, the leading unit pillar wall 3 and the trailing unit pillar wall 3
' are shifted and do not overlap, as shown in Figure 4, the counting rate (D
) will be outside the controlled area (between c and c). Therefore, when excavating, measure the distribution of the count rate (D) and compare it with the control value (C) to confirm that there is no deviation before proceeding with excavation. Adjust the auger position as necessary so that it enters the control area (between c and c). This allows the trailing unit column wall to be formed at an accurate position, making it possible to construct a continuous column column wall.

In this example, when excavating the succeeding unit column wall, cement milk added with a boron tracer was not used, and the counting rate distribution was measured to ensure overlap with the preceding unit column wall. Ta. Cement milk containing boron was used when pulling up the auger.

[0017] Furthermore, when forming unit column walls using boron-added cement milk, the distribution of count rate in the depth direction was determined to control homogeneity, continuity, etc. in the depth direction.

[0018]

Effects of the Invention This invention is as described above, and this control method measures the counting rate of the excavated ground in the process of excavating unit column walls, compares it with a preset control value, Since the construction can be carried out while confirming the lateral continuity with the wall, it is possible to construct a column wall that is accurately and continuously connected to the wall.

Furthermore, the homogeneity and continuity of each unit column wall in the depth direction can be controlled by measuring the count rate using a neutron moisture meter, and the homogeneity and continuity in both the lateral and depth directions can be ensured.

[Brief explanation of the drawing]

FIG. 1 is a perspective view, partially in cross section, of a columnar wall being constructed after excavating the ground with an auger.

[Figure 2] (a) is a cross-sectional view of the preceding unit column wall, (b)
are the counting rate of the ground (A) and the counting rate of the preceding unit pillar wall (B)
This is a correlation graph between the count rate control value (C) and the depth of the trailing unit column wall.

[Figure 3] (a) is a cross-sectional view of the leading unit column wall and the trailing unit column wall under construction, and (b) is the depth of the ground, the counting rate of the leading unit column wall, and the trailing unit column wall under construction. This is a correlation graph.

[Figure 4] (a) is a cross-sectional view of the trailing unit pillar wall at a position shifted from the leading unit pillar wall, and (b) is the depth of the ground, the counting rate of the leading unit pillar wall, and the trailing unit pillar wall. This is a correlation graph.

[Explanation of symbols]

1...triaxial auger, 2...ground, 3...unit column wall, 4...
Column wall, 5...neutron moisture meter.

Claims (1)

[Claims] Claim 1: The process of excavating the ground with an auger, injecting and mixing a solidifying material into the drilled hole, and forming a unit column wall is repeated laterally, and when constructing a continuous column wall, the auger is used. When a neutron moisture meter is attached to the tip and the ground adjacent to the preceding unit column wall is excavated, the count rate of the excavated ground at the tip of the auger is between the count rate of the preceding unit column wall layer and the count rate of the mountain ground. A control method during construction of a column wall characterized by selecting an excavation position that takes a set control value.