JPS6145014A - Measurement of subsidence amount of ground - Google Patents

Abstract

PURPOSE:To simply measure the amount of subsidence of the ground by a method in which a flexible long part on which magnetic markers are set at given intervals is driven, a measuring tube is driven in parallel adjacently with the long part, and a magnetic sensor is inserted into the measuring tube. CONSTITUTION:N-numbers of measuring points are set at given intervals on a long part 1, and magnetic markers 3 are fixed to the measuring points. The long part 1 is driven into the ground 2 to be improved, such as soft grout, and a measuring tube 6 is driven adjacently in parallel with the part 1. A cable 4 connected to the uppermost marker 3 is connected to a power source 5 to excite the marker 3 by electrification. The wire 8 is sent out, and while lowering a magnetic sensor 7, magnetic fields are measured to obtain places where maximum measured values are shown. The depth of hanging down of the sensor 7 is also measured, and measured values of depth are obtained from an imaginary line 11 on the basis of the maximum depth value. The cable 4 connected to each marker 3 is orderly changed to lower level ones and the same measuring operations are made.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for measuring the amount of ground subsidence in soft ground improvement work and the like.

(Conventional technology) Conventionally, in the improvement work of soft clay ground using the paper drain material method, etc., paper drain materials, etc. are driven into the improved ground, and then loaded embankment is performed in the improved area, and the soft clay ground is removed through the paper drain. The pore water in the clay ground was drained, and the subsidence of the improved layer due to this drainage was continuously measured, and the completion of the improvement work was determined when the amount of subsidence reached the target value.

To measure the amount of ground subsidence, drill holes at appropriate locations in the improved area by polling, bury screw settling plates, etc., and measure the subsidence of the settling plates at regular intervals using a leveling instrument. was.

(Problem to be solved by the invention) However, this type of method for measuring the amount of ground subsidence requires a large number of pollings, which not only requires a considerable amount of time and expense, but also requires a leveling survey to measure the amount of subsidence. Because it is a manual process, it is not something that anyone can easily do, and there are problems with automation, such as having to be automated.

The present invention was made with attention to these points, and by eliminating polling for burying screw sinking plates, etc., it significantly reduces the time and cost required for polling, and allows anyone to easily perform measurements. The purpose of this project is to provide a method for measuring the amount of ground subsidence that can be automated.

(Means for solving the problem) Therefore, the long member is formed of a non-magnetic material that has flexibility to bend appropriately according to the subsidence of the ground on which it is cast, and Place and fix the magnetic field generating means with
The long member is driven into the improved ground by a drain material driving machine, and a measuring tube made of a non-magnetic material is driven in parallel to the long member in the vicinity of the long member. A magnetic detector that detects the magnetic field generated by the magnetic marker is hung from the magnetic marker, and the magnetic field is sequentially measured by the magnetic detector, and based on the hanging depth of each magnetic detector when the measured value shows the maximum value. It is designed to measure the amount of ground subsidence.

(Function) In the method for measuring the amount of ground subsidence of the present invention configured as described above, a highly flexible long member on which magnetic detectors are fixedly arranged at predetermined intervals is cast by a drain material casting machine. This eliminates the need for polling for burying screw sinking plates, etc.
In addition to making it possible to significantly reduce the time and cost required for this polling work, the amount of subsidence can be measured using the maximum value of the magnetic field from the magnetic marker, which is a long member that bends depending on the degree of consolidation of the improved ground. This was achieved by sequentially taking measurements with a magnetic detector suspended inside a measuring tube, which not only made it easy for anyone to perform the measurement task, but also made it possible to automate the process.

(Example) Next, an example of implementation of the present invention will be described with reference to the drawings. The drawings are explanatory diagrams for explaining one embodiment of the method for measuring the amount of ground subsidence according to the present invention, with Fig. 1 showing the state immediately after pouring, and Fig. 2 showing the state after a predetermined period of time has elapsed. It is something.

In the drawing, 1 is a long member, and is a belt-shaped drain material used in ordinary ground improvement work, such as paper drain material made of paper, chemical drain material made of synthetic resin and chemical fiber nonwoven fabric, and other plastics. It is formed of the core drain material itself or a highly flexible strip-shaped non-magnetic material equivalent to it, and bends as appropriate as the poured improved ground 2 is consolidated. 3
4 is a magnetic marker fixedly arranged at each measurement point set at a predetermined interval on this elongated member 1, and is constituted by, for example, an electromagnet as a magnetic field generating means. 5 is a cable that supplies current.

Further, reference numeral 6 denotes a measuring tube, which is made of a non-magnetic pipe such as a hard vinyl chloride pipe or a stainless steel pipe. Reference numeral 7 denotes a magnetic detector for detecting the magnetic field generated by the magnetic marker 3. For example, a magnetic sensor using a ring core fluxgate method is used for detecting a minute magnetic field. This magnetic detector 7 is slidably suspended within the measuring tube 6 by a hanging wire 8. A display section 9 displays the detection results of the magnetic detector 7, and is connected to the magnetic detector 7 via a cable 10. Further, reference numeral 11 is an imaginary line indicating a reference level for measuring the amount of ground subsidence.

Next, the measurement procedure will be explained.

First, N measurement points are set on the elongated member 1 at predetermined intervals, and a magnetic marker 3 is fixedly arranged at each of the measurement points. The elongated member 1 to which the magnetic marker 3 is attached is cast into improved ground 2 such as soft clay ground by a drain material casting machine in the same way as paper drain material. At this time, the cables 4 from each magnetic marker 3 are extended from the upper end of the elongated member 1 to the ground, and are connected to a power source 5 as necessary. Next, the measuring tube 5 is driven in parallel to the elongated member 1 in close proximity to the elongated member.

At this time, good results were obtained when the distance between the measuring tube 5 and the elongated member 1 was set to 40 or less. 1st
The figure shows the state immediately after being poured in this way.

Next, the cable 4 connected to the uppermost magnetic marker 3 is connected to a power source 5 and energized. As a result, the uppermost magnetic marker 3 is excited and generates a predetermined magnetic field around it. Here, while letting out the hanging wire 8 and lowering the magnetic detector 7, the magnetic field is successively measured and the position where the measured value shows the maximum value is determined. At this time, each suspension depth of the magnetic detector 3 is also measured using a rotary encoder or the like (not shown). Based on the depth value indicating the maximum value at this time, a depth measurement value from the virtual line 11 indicating the reference level of the uppermost measurement point is obtained.

Hereinafter, the cable 4 from the magnetic detector 3 connected to the power source 5 is sequentially connected to the lower one, and the magnetic detector 7 is lowered, and the same measurement is performed at each measurement point to determine the depth of each measurement point. Measure.

As a result, an initial value of the depth of each measurement point is obtained.

The improved ground 2, on which a large number of paper drain materials and the like are placed and loaded with earth, is consolidated by draining pore water through the paper drains over time. As a result, the improved ground 2 sinks, and the cast long member 1 bends in the improved ground 2 according to the amount of the sinking. FIG. 2 shows the state after such a certain period of time has elapsed.

By bending the elongated member 1, the vertical distance between each measurement point is shortened. The depth of each measurement point from the virtual line 11 indicating the reference level is determined by the magnetic detector 7 as in the above case.
is measured by sliding it up and down inside the measuring tube 6. In this case, since the measuring tube 6 is made of a hard vinyl chloride, stainless steel, etc. pipe as described above, it will not bend like the elongated member 1.

Hereinafter, the above-mentioned measurement is sequentially repeated every predetermined period of time, and the depth measurement value from the virtual line indicating the reference level of each measurement point at that time is compared with the initial value of each measurement point. When it is confirmed that the amount of subsidence of the improved ground has reached the target value, a decision is made to end the improvement work.

Although the embodiments have been described in detail in accordance with the illustrated embodiments, it goes without saying that the present invention is not limited thereto. For example, the magnetic marker is not limited to one composed of an electromagnet, but can be replaced by a permanent magnet or the like.

When permanent magnets are used, the magnetic fields of each magnetic marker interfere with each other, making it impossible to narrow the distance between measurement points, but there are advantages in that a power supply can be omitted and cable connection work is not required.

Furthermore, the long member to which the magnetic marker is fixed is not limited to a belt-like member similar to paper drain material, etc., but has the flexibility to bend appropriately as the improved ground 2 is consolidated. It may be of a cylindrical shape as long as it has a cylindrical shape. In that case, the shape of the mandrel of the drain material casting machine etc. needs to be changed accordingly. Furthermore, the elongated member is not only cast separately from the measuring tube as in the previous embodiment;
The elongated member and the distal end of the measuring tube may be connected by a separately prepared member and then simultaneously cast by a drain material casting machine. In this case as well, the structure of the drain material placing machine needs to be changed accordingly, as described above.

(Effects of the Invention) The present invention is constructed as described above, and has a structure in which a flexible elongated member in which magnetic markers are arranged at predetermined intervals can be cast by a drain material casting machine. Polling for board embedding etc. can be eliminated,
It becomes possible to significantly reduce the time and cost required for polling.

Furthermore, the measurement process is extremely simple: detect the maximum point of the magnetic field of the magnetic marker while moving the magnetic detector up and down, and measure the amount of ground subsidence based on the hanging depth of the magnetic detector at that time. Not only can anyone easily carry out measurement work, but the work can also be automated, providing excellent results.

[Brief explanation of drawings]

The drawing is an explanatory diagram for explaining one embodiment of the method for measuring the amount of ground subsidence according to the present invention, and Fig. 1 shows the state immediately after pouring.
Further, FIG. 2 shows the state after a predetermined period of time has elapsed. 1... Long member, 3... Magnetic marker, 6... Measuring tube, 7... Magnetic detector.

Claims (1)

[Claims] (1) In a method for measuring the amount of ground subsidence in soft ground improvement work, etc., a long member is formed of a non-magnetic material with flexibility to bend appropriately according to the subsidence of the ground on which it is cast,
Magnetic field generating means are arranged and fixed at predetermined intervals on this elongated member, and the elongated member is driven into the improved ground by a drain material driving machine, and a measuring tube made of a non-magnetic material is attached to the elongated member. A magnetic detector that detects the magnetic field generated by the magnetic marker is suspended in this measuring tube, and the magnetic field is sequentially measured by this magnetic detector. A method for measuring the amount of ground subsidence, characterized by measuring the amount of ground subsidence based on each hanging depth of a magnetic detector when the maximum value is shown.