JP2867892B2 - How to detect the degree of injection of backfill material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to backfilling of underground passages constructed by shield construction, backfilling of buildings and shafts constructed by excavation, filling of caisson work, or filling of pneumatic caisson. The present invention relates to a method for detecting the degree of injection of an aqueous backfill material in the form of a slurry injected into the back surface of a plate-like member such as the above.

[0002]

In order to confirm the filling degree of a back filling material such as water or cement grout which has been poured into the back side of a conventionally assembled segment, a back filling hole previously provided in the segment is required. Therefore, a method has been adopted in which a sample container that can be split into two is driven and the injection material is directly collected.

[0003] Alternatively, a pressure gauge is attached to the back filling hole, and the degree of filling of the filling material is measured by measuring the pressure increase during the filling.

[0004] However, the method of driving the sample container sometimes involves spring water at the time of driving or pulling out, and has not been widely used for sand layers. Further, since the measurable position is limited to the position of the back injection hole, a continuous measurement result in a plane cannot be obtained.

In the method using a pressure gauge, the object to be measured is pressure, and the pressure propagates to water or muddy water. Therefore, even if the injected material is not always at the measurement position, the pressure may increase, resulting in poor accuracy. Was. In addition, since the position where measurement can be performed is limited, information continuous in a plane cannot be obtained.

The present invention has been made in view of the above circumstances. The purpose is to propose a method of detecting the degree of injection of the backfill material that can be detected in real time, in a continuous manner from the front side, in real time, from the front side, the degree of injection of the backfill material injected into the back surface of the plate-like member such as a segment. is there.

[0007]

According to this method of detecting the degree of injection of a backfilling material, a tracer substance that absorbs a predetermined amount of thermal neutrons is added to the backing material in advance, and a neutron source and a neutron source are added to the surface side of the plate member. A thermal neutron counter is provided, neutrons emitted to the back side are scattered in the backing material to become thermal neutrons, and the number of thermal neutrons after further absorption by the tracer is determined. It is characterized in that the degree of injection is detected.

[0008]

FIG. 1 shows an excavation by a shield method, assembling a segment 1 and a backfill material 3 between the segment 1 and a ground 2 on the back side thereof.
This shows the process of constructing an underpass to inject water.

In this construction step, an aqueous grout using cement as a hardening material is used as the backing filling material 3. A tracer having a large thermal neutron absorption cross-sectional area such as a boron compound is added to the injection material 3 in advance at a predetermined ratio.

Further, a neutron source 4 and a thermal neutron detector 6 having a counter tube 5 for counting the number of thermal neutrons are arranged near the surface of the segment 1.

High-speed neutrons emitted from the neutron source 4 of the thermal neutron detector 6 arranged as described above pass through the segment 1 and enter the implanted material 3 on the back surface, and hit and scatter hydrogen atoms in the implanted material 3. Then, it becomes thermal neutrons, and a part of the neutrons is absorbed by the tracer added to the injection material 3. The unabsorbed thermal neutrons are repeatedly scattered, and a part thereof is counted by a counter tube 5 arranged on the surface side of the segment 1 to obtain the number of thermal neutrons (also referred to as a counting ratio).

The back side of the segment 1 is generally a ground containing water, muddy water, or moisture, and the released neutrons scatter against hydrogen atoms and become thermal neutrons, so that a high number of thermal neutrons is detected. On the other hand, when the injection material to which the tracer is added is injected, neutrons hit hydrogen atoms in the injection material and change into thermal neutrons, and at the same time, are absorbed by the tracer and reduced. That is, the number of thermal neutrons decreases in proportion to the amount of injected material, that is, the amount of tracer. Therefore, the degree of injection of the injection material can be detected from the decrease in the number.

Prior to the injection of the backfilling material, the number of thermal neutrons in the background, that is, the counting ratio is measured, and the degree of the injection can be detected more accurately from the difference from the counting ratio after the injection. FIG. 2 is a graph showing an example in which the background count ratio before injection and the count ratio after injection are measured by continuously moving the measurement position. If the background thermal neutron measurement is not feasible, a sample of the local soil can be taken, a model can be created using the same segment, and measurements can be made to obtain the same results as when the background measurement was performed. it can.

[0014]

The operation and effect of the present invention are as described above. A tracer for absorbing thermal neutrons is added to the backing injection material in advance, and a neutron source and a heat source are added to the surface side of the plate-like member injected with the injection material. By arranging a neutron counter and measuring the number of thermal neutrons (counting ratio), the degree of injection of the injection material can be detected. Therefore, according to this method, simultaneously with the measurement of the number of thermal neutrons, the degree of injection can be detected in real time, and furthermore, by continuously moving the measuring device along the surface of the plate-like member, information on the degree of continuous injection in a plane is obtained. be able to.

[0015]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a measurement state of a back filling material injected into the back side of a segment in an example.

FIG. 2 is a graph showing a change in a counting ratio before and after injection of a back filling material.

[Explanation of symbols]

1 ... segment, 2 ... ground pile, 3 ... back filling material, 4
... neutron source, 5 ... counter tube, 6 ... thermal neutron detector.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01N 23/00-23/207

Claims (1)

(57) [Claims] 1. A method for detecting the degree of injection of a backfill material injected into the back surface of a plate-like member, wherein a predetermined amount of a tracer substance made of a material having a large thermal neutron absorption cross-sectional area is added to the backfill material in advance. A neutron source and a thermal neutron counter are arranged on the front side of the plate-like member, and neutrons emitted on the back side are scattered in the backing material, become thermal neutrons, and are further absorbed by the tracer. A method for detecting the degree of injection of the backfilling material, wherein the number is obtained, and the degree of injection of the backfilling material is detected from the number.